Silylation of Allylic Trifluoroacetates and Acetates Using Organodisilanes Catalyzed by Palladium Complex

Article abstract of DOI:10.1021/jo960345t

Silylation of allylic acetates (1) using organodisilanes (2) was carried out in the presence of a catalytic amount of Pd(DBA)2-LiCl at 100 deg C. The silylation proceeded smoothly without β-hydrogen elimination of a resulting (?-allyl)palladium intermediate. The added chloride salt such as LiCl or NaCl was indispensable for the catalytic activity. On the other hand, remarkable improvement of the silylation was realized by employing allylic trifluoroacetates (4) in place of the acetates (1) as the substrates. The silylation proceeded even at room temperature, and the added chloride salts was not necessary as the catalyst component. In the silylation, transmetalation of the disilanes (2) with (η³-allyl)palladium intermediate (7) might be a critical step in the catalytic cycle. Model reactions for the transmetalation were carried out.

Full text of DOI:10.1021/jo960345t

J . Org. Chem. 1996, 61, 5779-5787
5779
Silyla tion of Allylic Tr iflu or oa ceta tes a n d Aceta tes Usin g
Or ga n od isila n es Ca ta lyzed by P a lla d iu m Com p lex
Yasushi Tsuji,* Masahiro Funato, Masakatsu Ozawa, Hiroaki Ogiyama, Satoshi Kajita, and
Takashi Kawamura
Department of Chemistry, Faculty of Engineering, Gifu University, Gifu 501-11, J apan
Received February 20, 1996X
Silylation of allylic acetates (1) using organodisilanes (2) was carried out in the presence of a catalytic
amount of Pd(DBA)2-LiCl at 100 °C. The silylation proceeded smoothly without â-hydrogen
elimination of a resulting (π-allyl)palladium intermediate. The added chloride salt such as LiCl
or NaCl was indispensable for the catalytic activity. On the other hand, remarkable improvement
of the silylation was realized by employing allylic trifluoroacetates (4) in place of the acetates (1)
as the substrates. The silylation proceeded even at room temperature, and the added chloride
salts was not necessary as the catalyst component. In the silylation, transmetalation of the disilanes
(2) with (η3-allyl)palladium intermediate (7) might be a critical step in the catalytic cycle. Model
reactions for the transmetalation were carried out.
In tr od u ction
reacted dimethylphenylsilyl cuprates with allylic acetates
to obtain the corresponding allylic silanes.9 Trost and
co-workers attempted palladium-catalyzed silylations of
allylic acetates with tris(trimethylsilyl)aluminum ((Me3-
Si)3Al‚ether) as the silylating reagent.10 However, the
former reaction could not utilize other silyl moieties such
as trimethylsilyl cuprate, and the latter often suffered
from low regioselectivity. Furthermore, these silylating
reagents must be prepared prior to the silylation. In
contrast, hexamethyldisilane (Me3SiSiMe3, 2a ) is easily
accessible and used in a wide variety of silylation
reaction.11 Suzuki et al. utilized 2a in Pd(PPh3)4-cata-
lyzed silylation of allylic acetates at 160 °C.12 Unfortu-
nately, for this potentially useful reaction, applicable
substrates have severe limitation. In the reaction, (π-
allyl)palladium intermediates generated by oxidative
addition of allylic acetates to Pd(0) catalyst species
readily decomposed by â-hydrogen elimination at the
high reaction temperature.13 Thus, allylic acetates that
The palladium(0)-catalyzed nucleophilic substitution
of allylic esters has been used extensively in organic
synthesis,1-3 since it is truly one of the most useful and
general transition-metal-catalyzed process. Allylic ac-
etates and carbonates are by far the most often used
allylic substrates. As for nucleophiles, stabilized carb-
anions1-3 are mainly employed for alkylation, while other
nucleophiles such as amines4a,b and zinc or boron
enolates4c,d can be employed.
On the other hand, silylation of allylic esters must be
a promising synthetic method of allylic silanes. The
allylic silanes are highly versatile synthetic intermediates
and have a large number of applications in organic
synthesis.5 Therefore, much attention has been paid to
the preparation methods of allylic silanes, which include
allylic Grignard reactions,6 hydrosilylation of 1,3-dienes,7
and Wittig reactions with (â-silylethylidene)phospho-
rane.8 To date, however, only a few silylation reactions
of allylic esters have been attempted. Fleming et al.
(9) (a) Fleming, I.; Higgins, D.; Lawrence, N. J .; Thomas, A. P. J .
Chem. Soc., Perkin Trans. 1 1992, 3331. (b) Fleming, I.; Newton, T.
W. J . Chem. Soc., Perkin Trans. 1 1984, 1805.
X Abstract published in Advance ACS Abstracts, August 1, 1996.
(1) (a) Tsuji, J . Palladium Reagents and Catalysts; J ohn Wiley &
Sons: Chichester, 1995; pp 290-422. (b) Tsuji, J . Pure Appl. Chem.
1982, 54, 197; 1986, 58, 869. (c) Tsuji, J . Tetrahedron 1986, 42, 4361.
(d) Tsuji, J .; Minami, I. Acc. Chem. Res. 1987, 20, 140.
(2) (a) Trost, B. M. Acc. Chem. Res. 1980, 13, 385. (b) Trost, B. M.;
Verhoeven, T. R. In Comprehensive Organometallic Chemistry; Wilkin-
son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982;
Vol. 8, Chapter 57, p 799.
(3) (a) Consiglio, G.; Waymouth, R. M. Chem. Rev. 1989, 89, 257.
(b) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University
Science Books: Mill Valley, CA, 1987; Chapter 19.
(4) (a) Trost, B. M.; Genet, J . P. J . Am. Chem. Soc. 1976, 98, 8516.
(b) Trost, B. M.; Keinan, E. J . Org. Chem. 1979, 44, 3451. (c) Negishi,
E.; Matsushita, H.; Chatterjee, S.; J ohn, R. A. J . Org. Chem. 1982, 47,
3188. (d) Negishi, E.; J ohn, R. A. J . Org. Chem. 1983, 48, 4098.
(5) (a) Colvin, E. W. Silicon Reagents in Organic Synthesis; Aca-
demic: London, 1988; pp 25-37. (b) Weber, W. P. Silicon Reagents
for Organic Synthesis; Springer: Berlin, 1983; pp 173-205. (c) Colvin,
E. W. Silicon in Organic Synthesis; Butterworths: London, 1981; pp
97-124.
(6) (a) Sommer, L. H.; Tyler, L. J .; Whitmore, F. C. J . Am. Chem.
