Indium(III) chloride/chlorotrimethylsilane as a highly active Lewis acid catalyst system for the Sakurai-Hosomi reaction

Article abstract of DOI:10.1002/1099-0690(200205)2002:9<1578::AID-EJOC1578>3.0.CO;2-P

The indium(III) chloride/chlorotrimethylsilane system acts as a catalyst for the Sakurai-Hosomi reaction between allylsilanes and aldehydes. When γ-substituted allylsilanes such as crotylsilane and prenylsilane are used a high regioselectivity for γ-addit

Full text of DOI:10.1002/1099-0690(200205)2002:9<1578::AID-EJOC1578>3.0.CO;2-P

FULL PAPER
Indium(III) Chloride/Chlorotrimethylsilane as a Highly Active Lewis Acid
Catalyst System for the Sakurai؊Hosomi Reaction
[
a]
[a]
[a]
[a]
Yoshiyuki Onishi, Takeshi Ito, Makoto Yasuda, and Akio Baba*
Keywords: Allylation / Aldehydes / Indium / Silicon
The indium(III) chloride/chlorotrimethylsilane system acts as
a catalyst for the Sakurai−Hosomi reaction between allylsil-
larger amounts (20 mol %) gave no product whatsoever.
Other group 13 Lewis acids such as AlCl and BF ·OEt did
3
3
2
anes and aldehydes. When γ-substituted allylsilanes such as not have catalytic activity even when combined with chloro-
crotylsilane and prenylsilane are used a high regioselectivity trimethylsilane.
for γ-addition is observed. Smaller amounts of the catalyst (5
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
mol %) effectively afforded the allylation products, although
2002)
Introduction
Results and Discussion
The synthetic applications of indium compounds have at-
We found that the reaction between benzaldehyde (1a)
tracted much attention in the last decade.[ Barbier- or and allyltrimethylsilane (2a) depends, rather unusually, on
1]
Reformatsky-type reactions using indium species[ are the amount of the combined catalyst InCl /Me SiCl, as
2]
3
3
known to be powerful CϪC bond formation methods. A shown in Table 1. Based on reported conditions for the
selective addition of allylic dihaloindium, generated by the catalytic aldol reaction,[ we performed the first trial of our
transmetallation between trihaloindium and allylic tributyl- reaction with 10 mol % of the catalyst. However, the yields
7]
[
3]
tin reagents, has become an important synthetic method. of allylated product 3a were very low (entries 3 and 4); the
Indium(III) halides have also been used as water-tolerant use of 20 mol % of the catalyst completely depressed the
Lewis acid catalysts for DielsϪAlder, aldol and Mannich- formation of 3a (entries 1 and 2). Surprisingly, only 5 mol %
[
4]
type reactions. However, the catalytic use of indium com- of the catalyst gave 61% yield (entry 5). The yield was fur-
pounds is still limited to a narrow area, in contrast to the ther improved to 81% by changing the order of addition
III
extensive use of aluminum or boron compounds, as In
(entry 6): allylsilane was added to a premixed solution of
compounds have a lower Lewis acidity than the corres- aldehyde and the combined catalyst (Method B). When al-
III
III
[5]
ponding Al or B compounds.
We have previously reported
lyltrimethylsilane and 20 mol % of the combined catalyst
reductive was treated at room temperature without benzaldehyde, the
the
FriedelϪCrafts reaction of carbonyl compounds catalyzed complete decomposition of the allylsilane was observed
III [6]
29
by In . FriedelϪCrafts benzylation of benzene with within 2 hours ( Si NMR spectroscopy), and the formation
benzyl chloride is enhanced remarkably by the combination of propene was confirmed by GLC analysis of the gas in the
[6b]
of a catalytic amount of Me SiCl and InCl . The Mukai- flask. This test strongly suggests that the catalyst activates
3
3
yama group has also reported an aldol reaction catalyzed allylsilane, as neither InCl nor Me SiCl promote this de-
3
3
[7]
[10]
by tBuMe SiCl/InCl . In this context, we felt that the composition on their own. The proton source needed to
combination of In compounds and Me SiCl would work form propene is not yet known, although a trace amount
2
3
III
3
as a strong carbonyl-activating ‘‘catalyst’’.
of water is the most likely candidate. The decomposition of
The catalytic allylation of carbonyl compounds by allylsi- allyltrimethylsilane is considerably slower with only 5
lanes (SakuraiϪHosomi reaction)[ is a challenging theme mol % of the catalyst, and this is probably the reason why
because of the difficulty of regenerating the catalyst from the yield is improved by loading smaller amounts of the
the produced homoallylic metal oxides.[ We wish to report catalyst or by changing the addition order (Method B).
8]
9]
here the characteristic activation of the allylation by the
combined catalyst, InCl /Me SiCl.
The catalysts examined for the reaction between p-chlo-
robenzaldehyde (1b) and allyltrimethylsilane (2a) are sum-
marized in Table 2. The typical Lewis acids AlCl3 and
3
3
[
a]
Department of Molecular Chemistry, Graduate School of BF
·OEt
ometric yields of the product (entries 1 and 2). Although
neither Me SiCl nor InCl exhibited any catalytic ability on
did not catalyze the reaction, only giving stoichi-
3
2
Engineering, Osaka University,
2Ϫ1 Yamadaoka, Suita, Osaka, 565Ϫ0871, Japan
Fax: (internat.) ϩ 81-6-6879/7387
3
3
E-mail: baba@ap.chem.eng.osaka-u.ac.jp
their own (entries 3Ϫ5), their combined use gave 3b in 87%
1578
 WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ193X/02/0509Ϫ1578 $ 20.00ϩ.50/0 Eur. J. Org. Chem. 2002, 1578Ϫ1581

