Evaluation of β- and γ-Effects of Group 14 Elements Using Intramolecular Competition

Article abstract of DOI:10.1021/jo991977t

To evaluate β-effects and γ-effects of group 14 elements, we have devised a system in which the intramolecular competition between γ-elimination of tin and β-elimination of silicon, germanium, and tin can be examined. Thus, the reactions of α-acetoxy(arylmethyl)stannanes with allylmetals (metal = Si, Ge, Sn) in the presence of BF₃·OEt₂ were carried out. The reactions seem to proceed by the initial formation of an α-stannyl-substituted carbocation, which adds to an allylmetal to give the carbocation that is β to the metal and γ to tin. The β-elimination of the metal gives the corresponding allylated product, and the γ-elimination of tin gives the cyclopropane derivative. In the case of allylsilane, the cyclopropane derivative was formed as a major product, whereas in the case of allylgermane the allylated product was formed predominantly. In the case of the allystannane the allylated product was formed exclusively. These results indicate that the y-elimination of tin is faster than the β-elimination of silicon, but slower than the β-elimination of germanium and tin. The theoretical studies using ab initio molecular orbital calculations of the carbocation intermediates are consistent with the experimental results. The effect of substituents on silicon was also studied. The introduction of sterically demanding substituents on silicon disfavored the β-elimination of silicon probably because of the retardation of nucleophilic attack on silicon to cleave the carbon-silicon bond.

Full text of DOI:10.1021/jo991977t

J . Org. Chem. 2000, 65, 3135-3142
3135
Eva lu a tion of â- a n d γ-Effects of Gr ou p 14 Elem en ts Usin g
In tr a m olecu la r Com p etition
Masanobu Sugawara and J un-ichi Yoshida*
Department of Synthetic Chemistry & Biological Chemistry, Graduate School of Engineering,
Kyoto University, Sakyo-ku Kyoto, 606-8501, J apan
Received December 28, 1999
To evaluate â-effects and γ-effects of group 14 elements, we have devised a system in which the
intramolecular competition between γ-elimination of tin and â-elimination of silicon, germanium,
and tin can be examined. Thus, the reactions of R-acetoxy(arylmethyl)stannanes with allylmetals
(metal ) Si, Ge, Sn) in the presence of BF
3
2
‚OEt were carried out. The reactions seem to proceed
by the initial formation of an R-stannyl-substituted carbocation, which adds to an allylmetal to
give the carbocation that is â to the metal and γ to tin. The â-elimination of the metal gives the
corresponding allylated product, and the γ-elimination of tin gives the cyclopropane derivative. In
the case of allylsilane, the cyclopropane derivative was formed as a major product, whereas in the
case of allylgermane the allylated product was formed predominantly. In the case of the allystannane
the allylated product was formed exclusively. These results indicate that the γ-elimination of tin
is faster than the â-elimination of silicon, but slower than the â-elimination of germanium and tin.
The theoretical studies using ab initio molecular orbital calculations of the carbocation intermediates
are consistent with the experimental results. The effect of substituents on silicon was also studied.
The introduction of sterically demanding substituents on silicon disfavored the â-elimination of
silicon probably because of the retardation of nucleophilic attack on silicon to cleave the carbon-
silicon bond.
In tr od u ction
group 14 elements. The interaction of the C-M (M ) Si,
Ge, Sn) σ orbital with a vacant p orbital of the developing
carbocation has proved to play a central role, although
inductive effects cannot be ignored. In other words, the
σ-π conjugation or hyperconjugation is responsible for
the â-effect. The percaudal homohyperconjugation is
responsible for the γ-effect. These mechanistic insights
are consistent with significant geometric requirements
of these effects observed experimentally. The ground-
Enormous advances have been made in the study of
the electronic effects of group 14 elements such as silicon
and tin, and these studies uncovered a rich variety of
chemistry of organo group 14 element compounds. The
ability of group 14 elements to promote the formation of
a positive charge, such as a carbocation, at the â-position
is known as â-effect, and numerous synthetic transfor-
1
2
,3
mations based on this effect have been developed so far.
(
5) Synthetic applications of the γ-effect of tin: (a) Davis, D. D.;
Chambers, R. L.; J ohnson, H. T. J . Organomet. Chem. 1970, 25, C13.
b) Sato, T. Synthesis 1990, 259. (c) Plamondon, L.; Wuest, J . D. J .
Although the ability of group 14 elements to promote the
formation of a positive charge at the γ-position (γ-effect)
is less popular, it is also utilized in organic synthesis.4
Extensive experimental and theoretical studies have been
(
,5
Org. Chem. 1991, 56, 2066 and 2076. (d) Marshall, J . A.; J ablonowski,
J . A.; Luke, G. P. J . Org. Chem. 1994, 59, 7825. (e) Sato, T.; Nagatsuka,
S. Synlett 1995, 653. (f) Beddoes, R. L.; Lewis, M. L.; Quayle, P.; J ohal,
S. Tetrahedron Lett. 1995, 36, 471. (g) Isono, N.; Mori, M. J . Org. Chem.
6
4a,7
carried out on the origin of â-effects and γ-effects
of
1
1
996, 61, 7867. (h) Wakamatsu, H.; Isono, N.; Mori, M. J . Org. Chem.
997, 62, 8917. (i) Krief, A.; Provins, L. Tetrahedron Lett. 1998, 39,
(
1) For example, (a) Lambert, J . B.; Zhao, Y.; Emblide, R. W.;
Salvador, L. A.; Liu, X.; So, J .-H.; Chelius, E. C. Acc. Chem. Res. 1999,
2, 183-190. (b) Yoshida, J .; Nishiwaki, K. J . Chem. Soc., Dalton
2017. (j) Sugawara, M.; Yoshida, J . Chem. Commun. 1999, 505-506.
(6) (a) Brown, R. S.; Eaton, D. F.; Hosomi, A.; Traylor, T. G.; Wright,
J . M.; J . Organomet. Chem. 1974, 66, 249-254. (b) Lambert, J . B.;
Finzel, R. B. J . Am. Chem. Soc. 1982, 104, 2020-2022. (c) Wierschke,
S. G.; Chandrasekhar, J .; J orgensen, W. L. J . Am. Chem. Soc. 1985,
107, 7, 1496-1500. (d) Auner, N.; Walsh, R.; Westrup, J . J . Chem.
Soc., Chem. Commun. 1986, 207-208. (e) Magnus, P.; Cairns, P. M.;
Moursounidis, J . J . Am. Chem. Soc. 1987, 109, 2469-2471. (f) Lambert,
J . B.; Wang, G.; Finzel, R. B.; Teramura, D. H. J . Am. Chem. Soc. 1987,
109, 7838-7845. (g) Hajdasz, D.; Squires, R. J . Chem. Soc., Chem.
Commun. 1988, 1212-1214. (h) Lambert, J . B.; Wang, G.; Teramura,
D. H. J . Org. Chem. 1988, 53, 5422-5428. (i) Li, X.; Stone, J . A. J .
Am. Chem. Soc. 1989, 111, 5586-5592. (j) Lambert, J . B.; Chelius, E.
C. J . Am. Chem. Soc. 1990, 112, 8120-8126. (k) Brook, M. A.; Neuy,
A. J . Org. Chem. 1990, 55, 3609-3616. (l) Yoshida, J .; Maekawa, T.;
Murata, T.; Matsunaga, S.; Isoe, S. J . Am. Chem. Soc. 1990, 112, 1962-
1970. (m) Siehl, H.-U.; Kaufmann, F.-P.; Apeloig, Y.; Braude, V.;
Danovich, D.; Berndt, A.; Stamatis, N. Angew. Chem., Int. Ed. Engl.
1991, 30, 1479-1482. (n) Hage, G.; Mayr, H. J . Am. Chem. Soc. 1991,
113, 4954-4961. (o) White, J . M.; Robertson, G. B. J . Org. Chem. 1992,
57, 4638-4644. (p) Lambert, J . B.; Emblidge, R. W.; Malany, S. J . Am.
Chem. Soc. 1993, 115, 1317-1320. (q) Gabelica, V.; Kresge, A. J . J .