Soc. 1948, 70, 2872. (b) Gilman, H.; Zuech, E. A. J . Am. Chem. Soc.
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(b) Ojima, I.; Kumagi, M.; Miyazawa, Y. Tetrahedron Lett. 1977, 1385.
(c) Ojima, I.; Kumagi, M. J . Organomet. Chem. 1977, 134, C6.
(8) (a) Seyferth, D.; Wursthorn, K. R.; Mammarella, R. E. J . Org.
Chem. 1977, 42, 3104. (b) Fleming, I.; Paterson, I. Synthesis 1979,
446.
(10) Trost, B. M.; Yoshida, J .; Lautens, M. J . Am. Chem. Soc. 1983,
105, 4494.
(11) Organodisilanes as silylating reagents, see: (a) Obora, Y.; Tsuji,
Y.; Kawamura, T. J . Am. Chem. Soc. 1995, 117, 9814. (b) Obora, Y.;
Tsuji, Y.; Kawamura, T. J . Am. Chem. Soc. 1993, 115, 10414. (c)
Obora, Y.; Tsuji, Y.; Kawamura, T. Organometallics 1993, 12, 2853.
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M.; Kawamura, T. J . Chem. Soc., Perkin Trans. 1 1995, 599. (e) Tsuji,
Y.; Lago, R. M.; Tomohiro, S.; Tsuneishi, H. Organometallics 1992,
11, 2353. (f) Murakami, M.; Sugimome, M.; Fujimoto, K.; Nakamura,
H.; Anderson, P. G.; Ito, Y. J . Am. Chem. Soc. 1993, 115, 6487. (g)
Ito, Y.; Suginome, M.; Murakami, M. J . Org. Chem. 1991, 56, 1948.
(h) Yamashita, H.; Catellani, M.; Tanaka, M. Chem. Lett. 1991, 241.
(i) Sakurai, H.; Eriyama, Y.; Kamiyama, Y.; Nakadaira, Y. J . Orga-
nomet. Chem. 1984, 264, 229. (j) Carlson, C. W.; West, R. Organome-
tallics 1983, 2, 1801. (k) Watanabe, H.; Kobayashi, M.; Saito, M.;
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Organomet. Chem. 1980, 199, 185. (o) Tamao, K.; Okazaki, S.;
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S0022-3263(96)00345-3 CCC: $12.00 © 1996 American Chemical Society

5780 J . Org. Chem., Vol. 61, No. 17, 1996
Ta ble 1. Silyla tion of Allylic Aceta tes (1) in th e P r esen ce of LiCla
Tsuji et al.

Silylation of Allylic Esters Using Organodisilanes
J . Org. Chem., Vol. 61, No. 17, 1996 5781
Ta ble 1 (Con tin u ed )
have a primary or a secondary alkyl group at the R- or
γ-position of the allylic moiety could not be used in the
silylation.
substrates could not be silylated in the previous method
using 2a 12 because of the â-hydride elimination of the
resulting (π-allyl)palladium intermediates (vide supra).
Hence, the present reaction provides the first general
method for the silylation of allylic acetates using orga-
nodisilanes. Aromatic allylic acetates (1g-i) also af-
forded the corresponding allylic silanes in high yields
(entries 7-9). Substituted disilanes such as 2b and 2c
also provided the corresponding allylic silanes (entries
10 and 11).
In this paper, we report the first general silylation
reactions of the allylic esters using organodisilanes (2).
First, silylation of allylic acetates (1) using 2 is described,
in which the Pd(DBA)2-LiCl (DBA ) dibenzylideneac-
etone) catalyst system showed good catalytic activity at
100 °C without the â-hydride elimination of the resulting
(π-allyl)palladium intermediates. Furthermore, we have
succeeded in remarkable improvement of the catalytic
reaction by employing allylic trifluoroacetates (4) in place
of the acetates (1) as the substrate. The improvement
includes that (1) the reaction smoothly proceeds even at
room temperature and (2) the added LiCl is not necessary
in the catalytic system, i.e., Pd(DBA)2 alone shows high
catalytic activity.
Lithium chloride was indispensable in the reaction. No
reaction took place without the added salt. Varying the
amount of LiCl had only a small effect: yields of 3e from
1g were 92% with 0.5 equiv of LiCl (entry 7), 86% with
1.0 equiv, and 83% with 5 equiv. Other salts (4 equiv)
could replace LiCl in entry 7: yields of 3e from 1g were
92% with NaCl, 90% with KCl, 47% with KBr, and 15%
with LiI. No allylic silanes were obtained with fluoride
salts such as LiF, KF, and CsF. Thus, the chloride salts
were the most effective as the additive. The reaction also
proceeded in diglyme, but no reactions took place in
toluene presumably due to low solubility of the added
Resu lts a n d Discu ssion
Silyla tion of Allylic Aceta tes in th e P r esen ce of
LiCl. Allylic acetates (1) were smoothly silylated using
organodisilanes (2) in the presence of the Pd(DBA)2-LiCl
catalyst system at 100 °C (eq 1).14 The results are listed
in Table 1. No reactions occurred at room temperature.
salts. As for the effect of the catalyst precursor, Pd-
15,16
(DBA)2
showed high catalyst activity: yields of 3e
from 1g were 92% with Pd(DBA)2 (entry 7), 47% with
Pd(OAc)2(PPh3)2, 22% with PdCl2(PPh3)2, and 11% with
Pd(PPh3)4, respectively, under otherwise identical reac-
tion conditions to those of entry 7.
One of the two silyl moieties of the disilanes (2) was
incorporated in the product (3). The fate of the other silyl
moiety was determined in the reaction using 2a and 1g
(entry 7, with 0.5 equiv of LiCl) by taking a 29Si NMR
spectrum of the reaction mixture (locked with C6D6).
After the reaction, the expected amount of Me3SiOAc (5b,
21.5 ppm, lit.17a 22.0 ppm) was found along with (E)-3e
(0.78 ppm) and excess 2a (-20.5 ppm, lit.17b -20.5 ppm).
However, no trace of Me3SiCl (lit.17c 30.2 ppm) was
detected in the reaction mixture. The same results were
obtained even with 5 equiv of LiCl. Thus, one of the silyl
moieties of 2 was trapped by the leaving acetate group
effectively, not by the added chloride anion.
Aliphatic and alicyclic acetates (1a -f) were readily
silylated with Me3SiSiMe3 (2a ) and gave the correspond-
ing allylic silanes (3a -d ) in high isolated yields with good
regioselectivity (entries 1-6). It is noteworthy that these
(13) (a) Matsumoto et al. reported palladium-catalyzed silylation of
allylic halides with 2a at 120-170 °C.13b However, they only employed
simple allylic halides having no possibility of the â-hydride elimination
of resulting (π-allyl)palladium intermediates. (b) Matsumoto, H.; Yako,
T.; Nagashima, S.; Motegi, T.; Nagai, Y. J . Organomet. Chem. 1978,
148, 97.