Indium(III) Chloride/Chlorotrimethylsilane as a Highly Active Lewis Acid Catalyst
Table 1. Effect of the amount of combined catalyst
FULL PAPER
ture stirred for 2 hours. After confirming the disappearance
of the aldehyde by GLC, the reaction was quenched by ad-
dition of a 1  THF solution of tetra-n-butylammonium
fluoride (2 mL, 2 mmol) and stirring for 5 minutes.[ The
11]
reaction mixture was then extracted with Et O (40 mL) and
2
washed twice with H O (50 mL). The organic layer was
2
dried (MgSO ) and the solvents evaporated. Column chro-
Yield (%) matography of the residue on silica gel (eluting with 9:1
4
Entry
Catalyst (mol %)
Method[a]
hexane/ether) followed by distillation gave 3a.
1
2
3
4
5
6
20
20
10
10
5
A
B
A
B
A
B
0
0
5
15
61
81
The catalyst system Me SiCl/InCl was also applied to
3
3
the allylation of various carbonyl compounds and gave high
yields of homoallylic alcohols, as shown in Table 3. Func-
tional groups such as nitro, ester and cyano moieties toler-
ated the reaction conditions to give products allylated se-
lectively at the carbonyl group, perhaps because of the mild
non-protic conditions (entries 1Ϫ3). When p-methylbenzal-
dehyde was used as a substrate, the homoallyl alcohol 3f
was obtained in 56% yield, along with 25% of the dial-
lylation compound 3fa. The methoxy-substituted aldehyde
5
[
a]
Method A: addition order, i) InCl
3
/CH
2
Cl
3
2
, ii) Me
3
SiCl, iii) 2a,
/CH Cl , ii) 1a, iii)
iv) 1a.; method B: addition order, i) InCl
Me SiCl, iv) 2a.
3
2
2
(
1g) gave only the diallylation product 3ga. These results
Table 2. Effect of different catalysts
indicate that the Me SiCl/InCl system also possesses a high
3
3
catalytic ability for the allylation of initially formed homo-
allyl trimethylsilyl ethers.[
12]
Table 3. Allylation of various carbonyl compounds[a]
Entry Catalyst (mol %)
Yield (%) Recovery (%)[a]
1
2
3
4
5
6
7
8
9
0
1
2
AlCl
BF ·OEt
Me SiCl (20)
3
(20)[b]
(20)
37
26
6
0
9
35
20
94
99
84
0
0
72
0
[
b]
3
2
[
b]
3
InCl
InCl
InCl
InCl
InCl
InCl
3
3
3
3
3
3
(20)
(5)
(5) ϩ Me
(5) ϩ tBuMe
(5) ϩ Me
(1) ϩ Me
3
SiCl (5)
87
Entry RCHO
Time (h) Product Yield (%)
2
SiCl (5) 85
[
c]
3
SiCl (5)
SiCl (1)
SiCl (5)
0
77
9
1
2
3
4
5
6
7
p-MeOCO-C
p-NO -C CHO (1d)
p-CN-C CHO (1e)
p-Me-C CHO (1f)
p-MeO-C CHO (1g)
6
H
4
CHO (1c)
1
1
2
13
13
1
3c
3d
3e
3f
؊
3h
3i
97
93
99
56
3
2
6 4
H
1
1
1
AlCl
BF ·OEt
TiCl (5) ϩ Me
3
(5) ϩ Me
(5) ϩ Me
SiCl (5)
3
79
84
91
6
H
4
3
2
3
SiCl (5) 10
[
[
b]
b]
[c]
6
H
4
4
3
9
0[d]
6
H
4
[
a]
Recovery of 1b. [b] No allylated product 3b was obtained with 5
nHexCHO (1h)
75
78
mol % of these catalysts. [ Allytributylin was used instead of 2a.
c]
tBuCHO (1i)
2
[
[
a]
b]
3 3
InCl /Me SiCl/ 1/2a ϭ 0.1:0.1:2.0:3.0 mmol, solvent was 4 mL.
[c]
The reaction was performed at 0 °C. The diallylation product
fa was obtained in 25% yield. [ The diallylation product 3ga was
d]
3
yield (entry 6). It should be noted that even 1 mol % of the
combined catalyst afforded an acceptable yield of product
obtained in 49% yield.
(77%, entry 9).
AlCl , BF ·OEt and TiCl do not catalyze the allylation
3
3
2
4
An aliphatic aldehyde, n-heptanal (1h), also afforded the
expected allylated product 3h in high yield (entry 6). The
reaction with the sterically hindered aldehyde 1i proceeded
cleanly and afforded the homoallylic alcohol 3i in 78%
even in combination with Me SiCl (entries 10Ϫ12). The re-
3
action with allyltributyltin, which has a higher nucleophilic-
ity than allytrimethylsilane, resulted in the recovery of 1b in
this combined catalyst system (entry 8). These results
strongly indicate a strong interaction between indium and
silicon.
A typical reaction procedure is as follows: allyltrimethyl-
silane (2a, 0.33 g, 3.0 mmol) was added at 0 °C to a mixture
of dried indium(III) chloride (0.022 g, 0.1 mmol), chlorotri-
methylsilane (0.010 g, 0.1 mmol) and benzaldehyde (1a,
(
entry 7). Only trace amounts of the products were obtained
in the allylation of ketones such as acetophenone or benzo-
phenone.
0
.21 g, 2.0 mmol) in dichloromethane (4 mL), and the mix-
Eur. J. Org. Chem. 2002, 1578Ϫ1581
1579

