New Substituent Effects of the Trimethylsilyl Group: Photochemistry of 3-Trimethylsilyl-2,5-cyclohexadienones and Preparation of 4-Alkylidenecyclopentenones

Article abstract of DOI:10.1021/jo000209v

The 4-acetoxymethyl-4-alkyl-3-trimethylsilyl-2,5-cyclohexadien-1-ones 9a-g were prepared from methyl 2-trimethylsilylbenzoate by the Birch reduction-alkylation reaction. Type A photorearrangements of 9a-g were regiospecific to give mixtures of two diastereomers of the corresponding 5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-ones 11a-g. These bicyclohexenones are uniquely photostable; the diastereomers do not photointerconvert nor do they undergo the type B photorearrangement. Bicyclohexenones 11a-g undergo acid-catalyzed protiodesilylative rearrangement to give the 4-alkylidene-2-cyclopenten-1-ones 25a-g. It was of interest to find that the 4-(3′-butenyl)-2,5-cyclohexadienone 9e photorearranged to the 5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-one 11e rather than undergoing the intramolecular 2 + 2 photocycloaddition. Furthermore, the 4-acetoxymethyl-3-methoxy-4-methyl-5-trimethylsilyl-2,5-cyclohexadienone 30a did not show type A photobehavior at 366 and 300 nm, while the 4-(3′-butenyl) analogue 30b gave the intramolecular 2 + 2 cycloadduct 31b. The effects of the trimethylsilyl and methoxy substituents on the photochemical reactivity of 2,5-cyclohexadien-1-ones are discussed from the perspective of n → p* vs π → p* character of the triplet states of the dienones.

Full text of DOI:10.1021/jo000209v

6354
J . Org. Chem. 2000, 65, 6354-6361
New Su bstitu en t Effects of th e Tr im eth ylsilyl Gr ou p :
P h otoch em istr y of 3-Tr im eth ylsilyl-2,5-cycloh exa d ien on es a n d
P r ep a r a tion of 4-Alk ylid en ecyclop en ten on es
Arthur G. Schultz† and Larry O. Lockwood, J r.*
Department of Chemistry, Rensselaer Polytechnic Institute, Troy, New York 12180-3590
lockwl@rpi.edu
Received February 14, 2000
The 4-acetoxymethyl-4-alkyl-3-trimethylsilyl-2,5-cyclohexadien-1-ones 9a -g were prepared from
methyl 2-trimethylsilylbenzoate by the Birch reduction-alkylation reaction. Type A photore-
arrangements of 9a -g were regiospecific to give mixtures of two diastereomers of the corresponding
5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-ones 11a -g. These bicyclohexenones are uniquely photo-
stable; the diastereomers do not photointerconvert nor do they undergo the type B photorearrange-
ment. Bicyclohexenones 11a -g undergo acid-catalyzed protiodesilylative rearrangement to give
the 4-alkylidene-2-cyclopenten-1-ones 25a -g. It was of interest to find that the 4-(3′-butenyl)-2,5-
cyclohexadienone 9e photorearranged to the 5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-one 11e rather
than undergoing the intramolecular 2 + 2 photocycloaddition. Furthermore, the 4-acetoxymethyl-
3-methoxy-4-methyl-5-trimethylsilyl-2,5-cyclohexadienone 30a did not show type A photobehavior
at 366 and 300 nm, while the 4-(3′-butenyl) analogue 30b gave the intramolecular 2 + 2 cycloadduct
31b. The effects of the trimethylsilyl and methoxy substituents on the photochemical reactivity of
2,5-cyclohexadien-1-ones are discussed from the perspective of n f p* vs π f p* character of the
triplet states of the dienones.
Intramolecular cycloadditions of reactive intermediates
Alternatively, it is possible to carry out a two-photon
tandem rearrangement of 1 to the oxyallyl zwitterion 3,
from which intramolecular trapping with a tethered
furan gives the oxyallyl zwitterion-furan cycloadduct 5.4
A variety of other trapping reactions have been uncov-
ered.1,5,6
generated from irradiation of 2,5-cyclohexadien-1-ones
have provided a wide range of novel carbocyclic and
heterocyclic ring systems.1 For example, it has been
shown that the photoexcited state of 2,5-cyclohexadien-
1-one 1 can be trapped by 2 + 2 cycloaddition to a
tethered olefin to give the tricyclo[5.2.1.05,10]dec-2-en-4-
one 4 (Scheme 1).2 This process occurs in competition
with the type A photorearrangement3 to the bicyclo[3.1.0]-
hex-3-en-2-one 2; however, by judicious placement of
substituents on 1, the excited state of 1 can be completely
diverted to the intramolecular 2 + 2 cycloadduct 4.2
Substituents at C(3) of the 2,5-cyclohexadien-1-one 1
exert profound effects on the reactivity of the photo-
excited state [1]* and intermediates formed by photore-
arrangement of [1]*. The 3-methoxy substituent has been
studied in greatest detail;3-7 the focus of the photochemi-
cal study reported in this paper, 3-trimethylsilyl substi-
tution, has previously been examined in a single sub-
strate, 4-carbomethoxy-4-methyl-3-trimethylsilyl-2,5-
cyclohexadien-1-one (16).8 Although the earlier study
revealed unique potential for the 3-trimethylsilyl sub-
stituent, it appeared that the 4-carbomethoxy group was
responsible for the formation of multicomponent product
mixtures and, in any event, would not be compatible with
anticipated intramolecular oxyallyl zwitterion cycload-
ditions because of the migratory aptitude of the car-
bomethoxy group.4 Consequently, it was necessary to
consider modifications of the substitution at C(4) to
possibly control product distributions associated with the
photochemistry of the 3-trimethylsilyl-2,5-cyclohexadien-
1-ones. The 4-acetoxymethyl substituent is compatible
with the type A photorearrangement and the intramo-
lecular 2 + 2 photocycloaddition of 2,5-cyclohexadi-
enones.1 Intramolecular trapping reactions of the oxyallyl
zwitterion 3 with the acetoxymethyl substituent at the
quaternary center have been found to occur with high
chemical efficiency.1 We now describe the preparation
and photochemistry of the 4-acetoxymethyl-4-alkyl-3-
trimethylsilyl-2,5-cyclohexadien-1-ones 9a -g.
* Corresponding author.
† Deceased J anuary 20, 2000.
(1) For a review of the intramolecular trapping reactions of 2,5-
cyclohexadien-1-ones, see: Schultz, A. G. Cyclohexadienone Photo-
chemistry: Trapping Reactions. In CRC Handbook of Organic Photo-
chemistry; Horspool, W. M., Song; P.-S., Eds.; CRC Press: London,
1995; pp 716-727.
(2) Schultz, A. G.; Plummer, M.; Taveras, A. G.; Kullnig, R. K. J .
Am. Chem. Soc. 1988, 110, 5547-5555.
(3) Zimmerman, H. E.; Schuster, D. I. J . Am. Chem. Soc. 1962, 84,
4527-4540.
(4) Schultz, A. G.; Reilly, J . J . Am. Chem. Soc. 1992, 114, 5068-
5073.
(5) Schultz, A. G.; Reilly, J . E.; Wang, Y. Tetrahedron Lett. 1995,
36, 2893-2896.
(6) Schultz, A. G.; Taveras, A. G. Tetrahedron Lett. 1996, 37, 5853-
5856.
(7) Schultz, A. G.; Green, N. J . J . Am. Chem. Soc. 1992, 114, 1824-
1829.
(8) Schultz, A. G.; Antoulinakis, E. G. J . Org. Chem. 1996, 61, 4555-
4559.
(9) (a) Zimmerman, H. E.; Grunewald, J . O. J . Am. Chem. Soc. 1967,
89, 5163-5172. (b) Curran, W. V.; Schuster, D. I. J . Chem. Soc., Chem.
Commun. 1968, 699. (c) Rodgers, T. R.; Hart, H. Tetrahedron Lett.
1969, 4845-4848. (d) Schuster, D. I.; Curran, W. V. J . Org. Chem.
1970, 35, 4192-4201. (e) Schuster, D. I.; Prabhu, K. V.; Adcock, S.;
van der Veen, J .; Fujiwara, H. J . Am. Chem. Soc. 1971, 93, 1557-
1558.
(10) Schultz, A. G.; Lavieri, F. P.; Macielag, M.; Plummer, M. J . Am.
Chem. Soc. 1987, 109, 3991-4000.
