Inter- and intramolecular [2+2]-photocycloaddition of tetronates - Stereoselectivity, mechanism, scope and synthetic applications

Article abstract of DOI:10.1002/ejoc.200400551

[2+2]-photocycloaddition reactions of various tetronates (3-8, 12, 16, 20, 37) have been examined. The tetronates were prepared from the corresponding tetronic acid by O-alkylation with an alkyl bromide or with an alcohol (Mitsunobu protocol). If the photocycloaddition reaction (λ = 254 nm, solvent: diethyl ether or tert-butyl alcohol) was carried out in an intramolecular fashion the tri- and tetracyclic products 21-23, 27-36 were obtained in good yields (52-75%) and with excellent simple diastereoselectivity. The reaction tolerates a high degree of substitution at both the tetronate and at the alkene double bond. High facial diastereoselectivities were observed if stereogenic centers were present in the alkene tether (e.g. 7a → 33) or if the alkenyl substituent was attached to the stereogenic C5 carbon atom of the tetronate irradiation precursor (e.g. 20 → 32). The reaction was also conducted in an intermolecular fashion. The methoxyethoxymethoxy (MEM) protecting group was suitable to protect the free tetronate hydroxy group. The photocycloaddition of tetronate 8 to cyclopentene was highly selective delivering the tricyclic products 39 in an 8:1 exo/endo ratio (59% yield). The products obtained from the intermolecular reaction underwent a de Mayo-like ring expansion delivering oxepane-diones 45-47 in good yields (74-84%). In mechanistic studies it was found that the formation of the photoproduct was supressed upon addition of piperylene. Furthermore, in the presence of acetone as a sensitizer the reaction could be conducted at λ = 300 nm. At this wavelength no conversion occurred under direct irradiation. These observations suggest the involvement of triplet intermediates in the reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200400551

FULL PAPER
Inter- and Intramolecular [2؉2]-Photocycloaddition of Tetronates ؊
Stereoselectivity, Mechanism, Scope and Synthetic Applications
Michael Kemmler,[a] Eberhardt Herdtweck,[b] and Thorsten Bach*[a]
Keywords: Cycloadditions / Diastereoselectivity / Lactone / Oxygen heterocycles / Photochemistry
[2+2]-photocycloaddition reactions of various tetronates (3−8,
12, 16, 20, 37) have been examined. The tetronates were pre- free tetronate hydroxy group. The photocycloaddition of te-
pared from the corresponding tetronic acid by O-alkylation tronate 8 to cyclopentene was highly selective delivering the
with an alkyl bromide or with an alcohol (Mitsunobu proto- tricyclic products 39 in an 8:1 exo/endo ratio (59% yield). The
methoxy (MEM) protecting group was suitable to protect the
col). If the photocycloaddition reaction (λ = 254 nm, solvent:
diethyl ether or tert-butyl alcohol) was carried out in an intra-
molecular fashion the tri- and tetracyclic products 21−23,
products obtained from the intermolecular reaction under-
went a de Mayo-like ring expansion delivering oxepane-di-
ones 45−47 in good yields (74−84%). In mechanistic studies
27−36 were obtained in good yields (52−75%) and with ex- it was found that the formation of the photoproduct was sup-
cellent simple diastereoselectivity. The reaction tolerates a
high degree of substitution at both the tetronate and at the
alkene double bond. High facial diastereoselectivities were
observed if stereogenic centers were present in the alkene
tether (e.g. 7a Ǟ 33) or if the alkenyl substituent was at-
tached to the stereogenic C5 carbon atom of the tetronate
irradiation precursor (e.g. 20 Ǟ 32). The reaction was also
ressed upon addition of piperylene. Furthermore, in the pres-
ence of acetone as a sensitizer the reaction could be con-
ducted at λ = 300 nm. At this wavelength no conversion oc-
curred under direct irradiation. These observations suggest
the involvement of triplet intermediates in the reaction.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
conducted in an intermolecular fashion. The methoxyethoxy- Germany, 2004)
Introduction
ates in photocycloaddition reactions were known at this
time.[8,9] In a recent program we investigated the prep-
aration of a variety of bi-, tri- and tetracyclic heterocycles
of general formula A from substituted tetronates B by inter-
and intramolecular [2ϩ2]-photocycloaddition reactions
(Scheme 1).
The photochemical [2ϩ2]-cycloaddition[1Ϫ4] of two al-
kene units is a highly useful reaction in organic synthesis
since two new carbonϪcarbon bonds and up to four stere-
ogenic centers are formed during this process. In the course
of our studies towards the preparation of strained tetra-
hydrofurans by [2ϩ2]-photocycloaddition we investigated
the CuOTf-catalysed photocycloaddition of alkenes to enol
ethers. Despite the fact that successful applications of this
reaction are known,[5] we found that the lability of the enol
ether moiety under the Lewis acidic reaction conditions ac-
counts for a limited generality of this method. As a result
of our efforts to circumvent this problem we have disco-
vered the [2ϩ2]-photocycloaddition of tetronates and al-
kenes under direct irradiation.[6] Although many suitable
enone-type components for direct irradiation have been de-
veloped in the past,[1,3,7] no successful examples of tetron-
Scheme 1. Tetronates B as precursors of oxygen-containing hetero-
cycles of general formula A
In this paper, we report on the scope, mechanism and
synthetic applicability of this reaction.
[a]
Results and Discussion
Lehrstuhl für Organische Chemie I, Technische Universität
München
Lichtenbergstr. 4, 85747 Garching
Fax: (internat.) ϩ 49-(0)89-28913315
E-mail: thorsten.bach@ch.tum.de
Preparation of the Substrates: The substrates employed in
the [2ϩ2]-photocycloaddition reactions were routinely pre-
pared from the corresponding tetronic acids. Due to the
inefficient photoreactions of tetronic acids in their unpro-
tected form, the C4 hydroxy position had to be protected
[b]
Crystal Structure Determination, Lehrstuhl für Anorganische
Chemie
Technische Universität München,
Lichtenbergstr. 4, 85747 Garching
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DOI: 10.1002/ejoc.200400551
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Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
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prior to the cycloaddition step. Although several methods
are known to effect this transformation[10Ϫ13] we found two
conditions sufficient to deliver all desired substrates. One
method (method A) takes advantage of the relatively high
acidity of tetronic acid [pKa(H2O) ϭ 3.76][14] which allows
to employ it as acidic component under Mitsunobu con-
ditions (DIAD ϭ diisopropyl diazenedicarboxylate).[12]
Alternatively, cesium fluoride (CsF) in dimethylformamide
(DMF) has been reported to be an efficient agent for the
O-alkylation of tetronic acid (method B).[13] The substrates
we have prepared via the described routes are summarized
in Table 1.
Table 1. Preparation of O-substituted cycloaddition precursors
from unsubstituted tetronic acid (1) by methods A and B
Scheme 2. Preparation of photocycloaddition precursors incorpor-
ating substituted tetronic acids 9Ϫ11
the precursors 4e, 7b, 7c, and 12 (Scheme 2) using the Mit-
sunobu protocol (method A). Except for compound 12 all
chiral irradiation precursors were synthesized as racemates.
The substrates in which the alkene is attached to the te-
tronic acid core at C3 and C5 were accessible via short syn-
thetic routes. In the former case (C3 substitution), methyl
6-oxohexanoate was prepared from cyclohexanone (13)
following a procedure reported by Semple et al.[18] The al-
dehyde was transformed into the corresponding alkene (14)
using standard Wittig conditions. Following a literature
procedure reported for related compounds,[19] the tetronic
acid core was subsequently installed by acylation with chlo-
roacetyl chloride followed by base-assisted cyclization. The
reaction sequence was not further optimized. The acid 15
obtained from this sequence was then converted into its
methyl ester 16 by standard Mitsunobu chemistry
(Scheme 3).
For the synthesis of the C5-substituted system, diethyl
oxalate (17) was treated with homoallylmagnesium bromide
at Ϫ78 °C to give the Grignard mono-addition product
which was further reduced to the hydroxy ester 18.[20] The
hydroxy group was acetylated under standard conditions to
While the parent tetronic acid (1) is a commercially avail- give the corresponding acetate, which upon treatment with
able substance, its substituted derivatives had to be pre- LiHMDS underwent a smooth Dieckmann condensation to
pared. 3-Methyltetronic acid (9) was available from 2- give the tetronic acid 19 in 84% yield. Again, this com-
methyl acetoacetate in a two-step one-pot procedure in 40% pound was subsequently converted into its methyl ester 20
yield.[15] 3-tert-Butyltetronic acid (10) was prepared from using standard Mitsunobu conditions (Scheme 4).
tetronic acid (1) and tert-butyl alcohol under acidic con-
Irradiation Experiments: Intramolecular photocycloaddi-
ditions in 63% yield.[16] Enantiomerically pure (S)-(ϩ)-5- tion reactions were carried out in dilute solutions (approx.
methyltetronic acid (11) was obtained from (S)-(Ϫ)-ethyl 1 m) using Et2O or MeCN as standard solvents (ir-
˚
lactate via a two-step procedure in an overall yield of radiation source: Rayonet RPR-2537 A). These conditions
60%.[17] The tetronic acids were in turn used to synthesize allowed for reaction times of less than one hour and re-
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the straight photocycloaddition product. An indication for
the formation of crossed photocycloaddition products was
not found.
Starting from allyl tetronate 3 the formation of the
straight photocycloaddition product was unlikely. The short
chain connecting the reactive centers would in this reaction
mode only allow for a highly strained oxa[2.2.0]hexane. The
formation of the crossed cycloaddition product with an
oxa[2.1.1]hexane core, however, was more likely and was
therefore expected. Surprisingly, this product was not de-
tected. Instead carbon radicals, which were generated from
the solvent by hydrogen abstraction,[22] added to the ter-
minal double bond to give the substituted tetronates 24Ϫ26
(Scheme 6). The hydrogen abstraction from isopropanol
was most productive and gave the radical addition product
in 57% yield.
Scheme 3. Preparation of the C3-substituted methyl tetronate 16
from cyclohexanone (13): a) Ac2O (neat), TSA, 60% b) O3, MeOH,
DMS, then HOAc/THF/H2O (2:2:1), reflux, 48% c) CH3PPh3ϩIϪ,
nBuLi in Et2O, 46% d) TMS-Cl, LDA in THF e) ClCH2COCl in
THF f) DBU in toluene then 1  HCl, 27% from 14 g) MeOH,
PPh3, DIAD in THF, 92%
Scheme 4. Preparation of the C5-substituted methyl tetronate 20
from diethyl oxalate (17): a) C4H7MgBr in Et2O, 83% b)
Na(CN)BH3 in EtOH/H2O/HOAc, 7:3:1, 80% c) Ac2O in py, 83%
d) LiHMDS in THF, 84% e) MeOH, PPh3, DIAD in THF, 94%.
Scheme 6. Products obtained from solvent addition to allyl tetron-
ate (3) upon irradiation
In a subsequent series of experiments we investigated the
efficiency of the cycloaddition depending on the substi-
tution pattern of appropriate 3-butenyl tetronate precursors
(compounds 4). The least substituted parent compound 4a
had given the photocycloaddition product 21 in 74% yield
(Scheme 5). From the smooth formation of photoproducts
27Ϫ30 it can be concluded that the reaction is not sensitive
towards the degree of substitution on either reactive center.
Even the tetrasubstituted alkene 4d underwent the [2ϩ2]-
photocycloaddition in 61% yield (Scheme 7). The simple
diastereoselectivity was high in all cases, only one dia-
stereoisomer was detected.
sulted in clean conversions. In some cases it was favorable
to use tert-butyl alcohol as a solvent to minimize side reac-
tions caused by hydrogen abstraction from the solvent.
When the series of C4-substituted tetronates 4a, 5 and 6
was subjected to the standard irradiation conditions we
found that these substrates undergo an efficient photocy-
cloaddition to give the desired tricyclic products. In the co-
urse of the reaction tetrahydrofuran 21, tetrahydropyran 22,
and oxepane 23 were generated with the heterocyclic ring
directly anellated to the cyclobutane unit (Scheme 5). As
expected from literature precedence for related reac-
tions,[3,21] the photocycloaddition proceeded exclusively to
Scheme 5. Formation of strained tetrahydrofurans, tetrahydropy-
rans and oxepanes by intramolecular [2ϩ2]-PCA of tetronates 4a,
5 and 6
Scheme 7. Formation of substituted 2,9-dioxatricyclo[5.3.01,5]de-
canes 27Ϫ30 from tetronates 4bϪ4e
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Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
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Irradiation of tetronates bearing the alkene tether at-
tached to carbon atoms C3 (16) or C5 (20) of the tetronic
acid core delivered the cycloaddition products 31 and 32
possessing the all-carbon [3.2.0]bicycloheptane backbone
(Scheme 8). In both cases, diastereomerically pure com-
pounds were isolated in good yields. The facial diastereosel-
ectivity in the reaction of the 5-substituted tetronate 20 can
be readily explained by an attack at the tetronate face to
which the 3-butenyl chain is being directed by the stereog-
enic center at C5.
Scheme 9. Investigation of the facial diastereoselectivity in the
cycloaddition of tetronates 7aϪ7c
ity of the hydrogen atom H3 and the substituent at C10.
The cis-syn-cis products (33bϪ35b) suffer from Pitzer
(eclipsing) strain. The strain is particularly apparent at the
C7-C8 bond where the two anellated ring bonds C7ϪC6
and C8ϪC9 are synperiplanar. Any interaction between H3
and the substituent at C10 is, however, avoided in these
compounds (Figure 1).
Scheme 8. Formation of tricyclic products 31 and 32 from C3-sub-
stituted tetronate 16 and C5-substituted tetronate 20
In order to examine further the facial diastereoselectivity
of the [2ϩ2]-photocycloaddition, the substituted tetronate
7a, bearing two stereocenters in the side chain, was pre-
pared. The reaction would give access to the biologically
relevant skeleton of the natural product punctaporonin C.[23]
Upon irradiation, this compound, indeed, delivered a single
product that was identified as compound 33a (vide infra).
In connection with a projected synthesis of the natural
product we were also interested in the cycloaddition of the
methyl-substituted analog 7b. Again, under standard ir-
radiation conditions, we observed a smooth conversion, but
much to our surprise we found a 1:1 mixture of stereoiso-
Figure 1. Stereochemical situation in the tetracyclic photocyclo-
addition products 33a (cis-anti-cis-skeleton) and 35b (cis-syn-cis-
skeleton)
Under the premise that the steric interactions mentioned
mers in the product. The structure of both compounds were for compounds 33Ϫ35 are present in the transition states
elucidated by 2D NMR spectroscopy and were found to be leading to the products (product control), it is apparent that
the diastereomeric compounds 34a and 34b. Obviously, the 35b is favored because the severe repulsion between the C10
course of the reaction is strongly influenced by the steric tert-butyl group and hydrogen atom H3 is avoided while
bulk of the C3 substituent of the tetronate. In order to ver- 33a is preferred in the reaction of 7a minimizing Pitzer
ify this assumption we prepared compound 7c, bearing a strain at C7ϪC8. These arguments are in line with mechan-
tert-butyl instead of the methyl group. Upon irradiation, istic proposals concerning the photocycloaddition (vide in-
this compound delivered one single cycloaddition product fra).
which was shown to be tetracycle 35b. It appears to be pos-
Efforts to control the facial diastereoselectivity by groups
sible to completely control the facial diastereoselectivity of attached to the tetronate core proved to be less successful.
these [2ϩ2]-photocycloadditions by the size of the C3 sub- Tetronate 12 was chosen because of its easy availability
stituent in the irradiation precursor (Scheme 9).
from literature known tetronic acid 11 and of the obvious
A preliminary explanation for the observed relative prod- charme of producing enantiomerically pure products. The
uct configuration can be given on the basis of the relative photocycloaddition of compound 12 proceeded smoothly
size of the substituents at carbon atom C10 of the tetracyc- but without any differentiation of the diastereotopic faces
lic skeleton. In the cis-anti-cis products 33aϪ35a, the to give a 1:1 mixture of the diastereoisomers 36a and 36b
eclipse of the rings anellated to the central tetrahydrofuran (Scheme 10). In comparison to literature known examples
is avoided as the cyclopentane ring and the cyclobutane ring dealing with the stereocontrol exerted by γ-substituents of
point to opposite directions. Inspection of molecular α,β-unsaturated carbonyl compounds in [2ϩ2]-photocy-
models show, however, that an unfavorable steric interac- cloaddition reactions[24] this low degree of differentiation is
tion can occur in these compounds due to the close proxim- somewhat surprising but not unprecedented.[8,9,25]
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M. Kemmler, E. Herdtweck, T. Bach
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21 (Figure 2) and 33a (Figure 3) that were unambiguously
assigned by X-ray crystallographic analysis.[26]
Scheme 10. Investigation of the facial diastereoselectivity in the
cycloaddition of tetronate 12
In order to extend tetronate photocycloadditions to inter-
molecular cycloadditions commercially available tetronate
37 was reacted with cyclopentene. After some optimization
(concentration, solvent) the cycloaddition product 38 was
obtained in greater than 50% yield and in an exo/endo ratio
of 3:1. As already mentioned, the free tetronic acid reacted
sluggishly. Still, it was desirable for consecutive reactions
to have access to photocycloaddition products with a free
hydroxy group at carbon atom C2. Following this consider-
ation, the MEM protected tetronate 8 was subjected to the
optimized irradiation conditions. The cycloaddition prod-
uct 39 was obtained in yields similar to 38 and with an
improved exo/endo selectivity (8:1, Scheme 11).
