A simple and efficient protocol for Suzuki coupling reactions of aryl chlorides and aryl bromides in aqueous DMF

Article abstract of DOI:10.1016/j.jorganchem.2013.09.026

A simple, efficient and ligand-free palladium acetate catalyzed protocol was developed in aqueous N,N-dimethylformamide (DMF) under mild reaction conditions in the presence of Na₂CO₃ in air. This procedure showed good catalytic efficiency towards the Suzuki coupling of aryl bromide and arylboronic acid. Furthermore, under enhanced reaction conditions, various aryl chlorides could smoothly be coupled with arylboronic acids to afford biphenyls without any use of additives and ligands, and good yields were obtained in the Suzuki coupling of activated aryl chlorides.

Full text of DOI:10.1016/j.jorganchem.2013.09.026

Journal of Organometallic Chemistry 749 (2014) 83e87
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journal homepage: www.elsevier.com/locate/jorganchem
Note
A simple and efficient protocol for Suzuki coupling reactions of aryl
chlorides and aryl bromides in aqueous DMF
a
,
a
b
*
Leifang Liu , Wendi Wang , Chuanyong Xiao
a
Key Laboratory of Coordination Chemistry and Functional Materials in Universities of Shandong, Dezhou University, Dezhou 253023, People’s Republic of
China
b
Agricultural Product Quality and Safety Inspection Center, Dezhou 253023, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 July 2013
Received in revised form
A simple, efficient and ligand-free palladium acetate catalyzed protocol was developed in aqueous N,N-
dimethylformamide (DMF) under mild reaction conditions in the presence of Na CO in air. This pro-
2 3
cedure showed good catalytic efficiency towards the Suzuki coupling of aryl bromide and arylboronic
acid. Furthermore, under enhanced reaction conditions, various aryl chlorides could smoothly be coupled
with arylboronic acids to afford biphenyls without any use of additives and ligands, and good yields were
obtained in the Suzuki coupling of activated aryl chlorides.
11 September 2013
Accepted 17 September 2013
Keywords:
Ó 2013 Elsevier B.V. All rights reserved.
Palladium-catalyzed
Suzuki coupling reaction
Aryl chloride
Aqueous DMF
1. Introduction
had been focused on the use of ligands. With the presence of water-
soluble and sterically demanding alkylphosphines ligands, palla-
Palladium-catalyzed Suzuki coupling reaction of aryl halides
and arylboronic acids is one of the most important and powerful
synthetic methods for the construction of carbonecarbon bonds, in
particular for the formation of unsymmetrical biaryls which are
widely found in natural products, herbicides, pharmaceuticals, as
well as in conducting polymers and liquid-crystalline materials [1e
dium acetate could easily catalyzed the Suzuki coupling reaction of
aryl bromide and activated aryl chloride in aqueous media [21e26].
Due to the disadvantages of phosphine ligands, a number of
phosphine-free N-based ligands including N,O- or N,N-bidentate
ligand, N-heterocyclic carbenes, oxime-derived ligands and simple
amines have been used in the Suzuki coupling of aryl halides with
arylboronic acids in aqueous media [27e32]. Many heterogeneous
palladium catalysts were also utilized in aqueous Suzuki coupling
reaction, such as Pd/C, Pd-polyoxometalate nanoparticle, Pd-
amphiphilic polymer-assembled catalyst and so on [33e39]. Most
of them exhibited good catalytic efficiency towards the Suzuki
coupling reaction of aryl bromide and aryl iodides.
There is great interest in developing efficient and simple cata-
lytic systems for the Suzuki coupling reaction without any use of
ligands. The mixtures of water and organic solvent not only have
the advantages of water, which helps with the solvation of mineral
bases to promote the Suzuki reaction by activating arylboronic acid,
but also have the ability to dissolve organic substrates and corre-
sponding palladium catalysts. These characteristics of watere
organic solvent mixtures offer good chances for Suzuki coupling
reaction to develop simple and efficient catalytic systems in which
5
]. Water is cheap, nontoxic, and readily available green reaction
medium for organic synthesis [6e9]. Recently, many efforts have
been paid to develop efficient catalytic systems using pure water as
solvent for the Suzuki coupling reaction for the consideration of
economy, safety and environment problems. However, the low
solubility of substrates, bad reactivity and stability of catalyst in
pure water restrict its application in Suzuki reaction. These prob-
lems have to some extent been overcome by the use of water-
soluble substrate [10,11], phase-transfer catalyst [12e19], and
other additives [20].
