From α,β-unsaturated Fischer carbene complexes to highly substituted 3-ethoxycyclopentadienes, masked cyclopentenones

Article abstract of DOI:10.1002/ejoc.200300534

The β-amino-substituted α,β-unsaturated Fischer carbene complexes 3 are readily available by a four step one-pot procedure from terminal alkynes, chromium hexacarbonyl and secondary amines (24 examples with yields of 68-99% and 7 examples with yields of 26-63%). The formal [3+2] cycloadditions of complexes 3 with different alkynes including diynes and enynes performed in donor solvents such as pyridine or acetonitrile afforded highly substituted 5-(dialkylamino)-3-ethoxycyclopentadienes 7, generally in medium to excellent yields (25 examples with yields of 60-95% and 7 examples with yields of 18-53%). The steric and electronic effects of the substituents on the carbene complexes and the incorporated alkynes on the regio- and stereoselectivity of the ring-forming reaction have been elaborated. An interesting 1,5- or, more likely, 1,2-migration of the dimethylamino group was observed for 5-(dimethylamino)-3- ethoxycyclopentadienes with trimethylsilyl and iPr substituents at C-5. Attempted asymmetric syntheses of cyclopentadienes 7 from complexes 3 with chiral amino groups or substituents were only moderately successful. At a center of chirality in the secondary amino group, complexes of type 3 gave compounds 7 with diastereomeric excesses of, at best, 59% in yields of 54%, and with a stereogenic center in the substituent R¹ attached to the vinyl group of 3, diastereomeric excesses as high as 94% could be achieved, but with poor chemical yields (21%). In general, cyclopentenones 21 could be easily obtained from the cyclopentadienes 7 under acidic conditions in very good yields (4 examples with yields of 81-98%, 1 example with an overall yield of 50% from complex 3). Intramolecular aldol reactions of dicarbonyl compounds generated by hydrolysis of cyclopentadienes 7 with acetal-protected aldehyde or ketone carbonyl groups in either the 5-substituent R¹ or the N-substituent R² led to the bicyclic compounds 22 and 23. The dimethylamino group in cyclopentenones 21 could be either eliminated or transformed into other functional groups via the quaternary ammonium salts 24. The elimination product, cyclopentadienone 27 can undergo dimerization either by a formal [4+2] or [2+2] cycloaddition. Cyclopentenone 21naaa with a bromovinyl-terminated side chain undergoes an intramolecular Heck reaction to form 5-methyl-4,6- dimethylenebicyclo[3.3.0]oct-1-en-3-one (32) (37% yield). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200300534

FULL PAPER
From α,β-Unsaturated Fischer Carbene Complexes to Highly Substituted
3-Ethoxycyclopentadienes, Masked Cyclopentenones
Yao-Ting Wu,[a] Bernard Flynn,[a][‡] Heiko Schirmer,[a] Frank Funke,[a] Stefan Müller,[a]
Thomas Labahn,[b] Markus Nötzel,[a] and Armin de Meijere*[a]
Dedicated to Lawrence T. Scott on the occasion of his 60th birthday
Keywords: Cocyclization / Organometallics / Template synthesis / Cycloadditions / Aldol reactions / Fischer carbenes
The β-amino-substituted α,β-unsaturated Fischer carbene
complexes 3 are readily available by a four step one-pot pro- tached to the vinyl group of 3, diastereomeric excesses as
54%, and with a stereogenic center in the substituent R1 at-
cedure from terminal alkynes, chromium hexacarbonyl and
high as 94% could be achieved, but with poor chemical
secondary amines (24 examples with yields of 68−99% and 7
yields (21%). In general, cyclopentenones 21 could be easily
examples with yields of 26−63%). The formal [3+2] cycload- obtained from the cyclopentadienes 7 under acidic condi-
ditions of complexes 3 with different alkynes including di- tions in very good yields (4 examples with yields of 81−98%,
ynes and enynes performed in donor solvents such as pyri- 1 example with an overall yield of 50% from complex 3). In-
dine or acetonitrile afforded highly substituted 5-(dialkylam- tramolecular aldol reactions of dicarbonyl compounds gener-
ino)-3-ethoxycyclopentadienes 7, generally in medium to ex- ated by hydrolysis of cyclopentadienes 7 with acetal-pro-
cellent yields (25 examples with yields of 60−95% and 7
examples with yields of 18−53%). The steric and electronic
effects of the substituents on the carbene complexes and the
incorporated alkynes on the regio- and stereoselectivity of
the ring-forming reaction have been elaborated. An interest-
ing 1,5- or, more likely, 1,2-migration of the dimethylamino
tected aldehyde or ketone carbonyl groups in either the 5-
substituent R1 or the N-substituent R2 led to the bicyclic com-
pounds 22 and 23. The dimethylamino group in cyclopen-
tenones 21 could be either eliminated or transformed into
other functional groups via the quaternary ammonium salts
24. The elimination product, cyclopentadienone 27 can un-
group was observed for 5-(dimethylamino)-3-ethoxycyclo- dergo dimerization either by a formal [4+2] or [2+2] cycload-
pentadienes with trimethylsilyl and iPr substituents at C-5.
Attempted asymmetric syntheses of cyclopentadienes 7 from
dition. Cyclopentenone 21naaa with a bromovinyl-termin-
ated side chain undergoes an intramolecular Heck reaction
complexes 3 with chiral amino groups or substituents were to form 5-methyl-4,6-dimethylenebicyclo[3.3.0]oct-1-en-3-
only moderately successful. At a center of chirality in the sec-
ondary amino group, complexes of type 3 gave compounds
7 with diastereomeric excesses of, at best, 59% in yields of
one (32) (37% yield).
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
an important component in the tool box for organic syn-
thesis.[2] In particular, the formal [3ϩ2ϩ1] cycloaddition of
an α,β-unsaturated or an α-aryl-substituted Fischer carbene
complex and an alkyne with carbon monoxide insertion,
the so-called Dötz reaction, was convincingly applied
towards the preparation of a large variety of natural prod-
ucts and other interesting molecules.[3] Yet, quite a few α,β-
unsaturated Fischer carbene complexes do not undergo the
Dötz reaction with alkynes. Depending on the nature of the
substituents on the carbene carbon atom and on the vinyl
group as well as on the reaction conditions, such complexes
can yield a wide variety of different types of products, often
with high chemoselectivities upon careful choice of the re-
action conditions. This is particularly true for β-amino-sub-
stituted α,β-unsaturated Fischer carbene complexes, and
thus they can be regarded as chemical multitalents.[4] The
[3ϩ2] cocyclization of such a complex with an alkyne, yield-
When E. O. Fischer and his co-workers discovered a
straightforward route to alkoxycarbene complexes of chro-
mium and other transition metals about four decades ago,[1]
it was not obvious that these would soon start to become
[a]
Institut für Organische Chemie der Georg-August-Universität
Göttingen,
Tammannstrasse 2, 37077 Göttingen, Germany
Fax: (internat.) ϩ 49-(0)551-399475
E-mail: Armin.deMeijere@chemie.uni-goettingen.de
[b]
Institut für Anorganische Chemie der Georg-August-
Universität Göttingen,
Tammannstrasse 4, 37077 Göttingen, Germany
[‡]
Current address: Department of Medicinal Chemistry,
Victorian College of Pharmacy, Monash University,
381 Royal Pde, Parkville VIC 3052, Australia
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
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Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
ing a 5-dialkyamino-3-ethoxycyclopentadiene was first re-
Table 1. Preparation of (3-dialkylamino-1-ethoxyalkenylidene)penta-
carbonylchromium complexes 3 from terminal alkynes 1, chromium
hexacarbonyl, triethyloxonium tetrafluoroborate and dialkylamines
(see Scheme 1)
ported by us for a β-cyclopropyl-substituted example.[5]
Later this was greatly extended and found to be quite gen-
eral when carried out in a donor solvent, especially pyri-
dine.[6] Here we report on the full scope of the preparation
of such β-amino-substituted α,β-unsaturated Fischer car-
bene complexes and their application towards the synthesis
of 5-(dialkylamino)-3-ethoxycyclopentadienes, which have
also turned out to be useful building blocks for organic syn-
thesis.[4]
Results and Discussion
Certainly the most convenient access to β-amino-substi-
tuted α,β-unsaturated Fischer carbene complexes 3 is by a
Michael-type addition of secondary amines 2 to alkynylid-
enecarbene complexes 5. The latter are easily obtained from
lithiated terminal alkynes 1, chromium hexacarbonyl, and
triethyloxonium tetrafluoroborate (Scheme 1). In a previous
systematic study of this Michael-type reaction of complexes
5, it was observed that in addition to the 1,4-addition prod-
ucts 3, 1,2-addition-elimination (formal substitution) 4 and
1,4-addition-elimination products 6 can be formed.[7] The
ratio of the three complexes 3, 4 and 6 largely depends on
the polarity of the solvent, the reaction temperature, and
the substituents on the alkyne (R1) and amine (R2). By
working entirely in tetrahydrofuran instead of diethyl ether
for the first two steps, however, one can carry out all four
steps in a one-pot procedure and obtain complexes 3 con-
sistently in good to very good yields (Table 1) with only a
few exceptions.[6]
Scheme 1. Preparation of Fischer carbene complexes 3 in a one-
pot procedure; for details see Table 1
Upon heating a complex of type 3 with a terminal alkyne
1 in a donor solvent, such as pyridine or acetonitrile, at
temperatures between 55 and 80 °C, a 1,5-disubstituted 5-
(dialkylamino)-3-ethoxycyclopentadiene 7, in some cases
accompanied by its 2,5-disubstituted regioisomer 8, was ob-
tained in moderate to excellent yield (Scheme 2, Table 2).
Internal alkynes gave the 1,2,5-trisubstituted analogues 7/8.
In none of the cases was any Dötz-reaction product de-
tected. As has previously been discussed,[10] a donor solvent
molecule acting as a ligand on the intermediate complexes
in addition to the strongly donating β-dialkylamino group
[a]
[b]
E ϭ CO2Et.
One-pot procedure, if not otherwise mentioned.
[c] Two-step procedure, the chemical yield was calculated only for the
[d]
Michael-type addition to complex 5. In addition, 13% of 6bh was
[e]
[f]
isolated. In addition, 5% of 6bj was isolated. In addition, 17%
[g]
of 6da was isolated.
In addition, 15% of 6dk was isolated.
[h]
[i] [j] [k]
In addition, 25% of 4ga was isolated. Ref.[8]
.
Ref.[6]
.
Ref.[9]
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A. de Meijere et al.
FULL PAPER
prevents the CO insertion, which would lead to the formal
[3ϩ2ϩ1] cycloadducts thus favoring the formation of the
[3ϩ2] cocyclization products. The same chemoselectivity for
the formation of five-membered rings without CO insertion
has also been observed by Dötz et al.,[11] Wulff et al.,[12]
and Aumann et al.[13]
Table 2. 5-(Dialkylamino)-3-ethoxycyclopentadienes 7/8 from (3-
dialkylamino-1-ethoxyalkenylidene)pentacarbonylchromium com-
plexes 3 and alkynes 1 (see Scheme 2)
Scheme 2. A general synthesis of highly substituted 5-(dialkylam-
ino)-3-ethoxycyclopentadienes 7/8; conditions A: pyridine, 55Ϫ80
°C, 1.5Ϫ4 equiv. of alkyne; B: MeCN, 80 °C, lower concentration
of alkyne; for further details see Table 2 and 3
Scheme 3. Proposed mechanism for the formation of cyclopentadi-
enes 7 and their regioisomers 8; A: alkyne insertion; B: coordi-
nation with a donor ligand, C: 6π-electrocyclization; D: reductive
elimination
Mechanistically, the formation of the cyclopentadienes 7
and 8 can be rationalized in terms of following the sequence
in Scheme 3. Upon heating, complex 3 undergoes thermal,
dissociative ligand exchange of a carbonyl group for an al-
kyne to give 9. In accordance with the calculations of Hof-
mann et al., carbene complex 9 then undergoes insertion of
the alkyne, in a concerted fashion, to give the carbene/π-
chelate complex 10.[14] This pathway avoids the originally
proposed 16-electron chromacyclobutene intermediate (not
shown), which would be expected to be of much higher en-
ergy than the transition state along the concerted path-
way.[14] In the presence of a suitable coordinating agent or
solvent, complex 10 is dechelated to give 11. Complex 11
can then undergo a 4π- and/or 6π-electrocyclization to give 8lab was isolated.
[a]
[b]
E ϭ CO2Me, EЈ ϭ CO2Et.
Conditions A, if not otherwise
[c]
[d]
specified. In addition, 7% 8aar was isolated.
of 8aas was isolated.
was isolated. In addition, 11% of 8bam was isolated. Hexane
In addition, 7%
[e]
[f]
Conditions B. In addition, 8% of 8bal
[g]
[h]
[i]
was used as solvent.
In addition, 8% of 8lal was isolated.
[j]
[k]
In addition, 11% of 8laz was isolated.
In addition, 6% of
[l]
[6] [m]
Ref.
.
In addition, 4% of 8qag was
isolated.
the vinylchromacyclobutene 12 and/or the chromacyclo-
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Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
hexadiene 13, respectively, which would both be formed as
low energy 18-electron complexes. These two complexes, 12
and 13, may interconvert via ring expansion and contrac-
tion. Reductive elimination from 13 gives the cyclopen-
tadiene 7. Reductive elimination from 12 gives the vinyl-
cyclopropene 15, which would be expected to undergo re-
insertion of the chromium into the least congested cyclo-
Table 3. Steric influence of substituents on the complexes 3 and the
alkynes 1 on the regioselectivities of the formation of 5-dialkyl-
amino-3-ethoxycyclopentadienes 7/8
propene single bond to give
a
regiosomeric
vinylchromacyclobutene 14.[15] Ring expansion of 14 to the
chromacyclohexadiene 16 and reductive elimination then
leads to the regiosiomeric cyclopentadiene 8.
A high concentration of the coordinating agent L relative
to the alkyne 1 is very important in favoring formation of
cyclopentadienes 7 and 8 over carbonyl-insertion prod-
ucts.[10] In the presence of high concentrations of an alkyne,
the group L in 11 can be replaced by an alkyne to give an
alkyne complex (11, L ϭ alkyne). Unlike the usual groups
L, such as acetonitrile and pyridine, this alkyne ligand can
act as a 4π-electron donor and induce carbonyl insertion to
give an 18-electron ketene complex (not shown), which will
ultimately lead to the formation of carbonyl-containing co-
cyclization products.
Alkynes with a large variety of substituents, even enynes
and diynes can be applied in this formal [3ϩ2] cycload-
dition with complete chemoselectivity. Intramolecular an-
nelations[16] of α,β-unsaturated Fischer carbene complexes,
i.e. di- and triynyl complexes, and intermolecular cascade
cycloadditions[17] of alkyl complexes with enynes, diynes
etc. are well known. In the cases reported here, however,
additional multiple bonds in the molecule do not partici-
pate after the intermolecular cocyclization (Entries 15Ϫ17,
27Ϫ31, Table 2), and the substituents in the carbene com-
plexes and the alkynes do not influence the chemoselectivity
in the formation of the products 7. In the cocyclization of
complex 3ba with the unsymmetrical diyne 1x, only one
product was detected (Entry 17, Table 2), apparently arising
from the fact that the terminal triple bond must be more
reactive than the internal one with its two bulky substitu-
ents.
[a]
Conditions A are as in Scheme 2 unless otherwise specified.
[b]
[c]
[d]
Conditions B are as in Scheme 2.
Ref.[9].
Although the
product mixtures 7dahe/8dahe and 7dahc/8dahc could not be sepa-
rated, the regioisomers 8 are more easily hydrolyzed to cyclopen-
tenones than 7. After initial separation of the mixtures from other
components, slow elution with a mixture of pentane/Et2O (10:1)
allowed the non-polar isomer 7 to be isolated. The structures of 7
and 8 were assigned on the basis of their HMBC-2D NMR spectra.
[e]
It was not possible to rigorously assign the regioisomers 7dahh1/
8dahh1 and 7dah2h3/8dah2h3 so that the ratios may be reverse of
those stated.
rolidines were formed via a completely different reaction
process.[18]
In some examples (see Table 2), small amounts of re-
The internal alkynes 1-phenyloctyne (1he) and cyclopro-
gioisomers 8 as by-products could be detected. The steric pylphenylethyne (1hc), upon treatment with 3da, gave
bulk of the substituents either in the complexes 3 (R1) or in higher proportions of the regioisomer 7 than phenylethyne
the applied alkynes (RL) appears to have an important ef- (Entries 8Ϫ10, Table 3). Varying the electronic properties of
fect on the regioselectivity of the cocyclization, and it has the substituents on the phenyl groups of diphenylethyne did
more influence on the former than on the latter (Entries not influence the ratio between 7 and 8 greatly (Entries
1Ϫ8, Table 3). The substituents R1 in complexes 3 of the 11Ϫ12).
first six examples in Table 3 are primary alkyl groups, and
Cocyclizations of internal alkynes and the carbene com-
the cocyclization products of type 7 obviously still dominate plexes 3 with larger substituents R1 did not only lead to
even when alkynes 1f and 1g with bulky substituents were an increased formation of the regioisomer 8, but led to yet
applied as reaction partners. In contrast to these cases, com- another isomeric cyclopentadiene 17 which would result
plex 3da with the sterically more demanding isopropyl sub- from 7 by 1,5-migration of the dimethylamino group
stituent consistently gave larger fractions of the regioiso- (Scheme 4 and Table 4).[19] These 1,4,5-trisubstituted 5-(di-
meric cyclopentadienes 8. With trimethylsilylethyne (1g) and methylamino)-2-ethoxycyclopentadienes 17 have distinctly
some internal alkynes 1hh1 as well as 1h2h3, the products of different NMR spectra compared with the isomers 7 and 8.
type 8 became the major regioisomers (Entries 7, 11, 12, Due to the electron donating effect of the ethoxy group, the
Table 3). With even bulkier substituents on the alkyne (e.g. signals of the olefinic protons in 7/8 appear more upfield
tert-butyl, mesityl, adamantyl, etc.), 2-(acylmethylene)pyr- than that in 17 (δ ϭ 4.5Ϫ5 ppm versus δ ϭ 5.7Ϫ6.5 ppm).
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The same holds for the corresponding 13C NMR signals
(δ ϭ 95Ϫ100 ppm versus δ ϭ 110Ϫ120 ppm). The consti-
tution of 17daaa, one specimen of type 17, was rigorously
established by a single-crystal X-ray diffraction study of its
hydrolysis product 18 which was obtained by treatment of
17daaa with hydrochloric acid (Figure 1).[20]
Figure 1. Structure of 4-(dimethylamino)-3-isopropyl-4,5-dimeth-
ylcyclopent-2-enone (18) in the crystal[20]
Scheme 4. Steric and electronic effects of substituents in the applied
alkynes 1 on the distribution of cyclopentadienes 7, 8 and 17; for
further details see Table 4
1,4-Diphenylbutadiyne (1hz1) can be regarded as an in-
ternal alkyne with a phenyl and a phenylethynyl substituent
with the latter being more strongly electron withdrawing
than the former. With this acetylene, the cocyclization prod-
uct 17dahz1 was isolated in 9% yield (Entry 7, Table 4). In
order to determine the mode of formation of 17dahz1, iso-
lated samples of 7dahz1 and 8dahz1 in [D5]pyridine were
heated to 80 °C. In the sample of 7dahz1, the signal of
17dahz1 appeared slowly. After 17 days, 67% of 7dahz1 had
been converted into 17dahz1, while the isomer 8dahz1 re-
mained unchanged even upon prolonged heating
(Scheme 5). This shift of the dimethylamino group is revers-
ible but the rate constant for the transformation of 7dahz1
to 17dahz1 must be larger than that of the reverse reaction.
When pure 17dahz1 was heated in [D5]pyridine at 80 °C for
2 days, a 21% conversion to 7dahz1 could be observed. Un-
der the same conditions, 40% of 7dahz1 was converted
into 17dahz1.
Table 4. Formation of 1,4,5-trisubstituted 5-(dimethylamino)-2-
ethoxycyclopentadienes 17 from complexes 3 and internal alkynes
(see Scheme 4)
[a]
[b]
All starting materials had the (E) configuration. The product
was isolated as a 1:1 mixture of cyclopentadiene 7dacc and its hy-
drolysis adduct 21dacc in 78% yield. Complete hydrolysis of the
mixture gave the cyclopentenone 21dacc in 84% yield. [c] The struc-
tures of 7dahz1, 8dahz1 and 17dahz1 could be assigned on the basis
of NOESY-2D NMR spectroscopy, and the resultant information
could also be applied towards the assignment of isomers 7dah4z/
8dah4z/17dah4z and 7dah3z2/8dah3z2/17dah3z2.
In contrast to 2-butyne (1aa), the sterically more con-
gested and more electron-rich dicyclopropylethyne (1cc) did
not afford any product of type 17 (Entry 4, Table 4), while
complexes 3ia and 3ga with 2-butyne (1aa) gave only 17iaaa
and 17gaaa, respectively. Neither 7 nor 8 could even be de-
tected in the spectra of the crude products (Entries 2, 3,
Table 4).
Scheme 5. A possible mode of formation of 1,4,5-trisubstituted 5-
(dimethylamino)-3-ethoxycyclopentadiene 17dahz1 by 1,2-migra-
tion of the dimethylamino group in 7dahz1 via a bridged zwit-
terionic intermediate
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Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
These results seem to indicate that 17dahz1 is not formed
by a 1,5-shift of the dimethylamino group, but rather a 1,2-
migration via the bridged zwitterionic intermediate 19
which would be significantly stabilized by the strongly elec-
tron withdrawing phenylethynyl substituent and the elec-
tron donating ethoxy group. Indeed, even with the more
strongly electron withdrawing p-trifluorophenylethynyl sub-
stituent provided by 1,4-bis(p-trifluoromethylphenyl)buta-
diyne (1h4z), the ratio between 17 and 7 increased by
around six-fold. In contrast, the bis-donor-substituted di-
phenylbutadiyne 1h3z2 did afford traces (Յ1%) of a product
of type 17 (Entry 8, Table 4). Di(p-trifluoromethylphenyl)e-
thyne (1h4h4) also yielded none of the product 17dah4h4.
Table 5. Stereodirected synthesis of 5-(dialkylamino)-3-ethoxycy-
clopentadienes 7 from chirally modified β-(dialkylamino)alkenylid-
enechromium complexes 3 (see Scheme 6)
Asymmetric Induction in the Formation of 5-(Dialkylamino)-
3-ethoxycyclopentadienes
The 5-(dialkylamino)-3-ethoxycyclopentadienes 7, 8 and
17 are chiral with one stereogenic center each in their five-
membered rings. The stereochemical information contained
in enantiomerically pure derivatives would be carried over
into the 3-(dialkylamino)cyclopent-2-enones 21 which are
easily obtained, e.g. from 7,[9] and can be applied favorably
towards the construction of complex molecules.[9,19,21] It
was therefore desirable to prepare cyclopentadienes of type
7 in enantiomerically pure form. In view of the numerous
examples of the successful application of chiral auxiliaries
derived from proline, e.g. in the SAMP/RAMP methodo-
logy developed by Enders et al.,[22] pyrrolidinyl residues
were introduced into the α,β-unsaturated carbene com-
plexes 3 using the established methodology (see above,
Scheme 1). In the best example, however, the diastereomeric
excess was only 59% with a chemical yield of only 54%
(Scheme 6 and Table 5). In two cases yields were better, but
the diastereomeric excesses were lower, and in four cases
the yields and diastereoselectivities were unsatisfactory.
Substituents R1 in the carbene complexes 3 with stereo-
genic centers in the 1- and 2-positions relative to the double
bond were also tested for the asymmetric synthesis of cyclo-
pentadienes 7 (Scheme 7, Table 6). Although the dia-
stereomeric excesses obtained with complex 3ia containing
a 1-methoxyethyl substituent were quite good, especially
when the reactions were carried out at low temperatures,
the chemical yields were insufficient. Chemical yields were
better with the 2-(tert-butyldimethylsilyloxy)propyl-substi-
tuted complex 3ka, but diastereomeric excesses were con-
sistently lower.
Scheme 7. Asymmetric synthesis of cyclopentadienes 7 with chiral
substituents R1 on the complexes 3; for further details see Table 6
Table 6. Asymmetric synthesis of cyclopentadienes 7 with chiral
substituents R1 on the complexes 3; for further details see Scheme 7
Scheme 6. Asymmetric induction in the formation of cyclopentadi-
enes 7 by chiral amino group auxiliaries in the complexes 3; A: 80
°C, pyridine; B: 80 °C, MeCN; for further details see Table 5
The chiral complex 3bi with a cis-dimethylaziridinyl
group and the chiral one 3bj did not yield any cocyclization
products 7 with alkynes, and the chiral complex 3bh with a
trans-2,5-dimethylpyrrolidinyl group in a reaction with 2-
butyne (1aa) gave the corresponding cyclopentadiene
7bhaa, isolated as its hydrolysis product 21bhaa in poor
Synthetic Applications of (Dialkylamino)ethoxycyclo-
pentadienes 7/8
yield (22%) with only
a
50% diastereomeric excess
Many biologically active compounds contain highly sub-
stituted cyclopentenone subunits, and the variously substi-
(Table 5).[23]
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A. de Meijere et al.
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tuted 5-(dialkylamino)-3-ethoxycyclopentadienes 7 as well nary ammonium salts 24 are formed in good yields
as their regioisomers 8 and 17 are just enol ethers of func- (Scheme 9, Table 8). Under high pressure, the chemical
tionally substituted cyclopentenones. As such, they can yields can be improved to excellent levels.
easily be hydrolyzed under acidic conditions to furnish
cyclopentenones 21 in good to very good yields (Scheme 8
and Table 7). The latter can also be obtained in a one-pot
procedure directly from the carbene complexes 3 and
alkynes 1 by immediate addition of two to three drops of
concentrated hydrochloric acid to the reaction mixture be-
fore workup (Entry 2, Table 7). The silyl protecting group
Scheme 9. Quaternization of 4-(dimethylamino)cyclopentenones
21; A: 10 kbar, 25 °C, 20 h Ϫ 3 days; B: 25 °C, 3 days; for further
details see Table 8
on the hydroxy groups is retained when hydrogen chloride
is used for hydrolysis but can be cleaved off afterwards, or
simultaneously, with aqueous hydrogen fluoride (40%) (En-
tries 3 and 5, Table 7).
Table 8. Quaternization of 4-(dimethylamino)cyclopentenones 21
(see Scheme 9)
Entry Starting material RL RS Conditions Product Yield (%)
Scheme 8. Selected examples of the hydrolysis of ethoxycyclopenta-
1
2
3
4
21aaaa
21aaaa
21aahh
21aahh
Me Me
Me Me
Ph Ph
Ph Ph
A
B
A
B
24aaaa
24aaaa
24aahh
24aahh
93
70
96
70
dienes 7 to cyclopentenones 21; for further details see Table 7
Table 7. Selected examples of the hydrolysis of ethoxycyclopentadi-
enes 7 to cyclopentenones 21 (see Scheme 8)
Upon heating the cyclopentenone 21aaaa with methyl
iodide in acetone solution in a sealed thick-walled screw-
cap bottle at 100 °C for 2 h, the elimination product 25aa
was formed directly and isolated in 55% yield (Scheme 10)
instead of the quaternary ammonium salt 24aaaa. The am-
monium salt 24caaa from the cyclopropyl-substituted cyclo-
pentenone 21caaa could not be isolated even at ambient
temperature, but underwent ring opening by nucleophilic
attack of the iodide ion and elimination of trimethylamine
to yield 4-(3Ј-iodopropylidene)cyclopent-2-enone 26aa
(71%).
[a]
[b]
A: 2  HCl. B: 40% HF.
Overall yield for the one-pot pro-
cedure from the complex 3aa. [c] Without removal of the protecting
[d]
group.
The remaining silyl protecting group in 21bal could be
removed in 67% yield with hydrogen fluoride solution. [e] Including
removal of the silyl protecting group.
When an acetal-protected aldehyde or ketone carbonyl
group is present in either the 5-substituent R1 or the N-
substituent R2 on the cyclopentadiene 7, they will be
cleaved under hydrolytic conditions, and the resultant di-
ones will immediately undergo an intramolecular Aldol re-
action to afford 5-(dimethylamino)bicyclo[3.3.0]oct-3-en-2-
ones 22 or 6-azabicyclo[3.3.0]oct-3-en-2-ones 23,[9] which
can serve as oligofunctional building blocks for the syn-
thesis of terpenes and terpene analogues.[19,21]
Scheme 10. Direct formation of elimination products 25 and 26
from in situ formed quaternary ammonium salts
When the quaternary ammonium salts 24aaaa and
24aahh in tetrahydrofuran were treated with the sodium en-
olate of a dialkyl malonate, three types of products were
obtained namely the formal substitution product 27, the
The dialkylamino group, especially the dimethylamino [4ϩ2] dimer 29 and the [2ϩ2] dimer 31 of the cyclopen-
group, in a cyclopentenone of type 21 can be transformed tadienone 28, respectively, formed by elimination of tri-
into a better leaving group by alkylation with methyl iodide. methylamine from 24 (Scheme 11, Table 9). The ratio of the
In acetone at ambient temperature and pressure, the quater- three products 27:29:31 depends upon the applied reagents
730
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Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
(or bases) and the substituents RL and RS in the cyclopen- adduct of type 31 apparently forms only from the diphenyl-
tenone 24.
substituted cyclopentadienone 28ahh and most probably via
a 1,4-diradical intermediate 30. This preference must be due
to the efficient stabilization of 30 by two phenyl substituents
in the two allylic positions, which would also cause a signifi-
cant lowering of the energy of the transition state leading
to 30.[25]
Scheme 11. Further transformations of quaternary ammonium
salts 24; for further details see Table 9
Table 9. Further transformations of quaternary ammonium salts
24 (see Scheme 11)
Figure 2. Structure of the cyclopentadienone dimer 31ahh in the
crystal[24]
Starting Material Reagent
(RL, RS)
Product
Yield Combined
(%) Yields (%)
To demonstrate the utility of the highly functionalized
cyclopentadienes accessible by this methodology, the (di-
methylamino)ethoxycyclopentadiene 7naaa with a 5-(3Ј-
bromobut-3Ј-enyl) substituent was hydrolyzed to the corre-
sponding cyclopentenone 21naaa, and the latter was sub-
jected to conditions appropriate for an intramolecular
Heck-type coupling. This led to the formation of the inter-
esting 5-methyl-4,6-dimethylenebicyclo[3.3.0]oct-1-en-3-one
(32) in an overall yield of 37%. Under the basic conditions
of the Heck reaction, the cyclization product 33 apparently
undergoes facile elimination of dimethylamine to furnish
the α,β-unsaturated ketone.