Figure 2. A molecule of 2,9-dioxatricyclo[5.3.0.01,5]decane (21) in
the crystal
Scheme 11. Intermolecular cycloaddition of tetronates 8 and 37
and cyclopentene
Figure 3. A molecule of 2,12-dioxatetracyclo[6.5.0.03,7.01,10]tri-
decan-11-one (33a) in the crystal
In a series of experiments different alkenes as reaction
partners were tested in the intramolecular [2ϩ2]-photocy-
cloaddition. It was found that the cyclopentene homologs
cyclohexene and cyclooctene can be utilized giving the cor-
responding photoproducts in good yields. Electron rich ole-
fins like the ketene diethylactetal 40 can also be employed
giving bicyclic products such as 41 (Scheme 12). In this case
the yield dropped, however, to 33%. Electron poor sub-
strates (e.g. acrylonitrile, vinylcarbonate) did not give any of
the expected photoproducts but unidentified side products
accompanied by polymerization.
In addition to the structural assignment of compounds
21 and 33a by X-ray diffraction, a set of 2D NMR experi-
ments was carried out with these compounds. The NOESY
contacts obtained from this study were used to assign the
regio- and stereochemistry of the other cycloaddition prod-
ucts. The diagnostic contacts for the 2,9-dioxatricy-
clo[5.3.0.01,5] skeleton, as derived from compound 21, were
found between the protons at C5 and C10 (strong) as well
as between the protons at C3 and C7 (strong). The struc-
tural assignments of photocycloaddition products 21Ϫ23
and 27Ϫ30 rest on these observations. The carbocyclic sys-
tems 31 and 32 were also unambiguously assigned by 2D
NMR spectroscopy.
To distinguish between the two possible diastereoisomers
in compounds 33Ϫ36 and 38Ϫ39 data obtained from
NOESY experiments of compound 33a were taken for com-
parison. According to the acquired data strong through
space interaction of the protons at C3 and C10 as well as
C8 and C13 accounted for the cis-anti-cis diastereoisomers
whereas strong contacts between the protons connected to
Scheme 12. Intermolecular cycloaddition of tetronate 8 and ketene
diethyl acetal 40
Proof of Configuration: Structural assignments were car- C3 and C13, C7 and C8 and C8 and C13 were characteristic
ried out on the basis of the structures of photoproducts for the cis-syn-cis diastereoisomers. It is worth to note that
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Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
FULL PAPER
in the latter diastereoisomers the C10 substituent does not tion of piperylene in Et2O as a solvent the product forma-
produce any NOE contact to any proton, which indicates tion was completely supressed.
that it is obviously in a sterically uncrowded position (cf.
Figure 1). As an illustration the NOE data for two represen-
tative cycloaddition products, compounds 36a and exo-38,
are given in Figure 4 (--- ϭ medium, Ϫ ϭ strong).
It was also possible to carry out the reaction under sensit-
ized conditions. When a sample of 4a was irradiated under
˚
standard conditions using a 300 nm (Rayonet RPR-3000 A)
˚
or 350 nm (Rayonet RPR-3500 A) light source no conver-
sion was observed and the starting material was recovered
unchanged after 6 h of irradiation. In the presence of ace-
tone [E(T1) ϭ 332 kJ/mol] as a sensitizer the photocycload-
dition took place upon irradiation at 300 nm to give one
single product which was shown to be identical with prod-
uct 21 obtained by direct irradiation. This finding also sup-
ports the involvement of a triplet intermediate. When
benzophenone [E(T1) ϭ 287 kJ/mol] or acetophenone
[E(T1) ϭ 310 kJ/mol] were employed as sensitizers under
the same conditions no reaction was observed. The T1 en-
ergy for the examined tetronate 4a can thereby be estimated
to be 310 kJ/mol Ͻ E(T1) Ͻ 332 kJ/mol. For the intra-
molecular reactions to 21 and 27Ϫ35 the triplet pathway
consequently involves the initial cyclization to a five-
membered ring and the intermediate formation of a 1,4-
biradical. The 1,4-biradical can close to the product or if
steric factors prohibit this ring closure (cf. 7c Ǟ 35) it can
revert to the starting material. The diastereoselectivity is
consequently controlled by both reaction steps.
Figure 4. Structural assignments of photocycloaddition products
36a and 38 (exo) on the basis of NOESY experiments
Mechanistic Investigations: [2ϩ2]-Photocycloadditions
under direct irradiation are usually initiated by the absorp-
tion of a photon resulting in the excitation of the molecule
into its S1 singlet state. After fast ISC the molecule reaches
its T1 triplet excited state, the lifetime of which is usually
sufficient to allow photocycloadditions to occur.[27] Upon
reaction with an appropriate alkene the critical 1,4-biradical
Synthetic Applications: Apart from the direct application
is formed followed by cyclization to the final product. How- of the polycyclic ringsystems generated by the photocy-
ever, the biradicals can also revert to the starting materials cloadditions in synthesis the highly strained products are
thus, depending on the different rate constants, producing also suitable for further transformations. As already men-
the final product.[4] In order to find out if the tetronate tioned in our earlier communication[6] one of the obvious
[2ϩ2]-photocycloaddition follows the described reaction applications is the use of the generated β-hydroxy lactone
mechanism we carried out the photocycloaddition 4a to 21 moiety in a retro-aldol ring expansion. This reaction leads
in the presence of various amounts of piperylene [E(T1) ϭ to bicyclic oxepanediones and represents an useful expan-
240 kJ/mol for (Z)- and 247 kJ/mol for (E)-piperylene] sion of the de Mayo methodology[29] which is usually car-
which is known to be an efficient triplet quencher.[28] As ried out with β-diketo compounds and cannot be conduc-
can be deduced from Figure 5 the formation of the photop- ted with β-keto esters. In order to highlight this method-
roduct under standard irradiation conditions is decreased ology, a small series of cycloaddition-ring opening reactions
by an increasing amount of quencher added. This result was conducted. MEM-protected tetronate 8 was irradiated
strongly suggests the participation of an excited triplet state under standard conditions in the presence of cyclopentene,
in the examined reaction. Upon irradiation in a 0.5  solu- cyclohexene and cis-cyclooctene to the corresponding
Figure 5. Quenching of the photocycloaddition of 4a to 21 by various amounts of piperylene
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dried solvents. Microwave-assisted reactions were carried out in a
microwave oven (CEM-corporation, model MarsX) using tempera-
ture controlled conditions. Irradiation experiments were conducted
using dry solvents of spectroscopy grade quality (Merck Uvasol)
that had been thoroughly degassed before use (exception: tert-butyl
alcohol was of p.a. quality). Abbreviations: n-pentane (P), meth-
anol (MeOH), ethanol (EtOH), ethyl acetate (EtOAc), tetrahydro-
furan (THF), diethyl ether (Et2O), dichloromethane (DCM), tert-
butyl alcohol (tBuOH), isopropanol (iPrOH), acetic acid anhydride
(Ac2O), methoxyethoxymethyl choride (MEM-Cl). Relevant litera-
cycloaddition products. These products were immediately
deprotected with TiCl4 in CH2Cl2 to give, after purification,
the hydroxy lactones 42Ϫ44 in about 50% yield. For the
five- and six-membered ring system one major product, the
expected exo isomer, was isolated. In the cyclooctene case
a 3:2:2:1 mixture of diastereoisomers (as determined by
GC-MS) was obtained. Presumably, the reaction is not ster-
eospecific for the larger ring and the four diastereoisomers
are cis/trans-diastereoisomers of the exo and endo product.
Compounds 42Ϫ44 were in turn submitted to Cs2CO3 in ture known compounds: 5-Bromo-2,3-dimethylpent-2-ene,[31] 2,[32]
3,[13] 4a,[11] 9[15] 10,[16] 11,[17] 14,[33] and 18.[20] All other chemicals
not mentioned in the following section were commercially available.
THF under microwave irradiation for 30 min and gave the
ring-opened oxepane-diones 45Ϫ47 in good yields
Apparent multiplets which occur as a result of accidental equality
(Scheme 13).
of coupling constants to those of magnetically nonequivalent pro-
tons are marked as virtual (virt.).
5-(But-3-enyl)-4-hydroxyfuran-2(5H)-one (19): To a solution of
ethyl-2-hydroxyhex-5-enoate (18, 1.60 g, 10.0 mmol) in pyridine (10
mL) was added Ac2O (1.89 mL, 2.04 g, 20.0 mmol). The mixture
was stirred at room temp. for 8 h and was then quenched by the
addition of satd. NH4Cl (30 mL). The mixture was extracted with
EtOAc (3 ϫ 30 mL) and the combined organic phases were washed
with brine (20 mL) and then dried (Na2SO4). After filtration and
evaporation of the solvent under reduced pressure crude ethyl 2-
acetoxyhex-5-enoate (1.66 g, 8.30 mmol, 83%) was obtained as a
yellow oil. This crude product was dissolved in THF (15 mL), co-
oled to Ϫ78 °C and then treated with a solution of LiHMDS (1 
in THF, 20.0 mL, 20.0 mmol). The resulting mixture was stirred at
this temperature for 1 h and 2  HCl (30 mL) was added. It
was extracted with EtOAc (4 ϫ 30 mL) and the combined organic
layers were dried (Na2SO4). After filtration and evaporation of the
solvent under reduced pressure crude 5-(but-3-enyl)-4-hydroxyfu-
ran-2(5H)-one (19) was obtained as a yellow solid which was
recrystallized from P/EtOAc to give the title compound as colorless,
crystalline solid (1.07 g, 6.97 mmol, 84%, 70% from 18). M.p.
Scheme 13. Formation of oxepanediones 45Ϫ47 by retro aldol reac-
tion of cycloaddition products 42Ϫ44 (* at 50% conversion based
on recovered starting material; ** 1:1 diastereomeric mixture)
The stereochemistry remained unchanged in the course
of this process. In the cyclohexene case prolonged reaction
times or the use of stronger bases (NaH, LDA, KHMDS)
sometimes produced epimerized products at the stereoc-
enter adjacent to the newly formed carbonyl group. As ex-
pected, in the eight membered ring case the four dia-
stereoisomers produced a mixture of only two ring-opened
products in a ratio of 1:1.
55Ϫ56 °C; Rf
ϭ
0.40 (P/Et2O, 1:1). 1H NMR (360 MHz,
[D6]DMSO): δ ϭ 1.50 (virt. quint, 3J ϭ 2J ϭ 7.2 Hz, 1 H),
1.87Ϫ1.97 (m, 1 H), 2.10 (virt. q, 3J ϭ 2J ϭ 7.2 Hz, 1 H), 4.80 (dd,
3
3J ϭ 4.1 Hz, 7.2 Hz, 1 H), 4.90 (s, 1 H), 5.00 (br. d, J ϭ 10.1 Hz,
1 H), 5.06 (br. d, 3J ϭ 18.0 Hz, 1 H), 5.84 (ddt, 3J ϭ 7.1 Hz,
10.1 Hz, 18.0 Hz, 1 H), 12.4Ϫ13.1 (br. s, 1 H, OH) ppm. 13C NMR
(90.6 MHz, [D6]DMSO): δ ϭ 28.1 (t), 30.5 (t), 77,6 (d), 87.9 (d),
115.5 (t), 137.4 (d), 173.0 (s), 181.8 (s) ppm. IR (KBr): ν˜ϭ 3387
(br. m , OϪH), 2926 (s, CϪH), 2690 (br. m ), 1690 (vs, CϭO), 1624
(vs), 1570 (vs), 1340 (m), 1290 (vs), 1174 (m), 1084 (m), 1023 (m),
996 (m), 930 (m), 912 (m), 814 (m). MS (70 eV, EI): m/z (%) ϭ154
(1) [Mϩ], 136 (s), 126 (5), 112 (2), 100 (100), 83 (20), 72 (19), 69
(11), 55 (87). C8H10O3 (154.16): calcd. C 62.33, H 6.54; found C
61.97, H 6.61.
Conclusion
In conclusion, the [2ϩ2]-photocycloaddition of tetron-
ates has been established as a useful addition to the syn-
thetic methodology available to organic photochemists. The
substrates involved are easily available or, in some cases,
commercially available. The photocycloaddition step usu-
ally proceeds in good yields and excellent selectivity. It can
be carried out in an intra- and an intermolecular fashion,
tolerating various substitution patterns. The photocyclo-
addition can be conducted under direct irradiation (λ ϭ 4-Hydroxy-3-(pent-4-enyl)furan-2(5H)-one (15): This procedure was
adapted from White et al.[19] To a solution of LDA (1  in THF,
17.0 mL, 17.0 mmol) was added methyl hept-6-enoate (14, 2.40 g,
17.0 mmol) in a dropwise fashion and the mixture was stirred at
254 nm) or under sensitized conditions (λ ϭ 300 nm, ace-
tone as sensitizer) and is likely to proceed via the tetronate
T1 state. The reaction products obtained represent useful
this temperature for 1 h. During this period TMS-Cl (4.20 mL, 32.9
synthetic intermediates by themselves and can additionally
mol) was slowly added and the mixture was extracted with H2O (2
be transformed into oxepane-diones by de Mayo-type retro-
ϫ 20 mL). The remaining organic phase was dried (Na2SO4), fil-
aldol ring expansion.
tered and the solvent was evaporated under reduced pressure to
give a brown oil. The crude product was filtered through silica (P/
EtOAc, 10:1, 100 mL) After evaporation of the solvent a yellow oil
was obtained which was dissolved in toluene (40 mL). DBU (1.70
mL, 8.30 mmol) was added and the resulting brown mixture was
Experimental Section
General: For general remarks, see ref..[30] All reactions involving
sensitive chemicals were carried out under inert conditions using
stirred at room temp. for 18 h. MeOH (40 mL) and 1  HCl (10
4588
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2004, 4582Ϫ4595

Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
FULL PAPER
mL) were then added and the mixture was stirred for another 4 h.
