Geminal Acylation with Methyl-Substituted Analogues of 1,2-Bis[(trimethylsilyl)oxy]cyclobutene

Article abstract of DOI:10.1021/jo971055v

BF₃·Et₂O-catalyzed geminal acylation of ketones and acetals with 3-methyl-1,2-bis[(trimethylsilyl)oxy)]cyclobutene (3) provided methylcyclopentanediones in yields that ranged from 40 to 94%. The best substrates were unhindered cycloh

Full text of DOI:10.1021/jo971055v

8722
J . Org. Chem. 1997, 62, 8722-8729
Gem in a l Acyla tion w ith Meth yl-Su bstitu ted An a logu es of
1,2-Bis[(tr im eth ylsilyl)oxy]cyclobu ten e
Sheldon N. Crane, Tracy J . J enkins, and D. J ean Burnell*
Department of Chemistry, Memorial University of Newfoundland,
St. J ohn’s, Newfoundland A1B 3X7, Canada
Received J une 11, 1997X
BF3‚Et2O-catalyzed geminal acylation of ketones and acetals with 3-methyl-1,2-bis[(trimethylsi-
lyl)oxy)]cyclobutene (3) provided methylcyclopentanediones in yields that ranged from 40 to 94%.
The best substrates were unhindered cyclohexanones. With acetals, stereochemical preferences
in the initial Mukaiyama-like aldol step giving cyclobutanones translated into the stereochemistry
of the ultimate cyclopentanedione products. With ketones, equilibration of the initial cyclobutanone
compounds resulted in cyclopentanedione products with a different stereochemical preference. The
gem-dimethylcyclobutene reagent 4 reacted with ketones to give gem-dimethylcyclopentanediones
in modest yield. The process was much more stereochemically efficient than the reaction with 3.
Rearrangement from the initial cyclobutanone compound was partially diverted toward air-sensitive
3-furanone compounds and ring-opened 1,2-diones. Only furanones (e.g., 52 and 53) were isolated
from reactions with the tetramethylcyclobutene 51.
Sch em e 1
In tr od u ction
The Lewis acid-catalyzed geminal acylation of an acetal
with 1,2-bis[(trimethylsilyl)oxy]cyclobutene (1) was first
reported by Kuwajima and co-workers1 as a two-step
process. An initial Mukaiyama-like aldol reaction gave
a cyclobutanone derivative, which underwent acid-
induced rearrangement to provide a 2-substituted 1,3-
cyclopentanedione. Subsequent developments, mainly in
our laboratory, led to a one-pot procedure that was more
efficient for obtaining cyclopentanediones,2,3 to analogous
reactions with 2,4 and to reactions of 1 directly on ke-
tones,5 as illustrated in Scheme 1. Synthetic approaches
to diverse natural products, such as trichothecanes,6
â-bulnesene,7 estrone,8 khusimone,2 pentalenene,9 and
fredericamycin A,10 employed geminal acylation with 1
as a key step.11 Our one-pot geminal acylation method
has been cleverly incorporated into tandem processes by
Curran and co-workers.12,13
alkyl groups or a more elaborate functionality that could
survive the acyloin conditions14 by which 1 is prepared.
Cyclopentane moieties bearing a single methyl group or
a gem-dimethyl group are seen in many natural products.
Therefore, we chose initially to explore reactions with the
monomethylcyclobutene 3 and the gem-dimethylcy-
clobutene 4. Even in these simple analogues, questions
regarding reactivity in the initial, Mukaiyama-like step
and the course of rearrangement in the second step, as
well as issues of regio- and stereochemistry, could be
addressed. Many alkyl-substituted 1,2-bis[(trimethylsi-
lyl)oxy]cyclobutene compounds have been prepared, no-
tably by Ru¨hlmann,15 and one example of geminal
acylation with a vicinally disubstituted cyclobutene has
been reported.12
(9) (a) Wu, Y.-J .; Zhu, Y.-Y.; Burnell, D. J . J . Org. Chem. 1994, 59,
104-110. (b) Zhu, Y.-Y., Burnell, D. J . Tetrahedron: Asymmetry 1996,
7, 3295-3304.
(10) (a) Parker, K. A.; Koziski, K. A.; Breault, G. Tetrahedron Lett.
1985, 26, 2181-2184. (b) Saint-J almes, L.; Lila, C.; Xu, J . Z.; Moreau,
L.; Pfeiffer, B.; Eck, G.; Pelsez, L.; Rolando, C.; J ulia, M. Bull. Soc.
Chim. Fr. 1993, 130, 447-449. (c) Wendt, J . A.; Gauvreau, P. J .; Bach,
R. D. J . Am. Chem. Soc. 1994, 116, 9921-9926.
An important extension of the geminal acylation
methodology would be to employ analogues of 1 bearing
X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) (a) Nakamura, E.; Kuwajima, I. J . Am. Chem. Soc. 1977, 99,
961-963. (b) Shimada, J .; Hashimoto, K.; Kim, B. H.; Nakamura, E.;
Kuwajima, I. J . Am. Chem. Soc. 1984, 106, 1759-1773. (c) Nakamura,
E.; Kuwajima, I. Organic Syntheses; Wiley: New York, 1987; Vol. 65,
pp 17-25.
(2) (a) Wu, Y.-J .; Burnell, D. J . Tetrahedron Lett. 1988, 29, 4369-
4372. (b) Burnell, D. J .; Wu, Y.-J . Can. J . Chem. 1990, 68, 804-811.
(3) Wu, Y.-J .; Strickland, D. W.; J enkins, T. J .; Liu, P.-Y.; Burnell,
D. J . Can. J . Chem. 1993, 71, 1311-1318.
(4) Wu, Y.-J .; Burnell, D. J . Tetrahedron Lett. 1989, 30, 1021-1024.
(5) J enkins, T. J .; Burnell, D. J . J . Org. Chem. 1994, 59, 1485-1491.
(6) Anderson, W. K.; Lee, G. E. J . Org. Chem. 1980, 45, 501-506.
(7) Oppolzer, W.; Wylie, R. D. Helv. Chim. Acta 1980, 63, 1198-
1203.
(11) Other developments and synthetic uses of Lewis acid-catalyzed
geminal acylation with 1: (a) Anderson, W. K.; Lee, G. E. Synth.
Commun. 1980, 10, 351-354. (b) Nakamura, E.; Shimada, J ; Kuwa-
jima, I. J . Chem. Soc., Chem. Commun. 1983, 498-499. (c) Bunnelle,
W. H.; Shangraw, W. R. Tetrahedron 1987, 43, 2005-2011. (d)
Martinez, R. A.; Rao, P. N.; Kim, H. K. Synth. Commun. 1989, 19,
373-377. (e) Pandey, B.; Khire, U. R.; Ayyangar, N. R. Synth.
Commun. 1989, 19, 2741-2747. (f) Liu, P.-Y.; Burnell, D. J . J . Chem.
Soc., Chem. Commun. 1994, 1183-1184. (g) Liu, P.-Y.; Wu, Y.-J .;
Burnell, D. J . Can. J . Chem. 1997, 75, 656-664.
(12) Balog, A.; Curran, D. P. J . Org. Chem. 1995, 60, 337-344.
(13) Balog, A.; Geib, S. J .; Curran, D. P. J . Org. Chem. 1995, 60,
345-352.
(14) Bloomfield, J . J .; Nelke, J . M. Organic Syntheses; Wiley: New
York, 1988; Collect. Vol. VI, pp 167-172.
(8) Burnell, D. J .; Wu, Y.-J . Can. J . Chem. 1989, 67, 816-819.
(15) Ru¨hlmann, K. Synthesis 1971, 236-253.
S0022-3263(97)01055-4 CCC: $14.00 © 1997 American Chemical Society

Geminal Acylation
J . Org. Chem., Vol. 62, No. 25, 1997 8723
Ta ble 1. Rea ction s of 3 w ith Keton es a n d Th eir Cor r esp on d in g Aceta ls Der ived fr om 1,2-Eth a n ed iol
a
Ratio obtained from the dibenzyl acetal.
Resu lts a n d Discu ssion
ever. However, with 4-tert-butylcyclohexanone and its
acetal (Table 1, entry 7) some modest selectivity was
apparent. An X-ray crystal structure of a 2,4-dinitro-
phenylhydrazone derivative 11c revealed that the major
isomer obtained from the ketone was 11a . Selectivity
was also evident in reactions between 3 and other
substituted cyclohexanones and their acetals (Table 1,
entries 4-6). (Although it was not feasible to determine
rigorously the stereochemistry of each component in
these product mixtures, the relative stereochemistry at
the spiro centers was inferred from the results presented
below.) It is important to note that the selectivity was
clearly different, even complementary, with ketones and
their corresponding acetals.
R ea ct ion s of Ket on es a n d Acet a ls w it h Mon o-
m eth ylcyclobu ten e 3. A variety of ketones and their
corresponding acetals, derived from 1,2-ethanediol, were
treated with 3 and BF3‚Et2O following the procedure that
we had developed for the reaction of 1 with ketones.5 In
this procedure, the initial aldol reaction was mediated
by BF3‚Et2O in dichloromethane under anhydrous condi-
tions, and then the second, rearrangement step was
initiated by addition of water and a large excess of
BF3‚Et2O. As can be seen in Table 1, the yields of cyclo-
pentanediones ranged from modest to excellent. Trends
were similar to those seen previously in the reactions of
1 with both ketones5 and acetals.2,3 The ketones gave
similar, or better, yields than did the acetals. Unencum-
bered cyclohexanones and their acetals gave the best
yields (Table 1, entries 3, 6, and 7). Cyclopentanone and
its acetal (Table 1, entry 2) gave more modest yields of
the spirodiketone 6. R-Substitution had a deleterious
effect on the efficiency of geminal acylation, especially
with the acetal (Table 1, entries 4 and 5).
