Dehalogenation of 1,3-diiodotricyclo[3.3.0.03,7]octane: Generation of 1,3dehydrotricyclo[3.3.0.03,7]octane, a 2,5-methano-bridged [2.2.1]propellane

Article abstract of DOI:10.1002/chem.200600859

Compounds isolated from the reaction of (±)-1,3-diiodotricy-clo[3.3. 0.0^3,7]octane with molten sodium or tBuLi suggest the intermediate formation of (±)-1,3-dehydrotricyclo[3.3.0.0^3,7]octane. Worthy of note is the formation of stereoisomeric bi(5-methylenebicyclo[2.2.1]hept-2- ylidene) derivatives, probably by coupling of two units of (±)-1,3- dehydrotricyclo[3.3.0.0^3,7]octane of the same or different absolute configuration followed by fragmentation, processes that have been studied by theoretical calculations.

Full text of DOI:10.1002/chem.200600859

DOI: 10.1002/chem.200600859
3,7
Dehalogenation of 1,3-Diiodotricyclo[3.3.0.0 ]octane: Generation of 1,3-
3
,7
Dehydrotricyclo[3.3.0.0 ]octane, a 2,5-Methano-Bridged [2.2.1]Propellane
[
a]
Carles Ayats, Pelayo Camps,* JosØ A. Fernµndez, and Santiago Vµzquez*
Abstract: Compounds isolated from the reaction of (ꢁ)-1,3-diiodotricy-
3,7
clo[3.3.0.0 ]octane with molten sodium or tBuLi suggest the intermediate forma-
3
,7
tion of (ꢁ)-1,3-dehydrotricyclo[3.3.0.0 ]octane. Worthy of note is the formation
of stereoisomeric bi(5-methylenebicyclo[2.2.1]hept-2-ylidene) derivatives, probably
Keywords: dehalogenation
sity functional calculations · pro-
pellanes · strained molecules
· den-
A
H
R
U
G
ACHTREUNG
3
,7
by coupling of two units of (ꢁ)-1,3-dehydrotricyclo[3.3.0.0 ]octane of the same or
different absolute configuration followed by fragmentation, processes that have
been studied by theoretical calculations.
ACHTREUNG
[
6]
Introduction
eton, and have generated, trapped, and dimerized several
highly pyramidalized alkenes by dehalogenation of 1,2-diio-
[7]
In 1966, Ginsburg coined the name propellane for com-
pounds with three nonzero bridges and one zero bridge be-
tween a pair of bridgehead carbon atoms. Small-ring pro-
pellanes, such as 1–5, are particularly interesting, mainly
dobisnoradamantanes. We have also recently published an
attempt to generate tricyclo[3.3.0.0 ]octa-1(5),3(7)-diene
(7) by deiodination of 6 (Scheme 1). This reaction led to a
3
,7
[1]
[8]
[2]
because of the presence of two carbon atoms with inverted
geometries, that is, all of the groups attached to the bridge-
head carbon atoms lie on one side of a plane, with a conse-
[3]
quent unusual degree of reactivity. The unusual structure
[4]
[5]
of these compounds has attracted, and still attracts, much
attention from both experimental and theoretical chemists.
For more than 20 years, our group has been working on
the synthesis of bisnoradamantane derivatives. We have de-
veloped two general entries to this strained carbocyclic skel-
3
,7
Scheme 1. 1,3-Dehydrotricyclo[3.3.0.0 ]octane [(ꢁ)-9] and highly pyra-
midalized alkenes 7 and 11.
[
a] C. Ayats, Prof. Dr. P. Camps, J. A. Fernµndez, Dr. S. Vµzquez
Laboratori de Química Farmac›utica
complex mixture of products, probably because 1,2-deiodi-
nation to give the pyramidalized alkene can compete with
1,3-deiodination to give 1,3-dehydro derivatives. In fact, 9
(
Unitat Associada al CSIC), Facultat de Farmàcia
Universitat de Barcelona
Av. Diagonal 643, 08028 Barcelona (Spain)
Fax : (+34)934-035-941
ꢀ1
was predicted to be more stable [9.0 kcalmol , UB3LYP/6-
ꢀ
1
3
1G(d); 10.2kcalmol , UMP2/6-31G(d)] than the highly
E-mail: camps@ub.edu
3
,7
pyramidalized tricyclo[3.3.0.0 ]oct-1(5)-ene (11), a very re-
svazquez@ub.edu
active intermediate already generated by our group by de-
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
[7b,9]
A
H
R
U
G
1522
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Chem. Eur. J. 2007, 13, 1522 – 1532

FULL PAPER
To get more insight into this 1,3-deiodination, we have
angle in
9
(C1-C5-C4-C3) was calculated to be 318
now prepared (ꢁ)-8 (Scheme 2), and studied its possible de-
(UB3LYP/6-31G(d)) or 328 (UMP2/6-31G(d)). Although
the energy change resulting from hydrogenolysis of the C1ꢀ
3
,7
iodination to 1,3-dehydrotricyclo[3.3.0.0 ]octane ((ꢁ)-9,
Scheme 1). The isolated compounds from the deiodination
of (ꢁ)-8 suggest the intermediate formation of (ꢁ)-9
C3 bond in 9 was found to be only slightly higher (1.4 kcal
ꢀ
1
ꢀ1
mol , UB3LYP/6-31G(d); 2.5 kcalmol , UMP2/6-31G(d))
(
Schemes 3 and 4).
than that of the corresponding bond (C1ꢀC4) in 3, the zero-
bridge propellane bond length in 9 was calculated to be
1.725 Š (UB3LYP/6-31G(d)) and 1.789 Š (UMP2/6-
31G(d)), clearly larger than the corresponding bond in 3 of
1.583 Š (UB3LYP/6-31G(d)) and 1.619 Š (UMP2/6-
31G(d)). Taking into account that 3 is a very unstable com-
pound, an even more reactive behavior should be expected
for 9, if it can be generated at all.
Scheme 2. Preparation of (ꢁ)-8: a) Li, tBuOH, THF, D, 6 h, 80%;
b) IBDA, I
tate
2
, hn, acetonitrile, 24 h, 76%. IBDA=iodosobenzene diace-
Results and Discussion
[
8]
Although, at first sight, 9 can be seen as an irrelevant de-
Diiodide (ꢁ)-8 was prepared from diiododiacid (ꢁ)-12 by
[4]
[10]
rivative of the known [2.2.1]propellane 3, the additional
methano bridge connecting positions 5 and 7 in 9 strongly
distorts the molecular structure of 3 (Figure 1). Thus, while
reduction with Li/tBuOH to the known diacid (ꢁ)-13, fol-
lowed by double iododecarboxylation of (ꢁ)-13 using our
[7e]
improved conditions in acetonitrile as solvent (Scheme 2).
Notably, compounds 8, 12, and 13 are chiral 1,3-disubstitut-
3
,7
ed tricyclo[3.3.0.0 ]octane derivatives. All of them contain
four stereogenic centers, which correspond to the bridge-
head positions. However, in a more simple way, they can be
considered as having a chiral axis passing through the
middle of the C1ꢀC5 and C3ꢀC7 bonds. Their chirality
could then be defined in the same way as for chiral allenes.
The same is true for dehydro compound 9.
Reaction of (ꢁ)-8 with molten sodium in boiling 1,4-diox-
ane gave a complex mixture (Scheme 3), which by GC–MS
showed, in order of elution, the presence of the following
compounds (% area ratio (a.r.)): 14 (1.2), meso- and dl-15
(
(
4.7 and 5.2), (ꢁ)-16 (33.5), (ꢁ)
A
T
E
N
(Z,anti)-17 (1.5), (E,anti)-17
2.4), 18 (32.3), stereoisomers of 19 (13.7), and (ꢁ)-20 (5.5).
Figure 1. Minimum energy conformation [UMP2/6-31G(d)] of propellane
From this mixture, compounds (ꢁ)-16, a mixture of two ste-
9
.
reoisomers of 17, for which we propose the structures
(
E,anti)-17 and (ꢁ)
A
H
R
U
G
the dihedral C1-C2-C3-C4 angle in 3 was calculated to be 08
UB3LYP/6-31G(d) or UMP2/6-31G(d)), the corresponding
meric mixture 19, and (ꢁ)-20 were isolated in 20, 3.5, 27,
(
11, and 2% yield, respectively, and fully characterized.
Scheme 3. Reaction of (ꢁ)-8 with molten sodium in boiling 1,4-dioxane.
Chem. Eur. J. 2007, 13, 1522 – 1532
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1523

P. Camps, S. Vµzquez et al.
[
11]
Moreover, the formation of the known products 14 and
meso- and dl-15
the McMurry reaction was racemic, the four dimers shown
in Scheme 5 could be formed. Two of them are meso com-
pounds, formed from starting compounds of opposite abso-
lute configuration, while the other two are chiral, being
formed from starting compounds of the same absolute con-
figuration and, consequently, they should be racemic. In
fact, chiral GC–MS analysis showed the presence of six com-
ponents in the above mixture,
[12]
was detected by GC–MS analysis. To
secure the structure of 14, it was prepared by reduction of
(
ꢁ)-8 with Li/tBuOH.
Similarly, reaction of (ꢁ)-8 with tBuLi in anhydrous THF
gave a complex mixture (Scheme 4), which by GC–MS
showed the presence, in order of elution, of the following
confirming the presence of two
racemic and two meso compo-
nents. Achiral GC–MS analysis
of mixed samples of 17 from
the two reactions showed that
the minor and main compo-
nents of the mixture of 17 from
(
ꢁ)-8 coincide with the second
and third eluted components of
the McMurry reaction, respec-
tively. Similarly, chiral GC–MS
analysis showed the main and
minor components of the mix-
ture 17 from (ꢁ)-8 to be meso
Scheme 4. Reaction of (ꢁ)-8 with tBuLi in THF.