24aaaa
(Me, Me)
24aaaa
(Me, Me)
24aahh
(Ph, Ph)
24aahh
NaCH(CO2Me)2 27aaa-Me 33
29aaa 56
NaCH(CO2Et)2 27aaa-Et 74
NaCH(CO2Et)2 27ahh-Et 75
NaCH(CO2tBu)2 27ahh-tBu 45
89
74
75
91
96
(Ph, Ph)
24aahh
(Ph, Ph)
31ahh
31ahh
46
96
NaOMe
With diethyl sodiomalonate, only the formal substitution
product 27aaa-Et, most probably formed by elimination to
28aaa and subsequent Michael addition, was isolated from
the dimethylcyclopentenone derivative 24aaaa, while the
same starting material 24aaaa upon treatment with di-
methyl sodiomalonate gave, along with the Michael ad-
dition adduct 27aaa-Me (33%), the [4ϩ2] dimer 29aaa as
the major product (56%). The diphenylcyclopentenone de-
rivative 24aahh reacted with diethyl sodiomalonate in the
same way as the dimethyl derivative 24aaaa to give only the
elimination-addition product 27ahh-Et. With di-tert-butyl
sodiomalonate, however, equal amounts of the Michael ad-
duct 27ahh-tBu and the [2ϩ2] dimer 31ahh of the inter-
mediate 4-methyl-2,3-diphenylcyclopentadienone (28ahh)
were isolated. The [2ϩ2] dimer of the latter, namely 31ahh,
was obtained as the sole product upon treatment of 24aahh
with sodium methoxide in tetrahydrofuran (96% yield). Its
structure was rigorously established from a single-crystal X-
Scheme 12. An intramolecular Heck reaction leading to 5-methyl-
ray diffraction study (Figure 2).[24] The formal [2ϩ2] cyclo- 4,6-dimethylenebicyclo[3.3.0]oct-1-en-3-one (32)
Eur. J. Org. Chem. 2004, 724Ϫ748
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731

A. de Meijere et al.
FULL PAPER
Conclusion
Ϫ78 °C a solution of n-butyllithium (20 mmol). The mixture was
stirred at this temperature for an additional 1Ϫ3 h. After addition
of chromium hexacarbonyl (4.40 g, 20.0 mmol), the solution was
warmed to room temperature, stirred for another 30 min, and trie-
thyloxonium tetrafluoroborate (Et3OBF4, 20.5 mmol) was then ad-
ded at 0 °C. After an additional 10 min, 1.0Ϫ1.1 equiv. of a second-
ary amine was added to the dark red solution in THF upon which
the color changed to yellow or orange as the reaction proceeded to
completion. After filtration through Celite and removal of solvent,
the residue was purified by flash column chromatography.
Using the recently developed optimized conditions,[6]
a
wide range of β-amino-substituted α,β-unsaturated Fischer
carbenechromium complexes 3 (which are easily accessible
in a four-step one-pot procedure from terminal acetylenes,
chromium hexacarbonyl, triethyloxonium tetrafluoroborate
and secondary amines) react with terminal and internal
acetylenes forming di- and trisubstituted 5-(dialkylamino)-
3-ethoxycyclopentadienes 7/8, generally in good to very
good yields. The products are protected cyclopentenones
and, in a sense, even doubly protected cyclopentadienones,
and thus they open up multiple synthetic avenues to com-
plex skeletons of natural products and their analogues, e.g.
sesquiterpenes, including triquinanes,[19,21] (ϩ)-nortaylo-
rione-,[26a] and steroid-like compounds.[21a]
2) Michael Addition of a Secondary Amine to an Alkynylidenecar-
bene Complex 5 (GP1B): To a 2  solution of an alkynylidenecar-
bene complex 5 in Et2O was added at ambient temperature
1.0Ϫ1.1 equiv. of a secondary amine. The progress of the reaction
was monitored by TLC. After removal of the solvent, the residue
was purified by flash column chromatography.
General Procedure for Cocyclizations of Complexes 3 with Alkynes 1
1) In Pyridine as a Solvent (GP2A): A thick-walled, screw-cap Pyrex
bottle equipped with a magnetic stirring bar was charged with a
0.05  solution of the respective complex 3 in anhydrous pyridine.
Dry nitrogen was bubbled through the solution for 5 min, and
2Ϫ4 equiv. of the respective alkyne 1 was added immediately. The
sealed bottle was kept in an oil bath at 60Ϫ80 °C for 2Ϫ5 days.
The solvent was then removed under reduced pressure, the residue
diluted with Et2O, and the solution exposed to air for 2 h. After
filtration and removal of the solvent, the residue was purified by
column chromatography on aluminum oxide (activity grade II) or
silica gel.
Experimental Section
General: 1H and 13C NMR spectroscopy: Bruker AM 250 (250 and
62.9 MHz, respectively) and Bruker AMX 300 (300 and 75 MHz,
respectively) instruments. IR: Bruker IFS 66 (FT-IR) spectrometer.
Low-resolution EI MS: Varian MAT CH 7, MAT 731 instrument,
ionizing voltage 70 eV. High-resolution EI MS (HR EIMS): Varian
MAT 311 A spectrometer. X-ray crystal structure determination:
the data were collected on a StoeϪSiemens-AED diffractometer.
Melting points were determined with a Büchi melting point appar-
atus and are uncorrected. Elemental analyses: Mikroanalytisches
Laboratorium der Georg-August-Universität Göttingen. Chroma-
tography: Merck silica gel 60 (230Ϫ400 mesh) or ICN neutral alu-
mina (Super I, activity grade II). Solvents for chromatography were
technical grade and freshly distilled before use. Tetrahydrofuran
was distilled from sodium benzophenone ketyl and pyridine was
distilled from calcium hydride. The following were prepared ac-
cording to published procedures: 3-Methoxybut-1-yne (1i),[27] 4-
(trimethylsilyloxy)pent-1-yne (1j),[28] 4-(tert-butyldimethylsilyl-
oxy)pent-1-yne (1k),[29] 5-[tert-butyl(dimethyl)silyloxy]pent-1-yne
(1l),[30] 4-pentynyl benzyl sulfide (1m),[26b] diethyl 6-bromo-6-
2) In Acetonitrile as a Solvent (GP2B): To a 0.05  solution of the
complex 3 in anhydrous acetonitrile at 50Ϫ80 °C was added
2Ϫ4 equiv. of the respective alkyne 1 via a syringe pump over a
period of 8Ϫ36 h. After 2 h Ϫ 4 d, complex 3 was completely con-
sumed (TLC), and the solvent could then be removed. The mixture
was diluted with pentane (10 mL), left open to air for 1 h, and
filtered through Celite. The filtrate was concentrated under reduced
pressure, and the residue purified by chromatography on aluminum
oxide (activity grade II) or silica gel.
hepten-1-yne-4,4-dicarboxylate (1o),[31] 6-cyclopropylidenehex-1- General Procedure for the Hydrolysis of (Dimethylamino)ethoxycy-
yne (1p),[32] 1-(trimethylsilyl)hepta-1,6-diyne (1q),[32] 2-[(E)-ethoxy]- clopentadienes 7 to (Dimethylamino)cyclopentenones 21 (GP3): To a
1-ethynylcyclopropane (1y),[33] 1-hexen-5-yne (1z),[33] hexylphenyle- 0.5  solution of the respective ethoxycyclopentadiene 7 in THF
thyne (1he),[34] cyclopropylphenylethyne (1hc),[34] ethyl p-phenyle- was added two drops of 2  hydrochloric acid and a small amount
thynylbenzoate (1hh1),[35] methyl 4-(4-methoxyphenylethynyl)ben-
zoate (1h2h3),[35] bis(p-trifluoromethylphenyl)ethyne (1h4h4),[35] 1,4-
of silica gel (1Ϫ3 g). After stirring at room temperature for 5 min
and removal of the solvent, the residue was purified by column
bis(p-trifluoromethylphenyl)-1,3-butadiyne (1h4z),[36] 1,4-bis(p- chromatography on silica gel.
methoxyphenyl)-1,3-butadiyne (1h3z2),[36] (2S)-methoxymethyl-pyr-
General Procedure for the Methylation of (Dimethylamino)cyclopen-
tenones 21 with Methyl Iodide
rolidine (2e),[37] methyl (2S)-pyrrolidinecarboxylate (2f),[38] diethyl
(2S)-NЈ,NЈ-diethylpyrrolidinecarboxamide (2g),[39] (2R,5R)-di-
methylpyrrolidine (2h),[40] trans-2,3-dimethylaziridine (2i),[41] (1S)-
(1-phenyl)ethylmethylamine (2j),[42] pentacarbonyl[(2E)-3-(dimeth-
ylamino)-1-ethoxy-3-(trimethylsilyl)-2-propen-1-ylidene]chromium
(3ga),[8] pentacarbonyl(1-ethoxy-2-hexyn-1-ylidene)chromium (5,
1) Under a Pressure of 10 kbar (GP4A): To a solution of the re-
spective cyclopentenone 21 (0.61 mmol) in of acetone (8 mL) was
added 2Ϫ7 equiv. of methyl iodide and the mixture was sealed in
Teflon bags which were pressurized at ambient temperature to
10 kbar for 20 hϪ3 days. The reaction mixture was diluted with
Et2O (50 mL) and filtered. The collected solid was washed with
Et2O three times and dried under reduced pressure.
R1 ϭ nPr)[43]
.
For the experimental and spectroscopic data of all compounds not
presented here see the Supporting Informations (see also the foot-
note on the first page of this article).
2) At Ambient Pressure (GP4B): As for GP4A, but at 1 atm.
General Procedures for the Preparation of β-Amino-Substituted α,β-
Unsaturated Fischer Carbene Complexes 3
General Procedure for the Transformation of the Quaternary Am-
monium Salts (GP5): To a solution of the respective quaternary
ammonium salt 24 (0.15 mmol) in THF (10 mL) was added drop-
1) One-Pot Procedure from Terminal Alkynes (GP1A): To a solution
of a terminal alkyne 1 (20 mmol) in THF (100 mL) was added at wise a solution of a dialkylsodium malonate (or sodium meth-
732  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
oxylate) (0.40 mmol) in THF (5 mL), and the mixture was stirred 4), 119.1 (ϩ, C-2), 157.8 (Cquat., C-3), 220.3, 224.8 (Cquat., CO),
at ambient temperature for an additional 1 h. The mixture was then
284.7 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ 431 (11) [Mϩ], 403
treated with H2O (10 mL) and extracted with Et2O (3 ϫ 20 mL). (8) [Mϩ Ϫ CO], 388 (4), 347 (16) [Mϩ Ϫ 3CO], 319 (18) [Mϩ
Ϫ
The organic solution was dried with MgSO4, and the solvent re-
moved under reduced pressure.
4CO], 291 (100) [Mϩ Ϫ 5CO], 266 (16), 262 (50), 234 (31), 232
(12), 217 (10), 210 (10), 206 (17), 194 (10), 181 (12), 165 (31), 70
(35) [C4H8Nϩ], 52 (7) [Crϩ]. C19H25CrNO7 (431.4): calcd. C 52.90,
H 5.84, N 3.25; found C 52.73, H 5.77, N 3.24.
Pentacarbonyl[(2E)-3-(dimethylamino)-1-ethoxy-2-buten-1-ylidene]-
chromium (3aa): According to GP1A, propyne (1a) (1.60 g,
40.0 mmol) in THF (80 mL) was treated with n-butyllithium
(8.5 mL, 2.36  in n-hexane, 20 mmol), chromium hexacarbonyl
(4.51 g, 20.5 mmol), Et3OBF4 (4.56 g, 24.0 mmol) and then gaseous
dimethylamine. Flash chromatography on silica gel (50 g) eluting
with pentane/Et2O (from 3:1 to 1:1) gave 5.60 g (84%) of 3aa [Rf ϭ
0.41 (Et2O)] as a yellow solid. The spectroscopic data are consistent
with those previously reported.[44]
Pentacarbonyl{(2E)-1-ethoxy-3-[(2ЈS)-(2Ј-methoxycarbonyl)-
pyrrolidin-1Ј-yl]-2-hexen-1-ylidene}chromium (3bf): According to
GP1B, complex 5 (651 mg, 2.06 mmol) (R1 ϭ nPr) in Et2O (41 mL)
was treated with (2S)-(methoxycarbonyl)pyrrolidine (2f) (266 mg,
2.06 mmol). Flash chromatography on aluminum oxide (30 g, ac-
tivity grade II) eluting with pentane/CH2Cl2 (3:1) gave 889 mg
(97%) of 3bf [Rf ϭ 0.55 (Et2O); rotamer ratio ϭ 3:1] as an orange
solid, m.p. 75 °C (dec.). IR (KBr): ν˜ ϭ 2963 cmϪ1 (CϪH), 2046
(CϭO), 1907 (CϭO), 1505, 1251, 1099, 943. Major Rotamer: 1H
NMR (250 MHz, C6D6): δ ϭ 0.76 (t, 3J ϭ 7.3 Hz, 3 H, 6-H),
Pentacarbonyl[(2E)-3-(diethylamino)-1-ethoxy-2-buten-1-ylidene]-
chromium (3ab): According to GP1A, propyne (1a) (1.31 mL,
22.0 mmol) in THF (120 mL) was treated with n-butyllithium
(12.5 mL, 1.60  in n-hexane, 20.0 mmol), chromium hexacarbonyl
(4.40 g, 20.0 mmol), Et3OBF4 (4.18 g, 22.0 mmol) and diethylamine
(2.47 mL, 24.0 mmol). Flash chromatography on silica gel (40 g)
eluting with pentane/Et2O (3:1) gave 6.72 g (93%) of 3ab [Rf ϭ 0.32
(Et2O)] as a yellow solid, m.p. 63 °C (dec.). IR (KBr): ν˜ ϭ 2984
cmϪ1 (CϪH), 2045 (CϭO), 1890 (CϭO), 1446, 1292, 1261, 1081,
912. 1H NMR (250 MHz, CDCl3): δ ϭ 1.28 [m, 6 H,
3
0.85Ϫ1.60 (m, 2 H, 4Ј-H), 1.08 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3),
1.15Ϫ1.33 (m, 2 H, 5-H), 1.33Ϫ1.55 (m, 2 H, 4-H), 1.86Ϫ2.13 (m,
1 H, 3Ј-H), 2.22Ϫ2.70 (m, 2 H, 3Ј,5Ј-H), 2.82Ϫ3.06 (m, 1 H, 5Ј-
3
H), 3.42 (s, 3 H, OCH3), 4.19 (d, J ϭ 8.0 Hz, 1 H, 2Ј-H), 4.66 (q,
3J ϭ 7.0 Hz, 2 H, OCH2CH3), 6.36 (s, 1 H, 2-H) ppm. 13C NMR
(62.9 MHz, C6D6, plus DEPT): δ ϭ 14.2, 15.5 (ϩ, C-6,
OCH2CH3), 21.3, 23.2 (Ϫ, C-3Ј,4Ј), 30.3 (Ϫ, C-5), 35.1 (Ϫ, C-5Ј),
48.9 (Ϫ, C-4), 52.8 (ϩ, C-2Ј), 61.5 (ϩ, OCH3), 74.1 (Ϫ,
3
N(CH2CH3)2], 1.47 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.36 (s, 3 H,
OCH2CH3), 118.8 (ϩ, C-2), 155.8 (Cquat., C-3), 171.2 (Cquat.
,
CH3), 3.49 [m, 4 H, N(CH2CH3)2], 4.66 (q, 3J ϭ 7.0 Hz, 2 H,
OCH2CH3), 6.46 (s, 1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3,
plus DEPT): δ ϭ 13.6 [ϩ, N(CH2CH3)2], 15.7 (ϩ, OCH2CH3), 19.1
(ϩ, C-4), 46.2 [Ϫ, N(CH2CH3)2], 73.5 (Ϫ, OCH2CH3), 117.3 (ϩ,
C-2), 154.4 (Cquat., C-3), 219.4, 224.3 (Cquat., CO), 283.9 (Cquat., C-
1) ppm. MS (70 eV): m/z (%) ϭ 361 (7) [Mϩ], 333 (11) [Mϩ Ϫ CO],
305 (5) [Mϩ Ϫ 2CO], 277 (11) [Mϩ Ϫ 3CO], 249 (14) [Mϩ Ϫ 4CO],
221 (100) [Mϩ Ϫ 5CO], 192 (25), 164 (28), 162 (7), 149 (14), 124
(11), 123 (11), 122 (13), 94 (6), 93 (5), 52 (6) [Crϩ]. C15H19CrNO6
(361.3): calcd. C 49.86, H 5.30; found C 49.88, H 5.20.
CO2CH3), 219.1, 224.3 (Cquat., CO), 286.9 (Cquat., C-1) ppm. Minor
Rotamer: 1H NMR (250 MHz, C6D6): δ ϭ 0.76 (t, 3J ϭ 7.3 Hz,
3 H, 6-H), 0.85Ϫ1.60 (m, 2 H, 4Ј-H), 1.08 (t, 3J ϭ 7.0 Hz, 3 H,
OCH2CH3), 1.15Ϫ1.33 (m, 2 H, 5-H), 1.33Ϫ1.55 (m, 2 H, 4-H),
1.86Ϫ2.13 (m, 1 H, 3Ј-H), 2.51Ϫ3.06 (m, 2 H, 3Ј,5Ј-H), 3.15Ϫ3.36
3
(m, 1 H, 5Ј-H), 3.15 (s, 3 H, OCH3), 3.89 (d, J ϭ 8.0 Hz, 1 H, 2Ј-
H), 4.66 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 6.60 (s, 1 H, 2-H) ppm.
13C NMR (62.9 MHz, C6D6, plus DEPT): δ ϭ 14.2, 15.5 (ϩ, C-6,
OCH2CH3), 21.8, 22.9 (Ϫ, C-3Ј,4Ј), 30.3 (Ϫ, C-5), 31.2 (Ϫ, C-5Ј),
48.9 (Ϫ, C-4), 49.9 (ϩ, C-2Ј), 60.9 (ϩ, OCH3), 74.1 (Ϫ,
Pentacarbonyl{(2E)-1-ethoxy-3-[(2ЈS)-(2Ј-methoxymethyl)pyrrol-
idino]-2-hexen-1-ylidene}chromium (3be): According to GP1B, com-
plex 5 (989 mg, 3.13 mmol) (R1 ϭ nPr) in Et2O (63 mL) was treated
with (2S)-methoxymethylpyrrolidine (2e) (360 mg, 3.13 mmol).
Flash chromatography on aluminum oxide (30 g, activity grade II)
eluting with pentane/CH2Cl2 (3:1) gave 1.34 g (99%) of 3be [Rf ϭ
0.23 (pentane/CH2Cl2, 3:1); ratio of rotamers 2:1] as an orange
solid, m.p. 44 °C (dec.). IR (KBr): ν˜ ϭ 2975 cmϪ1 (CϪH), 2042
(CϭO), 1959 (CϭO), 1486, 1240, 1075, 943. Major Rotamer: 1H
OCH2CH3), 118.8 (ϩ, C-2), 154.8 (Cquat., C-3), 171.9 (Cquat.
,
CO2CH3), 219.1, 224.3 (Cquat., CO), 290.5 (Cquat., C-1) ppm. MS
(70 eV): m/z (%) ϭ 445 (36) [Mϩ], 417 (2) [Mϩ Ϫ CO], 389 (5) [Mϩ
Ϫ 2CO], 361 (28) [Mϩ Ϫ 3CO], 333 (34) [Mϩ Ϫ 4CO], 305 (100)
[Mϩ Ϫ 5CO], 276 (36), 262 (50), 244 (15), 179 (33), 108 (14), 70
(44) [C4H8Nϩ], 52 (62) [Crϩ]. C19H23CrNO8 (445.4): calcd. C
51.23, H 5.21, N 3.14; found C 51.30, H 5.33, N 3.25.
Pentacarbonyl[(2E)-1-ethoxy-4,4-dimethyl-3-morpholino-2-penten-1-
NMR (250 MHz, C6D6): δ ϭ 0.74 (t, 3J ϭ 7.3 Hz, 3 H, 6-H), ylidene)]chromium (3fk): 3,3-Dimethylbutyne (1f) (2.60 mL,
1.05Ϫ1.50 (m, 6 H, 4,5,4Ј-H), 1.10 (t, 3J
OCH2CH3), 1.99Ϫ2.18 (m, 2 H, 3Ј-H), 2.45Ϫ3.30 (m, 4 H, 5Ј-H, (8.50 mL, 2.36  in n-hexane, 20.1 mmol), chromium hexacarbonyl
CH2OCH3), 3.02 (s, 3 H, CH2OCH3), 3.90Ϫ3.98 (m, 1 H, 2Ј-H), (4.58 g, 20.8 mmol) and Et3OBF4 (4.17 g, 21.9 mmol). After evap-
ϭ
7.1 Hz, 3 H,
21.2 mmol) in THF (100 mL) was treated with n-butyllithium
4.67 (q, 3J ϭ 7.1 Hz, 2 H, OCH2CH3), 6.51 (s, 1 H, 2-H) ppm. oration of the solvent, the residue was dissolved in pentane (50 mL)
13C NMR (62.9 MHz, C6D6, plus DEPT): δ ϭ 14.2, 15.5 (ϩ, C-6,
OCH2CH3), 21.4 (Ϫ, C-5), 22.6 (Ϫ, C-4Ј), 28.2 (Ϫ, C-3Ј), 35.4 (Ϫ,
to which morpholine (1.97 mL, 22.6 mmol) was added. Flash chro-
matography on silica gel (100 g) eluting with pentane/Et2O (from
C-5Ј), 48.9 (Ϫ, CH2OCH3), 58.8, 59.9 (ϩ, C-2Ј, CH2OCH3), 71.0 10:1 to 0:1) gave 7.07 g (84%) of 3fk [Rf ϭ 0.74 (Et2O)] as a yellow
(Ϫ, OCH2CH3), 74.0 (Ϫ, C-4), 119.1 (ϩ, C-2), 157.9 (Cquat., C-3), solid, m.p. 106Ϫ108 °C (dec.). IR (KBr): ν˜ ϭ 2976 cmϪ1 (CϪH),
220.3, 224.8 (Cquat., CO), 283.3 (Cquat., C-1) ppm. Minor Rotamer: 2045 (CϭO), 1968 (CϭO), 1873 (CϭO), 1525 (CϭC), 1489, 1427,
3
1H NMR (250 MHz, C6D6): δ ϭ 0.74 (t, J ϭ 7.3 Hz, 3 H, 6-H),
1375, 1121, 667. 1H NMR (250 MHz, CDCl3): δ ϭ 1.34 [s, 9 H,
1.05Ϫ1.63 (m, 6 H, 4,5,4Ј-H), 1.10 (t, 3J
ϭ
7.1 Hz, 3 H, C(CH3)3], 1.47 (t, 3J ϭ 7.1 Hz, 3 H, OCH2CH3), 3.50 (t, 3J ϭ
OCH2CH3), 2.35Ϫ3.30 (m, 6 H, 3Ј,5Ј-H, CH2OCH3), 2.84 (s, 3 H, 4.6 Hz, 4 H, NCH2CH2O), 3.79 (t, 3J ϭ 4.6 Hz, 4 H, NCH2CH2O),
3
CH2OCH3), 3.51Ϫ3.66 (m, 1 H, 2Ј-H), 4.67 (q, J ϭ 7.1 Hz, 2 H,
4.68 (q, 3J ϭ 7.1 Hz, 2 H, OCH2CH3), 6.35 (s, 1 H, 2-H) ppm. 13
C
NMR (62.9 MHz, C6D6, plus DEPT): δ ϭ 15.8 (ϩ, OCH2CH3),
OCH2CH3), 6.48 (s, 1 H, 2-H) ppm. 13C NMR (62.9 MHz, C6D6,
plus DEPT): δ ϭ 14.2, 15.5 (ϩ, C-6, OCH2CH3), 21.4 (Ϫ, C-5), 29.5 [ϩ, C(CH3)3], 38.4 [Cquat., C(CH3)3], 54.6 (Ϫ, NCH2CH2O),
22.2 (Ϫ, C-4Ј), 27.8 (Ϫ, C-3Ј), 34.9 (Ϫ, C-5Ј), 48.6 (Ϫ, CH2OCH3), 66.4 (Ϫ, NCH2CH2O), 73.0 (Ϫ, OCH2CH3), 116.2 (ϩ, C-2), 170.3
58.8, 59.9 (ϩ, C-2Ј, CH2OCH3), 71.0 (Ϫ, OCH2CH3), 73.6 (Ϫ, C- (Cquat., C-3), 220.3, 224.8 (Cquat., CO), 276.10 (Cquat., C-1) ppm.
Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
733

A. de Meijere et al.
FULL PAPER
MS (70 eV): m/z (%) ϭ 417 (6) [Mϩ], 361 (5) [Mϩ Ϫ 2CO], 333 chromatography on silica gel (40 g) eluting with pentane/Et2O
(21) [Mϩ Ϫ 3CO], 305 (18) [Mϩ Ϫ 4CO], 277 (67) [Mϩ Ϫ 5CO], (from 8:1 to 0:1) gave 2.36 g (94%) of 3oa [Rf ϭ 0.62 (Et2O)] as an
249 (30) [Mϩ Ϫ 5CO Ϫ C2H4], 219 (100) [Mϩ Ϫ 5CO Ϫ C4H10], orange solid, m.p. 87 °C (dec.). IR (KBr): ν˜ ϭ 2918 cmϪ1 (CϪH),
1
203 (11), 192 (11), 137 (12), 52 (10) [Crϩ]. C18H23CrNO7 (417.4):
calcd. C 51.80, H 5.55; found C 52.03, H 5.75.
2045 (CϭO), 1735 (CϭO), 1617 (CϭC), 1533, 1330, 812, 673. H
NMR (250 MHz, C6D6): δ ϭ 0.87 (t, 3J
ϭ 7.2 Hz, 6 H,
3
CO2CH2CH3), 1.26 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.36 [s, 6 H,
N(CH3)2], 3.32 (s, 2 H, 6-H), 3.36 (s, 2 H, 4-H), 3.92 (q, 3J ϭ
7.2 Hz, 4 H, CO2CH2CH3), 4.78 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3),
5.32 (s, 1 H, 8-H), 5.40 (s, 1 H, 8-H), 6.38 (s, 1 H, 2-H) ppm. 13C
Pentacarbonyl[(2E)-5-tert-butyldimethylsiloxy-3-(dimethylamino)-1-
ethoxyhex-2-en-1-ylidene]chromium (3ka): According to GP1A, 4-
(tert-butyldimethylsilyloxy)pent-1-yne (1k) (1.98 g, 9.98 mmol) in
THF (50 mL) was treated with n-butyllithium (4.25 mL, 2.36  in
NMR (62.9 MHz, C6D6, plus DEPT): δ ϭ 12.7 (ϩ,
CO2CH2CH3), 15.1 (ϩ, OCH2CH3), 32.6 (Ϫ, C-6), 40.9 [ϩ,
N(CH3)2], 45.6 (Ϫ, C-4), 57.1 (Cquat., C-5), 61.1 (Ϫ, 2
2 ϫ
n-hexane,
10.0 mmol),
chromium
hexacarbonyl
(2.20 g,
10.0 mmol), Et3OBF4 (2.30 g, 12.1 mmol) and a 40% aqueous solu-
tion of dimethylamine (1.3 mL, 10.0 mmol). Flash chromatography
on silica gel (40 g) eluting with pentane/Et2O (1:1) gave 4.19 g
(85%) of 3ka [Rf ϭ 0.63 (Et2O/pentane, 1:1)] as a yellow solid, m.p.
72Ϫ75 °C (dec.). IR (KBr): ν˜ ϭ 2929 cmϪ1 (CϪH), 2044 (CϭO),
1913 (CϭO), 1567, 1535, 1433, 1273, 1091, 933. 1H NMR
(250 MHz, C6D6): δ ϭ Ϫ0.12 [s, 3 H, SiCH3], Ϫ0.06 [s, 3 H,
ϫ
CO2CH2CH3), 73.1 (Ϫ, OCH2CH3), 118.7 (ϩ, C-2), 120.6 (Ϫ, C-
8), 127.0 (Cquat., C-7), 154.1 (Cquat., C-3), 168.2 (Cquat., 2 ϫ
CO2CH2CH3), 219.1, 223.5 (Cquat., CO), 286.2 (Cquat., C-1) ppm.
MS (70 eV): m/z (%) ϭ 583/581 (1/1) [Mϩ Ϫ CO], 527/525 (3/3),
471/469 (37/36) [Mϩ Ϫ 5CO], 338 (61) [Mϩ Ϫ Cr(CO)5 Ϫ Br], 237
(100), 193 (99), 149 (79), 52 (90) [Crϩ]. C23H28BrCrNO10 (610.4):
calcd. C 45.26, H 4.62, N 2.29; found C 45.43, H 4.72, N 2.11.
3
SiCH3], 0.82 [s, 9 H, SiC(CH3)3], 1.00 (d, J ϭ 7.0 Hz, 3 H, 6-H),
1.05 (t, 3J ϭ 7.1 Hz, 3 H, OCH2CH3), 1.94 (dd, 2J ϭ 11.4, 3J ϭ
11.9 Hz, 1 H, 4-H), 2.32 [s, 3 H, N(CH3)2], 2.36 [s, 3 H, N(CH3)2],
5-(Dimethylamino)-3-ethoxy-1,2,5-trimethyl-1,3-cyclopentadiene
2.87 (dd, 2J ϭ 11.4, 3J ϭ 2.5 Hz, 1 H, 4-H), 4.02 (m, 1 H, 5-H), 4.62 (7aaaa): According to GP2A, a solution of complex 3aa (1.66 g,
(m, 2 H, OCH2CH3), 6.41 (s, 1 H, 2-H) ppm. 13C NMR (62.9 MHz, 4.98 mmol) in pyridine (100 mL) was treated with 2-butyne (1aa)
CDCl3, plus DEPT): δ ϭ Ϫ5.0, Ϫ4.9 [ϩ, Si(CH3)2], 15.7 (ϩ, (798 mg, 14.8 mmol), and the mixture was stirred at 80 °C for 3
OCH2CH3), 24.6 (ϩ, C-6), 25.82 [ϩ, SiC(CH3)3], 25.85 [Cquat.
SiC(CH3)3], 40.6 (Ϫ, C-4), 40.9, 41.6 [ϩ, N(CH3)2], 69.3 (ϩ, C-5), eluting with pentane/Et2O (from 20:1 to 1:2) gave 797 mg (82%) of
73.9 (Ϫ, OCH2CH3), 118.0 (ϩ, C-2), 156.0 (Cquat., C-3), 220.4, 7aaaa [Rf ϭ 0.46, (pentane/Et2O, 3:1)] as a colorless oil. IR (film):
224.2 (Cquat., CO), 285.3 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ ν˜ ϭ 2979 cmϪ1, 2818, 2779 (CϪH), 1633 (CϭC), 1594 (CϭC),
,
days. Chromatography on aluminum oxide (60 g, activity grade II)
491 (2) [Mϩ], 463 (7) [Mϩ Ϫ CO], 435 (4) [Mϩ Ϫ2 CO], 407 (8)
1457, 1204, 1042, 740. 1H NMR (250 MHz, CDCl3): δ ϭ 1.16 (s,
[Mϩ Ϫ 3CO], 379 (2) [Mϩ Ϫ 4CO], 351 (100) [Mϩ Ϫ 5CO], 322 3 H, CH3), 1.31 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.63 (s, 3 H,
(14), 307 (18), 305 (18), 294 (18), 281 (18), 170 (12), 168 (17), 126 CH3), 1.65 (s, 3 H, CH3), 2.10 [s, 6 H, N(CH3)2], 3.81 (m, 2 H,
(20), 124 (17), 52 (5) [Crϩ]. C21H33CrNO7Si (491.6): calcd. C 51.31, OCH2CH3), 4.77 (s, 1 H, 4-H) ppm. 13C NMR (62.9 MHz, CDCl3,
H 6.77; found C 51.25, H 6.89.
plus DEPT): δ ϭ 8.8 (ϩ, CH3), 9.7 (ϩ, CH3), 14.4 (ϩ, OCH2CH3),
22.1 (ϩ, CH3), 39.9 [ϩ, N(CH3)2], 64.3 (Ϫ, OCH2CH3), 71.3
(Cquat., C-5), 95.5 (ϩ, C-4), 128.4 (Cquat., C-2), 144.4 (Cquat., C-1),
160.2 (Cquat., C-3) ppm.