Silyla tion of Allylic Tr iflu or oa ceta tes. Remark-
able improvement of the silylation was realized by
employing allylic trifluoroacetates (4) in place of the
aecetates (1) as the substrate. The silylation proceeded
even at room temperature. Furthermore, the added
(14) For a preliminary account of this portion, see: Tsuji, Y.; Kajita,
S.; Isobe, S.; Funato, M. J . Org. Chem. 1993, 58, 3607.

5782 J . Org. Chem., Vol. 61, No. 17, 1996
Ta ble 2. Silyla tion of Allylic Tr iflu or oceta tes (4)a
Tsuji et al.

Silylation of Allylic Esters Using Organodisilanes
J . Org. Chem., Vol. 61, No. 17, 1996 5783
Ta ble 2 (Con tin u ed )
chloride salt is not necessary, i.e., Pd(DBA)2 alone showed
high catalyst activity (eq 2). The results are shown in
NMR 22.0 ppm; lit.17a 22.0 ppm) with concomitant
formation of palladium black powder in 5 min. In
contrast, Pd(OAc)2-PPh3 (P/Pd ) 2 or 3), PdCl2, PdCl2-
(COD), and PdCl2(PhCN)2 did not show any catalytic
activity as the catalyst precursor. Similar NMR tube
reaction of these catalyst precursors with excess 2a at
room temperature or at 40 °C did not show any sign of
reactions (monitored with 29Si NMR), indicating no in situ
reduction to catalytically active Pd(0). Moreover, Pd-
(PPh3)4 showed no catalytic activity, either. Hence, for
the present silylation reaction of 4, palladium(0) complex
without coordinating ligands, naked Pd(0), is most favor-
able as the catalyst precursor. Phenyl- and fluoro-
substituted disilanes (2b and 2d ) also reacted with 4 to
afford the corresponding allylic silanes (entries 21 and
22).
After the reaction, the formation of Me3SiOCOCF3 (5a )
was confirmed in entry 20 by taking a 29Si NMR spectrum
of the filtered reaction mixture: 5a appeared at 33.1 ppm
(lit.17a 33.1 ppm) as well as (E)-3e (at 0.78 ppm) and
excess 2a (at -20.5 ppm17b) with the expected intensities.
Similar to the reaction using allylic acetates (1), the
leaving trifluoroacetate group effectively trapped one silyl
moiety, with the other silyl group being incorporated in
the products. In both cases, strong oxophilicity of the
Table 2. Various allylic trifluoroacetates (4a -h ) were
silylated smoothly to the corresponding allylic silanes at
room temperature (entries 13-20). The acetates corre-
sponding to 4c, cis-4j, and trans-4j afforded the silylated
products in low yields (<10%) under the same reaction
conditions as those in eq 1. The reaction proceeded in
the presence of a catalytic amount (3 mol %) of Pd(DBA)2
in various solvents: yields of 3e from 4h were 94% in
THF (entry 20), 92% in toluene, and 61% in DMF,
15,16
respectively. As the catalyst precursor, Pd(DBA)2
showed high catalytic activity. Surprisingly, Pd(OAc)2
also had high catalytic activity: the yields of 3e from 4h
were 99% in toluene and 96% in THF. In these cases,
Pd(OAc)2 must be reduced to Pd(0) species in situ by 2a .
Actually, an NMR tube reaction of Pd(OAc)2 (1 equiv)
with 2a (50 equiv) at room temperature in toluene-d8
afforded the expected amount of Me3SiOAc (5b: 29Si
silicon (bond dissociation energy: Si-O 430-530 kJ
18
mol-1
)
may facilitate the silylation reaction.
Recently, Vitagliano et al. examined the stereochem-
istry of the oxidative addition of trans-4-acetoxy-2-
(17) (a) Bassingdale, A. R.; Posnan, T. B. J . Organomet. Chem. 1979,
175, 273. (b) Hunter, B. K.; Reewes, L. W. Can. J . Chem. 1967, 46,
1399. (c) Van den Berghe, E. V.; Van der Kelen, G. P. J . Organomet.
Chem. 1973, 59, 175.
(18) Armitage, D. A. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford,
1982; Vol. 2, pp 5-10.
(15) (a) Takahashi, Y.; Ito, T.; Sakai, S.; Ishii, Y. J . Chem. Soc.,
Chem. Commun. 1970, 1065. (b) Rettig, M. F.; Maitlis, P. M. Inorg.
Synth. 1977, 17, 134.
(16) (a) Pd2(DBA)3‚CHCl3
16b
showed similar catalytic activity. (b)
Ukai, T.; Kawazuka, H.; Ishii, Y.; Bonnett, J . J .; Ibers, J . A. J .
Organomet. Chem. 1974, 65, 253.

5784 J . Org. Chem., Vol. 61, No. 17, 1996
Tsuji et al.
cyclohexenyl trifluoroacetate (4i) to Pd(DBA)2.19 With
this particular trifluoroacetate, they found that the
stereochemistry of the oxidative addition was affected by
the nature of the solvent in the reaction. They reported
that the stereochemistry of the oxidative addition was
inversion (85% selectivity) in THF-acetonitrile mixed
solvent (4:1 in volume), but retention (90% selectivity)
in THF. In order to investigate stereochemistry of the
present silylation reaction, cis-4j was subjected to the
reaction. The reaction proceeded smoothly and afforded
the trans-isomer (trans-3r ) exclusively in the THF-
acetonitrile mixed solvent (4:1 in volume) (entry 23).20
The same clean overall inversion was also observed in
THF to afford only trans-3r (entry 24). Thus, in the case
of cis-4j, the nature of the solvent did not affect the
stereocourse of the silylation. On the other hand, the
silylation of trans-4j afforded a 1:1 mixture of trans- and
cis-3r in THF (entry 25), while the conversion was very
low in the THF-acetonitrile mixed solvent. Further-
more, the silylation of cis-4k provided only trans-3j in
the THF-acetonitrile mixed solvent (entry 26), while a
1:1 mixture of trans- and cis-3j was obtained in THF
(entry 27). The oxidative addition reaction of 4i to Pd-
(DBA)2 in THF is reported to be very slow as compared
with that in THF-acetonitrile mixed solvent.19 There-
fore, in the silylation of trans-4j and cis-4k carried out
in THF (entries 25 and 27), the (π-allyl)palladium
intermediate might undergo trans-cis isomerization,21
and this will cause the formation of stereoisomers as the
products. Concerning allylic acetates, the stereochem-
istry of the oxidative addition to Pd(0) complexes is
known to be inversion.22 In the silylation of allylic
acetate, cis-1j afforded only trans-3j with the Pd(DBA)2-
LiCl catalyst system in DMF at 100 °C: again clean
overall inversion (entry 12, Table 1). Accordingly, at least
when the silylation is stereospecific (entries 12, 23, 24,
and 26), the stereochemistry of the oxidative addition of
the allylic esters must be inversion and the silyl moiety
attacks the π-allyl face from the palladium side. Disi-
lanes (2) alone are not good nucleophiles. Therefore, 2
should be activated on the Pd catalyst center prior to the
silylation and, as a result, one of the silyl moieties of 2
will attack the π-allyl plane from the palladium side.
