Remarkable catalytic activity of [PdCl2(CH3CN) 2] in Suzuki-Miyaura cross-coupling reaction in aqueous media under mild conditions

Article abstract of DOI:10.1016/j.molcata.2013.01.029

[PdCl₂(CH₃CN)₂] (2 mol%) was found to be an efficient catalyst for the Suzuki-Miyaura cross coupling reaction between aryl bromide and aryl boronic acid in water solvent at 45 °C. The scope of the protocol was extended to various aryl bromides and aryl boronic acids. In general, an effective method has been developed for the Suzuki-Miyaura cross coupling reaction by using a phosphine-free Pd catalyst.

Full text of DOI:10.1016/j.molcata.2013.01.029

Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
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Remarkable catalytic activity of [PdCl2(CH3CN)2] in Suzuki–Miyaura
cross-coupling reaction in aqueous media under mild conditions
S. Ganesamoorthya,b, K. Shanmugasundaramb, R. Karvembua,∗
a Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015, India
b Synthetic Chemistry, Syngene International Ltd, Biocon Park, Bangalore 560 099, India
a r t i c l e i n f o
a b s t r a c t
Article history:
[PdCl2(CH3CN)2] (2 mol%) was found to be an efficient catalyst for the Suzuki–Miyaura cross coupling
reaction between aryl bromide and aryl boronic acid in water solvent at 45 ◦C. The scope of the protocol
was extended to various aryl bromides and aryl boronic acids. In general, an effective method has been
developed for the Suzuki–Miyaura cross coupling reaction by using a phosphine-free Pd catalyst.
© 2013 Elsevier B.V. All rights reserved.
Received 13 December 2012
Received in revised form 27 January 2013
Accepted 28 January 2013
Available online 9 February 2013
Keywords:
Palladium(II)
Suzuki–Miyaura coupling
Water solvent
Aryl halide
Boronic acid
1. Introduction
reactions. However, many of the phosphine ligands are sensitive to
air and they are also expensive, toxic and unrecoverable, which
The Suzuki–Miyaura cross coupling (SMC) reactions are the
most versatile and widely utilized method for the construction of
selective sp2–sp2 carbon–carbon bonds, particularly in the field
of pharmaceutical, agrochemicals and materials science [1–10].
By practice this transformation is carried out in volatile and nox-
ious organic solvents, urging a need for environmentally benign
conditions as well as minimization of chemical waste, of which
solvent contributes majority of waste [11]. Water is recognized as
cheaply available non-toxic and non-volatile green solvent for use
in organic transformations. Advantageously most of the boronic
acids and inorganic bases are highly soluble in water favoring
the coupling reaction to proceed smoothly under mild condi-
tions. Although there are some reports on SMC reactions in mixed
aqueous organic solvents in the presence of phase transfer cat-
alysts [12,13] or Pd catalysts having water soluble phosphine
ligands [14–16], these protocols necessitate a harsh reaction condi-
tion, tedious work up procedure and strenuous purification of the
desired product. Furthermore, these methods are not suitable for
products that have retention time close to that of phosphine related
by-products, especially heterocyclic compounds involved in SMC
reactions [17–19]. Generally phosphine ligands are required to sta-
bilize the active palladium species in the palladium-catalyzed SMC
results in significant limitations on their synthetic applications.
Therefore, the development of a water soluble, phosphine-free Pd
catalyst is a topic of enormous interest [20]. Herein we came across
such a simple, phosphine-free and water soluble Pd catalyst pre-
cursor for SMC reaction under mild conditions. Our study on this
Pd catalyst is proved to be useful for the coupling of broad range of
aryl and heteroaryl halides. The catalyst is highly chemoselective
especially for aryl bromides and bromo pyrimidines.