Pentacarbonyl[(2E)-6-bromo-3-(dimethylamino)-1-ethoxy-2,6-
heptadien-1-ylidene]chromium (3na): According to GP1A, 2-bromo-
hex-1-en-5-yne (1n) (3.18 g, 20.0 mmol) in Et2O (100 mL) was
treated with n-butyllithium (8.47 mL, 2.36  in n-hexane,
5-Dimethyamino-1-[2Ј-(1ЈЈ,3ЈЈ-dioxolan-2ЈЈ-yl)ethyl]-3-ethoxy-5-
20.0 mmol), chromium hexacarbonyl (4.40 g, 20.0 mmol), Et3OBF4 methyl-1,3-cyclopentadiene (7aar) and 5-(Dimethylamino)-2-[2Ј-
(4.37 g, 23.0 mmol) and a 40% aqueous solution of dimethylamine (1ЈЈ,3ЈЈ-dioxolan-2ЈЈ-yl)ethyl]-3-ethoxy-5-methyl-1,3-cyclopentadiene
(2.59 mL, 21.6 mmol). Flash chromatography on silica gel (120 g)
eluting with pentane/Et2O (from 5:1 to 0:1) gave 7.60 g (84%) of
(8aar): According to GP2A, a solution of complex 3aa (660 mg,
1.98 mmol) in pyridine (40 mL) was treated with 2-(pent-3Ј-ynyl)-
3na [Rf ϭ 0.51 (Et2O)] as a yellow solid, m.p. 77Ϫ78 °C (dec.). IR 1,3-dioxolane (1r) (750 mg, 5.95 mmol), and the mixture was stirred
(KBr): ν˜ ϭ 2979 cmϪ1, 2938, 2864 (CϪH), 2046 (CϭO), 1629 (Cϭ
C), 1443, 1344, 1144, 882, 743. 1H NMR (250 MHz, C6D6): δ ϭ
at 80 °C for 3 days. Chromatography on aluminum oxide (40 g,
activity grade II) eluting with pentane/Et2O (from 20:1 to 0:1) gave
1.10 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.80Ϫ2.32 [m, 8 H, 5-H, 458 mg (86%) of 7aar [Rf ϭ 0.70 (Et2O)] and 38 mg (7%) of 8aar
N(CH3)2], 2.46 (mc, 2 H, 4-H), 4.63 (q, 3J ϭ 7.0 Hz, 2 H,
OCH2CH3), 5.15 (s, 1 H, 7-H), 5.18 (s, 1 H, 7-H), 6.35 (s, 1 H, 2- 2818, 2775 (CϪH), 1635 (CϭC), 1581 (CϭC), 1444, 1403, 1198,
H) ppm. 13C NMR (62.9 MHz, C6D6, plus DEPT): δ ϭ 15.6 (ϩ, 1032, 733. 1H NMR (250 MHz, CDCl3): δ ϭ 1.21 (s, 3 H, CH3),
OCH2CH3), 30.0 (Ϫ, C-4), 38.9 (Ϫ, C-5), 40.9 [ϩ, N(CH3)2], 74.4 1.32 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.88 (mc, 2 H, 2Ј-H), 2.13
(Ϫ, OCH2CH3), 110.2 (Cquat., C-6), 117.3 (Ϫ, C-7), 118.2 (ϩ, C- [s, 6 H, N(CH3)2], 2.16 (mc, 2 H, 1Ј-H), 3.79Ϫ3.99 (m, 6 H, OCH2-
2), 156.4 (Cquat., C-3), 220.1, 224.8 (Cquat., CO), 287.9 (Cquat., C-1) CH2O, OCH2CH3), 4.84 (d, J ϭ 1.8 Hz, 1 H, 4-H), 4.91 (t, J ϭ
ppm. MS (70 eV): m/z (%) ϭ 453/451 (3/2) [Mϩ], 425/423 (3/2) 4.6 Hz, 1 H, 2ЈЈ-H), 5.63 (d, 4J ϭ 1.8 Hz, 1 H, 2-H) ppm. 13C NMR
[Mϩ Ϫ CO], 369/367 (22/20) [Mϩ
3CO], 180 (100) (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.5 (ϩ, OCH2CH3), 20.6
[Mϩ Ϫ Cr(CO)5 Ϫ Br], 152 (18), 101 (31), 55 (41), 52 (2) [Crϩ].
(Ϫ, C-2Ј), 22.5 (ϩ, CH3), 31.0 (Ϫ, C-1Ј), 39.9 [ϩ, N(CH3)2], 64.4,
C16H18BrCrNO6 (452.2): calcd. C 42.50, H 4.01, N 3.10; found 64.9 (Ϫ, OCH2CH2O, OCH2CH3), 72.9 (Cquat., C-5), 97.0 (ϩ, C-
[Rf ϭ 0.20 (Et2O)] as colorless oils. 7aar: IR (film): ν˜ ϭ 2970 cmϪ1
,
4
3
Ϫ
C 42.67, H 4.05, N 3.07.
4), 104.1 (ϩ, C-2ЈЈ), 121.0 (ϩ, C-2), 157.5 (Cquat., C-1), 159.2
(Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 267 (51) [Mϩ], 238 (100)
[Mϩ Ϫ C2H5], 229 (9), 163 (26), 148 (48), 136 (20), 108 (13), 99
(57), 84 (40), 73 (34), 45 (15). C15H25NO3 (267.4): calcd. C 67.38,
H 9.43; found C 67.26, H 9.43.
Pentacarbonyl[(2E)-7-bromo-5,5-bis(ethoxycarbonyl)-3-(dimethyl-
amino)-1-ethoxy-2,7-octadien-1-ylidene]chromium (3oa): According
to GP1A, diethyl 6-bromo-6-hepten-1-yne-4,4-dicarboxylate (1o)
(1.30 g, 4.10 mmol) in THF (100 mL) was treated with n-butyllith-
ium (1.74 mL, 2.36  in n-hexane, 4.10 mmol), chromium hexacar- 8aar: IR (film): ν˜ ϭ 2977 cmϪ1, 2883, 2779 (CϪH), 1636 (CϭC),
bonyl (0.90 g, 4.09 mmol), Et3OBF4 (0.95 g, 5.00 mmol) and a 40% 1584 (CϭC), 1446, 1372, 1199, 1042, 737. 1H NMR (250 MHz,
aqueous solution of dimethylamine (0.56 mL, 4.66 mmol). Flash
CDCl3): δ ϭ 1.22 (s, 3 H, CH3), 1.24 (t, 3J ϭ 7.0 Hz, 3 H,
734
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
OCH2CH3), 1.81 (mc, 2 H, 2Ј-H), 2.19 [s, 6 H, N(CH3)2], 2.21 (mc, OCH2CH3), 16.3 (Ϫ, CH2CH2CH3), 36.6 (Ϫ, CH2CH2CH3), 39.67
2 H, 1Ј-H), 3.79Ϫ3.90 (m, 6 H, OCH2CH2O, OCH2CH3), 4.77 (d, [ϩ, N(CH3)2], 49.4 (Ϫ, C-1Ј), 52.5 (ϩ, C-2Ј), 64.5 (Ϫ, OCH2CH3),
3
5J ϭ 1.8 Hz, 1 H, 4-H), 4.81 (t, J ϭ 4.6 Hz, 1 H, 2ЈЈ-H), 5.77 (d, 79.3 (Cquat., C-5), 81.3 (ϩ, CO2CH3), 96.0 (ϩ, C-4), 122.8 (ϩ, C-
4J ϭ 1.8 Hz, 1 H, 1-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus 2), 151.8 (Cquat., C-1), 159.4 (Cquat., C-3), 169.3 (Cquat., CO2CH3)
DEPT): δ ϭ 14.3 (ϩ, OCH2CH3), 20.9 (Ϫ, C-2Ј), 21.6 (ϩ, CH3),
ppm. MS (70 eV): m/z (%) ϭ 339 (27) [Mϩ], 310 (79) [Mϩ Ϫ C2H5],
31.8 (Ϫ, C-1Ј), 40.3 [ϩ, N(CH3)2], 64.4, 64.7 (Ϫ, OCH2CH2O, 296 (15), 208 (24), 163 (18), 111 (49), 59 (18), 41 (10). HRMS (EI)
OCH2CH3), 69.9 (Cquat., C-5), 102.1 (ϩ, C-4), 104.0 (ϩ, C-2ЈЈ), calcd. for C18H29NO5: 339.2045 (correct HRMS).
135.6 (ϩ, C-1), 139.6 (Cquat., C-2), 158.2 (Cquat., C-3) ppm. MS
5-(Dimethylamino)-3-ethoxy-5-propyl-1-(trimethylsilylmethyl)-1,3-
cyclopentadiene (7bau): Following GP2B, to a solution of complex
3ba (200 mg, 0.55 mmol) in acetonitrile (5.5 mL) at 80 °C was
(70 eV): m/z (%) ϭ 267 (71) [Mϩ], 238 (44) [Mϩ Ϫ C2H5], 222 (14),
166 (31), 152 (88), 136 (33), 109 (16), 99 (100), 73 (29), 45 (11).
5-(Dimethylamino)-3-ethoxy-5-methyl-1-[2Ј-(2ЈЈ-methyl-1ЈЈ,3ЈЈ-di-
oxolan-2ЈЈ-yl)ethyl]-1,3-cyclopentadiene (7aas) and 5-(Dimethyl-
amino)-3-ethoxy-5-methyl-2-[2Ј-(2ЈЈ-methyl-1ЈЈ,3ЈЈ-dioxolan-2ЈЈ-yl)-
ethyl]-1,3-cyclopentadiene (8aas): According to GP2A, a solution
of complex 3aa (2.00 g, 6.00 mmol) in pyridine (100 mL) was
slowly added a solution of 1-(trimethylsilyl)prop-2-yne (1u)
(187 mg, 1.67 mmol) in acetonitrile (2 mL) over a period of 10 h,
and the mixture was stirred at this temperature for an additional
2 h. Chromatography on aluminum oxide (20 g, activity grade II)
eluting with pentane/Et2O (5:1) gave 83 mg (53%) of 7bau [Rf ϭ
treated with 2-(but-3Ј-ynyl)-2-methyldioxolane (1s) (1.10 g, 0.23 (pentane/Et2O, 5:1)] as a yellow oil. IR (film): ν˜ ϭ 2993 cmϪ1
,
7.85 mmol), and the mixture was stirred at 80 °C for 3 days. Chro-
2838 (CϪH), 1608 (CϭC), 1345, 1207, 835, 688, 531. 1H NMR
matography on aluminum oxide (60 g, activity grade II) eluting (250 MHz, CDCl3): δ ϭ 0.08 [s, 9 H, Si(CH3)3], 0.71Ϫ0.98 (m, 5 H,
with pentane/Et2O (from 20:1 to 0:1) gave 1.32 g (78%) of 7aas CH2CH2CH3), 1.34 (t, 3J ϭ 7.2 Hz, 3 H, OCH2CH3), 1.68Ϫ1.84
[Rf ϭ 0.30 (Et2O)] and 110 mg (7%) of 8aas [Rf ϭ 0.08, (Et2O)] as
colorless oils. 7aas: IR (film): ν˜ ϭ 2967 cmϪ1 (CϪH), 2879 (CϪH),
(m, 2 H, CH2CH2CH3), 2.13 (s, 2 H, SiCH2), 2.16 [s, 6 H,
3
N(CH3)2], 3.87 (q, J ϭ 7.2 Hz, 2 H, OCH2CH3), 4.67 (s, 1 H, 4-
1609 (CϭC), 1456, 1260, 1211, 1084, 1052, 974, 948. 1H NMR H), 5.69 (s, 1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus
(250 MHz, CDCl3): δ ϭ 1.20 (s, 3 H, CH3), 1.30 (t, 3J ϭ 7.0 Hz,
DEPT): δ ϭ Ϫ0.7 [ϩ, Si(CH3)3], 14.5, 14.7 (ϩ, CH2CH2CH3,
3 H, OCH2CH3), 1.32 (s, 3 H, CH3), 1.85 (mc, 2 H, 2Ј-H), OCH2CH3), 14.9 (Ϫ, CH2CH2CH3), 16.6 (Ϫ, SiCH2), 36.2 (Ϫ,
2.09Ϫ2.13 [m, 8 H, N(CH3)2, 1Ј-H], 3.82 (q, 3J ϭ 7.0 Hz, 2 H, CH2CH2CH3), 39.9 [ϩ, N(CH3)2], 64.3 (Ϫ, OCH2CH3), 77.4
OCH2CH3), 3.91 (br. s, 4 H, OCH2CH2O), 4.81 (d, 4J ϭ 1.2 Hz,
(Cquat., C-5), 94.0 (ϩ, C-4), 123.3 (ϩ, C-2), 153.2 (Cquat., C-1),
1 H, 4-H), 5.58 (d, 4J ϭ 1.2 Hz, 1 H, 2-H) ppm. 13C NMR 160.2 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 281 (18) [Mϩ], 252
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.4 (ϩ, OCH2CH3), 20.5 (67) [Mϩ Ϫ C2H5], 238 (100), 209 (83), 181 (72), 73 (54)
(Ϫ, C-1Ј), 22.5, 23.9 (ϩ, CH3), 36.1 (Ϫ, C-2Ј), 39.9 [ϩ, N(CH3)2], [Si(CH3)3ϩ], 42 (11). HRMS (EI) calcd. for C16H31NOSi: 281.2174
64.4, 64.6 (Ϫ, OCH2CH3, OCH2CH2O), 72.9 (Cquat., C-5), 96.7 (ϩ, (correct HRMS).
C-4), 109.6 (Cquat., C-2ЈЈ), 120.1 (ϩ, C-2), 157.8 (Cquat., C-1), 159.2
1-[2Ј,2Ј-Bis(ethoxycarbonyl)-4Ј-bromopent-4Ј-enyl)-5-(dimethyl-
(Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 281 (28) [Mϩ], 252 (61)
amino)-3-ethoxy-5-propyl-1,3-cyclopentadiene (7bao): According to
[Mϩ Ϫ CH2CH3], 236 (8) [Mϩ Ϫ HN(CH3)2], 224 (8), 166 (10), 150
GP2A, a solution of complex 3ba (300 mg, 0.83 mmol) in pyridine
(17 mL) was treated with diethyl 6-bromo-6-hepten-1-yne-4,4-di-
carboxylate (1o) (525 mg, 1.66 mmol), and the mixture was stirred
at 80 °C for 20 h. Chromatography on aluminum oxide (20 g, ac-
(25), 136 (10), 108 (9), 87 (100) [CH3C(OCH2CH2O)ϩ], 44 (37)
[N(CH3)2ϩ]. C16H27NO3 (281.4): calcd. C 68.29, H 9.67; found
C 67.50, H 9.48.
8aas: IR (film): ν˜ ϭ 2979 cmϪ1 (CϪH), 2891 (CϪH), 2776 (CϪH),
tivity grade II) gave 280 mg (69%) of 7bao as a colorless oil. IR
1623 (CϭC), 1448, 1256, 1188, 1056, 859. 1H NMR (250 MHz, (film): ν˜ ϭ 2959 cmϪ1, 2935 (CϪH), 1733 (CϭO), 1636 (CϭC),
CDCl3): δ ϭ 1.26 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.29 (s, 3 H, 1334, 1191, 1043, 747, 666. 1H NMR (250 MHz, CDCl3): δ ϭ 0.73
3
CH3), 1.31 (s, 3 H, CH3), 1.79 (mc, 2 H, 2Ј-H), 2.18Ϫ2.26 [m, 8 H,
(t, J ϭ 7.2 Hz, 3 H, CH2CH2CH3), 0.85 (mc, 2 H, CH2CH2CH3),
N(CH3)2, 1Ј-H], 3.76 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 3.89 (br. s, 1.15 (t, 3J ϭ 7.1 Hz, 6 H, 2 CO2CH2CH3), 1.25 (t, 3J ϭ 7.1 Hz,
3
4 H, OCH2CH2O), 4.78 (s, 1 H, 4-H), 5.76 (s, 1 H, 1-H) ppm. 13C
3 H, OCH2CH3), 1.39 (mc, 1 H, CH2CH2CH3), 1.73 (mc, 1 H,
2
NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.4 (ϩ, OCH2CH3), CH2CH2CH3), 2.08 [s, 6 H, N(CH3)2], 2.60 (d, J ϭ 19.0 Hz, 1 H,
2
21.0 (Ϫ, C-1Ј), 21.6, 23.6 (ϩ, CH3), 36.9 (Ϫ, C-2Ј), 40.3 [ϩ, 1Ј-H), 2.83 (d, J ϭ 19.0 Hz, 1 H, 1Ј-H), 3.29 (s, 2 H, 3Ј-H), 3.76
3
N(CH3)2], 64.4, 64.5 (Ϫ, OCH2CH3, OCH2CH2O), 69.9 (Cquat., C- (q, J ϭ 7.1 Hz, 2 H, OCH2CH3), 4.12 (mc, 4 H, 2 CO2CH2CH3),
5), 102.0 (ϩ, C-4), 109.7 (Cquat., C-2ЈЈ), 135.0 (ϩ, C-1), 140.1 4.66 (s, 1 H, 5Ј-H), 5.44 (d, 4J ϭ 1.6 Hz, 1 H, 4-H), 5.59 (s, 1 H,
(Cquat., C-2), 158.3 (Cquat., C-3) ppm.
5Ј-H), 5.65 (d, 4J ϭ 1.6 Hz, 1 H, 2-H) ppm. 13C NMR (62.9 MHz,
CDCl3, plus DEPT): δ ϭ 13.5 (ϩ, OCH2CH3), 14.1 (ϩ, 2 ϫ
CO2CH2CH3), 14.3 (ϩ, CH2CH2CH3), 16.0 (Ϫ, CH2CH2CH3),
28.7 (Ϫ, C-3Ј), 29.4 (Ϫ, CH2CH2CH3), 36.4 [ϩ, N(CH3)2], 43.1
(Ϫ, C-1Ј), 55.5 (Cquat., C-2Ј), 61.3 (Ϫ, OCH2CH3), 64.1 (Ϫ, 2 ϫ
CO2CH2CH3), 76.3 (Cquat., C-5), 95.7 (ϩ, C-4), 121.3 (Ϫ, C-5Ј),
1-[2Ј,2Ј-Bis(methoxycarbonylethyl]-5-dimethyamino-3-ethoxy-5-
propyl-1,3-cyclopentadiene (7bat): According to GP2B, to a solu-
tion of complex 3ba (300 mg, 0.83 mmol) in acetonitrile (7 mL) at
80 °C was slowly added a solution of dimethyl prop-1-yn-3-ylma-
lonate (1t) (425 mg, 2.50 mmol) in acetonitrile (2 mL) over a period
of 18 h, and the mixture was stirred at this temperature for an ad-
ditional 2 h. Chromatography on aluminum oxide (30 g, activity
grade II) eluting with pentane/Et2O (5:1) gave 125 mg (44%) of
7bat [Rf ϭ 0.21 (pentane/Et2O, 5:1)] as a colorless oil. 1H NMR
(250 MHz, CDCl3): δ ϭ 0.78Ϫ0.92 (m, 5 H, CH2CH2CH3), 1.28 (t,
122.7 (ϩ, C-2), 127.2 (Cquat., C-4Ј), 149.6 (Cquat., C-1), 159.0 (Cquat.
,
C-3) 169.8 (Cquat., 2 ϫ CO2Et) ppm. MS (70 eV): m/z (%) ϭ 487/
485 (7/6) [Mϩ], 458/456 (11/10) [Mϩ Ϫ C2H5], 406 (18) [Mϩ Ϫ Br],
361 (5), 208 (100), 178 (22), 163 (9), 72 (4). C23H36BrNO5 (486.5):
calcd. C 56.79, H 7.46; found C 56.88, H 7.48.
3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.48 (mc, 1 H, CH2CH2CH3), 1.79 5-(Dimethylamino)-1,2-dimethyl-3-ethoxy-5-propyl-1,3-cyclopenta-
(mc, 1 H, CH2CH2CH3), 2.12 [s, 6 H, N(CH3)2], 2.64 (mc, 2 H, 1Ј-
diene (7baaa): According to GP2A, a solution of complex 3ba
H), 3.55Ϫ3.72 (m, 7 H, CO2CH3, 2Ј-H), 3.81 (q, 3J ϭ 7.0 Hz, 2 H, (300 mg, 0.83 mmol) in pyridine (6 mL) was treated with 2-butyne
OCH2CH3), 4.70 (s, 1 H, 4-H), 5.57 (s, 1 H, 2-H) ppm. 13C NMR (1aa) (250 mg, 4.62 mmol), and the mixture was stirred at 55 °C
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.3, 14.6 (ϩ, CH2CH2CH3, for 6 days. Chromatography on aluminum oxide (30 g, activity
Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
735

A. de Meijere et al.
FULL PAPER
grade II) eluting with pentane/Et2O (from 20:1 to 5:1) gave 177 mg
1-[5Ј-Bromo-3Ј-(tert-butyldimethylsilyloxy)hex-5Ј-enyl]-5-(dimethyl-
amino)-3-ethoxy-5-propyl-1,3-cyclopentadiene (7baw): According to
(95%) of 7baaa [Rf ϭ 0.48 (pentane/Et2O, 5:1)] as a colorless oil.
IR (film): ν˜ ϭ 2955 cmϪ1, 2870 (CϪH), 1658 (CϭC), 1593, 1378, GP2A, a solution of complex 3ba (300 mg, 0.83 mmol) in pyridine
1343, 1311, 1118, 918, 742. 1H NMR (250 MHz, CDCl3): δ ϭ
0.74Ϫ0.89 (m, 5 H, CH2CH2CH3), 1.31 (t, 3J ϭ 7.0 Hz, 3 H, oct-1-en-7-yne (1w) (300 mg, 0.94 mmol), and the mixture was
OCH2CH3), 1.45 (mc, 1 H, CH2CH2CH3), 1.57 (s, 3 H, CH3), 1.66 stirred at 80 °C for 4 days. Chromatography on aluminum oxide
(s, 3 H, CH3), 1.75 (mc, 1 H, CH2CH2CH3), 2.12 [s, 6 H, N(CH3)2], (30 g, activity grade II) eluting with pentane/Et2O (from 20:1 to
(17 mL) was treated with 4-(tert-butyldimethylsilyloxy)-2-bromo-
3.83 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.62 (s, 1 H, 4-H) ppm. 13
NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.5, 10.2 (ϩ, 2 ϫ
C
3:1) gave 345 mg (85%) of 7baw [Rf ϭ 0.27 (pentane/Et2O, 5:1)] as
a colorless oil. IR (film): ν˜ ϭ 2955 cmϪ1, 2856, 2820 (CϪH), 1653,
CH3), 14.4, 14.7 (ϩ, CH2CH2CH3, OCH2CH3), 16.6 (Ϫ, 1635 (CϭC), 1584, 1472, 1337, 1256, 1096, 836, 775. 1H NMR
CH2CH2CH3), 36.7 (Ϫ, CH2CH2CH3), 39.8 [ϩ, N(CH3)2], 64.3 (Ϫ, (250 MHz, CDCl3): δ ϭ 0.05 [s, 6 H, Si(CH3)2], 0.83 (t, 3J ϭ
3
OCH2CH3), 74.8 (Cquat., C-5), 93.7 (ϩ, C-4), 130.4 (Cquat., C-2), 7.1 Hz, 3 H, CH2CH2CH3), 0.85 [s, 9 H, SiC(CH3)3], 1.33 (t, J ϭ
142.3 (Cquat., C-1), 160.9 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 7.0 Hz, 3 H, OCH2CH3), 1.45 (mc, 1 H, 2Ј-H), 1.62Ϫ1.98 (m, 5 H,
223 (57) [Mϩ], 194 (79) [Mϩ Ϫ C2H5], 180 (78) [Mϩ Ϫ C3H7], 151
2Ј-H, 4Ј-H, CH2CH2CH3), 1.99Ϫ2.14 (m, 2 H, CH2CH2CH3), 2.15
3
(100) [Mϩ Ϫ C2H5 Ϫ C3H7], 123 (82), 91 (23), 67 (16). C14H25NO [s, 6 H, N(CH3)2], 2.57 (mc, 2 H, 1Ј-H), 3.85 (q, J ϭ 7.0 Hz, 2 H,
2
(223.4): calcd. C 75.28, H 11.28; found C 75.11, H 11.10.
OCH2CH3), 4.06 (mc, 1 H, 3Ј-H), 4.69 (s, 1 H, 4-H), 5.40 (d, J ϭ
1.2 Hz, 1 H, 6Ј-H), 5.58 (s, 1 H, 2-H), 5.66 (d, 2J ϭ 1.2 Hz, 1 H,
6Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ4.5
[ϩ, Si(CH3)2], 14.5 (ϩ, CH2CH2CH3), 14.7 (ϩ, OCH2CH3), 16.6
1-[3Ј-(tert-Butyldimethylsilyloxy)propyl]-5-(dimethylamino)-3-
ethoxy-5-propyl-1,3-cyclopentadiene (7bal) and 2-[3Ј-(tert-Butyldi-
methylsilyloxy)propyl]-5-(dimethylamino)-3-ethoxy-5-propyl-1,3-
cyclopentadiene (8bal): According to GP2A, a solution of complex
3ba (1.99 g, 5.51 mmol) in pyridine (110 mL) was treated with (tert-
butyltrimethylsilyloxy)pent-4-yne (1l) (1.64 g, 8.27 mmol), and the
mixture was stirred at 80 °C for 3 days. Chromatography on alumi-
num oxide (100 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 3:1) gave 1.51 g (74%) of 7bal [Rf ϭ 0.59 (pentane/
Et2O, 3:1)] and 163 mg (8%) of 8bal [Rf ϭ 0.43 (pentane/Et2O, 3:1)]
as colorless oils. 7bal: IR (film): ν˜ ϭ 2955 cmϪ1, 2857 (CϪH), 1660
(Ϫ, CH2CH2CH3), 18.0 (Ϫ, C-2Ј), 20.9 (Ϫ, C-1Ј), 21.8 [Cquat.
,
SiC(CH3)3], 25.8 [ϩ, SiC(CH3)3], 33.1 (Ϫ, CH2CH2CH3), 33.4 (Ϫ,
C-4Ј), 39.8 [ϩ, N(CH3)2], 64.4 (Ϫ, OCH2CH3), 69.2 (ϩ, C-3Ј), 76.4
(Cquat., C-5), 94.9 (ϩ, C-4), 119.0 (Ϫ, C-6Ј), 122.0 (ϩ, C-2), 131.2
(Cquat., C-5Ј), 155.8 (Cquat., C-1), 160.0 (Cquat., C-3) ppm. MS
(70 eV): m/z (%)
ϭ
487/485 (100/95) [Mϩ], 458/456 (97/91)
[Mϩ Ϫ C2H5], 406 (16) [Mϩ Ϫ Br], 321 (22), 222 (42), 139 (45),
107 (29), 59 (16). HRMS (EI) calcd. for C24H44BrNO2Si (486.6):
485.2324 (correct HRMS).
1
(CϭC), 1617, 1385, 1105, 964, 776. H NMR (250 MHz, CDCl3):
δ ϭ 0.02 [s, 6 H, Si(CH3)2], 0.77Ϫ0.96 (m, 5 H, CH2CH2CH3), 0.87 1-[2Ј,2Ј-Bis(ethoxycarbonyl)-3-ethoxy-5Ј-(trimethylsilyl)pent-4Ј-
[s, 9 H, SiC(CH3)3], 1.33 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.45
ynyl)-5-(dimethylamino)-5-propyl-1,3-cyclopentadiene (7bax): Ac-
(mc, 1 H, CH2CH2CH3), 1.68Ϫ1.85 (m, 3 H, CH2CH2CH3, 2Ј-H), cording to GP2A, a solution of complex 3ba (500 mg, 1.38 mmol)
3
1.98 (t, J ϭ 6.7 Hz, 2 H, 1Ј-H), 2.16 [s, 6 H, N(CH3)2], 3.66 (dt,
in pyridine (28 mL) was treated with diethyl 1-(trimethylsilyl)-1,6-
3J ϭ 6.4, 4J ϭ 2.2 Hz, 2 H, 3Ј-H), 3.86 (q, 3J ϭ 7.0 Hz, 2 H, heptadiynyl-4,4-dicarboxylate (1x) (925 mg, 3.00 mmol), and the
4
4
OCH2CH3), 4.67 (d, J ϭ 1.8 Hz, 1 H, 4-H), 5.68 (d, J ϭ 1.8 Hz,
1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ num oxide (30 g, activity grade II) eluting with pentane/Et2O (from
Ϫ5.3 [ϩ, Si(CH3)2], 14.5, 14.7 (ϩ, OCH2CH3, CH2CH2CH3), 16.6 20:1 to 5:1) gave 534 mg (81%) of 7bax [Rf ϭ 0.47 (pentane/Et2O,
(Ϫ, CH2CH2CH3), 18.2 [Cquat.
mixture was stirred at 60 °C for 36 h. Chromatography on alumi-
,
SiC(CH3)3], 23.0 (Ϫ, 5:1)] as a pale-yellow oil. IR (film): ν˜ ϭ 3012 cmϪ1, 2889 (CϪH),
CH2CH2CH3), 25.9 [ϩ, SiC(CH3)3], 29.8 (Ϫ, C-2Ј), 36.7 (Ϫ, C-1Ј), 2176 (CϵC), 1729 (CϭO), 1636 (CϭC), 1181, 1032, 837. 1H NMR
39.8 [ϩ, N(CH3)2], 62.9 (Ϫ, C-3Ј), 64.4 (Ϫ, OCH2CH3), 76.3 (250 MHz, CDCl3): δ ϭ 0.09 [s, 9 H, Si(CH3)3], 0.77Ϫ1.11 (m, 6 H,
(Cquat., C-5), 94.8 (ϩ, C-4), 122.4 (ϩ, C-2), 155.8 (Cquat., C-1),
OCH2CH3, CH2CH2CH3), 1.12 (mc, 6 H, CO2CH2CH3), 1.55 (mc,
160.1 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 367 (51) [Mϩ], 338 2 H, CH2CH2CH3), 1.81 (mc, 2 H, CH2CH2CH3), 2.18 [s, 6 H,
(100) [Mϩ Ϫ C2H5], 323 (17) [Mϩ Ϫ C3H8], 237 (18), 206 (15), 164 N(CH3)2], 2.70 (d, 2J ϭ 21.7 Hz, 1 H, 1Ј-H), 2.96 (d, 2J ϭ 21.7 Hz,
(11), 138 (18), 91 (13), 75 (39), 73 (27), 45 (46). C21H41NO2Si
(367.7): calcd. C 68.61, H 11.24, N 3.81; found C 68.77, H 11.13,
N 3.68.
1 H, 1Ј-H), 3.08 (s, 2 H, 3Ј-H), 3.83 (q, 3J ϭ 7.0 Hz, 2 H,
OCH2CH3), 4.16 (mc, 4 H, CO2CH2CH3), 4.73 (d, 4J ϭ 1.5 Hz,
1 H, 4-H), 5.63 (d, 4J ϭ 1.5 Hz, 1 H, 2-H) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ0.2 [ϩ, Si(CH3)3], 13.9 (ϩ,
OCH2CH3), 14.3 (ϩ, CH2CH2CH3), 14.7 (ϩ, 2 ϫ CO2CH2CH3),
16.0 (Ϫ, CH2CH2CH3), 23.9 (Ϫ, C-3Ј), 29.0 (Ϫ, CH2CH2CH3),
36.6 (Ϫ, C-1Ј), 39.7 [ϩ, N(CH3)2], 55.6 (Cquat., C-2Ј), 61.5 (Ϫ, 2 ϫ
CO2CH2CH3), 64.4 (Ϫ, OCH2CH3), 86.3, 88.0 (Cquat., C-5,4Ј), 95.2
(ϩ, C-4), 101.5 (Cquat., C-5Ј), 122.6 (ϩ, C-2), 149.7 (Cquat., C-1),
159.6 (Cquat., C-3), 169.8 (Cquat., 2 ϫ CO2Et) ppm. MS (70 eV):
m/z (%) ϭ 477 (7) [Mϩ], 448 (89) [Mϩ Ϫ C2H5], 404 (100), 359 (9),
208 (96), 164 (25), 75 (80), 44 (43). C26H43NO5Si (477.7): calcd. C
65.37, H 9.07; found C 65.49, H 9.10.