Reactions with 3 introduced a stereochemical complex-
ity that had not been present in reactions with 1. The
reaction with butanone and its acetal (Table 1, entry 1)
provided 5a and 5b with no diastereoselectivity whatso-
In an effort to illuminate the reason for the stereo-
chemical difference between the ketone and the acetal

8724 J . Org. Chem., Vol. 62, No. 25, 1997
Crane et al.
versions of the geminal acylation, we isolated the prod-
ucts after only the first step in the reactions of 4-tert-
butylcyclohexanone and its acetal with 3. The ketone
provided two cyclobutanone compounds in a 3.3:1 ratio,
which was very similar to the 3.1:1 ratio for the cyclo-
pentanedione products in entry 7 (Table 1). (Minor
amounts of 11a and 11b, in a 2.6:1 ratio, were also
detected in the crude product even when no water or
extra BF3‚Et2O was added.) Comparison of the 13C NMR
shifts of signals arising from the cyclohexyl moiety with
those of the known, equatorial product with 15 indicated
that both of the cyclobutanone compounds had arisen by
equatorial attack on the ketone.16 Considerable similari-
ties between the NMR spectra of 12a and 12b and the
spectra of 15a and 15b allowed unequivocal assignment
of the structures of 12a and 12b. The isolation of
intermediates from acetals was carried out in conjunction
with an evaluation of the stereoselectivity of the geminal
acylation with different acetals. Reaction of the acetal
derived from 2,2-dimethyl-1,3-propanediol gave cyclo-
pentanediones 11a and 11b in a 1:2.4 ratio, which was
not significantly different from the 1:2.2 ratio for the
acetal derived from 1,2-ethanediol. Cyclobutanone de-
rivatives from the dimethyl and dibenzyl acetals were
obtained by following Kuwajima’s procedure.1 The dim-
ethyl acetal provided cyclobutanone compounds 13a and
13b in a 1:4.1 ratio. When this mixture was stirred in
TFA, 11a and 11b were produced in a ratio of 1:3.6. The
use of a dibenzyl acetal further improved selectivity.
Cyclobutanones 14a and 14b were obtained in a 1:7.4
ratio. In TFA, this mixture rearranged to 11a and 11b
in a 1:7.5 ratio. Cyclobutanones 14a and 14b were
desilylated with tetrabutylammonium fluoride (TBAF) to
keto alcohols 15a and 15b, and these proved to be
separable by chromatography. During chromatography,
the stereochemistry of the cyclopentanediones derived
from acetals was largely determined by stereochemical
preferences in the first, aldol reaction. The stereochem-
istry of the cyclopentanediones derived from ketones was
generally opposite to that from acetals and appeared to
reflect equilibration to the thermodynamically preferred
cyclobutanone.
R ea ct ion s of Ket on es w it h gem -Dim et h ylcyclo-
bu ten e 4. The results of reactions of 4 with many
ketones are presented in Table 2.17 Cyclobutene 3 had
shown a considerable reluctance to add to its face syn to
the methyl, but with cyclobutene 4 steric hindrance
between a methyl on the cyclobutene and the ketone
substrate seemed unavoidable. Hence, it was not sur-
prising that in many examples with 4 the yields of the
cyclopentanediones were modest, and a very significant
proportion of intractable material was generally obtained.
Addition of water and extra BF3‚Et2O was not necessary
to effect rearrangement to cyclopentanediones from any
of the enone substrates. The reaction with cyclohexenone
(Table 2, entry 10) only gave a 32% yield of 40, but this
was still considerably better than had been seen in the
reaction of cyclohexenone with 1.5 Both isophorone and
4,4-dimethylcyclohex-2-en-1-one (Table 2, entries 11 and
12) gave good yields of cyclopentanediones, although with
the former there was some isomerization of the double
bond during reaction. A comparison of the 13C NMR
spectrum of the predominant cyclopentanedione product
from isophorone with the spectra of products from 13,5
led to the assignment of structure 41. Despite the poor
yields, cyclopentanediones were produced from 4 with
much higher stereoselectivity than had been seen from
3. In two instances (Table 2, entries 7 and 9) one
diastereomer of the cyclopentanedione was produced very
predominantly, and the structures of their 2,4-dinitro-
phenylhydrazone derivatives (33c and 36b) were deter-
mined by X-ray crystallography.
1
a fraction of 15a also showed a set of H NMR signals
attributable tentatively a very small amount of 16. NOE
measurements with both 15a and 15b established that
the hydrogen of the methine of the cyclobutanone moiety
was syn to the cyclohexane ring. Hydrogenolysis of the
benzyl groups of either 15a or 15b over Pd on charcoal
in ethanol/acetic acid provided both 12a and 12b in a
5.2:1 ratio, which provided evidence of acid-mediated
equilibration between 12a and 12b. This was exactly the
ratio predicted by an AM1 calculation.17
The yields with 4 suffered from synthetically trouble-
some, yet mechanistically interesting, side reactions that
repeatably produced substituted furanones, 1,2-diones,
and lactones. The proportion of furanone in the product
mixtures did not seem to correlate in a straightforward
way with the structure of the ketone substrate.
A
comparison of entries 7 and 8 (Table 2) illustrates this.
Furanones were formed with little to no geometrical
preference (Table 2, entries 2, 6, and 7), and they oxidized
readily in air to dihydroxy compounds. Characterization
of oxidation products 45 and 46a /b, derived from 18 and
30a /b, was helpful in establishing the general structure
of the furanones.
These results lead to the following generalizations
regarding reactions with 3. The cyclobutanones obtained
from acetals undergo rearrangement to cyclopentanedi-
ones by inversion at the cyclohexyl C-1, with little
stereochemical scrambling. This was also true for the
processes with 1 for both acetals1b and ketones.5 Thus,
1,2-Diones were isolated in lesser amounts. Careful
analysis by 1H NMR of the reactions with cyclohexanone
(Table 2, entry 5) and 4-tert-butylcyclohexanone (Table
2, entry 9) showed that the â,γ-unsaturated compounds
(28a , 38a , and 39a ) were initially formed, and these
rapidly isomerized in the reaction medium to conjugated,
R,â-unsaturated diones (28b, 38b, and 39b). A secondary
rearrangement process led to minor amounts of lactones
42a ,b and 44a ,b from enone substrates (Table 2, entries
11 and 12).
(16) With the norbornyl system, exo addition of 3 was very likely
favored with both the ketone and its acetal, but, as can be seen in
entry 5, this system showed the largest, yet obviously different,
stereoselectivities with ketone and acetal.
(17) Dewar, M. J . S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J . J . P.
J . Am. Chem. Soc. 1985, 107, 3902-3909 using SPARTAN, Version
4.1 (Wavefunction, Inc., Irvine, CA).

Geminal Acylation
Ta ble 2. Rea ction s of 4 w ith Keton es
J . Org. Chem., Vol. 62, No. 25, 1997 8725
Sch em e 2
the reaction mixture without addition of extra BF3‚Et2O
and water. The structure of 48 was determined un-
equivocally by X-ray crystallography. This showed the
reaction had resulted from equatorial addition with
respect to the cyclohexanone ring and that the new C-C
bond was to C-1 of cyclobutene 4. Prolonged treatment
of cyclopentanediones with BF3‚Et2O did not provide any
furanone, but when 47 was added to neat BF3‚Et2O the
result was a 3:1 mixture of 26 and 27. On the other
hand, treatment of 47 with dilute BF3‚Et2O in dichlo-
romethane provided only cyclopentanedione 26. Simi-
larly, cyclobutanone 48 in neat BF3‚Et2O provided 36a
and 37 in an 8:1 ratio. With dilute BF3‚Et2O in dichlo-
romethane the ratio improved to 13:1, and BF3‚Et2O in
dichloromethane in the presence of a small amount of
water provided 36a exclusively.
The formation of furanone and the 1,2-diones can be
rationalized as illustrated (Scheme 2) with the reaction
of 4-tert-butylcyclohexanone. The equilibrium between
12a and 12b suggests that 48 might equilibrate with
cyclobutanone 49. We were unable to observe 49, but
an AM1 calculation17 indicated that 49 should be 6.1 kcal/
mol higher in energy than 48. Whereas both 12a and
12b rearranged to 1,3-diketones, an alternate pathway
to the tertiary carbocation 50 presents itself with 49.
(Furanones were never observed in reactions with 1 or
3, so the intermediacy of a carbocationic intermediate was
suspected.) Cyclization of 50 gives the furanone 37, or
deprotonation of 50 with the internal assistance of an
oxygen would give the terminal double bond in 38a and
39a . Evidence for the latter stage of this hypothesis is
that treatment of a solution of the mixture of 31 and
32 in CDCl3 with BF3‚Et2O provided some 30a ,b, but
treatment of furanones with acid (with or without
water) under an inert atmosphere did not give any 1,2-
diketone.
Rea ction s w ith Tetr a m eth ylcyclobu ten e 51. Two
ketones were reacted with the tetramethylcyclobutene
5115 using the conditions employed with 4. No cyclopen-
tanedione was produced in these reactions. Instead,
furanone 52 was the only isolated product from the
reaction with acetone, and 53 was the only isolated
product from cyclohexanone.
a
Two molar equivalents of 4 were used in this reaction.
Chromatographic separation of 33a and 34a ,b was incomplete.
b
Yields reflect the isolated yields and the proportion of 33a and
34a ,b (GC-MS) in a mixed fraction.
The dimethylcyclobutanone compounds 47 and 48 were
prepared from the corresponding ketones by working up

8726 J . Org. Chem., Vol. 62, No. 25, 1997
Crane et al.
