Synthesis of 4-vinylbiphenyl derivatives by Pd(II)-1,2-diaminocyclohexane complex catalyzed Suzuki-Miyaura reaction

Article abstract of DOI:10.14233/ajchem.2014.16972

A series of 4-vinylbiphenyl derivatives were synthesized by Pd(II)-1,2-diaminocyclohexane complex catalyzed Suzuki-Miyaura reactions in the presence of K3PO4?3H2O as base in toluene at 80 ° C and the corresponding products achieved 39-95% yields. According to this efficient C-C bond-forming method, the obtained yields of 4-vinylbiphenyl liquid crystal compounds were up to 89%.

Full text of DOI:10.14233/ajchem.2014.16972

Asian Journal of Chemistry; Vol. 26, No. 23 (2014), 8022-8024
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16972
Synthesis of 4-Vinylbiphenyl Derivatives by Pd(II)-1,2-Diamino-
cyclohexane Complex Catalyzed Suzuki-Miyaura Reaction
*
Y. LIU, X.W. MA, P. LIU , J.W. XIE and B. DAI
School of Chemistry and Chemical Engineering/the Key Laboratory for Green Processing of Chemical Engineering of Xinjiang Bingtuan,
Shihezi University, Shihezi City, P.R. China
*
Corresponding author: Fax: +86 993 2057270; Tel: +86 993 2057213; E-mail: liuping1979112@aliyun.com
Received: 2 January 2014; Accepted: 2 April 2014; Published online: 15 November 2014;
AJC-16286
A series of 4-vinylbiphenyl derivatives were synthesized by Pd(II)-1,2-diaminocyclohexane complex catalyzed Suzuki-Miyaura reactions
in the presence of K PO ·3H O as base in toluene at 80 °C and the corresponding products achieved 39-95 % yields. According to this
efficient C-C bond-forming method, the obtained yields of 4-vinylbiphenyl liquid crystal compounds were up to 89 %.
3
4
2
Keywords: 4-Vinylbiphenyl derivatives, Synthesis, Suzuki-Miyaura reaction, Palladium, Catalyzed.
were of analytical grade quality, purchased commercially and
used as received.
INTRODUCTION
1
Detection method: H NMR spectral data were recorded
4-Vinylbiphenyl derivatives as important functional mono-
mers are frequently found in the polymer materials and organic
on a Bruker DPX-400 spectrometers using TMS as internal
1
-5
chemical reactions . Thus, the development of simple and
efficient methods for the synthesis of such compounds has
attracted considerable attention. In general, Pd-catalyzed
Suzuki-Miyaura reaction due to the broad functional group
tolerance and the low toxicity associated with boron com-
pounds is one of the most powerful methods for selective
carbon-carbon bond formation in the synthesis of biaryl
3
standard and CDCl as solvent. Mass spectra were recorded
on GC-MS (Agilent 7890A/5975C) instrument under EI
model.
The Schlenk tube (20 mL) equipped with a stir bar was
3 4 2
charged with complex 2 (1 mol %), K PO ·3H O (3 equiv.)
p-bromostyrene (0.5 mmol), phenylboronic acid (0.75 mmol)
and toluene (2 mL) were added and the mixture was stirred at
6
,7
molecules . But its application in the synthesis of 4-
8
vinylbiphenyl derivatives is very limited. McCluskey et al.
reported the synthesis of substituted 4-vinylbiphenyl
8
0 ºC until the substrate was completely consumed. After
cooling to room temperature, the solution was quenched with
water and extracted with EtOAc (3 × 10 mL). The combined
2
monomers by 1 mol % Pd(DIPHOS) -catalyzed Suzuki-Miyaura
2 4
EtOAc extracts were dried over anhydrous Na SO and
reactions, but this catalysis reaction was carried out under the
microwave-assisted condition at 100 °C, and 4-vinylphenyl-
boronic acid as a bifunctional substrate is prone to give the
undesired homo-coupling product at high temperature. Based
filtrated, and the solvent was removed under reduced pressure.
The residue was purified by flash column chromatography on
silica gel with petroleum ether as eluent to obtain the desired
products.All products reported herein are known products and
9
-14
1
on our previous research works , herein we report a simple
and efficient approach for the synthesis of 4-vinylbiphenyl
derivatives by Pd(II)-1,2-diaminocyclohexane complex
catalyzed Suzuki-Miyaura reactions.
were characterized by H NMR and GC-MS.
RESULTS AND DISCUSSION
Complexes 1-3 were synthesized by the literature methods
1
5,16
(
Fig. 1) . Initially, the catalytic activity of the complexes 1-
was evaluated to obtain an optimum catalytic system by the
coupling of p-bromostyrene with phenylboronic acid in the
presence of K PO ·3H O at 80 °C for 6 h in toluene (Table-1).
EXPERIMENTAL
3
All reactions were carried out under air using magnetic
stirring unless otherwise noted. Column chromatography was
performed with silica gel (300-400 mesh) purchased from
Qingdao Haiyang Chemical Co., Ltd. All the other reagents
3
4
2
Although complexes 1-3 examined the desired product, the
coupling reaction catalyzed by complex 2 produced the desired