(
corresponding to the fifth
eluted component of the
McMurry reaction) and racemic
compounds (% a.r.): 21 (7.2), (ꢁ)-22 (24.5), (ꢁ)
A
T
E
N
(Z,anti)-17
(corresponding to the third and fourth eluted components of
the McMurry reaction), respectively.
(
0.1), (E,anti)-17 (0.6), 18 (40.6), (ꢁ)-20 (14.3), and the ste-
reoisomeric mixture 23 (2.0). Traces of 14 were detected in
the organic extracts before concentration. From the above
mixture, compounds 18, (ꢁ)-20, (ꢁ)-22, and a stereoiso-
meric mixture of 23 were isolated in pure form in 20, 6, 7,
and 3% yield, respectively. The structure of compound 21,
which could not be isolated due to its high volatility, is pro-
posed on the basis of its mass spectrum and by analogy with
We also carried out several reactions of (ꢁ)-8 with differ-
ent reagents to obtain more information about the possible
formation of the bridged propellane (ꢁ)-9, without addi-
tional results to those described above. Thus, reaction of
(ꢁ)-8 with the radical anion derived from 4,4’-di-tert-butyl-
biphenyl (25), by treatment with lithium under ultrasound
[
15]
irradiation in anhydrous THF at ꢀ788C
followed by
[4,13]
previous related results.
quenching of the reaction mixture by bubbling CO (g), did
2
To confirm the structure of the stereoisomers of 17, we
not give an acidic fraction. Instead, a neutral fraction con-
taining mainly 25 was obtained. GC–MS analysis of this
mixture showed the presence, in order of elution, of the fol-
lowing significant components (% a.r.): 26 (0.1), (ꢁ)-22
(0.6), 18 (1.4), and 25 (87.6) (Scheme 6). An analytical
sample of the new compound 26 was obtained by controlled
catalytic hydrogenation of the starting diiodide (ꢁ)-8.
carried out an alternative synthesis (Scheme 5), starting
[14]
from the known ene ketal (ꢁ)-24. After acidic hydrolysis
of (ꢁ)-24, the obtained ketone was submitted to the
McMurry reduction. In this way, a new mixture of stereoiso-
1
mers of 17 was obtained and characterized by H and
13
C NMR spectroscopy. Achiral GC–MS analysis of this mix-
ture showed the presence of four components with similar
area ratios, whose mass spectra were essentially identical
and coincidental with those of the components of the mix-
ture 17 obtained from (ꢁ)-8. Since the starting material in
Moreover, (ꢁ)-8 was reacted with tBuLi in anhydrous di-
[4a,16]
ethyl ether
at ꢀ788C, which gave similar results to
those described above for the reaction carried out in THF
Scheme 6. Reaction of (ꢁ)-8 with the radical anion from 25 and Li, in
Scheme 5. Preparation of the stereoisomeric mixture of 17 from (ꢁ)-24.
THF.
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Chem. Eur. J. 2007, 13, 1522 – 1532

A 2,5-Methano-Bridged [2.2.1]Propellane
FULL PAPER
(
Scheme 7). GC–MS analysis of the obtained mixture
showed the presence, in order of elution, of the following
main components (% a.r.): 14 (5.7), 21 (31.2), (ꢁ)-27 (3.1),
Scheme 7. Reaction of (ꢁ)-8 with tBuLi in diethyl ether.
and 18 (50.8). The structure of (ꢁ)-27, which was formed in
very low yield, is proposed on the basis of its mass spectrum,
taking into account previous results, that is, the formation of
(
ꢁ)-16 and (ꢁ)-22. Not unexpectedly, the amount of (ꢁ)-27
formed was much lower than those of the corresponding
products (ꢁ)-16 (33.5% a.r.) and (ꢁ)-22 (24.5% a.r.)
formed in the similar reactions carried out in 1,4-dioxane
and THF, respectively.
Scheme 9. Possible pathways for the formation of products from the reac-
tions of (ꢁ)-8 with molten sodium or tBuLi.
Finally, reaction of (ꢁ)-8 with excess tBuLi in anhydrous
diethyl ether at ꢀ788C, followed by quenching of the reac-
tion mixture with trimethylsilyl chloride, gave a very com-
plex mixture from which no defined product could be isolat-
ed or identified. However, when the above reaction mixture
tBuLi. However, in this case, the formation of compound 21
reasonably implies 1) nucleophilic addition of tBuLi to (ꢁ)-
9, to give (ꢁ)-32, and 2) protonation. In a similar way, for-
mation of (ꢁ)-30 could be easily explained from (ꢁ)-9 via
[13a]
was quenched by bubbling CO (g),
a very complex mix-
2
ture of products was obtained as the neutral fraction, which
32 by 1) reaction with CO to give (ꢁ)-34, and 2) protona-
2
by GC–MS analysis was shown to contain di-tert-butyl
tion. Formation of (ꢁ)-29 may be easily explained from
(ꢁ)-34 by 1) reaction with tBuLi, to give diolate (ꢁ)-35,
and 2) hydrolysis. Alternatively, diolate (ꢁ)-35 could be ob-
tained from (ꢁ)-32 by reaction with lithium pivalate (33),
[17]
ketone (28)
(74.5% a.r.) and a compound whose mass
spectrum is compatible for ketone (ꢁ)-29 (7.2% a.r.) as the
main components (Scheme 8). Also, an acidic fraction was
itself obtained by reaction of tBuLi with CO . The formation
2
of (ꢁ)-27 (Scheme 7) could be similar to that of (ꢁ)-16,
while the formation of monoiodide 26 could take place with-
out the intermediate formation of (ꢁ)-9.
We carried out a density functional theory (DFT) study
(
UB3LYP/6-31G(d)) of the formation of the stereoisomers
[9]
of 17 from (ꢁ)-9, and the results are shown in Figure 2.
Reaction of two units of 9 of different absolute configura-
tion (path B) gives diradical meso-38. Conformational analy-
sis of meso-38 shows the anti conformation (meso-38180) to
Scheme 8. Reaction of (ꢁ)-8 with tBuLi in THF and quenching with
2
CO .
ꢀ
1
be much more stable (10.6 kcalmol ) than the enantiomeric
gauche conformations meso-38+60 and meso-38 . The for-
ꢀ60
isolated which, after esterification with a solution of diazo-
methane in diethyl ether, gave a complex mixture of prod-
ucts. GC–MS analysis of this mixture was shown to contain
mainly ester (ꢁ)-31 (43% a.r.) derived from acid (ꢁ)-30.
According to the known reactivity of small-ring propel-
mation of meso-38 takes place through a transition state
1
80
ꢀ
1
(1.4 kcalmol ) of lower energy than those leading to meso-
ꢀ1
38+60 or meso-38
(2.9 kcalmol ). Fragmentation of this
ꢀ60
diradical from the more stable meso-38180 conformation
ꢀ
1
gives (E,anti)-17 in a highly exothermic (ꢀ139.9 kcalmol )
[2a,b]
[2a,3,4]
[18]
A
C
H
T
R
E
U
N
G
lanes
and, in particular, of [2.2.1]propellane,
all of
and barrierless process.
As the zero-point vibrational
the products observed in the reaction of (ꢁ)-8 with sodium
in 1,4-dioxane may be explained by assuming the intermedi-
ate formation of (ꢁ)-9. This intermediate could abstract a
hydrogen atom from 1,4-dioxane to give the tricy-
energy (ZPVE) correction is larger than the difference in
electronic energies, the transition state appears to have a
lower energy than the starting minimum. This simply means
[22]
that the reaction is barrierless and highly exothermic.
A
3,7
clo[3.3.0.0 ]oct-1-yl and dioxan-2-yl radicals, from which
path from meso-38 to the corresponding fragmentation
ꢀ60
compounds 14–16 and 18–20 can be readily derived
product (Z,syn)-17 was not found. In a similar way, reaction
of two units of 9 of the same absolute configuration gives
diradicals d- or l-38 (dl-38, path A), whose conformational
(
Scheme 9). The same is true for the formation of most of
the compounds obtained in the reaction of (ꢁ)-8 with
Chem. Eur. J. 2007, 13, 1522 – 1532
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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1525

P. Camps, S. Vµzquez et al.
Figure 2. Possible intermediates, rotational interconversion, and transition states from (ꢁ)-9 to the stereoisomers of 17 as calculated by a DFT study at
the UB3LYP/6-31G(d) level. Path A corresponds to the coupling of two molecules of 9 of the same absolute configuration, while path B corresponds to
the coupling of two molecules of 9 of different absolute configuration. The suffixes 180, +60, and ꢀ60 are given to diradicals in approximate anti and
gauche conformations, respectively, around the CꢀC bond connecting the two tricyclic units. Similarly, these suffixes are applied to transition states for
the formation of these diradicals, in this case with reference to the arrangement around the CꢀC bond which is being formed. Transition states with suf-
fixes ꢀ60!180, 60!180, and +60!ꢀ60 are rotational transition states which connect the diradical minima indicated by the given suffixes. Relative en-
ꢀ
1
ergies are given in kcalmol . Values are taken from corrected enthalpy calculations using UB3LYP/6-31G(d). Transition states connecting meso-38ꢀ60
and dl-38+60 with (Z,syn)-17 and (E,syn)-17, respectively, were not located. The diradical meso-38+60, the enantiomer of meso-38ꢀ60, is not shown.
analysis shows the gauche conformation dl-38 60 to be much
carbene 45 and rearrangement through transition states 42,
43exo, 43endo, or 44, or via [2+2] retrocycloaddition through
transition state 41, as had been observed for [1.1.1]propel-
ꢀ
more stable than the conformations dl-38
and dl-38180 by
+
60
ꢀ
1
9.5 and 10.5 kcalmol , respectively. In this case, formation
[3]
of dl-38 takes place through a transition state (1.2kcal
lanes. In fact, theoretical calculations predicted very high
activation energies for these isomerizations (see Figure 3 for
ꢀ
60
ꢀ
1
mol ) of lower energy than those leading to dl-38
2.6 kcalmol ) and dl-38 (2.4 kcalmol ), and fragmenta-
+
60
ꢀ
1
ꢀ1
[9]
(
details).