Ca ta lytic Cycle. A possible catalytic cycle is shown
in Scheme 1. The catalytic cycle begins with oxidative
addition of 4 or 1 to Pd(0) active catalyst species (6) and
gives a (π-allyl)palladium trifluoroacetate (7a ) or acetate
(7b) intermediate. Transmetalation of disilane (2) with
7 might afford (π-allyl)silyl species (9) with concomitant
formation of silyl trifluoroacetate (5a ) or acetate (5b); the
formations of 5a and 5b has been confirmed by 29Si NMR
spectra of the resulting reaction mixtures (vide supra).
Finally, reductive elimination of 9 can provide the allylic
silanes (3) as the product and regenerates the active
catalyst species (6).
Sch em e 1
product (3b) in high yields (entries 13 and 14) via a
common palladium intermediate. However, the reaction
of 4a is much faster than that of 4b: 80 times faster on
the basis of their initial rates. Hence, the rate-determin-
ing step in the catalytic cycle must be the oxidative
addition stage, since the following catalytic steps are the
same between these two substrates.
There is no precedent for the transmetalation of
disilanes (2) with (π-allyl)palladium trifluoroacetate (7a )
or acetate (7b) complexes (7 + 2 f 9 + 5; Scheme 1).
Therefore, a model reaction of the transmetalation step
was carried out. As a model complex for 7a , 10a was
employed. In the reaction of 10a (1 equiv) with 2a (10
equiv) in toluene-d8 at room temperature (Scheme 2), a
clear yellow solution turned black within a few seconds
and a palladium black powder appeared. A 29Si NMR
spectrum of the colorless filtrate showed that 5a and
3e were formed in equal amounts; the yield of 3e was
55% by GC (with heptadecane as an internal standard
on Apieson grease L). The transmetalation might pro-
ceed via π-allyl silyl palladium intermediate (9, Scheme
2) with a transition state such as 823 (Scheme 1). We
attempted to trap the intermediate 9 by adding phos-
phines (PPh3, PMe3) or other ligands to the reaction
mixture. However, these added ligands often hindered
the transmetalation. Any silyl species such as 9 could
not be detected by 29Si, 1H, and 13C NMR spectra in
these reactions. As soon as an intermediate such as 9
is formed, very fast reductive elimination of this high-
ly unsaturated species (14-electron species) may afford
3 and 6. Moreover, to see how the transmetalation is
influenced electronically, the silylation of 4h was car-
ried out with unsymmetrical fluoropentamethyldisilane
(FMe2SiSiMe3, 2e) under the standard reaction condi-
tions. In the reaction, the silylation exclusively afforded
a trimethylsilylated product ((E)-3e) and a fluorodi-
methylsilylated product was not detected (eq 3). Simi-
lar results were obtained in the reaction of 4a with
2e, in which the trimethylsilylated product (3b) was
obtained as a major isomer and the fluorodimethylsi-
lylated product (3q, cf. entry 22) as a minor one (eq 4).
Hence, in the transmetalation stage, the more nucleo-
philic silyl moiety, SiMe3 rather than SiMe2F,26 attacked
the π-allyl moiety.
With regard to the catalyst cycle, the oxidative addition
of allylic trifluoroacetate (4) to Pd(0) is well-known.19
Indeed, reaction of 4h (1 equiv) with Pd(DBA)2 (1 equiv)
proceeded smoothly at room temperature to afford (π-
allyl)palladium trifluoroacetate dimer (10a in Scheme 2)
as yellow crystals in 55% yield, while the corresponding
acetate (1g) apparently did not react with Pd(DBA)2
under similar reaction conditions. In order to determine
the rate-determining step, the silylation rates of 4a and
4b were compared. Both substrates afforded the same
As for the oxidative addition of allylic acetates (1), the
(π-allyl)palladium acetate complex (10b in Scheme 2)
could not be prepared by direct oxidative addition of 1g
(19) Vitagliano, A.; A° kermark, B.; Hansson, S. Organometallics
1991, 10, 2592.

Silylation of Allylic Esters Using Organodisilanes
J . Org. Chem., Vol. 61, No. 17, 1996 5785
Sch em e 2
to give a chloropalladate species (eq 5).28 Such a palla-
date species would be nucleophilic enough to oxidative-
ly add to 1 at 100 °C and initiate the catalytic cycle
(Scheme 1).
to Pd(DBA)2: apparently no reactions occurred. There-
fore, 10b was prepared by reaction of the corresponding
chloro dimer (10c: Y ) Cl) with CH3COOAg.27 The
complex 10b (1 equiv) also reacted with 2a (10 equiv) in
toluene-d8 at room temperature (Scheme 2). The reac-
tion afforded trimethylsilyl acetate (5b, 29Si resonance
at 22.1 ppm17a), (E)-3e (29Si resonance at 0.78 ppm,
30% yield by GC), and palladium metal (black pow-
der) within a few seconds. Thus, this model reaction
might suggest that each catalytic step can proceed even
without added LiCl, if the (π-allyl)palladium acetate
intermediate (7b) is formed in the catalytic cycle (Scheme
1). These results may imply that the added LiCl is
indispensable only in oxidative addition stage. The
added chloride salt can react with a palladium complex
PdLn + LiCl -L8 Li+[PdLn-1Cl]-
(5)
Silyla tion of Allylic Aceta tes in th e P r esen ce of
Tr iflu or oa cetic Acid . It has been reported that (π-
allyl)palladium acetate complexes such as 10b can be
converted into the corresponding trifluoroacetate com-
plexes such as 10a by reaction with CF3COOH.19 This
result and the above investigation on the catalytic cycle
will strongly suggest that silylation of allylic acetates (1)
can proceed in the presence of a stoichiometric amount
of added CF3COOH under reaction conditions similar to
those of eq 2. Indeed, this is the case. When 1g was
reacted with 2a in the presence of 2 equiv of CF3COOH
at room temperature in toluene, 3e (E/Z ) 99/1) was
obtained in 92% yield (entry 28, Table 3). In the absence
of the CF3COOH, no reactions occurred. The reaction
proceeded smoothly in toluene, while the catalyst was
decomposed into insoluble materials in THF or diglyme.