215.6 (0), 60.4 (0), 45.1 (2), 40.0 (1), 34.9 (1), 32.8 (2), 28.9 (2),
25.3 (2), 20.1 (2), 18.5 (3), 14.8 (3). For 8b: 1H NMR δ 2.70
(1H, overlapped dd), 2.41 (1H, overlapped dd), 1.31 (3H, d, J
) 7.0 Hz), 0.74 (3H, d, J ) 6.9 Hz); 13C NMR δ 219.8 (0), 217.2
(0), 60.0 (0), 44.1 (2), 43.1 (1), 36.3 (1), 32.2 (2), 29.1 (2), 25.3
(2), 20.2 (2), 18.1 (3), 16.5 (3). For 8c: 1H NMR δ 3.08 (1H,
dd, J ) 10.5, 18.8 Hz), 2.18 (3H, dd, J ) 6.9 Hz), 0.715 (3H, d,
J ) 6.4 Hz); 13C NMR δ 218.3 (0), 216.5 (0), 60.7 (0), 44.6 (2),
39.9 (1), 35.2 (1), 32.9 (2), 28.9 (2), 25.4 (2), 20.2 (2), 18.3 (3),
14.8 (3). For 8d : 1H NMR δ 2.42 (1H, overlapped dd), 1.32
(3H, d, J ) 7.0 Hz), 0.75 (3H, d, J ) 6.3 Hz); 13C NMR δ
218.6 (0), 216.2 (0), 59.6 (0), 43.6 (2), 35.7 (1), 32.0 (2), 19.9
(2), 16.3 (3).
4′-Meth ylspir o(bicyclo[2.2.1]h eptan e-2,2′-cyclopen tan e)-
1′,3′-d ion e (9a -d ). From spectra of the mixture: for 9a : 1H
NMR δ 1.20 (3H, d, J ) 6.9 Hz); 13C NMR δ 215.5 (0), 213.1
(0), 66.4 (0), 49.2 (1), 44.0 (2), 39.5 (1), 37.3 (2), 36.9 (1), 33.0
(2), 28.0 (2), 24.1 (2), 15.4 (3). For 9b: 1H NMR δ 2.82 (1H,
dd, J ) 9.0, 16.5 Hz), 2.55 (1H, br m), 2.46 (1H, dd, J )
9.8, 16.5 Hz), 2.46 (1H, m), 2.36 (1H, m), 1.44 (3H, d, J )
7.2 Hz); 13C NMR δ 216.1 (0), 213.2 (0), 65.4 (0), 48.6 (1), 43.9
(2), 42.1 (1), 37.1 (2), 36.7 (1), 33.9 (2), 27.7 (2), 24.5 (2), 17.6
(3). For 9c: 1H NMR δ 3.23 (1H, dd, J ) 11.4, 19.0 Hz), 2.94
(1H, br m), 2.48 (1H, m), 2.36 (1H, m), 2.15 (1H, dd, J )
8.7, 19.0 Hz), 1.22 (3H, d, J ) 6.9 Hz); 13C NMR δ 215.2 (0),
212.4 (0), 66.5 (0), 49.1 (1), 43.2 (2), 40.5 (1), 37.0 (2), 36.8
(1), 32.8 (2), 27.8 (2), 24.5 (2), 14.3 (3). For 9d : 13C NMR δ
216.5 (0), 213.4 (0), 42.8 (2), 41.8 (1), 37.6 (2), 34.1 (2), 27.7
(2), 17.6 (3).
2,7-Dim eth ylsp ir o[4.5]d eca n e-1,4-d ion e (10a-d ). From
spectra of the mixture: (1H NMR for each isomer contains δ
3.03 (1H, m), 2.88 (1H, m), 2.33 (1H, m), 1.27 (3H, d, J ) 6.9
Hz), 0.857 ((0.007) (3H, d, J ) 6.3 Hz) 0.86 (3H, d, J ) 6.6
Hz), 0.85 (3H, d, J ) 6.6 Hz)). For 10a /b: 13C NMR δ 217.9/
217.9 (0), 215.64/215.59 (0), 56.5 (0), 43.3 (2), 40.9 (1), 38.1/
36.8 (2), 33.76 (2), 33.4 (2), 28.9 (2), 26.53/26.46 (1), 22.5/22.4
(3), 20.96/20.90 (2), 15.9 (3). For 10c/d : 13C NMR δ 218.2/
218.1 (0), 215.0 (0), 56.6/56.5 (0), 43.4/43.3 (2), 40.3/40.2 (1),
38.6/36.5 (2), 33.80 (2), 30.9 (2), 28.5 (2), 26.7/26.3 (1), 22.6/
22.3 (3), 21.02/20.8 (2), 15.7/15.6 (3).
t -8-t er t -Bu t yl-2-m e t h yl-r -1-sp ir o[4.5]d e ca n e -1,4-d i-
on e (11a) an d c-8-ter t-Bu tyl-2-m eth yl-r -1-spir o[4.5]decan e-
1,4-d ion e (11b). For the mixture: for 11a : 1H NMR δ 2.96
(1H, dd, J ) 10.4, 17.5 Hz), 2.33 (1H, dd, J ) 7.7, 17.2 Hz),
1.26 (3H, d, J ) 7.0 Hz); 13C NMR δ 218.2 (0), 215.4 (0), 55.3
(0), 46.8 (1), 43.2 (2), 40.8 (1), 32.3 (0), 31.2 (2), 29.7 (2), 27.3
(3C, 3), 21.68 (2), 21.62 (2), 15.7 (3). For 11b: 1H NMR δ 3.02
(1H, dd J ) 10.4, 18.0 Hz), 2.33 (1H, dd, J ) 8.9, 18.0 Hz),
1.27 (3H, d, J ) 6.9 Hz); 13C NMR δ 218.1 (0), 215.3 (0), 55.4
(0), 46.8 (1), 43.3 (2), 40.1 (1), 32.3 (0), 31.7 (2), 29.3 (2), 27.3
(3C, 3), 21.7 (2), 21.5 (2), 15.4 (3). For the 4-(2,4-dinitrophen-
ylhydrazone) derivative 11c (derived from 11a , purified by
recrystallization): orange solid; mp 194.5-197.5 °C; 1H NMR
δ 11.11 (1H, br s), 9.12 (1H, d, J ) 2.6 Hz), 8.31 (1H, dd, J )
2.5, 9.6 Hz), 7.92 (1H, d, J ) 9.6 Hz), 3.27 (1H, dd, J ) 10.4,
17.6 Hz), 2.83 (1H, br m), 2.43 (1H, dd, J ) 8.7, 17.6 Hz), 1.85-
1.60 (8H, m), 1.31 (3H, d, J ) 2.9 Hz), 1.14 (1H, br m), 0.95
(9H, s); 13C NMR δ 218.3 (0), 164.5 (0), 145.0 (0), 138.0 (0),
130.0 (1), 129.3 (0), 123.4 (1), 116.3 (1), 52.7 (0), 46.9 (1), 40.4
(1), 33.4 (2), 32.6 (2), 31.4 (2), 31.3 (2), 27.4 (3C, 3), 21.5 (2),
15.7 (3). The structure of 11c was determined by X-ray
crystallography.19
Exp er im en ta l Section
Gen er a l P r oced u r es. Compounds 3, 4, and 51 were
obtained using the method for the preparation of 1 of Bloom-
field and Nelke.14 The CH2Cl2 used in the geminal acylation
reactions was distilled from CaH2. All reactions were per-
formed under N2. Workup usually consisted of addition of the
reaction mixture to H2O, extraction of the aqueous layer with
CH2Cl2, washing with brine, drying of the combined organic
solutions over anhydrous MgSO4, and evaporation of the
solvent under vacuum. IR spectra were recorded as thin films
unless otherwise noted. 1H NMR spectra were obtained at 300
MHz in CDCl3 unless specified otherwise, and shifts are
relative to internal TMS. For spectral data obtained from
mixtures, only clearly distinguished signals are reported. Most
1
product ratios were determined by careful integration of H
NMR spectra. NOE measurements were made from difference
spectra and are reported as follows: saturated signal (observed
signal, enhancement). 13C NMR spectra were recorded at 75
MHz; chemical shifts are relative to solvent; each 13C chemical
shift is followed in parentheses by the number of attached
protons as determined by APT and heteronuclear correlation
spectra. Overlap may have prevented the reporting of all
resonances when the spectral data of minor components were
obtained from spectra of mixtures.
3-Met h yl-1,2-b is[(t r im et h ylsilyl)oxy]cyclob u t en e (3):
colorless liquid; bp5 mm 69-72 °C; 1H NMR δ 2.45 (1H, m), 2.36
(1H, dd, J ) 4.3, 10.0 Hz), 1.65 (1H, dd, J ) 1.2, 10.0 Hz),
1.10 (3H, d, J ) 6.6 Hz), 0.21 (9H, s), 0.20 (9H, s); 13C NMR δ
125.4 (0), 119.6 (0), 34.9 (2), 33.3 (1), 17.8 (3), 0.35 (6C, 3).
3,3-Dim et h yl-1,2-b is[(t r im et h ylsilyl)oxy]cyclob u t en e
(4): colorless liquid; bp3
60-61 °C; 1H NMR δ 1.97 (2H, s),
mm
1.12 (6H, s), 0.21 (9H, s), 0.18 (9H, s); 13C NMR δ 128.6 (0),
118.3 (0), 42.7 (2), 38.6 (0), 24.2 (2C, 3), 0.35 (6C, 3).
Gen er a l P r oced u r e for th e Rea ction s of 3 w ith Ke-
ton es or Aceta ls. On the basis of the procedure of J enkins
and Burnell,5 to a solution of ketone or acetal (2.0 mmol) in
CH2Cl2 (10.0 mL) were successively added BF3‚Et2O (0.30 mL,
2.4 mmol) and 3 (0.73 g, 3.0 mmol). The mixture was stirred
at rt for 24 h before H2O (0.30 mL) was introduced, followed
10 min later by BF3‚Et2O (3.7 mL, 30 mmol). The resulting
black solution was stirred for 24 h. Workup and decolorization
of a CH2Cl2 solution by activated charcoal and filtration
through Florisil gave the cyclopentanedione product(s). For
yields and product ratios see Table 1.
2-E t h yl-2,4-d im et h ylcyclop en t a n e-1,3-d ion e (5a ,b ).