1
80
tion of this diradical from the more stable dl-38
confor-
60
ꢀ
mation gives (ꢁ)
ꢀ139.3 kcalmol ) and barrierless process. A barrierless
path for the conversion of dl-38 (but not from dl-38 ) to
A
C
T
E
N
(Z,anti)-17 in
a
highly exothermic
ꢀ
1
(
Conclusion
1
80
+60
(
ꢁ)
A
C
H
T
R
E
U
N
G
(E,syn)-17 was also found. Worthy of note is the stability
We have prepared the diiodo compound (ꢁ)-8 and studied
its deiodination by reaction with molten sodium and tBuLi.
The isolated and/or detected products from the deiodination
reactions, in particular the formation of the two stereoiso-
mers of 17, suggest the intermediate formation of the 1,3-de-
hydro derivative (ꢁ)-9, a bridged and highly distorted
[2.2.1]propellane with a calculated central CꢀC bond about
of the meso-381 and dl-38 conformations. In both cases,
80
ꢀ60
the CꢀC bonds connecting the radical centers and implied
in the fragmentation processes show an essentially all-anti
arrangement. These results are in striking contrast to the
conformational analysis of compound 18 (a product formally
derived from diradical 38 by hydrogenation), which shows
ꢀ
1
the anti conformation to be 0.3 kcalmol less stable than
0.15 Š larger than that of the parent propellane. The possi-
ble monomolecular rearrangements of 9 have been studied
by DFT calculations, which show that they are not kinetical-
ly favored processes compared with the dimerization of
(ꢁ)-9 to give diradicals 38. These diradicals can experience
a highly exothermic multiple fragmentation reaction through
barrierless processes to give two stereoisomers of 17, proba-
bly by fragmentation of the intermediate diradicals in the
[9]
the enantiomeric gauche ones. In light of these calcula-
(Z,anti)- and (E,anti)-17 to be the ste-
tions, we propose (ꢁ)
ACHTREUNG
reoisomers of 17 formed in the reaction of (ꢁ)-8 with
molten sodium or tBuLi.
As in the case of [2.2.1]propellane, in trapping experi-
ments with 1,3-diphenylisobenzofuran we did not find evi-
dence for the formation of rearranged products, such as
dienes 46 or 47 derived from 9, via retrocyclopropanation to
unexpectedly stable conformations dl-38
and meso-38180,
ꢀ
60
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A 2,5-Methano-Bridged [2.2.1]Propellane
FULL PAPER
ꢀ
1
Figure 3. Theoretical study of the unimolecular rearrangements of 9. Relative energies are given in kcalmol . Values correspond to corrected enthalpy
calculations using UB3LYP/6-31G(d) or UMP2/6-31G(d) (in parentheses). Path A: thermally forbidden [2+2] retrocycloaddition to 46. Path B: retro-
A
C
H
T
R
E
U
N
G
cyclopropanation to carbene 45 and possible rearrangements to 46 or 47.
ꢀ
1
(
3
2min), then heating at a rate of 8 8C min to 3008C, then isothermic at
008C. For chiral GC–MS analyses a 30-m (0.25 mm internal diameter)
which contain an all-anti arrangement of the carbon skele-
ton implied in the fragmentation processes, a situation not
found in the corresponding hydrocarbons.
chiral column (Supelco, Beta Dex 120, containing permethylated b-cyclo-
dextrin as the chiral stationary phase) was used; conditions: 10 psi, initial
temperature 508C (2min), then heating at a rate of 10 8C min to 2408C,
then isothermic at 2408C. In both cases, the electron impact (EI, 70 eV)
ꢀ
1
4
or chemical ionization (CI, CH ) techniques were used. Only significant
ions are given: those with higher relative abundance, except for the ions
Experimental Section
with higher m/z values. Accurate mass measurements were performed on
General methods: Melting points were determined in open capillary
a Micromass Autospec spectrometer. IR spectra were recorded on
tubes with an MFB 595010 M Gallenkamp melting point apparatus.
Perkin–Elmer Spectrum RXI equipment. Absorption values are given as
wavenumbers (cm ). Column chromatography was performed on silica
gel 60 AC.C (35–70 mesh, sodium dodecyl sulfate (SDS), ref. 2000027).
Thin-layer chromatography (TLC) was performed on aluminum-backed
sheets with silica gel 60 F254 (Merck, ref. 1.05554), and spots were visual-
Unless otherwise stated, NMR spectra were recorded at 258C in CDCl
in H (500 MHz) and C (75.4 MHz) spectrometers. Chemical shifts (d)
3
ꢀ1
1
13
are reported in parts per million in relation to internal tetramethylsilane
(
TMS). Assignments given for the NMR spectra are based on distortion-
less enhanced polarization transfer (DEPT), correlation spectroscopy
4
ized with UV light and a 1% aqueous solution of KMnO . NMR spec-
1
1
(
COSY) H/ H, heteronuclear correlation spectroscopy (HETCOR)
troscopy and GC–MS were performed at the “Serveis Científico-T›cnics”
of the University of Barcelona, and elemental analyses were carried out
at the Microanalysis Service of the IIQAB (CSIC, Barcelona, Spain). Ac-
curate mass measurements were performed on a Micromass Autospec
spectrometer at the Mass Spectrometry Laboratory of the University of
Santiago de Compostela (Spain).
1
13
H/ C (heteronuclear single quantum correlation (HSQC) and heteronu-
clear multiple bond correlation (HMBC) sequences for one-bond and
long-range H/ C heterocorrelations, respectively), and nuclear Over-
hauser effect spectroscopy (NOESY) experiments for selected com-
pounds. Diastereotopic methylene protons in tricyclo[3.3.0.0 ]octane de-
rivatives are referred to as H and H , as shown in the corresponding
1
13
3
,7
a
b
3
,7
[10]
structures. MS and GC–MS analyses were carried out on a Hewlett-Pack-
ard 5988A spectrometer, the sample being introduced directly or through
a gas chromatograph (Hewlett-Packard model 5890 Series II). For achiral
GC–MS analyses a 30-m column (HP-5, 5% diphenyl–95% dimethyl-
(ꢁ)-Tricyclo[3.3.0.0 ]octane-1,3-dicarboxylic acid [(ꢁ)-13]:
Small
pieces of lithium (3.59 g, 517 mmol) were added to a boiling solution of
3
,7
(ꢁ)-5,7-diiodotricyclo[3.3.0.0 ]octane-1,3-dicarboxylic acid ((ꢁ)-12,
3.86 g, 8.62mmol) in a mixture of tBuOH (49 mL, 516 mmol) and THF
(170 mL) kept under argon, and the mixture was heated under reflux for
A
C
H
T
R
E
U
N
G
polysiloxane) was used; conditions: 10 psi, initial temperature 358C
A
C
H
T
R
E
U
N
G
Chem. Eur. J. 2007, 13, 1522 – 1532
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1527

P. Camps, S. Vµzquez et al.
6
h. The mixture was allowed to cool to room temperature and poured
ture showed the presence of the following compounds (retention time
onto ice water (300 g). The aqueous solution was washed with diethyl
ether (3”100 mL), cooled with an ice-water bath, made acidic (pH 1–2)
with aqueous 10% HCl (175 mL), and extracted with AcOEt (5”
(r.t., min); relative a.r.): 14 (4.43; 1.2%), stereoisomers of 15 (11.44 and
11.93; 4.7 and 5.2%), (ꢁ)-16 (14.29; 33.5%), (E,anti)- and (ꢁ)
A
C
H
T
R
E
U
N
G
(Z,anti)-17
(15.17 and 15.29; 1.5 and 2.4%), 18 (16.48; 32.3%), stereoisomers of 19
(23.35; 13.7%), (ꢁ)-20 (25.12; 5.5%). GC–MS analysis of the above fil-
trate through Celite showed a much higher content of compound 14
(about 13%). The identity of the stereoisomers of 15 was established by
comparison of their mass spectra with those of the described com-
2
00 mL). The combined organic extracts were dried (anhydrous Na
and concentrated under reduced pressure to give a light yellow residue
1.72g), which was washed with a small amount of cold diethyl ether to
give (ꢁ)-13 (1.36 g, 80% yield) as a white solid. M.p. 214–2168C (diethyl
ether), reported 215–215.58C (toluene/ethanol); H NMR (CD OD):
d=1.67 (brs, 2H; 6-H ), 1.75 (dt, J=9.5 Hz, J’=2.0 Hz, 2H; 4(8)-H ),
.91 (dm, J=9.5 Hz, 2H; 4(8)-H ), 2.00 (t, J=2.0 Hz, 2H; 2-H ), 2.71 (m,
H; 5(7)-H), 4.87 ppm (brs; 2COOH); C NMR (CD OD): d=44.0
, C6), 51.5 (CH , C4(8)), 54.2(C, C1(3)), 54.8
, C2), 178.1 ppm (C, 1(3)-COOH); IR (KBr): n˜ =3500–2250 (max.