Previously [PdCl2(CH3CN)2] catalyst has been used with specific
importance under several mild reaction conditions. The conver-
sion of o-allylanilines to indoles was effectively catalyzed by
[PdCl2(CH3CN)2] in THF [21]. The regioselectivity was addressed
during the ring-opening cycloisomerization of methylenecyclo-
propyl ketones in acetone/benzene [22]. The catalyst under study
was utilized efficiently to carry out one of the important intermedi-
ate steps during the total synthesis of radicicol [23] and rapamycin
[24]. The efficient synthetic route was developed for the prepara-
tion of functionalized tetra substituted furans in acetonitrile [25],
wherein [PdCl2(CH3CN)2] played a dual role as Lewis acid and
transition metal catalyst. Other catalytic roles of [PdCl2(CH3CN)2]
include chemoselective tetrahydropyranylation of primary alco-
hols and deprotection of tetrahydropyranyl ethers of phenols and
primary alcohols [26], regioselective cyclization of alkenyl ␤-keto
esters [27], C H bond functionalization on the indole and pyrrole
nucleus [28,29] and intramolecular hydroalkylation of unactivated
olefins [30–32]. High levels of regio- and diastereoselectivity were
∗
Corresponding author. Tel.: +91 431 2503631; fax: +91 431 2500133.
E-mail address: kar@nitt.edu (R. Karvembu).
1381-1169/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molcata.2013.01.029

S. Ganesamoorthy et al. / Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
119
obtained in intermolecular aminoacetoxylation of alkenes [33].
This catalyst was found to be a suitable one in water medium
for Sonogashira couplings of aryl bromides at room temperature
[34]. To the best of our knowledge [PdCl2(CH3CN)2]/H2O catalytic
system emerged as first of its kind for SMC reaction.
Scheme 1. Cross-coupling reaction of 4-bromoacetophenone.
2. Experimental
concentrated and chromatographed on a silica gel column using
hexane and ethylacetate as eluent to afford coupled product. The
products are characterized by NMR, GC MS and UPLC analyses.
2.1. Materials and methods
All the reagents used were of chemically pure and analar grade.
Commercial grade solvents were distilled according to standard
procedures and dried over molecular sieves before use. All the
chemicals were purchased from Aldrich and were used without fur-
ther purification. [PdCl2(CH3CN)2] was prepared by refluxing PdCl2
with acetonitrile [35] and characterized by 1H and 13C NMR, and
FT IR spectroscopy.
3. Results and discussion
3.1. Optimization of reaction conditions
In order to obtain persuasive results, the reaction variables such
as solvent, base, amount of aryl boronic acid and catalyst quan-
tity were optimized. For this purpose, 4-bromoacetophenone and
phenylboronic acid were chosen as model substrates (Scheme 1).
Initially the cross-coupling reaction was studied in different
solvents using 1:1.5:1.5 stoichiometric ratios of aryl halide, aryl
boronic acid and K2CO3 with 2 mol% of the catalyst at 45 ◦C for
an hour in air atmosphere (Table 1, entries 1–6). In water the
conversion was 85% including 9% of biphenyl resulted from homo
coupling of phenylboronic acid. In order to get good conversion in
other solvents as well, water was added and the coupling reaction
was continued for another 30 min. Now the starting material was
consumed and conversion has gone up to 90% in all other solvents
too. The addition of water increases the solubility of the catalyst
and K2CO3, which in turn favors the coupling reaction to proceed
well with promising yield. The different bases like Na2CO3, KOH,
Cs2CO3, K3PO4, N(C2H5)3 and (CH3)3COK were tested in the
Suzuki coupling reaction between 4-bromoacetophenone and
phenylboronic acid (Table 1, entries 7–12). Good conversion was
observed in all the bases. Na2CO3 being the cheapest material as
well as tolerant to many base sensitive functional groups, was
chosen as base for further coupling reactions. These optimization
studies revealed that water can serve as good solvent and Na2CO3
as suitable base for SMC reactions using this catalyst. Initially
the reaction between 4-bromoacetophenone and 1.5 equiv. of
phenylboronic acid in the presence of 2 mol% of catalyst and
1.5 equiv. of Na2CO3, in water was checked. The cross coupling
reaction was completed in 1 h with 5% biphenyl as by-product.