Am. Chem. Soc. 1996, 118, 3838-3841. (r) Chan, V. Y.; Clark, C. I.;
Giordano, J .; Green, A. J .; Karalis, A.; White, J . M. J . Org. Chem. 1996,
61, 5227-5233.
3
Trans. 1998, 2589-2596. (c) White, J . M. Aust. J . Chem. 1995, 48,
1
1
227-1251. (d) Hwu, J . R.; Chen, B.-L.; Shiao, S.-S. J . Org. Chem.
995, 60, 2448-2455. (e) Yoshida, J .; Murata, T.; Matsunaga, S.;
Maekawa, T.; Shiozawa, S.; Isoe, S. Rev. Heterotatom Chem. 1991, 5,
1
93-231. (f) Lambert, J . B. Tetrahedron 1990, 46, 2677-2689. (g)
Apeloig, Y. The chemistry of organic silicon compounds: Patai, S.,
Rappoport, Z., Eds.; Wiley: Chichester, 1989; pp 57-225. (g) Giordan,
J . C. J . Am. Chem. Soc. 1983, 105, 6544-6546.
(
2) Synthetic applications of the â-effect of silicon. (a) Weber, W. P.
Silicon Reagents for Organic Synthesis; Springer-Verlag: Berlin,
Heidelberg, 1983. (b) Colvin, E. W. Silicon Reagents in Organic
Synthesis; Academic Press: London, 1988. (c) Fleming, I. In Compre-
hensive Organic Synthesis; Trost, B. M., Fleming, I., Paquette, L. A.,
Eds; Pergamon Press: Oxford, 1991; Vol. 2, p 563. (d) Fleming, I.;
Dunogu e` s, J .; Smithers, R. Org. React. 1989, 37, 57.
(
3) Synthetic applications of the â-effect of tin. For example, (a)
Pereyre, M.; Quintard, J .-B.; Rahm, A. Tin in Organic Synthesis;
Butterworth & Co.: London, 1987. (b) Yamamoto, Y. Aldrichimica Acta
1
987, 20, 45.
(
4) Synthetic applications of the γ-effect of silicon: (a) Sakurai, H.;
Imai, T.; Hosomi, A. Tetrahedron Lett. 1977, 4045. (b) Hatanaka, Y.;
Kuwajima, I. Tetrahedron Lett. 1986, 27, 719.
1
0.1021/jo991977t CCC: $19.00 © 2000 American Chemical Society
Published on Web 04/26/2000

3
136 J . Org. Chem., Vol. 65, No. 10, 2000
Sugawara and Yoshida
Sch em e 1
Sch em e 2
Sch em e 3
state interaction of the C-M σ orbital with the σ* orbital
of the C-L (L ) leaving group) bond to be cleaved has
7
l
also been suggested. Studies on the relative magnitude
of these effects have been carried out mainly based on
solvolysis experiments; such studies indicate that the
magnitude of the effects increases in the order Si < Ge
<
Sn, and that the â-effect is larger than the γ-effect if
we employ the same group 14 element.
So, we can analyze the relative ease of the â-elimination
and the γ-elimination by the product analysis. As a
method for the generation of this type of carbocation, we
Another important aspect of â-effects and γ-effects of
group 14 elements is facile elimination. When a â-carbo-
cation is formed, the cleavage of the C-M bond takes
place smoothly to form a carbon-carbon double bond. In
the case of a γ-carbocation, the cleavage of the C-M bond
leads to the formation of a cyclopropane ring. Therefore,
group 14 elements such as silicon and tin have been
utilized to control the fate of carbocations in organic
1
chose the addition of a carbocation R to M onto an
2
allylmetal (allyl-M ). The addition should take place at
1
the terminal carbon to generate the carbocation γ to M
and â to M .
2
In a preliminary study, we were surprised to find that
the γ-elimination of tin was faster than the â-elimination
9
of silicon. On the basis of the facile γ-elimination of tin,
8
synthesis. Control of reaction pathways using â- and
we have developed a new cyclopropanation reaction of
γ-effects of silicon and tin opened a number of opportuni-
ties of cationic reactions in organic synthesis. Therefore,
the evaluation of the elimination process is significantly
important from a synthetic point of view, although
experimental and theoretical studies reported in the
literature have focused on the formation of carbocation
intermediates. The evaluation of the â-elimination and
the γ-elimination processes is rather difficult because
these processes are not usually rate-limiting processes.6,7
Thus, to evaluate the relative ease of the elimination,
we devised a system in which the intramolecular com-
10
“
tin carbenoid” with alkenes. Thus, we have studied the
relative ease of γ-elimination and â-elimination of group
4 elements in detail using this intramolecular competi-
1
tion protocol. To get a deeper insight into the competition,
we also carried out theoretical studies using ab initio
molecular orbital calculations, because the geometric and
electronic structures of the carbocation intermediates
having group 14 metals at both â- and γ-positions might
give us crucial information about the relative magnitude
of â- and γ-effects of group 14 elements. Herein we report
on the full details of these studies.
petition between the â- and the γ-elimination of group
9
1
4 elements can be examined (Scheme 2). If we generate
Resu lts a n d Discu ssion
1
2
a carbocation that is γ to M and â to M , there should
be the competition between the γ-elimination of M and
the â-elimination of M . The â-elimination leads to the
formation of the homoallyl M compound, and γ-elimina-
1
In tr a m olecu la r Com p etition . To generate a carbo-
cation having both γ-tin and â-M (M ) Sn, Ge, Si), we
carried out the addition of an R-tin-substituted carbo-
cation to the corresponding allylmetals.11 4-Methoxy-
phenyl(acetoxy)methyltributylstannane (1a ), which was
readily prepared by the addition of stannyllithium to
p-anisaldehyde followed by acetylation, was used as a
precursor of the carbocation.
2
1
tion leads to the formation of the cyclopropane derivative.
(7) (a) Kuivila, H. G.; Scarpa, N. M. J . Am. Chem. Soc. 1970, 92,
6
2
9
990-6991. (b) Clark, H. C.; Poller, R. C. Can. J . Chem. 1970, 48,
670-2673. (c) Davis, D. D.; J ohnson, H. T. J . Am. Chem. Soc. 1974,
6, 7576-7577. (d) McWilliam, D. C.; Balasubramanian, T. R.; Kuivila,
H. G. J . Am. Chem. Soc. 1978, 100, 6407-6413. (e) Shiner, V. J ., J r.;
Thus, the reaction of 1a with an allylmetal 2 was
Ensinger, M. W.; Kriz, G. S. J . Am. Chem. Soc. 1986, 108, 842-844.
carried out in the presence of BF
3
2
‚OEt (Scheme 3). The
(f) Davidson, E. R.; Shiner, V. J ., J r. J . Am. Chem. Soc. 1986, 108,
3
4
135-3137. (g) Cooper, J .; Shiner, V. J ., J r. J . Org. Chem. 1989, 54,
reaction with allyltributylstannane (2a ) gave rise to the
exclusive formation of the allylated product (3) (Table 1,
entry 1). The reaction seems to proceed by the following
mechanism: The elimination of the acetoxy group with
270-4271. (h) Fleming, I.; Patel, S. K.; Urch, C. J . J . Chem. Soc.,
Perkin Trans. 1 1989, 115-124. (i) Shiner, V. J ., J r.; Ensinger, M. W.
J . Org. Chem. 1990, 55, 653-661. (j) Coope, J .; Shiner, V. J ., J r.;
Ensinger, M. W. J . Am. Chem. Soc. 1990, 112, 2834-2835. (k) Lambert,
J . B.; Salvador, L. A.; So, J .-H. Organometallics, 1993, 12, 697-703.
the aid of BF
3
‚OEt
2
gives the R-stannyl-substituted
(l) Green, A. J .; Pigdon, T.; White, J . M.; Yamen, J . J . Org. Chem. 1998,
carbocation, which adds to 2a to give the carbocation
intermediate having two stannyl groups at both â- and
γ-positions. The exclusive formation of 3 indicates that
6
3, 3943-3951. (m) Nakashima, T.; Fujiyama, R.; Fujio, M.; Tsuno,
Y. Bull. Chem. Soc. J pn. 1999, 72, 741-750. (n) Nakashima, T.;
Fujiyama, R.; Fujio, M.; Tsuno, Y. Bull. Chem. Soc. J pn. 1999, 72,
1
043-1047. (o) Nakashima, T.; Fujiyama, R.; Fujio, M.; Tsuno, Y.