From spectra of the mixture: 1H NMR δ 3.10-2.96 (1H from
each, two overlapping dd), 2.96-2.77 (1H from each, m), 2.37
(1H, dd, J ) 8.7, 18.3 Hz), 2.29 (1H, dd, J ) 9.3, 18.0 Hz),
1.80-1.55 (2H from each, m), 1.29 (3H from each, d, J ) 6.9
Hz), 1.12 (3H, s), 1.09 (3H, s), 0.81 (3H, t, J ) 7.5 Hz), 0.76
(3H, t, J ) 7.5 Hz); 13C NMR δ 219.0 (0), 218.6 (0), 216.3 (0),
216.1 (0), 57.2 (0), 57.0 (0), 44.5 (2), 43.7 (2), 41.7 (1), 40.9 (1),
29.4 (2), 28.2 (2), 20.2 (3), 17.9 (3), 15.7 (3), 15.1 (3), 9.4 (3),
8.9 (3).
2-Meth ylsp ir o[4.4]n on a n e-1,4-d ion e (6): tan-colored oil;
1H NMR δ 3.02 (1H, dd, J ) 10.3, 17.7 Hz), 2.88 (1H, m), 2.35
(1H, dd, J ) 8.2, 17.7 Hz), 1.90-1.70 (8H, m), 1.29 (3H, d, J
) 7.0 Hz); 13C NMR δ 220.4 (0), 217.6 (0), 61.9 (0), 42.3 (2),
39.7 (1), 35.4 (2), 32.4 (2), 25.1 (2), 25.3 (2), 13.7 (3).
(2R/S,4R/S)-2-(c-4-ter t-bu tyl-r -1-h yd r oxycycloh exyl)-2-
h yd r oxy-4-m eth ylcyclobu ta n on e (12a ) a n d (2R/S,3S/R)-
2-(c-4-ter t -Bu t yl-r -1-h yd r oxycycloh exyl)-2-h yd r oxy-3-
m eth ylcyclobu ta n on e (12b). Compound 3 (0.34 g, 1.4
2-Meth ylsp ir o[4.5]d eca n e-1,4-d ion e (7): yellow oil; 1H
NMR δ 3.00 (1H, dd, J ) 10.4, 17.6 Hz), 2.90 (1H, m), 2.34
(1H, dd, J ) 8.2, 17.6 Hz), 1.90-1.42 (10H, m), 1.27 (3H, d, J
) 6.9 Hz); 13C NMR δ 218.0 (0), 215.3 (0), 55.5 (0), 43.1 (2),
40.3 (1), 30.5 (2), 28.6 (2), 24.9 (2), 20.5 (2), 20.3 (2), 15.6 (3).
2,6-Dim eth ylsp ir o[4.5]d eca n e-1,4-d ion e (8a -d ). From
spectra of the mixture: for 8a : 1H NMR δ 3.03 (1H, dd, J )
10.6, 18.2 Hz), 2.12 (1H, dd, J ) 9.0, 18.2 Hz), 1.25 (3H, d, J
) 6.9 Hz), 0.705 (3H, d, J ) 6.6 Hz); 13C NMR δ 219.6 (0),
(18) Reaction of the 1,3-dioxolane derived from 4-tert-butylcyclo-
hexanone with 4, under the one-pot conditions developed for acetals
with 1,3 gave a 1.2:1 mixture of 36a and its epimer 36c in a total yield
of 36%. As this process showed essentially no stereoselectivity,
reactions of acetals with 4 were not pursued further.
(19) Atomic coordinates for the X-ray structures of 11c, 33c, 36b,
46a , and 48 have been deposited with the Cambridge Crystallographic
Data Centre. The coordinates can be obtained, on request, from the
Director, Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK.

Geminal Acylation
J . Org. Chem., Vol. 62, No. 25, 1997 8727
mmol) was added to a solution of 4-tert-butylcyclohexanone
(219 mg, 1.42 mmol) and BF3‚Et2O (0.17 mL) in CH2Cl2 (7.0
mL). The mixture was stirred at rt for 4.5 h. Workup gave
an oily, tan solid (304 mg). 1H NMR analysis revealed this to
be a mixture of 12a and 12b in a 3.3:1 ratio, and 11a and 11b
in a 2.6:1 ratio, with the ratio of cyclobutanone compounds to
cyclopentanediones being 6:1. Highly enriched samples of 12a
and 12b were obtained by careful hydrogenolysis of 15a and
15b. For 12a : 1H NMR δ 3.30 (1H, br s), 3.05 (1H, br m),
2.58 (1H, apparent t, J ) 11.8 Hz), 1.86 (1H, m), 1.81-1.45
(4H, m), 1.45-1.27 (3H, m), 1.24 (3H, d, J ) 7.3 Hz), 0.96 (1H,
m), 0.87 (9H, s); 13C NMR δ 215.7 (0), 94.5 (0), 72.7 (0), 49.6
(1), 47.7 (1), 32.6 (2), 32.4 (0), 32.3 (2), 30.9 (2), 27.5 (3C, 3),
21.9 (2), 21.8 (2), 14.4 (3). For 12b: 1H NMR δ 2.48 (1H, dd,
J ) 6.0, 17.8 Hz), 1.18 (3H, d, J ) 6.9 Hz); 13C NMR δ 213.6
(0), 95.2 (0), 73.3 (0), 50.6 (1), 47.6 (1), 32.5 (0), 32.4 (2), 32.1
(2), 30.6 (2), 27.5 (3C, 3), 21.8 (2), 21.7 (2), 14.4 (3).
(2R/S,4R/S)-2-(c-4-ter t-Bu t yl-r -1-m et h oxycycloh exyl)-
4-m eth yl-2-[(tr im eth ylsilyl)oxy]cyclobu ta n on e (13a ) a n d
(2R/S,3S/R)-2-(c-4-ter t-Bu t yl-r -1-m et h oxycycloh exyl)-3-
m eth yl-2-[(tr im eth ylsilyl)oxy]cyclobu tan on e (13b). Based
on the procedure of Kuwajima,1 compound 3 (0.53 g, 2.1 mmol)
was added dropwise over 2-3 min to a solution at -78 °C of
4-tert-butylcyclohexanone dimethyl acetal (0.39 g, 2.0 mmol)
and BF3‚Et2O (0.24 mL) in CH2Cl2 (3.0 mL). After being
stirred at this temperature for 6 h, the reaction mixture was
poured into aqueous NaHCO3 solution (10 mL) and extracted
with Et2O (2 × 40 mL). The combined organic layers were
washed with H2O (40 mL) and brine (40 mL) and dried over
anhydrous MgSO4. Evaporation of the solvent under vacuum
left a viscous, colorless oil (0.66 g, 99%) as a 1:4.1 mixture of
13a and 13b. From spectra of the mixture: for 13a : 1H NMR
δ 3.29 (3H, s), 0.14 (9H, s); 13C NMR δ 214.2 (0), 97.1 (0), 22.5
(2), 22.3 (2), 14.5 (3), 1.7 (3C, 3). For 13b: 1H NMR δ 3.28
(3H, s), 2.94 (dd, J ) 10.7, 18.0 Hz), 2.83-2.68 (m), 2.33 (dd,
J ) 6.3, 18.1 Hz), 2.19-2.05 (2H, m), 1.84-1.70 (m), 1.67-
1.44 (2H, m), 1.40-1.00 (3H, m), 1.12 (3H, d, J ) 7.1 Hz),
1.00-0.87 (m), 0.84 (9H, s), 0.16 (9H, s); 13C NMR δ 212.2 (0),
99.3 (0), 75.9 (0), 51.7 (3), 50.1 (2), 47.3 (1), 32.2 (2), 27.5 (3C,
3 and 1C, 2), 27.1 (1), 22.2 (2), 22.1 (2), 15.2 (3), 1.8 (3C, 3).
This mixture of 13a and 13b (114 mg, 0.335 mmol) was
stirred in TFA (1.0 mL) at rt for 20 h. Workup afforded 82.6
mg of a pale brown oil consisting largely of 11a and 11b in a
1:3.6 ratio.
(2R/S,4R/S)-2-[r -1-(Ben zyloxy)-c-4-ter t-bu tylcycloh exyl]-
4-m eth yl-2-[(tr im eth ylsilyl)oxy]cyclobu ta n on e (14a ) a n d
(2R/S,3S/R)-2-[r -1-(Ben zyloxy)-c-4-ter t-bu tylcycloh exyl]-
3-m eth yl-2-[(tr im eth ylsilyl)oxy]cyclobu ta n on e (14b). On
the basis of the procedure of Kuwajima,1 compound 3 (0.54 g,
2.2 mmol) was added over 2-3 min to a CH2Cl2 (3.0 mL)
solution of 4-tert-butylcyclohexanone dibenzyl acetal (0.70 g,
2.0 mmol) and BF3‚Et2O (0.25 mL) at -78 °C. After being
stirred at this temperature for 9.5 h, workup and chromatog-
raphy of the solution gave 0.79 g (96%) of a white solid,
consisting of a 1:7.4 mixture of 14a and 14b. From spectra of
the mixture: for 14a : 1H NMR δ 4.68 (1H, d, J ) 9.7 Hz),
4.61 (1H, d, J ) 10.2 Hz), 0.16 (9H, s); 13C NMR δ 213.8 (0),
97.5 (0), 75.9 (0), 65.3 (2), 48.4 (1), 33.7 (2), 28.0 (2), 22.4 (2),
14.6 (3), 1.7 (3C, 3). For 14b: 1H NMR δ 7.50-7.18 (5H, m),
4.58 (1H, d, J ) 11.6 Hz), 4.49 (1H, d, J ) 11.8 Hz), 2.92 (1H,
dd, J ) 10.7, 28.9 Hz), 2.86 (1H, br m), 2.40-2.26 (2H,
overlapping m), 1.89 (1H, ddd, J ) 3.3, 6.6, 12.9 Hz), 1.68-
1.50 (2H, m), 1.42 (1H, remnants of dddd), 1.33-1.24 (2H, m),
1.20 (1H, apparent dd, J ) 4.7, 12.2 Hz), 1.13 (3H, d, J ) 7.0
Hz), 0.98 (1H, br m), 0.85 (9H, s), 0.19 (9H, s); 13C NMR δ
212.0 (0), 140.0 (0), 128.2 (1), 127.1 (1), 127.0 (1), 99.5 (0), 76.1
(0), 65.4 (2), 50.2 (2), 47.1 (1), 33.0 (2), 32.4 (0), 27.8 (2), 27.5
(3C, 3), 27.1 (1), 22.2 (2), 22.1 (2), 15.3 (3), 1.8 (3C, 3).