2 4
SO )
(
[
10]
1
[12]
3
pounds. The identity of compound 14 was established by comparison
2
a
of its mass spectrum with that of an authentic sample prepared by a
[
11]
1
2
b
2
modification of a known procedure, as described later on. All of the
remaining compounds were isolated as follows. The above residue
(1.41 g) was submitted to flash column chromatography on silica gel
(210 g, 5 cm internal diameter of the column, hexane/diethyl ether) to
obtain, in order of elution: a white solid mixture of 18 and (ꢁ)-20
1
3
3
(
(
CH, C5(7)), 47.4 (CH
CH
2
2
2
at 2996, 2950, 2903, 2706, 2606), 1705, 1482, 1416, 1317, 1286, 1259, 1218,
ꢀ
1
+
1
1
1
(
1
202, 1128, 1085, 893, 746 cm ; MS (EI): m/z (%): 178 ([MꢀH
2
O]C , 9),
(
(
263 mg; hexane); a white waxy mixture of (E,anti)- and (ꢁ)
A
C
H
T
R
E
U
N
G
(Z,anti)-17
+
+
50 ([MꢀH
2
OꢀCO]C , 53), 133 ([M+Hꢀ2H
2
OꢀCO] , 40), 132( 12 ),
22 mg, 3.5% yield; hexane); and a yellow oily mixture of (ꢁ)-16 and
+
11 (69), 105 ([M+Hꢀ2H
2
Oꢀ2CO] , 100), 104 (21), 93 (56), 91 (36), 79
stereoisomers of 19 (455 mg; hexane/diethyl ether from 9:1 to 8:2). The
above mixture of 18 and (ꢁ)-20 was sublimed, first at 60–708C/30 Torr to
give pure 18 (175 mg, 27% yield) as a white solid, and then at 115–
+
73), 77 (60), 67 (77), 65 (82); MS (CI, CH
4
): m/z (%): 197 ([M+H] ,
OꢀCO] , 100), 133 ([M+
+
+
8), 179 ([M+HꢀH
2
O] , 45), 151 ([M+HꢀH
2
+
+
Hꢀ2H
(
1
9
2
OꢀCO] , 25), 105 ([M+Hꢀ2H
2
Oꢀ2CO] , 14).
1
258C/30 Torr to give (ꢁ)-20 (12mg, 2% yield) as a white solid. The
3
,7
ꢁ)-1,3-Diiodotricyclo[3.3.0.0 ]octane [(ꢁ)-8]: A mixture of diacid (ꢁ)-
above mixture of (ꢁ)-16 and stereoisomeric mixture 19 was fractionally
distilled using rotary microdistillation equipment, first at 55–658C/1 Torr
to give (ꢁ)-16 (233 mg, 20% yield) and then at 150–1608C/1 Torr to give
3 (1.78 g, 9.07 mmol), iodine (5.06 g, 19.9 mmol), and IBDA (6.56 g,
8% content, 19.9 mmol) in anhydrous acetonitrile (185 mL) was irradi-
ated under reflux with two 100-W tungsten lamps in an argon atmos-
phere for 4 h. More iodine (5.06 g, 19.9 mmol) and IBDA (6.56 g,
the stereoisomeric mixture 19 (96 mg, 11% yield), both as colorless oils.
1
(
ꢁ)-16: H NMR: d=1.30–1.42(complex absorption, 8H; 2- H
2
, 4-H
), 2.28 (quint, J=2.5 Hz, 1H; 5-H), 2.30 (complex absorp-
tion, 2H; 3-H and 7-H), 3.44 (tm, J=11.0 Hz, 1H; 3-Hax dioxane), 3.60
dt, J=3.0 Hz, J’=11.0 Hz, 1H; 6-Hax dioxane), 3.70 (dd, J=11.5 Hz, J’=
.5 Hz, 1H; 6-Heq dioxane), 3.76 (dt, J=2.5 Hz, J’=11.5 Hz, 1H; 5-Hax
2
, 6-
1
2
9.9 mmol) were added and irradiation under reflux was continued for
0 h more. The resulting solution was distilled under atmospheric pres-
2 2
H , and 8-H
sure through a Vigreux column (10 cm). The residue was taken up in di-
ethyl ether (175 mL) and the organic solution was washed with aqueous
(
2
Na
3”165 mL), and brine (2”165 mL). The organic phase was dried (anhy-
drous Na SO ) and the solvent was distilled under atmospheric pressure
2 2 3 3
S O solution (10%, 3”165 mL), saturated aqueous NaHCO solution
dioxane), 3.77–3.83 ppm (complex absorption, 3H, 2-Hax, 3-Heq and 5-Heq
(
13
dioxane); C NMR: d=36.4 (CH) and 36.5 (CH) (C3 and C7), 39.2(CH,
2
4
C5), 46.8 (CH
C2and C8), 50.4 (C, C1), 66.6 (CH
ane), 69.4 (CH , C3 dioxane), 77.3 ppm (CH, C2dioxane); IR (NaCl):
n˜ =2962, 2890, 2851, 1481, 1448, 1350, 1270, 1121, 1103, 899, 880 cm
2
) and 46.9 (CH
2
) (C4 and C6), 47.8 (CH
2
) and 48.3 (CH
2
)
through a Vigreux column (10 cm). Most of the iodobenzene formed in
the reaction was distilled using rotary microdistillation equipment at 70–
(
2
, C6 dioxane), 67.3 (CH
2
, C5 diox-
2
8
08C/30 Torr. The light yellow residue (6.60 g) was separated into two
ꢀ1
;
fractions (3.35 and 3.25 g), which were independently submitted to
column chromatography (silica gel (600 g), n-pentane]. The solvent of
the chromatographic fractions was distilled off at atmospheric pressure
through a Vigreux column (10 cm). After the product isolated from the
two chromatographic columns was combined, diiodide (ꢁ)-8 was ob-
tained as a light yellow liquid (2.61 g), which was further purified by dis-
tillation on rotary microdistillation equipment at 100–1108C/30 Torr to
+
GC–MS (EI): m/z (%): 194 (MC , 15), 165 (9), 153 (9), 151 (13), 126 (12),
+
1
(
1
17 (24), 113 (21), 107 ([MꢀC
4
H
7
O
2
] , 19), 91 (41), 87 (35), 86 (21), 80
): m/z (%):
] , 22), 135 (100), 133
21), 79 (59), 77 (26), 73 (47), 67 (100), 66 (27); MS (CI, CH
4
+
+
+
95 ([M+H] , 6), 194 (MC , 9), 193 ([M+HꢀH
2
+
(
33), 107 ([MꢀC
4
H
7
+
O
2
] , 14), 73 (24); accurate mass measurement calcd
for [C12
H
18
O
2
+H] : 195.1385; found: 195.1382.
(Z,anti)-17: IR (KBr): n˜ =3071, 2968, 2938, 2900, 2888,
1
A
H
R
U
ACHTREUNG
give pure (ꢁ)-8 (2.48 g, 76% yield) as a colorless liquid. H NMR: d=
ꢀ
1
2
1
4
2
2
6
1
2
.64 (quint, J=2.0 Hz, 2H; 6-H ), 1.77 (dt, J=9.5 Hz, J’=2.0 Hz, 2H;
+
calcd for [C16
H
20 +H] : 213.1643; found: 213.1641. NMR data (from the
spectra of the mixture) of the main diastereomer (E,anti)-17: H NMR:
(8)-H
.0 Hz, 2H; 2-H
4.4 (C, C1(3)), 47.1 (CH
9.1 ppm (CH , C2); IR (NaCl): n˜ =2992, 2940, 2892, 1477, 1282, 1252,
a b
), 2.17 (dq, J=9.5 Hz, J’=2.0 Hz, 2H; 4(8)-H ), 2.31 (t, J=
1
1
3
2
), 2.40 ppm (q, J=2.0 Hz, 2H; 5(7)-H); C NMR: d=
, C6), 50.6 (CH, C5(7)), 58.9 (CH , C4(8)),
d=1.43 (s, 4H; 7(7’)-H
2
], 1.93 (dd, J=15.5 Hz, J’=2.0 Hz, 2H; 3(3’)-
2
2
H
endo), 1.98 (dd, J=14.5 Hz, J’=2.0 Hz, 2H; 6(6’)-Hendo), 2.20–2.24 (com-
2
ꢀ
1
plex absorption, 4H; 3(3’)-Hexo and 6(6’)-Hexo), 2.74 (m, 2H; 1(1’)-H),
2.80 (m, 2H; 4(4’)-H), 4.63 (m, 2H, =CHtrans), 4.90 ppm (m, 2H, =CHcis);
209, 1197, 1132, 1067, 1000, 944, 923, 809 cm ; MS (EI): m/z (%): 360
+
+
+
(
(
M
C
, 1), 233 ([MꢀI] , 28), 106 ([Mꢀ2I]
C
, 100), 105 (49), 91 (43), 79
: C 26.69,
1
3
C NMR (100.6 MHz): d=37.2(CH
2
, C6(6’)), 37.5 (CH
2
, C3(3’)), 40.2
, =CH ),
8 10 2
29), 78 (36), 77 (22); elemental analysis (%) calcd for C H I
(
CH , C7(7’)), 42.1 (CH, C1(1’)), 46.0 (CH, C4(4’)), 102.8 (CH
2
2
2
H 2.80, I 70.51; found: C 26.61, H 2.62, I 70.58.