10.1021/jo000209v CCC: $19.00 © 2000 American Chemical Society
Published on Web 09/06/2000

New Substituent Effects of the Trimethylsilyl Group
J . Org. Chem., Vol. 65, No. 20, 2000 6355
Sch em e 1
Sch em e 2
Sch em e 3
matographic separation of diastereomers. Inspection of
product mixtures immediately after photolysis by 1H
NMR spectroscopy indicated that bicyclohexenones had
formed in yields >90%. There was no evidence for
formation of the regioisomeric 4-trimethylsilylbicyclo-
hexenones 12a -g during irradiations of 9a -g at 366 nm
or during irradiations of 11a -g through Pyrex glass
(>300 nm).
Irradiation of the ∼1:1 mixtures of 11a -g at 300 nm
did not result in an observable change in the diastere-
omer ratio. Other workers have found that 6,6-diaryl- and
6,6-dialkyl-substituted bicyclohexenone epimers do not
photointerconvert under a variety of photochemical con-
ditions.9 However, 6-alkyl-6-carbomethoxy-4-methoxybi-
cyclohexenones 14 and 15, initially obtained from pho-
tolyses of 4-alkyl-4-carbomethoxy-3-methoxycyclohexa-
dienones 13 at 366 nm as ∼1:1 mixtures, were found to
undergo photoequilibration to ∼9:1 mixtures favoring the
endo-carbomethoxy epimer 14.10 An investigation of the
mechanism of photoequilibration for one case (R ) Me)
revealed that 14 and 15 interconverted by reversible
cleavage of the cyclopropane bonds exocyclic to the
cyclopentenone ring. Photointerconversions of bicyclo-
hexenone epimers appear to be associated with the
presence of electron-withdrawing substituents at C(6),
the carbomethoxy group in 14 and 15, and the cyano
substituent in an analogous series.4,10
Resu lts a n d Discu ssion
Cyclohexadienones 9a -g were prepared from methyl
2-(trimethylsilyl)benzoate 68 by standard procedures as
shown in Scheme 2. As demonstrated by the conversions
of 6 to 7a -f, the Birch reduction-alkylations of 6 were
carried out in good to excellent yields with a wide range
of alkyl halides. The bis-allylic oxidations of 8a -f to give
cyclohexadienones 9a -f were performed with generally
high efficiency, although yields were in the 50-70%
range for the allylic, benzylic, and 2-furylpropyl deriva-
tives; however, the 4-(3′-butenyl)-2,5-cyclohexadienone
was obtained in 89% yield. The 4-azidopropyl-2,5-cyclo-
hexadien-1-one 9g was prepared from chloride 9d by
substitution of the intermediate iodide with NaN3.
Typ e A P h otor ea r r a n gem en ts of 4-Acetoxym eth -
y l-4-a lk y l-3-t r im e t h y ls ily l-2,5-c y c lo h e x a d ie n -1-
on es. The photochemistry of 2,5-cyclohexadien-1-ones
9a -g in degassed benzene solution is outlined in Scheme
3. In contrast to the photochemistry of the 4-carbo-
methoxy analogue, which gave a complicated mixture of
products under similar conditions,8 irradiation of 9a -g
through uranyl glass provided mixtures of two diaster-
eomers of the corresponding 5-trimethylsilylbicyclo[3.1.0]-
hex-3-en-2-ones 11a -g. These bicyclohexenones were
stable to neutral conditions (bicyclohexenones 11a and
11f were recovered unchanged from refluxing benzene)
but underwent protiodesilylative rearrangement to 4-alkyl-
idene-2-cyclopenten-1-ones 25a-g during attempted chro-
There are several unique features of the photochem-
istry outlined in Scheme 3. It is obvious that there is a
complete shift in regiocontrol for the type A photorear-
rangement of 9a -g to give 11a -g compared to that for
the conversion of 13 to 14 and 15 (Scheme 4); however,

6356 J . Org. Chem., Vol. 65, No. 20, 2000
Schultz and Lockwood
Sch em e 4
tardation presumably is a result of the electropositive
character of silicon.
Acid -Ca ta lyzed Rea r r a n gem en ts of 5-Tr im eth yl-
silylbicyclo[3.1.0]h ex-3-en -2-on es to 4-Alk ylid en e-2-
cyclop en ten -1-on es. As already noted, attempted iso-
lation of bicyclohexenones 11a -g by chromatographic
methods resulted in protiodesilylative rearrangement to
4-alkylidene-2-cyclopenten-1-ones 25a -g as ∼1:1 mix-
tures of E- and Z-isomers. 4-Alkylidene-2-cyclopenten-
1-ones have been prepared by Friedel-Crafts type cy-
clizations,14 by Rh(CO)2Cl2-catalyzed cyclization of 3,4-
diacetoxy-1,5-diynes,15 and by the metal-catalyzed coupling
of allenes and alkynes in the presence of CO.16,17 Because
these dienones have become rather valuable intermedi-
ates in organic synthesis, we decided to develop a more
convenient conversion of 3-trimethylsilyl-2,5-cyclohexa-
dienones 9a-g to 4-alkylidene-2-cyclopenten-1-ones 25a-g
(Scheme 6).
the regiospecificity for formation of the 5-substituted
bicyclohexenones 11a -g is a result of not only a change
from the methoxy to a trimethylsilyl group, but also a
change from a carbomethoxy to an acetoxymethyl sub-
stituent. The second substituent effect is revealed by
comparing the photochemistry shown in Scheme 3 with
that shown in Scheme 5. Notably, the 4-carbomethoxy-
4-methyl-3-trimethylsilyl-2,5-cyclohexadien-1-one (16) has
been found to photorearrange to 4-trimethylsilylbicyclo-
hexenone 17 and 5-trimethylsilylbicyclohexenone 18.
Both 17 and 18 undergo the type B photorearrangement11
at 366 nm to give the intermediate oxyallyl zwitterions
19 and 20, from which 1,2-carbomethoxy group migra-
tions give phenols 21-23.8
Thus, the type A photorearrangements of 3-trimeth-
ylsilyl-2,5-cyclohexadienones 9a -g are not only regiospe-
cific, but the photoproducts, bicyclohexenones 11a -g,
also are uniquely photostable at 366 nm and even 300
nm. These observations have important synthetic con-
sequences; however, there is a mechanistic question to
consider: are reversible type B photorearrangements of
11 and even 12 to zwitterions corresponding to 19 and
20 (Scheme 5) occurring under the photolysis conditions
shown in Scheme 2? This possibility must be considered
in light of the reversible type B oxyallyl zwitterion
formation discovered during an investigation of the
photochemistry of 4-methoxy- and 5-methoxybicyclo-
[3.1.0]hex-3-en-2-ones.4 Reversible type B zwitterion
formation was demonstrated in the previous study4 by
inter- and intramolecular trapping reactions of the zwit-
terions. The absence of any trapping products from the
irradiation of the 4-[3′-(2-furyl)propyl]-2,5-cyclohexadi-
enone 9f or the corresponding 3′-azidopropyl derivative
9g12 or from photolysis of 9a in the presence of furan
suggests that two reversible type B zwitterion formation
does not occur on photoexcitation possibilities of bicyclo-
hexenones 11a -g or that the lifetime of the intermediate
zwitterions is not sufficiently long for the standard
trapping processes to take place.
Irradiation of 9a -f in the presence of CF3CO2H
provided 25a -f as ∼1:1 mixtures of E- and Z-isomers in
yields ranging from 73 to 94%. The direct procedure for
the photorearrangement of the 3′-azidopropyl derivative
9g gave 25g in only 30% yield; in this case it was better
to perform the conversion 9g f 11g f 25g in a stepwise
manner to give 25g in 70% yield. The acid-catalyzed
conversions of 11a -g to 25a -g are explained by proton-
ation of the ketone carbonyl group in 11 followed by
cleavage of the C(1)-C(6) bond to give carbocation 24.
Selective cleavage of the C(1)-C(6) bond in 11 is a result
of carbocation stabilization by the â effect of silicon.18 Loss
of the trimethylsilyl group and enolization results in
formation of 25.