To avoid the formation of biphenyl, the base and phenylboronic
acid equivalents were reduced to 1.1 with the catalyst loading of
2 mol%. As expected the reaction was completed in 30 min and
biphenyl formation was also reduced to less than 3% (Table 1, entry
2.2. Physical measurements and product analyses
NMR spectra were recorded on a Bruker AMX 400 MHz instru-
ment. The FT IR spectra were recorded on a Nicolet-6700 FT IR
spectrophotometer. Gas chromatographic analyses were done in
Shimadzu-2010 gas chromatograph equipped with 5% diphenyl
and 95% dimethyl siloxane, Restek capillary column (60 m length,
0.32 mm diameter) and a flame ionization detector (FID). The ini-
tial column temperature was increased from 60 to 150 ◦C at the
rate of 10 ◦C/min and then to 220 ◦C at the rate of 40 ◦C/min. Nitro-
gen gas was used as a carrier gas. The temperatures of the injection
port and FID were kept constant at 150 and 250 ◦C, respectively
during product analyses. GC MS analyses were done in Agilent
Technologies-7890N gas chromatograph equipped with SUPELCO
equity (12 m × 0.2 mm × 0.33 ␮m) column. The ultra performance
LC data were recorded using Waters Acquity liquid chromatograph
with Acquity HSS 13 (2.1 mm × 50 mm × 1.8 ␮m) column.
2.3. Procedure for Suzuki reaction
Catalyst (2 mol%), aryl halide (1 equiv.) and Na2CO3 (1.1 equiv.)
were stirred in H2O (5 mL) taken in the round bottom flask. The aryl
boronic acid (1.1 equiv.) was added to the stirring solution. Stirring
was continued for required time at 45 ◦C. After the requisite time,
the reaction mixture was diluted with water and the product was
extracted with ethyl acetate. The ethyl acetate extract was passed
through celite bed and then analyzed by GC. Authentic samples of
both reactant and product were used to verify the retention time
and to confirm the product formation. The ethyl acetate extract was
Table 1
Optimization of reaction condition.a
Entry
Solvent
Phenylboronic acid (equiv.)
Base
Base (equiv.)
Catalyst (mol%)
Time (h)
Conversionb (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
CH3CN
THF
1,4-Dioxane
DMF
C2H5OH
H2O
H2O
H2O
H2O
H2O
H2O
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.1
1.1
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
KOH
Cs2CO3
K3PO4
N(C2H5)3
(CH3)3COK
Na2CO3
Na2CO3
Na2CO3
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.1
1.1
2
2
2
2
2
2
2
2
2
2
2
2
2
1
1
1
1
1
1
1
4
5
4
3
5
1
0.5
0.5
60
60
65
75
70
85
80
84
81
75
80
90
95
81
H2O
H2O
H2O
a
4-Bromoacetophenone (1 equiv.), [PdCl2(CH3CN)2] (2 mol%), solvent (5 mL), 45 ◦C.
Determined by GC.