3
,7
131.3 (C, C2(2’)), 154.9 ppm (C, C5(5’)); GC–MS (EI): m/z (%): 212
Reaction of (ꢁ)-1,3-diiodotricyclo[3.3.0.0 ]octane [(ꢁ)-8] with molten
sodium in boiling 1,4-dioxane: isolation of 2-(tricyclo[3.3.0.0 ]oct-1-yl)-
(Z,anti)- and
(Z,anti)- and
(tricyclo[3.3.0.0 ]oct-1-yl) (18), stereoisomeric mixture of
+
3
,7
(MC , 32), 197 (11), 169 (14), 155 (15), 132 (23), 131 (22), 129 (28), 117
(
35), 115 (25), 105 (48), 92 (31), 91 (100), 80 (44), 79 (93), 77 (69); NMR
1
,4-dioxane [(ꢁ)-16], stereoisomeric mixture of (ꢁ)
ACHTREUNG
data (from the spectra of the mixture) of the minor diastereomer (ꢁ)-
(
(
E,anti)-bi(5-methylenebicyclo
E,anti)-17], bi
A
H
R
N
ACHTREUNG
1
3
,7
A
H
R
U
G
2
),
ACHTREUNG
3
,7
3,7
1.72(dm, J=13.5 Hz, 2H; 6(6’)-Hendo), 1.94–1.98 (m, 2H; 3(3’)-Hendo),
2.13 (dm, J=13.5 Hz, 2H; 6(6’)-Hexo), 2.23–2.28 (m, 2H; 3(3’)-Hexo), 2.80
(m, 2H; 4(4’)-H), 2.93 (m, 2H; 1(1’)-H), 4.63 (m, 2H, =CHtrans), 4.90 ppm
2
-[3-(tricyclo[3.3.0.0 ]oct-1-yl)-tricyclo[3.3.0.0 ]oct-1-yl]-1,4-dioxane (19),
3
,7
3,7
and 1,3-bis
A
C
H
T
R
E
U
N
G
(tricyclo[3.3.0.0 ]oct-1-yl)-tricyclo[3.3.0.0 ]octane, [(ꢁ)-20];
3,7
detection of tricyclo[3.3.0.0 ]octane (14) and stereoisomeric mixture of
1
3
(
(
1
m, 2H, =CHcis); C NMR (100.6 MHz): d=37.1 (CH
CH , C3(3’)), 40.7 (CH , C7(7’)), 42.5 (CH, C1(1’)), 46.0 (CH, C4(4’)),
02.7 (CH , =CH ), 131.7 (C, C2(2’)), 154.9 ppm (C, C5(5’)); GC–MS
EI): m/z (%): 212 (M
2
, C6(6’)), 38.3
2
6
,2’-bi(1,4-dioxan-2-yl) (15):
.0 mmol) in anhydrous 1,4-dioxane (5 mL) was added at once to molten
A
solution of diiodide (ꢁ)-8 (2.16 g,
2
2
sodium (1.38 g, 60 mmol) in boiling 1,4-dioxane (20 mL) and the mixture
was heated under reflux for 4 h under an argon atmosphere. The cold
mixture was filtered through Celite and the solid was washed with diethyl
ether (3”60 mL). The combined filtrate and washings were concentrated
at atmospheric pressure using a Vigreux column (10 cm) to give a residue
that still contained residual solvent (1.41 g). GC–MS analysis of this mix-
2
2
+
(
(
(
C
, 17), 141 (13), 133 (16), 132 (23), 131 (15), 129
24), 117 (34), 115 (24), 105 (45), 92 (33), 91 (100), 80 (43), 79 (91), 77
71).
1
18: M.p. 93.7–95.18C (sublimed); H NMR: d=1.26 (m, 4H; 2
A
C
H
T
R
E
U
N
G
(2’,8,8’)-
H
a
), 1.36–1.38 (complex absorption, 8H; 2
A
H
R
U
G
b
and 4
A
H
R
U
G
b
1528
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 1522 – 1532

A 2,5-Methano-Bridged [2.2.1]Propellane
FULL PAPER
1
2
C3
.43 (m, 4H; 4
.29 ppm (complex absorption, 4H; 3
(3’,7,7’)), 40.2(CH, C5(5 ’)), 47.3 (CH
(2’,8,8’)), 51.5 ppm (C, C1(1’)); IR (KBr): n˜ =2957, 2934, 2885, 1477,
A
C
H
T
R
E
U
N
G
(4’,6,6’)-H
a
), 2.11 (quint, J=2.5 Hz, 2H; 5(5’)-H), 2.27–
dried (anhydrous Na
2
SO
4
) and concentrated at atmospheric pressure
1
3
A
H
R
U
G
using a Vigreux column (10 cm) to give a yellowish residue (363 mg).
GC–MS analysis of this mixture showed the presence of the following
more significant compounds ((r.t., min); relative a.r.): 21 (9.19; 7.2%),
(ꢁ)-22 (12.8; 24.5%), (ꢁ)
A
C
H
T
R
E
U
N
G
2
A
H
R
U
G
2
ACHTREUNG
ꢀ
1
+
1
1
7
2
293, 1269 cm ; GC–MS (EI): m/z (%): 214 (M
C
, 1), 199 (3), 185 (13),
A
H
R
U
G
71 (13), 143 (16), 131 (20), 129 (25), 105 (28), 91 (63), 80 (22), 79 (50),
and 0.6%), 18 (16.43; 40.6%), (ꢁ)-20 (25.12; 14.3%), and stereoisomeric
mixture 23 (32.81; 2.0%). GC–MS analysis of the combined organic ex-
tracts, before evaporation of the solvent, showed the presence of a small
amount of 14 (0.4% relative area). This compound, together with minor
amounts of compounds 21, (ꢁ)-22, 18, and (ꢁ)-20, was shown to be pres-
ent (GC–MS) in the corresponding distillate. The above residue (363 mg)
was submitted to flash column chromatography on silica gel (80 g, 5 cm
internal diameter of the column, hexane/diethyl ether) to obtain in order
of elution: a white solid mixture containing hydrocarbon compounds
+
+
7 (29), 67 (100); MS (CI, CH
4
): m/z (%): 215 ([M+H] , 32), 214 (M
C
,
+
5), 213 ([M+HꢀH
2
] , 100), 185 (37), 135 (48), 133 (42), 121 (35), 107
(
31), 93 (58), 81 (63), 79 (56), 67 (68); accurate mass measurement calcd
+
for [C16
H
22+H] : 215.1800; found: 215.1799.
1
Stereoisomeric mixture 19: H NMR: d=1.23–1.53 (complex absorption,
1
1
H), 3.45 (ddd, J=12.0 Hz, J’=11.0 Hz, J’’=1.5 Hz, 1H; 3-Hax dioxane),
3
2
6H; methylenic protons), 2.09 (quint, J=2.5 Hz, 1H; 5’-H), 2.15 (m,
H; 7-H), 2.28 (complex absorption, 2H; 3’-H and 7’-H), 2.30 (m, 1H; 5-
(
171 mg; hexane) and a yellowish oil containing (ꢁ)-22 plus other minor
.60 (complex absorption, 1H; 6-Hax dioxane), 3.70 (dd, J=11.5 Hz, J’=
.5 Hz, 1H; 6-Heq dioxane), 3.73–3.83 ppm (complex absorption, 4H; 2-
ax, 3-Heq, 5-Hax (3.76 ppm, dt, J=2.5 Hz, J’=11.5 Hz) and 5-Heq diox-
products (102mg) (hexane/diethyl ether 9:1). The hydrocarbon fraction
was submitted to fractional sublimation, first at 60–708C/30 Torr to give
pure 18 (66 mg, 20% yield) as a white solid, then at 90–1008C/30 Torr to
give a mixture of 18, (ꢁ)-20, plus other minor compounds as a white
waxy product (26 mg), then at 115–1258C/30 Torr to give pure (ꢁ)-20,
H
ane); no different signals were observed for both diastereomers;
1
3
C NMR: d=36.8 (4CH, C3’ and C7’, both diastereomers), 40.06 (2CH,
C5’, both diastereomers), 40.12(CH) and 40.3 (CH) (C5), 40.9 ( 2C H,
C7, both diastereomers), 47.1 (CH ), 47.2(CH ), 47.3 (4 CH ), 48.1
), 49.14 (CH ), 49.18 (2CH ), 49.23
), (methylene C atoms, both diastereo-
(
20 mg, 6% yield) as a white solid, and finally at 170–1808C/30 Torr to
2
2
2
give the stereoisomeric mixture 23 (9 mg, 3% yield) as a white solid. The
above second chromatographic fraction (102mg) was distilled at 50–
(
CH
2
), 48.3 (CH
), 50.1 (CH
2
), 49.07 (CH
), 50.4 (CH
2
2
2
(
2CH
2
2
2
6
08C/1 Torr to give pure (ꢁ)-22 (40 mg, 7% yield) as a colorless oil.