Y. Onishi, T. Ito, M. Yasuda, A. Baba
FULL PAPER
The results of the allylation with substituted allylsilanes rohr) was accomplished in a Sibata GTO-250RS at the oven tem-
perature and pressure indicated. Yields were determined by GLC
or H NMR spectroscopy using internal standards.
are shown in Equations (1)Ϫ(3), as the reaction with substi-
1
tuted allylsilanes are very rare.[13] The β-methylated allylsil-
ane 2b reacted with p-chlorobenzaldehyde (1b) to give 4b
2
Dichloromethane was distilled from CaH . The substituted allysil-
quantitatively [Equation (1)]. When γ-substituted allylsil- anes 2c and 2d were prepared from the corresponding vinyl brom-
anes [crotyltrimethylsilane (2c) and trimethylprenylsilane ides and trimethylsilylmethylmagnesium chloride by known
(
3
2d)], which have lower reactivity than 2a and 2b because methods. The allylsilanes 2a and 2b, aldehydes 1aϪ1i, InCl ,
[14]
3 2
Me SiCl, tBuMe SiCl and TBAF (1.0  solution in THF) are com-
of their steric hindrance, were used, the addition readily
took place with highly γ-selective CϪC bond formation.[
15]
mercially available.
These results emphasize that the combination of InCl and
3
General Procedure for the Synthesis of Homoallylic Alcohols from
Me SiCl has opened up a new catalytic system for selective 1aϪi: The allylsilane 2aϪd (3.0 mmol) was added under nitrogen
3
carbonyl-group allylation.
3 3
to a mixture of InCl (0.2 mmol), Me SiCl (0.4 mmol) and alde-
hydes 1bϪi (2.0 mmol) in dichloromethane (4 mL) and this solu-
tion was stirred for the appropriate time at ambient temperature.
The resultant mixture was quenched with a 1.0  solution of TBAF
in THF and then extracted with Et
2
O (40 mL) and washed twice
) and the
(
(
1)
with H O (50 mL). The organic layer was dried (MgSO
2
4
solvents evaporated. Column chromatography of the evaporated
residue on silica gel (eluting with a 9:1 hexane/ether mixture) and
distillation gave pure products.
[
9b,16Ϫ19]
Product data: The spectroscopic data of the products 3aϪi,
fa, [ 3ga,
were in excellent agreement
9b]
[9b]
[21]
[21]
[17]
3
4b,
5i,
and 6a
2) with reported compounds.
1
-(4-Chlorophenyl)-2,2-dimethylbut-3-en-1-ol (6b): Prepared by the
typical procedure from 1b (2 mmol) and 2d (3 mmol). B.p.: 70 °C/
Ϫ1
1
1
4
ϫ 10 Torr. H NMR (270 MHz, CDCl
3
): δ ϭ 7.30Ϫ7.20 (m,
H, aromatics), 5.87 (dd, J ϭ 17.58 Hz, 10.74 Hz, 1 H, 3-H), 5.15
(
dd, J ϭ 10.74 Hz, 0.98 Hz, 1 H, 4-H-trans), 5.07 (dd, J ϭ
1
2
7.58 Hz, 0.98 Hz, 1 H, 4-H-cis), 4.40 (d, J ϭ 2.92 Hz, 1 H, 1-H),
.07 (d, J ϭ 2.92 Hz, 1 H, OH), 0.99 (s, 3 H, CH ), 0.93 (s, 3 H,
): δ ϭ 144.66 (C-3), 139.11 (1-
3
(
3)
1
3
3 3
CH ). C NMR (67.9 MHz, CDCl
Ph), 133.08 (4-Ph), 129.07 (arom. CH), 127.61 (arom. CH), 114.28
(
(
(
(
C-4), 79.87 (C-1), 42.24 (C-2), 24.33 (CH
3 3
), 20.77 (CH ). IR
neat): ν˜ ϭ 3467 (OH), 1635 (CϭC). HRMS (CI, 70 eV): calculated
ϩ
ϩ
12
C H
17ClO ) 211.0890 [M ϩ H ]; found 211.0885. C12
H16ClO
182.6516): calcd. C 68.40, H, 7.18; found C 68.20, H, 7.39.
Conclusion
Acknowledgments
This work was supported by a Grant-in Aid for Scientific Research
from the Ministry of Education, Culture, Sports, Science and Tech-
nology, of the Japanese Government.
We have shown that the combined system InCl /Me SiCl
3
3
exhibits a high catalytic activity for the SakuraiϪHosomi
reaction using various substrates, including aromatic and
aliphatic aldehydes. The use of small amounts of the cata-
lyst is effective for allylation. Substituted allylsilanes were
also applied to this catalytic reaction and gave the allylated
products with inversion of the allylic unit in a highly select-
ive manner.
[
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Eur. J. Org. Chem. 2002, 1578Ϫ1581