Tetrahedron Lett. 1999, 40, 539-542.
8) For example, Li, T.; J anda, K. D.; Lerner, R. A. Nature 1996,
79, 326-327 and references therein.
9) Sugawara, M.; Yoshida, J . J . Am. Chem. Soc. 1997, 119, 11986-
1987.
(
(10) (a) Sugawara, M.; Yoshida, J . Synlett. 1998, 1057-1058. (b)
Sugawara, M.; Yoshida, J . Tetrahedron Lett. 1999, 40, 1717-1720.
(11) Reactivities of allylsilanes, allylgermanes, and allylstannanes
with carbenium ions has been studied extensively. See ref 6n.
3
(
1

â- and γ-Effects of Group 14 Elements
J . Org. Chem., Vol. 65, No. 10, 2000 3137
Ta ble 1. Rea ction s of r-Acetoxyben zylsta n n a n e (1a ) w ith Allylm eta l (2)a
a
b
Reaction condition; 0.40 mmol of 1a , 1.1 equiv of 2, 1.1 equiv of BF3‚OEt2 in toluene at -23 °C for 25-80 min. Isolated yield of a
mixture of 3a and 4. Determined by H NMR analyses. d 1.3 equiv of 2a was used.
c
1
Ta ble 2. Rela tive En er gies a n d Geom etr ies of ASn a n d
Ta ble 3. Rela tive En er gies a n d Geom etr ies of AGe, BGe,
a n d CGe
BSn
ASn
BSn
AGe
BGe
CGe
relative energy (kcal/mol)a
0.00
1.54
relative energy (kcal/mol)a
0.0
1.99
7.11
Atom Distance (Å)
Atom Distance (Å)
Sn(1)-C(1)
C(1)-C(2)
C(2)-C(3)
C(1)-C(3)
C(3)-C(4)
C(4)-Sn(2)
2.19
1.59
1.51
2.47
1.40
2.46
2.19
1.58
1.52
2.58
1.40
2.45
Sn-C(1)
2.20
1.60
1.50
2.43
1.42
2.23
2.19
1.58
1.51
2.56
1.41
2.23
2.37
1.66
1.47
1.71
1.53
2.02
C(1)-C(2)
C(2)-C(3)
C(1)-C(3)
C(3)-C(4)
C(4)-Ge
Angle (deg)
Angle (deg)
102.9
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)-Sn(2)
105.7
-95.5
112.9
92.4
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)-Ge
111.9
90.6
65.7
144.2
-96.0
Mulliken Atomic Chargeb
Mulliken Atomic Charge b
Sn(1)
C(1)
C(2)
C(3)
C(4)
Sn(2)
0.45
-0.36
0.09
0.33
-0.17
0.65
0.45
-0.41
0.11
0.39
-0.20
0.65
Sn
0.47
-0.36
0.10
0.42
-0.19
0.56
0.46
-0.40
0.11
0.46
-0.20
0.57
0.70
-0.29
0.20
0.34
-0.30
0.35
C(1)
C(2)
C(3)
C(4)
Ge
a
Including correction for ZPE. b The atomic charge densities
a
Including correction for ZPE. b The atomic charge densities
of hydrogens are summed into the heavy atom.
of hydrogens are summed into the heavy atom.
γ-elimination of tin is faster than the â-elimination of
silicon. This result suggests that γ-effect can be stronger
than â-effect if we employ different elements.
These results indicate that the â-elimination of tin and
the â-elimination of germanium are much faster than the
γ-elimination of tin, whereas the γ-elimination of tin is
faster than the â-elimination of silicon. To the best of our
knowledge, this is the first example of the direct in-
tramolecular competition between the â-elimination and
the γ-elimination of group 14 elements.
the â-elimination of tin is much faster than the γ-elim-
ination of tin.
The reaction with allyltriethylgermane (2b) resulted
in the predominant formation of the allylated product 3,
although a small amount of cyclopropane 4b was ob-
tained as a byproduct (entry 2). This result indicates that
the â-elimination of germanium is faster than the
γ-elimination of tin, but the difference is smaller than
that between â-elimination of tin and γ-elimination of
tin.
The reaction of 1a with allyltrimethylsilane (2c),
however, mainly afforded cyclopropane 4c together with
a small amount of 3a (entry 3), indicating that the
In the elimination process, nucleophilic attack at group
14 elements plays a crucial role, because the cleavage of
the carbon-group 14 element bond is usually assisted

3
138 J . Org. Chem., Vol. 65, No. 10, 2000
Sugawara and Yoshida
Ta ble 4. Rela tive En er gies a n d Geom etr ies of ASi, BSi,
a n d CSi
Sch em e 4
ASi
BSi
CSi
relative energy (kcal/mol)a
0.0
2.92
3.31
Atom Distance (Å)
Sn-C(1)
2.22
1.63
1.47
2.28
1.44
2.05
2.20
1.60
1.49
2.50
1.42
2.09
2.38
1.67
1.47
1.69
1.53
1.94
C(1)-C(2)
C(2)-C(3)
C(1)-C(3)
C(3)-C(4)
C(4)-Si
Angle (deg)
94.6
C(1)-C(2)-C(3)
107.9
89.5
64.9
146.8
group seems to be much less favorable. Another possibil-
ity to be considered is as follows. The initial addition
takes place at the carbon bearing two methyl groups.
Facile γ-eliminatin of tin then takes place to give cyclo-
propane 4k . The presence of two methyl groups should
facilitate the cyclization to form the cyclopropane ring
(gem-dimethyl effect).
C(2)-C(3)-C(4)-Si
-99.9
Mulliken Atomic Chargeb
Sn
0.51
-0.36
0.11
0.51
-0.31
0.54
0.48
-0.39
0.10
0.53
-0.28
0.56
0.70
-0.28
0.19
0.32
-0.36
0.42
C(1)
C(2)
C(3)
C(4)
Si
The effect of the substituent on γ-tin is interesting
(Scheme 5). The reaction of 1b, which has triphenylstan-
nyl group instead of tributyl group, with allyltributyl-
stannane 2a gave the corresponding allylated product 3b
exclusively. The reaction with allyltriethylgermane 2b
also led to the exclusive formation of 3b, although the
reaction of 1a with 2b gave a small amount of the
cyclopropane derivative. To our surprise, the reaction of
1b with allyltrimethylsilane 2c gave rise to the predomi-
nant formation of 3b. The substitution of the tributyl-
stannyl group by triphenylstannyl group reversed the
selectivity. The â-effect of silicon is stronger than the
γ-effect of tin in this case. The retardation of the
nucleophilic attack on tin by bulky phenyl groups seems
to be responsible.
a
Including correction for ZPE. b The atomic charge densities
of hydrogens are summed into the heavy atom.
by the nucleophilic attack on the group 14 element.12 The
ease of such nucleophilic attack should be affected by the
nature of the substituent on the group 14 elements. To
examine this effect, we carried out the reaction of 1 with
several allylsilanes having different substituents on
silicon (entries 4-10). Cyclopropanes 4 were formed as
major products irrespective of the nature of the substitu-
ent, but there exist definite substituent effects on the
ratio of 3a /4. The introduction of bulky groups such as
tert-butyl group and phenyl group on silicon caused the
exclusive formation of cyclopropane 4. This is probably
because bulky substituents retard the nucleophilic attack
on silicon, and therefore, the elimination of the â-silyl
group becomes slower. The introduction of electronegative
substituents such as ethoxy groups on silicon also favors
the formation of the cyclopropane 4. The introduction of
electronegative groups on silicon might cause a slight
decrease of the energy level of C-Si σ orbital,13 which in
turn disfavors the interaction with the neighboring empty
p orbital of the carbocation, although more data should
be accumulated before the elucidation of the detailed
mechanism. It should be noted that in the case of the
disilanyl group, â-silicon elimination is more favorable
in comparison with the trimethylsilyl group. It has been
reported that a disilanyl group enhances the â-effect of
These results indicate that the relative ease of â- and
γ-elimination is quite sensitive to the nature of the
substituent on group 14 elements.