mers), 51.2 (2C), 51.5 (C), 51.6 (C), 52.26 (C) and 52.29 (C) (C1, C1’ and
C3, both diastereomers), 66.6 (2CH , C6 dioxane, both diastereomers),
7.3 (2CH , C5 dioxane, both diastereomers), 69.3 (2CH , C3 dioxane,
1
2
(ꢁ)-22: H NMR: d=1.26–1.46 (complex absorption, 8H; tricyclic meth-
ylenic protons), 1.58–1.65 (m, 1H; 3-Htrans tetrahydrofuryl), 1.85–1.96
(complex absorption, 3H; 3-Hcis, 4-Hcis, 4-Htrans tetrahydrofuryl) 2.18
(quint, J=2.5 Hz, 1H; 5-H), 2.30 (complex absorption, 2H; 3-H, 7-H),
3.73–3.77 (m, 1H) and 3.85–3.90 (m, 1H) (5-Hcis, 5-Htrans tetrahydrofuryl),
6
2
2
both diastereomers), 77.49 (CH) and 77.50 ppm (CH) (C2); IR (NaCl):
n˜ =2959, 2936, 2886, 2851, 1479, 1448, 1350, 1292, 1268, 1121, 1101, 909,
8
ꢀ
1
+
80 cm ; GC–MS (EI): m/z (%): 259 ([MꢀC
3 5
H ] , 6), 225 (4), 213
+
(
(
(
2
[MꢀC
4
H
7
O
2
] , 24), 171 (14), 143 (16), 131 (35), 129 (29), 119 (15), 117
4.09 ppm (dd, J=8.5 Hz, J’=6.5 Hz, 1H; 2-H tetrahydrofuryl);
+
13
24), 107 (17), 105 (31), 93 (28), 91 (76), 87 ([C
4
H
7
O
2
] , 33), 81 (26), 79
2 2
C NMR: d=26.3 (CH , C4 tetrahydrofuryl), 28.8 (CH , C3 tetrahydro-
+
83), 77 (32), 73 (27), 67 (100); MS (CI, CH
4
): m/z (%): 301 ([M+H] ,
] , 41), 259 ([MꢀC
furyl), 36.7 (CH) and 36.8 (CH) (C3 and C7), 39.2(CH, C5), 47.18 (CH
and 47.24 (CH ) (C4 and C6), 48.5 (CH ) and 48.7 (CH ) (C2and C8),
53.0 (C, C1), 68.2(CH , C5 tetrahydrofuryl), 80.9 ppm (CH, C2tetrahy-
drofuryl); IR (NaCl): n˜ =2963, 2888, 1480, 1315, 1283, 1066, 1041 cm
2
)
+
+
+
1), 300 (MC , 27), 299 ([M+HꢀH
H
] , 15), 242
2
3
5
2
2
2
+
(
(
(
20), 241 (93), 240 (24), 239 (100), 237 (24), 213 ([MꢀC
4
H
7
O
2
] , 72), 171
2
ꢀ1
22), 159 (25), 135 (23), 131 (25), 121 (22), 107 (22), 105 (27), 93 (20), 91
;
+
+
22), 87 ([C
4
H
7
O
2
] , 21), 81 (28), 78 (24), 73 (83), 67 (21); accurate mass
GC–MS (EI): m/z (%): 178 (M , 6), 149 (24), 137 (21), 135 (35), 119
(21), 110 (24), 97 (71), 93 (20), 80 (21), 79 (45), 77 (23), 71 (100), 67 (44),
55 (45); accurate mass measurement (ES+) calcd for [C H O+H] :
C
+
measurement calcd for [C20
H
28
O
2+H] : 301.2168; found: 301.2163.
+
1
(
ꢁ)-20: M.p. 156–1588C (sublimed); H NMR: d=1.24–1.27 (complex
12 18
1
79.1430; found: 179.1437.
Stereoisomeric mixture of meso- and (ꢁ)-23 (ratio close to 1:1 by
C NMR spectroscopy): M.p. 202–2048C (sublimed); H NMR (the indi-
absorption, 4H; 2’
H; 2-H and 4(8)-H
(8’’)-H , 4’(4’’)-H and 6’
(4’’)-H and 6’(6’’)-H ), 1.46–1.50 (complex absorption, 4H; 6-H
), 2.12 (quint, J=2.5 Hz, 2H; 5’(5’’)-H), 2.13 (m, 2H; 5(7)-H),
.28 ppm (complex absorption, 4H; 3’(3’’)-H and 7’
(3’’) and C7’(7’’)), 40.1 (CH, C5’(5’’)), 41.2(CH, C5(7)),
(4’’) and C6’(6’’)), 47.6 (CH , C6), 49.2(CH ) and 49.3
(2’’) and C8’(8’’)), 49.5 (CH , C4(8)), 51.7 (CH , C2), 51.9 (C)
and 52.4 ppm (C) (C1(3) and C1’(1’’)); IR (KBr): n˜ =2966, 2933, 2884,
A
C
H
T
R
E
U
N
G
(2’’)-H
), 1.35–1.39 (complex absorption, 8H; 2’
(6’’)-H ), 1.41–1.45 (complex absorption, 4H; 4’-
and
a
and 8’
A
H
R
U
(8’’)-H
a
), 1.30–1.33 (complex absorption,
4
2
a
A
H
R
U
G
b
1
3
1
A
C
H
T
R
E
U
N
G
b
A
C
H
T
R
E
U
N
G
b
A
C
H
T
R
E
U
N
G
b
A
C
H
T
R
E
U
N
G
a
A
C
H
T
R
E
U
N
G
a
2
cated number of H atoms corresponds to both stereoisomers, while the
shown H atoms belong to only half of each compound): d=1.24–1.28
4
2
(8)-H
b
A
H
R
U
G
1
3
A
H
E
N
A
H
R
U
G
(complex absorption, 8H; 2’-H
16H; 2-H , 2 -H, 4-H , 8-H ), 1.34–1.39 (complex absorption, 16H; 2’-H
4’-H , 6’-H , and 8’-H ), 1.41–1.45 (complex absorption, 8H; 4’-H and 6’-
), 1.45–1.50 (complex absorption, 16H; 4-H , 6-H , 6-H , 8-H ), 2.12
a a
, 8’-H ), 1.30–1.34 (complex absorption,
d=36.8 (CH, C3’
7.3 (CH , C4’
CH ) (C2’
A
C
H
T
R
E
U
N
G
A
H
R
N
A
H
R
U
G
a
b
a
b
b
,
4
(
2
A
C
H
T
R
E
U
N
G
A
T
E
G
2
2
b
b
b
a
2
A
C
H
T
R
E
U
N
G
A
C
H
T
R
E
U
N
G
2
2
H
a
b
a
b
a
A
T
E
N
(quint, J=2.5 Hz, 4H; 5’-H), 2.12–2.16 (complex absorption, 8H; 5-H, 7-
H), 2.26–2.30 ppm (complex absorption, 8H; 3’-H, 7’-H); C NMR
(100.6 MHz; the indicated number of C atoms corresponds to both ste-
reoisomers, while the shown C atoms belong to only half of each com-
pound): d=36.8 (8CH, C3’, C7’), 40.1 (4CH, C5’), 41.10 (2CH), 41.11
ꢀ
1
+
13
1
2
477, 1291 cm ; GC–MS (EI): m/z (%): 320 (M
C
, <1), 305 (1), 279 (4),
+
77 (5), 213 ([MꢀC
8
H
11) , 5), 211 (5), 185 (6), 171 (14), 143 (18), 131
+
(
8
,
24), 129 (34), 117 (22), 105 ([MꢀC
8
H11ꢀC
8
H12) , 31), 93 (23), 91 (68),
+
1 (25), 79 (75), 77 (33), 67 (100); MS (CI, CH
4
): m/z (%): 321 ([M+H]
] , 33), 241 (15), 239 (18), 227 (16),
+
+
11), 320 (MC , 11), 319 ([M+HꢀH
(2CH) and 41.3 (4CH) (C5, C7), 47.3 (8CH
49.2(4CH ) and 49.3 (4CH ) (C2’, C8’), 49.37 (2CH
49.6 (4CH ) (C4, C8), 51.5 (2CH ) and 51.6 (2CH
2
, C4’, C6’), 47.6 (4CH
), 49.45 (2CH
) (C2), 51.9 (4C),
, C6),
2
2
2
2
13 (29), 199 (22), 187 (37), 185 (35), 173 (30), 171 (30), 149 (28), 147
2
2
2
2
) and
+
(
9
31), 135 (42), 121 (37), 109 (33), 107 (57), 105 ([MꢀC
8
H
11ꢀC
8
H
12] , 37),
2
2
5 (41), 93 (64), 91 (36), 81 (100), 79 (79), 67 (94); accurate mass mea-
52.40 (2C), 52.41 (2C) and 52.8 ppm (4C) (C1, C1’, C3); IR (KBr): n˜ =
+
ꢀ1
surement calcd for [C24
Reaction of (ꢁ)-8 with tBuLi in anhydrous THF: isolation of bi-
(tricyclo[3.3.0.0 ]oct-1-yl) (18), (ꢁ)-2-(tricyclo[3.3.0.0 ]oct-1-yl)-tetra-
hydrofuran [(ꢁ)-22], trimer (ꢁ)-20, and stereoisomeric mixture of bi[3-
(tricyclo[3.3.0.0 ]oct-1-yl)-tricyclo[3.3.0.0 ]oct-1-yl] (23); detection of
(Z,anti)- and (E,anti)-17, and 21: A solution of tBuLi
10 mL, 1.5m in pentane, 15 mmol) was added dropwise to a cold
ꢀ788C), magnetically stirred solution of diiodide (ꢁ)-8 (1.08 g,
.0 mmol) in anhydrous THF (10 mL) under an argon atmosphere, and
H
32]C : 320.2504; found: 320.2510.
