Ring Expansion and Contraction of a Two-Carbon Bridged Spiropentane

Article abstract of DOI:10.1021/jo970980e

The reactions of tricyclo[4.1.0.0^1,3]heptan-4-one (5) and two related systems with diazomethane and m-CPBA were examined in order to determine the relative reactivity and migratory aptitudes for the three compounds. The reactions of 5 with diazomethane and m-CPBA yielded new derivatives of the tricyclo[5.1.0.0^1,3]octane ring system that showed that migration of cyclopropylcarbinyl is favored over cyclopropyl migration in this system. Photolysis of 5-diazotricyclo[4.1.0.0^1,3]heptan-4-one (23) in methanol and dimethylamine did not lead to ring contraction to the tricyclo[3.1.0.0^1,3]hexane ring system, but an interesting product was derived from an unusual rearrangement process in the photolysis in dimethylamine. Matrix photolysis of 23 at 15 K gave a decrease in the diazo band at 2085 cm^-1 and the appearance of a new band at 2117 cm^-1, which is a normal position expected for a small-ring ketene such as cyclopropylketene. Thus, matrix photolysis appears to have yielded a derivative of the previously unknown tricyclo[3.1.0.0^1,3]hexane ring system. The lithium enolate of 5 was characterized by NMR spectroscopy at -80 °C and was found to rearrange to m-cresol at -65 °C. The geometries of the bridged spiropentanes of this work were optimized at the MP2(frozen core)/6-31G* level of theory, and group equivalent values were derived in order to calculate the heats of formation for these compounds using the calculated energies.

Full text of DOI:10.1021/jo970980e

1390
J . Org. Chem. 1998, 63, 1390-1401
Rin g Exp a n sion a n d Con tr a ction of a Tw o-Ca r bon Br id ged
Sp ir op en ta n e
Kenneth B. Wiberg* and J ohn R. Snoonian
Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107
Received J une 2, 1997
The reactions of tricyclo[4.1.0.01,3]heptan-4-one (5) and two related systems with diazomethane
and m-CPBA were examined in order to determine the relative reactivity and migratory aptitudes
for the three compounds. The reactions of 5 with diazomethane and m-CPBA yielded new
derivatives of the tricyclo[5.1.0.01,3]octane ring system that showed that migration of cyclopropyl-
carbinyl is favored over cyclopropyl migration in this system. Photolysis of 5-diazotricyclo-
[4.1.0.01,3]heptan-4-one (23) in methanol and dimethylamine did not lead to ring contraction to the
tricyclo[3.1.0.01,3]hexane ring system, but an interesting product was derived from an unusual
rearrangement process in the photolysis in dimethylamine. Matrix photolysis of 23 at 15 K gave
a decrease in the diazo band at 2085 cm-1 and the appearance of a new band at 2117 cm-1, which
is a normal position expected for a small-ring ketene such as cyclopropylketene. Thus, matrix
photolysis appears to have yielded a derivative of the previously unknown tricyclo[3.1.0.01,3]hexane
ring system. The lithium enolate of 5 was characterized by NMR spectroscopy at -80 °C and was
found to rearrange to m-cresol at -65 °C. The geometries of the bridged spiropentanes of this
work were optimized at the MP2(frozen core)/6-31G* level of theory, and group equivalent values
were derived in order to calculate the heats of formation for these compounds using the calculated
energies.
1. In tr od u ction
1-3.7 We have now carried out geometry optimizations
for 1-4 and a number of their derivatives at the MP2/
6-31G* theoretical level. This has proven to give struc-
tures that are in good agreement with experimental
studies.8 The calculations provide estimates of heats of
formation that will be useful in interpreting the results
of some of the reactions that were studied.
We have been interested in the effects of structural
deformation on the structures, properties, and reactions
of organic compounds. One set of deformed compounds
are the bridged spiropentanes, 1-4. We have reported
the preparation of 1 and found it to have a short half-
life at -55 °C before rearranging to cyclopentadiene.1 The
two-carbon bridged compounds such as 3 and its deriva-
tives are easily prepared by the intramolecular carbene
addition discovered by Skattebøl.2 The three-carbon
bridged hydrocarbon, 4, has been prepared via a rear-
rangement,3 but no derivatives have been reported.
Furthermore, no preparation for 2 or its derivatives has
been forthcoming. The formation of derivatives of 2 and
4 is the major focus of this work.
2. Str u ctu r es a n d En er gies
The calculated energies are summarized in Table 1,
and the more interesting structural data are shown in
Figures 1 and 2. It should be noted that 1 has presented
a problem in that at the MP2/6-31G* level of theory it is
predicted to have a structure that is slightly asymmetric,4
whereas a symmetrical structure was reported at the
MP2/6-31G** level.7 However, we found the symmetrical
MP2/6-31G** structure to be a transition state (one
imaginary frequency). The difference in energy between
the symmetric and asymmetric structures was negligible
(less than 0.1 kcal/mol) and, thus, presents no problem
in estimating the heat of formation.
It is usually more convenient to work with heats of
formation rather than total energies. We have shown
that the HF/6-31G* calculated energies could be con-
verted to heats of formation via a group equivalent
approach5 where 627.5 is the conversion from
Theoretical calculations have proven to be a valuable
counterpart to preparative studies.4 We have previously
reported HF/6-31G* calculations5 for 1-4 and MP2/6-
31G* calculations for 1.6 Dodzuik, Leszczynski, and
Nowinski have reported MP2/6-31G** calculations for
∆Hf )
(1) Wiberg, K. B.; McClusky, J . V. Tetrahedron Lett. 1987, 28, 5411.
(2) Skattebøl, L. J . Org. Chem. 1966, 31, 2789.
627.5(ET - nCH ECH - nCH ECH - nCHECH- ...)
3
3
2
2
(3) Meibach, T.; Brinker, U. H. J . Org. Chem. 1993, 58, 6524.
(4) Wiberg, K. B.; McMurdie, N. D.; McClusky, J . V.; Hadad, C. M.
J . Am. Chem. Soc. 1993, 115, 10653. As a result of a typographical
error, the structure of 1 appeared to be more unsymmetrical than
calculated. The structure shown in Figure 1 is correct.
(5) Wiberg, K. B. J . Org. Chem. 1985, 50, 5285.
(7) Dodziuk, H.; Leszczynski, J erzy, Nowinski, K. S. J . Org. Chem.
1995, 60, 6860.
(8) Hehre, W. J .; Radom, L.; Scleyer, P. v. R.; Pople, J . A. Ab Initio
Molecular Orbital Theory; Wiley: New York, 1986.
(6) McClusky, J . V. Ph.D. Thesis, Yale University, 1988.
S0022-3263(97)00980-8 CCC: $15.00 © 1998 American Chemical Society
Published on Web 02/10/1998

Ring Expansion of a Two-Carbon Bridged Spiropentane
J . Org. Chem., Vol. 63, No. 5, 1998 1391
Ta ble 1. Ca lcu la ted MP 2/6-31G* En er gies a n d Hea ts of F or m a tion a
compd
MP2/6-31G*
∆Hf(MP2)
∆Hf(model)
strain energy
ketene
-152.147 48
-153.320 05
-194.618 15
-269.683 01
-234.992 43
-343.532 06
-193.285 82
-232.486 05
-271.709 91
-310.895 87
-345.574 76
-419.427 00
-383.545 18
-270.507 63
-309.676 84
-309.680 66
-345.541 67
-384.759 07
-384.761 89
-344.307 38
-268.436 42
-11.0 (-11.4)
-30.8 (-29.8)
+8.0 (+8.1)
-47.2 (-47.2)
-29.1 (-29.5)
-65.2
vinyl alcohol
cyclopentene
cyclopentanone
cyclohexane
+4.1
-51.3
-29.6
-78.0
-11.2
-16.2
-21.1
-26.0
-47.8
-74.4
-25.9
+7.6
4.0
4.1
0.1
cyclopentane-1,2-dione
12.2
137.2
115.5
79.2
66.0
77.1
83.1
74.0
78.3
78.1
75.3
78.3
65.3
63.5
120.5
34.6
tricyclo[2.1.0.01,3]pentane (1)
tricyclo[3.1.0.01,3]hexane (2)
+126.0
+99.3
tricyclo[4.1.0.01,3]heptane (3)
tricyclo[5.1.0.01,3]octane (4)
+57.8
+40.0
tricyclo[4.1.0.01,3]heptan-4-one
tricyclo[4.1.0.01,3]heptan-4,5-dione
5-methylenetricyclo[4.1.0.01,3]heptan-4-one
tricyclo[4.1.0.01,3]hept-4-ene
+29.3
+8.7
+4.1
+85.9
4-methylenetricyclo[4.1.0.01,3]heptane
4-methyltricyclo[4.1.0.01,3]hept-4-ene
4-hydroxytricyclo[4.1.0.01,3]hept-4-ene
tricyclo[5.1.0.01,3]octan-5-one
tricyclo[5.1.0.01,3]octan-4-one
tricyclo[3.1.0.01,3]hexane-4-ketene
cyclobutylketene
+78.8
+0.7
+76.5
+1.2
+43.3
-35.0
-52.7
-52.7
-18.9
-22.5
+12.6
+10.8
+101.6
+12.1
a
The total energies are given in hartrees (1 H ) 627.5 kcal/mol), and the other energies are given in kcal/mol. ∆Hf(MP2) is the heat
of formation derived from the MP2 energies. The values in parentheses are the observed energies. The ∆Hf(model) is the unstrained
heat of formation estimated using the Franklin group equivalents, and the strain energy is the difference between the MP2 energy and
the model energy.
Ta ble 2. Gr ou p En er gy Ter m s
a. aliphatic
CH3
CH2
CH
C
CH2 (cy-C3)
CH (cy-C3)
C(spiropentyl)
-39.731 44
-39.157 68
-38.583 25
-38.009 30
-39.156 27
-38.581 84
-38.010 39
b. olefinic
CH2
CH
C
-39.152 48
-38.578 94
-38.005 61
c. oxygen containing
CdO
OH (secondary)
-112.977 11
-75.539 53
highly strained compounds. Therefore, we have now
obtained a corresponding set of group equivalents based
on MP2/6-31G* energies, making use of the calculated
energies of a number of small acyclic compounds along
with cyclopropane and spiropentane. The values are
recorded in Table 2, and the origin of the values is
described in the Supporting Information. Making use of
these ab initio group equivalents, the heats of formation
of the compounds in Table 1 were calculated. Three
simple cyclic compounds were included (cyclopentene,
cyclopentanone, and cyclohexane) along with ketene and
vinyl alcohol as a test of the parameters, and the
calculated energies agreed with the experimental values
to about the uncertainties in the latter10 (the observed
heats of formation are given in parentheses).11
F igu r e 1. Calculated bond lengths (Å) for compounds opti-
mized at the MP2/6-31G* level of theory.
Another quantity of interest is the strain energy.12
Although different schemes give different answers, the
values are comparable as long as one scheme is consis-
tently used. We have made use of the Franklin group
equivalents13 to calculate the energies of the correspond-
Hartrees to kcal/mol, ET is the calculated total energy,
nCH is the number of CH3 groups, ECH is the correspond-
ing group equivalent, etc. The equivalents include the
zero-point energy terms and the change in energy on
going from 0 K to 25 °C. Similar schemes have been
developed by others.9
3
3
(10) The heats of formation of most of the compounds had an
uncertainty of 0.2-0.3 kcal/mol, and that for vinyl alcohol has an
uncertainty of 2.0 kcal/mol.
(11) The experimental data were taken from: Pedley, J . B. Ther-
mochemical Data and Structures of Organic Compounds; Thermody-
namics Research Center: College Station, TX, 1994; Vol. 1.
(12) Wiberg, K. B. Angew. Chem., Int. Ed. Engl. 1986, 25, 312.
One might expect that the HF theoretical level would
not be adequate for reproducing the relative energies of
(9) Ibrahim, M. R.; Schleyer, P. v. R. J . Comput. Chem. 1985, 6,
157.