8bal: IR (film): ν˜ ϭ 3026 cmϪ1, 2929 (CϪH), 1653 (CϭC), 1592,
1380, 1118, 702. 1H NMR (250 MHz, CDCl3): δ ϭ 0.02 [s, 6 H,
Si(CH3)2], 0.78Ϫ1.00 (m, 5 H, CH2CH2CH3), 0.89 [s, 9 H,
3
SiC(CH3)3], 1.32 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.55Ϫ1.69 (mc,
3 H, CH2CH2CH3, 2Ј-H), 1.74 (t, 3J ϭ 6.7 Hz, 2 H, 1Ј-H), 1.82 (m,
1 H, CH2CH2CH3), 2.26 [s, 6 H, N(CH3)2], 3.62 (t, 3J ϭ 6.4 Hz,
2 H, 3Ј-H), 3.82 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.80 (d, 4J ϭ
4
1.8 Hz, 1 H, 4-H), 5.82 (d, J ϭ 1.8 Hz, 1 H, 1-H) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ5.5 [ϩ, Si(CH3)2], 14.5, 14.8
(ϩ, OCH2CH3, CH2CH2CH3), 18.4 [Cquat., SiC(CH3)3], 18.6 (Ϫ,
CH2CH2CH3), 22.7 (Ϫ, CH2CH2CH3), 26.0 [ϩ, SiC(CH3)3], 31.1
5-Cyclopropyl-5-(dimethylamino)-3-ethoxy-1-(2Ј-ethoxycyclo-
(Ϫ, C-2Ј), 37.5 (Ϫ, C-1Ј), 40.2 [ϩ, N(CH3)2], 62.9 (Ϫ, C-3Ј), 64.5 propyl)-1,3-cyclopentadiene (7cay): According to GP2A, a solution
(Ϫ, OCH2CH3), 76.3 (Cquat., C-5), 100.9 (ϩ, C-4), 134.2 (ϩ, C-1), of complex 3ca (200 mg, 0.56 mmol) in hexane (11 mL) was treated
141.0 (Cquat., C-2), 158.9 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ with
367 (42) [Mϩ], 338 (52) [Mϩ Ϫ C2H5], 323 (82) [Mϩ Ϫ C3H8], 238
1.12 mmol), and the mixture was stirred at 80 °C for 42 h. Chroma-
(12), 220 (30), 205 (100), 164 (18), 73 (12), 53 (11). C21H41NO2Si tography on silica gel (30 g) eluting with pentane/Et2O (5:1) gave
(367.7): calcd. C 68.61, H 11.24; found C 67.55, H 10.80. 134 mg (87%) of 7cay [Rf ϭ 0.27 (pentane/Et2O, 5:1); dr 1.3:1] as a
(E)-2-ethoxy-1-ethynylcyclopropane
(1y)
(123 mg,
736
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
colorless oil. IR (film): ν˜ ϭ 2977 cmϪ1, 2938 (CϪH), 1632 (CϭC),
OCH2CH3), 73.1 (Cquat., C-5), 100.9 (ϩ, C-4), 134.1 (ϩ, C-1), 141.3
(Cquat., C-2), 159.0 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 497
1582, 1454, 1343, 1198, 1033, 938, 742. 1H NMR (250 MHz,
CDCl3): δ ϭ Ϫ0.85 (mc, 1 H, cPr-H), 0.17 (mc, 1 H, cPr-H), 0.32 (61) [Mϩ], 468 (32) [Mϩ Ϫ C2H5], 324 (100), 188 (37), 164 (14),
(mc, 1 H, cPr-H), 0.72 (mc, 1 H, cPr-H), 0.98Ϫ1.17 (m, 8 H, 2 ϫ
75 (38), 47 (10). HRMS (EI) calcd. for C27H55NO3Si2: 497.3720
OCH2CH3, cPr-H), 1.28 (mc, 1 H, cPr-H), 1.87Ϫ2.16 (m, 1 H, cPr- (correct HRMS).
H), 2.40 [s, 6 H, N(CH3)2], 3.17 (mc, 1 H, cPr-H), 3.30Ϫ3.72 (m,
1-(3Ј-Butenyl)-5-(3ЈЈ-tert-butyldimethylsilyloxypropyl)-5-(dimethyl-
4 H, OCH2CH3), 4.30 (mc, 1 H, 4-H), 5.23 (mc, 1 H, 2-H) ppm.
13C NMR (75.5 MHz, CDCl3, plus APT). Major Diastereomer: δ ϭ
Ϫ0.1, 8.1 (Ϫ, cPr-C), 11.2 (ϩ, cPr-C), 15.4 (ϩ, OCH2CH3), 16.2
(ϩ, cPr-C), 17.2 (Ϫ, cPr-C), 17.2 (ϩ, OCH2CH3), 40.8 [ϩ,
N(CH3)2], 62.1 (ϩ, cPr-C), 64.0, 65.9 (Ϫ, OCH2CH3), 77.8 (Ϫ, C-
5), 98.0 (ϩ, C-4), 115.9 (ϩ, C-2), 159.7 (Ϫ, C-1), 162.8 (Ϫ, C-3).
Minor Diastereomer: δ ϭ Ϫ0.2, 8.1 (Ϫ, cPr-C), 11.7 (ϩ, cPr-C),
15.5 (ϩ, OCH2CH3), 17.0 (ϩ, cPr-C), 17.1 (Ϫ, cPr-C), 17.5 (ϩ,
OCH2CH3), 40.6 [ϩ, N(CH3)2], 63.99 (ϩ, cPr-C), 64.5, 65.8 (Ϫ,
OCH2CH3), 77.8 (Ϫ, C-5), 97.8 (ϩ, C-4), 116.4 (ϩ, C-2), 159.6 (Ϫ,
C-1), 162.8 (Ϫ, C-3) ppm. MS (70 eV): m/z (%) ϭ 277 (2) [Mϩ],
248 (21) [Mϩ Ϫ C2H5], 232 (79) [Mϩ Ϫ OC2H5], 203 (42), 175 (23),
132 (18), 102 (100), 91 (19), 58 (37), 41 (6). HRMS (EI) calcd. for
C17H27NO2: 277.2041 (correct HRMS).
amino)-3-ethoxy-1,3-cyclopentadiene (7laz) and 2-(3Ј-Butenyl)-5-
(3ЈЈ-tert-butyldimethylsilyloxypropyl)-5-(dimethylamino)-3-ethoxy-
1,3-cyclopentadiene (8laz): According to GP2B, to a solution of
complex 3la (750 mg, 1.53 mmol) in CH3CN (31 mL) at 80 °C was
slowly added a solution of 1-hexen-5-yne (1z) (367 mg, 4.58 mmol)
in acetonitrile (2 mL) over a period of 8 h, and the mixture was
stirred at this temperature for an additional 2 h. Chromatography
on aluminum oxide (30 g, activity grade II) eluting with pentane/
Et2O (from 5:1 to 3:1) gave 144 mg (25%) of 7laz [Rf ϭ 0.42 (pen-
tane/Et2O, 5:1)] and 63 mg (11%) of 8laz [Rf ϭ 0.13 (pentane/Et2O,
5:1)] as colorless oils. 7laz: IR (film): ν˜ ϭ 2989 cmϪ1, 2874 (CϪH),
1636 (CϭC), 1584, 1471, 1250, 1038, 918, 769. 1H NMR
(250 MHz, CDCl3): δ ϭ 0.02 [s, 6 H, Si(CH3)2], 0.88 [s, 9 H,
SiC(CH3)3], 1.13 (mc, 2 H, 2ЈЈ-H), 1.37 (t, 3J ϭ 7.0 Hz, 3 H,
OCH2CH3), 1.51 (mc, 1 H, 1ЈЈ-H), 1.86Ϫ2.12 (m, 3 H, 1ЈЈ-H, 2Ј-
H), 2.18 [s, 6 H, N(CH3)2], 2.30 (mc, 2 H, 1Ј-H), 3.57 (t, 3J ϭ
7.0 Hz, 2 H, 3ЈЈ-H), 3.86 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.69 (d,
1,5-Bis(3Ј-tert-butyldimethylsilyloxypropyl)-5-(dimethylamino)-3-
ethoxy-1,3-cyclopentadiene (7lal) and 2,5-Bis(3Ј-tert-butyldimeth-
ylsilyloxypropyl)-5-(dimethylamino)-3-ethoxy-1,3-cyclopentadiene
(8lal): According to GP2A, a solution of complex 3la (500 mg,
1.02 mmol) in pyridine (20 mL) was treated with tert-butyl-trimeth-
ylsilyloxypent-4-yne (1l) (605 mg, 3.05 mmol), and the mixture was
stirred at 80 °C for 20 h. Chromatographic purification on alumi-
num oxide (30 g, activity grade II) eluting with pentane/Et2O (3:1)
gave 389 mg (77%) of 7lal [Rf ϭ 0.68 (pentane/Et2O, 5:1)] and
40 mg (8%) of 8lal [Rf ϭ 0.19 (pentane/Et2O, 5:1)] as colorless oils.
7lal: IR (film): ν˜ ϭ 2957 cmϪ1, 2855 (CϪH), 1636 (CϭC), 1472,
1339, 1144, 1043, 839, 663, 540. 1H NMR (250 MHz, CDCl3): δ ϭ
Ϫ0.01 (s, 6 H, SiCH3), 0.01 (s, 6 H, SiCH3), 0.86 [s, 18 H, 2 ϫ
SiC(CH3)3], 1.11 (mc, 2 H, OCH2CH2CH2), 1.31 (t, 3J ϭ 7.0 Hz,
3 H, OCH2CH3), 1.49 (mc, 2 H, OCH2CH2CH2), 1.68Ϫ2.12 (m,
2
3
4J ϭ 1.7 Hz, 1 H, 4-H), 4.95 (dd, J ϭ 1.7, J ϭ 10.1 Hz, 1 H, 4Ј-
H), 5.04 (dd, 4J ϭ 1.7, 3J ϭ 17.1 Hz, 1 H, 4Ј-H), 5.74 (d, 4J ϭ
1.7 Hz, 1 H, 2-H), 5.85 (mc, 1 H, 3Ј-H) ppm. 13C NMR (62.9 MHz,
CDCl3, plus DEPT): δ ϭ Ϫ5.4 [ϩ, Si(CH3)2], 14.4 (ϩ, OCH2CH3),
18.2 [Cquat., SiC(CH3)3], 25.9 [ϩ, SiC(CH3)3], 26.0, 26.8 (Ϫ, C-
2Ј,2ЈЈ), 30.5 ϫ 2 (Ϫ, C-1Ј,1ЈЈ), 39.8 [ϩ, N(CH3)2], 63.6, 64.4 (Ϫ,
OCH2CH3, C-3ЈЈ), 76.2 (Cquat., C-5), 94.8 (ϩ, C-4), 114.7 (Ϫ, C-4Ј),
122.7 (ϩ, C-2), 138.1 (ϩ, C-3Ј), 155.1 (Cquat., C-1), 160.2 (Cquat., C-
3) ppm. MS (70 eV): m/z (%) ϭ 379 (75) [Mϩ], 350 (83)
[Mϩ Ϫ C2H5], 338 (100), 206 (11), 174 (6), 89 (8), 73 (17) [SiMe3ϩ].
HRMS (EI) calcd. for C22H41NO2Si: 379.2906 (correct HRMS).
8laz: IR (film): ν˜ ϭ 2935 cmϪ1, 2858 (CϪH), 1640 (CϭC), 1580,
1256, 834, 598. 1H NMR (250 MHz, CDCl3): δ ϭ 0.03 [s, 6 H,
Si(CH3)2], 0.86 [s, 9 H, SiC(CH3)3], 1.32 (t, 3J ϭ 7.0 Hz, 3 H,
OCH2CH3), 1.51 (mc, 4 H, 1ЈЈ,2ЈЈ-H), 1.70 (mc, 2 H, 2Ј-H), 2.20 [s,
3
4 H, CH2CH2CH2O), 2.15 [s, 6 H, N(CH3)2], 3.49 (t, J ϭ 6.3 Hz,
2 H, OCH2CH2CH2), 3.65 (t, 3J ϭ 6.3 Hz, 2 H, OCH2CH2CH2),
3
3.83 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.67 (s, 1 H, 4-H), 5.69 (s,
1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
Ϫ5.3 [ϩ, 2 ϫ Si(CH3)2], 14.5 (ϩ, OCH2CH3), 18.3 [Cquat., 2 ϫ
SiC(CH3)3], 23.0 (Ϫ, CH2CH2CH2O), 25.9 [ϩ, 2 ϫ SiC(CH3)3],
26.9 (Ϫ, CH2CH2CH2O), 29.9, 30.5 (Ϫ, 2 ϫ CH2CH2CH2O), 39.9
[ϩ, N(CH3)2], 63.0, 63.7 (Ϫ, 2 ϫ CH2CH2CH2O), 64.4 (Ϫ,
OCH2CH3), 76.2 (Cquat., C-5), 94.8 (ϩ, C-4), 122.4 (ϩ, C-2), 155.7
(Cquat., C-1), 160.3 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 497
(100) [Mϩ], 468 (92) [Mϩ Ϫ C2H5], 324 (10), 73 (24) [SiMe3ϩ], 59
(5). HRMS (EI) calcd. for C27H55NO3Si2: 497.3720 (correct
HMRS).
3
6 H, N(CH3)2], 2.21 (mc, 2 H, 1Ј-H), 3.59 (t, J ϭ 7.0 Hz, 2 H, 3ЈЈ-
H), 3.82 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.68 (d, 5J ϭ 1.7 Hz,
2
3
1 H, 4-H), 4.96 (dd, J ϭ 1.5, J ϭ 10.0 Hz, 1 H, 4Ј-H), 5.04 (dd,
2J ϭ 1.5, J ϭ 17.2 Hz, 1 H, 4Ј-H), 5.81 (d, J ϭ 1.7 Hz, 1 H, 1-
3
5
H), 5.82 (mc, 1 H, 3Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus
DEPT): δ ϭ Ϫ5.3 [ϩ, Si(CH3)2], 14.5 (ϩ, OCH2CH3), 18.3 [Cquat.
,
SiC(CH3)3], 25.9 [ϩ, SiC(CH3)3], 26.0, 28.6 (Ϫ, C-2Ј,2ЈЈ), 30.24 (Ϫ,
C-1Ј), 32.1 (Ϫ, C-1ЈЈ), 40.3 [ϩ, N(CH3)2], 63.8, 64.6 (Ϫ, OCH2CH3,
C-3ЈЈ), 73.2 (Cquat., C-5), 100.8 (ϩ, C-4), 114.5 (Ϫ, C-4Ј), 134.4 (ϩ,
C-1), 138.5 (ϩ, C-3Ј), 141.0 (Cquat., C-2), 159.0 (Cquat., C-3) ppm.
MS (70 eV): m/z (%) ϭ 379 (11) [Mϩ], 350 (18) [Mϩ Ϫ C2H5], 293
(100), 206 (38), 132 (17), 84 (91), 75 (100), 59 (21), 47 (19).
8lal: IR (film): ν˜ ϭ 2953 cmϪ1, 2857 (CϪH), 1635 (CϭC), 1472,
1255, 1101, 774, 572. 1H NMR (250 MHz, CDCl3): δ ϭ 0.02 [s,
6 H, Si(CH3)2], 0.04 [s, 6 H, Si(CH3)2], 0.87 [s, 9 H, SiC(CH3)3], 5-(3Ј-Bromobut-3Ј-enyl)-5-(dimethylamino)-3-ethoxy-1,2-dimethyl-
0.89 [s, 9 H, SiC(CH3)3], 1.32 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3),
1,3-cyclopentadiene (7naaa): According to GP2A, a solution of
1.51 (mc, 2 H, CH2CH2CH2O), 1.69Ϫ1.80 (m, 4 H, complex 3na (200 mg, 0.44 mmol) in pyridine (10 mL) was treated
CH2CH2CH2O), 2.18Ϫ2.21 (m, 2 H, CH2CH2CH2O), 2.26 [s, 6 H, with 2-butyne (1aa) (95.0 mg, 1.76 mmol), and the mixture was
3
3
N(CH3)2], 3.55 (t, J ϭ 6.3 Hz, 2 H, OCH2CH2CH2), 3.62 (t, J ϭ stirred at 70 °C for 3 days. Chromatography on aluminum oxide
6.3 Hz, 2 H, OCH2CH2CH2), 3.83 (q, 3J
ϭ 7.0 Hz, 2 H, (30 g, activity grade II) eluting with pentane/Et2O (from 20:1 to
5
5
OCH2CH3), 4.78 (d, J ϭ 0.6 Hz, 1 H, 4-H), 5.80 (d, J ϭ 0.6 Hz,
2:1) gave 110 mg (79%) of 7naaa [Rf ϭ 0.27 (pentane/Et2O, 2:1)] as
1 H, 1-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus. DEPT): δ ϭ
a colorless oil. 1H NMR (250 MHz, CDCl3): δ ϭ 1.34 (t, 3J ϭ
Ϫ5.3 [ϩ, 2 ϫ Si(CH3)2], 14.5 (ϩ, OCH2CH3), 18.4 [Cquat., 2 ϫ 7.0 Hz, 3 H, OCH2CH3), 1.62 (s, 3 H, CH3), 1.69 (s, 3 H, CH3),
SiC(CH3)3], 22.7 (Ϫ, CH2CH2CH2O), 26.0 [ϩ, 2 ϫ SiC(CH3)3], 1.58Ϫ1.82 (m, 1 H, 1Ј-H), 1.84Ϫ2.04 (m, 3 H, 1Ј,2Ј-H), 2.15 [s, 6 H,
3
28.6 (Ϫ, CH2CH2CH2O), 31.3 (Ϫ, 2 ϫ CH2CH2CH2O), 40.3 [ϩ, N(CH3)2], 3.84 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.66 (s, 1 H, 4-
N(CH3)2], 62.9, 63.8 (Ϫ,
Eur. J. Org. Chem. 2004, 724Ϫ748
2 ϫ
CH2CH2CH2O), 64.5 (Ϫ, H), 5.28 (s, 1 H, 4Ј-H), 5.31 (s, 1 H, 4Ј-H) ppm. 13C NMR
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
737

A. de Meijere et al.
FULL PAPER
5
5
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.7, 10.2 (ϩ, CH3), 14.5 (ϩ, OCH2CH3), 4.72 (d, J ϭ 1.6 Hz, 1 H, 4-H), 6.29 (d, J ϭ 1.6 Hz,
OCH2CH3), 32.7 (Ϫ, C-1Ј), 36.0 (Ϫ, C-2Ј), 39.9 [ϩ, N(CH3)2], 64.5 1 H, 1-H).
(Ϫ, OCH2CH3), 74.2 (Cquat., C-5), 93.0 (ϩ, C-4), 115.8 (Ϫ, C-4Ј),
5-(Dimethylamino)-3-ethoxy-1,2-dimethyl-5-[5Ј-(trimethylsilyl)-4Ј-
131.3 (Cquat., C-2), 135.7 (Cquat., C-3Ј), 141.6 (Cquat., C-1), 161.3
pentynyl]-1,3-cyclopenta-2,4-diene (7qaaa): According to GP2A, a
(Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 315/313 (22/21) [Mϩ],
solution of complex 3qa (300 mg, 0.66 mmol) in pyridine (13 mL)
286/284 (67/65) [Mϩ Ϫ C2H5], 234 (53) [Mϩ Ϫ Br], 194 (63), 180
was treated with 2-butyne (1aa) (142 mg, 2.62 mmol), and the mix-
ture was stirred at 80 °C for 4 days. Chromatography on aluminum
oxide (20 g, activity grade II) eluting with pentane/Et2O (from 20:1
(70), 161 (100), 152 (62), 122 (42), 91 (27). HRMS (EI) calcd. for
C15H24BrNO: 313.1041 (correct HRMS).
5-[4Ј-Bromo-2Ј,2Ј-bis(ethoxycarbonyl)-4Ј-pentenyl]-5-(dimethyl- to 3:1)] gave 97 mg (46%) of 7qaaa [Rf ϭ 0.38 (pentane/Et2O, 5:1)]
amino)-3-ethoxy-1,2-dimethyl-1,3-cyclopentadiene (7oaaa): Accord-
ing to GP2A, a solution of complex 3oa (1.00 g, 1.64 mmol) in
pyridine (33 mL) was treated with 2-butyne (1aa) (352 mg,
6.51 mmol), and the mixture was stirred at 80 °C for 3 days. Chro-
as a colorless oil. IR (film): ν˜ ϭ 2955 cmϪ1, 2173 (CϵC), 1653 (Cϭ
C), 1384, 1249, 843, 760. 1H NMR (250 MHz, CDCl3): δ ϭ 0.12
3
[s, 9 H, Si(CH3)3], 1.11 (mc, 2 H, 2Ј-H), 1.34 (t, J ϭ 7.0 Hz, 3 H,
5
OCH2CH3), 1.61 (d, J ϭ 1.0 Hz, 3 H, CH3), 1.62 (mc, 2 H, 1Ј-H),
5
matography on aluminum oxide (50 g, activity grade II) eluting 1.69 (d, J ϭ 1.0 Hz, 3 H, CH3), 1.91 (mc, 2 H, 3Ј-H), 2.15 [s, 6 H,
3
with pentane/Et2O (from 20:1 to 5:1) gave 575 mg (74%) of 7oaaa
N(CH3)2], 3.84 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.64 (s, 1 H, 4-
[Rf ϭ 0.21 (pentane/Et2O, 5:1)] as a colorless oil. 1H NMR H) ppm. 13C NMR (62.9 MHz, plus DEPT, CDCl3): δ ϭ 0.1 [ϩ,
(250 MHz, CDCl3): δ ϭ 1.20 (mc, 6 H, 2 ϫ CO2CH2CH3), 1.34 (t, Si(CH3)3], 8.7, 10.2 (ϩ, CH3), 14.5 (ϩ, OCH2CH3), 20.3 (Ϫ, C-
3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.62 (s, 3 H, CH3), 1.64 (s, 3 H, 2Ј), 22.7 (Ϫ, C-3Ј), 33.3 (Ϫ, C-1Ј), 39.8 [ϩ, N(CH3)2], 64.4 (Ϫ,
CH3), 2.06 [s, 6 H, N(CH3)2], 2.30 (d, 2J ϭ 15.0 Hz, 1 H, 1Ј-H),
OCH2CH3), 74.5 (Cquat., C-5), 84.4 (Cquat., C-5Ј), 93.4 (ϩ, C-4),
2
2.79 (s, 1 H, 3Ј-H), 2.82 (s, 1 H, 3Ј-H), 3.19 (d, J ϭ 15.0 Hz, 1 H, 107.7 (Cquat., C-4Ј), 130.8 (Cquat., C-2), 142.1 (Cquat., C-1), 161.0
3
1Ј-H), 3.79 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.21 (mc, 4 H, 2 ϫ (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 319 (3) [Mϩ], 290 (38)
CO2CH2CH3), 4.54 (s, 1 H, 4-H), 5.46 (s, 1 H, 5Ј-H), 5.52 (s, 1 H,
[Mϩ Ϫ C2H5], 274 (50) [Mϩ Ϫ OC2H5], 246 (81) [Mϩ Ϫ SiMe3],
5Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 9.0, 180 (51), 152 (100), 73 (48) [SiMe3ϩ], 44 (9). HRMS (EI) calcd. for
10.6 (ϩ, 2 ϫ CH3), 13.7 (ϩ, 2 ϫ CO2CH2CH3), 14.4 (ϩ,
OCH2CH3), 33.6 (Ϫ, C-1Ј), 39.6 [ϩ, N(CH3)2], 43.72 (Ϫ, C-3Ј),
C19H33NOSi: 319.2331 (correct HRMS).
5-(Dimethylamino)-5-[2Ј-(1ЈЈ,3ЈЈ-dioxolan-2ЈЈ-yl)ethyl]-3-ethoxy-1-
methyl-1,3-cyclopentadiene (7raa): According to GP2A, a solution
of complex 3ra (839 mg, 2.00 mmol) in pyridine (40 mL) was
treated with propyne (1a) (1.19 mL, 20.0 mmol), and the mixture
was stirred at 80 °C for 4 days. Chromatographic purification on
aluminum oxide (60 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 0:1) gave 471 mg (88%) of 7raa [Rf ϭ 0.10 (pentane/
Et2O, 3:1)] as a colorless oil. IR (film): ν˜ ϭ 2978 cmϪ1, 2818, 2781
55.64 (Cquat.
OCH2CH3), 72.9 (Cquat., C-5), 91.9 (ϩ, C-4), 119.4 (Ϫ, C-5Ј), 128.8
(Cquat., C-4Ј), 132.3 (Cquat., C-2), 142.3 (Cquat., C-1), 161.5 (Cquat.
, C-2Ј), 61.2 (Ϫ, 2 ϫ CO2CH2CH3), 64.4 (Ϫ,
,
C-3), 169.9, 170.3 (Cquat., CO2Et) ppm. MS (70 eV): m/z (%) ϭ
473/471 (8/9) [Mϩ], 429/427 (17/18), 392 (55) [Mϩ Ϫ Br], 347 (18),
194 (100), 152 (31), 44 (9). HRMS (EI) calcd. for C22H34BrNO5:
471.1620 (correct HRMS). C22H34BrNO5 (472.4): calcd. C 55.93,
H 7.25; found C 55.74, H 7.38.
1
(CϪH), 1640 (CϭC), 1585, 1442, 1405, 1203, 1032, 743. H NMR
5-(Dimethylamino)-3-ethoxy-1-(trimethylsilyl)-5-(5Ј-(trimethylsilyl)-
4Ј-pentynyl)-1,3-cyclopentadiene (7qag) and 5-(Dimethylamino)-3-
ethoxy-2-(trimethylsilyl)-5-(5Ј-(trimethylsilyl)-4Ј-pentynyl)-1,3-
cyclopentadiene (8qag): According to GP2A, a solution of complex
3qa (550 mg, 1.20 mmol) in pyridine (24 mL) was treated with tri-
(250 MHz, CDCl3): δ ϭ 1.13 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3),
1.52Ϫ1.67 (m, 2 H, 1Ј-H), 1.71 (s, 3 H, CH3), 1.80Ϫ1.98 (mc, 2 H,
2Ј-H), 2.23 [s, 6 H, N(CH3)2], 3.37Ϫ3.47 (m, 2 H, OCH2CH3),
4
3.49Ϫ3.67 (m, 4 H, OCH2CH2O), 4.67 (d, J ϭ 1.7 Hz, 1 H, 4-H),
3
4
4.85 (t, J ϭ 5.5 Hz, 1 H, 2ЈЈ-H), 5.63 (d, J ϭ 1.8 Hz, 1 H, 2-H)
methylsilylethyne (1g) (471 mg, 4.80 mmol), and the mixture was ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 12.8 (ϩ,
stirred at 80 °C for 16 h. Chromatography on aluminum oxide
(30 g, activity grade II) eluting with pentane/Et2O (from 20:1 to
2:1) gave 210 mg (48%) of 7qag [Rf ϭ 0.71 (pentane/Et2O, 5:1)] and
CH3), 14.5 (ϩ, OCH2CH3), 28.3, 28.6 (Ϫ, C-1Ј,2Ј), 39.9 [ϩ,
N(CH3)2], 64.4, 64.8, 64.9 (Ϫ, OCH2CH2O, OCH2CH3), 76.0
(Cquat., C-5), 94.7 (ϩ, C-4), 105.1 (ϩ, C-2ЈЈ), 124.8 (ϩ, C-2), 152.0
17 mg (4%) of 8qag [Rf ϭ 0.13 (pentane/Et2O, 5:1)] as colorless oils. (Cquat., C-1), 161.0 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 267
7qag: IR (film): ν˜ ϭ 2956 cmϪ1, 2819, 2174 (CϵC), 1606 (CϭC),
(25) [Mϩ], 238 (100) [Mϩ Ϫ C2H5], 229 (7), 166 (20), 150 (5), 138
1
1322, 1248, 841, 760. H NMR (250 MHz, CDCl3): δ ϭ 0.12, 0.13 (13), 136 (9), 108 (3), 99 (24), 84 (10). C15H25NO3 (267.4): calcd.
[s, 18 H, Si(CH3)3], 1.31 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3),
C 67.38, H 9.42; found C 67.22, H 9.31.
3
1.48Ϫ1.62 (m, 2 H, 2Ј-H), 1.64Ϫ1.78 (m, 2 H, 1Ј-H), 2.17 (t, J ϭ
5-(Dimethylamino)-3-ethoxy-1-phenyl-5-propyl-1,3-cyclopentadiene
(7bah): According to GP2B, to a solution of complex 3ba (200 mg,
0.55 mmol) in acetonitrile (11 mL) at 80 °C was slowly added a
solution of phenylethyne (1h) (113 mg, 1.11 mmol) in acetonitrile
(2 mL) over a period of 15 h, and the mixture was stirred at this
temperature for an additional 2 h. Chromatography on aluminum
oxide (30 g, activity grade II) eluting with pentane/Et2O (5:1) gave
119 mg (80%) of 7bah [Rf ϭ 0.54 (pentane/Et2O, 5:1)] as a colorless
oil. IR (film): ν˜ ϭ 3058 cmϪ1, 2955, 2869 (CϪH), 1622 (CϭC),
1345, 1109, 769, 695. 1H NMR (250 MHz, CDCl3): δ ϭ 0.77 (t,
3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.30 (mc, 5 H, CH2CH2CH3),
1.74Ϫ2.06 (m, 2 H, CH2CH2CH3), 2.31 [s, 6 H, N(CH3)2], 4.00 (q,
7.2 Hz, 2 H, 3Ј-H), 2.26 [s, 6 H, N(CH3)2], 3.80 (q, 3J ϭ 7.0 Hz,
2 H, OCH2CH3), 4.76 (d, 4J ϭ 2.2 Hz, 1 H, 4-H), 6.35 (d, 4J ϭ
2.2 Hz, 1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT):
δ ϭ Ϫ1.3, 0.1 [ϩ, Si(CH3)3], 14.5 (ϩ, OCH2CH3), 20.4 (Ϫ, C-2Ј),
24.6 (Ϫ, C-1Ј), 33.9 (Ϫ, C-3Ј), 40.2 [ϩ, N(CH3)2], 64.5 (Ϫ,
OCH2CH3), 76.7 (Cquat., C-5), 84.44 (Cquat., C-4Ј), 99.3 (ϩ, C-4),
107.54 (Cquat., C-5Ј), 124.1 (ϩ, C-2), 142.9 (Cquat., C-1), 162.6
(Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 363 (17) [Mϩ], 334 (98)
[Mϩ Ϫ C2H5], 224 (58), 180 (19), 73 (100) [SiMe3ϩ]. C20H37NOSi2
(363.7): calcd. C 66.05, H 10.25; found C 67.01, H 10.42.