The volume was then reduced to ca. 5 mL and Et2O (30 mL) and
H2O (5 mL) were added. The phases were separated and the aque-
4-(3-Methylbut-3-enyloxy)furan-2(5H)-one (4b): Prepared from te-
tronic acid (1) (100 mg, 1.00 mmol) and 3-methyl-3-buten-1-ol (101
µL, 86.0 mg, 1.00 mmol) as pale yellow oil in a yield of 142 mg
ous phase was extracted with Et2O (2 ϫ 20 mL). The combined (0.85 mmol, 85%). Rf ϭ 0.25 (P/DCM/EtOAc, 10:5:2). 1H NMR
3
organic layers were dried (Na2SO4), filtered and the solvent was
evaporated under reduced pressure. The remaining yellow oil was
(360 MHz, CDCl3): δ ϭ 1.73 (s, 3 H), 2.44 (t, J ϭ 6.6 Hz, 2 H),
4.11 (t, 3J ϭ 6.6 Hz, 2 H), 4.57 (t, 4J ϭ 0.9 Hz, 2 H), 4.72 (s, 1 H),
purified by column chromatography (silica, P/EtOAc, 1:1 as eluent) 4.81 (s, 1 H), 5.06 (s, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3):
to yield the title compound 15 (0.76 g, 4.52 mmol, 27% from 14)
δ ϭ 22.3 (q), 36.1 (t), 67.7 (t), 70.8 (t), 88.7 (d), 112.8 (t), 140.4 (s),
as colorless crystals. M.p. 89Ϫ94 °C; Rf ϭ 0.80 (P/EtOAc, 1:1). 1H 173.3 (s), 179.2 (s) ppm. IR (NaCl): ν˜ ϭ 3120 (m, CϭCϪH), 2940
3
NMR (360 MHz, [D6]DMSO): δ ϭ 1.46 (virt. quint, J ϭ 7.7 Hz,
(m, CϪH), 1774 (vs, CϭO), 1748 (vs), 1628 (vs), 1367 (m), 1318
3
2 H), 2.00 (virt. q, 3J ϭ 7.7 Hz, 2 H), 2.08 (t, J ϭ 7.7 Hz, 2 H), (s), 1236 (m), 1149 (s), 1054 (s), 972 (w), 884 (m). MS (70 eV, EI):
4.55 (s, 2 H), 4.93 (br. d, 3J ϭ 10.4 Hz, 1 H), 5.00 (br. d, 3J ϭ m/z (%) ϭ168 (1) [Mϩ], 140 (20), 123 (10), 96 (86), 69 (100), 53
3
3
16.7 Hz, 1 H), 5.75 (ddt, Jd ϭ 10.4 Hz, 16.7, Jt ϭ 7.7 Hz, 1 H),
11.71 (br. s, 1 H, OH) ppm. 13C NMR (90.6 MHz, [D6]DMSO):
δ ϭ 20.3 (t), 26.6 (t), 32.8 (t), 66.3 (t), 98.8 (s), 114.8 (t), 138.4 (d),
173.2 (s), 174.8 (s) ppm. IR (NaCl): ν˜ ϭ 3100 cmϪ1 (br. s, OϪH),
3055 (CϭCϪH), 2939 (CϪH), 1732 (vs, CϭO), 1650 (vs,), 1442
(s), 1267 (s), 1097 (m), 1044 (s), 916 (m). MS (70 eV, EI): m/z (%) ϭ
168 (13) [Mϩ], 150 (8), 127 (10), 113 (92), 101 (75), 95 (48), 67
(100). HRMS calcd. for C9H12O3 168.07864, found 168.07859.
(46). C9H12O3 (168.19): calcd. C 64.27, H 7.19; found C 63.90,
H 7.17.
4-(4-Methylpent-3-enyloxy)furan-2(5H)-one (4c): Prepared from te-
tronic acid (1) (100 mg, 1.00 mmol) and 4-methyl-3-penten-1-ol
(116 µL, 100 mg, 1.00 mmol) as pale yellow oil in a yield of 146 mg
(0.80 mmol, 80%). Rf ϭ 0.25 (P/DCM/EtOAc, 10:5:2). 1H NMR
(360 MHz, CDCl3): δ ϭ 1.60 (s, 3 H), 1.68 (s, 3 H), 2.42 (virt. q,
3
4
3J ϭ 7.0 Hz, 2 H), 3.96 (t, J ϭ 7.0 Hz, 2 H), 4.58 (t, J ϭ 0.9 Hz,
2 H), 5.03 (s, 1 H), 5.08 (tt, J ϭ 7.0, J ϭ 1.3 Hz, 1 H) ppm. 13C
NMR (90.6 MHz, CDCl3): δ ϭ 17.7 (q), 25.6 (q), 27.3 (t), 67.7 (t),
72.4 (t), 88.6 (d), 117.9 (s), 135.5 (d), 173.5 (s), 179.4 (s) ppm. IR
(NaCl): ν˜ ϭ 3096 (m, CϭCϪH), 2934 (m, CϪH), 1775 (vs, CϭO),
1748 (vs), 1626 (vs), 1367 (m), 1317 (s), 1237 (m), 1149 (s), 1052
(s), 971 (w), 882 (w). MS (70 eV, EI): m/z (%) ϭ 182 (2) [Mϩ], 167
(1), 154 (3), 138 (20), 123 (13), 110 (5), 82 (21), 69 (62), 55 (100).
C10H14O3 (182.22): calcd. C 65.91, H 7.74; found C 65.71, H 7.78.
3
4
General Procedure for the Reaction of Tetronic Acids and Alcohols:
To a solution of the tetronic acid (1.00 mmol), PPh3 (262 mg,
1.00 mmol) and the alcohol (1.00 mmol) in 2.00 mL THF at room
temp., DIAD (194 µL, 202 mg, 1.00 mmol) was added under vigor-
ous stirring. The yellow mixture was stirred at this temperature for
another 6 h. The solvent was then evaporated under reduced press-
ure and the remaining oil was purified by column chromatography
to give the desired product.
4-(2-Vinylcyclopentanyloxy)furan-2(5H)-one (7a): Prepared from te-
tronic acid (1) (100 mg, 1.00 mmol) and trans-2-vinylcyclopentanol
(2, 112 mg, 1.00 mmol) as colorless crystals in a yield of 150 mg
4-(Pent-4-enyloxy)furan-2(5H)-one (5): Compound 5 was prepared
from tetronic acid (1) (100 mg, 1.00 mmol) and 4-penten-1-ol (103
µL, 86.0 mg, 1.00 mmol) as pale yellow oil in a yield of 143 mg
(0.85 mmol, 85%). Rf ϭ 0.15 (P/DCM/EtOAc, 10:2:1). 1H NMR
1
(0.77 mmol, 77%). M.p. 87Ϫ89 °C; Rf ϭ 0.15 (P/EtOAc, 8:1). H
NMR (360 MHz, CDCl3): δ ϭ 1.61Ϫ2.08 (m, 6 H), 2.58Ϫ2.69 (m,
3
(360 MHz, CDCl3): δ ϭ 1.88 (quint, J ϭ 6.5 Hz, 2 H), 2.19 (virt.
4
1 H), 4.53Ϫ4.62 (m, 3 H), 5.03 (t, J ϭ 1.0 Hz, 1 H), 5.08 (br. d,
q, 3J ϭ 6.5 Hz, 2 H), 4.04 (t, 3J ϭ 6.5 Hz, 2 H), 4.62 (t, 4J ϭ
0.9 Hz, 2 H), 5.04 (br. d, 3J ϭ 10.2 Hz, 1 H), 5.06 (br. d, 3J ϭ
18.6 Hz, 1 H), 5.06 (t, 4J ϭ 0.9 Hz, 1 H), 5.80 (ddt, 3Jd ϭ 10.2 Hz,
3J ϭ 10.0 Hz, 1 H), 5.12 (br. d, 3J ϭ 18.3 Hz, 1 H), 5.84 (ddd, 3J ϭ
7.7 Hz, 10.0 Hz, 18.3 Hz, 1 H) ppm. 13C NMR (90.6 MHz,
CDCl3): δ ϭ 22.1 (t), 29.2 (t), 31.3 (t), 48.9 (d), 68.0 (t), 87.5 (d),
89.3 (d), 116.8 (t), 135.6 (d), 173.8 (s), 178.5 (s) ppm. IR (KBr):
ν˜ ϭ 3073 (w, CϭCϪH), 2976 (m, CϪH), 1774 (vs, CϭO), 1743
(vs), 1624 (vs), 1316 (s), 1235 (m), 1147 (s), 1050 (s), 926 (m), 800
(m). MS (70 eV, EI): m/z (%) ϭ 194 (5) [Mϩ], 176 (3), 165 (5), 149
(8), 139 (11), 101 (14), 95 (75), 79 (100), 67 (70), 55 (18). C11H14O3
(194.23): calcd. C 68.02, H 7.27; found C 67.83, H 6.90.
3
18.6, Jt ϭ 6.5 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ
27.5 (t), 29.6 (t), 67.8 (t), 72.0 (t), 88.8 (d), 116.0 (t), 136.7 (d),
173.5 (s), 179.3 (s) ppm. IR (NaCl): ν˜ ϭ 3120 (w, CϭCϪH), 3077
(w, CϭCϪH), 2943 (s, CϪH), 1774 (vs, CϭO), 1747 (vs), 1626 (vs),
1450 (m), 1371 (s), 1319 (s), 1238 (m), 1150 (vs), 1052 (vs), 980 (m),
882 (s), 803 (s). MS (70 eV, EI): m/z (%) ϭ 168 (3) [Mϩ], 150 (2),
140 (10), 139 (14), 123 (12), 114 (42), 113 (43), 96 (12), 69 (100),
53 (24). C9H12O3 (168.19): calcd. C 64.27, H 7.19; found C 63.96,
H 7.14.
4-(But-3-enyloxy)-3-methylfuran-2(5H)-one (4e): Prepared from te-
tronic acid 9 (114 mg, 1.00 mmol) and 3-buten-1-ol (86.0 µL,
74.0 mg, 1.00 mmol) as pale yellow oil in a yield of 133 mg
(0.79 mmol, 79%). Rf ϭ 0.15 (P/DCM/EtOAc, 10:2:1). 1H NMR
(360 MHz, CDCl3): δ ϭ 1.77 (t, 4J ϭ 1.4 Hz, 3 H), 2.46 (virt. q,
4-(Hex-5-enyloxy)furan-2(5H)-one (6): Compound 6 was prepared
from tetronic acid (1) (100 mg, 1.00 mmol) and 5-hexen-1-ol (114
µL, 100 mg, 1.00 mmol) as pale yellow oil in a yield of 151 mg
(0.83 mmol, 83%). Rf ϭ 0.15 (P/DCM/EtOAc, 10:2:1). 1H NMR
(360 MHz, CDCl3): δ ϭ 1.47Ϫ1.56 (m, 2 H), 1.72Ϫ1.82 (m, 2 H),
3
3J ϭ 6.6 Hz, 2 H), 4.17 (t, J ϭ 6.6 Hz, 2 H), 4.58 (s, 2 H), 5.09
(br. d, 3J ϭ 9.3 Hz, 1 H), 5.13 (br. d, 3J ϭ 18.3 Hz, 1 H), 5.77 (ddt,
3Jd ϭ 18.3 Hz, 9.3, 3Jt ϭ 6.6 Hz, 1 H) ppm. 13C NMR (90.6 MHz,
CDCl3): δ ϭ 7.4 (q), 33.8 (t), 65.9 (t), 69.8 (t), 98.6 (s), 118.3 (t),
132.7 (d), 171.3 (s), 175.4 (s) ppm. IR (NaCl): ν˜ ϭ 3079 (w, Cϭ
CϪH), 2958 (m, CϪH), 2923 (m, CϪH), 1755 (vs, CϭO), 1677
(vs), 1409 (s), 1389 (s), 1326 (s), 1251 (s), 1129 (s), 1048 (s), 920
(m), 756 (s). MS (70 eV, EI): m/z (%) ϭ 168 (3) [Mϩ], 150 (1), 139
(9), 144 (4), 96 (3), 83 (12), 69 (7), 55 (100). HRMS calcd. for
C9H12O3 168.07864, found 168.07868.
3
3
2.09 (virt. q, J ϭ 6.8 Hz, 2 H), 4.03 (t, J ϭ 6.8 Hz, 2 H), 4.60 (t,
4J ϭ 0.9 Hz, 2 H), 4.97 (br. d, 3J ϭ 10.2 Hz, 1 H), 5.01 (br. d, 3J ϭ
16.5 Hz, 1 H), 5.05 (t, 4J ϭ 0.9 Hz, 1 H), 5.78 (ddt, 3Jd ϭ 10.2 Hz,
3
16.5, Jt ϭ 6.8 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ
24.8 (t), 27.8 (t), 33.0 (t), 67.8 (t), 72.7 (t), 88.7 (d), 115.2 (t), 137.8
(d), 173.5 (s), 179.4 (s) ppm. IR (NaCl): ν˜ ϭ 3120 (w, CϭCϪH),
3076 (w, CϭCϪH), 2940 (m, CϪH), 1774 (vs, CϭO), 1747 (vs),
1627 (vs), 1370 (m), 1319 (vs), 1239 (m), 1149 (s), 1052 (s), 882 (m),
802 (m). MS (70 eV, EI): m/z (%) ϭ 182 (2) [Mϩ], 164 (1), 153 (8),
3-Methyl-4-(2-vinylcyclopentanyloxy)furan-2(5H)-one (7b): Pre-
137 (3), 124 (2), 110 (4), 101 (4), 82 (9), 69 (35), 55 (100). C10H14O3 pared from tetronic acid 9 (114 mg, 1.00 mmol) and trans-2-vinyl-
(182.22): calcd. C 65.91, H 7.74; found C 65.85, H 7.81. cyclopentanol (2, 112 mg, 1.00 mmol) as colorless crystals in a yield
Eur. J. Org. Chem. 2004, 4582Ϫ4595
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4589

M. Kemmler, E. Herdtweck, T. Bach
FULL PAPER
of 142 mg (0.68 mmol, 68%). M.p. 51Ϫ53 °C; Rf ϭ 0.25 (P/EtOAc,
1.00 mmol) as pale yellow oil in a yield of 167 mg (0.92 mmol,
1
8:1). H NMR (360 MHz, CDCl3): δ ϭ 1.62Ϫ2.06 (m, 6 H), 1.79 92%). Rf ϭ 0.25 (P/EtOAc, 2:1). 1H NMR (360 MHz, CDCl3): δ ϭ
3
(s, 3 H), 2.53Ϫ2.63 (m, 1 H), 4.58 (br. s, 2 H), 4.69 (virt. t, J ϭ
1.60 (quint, 3J ϭ 7.7 Hz, 2 H), 2.07 (virt. q, 3J ϭ 7.7 Hz, 2 H),
4.0 Hz, 1 H), 5.09 (br. d, 3J ϭ 10.0 Hz, 1 H), 5.13 (br. d, 3J ϭ 2.25 (t, J ϭ 7.7 Hz. 2 H), 3.93 (s, 3 H), 4.65 (s, 2 H), 4.95 (br. d,
3
16.8 Hz, 1 H), 5.84 (ddd, 3J ϭ 7.8 Hz, 10.0 Hz, 16.8 Hz, 1 H) ppm.
13C NMR (90.6 MHz, CDCl3): δ ϭ 7.42 (q), 22.2 (t), 29.5 (t), 33.2 3Jd ϭ 10.1 Hz, 17.6, 3Jt ϭ 7.4 Hz, 1 H) ppm. 13C NMR (90.6 MHz,
(t), 49.8 (d), 66.3 (t), 85.0 (d), 98.5 (s), 117.0 (t), 136.2 (d), 171.1 CDCl3): δ ϭ 21.6 (t), 27.5 (t), 33.4 (t), 57.4 (q), 65.2 (d), 103.5 (s),
(s), 175.6 (s) ppm. IR (KBr): ν˜ ϭ 3081 (w, CϭCϪH), 2941 (m, 114.8 (t), 138.2 (d), 172.3 (s), 174.7 (s) ppm. IR (NaCl): ν˜ ϭ 3081
CϪH), 1775 (vs, CϭO), 1743 (vs), 1627 (vs), 1368 (m), 1320 (s), (w, CϭCϪH), 2931 (s, CϪH), 1748 (vs, CϭO), 1668 (vs), 1456 (m),
3J ϭ 10.5 Hz, 1 H), 5.01 (br. d, 3J ϭ 16.8 Hz, 1 H), 5.82 (ddt,
1238 (m), 1151 (s), 1053 (s), 972 (m), 919 (m), 884 (m), 803 (m). 1384 (s), 1255 (m), 1097 (m), 1049 (s). MS (70 eV, EI): m/z (%) ϭ
MS (70 eV, EI): m/z (%) ϭ 208 (5) [Mϩ], 179 (3), 114 (6), 103 182 (13) [Mϩ], 167 (9), 153 (30), 140 (31), 128 (90), 127 (80), 113
(4), 95 (100), 79 (16), 67 (45), 55 (16). HRMS calcd. for C12H16O3
208.10994, found 208.10985.