(2R/S,4R/S)-2-[r -1-(Ben zyloxy)-c-4-ter t-bu tylcycloh exyl]-
2-h yd r oxy-4-m eth ylcyclobu ta n on e (15a ) a n d (2R/S,3S/R)-
2-[r -1-(Ben zyloxy)-c-4-ter t-bu tylcycloh exyl]-2-h yd r oxy-3-
m eth ylcyclobu tan on e (15b). Treatment of the above mixture
of 14a ,b (0.20 g, 0.48 mmol) with TBAF (0.60 mL, 1.0 M in
THF) in Et2O (4.0 mL) followed by chromatography afforded
15a and 15b (total 0.142 g, 84%). 1H NMR signals for a very
minor third isomer, tentatively ascribed structure 16, were
noted in some fractions that were mainly 15a . For 15a : 1H
NMR δ 7.60-7.21 (5H, m), 4.71 (1H, d, J ) 11.1 Hz), 4.40 (1H,
d, J ) 11.0 Hz), 3.45 (1H, s), 3.00 (1H, m), 2.59 (1H, apparent
t, J ) 12.1 Hz), 2.04 (1H, ddd, J ) 3.0, 6.0, 13.4 Hz), 1.96 (1H,
ddd, J ) 3.1, 6.1, 13.1 Hz), 1.72 (1H, dd, J ) 9.2, 12.4 Hz),
1.71-1.58 (2H, m), 1.55-1.27 (4H, m), 1.24 (3H, d, J ) 7.2
Hz), 1.01 (1H, unresolved dddd), 0.87 (9H, s); NOE data 3.00
(2.59, 2%; 2.04-1.96, 1.6%; 1.24, 6%), 2.59 (3.00, 3%; 1.72, 22%;
1.48-1.39, 9%), 2.04-1.96 (4.71, 1.2%; 3.00, 1%; 4.40, 3%;
1.48-1.39, 31%), 1.72 (2.59, 9%; 1.24, 2%); 13C NMR δ 214.8
(0), 138.7 (0), 128.4 (2C, 1), 127.5 (2C, 1), 95.6 (0), 76.9 (0),
64.4 (2), 49.0 (1), 47.4 (1), 32.8 (2), 32.4 (0), 31.2 (2), 28.3 (2),
27.5 (3C, 3), 22.0 (2C, 2), 14.4 (3). For 15b: 1H NMR δ 7.54-
7.20 (5H, m), 4.73 (1H, d, J ) 11.2 Hz), 4.42 (1H, d, J ) 11.2
Hz), 3.35 (1H, s), 2.99 (1H, dd, J ) 10.4, 17.7 Hz), 2.62 (1H,
br m), 2.48 (1H, dd, J ) 6.4, 17.7 Hz), 2.08 (1H, ddd, J ) 3.2,
6.2, 13.7 Hz), 1.93 (1H, ddd, J ) 3.1, 6.0, 12.9 Hz), 1.64 (2H,
m), 1.55-1.26 (4H, m), 1.20 (3H, d, J ) 7.0 Hz), 1.02 (1H,
unresolved dddd), 0.87 (9H, s); NOE data 4.73 (2.08, 3%), 2.99
(2.62, 4.5%; 2.48, 13%), 2.62 (2.99, 4%); 1.49-1.36, 6.5%; 1.20,
4%), 2.48 (2.99, 8%; 1.20, 1.6%), 2.08 (4.42, 3%; 1.49-1.36,
13%), 1.93 (1.36, 16%), 1.20 (2.62, 4%; 2.48, 4%); 13C NMR δ
212.2 (0), 138.8 (0), 128.4 (2C, 1), 127.5 (2C, 1), 95.9 (0), 77.5
(0), 64.6 (2), 50.1 (2), 47.4 (1), 32.4 (0), 30.8 (2), 28.3 (1), 27.8
(2), 27.4 (3C, 3), 22.0 (2C, 2), 14.1 (3). For tentative 16 (from
mixture): 1H NMR δ 4.75 (1H, overlapped d), 4.49 (1H, d, J )
11.3 Hz), 2.29 (1H, dd, J ) 11.4, 12.9 Hz), 1.84 (1H, dd, J )
9.9, 12.9 Hz), 1.17 (3H, d, J ) 6.5 Hz).
A mixture of 15a ,b (105 mg, 0.251 mmol) was stirred in TFA
(1.0 mL) at rt for 4 h. Workup afforded 76 mg of an oily, yellow
solid consisting largely of 11a and 11b in a ratio of 1:7.5.
Hyd r ogen olysis of 15a a n d 15b. A mixture of 15a and
15b (4.3:1; 64 mg, 187 mmol) in EtOH (3.5 mL) and AcOH
(0.5 mL) with 10% Pd on charcoal (15 mg) under H2 (1 atm)
for 18 h gave 42 mg (96%) of 12a and 12b (5.1:1).
Homogeneous 15b (58 mg, 169 mmol) in EtOH (3.5 mL) and
AcOH (0.5 mL) with 10% Pd on charcoal (13 mg) under H2 (1
atm) for 48 h gave 42 mg (100%) of 12a and 12b (5.2:1).
Gen er a l P r oced u r e for th e Rea ction s of 4 w ith Ke-
ton es. BF3‚Et2O (0.30 mL, 2.4 mmol) and 4 (0.84 g 3.2 mmol)
were added in succession to a solution of the ketone (2.0 mmol)
in CH2Cl2 (10.0 mL). The mixture was stirred at rt for 24 h.
H2O (0.30 mL) was introduced followed 10 min later by
BF3‚Et2O (3.7 mL, 30 mmol). The resulting black solution was
stirred for 1-3 h, except for 2-methylcyclohexanone, which
required 24 h. Workup gave the crude product, consisting of
cyclopentanedione(s), furanone(s), and 1,2-dione(s). Flash
chromatography (hexane with an increasing proportion of
EtOAc) could usually effectively separate the three types of
product, but cyclopentanedione, furanone, and 1,2-dione iso-
mers were generally not separable in this way. Furanones
were susceptible to oxidation in air. Yields and product ratios
for the individual reactions are given in Table 2.
2,2,4,4-Tetr a m eth yl-1,3-cyclop en ta n ed ion e (17): light
yellow oil, which solidified below 4 °C; 1H NMR δ 2.66 (2H, s),
1.25 (6H, s), 1.17 (6H, s); 13C NMR δ 220.8 (0), 216.4 (0), 51.6
(0), 50.1 (2), 46.6 (0), 25.5 (2C, 3), 21.4 (2C, 3).
4,5-Dih yd r o-2-isop r op ylid en e-5,5-d im eth yl-3(2H)-fu r a -
n on e (18): yellow oil;
1H NMR δ 2.48 (2H, s), 2.07 (3H, s),
1.79 (3H, s), 1.39 (6H, s); 13C NMR δ 199.7 (0), 143.3 (0), 120.1
(0), 77.9 (0), 50.5 (2), 28.1 (2C, 3), 19.5 (3), 16.8 (3).
2,6-Dim eth ylh ep t-5-en e-3,4-d ion e (19): yellow oil; 1H
NMR δ 6.71 (1H, m), 3.47 (1H, septet, J ) 6.9 Hz), 2.26 (3H,
d, J ) 1.2 Hz), 2.02 (3H, d, J ) 1.2 Hz), 1.10 (6H, d, J )
6.9 Hz).
2-Eth yl-2,4,4-tr im eth ylcyclopen tan e-1,3-dion e (20): yel-
low oil; 1H NMR δ 2.67 (1H, d, J ) 18.2 Hz), 2.57 (1H, d, J )
18.2 Hz), 1.75-1.60 (2H, m), 1.25 (3H, s), 1.24 (3H, s), 1.15
(3H, s), 0.80 (3H, t, J ) 7.5 Hz); 13C NMR δ 221.2 (0), 216.5
(0), 56.7 (0), 51.1 (2), 46.2 (0), 29.0 (2), 26.5 (3), 24.5 (3), 20.3
(3), 9.3 (3).
4,5-Dih yd r o-2-isobu tylid en e-5,5-d im eth yl-3(2H)-fu r a -
n on e (21a ,b). From spectra of the mixture: 1H NMR δ 2.58
(2H, q, J ) 7.5 Hz), 2.16 (2H, q, J ) 7.5 Hz), 2.482 (2H, s),
2.475 (2H, s), 2.06 (3H, s), 1.78 (3H, s), 1.39 (6H, s), 1.38 (6H,
s), 1.02 (3H, t, J ) 7.5 Hz), 1.00 (3H, t, J ) 7.5 Hz); 13C NMR

8728 J . Org. Chem., Vol. 62, No. 25, 1997
Crane et al.
δ 200.5 (0), 199.6 (0), 143.3 (0), 142.9 (0), 126.6 (0), 126.0 (0),
78.1 (0), 78.0 (0), 50.7 (2), 50.6 (2), 28.21 (3), 28.16 (3), 26.4
(2), 23.4 (2), 16.9 (3), 14.5 (3), 12.9 (3), 11.4 (3).