The reaction did not proceed via the corresponding
(20) A chiral gas chromatography analysis (on CP-Chirasil Dex CB,
CHROMPACK) showed the product was a 1:1 mixture of two enanti-
omers, even if an optically pure cis-4j ((1R,5R) or (1S,5S)) was
employed. If stereochemistry of oxidative addition of cis-4j to Pd(0) is
stereoselectively inversion (or even retention), each optically pure cis-
4j affords the same optically inactive (π-allyl)palladium species (i).
Since regioselectivity of the silylation cannot be regulated without a
chiral auxiliary ligand, the present silylation inevitably affords trans-
3r as a 1:1 mixture of the two enantiomers ((1S,5R) or (1R,5S)).
(23) Oxidative addition of disilane to Pd(0)24a or Pt(0)24b complexes
containing basic phosphines has been reported. However, for these
oxidative addition reactions, the Si-Si bond must be activated by a
substituent such as F or Cl on the silicon. In these cases, a simple
disilane such as 2a was totally inert toward the oxidative addition.
Even if oxidative addition of 2a to 7 was considered, some Pd(IV)
intermediates must be presumed in the catalytic cycle. However, such
a catalytic cycle including a Pd(0)-Pd(II)-Pd(IV) four-electron redox
system should be highly unlikely, especially for those active even at
room temperature. Hence, the transmetalation might proceed via a
four-centered σ-metathesis25 transition state such as 8 rather than the
oxidative addition-reductive elimination sequence.
(24) (a) Ozawa, F.; Sugawara, M.; Hayashi, T. Organometallics 1994,
13, 3237. (b) Yamashita, H.; Kobayashi, T.; Hayashi, T.; Tanaka, M.
Chem. Lett. 1990, 1447.
(25) (a) Hartwig, J . F.; Bhandari, S.; Rablen, P. R. J . Am. Chem.
Soc. 1994, 116, 1839. (b) Woo, H.-G.; Tilley, T. D. J . Am. Chem. Soc.
1989, 111, 3757. (c) Thompson, M. E.; Bercaw, J . E. J . Am. Chem.
Soc. 1987, 109, 203. (d) Fendrick, C. M.; Marks, T. J . J . Am. Chem.
Soc. 1984, 106, 2214.
(26) (a) Populations of the HOMO on each Si atom of 2e were
calculated with the Gaussian 92 program.26b Geometrical parameters
were optimized under the Cs symmetry with the STO-3G basis set,
and molecular orbitals were calculated with 3-21G*. The contour map
indicates that the HOMO spreads slightly more over the trimethylsilyl
Si(2) atom than the Si(1) atom attached to F: Mulliken point charge
population of the HOMO on the Si(1) is 0.266 and 0.322 on the Si(2).
Therefore, the calculation suggested that more nucleophilic silyl moiety
attacks the allyl system. (b) Frisch, M. J .; Gordon, M. H.; Trucks, G.
W.; Foresman, J . B.; Schlegel, H. B.; Raghavachari, K.; Robb, M. A.;
Binkley, J . S.; Gonzalez, C.; Defrees, D. J .; Fox, D. J .; Whiteside, R.
A.; Seeger, R.; Melius, C. F.; Baker, J .; Martin, R. L.; Kahn, L. R.;
Stewart, J . J . P.; Topiol, S.; Pople, J . A. Gaussian 92; Gaussian, Inc.,
Pittsburgh, PA, 1992.
(i)
(21) (a) Granberg, K. L.; Ba¨ckvall, J .-E. J . Am. Chem. Soc. 1992,
114, 6858. (b) MacKenzie, P. B.; Whelan, J .; Bosnich, B. J . Am. Chem.
Soc. 1985, 107, 2046.
(22) (a) Hayashi, T.; Hagihara, T.; Konishi, M.; Kumada, M. J . Am.
Chem. Soc. 1983, 105, 7767. (b) Trost, B. M.; Verhoeven, T. R. J . Am.
Chem. Soc. 1980, 102, 4730.
(27) (a) Robinson, S. D.; Shaw, B. L. J . Organomet. Chem. 1965, 3,
367. (b) Takahashi, Y.; Tsukiyama, K.; Sakai, S.; Ishii, Y. Tetrahedron
Lett. 1970, 1913.
(28) (a) Henry, P. M. Inorg. Chem. 1972, 11, 1876. (b) Scott, W. J .;
Stille, J . K. J . Am. Chem. Soc. 1986, 108, 3033.

5786 J . Org. Chem., Vol. 61, No. 17, 1996
Tsuji et al.
Ta ble 3. Silyla tion of Allylic Aceta tes in th e P r esen ce of
CF 3COOHa
LiCl at 100 °C. The silylation proceeded even at room
temperature by employing allylic trifluoroacetates (4) as
the substrate in place of 1, in which the added LiCl was
not necessary as the catalyst component.
added acid
(equiv)b
relative
solvent yield/%c rated
entry substrate
28
29
30
31
32
33
34
35
36f
1g
1b
1f
1g
1g
1g
4h
4h
4h
CF3COOH (2)
CF3COOH (1)
CF3COOH (1)
CF3COOH (0.7) toluene
CF3COOH (1.4) toluene
CF2ClCOOH (2) toluene
none
none
CF3COOH (2)
toluene
toluene
toluene
92
99
2.36
Exp er im en ta l Section
(52)e
4
0.07
0.92
1.18
1.00
1.59
28.0
Ma ter ia ls. The reagents and the solvents were dried and
purified before use by usual methods.31 Hexamethyldisilane
(2a ) was purchased from Aldrich. 1,2-Difluorotetramethyl-
disilane (2d ),32a fluoropentamethyldisilane (2e),32a and dichlo-
rotetramethyldisilane (2f)32b were prepared by the methods
reported by Kumada. Other disilanes (2b and 2c) were
synthesized from 2f using the corresponding organolithiums.
Allylic esters such as 1j,33 4j,34 and 4k 33 were prepared from
the corresponding alcohols with acetyl chloride or trifluoro-
acetic anhydride. The following catalyst precursors were
prepared by the published methods: Pd(DBA)2,15 Pd(PPh3)4,35a
PdCl2(PhCN)2,35b Pd(OAc)2(PPh3)2,35c PdCl2(PPh3)2,35d and PdCl2-
(COD).35e Elemental analysis was performed at the Microana-
lytical Center of Kyoto University.