Ab In itio Molecu la r Or bita l Ca lcu la tion s of Ca r -
boca tion In ter m ed ia te. To get a deeper insight into
the factors which govern the reaction pathways, we
carried out ab initio molecular orbital calculations of the
carbocation intermediates.15 The cations of SnH
CHCH MH
CH
3
2 2
CH -
2
3
(M ) Sn, Ge, and Si) were chosen as model
compounds, and the calculations were carried out at MP2/
LANL2DZ level with full geometry optimization.
M ) Sn . In the case of M ) Sn, two structures (ASn
and BSn ) were obtained as local minima as shown in
Figure 1. In ASn two tin atoms are located in the opposite
side of the plane of the formal carbon-carbon double
bond of the allylstannane, whereas in BSn they are in
1
4
silicon in electrophilic reactions of vinylsilanes, and the
present result is consistent with this report.
the same side. ASn is 1.54 kcal/mol more stable than BSn
In both structures, the distance between C(3) and C(4)
1.4 A) is very close to the bond length of normal carbon-
.
The effect on the substituent on carbon was also
examined. The reaction with 2k , which has two methyl
groups at the terminal position, gave rise to exclusive
formation of cyclopropane derivative (entry 11). This
result might be explained by the attack of the tin-
substituted carbocation at â carbon to form the tertiary
carbocation γ to both tin and silicon (Scheme 4). Then,
the γ-elimination of the stannyl group took place to give
cyclopropane 4k because the γ-elimination of the silyl
(
carbon double bond. The torsion angles of C(2)-C(3)-
C(4)-Sn(2) indicate that the C(2)-C(3) bond and the
C(4)-Sn(2) bond are perpendicular with each other.
These data indicate that the carbocation at C(3) interacts
with the neighboring C(4)-Sn(2) σ orbital quite ef-
fectively. The longer bond length of C(4)-Sn(2) in com-
parison with that of C(1)-Sn(1) suggests that the C(4)-
Sn(2) bond is weakened by such interaction and ready
to be cleaved to form the carbon-carbon double bond.
On the other hand, the distance between C(1) and C(3)
(
12) For example, Bassindale, A. R.; Taylor, P. G. The chemistry of
organic silicon compounds; Patai, S., Rappoport, Z., Eds.; Wiley:
Chichester, 1989; pp 839-892.
(
13) Yoshida, J .; Tsujishima, H.; Nakano, K.; Isoe, S. Inorg. Chim.
Acta 1994, 220, 129-135.
+
(
14) It has been reported that a disilanyl group is able to enhance
(15) The MO calculations of H
3
MCH
2
CH
2
(M ) Si, Ge, Sn) were
the â effect of silicon in the electrophilic reaction of vinylsilane. Dixon,
T. A.; Steele, K. P.; Weber, W. P. J . Organomet. Chem. 1982, 231, 299.
reported in the literature. Nguyen, K. A.; Gordon, M. S.; Wang, G.-T.;
Lambert, J . B. Organometallics 1991, 10, 2798-2803.

â- and γ-Effects of Group 14 Elements
J . Org. Chem., Vol. 65, No. 10, 2000 3139
F igu r e 1. Optimized geometries of cationic intermediates.
Sch em e 5
is very long, and this distance indicates that the interac-
tion between the p orbital of the carbocation at C(3) and
the back lobe of C(1)-Sn(1) σ orbital is negligible. The
large angle of C(1)-C(2)-C(3) also indicates the absence
of such percaudal interaction. Therefore, in structures
A
Sn and BSn , the â-tin (Sn(2)) stabilizes the carbocation
at C(3) more effectively than γ-tin (Sn(1)). The larger
atomic charge at Sn(2) in comparison with that at Sn(1)
also indicates the larger effects of â-tin and the predomi-
nant cleavage of the Sn(2)-C bond.

3
140 J . Org. Chem., Vol. 65, No. 10, 2000
Sugawara and Yoshida
M ) Ge. In the case of germanium, three structures
Ge, BGe, and CGe) were obtained as local minima
Figure 1). Geometries of AGe and BGe are similar to those
of ASn and BSn , respectively, and these structures seem
to be the intermediates for the formation of the allylated
product 3 as in the case of the allylstannane. Structure
ination of silicon and the γ-elimination of tin take place
with similar possibilities. This seems to be consistent
(
(
A
with the experimental results: The γ-elimination of Bu
Sn is faster than the â-elimination of Me Si, whereas the
γ-elimination of Ph Sn is slower than the â-elimination
of Me Si.
3
-
3
3
3
C
Ge is quite different from structures AGe and BGe. In
All of the calculations described above were carried out
for carbocations in a vacuum without a counterion. Under
this condition the formation of the carbocation A, B, and
C from the R-tin-substituted carbocation and the allyl-
metal is quite exothermic. The real reactions, however,
take place in the solution phase and the solvent molecules
should play crucial roles for both the formation of these
cations and the elimination of the metal. The counter-
anion should also play a significant role in these pro-
cesses. Although these factors are omitted in the present
calculations, the information obtained here still helps us
to elucidate the mechanistic insight into the nature of
group 14 elements in the γ- and â-effects. Future theo-
retical studies involving the solvent molecules and coun-
teranions will hopefully delineate detailed mechanistic
insights of the present problem.
structure CGe the cyclopropane ring is almost formed
because the distance between C(1) and C(3) (1.71 A) is
close to that of a normal carbon-carbon single bond and
the angle of C(1)-C(2)-C(3) (65.7°) is close to 60°,
indicating the existence of the strong percaudal interac-
tion. The longer bond length of Sn-C(1) of CGe, in
comparison with those in AGe and BGe, is also consistent
with the presence of such interaction. The bond length
of C(3)-C(4) of CGe is much longer than those of AGe and
B
Ge and the bond length of C(4)-Ge of CGe is much
shorter than those of AGe and BGe. These results indicate
that in CGe γ-tin stabilizes the carbocation at C(3) more
effectively than â-germanium and that this structure
leads to the γ-elimination of tin to form cyclopropane 4.
The larger atomic charge at Sn of CGe compared with
those in AGe and BGe also suggest the larger effect of tin
in CGe. The structure of CGe seems to be similar to those
of protonated cyclopropanes which play important roles
in biological and chemical transformations involving
carbocations, although the edged hydrogen is replaced
by the stannyl group.
Con clu sion
1
6
The intramolecular competition revealed that the
γ-elimination of Bu Sn is faster than the â-elimination
3
of Me Si but slower than the â-elimination of Et Ge and
3
3
As to the energies of these structures, AGe is 1.99 kcal/
mol more stable than BGe and 7.11 kcal/mol more stable
than CGe. These data imply that the â-elimination is more
favorable than γ-elimination of tin, which is consistent
with the experimental result, i.e., allylated product 3 was
obtained preferentially together with a small amount of
cyclopropane 4.
3
Bu Sn. The introduction of sterically demanding substi-
tutents on silicon disfavors the â-elimination of silicon.
The introduction of phenyl groups on tin reversed the
selectivity (â-Me
3
3
Si > γ-Ph Sn). Therefore, relative ease
of γ-elimination and â-elimination is quite sensitive to
the substituents. The ab initio molecular orbital calcula-
tions of the carbocation intermediate are, in principle,
consistent with the experimental results. The results of
these studies will provide a significant insight into the
â- and γ-effects of group 14 elements and a valuable guide
to the control of the reactions involving carbocation
intermediates.