4-Alkylidene-2-cyclopenten-1-ones 25a -g possess a
dense array of functional groups that should display
useful chemical reactivity. In attempts to alter the E:Z-
isomer ratio, solutions of 25a in benzene were irradiated
(366 nm) in the absence or presence of Michler’s ketone,
but no change in isomer distribution was observed. The
1:1 ratio of isomers may represent the photostationary
state for 25a in analogy with that previously observed
for a derivative of 25a .8 A productive process under
current development is illustrated by the Baeyer-Villiger
oxidation of 25a to give the valerolactone derivative 26
(Scheme 7). Preferential migration of the vinyl group in
(13) (a) Paquette, L. A.; Wells, G. J .; Horn, K. A.; Yan, T.-H.
Tetrahedron 1983, 39, 913-914. (b) Paquette, L. A. Chem. Rev. 1986,
86, 733-750.
The apparent absence of a pathway for interconversion
of 5-trimethylsilylbicyclohexenones 11a -g with the 4-tri-
methylsilyl isomers 12a -g suggests that bicyclohex-
enones 11a -g are formed as kinetic products in the type
A photorearrangements of 2,5-cyclohexadienones 9a -g.
Unlike the 6-carbomethoxy-substituted bicyclohexenones
14 and 15 and analogues,4 there is no evidence for
reversible photocleavage of the C(1)-C(6) bond in 11a -
g. This means that there is a kinetic preference for the
thermal 1,4-sigmatropic rearrangement of the least
substituted cyclopropane bond in the intermediate oxy-
allyl zwitterion 10. This interesting effect of silicon
appears to be related to the rate retardation of a silyl
group compared to hydrogen in the thermal vinylcyclo-
propane to cyclopentene rearrangement.13 The rate re-
(14) (a) Martin, G. J .; Rabiller, C.; Mabon, G. Tetrahedron 1972,
28, 4027-4037. (b) Nakamura, E.; Fukuzaki, K.; Kuwajima, I. J . Chem.
Soc., Chem. Commun. 1983, 499-501.
(15) Purro, S.; Pryde, A.; Zsindely, J .; Schmid, H. Helv. Chim. Acta
1978, 61, 266-278.
(16) (a) Aumann, R.; Melchers, H. D.; Weidenhaupt, H. J . Chem.
Ber. 1990, 123, 351-356. (b) Aumann, R.; Weidenhaupt, H. J . Chem.
Ber. 1987, 120, 23-27. (c) Hicks, F. A.; Kablaoui, N. M.; Buchwald, S.
L. J . Am. Chem. Soc. 1996, 118, 9450-9451. (d) Ahmar, M.; Chabanis,
O.; Gauthier, J .; Cazes, B. Tetrahedron Lett. 1997, 38, 5277-5280. (e)
Ahmar, M.; Antras, F.; Cazes, B. Tetrahedron Lett. 1995, 36, 4417-
4420. (f) Ahmar, M.; Locatelli, C.; Colombier, D.; Cazes, B. Tetrahedron
Lett. 1997, 38, 5281-5284. (g) Brummond, K. M.; Wan, H.; Kent, J . L.
J . Org. Chem. 1998, 63, 6535-6545. (h) Brummond, K. M.; Wan, H.
Tetrahedron Lett. 1998, 39, 931-934. (i) Brummond, K. M.; Lu, J . J .
Am. Chem. Soc. 1999, 121, 5087-5088.
(17) 4-Alkylidene-2-cyclopenten-1-ones also have been obtained as
reaction byproducts; for example, see: (a) Ackroyd, J .; Karpf, M.;
Dreiding, A. S. Helv. Chim. Acta 1985, 68, 338-344. (b) Wolff, S.;
Agosta, W. J . Org. Chem. 1981, 46, 4821-4825. (c) Rizzo, C. J .; Dunlap,
N. K.; Smith, A. B. J . Org. Chem. 1987, 52, 5280-5283.
(18) Lambert, J . B.; Zhao, Y.; Emblidge, R. W.; Salvador, L. A.; Liu,
X.; So, J .-H.; Chelius, E. C. Acc. Chem. Res. 1999, 32, 183-190 and
references therein.
(11) Zimmerman, H. E.; Epling, G. A. J . Am. Chem. Soc. 1972, 94,
7806-7811.
(12) Schultz, A. G.; Macielag, M.; Plummer, M. J . Org. Chem. 1988,
53, 391-395.

New Substituent Effects of the Trimethylsilyl Group
J . Org. Chem., Vol. 65, No. 20, 2000 6357
Sch em e 5
Sch em e 6
Sch em e 8
cycloaddition reaction of 4-(3′-butenyl)-2,5-cyclohexadi-
enones also has been examined (Scheme 8). Remarkably,
9e was found to undergo only the type A photorearrange-
ment to bicyclohexenone 11e. This result should be
contrasted to the corresponding 3-methoxy analogue
which gives the photocycloaddition product 27 in es-
sentially quantitative yield.2 The unsubstituted deriva-
tive gave both the cycloadduct 28 and phenol 29 (the
product of consecutive type A and type B photorear-
rangements) in approximately equivalent amounts.
The n f π* triplet state is generally considered to be
responsible for type A photobehavior,21 and we have
suggested that the effect of the 3-methoxy substituent is
to lower the energy of the π f p* triplet state to make
triplet-state photocycloadditions more competitive with
the type A photorearrangement.2 Upon comparing the
photoreactivity of 9e with that of the unsubstituted
analogue and the 3-methoxy variant (Scheme 8), it
appears it is reasonable that the 3-trimethylsilyl group
serves to enhance the n f p* reactivity of the 2,5-
cyclohexadien-1-one ring system.
Sch em e 7
R,â-unsaturated primary alkyl ketones is well-known;19
however, it is noteworthy that the Baeyer-Villiger
oxidation occurs without competing epoxidation of the
tetrasubstituted double bond in both 25a and 26.20
In tr a m olecu la r 2 + 2-Cycloa d d ition s of 4-(3′-Bu -
ten yl)-2,5-cycloh exa d ien on es. The effect of the 3-tri-
methylsilyl substituent on the intramolecular 2 + 2
(19) (a) Bocecken, M.; J acobs, R. Recl. Trav. Chim. 1936, 55, 804-
814. (b) Krafft, G. A.; Katzenellenbogen, J . A. J . Am. Chem. Soc. 1981,
103, 5459-5466.
(21) Zimmerman, H. E.; Lynch, D. C. J . Am. Chem. Soc. 1985, 107,
7745-7756.
(20) Paquette, L. A.; Barrett, J . H. Org. Syn. 1969, 49, 62-65.

6358 J . Org. Chem., Vol. 65, No. 20, 2000
Schultz and Lockwood
Sch em e 9
cyclohexadienones. Although it has not been possible to
realize the tandem type A-type B photorearrangements
to give oxyallyl zwitterions 3 from 9f and 9g, several
other synthetically useful processes have evolved from a
careful study of the preparation and photochemistry of
the 3-trimethylsilyl-2,5-cyclohexadien-1-ones 9a -g. Note-
worthy discoveries include (1) the high chemical efficien-
cies for the Birch reduction-alkylations of methyl 2-tri-
methylsilyl benzoate 6;22 (2) the regiospecificity and high
chemical efficiencies for the type A photorearrangements
of the 3-trimethylsilyl-2,5-cyclohexadienones 9a -g to
give the 5-trimethylsilylbicyclo[3.1.0]hex-3-en-2-ones 11a-
g; (3) the photostability of the bicyclohexenones 11a -g,
especially when compared to the photoreactivity of bicy-
clohexenones 17 and 18 obtained from type A photore-
arrangements of the 4-carbomethoxy analogue 16; (4) the
generality and high chemical efficiencies for the acid-
catalyzed rearrangements of 5-trimethylsilylbicyclo[3.1.0]-
hex-3-en-2-ones to 4-alkylidene-2-cyclopenten-1-ones 25a-
g; and (5) the effect of the 3-trimethylsilyl substituent
on the intramolecular 2 + 2 photocycloadditions of 4-(3′-
butenyl)-2,5-cyclohexadienones.
Sch em e 10
Exp er im en ta l Section
Gen er a l P r oced u r es. Tetrahydrofuran and diethyl ether
were distilled from benzophenone sodium ketyl under nitrogen.
Benzene was distilled from CaH2. Analytical thin-layer chro-
matography was performed on 0.25 mm E. Merck silica gel
(60F-254) plates using UV light and aqueous KMnO4/K2CO3
for visualization. Flash column chromatography was carried
out on Baker silica gel (40 µm). Low-resolution mass spectra
were obtained by GC-MS using isobutane for chemical ioniza-
tion. High-resolution mass spectra were obtained from the
mass spectrometry laboratory at the University of Illinois at
Urbana/Champaign. Elemental analyses were performed by
Atlantic Microlabs, Inc., Norcross, GA. The light source for all
photochemistry was a Hanovia 450-W medium-pressure mer-
cury arc lamp. The lamp was placed in a water-cooled Pyrex
immersion well and when necessary fitted with a uranyl glass
filter to give light with wavelength mainly at 366 nm.