The mixtures of watereorganic solvent (aqueous media), such
as aqueous acetonitrile, acetone, toluene, EtOH and DMF, are widely
used as solvent in Suzuki reaction. However, almost all attention
2 2
only simple palladium salts, such as Pd(OAc) or PdCl , are used
*
Corresponding author. No. 566, West of University Road, Dezhou University,
without any presence of ligands under mild reaction conditions. To
our knowledge, there were only a few reports about such catalytic
systems reported in literature. It was reported by Wallow and
Dezhou 253023, People’s Republic of China. Tel.: þ86 0534 8987866; fax: þ86 0534
8
985835.
E-mail address: orgllf@163.com (L. Liu).
0
022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.09.026

84
L. Liu et al. / Journal of Organometallic Chemistry 749 (2014) 83e87
Table 1
Effect of solvent, base on the Suzuki coupling of 4-bromotoluene and phenylboronic acid.
a
Pd(OAc) , Base
2
H C
3
Br
B(OH)2
CH3
o
Solvent, 35 C, 0.5 h
Entry
Solvent
Base
Yieldb (%)
1
2
3
4
5
6
7
8
9
DMF (3 mL)
Na
Na
Na
Na
Na
Na
Na
Na
Na
Na
2
2
2
2
2
2
2
2
2
2
CO
CO
CO
CO
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
3
3
3
3
5
42
52
92
98
98
96
95
89
9
97
96
96
95
68
72
52
40
63
54
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
H
2
O/DMF (0.5/3 mL)
O/DMF (1/3 mL)
O/DMF (2/3 mL)
O/DMF (3/3 mL)
O/DMF (4/3 mL)
O/DMF (5/3 mL)
O/DMF (7/3 mL)
O/DMF (9/3 mL)
O (3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
O/DMF (3.5/3 mL)
10
11
12
13
14
15
16
17
18
19
20
K
2
CO
3
NaOH
KOH
K
K
3
PO
HPO
4
2
4
NaHCO
KF
NaOAc
NEt
Pyridine
3
3
a
ꢀ
Reaction conditions: 4-bromotoluene (1 mmol), Ph(OH)
Isolated yields.
2
(1.5 mmol), base (2 mmol), Pd(OAc)
2
(1 mol%), 35 C, 0.5 h, in air.
b
Novak that Pd(OAc)
2
in aqueous acetone could catalyze the Suzuki
amount of water used was 3 mL or 4 mL (Table 1, entries 5 and 6).
Further addition of water caused a very little decrease in the yield
(Table 1, entries 7e9). Using pure water as the solvent under the
same reaction condition, only 9% yield was obtained (Table 1, entry
10). These results suggested that the ratio of water and DMF was
critical to this catalytic system. In the following optimization pro-
coupling reaction of aryl bromide and aryl iodide [40,41]. But the
complex experimental operations and the tedious measures taken
to exclude oxygen at various stages of the reaction restrict its
application. In 2006, Zhang et al. reported that Pd(OAc) could
2
catalyze smoothly the Suzuki coupling reaction of aryl bromide to
prepare biaryls in aqueous acetone and polyaryls in aqueous DMF
cess, the mixture of 3 mL DMF and 3.5 mL H
solvent for the coupling of 4-bromotoluene.
2
O was chosen as the
[
42]. Later, aqueous DMF, combined with Pd(OAc)
used in the Suzuki coupling of aryl bromide, but the reactions must
be carried out under N atmosphere [43]. Very recently, Liu and co-
2 3 4
and K PO , was
We further wish to investigate the effect of different common
2
bases on the Suzuki coupling reaction of 4-bromotoluene and
ꢀ
workers have developed a simple and efficient protocol for the
Suzuki coupling of aryl bromides and N-heteroaryl halides using
phenylboronic acid using Pd(OAc)
2
(1 mol%) at 35 C for 0.5 h.