M ) Si. In the case of silicon, three structures (ASi
,
B
Si, and CSi) were obtained as local minima as shown in
Figure 1. The most stable structure is ASi, which is 2.92
kcal/mol more stable than structure BSi and 3.31 kcal/
mol more stable than CSi. The structure ASi is, however,
somewhat different from ASn and AGe. In ASi, the bond
length of C(3)-C(4) is slightly longer than those in ASn
and AGe. This indicates that the interaction of the
carbocation at C(3) with the neighboring C-Si σ orbital
is less effective than similar interactions with C-Sn and
C-Ge σ orbitals. On the other hand, the distance between
C(1) and C(3) is slightly shorter than those in ASn and
Exp er im en ta l Section
(
Acet oxy)(t r ib u t ylst a n n yl)(p -m et h oxyp h en yl)m et h -
a n e (1a ). To a solution of lithium diisopropyl amide (LDA)
15.5 mmol) in THF (30 mL) was added Bu SnH (4.80 mL,
8.0 mmol) at -72 °C. After being stirred at 0 °C for 35 min,
(
3
1
a solution of p-anisaldehyde (1.85 mL, 15.1 mmol) in THF (2.0
mL) was added at -72 °C, and the reaction mixture was stirred
at the same temperature for 40 min. After the reaction mixture
was warmed to 0 °C, sat. aq NH Cl (ca. 10 mL) was added,
4
and the organic phase was separated. The aqueous phase was
A
Ge, implying the existence of the percaudal interaction
between the p orbital of the carbcation at C(3) and the
back-lobe of the C-Sn σ orbital. The smaller angle of
C(1)-C(2)-C(3) of ASi (94.6°) in comparison with those
of ASn (105.7°) and AGe (102.9°) also suggests the presence
of such interaction. Therefore, structure ASi seems to lead
to the formation of both allylated product 3 and cyclo-
propane 4.
extracted with ether (×3), and the combined organic phase was
4
washed with sat. aq NaCl, and dried over MgSO . After
removal of the solvent, the corresponding R-hydroxystannane
was obtained which was used for the acetylation without
purification.
To a solution of the R-hydroxystannane thus obtained in 1,2-
dichloroethane (30 mL) was added pyridine (2.40 mL, 21.2
mmol) and Ac O (2.0 mL, 29.6 mmol) at 0 °C. The reaction
2
Structure BSi seems to lead to the formation of ally-
lated product 3. The structural analyses of CSi indicate
that this structure leads to the formation of cyclopropane
mixture was stirred at room-temperature overnight. After
removal of the solvent, water and ether was added, and the
organic phase was separated. The aqueous phase was ex-
tracted with ether (×3), and the combined organic phase was
4
as in the cases of germanium. It is noteworthy that
the energy of CSi is comparable to that of BSi. Therefore,
the results of calculations suggest that both the â-elim-
3
washed with 1 N HCl aq and sat. aq NaHCO , and dried over
MgSO
4
. After removal of the solvent, the residue was purified
(
16) For example, (a) Sieber, S.; Buzek, P.; Schleyer, P. v. R.; Koch,
via flash chromatography to obtain 5.81 g (83%) of the title
compound. TLC R
W.; Carneiro, J . W. de M. J . Am. Chem. Soc. 1993, 115, 259-270. (b)
Saunders, M.; Vogel, P.; Hagen, E. L.; Rosenfeld, J . Acc. Chem. Res.
1
f
0.20 (hexane/AcOEt 50/1); H NMR (300
1
973, 6, 53-59. (c) Collins, C. J . Chem. Rev. 1969, 69, 534-550.
MHz, CDCl ) δ 0.7-0.95 (m, 15 H), 1.10-1.35 (m, 6 H), 1.35-
3

â- and γ-Effects of Group 14 Elements
J . Org. Chem., Vol. 65, No. 10, 2000 3141
1
.45 (m, 6 H), 2.11 (s, 3 H), 3.79 (s, 3 H), 5.83 (t, J Sn-H ) 9.0
J ) 8.1 Hz, 9 H), 2.00 (td, J ) 8.4, 6.0 Hz, 1 H), 3.79 (s, 3 H),
6.82 (d, J ) 8.7 Hz, 2 H), 7.09 (d, J ) 8.4 Hz, 2 H), For trans-
Hz, 1 H), 6.83 (d, J ) 8.7 Hz, 2 H), 7.05 (d, J ) 8.7 Hz, 2 H);
1
3
13
C NMR (75 MHz, CDCl
3
) δ 9.84, 13.53, 20.98, 27.25, 28.72,
4b, the characteristic signal, 3.77 (s, 3 H, OMe); C NMR (75
5
1
5.26, 73.19, 113.98, 125.58, 134.95, 157.58, 171.08; IR (neat)
MHz, CDCl
113.33, 130.17, 131.70, 157.72.; MS (EI) m/e (%) 322 (M , 20);
HRMS calcd for C17 28OGe 322.1352, found 322.1362.
cis-1-(p-Meth oxyp h en yl)-2-[(tr im eth ylsilyl)m eth yl]cy-
3
) δ 3.90, 8.84, 10.35, 11.70, 15.21, 21.18, 55.18,
-
1
+
+
720 (C ) O) cm ; MS (EI) m/e (%) 413 (M - C
Sn - C 413.1138, found 413.1123.
Sn: C, 56.31; H, 8.16. Found: C,
4 9
H , 32);
HRMS calcd for C22
Anal. Calcd for C22
6.18, H, 8.34.
Acetoxy)(tr ip h en ylsta n n yl)(p-m eth oxyp h en yl)m eth -
a n e (1b). To a solution of lithium diisopropylamide (LDA)
2.80 mmol) in THF (5 mL) was added Ph SnH (934 mg, 2.66
H
38
O
4
4
H
9
H
H
38
O
3
1
5
clop r op a n e (cis-4c). TLC R
f
0.41 (hexane/AcOEt 20/1); H
) δ -0.13 (dd, J ) 10.5, 9.9 Hz, 1 H),
(
NMR (300 MHz, CDCl
3
-0.03 (s, 9 H), 0.40-0.54 (m, 2 H), 0.95-1.10 (m, 2 H), 1.98
(
3
(td, J ) 8.7, 6.0 Hz, 1 H), 3.79 (s, 3 H), 6.82 (d, J ) 8.7 Hz, 2
mmol) at -78 °C. After being stirred at -20 °C for 25 min,
p-anisaldehyde (0.30 mL, 2.45 mmol) was added at -72 °C,
and the reaction mixture was stirred at the same temperature
for 10 min. To the obtained solution of the R-hydroxystannane
H), 7.10 (d, J ) 8.7 Hz, 2 H); 13C NMR (75 MHz, CDCl
) δ
3
-1.55, 11.25, 14.15, 15.18, 20.21, 55.15, 113.28, 130.26, 131.87,
+
157.71; MS (EI) m/e (%) 234 (M , 90); HRMS calcd for C14
22
H -
OSi 234.1440, found 234.1436. Anal. Calcd for C14
71.73; H, 9.46. Found: C, 71.47, H, 9.64.
H22OSi: C,
was added pyridine (0.33 mL, 4.10 mmol) and Ac
.49 mmol) at -78 °C. The reaction mixture was stirred at
room-temperature overnight. Water and CH Cl was added,
and the organic phase was separated. The aqueous phase was
extracted with CH Cl
(×2), and the combined organic phase
was washed with 1N HCl aq, sat. aq NaHCO , and dried over
MgSO . After removal of the solvent, the residue was purified
via flash chromatography to obtain 564.7 mg (44%) of the title
2
O (0.33 mL,
3
tr a n s-1-(p-Meth oxyp h en yl)-2-[(tr im eth ylsilyl)m eth yl]-
cyclop r op a n e (tr a n s-4c). TLC R 0.41 (hexane/AcOEt 20/
) δ 0.03 (s, 9 H), 0.54-0.74 (m,
2
2
f
1
1); H NMR (300 MHz, CDCl
3
2
2
3 H), 0.80-0.92 (m, 2 H), 1.49 (dt, J ) 8.4, 4.8 Hz, 1 H), 3.77
(s, 3 H), 6.80 (d, J ) 8.7 Hz, 2 H), 6.93 (d, J ) 8.7 Hz, 2 H);
3
1
3
4
3
C NMR (75 MHz, CDCl ) δ -1.52, 17.55, 18.99, 22.13, 24.06,
+
55.25, 113.77, 126.49, 136.21, 157.48; MS (EI) m/e (%) 234 (M ,
1
compound. TLC R
MHz, CDCl ) δ 1.91 (s, 3 H), 3.77 (s, 3 H), 6.18 (t, J Sn-H ) 11.1
Hz, 1 H), 6.78 (d, J ) 8.7 Hz, 2 H), 7.05-7.20 (m, 2 H), 7.30-
7
1
1
5
f
0.22 (hexane/AcOEt 5/1); H NMR (300
90), 219 (100); HRMS calcd for C14
234.1433.