Bir ch Red u ction a n d Alk yla tion of Meth yl-2-tr im eth -
ylsilylben zoa te (6) a n d Eth yl-2-m eth oxy-6-tr im eth ylsi-
lylben zoa te (30).22 To a flame-dried three-necked flask under
argon was added 6 dissolved in 10-15 mL of THF and 1.0
equiv of t-BuOH. The solution was cooled to -78 °C and 100
mL of twice distilled NH3 was added. Small pieces of lithium
wire (2.5-3.0 equiv) were added until the deep blue coloration
persisted for 30 min. Excess metal was quenched with pip-
erylene to give a dark orange solution, the appropriate
alkylation agent (1.5-2.0 equiv) was added, and the resulting
yellow solution was stirred for 1 h at -78 °C before quenching
with 1-2 g of solid NH4Cl. The solution was warmed slowly
to room temperature while the NH3 was evaporated under a
stream of argon. The thick mixture was diluted with H2O and
Et2O, the phases were separated, and the organic phase was
twice extracted with Et2O. The organic phases were combined,
washed with saturated NaHCO3 and saturated NaCl, and
dried over MgSO4. Filtration, removal of solvent in vacuo, and
flash chromatography on silica gel with 5% EtOAc in hexane
gave the 1,4-cyclohexadiene.23 See ref 8 for the preparation
and characterization of 7a .
The ability of the trimethylsilyl substituent to promote
type A photoreactivity can be completely nullified by
installation of a methoxy substituent on the second
dienone double bond (Scheme 9). The method of Kleschick
and Thornburgh provided ethyl benzoate 30 in 75%
yield.24 In an unoptimized series of steps the previously
detailed sequence was followed to provide cyclohexadi-
enones 33. Thus, the 4-acetoxymethyl-3-methoxy-5-tri-
methylsilyl-2,5-cyclohexadienone 33a is photostable for
extended periods of time at both 366 and 300 nm, but
the 4-(3′-butenyl) analogue 33b undergoes efficient in-
tramolecular 2 + 2 photocycloaddition to give 34 (Scheme
10).
Con clu sion
The trimethylsilyl group has been found to be a very
effective agent of control of the photochemistry of 2,5-
6-Ca r b om et h oxy-6-a llyl-1-(t r im et h ylsilyl)-1,4-cyclo-
h exa d ien e (7b) was prepared from 6 (1.1 g, 5.3 mmol) and
allyl bromide; colorless oil (940 mg, 70%); 1H NMR (C6D6, 300
MHz) δ 6.13 (s, 1 H), 5.69 (m, 2 H), 5.55 (d, 1 H, J ) 11 Hz),
5.06 (d, 1 H, J ) 9.9 Hz), 5.04 (s, 1 H), 3.32 (s, 3 H), 2.82 (m,
2 H), 2.37 (m, 2 H), 0.17 (s, 9 H); 13C NMR (C6D6, 75 MHz) δ
175.30, 138.24, 137.36, 135.09, 129.28, 125.63, 117.88, 51.92,
(22) The asymmetric Birch reduction-alkylations of a chiral 2-tri-
methylsilylbenzamide also have been reported; see: (a) Schultz, A. G.;
Pettus, L. J . Org. Chem. 1997, 62, 6855-6861. (b) Schultz, A. G.;
Pettus, L. Tetrahedron Lett. 1997, 38, 5433-5436.
(23) Hauser, C. R.; Hance, C. R. J . Am. Chem. Soc. 1951, 73, 5846-
5848.
51.28, 42.67, 27.85, 0.91; IR (film) 2951, 1730 cm-1
.
6-Ca r bom eth oxy-6-ben zyl-1-(tr im eth ylsilyl)-1,4-cyclo-
h exa d ien e (7c) was prepared from 6 (548 mg, 2.1 mmol) and
(24) Kleschick, W. A. and Thornburgh, S. Synth. Commun. 1997,
27, 1793-1799.

New Substituent Effects of the Trimethylsilyl Group
J . Org. Chem., Vol. 65, No. 20, 2000 6359
1
benzyl bromide; colorless oil (500 mg, 79%); H NMR (CDCl3,
6-Acetoxym eth yl-6-ben zyl-1-(tr im eth ylsilyl)-1,4-cyclo-
h exa d ien e (8c) was prepared from 7c (1.6 g, 5.3 mmol); a
colorless oil (1.2 g, 72%); 1H NMR (C6D6, 300 MHz) δ 7.03 (m,
5 H), 6.06 (s, 1 H), 5.58 (d, 1 H, J ) 11.5 Hz), 5.46 (d, 1 H,
J ) 11.5 Hz), 4.27 (d, 1 H, J ) 9.2 Hz), 4.16 (d, 1 H, J ) 9.2
Hz), 2.63 (q, 2 H, J ) 6 Hz), 2.15 (d, 1 H, J ) 15 Hz), 1.76 (d,
1 H, J ) 15 Hz), 1.64 (s, 3 H), 0.19 (s, 9 H); 13C NMR (C6D6,
75 MHz) δ 170.59, 140.35, 139.67, 138.04, 135.34, 131.68,
127.88, 126.59, 125.96, 71.40, 66.94, 44.15, 28.22, 20.90, 1.90;
500 MHz) δ 7.21 (m, 3 H), 7.16 (m, 2 H), 6.24 (s, 1 H), 5.82 (d,
1 H, J ) 6.6 Hz), 5.65 (d, 1 H, J ) 6.6 Hz), 3.78 (s, 3 H), 3.30
(d, 1 H, J ) 6.6 Hz), 3.02 (d, 1 H, J ) 6.6 Hz), 2.48 (d, 1 H,
J ) 11.5 Hz), 1.86 (d, 1 H, J ) 11.5 Hz), 0.24 (s, 9 H); 13C
NMR (CDCl3, 75 MHz) δ 175.81, 138.33, 137.71, 137.42,
131.50, 128.39, 127.36, 126.19,126.12, 52.38, 52.28, 43.66,
27.26, 0.73; IR (film) 2952, 1731 cm-1; CIMS m/z (relative
intensity) 301 (M+ + 1, 100%), 193 (68.7).
IR (film) 2953, 1737 cm-1
.
6-Ca r bom eth oxy-6-(3′-ch lor op r op yl)-1-(tr im eth ylsilyl)-
1,4-cycloh exa d ien e (7d ) was prepared from 6 (1.24 g, 6
mmol) and 3-chloro-1-iodopropane; a colorless oil (1.40 g, 68%);
1H NMR (C6D6, 500 MHz) δ 6.09 (s, 1 H), 5.62 (d, 1 H, J ) 6.4
Hz), 5.39 (d, 1 H, J ) 6.4 Hz), 3.31 (s, 3 H), 3.17 (m, 2 H), 2.41
(d, 1 H, J ) 4.2 Hz), 2.33 (d, 1 H, J ) 4.2 Hz), 1.98 (m, 2 H),
1.48 (m, 2 H), 0.15 (s, 9 H); 13C NMR (C6D6, 125 MHz) δ 175.35,
137.95, 137.47, 129.03,126.11, 51.95, 51.05, 45.58, 44.95, 35.92,
35.32, 28.60, 27.73, 0.79; IR (film) 2955, 1735 cm-1; CIMS m/z
(relative intensity) 287 (M+ + 1, 36), 271 (83), 179 (100).