Indium(III) Chloride/Chlorotrimethylsilane as a Highly Active Lewis Acid Catalyst
FULL PAPER
[
6] [6a]
and aromatics.[6] Diallylation of p-methylbenzaldehyde and p-
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[
6b]
6
5
291Ϫ6294.
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3
methoxybenzaldehyde was reported in the Sc(OTf) -catalyzed
SakuraiϪHosomi reaction.[
9e]
[
13]
14]
[
[
7]
There are only two reports of a catalytic SakuraiϪHosomi re-
T. Mukaiyama, T. Ohno, J. S. Han, S. Kobayashi, Chem. Lett.
991, 949Ϫ952.
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9b,9g]
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[
8] [8a]
β-Substituted allylsilanes possess considerably higher nucleo-
philicity than allyltrimethylsilane, see: G. Hagen, H. Mayr, J.
Am. Chem. Soc. 1991, 113, 4954Ϫ4961.
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[
8b]
1
295Ϫ1296.
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or YbCl
3
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[
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The coordination of a Lewis acid to allyltributylstannane is
[
10]
The decomposition of allyltrimethylsilane indicates that the
combined catalyst interacts with allylsilanes. On the contrary,
we observed the color change of the solution from colorless to
known, see: J. M. Blackwell, W. E. Piers, M. Parves, Org. Lett.
2
000, 2, 695Ϫ698.
[23]
No transmetallation occurred between the combined catalyst
and allyltrimethylsilane, because TMSCl was not observed in
yellowish orange by mixing InCl
3
/Me
3
SiCl and benzaldehyde
in dichloromethane. This result indicates an interaction be-
3
the mixture of allyl-TMS, InCl and TBDMSCl. On the con-
trary, facile transmetallation between InCl and allyltributyltin
3
has been reported.
M. Yasuda, Y. Onishi, T. Ito, A. Baba, Tetrahedron Lett. 2000,
tween the combined catalyst and benzaldehyde.[
22,23]
Although
the activation mechanism of the combined catalyst system is
not clear yet at this stage, we assume that the combined catalyst
interacts with both the aldehyde and the allylsilane.
We verified that tetra-n-butylammonium fluoride (TBAF)
worked only as the quenching reagent of silyl ethers to alco-
hols.
[3]
[24]
4
1, 2425Ϫ2428.
[
[
11]
12]
[25] [25a]
T. Miyai, M. Ueba, A. Baba, Synlett 1999, 182Ϫ184. [25b]
M. Yasuda, Y. Onishi, M. Ueba, T. Miyai, A. Baba, J. Org.
Chem. 2001, 66, 7741Ϫ7744.
We have previously reported that activated silyl ethers are re-
Received October 22, 2001
[24]
[25]
ceptive to nucleophilic attack by allylsilane,
hydrosilane,
[O01502]
Eur. J. Org. Chem. 2002, 1578Ϫ1581
1581