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Direct coupling reaction between alcohols and allyltrimethylsilane catalyzed by phosphomolybdic acid.

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Full Paper
Received: 19 April 2009
Revised: 4 June 2009
Accepted: 4 June 2009
Published online in Wiley Interscience: 16 July 2009
(www.interscience.com) DOI 10.1002/aoc.1527
Direct coupling reaction between alcohols
and allyltrimethylsilane catalyzed
by phosphomolybdic acid
Santosh T. Kadam, Hanbin Lee and Sung Soo Kim∗
Phosphomolybdic acid (PMA) is a simple and efficient catalyst for direct coupling reaction of alcohols with allyltrimethylsilane.
Direct nucleophilic allylation of alcohol with allyltrimethylsilane proceeds in considerably good yield in the presence of catalytic
c 2009 John Wiley & Sons, Ltd.
amount of (0.5 mol %) PMA at room temperature. Copyright Supporting information may be found in the online version of this article.
Keywords: allylation; alcohols; allyltrimethylsilane; PMA
Introduction
Appl. Organometal. Chem. 2010, 24, 67–70
In all cases the 1 H NMR (200 MHz) spectra were recorded with a
Varian Gemini 200. Chemical shifts were reported in ppm in CDCl3
with TMS as an internal standard. 13 C NMR data were collected on
a Varian Gemini 400 (100 MHz). GC-MS data were treated with a
1200L Single Quadrupole GC/MS System with 3800GC/Varian.
General Procedure for Allylation of Alcohols
The mixture of PMA (0.5 mol%, 9 mg) and alcohol (1.0 mmol,
184 mg) in CH2 Cl2 (2 ml) was stirred for 5 min and allyltrimethylsilane (1.2 mmol, 136 mg) was added. The reaction mixture was
stirred at rt for the appropriate time and monitored by TLC. The
solvent was removed in vacuo and the residue was purified by
column chromatography with silica gel.
All the known products of 1 H and 13 C NMR values were indentical
to literature values.[2,3,5,29] Spectral data and GC-MS values for the
new products are given below (entries 5 and 8; Table 2, entry 1):[2]
2
6′
7′
8′
9′
3
5′
4
5
10′ 10
1
6
7
8
9
1 H NMR (CDCl
3 , 200 MHz): δ 2.81 (t, J D 17.2 Hz, 2H, C-3), 4.00 (t,
J D 15.6 Hz, 1H, C-4), 4.90–5.07 (m, 2H, C-1), 5.645.73 (m, 1H, C-2),
7.12–7.28 (m, 10H, C-Ar). 13 C NMR (CDCl3 ,100 MHz): δ 40.0 (C-3),
51.3 (C-4), 116.43 (C-1), 126.3 (C-8,80 ), 128.0 (C-6,10,60 ,100 ), 129.5
(C-7,9,70 , 90 ), 136.9 (C-2), 144.5 (C-4,40 ) (Table 2, entry 4).[29]
Ł
Correspondence to: Sung Soo Kim, Department of Chemistry, Inha University,
Incheon 402-751, South Korea. E-mail: sungsoo@inha.ac.kr
Department of Chemistry, Inha University, Incheon-402-751, South Korea
c 2009 John Wiley & Sons, Ltd.
Copyright 67
Direct substitution of hydroxyl group in alcohol by various nucleophiles is a powerful protocol for the synthesis of carbon–carbon
bond formation. The direct substitution requires large amounts
of acid because the hydroxyl group is a poor leaving group.
An alternative way to avoid the use of excess amount of acid
consists in the transformation of the hydroxyl group into the
corresponding halides or other good leaving groups prior to the
reaction with nucleophiles. In this regard, direct catalytic substitution reaction of alcohol would be the ideal procedure for
synthesis. Many workers have recently reported the direct allylation of alcohol with allylsilane employing B(C6 F5 )3 ,[1] BiCl3 ,[2]
InCl3 ,[3] bis(fluorosulfuryl)imide[4] and BF3 [5] as the catalyst. BF3 requires more than equimolar amount and gives significant amounts
of side product. Furthermore bis(fluorosulfuryl)imide demands inert atmosphere at 78 Ž C and relatively high catalyst loading.[4]
Accordingly, development of an efficient and environmentally
benign catalytic methodology for allylation of alcohol is desirable.