8qag: IR (film): ν˜ ϭ 2955 cmϪ1, 2816, 2778 (CϪH), 2174 (CϵC),
1
1618 (CϭC), 1320, 1250, 1024, 736. H NMR (250 MHz, CDCl3): 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 5.05 (d, 4J ϭ 1.8 Hz, 1 H, 4-H), 6.47
δ ϭ 0.03, 0.09 [s, 18 H, Si(CH3)3], 1.22 (mc, 2 H, 2Ј-H), 1.32 (t, 3J ϭ (d, 4J ϭ 1.8 Hz, 1 H, 2-H), 7.24Ϫ7.48 (m, 3 H, PhϪH), 7.82Ϫ7.98
7.0 Hz, 3 H, OCH2CH3), 1.69Ϫ2.08 (m, 2 H, 1Ј-H), 2.14 (mc, 2 H, (m, 2 H, PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT):
3Ј-H), 2.18 [s, 6 H, N(CH3)2], 3.82 (q, 3J
ϭ
7.0 Hz, 2 H,
δ ϭ 14.5, 14.7 (ϩ, CH2CH2CH3, OCH2CH3), 16.6 (Ϫ,
738
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
3
CH2CH2CH3), 37.2 (Ϫ, CH2CH2CH3), 40.1 [ϩ, N(CH3)2], 64.6 (Ϫ, 1 H, 4-H), 7.11Ϫ7.27 (m, 5 H, PhϪH), 7.39 (d, J ϭ 8.4 Hz, 2 H,
OCH2CH3), 81.4 (Cquat., C-5), 98.5 (ϩ, C-4), 126.3, 127.20, 128.2 PhϪH), 7.83 (d, 3J ϭ 8.4 Hz, 2 H, PhϪH) ppm. 13C NMR
ϫ 2 (ϩ, C-2, PhϪC), 135.0 (Cquat., PhϪC), 150.8 (Cquat., C-1), (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.3, 14.4 (ϩ, OCH2CH3),
159.6 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 271 (1) [Mϩ], 242
(1) [Mϩ Ϫ C2H5], 174 (18), 159 (100), 105 (12), 43 (9) [C3H7ϩ].
16.9 (ϩ, iPr-C), 18.0 (ϩ, iPr-C), 30.0 (ϩ, iPr-C), 39.6 [ϩ, N(CH3)2],
60.7 (Ϫ, OCH2CH3), 64.9 (Ϫ, OCH2CH3), 79.6 (Cquat., C-5), 99.4
(ϩ, C-4), 126.9, 128.0, 128.9, 129.7, 130.1 (ϩ, PhϪC), 128.2, 133.2,
5-(Dimethylamino)-3-ethoxy-2-hexyl-5-isopropyl-1-phenyl-1,3-
cyclopentadiene (7dahe) and 5-(Dimethylamino)-3-ethoxy-1-hexyl-5-
isopropyl-2-phenyl-1,3-cyclopentadiene (8dahe): According to
GP2A, a solution of complex 3da (553 mg, 1.53 mmol) in pyridine
(31 mL) was treated with 1-phenyloct-1-yne (1he) (295 mg,
1.58 mmol), and the mixture was stirred at 80 °C for 3 days. Chro-
matography on aluminum oxide (40 g, activity grade II) eluting
with pentane/Et2O (from 20:1 to 1:1) gave 382 mg (70%) of 7dahe
and 8dahe [Rf ϭ 0.59, pentane/Et2O (3:1); ratio 2.2:1] as a colorless
oil. After identification of the mixture and chromatography again
on aluminum oxide [40 g, activity grade II; elution with pentane/
Et2O (10:1)], 7dahe was obtained. IR (film): ν˜ ϭ 2929 cmϪ1 (CϪH),
2859, 2823, 1636 (CϭC), 1601, 1586, 1457, 1373, 1192, 1139, 701.
7dahe: (major stereoisomer): 1H NMR (250 MHz, CDCl3): δ ϭ
0.76 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 0.83 (t, 3J ϭ 6.5 Hz, 3 H, 6Ј-H),
138.5, 143.2 (Cquat., C-2, PhϪC), 144.7 (Cquat., C-1), 158.2 (Cquat.
,
C-3), 166.6 (Cquat.
,
CO2Et). Minor Stereoisomer: 1H NMR
3
(250 MHz, CDCl3): δ ϭ 0.94 (d, J ϭ 6.8 Hz, 3 H, iPr-H), 0.98 (d,
3J ϭ 6.8 Hz, 3 H, iPr-H), 1.35 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3),
1.36 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.36 [s, 6 H, N(CH3)2],
3
2.40Ϫ2.60 (m, 1 H, iPr-H), 3.97 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3),
4.33 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.97 (s, 1 H, 4-H),
7.11Ϫ7.27 (m, 5 H, PhϪH), 7.39 (d, 3J ϭ 8.4 Hz, 2 H, PhϪH),
7.86 (d, 3J ϭ 8.2 Hz, 2 H, PhϪH) ppm. 13C NMR (62.9 MHz,
CDCl3, plus DEPT): δ ϭ 14.3, 14.4 (ϩ, OCH2CH3), 17.1 (ϩ, iPr-
C), 17.8 (ϩ, iPr-C), 30.4 (ϩ, iPr-C), 39.8 [ϩ, N(CH3)2], 60.7 (Ϫ,
OCH2CH3), 64.9 (Ϫ, OCH2CH3), 79.6 (Cquat., C-5), 99.8 (ϩ, C-4),
127.1, 127.8, 129.0, 129.6, 130.0 (ϩ, PhϪC), 128.5, 137.8, 137.9,
140.2 (Cquat., C-2, PhϪC), 147.7 (Cquat., C-1), 158.4 (Cquat., C-3),
166.6 (Cquat., CO2Et) ppm. MS (70 eV): m/z (%) ϭ 419 (20) [Mϩ],
390 (24) [Mϩ Ϫ C2H5], 376 (100) [Mϩ Ϫ C3H7], 348 (12), 347 (10),
250 (11), 211 (10). HRMS (EI) calcd. for C27H33NO3: 419.2460
(correct HRMS).
3
0.92 (d, J ϭ 6.8 Hz, 3 H, iPr-H), 1.13Ϫ1.30 (m, 8 H, 2Ј,3Ј,4Ј,5Ј-
H), 1.38 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.19 (t, 3J ϭ 7.7 Hz,
2 H, 1Ј-H), 2.25 [s, 6 H, N(CH3)2], 2.43 (sept, 3J ϭ 6.8 Hz, 1 H,
3
iPr-H), 3.92 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.76 (s, 1 H, 4-H),
7.22Ϫ7.38 (m, 5 H, PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3,
plus DEPT): δ ϭ 14.0, 14.5 (ϩ, OCH2CH3, C-6Ј), 17.1 (ϩ, iPr-C),
18.1 (ϩ, iPr-C), 22.5, 24.6, 29.0, 29.2 (Ϫ, C-2Ј,3Ј,4Ј,5Ј), 29.6 (ϩ,
iPr-C), 31.4 (Ϫ, C-1Ј), 39.7 [ϩ, N(CH3)2], 64.4 (Ϫ, OCH2CH3),
79.4 (Cquat., C-5), 98.3 (ϩ, C-4), 126.2, 127.8, 128.9 (ϩ, PhϪC),
5-(Dimethylamino)-3-ethoxy-5-isopropyl-1-[4Ј-(methoxycarbonyl)-
phenyl]-2-(4ЈЈ-methoxyphenyl)-1,3-cyclopentadiene (7dah2h3) and 5-
(Dimethylamino)-3-ethoxy-5-isopropyl-2-[(4ЈЈ-methoxycarbonyl)-
phenyl]-1-(4Ј-methoxyphenyl)-1,3-cyclopentadiene (8dah2h3): Ac-
cording to GP2A, a solution of complex 3da (723 mg, 2.00 mmol)
in pyridine (40 mL) was treated with 4-(4Ј-methoxyphenylethynyl)-
benzoic acid methyl ester (1h2h3) (586 mg, 2.20 mmol), and the
mixture was stirred at 80 °C for 3 days. The alkyne 1h2h3 with very
low solubility could not be completely removed. Two successive
chromatographic separations on aluminum oxide (60 g, activity
grade II) eluting with pentane/Et2O (first time: from 20:1 to 3:1,
second time: from 6:1 to 3:1) gave 548 mg of a yellow solid, which
contained 1h2h3 (30%) and products [7dah2h3 and 8dah2h3; 70%;
ratio 1:1.1; Rf ϭ 0.59 (pentane/Et2O, 3:1)]. The amount of products
totaled 384 mg (44% from complex 3da). Major Stereoisomer: 1H
NMR (250 MHz, CDCl3): δ ϭ 0.76 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H),
0.80 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 1.34 (t, 3J ϭ 7.0 Hz, 3 H,
OCH2CH3), 2.35 [s, 6 H, N(CH3)2], 2.40Ϫ2.60 (m, 1 H, iPr-H),
139.0, 140.0 (Cquat., C-2, PhϪC), 142.8 (Cquat., C-1), 159.8 (Cquat.
,
C-3). 8dahe: (Minor stereoisomer). 1H NMR (250 MHz, CDCl3):
δ ϭ 0.83 (t, 3J ϭ 6.5 Hz, 3 H, 6Ј-H), 0.98 (d, 3J ϭ 6.8 Hz, 3 H, iPr-
H), 1.02Ϫ1.25 (m, 11 H, 2Ј,3Ј,4Ј,5Ј-H, iPr-H), 1.27 (t, 3J ϭ 7.0 Hz,
3 H, OCH2CH3), 2.19 (t, 3J ϭ 7.7 Hz, 2 H, 1Ј-H), 2.37 [s, 6 H,
N(CH3)2], 2.43 (sept, 3J ϭ 6.8 Hz, 1 H, iPr-H), 3.92 (q, 3J ϭ
7.0 Hz, 2 H, OCH2CH3), 4.68 (s, 1 H, 4-H), 7.22Ϫ7.38 (m, 5 H,
PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.0,
14.3 (ϩ, OCH2CH3, C-6Ј), 17.3 (ϩ, iPr-C), 18.4 (ϩ, iPr-C), 22.5,
27.0, 28.0, 30.0 (Ϫ, C-2Ј,3Ј,4Ј,5Ј), 30.4 (ϩ, iPr-C), 31.2 (Ϫ, C-1Ј),
39.5 [ϩ, N(CH3)2], 64.5 (Ϫ, OCH2CH3), 78.4 (Cquat., C-5), 97.2
(ϩ, C-4), 126.6, 127.6, 129.2 (ϩ, PhϪC), 134.7, 137.2 (Cquat., C-2,
PhϪC), 149.4 (Cquat., C-1), 158.9 (Cquat., C-3) ppm. MS (70 eV):
m/z (%) ϭ 355 (14) [Mϩ], 326 (13) [Mϩ Ϫ C2H5], 312 (100) [Mϩ Ϫ
C3H7], 284 (10). HRMS (EI) calcd. for C24H37NO: 355.2875 (cor-
rect HRMS).
3
3.75 (s, 3 H, CO2CH3), 3.87 (s, 3 H, OCH3), 3.97 (q, J ϭ 7.0 Hz,
2 H, OCH2CH3), 4.95 (s, 1 H, 4-H), 6.70 (d, 3J ϭ 8.8 Hz, 2 H,
3
3
PhϪH), 7.17 (d, J ϭ 8.8 Hz, 2 H, PhϪH), 7.38 (d, J ϭ 8.4 Hz,
2 H, PhϪH), 7.85 (d, 3J ϭ 8.4 Hz, 2 H, PhϪH) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.4 (ϩ, OCH2CH3), 17.1
(ϩ, iPr-C), 17.8 (ϩ, iPr-C), 30.4 (ϩ, iPr-C), 39.8 [ϩ, N(CH3)2],
5-(Dimethylamino)-3-ethoxy-5-isopropyl-1-[(4Ј-ethoxycarbonyl)-
phenyl]-2-phenyl-1,3-cyclopentadiene (7dahh1) and 5-(Dimethyl-
amino)-3-ethoxy-5-isopropyl-2-[(4Ј-ethoxycarbonyl)- 52.2, 55.3 (ϩ, CO2CH3, OCH3), 64.4 (Ϫ, OCH2CH3), 79.5 (Cquat.
,
phenyl]-2-phenyl-1,3-cyclopentadiene (8dahh1): According to GP2A,
a solution of complex 3da (469 mg, 1.30 mmol) in pyridine (23 mL)
C-5), 99.7 (ϩ, C-4), 113.3 (ϩ, PhϪC), 114.7, 125.4, 127.7 (Cquat.
,
C-2, PhϪC), 129.1, 129.8, 131.3 (ϩ, PhϪC), 139.7, 143.6 (Cquat., C-
was treated with 1-[(4Ј-ethoxycarbonyl)phenyl]-2-phenylethyne 1, PhϪC), 158.5, 158.6 (Cquat., C-3, PhϪC), 166.6 (Cquat., CO2Me).
(1hh1) (325 mg, 1.30 mmol), and the mixture was stirred at 80 °C Minor Stereoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ 0.93 (d,
3
for 3 days. Chromatography on aluminum oxide (40 g, activity
grade II) eluting with pentane/Et2O (from 20:1 to 3:1) gave 194 mg
(36%) of 7dahh1 and 8dahh1 [Rf ϭ 0.53 (pentane/Et2O, 3:1); ratio
1:1.3] as a yellow oil. IR (film): ν˜ ϭ 2976 cmϪ1 (CϪH), 1717 (Cϭ
O), 1635 (CϭC), 1457, 1368, 1321, 1196, 1106, 1021. Major Stereo-
3J ϭ 6.8 Hz, 3 H, iPr-H), 0.97 (d, J ϭ 6.8 Hz, 3 H, iPr-H), 1.36
(t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.36 [s, 6 H, N(CH3)2], 2.40Ϫ2.60
(m, 1 H, iPr-H), 3.75 (s, 3 H, CO2CH3), 3.87 (s, 3 H, OCH3), 3.97
3
3
(q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.98 (s, 1 H, 4-H), 6.71 (d, J ϭ
8.8 Hz, 2 H, PhϪH), 7.05 (d, 3J ϭ 8.8 Hz, 2 H, PhϪH), 7.22 (d,
3
isomer: 1H NMR (250 MHz, CDCl3): δ ϭ 0.76 (d, 3J ϭ 6.8 Hz, 3J ϭ 8.4 Hz, 2 H, PhϪH), 7.83 (d, J ϭ 8.4 Hz, 2 H, PhϪH) ppm.
3 H, iPr-H), 0.80 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 1.35 (t, 3J ϭ 7.0 Hz,
3 H, OCH2CH3), 1.36 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.37 [s,
13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.4 (ϩ,
OCH2CH3), 16.8 (ϩ, iPr-C), 17.9 (ϩ, iPr-C), 30.1 (ϩ, iPr-C), 39.6
6 H, N(CH3)2], 2.40Ϫ2.60 (m, 1 H, iPr-H), 3.97 (q, 3J ϭ 7.0 Hz, [ϩ, N(CH3)2], 52.2, 55.3 (ϩ, CO2CH3, OCH3), 64.4 (Ϫ,
2 H, OCH2CH3), 4.33 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 5.00 (s,
OCH2CH3), 79.5 (Cquat., C-5), 99.7 (ϩ, C-4), 113.4 (ϩ, PhϪC),
Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
739

A. de Meijere et al.
FULL PAPER
114.7, 125.4, 128.0 (Cquat., C-2, PhϪC), 128.9, 130.1, 130.8 (ϩ,
PhϪC), 138.9, 143.6 (Cquat., C-1, PhϪC), 158.3, 158.6 (Cquat., C-3, 1 H, 4-H), 7.50Ϫ7.64 (m, 6 H, PhϪH), 8.15 (d, J ϭ 8.2 Hz, 2 H,
6.8 Hz, 1 H, iPr-H), 4.03 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.98 (s,
3
PhϪC), 166.6 (Cquat., CO2Me) ppm. MS (70 eV): m/z (%) ϭ 435
2Ј,6Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.4
(28) [Mϩ], 406 (13) [Mϩ Ϫ C2H5], 392 (60) [Mϩ Ϫ C3H7], 266 (100) (ϩ, OCH2CH3), 17.0 (ϩ, iPr-C), 17.4 (ϩ, iPr-C), 31.4 (ϩ, iPr-C),
[Mϩ of 1h2h3]. HRMS (EI) calcd. for C27H33NO4: 435.2410 (cor-
40.1 [ϩ, N(CH3)2], 65.3 (Ϫ, OCH2CH3), 80.9 (Cquat., C-5), 85.6,
94.0 (Cquat., CϵC), 99.4 (ϩ, C-4), 121.7 (Cquat., PhϪC), 124.6,
rect HRMS).
3
125.2 (ϩ, q, JC,F ϭ 3.8 Hz, PhϪCh), 126.9 (Cquat., PhϪC), 129.5,
5-(Dimethylamino)-3-ethoxy-5-isopropyl-1,2-dimethyl-1,3-cyclo-
pentadiene (7daaa) and 5-(Dimethylamino)-2-ethoxy-4-isopropyl-
1,5-dimethyl-1,3-cyclopentadiene (17daaa): According to GP2A, a
solution of complex 3da (903 mg, 2.50 mmol) in pyridine (50 mL)
was treated with 2-butyne (1aa) (348 mg, 6.43 mmol), and the mix-
ture was stirred at 80 °C for 3 days. Chromatography on aluminum
oxide (30 g, activity grade II) eluting with pentane/Et2O (from 20:1
2
130.0 (Cquat., q, JC,F ϭ 32.3 Hz, C-4Ј,4ЈЈЈ), 129.1, 131.8 (ϩ,
PhϪC), 140.4 (Cquat., C-2), 153.4 (Cquat., C-1), 156.5 (Cquat., C-3)
ppm. The signals of CF3 were not detected. MS (70 eV): m/z (%) ϭ
507 (80) [Mϩ], 478 (38), 464 (100) [Mϩ Ϫ C3H7], 462 (75), 436 (12),
338 (10). HRMS (EI) calcd. for C28H27F6NO: 507.1997 (correct
HRMS).
to 1:2) gave 218 mg (39%) of 17daaa [Rf ϭ 0.58 (pentane/Et2O, 3:1)] 8dah4z: IR (film): ν˜ ϭ 2981 cmϪ1 (CϪH), 2873 (CϪH), 2782
and 212 mg (38%) of 7daaa [Rf ϭ 0.22 (pentane/Et2O, 3:1)] as col- (CϪH), 2187 (CϵC), 1653 (CϭC), 1617, 1559, 1457, 1324, 1127,
orless oils. 7daaa: IR (film): ν˜ ϭ 2945 cmϪ1 (CϪH), 2819 (CϪH), 1067. 1H NMR (250 MHz, CDCl3): δ ϭ 0.98 (d, J ϭ 6.7 Hz, 3 H,
3
2779 (CϪH), 1643 (CϭC), 1596 (CϭC), 1462, 1382, 1323, 1201,
iPr-H), 1.17 (d, 3J ϭ 6.7 Hz, 3 H, iPr-H), 1.42 (t, 3J ϭ 7.0 Hz, 3 H,
1
3
3
1043, 998. H NMR (250 MHz, CDCl3): δ ϭ 0.84 (d, J ϭ 6.8 Hz, OCH2CH3), 2.57 [s, 6 H, N(CH3)2], 2.62 (sept, J ϭ 6.8 Hz, 1 H,
3 H, iPr-H), 0.85 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 1.33 (t, 3J ϭ 7.0 Hz, iPr-H), 4.03 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 5.01 (s, 1 H, 4-H),
3
3 H, OCH2CH3), 1.67 (s, 6 H, CH3), 2.13 (sept, J ϭ 6.8 Hz, 1 H, 7.49 (d, 3J ϭ 8.3 Hz, 2 H, PhϪH), 7.59 (d, 3J ϭ 8.3 Hz, 2 H,
3
iPr-H), 2.23 [s, 6 H, N(CH3)2], 3.85 (q, 3J ϭ 7.0 Hz, 2 H,
PhϪH), 7.70 (d, J ϭ 8.2 Hz, 2 H, PhϪH), 7.99 (d, J ϭ 8.0 Hz,
OCH2CH3), 4.55 (s, 1 H, 4-H) ppm. 13C NMR (62.9 MHz, CDCl3, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
plus DEPT): δ ϭ 8.4 (ϩ, CH3), 13.0 (ϩ, CH3), 14.5 (ϩ, 14.3 (ϩ, OCH2CH3), 16.8 (ϩ, iPr-C), 18.6 (ϩ, iPr-C), 30.5 (ϩ, iPr-
OCH2CH3), 16.9 (ϩ, iPr-C), 18.1 (ϩ, iPr-C), 29.9 (ϩ, iPr-C), 39.5 C), 39.4 [ϩ, N(CH3)2], 65.4 (Ϫ, OCH2CH3), 79.1 (Cquat., C-5), 89.2,
3
3
1
[ϩ, N(CH3)2], 65.3 (Ϫ, OCH2CH3), 77.0 (Cquat., C-5), 96.2 (ϩ, C- 99.1 (Cquat., CϵC), 104.0 (ϩ, C-4), 123.9, 124.2 (Cquat., q, JC,F
ϭ
3
4), 131.4 (Cquat., C-2), 141.5 (Cquat., C-1), 160.3 (Cquat., C-3) ppm. 270.3 Hz, CF3), 124.5, 125.3 (ϩ, q, JC,F ϭ 3.8 Hz, PhϪC), 127.2,
MS (70 eV): m/z (%) ϭ 223 (28) [Mϩ], 194 (17) [Mϩ Ϫ C2H5], 180 (Cquat., PhϪC), 129.4 (ϩ, PhϪC), 129.9 ϫ 2 (Cquat., q, JC,F
ϭ
2
(100) [Mϩ Ϫ C3H7], 151 (75) [Mϩ Ϫ C3H7 Ϫ C2H5], 136 (18), 123 32.5 Hz, C-4Ј,4ЈЈЈ), 130.1 (Cquat., PhϪC), 131.2 (ϩ, PhϪC), 132.5
(8), 107 (6), 91 (7), 77 (5), 58 (10).
(Cquat., C-2), 144.7 (Cquat., C-1), 157.3 (Cquat., C-3) ppm. MS
(70 eV): m/z (%) ϭ 507 (8) [Mϩ], 478 (7), 465 (26), 464 (100)
[Mϩ Ϫ C3H7], 436 (17). C28H27F6NO (507.5): calcd. C 66.27,
H 5.36; found C 66.05, H 5.15.
17daaa: IR (film): ν˜ ϭ 2968 cmϪ1 (CϪH), 2866 (CϪH), 1654 (Cϭ
1
C), 1457, 1379, 1109, 976, 837. H NMR (250 MHz, CDCl3): δ ϭ
3
3
1.08 (d, J ϭ 6.8 Hz, 3 H, iPr-H), 1.12 (d, J ϭ 6.8 Hz, 3 H, iPr-
3
H), 1.21 (s, 3 H, CH3), 1.25 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.69 17dah4z: IR (film): ν˜ ϭ 2968 cmϪ1 (CϪH), 2183 (CϵC), 1653 (Cϭ
(s, 3 H, CH3), 2.25 [s, 6 H, N(CH3)2], 2.55 (sept, J ϭ 6.8 Hz, 1 H, C), 1616, 1559, 1457, 1323, 1125, 1068. 1H NMR (250 MHz,
3
iPr-H), 3.90 (q, 3J ϭ 7.0 Hz, 1 H, OCH2CH3), 3.91 (q, 3J ϭ 7.0 Hz,
CDCl3): δ ϭ 0.33 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 1.15 (d, 3J ϭ 6.8 Hz,
4
1 H, OCH2CH3), 5.95 (d, J ϭ 1.0 Hz, 1 H, 3-H) ppm. 13C NMR 3 H, iPr-H), 1.25 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.45 (sept, 3J ϭ
3
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 9.8 (ϩ, CH3), 15.4 (ϩ,
6.8 Hz, 1 H, iPr-H), 2.48 [s, 6 H, N(CH3)2], 4.67 (q, J ϭ 7.0 Hz,
OCH2CH3), 20.9 (ϩ, CH3), 23.3 (ϩ, iPr-C), 24.8 (ϩ, iPr-C), 26.1 1 H, OCH2CH3), 4.69 (q, 3J ϭ 7.0 Hz, 1 H, OCH2CH3), 5.83 (s,
(ϩ, iPr-C), 39.5 [ϩ, N(CH3)2], 65.0 (Ϫ, OCH2CH3), 72.7 (Cquat.
,
1 H, 3-H), 7.27 (d, 3J ϭ 8.0 Hz, 2 H, PhϪH), 7.46 (d, 3J ϭ 8.3 Hz,
C-5), 117.9 (ϩ, C-3), 118.6 (Cquat., C-4), 150.9 (Cquat., C-1), 162.1 2 H, PhϪH), 7.58 (d, 3J ϭ 8.3 Hz, 2 H, PhϪH), 7.76 (d, 3J ϭ
(Cquat., C-2) ppm. MS (70 eV): m/z (%) ϭ 223 (23) [Mϩ], 194 (12) 8.0 Hz, 2 H, 2Ј,6Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus
[Mϩ Ϫ C2H5], 180 (100) [Mϩ Ϫ C3H7], 152 (58), 136 (18), 121 (8),
107 (8), 77 (5).
DEPT): δ ϭ 15.5 (ϩ, OCH2CH3), 22.6 (ϩ, iPr-C), 24.7 (ϩ, iPr-C),
25.9 (ϩ, iPr-C), 40.3 [ϩ, N(CH3)2], 66.4 (Ϫ, OCH2CH3), 83.0
(Cquat., C-5), 90.1, 94.7, 95.2 (Cquat., C-1, CϵC), 120.5 (ϩ, C-3),
124.0, 124.3 (Cquat., q, 1JC,F ϭ 271.9 Hz, CF3), 125.1 (ϩ, q, 3JC,F ϭ
5-(Dimethylamino)-3-ethoxy-5-isopropyl-1-(4Ј-trifluoromethyl-
phenyl)-2-[2ЈЈ-(4ЈЈЈ-trifluoromethylphenyl)ethynyl]-1,3-cyclopenta-
diene (7dah4z), 5-(Dimethylamino)-3-ethoxy-5-isopropyl-2-(4Ј-tri-
fluoromethylphenyl)-1-[2ЈЈ-(4ЈЈЈ-trifluoromethylphenyl)ethynyl]-1,3-
cyclopentadiene (8dah4z) and 5-(Dimethylamino)-2-ethoxy-4-isopro-
pyl-5-(4Ј-trifluoromethylphenyl)-1-[2ЈЈ-(4ЈЈЈ-trifluoromethyl-
phenyl)ethynyl]-1,3-cyclopentadiene (17dah4z): According to GP2A,
a solution of complex 3da (723 mg, 2.00 mmol) in pyridine (40 mL)
was treated with 1,4-bis(p-trifluoromethylphenyl)butadiyne (1h4h4)
(713 mg, 2.11 mmol), and the mixture was stirred at 80 °C for 3
days. Chromatography on aluminum oxide (60 g, activity grade II)
3
3.8 Hz, PhϪC), 125.2 (ϩ, q, JC,F ϭ 3.8 Hz, PhϪC), 125.2 (ϩ,
2
PhϪC), 128.46 (Cquat., PhϪC), 128.54, 129.4 (Cquat., q, JC,F
ϭ
32.5 Hz, C-4Ј,4ЈЈЈ), 130.1 (ϩ, PhϪC), 144.3 (Cquat., PhϪC), 165.6
(Cquat., C-4), 167.4 (Cquat., C-2) ppm. MS (70 eV): m/z (%) ϭ 507
(88) [Mϩ], 478 (40), 464 (100) [Mϩ Ϫ C3H7], 436 (10), 342 (42), 340
(18), 237 (26), 185 (18), 159 (15). C28H27F6NO (507.5): calcd. C
66.27, H 5.36; found C 66.58, H 5.68.
5-(Dimethylamino)-3-ethoxy-5-isopropyl-1-phenyl-2-(phenylethynyl)-
1,3-cyclopentadiene (7dahz1), 5-(Dimethylamino)-3-ethoxy-5-isopro-
eluting with pentane/Et2O (from 20:1 to 1:1) gave 172 mg (17%) of pyl-2-phenyl-1-(phenylethynyl)-1,3-cyclopentadiene (8dahz1) and 5-
17dah4z [Rf ϭ 0.89 (pentane/Et2O, 3:1)], 68 mg (7%) of 7dah4z
[Rf ϭ 0.84 (pentane/Et2O, 3:1)] and 501 mg (49%) of 8dah4z [Rf ϭ
0.31 (pentane/Et2O, 3:1)] as yellow oils. 7dah4z: IR (film): ν˜ ϭ
(Dimethylamino)-2-ethoxy-4-isopropyl-5-phenyl-1-(phenylethynyl)-
1,3-cyclopentadiene (17dahz1): According to GP2A, a solution of
complex 3da (723 mg, 2.00 mmol) in pyridine (40 mL) was treated
2979 cmϪ1 (CϪH), 2187 (CϵC), 1653 (CϭC), 1616, 1559, 1457, with 1,4-diphenylbutadiyne (1hz1) (607 mg, 3.00 mmol), and the
1
3
1323, 1126, 1062. H NMR (250 MHz, CDCl3): δ ϭ 0.75 (d, J ϭ
mixture was stirred at 80 °C for 3 days. Chromatography on alumi-
6.8 Hz, 3 H, iPr-H), 0.81 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 1.47 (t, 3J ϭ num oxide (60 g, activity grade II) eluting with pentane/Et2O (from
7.0 Hz, 3 H, OCH2CH3), 2.33 [s, 6 H, N(CH3)2], 2.37 (sept, J ϭ 20:1 to 1:1) gave 67 mg (9%) of 17dahz1 [Rf ϭ 0.81 (pentane/Et2O,
3
740
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
3:1)] as a yellow solid, 163 mg (22%) of 7dahz1 [Rf ϭ 0.67 (pentane/
IR (film): ν˜ ϭ 2926 cmϪ1 (CϪH), 1734, 1700 (CϭO), 1653 (CϭC),
Et2O, 3:1)] as a yellow solid and 278 mg (37%) of 8dahz1 [Rf ϭ 1550, 1457, 1096, 804, 668, 641. 1H NMR (300 MHz, CDCl3): δ ϭ
0.31 (pentane/Et2O, 3:1)] as a yellow oil. The structures of all three
compounds were assigned on the basis of HH COSY, HH NOESY
and CH COSY spectra.
0.89 (t, 3J ϭ 7.5 Hz, 3 H, CH2CH2CH3), 0.95Ϫ1.25 (m, 2 H, 4Ј-
H), 1.25 [s, 9 H, C(CH3)3], 1.65Ϫ2.08 (m, 6 H, 3Ј-H, CH2CH2CH3),
2.17 (AB, d, 2J ϭ 18.0 Hz, 1 H, 5-H), 2.48Ϫ2.58 (m, 1 H, 5Ј-H),
2.60Ϫ2.70 (m, 1 H, 5Ј-H), 2.65 (AB, d, 2J ϭ 18.0 Hz, 1 H, 5-H),
7dahz1: 1H NMR (250 MHz, CDCl3): δ ϭ 0.84 (d, 3J ϭ 6.8 Hz,
3 H, iPr-H), 0.90 (d, 3J ϭ 6.8 Hz, 3 H, iPr-H), 1.51 (t, 3J ϭ 7.0 Hz,
3 H, OCH2CH3), 2.38 [s, 6 H, N(CH3)2], 2.43 (sept, 3J ϭ 6.8 Hz,
1 H, iPr-H), 4.05 (q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.94 (s, 1 H, 4-
2
3
2
3.12 (dd, J ϭ 9.0, J ϭ 6.0 Hz, 1 H, CH2OCH3), 3.26 (dd, J ϭ
3
9.0, J ϭ 6.0 Hz, 1 H, CH2OCH3), 3.28 (s, 3 H, OCH3), 3.52 (mc,
1 H, 2Ј-H), 6.05 (s, 1 H, 2-H) ppm. 13C NMR (75.5 MHz, CDCl3,
plus APT): δ ϭ 14.3 (ϩ, CH2CH2CH3), 18.1 (Ϫ, CH2CH2CH3),
21.8 (Ϫ, C-4Ј), 27.6 (Ϫ, C-3Ј), 31.2 [ϩ, C(CH3)3], 36.3 [Ϫ,
C(CH3)3], 38.3 (Ϫ, CH2CH2CH3), 43.9 (Ϫ, C-5), 44.9 (Ϫ, C-5Ј),
55.9, 59.1 (ϩ, C-2Ј, OCH3), 70.5 (Ϫ, C-4), 77.2 (Ϫ, CH2OCH3),
132.3 (ϩ, C-2), 192.3 (Ϫ, C-3), 207.1 (Ϫ, C-1) ppm. MS (70 eV):
m/z (%) ϭ 239 (1) [Mϩ], 278 (1), 248 (72), 179 (19), 153 (18), 84
(35), 70 (100) [C4H8Nϩ]. HRMS (EI) calcd. for C18H31NO2:
293.2354 (correct HRMS).