1392 J . Org. Chem., Vol. 63, No. 5, 1998
Wiberg and Snoonian
F igu r e 2. Calculated bond angles (deg) for compounds optimized at the MP2/6-31G* level of theory.
Ta ble 3. Ben d in g a n d Tw istin g Distor tion s
ing unstrained model. The difference between these
values and the heats of formation gives the strain
energies. The ketene and enol groups are not included
in Franklin’s table, and we have estimated a value of
-7.7 kcal/mol for the CdCdO group and -23.8 for cis-
HCdCOH.
compd
twist
bend
tricyclo[2.1.0.01,3]pentane (1)
tricyclo[3.1.0.01,3]hexane (2)
tricyclo[4.1.0.01,3]heptane (3)
tricyclo[5.1.0.01,3]octane (4)
21.3°
6.1°
6.3°
1.5°
71.5°
47.8°
26.1°
15.0°
The estimated strain energies of compounds 1-4 are
137, 116, 79, and 66 kcal/mol, respectively. As a com-
parison, the strain energy of spiropentane is 63 kcal/mol.
Thus, 4 has essentially the same strain energy as
spiropentane. As the bridge becomes smaller, the strain
energy increases fairly rapidly.
A comparison of the strain energies in Table 1 il-
lustrates the different factors that affect the total strain
in a molecule. Relative to 3, the introduction of a double
bond (35) into the bridge leads to a 1 kcal/mol decrease
in strain energy, despite the fact that the shorter bridging
bond in 35 as compared to 3 leads to a greater distortion
of the spiropentyl group in the former (Figures 1 and 2).
The lower strain energy in 35 is presumably due to a
decrease in the number of hydrogen-hydrogen eclipsing
interactions in 3. Similarly, the introduction of a car-
bonyl group (5) into the bridge results in a 2 kcal/mol
decrease in strain relative to 3. Part of this may result
from the stabilizing interaction between the carbonyl
group and the cyclopropane ring.14 In the case of 4,
introduction of a carbonyl group into the 5 position (11)
reduces the strain energy by 1 kcal/mol as a result in
the decrease in eclipsing interactions, and at the 4
position (10) the decrease is 2.5 kcal/mol because of the
additional interaction between the carbonyl group and
the cyclopropane ring.
the angle to 164.6° (35), and the introduction of a
carbonyl group (5) changes the angle to 159.6°.
We have discussed the distortion of the spiropentane
ring in terms of bending one ring toward the other and
of twisting one ring with respect to the other.5 These
angular terms are summarized for 1-4 in Table 3.
3. P r ep a r a tion of Tr icyclo[4.1.0.01,3]h ep ta n -4-on e
The key compound for the present study is tricyclo-
[4.1.0.01,3]heptan-4-one (5), which has been prepared15
from 1,5-hexadien-3-ol by addition of dibromocarbene,
followed by protection of the hydroxyl group as the
trimethylsilyl ether and treatment with methyllithium
at -78 °C. The main product was the allene (8) formed
by cleavage of the intermediate cyclopropylidene. The
desired TMS ether was isolated in 7% yield by distillation
and preparative gas chromatography. The TMS ether
was treated with PCC to give 5 (Scheme 1). It was
possible to improve this procedure16 by eliminating the
silation step, and treatment of the crude mixture of 7,
8a , and 8b with ozone destroyed the allenes and oxidized
The structures of the compounds are of some interest
(Figures 1 and 2). As noted previously,5-7 the geometry
at the central carbon of 1 is pyramidal, and for 2, the
CH2-C-CH2 bond angle is close to 180°. The angle
decreases to 158.1° with 3 and to 149.1° with 4. The
introduction of a double bond into the bridge in 3 changes
(13) Franklin, J . L. Ind. Eng. Chem. 1949, 41, 1070.
(14) Peterson, M. B.; De Mare G. R. J . Mol. Struct. 1983, 104, 115.
(15) Brinker, U.; Gomann, K.; Zorn, R. Angew. Chem., Int. Ed. Engl.
1983, 22, 869.

Ring Expansion of a Two-Carbon Bridged Spiropentane
J . Org. Chem., Vol. 63, No. 5, 1998 1393
Sch em e 1a
4. Rin g Exp a n sion
An obvious approach to the formation of 4 and its
derivatives involves dibromocarbene addition to 1,6-
heptadiene followed treatment with methyllithium. This
was examined by Skattebøl, who reported the formation
of a new compound in small yield.2 The experiment was
repeated by McClusky6 and by Meibach, Wu¨ster, and
Brinker,17 and the product was shown to be 2-vinyl-
bicyclo[3.1.0]hexane (9) rather than the desired tricyclo-
[5.1.0.01,3]octane (4). Compound 9 was formed by inser-
tion of the carbene into the allylic CH bond instead of
addition to the CdC double bond.
a
Conditions: (a) MeLi, Et2O, -78 °C; (b) (1) O3, MeOH, -78
°C; (2) Me2S.
the hydroxyl group of 7 to a carbonyl, thus giving 5 in a
5% yield with a relatively facile workup.
An alternate approach to the preparation of three-
carbon-bridged spiropentanes was the ring expansion of
the ketone, 5. With strained ketones, diazomethane is
often able to effect ring expansion directly.18 The reaction
with 5 proceeded rapidly in ether solution at ambient
temperature to give tricyclo[5.1.0.01,3]octan-4-one (10)
and -5-one (11) in a 20:1 ratio. The compounds were
readily separated by chromatography over silica gel and
were easily identified by their 13C NMR spectra. Since
10 is asymmetric, it displayed eight bands in its 13C NMR
spectrum at δ 13.0 (d), 17.1 (t), 18.6 (t), 22.7 (d), 23.2 (s),
30.6 (t), 38.5 (t), and 212.4 (s) ppm. In contrast, 11
displayed five bands at δ 11.5, 14.3, 15.8, 41.1, and 214.9
ppm in its 13C NMR spectrum because it possesses a C2
axis of symmetry. The MP2/6-31G* optimized structure
of 11 is not C2 symmetric, but rather the cyclohexanone
fragment adopts a twist-boat conformation. It is likely
that the three-carbon bridge in 11 has sufficient confor-
mational freedom that an averaged structure is seen on
the NMR time scale.
It has been noted that 5 undergoes a fairly facile base-
catalyzed rearrangement to m-cresol.15 Treatment of 5
with lithium bis(trimethylsilyl)amide (LHDMS) at -78
°C followed by addition of methanol-d at -78 °C gave 5
labeled with deuterium, indicating that the lithium
enolate is stable under these conditions. To examine the
stability at higher temperatures, a tetrahydrofuran-d8
solution of 5 was added to a freshly prepared THF-d8
solution of LHMDS contained in an NMR tube at -78
°C. The tube was inserted into the probe of an NMR
spectrometer that had been cooled to -80 °C. The proton
NMR spectrum had a band at δ 4.15 ppm corresponding
to an enolate proton. The remaining bands were those
expected for 5 except for the loss of the ABX pattern for
the methylene group R to the carbonyl at 2.4 and 2.6 ppm.
No bands downfield from the 4.15 ppm band were
observed. The spectrum was unchanged after 1 h at -80
°C.
The calculations suggest that 10 has a lower energy
than 11 by about 1.8 kcal/mol, which corresponds to a
21:1 ratio at 25 °C. Thus, the observed product ratio (20:
1) may be thermodynamically controlled. The rearrange-
ment forming 10 involves the migration of a cyclopropyl-
carbinyl group, whereas 11 is formed via the migration
of a cyclopropyl group. To examine the migratory prefer-
ence for these groups in less strained compounds, the
reactions of both bicyclo[3.1.0]hexan-2-one (12) and cy-
clopropyl cyclopropylcarbinyl ketone (13) with diazo-
methane were studied. Compound 12 corresponds to 5
with the loss of one cyclopropane ring, and compound 13
contains the cyclopropyl and cyclopropylcarbinyl groups
found in 5, but in an acyclic arrangement.
When the probe was warmed to -65 °C, in addition to
the bands observed at -80 °C, four bands from 6 to 7
ppm were found. After the probe was warmed to -50
°C, the signal at 4.15 ppm disappeared along with the
bands characteristic of the tricyclo[4.1.0.01,3]heptane ring
system. Thus, the enolate ion is stable at low tempera-
ture but rearranges readily above -70 °C. Attempts to
trap the enolate ion will be described in a later section.
Unlike 5, neither ketone reacted with diazomethane
in ether at an appreciable rate. It is known that
(17) Meibach, T.; Wuster, H.; Brinker, U. H. J . Org. Chem. 1993,
58, 6520.
(16) For a preliminary report of this work, see: Wiberg, K. B.;
Snoonian, J . R. Tetrahedron Lett. 1995, 36, 1171.
(18) For a review, see: Gutsche, C. D. In Organic Reactions; J ohn
Wiley and Sons: New York, 1954; pp 364-430 and references therein.