b

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S. Ganesamoorthy et al. / Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
Table 2
Cross-coupling reaction of aryl halides.a
Entry
Aryl halide
Aryl boronic acid
Biaryl
Temp. (◦C)
45/27
Time (h)
0.5
Isolated yieldb/conversionc (%)
Br
HO
OH
B
1
94b/78c
O2N
NO2
Br
HO
OH
B
2
45
0.5
97b
O
O
Br
HO
OH
B
3
45/27
1
96c/70c
HO
O
OH
Br
OH
B
OH
4d
60
1.5
67b
N
N
O
HO
OH
OH
Br
B
B
5
6
45
45
3
1
83c
Br
HO
HO
HO
91b
HO
OH
Br
OH
OH
F
F
B
B
7
45
6
68c
F
F
F
F
Br
8
O
60
50
45
8
9
4
68b
35b
85b
O
Br
OH
B
OH
9
N
N
Br
Cl
HO
OH
B
Cl
10

S. Ganesamoorthy et al. / Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
121
Table 2 (Continued)
Entry
Aryl halide
Aryl boronic acid
Biaryl
Temp. (◦C)
Time (h)
Isolated yieldb/conversionc (%)
HO
OH
B
Br
11
60
8
71b
Br
HO
HO
HO
OH
OH
OH
B
B
B
HO
O
12e
45
45
60
0.5
98b
89b
30c
HO
Br
O
13
1
OH
HO
Cl
14
6
O
O
O
O
Cl
Cl
HO
OH
B
15
16
60
8
15c
HO
HO
OH
OH
B
B
60
50
5
4
20c
O2N
NO2
Br
17
82c
NC
CN
a
Reaction conditions: substrate (1 equiv.), aryl boronic acid (1.1 equiv.), PdCl2(CH3CN)2 (2 mol%), Na2CO3 (1.1 equiv.), water (5 mL).
Isolated yield.
Determined by GC analysis.
H2O–C2H5OH (4:1) mixture was used as a solvent.
Na2CO3 (2.4 equiv.).
b
c
d
e
13). The same SMC reaction with 1 mol% of the catalyst exhibited
only 81% conversion after 30 min (Table 1, entry 14).
electron donating group on aryl boronic acid (Table 2, entries 8 and
11) slows down the reaction, which leads to moderate yield. Inter-
estingly 4-bromobenzoic acid was converted in excellent yield into
corresponding coupled product using 2.4 equiv. of base (Table 2,
entry 12). 3-Bromo benzyl alcohol was converted in 86% isolated
yield without oxidation to corresponding benzaldehyde (Table 2,
entry 13). This catalytic system worked well for the coupling of
4-cyanobromobenzene without undergoing CN group hydrolysis
(Table 2, entry 17). The compatibility of the catalyst with differ-
ent aryl boronic acids was studied using 2,4,6-trimethyl boronic
acid and pyridine-3-boronic acid. In the case of pyridine-3-boronic
acid, only 35–67% conversion was obtained (Table 2, entries 4
and 9). 2,4,6-Trimethyl boronic acid (Table 2, entries 8 and 11)
gave moderate conversion with extended reaction time of up to
3.2. Extension of scope
To understand the substrate generality for [PdCl2(CH3CN)2]/
H2O catalytic system, the coupling between a range of aryl halides
and various aryl boronic acids were examined systematically. Aryl
bromides bearing an electron withdrawing group (Table 2, entries
1, 2, 7, 10 and 12) or an electron donating group (Table 2, entries 4, 5
and 9) were reacted with phenylboronic acid. All the SMC reactions
have been performed using 1:1.1:1.1 stoichiometric ratio of aryl
halide, aryl boronic acid and base in contrast to the 1:1.5:2 ratios
often used in the Suzuki reaction in aqueous medium [13]. The

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S. Ganesamoorthy et al. / Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
8 h. Further substrate scope was extended to different aryl chlo-
rides (Table 2, entries 14, 15 and 16). As we expected only the
low conversion was observed even after prolong heating. How-
ever reaction conditions were not optimized for aryl chlorides.
Most of the reactions were carried out at 45 ◦C (Table 2, entries
1–3, 5–7, 10, 12 and 13) but some require 50 ◦C or 60 ◦C as the
conversion was lower at 45 ◦C (Table 2, entries 4, 8, 9, 11, 14, 15,
16 and 17).