3
4
H), 7.30Ϫ7.51 (m, 8 H, PhϪH), 8.06 (dd, J ϭ 7.0, J ϭ 1.5 Hz,
2 H, 2Ј,6Ј-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
14.4 (ϩ, OCH2CH3), 16.8 (ϩ, iPr-C), 17.5 (ϩ, iPr-C), 31.1 (ϩ, iPr-
C), 40.0 [ϩ, N(CH3)2], 65.0 (Ϫ, OCH2CH3), 80.5 (Cquat., C-5), 83.9,
94.6 (Cquat., CϵC), 98.2 (ϩ, C-4), 120.5, 123.4 (Cquat., PhϪC),
127.5, 127.6, 128.0, 128.1, 128.9, 131.6 (ϩ, PhϪC), 137.2 (Cquat.
,
C-2), 154.1 (Cquat., C-1), 156.8 (Cquat., C-3) ppm. MS (70 eV): m/z
(%) ϭ 371 (100) [Mϩ], 356 (12), 342 (59), 328 (78) [Mϩ Ϫ C3H7],
326 (90), 299 (16), 284 (17), 202 (13). HRMS (EI) calcd. for
C26H29NO: 371.2349 (correct HRMS).
2nd Stereoisomer: IR (film): ν˜ ϭ 2957 cmϪ1 (CϪH), 1996, 1696
1
(CϭO), 1582, 1462, 1066, 882, 641. H NMR (250 MHz, CDCl3):
3
δ ϭ 0.91 (t, J ϭ 7.0 Hz, 3 H, CH2CH2CH3), 0.97Ϫ1.22 (m, 2 H,
8dahz1: IR (film): ν˜ ϭ 2978 cmϪ1 (CϪH), 2870 (CϪH), 2185
4Ј-H), 1.29 [s, 9 H, C(CH3)3], 1.60Ϫ2.03 (m, 6 H, 3Ј-H,
CH2CH2CH3), 2.28Ϫ2.43 (m, 1 H, 5Ј-H), 2.31 (AB, d, 2J ϭ
17.4 Hz, 1 H, 5-H), 2.41 (AB, d, 2J ϭ 18.0 Hz, 1 H, 5-H),
2.58Ϫ2.65 (m, 1 H, 5Ј-H), 2.96Ϫ3.15 (m, 2 H, 2Ј-H, CH2OCH3),
3.33Ϫ3.38 (m, 1 H, CH2OCH3), 3.34 (s, 3 H, OCH3), 6.08 (s, 1 H,
2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.2
(ϩ, CH2CH2CH3), 18.0 (Ϫ, CH2CH2CH3), 23.6 (Ϫ, C-4Ј), 29.1 (Ϫ,
1
(CϵC), 1617 (CϭC), 1576, 1485, 1443, 1211, 1054, 755. H NMR
3
(250 MHz, CDCl3): δ ϭ 1.00 (d, J ϭ 6.7 Hz, 3 H, iPr-H), 1.22 (d,
3J ϭ 6.7 Hz, 3 H, iPr-H), 1.44 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3),
3
2.63 [s, 6 H, N(CH3)2], 2.67 (sept, J ϭ 6.8 Hz, 1 H, iPr-H), 4.06
(q, 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.97 (s, 1 H, 4-H), 7.30Ϫ7.51 (m,
8 H, PhϪH), 7.95 (dd, 3J ϭ 7.0, 4J ϭ 1.5 Hz, 2 H, 2ЈЈЈ,6ЈЈЈ-H) ppm.
13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.4 (ϩ,
OCH2CH3), 16.9 (ϩ, iPr-C), 18.7 (ϩ, iPr-C), 30.3 (ϩ, iPr-C), 39.3
[ϩ, N(CH3)2], 65.0 (Ϫ, OCH2CH3), 78.3 (Cquat., C-5), 87.6, 99.7
(Cquat., CϵC), 102.8 (ϩ, C-4), 123.5, 128.2 (Cquat., PhϪC), 127.6,
127.9 ϫ 2, 128.6, 129.0, 130.9 (ϩ, PhϪC), 132.5 (Cquat., C-2), 144.6
(Cquat., C-1), 157.9 (Cquat., C-3) ppm. MS (70 eV): m/z (%) ϭ 371
(17) [Mϩ], 342 (13), 328 (100) [Mϩ Ϫ C3H7], 300 (17). HRMS (EI)
calcd. for C26H29NO: 371.2349 (correct HRMS).
C-3Ј), 31.4 [ϩ, C(CH3)3], 36.1 [Cquat., C(CH3)3], 40.1 (Ϫ,
CH2CH2CH3), 42.4 (Ϫ, C-5), 49.8 (Ϫ, C-5Ј), 58.3, 59.0 (ϩ, C-2Ј,
OCH3), 73.3 (Cquat., C-4), 77.8 (Ϫ, CH2OCH3), 133.4 (ϩ, C-2),
191.3 (Cquat., C-3), 206.7 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ
239 (1) [Mϩ], 278 (1), 248 (54), 179 (19), 138 (12), 123 (17), 84 (14),
70 (100) [C4H8Nϩ]. C18H31NO2: calcd. C 73.67, H 10.65, N 4.77;
found C 73.70, H 10.68, N 4.82.
(4R,2ЈS)- and (4S,2ЈS)-4-[2Ј-(Methoxymethyl)pyrrolidino]-2,3-di-
methyl-4-propyl-2-cyclopentenone (21beaa): According to GP2A, a
solution of complex 3be (179 mg, 0.42 mmol) in pyridine (8 mL)
was treated with 2-butyne (1aa) (67.3 mg, 1.24 mmol), and the mix-
ture was stirred at 80 °C for 3 days. Chromatography on aluminum
oxide (10 g, activity grade II) eluting with pentane/Et2O (from 20:1
to 1:2) gave 108 mg (98%) of 21beaa [Rf ϭ 0.10 (pentane/Et2O, 3:1);
dr 1.9:1] as a colorless oil. IR (film): ν˜ ϭ 2926 cmϪ1 (CϪH), 1700
(CϭO), 1653 (CϭC), 1457, 1383, 1321, 1197, 1112, 971, 923, 734,
666. Major Stereoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ
0.70Ϫ0.98 (m, 2 H, 4Ј-H), 0.84 (t, 3J ϭ 3.8 Hz, 3 H, CH2CH2CH3),
1.50Ϫ2.05 (m, 6 H, 3Ј-H, CH2CH2CH3), 1.64 (s, 3 H, CH3), 1.88
(s, 3 H, CH3), 2.10Ϫ2.57 (m, 2 H, 5Ј-H), 2.21 (AB, d, 2J ϭ 18.7 Hz,
1 H, 5-H), 2.30 (AB, d, 2J ϭ 18.7 Hz, 1 H, 5-H), 3.00 (mc, 2 H,
CH2OCH3), 3.28 (mc, 1 H, 2Ј-H), 3.21 (s, 3 H, OCH3) ppm. 13C
NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 7.8, 12.4 (ϩ, CH3),
14.5 (ϩ, CH2CH2CH3), 17.6 (Ϫ, CH2CH2CH3), 23.3 (Ϫ, C-4Ј),
29.0 (Ϫ, C-3Ј), 39.9 (Ϫ, CH2CH2CH3), 40.7 (Ϫ, C-5), 48.8 (Ϫ, C-
5Ј), 58.2, 58.9 (ϩ, C-2Ј, OCH3), 69.0 (Cquat., C-4), 77.9 (Ϫ,
17dahz1: IR (film): ν˜ ϭ 2964 cmϪ1 (CϪH), 2868 (CϪH), 2183
1
(CϵC), 1626 (CϭC), 1569, 1488, 1333, 1070, 1030, 753. H NMR
3
(250 MHz, CDCl3): δ ϭ 0.32 (d, J ϭ 6.8 Hz, 3 H, iPr-H), 1.13 (d,
3J ϭ 6.8 Hz, 3 H, iPr-H), 1.48 (t, 3J ϭ 7.1 Hz, 3 H, OCH2CH3),
2.48 (sept, 3J ϭ 6.8 Hz, 1 H, iPr-H), 2.50 [s, 6 H, N(CH3)2], 4.67
(q, 3J ϭ 7.1 Hz, 1 H, OCH2CH3), 4.68 (q, 3J ϭ 7.0 Hz, 1 H,
OCH2CH3), 5.75 (d, 4J ϭ 0.7 Hz, 1 H, 3-H), 7.17Ϫ7.34 (m, 8 H,
PhϪH), 7.61Ϫ7.66 (m, 2 H, 2ЈЈЈ,6ЈЈЈ-H) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 15.6 (ϩ, OCH2CH3), 22.6
(ϩ, iPr-C), 24.7 (ϩ, iPr-C), 25.7 (ϩ, iPr-C), 40.3 [ϩ, N(CH3)2],
66.1 (Ϫ, OCH2CH3), 83.2 (Cquat., C-5), 87.4, 95.5, 95.8 (Cquat., C-
1, CϵC), 119.9 (ϩ, C-3), 124.9 (Cquat., PhϪC), 126.8, 126.9, 127.8,
128.1, 128.2, 130.1 (ϩ, PhϪC), 139.9 (Cquat., PhϪC), 164.0 (Cquat.
,
C-4), 167.0 (Cquat., C-2) ppm. MS (70 eV): m/z (%) ϭ 371 (100)
[Mϩ], 356 (12), 342 (52), 328 (80) [Mϩ Ϫ C3H7], 326 (92), 299 (14),
284 (13), 202 (13). HRMS (EI) calcd. for C26H29NO: 371.2349 (cor-
rect HRMS).
(4R,2ЈS)- and (4S,2ЈS)-3-tert-Butyl-4-[2Ј-(methoxymethyl)pyrroli-
dino]-4-propyl-2-cyclopentenone (21bef): According to GP2B, to a CH2OCH3), 138.6 (Cquat., C-2), 172.2 (Cquat., C-3), 206.9 (Cquat.
,
solution of complex 3be (146 mg, 0.34 mmol) in acetonitrile (7 mL)
at 80 °C was slowly added a solution of 3,3-dimethylbutyne (1f)
(83.4 mg, 1.02 mmol) in acetonitrile (2 mL) over a period of 8 h,
C-1). Minor Stereoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ
0.70Ϫ0.98 (m, 2 H, 4Ј-H), 0.84 (t, 3J ϭ 3.8 Hz, 3 H, CH2CH2CH3),
1.50Ϫ2.05 (m, 6 H, 3Ј-H, CH2CH2CH3), 1.66 (s, 3 H, CH3), 1.92
and the mixture was stirred at this temperature for an additional (s, 3 H, CH3), 2.10Ϫ2.57 (m, 2 H, 5Ј-H), 2.18 (AB, d, 2J ϭ 18.8 Hz,
16 h. Chromatography on aluminum oxide (10 g, activity grade II)
eluting with pentane/Et2O (from 20:1 to 1:2) gave 11 mg (11%) of
1 H, 5-H), 2.32 (AB, d, 2J ϭ 18.8 Hz, 1 H, 5-H), 3.00 (mc, 2 H,
CH2OCH3), 3.21 (s, 3 H, OCH3), 3.28 (mc, 1 H, 2Ј-H) ppm. 13C
1st stereoisomer [Rf ϭ 0.28 (pentane)] and 43 mg (43%) of 2nd ste- NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 7.8, 13.2 (ϩ, CH3),
reoisomer [Rf ϭ 0.20 (pentane)] as colorless oils. 1st Stereoisomer: 14.5 (ϩ, CH2CH2CH3), 17.4 (Ϫ, CH2CH2CH3), 23.6 (Ϫ, C-4Ј),
Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
741

A. de Meijere et al.
29.0 (Ϫ, C-3Ј), 39.1 (Ϫ, CH2CH2CH3), 40.3 (Ϫ, C-5), 49.9 (Ϫ, C- CO2CH3) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
FULL PAPER
5Ј), 56.7, 58.7 (ϩ, C-2Ј, OCH3), 68.7 (Cquat., C-4), 75.9 (Ϫ,
CH2OCH3), 138.6 (Cquat., C-2), 172.2 (Cquat., C-3), 206.9 (Cquat.
C-1) ppm. MS (70 eV): m/z (%) ϭ 222 (5) [Mϩ], 278 (1), 248 (54),
7.7, 12.4 (ϩ, CH3), 14.2 (ϩ, CH2CH2CH3), 17.4 (Ϫ,
CH2CH2CH3), 24.2 (Ϫ, C-4Ј), 31.3 (Ϫ, C-3Ј), 39.0, 39.6 (Ϫ,
CH2CH2CH3, C-5), 48.4 (Ϫ, C-5Ј), 51.7, 60.7 (ϩ, C-2Ј, OCH3),
,
179 (19), 138 (12), 123 (17), 84 (14), 70 (100) [C4H8Nϩ]. 68.6 (Cquat., C-4), 138.3 (Cquat., C-2), 172.1 (Cquat., C-3), 176.8
C16H27NO2 (265.4): calcd. C 72.41, H 10.25; found C 71.52,
H 10.10.
(Cquat., CO2CH3), 206.3 (Cquat., C-1). Minor Stereoisomer: 1H
NMR (250 MHz, CDCl3): δ ϭ 0.62Ϫ0.95 (m, 2 H, CH2CH2CH3),
0.81 (t, 3J ϭ 3.5 Hz, 3 H, CH2CH2CH3), 1.47Ϫ1.98 (m, 6 H, 3Ј,4Ј-
H, CH2CH2CH3), 1.60 (s, 3 H, CH3), 1.74 (s, 3 H, CH3), 2.13 (AB,
(4R,2ЈS)- and (4S,2ЈS)-3-tert-Butyl-4-[2Ј-(methoxycarbonyl)pyrroli-
dino]-4-propyl-2-cyclopentenone (21bff): According to GP2B, to a
solution of complex 3bf (197 mg, 0.44 mmol) in acetonitrile (9 mL)
at 80 °C was slowly added a solution of 3,3-dimethylbutyne (1f)
(109 mg, 1.33 mmol) in acetonitrile (2 mL) over a period of 8 h,
and the mixture was stirred at this temperature for an additional
12 h. Chromatography on aluminum oxide (10 g, activity grade II)
eluting with pentane/Et2O (from 20:1 to 1:2) gave 98 mg (72%) of
21bff [Rf ϭ 0.12 (pentane/Et2O, 1:1); dr 2.3:1] as a colorless oil. IR
(film): ν˜ ϭ 2995 cmϪ1 (CϪH), 2873, 1740, 1700 (CϭO), 1653 (Cϭ
C), 1559, 1457, 1009, 732, 667. Major Stereoisomer: 1H NMR
2
2
d, J ϭ 18.7 Hz, 1 H, 5-H), 2.27 (AB, d, J ϭ 18.7 Hz, 1 H, 5-H),
2.35Ϫ2.52 (m, 1 H, 5Ј-H), 3.05Ϫ3.16 (m, 1 H, 5Ј-H), 3.30 (dd, 3J ϭ
6.5, 3J ϭ 1.6 Hz, 1 H, 2Ј-H), 3.56 (s, 3 H, CO2CH3) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 7.7, 12.3 (ϩ, CH3), 14.3 (ϩ,
CH2CH2CH3), 17.4 (Ϫ, CH2CH2CH3), 23.9 (Ϫ, C-4Ј), 30.9 (Ϫ, C-
3Ј), 39.2, 39.3 (Ϫ, CH2CH2CH3, C-5), 48.8 (Ϫ, C-5Ј), 51.2, 59.3 (ϩ,
C-2Ј, OCH3), 68.2 (Cquat., C-4), 138.8 (Cquat., C-2), 172.2 (Cquat., C-
3), 175.9 (Cquat., CO2CH3), 206.5 (Cquat., C-1) ppm. MS (70 eV):
m/z (%) ϭ 279 (5) [Mϩ], 250 (1), 236 (100) [Mϩ Ϫ C3H7], 220 (48),
151 (28), 109 (27), 84 (51), 70 (85) [C4H8Nϩ]. C16H25NO3 (279.4):
calcd. C 68.79, H 9.02; found C 67.72, H 9.18.
3
(250 MHz, CDCl3): δ ϭ 0.83 (t, J ϭ 7.0 Hz, 3 H, CH2CH2CH3),
0.95Ϫ1.09 (m, 2 H, CH2CH2CH3), 1.33 [s, 9 H, C(CH3)3],
1.45Ϫ2.12 (m, 6 H, 3Ј,4Ј-H, CH2CH2CH3), 2.08 (AB, d, 2J ϭ
(5R,2ЈR)- and (5S,2ЈR)-5-[2Ј-(Diethylaminocarbonyl)pyrrolidino]-3-
18.9 Hz, 1 H, 5-H), 2.38Ϫ2.55 (m, 1 H, 5Ј-H), 2.73Ϫ2.86 (m, 1 H, ethoxy-1,2-dimethyl-5-propyl-1,3-cyclopentadiene (7bgaa): Accord-
5Ј-H), 2.93 (AB, d, 2J ϭ 18.9 Hz, 1 H, 5-H), 3.53 (dd, 3J ϭ 9.2,
ing to GP2A, a solution of complex 3bg (201 mg, 0.41 mmol) in
3J ϭ 4.3 Hz, 1 H, 2Ј-H), 3.69 (s, 3 H, CO2CH3), 6.07 (s, 1 H, 2- pyridine (8 mL) was treated with 2-butyne (1aa) (67.3 mg,
H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.0 (ϩ, 1.24 mmol), and the mixture was stirred at 82 °C for 3 days. Chro-
CH2CH2CH3), 18.0 (Ϫ, CH2CH2CH3), 24.6 (Ϫ, C-4Ј), 31.3 [ϩ,
C(CH3)3], 31.5 (Ϫ, C-3Ј), 36.1 [Cquat. C(CH3)3], 39.2 (Ϫ, with pentane/Et2O (from 20:1 to 1:2) gave 50 mg (35%) of 1st ste-
CH2CH2CH3), 42.0 (Ϫ, C-5), 49.6 (Ϫ, C-5Ј), 51.7, 61.3 (ϩ, C-2Ј, reoisomer [Rf ϭ 0.16 (pentane/Et2O, 1:3)] and 55 mg (39%) of 2nd
matography on aluminum oxide (10 g, activity grade II) eluting
,
OCH3), 72.8 (Cquat., C-4), 133.1 (ϩ, C-2), 176.8 (Cquat., CO2CH3),
stereoisomer [Rf ϭ 0.09 (pentane/Et2O, 1:3)] as colorless oils. 1st
191.2 (Cquat., C-3), 206.0 (Cquat., C-1). Minor Stereoisomer: 1H Stereoisomer: IR (film): ν˜ ϭ 2960 cmϪ1, 2872 (CϪH), 1700 (CϭO),
NMR (250 MHz, CDCl3): δ ϭ 0.83 (t, 3J
ϭ
7.0 Hz, 3 H,
1653 (CϭC), 1457, 1258, 1132, 795. H NMR (250 MHz, CDCl3):
1
3
CH2CH2CH3), 0.95Ϫ1.09 (m, 2 H, CH2CH2CH3), 1.23 [s, 9 H,
δ ϭ 0.87 (t, J ϭ 7.1 Hz, 3 H, CH2CH2CH3), 0.72Ϫ1.38 (m, 4 H,
C(CH3)3], 1.45Ϫ2.12 (m, 6 H, 3Ј,4Ј-H, CH2CH2CH3), 2.26 (AB, d, CH2CH2CH3), 1.09 (t, 3J ϭ 7.0 Hz, 3 H, NCH2CH3), 1.13 (t, J ϭ
2J ϭ 18.5 Hz, 1 H, 5-H), 2.37 (AB, d, 2J ϭ 18.5 Hz, 1 H, 5-H), 7.1 Hz, 3 H, NCH2CH3), 1.31 (t, 3J ϭ 7.1 Hz, 3 H, OCH2CH3),
2.57Ϫ2.70 (m, 1 H, 5Ј-H), 2.89Ϫ3.01 (m, 1 H, 5Ј-H), 3.53 (dd, 3J ϭ 1.40Ϫ2.10 (m, 4 H, 3Ј,4Ј-H), 1.67 (s, 6 H, CH3), 2.50Ϫ2.62 (m, 1 H,
3
3
9.2, J ϭ 4.3 Hz, 1 H, 2Ј-H), 3.65 (s, 3 H, CO2CH3), 6.06 (s, 1 H, 5Ј-H), 2.82Ϫ2.90 (mc, 1 H, 5Ј-H), 3.15Ϫ3.71 [mc, 5 H, 2Ј-H,
2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 14.1 N(CH2CH3)2], 3.79 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.70 (s, 1 H,
3
(ϩ, CH2CH2CH3), 18.2 (Ϫ, CH2CH2CH3), 22.1 (Ϫ, C-4Ј), 29.4 (Ϫ, 4-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.6 (ϩ,
C-3Ј), 31.0 [ϩ, C(CH3)3], 36.1 [Cquat.
CH2CH2CH3), 43.0 (Ϫ, C-5), 45.2 (Ϫ, C-5Ј), 51.4, 58.7 (ϩ, C-2Ј, N(CH2CH3)2, OCH2CH3], 16.7 (Ϫ, CH2CH2CH3), 24.5 (Ϫ, C-4Ј),
OCH3), 70.4 (Cquat., C-4), 132.3 (ϩ, C-2), 176.4 (Cquat., CO2CH3), 31.4 (Ϫ, C-3Ј), 37.3 (Ϫ, CH2CH2CH3), 40.4, 40.8 [Ϫ,
190.5 (Cquat., C-3), 206.6 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ N(CH2CH3)2], 47.7 (Ϫ, C-5Ј), 61.0 (ϩ, C-2Ј), 64.4 (Ϫ, OCH2CH3),
, C(CH3)3], 38.7 (Ϫ, CH3), 11.0 (ϩ, CH3), 12.5, 14.4, 14.5, 14.6 [ϩ, CH2CH2CH3,
307 (2) [Mϩ], 292 (4) [Mϩ Ϫ CH3], 264 (4) [Mϩ Ϫ C3H7], 250 (7)
74.3 (Cquat., C-5), 97.4 (ϩ, C-4), 130.3 (Cquat., C-2), 142.8 (Cquat.,
[Mϩ Ϫ C4H9], 248 (18) [Mϩ Ϫ OCOCH3], 179 (12), 135 (10), 97 C-1), 160.1 (Cquat., C-3), 175.9 (Cquat., NCO) ppm. MS (70 eV):
(12), 70 (100) [C4H8Nϩ], 59 (14) [OCOCH3ϩ], 57 (9) [C4H9ϩ], 43 m/z (%) ϭ 348 (7) [Mϩ], 319 (6), 248 (7), 220 (31), 179 (65), 151
(10) [C3H7ϩ]. C18H29NO3 (307.4): calcd. C 70.32, H 9.51, N 4.56;
found C 70.15, H 9.61, N 4.54.
(19), 109 (15), 84 (45), 70 (100) [C4H8Nϩ]. HRMS (EI) calcd. for
C21H36N2O2: 348.2276 (correct HRMS).
(4R,2ЈS)- and (4S,2ЈS)-4-[2Ј-(Methoxycarbonyl)pyrrolidino]-2,3-di-
methyl-4-propyl-2-cyclopentenone (21bfaa): According to GP2A, a
2nd Stereoisomer: IR (film): ν˜ ϭ 2961 cmϪ1, 2872 (CϪH), 1699
1
(CϭO), 1646 (CϭC), 1456, 1256, 1131, 731. H NMR (250 MHz,
solution of complex 3bf (191 mg, 0.43 mmol) in pyridine (9 mL) CDCl3): δ ϭ 0.74 (t, 3J ϭ 7.0 Hz, 3 H, CH2CH2CH3), 0.65Ϫ1.10
was treated with 2-butyne (1aa) (69.6 mg, 1.29 mmol), and the mix-
ture was stirred at 72 °C for 3.5 days. Chromatography on alumi-
(m, 4 H, CH2CH2CH3), 0.96 (t, 3J ϭ 7.1 Hz, 3 H, NCH2CH3), 1.00
(t, 3J ϭ 6.9 Hz, 3 H, NCH2CH3), 1.30 (t, 3J ϭ 7.0 Hz, 3 H,
num oxide (10 g, activity grade II) eluting with pentane/Et2O (from OCH2CH3), 1.40Ϫ2.20 (m, 4 H, 3Ј,4Ј-H), 1.49 (s, 3 H, CH3), 1.60
20:1 to 1:4) gave 94 mg (78%) of 21bfaa [Rf ϭ 0.71 (Et2O); dr 1.6:1] (s, 3 H, CH3), 2.49Ϫ3.70 [m, 7 H, 2Ј,5Ј-H, N(CH2CH3)2], 3.84 (q,
as a colorless oil. IR (film): ν˜ ϭ 2926 cmϪ1 (CϪH), 1700 (CϭO), 3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.78 (s, 1 H, 4-H) ppm. 13C NMR
1653 (CϭC), 1457, 1383, 1321, 1197, 1112, 971, 923, 734, 666.
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.7 (ϩ, CH3), 10.3 (ϩ, CH3),
1
Major Stereoisomer: H NMR (250 MHz, CDCl3): δ ϭ 0.62Ϫ0.95 13.0, 14.3, 14.47, 14.52 [ϩ, CH2CH2CH3, N(CH2CH3)2,
(m, 2 H, 4Ј-H), 0.76 (t, 3J ϭ 3.5 Hz, 3 H, CH2CH2CH3), 1.47Ϫ1.98 OCH2CH3], 16.2 (Ϫ, CH2CH2CH3), 24.8 (Ϫ, C-4Ј), 32.5 (Ϫ, C-3Ј),
(m, 6 H, 3Ј-H, CH2CH2CH3), 1.62 (s, 3 H, CH3), 1.90 (s, 3 H, 37.2 (Ϫ, CH2CH2CH3), 40.6, 41.1 [Ϫ, N(CH2CH3)2], 50.8 (Ϫ, C-
CH3), 2.14 (AB, d, 2J ϭ 17.3 Hz, 1 H, 5-H), 2.27 (AB, d, 2J ϭ
5Ј), 55.3 (ϩ, C-2Ј), 64.4 (Ϫ, OCH2CH3), 74.9 (Cquat., C-5), 94.5 (ϩ,
17.3 Hz, 1 H, 5-H), 2.17Ϫ2.32 (m, 1 H, 5Ј-H), 2.57Ϫ2.69 (m, 1 H, C-4), 130.2 (Cquat., C-2), 144.2 (Cquat., C-1), 161.4 (Cquat., C-3),
5Ј-H), 3.42 (dd, 3J ϭ 9.2, 3J ϭ 2.9 Hz, 1 H, 2Ј-H), 3.63 (s, 3 H, 175.2 (Cquat., NCO) ppm. MS (70 eV): m/z (%) ϭ 348 (2) [Mϩ],
742
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
319 (2), 248 (2), 179 (100), 151 (11), 70 (43) [C4H8Nϩ]. HRMS (EI) methylbutyne (1f) (204 mg, 2.48 mmol), and the mixture was stirred
1
calcd. for C21H36N2O2: 348.2276 (correct HRMS).
at 40 °C for 528 h. The H NMR spectrum of the crude product
showed two diastereomers in a ratio of 15:1. Chromatography on
aluminum oxide (30 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 3:1) gave 47 mg (21%) of diastereomerically pure 7iaf.
(4R,2ЈR,5ЈR)- and (4S,2ЈR,5ЈR)-4-(2Ј,5Ј-Dimethylpyrrolidino)-2,3-
dimethyl-4-propyl-2-cyclopentenone (21bhaa): According to GP2A,
a solution of complex 3bh (168 mg, 0.40 mmol) in pyridine (8 mL)
was treated with 2-butyne (1aa) (65.6 mg, 1.21 mmol), and the mix-
ture was stirred at 80 °C for 4 days. The 1H NMR spectrum of the
crude product showed two diastereomers in a ratio of 3:1. Chroma-
tography on aluminum oxide (10 g, activity grade II) eluting with
pentane/Et2O (from 20:1 to 1:2) gave 22 mg (22%) of 21bhaa [Rf ϭ
0.45 (pentane/Et2O, 3:1); dr 3:1] as a colorless oil. IR (film): ν˜ ϭ
2960 cmϪ1, 2872 (CϪH), 1700 (CϭO), 1653 (CϭC), 1457, 1375,
1074. 1H NMR (250 MHz, CDCl3): Major Product: δ ϭ 0.81Ϫ1.01
(m, 3 H, CH2CH2CH3), 0.86 (d, 3J ϭ 6.2 Hz, 6 H, CH3), 1.08Ϫ1.40
(m, 4 H, CH2CH2CH3), 1.43Ϫ2.05 (m, 4 H, 3Ј,4Ј-H), 1.66, 1.69 (s,
6 H, CH3), 2.17 (AB, d, 2J ϭ 19.2 Hz, 1 H, 5-H), 2.32 (AB, d, 2J ϭ
19.2 Hz, 1 H, 5-H), 3.10Ϫ3.34 (m, 2 H, 2Ј,5Ј-H). Minor Product:
Variation D: According to GP2A, a solution of complex 3ia
(350 mg, 0.93 mmol) in pyridine (19 mL) was treated with 3,3-di-
methylbutyne (1f) (228 mg, 2.78 mmol), and the mixture was stirred
1
at 20 °C for 336 h. The H NMR spectrum of the crude product
showed two diastereomers in a ratio of 15:1. Chromatography on
aluminum oxide (30 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 3:1) gave 41 mg (17%) of diastereomerically pure 7iaf.
5-(Dimethylamino)-3-ethoxy-5-(1Ј-methoxyethyl)-1-phenyl-1,3-
cyclopentadiene (7iah): According to GP2A, a solution of complex
3ia (333 mg, 0.88 mmol) in pyridine (18 mL) was treated with phen-
ylethyne (1h) (271 mg, 2.65 mmol), and the mixture was stirred at
80 °C for 42 h. The 1H NMR spectrum of the crude product
showed two diastereomers in a ratio of 30:1. Chromatography on
aluminum oxide (30 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 3:1) gave 54 mg (21%) of diastereomerically pure 7iah
[Rf ϭ 0.62 (pentane/Et2O, 3:1)] as a colorless oil. IR (film): ν˜ ϭ
2977 cmϪ1 (CϪH), 2822 (CϪH), 2782 (CϪH), 1622, 1577 (CϭC),
1446, 1372, 1135, 962, 854. 1H NMR (250 MHz, CDCl3): δ ϭ 0.72
3
δ ϭ 0.81Ϫ1.01 (m, 3 H, CH2CH2CH3), 0.90 (d, J ϭ 9.8 Hz, 6 H,
CH3), 1.08Ϫ1.40 (m, 4 H, CH2CH2CH3), 1.43Ϫ2.05 (m, 4 H, 3Ј,4Ј-
2
H), 1.64, 1.91 (s, 6 H, CH3), 2.48 (AB, d, J ϭ 19.7 Hz, 1 H, 5-H),
2
2.63 (AB, d, J ϭ 19.7 Hz, 1 H, 5-H), 3.10Ϫ3.34 (m, 2 H, 2Ј,5Ј-H)
ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): Major Product:
δ ϭ 7.9, 13.7 (ϩ, CH3), 14.6 (ϩ, CH2CH2CH3), 17.3 (Ϫ,
CH2CH2CH3), 31.2 ϫ 2 (ϩ, 2Ј,5Ј-CH3), 31.9 ϫ 2 (Ϫ, C-3Ј,4Ј), 39.0
(Ϫ, CH2CH2CH3), 41.5 (Ϫ, C-5), 52.9, 55.2 (ϩ, C-2Ј,5Ј), 65.9
3
3
[d, J ϭ 6.2 Hz, 3 H, 2Ј-H), 1.48 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3),
2.28 [s, 6 H, N(CH3)2], 3.31 (s, 3 H, OCH3), 3.74 (q, J ϭ 6.2 Hz,
3
(Cquat., C-4), 137.2 (Cquat., C-2), 175.4 (Cquat., C-3), 206.9 (Cquat.