Phosphomolybdic acid (PMA) belongs to the class of heteropolyacids (HPA). Recently HPA has attracted much attention as the
catalyst for various organic transformations as well as in processes
related to fine chemical synthesis.[6,7] Considering the importance
of environmental awareness in chemical technology, it is important to minimize undesirable hazardous chemical substances that
are dangerous to human health and the environment. HPA is
emerging as a green catalyst for various chemical reactions due
to its high catalytic activity and environmental friendliness.[8] HPA
is stronger than conventional acids, yet noncorrosive and used
in low concentrations which minimize the disposal problem.[9,10]
PMA is stronger than sulfuric acid, which makes it possible to
carry out reactions in low concentrations at ambient temperature. Accordingly PMA is used as the catalyst in various methods
such as Friedel–Crafts acylation of phenol,[11] Fries rearrangement
of phenyl acetate,[12] oxidation of hydroxyl group,[13] regioselective opening of N-tosyl aziridine[14] and selective deprotection of
t-butyldimethylsilyl ether.[15]
Experimental
S. T. Kadam, H. Lee and S. S. Kim
Table 1. Allylation of benzhydrol with allyltrimethylsilane under different reaction conditiona
Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
a
b
Catalyst
Mol (%)
Solvent
Time (min)
Yield (%)b
Nafion SAC-13
Nafion-NR-50
NbF5
NbCl5
Y(NO3 )3 .6H2 O
SmI2
Phosphotungstic acid
Phosphomolybdic acid (PMA)
PMA
PMA
PMA
PMA
PMA
PMA
PMA
PMA
10
10
10
10
10
10
10
10
10
10
10
10
10
5
1
0.5
CH2 Cl2
CH2 Cl2
CH2 Cl2
CH2 Cl2
CH2 Cl2
CH2 Cl2
CH2 Cl2
CH2 Cl2
THF
CH3 CN
CHCl3
Et2 O
CH3 NO2
CH2 Cl2
CH2 Cl2
CH2 Cl2
3 h
3 h
3 h
3 h
3 h
3 h
1 h
30
30
30
30
30
30
30
30
30
30
32
NR
NR
NR
NR
52
88
28
57
Trace
Trace
48
85
90
90
Reagents and conditions: benzhydrol (1.0 mmol); allyltrimethysilane (1.2 mmol) at room temperature.
Isolated yield.
OH
SiMe3
Catalyst
Me3SiOH
Scheme 1. Allylation of benzhydrol with allyltrimethylsilane under various reaction condition.
1
2
7′
1
5 6
3
6′
5′
F 8′ 9′
4
10′10
7
8 F
9
1
H NMR (CDCl3 , 200 MHz): δ 2.74 (t, J D 17.2 Hz, 2H,C-3), 3.97
(t, J D 15.6 Hz, 1H,C-4), 5.05–4.92 (m, 2H,C-1), 5.74–5.60 (m,
1H,C-2), 6.97 (d, J D 8 Hz, 4H,C-7,9,70 ,90 ), 7.20 (d, J D 8 Hz, 4H,
C-6,10,60 ,100 ). 13 C NMR (CDCl3 ,100 MHz): δ 40.2 (C-3), 49.6 (C-4),
115.0 (C-1), 116.7 (C-7,9,70 90 ), 129.2 (6,10,60 ,100 ), 136.3(C-2), 140.0
(C-5.50 ), 163.8(C-8,80 ) (Table 2, entry 5).
2
1
3
6′ 5′ 5 6
7′
4
7
10′ 10 8
Cl 8′
9 Cl
9′
1
H NMR (CDCl3 , 200 MHz): δ 1.20 (d, J D 7.8 Hz, 3H,C-5),
2.14–2.19(m, 2H,C-3), 2.24 (s, 3H,C-12), 2.33–2.72 (m, 1H,C-4),
5.49–4.86 (m, 2H,C-1), 5.69–5.61 (m, 1H,C-2), 6.72 (d, J D 7.6 Hz,
2H,7,11), 7.06 (d, J D 7.9 Hz, 2H,8,10). 13 C NMR (CDCl3 ,100 MHz):
δ 20.9(C-5,12), 39.3(C-3), 42.7(C-4), 115.7(C-1), 126.8 (C-7,11),
128.9(8,10), 137.3(C-9), 146.3(C-6) (Table 2, entry 7).[2]
2
3
7
MeO 9
10
12
NMR (CDCl3 , 200 MHz): δ 1.18 (d, J D 6.8 Hz, 3H,C-5),
2.33–2.20 (m, 2H,C-3), 2.73–2.68 (m, 1H,C-4), 3.73 (s, 3H,C12), 4.97–4.90 (m, 2H,C-1), 5.70–5.62 (m, 1H,C-2), 6.81 (d,
J D 7.9 Hz, 2H,C-7,11), 7.06 (d, J D 7.9 Hz, 2H,C-8,10). 13 C
NMR (CDCl3 ,100 MHz): δ 21.7(C-5), 38.9(C-3), 42.9(C-4), 55.1C12), 113.7(C-8,10), 115.8(C-1), 127.8(C-7,11), 137.3(C-6), 139.1(C-2),
157.8(C-9) (Table 2, entry 8).