1394 J . Org. Chem., Vol. 63, No. 5, 1998
Wiberg and Snoonian
methanol catalyzes the reaction,18 and therefore 12 and
13 were treated with diazomethane in 1:1 methanol-
ether. The reaction of 12 gave bicyclo[4.1.0]heptan-2-
(14) and -3-one (15) in a 3:1 ratio, which was determined
by gas chromatography through comparison of the reac-
tion mixture with authentic samples of 1419 and 15.20 The
reaction of 13 led to 1,3-dicyclopropylacetone (16)21 and
1,3-dicyclopropyl-1-propanone (17)21 in a 2:1 ratio. The
product ratio 16:17 was determined in the same manner
used for determination of the ratio of 14:15.
migration. When 13 was treated with the peroxyacid,
again only one product (21) was formed, but here it was
the cyclopropylcarbinyl group that migrated. Clearly,
there are several factors that control the Baeyer-Villiger
reaction, and it is not simply comparable to the diazo-
methane homologation.
5. Rin g Con tr a ction
The simplest approach to the formation of 2 and its
derivatives would be the ring contraction of 5. The
photochemical Wolff rearrangement of R-diazo ketones
is one of the more general methods for ring contraction.23
It is known that the reaction is successful for cases where
the ring strain increases by 35 kcal/mol or less. The
increase in strain on going from 3 to 2 (Table 1) is 37
kcal/mol, at the upper end of the range of applicability.
It is possible to convert the ketone,24 5, to R-enamino
ketone 22 in 85% yield via its reaction with Bredereck’s
reagent.25 The reaction of 22 with tosyl azide gave only
a small yield of the R-diazo ketone 23. However, the use
of methanesulfonyl azide26 led to a more satisfactory
reaction and gave 23 in a 35% yield. The R-diazo ketone
was quite stable and could be purified via chromatogra-
phy over silica gel using 1:1 pentane-ether containing
1.5% triethylamine.
The results clearly indicate that the differences in
migratory aptitude in these systems are small. This
supports the proposal that the product ratio found with
5 is thermodynamically controlled.
The origin of the difference in reactivity between 5, 12,
and 13 was also of interest. The relative reactivities were
determined by competition, with the ratio of products
extrapolated back to zero time. Compound 12 was found
to be 3.5 times as reactive as 13, and 5 was found to be
275 times as reactive. The strain energy decrease on
going from 5 to 10 is about 13 kcal/mol (Table 1), whereas
with 12, the strain relief on homologation will be only a
few kcal/mol. This factor is more than enough to account
for the higher reactivity of 5.
It was of interest to compare the diazomethane ho-
mologation with another ring expansion reaction. One
of the more common is the Baeyer-Villiger reaction,22
which converts cyclic ketones to lactones. Treatment of
5 with m-CPBA in dichloromethane buffered with sodium
bicarbonate led to two ring-expanded lactones (18 and
19) in a 15:1 ratio. The product ratio and the regiochem-
istry is essentially the same as that observed in the
diazomethane reaction.
In view of the relatively low yield of 23, another
approach was examined. Treatment of 22 with singlet
oxygen led to the diketone 24, which could be converted
to the monotosylhydrazone 25. The reaction of 25 with
base gave 23. Although each step was satisfactory, the
overall yield was not much improved as compared to the
diazo group transfer method using methanesulfonyl
azide.
However, this was not the case in the reaction of 12,
which led only to the product (20) formed via cyclopropyl
(23) For
a review, see: Gill, G. B. In Comprehensive Organic
Synthesis; Pergamon Press: Oxford, 1991; Vol. 3, pp 887-912 and
(19) J ohnson, C. R.; Rogers, P. E. J . Org. Chem. 1973, 38, 1793.
(20) Proksch, E.; deMeijere, A. Angew. Chem., Int. Ed. Engl. 1976,
15, 761.
(21) Hanack, M.; Ensslin, H. M. Ann. 1966, 697, 100. Hanack, M.;
Bocher, S.; Herterich, I.; Hummel, K.; Vo¨tt, V. Ann. 1970, 733, 5.
(22) For a review, see: Smith, P. A. S. In Molecular Rearrangements;
DeMayo, P., Ed.; J ohn Wiley and Sons: New York, 1963; pp 457-592.
references therein.
(24) For a preliminary report of this work, see: Wiberg, K. B.;
Snoonian, J . R.; Lahti, P. M. Tetrahedron Lett. 1996, 37, 8285.
(25) Bredereck, H.; Simchem, G.; Rebsdat, S.; Kantlehner, W.; Horn,
P.; Wahl, R.; Hoffman, H. Grieshaben, P. Chem. Ber. 1968, 101, 41.
(26) Taber, D. F.; Ruckle, R. E., J r.; Hennessy, M. J . Org. Chem.
1986, 51, 4077.

Ring Expansion of a Two-Carbon Bridged Spiropentane
J . Org. Chem., Vol. 63, No. 5, 1998 1395
Sch em e 2
Photolysis of 23 in methanol gave only the methoxy
ketone 26. It was identified by comparison with an
authentic sample prepared from the diol 27 by methy-
lation and oxidation with tetrapropylammonium perru-
thenate (TPAP).27 The R-diazo ketone is quite stable in
methanol, and it is likely that the excited state of 23 is
sufficiently basic to abstract a proton from methanol,
leading to a diazonium ion that can form 26. A similar
observation was made by Eaton and Temme in their
studies leading to a [2.2.2]propellane derivative.28
rangement to ketenes, 29 is not only an R-keto carbene
but may be thought of as a cyclopropylcarbene as well.
Fragmentation of cyclopropylcarbenes to give alkene and
alkyne groups is well known,29 and would give 30.
Michael addition of dimethylamine to 30 would yield 28.
To gain further information on the photochemistry of
23, the photolysis was carried out in a Nujol matrix at
15 K using a 1000 W Xenon lamp. As a test of the
photolysis, the diazo ketone 31 prepared from 32 was first
examined. This diazo ketone undergoes the Wolff rear-
rangement in methanol to give the expected methyl ester,
indicating that the ketene 33 is an intermediate. In the
matrix photolysis, the diazo band at 2080 cm-1 decreased
in intensity and a new band at 2140 cm-1 appeared. The
latter is at the normal position for a small-ring ketene
such as cyclopropylketene.30
To minimize proton transfer, the photolysis was carried
out in dimethylamine at 0 °C. After the excess amine
had been allowed to evaporate, the remaining product
had a mass (151) corresponding to the loss of nitrogen
from 23 and the addition of the elements of dimethyl-
amine. The spectral data for 28 are not compatible with
the expected ring-contracted N,N-dimethylamide. Homo-
nuclear decoupling studies indicated that it had the
structure
The photolysis of 23 in a matrix under the same
conditions led to the same result: a decrease in the diazo
band at 2085 cm-1 with the formation of a new band at
2117 cm-1
.
A possible mechanism for the formation of 28 is shown
in Scheme 2. Although R-keto carbenes locked into an
s-cis conformation are thought to undergo facile rear-
(27) Griffith, W.; Ley, S. V.; Whitcombe, G. P.; White, A. J . Chem.
Soc., Chem. Commun. 1987, 1625.
(28) Eaton, P. E.; Temme, G. H. J . Am. Chem. Soc. 1973, 95, 7508.
(29) Cristol, S. J .; Harrington, J . K. J . Org. Chem. 1963, 28, 1413.