6-Ca r b om et h oxy-6-(3′-b u t en yl)-1-(t r im et h ylsilyl)-1,4-
cycloh exa d ien e (7e) was prepared from 6 (1.16 g, 5.6 mmol)
and 4-bromo-1-butene; a colorless oil (1.2 g, 82%); 1H NMR
(C6D6, 300 MHz) δ 6.14 (s, 1 H), 5.83 (m, 1 H), 5.66 (d, 1 H,
J ) 10.2 Hz), 5.45 (d, 1 H, J ) 10.8 Hz), 5.60 (d, 1 H, J ) 17
Hz), 4.96 (d, 1 H, J ) 10.2), 3.32 (s, 3 H), 2.42 (d, 1 H, J ) 5.4
6-Acetoxym eth yl-6-(3′-ch lor op r op yl)-1-(tr im eth ylsilyl)-
1,4-cycloh exa d ien e (8d ) was prepared from 7d (1.40 g, 5.0
mmol); a colorless oil (910 mg, 60%); 1H NMR (C6D6, 300 MHz)
δ 6.14 (s, 1 H), 5.66 (d, 1 H, J ) 10.2 Hz), 5.25 (d, 1 H, J )
10.2 Hz), 4.10 (d, 1 H, J ) 10.8 Hz), 3.94 (d, 1 H, J ) 10.8 Hz),
3.12 (m, 2 H), 2.30 (q, 2 H, J ) 3.6 Hz), 1.67 (s, 3 H), 1.49 (m,
3 H), 1.14 (m, 1 H), 0.14 (s, 9 H); 13C NMR (C6D6, 75 MHz) δ
170.63, 143.24, 139.28, 132.03, 125.55, 71.70, 45.75, 44.31,
34.87, 28.72, 28.31, 20.89, 1.72; IR (film) 2953, 1738 cm-1
;
CIMS m/z (relative intensity) 241 (M+ + 1, 30), 207 (22), 167
(49), 133 (100).
6-Acetoxym eth yl-6-(3′-bu ten yl)-1-(tr im eth ylsilyl)-1,4-
cycloh exa d ien e (8e) was prepared from 7e (630 mg, 2.4
mmol); a colorless oil (380 mg, 58%); 1H NMR (C6D6, 300 MHz)
δ 6.19 (s, 1 H), 5.76 (m, 2 H), 5.34 (d, 1 H, J ) 10.2 Hz), 5.03
(d, 1 H, J ) 17.1 Hz), 4.96 (d, 1 H, J ) 8.7 Hz), 4.08 (q, 2 H,
J ) 10.8), 2.37 (m, 2 H), 1.96 (m, 2 H), 1.67 (s, 3 H), 1.58 (m,
1 H), 1.32 (m, 1 H), 0.16 (s, 9 H); 13C NMR (C6D6, 75 MHz) δ
170.49, 139.75, 139.34, 132.26, 125.38, 114.74, 71.84, 44.66,
Hz), 2.36 (d, 1 H, J ) 5.4 Hz), 2.03 (m, 4 H), 0.15 (s, 9 H); 13
C
NMR (C6D6, 75 MHz) δ 175.46, 139.18, 138.05, 137.40, 129.22,
125.94, 114.94, 51.94, 51.43, 36.96, 29.68, 27.85, 0.829; IR
(film) 2954, 1735 cm-1
.
36.54, 29.89, 28.39, 20.89, 1.75; IR (film) 2953, 1744 cm-1
;
6-Ca r bom eth oxy-6-(3′-(2′-fu r a n ylp r op yl))-1-(tr im eth yl-
silyl)-1,4-cycloh exa d ien e (7f) was prepared from 6 and
1-iodo-3-(2-furanyl)propane; flash chromatography gave a
mixture of 7e and alkylation agent that was carried to the
next step.
6-Ca r bom eth oxy-6-m eth yl-1-m eth oxy-4-tr im eth ylsilyl-
1,4-cycloh exa d ien e 31a was prepared from 30 (675 mg, 2.8
mmol) and iodomethane, a yellow oil that was carried to the
next step.
6-Ca r bom eth oxy-6-(3′-bu ten yl)-1-m eth oxy-4-tr im eth yl-
silyl-1,4-cycloh exa d ien e 31b was prepared from 30 (540 mg,
2.3 mmol) and 4-bromo-1-butene, a yellow oil that was carried
to the next step.
CIMS m/z (relative intensity) 277 (M+ + 1, 6) 233 (100).
6-Acet oxym et h yl-6-(3′-(2′-fu r a n yl)p r op yl)-1-(t r im et h -
ylsilyl)-1,4-cycloh exa d ien e (8f) was prepared from 7f (540
mg, 1.8 mmol), a light yellow oil that was carried to the next
step.
6-Acetoxym eth yl-6-m eth yl-1-m eth oxy-4-tr im eth ylsilyl-
1,4-cycloh exa d ien e (32a ) was prepared from crude 31a (650
mg, 2.4 mmol), a light yellow oil that was carried to the next
step.
6-Acetoxym eth yl-6-(3′-bu ten yl)-1-m eth oxy-4-tr im eth -
ylsilyl-1,4-cycloh exa d ien e (32b) was prepared from crude
31b (580 mg, 2.1 mmol), a light yellow oil that was carried to
the next step.
Red u ction of 7a -f a n d 31a -b a n d Acyla tion . To a 0.5
M solution of 7 in Et2O at 0 °C was added 1.5 equiv of lithium
aluminum hydride (1 M in Et2O). After 30 min at 0 °C, the
reaction was quenched with 1.5 equiv of H2O, 1.5 equiv of 15%
NaOH, and 3 equiv of H2O. The mixture was filtered through
Celite, dried over MgSO4, and filtered, and the solvent was
removed in vacuo. The resulting oil was redissolved in pyridine
to give a 1 M solution. Then, 2 equiv of Ac2O and 1 mg of
DMAP were added and stirring at room temperature was
continued for 4-6 h. The reaction mixture was diluted with
H2O and extracted three times with Et2O. The organic phases
were combined and washed successively with 5% HCl, H2O,
and saturated NaHCO3. The solution was dried with MgSO4,
filtered, and concentrated in vacuo. Flash chromatography of
the resulting oil on silica gel with 10% Et2O in hexane gave 8.
6-Acetoxym eth yl-6-m eth yl-1-(tr im eth ylsilyl)-1,4-cyclo-
h exa d ien e (8a ) was prepared from 7a (5.37 g, 24 mmol); a
Oxid a tion of 8a -f a n d 32a -b. A 0.2 M solution of 8 or
32 in benzene was cooled to 0 °C, addition of 1 equiv by weight
of Celite, 0.2 equiv of pyridinium dichromate, and 3 equiv of
tert-butyl hydrogen peroxide in decane was followed by stirring
at room temperature for 8-12 h. Filtering through Celite with
EtOAc followed by concentration gave the crude oil. Flash
chromatography on silica gel with 30% EtOAc in hexane yields
9.
4-Acetoxym eth yl-4-m eth yl-3-(tr im eth ylsilyl)-2,5-cyclo-
h exa d ien -1-on e 9a was prepared from 8a (3.15 g, 13.2 mmol)
to give a yellow oil (2.8 g, 94%): 1H NMR (CDCl3, 500 MHz) δ
6.83 (d, 1 H, J ) 10.3 Hz), 6.58 (s, 1 H), 6.25 (d, 1 H, J ) 10.3
Hz), 4.18 (q, 2 H, J ) 11 Hz), 1.93 (s, 3 H), 1.27 (s, 3 H), 0.24
(s, 9 H), 13C NMR (CDCl3, 125 MHz) δ 184.35, 170.71, 166.96,
156.80, 142.02, 139.08, 128.78, 68.47, 45.45, 22.24, 20.78, 0.53;
IR (film) 2957, 1747, 1664 cm-1; CIMS m/z (relative intensity)
253 (M+ + 1, 25.45), 193 (100). Anal. Calcd for C13H20O3Si: C,
61.83; H, 8.01. Found: C, 61.85; H, 7.88.
1
colorless oil (4.7 g, 82%); H NMR (C6D6, 300 MHz) δ 6.13 (s,
1 H), 5.65 (d, 1 H, J ) 7.5 Hz), 5.52 (d, 1 H, J ) 7.5 Hz), 4.08
(d, 1 H, J ) 12.1 Hz), 4.02 (d, 1 H, J ) 12.1 Hz), 2.41 (s, 2 H),
1.68 (s, 3 H), 1.08 (s, 3 H), 0.165 (s, 9 H); 13C NMR (C6D6, 75
MHz) δ 170.65, 141.78, 137.68, 134.33, 124.02, 71.75, 40.67,
28.26, 25.97, 20.90, 1.73; IR (film) 2957, 1743 cm-1; CIMS m/z
(relative intensity) 237 (M+ + 1, 2.5), 179 (36), 105 (100).