Many biologically active hetero-biaryl compounds were syn-
thesized from corresponding hetero aryl halides using the Suzuki
reaction. The potential coordination behavior of hetero atoms in
the hetero aryl halides with the catalyst leads to the formation of
inactive substrate-metal complexes, which ultimately retard the
catalyst to take part in the catalytic cycle [36–39]. Hence these
halides are predicted to be unsuitable coupling partners in the SMC
reaction. But using this protocol, hetero aryl halides provided the
coupled products in 70–90% conversion (Table 3, entries 1, 2, 4,
5, 6 and 7). In the case of pyridine-3-boronic acid only 67% con-
version was obtained (Table 3, entry 3). Pyrimidine-5-boronic acid
gave good conversion after 8 h (Table 3, entry 7). The SMC reac-
tion between thiophene-2-boronic acid and 5-bromopyrimidine
yielded the trace amount of coupled product along with the
thiophene-2-boronic acid self coupled product (Table 3, entry 8).
However, the reaction condition was not optimized for this sub-
strate. Some reactions were carried out at 60 ◦C as the conversion
was lower at 45 ◦C (Table 3, entries 2 and 3). Due to the poor solubil-
ity of some of the substrates in water, H2O-C2H5OH (4:1) mixture
was used as solvent in few cases (entry 4 in Table 2, and entries 1,
3, 6, 7 and 8 in Table 3).
3.3. Chemoselectivity
To compare the chemoselectivity of our catalytic system with
various cross coupling Pd catalysts, biologically active intermediate
Table 3
Cross-coupling reaction of heteroaryl halides.a
Entry
Aryl halide
Aryl boronic acid
Heterobiaryl
Temp. (◦C)
Time (h)
0.5
Isolated yieldb/conversionc (%)
HO
OH
Cl
N
B
N
1d
45
86b
Cl
N
N
Br
HO
OH
B
2
60
60
45
8
78c
67c
80c
N
N
Cl
OH
B
N
N
OH
3d
8
N
Cl
N
HO
HO
HO
OH
OH
OH
B
B
B
N
4
1.5
N
Br
Br
N
5
45
45
10
70c
N
N
N
N
6d
0.5
90c
N
Br
N
N
N
N
7d
45
45
8
1
88c
10c
N
OH
B
N
Br
OH
N
N
N
S
OH
B
8d
S
N
OH
Br
a
Reaction conditions: substrate (1 equiv.), aryl boronic acid (1.1 equiv.), PdCl2(CH3CN)2 (2 mol%), Na2CO3 (1.1 equiv.), water (5 mL).
Isolated yield.
Determined by GC analysis.
H2O–C2H5OH (4:1) mixture was used as a solvent.
b
c
d

S. Ganesamoorthy et al. / Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
123
first step the catalyst is transformed as water soluble Pd(II)
aqua complex by losing weakly coordinated CH3CN and stabi-
lizes itself in aqueous reaction medium by coordinating with
water molecules. This is evident from the FT IR and 13C NMR
spectra of [PdCl2(CH3CN)2], and the catalytic species recovered
from the mixture of [PdCl2(CH3CN)2] and Na2CO3 in water
(Fig. S2 and S3 in supplementary data). FT IR spectrum (Fig. S2)
of the residue recovered from the mixture of [PdCl2(CH3CN)2] and
Na2CO3 in water showed a broad band around 3100–3500 cm−1
due to the coordinated water molecules. The disappearance of
Scheme 2. Chemoselectivity of [PdCl2(CH3CN)2]/H2O catalytic system.
Table 4
Effect of different Pd catalysts on SMC reaction of 2-chloro-5-bromopyrimidine.a
Entry
Catalyst
Conversion (%)b
Des-halo (%)
C
N stretching frequency at 2300 cm−1 in the IR spectrum of
Disubstituted (%)
Product (%)
residue confirms the absence of CH3CN in Pd complex after stir-
ring with Na2CO3 in water. The formation of aqua complex was
further supported by 13C NMR spectral data (Fig. S3). The sig-
nal at 1.61 ppm in the 13C NMR spectrum of [PdCl2(CH3CN)2]
corresponding to methyl carbon of CH3CN has completely disap-
peared in the spectrum of residue. The Pd(II) aqua complex is then
reduced to Pd(0) species which undergoes oxidative addition with
aryl halide, followed by reaction with activated aryl boronic acid
[Ar1B(OH)2(CO3)]− enhances the polarization of bonds and induces
the transmetallation. Finally reductive elimination occurs and the
catalyst is regenerated.