40
40
(94)
92
82
THF
toluene
toluene
a
Conditions: 1 (1.0 mmol), 2a (2.0 mmol), Pd(DBA)2 (0.030
b
mmol), toluene (5.5 mL) at room temperature for 12 h. Amount
of the added acid based on 1 or 4. c GC yields determined by
the internal standard method. Numbers in parentheses show
isolated yields. Determined by initial rates. eE/Z ) 54/46. f For
d
1 h.
Sch em e 3
Silyla t ion of Allylic Acet a t es (1) in t h e P r esen ce of
LiCl. A typical procedure is as follows (entry 4): Pd(DBA)2
(23 mg, 0.040 mmol) and dry LiCl (21 mg, 0.50 mmol) were
placed in a 20 mL flask equipped with a three-way stopcock,
and the whole system was evacuated for 30 min. Then, DMF
(3.8 mL), geranyl acetate (1d ; 196 mg, 1.0 mmol), and
hexamethyldisilane (2a ; 293 mg, 2.0 mmol) were added in this
order under argon flow. The color of the solution changed from
reddish brown to yellow upon the addition of 1d . The
homogeneous solution was stirred for 40 h at 100 °C. The
mixture was then passed through a short Florisil column (8
mm i.d. × 70 mm) to give a clear pale yellow solution.
Kugelrohr distillation (Bu¨chi) gave a mixture of geranyl- and
neryltrimethylsilanes (3d ) in 78% yield (164 mg, 0.78 mmol;
pot temperature 100 °C/8 mmHg). 13C NMR and GC analyses
showed the E/Z ratio to be 56/44.
Silyla tion of Allylic Tr iflu or oa ceta tes (4). The silyla-
tion of 4a is typical (entry 13). A 20 mL flask was charged
with Pd(DBA)2 (17 mg, 0.030 mmol) and THF (5.5 mL) under
an argon atmosphere. The palladium complex was dissolved
with stirring to afford a deep purple solution. Then, 2a (293
mg, 2.0 mmol) and 4a (222 mg, 1.0 mmol) were added in this
order. The reaction mixture turned pale yellow, and the
reaction was carried out at room temperature for 12 h. After
the reaction, the reaction mixture was diluted with diethyl
trifluoroacetate (4h ), since reaction between 1g and
CF3COOH in toluene at room temperature did not af-
ford 4h at all in the presence or absence of Pd(DBA)2
as the catalyst precursor. Other allylic acetates such as
1b and 1f were also smoothly silylated with 2a into 3b
and 3d , respectively, in the presence of 1 equiv of CF3-
COOH at room temperature (entries 29 and 30). Again,
no reaction occurred in the absence of the added CF3-
COOH. In order to get good conversion of 1, a stoichio-
metric amount of CF3COOH is required (entries 28, 31,
and 32). However, a large amount of the acid caused a
protodesilylation reaction.29 With 1b and 1f, the pro-
todesilylation is predominant and even 2 equiv of CF3-
COOH lowered the yields considerably. As for the added
acid, CF2ClCOOH in place of CF3COOH reduced the yield
and relative rate considerably (entry 33), while the
addition of CCl3COOH, TsOH, or H2SO4 did not afford
the allylic silane (3) at all. Interestingly, even in the
silylation of the allylic trifluoroacetate (4h ), the addition
of CF3COOH enhanced the reaction rate considerably
(entries 34-36).
A plausible reaction path is shown in Scheme 3. The
oxidative addition of 1 with Pd(DBA)2 would afford the
(π-allyl)palladium acetate intermediate (7b), but in a very
low equilibrium concentration.30 The concentration must
be so low that the reaction with 2 will not proceed with
a reasonable reaction rate. However, in the presence of
CF3COOH, the acid can protonate 7b to the correspond-
ing 7a .19 Once 7a is formed, transmetalation followed
by reductive elimination as shown in Scheme 1 will
follow.
(29) Fleming, I.; Paterson, I. Synthesis 1979, 446.
(30) (a) Yamamoto et al. reported oxidative addition reaction of allyl
acetate with several Pd(0) complexes.30b,c With Pd(PPh3)4, no apparent
changes were observed at room temperature or even at 80 °C.
However, when deuterium-labeled CH2dCHCD2OAc was used as the
substrate in the reaction, the recovered allyl acetate consisted of
CD2dCHCH2OAc and CH2dCHCD2OAc, indicating that equilibrium
between the substrate and oxidative addition product did exist, but
the concentration of the adduct was too low to be detected. In order
to isolate the oxidative adducts, more basic phosphine is required.
Thus, with Pd(PCy3)2 (PCy3 ) tricyclohexylphosphine), the oxidative
addition afforded yellow isolable Pd(η3-C3H5)(OAc)(PCy3). In the
present silylation reaction, the catalyst species (6) does not contain
any phosphines or other donating ligands. Therefore, concentration
of the oxidative addition species (7b) must be much lower (Scheme 3).
(b) Yamamoto, T.; Saito, O.; Yamamoto, A. J . Am. Chem. Soc. 1981,
103, 5600. (c) Yamamoto, T.; Akimoto, M.; Saito, O.; Yamamoto, A.
Organometallics 1986, 5, 1559.
(31) Perrin, D. D.; Armagego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: Oxford, 1988.
(32) (a) Kumada, M.; Yamaguchi, M.; Yamamoto, Y.; Nakajima, J .;
Shiina, K. J . Org. Chem. 1956, 21, 1264. (b) Sakurai, H.; Tominaga,
K.; Watanabe, T.; Kumada, M. Tetrahedron Lett. 1966, 5493.
(33) Ba¨ckvall, J .-E.; Granberg, K. L.; Heumann, A. Israel J . Chem.
1991, 31, 17 and references cited therein.
(34) (a) Grandi, R.; Pagnoni, U. M.; Trave, R.; Garanti, L. Tetrahe-
dron 1974, 30, 4037. (b) Castedo, L.; Mascaren˜as, J . L.; Mourin˜o, A.
Tetrahedron Lett. 1987, 28, 2099.
(35) (a) Coulson, D. R. Inorg. Synth. 1972, 13, 121. (b) Hertley, F.
R. The Chemistry of Platinum and Palladium; Applied Science:
London, 1973; p 462. (c) Yoshimoto, H.; Itatani, H. Bull. Chem. Soc.
J pn. 1973, 46, 2490. (d) Hertley, F. R. The Chemistry of Platinum
and Palladium; Applied Science: London, 1973; p 458. (e) Drew, D.;
Doyle, J . R. Inorg. Synth. 1972, 13, 52.