2956, 2933, 2883, 1477, 1292 cm
;
GC–MS (EI): m/z (%): 385
+
+
+
(
[MꢀC
3
H
5
] , 3), 383 (3), 319 ([MꢀC
8
H
11] , 3), 213 ([MꢀC16
H
21] , 22),
3
,7
3,7
171 (32), 157 (23), 145 (22), 143 (35), 131 (53), 129 (52), 119 (27), 117
ACHTREUNG
(
36), 107 (31), 105 (52), 93 (41), 91 (90), 81 (41), 79 (99), 77 (25), 67
AHCTUNG-
+
+
3
,7
3,7
(100); MS (CI, CH ): m/z (%): 427 ([M+H] , 2), 426 (MC , 2), 425
T
R
E
U
N
G
4
+
+
+
(
(
[M+HꢀH
2
] , 4), 319 ([MꢀC
8
H
11] , 2), 213 ([MꢀC16
H
21] , 12), 187
compounds 14, (ꢁ)
ACHTREUNG
12), 185 (14), 173 (12), 171 (13), 149 (17), 135 (17), 131 (21), 129 (20),
(
(
3
1
07 (34), 105 (33), 93 (35), 91 (50), 81 (59), 79 (94), 67 (100); accurate
+
mass measurement calcd for [C32
H
42
]
C
: 426.3282; found: 426.3287.
+
the mixture was allowed to warm to room temperature. Methanol (5 mL)
and water (10 mL) were successively added and the mixture was extract-
ed with diethyl ether (3”20 mL). The combined organic phases were
21: GC–MS (EI): m/z (%): 149 ([MꢀCH
3
] , 26), 123 (19), 122 (31), 121
+
(17), 108 (19), 107 ([MꢀC
4
H
9
] , 100), 93 (35), 91 (25), 81 (26), 80 (35),
79 (53), 67 (24), 57 (60).
Chem. Eur. J. 2007, 13, 1522 – 1532
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1529

P. Camps, S. Vµzquez et al.
3
,7
[13]
Tricyclo[3.3.0.0 ]octane (14): Lithium (60 mg, 8.4 mmol) was added in
small pieces to a solution of (ꢁ)-8 (100 mg, 0.28 mmol) in a mixture of
tBuOH (0.8 mL, 8.4 mmol) and anhydrous THF (6 mL), heated under
reflux and magnetically stirred, and heating under reflux was continued
for 6 h with vigorous stirring. The mixture was allowed to cool to room
temperature and was poured onto ice water (10 g). The organic phase
was separated and analyzed by GC–MS, and was shown to contain
mainly compounds 14, 18, and (ꢁ)-22 (relative areas by GC–MS: 82.4,
Reaction of (ꢁ)-8 with the radical anion from 4,4’-di-tert-butylbiphenyl
and lithium in anhydrous THF: Small pieces of lithium (6 mg,
0.83 mmol) were added to a solution of 4,4’-di-tert-butylbiphenyl (25,
370 mg, 1.39 mmol) in anhydrous THF (4 mL) placed in a Schlenk tube
at room temperature under an argon atmosphere, and the mixture was
ultrasound irradiated in a cold (08C) bath until consumption of the metal
(1 h) with formation of a dark green solution. Then, a cold (08C) solution
of (ꢁ)-8 (51 mg, 0.14 mmol) in anhydrous THF (1.5 mL) was added
dropwise. The solution became red and the color remained for 1 h. Then,
6
.7, and 5.9%, respectively). MS of compound 14: m/z (%): 109 ([M+
+ + +
H] , 46), 108 (M
C
, 5), 107 ([M+HꢀH
(Z,anti)-, (E,anti)-, (ꢁ)
[2.2.1]hept-2-ylidene)
[(ꢁ)
(E,syn)- and (Z,syn)-17]: HCl (1n, 1.8 mL) was added to a
2
] , 42), 79 (64), 67 (100).
(E,syn)- and
(Z,anti)-,
the solution was cooled to ꢀ788C, excess CO
mixture was allowed to warm to room temperature. A saturated aqueous
solution of NaHCO (5 mL) was added and the mixture was extracted
2
(g) was bubbled, and the
Stereoisomeric mixture of (ꢁ)
A
H
R
N
ACHTREUNG
3
(
(
Z,syn)-bi(5-methylenebicyclo
A
H
R
U
G
ACHTREUNG
with diethyl ether (2”10 mL). The combined organic phases were ana-
lyzed by GC–MS, which showed the presence of 25 as the main compo-
nent (87.6% a.r.) and traces of other components, such as the following
ones (% a.r.), in order of elution: 26 (0.1), (ꢁ)-22 (0.6), 18 (1.4). The al-
kaline aqueous phase was acidified to pH 1–2with 5N HCl (1.2mL) at
E,anti)-, (ꢁ)
ACHTREUNG
cold (08C) solution of acetal (ꢁ)-24 (298 mg, 1.79 mmol), prepared as de-
scribed, in THF (31 mL), and the mixture was allowed to warm to
room temperature and was stirred at this temperature for 45 h. Saturated
aqueous NaHCO solution (15 mL) was added to give pH 8. The organic
phase was separated and the aqueous phase was extracted with diethyl
ether (3”50 mL). The combined organic phases were dried (anhydrous
Na SO ) and the solvent was distilled at atmospheric pressure through a
2 4
Vigreux column (10 cm) to give a yellowish liquid residue (279 mg) con-
taining mainly the expected ketone.
[
14]
3
0
8C and was extracted with AcOEt (5”15 mL). The combined organic
phases were dried (anhydrous Na SO ) and concentrated under reduced
pressure to give a residue (5 mg) constituted mainly of 25.
2
4
3
,7
1
-Iodotricyclo[3.3.0.0 ]octane (26): Solid NaOH (67 mg) and 10% Pd
on charcoal (44 mg) were added to
solution of (ꢁ)-8 (199 mg,
.55 mmol) in methanol (6 mL), and the mixture was placed in a hydro-
a
0
Pyridine (0.9 mL) and powdered Zn (1.65 g, 25.2 mmol) were added to a
magnetically stirred mixture of TiCl
,4-dioxane (12mL), kept under argon, and the mixture was heated
under reflux for 1 h. Then, a solution of the above ketone (279 mg) in an-
hydrous 1,4-dioxane (8 mL) was added dropwise and the mixture was
heated under reflux for 15 h more. The mixture was allowed to cool to
room temperature and was treated with a 10% aqueous solution of
gen atmosphere (1 atm) and magnetically stirred at room temperature
for 3 h. GC control showed total consumption of the starting compound
and the presence of 26 and 14 with an area ratio of 93:7. The mixture
was filtered through a pad of Celite and the solid was washed with meth-
anol (2mL). Water (5 mL) was added to the combined filtrate and wash-
4
(1.4 mL, 12.8 mmol) in anhydrous
1
ings and the mixture was extracted with CH
bined organic phases were dried (anhydrous Na
under atmospheric pressure using a Vigreux column (10 cm) to give 26
107 mg, 83% yield) as a colorless oil. The analytical sample was ob-
2
Cl
2
(5”5 mL). The com-
2
SO ) and concentrated
4
K
2
CO
was diluted with CH
the solid was washed with CH
combined filtrate and washings was separated, washed with 1n HCl (3”
0 mL) and brine (2”10 mL), dried (anhydrous Na SO ), and concentrat-
3
(40 mL) until a basic pH was achieved. The deep blue mixture
Cl (30 mL), filtered through a pad of Celite, and
Cl (3”10 mL). The organic phase of the
2
2
(
1
2
2
tained by distillation at 60–708C/30 Torr; H NMR: d=1.32(dt, J=
9
.0 Hz, J’=2.5 Hz, 2H; 4(6)-H
b a
), 1.63 (m, 2H; 4(6)-H ), 1.81 (m, 2H;
1
2
4
2
(8)H ), 1.92(m, 2H ; 2( 8)H ), 2.10 (m, 2H; 3(7)-H), 2.62 ppm (quint,
a
b
1
3
ed under reduced pressure to give a yellowish oil (107 mg). This product
was submitted to column chromatography (15 g, 2cm internal diameter
of the column, hexane) to give a stereoisomeric mixture 17 in the approx-
J=2.5 Hz, 1H; 5-H); C NMR: d=30.4 (C, C1), 36.5 (CH, C3(7)), 47.0
(CH , C4(6)), 49.7 (CH, C5), 59.2ppm (CH , C2(8)); IR (NaCl): n˜ =
2972, 2940, 2892, 1479, 1288, 946 cm ; MS (EI): m/z (%): 234 (MC , 15),
2
2
ꢀ
1
+
1
+
imate ratio 1:1.2:1.3:1.2 by H NMR spectroscopy and GC–MS (27 mg,
107 ([MꢀI) , 29), 91 (28), 79 (100), 77 (24), 67 (62); MS (CI, CH ): m/z
4
+
+
+
1
4% yield from (ꢁ)-24) as a colorless oil. Achiral GC–MS analysis of
(%): 235 ([M+H] , 5), 234 (MC , 3), 108 (12), 107 ([MꢀI] , 100), 79
+
this mixture showed the presence of four components (r.t. (min), relative
a.r.): 14.87, 29.45%; 15.03, 22.2%; 15.13, 25.4%; 15.29, 22.95%. The four
mass spectra were essentially coincidental among them and comparable
(93); accurate mass measurement calcd for [C H I]C : 233.99055; found:
8
11
233.99050.
Reaction of (ꢁ)-8 with tBuLi in anhydrous diethyl ether: A solution of
tBuLi (1.4 mL, 0.7m in pentane, 1 mmol) was added dropwise to a cold
with those previously described for (ꢁ)
GC–MS analysis of the mixture showed the presence of six components
r.t. (min), relative a.r.): 18.02, 12.2%; 18.14, 14.8%; 18.24, 10.4%; 18.32,
.6%; 18.40, 26.7%; 18.54, 28.36%. These results show that two compo-
nents of the mixture are racemic. Achiral GC–MS analysis of the above
stereoisomeric mixture 17, mixed with product 17 from the reduction of
ꢁ)-8 with molten sodium, showed the main and minor components of
the last product to coincide with the third and second components (r.t.
