A novel efficient method for the synthesis of substituted olefins; Cross coupling of two different alcohols using NaHSO4/SiO2

Article abstract of DOI:10.1039/c3cc42746c

Simple and efficient cross coupling of alcohols was developed in the presence of NaHSO₄/SiO₂ to give the corresponding substituted olefins. Direct coupling of alcohols and alkenes was also achieved to give substituted olefins. NaHSO₄/SiO₂ could be recycled 7 times without loss of catalytic activity.

Full text of DOI:10.1039/c3cc42746c

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A novel efficient method for the synthesis of
substituted olefins; cross coupling of two different
alcohols using NaHSO4/SiO2†
Tadashi Aoyama,*a Shuichi Koda,a Yuka Takeyoshi,a Tetsuhiro Ito,a Toshio Takidoa
and Mitsuo Kodomarib
Cite this: Chem. Commun., 2013,
49, 6605
Received 15th April 2013,
Accepted 1st June 2013
DOI: 10.1039/c3cc42746c
www.rsc.org/chemcomm
Simple and efficient cross coupling of alcohols was developed in
the presence of NaHSO4/SiO2 to give the corresponding substi-
tuted olefins. Direct coupling of alcohols and alkenes was also
achieved to give substituted olefins. NaHSO4/SiO2 could be
recycled 7 times without loss of catalytic activity.
Scheme 1 Formation of 3-methyl-1,1-diphenyl-2-butene.
Wawzonek and Dufek6 and the direct coupling of benzylic alcohols
in the presence of the combination of FeCl3H2O and TsOH by Liu
et al.,7 have appeared. However, application of Wawzonek’s method
is limited and Liu described that aliphatic alcohols were not
effective. Direct coupling of alcohols with alkenes is also important
in organic synthesis. Few studies on this reaction, however, have
been reported.8 Recently, Brønsted acid-catalyzed alkenylation of
N-benzylic sulphonamides with alkenes has been developed by
Tian et al. for synthesis of substituted olefins.9 We wish to report
herein the novel and simple cross coupling of alcohols and direct
coupling of alcohols with alkenes using NaHSO4/SiO2.
The reaction of tert-butyl alcohol (1a, 3 equiv.) with benzhydrol
(2a, 1 equiv.) was carried out in the presence of NaHSO4/SiO2
(1.05 equiv.) in 1,2-dichloroethane at 80 1C for 1 h to afford 3aa in
77% isolated yield (see ESI†). The other analogues (2) also reacted
with 1a under the same conditions to give the corresponding
olefins in moderate to good yields. Compound 3ae was obtained
from the reaction of 4,40-dichlorobenzhydrol (2e) with 1a in
70% yield along with trace amounts of the regioisomer 4,4-bis-
(4-chlorophenyl)-2-methyl-1-butene (Table 1).
Carbon–carbon bond formation reaction is one of the most impor-
tant reactions in organic synthesis. In particular, direct coupling of
alcohols with the other partners such as compounds containing allyl,
aryl, alkynyl and active methylene groups has attracted much
attention as an environmentally friendly reaction, because only
H2O is formed as a by-product. However, there have been few
successful studies on the formation of a carbon–carbon bond using
alcohols as coupling partners instead of halides,1 due to the poor
leaving ability of the hydroxyl group. We have recently reported the
direct alkylation of 1,3-dicarbonyls and aromatics with alcohols in
the presence of NaHSO4/SiO2.2 NaHSO4/SiO2 has been widely used
for several types of acid-catalyzed reactions such as selective silyl
deprotection of sylilethers,3 selective monoacetylation of diols,4 etc.5
In the course of our studies, the reaction of benzhydrol and
acetoacetic acid tert-butyl ester in the presence of NaHSO4/SiO2
gave the undesired product 3-methyl-1,1-diphenyl-2-butene in
moderate yield. We confirmed that the undesired product was
formed from the reaction of benzhydrol and 2-butene, which is
generated by dehydration of tert-butyl alcohol formed by hydro-
lysis of acetoacetic acid tert-butyl ester (Scheme 1).
Table 1 Cross-coupling of tert-butylalcohol (1a) and benzhydrols
This result is interesting and suggests that direct coupling of
tert-butyl alcohol and other alcohols can be used for the synthesis
of substituted olefins. The direct coupling of alcohols into sub-
stituted olefins has been scarcely reported. Only two studies, the
acid-catalyzed reaction of 9-fluorenol with 9-alkylidenefluorenes by
Yield of 3 a (%)
Entry 1a/2 (mmol)
2
Ar1
Ar2
a Department of Materials and Applied Chemistry, College of Science and
Technology, Nihon University, Kanda Surugadai, Chiyoda-ku, Tokyo, Japan.