1
2
3
4
5
6
PdCl2
Pd(OAc)2
[PdCl2(dppf)]
[Pd(dba)3]/X-phos
[Pd(PPh3)4]
[PdCl2(CH3CN)2]
11
13
3
34
6
19
10
34
4
15
2
61
68
54
2
64
81
6
a
Reaction conditions: substrate (1 equiv.), phenylboronic acid (1.1 equiv.),
[PdCl2(CH3CN)2] (2 mol%), Na2CO3 (1.1 equiv.), H2O-C2H5OH (4:1, 5 mL), 45 ◦C.
b
Determined by Ultra Performance Liquid Chromatography (UPLC).
5-bromo-2-chloro pyrimidine was subjected to cross coupling
reaction with phenylboronic acid in the presence of 2 mol% of cat-
alyst (Scheme 2). To our delight the substrate under study was
chemoselectively cross coupled and yielded C-5 bromo substi-
tuted pyrimidine in 85% isolated yield. Favorably there was no
C-2 dehalogenation observed. Whereas other catalysts under same
reaction condition (Table 4) yielded bromo substituted pyrimidine
in less than 60% isolated yield along with disubstituted and des-halo
products (Fig. S1 in supplementary data). 4-Bromochlorobenzene
(Table 2, entry 10) also gets selectively coupled at carbon containing
bromo group and gave 85% isolated yield. This study clearly reveals
that this protocol can be applied for the chemoselective cross cou-
pling of heteroaryl bromides and aryl bromides in the presence of
corresponding chlorides.
5. Conclusion
In summary, we have demonstrated [PdCl2(CH3CN)2]/H2O as
an effective, simple and chemoselective catalytic system for SMC
reaction under mild condition. This catalytic system is green and
tolerant to many functional groups, which makes this an efficient
synthetic protocol for C C coupling reaction.
Acknowledgements
We thank Dr. G. Manickam and Syngene International Ltd., for
their generous help during this work. R.K. thanks Department of
Science and Technology [SR/S1/IC-72/2010(G)], Ministry of Science
and Technology, Government of India, for financial support.
4. Expected mechanism
Appendix A. Supplementary data
Typical mechanism proposed for [PdCl2(CH3CN)2]-catalyzed
SMC reaction in aqueous medium is given in Scheme 3. In the
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.molcata.
2013.01.029.
References
[1] A. Suzuki, in: F. Diederich, P.J. Stang (Eds.), Metal-Catalyzed Cross-Coupling
Reactions, Wiley-VCH, Weinheim, Germany, 1998, pp. 49–97.
[2] N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457–2483.
[3] A. Suzuki, J. Organomet. Chem. 576 (1999) 147–168.
[4] J. Hassan, M. Sevignon, C. Gozzi, E. Schulz, M. Lemaire, Chem. Rev. 102 (2002)
1359–1469.
[5] G.A. Molander, N. Ellis, Acc. Chem. Res. 40 (2007) 275–286.
[6] R. Martin, S.L. Buchwald, Acc. Chem. Res. 41 (2008) 1461–1473.
[7] K.C. Nicolaou, C.N.C. Boddy, S. Brase, N. Winssinger, Angew. Chem. Int. Ed. 38
(1999) 2096–2152.
[8] O. Baudoin, M. Cesario, D. Guenard, F. Gueritte, J. Org. Chem. 67 (2002)
1199–1207.
[9] L. Pu, Chem. Rev. 98 (1998) 2405–2494.
[10] J. Tsuji, Palladium Reagents and Catalysts, John Wiley and Sons, New York, 1995.
[11] K.H. Shaughnessy, R.B. DeVasher, Curr. Org. Chem. 9 (2005) 585–604.
