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ethanol (2g) gave 3g without any side products (entry 3)
while the reaction using allylchlorosilane (1) gave polymeric
side products (see Table 2, entries 7 and 8). As those side
products probably came from the benzylic chloride generated
in situ, the Cl-free system with 7 was able to give a clean
reaction with 2g. The yield was increased to 87% by using
three equivalents of 7 (entry 4). It is interesting that the
reaction of g-substituted allylsilanes 8 and 10 gave the
products regioselectively in an exclusively g-addition
manner (entries 5–8). This system can be applied to other
types of nucleophiles. In the case of the propargylsilane 12,
the regioselective formation of the allene 13 occurred
exclusively through g-addition (entries 9 and 10). The alky-
nylsilane 14 gave the desired products 15 in high yields
(entries 11 and 12). As various types of trimethylsilyl
compounds are available, the Cl-free system will expand the
synthetic applications of this method.
detected; signals for the dimeric ether 5 and a small amount of
chloride 6 were observed instead (RT, 20 min), together with
the allylated product 3a.[12] In fact, no HCl was detected
during the course of this reaction, whereas the reduction
system with Ph2SiHCl definitely generates HCl.[1] These
results surprised us and showed that the mechanism of
allylation is different from that of the reduction system,[1]
although the exact reaction course is not yet clear.[13] The most
important factor in this reaction is the unique character of the
indium catalyst, which has 1) enough Lewis acidity to activate
À
the C O bond, 2) lowoxophilicity to regenerate a catalysis
from the substrate, and 3) stability under protic conditions.
Those factors were realized in the direct substitution system
with alcohols.
In summary, we have demonstrated the direct substitution
of the hydroxy group in alcohols by nucleophiles such as
allylic-, propargyl-, and alkynylsilanes. The silyl nuclophile
and InCl3 make an indispensable combination to accelerate
the unprecedented alkylative substitution with formation of a
Since the removal of HCl was not observed during the
course of the reaction, it might not be necessary to use the
silane bearing the chlorine atom on its metal center. We
examined some allylsilanes such as allyltrimethyl-, diallyldi-
methyl-, and trimethoxysilanes for the allylation of alcohols.
Among these silanes, the desired alkylated product was only
formed in satisfactory yield in the reaction with 2a when
allyltrimethylsilane (7) was used at 808C in dichloroethane
(Table 3, entry 1). The reaction performed at room temper-
ature gave no alkylated product. No 3a was formed in the
absence of the InCl3 catalyst (entry 2). Gratifyingly, 1-phenyl-
À
C C bond. The details of the mechanism are nowunder
investigation.
Received: October 21, 2003 [Z53121]
Keywords: alcohols · alkylation · homogeneous catalysis ·
.
indium · silanes
[1] M. Yasuda, Y. Onishi, M. Ueba, T. Miyai, A. Baba, J. Org. Chem.
2001, 66, 7741 – 7744.
À
[2] For recent reports of transition-metal-catalyzed C C bond
Table 3: Alkylation of alcohols 2 with trimethylsilyl nucleophiles cata-
formation through direct substitution of allylic or propargylic
alcohols with nucleophiles other than allylic ones, see: a) F.
Ozawa, H. Okamoto, S. Kawagishi, S. Yamamoto, T. Minami, M.
Yoshifuji, J. Am. Chem. Soc. 2002, 124, 10968 – 10969; b) Y.
Nishibayashi, M. Yoshikawa, Y. Inada, M. Hidai, S. Uemura, J.
Am. Chem. Soc. 2002, 124, 11846 – 11847.
lyzed by InCl3.[a]
Entry Silane
Alcohol t [h]
Product
Yield [%]
[3] J. A. Cella, J. Org. Chem. 1982, 47, 2125 – 2130.
[4] A. Schmitt, H.-U. Reißig, Eur. J. Org. Chem. 2000, 3893 – 3901.
[5] M. Rubin, V. Gevorgyan, Org. Lett. 2001, 3, 2705 – 2707.
[6] T. Miyai, M. Ueba, A. Baba, Synlett 1999, 182 – 184.
[7] For InCl3-catalyzed allylation of gem-diacetates by allylsilane,
see: J. S. Yadav, B. V. Subba Reddy, C. Madhuri, G. Sabitha,
Chem. Lett. 2001, 18 – 19.
1
2a
2a
2g
2g
3
3
3
3
3a
3a
3g
3g
99
0
51
87
2[b]
3
4[c]
5
2a
3
9a
100
[8] The polymeric side products were observed in a similar type of
reaction.[3,5]
[9] About 10% of a dehydrated product, ethyl 3-phenyl-2-prope-
noate, contaminated the reaction mixture and could be sepa-
rated from the product by column chromatography.
[10] N. Kuhnert, J. Peverley, J. Robertson, Tetrahedron Lett. 1998, 39,
3215 – 3216.
[11] The NMR spectroscopy experiment was performed in dilute
conditions (approximately 0.1m) to slowdown the reaction.
[12] Our previous report[13b] suggests that the allylated silyl ether 4
could be formed by silanes, but 4 was not found in the reaction
described in this paper.
6
2a
2g
2g
3
3
3
11a
11g
11g
64
72
81
7
8[c]
9
10
2a
2g
3
6
13a
13g
64
55
11
2a
2g
2
3
15a
15g
93
62
12[c]
À
[13] For the example including C O bond cleavage with the silicon–
indium system, see: a) Y. Onishi, D. Ogawa, M. Yasuda, A.
Baba, J. Am. Chem. Soc. 2002, 124, 13690 – 13691; b) Y. Onishi,
T. Ito, M. Yasuda, A. Baba, Tetrahedron 2002, 58, 8227 – 8235.
[a] The reactions were carried out in 1,2-dichloethane (2 mL) with silane
(2.0 mmol), alcohol 2 (1.0 mmol), and InCl3 (0.05 mmol) at 808C.
[b] InCl3 was not added. [c] Silane (3.0 mmol).
1416
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2004, 43, 1414 –1416