2
3
9
8
68
Me
12
9
4
11
5
10
www.interscience.wiley.com/journal/aoc
5
8
4
13
11
1
1
3
10
7 6
4 5
11
1H
H NMR (CDCl3 , 200 MHz): δ 2.67 (t, J D 14 Hz, 2H, C-3), 3.89
(t, J D 14 Hz, 1H,C-4), 4.99–4.87 (m, 2H,C-C-1), 5.61–5.56 (m,
1H,C-2), 7.04 (d, J D 8 Hz, 4H,C-6,10,60 ,100 ), 7.20 (d, J D 8 Hz,
4H,C-7,9,70 ,90 ). 13 C NMR (CDCl3 ,100 MHz): δ 39.7(C-3), 49.8(C-4),
116.9(C-1), 127.7(C-, 128.4(C-6,10,60,100 ), 128.6(C-7,9,70 ,90 ), 135.9(Cž
5,50 ), 142.9 (C-8,80 ). GCMS: m/z: 277 [MC ], 276, 235, 236, 238
(Table 2, entry 6).[3]
2
1
6
8
6
7
12
1 H NMR (CDCl
3 , 200 MHz): δ 0.04–0.01(m, 1H,C-6), 0.20–0.14 (m,
1H,C-7), 0.35–0.28 (m, 1H,C-6), 0.56–0.50 (m, 1H,C-7), 0.97–0.92
c 2009 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 67–70
Direct coupling reaction between alcohols and allyltrimethylsilane
Table 2. PMA catalyzed allylation of alcohols with allyltrimethylsilane
at room temperaturea
Entry
Substrate
1
OH
2c
OH
Time (min) Yield (%)b
Product
30
90
3 h
100
(m, 1H,C-5), 1.82 (q, J D 24 Hz, 1H,C-4), 2.51–2.41(m, 2H,C3), 4.93–4.82 (m, 2H,C-1), 5.71–5.61 (m, 1H,C-2), 7.24–7.10 (m,
5H,C-8-13). 13 C NMR (CDCl3 ,100 MHz): δ 3.7(C-6), 5.6(C-7), 17.0(C,5) 41.1(C-3), 51.0(C-4), 115.6(C-1), 126.0(C-11), 127.6(C-10,12),
ž
128.1(C-9,13), 137.1(C-2), 145.2(C-2). GCMS: m/z: 173 [MC ], 172,
[2]
131.128 (Table 2, entry 9).
2
Ph
3
5′
1
5′′
4 5
3c
3 h
OH
4
OH
F F
F
5
Cl Cl
Cl
OH
OH
OH
OH
10
30
82
50
91
50
87
50
90
5 h
69
50
NRd
50
NRd
Cl
MeO
MeO
9
75
Me
Me
7
8
30
OH
11
OH
Cl
Cl
12
OH
50
NRd
13
OH
50
NRd
Result and Discussion
Several catalytic methods for the oxidation[16 – 18] and the acylation
of alcohols[19 – 21] as well as cyanosilylation of carbonyl compounds
have been developed.[22 – 27] We wish to herein report a simple
method for the allylation of alcohols with allyltrimethylsilane in
presence of catalytic amount of PMA at rt. This may be the first
example of PMA catalyzed allylation of alcohols.