1396 J . Org. Chem., Vol. 63, No. 5, 1998
Wiberg and Snoonian
Ta ble 4. Sca led In fr a r ed F r equ en cies a n d
Cor r esp on d in g In ten sities for 34 Ca lcu la ted a t th e
HF /6-31G* Level of Th eor ya (F r equ en cies Ar e in cm -1
)
frequency
intensity
frequency
intensity
90
154
294
353
455
498
523
605
630
748
758
878
880
896
956
986
1013
1034
0.2
2.4
2.1
4.2
4.6
1081
1088
1092
1120
1124
1246
1262
1403
1406
1453
1495
2109
2943
2943
2991
2991
3018
3018
2.2
6.2
1.8
3.6
8.6
12.4
17.6
0.0
0.7
0.3
0.4
34.0
17.5
13.3
0.6
0.3
9.1
10.0
18.9
0.2
14.5
0.8
1460
53.0
15.4
2.9
39.2
31.5
4.2
essentially no reaction occurred under 100 °C. Desul-
furization was complete on heating at 125 °C for 6 h, and
the products were toluene and triethyl thiophosphate. It
seems likely that 35 was formed and rearranged to
toluene under the reaction conditions.
17.9
0.1
a
The scaling factor was 0.893.
The calculated frequencies for 34 are given in Table 4.
No imaginary frequencies were calculated for 34 at the
HF/6-31G* level of theory. An intense band calculated
at 2362 cm-1 corresponds to the experimentally observed
intense ketene stretch at 2117 cm-1. When the calculated
values are scaled by a factor of 0.893, the frequency of
this intense band was found to be 2109 cm-1, which is in
excellent agreement with the experimentally observed
value of 2117 cm-1. A scaling factor of 0.893 is often used
to correct for anharmonicity and other effects when
frequencies are calculated at the HF/6-31G* level of
theory.31 Thus, it appears that under matrix isolation
conditions 23 does undergo the normal Wolff rearrange-
ment.
Some highly strained alkenes, such as trans-cyclohep-
tene, have been formed and trapped by 1,3-diphenyl-
isobenzofuran in situ.35 This reaction was carried out
with 38, and besides triethyl thiophosphate and excess
1,3-diphenylisobenzofuran, analysis by GC/MS indicated
there was a product having two main fragments at 271
and 91. The desired adduct would have a mass of 362,
the sum of the observed masses. However, it was not
the adduct with 35 since the NMR spectrum did not
contain any bands characteristic of cyclopropane rings.
Another elimination reaction that usually occurs at a
lower temperature is the cleavage of the anion derived
from a 2-phenyl-1,3-dioxolane derivative.36 The requisite
benzylidene acetal was formed by treatment of the diol,
27, with benzaldehyde dimethyl acetal and a catalytic
amount of p-toluenesulfonic acid. The NMR spectrum
indicated that the two epimeric dioxolanes (39a ) and
(39b) were formed in approximately equal amounts, and
it was possible to separate the epimers by silica gel
column chromatography. When a petroleum ether solu-
tion of 39a and 39b was treated with 2 equiv of n-
butyllithium in hexane, the color slowly changed from
colorless to orange. After 3 h, the solution was treated
with D2O, which discharged the orange color. The
starting materials were the only products isolated, but
they now contained one deuterium. When the reaction
solution was allowed to stand for 30 h before workup,
the products were toluene and valerophenone.
6. Tr icyclo[4.1.0.01.3]h ep t-4-en e Der iva tives
Tricyclo[4.1.0.01,3]hept-4-ene (35) has not been re-
ported, and in view of the thermal instability of the
enolate ion 36 it is likely that it would not be stable at
room temperature. The alkene was of interest in that
the distortion in the spiropentane unit would be increased
as a result of decreasing the bridging C-C bond length.
However, the calculations (Table 1) suggest that the
strain energy for 35 would be less than that of 3,
presumably due to loss of some eclipsing interactions. It
should be noted that 37 has been prepared and is quite
stable.32 However, here the opportunities for rearrange-
ment are minimized.
Two approaches were taken for the attempted prepa-
ration of 35 by deoxygenation of the vicinal diol 27. The
synthesis and additional studies of 27 and thiocarbonate
38 are reported elsewhere.33 Corey and Winter have
shown that thiocarbonate esters may be converted to
alkenes using trialkyl phosphites.34 The reaction of 38
with triethyl phosphite was remarkably slow, and
(30) Maquestiau, A.; Pauwels, P.; Flammang, R.; Lorencak, P.;
Wentrup, C. Org. Mass. Spectrom. 1986, 21, 259. Maier, G.; Heider,
M.; Sierakowski, C. Tetrahedron Lett. 1991, 32, 1961.
(31) Pople, J . A.; Head-Gordon, M.; Fox, D. J .; Raghavachari, K.;
Curtiss, L. A. J . Chem. Phys. 1989, 90, 5622. Pople, J . A.; Scott, A. P.;
Wong, M. W.; Radom, L. Isr. J . Chem. 1993, 33, 345.
(32) Brinker, U.; Streu, J . Angew. Chem., Int. Ed. Engl. 1980, 19,
631.
(35) Corey, E. J .; Winter, R. A. E. J . Am. Chem. Soc. 1965, 87, 934.
(36) Wharton, P. S.; Hiegel, G. A.; Ramaswami, S. J . Org. Chem.
1964, 29, 2441.
(33) Wiberg, K. B.; Snoonian, J . R. J . Org. Chem. 1998, 63, 1402.
(34) Corey, E. J .; Winter, R. A. E. J . Am. Chem. Soc. 1963, 85, 2677.

Ring Expansion of a Two-Carbon Bridged Spiropentane
J . Org. Chem., Vol. 63, No. 5, 1998 1397
7. Discu ssion
This work has led to the preparation of the first-known
derivatives of 4 via the homologation of 5 with diazo-
methane. Although the cyclopropylcarbinyl group mi-
grated in preference to cyclopropyl in this reaction, an
examination of related ketones found little preference
between these groups. Thus, it appears that the migra-
tory preference is determined largely by the difference
in energy between the two ketones that are formed. The
high reactivity of 5 toward diazomethane also appears
to be derived from thermochemical factors.
The Corey-Winter reaction of 38 and the base-induced
elimination of lithium benzoate from 39a and 39b yielded
toluene by rearrangement of 35. The facile rearrange-
ment of 35 to toluene is supported by the NMR studies
of 36, which showed that it rearranges at -65 °C. A
similar mechanism can be written for the reaction of 22
with lithium aluminum hydride, in which the benzene
derivative 44 was produced in 72% yield.
Given the ease with which 35 rearranges to toluene,
our efforts were now directed toward the trapping of the
enolate ion 36 and observing whether the compound thus
formed would survive warming to room temperature.
Since we have determined that 36 is stable at -78 °C, a
THF solution of 36 at -78 °C was treated with tert-
butyldimethylsilyl triflate, which normally reacts at the
oxygen of an enolate. On warming to room temperature,
the product was found to be the silyl ether of m-cresol,
indicating that the enol ether 40 underwent rearrange-
ment below room temperature.
Matrix photolysis of 23 produced a band in the IR at
2117 cm-1 attributed to ketene 34, which indicates that
for the first time a derivative of the tricyclo[3.1.0.01,3]-
hexane ring system 2 has been prepared. The apparent
dichotomy in the behavior of 23 between solution and
low-temperature matrix photolysis is interesting and will
receive further study. One of several possibilities is that
the ketocarbene 29 forms an ylide with dimethylamine
and this ylide, not ketocarbene 29, undergoes rearrange-
ment leading to 28. It is known that carbenes react with
amines such as pyridine to form relatively stable ylides,37
and studies directed toward the detection and measure-
ment of the lifetime of 29 are in progress.
Finally, a group-equivalent scheme was developed that
has shown good agreement with experimental thermo-
chemical data and has been useful in the interpretation
of our experimental observations. This scheme should
be of use to others that wish to convert total energies
calculated at the MP2/6-31G* level of theory to heats of
formation at 298 K.
8. Exp er im en ta l Section
Gen er a l In for m a tion . All reactions were conducted in
oven-dried or flame-dried glassware under an argon atmo-
sphere. Reagents were purchased from Aldrich, Fisher, J . T.
Baker, or Lancaster Chemical Co. and were used without
further purification unless otherwise stated. Air-sensitive
solutions were transferred via oven-dried syringe needles or
When 36 at -78 °C was treated with 2,2,2-trifluoro-
ethyl trifluoroacetate, which normally gives C acylation,
followed by aqueous workup, the NMR spectrum showed
no aromatic or olefinic protons. The EI mass spectrum
showed a parent peak at 204, along with an intense peak
at 135 corresponding to the loss of the trifluoromethyl
group. The compound 41 was quite unstable, and at-
tempts to purify it were unsuccessful.
(37) Modarelli, D. A.; Platz, M. S. J . Am. Chem. Soc. 1991, 113, 8985.
Wang, J . L.; Toscano, J . P.; Platz, M. S.; Nikolaev, V.; Popik, V. J .
Am. Chem. Soc. 1995, 117, 5477.