213.6 (0), 64.8 (0), 51.2 (2), 49.1 (1), 46.1 (0), 37.4 (2), 36.7 (1),
34.5 (2), 27.7 (2), 26.5 (3), 25.6 (3), 24.6 (2). For the 1′-(2,4-
dinitrophenylhydrazone) derivative 33c (purified by recrys-
2,6-Dim eth yloct-2-en e-4,5-dion e (22): yellow oil; 1H NMR
δ 6.72 (1H, m), 3.36 (1H, q, J ) 6.7 Hz), 2.06 (3H, s), 2.02 (3H,
s), 1.69 (1H, m), 1.38 (1H, m), 1.07 (3H, d, J ) 7.0 Hz), 0.88
(3H, t, J ) 7.4 Hz); 13C NMR δ 205.2 (0, 188.2 (0), 163.4 (0),
117.5 (1), 40.0 (1), 28.5 (3), 25.3 (2), 21.6 (3), 15.0 (3), 11.5 (3).
2,2-Dim eth ylsp ir o[4.4]n on a n e-1,4-d ion e (23): very pale
tallization): red-orange solid; mp 199.5-201 °C;
1H NMR δ
11.2 (1H, br s), 9.15 (1H, d, J ) 2.6 Hz), 8.36 (1H, dd, J )
2.5, 9.6 Hz), 7.99 (1H, d, J ) 9.6 Hz), 2.81 (1H, d, J ) 16.6
Hz), 2.49 (1H, d, J ) 16.6 Hz), 2.41 (2H, apparent t, J ) 4.2
Hz), 2.15 (1H, apparent d of pentets, J ) 2.6, 10.2 Hz), 1.96
(1H, ddd, J ) 2.7, 3.9, 12.0 Hz), 1.73 (1H, dd, J ) 2.8, 12.1
Hz), 1.69-1.55 (2H, m), 1.49 (1H, br m), 1.40-1.28 (2H, m);
13C NMR δ 218.9 (0), 162.1 (0), 145.1 (0), 138.0 (0), 130.2 (1),
129.2 (0), 123.4 (1), 116.1 (1), 61.1 (0), 48.6 (1), 45.7 (0), 39.4
(2), 37.6 (2), 37.3 (2), 36.8 (1), 28.1 (2), 26.6 (3), 26.2 (3), 24.4
(2). The structure of 33c was determined by X-ray crystal-
lography.19
1
yellow oil; H NMR δ 2.62 (2H, m), 1.93-1.75 (8H, m), 1.24
(6H, s); 13C NMR δ 221.6 (0), 216.4 (0), 61.6 (0), 50.9 (2), 46.4
(0), 36.5 (2C, 2), 27.2 (2C, 2), 25.2 (2C, 3).
2-Cyclop en t ylid en e-4,5-d ih yd r o-5,5-d im et h yl-3(2H )-
fu r a n on e (24): 1H NMR (impure sample) δ 2.78 (2H, m), 2.48
(2H, s), 1.42 (6H, s).
(1R /S ,2R /S ,4S /R )-4′,4′-Dim e t h ylsp ir o(b icyclo[2.2.1]-
h ep ta n e-2,2′-cyclop en ta n e)-1′,3′-d ion e (33b). One chro-
matographic fraction contained a minor amount of the isomer
33b along with 33a . Signals for 33b in the mixture: 1H NMR
δ 2.88 (1H, d, J ) 18.1 Hz), 1.33 (3H, s), 1.13 (3H, s).
2-(2-Bicyclo[2.2.1]h eptyliden e)-4,5-dih ydr o-5,5-dim eth yl-
3(2H)-fu r a n on e (34a ,b). From spectra of the mixture: for
the major isomer: 1H NMR δ 3.87 (1H, m), 2.47 (1H, m), 1.41
(6H, s); 13C NMR δ 199.4, 140.2, 133.3, 78.9. For the minor
2,2,7-Tr im eth ylspir o[4.4]n on an e-1,4-dion e (25a,b). From
spectra of the mixture: for the major isomer: 1H NMR δ 2.64
(1H, d, J ) 17.8 Hz), 2.56 (1H, d, J ) 17.8 Hz), 2.25 (1H, br
m), 2.05-1.68 (4H, m), 1.55-1.30 (2H, m), 1.22 (6H, s), 1.04
(1H, d, J ) 6.6 Hz); 13C NMR δ 221.5 (0), 216.0 (0), 61.9 (0),
50.9 (2), 46.2 (0), 44.3 (2), 36.2 (2), 35.9 (1), 35.3 (2), 25.3 (3),
25.1 (3), 18.6 (3). For the minor isomer: 1H NMR δ 1.23 (6H,
s); 13C NMR δ 221.3 (0), 216.2 (0), 62.0 (0), 50.7 (2), 46.3 (0),
43.8 (2), 35.8 (1), 35.6 (2), 35.2 (2), 25.2 (3), 25.0 (3), 19.5 (3).
2,2-Dim eth ylspir o[4.5]decan e-1,4-dion e (26): white solid;
mp 41.5-43 °C; 1H NMR δ 2.61 (2H, m), 1.75-1.40 (10H, m),
1.22 (6H, s); 13C NMR δ 220.3 (0), 216.3 (0), 54.9 (0), 50.3 (2),
46.2 (0), 30.5 (2), 25.7 (2C, 3), 25.0 (2C, 2), 20.6 (2C, 2).
2-Cycloh exyliden e-4,5-dih ydr o-5,5-dim eth yl-3(2H)-fu r a-
isomer: 1H NMR δ 3.05 (1H, m), 2.45 (2H, s), 1.38 (6H, s); 13
NMR δ 200.3, 139.5, 132.5, 79.0.
C
4′,4′-Dim eth ylsp ir o(bicyclo[2.2.2]octa n e-2,2′-cyclop en -
ta n e)-1′,3′-d ion e (35): tan-colored solid; mp 30-32 °C; 1H
NMR δ 2.88 (1H, d, J ) 17.3 Hz), 2.40 (1H, d, J ) 17.3 Hz),
1.82 (1H, m), 1.78-1.71 (3H, m), 1.71-1.63 (2H, m), 1.63-
1.52 (2H, m), 1.52-1.41 (2H, m), 1.38 (3H, s), 1.37-1.29 (2H,
m), 1.06 (3H, s); 13C NMR δ 218.4 (0), 214.3 (0), 61.5 (0), 49.9
(2), 45.7 (0), 32.4 (1), 28.1 (2), 26.7 (3), 25.8 (3), 24.4 (2), 24.0
(2), 23.1 (1), 21.6 (2), 20.9 (2).
1
n on e (27): yellow oil; H NMR δ 2.74 (2H, m), 2.48 (2H, s),
2.25 (2H, apparent triplet, J ) 5.4 Hz), 1.65-1.40 (6H, m),
1.38 (6H, s); 13C NMR δ 200.8 (0), 140.8 (0), 128.7 (0), 77.8 (0),
50.9 (2), 28.6 (2), 28.1 (2C, 3), 27.9 (2), 27.3 (2), 26.3 (2), 25.9
(2).
1-Cycloh exyl-5-m eth ylp en t-4-en e-1,2-d ion e (28a ) a n d
1-Cycloh exyl-5-m eth ylp en t-3-en e-1,2-d ion e (28b). An at-
tempt to separate a 1.2:1 mixture by preparative TLC led
predominantly to isomerization of 28a to 28b. For 28a (from
the mixture): 1H NMR δ 4.97 (1H, m), 4.79 (1H, m), 3.13 (1H,
m), 3.44 (2H, s), 1.77 (3H, s). For 28b: yellow oil; 1H NMR δ
6.69 (1H, m), 3.24 (1H, m), 2.26 (3H, s), 2.01 (3H, s), 1.79 (3H,
m), 1.70 (1H, m), 1.30 (4H, m); 13C NMR δ 204.5 (0), 188.3 (0),
163.3 (0), 117.6 (1), 43.1 (1), 28.5 (3), 27.8 (2C, 2), 25.8 (2),
25.4 (2C, 2), 21.6 (3).
2,2,6-Tr im eth ylspir o[4.5]decan e-1,4-dion e (29a,b). From
spectra of the mixture: major isomer: 1H NMR δ 2.69 (1H, d,
J ) 18.3 Hz), 2.39 (1H, d, J ) 18.3 Hz), 1.26 (3H, s), 1.20 (3H,
s), 0.74 (3H, d, J ) 6.5 Hz); 13C NMR δ 222.0 (0), 216.2 (0),
60.4 (0), 51.9 (2), 45.6 (0), 35.7 (1), 33.8 (2), 29.0 (2), 26.8 (3),
25.4 (2), 24.6 (3), 20.4 (2), 18.7 (3). Minor isomer: 1H NMR δ
2.74 (1H, d, J ) 18.6 Hz), 2.46 (1H, d, J ) 18.6 Hz), 1.29 (3H,
s), 1.16 (3H, s), 0.73 (3H, d, J ) 6.2 Hz).