(100), 99 (90), 82 (50), 69 (60), 53 (90). HRMS calcd. for C10H14O3
182.09430, found 182.09455.
3-tert-Butyl-4-(2-vinylcyclopentanyloxy)furan-2(5H)-one (7c): Pre-
pared from tetronic acid 10 (156 mg, 1.00 mmol) and trans-2-vinyl-
cyclopentanol (2, 112 mg, 1.00 mmol) as colorless crystals in a yield
of 135 mg (0.54 mmol, 54%). M.p. 60Ϫ61 °C; Rf ϭ 0.25 (P/DCM/
EtOAc, 10:2:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.27 (s, 9 H),
General Procedure for the Reaction of Tetronic Acids and Alkyl Hal-
ides: To a solution of the tetronic acid (1.00 mmol) and CsF
(304 mg, 2.00 mmol) in 10.0 mL DMF at room temp. was added
the alkyl halide (2.00 mmol) and the yellow mixture was stirred at
this temperature for another 10 h. The solvent was then evaporated
under reduced pressure and the remaining residue was partitioned
between H2O (20 mL) and EtOAc (20 mL). The phases were sepa-
rated and the aqueous phase was extracted with EtOAc (3 ϫ 10
mL). The combined organic layers were washed with brine (10 mL)
and were dried (Na2SO4). After filtration the solvent was removed
under reduced pressure and the remaining residue was purified by
column chromatography to give the desired product.
3
1.62Ϫ2.01 (m, 6 H), 2.52Ϫ2.62 (m, 1 H), 4.42 (virt. t, J ϭ 4.4 Hz,
3
1 H), 4.61 (br. s, 2 H), 5.10 (br. d, J ϭ 10.0 Hz, 1 H), 5.14 (br. d,
3J ϭ 18.3 Hz, 1 H), 5.84 (ddd, 3J ϭ 8.0 Hz, 10.0 Hz, 18.3 Hz, 1 H)
ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 22.2 (t), 28.8 (q), 29.4
(t), 31.4 (s), 33.2 (t), 49.9 (d), 64.6 (t), 84.8 (d), 110.3 (d), 117.1 (t),
136.4 (d), 170.2 (s), 173.4 (s) ppm. IR (KBr): ν˜ ϭ 3071 (w, Cϭ
CϪH), 2983 (s, CϪH), 1741 (vs, CϭO), 1647 (s), 1374 (s), 1241 (s),
1047 (s), 846 (m). MS (70 eV, EI): m/z (%) ϭ 250 (3) [Mϩ], 157
(10), 141 (12), 95 (100), 79 (16), 67 (75), 55 (17). C15H22O3 (250.33):
calcd. C 71.97, H 8.86; found C 71.87, H 9.15.
4-(3,4-Dimethylpent-3-enyloxy)furan-2(5H)-one (4d): Prepared from
tetronic acid (1) (100 mg, 1.00 mmol) and 5-bromo-2,3-dimeth-
ylpent-2-ene (354 mg, 2.00 mmol) as colorless crystals in a yield of
169 mg (0.86 mmol, 86%). M.p. 62Ϫ63 °C; Rf ϭ 0.25 (P/DCM/
(S)-(؉)-4-(But-3-enyloxy)-5-methylfuran-2(5H)-one (12): Prepared
from tetronic acid 11 (114 mg, 1.00 mmol) and 3-buten-1-ol (86.0
µL, 74.0 mg, 1.00 mmol) as pale yellow oil in a yield of 143 mg
(0.85 mmol, 85%). Rf ϭ 0.20 (P/DCM/EtOAc, 10:2:1). [α]2D0 ϭ Ϫ6.6
(c ϭ 0.10, CHCl3). 1H NMR (360 MHz, CDCl3): δ ϭ 1.44 (d, 3J ϭ
1
EtOAc, 10:2:1). H NMR (360 MHz, CDCl3): δ ϭ 1.64Ϫ1.70 (m,
3
3
9 H), 2.52 (t, J ϭ 7.3 Hz, 2 H), 4.02 (t, J ϭ 7.3 Hz, 2 H), 4.62
(d, 4J ϭ 0.7 Hz, 2 H), 5.08 (s, 1 H) ppm. 13C NMR (90.6 MHz,
CDCl3): δ ϭ 18.8 (q), 20.3 (q), 20.7 (q), 33.4 (t), 67.9 (t), 71.3 (t),
88.7 (d), 121.8 (s), 128.4 (s), 173.7 (s), 179.4 (s) ppm. IR (KBr):
ν˜ ϭ 3098 (m, CϭCϪH), 2981 (m, CϪH), 2937 (m, CϪH), 1775
(vs, CϭO), 1751 (vs), 1631 (vs), 1367 (s), 1328 (s), 1252 (m), 1154
(s), 1052 (s), 970 (s), 886 (s), 839 (m). MS (70 eV, EI): m/z (%) ϭ
196 (8) [Mϩ], 181 (2), 152 (4), 137 (5), 101 (10), 96 (47), 81 (79),
69 (50), 55 (100). HRMS calcd. for C11H16O3 196.10994, found
196.10991.
3
6.8 Hz, 3 H), 2.51 (virt. q, J ؍ 6.6 Hz, 2 H), 3.96Ϫ4.08 (m, 2 H),
3
3
4.80 (q, J ϭ 6.8 Hz, 1 H), 5.00 (s, 1 H), 5.13 (br. d, J ϭ 10.0 Hz,
1 H), 5.15 (br. d, 3J ϭ 17.2 Hz, 1 H), 5.79 (ddt, 3Jd ϭ 10.0 Hz,
17.2, Jt ϭ 6.6 Hz,1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ
3
17.8 (q), 32.7 (t), 71.6 (d), 75.3 (t), 88.1 (d), 118.1 (t), 132.7 (d),
172.6 (s), 182.3 (s) ppm. IR (NaCl): ν˜ ϭ 3117 (w, CϭCϪH), 3080
(w, CϭCϪH), 2984 (s, CϪH), 2936 (m, CϪH), 1755 (vs, CϭO),
1630 (vs), 1450 (s), 1359 (s), 1295 (s), 1237 (s), 1161 (s), 1086 (s),
1058 (w), 952 (s), 900 (w), 804 (m). MS (70 eV, EI): m/z (%) ϭ 168
(1) [Mϩ], 137 (2), 126 (13), 113 (3), 96 (5), 69 (46), 55 (100).
C9H12O3 (168.19): calcd. C 64.27, H 7.19; found C 64.03, H 7.07.
4-(2-Methoxyethoxymethoxy)furan-2(5H)-one (8): Prepared from
tetronic acid (1) (100 mg, 1.00 mmol) and MEM-Cl (249 mg,
2.00 mmol) as pale yellow oil in a yield of 162 mg (0.86 mmol,
86%); Rf ϭ 0.15 (P/EtOAc, 2:1). 1H NMR (360 MHz, CDCl3): δ ϭ
3.38 (s, 3 H), 3.48Ϫ3.53 (m, 2 H), 3.73Ϫ3.84 (m, 2 H), 4.65 (d,
4J ϭ 0.8 Hz, 2 H), 5.25 (s, 2 H), 5.28 (s, 1 H) ppm. 13C NMR
(90.6 MHz, CDCl3): δ ϭ 59.1 (q), 67.8 (t), 69.3 (t), 71.3 (t), 91.5
(d), 95.9 (t), 173.4 (s), 176.7 (s) ppm. IR (NaCl): ν˜ ϭ 3121 (w, Cϭ
CϪH), 2934 (s, CϪH), 2887 (s), 1774 (vs, CϭO), 1744 (vs), 1628
(vs), 1450 (m), 1374 (s), 1319 (s), 1222 (m), 1155 (vs), 1113 (vs),
1048 (s), 946 (s), 885 (s). MS (70 eV, EI): m/z (%) ϭ 188 (1) [Mϩ],
157 (1), 143 (1), 112 (8), 100 (3), 89 (88), 82 (12), 69 (12), 59 (100),
54 (48). C8H12O3 (188.18): calcd. C 51.06, H 6.43; found C 50.74,
H 6.46.
5-(But-3-enyl)-4-methoxyfuran-2(5H)-one (20): Prepared from te-
tronic acid 19 (154 mg, 1.00 mmol) and MeOH (40.5 µL, 32.2 mg,
1.00 mmol) as pale yellow oil in a yield of 156 mg (0.94 mmol,
94%). Rf ϭ 0.30 (P/EtOAc, 2:1). 1H NMR (360 MHz, CDCl3): δ ϭ
1.70 (virt. quint, 2J ϭ 3J ϭ 7.4 Hz, 1 H), 1.92Ϫ2.03 (m, 1 H), 2.20
(virt. q, 3J ϭ 7.4 Hz, 2 H), 3.87 (s, 3 H), 4.76 (dd, 3J ϭ 3.5 Hz,
3
4
7.4 Hz, 1 H), 5.01 (br. d, J ϭ 10.1 Hz, 1 H), 5.06 (d, J ϭ 0.8 Hz,
1 H), 5.07 (br. d, 3J ϭ 17.6 Hz, 1 H), 5.77 (ddt, 3Jd ϭ 10.1 Hz,
17.6, Jt ϭ 7.4 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ
3
28.4 (t), 31.0 (t), 59.3 (q), 78.0 (d), 88.7 (d), 115.9 (t), 136.7 (d),
172.4 (s), 182.3 (s) ppm. IR (KBr): ν˜ ϭ 3119 (w, CϭCϪH), 3078
(w, CϭCϪH), 2980 (m, CϪH), 2945 (m, CϪH), 1747 (vs, CϭO),
1633 (vs), 1446 (m), 1376 (s), 1307 (s), 1245 (s), 1158 (s), 949 (s).
MS (70 eV, EI): m/z (%) ϭ 168 (4) [Mϩ], 140 (2), 126 (13), 114
(100), 113 (72), 96 (10), 85 (68), 69 (70), 59 (25). HRMS calcd. for
C9H12O3 168.07864, found 168.07863.
General Irradiation Procedure for Intramolecular Cycloaddition: In a
quartz vessel, a solution of the tetronate (0.1 mmol) in the specified
solvent (100 mL) was irradiated at room temp. and 254 nm until
GC analysis indicated complete conversion (0.5Ϫ3 h) (light source:
˚
Rayonet RPR-2537 A). The solvent was then evaporated under re-
4-Methoxy-3-(pent-4-enyl)furan-2(5H)-one (16): Prepared from te-
duced pressure and the remaining residue was purified by column
tronic acid 15 (168 mg, 1.00 mmol) and MeOH (40.5 µL, 32.2 mg, chromatography to give the desired product.
4590  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org
Eur. J. Org. Chem. 2004, 4582Ϫ4595

Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
2,9-Dioxatricyclo[5.3.0.01,5]decan-8-one (21): Prepared from tetron-
FULL PAPER
4-[3-(Tetrahydrofuran-2-yl)propoxy)furan-2(5H)-one (25): Prepared
ate 4a (15.4 mg, 0.10 mmol) in Et2O as colorless crystals in a yield from tetronate 3 (138 mg, 1.00 mmol) in THF as pale yellow oil in
of 11.4 mg (0.07 mmol, 74%); M.p. 88Ϫ90 °C; Rf ϭ 0.20 (P/DCM/ a yield of 78.0 mg (0.36 mmol, 36%); Rf ϭ 0.25 (P/EtOAc, 2:1). 1H
1
3
EtOAc, 10:2:1). H NMR (360 MHz, CDCl3): δ ϭ 1.80 (dd, J ϭ NMR (360 MHz, CDCl3): δ ϭ 1.40Ϫ1.50 (m, 1 H), 1.60Ϫ1.69 (m,
5.4, 2J ϭ 12.7 Hz, 1 H), 1.95Ϫ2.05 (m, 2 H), 2.24 (ddd, 3J ϭ 2 H), 1.81Ϫ2.05 (m, 5 H), 3.73 (virt. q, 3J ϭ 7.0 Hz, 1 H),
4.4 Hz, 8.1 Hz, 12.8 Hz, 1 H), 2.94 (ddd, 4J ϭ 1.3, 3J ϭ 4.4 Hz, 3.78Ϫ3.90 (m, 2 H), 4.03Ϫ4.14 (m, 2 H), 4.62 (br. d, 2 H), 5.07 (s,
10.4 Hz, 1 H), 2.99 (virt. q, 3J ϭ 8.1 Hz, 1 H), 3.95 (ddd, 3J ϭ
1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 25.5 (t), 25.7 (t),
5.4 Hz, 11.5, 2J ϭ 8.9 Hz, 1 H), 4.22 (t, J ϭ 8.9 Hz, 1 H), 4.24 (d, 31.4 (t), 31.6 (t), 67.8 (t), 67.8 (t), 72.8 (t), 78.6 (d), 88.8 (d), 173.6
2J ϭ 9.8 Hz, 1 H), 4.33 (d, 2J ϭ 9.8 Hz, 1 H) ppm. 13C NMR (s), 179.4 (s) ppm. IR (NaCl): ν˜ ϭ 3056 (m, CϭCϪH), 2954 (s,
(90.6 MHz, CDCl3): δ ϭ 25.0 (t), 31.7 (t), 40.3 (d), 41.6 (d), 68.8 CϪH), 1770 (vs, CϭO), 1746 (vs), 1626 (vs), 1455 (m), 1372 (m),
(t), 72.5 (t), 86.5 (s), 177.9 (s) ppm. IR (KBr): ν˜ ϭ 2985 (m, CϪH), 1319 (s), 1239 (m), 1149 (w), 1051 (s). MS (70 eV, EI): m/z (%) ϭ
3
2876 (m, CϪH), 1757 (vs, CϭO), 1629 (w), 1472 (m), 1376 (s),
212 (1) [Mϩ], 184 (2), 169 (4), 153 (2), 129 (5), 113 (9), 97 (20),
1293 (s), 1246 (m), 1190 (m), 1163 (s), 1140 (m), 1029 (vs), 991 (m), 84 (10), 71 (100), 55 (17). HRMS calcd. for C11H16O4 212.10486,
960 (m). MS (70 eV, EI): m/z (%) ϭ 154 (15) [Mϩ], 136 (2), 126
(12), 125 (9), 109 (7), 99 (25), 82 (10), 69 (10), 55 (100). C8H10O3
(154.16): calcd. C 62.33, H 6.54; found C 62.07, H 6.71.
found 212.10774.
4-(4-Hydroxy-4-methylpentyloxy)furan-2(5H)-one (26): Prepared
from tetronate 3 (138 mg, 1.00 mmol) in iPrOH as colorless crystals
in a yield of 114 mg (0.57 mmol, 57%); M.p. 72Ϫ74 °C; Rf ϭ 0.15
(P/EtOAc, 2:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.25 (s, 6 H),
2,10-Dioxatricyclo[6.3.0.01,6]decan-9-one (22): Prepared from te-
tronate 5 (16.5 mg, 0.10 mmol) in tBuOH as pale yellow oil in a
yield of 12.2 mg (0.07 mmol, 72%); Rf ϭ 0.20 (P/DCM/EtOAc,
10:2:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.41Ϫ1.62 (m, 3 H),
1.90Ϫ2.04 (m, 2 H), 2.19Ϫ2.29 (m, 1 H), 2.29Ϫ2.38 (m, 1 H), 3.40
(dd, 3J ϭ 6.8 Hz, 9.7 Hz, 1 H), 3.53Ϫ3.63 (m, 1 H), 3.77Ϫ3.83 (m,
1 H), 4.27 (d, 2J ϭ 10.1 Hz, 1 H), 4.41 (d, 2J ϭ 10.1 Hz, 1 H) ppm.
13C NMR (90.6 MHz, CDCl3): δ ϭ 22.6 (t), 25.5 (t), 28.2 (t), 36.0
(d), 40.9 (d), 64.5 (t), 76.6 (t), 79.6 (s), 177.3 (s) ppm. IR (NaCl):
ν˜ ϭ 2944 (s, CϪH), 2863 (m, CϪH), 1770 (vs, CϭO), 1626 (m),
1470 (m), 1455 (m), 1371 (m), 1281 (m), 1183 (m), 1107 (m), 1004
(s), 973 (m). MS (70 eV, EI): m/z (%) ϭ 168 (7) [Mϩ], 139 (15), 123
(10), 113 (52), 96 (40), 69 (39), 55 (100). HRMS calcd. for C9H12O3
168.07864, found 168.07878.