H22OSi 234.1440, found
3
cis-1-(p -Met h oxyp h en yl)-2-[(ter t-b u t yld im et h ylsilyl)-
m eth yl]cyclop r op a n e (cis-4d ). TLC R 0.39 (hexane/AcOEt
) δ -0.09 (s, 3 H), -0.04 (s, 3
1
3
.45 (m, 15 H); C NMR (75 MHz, CDCl
3
) δ 20.71, 55.29, 74.45,
f
1
14.09, 127.11, 128.47, 129.03, 132.76, 137.35, 138.35, 158.34,
71.55; IR (neat) 1711 (C ) O) cm ; MS (EI) m/e (%) 530 (18),
28 (13); HRMS calcd for C28 Sn 528.0904, found 530.0900.
20/1); H NMR (300 MHz, CDCl
3
-1
H), -0.09-0.0 (m, 1 H), 0.42-0.60 (m, 2 H), 0.81 (s, 9 H), 0.95-
1.10 (m, 2 H), 2.00 (td, J ) 8.4, 6.0 Hz, 1 H), 3.80 (s, 3 H), 6.83
26 3
H O
1
3
Allylsila n es. Allylsilanes (2c-k ) were prepared by the
(d, J ) 8.7 Hz, 2 H), 7.08 (d, J ) 8.7 Hz, 2 H); C NMR (75
reaction of allylmagnesium bromide with the corresponding
chlorosilanes in good yields.
MHz, CDCl
3
) δ -6.15, -5.89, 10.98, 11.80, 14.59, 16.41, 20.75,
26.43, 55.17, 113.30, 130.14, 131.73, 157.71; MS (EI) m/e (%)
+
(
Allyl)(tr ibu tylstan n yl)(p-m eth oxyph en yl)m eth an e (3a).
276 (M , 30); HRMS calcd for C17
H
28OSi 276.1910, found
A Typ ica l P r oced u r e of In t r a m olecu la r Com p et it ion
Rea ction . To a solution of (acetoxy)(tributylstannyl)(p-meth-
oxyphenyl)methane 1a (189.4 mg, 0.40 mmol) and allyltribu-
tylstannane (160 µL, 0.52 mmol) in toluene (1.0 mL) was added
276.1918. Anal. Calcd for C17
Found: C, 73.57, H, 10.49.
H28OSi: C, 73.85; H, 10.21.
tr a n s-1-(p-Meth oxyph en yl)-2-[(ter t-bu tyldim eth ylsilyl)-
m eth yl]cyclop r op a n e. (tr a n s-4d ). TLC R 0.39 (hexane/
) δ -0.02 (s, 3 H), 0.0
f
1
BF
3
‚OEt
2
(56.0 µL, 0.44 mmol) at -23 °C. The reaction mixture
AcOEt 20/1); H NMR (300 MHz, CDCl
3
was stirred at the same temperature for 1 h until most of 1a
was consumed (by TLC). The reaction was quenched by the
(s, 3 H), 0.54-0.70 (m, 2 H), 0.71-0.82 (m, 2 H), 0.84-0.90
(m, 1 H), 0.87 (s, 9 H), 1.50 (dt, J ) 8.4, 4.8 Hz, 1 H), 3.78 (s,
1
3
addition of Et
3
N (100 µL). The mixture was passed through a
3 H), 6.80 (d, J ) 8.7 Hz, 2 H), 6.95 (d, J ) 8.7 Hz, 2 H);
NMR (75 MHz, CDCl
24.52, 26.43, 55.25, 113.79, 126.43, 136.16, 157.49; MS (EI)
C
silica gel short column to remove insoluble materials (Et
2
O
3
) δ -6.03, 16.30, 17.99 (2 carbons), 19.23,
eluted). After removal of the solvent, the residue was purified
+
via flash chromatography to obtain 149.0 mg (83%) of the title
m/e (%) 276 (M , 40); HRMS calcd for C17H28OSi 276.1910,
1
compounds. TLC R
MHz, CDCl
.18-1.50 (m, 12 H), 2.56-2.80 (m, 4 H), 3.77 (s, 3 H), 4.92
ddt, J ) 10.2, 1.2, 1.2 Hz, 1 H), 5.01 (ddt, J ) 17.1, 1.8, 1.5
Hz, 1 H), 5.76 (ddt, J ) 17.1, 10.2, 6.6 Hz, 1 H), 6.78 (d, J )
.5 Hz, 2 H), 6.93 (t, J ) 8.7 Hz, 2 H); 13C NMR (75 MHz,
CDCl ) δ 9.00, 13.54, 27.37, 28.97, 32.64, 37.00, 55.21, 113.79,
14.91, 127.25, 138.62, 139.11, 156.26; MS (EI) m/e (%) 452
f
0.39 (hexane/AcOEt 20/1); H NMR (300
found 276.1900.
cis-1-(p-Meth oxyp h en yl)-2-[(tr iisop r op ylsilyl)m eth yl]-
3
) δ 0.73-0.79 (m, 6 H), 0.85 (t, J ) 7.5 Hz, 9 H),
1
1
cyclop r op a n e (cis-4e). TLC R
NMR (300 MHz, CDCl
0.53 (q, J ) 4.5 Hz, 1 H), 0.59 (dd, J ) 15.0, 3.3 Hz, 1 H),
0.88-1.15 (m, 23 H), 2.01 (td, J ) 8.4, 5.7 Hz, 1 H), 3.80 (s, 3
f
0.40 (hexane/AcOEt 20/1); H
(
3
) δ -0.04 (dd, J ) 15.0, 9.9 Hz, 1 H),
7
1
3
3
H), 6.84 (d, J ) 8.7 Hz, 2 H), 7.09 (d, J ) 8.7 Hz, 2 H);
NMR (75 MHz, CDCl
21.54, 55.15, 113.31, 130.06, 131.59, 157.66; MS (EI) m/e (%)
C
1
3
) δ 7.65, 10.87, 12.71, 14.26, 18.64, 18.67,
+
(M , 8); HRMS calcd for C23
H40OSn 452.2101, found 452.2081.
+
The reactions of 1a and 1b with allylmetals were carried
318 (M , 35); HRMS calcd for C20
H
34OSi 318.2379, found
out in a similar fashion. The products were isolated via flash
chromatography as a mixture of isomers. Each isomers were
isolated by GPC. Stereochemistry of the cyclopropane deriva-
318.2386. Anal. Calcd for C20
Found: C, 75.67, H, 11.01.
H34OSi: C, 75.40; H, 10.76.
tr a n s-1-(p-Meth oxyp h en yl)-2-[(tr iisop r op ylsilyl)m eth -
yl]cyclop r op a n e (tr a n s-4e). TLC R 0.40 (hexane/AcOEt 20/
1
tives was determined by H NMR analyses based on the vicinal
f
1
coupling constant (for cis J ) 8.7-8.0 Hz, for trans J ) 5.4-
3
1); H NMR (300 MHz, CDCl ) δ 0.55-0.68 (m, 1 H), 0.70-
4
.8 Hz).
0.75 (m, 1 H), 0.80-1.00 (m, 3 H), 1.05-1.15 (m, 21 H), 1.55
(
Allyl)(tr ip h en ylsta n n yl)(p-m eth oxyp h en yl)m eth a n e
(dt, J ) 8.1, 4.5 Hz, 1 H), 3.78 (s, 3 H), 6.79 (d, J ) 8.7 Hz, 2
1
13
(
3b). TLC R
f
0.39 (hexane/AcOEt 5/1); H NMR (300 MHz,
H), 6.94 (d, J ) 8.7 Hz, 2 H); C NMR (75 MHz, CDCl ) δ
3
CDCl
3
) δ 2.80-3.00 (m, 2 H), 3.33 (t, J ) 7.2 Hz, 1 H), 3.79 (s,
10.82, 14.77, 18.69, 19.13, 25.52, 55.23, 113.74, 126.36, 136.19,
+
3
5
7
5
1
H), 4.92 (d, J ) 10.2 Hz, 1 H), 4.99 (d, J ) 17.1 Hz, 1 H),
34
157.43; MS (EI) m/e (%) 318 (M , 40); HRMS calcd for C20H -
.72-5.85 (m, 1 H), 6.75-6.78 (m, 2 H), 7.00-7.04 (m, 2 H),
OSi 318.2379, found 318.2368.