,
1 H, 1Ј-H), 3.96 (m, 2 H, OCH2CH3), 5.19 (d, 4J ϭ 1.9 Hz, 1 H, 4-
H), 6.38 (d, 4J ϭ 1.9 Hz, 1 H, 2-H), 7.15Ϫ7.38 (m, 3 H, PhϪH),
7.70Ϫ7.90 (m, 2 H, PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3,
plus DEPT): δ ϭ 13.8, 14.5 (ϩ, C-2Ј, OCH2CH3), 41.6 [ϩ,
N(CH3)2], 56.3 (ϩ, OCH3), 64.7 (Ϫ, OCH2CH3), 80.8 (ϩ, C-1Ј),
82.7 (Cquat., C-5), 95.8 (ϩ, C-4), 125.3 (ϩ, C-2), 126.2, 127.4, 128.4
C-1) ppm. MS (70 eV): m/z (%) ϭ 249 (9) [Mϩ], 206 (100)
[Mϩ Ϫ C3H7], 151 (37), [Mϩ Ϫ C6H12N], 109 (16), 84 (46). HRMS
(EI) calcd. for C16H27NO: 249.2092 (correct HRMS).
1-tert-Butyl-5-(dimethylamino)-3-ethoxy-5-(1Ј-methoxyethyl)-1,3-
cyclopentadiene (7iaf). Variation A: According to GP2A, a solution
of complex 3ia (400 mg, 1.06 mmol) in pyridine (20 mL) was
treated with 3,3-dimethylbutyne (1f) (261 mg, 3.18 mmol), and the
(ϩ, PhϪC), 135.1 (Cquat., PhϪC), 150.4 (Cquat., C-1), 160.5 (Cquat.
,
C-3) ppm. MS (70 eV): m/z (%) ϭ 287 (13) [Mϩ], 272 (4), 258 (3),
[Mϩ Ϫ C2H5], 228 (9), 200 (25). C18H25NO2 (287.4): calcd. C 75.22,
H 8.77; found C 75.13, H 8.88.
1
mixture was stirred at 80 °C for 24 h. The H NMR spectrum of
the crude product showed two diastereomers in a ratio of 7.1:1.
Chromatography on aluminum oxide (30 g, activity grade II) elut-
ing with pentane/Et2O (from 20:1 to 3:1) gave 83 mg (29%) of dia-
stereomerically pure 7iaf [Rf ϭ 0.62 (pentane/Et2O, 3:1)] as a color-
less oil. IR (film): ν˜ ϭ 2977 cmϪ1 (CϪH), 2784 (CϪH), 1628 (Cϭ
C), 1572, 1457, 1372, 1271, 1084, 969, 851. 1H NMR (250 MHz,
CDCl3): δ ϭ 0.89 [d, 3J ϭ 6.0 Hz, 3 H, 2Ј-H), 1.18 [s, 9 H,
C(CH3)3], 1.32 (t, 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 2.23 [s, 6 H,
N(CH3)2], 3.28 (s, 3 H, OCH3), 3.75 (q, 3J ϭ 6.0 Hz, 1 H, 1Ј-H),
3.84 (pq, 3J ϭ 7.0 Hz, 1 H, OCH2CH3), 3.91 (pq, 3J ϭ 7.0 Hz, 1 H,
5-(Dimethylamino)-3-ethoxy-1-phenyl-5-(2Ј-trimethylsiloxypropyl)-
1,3-cyclopentadiene (7jah): According to GP2A, a solution of com-
plex 3ja (358 mg, 0.80 mmol) in pyridine (16 mL) was treated with
phenylethyne (1h) (245 mg, 2.40 mmol), and the mixture was stirred
at 80 °C for 4 days. Chromatography on aluminum oxide (30 g,
activity grade II) eluting with pentane/Et2O (from 20:1 to 3:1) gave
137 mg (48%) of 7jah [Rf ϭ 0.88 (pentane/Et2O, 3:1); dr 1.9:1] as a
colorless oil. IR (film): ν˜ ϭ 2975 cmϪ1 (CϪH), 2823 (CϪH), 2782
(CϪH), 1622, 1576 (CϭC), 1445, 1371, 1248, 1106, 977, 839. Major
Stereoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ 0.01 [s, 9 H,
Si(CH3)3], 0.72 [d, 3J ϭ 6.4 Hz, 3 H, 3Ј-H), 1.39 (t, 3J ϭ 7.0 Hz,
3 H, OCH2CH3), 1.92 (dd, 2J ϭ 12.8, 3J ϭ 6.4 Hz, 1 H, 1Ј-H), 2.19
[s, 6 H, N(CH3)2], 2.35 (dd, 2J ϭ 12.8, 3J ϭ 6.4 Hz, 1 H, 1Ј-H),
4
4
OCH2CH3), 4.87 (d, J ϭ 1.9 Hz, 1 H, 4-H), 5.84 (d, J ϭ 1.9 Hz,
1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
14.2, 14.5 (ϩ, C-2Ј, OCH2CH3), 31.0 [ϩ, C(CH3)3], 34.4 [Cquat.
,
C(CH3)3], 41.5 [ϩ, N(CH3)2], 55.8 (ϩ, OCH3), 64.3 (Ϫ,
OCH2CH3), 79.5 (ϩ, C-1Ј), 82.7 (Cquat., C-5), 94.8 (ϩ, C-4), 125.0
(ϩ, C-2), 159.1 (Cquat., C-1), 162.0 (Cquat., C-3) ppm. MS (70 eV):
m/z (%) ϭ 267 (18) [Mϩ], 252 (4), 236 (3), 222 (9) [Mϩ Ϫ OC2H5],
210 (37), 208 (100), 193 (11), 180 (10), 59 (19). C16H29NO2 (267.4):
calcd. C 71.87, H 10.93; found C 71.94, H 11.10.
3
3.30 (mc, 1 H, 2Ј-H), 3.92 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 5.06
(d, 4J ϭ 1.6 Hz, 1 H, 4-H), 6.97 (d, 4J ϭ 1.9 Hz, 1 H, 2-H),
7.10Ϫ7.35 (m, 4 H, PhϪH), 7.75Ϫ7.90 (m, 1 H, PhϪH) ppm. 13C
NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 0.37 [ϩ, Si(CH3)3],
14.5 (ϩ, OCH2CH3), 25.6 (ϩ, C-3Ј), 40.0 [ϩ, N(CH3)2], 45.3 (Ϫ,
C-1Ј), 64.5 (Ϫ, OCH2CH3), 66.0 (ϩ, C-2Ј), 76.3 (Cquat., C-5), 99.2
(ϩ, C-4), 124.7 (ϩ, C-2), 126.2, 126.6, 127.5 (ϩ, PhϪC), 134.7
(Cquat., PhϪC), 149.9 (Cquat., C-1), 158.9 (Cquat., C-3). Minor Ste-
reoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ Ϫ0.31 [s, 9 H,
Si(CH3)3], 0.94 [d, 3J ϭ 6.4 Hz, 3 H, 3Ј-H), 1.39 (t, 3J ϭ 7.0 Hz,
3 H, OCH2CH3), 1.92 (dd, 2J ϭ 12.8, 3J ϭ 6.4 Hz, 1 H, 1Ј-H), 2.19
[s, 6 H, N(CH3)2], 2.35 (dd, 2J ϭ 12.8, 3J ϭ 6.4 Hz, 1 H, 1Ј-H),
Variation B: According to GP2A, a solution of complex 3ia
(300 mg, 0.80 mmol) in pyridine (16 mL) was treated with 3,3-di-
methylbutyne (1f) (196 mg, 2.39 mmol), and the mixture was stirred
at 60 °C for 42 h. The 1H NMR spectrum of the crude product
showed two diastereomers in a ratio of 8.5:1. Chromatography on
aluminum oxide (30 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 3:1) gave 70 mg (33%) of diastereomerically pure 7iaf.
3
Variation C: According to GP2A, a solution of complex 3ia
(313 mg, 0.83 mmol) in pyridine (12 mL) was treated with 3,3-di-
3.30 (mc, 1 H, 2Ј-H), 3.92 (q, J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.96
(d, 4J ϭ 1.6 Hz, 1 H, 4-H), 6.89 (d, 4J ϭ 1.9 Hz, 1 H, 2-H),
Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
743

A. de Meijere et al.
FULL PAPER
7.10Ϫ7.35 (m, 4 H, PhϪH), 7.75Ϫ7.90 (m, 1 H, PhϪH) ppm. 13C (ϩ, OCH2CH3), 18.0 [Cquat., SiC(CH3)3], 25.7 [ϩ, SiC(CH3)3], 25.9
NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ0.3 [ϩ, Si(CH3)3], (ϩ, C-3Ј), 40.0 [ϩ, N(CH3)2], 45.6 (Ϫ, C-1Ј), 64.6 (Ϫ, OCH2CH3),
15.6 (ϩ, OCH2CH3), 25.6 (ϩ, C-3Ј), 39.8 [ϩ, N(CH3)2], 45.6 (Ϫ, 66.0 (ϩ, C-2Ј), 76.3 (Cquat., C-5), 98.8 (ϩ, C-4), 124.8 (ϩ, C-2),
C-1Ј), 64.7 (Ϫ, OCH2CH3), 65.6 (ϩ, C-2Ј), 75.3 (Cquat., C-5), 98.9 126.2, 127.3, 128.3 (ϩ, PhϪC), 134.8 (Cquat., PhϪC), 150.5 (Cquat.
(ϩ, C-4), 124.9 (ϩ, C-2), 126.6, 127.5, 128.3 (ϩ, PhϪC), 134.7 C-1), 159.4 (Cquat., C-3). Minor Stereoisomer: 1H NMR (250 MHz,
(Cquat., PhϪC), 150.1 (Cquat., C-1), 159.1 (Cquat., C-3) ppm. MS CDCl3): δ ϭ Ϫ0.05 (s, 3 H, SiCH3), Ϫ0.03 (s, 3 H, SiCH3), 0.65 (d,
(70 eV): m/z (%) ϭ 359 (45) [Mϩ], 330 (35) [Mϩ Ϫ C2H5], 242 (61), 3J ϭ 6.1 Hz, 3 H, 3Ј-H), 0.95 [s, 9 H, SiC(CH3)3], 1.32 (t, 3J ϭ
199 (28), 159 (26), 131 (100), 117 (31), 73 (60), 52 (88). 7.0 Hz, 3 H, OCH2CH3), 1.90Ϫ2.45 (m, 2 H, 1Ј-H), 2.20 [s, 6 H,
C21H33NO2Si (359.6): calcd. C 70.15, H 9.25; found C 70.43, N(CH3)2], 3.28 (mc, 1 H, 2Ј-H), 3.95 (m, 2 H, OCH2CH3), 4.99 (br.
,
H 9.20.
s, 1 H, 4-H), 6.41 (br. s, 1 H, 2-H), 7.05Ϫ7.80 (m, 5 H, PhϪH)
ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ5.3, Ϫ5.2
(s, 3 H, SiCH3), 14.6 (ϩ, OCH2CH3), 17.9 [Cquat., SiC(CH3)3], 25.6
[ϩ, SiC(CH3)3], 26.6 (ϩ, C-3Ј), 39.9 [ϩ, N(CH3)2], 45.6 (Ϫ, C-1Ј),
64.7 (Ϫ, OCH2CH3), 66.0 (ϩ, C-2Ј), 72.3 (Cquat., C-5), 99.0 (ϩ, C-
1-tert-Butyl-5-(2Ј-tert-butyldimethylsiloxy)propyl-5-(dimethyl-
amino)-3-ethoxy-1,3-cyclopentadiene (7kaf): According to GP2A, a
solution of complex 3ka (500 mg, 1.02 mmol) in pyridine (20 mL)
was treated with 3,3-dimethylbutyne (1f) (250 mg, 3.04 mmol), and
the mixture was stirred at 80 °C for 3 days. Chromatography on
aluminum oxide (30 g, activity grade II) eluting with pentane/Et2O
(from 20:1 to 3:1) gave 169 mg (43%) of 7kaf [Rf ϭ 0.08 (pentane);
dr 2.6:1] as a colorless oil. IR (film): ν˜ ϭ 2957 cmϪ1 (CϪH), 2780
(CϪH), 1702, 1629 (CϭC), 1463, 1362, 1254, 1050, 907, 835. Major
Stereoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ Ϫ0.22 (s, 3 H,
4), 124.8 (ϩ, C-2), 126.4, 127.5, 128.4 (ϩ, PhϪC), 134.8 (Cquat.
,
PhϪC), 150.3 (Cquat., C-1), 159.3 (Cquat., C-3) ppm. MS (70 eV):
m/z (%) ϭ 401 (100) [Mϩ], 372 (49) [Mϩ Ϫ C2H5], 356 (12), 271
(14), 242 (87), 199 (35), 171 (11), 159 (22), 131 (45), 115 (14), 73
(52), 52 (28). C24H39NO2Si (401.7): calcd. C 71.77, H 9.79; found
C 71.69, H 9.88.
SiCH3), 0.00 (s, 3 H, SiCH3), 0.82 [s, 9 H, SiC(CH3)3], 1.10 (d, 3J ϭ 5-(2Ј-tert-Butyldimethylsiloxy)propyl-5-(dimethylamino)-3-ethoxy-
6.1 Hz, 3 H, 3Ј-H), 1.21 [s, 9 H, C(CH3)3], 1.32 (t, 3J ϭ 7.0 Hz,
1,2-dimethyl-1,3-cyclopentadiene (7kaaa): According to GP2A, a
3 H, OCH2CH3), 1.85Ϫ2.35 (m, 2 H, 1Ј-H), 2.17 [s, 6 H, N(CH3)2], solution of complex 3ka (404 mg, 0.82 mmol) in pyridine (20 mL)
3.40 (mc, 1 H, 2Ј-H), 3.82 (mc, 2 H, OCH2CH3), 4.74 (d, 4J ϭ
was treated with 2-butyne (1aa) (197 µL, 2.51 mmol), and the mix-
1.6 Hz, 1 H, 4-H), 5.85 (d, 4J ϭ 1.6 Hz, 1 H, 2-H) ppm. 13C NMR ture was stirred at 80 °C for 3 days. Chromatography on aluminum
(62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ4.4, Ϫ3.8 (ϩ, SiCH3), 14.5 oxide (30 g, activity grade II) eluting with pentane/Et2O (from 20:1
(ϩ, OCH2CH3), 18.0 [Cquat., SiC(CH3)3], 25.98 (ϩ, C-3Ј), 26.04 to 0:1) gave 79 mg (27%) of 7kaaa [Rf ϭ 0.08 (pentane/Et2O, 1:1);
[ϩ, SiC(CH3)3], 31.5 [ϩ, C(CH3)3], 34.5 [Cquat., C(CH3)3], 40.8 [ϩ, dr ϭ 2.1:1] as a colorless oil. IR (film): ν˜ ϭ 2929 cmϪ1 (CϪH), 2856
N(CH3)2], 44.8 (Ϫ, C-1Ј), 64.2 (Ϫ, OCH2CH3), 67.0 (ϩ, C-2Ј), 78.1 (CϪH), 2779 (CϪH), 1665, 1592 (CϭC), 1472, 1378, 1253, 1042,
(Cquat., C-5), 96.5 (ϩ, C-4), 125.1 (ϩ, C-2), 157.5 (Cquat., C-1),
915, 835. Major Stereoisomer: 1H NMR (250 MHz, CDCl3): δ ϭ
162.2 (Cquat., C-3). Minor Stereoisomer: 1H NMR (250 MHz,
Ϫ0.03 [s, 6 H, Si(CH3)2], 0.83 [s, 9 H, SiC(CH3)3], 0.97 (d, 3J ϭ
3
CDCl3): δ ϭ 0.02 (s, 3 H, SiCH3), 0.06 (s, 3 H, SiCH3), 0.84 [s, 9 H, 6.1 Hz, 3 H, 3Ј-H), 1.34 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.62 (s,
SiC(CH3)3], 1.02 (d, 3J ϭ 5.6 Hz, 3 H, 3Ј-H), 1.24 [s, 9 H, C(CH3)3], 3 H, CH3), 1.68 (s, 3 H, CH3), 1.80Ϫ2.30 (m, 2 H, 1Ј-H), 2.12 [s,
3
1.32 (t, J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.85Ϫ2.35 (m, 2 H, 1Ј-H), 6 H, N(CH3)2], 3.32 (m, 1 H, 2Ј-H), 3.84 (q, 3J ϭ 7.0 Hz, 2 H,
2.17 [s, 6 H, N(CH3)2], 3.55 (mc, 1 H, 2Ј-H), 3.82 (mc, 2 H, OCH2CH3), 4.69 (s, 1 H, 4-H) ppm. 13C NMR (62.9 MHz, CDCl3,
4
4
OCH2CH3), 4.63 (d, J ϭ 1.6 Hz, 1 H, 4-H), 5.84 (d, J ϭ 1.6 Hz,
1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ (ϩ, OCH2CH3), 18.0 [Cquat., SiC(CH3)3], 25.6 (ϩ, C-3Ј), 25.9 [ϩ,
Ϫ4.4, Ϫ3.4 (ϩ, SiCH3), 14.6 (ϩ, OCH2CH3), 17.9 [Cquat. SiC(CH3)3], 39.7 [ϩ, N(CH3)2], 44.7 (Ϫ, C-1Ј), 64.4 (Ϫ,
plus DEPT): δ ϭ Ϫ4.7, Ϫ4.2 (ϩ, SiCH3), 8.8, 10.9 (ϩ, CH3), 14.5
,
SiC(CH3)3], 26.0 [ϩ, SiC(CH3)3], 26.6 (ϩ, C-3Ј), 31.5 [ϩ, C(CH3)3], OCH2CH3), 66.0 (ϩ, C-2Ј), 73.8 (Cquat., C-5), 93.9 (ϩ, C-4), 131.3
34.7 [Cquat., C(CH3)3], 40.6 [ϩ, N(CH3)2], 45.1 (Ϫ, C-1Ј), 64.3 (Ϫ, (Cquat., C-2), 142.1 (Cquat., C-1), 160.7 (Cquat., C-3). Minor Stereo-
OCH2CH3), 67.0 (ϩ, C-2Ј), 77.3 (Cquat., C-5), 96.8 (ϩ, C-4), 125.1 isomer: 1H NMR (250 MHz, CDCl3): δ ϭ Ϫ0.03 [s, 6 H, Si(CH3)2],
3
(ϩ, C-2), 157.6 (Cquat., C-1), 161.8 (Cquat., C-3) ppm. MS (70 eV):
0.82 [s, 9 H, SiC(CH3)3], 0.97 (d, J ϭ 6.1 Hz, 3 H, 3Ј-H), 1.34 (t,
m/z (%) ϭ 381 (90) [Mϩ], 336 (28), 324 (38) [Mϩ Ϫ C4H9], 222 3J ϭ 7.0 Hz, 3 H, OCH2CH3), 1.68 (s, 6 H, 2 ϫ CH3), 1.80Ϫ2.30
(100), 209 (22), 179 (43), 159 (43), 151 (21), 115 (24), 103 (20), 73 (m, 2 H, 1Ј-H), 2.10 [s, 6 H, N(CH3)2], 3.21 (mc, 1 H, 2Ј-H), 3.84 (q,
(78). C22H43NO2Si (381.7): calcd.
C 69.42, H 11.45.
C
69.23, H 11.36; found
3J ϭ 7.0 Hz, 2 H, OCH2CH3), 4.62 (s, 1 H, 4-H) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ4.7, Ϫ4.3 (ϩ, SiCH3), 8.8,
10.7 (ϩ, CH3), 14.5 (ϩ, OCH2CH3), 18.0 [Cquat., SiC(CH3)3], 25.9
[ϩ, SiC(CH3)3], 26.6 (ϩ, C-3Ј), 39.6 [ϩ, N(CH3)2], 45.0 (Ϫ, C-1Ј),
64.4 (Ϫ, OCH2CH3), 66.0 (ϩ, C-2Ј), 73.1 (Cquat., C-5), 94.0 (ϩ, C-
4), 131.1 (Cquat., C-2), 141.8 (Cquat., C-1), 160.5 (Cquat., C-3) ppm.
MS (70 eV): m/z (%) ϭ 353 (40) [Mϩ], 324 (63) [Mϩ Ϫ C2H5], 308
(13), 194 (100), 159 (46), 151 (29), 115 (22), 73 (58). C20H39NO2Si
(353.6): calcd. C 67.93, H 11.12; found C 68.08, H 11.11.
5-(2Ј-tert-Butyldimethylsiloxy)propyl-5-(dimethylamino)-3-ethoxy-1-
phenyl-1,3-cyclopentadiene (7kah): According to GP2A, a solution
of complex 3ka (560 mg, 1.14 mmol) in pyridine (20 mL) was
treated with phenylethyne (1h) (356 mg, 3.49 mmol), and the mix-
ture was stirred at 80 °C for 3 days. Chromatography on aluminum
oxide (30 g, activity grade II) eluting with pentane/Et2O (from 20:1
to 3:1) gave 287 mg (63%) of 7kah [Rf ϭ 0.95 (pentane/Et2O, 5:1);
dr 1.8:1] as a colorless oil. IR (film): ν˜ ϭ 2928 cmϪ1 (CϪH), 2823
4-(Dimethylamino)-2,3,4-trimethyl-2-cyclopentenone (21aaaa): Ac-
(CϪH), 2782 (CϪH), 1622, 1577 (CϭC), 1471, 1372, 1253, 1047, cording to GP3, a solution of 7aaaa (756 mg, 3.87 mmol) in THF
1
937, 835. Major Stereoisomer: H NMR (250 MHz, CDCl3): δ ϭ
(5 mL) was treated with two drops of 2  hydrochloric acid. Chro-
Ϫ0.05 (s, 3 H, SiCH3), Ϫ0.03 (s, 3 H, SiCH3), 0.69 (d, 3J ϭ 6.1 Hz, matography on silica gel (30 g) eluting with Et2O gave 635 mg
3 H, 3Ј-H), 0.82 [s, 9 H, SiC(CH3)3], 1.32 (t, 3J ϭ 7.0 Hz, 3 H, (98%) of 21aaaa [Rf ϭ 0.18 (Et2O)] as a colorless oil. IR (film): ν˜ ϭ
OCH2CH3), 1.90Ϫ2.45 (m, 2 H, 1Ј-H), 2.20 [s, 6 H, N(CH3)2], 3.28 2968 cmϪ1 (CϪH), 2824 (CϪH), 2780 (CϪH), 1700 (CϭO), 1653
(mc, 1 H, 2Ј-H), 3.95 (m, 2 H, OCH2CH3), 5.18 (br. s, 1 H, 4-H),
(CϭC), 1456, 1382, 1323, 1288, 1261, 1228, 1189, 1158, 1083, 977,
1
6.48 (br. s, 1 H, 2-H), 7.05Ϫ7.80 (m, 5 H, PhϪH) ppm. 13C NMR 840. H NMR (250 MHz, CDCl3): δ ϭ 1.21 (s, 3 H, CH3), 1.55 (s,
(62.9 MHz, CDCl3, plus DEPT): δ ϭ Ϫ4.6, Ϫ4.2 (ϩ, SiCH3), 14.6 3 H, CH3), 1.76 (AB, d, 2J ϭ 18.4 Hz, 1 H, 5-H), 1.84 (s, 3 H,
744
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
2
CH3), 1.98 [s, 6 H, N(CH3)2], 2.46 (AB, d, J ϭ 18.4 Hz, 1 H, 5-H) (250 MHz, CDCl3): δ ϭ 0.79Ϫ0.92 (m, 5 H, CH2CH2CH3), 1.53
ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 7.7 (ϩ, (mc, 1 H, CH2CH2CH3), 1.69Ϫ1.85 (m, 3 H, CH2CH2CH3, 1Ј-H),
2
CH3), 11.7 (ϩ, CH3), 25.3 (ϩ, CH3), 37.3 (Ϫ, C-5), 39.2 [ϩ, 1.90 (AB, d, J ϭ 18.6 Hz, 1 H, 5-H), 2.12 [s, 6 H, N(CH3)2], 2.31
2
N(CH3)2], 65.6 (Cquat., C-4), 135.9 (Cquat., C-2), 174.0 (Cquat., C-3), (m, 2 H, 2Ј-H), 2.48 (AB, d, J ϭ 18.6 Hz, 1 H, 5-H), 2.85 (br. s,
206.5 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ 167 (25) [Mϩ], 152
1 H, OH), 3.67 (t, 3J ϭ 6.3 Hz, 2 H, 3Ј-H), 5.94 (t, 4J ϭ 1.5 Hz,
(38) [Mϩ Ϫ CH3], 123 (100) [Mϩ Ϫ N(CH3)2], 112 (5), 95 (25), 79 1 H, 2-H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
(8), 67 (8), 55 (7), 44 (10) [N(CH3)2ϩ]. C10H17NO (167.2): calcd. C 14.5 (ϩ, CH2CH2CH3), 17.9 (Ϫ, CH2CH2CH3), 24.6, 29.5 (Ϫ, C-
71.81, H 10.25; found C 71.94, H 10.28.
2Ј, CH2CH2CH3), 36.7 (Ϫ, C-1Ј), 38.9 (Ϫ, C-5), 39.3 [ϩ, N(CH3)2],
62.0 (Ϫ, C-3Ј), 71.0 (Cquat., C-4), 130.2 (ϩ, C-2), 184.6 (Cquat., C-
3), 206.5 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ 225 (2) [Mϩ],
181 (100) [Mϩ Ϫ N(CH3)2], 138 (23), 108 (12), 91 (13), 77 (16), 55
(14), 44 (21) [N(CH3)2ϩ]. C13H23NO2 (225.3): calcd. C 69.29,
H 10.29, N 6.22; found C 69.55, H 10.20, N 6.15.
4-(Dimethylamino)-4-methyl-2,3-diphenyl-2-cyclopentenone
(21aahh): According to GP2A, a solution of complex 3aa (1.25 g,
3.75 mmol) in pyridine (80 mL) was treated with diphenylethyne
(1hh) (1.33 g, 7.46 mmol), and the mixture was stirred at 80 °C for
4 days. After evaporation of the solvent, the residue was dissolved
in THF (10 mL), to which 2  hydrochloric acid was added (2 mL).
Chromatography on silica gel (30 g) eluting with pentane/Et2O
(from 5:1 to 0:1) gave 550 mg (50%) of 21aahh [Rf ϭ 0.61 (Et2O)]
4-Cyclopropyl-4-(dimethylamino)-2,3-dimethyl-2-cyclopentenone
(21caaa): According to GP3,
a solution of 7caaa (434 mg,
1.96 mmol) in THF (5 mL) was treated with two drops of 2  hy-
as colorless crystals, m.p. 115 °C. IR (KBr): ν˜ ϭ 3048 cmϪ1 (CϪH), drochloric acid. Chromatography on silica gel (30 g) eluting with
2971 (CϪH), 2938 (CϪH), 2821 (CϪH), 2776 (CϪH), 1702 (Cϭ
pentane/Et2O (1:1) gave 360 mg (95%) of 21caaa [Rf ϭ 0.14 (Et2O)]
O), 1624 (CϭC), 1485, 1441, 1362, 1340, 1280, 1232, 1175, 1116, as a colorless oil. IR (film): ν˜ ϭ 3021 cmϪ1 (CϪH), 2934 (CϪH),
1068, 1033, 971, 930, 797, 774, 695, 635, 522, 481. 1H NMR 2780 (CϪH), 1699 (CϭO), 1653 (CϭC), 1456, 1237, 1084, 1050,
(250 MHz, CDCl3): δ ϭ 1.41 (s, 3 H, CH3), 2.22 (AB, d, 2J ϭ
780. 1H NMR (250 MHz, CDCl3): δ ϭ Ϫ0.35 (mc, 1 H, cPr-H),
19.3 Hz, 1 H, 5-H), 2.35 [s, 6 H, N(CH3)2], 2.98 (AB, d, 2J ϭ 0.38Ϫ0.47 (m, 2 H, cPr-H), 0.72 (mc, 1 H, cPr-H), 1.10 (mc, 1 H,
19.3 Hz, 1 H, 5-H), 7.18Ϫ7.27 (m, 8 H, PhϪH), 7.54 (d, 3J ϭ
cPr-H), 1.21 (AB, d, J ϭ 18.8 Hz, 1 H, 5-H), 1.68 (s, 3 H, CH3),
2
7.2 Hz, 2 H, PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3, plus 2.04 (s, 3 H, CH3), 2.11 (AB, d, J ϭ 18.8 Hz, 1 H, 5-H), 2.18 [s,
2
DEPT): δ ϭ 25.9 (ϩ, CH3), 39.3 (Ϫ, C-5), 39.6 [ϩ, N(CH3)2], 66.3
6 H, N(CH3)2]. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ
(Cquat., C-4), 127.8, 127.9, 128.1, 128.9, 129.65, 129.72 (ϩ, PhϪC), Ϫ0.4 (Ϫ, cPr-C), 6.0 (Ϫ, cPr-C), 7.7 (ϩ, CH3), 12.0 (ϩ, CH3), 16.3
131.5, 134.4 (Cquat., PhϪC), 140.0 (Cquat., C-2), 172.5 (Cquat., C-3), (ϩ, cPr-C), 29.2 (Ϫ, C-5), 39.7 [ϩ, N(CH3)2], 69.4 (Cquat., C-4),
205.4 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ 291 (52) [Mϩ], 276
135.6 (Cquat., C-2), 173.8 (Cquat., C-3), 206.7 (Cquat., C-1) ppm. MS
(31) [Mϩ Ϫ CH3], 247 (100) [Mϩ Ϫ N(CH3)2], 204 (11), 178 (12), (70 eV): m/z (%) ϭ 193 (8) [Mϩ], 178 (3) [Mϩ Ϫ CH3], 152 (19)
112 (55), 85 (19), 70 (20), 44 (6) [N(CH3)2ϩ]. C20H21NO (291.4): [Mϩ Ϫ C3H5], 149 (100) [Mϩ Ϫ N(CH3)2], 121 (95), 107 (55), 93
calcd. C 82.44, H 7.26; found C 82.63, H 7.14.
(72), 79 (32), 65 (11), 55 (13), 44 (13) [N(CH3)2ϩ], 41 (15) [C3H5ϩ].
C12H19NO (193.3): calcd. C 74.56, H 9.91; found C 74.30, H 10.29.