3
1.57 (dd, J ϭ 5.0 Hz, 8.0 Hz, 2 H). 1.84Ϫ1.95 (m, 2 H), 4.07 (t,
3J ϭ 6.4 Hz, 2 H), 4.62 (s, 2 H), 5.07 (s, 1 H) ppm. 13C NMR
(90.6 MHz, CDCl3): δ ϭ 23.5 (t), 29.4 (q), 39.4 (t), 67.8 (t), 70.4
(s), 73.3 (t), 88.8 (d), 173.6 (s), 179.4 (s) ppm. IR (KBr): ν˜ ϭ 3458
(m br, OH), 3053 (m, CϭCϪH), 2973 (s, CϪH), 1776 (vs, CϭO),
1746 (vs), 1626 (vs), 1450 (m), 1366 (m), 1320 (s), 1237 (m), 1154
(w), 1053 (s), 910 (s). MS (70 eV, EI): m/z (%) ϭ 200 (1) [Mϩ], 182
(4), 154 (5), 141 (3), 127 (7), 112 (8), 101 (10), 85 (29), 69 (56), 59
(100). HRMS calcd. for C10H16O4 200.10486, found 200.10474.
7-Methyl-2,9-dioxatricyclo[5.3.0.01,5]decan-8-one (30): Prepared
from tetronate 4e (16.8 mg, 0.10 mmol) in Et2O as colorless crystals
in a yield of 12.8 mg (0.08 mmol, 76%); M.p. 64Ϫ65 °C; Rf ϭ 0.20
(P/DCM/EtOAc, 10:2:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.25
(s, 3 H), 1.61 (dd, 2J ϭ 13.2, 3J ϭ 7.9 Hz, 1 H), 1.79 (dd, 2J ϭ
12.7, 3J ϭ 5.5 Hz, 1 H), 1.99 (dddd, 2J ϭ 12.7, 3J ϭ 7.9 Hz, 9.3 Hz,
10.1 Hz, 1 H), 2.44 (dd, 2J ϭ 13.2, 3J ϭ 7.9 Hz, 1 H), 2.92 (virt. q,
3J ϭ 7.9 Hz, 1 H), 4.05 (ddd, 2J ϭ 9.3, 3J ϭ 5.5 Hz, 10.1 Hz, 1 H),
2,11-Dioxatricyclo[7.3.0.01,7]decan-10-one (23): Prepared from te-
tronate 6 (18.2 mg, 0.10 mmol) in tBuOH as pale yellow oil in a
yield of 5.46 mg (0.03 mmol, 30%); Rf ϭ 0.20 (P/DCM/EtOAc,
10:2:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.29Ϫ1.35 (m, 1 H),
1.69Ϫ1.80 (m, 3 H), 1.82Ϫ1.88 (m, 1 H), 1.93Ϫ2.04 (m, 3 H),
2.37Ϫ2.44 (m, 1 H), 3.04 (t, 3J ϭ 9.4 Hz, 1 H), 3.17Ϫ3.23 (m, 1
2
4.14 (d, J ϭ 10.4 Hz, 1 H), 4.22 (d, 2J ϭ 10.4 Hz, 1 H), 4.26 (virt.
t, 2J ϭ 3J ϭ 9.3 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ
15.1 (q), 31.2 (t), 33.4 (t), 39.5 (d), 44.2 (d), 69.7 (t), 71.0 (t), 88.0
(s), 181.2 (s) ppm. IR (KBr): ν˜ ϭ 2969 (s, CϪH), 1772 (vs, CϭO),
1448 (m), 1378 (m), 1304 (m), 1231 (m), 1097 (s), 1029 (s), 979 (m).
MS (70 eV, EI): m/z (%) ϭ 168 (11) [Mϩ], 150 (2), 139 (23), 123
(12), 112 (8), 98 (10), 81 (9), 69 (100), 55 (38). HRMS calcd. for
C9H12O3 168.07864, found 168.07862.
2
2
H), 3.81Ϫ3.90 (m, 1 H), 4.47 (d, J ϭ 9.9 Hz, 1 H), 4.51 (d, J ϭ
9.9 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 22.8 (t), 28.7
(t), 32.1 (t), 32.8 (t), 40.7 (d), 44.4 (d), 68.1 (t), 80.1 (t), 81.1 (q),
177.8 (q) ppm. IR (NaCl): ν˜ ϭ 2924 (s, CϪH), 2853 (m, CϪH),
1770 (vs, CϭO), 1634 (m), 1456 (m), 1372 (m), 1304 (m), 1242 (w),
1176 (m), 1105 (m), 1019 (s). MS (70 eV, EI): m/z (%) ϭ 182 (1)
[Mϩ], 154 (5), 153 (4), 127 (3), 110 (6), 101 (3), 95 (4), 79 (10), 67
(20), 55 (100). HRMS calcd. for C10H14O3 182.09430, found
182.09417.
5-Methyl-2,9-dioxatricyclo[5.3.0.01,5]decan-8-one (27): Prepared
from tetronate 4b (16.8 mg, 0.10 mmol) in Et2O as colorless crystals
in a yield of 10.6 mg (0.06 mmol, 61%); Rf ϭ 0.20 (P/DCM/EtOAc,
4-(4-Ethoxypentyloxy)furan-2(5H)-one (24): Prepared from tetron-
ate 3 (138 mg, 1.00 mmol) in Et2O as pale yellow oil in a yield of
1
10:2:1). H NMR (360 MHz, CDCl3): δ ϭ 1.30 (s, 3 H), 1.65 (virt.
3
2
3
dt, Jd ϭ 6.0, Jt ϭ Jt ϭ 11.8 Hz, 1 H), 1.84Ϫ1.94 (m, 2 H), 2.24
1
92.0 mg (0.43 mmol, 43%); Rf ϭ 0.10 (P/DCM/EtOAc, 10:2:1). H
(dd, 2J ϭ 13.2, 3J ϭ 10.4 Hz, 1 H), 2.92 (dd, J ϭ 4.1 Hz, 10.4 Hz,
1 H), 3.93 (ddd, J ϭ 9.3, J ϭ 6.0 Hz, 11.8 Hz, 1 H), 4.19 (virt. t,
3
3
NMR (360 MHz, CDCl3): δ ϭ 1.17 (t, J ϭ 7.0 Hz, 3 H), 1.19 (t,
2
3
3J ϭ 7.0 Hz, 3 H), 1.53Ϫ1.60 (m, 2 H), 1.73Ϫ2.00 (m, 2 H), 3.37
2J ϭ J ϭ 9.3 Hz, 1 H), 4.21 (d, J ϭ 10.2 Hz, 1 H), 4.34 (d, J ϭ
10.2 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 21.4 (q),
31.9 (d), 38.2 (d), 39.5 (t), 46.2 (s), 68.0 (t), 68.7 (t), 87.4 (s), 178.3
(s) ppm. IR (KBr): ν˜ ϭ 2961 (s, CϪH), 2868 (CϪH), 1779 (vs, Cϭ
O), 1447 (m), 1371 (m), 1280 (s), 1186 (m), 1148 (s), 1084 (m), 1066
(m), 1034 (s), 996 (s), 963 (m), 896 (m). MS (70 eV, EI): m/z (%) ϭ
168 (4) [Mϩ], 153 (1), 137 (1), 123 (3), 113 (5), 101 (8), 96 (100),
81 (12), 69 (23), 55 (34). HRMS calcd. for C9H12O3 168.07864,
found 168.07861.
3
2
2
2
(dq, Jd ϭ 9.2, 3Jq ϭ 7.0 Hz), 3.43 (virt. q, 3J ϭ 7.0 Hz, 1 H), 3.58
(dq, 2Jd ϭ 9.2, 3Jq ϭ 7.0 Hz, 1 H), 4.07 (dt, 2Jd ϭ 1.6, 3Jt ϭ 6.7 Hz,
1 H), 4.62 (s, 2 H), 5.07 (s, 1 H) ppm. 13C NMR (90.6 MHz,
CDCl3): δ ϭ 15.6 (q), 19.7 (q), 24.8 (t), 32.8 (t), 63.7 (t), 67.8 (t),
73.1 (t), 74.4 (d), 88.8 (d), 173.5 (s), 179.4 (s) ppm. IR (NaCl): ν˜ ϭ
3078 (w, CϭCϪH), 2924 (s, CϪH), 1777 (vs, CϭO), 1747 (vs),
1627 (vs), 1455 (m), 1373 (s), 1318 (m), 1148 (m), 1019 (m), 880
(m). MS (70 eV, EI): m/z (%) ϭ 214 (0) [Mϩ], 199 (2), 170 (3), 153
(5), 142 (7), 126 (7), 115 (11), 99 (13), 73 (87), 69 (100), 59 (15).
HRMS calcd. for C9H12O4 [Mϩ
199.09711.
Ϫ
CH3] 199.09703, found 6,6-Dimethyl-2,9-dioxatricyclo[5.3.0.01,5]decan-8-one (28): Prepared
from tetronate 4c (18.2 mg, 0.10 mmol) in tBuOH as pale yellow
Eur. J. Org. Chem. 2004, 4582Ϫ4595
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4591

M. Kemmler, E. Herdtweck, T. Bach
FULL PAPER
oil in a yield of 8.74 mg (0.05 mmol, 52%); Rf ϭ 0.25 (P/DCM/
1
(P/EtOAc, 8:1). H NMR (360 MHz, CDCl3): δ ϭ 1.19Ϫ1.31 (m,
EtOAc, 10:2:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.18 (s, 3 H), 1 H), 1.54Ϫ1.64 (m, 1 H), 1.73Ϫ1.84 (m, 2 H), 1.85Ϫ1.91 (m, 1
3
1.19 (s, 3 H), 1.88Ϫ2.02 (m, 2 H), 2.53 (d, J ϭ 9.1 Hz, 1 H), 2.65
H), 1.92Ϫ1.98 (m, 1 H), 2.10 (ddd, 2J ϭ 13.1, 3J ϭ 6.8 Hz, 10.4 Hz,
4
2
3
2
3
(d, J ϭ 1.1 Hz, 1 H), 3.82 (ddd, J ϭ 9.6, J ϭ 6.4 Hz, 10.9 Hz, 1 1 H), 2.22 (ddd, J ϭ 13.1, J ϭ 4.4 Hz, 6.8 Hz, 1 H), 2.40 (virt.
H), 4.22 (dt, 3Jd ϭ 1.8, 2Jt ϭ 3Jt ϭ 9.6 Hz, 1 H), 4.38 (d, 2J ϭ q, 3J ϭ 6.8 Hz, 1 H), 2.81 (virt. t, 3J ϭ 6.8 Hz, 1 H), 2.98 (dd, 3J ϭ
10.2 Hz, 1 H), 4.45 (d, 2J ϭ 10.2 Hz, 1 H) ppm. 13C NMR 4.4 Hz, 10.4 Hz, 1 H), 4.27 (d, 2J ϭ 9.6 Hz, 1 H), 4.34 (d, 2J ϭ
(90.6 MHz, CDCl3): δ ϭ 24.3 (q), 26.2 (q), 26.8 (t), 32.9 (s), 51.0
(d), 52.7 (d), 69.8 (t), 74.1 (t), 82.1 (s), 175.7 (s) ppm. IR (NaCl):
ν˜ ϭ 2959 (s, CϪH), 2870 (CϪH), 1770 (vs, CϭO), 1470 (m), 1371
9.6 Hz, 1 H), 4.77 (virt. t, 3J ϭ 4.6 Hz, 1 H) ppm. 13C NMR
(90.6 MHz, CDCl3): δ ϭ 24.6 (t), 26.0 (t), 31.6 (t), 32.4 (t), 40.2
(d), 49.3 (d), 51.4 (d), 73.0 (t), 87.6 (d), 87.8 (s), 178.2 (s) ppm. IR
(m), 1278 (m), 1172 (m), 1147 (s), 1030 (vs), 988 (m). MS (70 eV, (KBr): ν˜ ϭ 2955 (s, CϪH), 1779 (vs, CϭO), 1626 (m), 1446 (m),
EI): m/z (%) ϭ 182 (4) [Mϩ], 167 (1), 154 (1), 138 (10), 123 (10),
1372 (m), 1288 (m), 1230 (w), 1175 (m), 1031 (s), 958 (m). MS
100 (7), 96 (7), 91 (5) (2), 83 (100), 69 (14), 55 (52). C10H14O3 (70 eV, EI): m/z (%) ϭ 194 (30) [Mϩ], 176 (5), 165 (23), 149 (10),
(182.22): calcd. C 65.91, H 7.74; found C 65.64, H 7.71.
139 (45), 123 (47), 109 (115), 101 (20), 94 (90), 79 (100), 67 (56),
55 (70). HRMS calcd. for C11H14O3 194.09430, found 194.09410.
5,6,6-Trimethyl-2,9-dioxatricyclo[5.3.0.01,5]decan-8-one (29): Pre-
pared from tetronate 4d (19.6 mg, 0.10 mmol) in tBuOH as pale
yellow oil in a yield of 12.0 mg (0.06 mmol, 61%); M.p. 77Ϫ79 °C;
10-Methyl-2,12-dioxatetracyclo[6.5.0.03,7.01,10]tridecan-11-one (34):
Prepared from tetronate 7b (20.8 mg, 0.10 mmol) in Et2O as color-
less oil as a 1:1 diastereomeric mixture in a yield of 12.1 mg
(0.06 mmol, 58%); cis-anti-cis diastereoisomer (34a): Rf ϭ 0.25 (P/
EtOAc, 9:1). 1H NMR (360 MHz, CDCl3): δ ϭ 1.27 (s, 3 H),
1.28Ϫ1.35 (m, 1 H), 1.59Ϫ1.95 (m, 6 H), 2.41Ϫ2.45 (m, 2 H), 2.72
1
Rf ϭ 0.30 (P/DCM/EtOAc, 10:2:1). H NMR (360 MHz, CDCl3):
2
δ ϭ 1.08 (s, 3 H), 1.14 (s, 3 H), 1.22 (s, 3 H), 1.64 (ddd, J ϭ 12.8,
3J ϭ 9.1 Hz, 11.1 Hz, 1 H), 2.26 (ddd, 2J ϭ 12.8, 3J ϭ 1.7 Hz,
2
3
6.4 Hz, 1 H), 3.80 (ddd, J ϭ 9.1, J ϭ 6.4 Hz, 11.1 Hz, 1 H), 4.15
3
2
3
2
3
2
(dd, J ϭ 6.6 Hz, 8.5 Hz, 1 H), 4.13 (d, J ϭ 10.5 Hz, 1 H), 4.24
(dt, Jd ϭ 1.7, Jt ϭ Jt ϭ 9.1 Hz, 1 H), 4.23 (d, J ϭ 10.5 Hz, 1
H), 4.40 (d, 2J ϭ 10.5 Hz, 1 H) ppm. 13C NMR (90.6 MHz,
CDCl3): δ ϭ 18.4 (q), 22.2 (q), 25.6 (q), 35.3 (s), 36.2 (t), 50.9 (s),
51.1 (d), 68.0 (t), 69.7 (t), 85.1 (s), 175.9 (s) ppm. IR (NaCl): ν˜ ϭ
2969 (s, CϪH), 1769 (vs, CϭO), 1629 (w), 1454 (m), 1370 (m), 1284
(m), 1163 (s), 1120 (m), 1033 (s), 985 (m). MS (70 eV, EI): m/z
(%) ϭ 196 (3) [Mϩ], 181 (2), 165 (2), 152 (5), 137 (7), 101 (8), 96
(100), 83 (48), 81 (40), 69 (28), 55 (79). C11H16O3 (196.24): calcd.