1
3
.30-7.50 (m, 15 H),; C NMR (75 MHz, CDCl
5.21, 113.95, 115.87, 128.42, 128.47, 128.92, 135.92, 137.41,
38.11, 138.59, 157.07; MS (EI) m/e (%) 512 (8), 510 (6); HRMS
3
) δ 35.16, 37.19,
cis-1-(p-Meth oxyph en yl)-2-[(ph en yldim eth ylsilyl)m eth -
yl]cyclop r op a n e (cis-4f). TLC R 0.39 (hexane/AcOEt 20/1);
) δ 0.12 (dd, J ) 15.0, 10.2 Hz, 1
f
1
H NMR (300 MHz, CDCl
3
calcd for C29
-(p-Meth oxyp h en yl)-2-[(tr ieth ylger m yl)m eth yl]cyclo-
p r op a n e (4b) (a mixture of isomers, cis/ trans ) 88/12). TLC
H
28OSn 512.1162, found 512.1185.
H), 0.25 (s, 3 H), 0.27 (s, 3 H), 0.44 (q, J ) 5.7 Hz, 1 H), 0.75
(dd, J ) 15.0, 4.2 Hz, 1 H), 0.90-1.10 (m, 2 H), 1.97 (td, J )
8.4, 6.0 Hz, 1 H), 3.80 (s, 3 H), 6.82 (d, J ) 8.7 Hz, 2 H), 7.06
(d, J ) 8.7 Hz, 2 H), 7.34-7.36 (m, 3 H), 7.46-7.50 (m, 2 H);
1
1
f 3
R 0.45 (hexane/AcOEt 20/1); H NMR (300 MHz, CDCl ) δ For
1
3
cis-4b, 0.11 (dd, J ) 13.8, 10.2 Hz, 1 H), 0.45 (dd, J ) 6.0, 5.4
Hz, 1 H), 0.70 (q, J ) 8.1 Hz, 6 H), 0.75-1.10 (m, 3 H), 0.97 (t,
C NMR (75 MHz, CDCl
3
) δ -3.08, -2.89, 11.37, 14.04, 14.39,
20.37, 55.15, 113.35, 127.72, 128.83, 130.21, 131.62, 133.67,

3
142 J . Org. Chem., Vol. 65, No. 10, 2000
Sugawara and Yoshida
+
+
1
39.65, 157.75; MS (EI) m/e (%) 296 (M , 65); HRMS calcd for
131.30, 157.83; MS (EI) m/e (%) 324 (M , 25); HRMS calcd for
C
19
H
24OSi 296.1596, found 296.1602. Anal. Calcd for C19
OSi: C, 76.97; H, 8.16. Found: C, 77.26, H, 8.45.
tr a n s-1-(p -Met h oxyp h en yl)-2-[(p h en yld im et h ylsilyl)-
m eth yl]cyclop r op a n e (tr a n s-4f). TLC R 0.39 (hexane/
) δ 0.31 (s, 3 H), 0.32
s, 3 H), 0.62-0.70 (m, 1 H), 0.80-1.00 (m, 4 H), 1.49 (dt, J )
H
24
-
C
17
H
28
O
4
Si 324.1757, found 324.1759.
cis-1-(p-Meth oxyp h en yl)-2-[(p en ta m eth yld isilyl)m eth -
yl]cyclop r op a n e (cis-4j). TLC R 0.42 (hexane/benzene 1/1);
) δ -0.04 (dd, J ) 15.0, 10.5 Hz, 1
f
1
f
H NMR (300 MHz, CDCl
3
1
AcOEt 20/1); H NMR (300 MHz, CDCl
(
3
H), 0.00 (s, 3 H), 0.01 (s, 3 H), 0.03 (s, 9 H), 0.45 (dt, J ) 5.7,
4.5 Hz, 1 H), 0.59 (dd, J ) 14.4, 3.6 Hz, 1 H), 0.95-1.10 (m, 2
H), 1.98 (td, J ) 8.7, 5.7 Hz, 1 H), 3.79 (s, 3 H), 6.83 (d, J )
8
.4, 4.5 Hz, 1 H), 3.78 (s, 3 H), 6.78 (d, J ) 8.7 Hz, 2 H), 6.90
1
3
(
d, J ) 8.7 Hz, 2 H), 7.33-7.36 (m, 3 H), 7.40-7.53 (m, 2 H);
8.7 Hz, 2 H), 7.07 (d, J ) 8.7 Hz, 2 H); C NMR (75 MHz,
CDCl ) δ -4.12, -4.09, -2.22, 11.70, 13.57, 14.76, 20.68, 55.17,
113.33, 130.20, 131.73, 157.74; MS (EI) m/e (%) 292 (M , 20);
HRMS calcd for C16 292.1679, found 292.1676. Anal.
: C, 65.69; H, 9.65. Found: C, 65.39, H,
1
3
C NMR (75 MHz, CDCl
3
) δ -3.01, -2.89, 17.60, 18.75, 21.28,
3
+
2
1
4.18, 55.25, 113.72, 126.51, 127.80, 128.92, 133.67, 135.97,
39.44, 157.49; MS (EI) m/e (%) 296 (M , 95); HRMS calcd for
+
H28OSi
2
H28OSi
2
C
19
H
24OSi 296.1596, found 296.1599.
cis-1-(p-Meth oxyph en yl)-2-[(diph en ylm eth ylsilyl)m eth -
yl]cyclop r op a n e (cis-4g). TLC R 0.36 (hexane/AcOEt 20/
) δ 0.43-0.51 (m, 2 H), 0.57 (s,
Calcd for C16
9.42.
f
tr a n s-1-(p -Met h oxyp h en yl)-2-[(p en t a m et h yld isilyl)-
m eth yl]cyclop r op a n e (tr a n s-4j). TLC R 0.42 (hexane/
) δ 0.04 (s, 9 H), 0.07
1
1
3
); H NMR (300 MHz, CDCl
3
f
1
H), 0.96 (td, J ) 8.4, 5.1 Hz, 1 H), 1.02-1.20 (m, 1 H), 1.09
benzene 1/1); H NMR (300 MHz, CDCl
3
(
(
7
dd, J ) 12.0, 3.9 Hz, 1 H), 2.00 (td, J ) 8.4, 6.0 Hz, 1 H), 3.81
s, 3 H), 6.84 (d, J ) 8.4 Hz, 2 H), 7.07 (d, J ) 8.4 Hz, 2 H),
(s, 3 H), 0.60-0.70 (m, 2 H), 0.80-0.92 (m, 3 H), 1.50 (dt, J )
8.4, 4.8 Hz, 1 H), 3.77 (s, 3 H), 6.80 (d, J ) 8.7 Hz, 2 H), 6.95
.30-7.40 (m, 6 H), 7.50-7.60 (m, 4 H); 13C NMR (75 MHz,
(d, J ) 8.7 Hz, 2 H); C NMR (75 MHz, CDCl
13
) δ -4.22, -4.12,
3
CDCl
3
) δ -4.33, 11.61, 12.87, 13.94, 20.65, 55.17, 113.39,
-2.29, 17.96, 19.45, 20.37, 24.40, 55.25, 113.79, 126.43, 136.15,
+
1
27.80, 129.15, 130.20, 131.43, 134.57, 137.36, 157.78; MS (EI)
157.49; MS (EI) m/e (%) 292 (M , 90); HRMS calcd for C16
OSi 292.1679, found 292.1676.
28
H -
+
m/e (%) 358 (M , 11); HRMS calcd for C24
H
26OSi 358.1753,
2
found 358.1755. Anal. Calcd for C24
Found: C, 80.37, H, 7.34.
H
26OSi: C, 80.40; H, 7.31.