Besides Na CO , K CO , NaOH, KOH, and K
2
3
2
3
3
PO
4
had a good effect on
PdCl
2
as catalyst in watereDMF in air [44]. However, the pro-
the coupling of 4-bromotoluene and desirable yields of product
cedures mentioned above focused mainly on the Suzuki coupling of
aryl bromide. There is great interest to develop simple and efficient
catalytic system using aryl chlorides in Suzuki coupling reaction.
We report herein a simple and efficient catalytic system for the
Suzuki coupling of aryl halide, especially for the Suzuki coupling of
aryl chloride, in aqueous DMF without any presence of ligands and
were obtained (Table 1, entries 5 and 6, 11e14). However, other
inorganic bases, such as K
base, such as pyridine, NEt
15e20). With consideration of product yield and economy, Na
2
HPO
gave much lower yields (Table 1, entries
CO
4 3
, NaHCO , KF, NaOAc and organic
3
2
3
was used as the most suitable base in the following Suzuki coupling
reaction of aryl bromides and aryl chlorides.
protection of inert gases. This catalytic system, using Pd(OAc)
2
,
To evaluate the scope and limitations of the procedure, we
studied the Suzuki coupling reaction of aryl bromides with aryl-
Na CO and aqueous DMF, was applicable to aryl bromide under
2
3
milder reaction conditions. With enhanced reaction conditions, this
catalytic system could be applied to the Suzuki coupling of aryl
chloride, and good yields were obtained for activated aryl chlorides.
boronic acid in H
Na CO
2
OeDMF (3.5:3 mL) with Pd(OAc)
(2 mmol) at 35 C for 0.5 h. The results were presented in
2
(1 mol%) and
ꢀ
2
3
Table 2. Good yields were obtained in the reaction of aryl bromide
with electron withdrawing and electron donating substituent with
phenylboronic acid (Table 2, entries 1e7). Sterically demanding aryl
bromide could also be coupled with phenylboronic acid to give
excellent yield (Table 2, entry 5). Both the electron-rich and the
electron-deficient arylboronic acids gave desirable products in high
yields (Table 2, entries 8e10). Good yield was also obtained in the
reaction of 4-bromotoluene with sterically demanding o-tolylbor-
onic acid (Table 2, entry 9).
2
. Results and discussions
To optimize the reaction conditions, the coupling of 4-
bromotoluene (1 mmol) and phenylboronic acid (1.5 mmol) was
chosen as model reaction. The effect of the amount of water in
aqueous DMF was initially investigated. The reaction was carried
out in DMF (3 mL) in the presence of Pd(OAc)
2
(1 mol%) using
ꢀ
Na
2
CO
3
(2 mmol) as base at 35 C for 0.5 h in ambient atmosphere.
The coupling of aryl chlorides was also screened using our
Using pure DMF as the solvent, only trace amount of product 4-
methylbiphenyl was obtained (Table 1, entry 1). However, the
additional of incremental amount of water led to a very rapid in-
crease in yield and the highest yield (98%) was achieved when the
methodology (Table 2, entries 11e26). Using Pd(OAc)
2
(1 mol%),
Na CO (2 mmol), and H OeDMF (3.5:3 mL) as the reaction con-
2
3
2
ditions, 4-nitrochlorobenzene was coupled with phenylboronic
ꢀ
acid at 35 C for 3 h and the product was achieved only in 32% yield

L. Liu et al. / Journal of Organometallic Chemistry 749 (2014) 83e87
85
Table 2
2 2
Suzuki reaction of aryl halides with arylboronic acids catalyzed by Pd(OAc) in DMFeH O.