C 67.32, H 8.22; found C 67.00, H 7.94.
(d, J ϭ 10.5 Hz, 1 H), 4.86 (virt. t, 3J ϭ 5.5 Hz, 1 H) ppm. 13C
2
NMR (90.6 MHz, CDCl3): δ ϭ 15.9 (q), 24.6 (t), 32.0 (t), 33.2 (t),
34.5 (t), 43.9 (s), 47.3 (d), 51.1 (d), 71.6 (t), 88.7 (d), 89.3 (s), 181.3
(s) ppm. IR (NaCl): ν˜ ϭ 2961 (s, CϪH), 2869 (CϪH), 1770 (vs,
CϭO), 1448 (s), 1377 (s), 1301 (m), 1221 (m), 1095 (s), 1027 (s).
MS (70 eV, EI): m/z (%) ϭ 208 (31) [Mϩ], 179 (30), 163 (22), 139
(23), 123 (65), 113 (12), 109 (19), 95 (44), 79 (63), 69 (100). HRMS
calcd. for C12H16O3 208.10994, found 208.10986. cis-syn-cis dia-
stereoisomer (34b): Rf ϭ 0.20 (P/EtOAc, 9:1). 1H NMR (360 MHz,
CDCl3): δ ϭ 1.21 (s, 3 H), 1.54Ϫ1.74 (m, 5 H), 1.87 (dd, 2J ϭ 13.1,
9-Methoxy-2-oxatricyclo[4.2.1.04,9]nonan-2-one (32): Prepared from
tetronate 20 (16.8 mg, 0.10 mmol) in Et2O as colorless crystals in
a yield of 12.6 mg (0.07 mmol, 75%); M.p. 63Ϫ65 °C; Rf ϭ 0.30
2
3
3J ϭ 8.2 Hz, 1 H), 1.91Ϫ1.97 (m, 1 H), 2.21 (dd, J ϭ 13.1, J ϭ
3
8.2 Hz, 1 H), 2.79Ϫ2.88 (m, 1 H), 2.95 (virt. q, J ϭ 8.2 Hz, 1 H),
1
2
4.04 (d, 2J ϭ 9.4 Hz, 1 H), 4.18 (d, 2J ϭ 9.4 Hz, 1 H), 4.78 (dt,
3Jd ϭ 2.1, 3Jt ϭ 7.0 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3):
δ ϭ 15.6 (q), 25.7 (t), 27.4 (t), 28.8 (t), 33.8 (t), 40.3 (s), 43.1 (d),
45.1 (d), 72.5 (t), 90.3 (s), 92.2 (d), 181.2 (s) ppm. IR (NaCl): ν˜ ϭ
2958 (s, CϪH), 2872 (CϪH), 1769 (vs, CϭO), 1449 (s), 1376 (s),
1296 (m), 1192 (m), 1097 (s), 1020 (s), 957 (m). MS (70 eV, EI): m/
z (%) ϭ 208 (30) [Mϩ], 179 (30), 139 (13), 123 (65), 113 (28), 109
(25), 95 (44), 79 (43), 69 (100). HRMS calcd. for C12H16O3
208.10994, found 208.10974.
(P/EtOAc, 2:1). H NMR (360 MHz, CDCl3): δ ϭ 1.54 (dt, Jd ϭ
3
12.8, Jt ϭ 4.4 Hz, 1 H), 1.72Ϫ1.83 (m, 1 H), 2.02Ϫ2.11 (m, 1 H),
2.11Ϫ2.20 (m, 1 H), 2.22Ϫ2.32 (m, 1 H), 2.68 (ddd, 2J ϭ 12.8,
3J ϭ 10.0 Hz, 11.7 Hz, 1 H), 2.84Ϫ2.89 (m, 1 H), 3.13 (ddd, J ϭ
3
4.4 Hz, 11.7, 4J ϭ 1.6 Hz, 1 H), 3.32 (s, 3 H), 4.84 (dd, 3J ϭ 3.2 Hz,
6.4 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 23.8 (t), 31.2
(t), 32.8 (t), 37.0 (d), 38.4 (d), 52.4 (q), 87.7 (d), 92.6 (s), 177.9 (s)
ppm. IR (KBr): ν˜ ϭ 2940 (s, CϪH), 1770 (vs, CϭO), 1634 (vs),
1462 (m), 1353 (s), 1319 (s), 1268 (m), 1184 (vs), 1052 (vs), 1027
(m). MS (70 eV, EI): m/z (%) ϭ 168 (9) [Mϩ], 140 (2), 126 (13), 114
(100), 113 (42), 96 (28), 85 (23), 69 (15), 59 (45). HRMS calcd. for
C9H12O3 168.07864, found 168.07875.
10-tert-Butyl-2,12-dioxatetracyclo[6.5.0.03,7.01,10]tridecan-11-one
(35): Prepared from tetronate 7c (25.0 mg, 0.10 mmol) in Et2O as
colorless crystals in a yield of 18.0 mg (0.07 mmol, 72%); M.p.
59Ϫ61 °C, Rf ϭ 0.25 (P/Et2O ϭ 4:1). 1H NMR (360 MHz, CDCl3):
δ ϭ 1.05 (s, 9 H), 1.45Ϫ1.88 (m, 5 H), 1.95Ϫ2.01 (m, 2 H), 2.21
5-Methoxy-3-oxatricyclo[5.3.0.01,5]decan-2-one (31): Prepared from
tetronate 16 (18.2 mg, 0.10 mmol) in Et2O as colorless oil in a yield
1
2
3
of 13.1 mg (0.07 mmol, 72%); Rf ϭ 0.45 (P/EtOAc, 2:1). H NMR
(dd, J ϭ 12.1, J ϭ 8.2 Hz, 1 H), 2.72Ϫ2.79 (m, 1 H), 2.83 (virt.
q, 3J ϭ 8.2 Hz, 1 H), 3.97 (d, 2J ϭ 8.8 Hz, 1 H), 4.02 (d, 2J ϭ
8.8 Hz, 1 H), 4.74 (virt. t, 3J ϭ 5.8 Hz, 1 H) ppm. 13C NMR
(90.6 MHz, CDCl3): δ ϭ 24.4 (t), 26.0 (t), 26.1 (q), 27.7 (t), 33.3
(t), 34.1 (s), 43.1 (d), 44.6 (d), 50.3 (s), 70.8 (t), 93.2 (d), 94.0 (s),
180.0 (s) ppm. IR (KBr): ν˜ ϭ 2955 (s, CϪH), 1769 (vs, CϭO), 1634
(m), 1456 (m), 1362 (m), 1278 (m), 1164 (m), 1033 (s). MS (70 eV,
EI): m/z (%) ϭ 250 (2) [Mϩ] 221 (51), 193 (21), 165 (15), 123 (64),
111 (45), 95 (34), 79 (35), 67 (100), 55 (41). C15H22O3 (250.33):
calcd. C 71.97, H 8.86; found C 72.17, H 8.42.
(360 MHz, CDCl3): δ ϭ 1.62Ϫ1.70 (m, 2 H), 1.85 (ddd, 2J ϭ 12.2,
3J ϭ 1.5 Hz, 7.3 Hz, 1 H), 1.91Ϫ2.12 (m, 4 H), 2.23 (dd, 2J ϭ 12.2,
3
3J ϭ 7.3 Hz, 1 H), 2.65 (virt. q, J ϭ 7.3 Hz, 1 H), 3.18 (s, 3 H),
4.27 (d, 2J ϭ 12.4 Hz, 1 H), 4.56 (dd, 2J ϭ 12.4, 4J ϭ 1.5 Hz, 1 H)
ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 26.1 (t), 27.0 (t), 32.2 (t),
33.4 (t), 38.3 (d), 50.6 (q), 55.7 (s), 76.4 (s), 76.5 (t), 179.4 (s) ppm.
IR (NaCl): ν˜ ϭ 2951 (s, CϪH), 1759 (vs, CϭO), 1466 (m), 1372
(m), 1263 (m), 1248 (m), 1140 (s), 1108 (m), 1066 (m), 1037 (s). MS
(70 eV, EI): m/z (%) ϭ 182 (3) [Mϩ], 167 (2), 153 (8), 140 (4), 137
(7), 128 (10), 113 (10), 109 (6), 95 (100), 91 (12), 79 (9), 67 (12), 53
(6). HRMS calcd. for C10H14O3 182.09430, found 182.09419.
10-Methyl-2,9-dioxatricyclo[5.3.0.01,5]decan-8-one (36): Prepared
from tetronate 12 (16.8 mg, 0.10 mmol) in MeCN as a 1:1 dia-
2,12-Dioxatetracyclo[6.5.0.03,7.01,10]tridecan-11-one (33): Prepared stereomeric mixture as colorless oil in
a
yield of 12.1 mg
(0.07 mmol, 72%); diastereoisomer I (36a): Rf ϭ 0.20 (P/DCM/
in a yield of 13.6 mg (0.07 mmol, 70%); M.p. 81Ϫ83 °C, Rf ϭ 0.15 EtOAc, 10:2:1). [α]2D0 ϭ ϩ43.8 (c ϭ 0.10, CHCl3). 1H NMR
from tetronate 7a (19.4 mg, 0.10 mmol) in Et2O as colorless crystals
4592
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2004, 4582Ϫ4595

Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
FULL PAPER
3
(360 MHz, CDCl3): δ ϭ 1.33 (d, J ϭ 6.8 Hz, 3 H), 1.71Ϫ2.03 (m, tene (1.32 mL, 1.02 g, 15.0 mmol) in tBuOH as pale yellow oil in
2
3
3 H), 2.14 (ddd, J ϭ 12.2, J ϭ 4.0 Hz, 8.2 Hz, 1 H), 2.98 (ddd,
a yield of 151 mg (0.59 mmol, 59%, exo/endo ϭ 8:1); exo-dia-
3J ϭ 4.0 Hz, 8.2, J ϭ 1.3 Hz, 1 H), 3.13 (virt. q, J ϭ 7.6 Hz, 1 stereoisomer: Rf ϭ 0.25 (P/EtOAc, 2:1). 1H NMR (360 MHz,
4
3
H), 3.94 (ddd, 2J ϭ 11.1, 3J ϭ 7.4 Hz, 9.3 Hz, 1 H), 4.21Ϫ4.29 (m, CDCl3) δ ϭ 1.55Ϫ1.80 (m, 3 H), 1.82Ϫ1.91 (m, 2 H), 1.97 (dd,
1 H), 4.56 (q, 3J ϭ 6.8 Hz, 1 H) ppm. 13C NMR (90.6 MHz, 3J ϭ 6.0 Hz, 13.0 Hz, 1 H), 2.64 (virt. q, J ϭ 6.2 Hz, 1 H), 2.70
3
CDCl3): δ ϭ 14.7 (q), 25.2 (t), 32.0 (t), 36.8 (d), 42.3 (d), 68.9 (t), (d, 3J ϭ 6.2 Hz, 1 H), 2.81 (virt. t, 3J ϭ 6.2 Hz, 1 H), 3.40 (s, 3 H),
78.3 (d), 90.4 (s), 177.9 (s) ppm. IR (NaCl): ν˜ ϭ 2980 (m, CϪH), 3.53 (t, 3J ϭ 4.5 Hz, 2 H), 3.61Ϫ3.69 (m, 2 H), 3.79 (dt, 2Jd ϭ 11.4,
2870 (m, CϪH), 1768 (vs, CϭO), 1630 (w), 1448 (m), 1383 (m),
3Jt ϭ 4.1 Hz, 1 H), 4.39 (d, 2J ϭ 10.5 Hz, 1 H), 4.74 (d, 2J ϭ
2
2
1287 (s), 1238 (m), 1176 (s), 1074 (s), 1050 (s), 975 (s), 919 (m). MS 10.5 Hz, 1 H), 4.73 (d, J ϭ 7.3 Hz, 1 H), 4.78 (d, J ϭ 7.3 Hz, 1
(70 eV, EI): m/z (%) ϭ168 (2) [Mϩ], 153 (1), 140 (1), 137 (4), 126 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 24.9 (t), 26.3 (t), 32.9
(28), 113 (6), 96 (7), 81 (7), 69 (7), 55 (100). C9H12O3 (168.19): (t), 37.8 (d), 46.1 (d), 47.7 (d), 59.0 (q), 67.8 (t), 71.6 (t), 76.6 (d),
calcd. C 64.27, H 7.19; found C 63.90, H 6.83. diastereoisomer II
79.4 (t), 91.8 (t), 177.8 (s) ppm. IR (NaCl): ν˜ ϭ 2949 (s, CH), 1774
(vs, CϭO), 1470 (m), 1368 (s), 1247 (m), 1185 (m), 1106 (m), 1012
(36b): Rf ϭ 0.15 (P/EtOAc, 9:1). [α]2D0 ϭ Ϫ47.9 (c ϭ 0.10, CHCl3),
3
1H NMR (360 MHz, CDCl3): δ ϭ 1.44 (d, J ϭ 6.6 Hz, 3 H), 1.78 (s). MS (70 eV, EI): m/z (%) ϭ 256 (1) [Mϩ], 197 (2), 189 (10), 151
2
3
2
3
(dd, J ϭ 12.1, J ϭ 5.3 Hz, 1 H), 1.95 (dt, Jd ϭ 12.1, Jt ϭ 7.8,
(12), 123 (6), 105 (6), 89 (56), 77 (20), 67 (30), 59 (100).
2
3
1 H), 2.02 (ddd, J ϭ 12.8, J ϭ 6.6 Hz, 7.8 Hz, 1 H), 2.24 (ddd,
2J ϭ 12.8, 3J ϭ 3.9 Hz, 7.8 Hz, 1 H), 2.97 (dd, 3J ϭ 3.9 Hz, 6.6 Hz,
1 H), 3.00 (virt. q, 3J ϭ 7.8 Hz, 1 H), 3.96 (ddd, 2J ϭ 7.8, 3J ϭ
4.0 Hz, 6.1 Hz, 1 H), 4.23 (virt. q, 2J ϭ 3J ϭ 7.8 Hz, 1 H), 4.59 (q,
3J ϭ 6.6 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 16.8
(q), 25.4 (t), 31.4 (t), 40.0 (d), 42.2 (d), 69.0 (t), 80.5 (d), 87.9 (s),
177.7 (s) ppm. IR (NaCl): ν˜ ϭ 2978 (m, CϪH), 2869 (m, CϪH),
1765 (vs, CϭO), 1629 (w), 1448 (m), 1337 (m), 1283 (m), 1165 (s),
1071 (s), 1051 (s), 969 (m), 918 (m). MS (70 eV, EI): m/z (%) ϭ 168
(2) [Mϩ], 153 (1), 140 (1), 137 (4), 126 (18), 113 (6), 96 (17), 81 (7),
69 (8), 55 (100). C9H12O3 (168.19): calcd. C 64.27, H 7.19; found
C 64.09, H 6.98.