Con clu sion
Allylic acetates (1) were silylated with organodisilanes
(2) in the presence of a catalytic amount of Pd(DBA)2-

Silylation of Allylic Esters Using Organodisilanes
J . Org. Chem., Vol. 61, No. 17, 1996 5787
ether (20 mL), washed with saturated NaHCO3 aqueous
solution (20 mL), and dried over anhydrous MgSO4. Kugelrohr
distillation afforded 3b in 92% yield (168 mg, 0.92 mmol; pot
temperature 80 °C/1 mmHg).
cis-3j:10 1H NMR δ -0.03 (s, 9H), 1.41 (q, J gem ) J ax-ax ) 12
Hz, 1H), 1.52-1.62 (m, 1H), 1.97-2.07 (m, 1H), 2.12-2.34 (m,
2H), 2.38-2.47 (m, 1H), 3.66 (s, 3H), 5.55-5.66 (m, 2H); 13C
NMR δ -3.82 (q), 25.9 (d), 27.0 (t), 27.7 (t), 40.1 (d), 123.5 (d),
127.3 (d), 175.9 (s).
Silyla t ion of Allylic Acet a t es (1) in t h e P r esen ce of
CF 3COOH. A typical procedure is described for the silylation
of 1g (entry 28). Toluene (5.5 mL) and Pd(DBA)2 (17 mg, 0.030
mmol) were placed in a 20 mL flask under argon atmosphere.
To the stirred deep purple solution were added heptadecane
(180 mg, 0.75 mmol; as an internal standard for GC analysis),
1g (176 mg, 1.0 mmol), 2a (293 mg, 2.0 mmol), and CF3COOH
(228 mg, 2.0 mmol) in this order. The solution was stirred at
room temperature for 12 h. Gas chromatograph analysis
showed that 3e was obtained in a 92% yield (E/Z ) 99/1).
Rea ction of 10a or 10b w ith 2a . In a 5 mm i.d. NMR
tube, 10a (20 mg, 0.03 mmol) or 10b (17 mg, 0.03 mmol) was
dissolved in argon-degassed toluene-d8 (0.5 mL). Hexameth-
yldisilane (2a ) (88 mg, 0.6 mmol) was added into the solution
at room temperature. Within a few seconds, a black powder
appeared. The liquid part was transferred through a short
Celite plug into another NMR tube. The formation of 3e was
3k : 1H NMR δ -0.01 (s, 9H), 1.40 (s, 2H), 1.39-1.66 (m,
2H), 1.71 (s, 3H), 1.70-1.75 (m, 1H), 1.85-1.96 (m, 2H), 1.96-
2.12 (m, 2H), 4.69 (s, 2H), 5.19 (m, 1H); 13C NMR δ -1.19 (q),
20.8 (q), 27.6 (t), 28.1 (t), 30.9 (t), 31.5 (t), 41.2 (d), 108.3 (t),
118.3 (d), 135.1 (s), 150.3 (s). Anal. Calcd for C13H24Si: C,
74.92; H, 11.61. Found: C, 74.84; H, 11.67.
3l: 1H NMR δ 0.00 (s, 9H), 0.91 (t, J ) 7.4 Hz, 3H), 0.93 (t,
J ) 7.4 Hz, 3H), 1.17-1.56 (m, 9H), 1.98-2.06 (m, 2H); 13C
NMR δ -3.17 (q), 13.6 (q), 13.9 (q), 22.3 (t), 23.2 (t), 31.2 (t),
32.8 (t), 35.1 (d), 128.0 (d), 131.7 (d). Anal. Calcd for C12H26
Si: C, 72.64; H, 13.21. Found: C, 72.69; H, 13.48.
-
3m :43,44 1H NMR δ 0.00 (s, 9H), 1.74 (ddd, J ) 6.4 Hz, 1.8
Hz, 0.8 Hz, 3H), 2.92 (d, J ) 10 Hz, 1H), 5.45 (dqd, J ) 15 Hz,
6.4 Hz, 0.8 Hz, 1H), 5.85 (ddq, J ) 15 Hz, 10 Hz, 1.6 Hz, 1H),
7.08-7.46 (m, 5H); 13C NMR δ -3.00 (q), 18.1 (q), 42.8 (d),
123.5 (d), 125.6 (d), 127.1 (d), 128.2 (d), 130.2 (d), 138.6 (s).
3n :44 1H NMR δ 0.07 (s, 9H), 1.22 (d, J ) 7.6 Hz, 3H), 1.83
(pd, J ) 7.6 Hz, 0.8 Hz, 1H), 6.25 (d, 16 Hz, 1H), 6.35 (dd, J
) 16 Hz, 7.6 Hz, 1H), 7.06-7.44 (m, 5H); 13C NMR δ -3.39
(q), 13.5 (q), 27.3 (d), 124.4 (d), 125.7 (d), 126.2 (d), 128.4 (d),
134.4 (d), 143.1 (s).
1
confirmed by H, 13C, and 29Si NMR spectra. The yield of 3e
was determined by GC using heptadecane as an internal
standard on Apieson grease L. The 29Si NMR spectrum is most
diagnostic of the formation of 5a (33.1 ppm; lit.17a 33.1 ppm)
or 5b (22.1 ppm, lit.17a 22.0 ppm).
3p : 1H NMR δ 0.00 (s, 3H), 0.01 (s, 3H), 1.02-1.81 (m, 7H),
1.37 (s, 2H), 1.43 (s, 3H), 4.39-4.32 (m, 2H), 4.90-4.96 (m,
1H), 7.04-7.07 (m, 3H), 7.20-7.27 (m, 2H); 13C NMR δ -2.73
(q), 20.8 (q), 26.6 (t), 28.0 (t), 30.9 (t), 31.5 (t), 41.0 (d), 108.3
(t), 119.1 (d), 127.6 (d), 128.8 (d), 133.0 (s), 133.6 (d), 134.4 (s),
150.2 (s). Anal. Calcd for C18H26Si: C, 79.93; H, 9.69.
Found: C, 80.22; H, 9.66.
Some products have been identified by comparison with
published spectral data; 3b,36 3c,37 3d ,38 3e,39,40 3f,40 and 3o.41
(E)-3a :42 1H NMR δ -0.01 (s, 9H), 0.89 (t, J ) 7.4 Hz, 3H),
1.28 (m, 10H), 1.40 (d, J ) 8 Hz, 2H), 1.97 (q, J ) 7.4 Hz, 2H),
5.24 (dt, J ) 15 Hz, 7.4 Hz, 1H), 5.37 (dt, J ) 15 Hz, 8 Hz,
1H); 13C NMR δ -1.94 (q), 14.2 (q), 22.7 (t), 22.8 (t), 29.2 (t),
29.3 (t), 30.2 (t), 32.0 (t), 32.9 (t), 126.0 (d), 129.2 (d); MS m/e
212 (M+).