Vol. 26, No. 23 (2014)
Synthesis of 4-Vinylbiphenyl Derivatives by Pd(II)-1,2-Diamino-cyclohexane Complex 8023
product in excellent yield (95 %, Table-1, entries 1-3). When
the reaction was conducted at 50 °C or 100 °C, the low yield
not was obtained (Table-1, entries 4 and 5). Similarly, the yield
was increased with extending the reaction time to 10 h (Table-1,
entry 6). Subsequently, we select the complex 2 as the precatalyst
to further investigate the effect of bases on the coupling
phenyl)boronic acid resulted in a decreased the yield of 3c
(Table-2, entry 3), whereas the reaction worked well with 1b-
1d, furnishing the expected products 3d-3f in good yields
(Table-2, entries 4-6). Aryl bromides with electron-with-
drawing groups, such as 4-COMe, 4-F and 3,4-difluoro also
afforded the corresponding coupling products in 39-81 %
yields (Table-2, entries 7-9). But a steric effect was observed
in this reaction when aryl bromide 1j has a substituent in the
ortho position, the reaction gave a lower yield in comparison
with 1i (3k vs. 3j) (Table-2, entries 10 and 11). In order to
expand the scope of the methodology, this new catalytic system
was applied to the synthesis of 4-vinyl biphenyl liquid crystal
compounds. The liquid crystal products could be obtained
successfully in 84-89 % yields (Table-2, entries 12-14).
reaction. When the NaF, Na CO
2
3
were used as base, the desired
CO
product was not obtained (Table-1, entries 7 and 8). K
2
3
also promoted the occurrence of the coupling reaction, but
the corresponding product was obtained only in 78 % yield
(
3 4 2
Table-1, entry 9). So K PO ·3H O was used in the subsequent
studies. Solvent is another important factor affecting catalysis.
It was found that toluene performed well as the prime solvent.
EtOH and DMF were not the good reaction solvents (Table-1,
entries 10 and 11). Finally, the combination of complex 2
(
as the optimal conditions for the coupling reaction of p-
1 %), K
3
PO
4
·3H
2
O (3 equiv.) at 80 °C in toluene was chosen
TABLE-2
SUZUKI-MIYAURA REACTIONS
CATALYZED BY COMPLEX 2
a
bromostyrene with phenylboronic acid.
complex 2
K3PO4·3H2O
TABLE-1
OPTIMIZATION OF THE REACTION CONDITIONS
Br +
R2
R2
(
HO)2B
a
R1
Toluene, 80°C
R1
1
a-1m
2a-2c
3a-3m
Br
B(OH)2
complex 1-3
+
Yield
b
(
base, solvent
Entry
R
1
R
2
Product
%)
86
95
48
80
70
75
64
39
61
81
46
89
84
88
8
0°C
1
2
4-Ethenyl (1a)
1a
4-H (2a)
3a
3b
3c
3d
3b
3e
3f
Temp. Time Yield
4-OMe (2b)
Entry Complex Solvent
Base
b
(
°C)
80
80
80
50
(h)
6
(%)
76
3
1a
4-Ethenyl (2c)
1
2
3
4
5
6
7
8
9
1
2
3
2
2
2
2
2
2
2
2