6,6-Diethoxy-5-(2-methoxyethoxymethoxy)-3-oxabicyclo[3.2.0]-
heptan-5-one (41): Prepared from tetronate 8 (188 mg, 1.00 mmol)
and ketene diethyl acetal (40, 1.54 mL, 1.74 g, 15.0 mmol) in
tBuOH as pale yellow oil in a yield of 100 mg (0.33 mmol, 33%)
1
Rf ϭ 0.35 (P/EtOAc, 2:1). H NMR (360 MHz, CDCl3) δ ϭ 1.21
(t, 3J ϭ 7.0 Hz, 3 H), 1.25 (t, 3J ϭ 7.0 Hz, 3 H), 1.97 (dd, 2J ϭ
3
2
3
13.0, J ϭ 7.4 Hz, 1 H), 2.64 (dd, J ϭ 13.0, J ϭ 10.9 Hz, 1 H),
3
3.29Ϫ3.33 (m, 1 H), 3.33 (dd, J ϭ 7.4 Hz, 10.9 Hz, 1 H), 3.40 (s,
3 H), 3.53Ϫ3.63 (m, 5 H), 3.67Ϫ3.72 (m, 1 H), 3.74Ϫ3.80 (m, 1
2
2
H), 4.41 (d, J ϭ 10.8 Hz, 1 H), 4.75 (d, J ϭ 10.8 Hz, 1 H), 4.85
(d, J ϭ 7.5 Hz, 1 H), 5.14 (d, J ϭ 7.5 Hz, 1 H) ppm. 13C NMR
(90.6 MHz, CDCl3): δ ϭ 14.9 (q), 15.3 (q), 31.1 (t), 36.6 (d), 57.7
(t), 58.6 (t), 59.0 (q), 67.4 (t), 71.6 (t), 74.2 (t), 85.9 (s), 93.0 (t),
2
2
General Irradiation Procedure for Intermolecular Cycloaddition: In
a quartz vessel, a solution of the tetronate (1.00 mmol) and the 101.4 (s), 176.4 (s) ppm. IR (NaCl): ν˜ ϭ 2977 (s, CϪH), 2932 (s,
alkene (15.0 mmol) in the specified solvent (60 mL) was irradiated
at room temp. and 254 nm for 10 h (light source: Rayonet RPR-
2537 A). The solvent was then evaporated under reduced pressure
and the remaining residue was purified by column chromatography
to give the desired product.
CϪH), 1779 (vs, CϭO), 1630 (m), 1452 (m), 1369 (s), 1310 (m),
1282 (s), 1249 (s), 1188 (vs), 1132 (vs), 1099 (vs), 1027 (vs), 848
(w). MS (70 eV, EI): m/z (%) ϭ 304 (0) [Mϩ], 215 (7). 187 (2), 153
(2), 141 (9), 116 (13), 89 (33), 59 (100), 55 (78).
˚
General Procedure for the Preparation of β-Hydroxy Lactones: A
solution of the tetronate (1.00 mmol) and the alkene (15.0 mmol)
2-Methoxy-4-oxatricyclo[5.3.0.02,6]decan-5-one (38): Prepared from
tetronate 37 (114 mg, 1.00 mmol) and cyclopentene (1.32 mL,
1.02 g, 15.0 mmol) in tBuOH as pale yellow oil in a yield of 104 mg 10 h (light source: Rayonet 2537 A). The solvent was then evapo-
in tBuOH (60 mL) was irradiated at room temp. and 254 nm for
˚
(0.57 mmol, 57%, exo/endo ϭ 3:1); exo-diastereoisomer: Rf ϭ 0.15
rated under reduced pressure and the remaining residue was di-
(P/EtOAc, 4:1). 1H NMR (360 MHz, CDCl3) δ ϭ 1.47Ϫ1.56 (m, 1 rectly dissolved in DCM (30 mL). TiCl4 (0.33 mL, 0.57 g,
H), 1.58Ϫ1.69 (m, 2 H), 1.82Ϫ1.94 (m, 2 H), 2.02 (dd, 3J ϭ 5.5 Hz, 3.00 mmol) was added at room temp. and the resulting mixture was
13.1 Hz, 1 H), 2.54 (d, 3J ϭ 5.5 Hz, 1 H), 2.64 (virt. q, 3J ϭ 5.5 Hz, stirred for 6 h. Satd. aqueous NaHCO3 (50 mL) was then added
3
2
1 H), 2.80 (virt. t, J ϭ 5.5 Hz, 1 H), 3.20 (s, 3 H), 4.32 (d, J ϭ and the mixture was filtered. The organic phase was separated and
10.5 Hz, 1 H), 4.53 (d, 2J ϭ 10.5 Hz, 1 H) ppm. 13C NMR the aqueous phase was extracted with DCM (3 ϫ 30 mL). The
(90.6 MHz, CDCl3): δ ϭ 24.9 (t), 26.2 (t), 32.9 (t), 37.3 (d), 44.6 combined organic layers were dried (Na2SO4), filtered and the sol-
(d), 47.0 (d), 50.7 (q), 76.6 (s), 77.0 (t), 178.0 (s) ppm. IR (NaCl):
vent was evaporated under reduced pressure. The remaining yellow
ν˜ ϭ 2951 (s, CH), 1754 (vs, CϭO), 1470 (m), 1372 (m), 1266 (m), oil was purified by column chromatography to yield the pure prod-
1248 (m), 1185 (s), 1085 (m), 1030 (s), 998 (m), 934 (m), 905 (m). ucts.
MS (70 eV, EI): m/z (%) ϭ 182 (1) [Mϩ], 167 (1), 123 (5), 115 (100),
109 (3), 105 (2), 91 (10), 69 (13), 68 (12), 67 (18),65 (8), 53 (4).
2-Hydroxy-4-oxatricyclo[5.3.0.02,6]decan-5-one (42): Prepared from
tetronate 8 (188 mg, 1.00 mmol) and cyclopentene (1.32 mL, 1.02 g,
15.0 mmol) as colorless crystals in a yield of 86.1 mg (0.53 mmol,
C10H14O3 (182.22): calcd. C 65.91, H 7.74; found C 65.66, H 7.23.
endo-diastereoisomer: Rf
ϭ
0.10 (P/EtOAc, 4:1). 1H NMR
53%, exo/endo ϭ 8:1); exo-diastereoisomer: M.p. 69Ϫ70 °C; Rf ϭ
(360 MHz, CDCl3) δ ϭ 1.50Ϫ1.78 (m, 6 H), 3.02Ϫ3.08 (m, 1 H),
1
0.30 (P/EtOAc, 2:1). H NMR (360 MHz, CDCl3) δ ϭ 1.52Ϫ1.80
3.11Ϫ3.19 (m, 2 H), 3.24 (s, 3 H), 4.11 (d, 2J ϭ 10.3 Hz, 1 H), 4.43
(m, 3 H), 1.84Ϫ2.06 (m, 3 H), 2.43 (d, 3J ϭ 6.5 Hz, 1 H), 2.63 (virt.
2
(d, J ϭ 10.3 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ
3
3
2
q, J ϭ 6.5 Hz, 1 H), 2.85 (virt. t, J ϭ 6.5 Hz, 1 H), 4.39 (d, J ϭ
10.0 Hz, 1 H), 4.47 (d, 2J ϭ 10.0 Hz, 1 H) ppm. 13C NMR
(90.6 MHz, CDCl3): δ ϭ 24.9 (t), 26.1 (t), 32.9 (t), 37.5 (d), 48.4
(d), 49.6 (d), 72.1 (s), 81.9 (t), 178.4 (s) ppm. IR (KBr): ν˜ ϭ 3425
(br vs, OH), 2945 (s, CH), 1738 (vs, CϭO), 1622 (m), 1483 (m),
1269 (m), 1199 (m), 1163 (m), 1019 (vs). MS (70 eV, EI): m/z (%) ϭ
168 (2) [Mϩ] 138 (5), 109 (6), 101 (95), 95 (10), 79 (15), 67 (100),
55 (40). C9H12O3 (168.19): calcd. C 64.27, H 7.19; found C 64.14,
26.6 (t), 27.7 (t), 27.9 (t), 35.4 (d), 41.8 (d), 44.6 (d), 50.8 (q), 70.4
(t), 80.9 (s), 1761 (s) ppm. IR (NaCl): ν˜ ϭ 3442 (br vs, OH), 2959
(s, CH), 1769 (vs, CϭO), 1373 (m), 1184 (vs), 1128 (s), 1030 (vs),
931 (m). MS (70 eV, EI): m/z (%) ϭ 182 (1) [Mϩ], 167 (1), 153 (1),
137 (2), 123 (3), 115 (100), 109 (4), 91 (5), 83 (5), 67 (18). C10H14O3
(182.22): calcd. C 65.91, H 7.74; found C 65.68, H 7.28.
2-(2-Methoxyethoxymethoxy)-4-oxatricyclo[5.3.0.02,6]decan-5-one
(39): Prepared from tetronate 8 (188 mg, 1.00 mmol) and cyclopen- H 7.12.
Eur. J. Org. Chem. 2004, 4582Ϫ4595
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4593

M. Kemmler, E. Herdtweck, T. Bach
FULL PAPER
1-Hydroxy-9-oxatricyclo[6.3.0.02,7]undecan-8-one (43): Prepared
from tetronate 8 (188 mg, 1.00 mmol) and cyclohexene (1.52 mL,
1.23 g, 15.0 mmol) as colorless oil in a yield of 95.2 g (0.52 mmol,
52%, exo/endo ϭ 10:1); exo-diastereoisomer: Rf ϭ 0.30 (P/EtOAc,
11-Oxabicyclo[6.5.0]tridecan-9,12-dione (47): Prepared from the
1:2:1 diastereomeric mixture of β-hydroxy lactone 44 (210 mg,
1.00 mmol) as colorless oil in a yield of 80.0 mg (0.38 mmol, 38%,
76% b.r.s.m.) as a 1:1 diastereomeric mixture of cis/trans isomers
2:1). 1H NMR (360 MHz, CDCl3) δ ϭ 1.10Ϫ1.20 (m, 1 H), together with 105 mg (0.50 mmol, 50%) of unchanged starting ma-
1.22Ϫ1.44 (m, 1 H), 1.47Ϫ1.54 (m, 1 H), 1.55Ϫ1.83 (m, 4 H), terial. Rf ϭ 0.55 (P/EtOAc, 2:1). 1H NMR (360 MHz, CDCl3) δ ϭ
1.84Ϫ1.90 (m, 1 H), 2.23Ϫ2.32 (m, 1 H), 2.45 (virt. q, 3J ϭ 7.9 Hz,
1.19Ϫ2.20 (m, 24 H), 2.31 (d, J ϭ 12.7 Hz, 1 H), 2.43 (dd, J ϭ
2
2
3
2
3
2
3
1 H), 2.94 (d, J ϭ 7.9 Hz, 1 H), 4.43 (d, J ϭ 9.8 Hz, 1 H), 4.48 13.8, J ϭ 2.5 Hz), 2.55Ϫ2.65 (m, 2 H), 2.76 (dd, J ϭ 12.7, J ϭ
(d, 2J ϭ 9.8 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 6.8 Hz, 1 H), 2.81 (dd, 2J ϭ 13.8, 3J ϭ 6.6 Hz, 1 H), 2.97 (dt, 3Jd ϭ
3
3
21.4 (t), 21.7 (t), 22.5 (t), 25.3 (t), 29.5 (d), 40.9 (d), 49.7 (d), 75.1
(t), 80.7 (s), 177.7 (s) ppm. IR (NaCl): ν˜ ϭ 3418 (br vs, OH), 2934
3.2, Jt ϭ 9.5 Hz, 1 H), 3.14 (ddd, J ϭ 3.5 Hz, 8.0 Hz, 11.7 Hz, 1
2
2
H), 4.44 (d, J ϭ 18.6 Hz, 1 H), 4.49 (d, J ϭ 18.6 Hz, 1 H), 4.50
(s, CH), 2856 (s, CϪH), 1748 (vs, CϭO), 1467 (m), 1450 (m), 1377 (d, 2J ϭ 18.6 Hz, 1 H), 4.53 (d, 2J ϭ 18.6 Hz, 1 H) ppm. 13C NMR
(m), 1276 (s), 1248 (m), 1185 (s), 1124 (m), 1007 (s), 990 (s), 906 (90.6 MHz, CDCl3): δ ϭ 21.7 (t), 24.7 (t), 24.9 (t), 25.1 (t), 25.1 (t),
(m). MS (70 eV, EI): m/z (%) ϭ 182 (1) [Mϩ], 164 (1), 152 (4), 124
(6), 101 (100), 95 (5), 82 (10), 67 (34), 54 (11). HRMS calcd. for
C10H14O3 182.09430, found 182.09416.
26.1 (t), 26.1 (t), 26.5 (t), 27.0 (t), 28.6 (t), 30.0 (t), 33.4 (d), 35.1
(t), 36.6 (d), 39.3 (t), 39.8 (t), 49.6 (d), 49.7 (d), 73.3 (t), 73.6 (t),
171.6 (s), 171.7 (s), 208.7 (s), 209.2 (s) ppm. IR (KBr): ν˜ ϭ 2931
(vs, CϪH), 2855 (s, CϪH), 1755 (vs, CϭO), 1716 (vs, CϭO), 1481
(s), 1446 (s), 1362 (m), 1262 (m), 1171 (m), 1078 (s). MS (70 eV,
EI): m/z (%) ϭ 210 (10) [Mϩ], 180 (34), 167 (16), 152 (12), 124
(11), 110 (100), 96 (70), 81 (95), 67 (97), 55 (55). HRMS calcd. for
C12H18O3 210.12560, found 210.12563.
1-Hydroxy-12-oxatricyclo[8.3.0.02,9]tridecan-11-one (44): Prepared
from tetronate 8 (188 mg, 1.0 mmol) and cis-cyclooctene (1.95 mL,
1.65 g, 15.0 mmol) as colorless oil in a yield of 114 mg (0.54 mmol,
54%, 1:2:1 diastereomeric mixture); Rf ϭ 0.30 (P/EtOAc, 2:1); as
inseparable mixture this compound was directly submitted to ring
opening conditions
General Procedure for the Retro-Aldol Ring Expansion: A solution
of the β-hydroxy lactone (1.00 mmol) and Cs2CO3 (2.00 mmol) in
THF (20 mL) was transferred into a Teflon tube and irradiated in
the microwave oven for 30 min. (temperature gradient: room temp.
Ǟ 100 °C in 15 min at 800 W). The mixture was cooled to room
temp., filtered and the solvent was removed under reduced pressure.
The remaining oil was subjected to column chromatography to
yield the desired products.
Acknowledgments
This project was supported by the Deutsche Forschungsgemein-
schaft (Ba 1372Ϫ6/1) and the Fonds der Chemischen Industrie. We
would also like to acknowledge the undergraduate research partici-
pants Thomas Deschner, Markus Gretz, Frederik Naraschewski,
Christof Schröfl and Simon Stelzig whose enthusiastic work con-
tributed to the presented results.
4-Oxabicyclo[5.3.0]decan-2,5-dione (45): Prepared from β-hydroxy
lactone 42 (168 mg, 1.00 mmol) as colorless crystals in a yield of
125 mg (0.74 mmol, 74%, M.p. 94Ϫ96 °C; Rf ϭ 0.50 (P/EtOAc,
[1]
[1a] S. L. Schreiber, Science 1985, 227, 857Ϫ863. [1b] S. A. Flem-
1
3
ing, C. L. Bradford, J. J. Gao, in: Molecular and Supramolecular
Photochemistry, Organic Photochemistry, 1 (Ed.: K. S. S. V. Ra-
2:1). H NMR (360 MHz, CDCl3) δ ϭ 1.10 (virt. q, J ϭ 8.0 Hz,
1 H), 1.52Ϫ1.68 (m, 2 H), 1.82Ϫ2.00 (m, 2 H), 2.31Ϫ2.47 (m, 2
H), 2.54Ϫ2.72 (m, 1 H), 2.85 (dd, 2J ϭ 13.2, 3J ϭ 5.2 Hz, 1 H),
3.44 (dt, 3Jd ϭ 3.5, 3Jt ϭ 8.2 Hz, 1 H), 4.51 (d, 2J ϭ 18.5 Hz, 1 H),
mamurthy), Marcel Dekker, New York, 1997, 186Ϫ243. [1c]T.
[1d]
Bach, Synthesis 1998, 683Ϫ703.
J.-P. Pete, in: CRC Hand-
book of Organic Photochemistry and Photobiology, 2nd ed. (Ed.:
F. Lenci, W. M. Horspool), CRC Press, New York, 2004,
71.1Ϫ71.14.