4,5-Dih ydr o-5,5-dim eth yl-2-(2-m eth ylcycloh exyliden e)-
3(2H)-fu r a n on e (30a ,b). From spectra of the mixture: 1H
NMR δ 4.02 (1H, m), 3.64 (1H, br d, J ) 14.6 Hz), 2.98 (1H,
m), 2.60 (1H, m), 2.48 (4H, narrow m), 1.40 (3H, s), 1.384 (3H,
s), 1.376 (3H, s), 1.36 (3H, s), 1.11 (6H, d, J ) 7.2 Hz); 13C
NMR δ 201.1 (0), 200.4 (0), 140.8 (0), 140.6 (0), 133.0 (0), 132.6
(0), 77.9 (0), 77.8 (0), 51.0 (2), 33.1 (2), 32.7 (2), 29.7 (1), 26.7
(1), 28.1 (3), 27.5 (2), 27.1 (2), 23.7 (2), 21.3 (2), 20.6 (2), 20.4
(2), 19.0 (3), 17.7 (3).
tr a n s- (31) a n d cis-4-Meth yl-1-(2-m eth ylcycloh exyl)-
p en t-3-en e-1,2-d ion e (32). From spectra of a 2.4:1 mixture:
for 31: 1H NMR δ 6.74 (1H, m), 3.06 (1H, m), 2.26 (3H, s),
2.02 (3H, s), 0.79 (3H, d, J ) 6.2 Hz); 13C NMR δ 204.9 (0),
187.9 (0), 163.5 (0), 117.1 (1), 49.4 (1), 20.6 (3). For 32: 1H
NMR δ 6.67 (1H, m), 3.46 (1H, m), 2.26 (3H, s), 2.02 (3H, s),
0.81 (3H, d, J ) 6.4 Hz); 13C NMR δ 204.8 (0), 188.5 (0), 163.2
(0), 117.4 (1), 45.7 (1), 14.9 (3).
t-8-ter t-Bu tyl-2,2-d im eth yl-r -1-sp ir o[4.5]d eca n e-1,4-d i-
on e (36a ): white solid; mp 84-86 °C; 1H NMR δ 2.60 (2H,
m), 1.80-1.37 (8H, m), 1.21 (6H, s), 1.06 (1H, br m), 0.87 (9H,
s); 13C NMR δ 220.5 (0), 216.1 (0), 55.0 (0), 50.4 (2), 46.8 (1),
46.3 (0), 32.4 (0), 31.4 (2C, 2), 27.3 (3C, 3), 25.3 (2C, 3), 21.9
(2C, 2). For the 4-(2,4-dinitrophenylhydrazone) derivative 36b
(purified by recrystallization): orange solid; mp 234-235 °C;
1H NMR δ 11.12 (1H, br s), 9.13 (1H, d, J ) 2.5 Hz), 8.32 (1H,
dd, J ) 2.5, 9.6 Hz), 7.93 (1H, d, J ) 9.6 Hz), 2.78 (2H, m),
1.75-1.65 (8H, m), 1.25 (6H, s), 1.17 (1H, br m), 0.95 (9H, s);
13C NMR δ 220.8 (0), 164.6 (0), 145.0 (0), 137.9 (0), 130.0 (1),
129.2 (0), 123.4 (1), 116.3 (1), 52.6 (0), 46.8 (1), 46.0 (0), 38.7
(2), 33.1 (2C, 3), 32.6 (0), 27.4 (3C, 3), 25.8 (2C, 3), 21.7 (2C,
2). The structure of 36b was determined by X-ray crystal-
lography.19
c-8-ter t-Bu tyl-2,2-d im eth yl-r -1-sp ir o[4.5]d eca n e-1,4-d i-
on e (36c). Only unequivocal signals, from mixture: 1H NMR
δ 2.59 (2H, s), 1.25 (6H, s), 0.88 (9H, s); 13C NMR δ 220.6 (0),
216.4 (0), 54.1 (0), 50.1 (2), 46.8 (1), 46.3 (0), 32.4 (0), 31.3 (2C,
2), 27.4 (3C, 3), 25.9 (2C, 3), 21.3 (2C, 2).
2-(4-t er t -Bu t ylcycloh e xylid e n e )-4,5-d ih yd r o-5,5-d i-
m eth yl-3(2H)-fu r a n on e (37): yellow oil; 1H NMR δ 3.82 (1H,
unresolved ddd), 2.80 (1H, unresolved ddd), 2.51 (1H, d, J )
17.7 Hz), 2.45 (1H, d, J ) 17.4 Hz), 1.89 (2H, m), 1.73 (2H,
m), 1.40 (3H, s), 1.38 (3H, s), 1.14 (1H, unresolved dddd); 13C
NMR δ 200.8 (0), 140.5 (0), 128.4 (0), 77.9 (0), 50.9 (2), 47.8
(1), 32.5 (0), 28.7 (2), 28.5 (2), 28.2 (3), 28.1 (3), 28.0 (2), 27.5
(3C, 3), 25.9 (2).
cis-1-(4-ter t-Bu tylcycloh exyl)-4-m eth ylp en t-4-en e-1,2-
d ion e (38a ), cis-1-(4-ter t-bu tylcycloh exyl)-4-m eth ylp en t-
4-en e-1,2-d ion e (38b), tr a n s-1-(4-ter t-bu tylcycloh exyl)-4-
m eth ylp en t-3-en e-1,2-d ion e (39a ), a n d tr a n s-1-(4-ter t-
b u t ylcycloh exyl)-4-m et h ylp en t -3-en e-1,2-d ion e (39b ).
Initially obtained in a 7.7:2.5:1.1:1 ratio, respectively. Pre-
parative TLC gave only 38b and 39b in a 2.6:1 ratio. From
spectra of the mixtures: for 38a : 1H NMR δ 5.01 (1H, m),
4.84 (1H, m), 3.44 (2H, s), 1.79 (3H, s), 0.83 (9H, s). For 38b:
1H NMR δ 6.61 (1H, m), 3.44 (1H, m), 2.25 (3H, s), 2.00 (3H,
s), 0.86 (9H, s); 13C NMR δ 205.9 (0), 189.4 (0), 163.1 (0), 117.9
(1), 48.0 (1), 39.1 (3), 32.5 (0), 28.5 (2), 28.4 (2), 27.4 (3C, 3),
26.6 (2C, 2), 23.6 (3). For 39a : 1H NMR δ 4.97 (1H, m), 4.80
(1H, m), 3.04 (1H, m). For 39b: 1H NMR δ 6.70 (1H, m), 3.15
(1R /S ,2S /R ,4S /R )-4′,4′-Dim e t h ylsp ir o(b icyclo[2.2.1]-
h ep ta n e-2,2′-cyclop en ta n e)-1′,3′-d ion e (33a ): yellow oil; 1H
NMR δ 2.72 (1H, d, J ) 16.9 Hz), 2.43 (1H, d, J ) 16.9 Hz),
2.49 (1H, m), 2.36 (1H, m), 2.05 (1H, apparent d of pentets, J
) 1.9, 9.9 Hz), 1.69 (1H, ddd, J ) 2.9, 4.0, 12.2 Hz), 1.53 (1H,
br m), 1.43 (3H, s), 1.42-1.28 (4H, m), 1.23 (1H, apparent d
of pentets, J ) 1.5, 9.9 Hz), 1.04 (3H, s); 13C NMR δ 218.5 (0),

Geminal Acylation
J . Org. Chem., Vol. 62, No. 25, 1997 8729
(1H, tt, J ) 3.2, 11.8 Hz), 2.25 (3H, s), 2.00 (3H, s); 13C NMR
δ 204.6 (0), 188.2 (0), 163.3 (0), 117.6 (1), 47.4 (1), 43.3 (3),
32.4 (0), 28.6 (2), 27.5 (2C, 2), 26.5 (2C, 2), 21.6 (3).
P r oced u r e for th e Rea ction s of 4 w ith En on es. BF3‚
Et2O (0.74 mL, 6.0 mmol) and 4 (1.55 g, 6.0 mmol) were added
in succession to a solution of the ketone (2.0 mmol) in CH2Cl2
(10 mL) at -78 °C. The mixture was stirred at rt for 24 h
before workup. Chromatography provided the products. Yields
and product ratios for the individual reactions are given in
Table 2.
2,2-Dim eth ylsp ir o[4.5]d ec-6-en e-1,4-d ion e (40): oily tan
solid; mp 30-32 °C; 1H NMR δ 6.16 (1H, ddd, J ) 3.8, 3.8, 9.9
Hz), 5.22 (1H, ddd, J ) 2.2, 2.2, 9.9 Hz), 2.75 (1H, d, J ) 17.8
Hz), 2.63 (1H, d, J ) 17.6 Hz), 2.20-2.04 (2H, m), 1.95-1.68
(4H, m), 1.31 (3H, s), 1.22 (3H, s); 13C NMR δ 218.5 (0), 214.1
(0), 133.3 (1), 120.6 (1), 58.5 (0), 50.2 (2), 46.9 (0), 29.2 (2),
25.7 (3), 25.1 (3), 23.8 (2), 17.2 (2).
was determined by X-ray crystallography.19 For 46b: 1H NMR
δ 3.74 (1H, s), 2.58 (1H, d, J ) 18.4 Hz), 2.49 (1H, d, J ) 18.4
Hz), 2.22 (1H, s), 1.48 (3H, s), 1.47 (3H, s), 1.05 (3H, d, J )
7.4 Hz), 1.77 (2H, apparent triplet); 13C NMR δ 214.0 (0), 100.4
(0), 78.6 (0), 76.8 (0), 48.5 (2), 35.4 (1), 30.0 (3), 29.6 (3), 24.8
(2), 21.1 (2), 20.8 (2), 19.7 (2), 16.6 (3).
2-H yd r oxy-2-(1-h yd r oxycycloh exyl)-4,4-d im et h ylcy-
1
clobu ta n on e (47): white solid; mp 145-148 °C; H NMR δ
3.38 (1H, br s), 2.18 (1H, d, J ) 12.8 Hz), 1.91 (1H, d, J ) 12.9
Hz), 1.83 (1H, m), 1.73 (1H, br m), 1.67-1.40 (6H, m), 1.36
(3H, s), 1.27-1.16 (2H, m), 1.15 (3H, s); 13C NMR δ 220.0 (0),
92.6 (0), 73.3 (0), 55.2 (0), 38.6 (2), 32.1 (2), 29.6 (2), 25.6 (2),
24.7 (3), 20.9 (3), 20.8 (2), 20.7 (2).
Compound 47 (10.1 mg, 47.5 mmol) was stirred with BF3‚
Et2O (1.1 mL) for 2 h. Workup gave a yellow oil (11.8 mg),
which 1H NMR revealed to be a 3.0:1 mixture of 26 and 27.
A solution of 47 (18.3 mg, 86.2 mmol) in CH2Cl2 (1.7 mL)
and BF3‚Et2O (0.18 mL) was stirred for 15 h at rt. Workup
gave an oily, brown solid (24.4 mg), which contained only 26
but no trace of 27.