1398 J . Org. Chem., Vol. 63, No. 5, 1998
Wiberg and Snoonian
an oven-dried cannula under positive pressure of argon.
Concentration in vacuo refers to removal of volatiles on a
rotary evaporator at water aspirator pressure. FT NMR
spectra were taken in CDCl3. Proton spectra were recorded
at 300 MHz, and 13C NMR were recorded at 75 MHz. In both
cases, residual CHCl3 served as the internal standard with
proton spectra referenced to δ 7.26 ppm and carbon spectra
referenced to δ 77.0 ppm (center of triplet). In ozonolyses
reactions, the ozone was generated by passing oxygen through
an OREC V-10 ozone generator. Low-resolution mass spectra
obtained in the EI mode by GC/MS were obtained at an
ionizing voltage of 70 eV using a gas chromatograph fitted with
a 30 m × 0.25 mm i.d. capillary column coated with a 0.25 µm
layer of SE-30. Mass spectra obtained in the CI mode were
obtained using isobutane as the reagent gas. Where mass
spectral data are given, the peak value is immediately followed
by its relative abundance in parentheses. FT IR spectra were
taken in CCl4 using an NaCl solution cell. Silica gel column
chromatography was performed using 230-400 mesh silica gel.
TLC analyses were done on glass plates coated with 250 µm
of silica gel. Plates were visualized with vanillin stain, UV
light, or iodine vapor. In cases where a product was purified
by silica gel column chromatography, the Rf value given is that
of the compound using the eluant employed for purification
unless otherwise stated. Boiling and melting points are
uncorrected. Combustion analyses were performed by Atlantic
Microlab, Norcross, GA. High-resolution mass spectra were
obtained at the University of Illinois Urbana-Champaign.
Unless otherwise stated, HRMS data was obtained in the EI
mode. All calculations were performed using the developmen-
tal version of GAUSSIAN 95.38 Unless otherwise stated, all
of the calculated energy values and geometrical parameters
were obtained by using the FOPT option at the MP239 level of
theory, the 6-31G* basis set,40 and the frozen core approxima-
tion.41 Although no difficulties were encountered using p-
toluenesulfonyl azide, methanesulfonyl azide, and diazomethane,
due to their explosive nature these reagents should be handled
with care behind a safety shield.
1,1-Dibr om o-2-(2-h ydr oxy-3-bu ten yl)cyclopr opan e (6a)
a n d 1,1-Dibr om o-2-(1-h yd r oxy-3-bu ten yl)cyclop r op a n e
(6b). To a solution of 73 g (0.75 mol) of 1,5-hexadien-3-ol, 289
g (1.14 mol) of bromoform, and 6.7 g (29 mmol) of benzytri-
ethylammonium chloride in 150 mL of CH2Cl2 was added
dropwise with vigorous stirring 135 g of NaOH in 270 mL of
water over 30 min. The solution refluxed strongly and became
deep brown and viscous. After vigorous stirring for 36 h, 1 L
of cold water was added. The layers were separated, and the
aqueous layer was extracted with 300 mL of CH2Cl2. The total
organic phase was washed with two 300 mL portions of 0.1 N
HCl, dried over Na2SO4, and concentrated in vacuo. The tarry,
brown residue was vacuum distilled (bp 85-95 °C, 0.15 Torr)
using a 15 cm × 1.5 cm Vigreux column to give a 62.0 g (31%
yield) mixture of the regioisomeric dibromides: 1H NMR δ
1.21-2.79 (10H, m), 3.48-3.54 (1H, m), 4.30-4.41 (1H, m),
5.14-5.37 (4H, m), 5.82-6.01 (2H, m); CIMS 255 (20), 253 (40)
) [(M + H)] - 18, 251 (21), 173 (45), 171 (42), 91 (100).
Tr icyclo[4.1.0.01,3]h ep ta n -4-on e (5). To 220 mL of 1.4 M
MeLi (salt free, diethyl ether solution) at -78 °C was added
dropwise a 35.0 g (0.13 mol) mixture of 6a and 6b in 450 mL
of Et2O over 6 h. After the addition was complete, the solution
was stirred at -78 °C for an additional hour and then allowed
to warm to 0 °C. Excess MeLi was decomposed through careful
addition of water. The quenched solution was washed with
two 200 mL portions of saturated NH4Cl, dried over Na2SO4,
and concentrated in vacuo. Approximately 14 g of a yellow
liquid remained. This mixture of 7, 8a , and 8b was dissolved
in 75 mL of absolute MeOH and treated with O3 at -78 °C
until an opaque-blue-white color persisted. After the solution
was purged of excess O3, 50 mL of Me2S was added at -78 °C.
The solution was allowed to warm to room temperature and
then concentrated in vacuo. The concentrate was poured into
water, and this aqueous layer was repeatedly extracted with
pentane until TLC (Et2O, Rf ) 0.8) revealed that no more
ketone remained in the aqueous layer. The pentane extracts
were combined, dried over Na2SO4, and concentrated in vacuo.
Silica gel column chromatography using 3:1 pentane:Et2O as
the eluant typically gave 0.8 g of 5 (6% yield) (Rf ) 0.55).
1
5: IR 1721 cm-1; H NMR δ 0.98-1.01 (1H, m), 1.57-1.61
(1H, m), 1.69-1.73 (1H, m), 1.98-2.02 (1H, t), 2.16-2.18 (1H,
m), 2.18-2.24 (1H, m), 2.43, 2.64 (2H, ABX); 13C NMR δ 11.56,
20.80, 22.65, 29.67, 30.25, 46.20, 216.59; GC/MS 108 (50), 107
(21), 79 (96), 39 (100).
Tr icyclo[5.1.0.01,3]octan -4-on e (10) an d Tr icyclo[5.1.0.01,3]-
octa n -5-on e (11). Diazomethane was formed from 2.5 g (11.7
mmol) of Diazald using the procedure described by the Aldrich
Chemical Co.42 and added to 0.550 g (5.1 mmol) of 5 (neat) so
as to react in situ with the diazomethane. After being stirred
for 18 h at room temperature, the solution was cooled in an
ice bath, and excess CH2N2 was decomposed through careful
addition of an ethereal solution of acetic acid. The solution
was concentrated in vacuo, and the yellow residue was purified
by silica gel column chromatography using 2:1 CH2Cl2:pentane
as the eluant. This gave 0.435 g of pure 10 (Rf ) 0.19).
A
second, less polar fraction with an Rf ) 0.50 containing 5 and
11 was inseparable by various column chromatographic condi-
tions. These two compounds were separated by preparative
gas chromatography using a 13% OV101 on AWDMS column
at 165 °C. Approximately 20 mg of 11 was obtained.
10: IR 1700 cm-1; 1H NMR δ 1.11-1.20 (2H, m), 1.24-1.36
(1H, m), 1.51-1.55 (1H, q), 1.59-1.61 (1H, t), 1.68-1.77 (2H,
m), 2.05-2.11 (2H, m), 2.31-2.37 (1H, m); 13C NMR δ 13.04
(d), 17.09 (t), 18.57 (t), 22.68 (d), 23.17 (s), 30.60 (t), 38.52 (t),
212.41 (s); GC/MS 122 (8), 94 (12), 79 (100); CIMS 123 (100);
HRMS calcd for C8H10O 122.0732, found 122.0730.
11: IR 1714 cm-1 1H NMR δ 0.83 (2H, s, broad), 1.38-
;
1.59 (4H, m), 1.85-1.94 (2H, d of d), 2.55-2.63 (2H, d of d);
13C NMR δ 11.49, 14.30, 15.82, 41.05, 214.92. MS (EI): 122
(7), 79 (100); CIMS 123 (100); HRMS calcd for C8H10
122.0732, found 122.0730.
O
5-Oxa tr icyclo[5.1.0.01,3]octa n -4-on e (18) a n d 4-Oxa tr i-
cyclo[5.1.0.01,3]octa n -5-on e (19). To a mixture of 0.70 g (4.1
mmol) of m-CPBA and 1.3 g (15.5 mmol) of NaHCO3 in 10 mL
of CH2Cl2 was added 0.25 g (2.3 mmol) of 5 in 2 mL of CH2Cl2.
After being stirred for 18 h, the mixture was washed with 5
mL of 10% Na2SO3 and then 5 mL of saturated NaHCO3. The
organic layer was dried over Na2SO4 and concentrated in
vacuo. The lactones were purified by silica gel column
chromatography using 3:1 Et2O:pentane as the eluant, and
0.013 g of 19 eluted first (Rf ) 0.61). The major product was
18 (Rf ) 0.30), and 0.150 g was isolated. Recovered starting
material accounted for the remaining material.
1
18: IR 1746 cm-1; H NMR δ 1.31-1.39 (1H, t),1.42-1.50
(2H, m) 1.63-1.67 (1H, t), 1.69-1.82 (ABX, 2H), 3.72-3.79
(1H, d of d), 4.62-4.69 (1H, d of d); 13C NMR δ 11.29, 12.86,
15.35, 16.73, 18.22, 75.64, 171.89; GC/MS 124 (2), 95 (18), 79
(100), 67 (41), 39 (52); CIMS 125 (100). Anal. Calcd for
C7H8O2: C, 67.7; H, 6.5. Found: C, 67.6; H, 6.4.
(38) Gaussian 95, Development Version (Revision D.2): Frisch, M.
J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J . R.; Strain, M. C.; Burant, J . C.; Stratman, E.; Petersson,
G. A.; Montgomery, J . A.; Zakrzewski, V. G.; Keith, T.; Raghavachari,
K.; Al-Laham, M. A.; Ortiz, J . V.; Foresman, J . B.; Cioslowski, J .;
Stefanov, B. B.; Nanayakkara, A.; Challacombe, M.; Peng, C. Y.; Ayala,
P. Y.; Chen, W.; Wong, M. W.; Andres, J . L.; Replogle, E. S.; Gomperts,
R.; Martin, R. L.; Fox, D. J .; Binkley, J . S.; Defrees, D. J .; Baker, J .;
Stewart, J . P.; Gonzalez, C.; Head-Gordon, M.; Gill, P. M. W.; J ohnson,
B. G.; Pople, J . A. Gaussian, Inc., Pittsburgh, PA, 1996.
19: IR 1763, 1751 cm-1 13C NMR δ 11.14, 12.04, 14.62,
;
16.01, 33.39, 56.91, 173.48; GC/MS 95 (96), 67 (100), 53 (54),
41 (57), 39 (79); CIMS 125 (100).
Rea ction of th e Keton e 12 w ith m -CP BA. To a mixture
of 3.6 g (20.9 mmol) of m-CPBA and 7.0 g (83.3 mmol) of
NaHCO3 in 50 mL of CH2Cl2 was added 1.1 g (10.4 mmol) of
(39) Møller, C.; Plesset, M. S. Phys. Rev. 1934, 46, 618.
(40) Hariharan, P. C.; Pople, J . A. Chem. Phys. Lett. 1972, 66, 217.
(41) Hehre, W. J .; Radom, L.; Schleyer, P.v. R.; Pople, J . A. Ab Initio
Molecular Orbital Theory; J ohn Wiley and Sons: New York, 1986; p
36.
(42) Aldrichim. Acta 1983, 16, 3.