ž
Lewis acids such as SmI2 , NbF5 , Y(NO3 )3 6H2 O, NbCl5 do not
give the product while heterogeneous catalysts, Nafion SAC-13
and Nafion NR-50 produce only the moderate yield of desired
alkene (Table 1, Scheme 1; entries 1–6). Upon addition of PMA
to the mixture of benzhydrol and allyltrimethylsilane, the desired
alkene was formed in 30 min in good yield. No side product was
detected. Phosphotungstic acid also shows comparable catalytic
activity towards the allylation under same reaction condition but
with longer reaction time and lower yield (entry 7). Therefore, PMA
is found to be an effective catalyst for the allylation with excellent
yield and relatively shorter reaction time at room tempterature.
The suitability of solvent for allylation reaction is explored. As the
data in Table 1 indicate, CH2 Cl2 is the most appropriate solvent
(entry 8). CH3 CN and CH3 NO2 also act as good solvents for this
system but with lower yield (entry 10 and 13). Optimization studies
with various amounts of the catalyst (0.5–5 mol%) showed that
the optimal amount of catalyst is 0.5 mol%.
Benzhydrol undergoes smooth allylation and yields excellent
yield of the product (Table 2, entry 1). Reactions of cinnamylsilane
and prenylsilane with benzhydrol also showed the similar yield by
other workers (entry 2 and 3).[3] Benzhydrols containing chlorine
or fluorine atom at para-position afford corresponding alkenes in
high yields within 30 min (entries 4 and 5). sec-1-Phenylethanol
having methyl and methoxy group at para-position are efficiently
converted to corresponding desired allylation products (entries 6
and 7). It should be noted that an alcohol bearing cyclopropyl ring
in the side chain (α-cyclopropylbenzyl alcohol) also proved good
substrate for direct coupling reaction with allyltrimethylsilane (entry 8). Sterically hindered triphenylmetahnol, which is known to be
a difficult substrate for allylation reaction, produces slightly lower
yield within quite longer reaction time (69%, 5 h; entry 9). This may
indicate that steric hindrance is actually playing considerable role
for the allylation reaction. Interestingly, other phenylethanols yield
no allylation product at all with allyltrimethylsilane under present
c 2009 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
69
a Reagents and condition: alcohols (1.0 mmol), allyltrimethysilane
(1.2 mmol) and PMA (0.5 mol %) at room temperature. b Isolated
yield. c These are taken from Yasuda et al.,[3] where cinnamylsilane
and prenylsilane were used for the reaction. d Side product formation
was observed as reported in the literature.[3,5,28]
Appl. Organometal. Chem. 2010, 24, 67–70
1 H NMR (CDCl , 200 MHz): δ 3.34 (d, J D 6.4 Hz, 2H,C-3),
3
4.96–5.60 (m, 2H,C-1), 5.60–5.53 (m, 1H,C-4), 7.22–7.11 (m, 15H,
Ar-H). 13 C NMR (CDCl3 ,100 MHz): δ 42.3(C-3), 45.7(C-4), 117.7(C-1),
125.9(Ar-H), 127.6(Ar-H), 128.6(Ar-H), 135.9(C-2), 147.2(C-5,50 ,500 ).
F
OH
6
64
S. T. Kadam, H. Lee and S. S. Kim
OH
O
OH
SiMe3
H
H
PMA, 3 h,
CH2Cl2
88%
0%
Scheme 2. Selective allylation of benzhydrol against benzaldehyde.
reaction conditions (entries 10–14). Instead of producing desired
alkene the three alcohols undergo the intermolecular nucleophilic
reaction with alcohol to produce dimeric ether.[3,5,28] The reaction of allyltrimethylsilane with equimolar amount of bezhydrol
and benzaldehyde in presence of catalytic amount of PMA was
performed. The benzhydrol was exclusively allylated while benzaldehyde was completely recovered (Scheme 2). The reactivity of
allyltrimehtylsilane is compared with that of allyltributyltin, which
is also highly nucleophilic. However the reaction of benzydrol
with allyltributyltin in presence PMA did not yield the desired
product.
Conclusion
A simple and efficient catalytic method for the direct coupling
reaction between secondary alcohol and allyltrimethylsilane in
presence of PMA is performed. The catalytic system demonstrates
the selectivity towards the allylation of the alcohol against
the aldehyde. The mildness and non-corrosive catalytic system
make this method as valuable tool for carbon-carbon bond
formation.
Supporting information
Supporting information may be found in the online version of this
article.
Acknowledgments
The authors thank the Centre for Biological Modulators of KRICT for
the financial support. We also appreciate the assistance through
BK21 provided by Korea Research Council.
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