E-mail: aoyama.tadashi@nihon-u.ac.jp; Fax: +81 3 3259 0818;
Tel: +81 3 3259 0818
1
2
3
4
5
6
7
1/3
3/2
6/2
6/2
6/2
6/2
6/2
2a C6H5
2a C6H5
2a C6H5
2b C6H5
2c C6H5
2d p-MeOC6H4 p-MeOC6H4 3ad
2e p-ClC6H4 p-ClC6H4 3ae
C6H5
C6H5
C6H5
p-MeOC6H4 3ab
p-ClC6H4 3ac
3aa
3aa
3aa
0
44
77
83
44
85
70
b The Institute of Natural Sciences, College of Humanities and Science,
Nihon University, Japan. Tel: +81 3 53179366
† Electronic supplementary information (ESI) available: Experimental section
and spectroscopic data. See DOI: 10.1039/c3cc42746c
a
Isolated yield.
c
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Table 2 Cross-coupling of various alcohols
R1
R2
2
R3
R4
1 (mmol)
Yield 3 or 4a (%)
Entry
1
2
3
4
6
6
6
6
1a
1a
1b
1b
CH3
CH3
C2H5
C2H5
CH3
CH3
CH3
CH3
2f
C6H5
CH3
C6H5
p-ClC6H4
CHCHC6H5
p-MeOC6H4
C6H5
3af
68
2g
2a
2e
3ag
3ba
3be
20b
52b
35
p-ClC6H4
5
4
1c
2a
C6H5
C6H5
3ca
85
6
7
4
4
1d
1d
C6H5
C6H5
H
H
2a
2c
C6H5
C6H5
C6H5
p-ClC6H4
3da
3dc
95
67
8c
4
1d
1c
C6H5
H
—
—
—
—
—
—
58
82
9c
4
a
b
c
Isolated yield. Yield determined by 1H NMR. Self-coupling of 1.
The results of the cross coupling involving two different alcohols
are shown in Table 2. The reaction of 1a with 1,3-diphenyl propene-
3-ol (2f) afforded a mixture of 1,3-diphenyl-5-methylhexa-1,4-diene
(3af) and 1,3-diphenyl-5-methylhexa-1,5-diene (3af0) in 84% total
yield, in which 3af was isolated from the mixture by column
chromatography in 68% yield (entry 1). The reactions of 1a with
1-arylethanols gave the corresponding substituted olefins in low
yields. For instance, the reaction of 1-(p-methoxyphenyl) ethanol
(2g) and 1a gave 3ag in 20% yield along with the by-products with
m/z = 268 and 324, observed by mass spectroscopy (entry 2).
Reaction of 2a with tert-amyl alcohol (1b) yielded 3ba in 52% yield
along with 41% of 1-phenyl-2,3,3-trimethyl-2,3-dihydro-1H-indene
(5) (entry 3 and Scheme 2). Compound 2e was used instead of 2a in
order to avoid a cyclization reaction and obtain 3be selectively.
However, the yield of 3be was only 35% and the regioisomer 30be
was formed in 65% yield (entry 4 and Scheme 2). In the formation
of 5 and 30be, it seems that the reaction proceeds via the initial
generation of a tertiary cation. The plausible reaction pathway is (1)
benzhydorylic cation 20 is generated from 2a or 2e by NaHSO4/SiO2,
(2) 2-methyl-2-butene, which was formed from 1b by elimination of
H2O, adds to 20 and a tertiary cationic intermediate 3* is formed, (3)
in the case of 2a (Y = H) intramolecular cyclization occurs, whereas
in the case of 2e (Y = Cl) deprotonation takes place predominantly
to form a-olefin (Scheme 2).
When the reaction of 1c with 2a was carried out under the same
conditions, the yield of 3ca was low owing to the formation of
1,2,3,30,4,40-hexahydro-1,20-binaphthalene (4c). Compound 3ca was
obtained in excellent yield when the reaction of 1c (4 mmol) with 2a
(2 mmol) was performed at 90 1C for 1 h (entry 5). The other benzylic
alcohol (1d) also reacted with 2a and yielded 3da in excellent yield.