2
4.56 (d, J ϭ 18.5 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3):
δ ϭ 23.0 (t), 24.5 (t), 32.5 (t), 36.0 (t), 39.5 (d), 50.7 (d), 73.5 (t),
171.9 (s), 206.9 (s) ppm. IR (KBr): ν˜ ϭ 2960 (s, CH), 1735 (vs, Cϭ
O), 1717 (vs, CϭO), 1636 (vs), 1430 (m), 1320 (m), 1271 (m), 1170
(m), 1114 (m), 1071 (m). MS (70 eV, EI): m/z (%) ϭ 168 (4) [Mϩ],
138 (10), 110 (6), 82 (46), 67 (100), 53 (41). C9H12O3 (168.19): calcd.
C 64.27, H 7.19; found C 64.03, H 7.18.
[2] [2a]
P. A. Wender, in: Photochemistry in Organic Synthesis (Ed.:
J. D. Coyle), Royal Society of Chemistry, London, 1986,
163Ϫ188. [2b]M. Demuth, G. Mikhail, Synthesis 1989,
145Ϫ161. [2c] D. De Keukeleire, S.-L. He, Chem. Rev. 1993, 93,
[2d]
359Ϫ380.
B. Grosch, T. Bach, in: CRC Handbook of Or-
ganic Photochemistry and Photobiology, 2nd ed. (Eds.: F. Lenci,
W. M. Horspool), CRC Press, New York, 2004, 61.1Ϫ61.14.
4-Oxa-bicyclo[5.4.0]undecan-2,5-dione (46): Prepared from β-
hydroxy lactone 43 (182 mg, 1.00 mmol) as colorless crystals in a
yield of 153 mg (0.84 mmol, 84%). M.p. 119Ϫ122 °C; Rf ϭ 0.55
[3] [3a]
[3b]
M. T. Crimmins, Chem. Rev. 1988, 88, 1453Ϫ1473.
M.
T. Crimmins, T. L. Reinhold, Org. React. 1993, 44, 297Ϫ588.
D. I. Schuster, in: CRC Handbook of Organic Photochemistry
and Photobiology, 2nd ed. (Eds.: F. Lenci, W. M. Horspool),
CRC Press, New York, 2004, 72.1Ϫ72.24.
[4]
1
(P/EtOAc, 2:1). H NMR (360 MHz, CDCl3) δ ϭ 0.89Ϫ1.10 (m, 1
H), 1.16Ϫ1.30 (m, 1 H), 1.32Ϫ1.49 (m 1 H), 1.52Ϫ1.88 (m, 4 H),
2
3
[5] [5a]
2.06Ϫ2.13 (m, 1 H), 2.25Ϫ2.37 (m, 1 H), 2.38 (virt. t, J ϭ J ϭ
S. Ghosh, S. R. Raychaudhury, R. G. Salomon, J. Org.
2
3
[5b]
11.7 Hz, 1 H), 2.78 (dd, J ϭ 11.7, J ϭ 5.5 Hz, 1 H), 3.22 (virt. t,
3J ϭ 3.5 Hz, 1 H), 4.43 (d, 2J ϭ 18.3 Hz, 1 H), 4.49 (d, 2J ϭ
18.3 Hz, 1 H) ppm. 13C NMR (90.6 MHz, CDCl3): δ ϭ 21.5 (t),
24.6 (t), 25.2 (t), 31.1 (t), 33.4 (d), 38.3 (t), 44.8 (d), 73.4 (t), 171.4
(s), 207.8 (s) ppm. IR (KBr): ν˜ ϭ 2944 (s, CH), 2922 (s, CϪH),
2878 (m, CϪH), 2850 (m, CϪH), 1732 (vs, CϭO), 1727 (vs, Cϭ
O), 1449 (m), 1348 (m), 1283 (s), 1271 (s), 1242 (m), 1182 (m), 1144
(m), 1089 (m), 1070 (vs), 906 (s). MS (70 eV, EI): m/z (%) ϭ 182
(8) [Mϩ], 152 (22), 139 (5), 124 (56), 96 (10), 82 (48), 81 (51), 67
(100), 54 (44). HRMS calcd. for C10H14O3 182.09430, found
182.09418.
Chem. 1987, 52, 83Ϫ90.
S. Ghosh, in Handbook of Photo-
chemistry and Photobiology, 2nd ed. (Eds.: F. Lenci, W. M. Hor-
spool), CRC Press, New York, 2004, 18.1Ϫ18.19.
M. Kemmler, T. Bach, Angew. Chem. Int. Ed. 2003, 42,
4824Ϫ4826; Angew. Chem. 2003, 115, 4973Ϫ4975.
P. G. Bauslaugh, Synthesis 1970, 287Ϫ300.
H. Kosugi, S. Segiguchi, R.-I. Sekita, H. Uda, Bull. Chem.
Soc., Jpn. 1976, 49, 520Ϫ528.
[6]
[7]
[8]
[9]
F. W. Curtius, H.-D. Scharf, Tetrahedron: Asymmetry 1996, 7,
2957Ϫ2961.
[10] [10a]
[10b]
S. Gelin, P. Pollet, Synth. Commun. 1980, 10, 805Ϫ811.
T. Momose, N. Toyooka, H. Fujii, H. Yanagino, Hetero-
4594
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 4582Ϫ4595

Inter- and Intramolecular [2ϩ2]-Photocycloaddition of Tetronates
FULL PAPER
[10c]
cycles 1989, 29, 453Ϫ458.
J. W. J. F. Thuring, A. A. M. A.
ence-Fourier map shows no striking features (∆ρe, min./max.
ϭ
ϩ0.19/-0.19 e·AϪ3).
˚
V. Gaal, S. J. Hornes, M. M. D. Kok, G. H. L. Nefkens, B.
Zwanenburg, J. Chem. Soc., Perkin Trans. 1 1997, 767Ϫ774.
Crystal structure analysis of compound 33a: C11H14O3, Mr ϭ
[10d]
[10e]
W. Zhang, Tetrahedron Lett. 2000, 41, 2523Ϫ2527.
T.
194.22, colorless fragment (0.56 ϫ 0.64 ϫ 0.89 mm3), ortho-
Mukaiyama, T. Shintou, K. Fukumoto, J. Am. Chem. Soc.
2003, 125, 10538Ϫ10539.
G. Bauschke, Synlett 2003, 83Ϫ86.
rhombic, Pbca (No. 61), a ϭ 10.4048(5), b ϭ 10.6301(5), c ϭ
[10f]
3
17.5821(8) A, V ϭ 1944.7(2) A , Z ϭ 8, Dcalcd. ϭ 1.327 g·cmϪ3
,
˚
˚
F. F. Paintner, L. Allmendinger,
F
000 ϭ 832, µ(Mo-Kα) ϭ 0.786 mmϪ1. Preliminary examination
[11]
[12]
and data collection were carried out on a four-circle dif-
fractometer (NONIUS CAD4) at the window of a sealed tube
(NONIUS FR590) with graphite-monochromated Cu-Kα radi-
H. Martin, R. Hoffmann, B. Schmidt, S. Wolff, Tetrahedron
1989, 45, 6113Ϫ6126.
J. S. Bajwa, R. C. Anderson, Tetrahedron Lett. 1990, 31,
6973Ϫ6976.
T. Sato, K. Yoshimatsu, J. Otera, Synlett 1995, 843Ϫ846.
W. D. Kumler, J. Am. Chem. Soc. 1938, 60, 859Ϫ864.
H. Wyss, U. Voegeli, R. Scheffold, Helv. Chim. Acta 1981, 64,
775Ϫ786.
˚
ation (λ ϭ 1.5480 A). Data collection were performed at 293 K
[13]
[14]
[15]
within the range of 5.05° Ͻ Θ Ͻ 70.60°. A total of 7810 reflec-
tions were collected and corrected for Lorentz, polarization
and decay (113 h, Ϫ29.6%) effects. No correction for absorp-
tion effects was applied. After rejecting 777 systematically ab-
sent intensities and merging (Rint ϭ 0.044), 1842 [1622: Io
Ͼ
[16]
[17]
[18]
[19]
[20]
H. Zimmer, A. Amer, C. Van Pham, D. Grob-Schmidt, J. Org.
Chem. 1988, 53, 3368Ϫ3370.
S. Brandaenge, L. Flodman, A. Norberg, J. Org. Chem. 1984,
49, 927Ϫ928.
L. W. Rotherham, J. E. Semple, J. Org. Chem. 1998, 63,
6667Ϫ6672.
J. D. White, T. Nishiguchi, R. W. Skeean, J. Am. Chem. Soc.
1982, 104, 3923Ϫ3928.
J. A. Macritchie, A. Silcock, C. L. Willis, Tetrahedron: Asym-
2σ(Io)] independent reflections remained and all were used to
refine 127 parameters. The structure was solved by a combi-
nation of direct methods and difference-Fourier syntheses. All
non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All hydrogen atoms were placed in calculated
positions (riding model). Full-matrix least-squares refinements
were carried out by minimizing Σw(F2o Ϫ F2o)2 and converged
with R1 ϭ 0.0537 [Io Ͼ 2σ(Io)], wR2 ϭ 0.1573 [all data],
GOF ϭ 1.051, all parameters, and shift/error Ͻ 0.001. The
final difference-Fourier map shows no striking features
metry 1997, 8, 3895Ϫ3902.
[21] [21a]
A. R. Matlin, C. F. Albert, S. Wolff, W. C. Agosta, J. Am.
(∆ρmin./max. ϭ ϩ0.28/Ϫ0.25 e·AϪ3).
˚
[21b]
Chem. Soc. 1986, 108, 3385Ϫ3394.
M. T. Crimmins, P. S.
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre. CCDC-239366 (33a)
and CCDC-239365 (21) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from
the Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB2 1EZ, UK; Fax: ϩ44 1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
Watson, Tetrahedron Lett. 1993, 34, 199Ϫ202.
[22] [22a]
[22b]
T. W. Flechtner, J. Org. Chem. 1977, 42, 901Ϫ903.
E.
Anklam, P. Margaretha, Helv. Chim. Acta 1983, 66,
1466Ϫ1474.
[22c]
A. Naim, G. Mills, P. B. Shevlin, Tetrahedron
Lett. 1992, 33, 6779Ϫ6782.
[23] [23a] J. R. Anderson, R. L. Edwards, A. A. Freer, R. P. Mabelis,
J. P. Poyser, H. Spencer, A. J. S. Whalley, J. Chem. Soc., Chem.
[23b]
Commun. 1984, 917Ϫ919.
J. R. Anderson, R. L. Edwards,
J. P. Poyser, A. J. S. Whalley, J. Chem. Soc., Perkin Trans. 1
Data Collection Software for NONIUS DIP devices, Delft
(The Netherlands), 1997; L. Straver, EnrafϪNonius CAD4
Operating System Version 5.0. B.V. EnrafϪNonius, Delft, The
Netherlands, 1989; C.K. Fair, MoleN An Interactive Intelligent
System for Crystal Structure Analysis. EnrafϪNonius, Delft,
The Netherlands, 1990. Z. Otwinowski, W. Minor, Methods in
Enzymology 1997, 276, 307Ϫ326; A. Altomare, G. Cascarano,
C. Giacovazzo, A. Guagliardi, M. C. Burla, G. Polidori, M.
Camalli, SIR92, J. Appl. Crystallogr. 1994, 27, 435Ϫ436; Inter-
national Tables for Crystallography, Vol. C, Tables 6.1.1.4,
4.2.6.8, and 4.2.4.2 (Ed.: A. J. C. Wilson), Kluwer Academic
Publishers, Dordrecht (The Netherlands), 1992; A. L. Spek,
PLATON, A Multipurpose Crystallographic Tool, Utrecht
University, Utrecht (The Netherlands), 2001; G. M. Sheldrick,
SHELXL-97, University of Göttingen, Göttingen (Germany),
1998.
1988, 823Ϫ831.
[24] [24a]
S. W. Baldwin, T. J. Mazzuckelli, Tetrahedron Lett. 1986,
[24b]
27, 5975Ϫ5978.
Gregori, T. Parella, Tetrahedron 1996, 52, 1267Ϫ1278.
Gregori, R. Alibes, J. L. Bourdelande, J. Font, Tetrahedron
R. Alibes, J. L. Bourdelande, J. Font, A.
[24c]
A.
Lett. 1998, 39, 6961Ϫ6962.
K. Tomioka, K. K. M. Tanaka, Tetrahedron Lett. 1982, 23,
3401Ϫ3404.
[25]
[26]
Crystal structure analysis of compound 21: C8H10O3, Mr ϭ
154.16, colorless fragment (0.32 ϫ 0.34 ϫ 0.51 mm3), triclinic,
˚
¯
P1 (No. 2), a ϭ 6.3159(3), b ϭ 8.4407(4), c ϭ 8.0125(5) A, α ϭ
101.315(2)°, β ϭ 104.856(2)°, γ ϭ 112.969(4)°, V ϭ 358.46(4)
3
A , Z ϭ 2, Dcalcd. ϭ 1.428 g·cmϪ3, F000 ϭ 164, µ(Mo-Kα) ϭ
˚
0.109 mmϪ1. Preliminary examination and data collection were
carried out on an imaging plate device (NONIUS DIP2020)
with a NONIUS cooling system at the window of a sealed tube
(NONIUS FR590) with graphite-monochromated Mo-Kα radi-
[27] [27a]
R. A. Caldwell, W. Tang, D. I. Schuster, G. E. Heibel,
Photochem. Photobiolog. 1991, 53, 159Ϫ164. [27b] D. I. Schuster,
˚
ation (λ ϭ 0.71073 A). Data collection were performed at
D. A. Dunn, G. E. Heibel, P. B. Brown, J. M. Rao, J. Woning,
[27c]
143 K within the Θ range of 2.78° Ͻ Θ Ͻ 25.34°. A total of
6003 intensities were integrated. Raw data were corrected for
Lorentz, polarization, and, arising from the scaling procedure,
R. Bonneau, J. Am. Chem. Soc. 1991, 113, 6245Ϫ6255.
N.
A. Kaprinidis, G. Lem, S. H. Courtney, D. I. Schuster, J. Am.
Chem. Soc. 1993, 115, 3324Ϫ3325.
M. W. Schmidt, E. K. C. Lee, J. Am. Chem. Soc. 1970, 92,
3579Ϫ3586.
[28]
for latent decay and absorption effects. After merging (Rint
ϭ
0.068), 1231 [1195: Io Ͼ 2σ(Io)] independent reflections re-
mained and all were used to refine 141 parameters. The struc-
ture was solved by a combination of direct methods and differ-
ence-Fourier syntheses. All non-hydrogen atoms were refined
with anisotropic displacement parameters. All hydrogen atoms
were found and refined with individual isotropic displacement
parameters. Full-matrix least-squares refinements were carried
out by minimizing Σw(F2o Ϫ F2o)2 and converged with R1 ϭ
0.0444 [Io Ͼ 2σ(Io)], wR2 ϭ 0.1212 [all data], GOF ϭ 1.072,
and shift/error Ͻ 0.001. Small extinction effects were corrected
with the SHELXL-97 procedure [ε ϭ 0.12(3)]. The final differ-
[29] [29a]
P. De Mayo, H. Takeshita, Can. J. Chem. 1963, 41,
[29b]
440Ϫ449.
P. De Mayo, Acc. Chem. Res. 1971, 4, 41Ϫ48.
[30]
T. Bach, S. Heuser, Chem. Eur. J. 2002, 8, 5585Ϫ5592.
A. N. De Silva, C. L. Francis, A. D. Ward, Aust. J. Chem. 1993,
46, 1657Ϫ1671.
[31]
[32]
[33]
R. W. Hoffmann, G. Niel, Liebigs Ann. Chem. 1991,
1195Ϫ1201.
L. A. Arnold, R. Naasz, A. J. Minaard, B. L. Feringa, J. Org.
Chem. 2002, 67, 7244Ϫ7254.
Received August 3, 2004
Eur. J. Org. Chem. 2004, 4582Ϫ4595
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4595