R1
Pd(OAc) , Na CO
3
2
2
R
1
X
R2
B(OH)2
R
2
H O/DMF
2
Entry
1a
Aryl halides
Arylboronic acid
Time (h)
0.5
Yielde (%)
O N
Br
B(OH)2
B(OH)2
B(OH)2
B(OH)2
99
99
99
98
2
2a
0.5
H COC
Br
3
3a
0.5
NC
Me
Br
4a
0.5
Br
CH3
Br
5a
0.5
0.5
97
97
B(OH)2
B(OH)2
B(OH)2
H C
3
6a
Br
7a
8a
0.5
0.5
97
99
MeO
Br
Me
Br
Br
MeO
B(OH)2
CH3
B(OH)2
9a
0.5
98
Me
Me
1
1
1
0a
1b
2b
Br
F3C
B(OH)2
0.5
3
97
32
98
O N
2
Cl
B(OH)2
O N
2
Cl
B(OH)2
B(OH)2
3
NO2
Cl
1
1
3b
5
75
54
O N
2
4b
10
B(OH)2
Cl
1
1
1
1
5b
6b
7b
8b
NC
Cl
B(OH)2
B(OH)2
B(OH)2
B(OH)2
8
24
24
24
56 (98c)
48
F3C
Cl
98d
MeOOC
Cl
96
H COC
3
Cl
(
continued on next page)

86
L. Liu et al. / Journal of Organometallic Chemistry 749 (2014) 83e87
Table 2 (continued )
Entry
Aryl halides
Arylboronic acid
Time (h)
24
Yielde (%)
50
1
2
2
2
9b
0b
1b
2b
B(OH)2
F
Cl
H C
Cl
B(OH)2
B(OH)2
B(OH)2
48
48
24
30
20
25
3
H CO
Cl
3
Cl
Cl
N
2
2
3b
B(OH)2
24
48
11
45
N
4b
Cl
H C
B(OH)2
3
2
5b
6b
O N
Cl
Cl
MeO
F3C
B(OH)2
B(OH)2
5
5
98
94
2
2
O N
2
a
b
c
ꢀ
Reaction conditions: aryl bromide (1 mmol), ArB(OH)
2
(1.5 mmol), Na
(1.5 mmol), Na
2
CO
3
(2 mmol), Pd(OAc)
(2 mmol), Pd(OAc)
2
(1 mol%), H
(2 mol%), H
2
O:DMF ¼ 3.5:3 mL, 35 C.
ꢀ
Reaction conditions: aryl chloride (1 mmol), ArB(OH)
The reaction time was 24 h.
2
2
CO
3
2
2
O:DMF ¼ 3.5:3 mL, 100 C.
d
e
The product was 4-biphenylcarboxylic acid.
Isolated yields.
ꢀ
(
Table 2, entry 11). When the temperature was raised to 100 C, the
enhanced reaction conditions without any presence of additives
and ligands, and good yields were achieved in the Suzuki coupling
of activated aryl chlorides.
yield of 4-nitrobiphenyl was dramatically increased to 98% (Table 2,
entry 12). Encouraged by this result, we further studied the activity
of other aryl chlorides (Table 2, entries 13e24). The aryl chlorides
bearing electron-withdrawing substituent, such as eCN, eCOOMe,
4. Experimental section
3
eCF , eCOMe and eF (Table 2, entries 15e19) gave superior yields
than those with electron-donating substituent, such as eMe and e
OMe (Table 2, entries 20 and 21), even with longer reaction times. It
was worthy to note that 4-biphenylcarboxylic acid was the product
of the Suzuki reaction of methyl 4-chlorobenzoate with phenyl-
boronic acid due to the hydrolysis of eCOOMe, and 98% isolated
yield for the product was obtained (Table 2, entry 17). Under the
same reaction conditions, we also studied the coupling reactions of
4.1. General
All materials were purchased from common commercial sources
and used without further purification. H NMR spectra were
1
recorded at 400 MHz using TMS as internal standard. Mass spec-
troscopy data of the product were collected on an MS-EI instru-
ment. All the reactions were carried out in air and all products were
isolated by chromatography on a silica gel (300e400 mesh) column
using petroleum ether or the mixture of petroleum and ethyl
acetate.