5.13 and 15.03 min) of the present mixture, respectively. Chiral GC–MS
analysis of product 17 from the reduction of (ꢁ)-8 with molten sodium,
alone and mixed with the stereoisomeric mixture 17 obtained in the pres-
ent reaction, showed the presence of three components, which coincide
with those of r.t. values 18.24, 18.32, and 18.40 min, the main component
A
H
R
U
G
(
0
ꢀ788C) and magnetically stirred solution of diiodide (ꢁ)-8 (73 mg,
(
7
.2mmol) in anhydrous diethyl ether (1 mL) under an argon atmosphere,
and the mixture was stirred at this temperature for 30 min and then al-
lowed to warm to room temperature. Methanol (1 mL) and water (2mL)
were successively added and the mixture was extracted with diethyl ether
(3”5 mL). The combined organic phases were dried (anhydrous Na SO )
(
2
4
and concentrated under atmospheric pressure using a Vigreux column
(10 cm) to give a white residue (70 mg). GC–MS analysis of this residue
showed the presence of the following significant components, in order of
elution (% a.r.): 14 (5.7), 21 (31.2), (ꢁ)-27 (3.1), and 18 (50.8). GC–MS
1
+
+
(EI) (ꢁ)-27: m/z (%): 180 (MC , 5), 165 ([MꢀCH ] , 18), 137 (23), 134
3
+
([MꢀC
2
H
5
OH]C , 17), 119 (30), 105 (22), 99 (63), 95 (31), 93 (84), 92
(32), 91 (57), 80 (36), 79 (66), 77 (42), 73 (100), 71 (63), 67 (58).
1
being the last one. H NMR (300 MHz): d=1.40–2.40 (complex absorp-
tion, 48H; methylenic protons of four stereoisomers), 2.81 (brs, 8H; 4-H
of four stereoisomers), 2.70 (brd, J=2.5 Hz), 2.74 (brd, J=2.5 Hz), 2.93
Reaction of (ꢁ)-8 with tBuLi in anhydrous diethyl ether followed by
quenching with trimethylsilyl chloride: A solution of diiodide (ꢁ)-8
(261 mg, 0.72 mmol) in anhydrous diethyl ether (5 mL) was added drop-
wise to a cold (ꢀ788C) and magnetically stirred solution of tBuLi
(8.3 mL, 0.7m in pentane, 5.8 mmol) under an argon atmosphere, and the
mixture was stirred at this temperature for 30 min. Then freshly distilled
trimethylsilyl chloride (1.9 mL, 14.6 mmol) was added at this temperature
and the mixture was allowed to warm to room temperature. Methanol
(2mL) and water (3 mL) were successively added and the mixture was
extracted with diethyl ether (3”5 mL). The combined organic phases
(
4
brd, J=2.5 Hz) and 2.97 (brd, J=2.5 Hz) (1-H of four stereoisomers),
.63 (m, 8H, =CHtrans of four stereoisomers), 4.89 ppm (m, 8H, =CHcis of
1
3
four stereoisomers); C NMR of (E,syn)- plus (Z,syn)-17, deduced from
the spectrum of the mixture of the four stereoisomers by subtracting the
signals of the mixture of (E,anti)- and (ꢁ)
A
T
E
N
(Z,anti)-17 (the given C atoms
correspond to both stereoisomers, one half of each compound): d=36.9
(
(
(
CH
2
), 37.1 (CH
2
), 37.5 (CH
2
), 38.2(CH
2
), 39.9 (CH
2
), 40.6 (CH
2
), 41.8
CH), 42.6 (CH), 45.9 (CH), 46.1 (CH), 102.7 (CH
C), 131,6 (C), 154.90 (C), 154.91 ppm (C).
2
), 102.8 (CH ), 131.3
2
were dried (anhydrous Na
2
SO
4
) and analyzed by GC–MS, which indicat-
1530
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 1522 – 1532

A 2,5-Methano-Bridged [2.2.1]Propellane
FULL PAPER
ed a complex mixture of products from which no single component could
be isolated or characterized.
Pigg, Jr., P. Kaszynski, Z. H. Kudzin, Tetrahedron 2005, 61, 89–95;
e) N. Sandstrçm, H. Ottosson, Chem. Eur. J. 2005, 11, 5067–5079.
6] a) P. Camps, C. Iglesias, M. J. Rodríguez, M. D. Grancha, M. E. Gre-
gori, R. Lozano, M. A. Miranda, M. Figueredo, A. Linares, Chem.
Ber. 1988, 121, 647–654; b) P. Camps, M. A. Estiarte, S. Vµzquez, F.
PØrez, Synth. Commun. 1995, 25, 1287–1293.
[
[
Reaction of (ꢁ)-8 with tBuLi in anhydrous diethyl ether followed by
quenching with CO
2
: A solution of diiodide (ꢁ)-8 (100 mg, 0.28 mmol)
in anhydrous diethyl ether (2mL) was added dropwise to a cold ( ꢀ788C)
and magnetically stirred solution of tBuLi (4 mL, 0.7m in pentane,
7] a) P. Camps, M. Font-Bardia, F. PØrez, X. Solans, S. Vµzquez,
Angew. Chem. 1995, 107, 1011–1013; Angew. Chem. Int. Ed. Engl.
2
.8 mmol) under an argon atmosphere, and the mixture was stirred at
this temperature for 30 min. Then, excess CO (g) was bubbled at this
2
1
995, 34, 912–914; b) P. Camps, F. J. Luque, M. Orozco, F. PØrez, S.
temperature and the mixture was allowed to warm to room temperature.
Methanol (2mL) and water (5 mL) were successively added and the mix-
ture was extracted with diethyl ether (10 mL). The combined organic
Vµzquez, Tetrahedron Lett. 1996, 37, 8605–8608; c) P. Camps, X.
Pujol, S. Vµzquez, Tetrahedron 2002, 58, 10081–10086; d) P. Camps,
J. A. Fernµndez, S. Vµzquez, M. Font-Bardia, X. Solans, Angew.
Chem. 2003, 115, 4183–4185; Angew. Chem. Int. Ed. 2003, 42, 4049–
4051; e) P. Camps, M. R. MuÇoz, S. Vµzquez, J. Org. Chem. 2005,
70, 1945–1948; f) P. Camps, M. R. MuÇoz, S. Vµzquez, Tetrahedron
2006, 62, 7645–7652. For a review on pyramidalized alkenes, see:
g) S. Vµzquez, P. Camps, Tetrahedron 2005, 61, 5147–5208.
phases were dried (anhydrous Na
pheric pressure using a Vigreux column (10 cm) to give a yellow oil
25 mg). GC–MS analysis of the organic extracts showed the presence of
2 4
SO ) and concentrated under atmos-
(
many components, the two main ones being in order of elution (% a.r.):
di-tert-butyl ketone, 28 (74.5), and a compound which, on the basis of its
mass spectrum, seems to be ketone (ꢁ)-29 (7.2). GC–MS (EI) (ꢁ)-29:
+
+
+
m/z (%): 248 (MC , 3), 233 ([MꢀCH
] , 3), 207 (15), 191 ([MꢀC
4 9
H ] ,
[8] C. Ayats, P. Camps, M. Font-Bardia, M. R. MuÇoz, X. Solans, S.
Vµzquez, Tetrahedron 2006, 62, 7436–7444.
3
+
3
1
4), 163 ([MꢀC
4
H
9
ꢀCO]C , 82), 149 (23), 135 (20), 123 (23), 121 (36),
+
07 (73), 93 (29), 69 (20), 57 (C
4
H
9
, 100). The alkaline aqueous phase
[9] Geometry optimizations were carried out using the Gaussian 03
[
19]
was acidified to pH 1–2with 5 n HCl (3 mL) at 08C and was extracted
with AcOEt (5”15 mL). The combined organic phases were dried (anhy-
suite of programs on a Compaq HPC320 computer, at the unre-
stricted Beckeꢁs three-parameter hybrid functional with the Lee,
[
20]
drous Na
2
SO
4
) and concentrated under reduced pressure to give a yellow
Yang, and Parr correlation functional (UB3LYP) level and at the
[
21]
residue (20 mg), which was reacted with an excess of a solution of diazo-
methane in diethyl ether until the yellow color remained. The excess di-
azomethane was destroyed by addition of AcOH, the volatile compo-
nents of the mixture were distilled off in vacuo, and the residue was ana-
lyzed by GC–MS, which indicated a complex mixture whose main com-
unrestricted Møller–Plesset (UMP2) level,
using the 6-31G(d)
[22]
basis set. Analytical energy second derivatives were calculated at
all optimized structures to confirm that these are minima or transi-
tion states. For details about the calculations, see the Supporting In-
formation.
ponent seems to be ester (ꢁ)-31 (43% a.r.) on the basis of its mass spec-
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1609–1612.
+
trum. GC–MS (EI) (ꢁ)-31: m/z (%): 207 ([MꢀCH
3
] , 2), 180 (14), 165
+
+
(
[MꢀC
4
H
9
] , 33), 163 ([MꢀCO
2 3
CH ] , 53), 123 (37), 122 (42), 121 (37),
+
1
07 (100), 57 (C
4
H
9
, 81).
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4
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1
Financial support from the Ministerio de Ciencia y Tecnología and
FEDER (Project CTQ2005-02192) and Comissionat per a Universitats i
Recerca (Project 2005-SGR-00180) is gratefully acknowledged. C.A.
thanks the Generalitat de Catalunya (Beca predoctoral). We thank the
Serveis Cientifico-T›cnics of the University of Barcelona for performing
the NMR spectroscopy, the Centre de Supercomputació de Catalunya
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Received: June 19, 2006
Published online: November 8, 2006
1532
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 1522 – 1532