6-Acet oxym et h yl-6-a llyl-1-(t r im et h ylsilyl)-1,4-cyclo-
h exa d ien e (8b) was prepared from 7b (700 mg, 3.3 mmol); a
4-Acet oxym et h yl-4-a llyl-3-(t r im et h ylsilyl)-2,5-cyclo-
h exa d ien -1-on e 9b was prepared from 8b (497 mg, 1.8 mmol)
to give a yellow oil (330 mg, 65%): 1H NMR (C6D6, 300 MHz)
δ 6.84 (d, 1 H, J ) 1.8 Hz), 6.36 (dd, 1 H, J ) 1.8 Hz, J ) 10.2
Hz), 6.12 (d, 1 H), 5.53 (m, 1 H), 4.92 (m, 2 H), 3.92 (q, 2 H,
J ) 11.1 Hz), 1.53 (m, 3 H), 1.51 (s, 3 H), 1.18 (m, 1 H), 0.01
(s, 9 H); 13C NMR (C6D6, 75 MHz) δ 183.67, 170.15, 163.77,
154.46, 142.11, 137.83, 131.23, 115.50, 68.68, 49.78, 34.01,
20.44, 0.57; IR (film) 2956, 1746, 1663 cm-1; CIMS m/z (relative
intensity) 279 (M+ + 1, 3.6), 219 (100). Anal. Calcd for
1
colorless oil (497 mg, 73%); H NMR (C6D6, 300 MHz) δ 6.15
(s, 1 H), 5.71 (m, 2 H), 5.40 (d, 1 H), 4.97 (s, 1 H), 4.92 (d, 1
H), 4.12 (d, 1 H, J ) 11.0), 4.01 (d, 1 H, J ) 11.0 Hz), 2.34 (m,
2 H), 2.25 (m, 1 H), 2.03 (m, 1 H), 1.65 (s, 3 H), 0.137 (s, 9 H);
IR (film) 2953, 1741 cm-1; CIMS m/z (relative intensity) 265
(1.5), 205 (39), 131 (100).
C
15H22O3Si: C, 64.70; H, 7.99. Found: C, 64.85; H, 7.82.
4-Acetoxym eth yl-4-ben zyl-3-(tr im eth ylsilyl)-2,5-cyclo-
h exa d ien -1-on e 9c was prepared from 8c (1.2 g, 3.8 mmol)
to give a yellow oil (700 mg, 56%): 1H NMR (C6D6, 300 MHz)

6360 J . Org. Chem., Vol. 65, No. 20, 2000
Schultz and Lockwood
δ 7.03 (m, 3 H), 6.81 (m, 2 H), 6.76 (d, 1 H, J ) 1.8 Hz), 6.37
(d, 1 H, 10.2 Hz), 6.26 (dd, 1 H, J ) 1.8 Hz, J ) 10.2 Hz), 4.15
(q, 2 H, J ) 11.1 Hz), 2.63 (q, 2 H, J ) 5.4 Hz), 1.53 (s, 3 H)
0.01 (s, 9 H); 13C NMR (C6D6, 75 MHz) δ 183.35, 170.23, 164.65,
154.04, 141.40, 135.82, 130.72, 130.66, 128.07, 127.63, 68.32,
50.05, 42.33, 20.51, 0.95; IR (film) 2956, 1744, 1662 cm-1; CIMS
m/z (relative intensity) 328 (M+ + 1, 41), 269 (100), 179 (41).
Anal. Calcd for C19H24O3Si: C, 69.51; H, 7.39. Found: C, 69.35;
H, 7.48.
4-Acetoxym eth yl-3-m eth oxy-4-m eth yl-5-tr im eth ylsilyl-
2,5-cycloh exa d ien -1-on e 33a was prepared from 32a (547
mg, 2.3 mmol) to give a yellow oil (375 mg, 65%): 1H NMR
(CDCl3, 300 MHz) 7.15 (s, 1 H), 6.78 (s, 1 H), 4.37 (d, 1 H, J )
11.0 Hz), 4.18 (d, 1 H, J ) 11.0 Hz), 2.99 (s, 3 H), 1.51 (s, 3 H),
1.03 (s, 3 H), 0.06 (s, 9 H); 13C NMR (CDCl3, 125 MHz) 186.82,
178.95, 170.60, 162.80, 138.30, 102.94, 67.34, 55.95, 47.42,
21.55, 20.77, 0.87. Anal. Calcd for C14H22O4Si: C, 59.50; H,
7.87. Found: C, 59.65; H, 7.77.
4-Acetoxym eth yl-4-(3′-bu ten yl)-3-m eth oxy-5-tr im eth -
ylsilyl-2,5-cycloh exa d ien -1-on e 33b was prepared from 32b
(547 mg, 2.3 mmol) to give a yellow oil (375 mg, 65%): 1H NMR
(CDCl3, 300 MHz) 7.15 (s, 1 H), 6.87 (d, 1 H, J ) 1.4 Hz), 5.72
(s, 1 H), 5.56 (m, 1 H), 4.93 (d, 1 H, J ) 1.7 Hz), 4.87 (s, 1 H),
4.44 (d, 1 H, J ) 10.6 Hz), 4.18 (d, 1 H, J ) 10.6 Hz), 2.97 (s,
3 H), 1.71 (m, 3 H), 1.50 (m, 4 H), 0.07 (s, 9 H); 13C NMR
(CDCl3, 125 MHz), 186.88, 177.07, 170.54, 161.24, 140.45,
137.06, 115.41, 104.83, 67.38, 55.88, 51.78, 32.36, 27.97, 20.69,
0.83. Anal. Calcd for C17H26O4Si: C, 63.29; H, 8.15. Found:
C, 63.33; H, 8.00.
4-Acetoxym eth yl-4-(3′-ch lor op r op yl)-3-(tr im eth ylsilyl)-
2,5-cycloh exa d ien -1-on e 9d was prepared from 8d (910 mg,
3.0 mmol) to give a yellow oil (630 mg, 68%): 1H NMR (CDCl3,
500 MHz) δ 6.79 (d, 1 H, J ) 10.2 Hz), 6.69 (s, 1 H), 6.37 (d,
1 H, J ) 10.2 Hz), 4.36 (d, 1 H, J ) 11 Hz), 4.13 (d, 1 H, J )
11 Hz), 3.46 (m, 2 H), 2.00 (m, 1 H), 1.96 (s, 3 H), 1.74 (m, 1
H), 1.47 (m, 2 H), 0.27 (s, 9 H); 13C NMR (CDCl3, 125 MHz) δ
184.12, 170.45, 165.34, 154.95, 140.92, 130.53, 68.12, 49.16,
44.58, 31.78, 26.94, 20.55, 0.32; IR (film) 2957, 1745, 1662
cm-1. Anal. Calcd for C15H23O3ClSi: C, 57.26; H, 7.39. Found:
C, 57.15; H, 7.23.
In ter m olecu la r Tr a p p in g w ith F u r a n . Compound 9a (50
mg) in 5 mL of benzene and 3 equiv of furan was degassed by
bubbling argon into the solution for 15 min and then irradiated
through uranyl glass for 3 h. Concentration in vacuo and crude
1H NMR showed only the bicyclohexenone mixture 11a .
Gen er a l P r oced u r e for P r ep a r a tion a n d Cr u d e An a ly-
sis of 11a -g. A 0.06-0.08 M solution of 9 in benzene-d6 was
degassed by bubbling argon through the solution for 15 min.
Irradiation through uranyl glass for 3 h was followed by 1H
NMR analysis.
Gen er a l P r oced u r e for Dir ect P r ep a r a tion of 25a -f.
A 0.06-0.08 M solution of 9 in benzene with 2 equiv of
trifluoroacetic acid was degassed by bubbling argon into the
solution for 15 min. Irradiation through uranyl glass for 3 h
is followed by washing the organic phase with H2O, saturated
NaHCO3, and saturated NaCl and drying over MgSO4. After
filtration and concentration in vacuo the oil was flash chro-
matographed with 40% EtOAc in hexane to yield a 1:1 mixture
of E/Z isomers 25a -e.
Gen er a l P r oced u r e for Step w ise P r ep a r a tion of 25a -
g. A 0.06-0.08 M solution of 9 in benzene was degassed by
bubbling argon through the solution for 15 min and irradiated
through uranyl glass for 3 h. To the photolysis mixture was
added 1.1 equiv of TFA at room temperature and the solution
was stirred for 30 min. The organic phase was washed with
water, saturated NaHCO3, and saturated NaCl and dried over
MgSO4. After filtration and concentration in vacuo the oil was
flash chromatographed on silica gel with 40% EtOAc in hexane
to yield a 1:1 mixture of E/Z isomers.