[12] D. Badone, M. Baroni, R. Cardamone, A. Ielmini, U. Guzzi, J. Org. Chem. 62 (1997)
7170–7173.
[13] L. Botella, C. Najera, Angew. Chem. Int. Ed. 41 (2002) 179–181.
[14] C. Dupuis, K. Adiey, L. Charruault, V. Michelet, M. Savignac, J.-P. Genet, Tetra-
hedron Lett. 42 (2001) 6523–6526.
[15] K.H. Shaughnessy, R.S. Booth, Org. Lett. 3 (2001) 2757–2759.
[16] L.R. Moore, K.H. Shaughnessy, Org. Lett. 6 (2004) 225–228.
[17] N. Kataoka, Q. Shelby, J.P. Stambuli, J.F. Hartwig, J. Org. Chem. 67 (2002)
5553–5566.
[18] G. Adjabeng, T. Brenstrum, J. Wilson, C. Frampton, A. Robertson, J. Hillhouse, J.
McNulty, A. Capretta, Org. Lett. 5 (2003) 953–955.
Scheme 3. Plausible mechanism for the [PdCl2(CH3CN)2]/H2O catalytic system.

124
S. Ganesamoorthy et al. / Journal of Molecular Catalysis A: Chemical 371 (2013) 118–124
[19] B. Cornils, W.A. Herrmann, R.W. Eckl, J. Mol. Catal. A: Chem. 116 (1997) 27–33.
[20] M. Mondal, U. Bora, Green Chem. 14 (2012) 1873–1876.
[21] L.S. Hegedus, G.F. Allen, J.J. Bozell, E.L. Waterman, J. Am. Chem. Soc. 100 (1978)
5800–5807.
[22] S. Ma, J. Zhang, J. Am. Chem. Soc. 125 (2003) 12386–12387.
[23] M. Lampilas, R. Lett, Tetrahedron Lett. 33 (1992) 777–780.
[24] K.C. Nicolaou, T.K. Chakraborty, A.D. Piscopio, N. Minowa, P. Bertinato, J. Am.
Chem. Soc. 115 (1993) 4419–4420.
[25] Y. Xiao, J. Zhang, Angew. Chem. Int. Ed. 47 (2008) 1903–1906.
[26] Y.G. Wang, X.X. Wu, Z.Y. Jiang, Tetrahedron Lett. 45 (2004) 2973–2976.
[27] T. Pei, R.A. Widenhoefer, Chem. Commun. (2002) 650–651.
[28] C. Liu, R.A. Widenhoefer, J. Am. Chem. Soc. 126 (2004) 10250–10251.
[29] C. Liu, R.A. Widenhoefer, Chem. Eur. J. 12 (2006) 1371–2382.
[30] X. Wang, T. Pei, X. Han, R.A. Widenhoefer, Org. Lett. 5 (2003) 2699–2701.
[31] T. Pei, R.A. Widenhoefer, J. Am. Chem. Soc. 123 (2001) 11290–11291.
[32] T. Pei, X. Wang, R.A. Widenhoefer, J. Am. Chem. Soc. 125 (2003) 648–649.
[33] G. Liu, S.S. Stahl, J. Am. Chem. Soc. 128 (2006) 7179–7181.
[34] B.H. Lipshutz, D.W. Chung, B. Rich, Org. Lett. 10 (2008) 3793–3796.
[35] G.K. Anderson, M. Lin, Inorg. Synth. 28 (1990) 60–63.
[36] M. Kertesz, C.H. Choi, S. Yang, Chem. Rev. 105 (2005) 3448–3481.
[37] H. Tomori, J.M. Fox, S.L. Buchwald, J. Org. Chem. 65 (2000) 5334–5341.
[38] R. Capdeville, E. Buchdunger, J. Zimmermann, A. Matter, Nat. Rev. Drug Discov.
1 (2002) 493–502.
[39] S. Lightowler, M. Hird, Chem. Mater. 17 (2005) 5538–5549.