2
-nitrochlorobenzene and 3-nitrochlorobenzene with phenyl-
boronic acid (Table 2, entries 13 and 14). The results showed that
the position of eNO had great influence on the efficiency of this
2
catalytic system. The Suzuki coupling of 2-chloropyridine and 3-
chloropyridine with phenylboronic acids were also investigated
under the same reaction conditions (Table 2, entries 22 and 23),
with isolated yields were 25% and 11%, respectively. The effect of
substituents on arylboronic acids was also investigated (Table 2,
entries 25 and 26). The arylboronic acid with electron-rich group
gave better result than that with electron-deficient group. Chloro-
benzene could be coupled with p-tolylboronic acid to give moder-
ate yield (Table 2, entry 24).
4.2. General procedure for the Suzuki reaction of aryl halide with
arylboronic acids
A mixture of aryl halide (1 mmol), arylboronic acid (1.5 mmol),
Pd(OAc) (for aryl bromide 1 mol%, for aryl chloride 2 mol%), and
2
Na CO (2 mmol) was stirred in the mixture of H O/DMF (3.5: 3 mL)
2
3
2
at suitable temperature for indicated time in air. The reaction
mixture was cooled to room temperature, and extracted by Et O
2
(10 mL) for three times. And then the organic phase was combined
3
. Conclusion
and evaporated under reduced pressure. The residue was purified
on a silica gel (300e400 mesh) column to afford the desired
product.
In conclusion, we have developed a highly efficient and simple
ligand-free protocol for the Suzuki reaction of aryl bromide in
aqueous system under mild reaction conditions in air. This catalytic
system showed great efficiency towards aryl bromide and aryl-
boronic acid with different substituent. Moreover, this protocol
could be extended to the Suzuki coupling of aryl chloride with
4.3. Analytical data of representative products
1
4-Methyl-biphenyl (Table 1): H NMR (400 MHz, DMSO)
d 7.63
(d, J ¼ 8.5 Hz, 2H), 7.55 (d, J ¼ 8.1 Hz, 2H), 7.44 (t, J ¼ 7.7 Hz, 2H), 7.34

L. Liu et al. / Journal of Organometallic Chemistry 749 (2014) 83e87
87
(
d, J ¼ 7.3 Hz, 1H), 7.27 (d, J ¼ 8.0 Hz, 2H), 2.34 (s, 3H). MS (EI): m/e
%) 168 (100), 167 (51), 153 (24.4), 152 (24), 115 (7), 83 (10).
4
[11] N.A. Bumagin, V.V. Bykov, Tetrahedron 53 (1997) 14437e14450.
[12] R.B. Bedford, M.E. Blake, C.P. Butts, D. Holder, Chem. Commun. (2003)
(
466e467.
-Methoxy-4 -methyl-biphenyl (Table 2, entry 8): 1H NMR
400 MHz, CDCl
7.51 (d, J ¼ 8.6 Hz, 2H), 7.45 (d, J ¼ 7.9 Hz, 2H),
.23 (t, J ¼ 7.2 Hz, 2H), 6.96 (d, J ¼ 8.5 Hz, 2H), 3.84 (s, 3H), 2.38 (s,
H). MS (EI): m/e (%) 198 (100), 183 (52), 155 (39), 115 (7).
0
[13] D. Badone, M. Baroni, R. Cardamone, A. Ielmini, U. Guzzi, J. Org. Chem. 62
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(
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[
14] R.K. Arvela, N.E. Leadbeater, Org. Lett. 7 (2005) 2101e2104.
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(
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NMR (400 MHz, CDCl
8.34 (d, J ¼ 8.4 Hz, 2H), 7.81e7.70 (m, 6H).
MS (EI): m/e (%) 267 (100), 237 (33), 221 (7), 209 (27), 201 (34), 170
7), 152 (58), 151 (17), 75 (7).
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The authors are thankful for financial support from Dezhou
University (08RC14) and Natural Science Foundation of Shandong
Province (ZR2010BQ022, ZR2010BL015, J10LB55).
[
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Appendix A. Supplementary data
[
[
Supplementary data related to this article can be found at http://
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