Ring Expansion of a Two-Carbon Bridged Spiropentane
J . Org. Chem., Vol. 63, No. 5, 1998 1399
12. After being stirred for 48 h, the mixture was washed with
two 100 mL portions of 10% Na2SO3 and then 200 mL of
saturated NaHCO3. The organic layer was dried over Na2SO4
and concentrated in vacuo. The product was purified by silica
gel column chromatography using 1:1 Et2O:pentane as the
eluant. The reaction was extremely slow, and only 0.115 g of
20 (Rf ) 0.37) was isolated. Recovered starting material
accounted for the remaining material.
5-[(N,N-Dim eth yla m in o)m eth ylen e]tr icyclo[4.1.0.01,3]-
h ep ta n -4-on e (22). To 1.07 g (9.9 mmol) of the ketone 5 was
added 2.86 g (16.4 mmol) of tert-butoxybis(dimethylamino)-
methane dropwise over 45 min. The mixture was stirred
under argon at room temperature for 36 h. The mixture was
transferred to a 100 mL flask with the aid of Et2O. The Et2O
was removed in vacuo, and the excess tert-butoxybis(dimethyl-
amino)methane was removed under high vacuum (1.5-2.0
Torr) at room temperature. Silica gel column chromatography
of the viscous, maroon residue using 85:15 Et2O:MeOH (Rf )
0.82) as the eluant gave 1.37 g of 22 as a deep red-orange oil.
20: 1H NMR δ 0.79-0.84 (1H, t of d), 0.92-0.99 (1H, m),
1.28-1.32 (1H, m), 1.81-1.84 (1H, m), 2.30-2.48 (3H, m),
4.05-4.10 (1H, t of d); 13C NMR δ 9.32 (d), 12.63 (t), 21.19 (t),
28.27 (t), 55.42 (d), 171 (s); GC/MS 84 (100), 55 (55), 42 (50);
CIMS 113 (100); HRMS calcd for C6H8O2 112.0524, found
112.0524.
Rea ction of th e Keton e 13 w ith m -CP BA. To 2.8 g (16.1
mmol) of m-CPBA and 5.4 g (64.3 mmol) of NaHCO3 in 40 mL
of CH2Cl2 was added 1.0 g (8.2 mmol) of 13 in 8 mL of CH2Cl2.
After being stirred for 48 h, the mixture was washed with 20
mL of 10% Na2SO3 and then 20 mL of saturated NaHCO3. The
organic layer was dried over Na2SO4 and concentrated in
vacuo. Silica gel column chromatography using 3:1 pentane:
CH2Cl2 as the eluant gave 0.083 g of 21 (Rf ) 0.31). The
reaction was extremely slow, and recovered starting material
accounted for the remaining material.
22: IR 1686, 1597 cm-1 1H NMR δ 1.50-1.54 (m, 2H),
;
1.64-1.68 (t, 1H), 1.79-1.84 (m, 2H), 1.98-2.01 (d of d, 1H),
3.11 (s, 6H), 7.03 (s, 1H); 13C NMR δ 18.31 (d), 19.87 (t), 19.99
(t), 22.94 (s), 29.84 (d), 109.48 (s), 146.69 (d), 204.56 (s), the
nitrogen methyl groups were not observed even using a pulse-
delay of 10 s; GC/MS 163 (100), 120 (59), 108 (50), 94 (43), 81
(55), 42 (89); CIMS 164 (100); HRMS calcd for C10H13NO
163.0998, found 163.0997.
5-Dia zotr icyclo[4.1.0.01,3]h ep ta n -4-on e (23). To 1.37 g
(8.40 mmol) of 22 in 50 mL of CH2Cl2 was added 1.70 g (14.1
mmol) of methanesulfonyl azide in one portion. The flask was
kept in the dark, and the progress of the reaction was
monitored by TLC (85:15 Et2O:MeOH). After the mixture was
stirred for 72 h under argon, no starting material could be
detected, and to the deep red solution was added 150 mL of
CH2Cl2. The organic solution was washed with three 50 mL
portions of 10% aqueous NaOH. The combined aqueous
washings were extracted with 50 mL of CH2Cl2, and then the
total organic layer was dried over Na2SO4. The CH2Cl2 was
removed in vacuo, and silica gel column chromatography of
the remaining red, viscous oil using 1:1 pentane:Et2O contain-
ing 1.5% Et3N by volume afforded 0.327 g of 23 as a deep
orange-red oil.
21: IR 1728 cm-1; 1H NMR δ 0.23-0.28 (2H, q), 0.52-0.58
(2H, m), 0.80-0.89 (2H, m), 0.95-1.05 (2H, m), 1.08-1.16 (1H,
m), 1.57-1.65 (1H, m), 3.87-3.89 (2H, d); 13C NMR δ 3.11,
8.25, 9.84, 12.88, 69.13, 174.90; GC/MS 69 (100), 39 (24); CIMS
141 (100). Anal. Calcd for C8H12O2: C, 68.6; H, 8.6. Found:
C, 68.4; H, 8.6.
Rea ction of Keton e 12 w ith Dia zom eth a n e. Diazo-
methane was formed from 3.5 g (16.4 mmol) of Diazald using
the procedure described by the Aldrich Chemical Co.42 and
added to 1.0 g (10.4 mmol) of 12 in 10 mL of absolute MeOH.
After the mixture was stirred at room temperature for 36 h,
the flask was cooled in an ice bath and excess diazomethane
was decomposed through careful addition of an ethereal
solution of acetic acid. Product analysis by GC and GC/MS
showed that bicyclo[4.1.0]heptan-2-one (14) and bicyclo[4.1.0]-
heptan-3-one (15) were present in a 3:1 ratio, respectively.
Rea ction of th e Keton e 13 w ith Dia zom eth a n e. Dia-
zomethane was formed from 2.5 g (11.7 mmol) of Diazald using
the procedure described by the Aldrich Chemical Co.42 and
added to 0.50 g (4.03 mmol) of 13 in 4 mL of absolute MeOH.
After the mixture was stirred at room temperature for 36 h,
the flask was cooled in an ice bath, and excess diazomethane
was decomposed through careful addition of an ethereal
solution of acetic acid. Product analysis by GC and GC/MS
showed that 1,3-dicyclopropyl-2-propanone (16) and 1,3-dicy-
clopropyl-1-propanone (17) were present in a 2:1 ratio, respec-
tively.
Rela tive Ra te Con sta n ts for Rea ction of th e Keton es
5, 12, a n d 13 w ith Dia zom eth a n e. Gen er a l p r oced u r e.
To an ethereal solution of diazomethane cooled in an ice bath
was added a mixture of two ketones dissolved in absolute
MeOH. Aliquots were removed at regular time intervals,
immediately transferred to test tubes that had been precooled
in ice, and quenched by addition of an ethereal solution of
acetic acid. Product analyses were determined by GC through
comparison with the retention times of authentic samples.
Typically, an excess of the less reactive ketone was used in
order to detect its respective products. The product ratios were
corrected to account for this and were plotted as a function of
reaction time. The product ratio was extrapolated to time zero,
thus giving the relative rate constants.
23: IR 2080, 1687 cm-1; 1H NMR δ 1.65-1.69 (d of d, 1H),
1.81-1.86 (t of d, 1H), 1.98-2.09 (m, 3H), 2.10-2.14 (d of d,
1H); 13C NMR δ 14.97, 18.86, 19.03, 22.12, 29.43, 65.69, 199.20;
CIMS 135 (24), 107 (21), 79 (100).
Attem p ted Wolff Rea r r a n gem en t of th e Dia zo Keton e
23 in Meth a n ol. A solution of 0.050 g (0.37 mmol) of 23 in 7
mL of absolute MeOH was purged with argon, immersed in
an ice-water bath, and irradiated for 1 h with a 450 W
medium-pressure mercury arc lamp. Thin-layer chromatog-
raphy (1:1 pentane:Et2O) indicated that 23 had been con-
sumed. Many spots were present, and the solution contained
a tan polymeric mass. Proton NMR analysis of the mixture
did not support the presence of the desired ring-contracted
product. The only product isolated from this reaction was
5-methoxytricyclo[4.1.0.01,3]heptan-4-one (26).
26: IR 1747 cm-1; 1H NMR δ 1.05-1.09 (1H, q), 1.16-1.20
(1H, m), 1.44-1.46 (1H, t), 1.69-1.73 (2H, d), 1.86-1.90 (1H,
t), 3.31 (3H, s), 3.41 (3H, s), 4.05-4.08 (1H, t); GC/MS 138 (5),
107 (99), 79 (100), 67 (60), 39 (94).
5-Meth oxytr icyclo[4.1.0.01,3]h ep ta n -4-on e (26). To 5.7
mL of a 1.0 M THF solution of NaHMDS cooled in ice-water
was added 0.355 g (2.82 mmol) of 27 in 28 mL of THF dropwise
over 2.5 h. The solution was stirred for 30 min, and then 0.40
g (2.82 mmol) of CH3I in 7 mL of THF was added dropwise
over 1 h. The solution was stirred at room temperature for
24 h and then poured into 50 mL of Et2O and 50 mL of water.
The aqueous layer was extracted with two 40 mL portions of
Et2O. The total organic layer was washed with 40 mL of
saturated NH4Cl, dried over Na2SO4, and concentrated in
vacuo. Silica gel column chromatography of the pink residue
afforded 0.224 g of the monomethyl ether of 27 (Rf ) 0.8). To
0.125 g (0.893 mmol) of the monomethyl ether of 27 and 0.167
g (1.427 mmol) of N-methylmorpholine N-oxide in 9 mL of
CH2Cl2 was added two spatulafuls of 4 Å molecular sieves.
Then 0.015 g (0.045 mmol) of TPAP was added in one portion.
After 18 h, the solution was diluted to 50 mL with additional
CH2Cl2 and then washed with 15 mL of saturated Na2SO3, 15
mL of saturated NaCl, and 15 mL of saturated CuSO4. The
solution was dried over Na2SO4 and concentrated in vacuo.
Silica gel column chromatography using 2:1 pentane:Et2O as
the eluant gave 0.054 g of 26 (Rf ) 0.27). Spectral data for
A. 12 vs 13. A solution of 0.284 g (2.29 mmol) of 13 and
0.105 g (0.96 mmol) of 12 in 15.0 mL of absolute MeOH was
added to an excess of diazomethane (9.2 mmol). Aliquots were
removed and quenched 5, 10, 15, 20, 30, 45, and 60 min
following the start of the reaction.
B. 12 vs 5. A solution of 0.900 g (9.34 mmol) of 12 and
0.011 g (0.10 mmol) of 5 in 2.0 mL of absolute MeOH was
added to an excess of diazomethane (20 mmol). Aliquots were
removed 1, 2, 3, 4, 5, and 10 min following the start of the
reaction.