3q: 1H NMR δ 0.22 (s, 6H), 1.45-1.59 (m, 5H), 1.60 (dd,
(Z)-3a :42 13C NMR δ -1.72 (q), 14.2 (q), 18.5 (t), 22.7 (t),
27.2 (t), 29.3 (t), 30.2 (t), 32.0 (t), 32.9 (t), 125.2 (d), 127.9 (d);
MS m/e 212 (M+).
3
J H-H ) 8.4 Hz, J H-F ) 5.2 Hz, 2H), 2.04-2.12 (m, 5H), 5.07
2
(tp, J ) 8.4 Hz, 1.2 Hz, 1H); 13C NMR δ -1.66 (q, J C-F ) 15
2
Hz), 17.5 (t, J C-F ) 13 Hz), 26.9 (t), 27.5 (t), 28.4 (t), 28.7 (t),
3g: 1H NMR δ 0.01 (s, 9H), 1.68 (dd, J ) 7.7 Hz, 1 Hz, 2H),
6.11 (dt, J ) 15 Hz, 7.7 Hz, 1H), 6.85 (d, J ) 15 Hz, 1H), 7.25-
8.05 (m, 7H); 13C NMR δ -1.74 (q), 24.5 (t), 123.2 (d), 124.1
(d), 125.5 (d), 125.6 (d), 125.70 (d), 125.73 (d), 128.5 (d), 131.1
(d), 131.2 (s), 133.7 (s), 136.4 (s); MS m/e 240 (M+). Anal. Calcd
for C16H20Si: C, 79.93; H, 8.38. Found: C, 79.80; H, 8.45.
(E)-3h : 13C NMR δ -3.21 (q), 15.8 (q), 17.70 (q), 17.8 (t),
25.8 (q), 26.9 (t), 40.0 (t), 119.7 (d), 124.7 (d), 127.7 (d), 128.9
(d), 131.0 (s), 133.0 (s), 133.6 (d), 139.3 (s). Anal. Calcd for
C18H28Si: C, 79.34; H, 10.36. Found: C, 79.21; H, 10.49.
(Z)-3h : 13C NMR δ -3.12 (q), 17.4 (t), 17.67 (q), 23.4 (q),
25.7 (q), 26.5 (t), 31.8 (t), 119.9 (d), 124.7 (d), 127.7 (d), 128.9
(d), 131.2 (s), 133.0 (s), 133.6 (d), 139.2 (s). Anal. Calcd for
C18H28Si: C, 79.34; H, 10.36. Found: C, 79.19; H, 10.40.
3i: 1H NMR δ -0.01 (s, 6H), 1.55 (d, J ) 6.8 Hz, 2H), 5.79-
3
37.3 (t), 113.5 (d, J C-F ) 1.6 Hz), 139.1 (s). Methylation of
3q with MeLi in THF at -40 °C afforded 3b quantitatively.
1
tr a n s-3r : H NMR δ 0.06 (s, 9H), 1.53-1.57 (m, 1H), 1.66
(td, J gem ) 12 Hz, J ax-ax ) 12 Hz, J ax-ex ) 5.7 Hz, 1H), 1.65-
1.67 (m, 3H), 1.71 (t, J ) 1.1 Hz, 3H), 1.84 (ddd, J gem ) 12 Hz,
J ex-ax ) 4.0 Hz, J ex-ex ) 1.8 Hz, 1H), 1.90-2.18 (m, 3H), 4.66-
4.70 (m, 2H), 5.27-5.31 (m, 1H); 13C NMR δ -0.50 (q), 20.5
(q), 24.77 (q), 30.5 (t), 30.74 (t), 31.8 (d), 39.4 (d), 108.3 (t),
118.5 (d), 135.7 (s), 150.3 (s). Anal. Calcd for C13H24Si: C,
74.92; H, 11.61. Found: C, 74.96; H, 11.59.
cis-3r (obtained as a 1:1 mixture of the cis- and trans-
isomers): 13C NMR δ -2.33 (q), 21.0 (q), 24.67 (q), 30.68 (t),
30.9 (t), 31.4 (d), 41.8 (d), 108.1 (t), 120.8 (d), 135.0 (s), 150.8
(s). Anal. Calcd for C13H24Si: C, 74.92; H, 11.61. Found (as
a 1:1 mixture of the cis- and trans-isomers): C, 74.89; H, 11.62.
5.94 (m, 2H), 6.64-6.86 (m, 3H), 6.91-6.94 (m, 2H), 7.11-
2
7.20 (m, 4H). 13C NMR δ -3.15 (q), 23.1 (t), 114.9 (d, J C-F
)
Ack n ow led gm en t. This work was supported by
Grant-in-Aid for Scientific Research on Priority Area of
Reactive Organometallics No. 06227228 from the Min-
istry of Education, Science and Culture, J apan. Finan-
cial supports from the Sumitomo Foundation and the
Asahi Glass Foundation are also gratefully acknowl-
edged.
20 Hz), 125.6 (d), 126.4 (d), 126.8 (d), 128.5 (d), 129.2 (d), 133.9
(s, J C-F ) 4.4 Hz), 135.6 (d, J C-F ) 7.3 Hz), 138.3 (s), 163.9
4
3
1
(s, J C-F ) 246 Hz).
tr a n s-3j:10 1H NMR δ 0.01 (s, 9H), 1.55-1.64 (m, 1H), 1.84
(dt, J gem ) 14 Hz, J eq-ax ) J eq-eq ) 4.2 Hz, 1H), 1.97 (ddd, J gem
) 14 Hz, J ax-ax ) 9.2 Hz, J ax-eq ) 6.6 Hz), 2.13-2.33 (m, 2H),
2.56-2.63 (m, 1H), 3.65 (s, 3H), 5.54-5.66 (m, 2H); 13C NMR
δ -2.82 (q), 25.1 (d), 25.7 (t), 26.9 (t), 37.6 (d), 51.6 (q), 122.5
(d), 127.8 (d), 176.1 (s).
Su p p or tin g In for m a tion Ava ila ble: 1H and 13C NMR
spectra of 3i, 3q, and cis-3r (6 pages). This material is
contained in libraries on microfiche, immediately follows this
article in the microfilm version of the journal, and can be
ordered from the ACS; see any current masthead page for
ordering information.
(36) Fleming, I.; Paterson, I. Synthesis 1979, 446.
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