2,2,7,9,9-P en tam eth ylspir o[4.5]dec-6-en e-1,4-dion e (41):
yellow oil; contaminated with isomeric compound(s) (ap-
1
proximately 15%); H NMR δ 5.00 (1H, d, J ) 1.4 Hz), 2.70
(1H, d, J ) 17.0 Hz), 2.64 (1H, d, J ) 17.0 Hz), 1.86 (1H, d, J
) 16.8 Hz), 1.77 (1H, overlapped d), 1.71 (3H, d, J ) 1.2 Hz),
1.65 (1H, d, J ) 13.8 Hz), 1.52 (1H, d, J ) 13.8 Hz), 1.22 (3H,
s), 1.21 (3H, s), 1.00 (3H, s), 0.95 (3H, s); 13C NMR δ 218.4 (0),
213.6 (0), 139.3 (0), 113.9 (1), 61.5 (0), 50.2 (2), 47.0 (0), 43.1
(2), 39.9 (2), 30.2 (3), 30.0 (0), 28.2 (3), 25.5 (3), 25.3 (3), 24.5
(3).
2-(c-4-ter t-Bu t yl-r -1-h yd r oxycycloh exyl)-2-h yd r oxy-
4,4-d im eth ylcyclobu ta n on e (48): white solid; mp 158-
159.5 °C; 1H NMR δ 3.30 (1H, br s), 2.15 (1H, dd, J ) 0.9,
12.9 Hz), 1.91 (1H, d, J ) 12.9 Hz), 1.90 (1H, m), 1.72-1.40
(6H, m), 1.37 (3H, s), 1.31 (1H, br m), 1.16 (3H, s), 0.96 (1H,
apparent tt, J ) 2.9, 11.8 Hz), 0.87 (9H, s); 13C NMR δ 220.0
(0), 92.6 (0), 72.9 (0), 55.2 (0), 47.7 (1), 38.7 (2), 32.6 (2), 32.4
(0), 30.2 (2), 27.5 (3C, 3), 24.7 (3), 21.8 (2), 21.6 (2), 20.9 (3).
The structure of 48 was determined by X-ray crystallography.19
Compound 48 (60.8 mg, 0.227 mmol) was stirred with
BF3‚Et2O (1.0 mL) for 20 h. Workup gave 56.0 mg of a mixture
of 36a and 37 in a 8:1 ratio by GC-MS.
A solution of 48 (122 mg, 0.489 mmol) in CH2Cl2 (10 mL)
and BF3‚Et2O (0.90 mL) was stirred for 21 h at rt. Workup
gave an oily, tan solid (107 mg), consisting of a 13:1 mixture
of 36a and 37 by GC-MS.
A solution of 48 (84 mg, 0.31 mmol) in CH2Cl2 (1.6 mL) with
BF3‚Et2O (0.58 mL) and H2O (50 µL) was stirred for 23 h at
rt. Workup gave 36a as pale yellow solid (77 mg, 98%).
3,3,4,4-Te t r a m e t h yl-1,2-b is[(t r im e t h ylsilyl)oxy]cy-
clobu ten e (51): colorless liquid; bp2.5 mm 83-87.8 °C; 1H NMR
δ 1.01 (12H, s), 0.20 (6H, s); 13C NMR δ 128.2 (2C, 0), 43.9
(2C, 0), 21.8 (4C, 3), 0.6 (6C, 3).
2-Isopr opyliden e-4,5-dih ydr o-4,4,5,5-tetr am eth yl-3(2H)-
fu r a n on e (52): yellow oil (31% yield from acetone); 1H NMR
δ 2.08 (3H, s), 1.79 (3H, s), 1.22 (6H, s), 1.00 (6H, s); 13C NMR
δ 205.2 (0), 141.8 (0), 121.1 (0), 83.1 (0), 51.0 (0), 23.5 (2C, 3),
19.5 (3C, 3), 17.1 (3).
2-Cycloh e xylid e n e -4,5-d ih yd r o-4,4,5,5-t e t r a m e t h yl-
3(2H)-fu r a n on e (53): tan-colored oil (35% yield from cyclo-
hexanone); 1H NMR δ 2.74 (2H, m), 2.25 (2H, distorted t),
1.75-1.40 (6H, m), 1.22 (3H, s), 1.00 (3H, s); 13C NMR δ 206.0
(0), 139.0 (0), 129.4 (0), 82.9 (0), 51.2 (0), 28.6 (2), 28.1 (2),
27.2 (2), 26.4 (2), 26.2 (2), 23.4 (3), 19.6 (3).
(E)- (42a ) a n d (Z)-3,4-Dih yd r o-3,3-d im eth yl-5-(3,5,5-tr i-
m eth ylcycloh ex-2-en yliden e)-2-fu r an on e (42b). From spec-
tra of the mixture: for 42a : 1H NMR δ 5.74 (1H, dd, J ) 1.4,
3.0 Hz), 2.76 (2H, s), 2.15 (2H, apparent t, J ) 1.8 Hz), 1.85
(2H, br s), 1.77 (3H, br s), 1.29 (6H, s), 0.91 (6H, s); NOE data
5.74 (2.76, 7%; 1.77, 4%), 2.76 (5.74, 13%, 1.29, 6%); 13C NMR
δ 180.4 (0), 145.0 (0), 135.8 (0), 116.9 (1), 113.0 (0), 44.8 (2),
40.0 (0), 38.6 (2), 36.5 (2), 29.8 (0), 28.32 (3), 25.0 (3), 24.3 (3).
For 42b: 1H NMR δ 6.26 (1H, dd, J ) 1.4, 2.8 Hz), 2.69 (2H),
1.85 (4H), 1.77 (3H, br s), 1.28 (6H, s), 0.92 (6H, s); NOE data
6.26 (1.77, 2%), 2.69 (1.85, 6%, 1.28, 8%); 13C NMR δ 180.3
(0), 140.6 (0), 135.1 (0), 116.6 (1), 112.0 (0), 44.8 (2), 39.9 (0),
39.0 (2), 37.8 (2), 30.3 (0), 28.38 (3), 25.0 (3), 24.0 (3).
2,2,8,8-Tetr a m eth ylsp ir o[4.5]d ec-6-en e-1,4-d ion e (43):
white solid; mp 41-42 °C; 1H NMR δ 5.87 (1H, d, J ) 9.9 Hz),
5.09 (1H, d, J ) 9.8 Hz), 2.74 (1H, d, J ) 17.6 Hz), 2.66 (1H,
d, J ) 17.6 Hz), 1.84-1.50 (4H, m), 1.30 (3H, s), 1.22 (3H, s),
1.06 (3H, s), 1.04 (3H, s); 13C NMR δ 218.3 (0), 213.9 (0), 143.3
(1), 118.3 (1), 58.8 (0), 50.3 (2), 46.9 (0), 31.9 (2), 31.1 (0), 29.2
(3), 29.1 (3), 26.9 (2), 25.7 (3), 25.2 (3).
(E)- a n d (Z)-3,4-d ih yd r o-3,3-d im eth yl-5-(4,4-d im eth yl-
cycloh ex-2-en ylid en e)-2-fu r a n on e (44a ,b): 1H NMR (se-
lected signals from mixture) δ 6.37 (1H, d, J ) 10.0 Hz), 5.86
(1H, d, J ) 9.9 Hz), 5.56 (1H, d, J ) 9.9 Hz), 5.52 (1H, d, J )
9.9 Hz), 2.75 (2H, apparent t, J ) 1.6 Hz), 2.70 (2H, br s),
1.31 (6H, s), 1.02 (6H, s).
4,5-Dih yd r o-2-h yd r oxy-2-(1-h yd r oxy-1-m et h ylet h yl)-
5,5-d im eth yl-3(2H)-fu r a n on e (45). Exposure of 18 to air
and then chromatography provided 45 as a yellow oil: 1H NMR
δ 3.64 (1H, OH), 2.64 (1H, d, J ) 18.0 Hz), 2.55 (1H, OH),
2.43 (1H, d, J ) 18.0 Hz), 1.49 (3H, s), 1.46 (3H, s), 1.27 (3H,
s), 1.26 (3H, s); 13C NMR δ 213.6 (0), 100.2 (0), 78.1 (0), 73.9
(0), 49.1 (2), 29.7 (3), 29.4 (3), 23.9 (3), 22.9 (3).
Ack n ow led gm en t. We are grateful to Dr. J ohn N.
Bridson and Mr. David O. Miller of this Department for
the X-ray crystallography. This work was supported by
a grant from the Natural Sciences and Engineering
Research Council of Canada.
(1′R/S,2R/S,2′R/S)- (46a ) a n d (1′R/S,2R/S,2′S/R)-4,5-Di-
h yd r o-2-h yd r oxy-2-(1-h yd r oxy-2-m eth ylcycloh exyl)-5,5-
d im eth yl-3(2H)-fu r a n on e (46b). Exposure of 30a /b to air
left a waxy yellow solid. Chromatography provided a colorless
oil consisting of 46a and 46b in a 1.5:1 ratio. Crystallization
occurred during refrigeration to provide a small, homogeneous
sample of 46a : 1H NMR δ 3.69 (1H, s), 2.63 (1H, d, J ) 18.7
Hz), 2.53 (1H, s), 2.42 (1H, d, J ) 18.7 Hz), 2.08-1.84 (3H,
m), 1.70-1.50 (3H, m), 1.49 (3H, s), 1.43 (3H, s), 1.42-1.20
(3H, m), 1.00 (3H, d, J ) 7.3 Hz); 13C NMR δ 213.6 (0), 100.5
(0), 77.7 (0), 77.2 (0), 48.3 (2), 34.2 (1), 30.3 (3), 29.8 (3), 29.4
(2), 26.5 (2), 21.0 (2), 19.8 (2), 16.2 (3). The structure of 46a
Su p p or tin g In for m a tion Ava ila ble: Additional charac-
terization data (UV, IR, MS, HRMS); 1H and 13C NMR spectra
of 3, 4, 6, 7, 11c, 12a ,b, 15a ,b, 17, 18, 20, 23, 26, 27, 28b,
29a ,b (8:1), 33a ,c, 35, 36a ,b, 37, 40, 43, 45, 46a , 47, 48, 51-
53; X-ray crystal structures for 11c, 33c, 36b, 46a , and 48
(75 pages). This material is contained in libraries on micro-
fiche, 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 O971055V