1400 J . Org. Chem., Vol. 63, No. 5, 1998
Wiberg and Snoonian
this sample were identical to that obtained from photolysis of
23 in methanol.
of benzaldehyde dimethyl acetal. The mixture was stirred for
5 min, and then 15 mg of p-toluenesulfonic acid monohydrate
was added in one portion. After 6 h, TLC (Et2O) showed that
the diol had been consumed. The reaction mixture was diluted
with 7 mL of CH2Cl2. The organic solution was washed with
5 mL of 0.1 M NaOH and then dried over Na2SO4. After
concentration in vacuo, proton NMR analysis of the crude
residue showed that two benzylic resonances were present in
the spectrum, but the spectrum also showed that benzaldehyde
was also present. The benzaldehyde was removed by heating
the mixture to 40 °C at 2 Torr for 6 h. Silica gel column
chromatography using 4:1 pentane:Et2O as the eluant gave
each epimer of the benzylidene acetal of 27 as clear, colorless
liquids.
Attem p ted Wolff Rea r r a n gem en t of 23 in Dim eth yl-
a m in e. To 0.050 g (0.37 mmol) of 23 in a Pyrex tube cooled
in an ice-water bath was added 7 mL of dimethylamine with
the aid of a coldfinger. The mixture remained immersed in
the ice-water bath and fitted with the coldfinger while being
irradiated with a 450 W medium-pressure mercury arc lamp.
Once TLC (1:1 pentane:Et2O) had indicated 23 had been
consumed, the dimethylamine was allowed to evaporate at
room temperature. The product was purified by silica gel
column chromatography using 3:1 Et2O:pentane as the eluant
(Rf ) 0.23). The product was determined to be 2-(N,N-
dimethylamino)vinyl 2-methylenecyclopropyl ketone, 28, via
the decoupling experiments described in the Supporting
Information.
39a : 1H NMR δ 1.12-1.15 (m, 1H), 1.23-1.27 (d of d, 1H),
1.52-1.57 (m, 2H), 1.71-1.75 (d of d, 1H), 1.94-1.97 (d of d,
1H), 2.38-2.41 (t of d, 1H), 4.86-4.88 (d, 2H), 5.84 (s, 1H),
7.37-7.53 (m, 5H); GC/MS 214 (15), 185 (43), 167 (37), 141
(28), 129 (84), 115 (64), 91 (81), 84 (67), 79 (100); CIMS 215
(100), 107 (93), Rf ) 0.62.
28: IR 1658, 1620, 1579 cm-1; 1H NMR δ 1.51-1.59 (1H, t
of t), 1.77-1.83 (1H, m), 2.40-2.46 (1H, m), 2.83 (NCH3,
broad), 3.05 (NCH3, broad), 5.03-5.07 (1H, d, J ) 12.6 Hz),
5.41-5.49 (2H, d of t) 7.56-7.60 (1H, d, J ) 12.6 Hz); 13C NMR
δ 11.7 (t), 25.7 (d), 94.1 (d), 103.2 (t), 133.7 (s), 152.5 (d), 194.5
(s); CIMS 152 ) M + 1, (100).
Attem p ted Syn th esis of th e Alk en e 35 by Cor ey-
Win ter Rea ction of 38. A solution of 0.100 g (0.595 mmol)
of 38 in 2 mL of triethyl phosphite was heated to reflux using
a 125 °C oil bath. The progress of the reaction was monitored
by TLC (Et2O) and was complete after stirring for 5 h at 125
°C as evidenced by the consumption of the thiocarbonate (Rf
) 0.77). A small amount of the cooled reaction mixture was
dissolved in CH2Cl2, and analysis by GC/MS found only
(EtO)3P and (EtO)3PdS. Analysis by GC showed that a third
peak was present and was determined to be toluene by
comparison with authentic toluene. The toluene was not
detected by GC/MS because it eluted during the initial 3 min
solvent delay.
Attem p ted Syn th esis of th e Alk en e 35 by Rea ction of
39a a n d 39b w ith n -Bu tyllith iu m . To 0.185 g (0.864 mmol)
of the acetals 39a and 39b in 4 mL of petroleum ether (bp
35-65 °C) was added 1.1 mL of a 1.6 M hexane solution of
n-BuLi (1.73 mmol) dropwise over 30 min. The reaction
progress was monitored by TLC (4:1 pentane:Et2O). After 1
h, only the starting material was detected, and after 3 h, the
solution was now orange, but again only starting material was
present. A small aliquot of this orange solution was removed
and quenched with D2O (99.8% atom-d). This sample was
dried, and analysis by GC/MS showed that in addition to small
baseline peaks 39a and 39b were still present, but their mass
had increased by 1. After 30 h, the deep orange solution was
quenched with 2 mL of water and added to 20 mL of Et2O
and 10 mL of water. The aqueous layer was extracted with
10 mL of Et2O. The total organic layer was washed with 10
mL of saturated NH4Cl, and dried over Na2SO4. The reaction
mixture was analyzed by gas chromatography. Toluene and
valerophenone (n-butyl phenyl ketone) were detected. The
peaks had retention times identical to those of authentic
samples of toluene and valerophenone.
39b: 1H NMR δ 1.08-1.13 (m, 1H), 1.18-1.21 (d of d, 1H),
1.61-1.64 (t of d), 1.88-1.92 (d of d, 1H), 1.99-2.03 (d of d,
1H), 2.23-2.27 (t of d, 1H), 4.79-4.82 (t of d, 1H), 5.09-5.10
(d of d, 1H), 6.01 (s, 1H), 7.37-7.53 (m, 5H); GC/MS 214 (9),
185 (31), 167 (20), 141 (18), 129 (60), 115 (38), 91 (44), 84 (100),
79 (38); CIMS 215 (100.0), 107 (93.0), Rf ) 0.69.
3-[(N,N-Dim eth ylam in o)m eth ylen e]bicyclo[3.1.0]h exan -
2-on e (32). To 2.0 g (2.1 mmol) of 12 was added dropwise 5.4
g (3.1 mmol) of tert-butoxybis(dimethylamino)methane fol-
lowed by heating in a 70 °C oil bath for 36 h. The viscous,
maroon mixture was distilled (0.5 Torr, 35-90 °C) to remove
excess Bredereck’s reagent. The remaining material was a
solid and proved to be 2.8 g (90% yield) of 32.
32: IR 1688, 1597 cm-1; 1H NMR δ 0.44-0.48 (q, 1H), 1.02-
1.09 (1H, t of d), 1.77-1.81 (2H, d of d), 2.86-2.95 (m, 2H),
2.99 (s, 6H), 7.09 (s, 1H); 13C NMR δ 13.79, 15.39, 26.81, 29.51,
41.90, 99.70, 146.79, 203.4; GC/MS 151 (100), 122 (19), 108
(19), 94 (14); HRMS calcd for C9H13NO 151.0997, found
151.1000.
3-Dia zobicyclo[3.1.0]h exa n -2-on e (31). To a solution of
0.70 g (4.64 mmol) of 32 in 16 mL of CH2Cl2 was added 1.10
g (5.58 mmol) of p-toluenesulfonyl azide in one portion. The
solution was kept in the dark. After 72 h, the red solution
was concentrated by rotary evaporation to give a yellow-orange
solid. This solid was washed with 75 mL of a 1:1 pentane:
Et2O solution and then filtered through a funnel containing a
glass wool plug to give a yellow filtrate. It was concentrated
by rotary evaporation, and silica gel column chromatography
using 1:1 pentane:Et2O as the eluant (Rf ) 0.32) gave 0.40 g
of 31 as an orange oil.
31: IR 2086, 1681 cm-1 1H NMR δ 0.71-0.755 (m, 1H),
;
1.20-1.27 (m, 1H), 1.78-1.84 (m, 2H), 2.94-3.01 (1H) 3.12-
3.26 (1H); GC/MS 122 (100), 94 (12), 66 (82), 39 (85); HRMS
calcd for C6H6N2O 122.0480, found 122.0479.
Wolff R ea r r a n gem en t of t h e Dia zo Ket on e 31 in
MeOH. A solution of 0.20 g (1.65 mmol) of 31 in 8 mL of
MeOH that had been purged with argon was immersed in an
ice-water bath that also contained a 450 W medium-pressure
mercury arc-lamp. The yellow color of the solution was gone
after 3 h of photolysis. Analysis by GC/MS showed that two
products with very similar retention times were produced in
a 2:1 ratio in 90% yield. These two products were purified by
preparative gas chromatography using a column of 13% OV101
on AWDMS at 115 °C. The two products were not separable
Tr icyclo[4.1.0.01,3]h ep ta n -4,5-d ion e (24). To 0.100 g
(0.613 mmol) of 22 in 5 mL of CH2Cl2 in a Pyrex tube was
added 3 mg of Rose Bengal. A 500 W tungsten lamp was
placed 15 cm away from the tube, and oxygen was bubbled
through the solution. The bottom of the tube was immersed
in a dry ice/acetone bath such that most of the tube was
exposed to the incident light from the tungsten lamp. The
R-enamino ketone (22) was consumed in 1.5 h (TLC, 85:15
Et2O:MeOH), and then the CH2Cl2 solution was concentrated
to a volume of 0.5 mL. This concentrated solution was passed
through a plug of silica gel using Et2O as the eluant. One
product that was UV-active with an Rf ) 0.6 (Et2O) was
obtained. Concentration in vacuo gave 3 mg of a yellow solid
that was the desired R-diketone (24). The compound decom-
posed upon standing.
1
under these conditions but were determined by H NMR and
GC/MS to be a 2:1 mixture of endo- and exo-2-carbomethoxy-
bicyclo[2.1.0]pentane. The 1H NMR spectral data were in
complete agreement with those reported for these compounds.9
Rea ction of LiAlH4 w ith th e r-En a m in o Keton e 22. To
0.170 g (1.04 mmol) of 22 in 13 mL of Et2O and 4.0 mL of
THF cooled in an ice bath was added 1.2 mL of a 1.0 M Et2O
solution of LiAlH4 over 5 min. The solution was stirred in the
ice bath for 30 min. TLC (85:15 Et2O:MeOH) indicated that
the starting material had been consumed and suggested that
one product had formed. Excess hydride was then quenched
24: IR 1751, 1740 cm-1 13C NMR δ 26.05, 28.33, 30.53,
;
198.22; CIMS 123 (30), 94 (82), 66 (100).
Ben zylid en e Aceta l of th e Diol 27. To 0.170 g (1.35
mmol) of 27 in 3 mL of CH2Cl2 was added 0.442 g (2.90 mmol)