Toluene K PO ·3H O
3
4
4
2
4-CHO (1b)
4-OMe (1c)
4-Me (1d)
4-COMe (1f)
4-F (1g)
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
2c
Toluene K PO ·3H O
3
6
95
5
4
2
Toluene K PO ·3H O
4
6
30
6
3
2
Toluene K PO ·3H O
3
6
10
7
4
2
Toluene K PO ·3H O
2
100
80
80
80
80
80
80
6
68
8
3
4
3g
3h
3i
Toluene K PO ·3H O
3
10
6
86
9
4
2
3,4-Difluoro (1h)
Toluene NaF
0
10
11
12
13
3,4,5-Trifluoro (1i)
Toluene Na CO
2
6
Trace
78
3
2,4,5-Trifluoro (1j)
3j
Toluene K CO
2
6
3
4,4'-Propyl-cyclohexyl (1l)
4,4'-Pentyl-cyclohexyl (1k)
4,4'-Pentyl-bicyclohexyl (1m)
3k
3l
1
0
1
EtOH
DMF
K PO ·3H O
3
6
Trace
Trace
4
2
1
K PO ·3H O
3
6
14
4
2
3m
a
a
Reaction conditions: 0.50 mmol 4-bromostyrene, 0.75 mmol phenyl-
boronic acid, 1.50 mmol base, 0.5% mmol complex 1-3, 2.0 mL
Reaction conditions: aryl bromide (0.5 mmol), arylboronic acid (0.75
mmol), complex 2 (0.5 mol%), K PO .3H O (3.0 equiv), toluene (2.0
3
4
2
b
solvent; Isolated yields
b
mL), 80 ºC, 6 h; Isolated yields
Conclusion
H
H
In summary, we have developed a simple and efficient
catalyst system for the synthesis of 4-vinylbiphenyl derivatives
by Pd(II)-1,2-diaminocyclohexane complex catalyzed Suzuki-
Miyaura reactions in moderate to excellent yields under mild
conditions. With simple reaction procedure and broad available
substrate range, this method was particularly useful for the
efficient synthesis of 4-vinylbiphenyl functional monomers
and liquid crystal compounds.
H N
2
NH2
C l
H N
NH2
H N
NH2
2
2
P d
P d
P d
C l
C l
C l
C l
C l
1
2
3
Fig. 1. List of complexes 1-3
Under the optimized reaction conditions, a number of aryl
bromides were successfully employed in this transformation
ACKNOWLEDGEMENTS
(
Table-2). 1-Bromo-4-vinylbenzene reacted with phenylboronic
acid smoothly to afford the desired product 3a in 86 % yield
Table-2, entry 1) and arylboronic acid with electron-donating
The authors gratefully acknowledge financial support of
this work by the National Basic Research Program of China
(973 Program: 2012CB722603), the NSFC (No. 21103114),
the Ministry of Education Innovation Team (No. IRT1161)
and the Training Program for OutstandingYoung Scientists of
Shihezi University (No. 2012ZRKXYQ-YD02).
(
groups such as (4-methoxyphenyl)boronic acid could also be
coupled with the 1-bromo-4-vinylbenzene to give the product
3
b in 95 % yield (Table-2, entry 2). The substrate (4-vinyl-

8
024 Liu et al.
Asian J. Chem.
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P. Liu, L. Zhou, X.G. Li and R. He, J. Organomet. Chem., 694, 2290
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