(1S *,2R *)-1-(p -Me t h oxyp h e n yl)-2-[(t r im e t h ylsilyl)-
m eth yl]-3,3-d im eth ylcyclop r op a n e (4k ) (a mixture of iso-
1
tr a n s-1-(p -Met h oxyp h en yl)-2-[(d ip h en ylm et h ylsilyl)-
m eth yl]cyclop r op a n e. (tr a n s-4g). TLC R 0.36 (hexane/
) δ 0.60 (s, 3 H), 0.68
dt, J ) 8.4, 5.1 Hz, 1 H), 0.84 (dt, J ) 8.4, 5.1 Hz, 1 H), 0.90-
mers, 84/16). TLC R
MHz, CDCl
f
0.41 (hexane/AcOEt 20/1); H NMR (300
f
3
) δ For (1S*,2R*)-4k 0.22 (s, 9 H), 0.10 (dd, J )
1
AcOEt 20/1); H NMR (300 MHz, CDCl
3
14.7, 11.1 Hz, 1 H), 0.73 (dd, J ) 15.0, 3.6 Hz, 1 H), 0.80-0.90
(m, 1 H), 0.88 (s, 3 H), 1.21 (s, 3 H), 1.67 (d, J ) 8.7 Hz, 1 H),
3.79 (s, 3 H), 6.82 (d, J ) 8.7 Hz, 2 H), 7.11 (d, J ) 8.7 Hz, 2
H), For (1S*,2S*)-4k , the characteristic signal, 1.34 (d, J )
(
1
1
6
.00 (m, 1 H), 1.20 (dd, J ) 15.0, 6.6 Hz, 1 H), 1.29 (dd, J )
5.0, 6.6 Hz, 1 H), 1.52 (dt, J ) 8.4, 4.8 Hz, 1 H), 3.77 (s, 3 H),
.76 (d, J ) 9.0 Hz, 2 H), 6.82 (d, J ) 9.0 Hz, 2 H), 7.30-7.42
5.7 Hz, 1 H, ArCH); 13C NMR (75 MHz, CDCl
) δ -1.44, 12.57,
3
1
3
(
-
1
m, 6 H), 7.50-7.59 (m, 4 H); C NMR (75 MHz, CDCl
4.30, 17.72, 18.54, 19.84, 24.41, 55.23, 113.68, 126.55, 127.87,
29.23, 130.20, 134.60, 135.77, 137.26, 157.51; MS (EI) m/e
3
) δ
17.34, 19.48, 24.32, 29.33, 30.06, 55.11, 113.39, 131.02, 132.16,
+
26
157.63; MS (EI) m/e (%) 262 (M , 100); HRMS calcd for C16H -
OSi 262.1753, found 262.1755. Anal. Calcd for C16
73.22; H, 9.98. Found: C, 73.13, H, 10.14.
H26OSi: C,
+
(%) 358 (M , 20); HRMS calcd for C24H26OSi 358.1753, found
3
58.1764.
cis-1-(p-Meth oxyp h en yl)-2-[(tr ip h en ylsilyl)m eth yl]cy-
Molecu la r Or bita l Ca lcu la tion s. The ab initio calcula-
1
7
tions were carried out using the GAUSSIAN 98 program at
the MP2/LANL2DZ level. All geometries were fully optimized,
and all the optimized structures were local minima according
to the vibration frequency analysis. Relative energies were
corrected for ZPE (zero point energy) calculated at MP2/
LANL2DZ.
1
clop r op a n e (cis-4h ). TLC R
f
0.36 (hexane/AcOEt 20/1); H
NMR (300 MHz, CDCl ) δ 0.45 (q, J ) 5.7 Hz, 1 H), 0.77 (dd,
3
J ) 15.3, 9.9 Hz, 1 H), 0.89 (td, J ) 8.1, 4.8 Hz, 1 H), 1.14-
1
8
.28 (m, 1 H), 1.35 (dd, J ) 15.3, 3.9 Hz, 1 H), 1.98 (td, J )
.4, 6.3 Hz, 1 H), 3.78 (s, 3 H), 6.80 (d, J ) 8.7 Hz, 2 H), 7.00
(
d, J ) 8.7 Hz, 2 H), 7.30-7.42 (m, 9 H), 7.45-7.55 (m, 6 H);
1
3
C NMR (75 MHz, CDCl
13.42, 127.81, 129.41, 130.20, 131.23, 135.31, 135.84, 157.78;
3
) δ 12.01, 12.07, 13.94, 21.10, 55.17,
Ack n ow led gm en t. This work was supported by
Grant-in-Aid for Scientific Research from Monbusho. We
also thank Shin-etsu Chemical for the gifts of some
organosilicon compounds.
1
+
MS (EI) m/e (%) 420 (M , 12); HRMS calcd for C29
20.1909, found 420.1921. Anal. Calcd for C29 28OSi: C, 82.81;
H, 6.71. Found: C, 82.31, H, 6.56.
tr a n s-1-(p-Meth oxyp h en yl)-2-[(tr ip h en ylsilyl)m eth yl]-
cyclop r op a n e (tr a n s-4h ). TLC R 0.36 (hexane/AcOEt 20/
) δ 0.65 (dt, J ) 8.7, 5.1 Hz, 1
H), 0.80 (dt, J ) 8.4, 4.8 Hz, 1 H), 1.00-1.10 (m, 1 H), 1.45-
H28OSi
4
H
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra for compounds 1a , 1b, 3a , 3b, 4b, 4c, 4d , 4e, 4e, 4f,
g, 4h , 4j, and 4k . This material is available free of charge
f
1
1
); H NMR (300 MHz, CDCl
3
4
via the Internet at http://pubs.acs.org.
1
7
1
1
.63 (m, 3 H), 3.75 (s, 3 H), 6.71 (s, 4 H), 7.25-7.40 (m, 9 H),
.45-7.50 (m, 6 H); 13C NMR (75 MHz, CDCl
) δ 18.11, 18.57,
3
J O991977T
9.11, 24.87, 55.25, 113.60, 126.58, 127.90, 129.48, 135.12,
+
35.87, 135.68, 157.49; MS (EI) m/e (%) 420 (M , 15); HRMS
(17) Gaussian 98, Revision A.7, Frisch, M. J .; Trucks, G. W.;
Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J . R.;
Zakrzewski, V. G.; Montgomery, J . A., J r.; Stratmann, R. E.; Burant,
J . C.; Dapprich, S.; Millam, J . M.; Daniels, A. D.; Kudin, K. N.; Strain,
M. C.; Farkas, O.; Tomasi, J .; Barone, V.; Cossi, M.; Cammi, R.;
Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J .;
Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J . B.; Cioslowski, J .; Ortiz,
J . V.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi,
I.; Gomperts, R.; Martin, R. L.; Fox, D. J .; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challacombe, M.; Gill, P.
M. W.; J ohnson, B.; Chen, W.; Wong, M. W.; Andres, J . L.; Gonzalez,
C.; Head-Gordon, M.; Replogle, E. S.; Pople, J . A. Gaussian, Inc.,
Pittsburgh, PA, 1998.
calcd for C29
-(p-Meth oxyp h en yl)-2-[(tr ieth oxysilyl)m eth yl]cyclo-
p r op a n e (4i) (a mixture of isomers, cis/ trans ) 87/13). TLC
R 0.22 (hexane/AcOEt 20/1); H NMR (300 MHz, CDCl ) δ For
f 3
cis-4i 0.01 (dd, J ) 15.6, 9.9 Hz, 1 H), 0.55 (q, J ) 5.4 Hz, 1
H), 0.62 (dd, J ) 15.6, 3.9 Hz, 1 H), 1.02 (td, J ) 8.7, 5.7 Hz,
1
)
2
H28OSi 420.1909, found 420.1926.
1
1
H), 1.18-1.25 (m, 1 H), 1.21 (t, J ) 6.9 Hz, 9 H), 2.03 (td, J
8.7, 6.3 Hz, 1 H), 3.70-3.90 (m, 10 H), 6.81 (d, J ) 8.7 Hz,
H), 7.09 (d, J ) 8.7 Hz, 2 H), For tr a n s-4i, the characteristic
1
3
signal, 6.98-7.02 (m, 2 H, Ar); C NMR (75 MHz, CDCl
9
3
) δ
.34, 11.31, 12.43, 18.17, 20.66, 55.20, 58.27, 113.39, 130.32,