3-[3Ј-(tert-Butyldimethylsilyloxy)propyl]-4-(dimethylamino)-4-
propyl-2-cyclopentenone (21bal): According to GP3, a solution of
7bal (1.12 g, 3.05 mmol) in THF (5 mL) was treated with 2 drops
of 2  hydrochloric acid. Chromatography on silica gel (40 g) elut-
ing with pentane/Et2O (3:1) gave 963 mg (93%) of 21bal [Rf ϭ 0.18
4-(Dimethylamino)-4-(3Ј-hydroxypropyl)-2,3-dimethyl-2-cyclo-
pentenone (21laaa): A solution of 7laaa (393 mg, 1.11 mmol) in
acetonitrile (12 mL) was treated with 40% hydrofluoric acid
(220 µL, 4.44 mmol), and the mixture was stirred at room tempera-
ture for 1 h. After addition of saturated K2CO3 solution (10 mL),
(pentane/Et2O, 1:1)] as a colorless oil. IR (film): ν˜ ϭ 2929 cmϪ1
,
2855 (CϪH), 1700 (CϭO), 1617 (CϭC), 1463, 1384, 1102, 963, the mixture was extracted with CH2Cl2 (5 ϫ 20 mL) and the com-
776. 1H NMR (250 MHz, CDCl3): δ ϭ 0.02 [s, 6 H, Si(CH3)2], 0.85
bined organic extracts were dried with MgSO4. The solvent was
[s, 9 H, SiC(CH3)3], 0.86Ϫ0.90 (m, 5 H, CH2CH2CH3), 1.55 (mc, removed under reduced pressure. The residue was dissolved in pen-
1 H, CH2CH2CH3), 1.70Ϫ1.84 (m, 3 H, CH2CH2CH3, 1Ј-H), 1.90 tane/Et2O (1:1) and crystallized at 0 °C. 190 mg (81%) of 21laaa
2
(AB, d, J ϭ 18.6 Hz, 1 H, 5-H), 2.11 [s, 6 H, N(CH3)2], 2.33 (m, was obtained as colorless crystals, m.p. 76 °C. IR (film): ν˜ ϭ
2 H, 2Ј-H), 2.52 (AB, d, 2J ϭ 18.6 Hz, 1 H, 5-H), 3.66 (t, 3J ϭ 3177 cmϪ1 (OH), 1704 (CϭO), 1652 (CϭC), 1460, 1341, 1163, 914,
1
6.7 Hz, 2 H, 3Ј-H), 5.94 (s, 1 H, 2-H) ppm. 13C NMR (62.9 MHz,
840. H NMR (250 MHz, CDCl3): δ ϭ 1.09 (mc, 2 H, 2Ј-H), 1.64
CDCl3, plus DEPT): δ ϭ Ϫ5.4 [ϩ, Si(CH3)2], 15.0 (ϩ, (s, 3 H, CH3), 1.66 (mc, 1 H, 1Ј-H), 1.85 (AB, d, 2J ϭ 18.6 Hz, 1 H,
CH2CH2CH3), 17.9 (Ϫ, CH2CH2CH3), 18.2 [Cquat., SiC(CH3)3], 5-H), 1.87 (s, 3 H, CH3), 1.89 (mc, 1 H, 1Ј-H), 2.07 [s, 6 H,
24.5 (Ϫ, CH2CH2CH3), 25.8 [ϩ, SiC(CH3)3], 29.9 (Ϫ, C-2Ј), 36.8
N(CH3)2], 2.45 (AB, d, 2J ϭ 18.6 Hz, 1 H, 5-H), 2.85 (br. s, 1 H,
(Ϫ, C-1Ј), 39.2 (Ϫ, C-5), 39.3 [ϩ, N(CH3)2], 62.2 (Ϫ, C-3Ј), 70.9 OH), 3.53 (t, J ϭ 6.3 Hz, 2 H, 3Ј-H) ppm. 13C NMR (62.9 MHz,
3
(Cquat., C-4), 130.0 (ϩ, C-2), 184.9 (Cquat., C-3), 206.4 (Cquat., C-1) CDCl3, plus DEPT): δ ϭ 7.7, 12.4 (ϩ, CH3), 27.9, 33.0, 35.8 (Ϫ,
ppm. MS (70 eV): m/z (%)
ϭ
339 (8) [Mϩ], 295 (100)
C-5,1Ј,2Ј), 39.3 [ϩ, N(CH3)2], 62.4 (Ϫ, C-3Ј), 69.0 (Cquat., C-4),
138.4 (Cquat., C-3), 172.1 (Cquat., C-2), 206.4 (Cquat., C-1) ppm. MS
(70 eV): m/z (%) ϭ 211 (8) [Mϩ], 167 (12) [Mϩ Ϫ N(CH3)2], 152
(100), 149 (10). C12H21NO2 (211.3): calcd. C 68.21, H 10.02; found
C 68.68, H 10.00.
[Mϩ Ϫ N(CH3)2], 282 (10), 237 (18), 181 (12), 138 (46), 73 (12).
4-(Dimethylamino)-3-(3Ј-hydroxypropyl)-4-propyl-2-cyclopentenone
(21balЈ): A solution of 21bal (152 mg, 0.45 mmol) in acetonitrile
(5 mL) was treated with 40% hydrofluoric acid (100 µL, 2.05 mmol)
and the mixture was stirred at room temperature for 1 h. After
addition of saturated K2CO3 solution (10 mL), the mixture was
extracted with CH2Cl2 (5 ϫ 20 mL), and the combined organic
(1,2,3-Trimethyl-4-oxo-2-cyclopentenyl)trimethylammonium Iodide
(24aaaa). Variation A: According to GP4A, 4-(dimethylamino)-
2,3,4-trimethyl-2-cyclopentenone (21aaaa) (102 mg, 0.61 mmol)
extracts were dried with MgSO4. The solvent was removed under and methyl iodide (796 mg, 5.61 mmol) in acetone (8 mL) were
reduced pressure. The residue was dissolved in pentane/Et2O (1:1)
and crystallized at 0 °C. 68 mg (67%) of 21balЈ was obtained as
colorless crystals, m.p. 74 °C. IR (film): ν˜ ϭ 3258 cmϪ1 (OH), 1695
(CϭO), 1610 (CϭC), 1461, 1331, 1123, 929, 751. 1H NMR
stirred under 10 kbar for 20 h. After filtration and washing with
Et2O (3 ϫ 20 mL), 175 mg (93%) of 24aaaa was isolated as a color-
less solid, m.p. 156 °C. IR (KBr): ν˜ ϭ 3027 cmϪ1 (CϪH), 3007
(CϪH), 2917 (CϪH), 1717 (CϭO), 1637 (CϭC), 1470, 1387, 1327,
Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
745

A. de Meijere et al.
FULL PAPER
1288. 1H NMR (250 MHz, [D6]DMSO): δ ϭ 0.83 (s, 3 H, CH3), pentane/Et2O (5:1) gave 347 mg (71%) of 26aa [Rf ϭ 0.18 (pentane/
2
0.85 (s, 3 H, CH3), 1.34 (s, 3 H, CH3), 1.67 (AB, d, J ϭ 19.0 Hz, Et2O, 3:1] as colorless crystals: m.p. 41 °C. IR (KBr): ν˜ ϭ
1 H, 5-H), 2.19 [s, 9 H, N(CH3)3ϩ], 2.47 (AB, d, 2J ϭ 19.0 Hz, 1 H, 3025 cmϪ1 (CϪH), 2913 (CϪH), 2832 (CϪH), 1706 (CϭO), 1645
1
5-H) ppm. 13C NMR (62.9 MHz, [D6]DMSO, plus DEPT): δ ϭ 8.5 (CϭC), 1607 (CϭC), 1448, 1428, 1328, 920. H NMR (250 MHz,
3
(ϩ, CH3), 14.9 (ϩ, CH3), 19.6 (ϩ, CH3), 43.9 (Ϫ, C-5), 50.4 [ϩ, CDCl3): δ ϭ 1.76 (s, 3 H, CH3), 2.06 (s, 3 H, CH3), 2.73 (dt, J ϭ
N(CH3)3ϩ], 78.9 (Cquat., C-4), 143.4 (Cquat., C-2), 162.5 (Cquat., C-
7.1, 3J ϭ 7.1 Hz, 2 H, 2Ј-H), 2.87 (s, 2 H, 5-H), 3.20 (t, 3J ϭ 7.1 Hz,
3), 201.3 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ 263 (18), 253 2 H, 3Ј-H), 5.61 (t, 3J ϭ 7.1 Hz, 1 H, 1Ј-H) ppm. 13C NMR
(17), 122 (88) [Mϩ Ϫ HN(CH3)3I], 108 (21), 95 (22), 79 (95), 59 (62.9 MHz, CDCl3, plus DEPT): δ ϭ 4.5 (Ϫ, C-3Ј), 8.4 (ϩ, CH3),
(100) [N(CH3)3ϩ], 44 (87) [N(CH3)2ϩ]. C11H20INO (309.2): calcd.
C 42.73, H 6.52; found C 42.53, H 6.44.
11.8 (ϩ, CH3), 33.5 (Ϫ, C-2Ј), 36.9 (Ϫ, C-5), 121.9 (ϩ, C-1Ј), 139.2,
139.9 (Cquat., C-2, C-4), 162.6 (Cquat., C-3), 204.2 (Cquat., C-1) ppm.
MS (70 eV): m/z (%) ϭ 276 (58) [Mϩ], 149 (100) [Mϩ Ϫ I], 122 (95)
[Mϩ Ϫ C2H3I], 105 (19), 91 (23), 77 (17), 65 (9), 41 (10) [C3H5ϩ].
C10H13IO (276.1): calcd. C 43.50, H 4.75; found C 44.45, H 4.90.
Variation B: According to GP4B, 21aaaa (263 mg, 1.57 mmol) and
methyl iodide (1.40 g, 9.86 mmol) in acetone (30 mL) were stirred
at ambient pressure for 3 days. After filtration and washing with
Et2O (3 ϫ 20 mL), 342 mg (70%) of 24aaaa was isolated.
Dimethyl (2,3,4-Trimethyl-2-cyclopentenon-4-yl)malonate (27aaa-
Me) and 2,3,4,7,8,9-Hexamethyltricyclo[5.2.1.02,6]deca-3,8-diene-
5,10-dione (29aaa): According to GP5, (2,3,4-trimethyl-2-cyclopen-
(4-Methyl-2,3-diphenyl-2-cyclopentenon-4-yl)trimethylammonium
Iodide (24aahh). Variation A: According to GP4A, 4-(dimethylam-
ino)-4-methyl-2,3-diphenyl-2-cyclopentenone (21aahh) (166 mg,
0.57 mmol) and methyl iodide (518 mg, 3.65 mmol) in acetone
(8 mL) were stirred under 10 kbar for 3 days. After filtration and
washing with Et2O (3 ϫ 20 mL), 236 mg (96%) of 24aahh was iso-
lated as a colorless solid, m.p. 159 °C. IR (KBr): ν˜ ϭ 3014 cmϪ1
(CϪH), 2737 (CϪH), 1699 (CϭO), 1621 (CϭC), 1473, 1444, 1416,
1377, 1344, 1253. 1H NMR (250 MHz, [D6]DMSO): δ ϭ 1.45 (s,
3 H, CH3), 2.72Ϫ2.78 [m, 10 H, N(CH3)3ϩ, 5-H], 3.78 (AB, d, 2J ϭ
19.0 Hz, 1 H, 5-H), 7.10Ϫ7.41 (m, 10 H, PhϪH) ppm. 13C NMR
(62.9 MHz, [D6]DMSO, plus DEPT): δ ϭ 21.0 (ϩ, CH3), 44.3 [ϩ,
N(CH3)3ϩ], 44.6 (Ϫ, C-5), 78.9 (Cquat., C-4), 127.7, 128.0, 128.2,
128.3, 128.7, 128.9 (ϩ, PhϪC), 133.7, 133.8 (Cquat., PhϪC), 146.8
(Cquat., C-2), 162.9 (Cquat., C-3), 204.6 (Cquat., C-1).
tenon-4-yl)trimethylammonium
iodide
(24aaaa)
(59 mg,
0.19 mmol) in THF (5 mL) was treated with a solution of sodium
dimethylmalonate (0.40 mmol) in THF (5 mL) and the mixture was
stirred at ambient temperature for 6 h. Chromatography on silica
gel (10 g) eluting with pentane/Et2O (3:1) gave 13 mg (56%) of
29aaa [Rf ϭ 0.42 (pentane/Et2O, 2:1)] as colorless crystals, m.p. 76
°C and 16 mg (33%) of 27aaa-Me [Rf ϭ 0.15 (pentane/Et2O, 2:1)]
as a colorless oil, respectively. 27aaa-Me: IR (film): ν˜ ϭ 2955 cmϪ1
(CϪH), 1734 (CϭO), 1700 (CϭO), 1653 (CϭC), 1436, 1386, 1326,
1
1241, 1195. H NMR (250 MHz, CDCl3): δ ϭ 1.30 (s, 3 H, CH3),
2
1.66 (s, 3 H, CH3), 1.96 (s, 3 H, CH3), 2.23 (AB, d, J ϭ 19.1 Hz,
1 H, 5-H), 3.14 (AB, d, 2J ϭ 19.1 Hz, 1 H, 5-H), 3.58 (s, 3 H,
CO2CH3), 3.61 [s, 1 H, CH(CO2CH3)2], 3.75 (s, 3 H, CO2CH3)
ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.1 (ϩ,
CH3), 12.22 (ϩ, CH3), 25.06 (ϩ, CH3), 45.2 (Ϫ, C-5), 46.1 (Cquat.
,
Variation B: According to GP4B, 4-(dimethylamino)-4-methyl-2,3-
diphenyl-2-cyclopentenone (21aahh) (137 mg, 0.47 mmol) and
methyl iodide (456 mg, 3.21 mmol) in acetone (20 mL) were stirred
at ambient pressure for 3 days. After filtration and washing with
Et2O (3 ϫ 20 mL), 142 mg (70%) of 24aahh was isolated.
C-4), 52.4 (ϩ, CO2CH3), 52.5 (ϩ, CO2CH3), 56.8 [ϩ,
CH(CO2CH3)2], 137.1 (Cquat., C-2), 167.4 [Cquat., CH(CO2CH3)2],
168.0 [Cquat., CH(CO2CH3)2], 171.2 (Cquat., C-3), 207.0 (Cquat., C-
1) ppm. MS (70 eV): m/z (%)
ϭ
254 (10) [Mϩ], 223 (8)
[Mϩ Ϫ OCH3], 195 (4), 163 (5), 133 (5), 122 (100)
[Mϩ Ϫ CH2(CO2CH3)2], 95 (20), 79 (4). HRMS (EI) calcd. for
C13H18O5: 254.1154 (correct HMRS).
2,3-Dimethyl-4-methylene-2-cyclopentenone (25aa):
A high-pres-
sure-resistant bottle was charged with 4-(dimethylamino)-2,3,4-tri-
methyl-2-cyclopentenone (21aaaa) (393 mg, 2.35 mmol), acetone
(30 mL) and methyl iodide (2.07 g, 14.6 mmol), sealed and the mix-
ture stirred at 100 °C for 2 h. After dilution with Et2O (50 mL),
filtration and washing with Et2O (3 ϫ 20 mL), the white solid
(434 mg) was identified as tetramethylammonium iodide. The sol-
vent of the filtrate was removed under reduced pressure. Chroma-
tography on silica gel (30 g) eluting with pentane/Et2O (5:1) gave
158 mg (55%) of 25aa [Rf ϭ 0.39 (pentane/Et2O, 3:1)] as a yellow
oil. IR (film): ν˜ ϭ 2920 cmϪ1 (CϪH), 2785 (CϪH), 1700 (CϭO),
29aaa: IR (KBr): ν˜ ϭ 2967 cmϪ1 (CϪH), 2937 (CϪH), 2843
(CϪH), 1772 (CϭO), 1686 (CϭO), 1639 (CϭC), 1436, 1383. 1H
NMR (250 MHz, CDCl3): δ ϭ 1.29 (s, 3 H, CH3), 1.37 (s, 3 H,
4
CH3), 1.53 (s, 3 H, CH3), 1.58 (s, 3 H, CH3), 1.65 (d, J ϭ 1.1 Hz,
3 H, CH3), 1.95 (s, 3 H, CH3), 1.98 (s, 1 H, 6-H), 2.62 (s, 1 H, 1-
H) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 6.2 (ϩ,
CH3), 10.6 (ϩ, CH3), 10.8 (ϩ, CH3), 13.7 (ϩ, CH3), 13.7 (ϩ, CH3),
20.4 (ϩ, CH3), 49.9 (Cquat., C-2), 57.2 (ϩ, C-6), 57.4 (Cquat., C-7),
60.5 (ϩ, C-1), 131.6, 134.0 (Cquat., C-4, C-9), 141.9 (Cquat., C-8),
1
1652 (CϭC), 1616 (CϭC), 1558, 1540, 1506, 1394, 1071, 887. H
168.9 (Cquat.
, C-3), 201.7 (Cquat., C-10), 205.3 (Cquat., C-5).
NMR (250 MHz, CDCl3): δ ϭ 1.75 (s, 3 H, CH3), 2.02 (s, 3 H,
CH3), 2.89 (s, 2 H, 5-H), 5.06 (s, 1 H, ϭCH2), 5.24 (s, 1 H, ϭCH2)
ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.4 (ϩ,
C16H20O2 (244.3): calcd. C 78.65, H 8.25; found C 77.80, H 8.45.
Diethyl (2,3,4-Trimethyl-2-cyclopentenon-4-yl)malonate (27aaa-Et):
According to GP5, (2,3,4-trimethyl-2-cyclopentenon-4-yl)tri-
methylammonium iodide (24aaaa) (120 mg, 0.39 mmol) in THF
(10 mL) was treated with a solution of sodium diethylmalonate
(0.80 mmol) in THF (5 mL) and the mixture was stirred at ambient
temperature for 2 h. Chromatography on silica gel (10 g) eluting
with pentane/Et2O (1:1) gave 82 mg (74%) of 27aaa-Et [Rf ϭ 0.10
(pentane/Et2O, 3:1)] as a colorless oil, which later became a color-
less crystal, m.p. 54 °C. IR (KBr): ν˜ ϭ 2993 cmϪ1 (CϪH), 2924
(CϪH), 2876 (CϪH), 1725 (CϭO), 1695 (CϭO), 1645 (CϭC),
CH3), 11.4 (ϩ, CH3), 39.1 (Ϫ, C-5), 107.3 (Ϫ, ϭCH2), 140.8 (Cquat.
,
C-2), 144.3 (Cquat., C-4), 162.2 (Cquat., C-3), 204.9 (Cquat., C-1)
ppm. MS (70 eV): m/z (%) ϭ 122 (92) [Mϩ], 107 (18) [Mϩ Ϫ CH3],
93 (20) [Mϩ Ϫ CH3 Ϫ CH2], 79 (100), 53 (8), 41 (4).
4-(3Ј-Iodopropylidene)-2,3-dimethyl-2-cyclopentenone (26aa): Ac-
cording to GP4B, 4-cyclopropyl-4-(dimethylamino)-2,3-dimethyl-2-
cyclopentenone (21caaa) (341 mg, 1.76 mmol) and methyl iodide
(1.53 mg, 10.8 mmol) in acetone (30 mL) were stirred at ambient
pressure for 3 days. After filtration and washing with Et2O (3 ϫ
20 mL), the white solid (268 mg) was identified as tetramethylam-
1
3
1475, 1454, 1388. H NMR (250 MHz, CDCl3): δ ϭ 1.10 (t, J ϭ
monium iodide. The solvent of the filtrate was removed under re- 7.1 Hz, 3 H, OCH2CH3), 1.24 (t, 3J ϭ 7.1 Hz, 3 H, OCH2CH3),
duced pressure. Chromatography on silica gel (30 g) eluting with 1.27 (s, 3 H, CH3), 1.62 (s, 3 H, CH3), 1.94 (s, 3 H, CH3), 2.20 (AB,
746
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748

Highly Substituted 3-Ethoxycyclopentadienes, Masked Cyclopentenones
FULL PAPER
d, 2J ϭ 19.2 Hz, 1 H, 5-H), 3.14 (AB, d, 2J ϭ 19.2 Hz, 1 H, 5-
(70 eV): m/z (%) ϭ 462 (15) [Mϩ], 405 (8) [Mϩ Ϫ C(CH3)3], 350
H), 3.61 [s, 1 H, CH(CO2CH2CH3)2], 4.00 (q, 3J ϭ 7.1 Hz, 1 H, (100) [Mϩ
Ϫ
2C4H8], 233 (17), 261 (10), 247 (30)
3
3
OCH2CH3), 4.01 (q, J ϭ 7.1 Hz, 1 H, OCH2CH3), 4.17 (q, J ϭ
[Mϩ Ϫ CH(CO2tBu)2], 234 (9), 178 (17), 57 (44) [C(CH3)3ϩ].
7.1 Hz, 1 H, OCH2CH3), 4.18 (q, 3J ϭ 7.1 Hz, 1 H, OCH2CH3) C29H34O5 (462.6): calcd. C 75.29, H 7.41; found C 75.09, H 7.91.
ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT): δ ϭ 8.0 (ϩ,
31ahh: IR (KBr): ν˜ ϭ 3051 cmϪ1 (CϪH), 2967 (CϪH), 2912
CH3), 12.3 (ϩ, CH3), 13.8 (ϩ, OCH2CH3), 14.0 (ϩ, OCH2CH3),
(CϪH), 1700 (CϭO), 1488, 1444, 1345, 1159, 1031. 1H NMR
25.1 (ϩ, CH3), 45.2 (Ϫ, C-5), 45.9 (Cquat., C-4), 57.1 [ϩ,
(250 MHz, CDCl3): δ ϭ 1.54 (s, 6 H, CH3), 2.69 (s, 2 H, 6-H, 7-H),
CH(CO2Et)2], 61.4 (Ϫ, OCH2CH3), 61.4 (Ϫ, OCH2CH3), 136.9
7.09Ϫ7.32 (m, 20 H, PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3,
(Cquat., C-2), 166.9, 167.5 [Cquat., CH(CO2Et)2], 171.6 (Cquat., C-3),
plus DEPT): δ ϭ 20.6 (ϩ, CH3), 48.5 (ϩ, C-6, C-7), 55.8 (Cquat.
,
207.2 (Cquat., C-1) ppm. MS (70 eV): m/z (%) ϭ 282 (10) [Mϩ], 237
(5) [Mϩ Ϫ OCH2CH3], 209 (4), 161 (9), 122 (100)
[Mϩ Ϫ CH2(CO2CH2CH3)2], 107 (5), 95 (9), 79 (4), 67 (4), 43 (4).
C15H22O5 (282.3): calcd. C 63.81, H 7.85; found C 63.94, H 7.84.
C-1, C-2), 128.1, 128.29 128.32, 129.2, 129.3, 129.6 (ϩ, PhϪC),
131.4, 134.2 (Cquat., PhϪC), 143.9 (Cquat., C-4, C-9), 171.6 (Cquat.
,
C-3, C-10), 204.8 (Cquat., C-5, C-8) ppm. MS (70 eV): m/z (%) ϭ
492 (35) [Mϩ], 246 (100) [C18H14Oϩ], 218 (15), 178 (16), 116 (18).
Diethyl
(27ahh-Et): According to GP5, (4-methyl-2,3-diphenyl-2-cyclopen-
tenon-4-yl)trimethylammonium iodide (24aahh) (74 mg,
0.17 mmol) in THF (10 mL) was treated with a solution of sodium
diethylmalonate (0.60 mmol) in THF (5 mL) and the mixture was
stirred at ambient temperature for 1 h. Chromatography on silica
gel (10 g) eluting with pentane/Et2O (3:1) gave 52 mg (75%) of
27ahh-Et [Rf ϭ 0.30 (pentane/Et2O, 2:1)] as colorless crystals, m.p.
64 °C. IR (KBr): ν˜ ϭ 3051 cmϪ1 (CϪH), 2975 (CϪH), 2934
(CϪH), 1750 (CϭO), 1728 (CϭO), 1704 (CϭO), 1620 (CϭC),
(4-Methyl-2,3-diphenyl-2-cyclopentenon-4-yl)malonate
5-Methyl-4,6-dimethylenebicyclo[3.3.0]oct-1-en-3-one (32): A solu-
tion of 5-(3Ј-bromobut-3Ј-enyl)-5-(dimethylamino)-3-ethoxy-1,2-
dimethyl-1,3-cyclopentadiene (7naaa) (90 mg, 0.29 mmol) in THF/
MeOH (5:1, 5 mL) was treated with a small amount of silica gel
and the mixture was stirred for 24 h. After filtration through silica
gel and removal of the solvent, the residue was dissolved in DMF
(10 mL) and transferred to a Pyrex bottle. Palladium acetate
(7.0 mg, 11 mol %), triphenylphosphane (15 mg, 20 mol %) and tri-
ethylamine (500 mg, 4.94 mmol) were added to the solution. Dry
nitrogen was bubbled through the solution for 5 min, and the mix-
ture was stirred at 100 °C for an additional 20 h. The reaction mix-
ture was diluted with H2O and extracted with pentane (3 ϫ 50 mL).
The organic extract was dried with MgSO4 and the solvent was
removed under reduced pressure. Chromatography on flash silica
gel (20 g) eluting with pentane/Et2O (10:1) gave 17 mg (37%) of 32
[Rf ϭ 0.21 (pentane/Et2O, 10:1)] as a colorless oil. IR (film): ν˜ ϭ
2963 cmϪ1, 2925, 2853 (CϪH), 1703 (CϭO), 1655, 1623 (CϭC),
1451, 1126, 876. 1H NMR (250 MHz, CDCl3): δ ϭ 1.38 (s, 3 H,
CH3), 2.57 (mc, 1 H, 8-H), 2.70Ϫ2.83 (m, 2 H, 7-H, 8-H),
1
3
1570, 1488, 1462. H NMR (250 MHz, CDCl3): δ ϭ 1.17 (t, J ϭ
7.1 Hz, 3 H, OCH2CH3), 1.28 (t, 3J ϭ 7.1 Hz, 3 H, OCH2CH3),
1.47 (s, 3 H, CH3), 2.52 (AB, d, 2J ϭ 19.2 Hz, 1 H, 5-H), 3.58 (AB,
2
d, J ϭ 19.2 Hz, 1 H, 5-H), 3.63 [s, 1 H, CH(CO2CH2CH3)2], 4.12
(q, 3J ϭ 7.1 Hz, 2 H, OCH2CH3), 4.21 (q, 3J ϭ 7.1 Hz, 1 H,
3
OCH2CH3), 4.22 (q, J ϭ 7.1 Hz, 1 H, OCH2CH3), 7.11Ϫ7.34 (m,
10 H, PhϪH) ppm. 13C NMR (62.9 MHz, CDCl3, plus DEPT):
δ ϭ 13.9 (ϩ, OCH2CH3), 14.0 (ϩ, OCH2CH3), 26.1 (ϩ, CH3), 46.2
(Ϫ, C-5), 46.8 (Cquat., C-4), 56.9 [ϩ, CH(CO2Et)2], 61.6 (Ϫ, 2 ϫ
OCH2CH3), 127.6, 127.8, 128.3, 128.4, 128.5, 129.4 (ϩ, PhϪC),
2
2.84Ϫ3.05 (m, 1 H, 7-H), 4.78 (d, J ϭ 1.7 Hz, 1 H, 6-CH2), 5.31
130.9, 134.5 (Cquat., PhϪC), 141.1 (Cquat., C-2), 167.1, 167.7 [Cquat.
,
(d, 2J ϭ 1.7 Hz, 1 H, 6-CH2), 5.49 (s, 1 H, 2-H), 6.54 (s, 1 H, 4-
CH2), 6.93 (s, 1 H, 4-CH2) ppm. 13C NMR (125.7 MHz, CDCl3):
δ ϭ 25.1 (CH3), 27.2 (C-6), 31.2 (C-7), 55.1 (C-5), 106.4 (6-CH2),
114.7 (C-6), 124.8 (4-CH2), 150.06 (C-4), 150.10 (C-2), 185.7 (C-
1), 197.0 (C-3) ppm. MS (70 eV): m/z (%) ϭ 160 (95) [Mϩ], 145
(100) [Mϩ Ϫ CH3], 132 (38) [Mϩ Ϫ CO], 117 (61), 91 (53), 77 (18),
51 (19). HRMS (EI) calcd. for C11H12O: 160.0888 (correct HMRS).
CH(CO2Et)2], 171.3 (Cquat., C-3), 205.6 (Cquat., C-1) ppm. MS
(70 eV): m/z (%) ϭ 406 (65) [Mϩ], 361 (5) [Mϩ Ϫ OCH2CH3], 247
(100) [Mϩ Ϫ CH(CO2CH2CH3)2], 219 (20), 204 (16), 178 (10), 141
(4), 91 (7). C25H26O5 (406.5): calcd. C 73.87, H 6.45; found
C 73.59, H 6.68.
Di-tert-butyl (4-Methyl-2,3-diphenyl-2-cyclopentenon-4-yl)malonate
(27ahh-tBu) and 1,2-Dimethyl-3,4,9,10-tetraphenyltricyclo[5.3.0.02,-
6]deca-3,9-diene-5,8-dione (31ahh): According to GP5, (4-methyl-
Supporting Information (see also the footnote on the first page of
this article): For the following compounds experimental details are
available: 3la, 3ra, 3sa, 7raf, (7rag, 8rag), 7saf and 7dacc.
2,3-diphenyl-2-cyclopentenon-4-yl)trimethylammonium
iodide
(24aahh) (61 mg, 0.14 mmol) in THF (10 mL) was treated with a
solution of sodium di(tert-butyl)malonate (0.60 mmol) in THF
(5 mL) and the mixture was stirred at ambient temperature for 1 h.
Chromatography on silica gel (10 g) eluting with pentane/Et2O
(4:1) gave 29 mg (45%) of 27ahh-tBu [Rf ϭ 0.45 (pentane/Et2O,
2:1)] as colorless crystals, m.p. 174 °C and 16 mg (46%) of 31ahh
[Rf ϭ 0.21 (pentane/Et2O, 2:1)] as colorless crystals, m.p. 124 °C.
27ahh-tBu: IR (KBr): ν˜ ϭ 3057 cmϪ1 (CϪH), 2978 (CϪH), 2931
(CϪH), 1752 (CϭO), 1707 (CϭO), 1594 (CϭC), 1489, 1445, 1394,
1371. 1H NMR (250 MHz, CDCl3): δ ϭ 1.38 [s, 9 H, C(CH3)3],
1.43 (s, 3 H, CH3), 1.48 [s, 9 H, C(CH3)3], 2.47 (AB, d, 2J ϭ
Acknowledgments
This work was supported by the Volkswagen-Stiftung and the
Fonds der Chemischen Industrie. Generous gifts of chemicals by
BASF, Bayer, Degussa-Hüls AG and Chemetall GmbH are grate-
fully acknowledged. The authors are indebted to Dr. Burkhard
Knieriem, Göttingen, for his careful proofreading of the final
manuscript.
[1]
2
E. O. Fischer, A. Maasböl, Angew. Chem. 1964, 76, 645; Angew.
19.2 Hz, 1 H, 5-H), 3.45 [s, 1 H, CH(CO2tBu)2], 3.56 (AB, d, J ϭ
Chem. Int. Ed. Engl. 1964, 3, 580.
19.2 Hz, 1 H, 5-H), 7.15Ϫ7.32 (m, 10 H, PhϪH) ppm. 13C NMR
(62.9 MHz, CDCl3, plus DEPT): δ ϭ 26.2 (ϩ, CH3), 27.7 [ϩ,
C(CH3)3], 27.9 [ϩ, C(CH3)3], 46.1 (Cquat., C-4), 47.0 (Ϫ, C-5), 58.8
[2] [2a]
K. H. Dötz, Reactions of Coordinated Ligands (Ed.: P. S.
[2b]
Braterman), Plenum, New York, 1986, 285Ϫ370.
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Eur. J. Org. Chem. 2004, 724Ϫ748
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
747

A. de Meijere et al.
FULL PAPER
Organic Synthesis (Eds.: M. Beller, C. Bolm), Wiley-VCH,
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P1, unit cell dimensions: a ϭ 6.195(7), b ϭ 8.717(10), c ϭ
˚
12.256(3) A,
α ϭ 102.644(12),
β ϭ 101.826(13),
γ ϭ
3
˚
105.706(12)°, V ϭ 5965(5) A , 4127 reflections. CCDC-207626
contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cam-
bridge Crystallographic Data Center, 12, Union Road, Cam-
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Copies of the data can be obtained free of charge
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Compound 18: C12H21NO, triclinic crystals of space group
Received August 27, 2003
748
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 724Ϫ748