4-(Acetoxym eth ylm eth ylm eth ylen e)cyclop en t-2-en -1-
on e 25a was prepared from 9a (530 mg, 2.1 mmol) to yield a
pale yellow oil (350 mg, 92%): 1H NMR (C6D6, 300 MHz) δ
major isomer, 7.36 (d, 1 H, J ) 5.7 Hz), 5.93 (d, 1 H, J ) 5.6
Hz), 4.38 (s, 2 H), 2.36 (s, 2 H), 1.64 (s, 3 H), 1.32 (s, 3 H); δ
minor isomer, 7.14 (d, 1 H, J ) 5.6 Hz), 5.96 (d, 1 H, J ) 5.6
Hz), 4.19 (s, 2 H), 2.59 (s, 2 H), 1.61 (s, 3 H), 1.44 (s, 3 H); IR
(film) 2921, 1738, 1708 cm-1. Anal. Calcd for C10H12O3: C,
66.62; H, 6.73. Found: C, 66.87; H, 6.59.
4-Acetoxym eth yl-4-(3′-bu ten yl)-3-(tr im eth ylsilyl)-2,5-
cycloh exa d ien -1-on e 9e was prepared from 8e (230 mg, 0.84
mmol) to give a yellow oil (220 mg, 89%): 1H NMR (C6D6, 300
MHz) δ 6.85 (s, 1 H), 6.36 (dd, 1 H, J ) 2.1 Hz, J ) 9.9 Hz),
6.12 (dd, 1 H, J ) 2.1 Hz, J ) 9.9 Hz), 5.54 (m, 1 H), 4.89 (m,
2 H), 3.96 (q, 2 H, J ) 10.8 Hz), 1.58 (m, 3 H), 1.52 (s, 3 H),
1.20 (m, 1 H), 0.01 (s, 9 H); 13C NMR (C6D6, 75 MHz) δ 183.65,
170.15, 163.76, 154.45, 142.13, 137.82, 131.23, 115.49, 68.68,
49.78, 34.01, 28.81, 20.44, 0.57; CIMS m/z (relative intensity)
319 (M+ + 1, 14.63), 193 (100). Anal. Calcd for C16H24O3Si: C,
65.75; H, 8.30. Found: C, 65.86; H, 8.33.
4-Acet oxym et h yl-4-(3′-(2′-fu r a n ylp r op yl))-3-(t r im et h -
ylsilyl)-2,5-cycloh exa d ien -1-on e 9f was prepared from 8f
(1.03 g, 3.1 mmol) to give a yellow oil (650 mg, 65%): 1H NMR
(C6D6, 500 MHz) δ 7.05 (s, 1 H), 6.79 (s, 1 H), 6.31 (d, 1 H,
J ) 10.2 Hz), 6.11 (d, 1 H, J ) 10.2 Hz), 6.05 (s, 1 H), 5.75 (s,
1 H), 3.92 (q, 2 H, J ) 9 Hz), 2.25 (m, 2 H), 1.47 (s, 3 H), 1.43
(m, 1 H), 1.13 (m, 3 H), -0.02 (s, 9 H); 13C NMR (C6D6, 125
MHz) δ 183.72, 170.18, 164.19, 155.62, 154.71, 141.96, 141.62,
131.15, 110.88, 106.12, 68.69, 50.09, 34.37, 28.27, 23.36, 20.42,
0.47; IR (film) 2953, 1745, 1662 cm-1. Anal. Calcd for C19H26O4-
Si: C, 65.83; H, 7.58. Found: C, 65.68; H, 7.48.
4-Acetoxym eth yl-4-(3′-a zid op r op yl)-3-(tr im eth ylsilyl)-
2,5-cycloh exa d ien -1-on e 9g was prepared by stirring a 1 M
solution of 8d (214 mg, 0.7 mmol) in acetone with 4 equiv of
sodium iodide for 48 h. The solution was filtered and concen-
trated in vacuo. Redissolving the oil in EtOAc and washing
with saturated Na2S2O5 and saturated NaCl followed by drying
with MgSO4, filtration, concentration in vacuo, and flash
chromatography with 30% EtOAc in hexane yields the iodide
as a yellow oil (260 mg, 90%): 1H NMR (CDCl3, 500 MHz) δ
6.80 (d, 1 H, J ) 10 Hz), 6.70 (s, 1 H), 6.38 (d, 1 H, J ) 10 Hz),
4.36 (d, 1 H, J ) 10.7 Hz), 4.14 (d, 1 H, J ) 10.7 Hz), 3.10 (m,
2 H), 1.97 (s, 3 H), 1.92 (m, 1 H), 1.73 (m, 1 H), 1.52 (m, 2 H),
0.28 (s, 9 H); 13C NMR (CDCl3, 125 MHz) δ 184.35, 170.72,
165.69, 155.22, 141.14, 130.82, 68.29, 50.15, 49.35, 35.64,
27.80, 20.83, 0.68; IR (film) 2955, 1745, 1660 cm-1. Anal. Calcd
for C15H23O3ISi: C, 44.31; H, 5.72. Found: C, 44.60; H, 5.75.
The iodide was then dissolved in 2 mL of DMF before adding
3 equiv of sodium azide and stirring for 3 h at room temper-
ature. The reaction mixture was diluted with Et2O and water,
and the aqueous phase was extracted twice with Et2O. The
organic phases were combined and washed with water, satu-
rated Na2S2O5, and saturated NaCl, and dried over MgSO4.
Filtration and concentration in vacuo followed by flash chro-
matography with 30% EtOAc in hexane yields a yellow oil (165
mg, 80%): 1H NMR (CDCl3, 500 MHz) δ 6.79 (d, 1 H, J ) 10
Hz), 6.70 (s, 1 H), 6.38 (d, 1 H, J ) 10 Hz), 4.35 (d, 1 H, J )
11 Hz), 4.12 (d, 1 H, J ) 11 Hz), 3.25 (m, 2 H), 1.97 (s, 3 H),
1.66 (m, 1 H), 1.24 (m, 2 H), 0.27 (s, 9 H); 13C NMR (CDCl3,
125 MHz) δ 184.42, 170.74, 165.45, 155.15, 141.26, 130.86,
68.43, 49.57, 31.87, 24.00, 20.83, 0.57; IR (film) 2959, 2098,
1744, 1660 cm-1. Anal. Calcd for C15H23O3N3Si: C, 56.02; H,
7.24. Found: C, 55.88; H, 7.18.
4-(Acetoxym eth yla llylm eth ylen e)cyclop en t-2-en -1-on e
25b was prepared from 9b (200 mg, 0.7 mmol) to yield a pale
yellow oil (100 mg, 73%): 1H NMR (C6D6, 300 MHz) δ major
isomer, 7.48 (d, 1 H, J ) 5.9 Hz), 5.97 (t, 1 H, J ) 4.2 Hz),
5.50 (m, 1 H), 4.87 (m, 2 H), 4.51 (s, 2 H), 2.55 (d, 2 H, J ) 6.4
Hz), 2.49 (s, 2 H), 1.66 (s, 3 H); δ minor isomer, 7.23 (d, 1 H,
J ) 5.8 Hz), 5.97 (t, 1 H, J ) 4.2 Hz) 5.50 (m, 1 H), 4.87 (m,
2 H), 4.34 (s, 2 H), 2.71 (d, 2 H, J ) 6.4 Hz), 2.66 (s, 2 H), 1.63
(s, 3 H); IR (film) 2978, 1739, 1712 cm-1. Anal. Calcd for
C
12H14O3: C, 69.86; H, 6.86. Found: C, 70.10; H, 6.91.
4-(Acetoxym eth ylben zylm eth ylen e)cyclop en t-2-en -1-
on e 25c was prepared from 9c (230 mg, 0.7 mmol) to yield a
pale yellow oil (140 mg, 79%): 1H NMR (C6D6, 300 MHz) δ
major isomer, 8.19 (d, 1 H, J ) 5.6 Hz), 7.28 (m, 2 H), 7.23 (m,
1 H), 7.15 (m, 2 H), 6.37 (d, 1 H, J ) 5.6 Hz), 4.74 (s, 2 H),
3.59 (s, 2 H), 3.08 (s, 2 H), 2.00 (s, 3 H); δ minor isomer, 8.16
(d, 1 H, J ) 5.6 Hz), 7.28 (m, 2 H), 7.23 (m, 1 H), 7.15 (m, 2

New Substituent Effects of the Trimethylsilyl Group
J . Org. Chem., Vol. 65, No. 20, 2000 6361
H), 6.41 (d, 1 H, J ) 5.6 Hz), 4.58 (s, 2 H), 3.71 (s, 2 H), 3.12
(s, 2 H), 1.95 (s, 3 H); IR (film) 2932, 1739, 1711 cm-1. Anal.