In the reaction of 1c and 1d, self-coupling of alcohols occurred and Scheme 2 Plausible reaction pathway.
c
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Scheme 3 Reusability of NaHSO4/SiO2 for the cross-coupling.
substituted olefins were formed. For instance the reaction of 1c in the
presence of NaHSO4/SiO2 gave 4c in 82% yield (entry 9). When
2-butanol as sec-alcohol was used instead of tert- and benzylic-alcohols,
2-butyl benzhydryl ether for the reaction of 2a was mainly formed.
We checked the reusability of NaHSO4/SiO2 for cross-
coupling of 1a and 2a. NaHSO4/SiO2 was recovered from the
reaction mixture by filtration and regenerated by drying
in vacuo at 150 1C for 2 h, and used for a subsequent reaction.
As shown in Scheme 3, NaHSO4/SiO2 was able to recycle at least
7 times and 3aa was obtained in a satisfactory yield.
Direct coupling of alcohols and alkenes was investigated
(Table 3). When reaction of a-methyl styrene with benzhydrol was
carried out under the same conditions as those used for the cross
coupling of two different alcohols, dimerization of a-methyl styrene
occurred and the yield of expected olefin was low. The reaction
conditions were 60 mol% of NaHSO4/SiO2 at 60 1C in order to
obtain substituted olefins in good yield. Reactions of a-methyl and
a-phenyl styrene with benzhydrols gave the corresponding substi-
tuted olefins in good to excellent yields (entries 1–5 and 11). On the
other hand, styrene gave substituted olefins in moderate to good
yields. Reactions of styrene with 1-phenylethanol derivatives
(1d and 2g–2i) gave the corresponding substituted olefins in
moderate yield except 2g (entries 7–10). In these reactions, self-
coupling of 1-phenylethanols occurred. For instance, formation of
1,3-bis(p-chlorophenyl)-1-butene (4i) was observed in the reaction of
styrene with 2i (entry 10). Reaction of p-chlorostyrene and 2i in the
presence of NaHSO4/SiO2 gave 4i. The plausible reaction pathway is
shown in Scheme 4. In the reaction of 2i, cation intermediate 20,
which is generated from 2i and NaHSO4/SiO2, reacts with styrene to
give 3di (path A) and a proton is eliminated from 20 to form
p-chlorostyrene (path B) which reacts with 2i again to give 4i.
When 2g was used for the reaction with styrene, the expected
product was obtained in 80% yield without self-coupled
Scheme 4 Plausible reaction pathway.
olefin (entry 8). In the reaction of 2a and styrene, the corresponding
alkene was not formed by dehydration of 2a (entry 6). When this
reaction was carried out at 0 1C, bisbenzhydryl ether was formed.
The yield of this ether decreased with increasing reaction
temperature. Thus, in these reactions, a formed cation inter-
mediate was converted into the corresponding alkene (path A)
and ether (path C). The ether was activated with NaHSO4/SiO2
again and reacted with styrene to afford 3da and 3dg.
In conclusion, we developed a simple and efficient method for
synthesis of substituted alkenes by cross-coupling of two different
alcohols using NaHSO4/SiO2. Moreover synthesis of substituted
alkenes from direct coupling of alkenes and alcohols was also
achieved. This method is simpler than general coupling of alkenes
and alcohols. NaHSO4/SiO2 could be easily recovered and reused at
least 7 times without loss of activity. Further investigations into
these reactions, e.g. sec- and allylic-alcohols, are now in progress.
Notes and references
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Table 3 Direct coupling of alkenes using alcohols
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Entry R1
2 (1) R2
R3
6/2
Yielda (%)
1
2
3
4
CH3 2a C6H5
C6H5
3.0 3ea 92
CH3 2b
CH3 2c
CH3 2d
CH3 2e
H
H
H
H
H
C6H5
C6H5
p-MeOC6H4 3.0 3eb 93
p-ClC6H4 3.0 3ec 86
p-MeOC6H4 p-MeOC6H4 3.0 3ed 97
5
p-ClC6H4
C6H5
CH3
CH3
CH3
p-ClC6H4
C6H5
C6H5
3.0 3ee 78
2.0 3da 85
1.0 4d
6b
7
2a
1d
2g
2h
2i
55
8
9
10
11
p-MeOC6H4 1.0 3dg 80
p-MeC6H4
p-ClC6H4
C6H5
1.0 3dh 51
1.0 3di 45
1.0 3fa 90
CH3
C6H5 2g
C6H5
a
b
Isolated yield. 70 1C.
c
This journal is The Royal Society of Chemistry 2013
Chem. Commun., 2013, 49, 6605--6607 6607