Ring Expansion of a Two-Carbon Bridged Spiropentane
J . Org. Chem., Vol. 63, No. 5, 1998 1401
by careful addition of water. The suspension was diluted with
Et2O to a volume of 50 mL and washed with 20 mL of
saturated NH4Cl and then 20 mL of saturated NaCl. The
combined aqueous layer was extracted with 40 mL of Et2O,
and the total organic layer was dried over Na2SO4. The Et2O
was removed in vacuo, and silica gel column chromatography
of orange residue using 85:15 Et2O:MeOH as the eluant (Rf )
0.36) gave 0.124 g of 3-hydroxy-4-[(N,N-dimethylamino)meth-
yl]toluene (44) as a clear, colorless liquid that solidified as a
white solid when stored at -10 °C.
atom-d) was added to the flask. A standard NMR tube was
capped with a rubber septum and purged with argon, and 280
µL of the 1.0 M THF-d8 solution of LHMDS was added to the
tube by syringe. The tube was placed in the NMR sample tube
holder to the required level, and the tube was placed in a dry
ice/acetone bath while still under the argon purge. A solution
of 0.020 g (0.185 mmol) of 5 in 300 µL of THF-d8 was added
dropwise by syringe to the NMR tube over 2 min. The tube
was then quickly taken out of the cold bath and lowered into
the probe of the spectrometer that was precooled to -80 °C.
The residual THF signal at 3.7 ppm served as the lock
frequency, the block size was 32K, and a recycle delay time of
10 s between successive pulses was used to avoid signal/noise
problems due to possible saturation broadening. The spectra
at -80 °C 5 and 60 min following addition of the ketone were
recorded. Then the probe was warmed to -65 °C over 20 min
and new signals between 6 and 7 ppm started to appear. The
probe was then warmed to -50 °C, and the enolate proton at
4.15 ppm was now gone as were the cyclopropane signals. The
peaks at 6-7 ppm were the only peaks in the spectrum. At
each temperature where the spectrum was recorded, the
fluctuation in temperature was only (1°.
Ma t r ix P h ot olysis of t h e Dia zok et on es 23 a n d 31.
Gen er a l P r oced u r e. Samples were prepared by 40:60 dilu-
tion of the respective R-diazo ketone with Nujol by weight and
layered on a 2.5 cm × 0.3 cm polished NaCl disk. The NaCl
disk was then placed in a copper optical sample holder and
screwed onto the cooling tip of a Displex closed-cycle helium
cryostatic unit. The sample was quickly frozen to 77 K with
liquid nitrogen. After the mixture was cooled to 77 K, a
vacuum shroud equipped with NaCl optical windows was
quickly placed over the sample holder, the sample chamber
was evacuated, and the sample was cooled to 15 K. The
experiments were carried out at a pressure of 1.0 × 10-5 Torr.
The sample was irradiated with a 1000 W xenon arc lamp at
a distance of 3 cm from the sample. Due to thermal heating
of the sample by the xenon arc, the temperature of the sample
was closely monitored during irradiation. When the temper-
ature would reach 20 K, irradiation was briefly interrupted
until the temperature of the sample had cooled back down to
15 K. Thus, irradiation was carried out in intervals of 5-15
min at 15-20 K. After each irradiation period, the sample
chamber on the Displex was placed into a CW infrared
spectrometer. Once irradiation of the sample at 15-20K was
completed, the temperature was increased in 20-30 K incre-
ments, and the infrared spectra were recorded at these
temperatures.
44: 1H NMR δ 2.30 (s, 3H), 2.33 (s, 6H), 3.61 (s, 2H), 6.59-
6.62 (d, 1H, J ) 7.5 Hz), 6.67 (s, 1H), 6.84-6.86 (d, 1H, J )
7.5 Hz); 13C NMR δ 21.17, 44.38, 62.53, 116.58, 118.90, 119.61,
128.01, 138.64, 157.79; GC/MS 165 (60), 121 (52), 91 (32), 44
(100); HRMS calcd for C10H15NO 165.1153, found 165.1153.
Attem p ted Tr a p p in g of th e En ola te Ion 36. To 0.329 g
(2.0 mmol) of 1,1,1,3,3,3-hexamethyldisilazane in 5.1 mL of
THF cooled an ice-water bath was added 1.3 mL of a 1.6 M
hexane solution of n-BuLi dropwise over 5 min. The light tan
solution was stirred for an additional 10 min, the flask was
cooled to -78 °C, and 0.2 g (1.9 mmol) of 5 in 3.7 mL of THF
was added dropwise over 30 min. The solution was stirred at
-78 °C for an additional 45 min, and then 0.733 g (2.8 mmol)
of tert-butyldimethylsilyl trifluoromethanesulfonate in 5.5 mL
of THF was added over 2 min. The solution was stirred at
-78 °C for 15 min and then added to 20 mL of saturated,
aqueous K2CO3 and 20 mL of Et2O. The aqueous layer was
extracted with 10 mL of Et2O. The total organic layer was
dried over Na2SO4 and then concentrated in vacuo. Analysis
by proton NMR and GC/MS showed that the only product
obtained from this reaction was the tert-butyldimethylsilyl
ether of m-cresol.
1H NMR: δ 0.20 (s, 6H), 0.99 (s, 9H), 2.31 (s, 3H), 7.09-
7.14 (t, 1H), 6.77-6.79 (d, 1H, J ) 7.6 Hz), 6.64-6.67 (m, 2H);
GC/MS 223 (3), 222 (14), 166 (19), 165 (100).
Rea ction of th e En ola te Ion 36 w ith CH3OD. To 0.329
g (2.0 mmol) of 1,1,1,3,3,3-hexamethyldisilazane in 5.1 mL of
THF cooled in an ice-water bath was added 1.3 mL of a 1.6
M hexane solution of n-BuLi dropwise over 5 min. The
solution was stirred for an additional 10 min and then cooled
to -78 °C, and 0.2 g (1.9 mmol) of 5 in 3.7 mL of THF was
added dropwise over 30 min. It was stirred at -78 °C for an
additional 45 min, and then 2 mL of CH3OD was added at
-78 °C over 1 min. The solution was stirred at -78 °C for 15
min and then added to 20 mL of water and 20 mL of Et2O.
The layers were separated, and TLC (3:1 pentane:Et2O)
showed only one spot with an Rf ) 0.55 that was identical to
that of the starting material. The organic layer was dried over
Na2SO4 and then concentrated in vacuo. The 1H NMR
spectrum of the crude residue did not display any aromatic or
olefinic signals. Silica gel column chromatography using 3:1
pentane:Et2O as the eluant afforded pure product that by GC/
Ack n ow led gm en t . This investigation was sup-
ported by the National Science Foundation. We thank
Prof. Paul Lahti for his assistance with the matrix
isolation experiments.
2
MS, 1H NMR, and H NMR was determined to be R-monodeu-
terated 5-d a and 5-d b.
5-d a a n d 5-d b: IR 1734 cm-1; 1H NMR δ 0.95-1.02 (q, 1H),
1.55-1.61 (d of d, 1H), 1.65-1.75 (t of d, 1H), 1.98-2.02 (t,
1H), 2.16-2.28 (m, 2H), 2.39-2.47 and 2.67-2.70 (1H, ABX),
2.61-2.65 (d of d, 1H); 2H NMR (CHCl3) δ 2.37 (5-d b), 2.46
(5-d a ); GC/MS 109 (39), 81 (36), 80 (95), 79 (39), 67 (46), 51
(24), 39 (100).
Low -Tem p er a tu r e NMR Obser va tion of 36. In a dry-
box, 0.341 g (2.04 mmol) of solid LiHMDS was transferred into
a 25 mL flask capped with a rubber septum. The flask was
removed from the drybox, and then 2.0 mL of THF-d8 (99.5%
Su p p or tin g In for m a tion Ava ila ble: Calculated energies
of reference compounds for group energies and estimation of
group equivalents. Analysis of NMR data for compound 28.
NMR data for compounds 5, 10, 11, 18-20, 22-24, 26, 28,
31, 32, 39, and 44 (28 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
J O970980E