Calcd for C16H16O3: C, 75.04; H, 6.32. Found: C, 72.42; H,
6.23.
(m, 1 H), 2.08 (s, 3 H), 2.01 (m, 2 H); δ minor isomer, 8.06 (m,
1 H), 6.34 (m, 1 H), 4.66 (s, 2 H), 3.54 (m, 2 H), 2.97 (s, 3 H),
2.54 (m, 1 H), 2.44 (m, 1 H), 2.08 (s, 3 H), 1.78 (m, 2 H); IR
(film) 2953, 2098, 1708, 1648 cm-1. Anal. Calcd for C12H15
O3N3: C, 57.79; H, 6.08. Found: C, 57.71; H, 6.25.
-
4-[Acet oxym et h yl(3′-ch lor op r op yl)m et h ylen e]cyclo-
p en t-2-en -1-on e 25d was prepared from 9d (75 mg, 0.2 mmol)
to yield a pale yellow oil (45 mg, 78%): 1H NMR (C6D6, 300
MHz) δ major isomer, 7.42 (d, 1 H, J ) 5.6 Hz), 5.98 (t, 1 H,
J ) 5.6 Hz), 4.40 (s, 2 H), 2.97 (t, 2 H, J ) 6.3 Hz), 2.51 (s, 2
H), 1.86 (t, 2 H, J ) 6.3 Hz), 1.66 (s, 3 H), 1.42 (m, 2 H); δ
minor isomer, 7.36 (d, 1 H, J ) 5.6 Hz), 5.98 (t, 1 H, J ) 5.6
Hz), 4.23 (s, 2 H), 3.02 (t, 2 H, J ) 6.3 Hz), 2.61 (s, 2 H), 2.05
(t, 2 H, J ) 6.3 Hz), 1.63 (s, 3 H), 1.42 (m, 2 H); IR (film) 2960,
1738, 1712 cm-1. Anal. Calcd for C12H15O3Cl: C, 59.36; H, 6.24.
Found: C, 59.18; H, 6.11.
4-(Acetoxym eth yl(3′-(2-fu r a n yl))m eth ylen e)cyclop en t-
2-en -1-on e 25f was prepared from 9f (100 mg, 0.3 mmol) to
yield a pale yellow oil (60 mg, 73%): 1H NMR (CDCl3, 500
MHz) δ major isomer, 8.10 (d, 1 H, J ) 5.8 Hz), 7.31 (m, 1 H),
6.29 (m, 2 H), 5.99 (m, 1 H), 4.80 (s, 3 H), 2.89 (s, 2 H), 2.65
(m, 2 H), 2.25 (t, 2 H, J ) 7.9 Hz), 2.07 (s, 3 H), 1.85 (m, 2 H);
δ minor isomer, 7.90 (d, 1 H, J ) 5.9 Hz), 7.31 (m, 1 H), 6.29
(m, 2 H), 5.99 (m, 1 H), 4.65 (s, 2 H), 3.01 (s, 2 H), 2.65 (m, 2
H), 2.38 (t, 2 H, J ) 7.3 Hz), 2.07 (s, 3 H), 1.85 (m, 2 H); IR
(film) 2958, 1736, 1710. Anal. Calcd for C16H18O4: C, 70.03;
H, 6.63. Found: C, 70.15; H, 6.88.
4-(Acetoxym eth yl(3′-bu ten yl)m eth ylen e)cyclop en t-2-
en -1-on e 25e was prepared from 9e (200 mg, 0.5 mmol) to
yield a pale yellow oil (120 mg, 80%): 1H NMR (C6D6, 500
MHz) δ major isomer, 7.42 (d, 1 H, J ) 5.6 Hz), 5.93 (d, 1 H,
J ) 5.6 Hz), 5.54 (m, 1 H), 4.88 (m, 2 H), 4.45 (s, 3 H), 2.45 (s,
3 H), 1.94 (q, 2 H, J ) 7.1 Hz), 1.87 (s, 2 H), 1.60 (s, 3 H); δ
minor isomer, 7.20 (d, 1 H, J ) 5.3 Hz), 5.92 (d, 1 H, J ) 5.3
Hz), 5.54 (m, 1 H), 4.88 (m, 2 H), 4.28 (s, 3 H), 2.59 (s, 3 H),
2.03 (t, 2 H, J ) 7 Hz), 1.88 (s, 2 H), 1.57 (s, 3 H); IR (film)
2952, 1739, 1711 cm-1. Anal. Calcd for C13H16O3: C, 70.86; H,
7.34. Found: C, 70.69; H, 7.15.
4-(Acetoxym eth ylm eth ylm eth ylen e)-5,6-d eh yd r oca p -
r ola cton e 26 was prepared from 25 (50 mg, 0.3 mmol) by
treating a 0.1 M solution in CH2Cl2 at room temperature with
2 equiv of m-chloroperbenzoic acid for 4 h. Dilution with CH2-
Cl2 and washing the organic phase with water, 10% NaHCO3
solution, and saturated NaCl solution was followed by drying
with MgSO4, filtration, and concentrating in vacuo. Flash
chromatography with 1:1 EtOAc in hexane yields the pure
lactone as a yellow oil (43 mg, 80%): 1H NMR (CDCl3, 500
MHz) δ major isomer, 7.34 (d, 1 H, J ) 5.9 Hz), 6.43 (d, 1 H,
J ) 5.9 Hz), 4.25 (q, 2 H, J ) 12.0 Hz), 2.45 (q, 2 H, J ) 12.9
Hz), 2.10 (s, 3 H), 1.46 (s, 3 H); δ minor isomer, 7.27 (d, 1 H,
J ) 5.8 Hz), 6.47 (d, 1 H, J ) 5.8 Hz), 4.13 (q, 2 H, J ) 12.1
Hz), 2.69 (t, 2 H, J ) 19.3 Hz), 2.10 (s, 3 H), 1.50 (s, 3 H) IR
(film) 2963, 1722; CIMS m/z (relative intensity) 197 (M+ + 1,
100). Anal. Calcd for C10H12O4: C, 61.19; H, 6.18. Found: C,
61.28; H, 6.01.
1-Acetoxym eth yl-2-m eth oxy-6-tr im eth ylsilyltr icyclo-
[5.2.1.0]d ec-2-en -4-on e 34 was prepared from 33b (50 mg)
in benzene (5 mL), degassed for 15 min by bubbling argon, by
irradiation for 3 h through uranyl glass. Concentration in
vacuo and recrystallization from 10:1 Hex:EtOAc yields 38 mg
(76%) of colorless, needlelike crystals, mp 80-82 °C: 1H NMR
(500 MHz) 5.41 (s, 1 H), 4.34 (d, 1 H, J ) 11.2 Hz), 3.87 (d, 1
H, J ) 11.5 Hz), 3.69 (s, 3 H), 2.95 (m, 1 H), 2.82 (m, 1 H),
2.64 (q, 1 H, J ) 1.0 Hz, J ) 8.1 Hz), 2.16 (m, 2 H), 2.01 (s, 3
H), 1.82 (m, 1 H), 1.74 (m, 1 H), 1.53 (m, 1 H), 0.09 (s, 9 H);
13C NMR (125 MHz) 200.59, 182.14, 170.76, 101.47, 65.61,
56.45, 52.49, 41.98, 41.30, 39.93, 39.57, 31.45, 30.31, 21.17,
-1.94. Anal. Calcd for C17H26O4: C, 69.33; H, 8.92. Found: C,
69.21; H, 8.70.
4-(Acetoxym eth yl(3′-azidopr opyl)m eth ylen e)cyclopen t-
2-en -1-on e 25 g was prepared from 9g (20 mg, 0.1 mmol) to
yield a pale yellow oil (10 mg, 70%): 1H NMR (CDCl3, 500
MHz) δ major isomer, 8.10 (m, 1 H), 6.32 (d, 1 H, J ) 5.6 Hz),
4.81 (s, 2 H), 3.32 (m, 2 H), 3.03 (s, 2 H), 2.40 (m, 1 H), 2.32
Ack n ow led gm en t. This work was supported by the
National Institutes of Health (GM 33061).
J O000209V