Immobilized palladium nanoparticles within polymers as active catalysts for Suzuki-Miyaura reaction

Article abstract of DOI:10.1039/c5ra25925h

A highly active and reusable catalyst Pd@PNP was developed for Suzuki-Miyaura reaction of aryl chlorides and bromides with aryl boronic acids, and the corresponding biphenyl compounds were obtained in good to excellent yields. Triphenylphosphine and palladium nanoparticles were immobilized in situ in the polymer formed from Pd catalyzed coupling of tris(4-bromophenyl)amine and benzene-1,4-diboronic acid. The immobilized triphenylphosphine enhanced the activity and the stability of the catalyst Pd@PNP, and the catalyst Pd@PNP can be reused at least 5 times with good activity. Functional groups, such as methoxyl, nitrile, tert-butyl, nitro, acyl and formyl groups, were well tolerated under the reaction conditions, and the corresponding products were obtained in high yields.

Full text of DOI:10.1039/c5ra25925h

RSC Advances
View Article Online
View Journal | View Issue
COMMUNICATION
Immobilized palladium nanoparticles within
polymers as active catalysts for Suzuki–Miyaura
reaction†
Cite this: RSC Adv., 2016, 6, 16899
Received 5th December 2015
Accepted 30th January 2016
*
Ting Chen, Fei Mao, Zhengliang Qi, Yan Li, Rizhi Chen, Yong Wang and Jun Huang
DOI: 10.1039/c5ra25925h
www.rsc.org/advances
A highly active and reusable catalyst Pd@PNP was developed for the activation of aryl chlorides is difficult as the C–Cl bond is
Suzuki–Miyaura reaction of aryl chlorides and bromides with aryl much stronger than C–Br and C–I bonds. Thus, it is highly
boronic acids, and the corresponding biphenyl compounds were desirable to develop highly active heterogeneous catalysts for
obtained in good to excellent yields. Triphenylphosphine and palla- the cross coupling reactions.
dium nanoparticles were immobilized in situ in the polymer formed
Recently, we reported highly active Pd heterogeneous cata-
from Pd catalyzed coupling of tris(4-bromophenyl)amine and lysts for Suzuki–Miyaura reaction, and the catalysts can be
benzene-1,4-diboronic acid. The immobilized triphenylphosphine reused several times and no P/Pd contamination was found in
enhanced the activity and the stability of the catalyst Pd@PNP, and the the products.10 The electron rich and bulky P ligands were
catalyst Pd@PNP can be reused at least 5 times with good activity. anchored into the Pd catalyzed polyphenylene polymers, and
Functional groups, such as methoxyl, nitrile, tert-butyl, nitro, acyl and the active Pd nanoparticles were in situ formed and trapped into
formyl groups, were well tolerated under the reaction conditions, and the polymers as highly active Pd heterogeneous catalysts.
the corresponding products were obtained in high yields.
Moreover, Pd nanoparticles supported in ionic solid polymers
were reported as highly active heterogeneous catalysts for
Suzuki–Miyaura reaction, and only 10 ppm of Pd catalyst was
required for Suzuki–Miyaura reaction of aryl bromides.11 In
addition, we also reported the C–O coupling and C–CN coupling
of aryl chlorides and bromides with heterogeneous or homo-
geneous catalyst systems.12
Here, the in situ formed Pd nanoparticles were trapped and
immobilized into the polymers with triphenylphosphine ligand
giving highly active Pd heterogeneous catalysts for Suzuki–
Miyaura reaction. The Pd@PNP catalysts were found to be
highly active for the Suzuki–Miyaura coupling of the aryl
bromides and chlorides with aryl boronic acids. As the P ligands
and Pd were both immobilized into the polymers, the biphenyl
products can be separated easily without contamination from P
and Pd. Additionally, the Pd@PNP catalysts are stable in air
since the TPP ligand is not sensitive to air.
The Pd@PNP catalysts were synthesized by palladium cata-
lyzed Suzuki–Miyaura reaction of tris(4-bromophenyl) amine
with benzene-1,4-diboronic acid. Tris(dibenzylideneacetone)-
dipalladium with tris(4-chlorophenyl)phosphine was selected
as the Pd catalyst, and then the ligand tris(4-chlorophenyl)
phosphine could participate in the Suzuki–Miyaura reaction
of tris(4-bromophenyl)amine with benzene-1,4-diboronic acid
to form the polymers. Moreover, Pd nanoparticles were trapped
and immobilized into polymers to form the Pd@PNP catalysts
(see Scheme 1).
Introduction
Palladium catalyzed cross-coupling reactions are applied widely
for synthesis of pharmaceuticals,1 agricultural chemicals and
natural products.2 Although some highly active ligand/
palladium systems were designed and used for Pd catalyzed
Suzuki–Miyaura reactions,3 Heck reactions,4 Sonogashira reac-
tions and Negishi reactions,5 heterogeneous Pd catalyst systems
are more convenient for the cross-coupling reactions in prac-
tical applications, as Pd/ligand systems are difficult to recycle,
and the Pd/ligand may be leaked into the products. The recovery
of the active Pd/ligand catalyst systems is highly valuable not
only for economic reasons but also for avoiding product
contamination. Therefore, active heterogeneous Pd catalysts
were designed and applied for cross-coupling reactions,
including Pd supported on carbon,6 graphite,7 metal oxides,8
hybrid materials and polymers.9 But heterogeneous Pd catalysts
are usually less active than Pd/ligand systems, especially for
activation of aryl chlorides. Aryl chlorides are cheaper than aryl
bromides and iodides and commercially available widely, but
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical
Engineering, Nanjing Tech University, Nanjing 210009, China. E-mail: junhuang@
njtech.edu.cn; Fax: +86 25-83172261
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c5ra25925h
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 16899–16903 | 16899

View Article Online
RSC Advances
Communication
puried in a column with silica gel (eluting with ethyl acetate/
hexane).
Reusability of catalyst Pd@PNP
The coupling of 4-chlorotoluene with phenylboronic acid was
used to test the reusability of catalyst Pd@PNP. Aer centrifu-
gation and washing with ethyl acetate, the catalyst Pd@PNP was
added to the reaction mixture again for the coupling of 4-
chlorotoluene with phenylboronic acid, and the yield of methyl
biphenyl was determined by GC.
Scheme 1 The preparation of the Pd nanocatalysts.
Experimental section
Preparation of Pd@PNP catalysts
Results and discussions
The procedure for the synthesis of the Pd@PNP catalyst was as
follows. 0.482 g (1.0 mmol) of tris(4-bromophenyl)amine, 0.348
g (2.1 mmol) of benzene-1,4-diboronic acid, 0.0458 g (0.05
mmol) of Pd2(dba)3, 0.146 g (0.4 mmol) of tris(4-chlorophenyl)
phosphine and 0.4119 g (3.0 mmol) of K2CO3 were added into
a Schlenk tube with 30 mL of DMF under argon. And then the
Catalyst characterization
To study the structure of the catalyst, the Pd@PNP was char-
acterized by TEM (transmission electron microscope) and SEM
(scanning electron microscopy) presented in Fig. 1 and S1,†
respectively. From Fig. 1, we can see that Pd nanoparticles were
dispersed on the PNP polymers, and the diameter size of the Pd
particles is about 1–5 nm (Fig. 1, le). The Pd nanoparticles
were retained well and the average diameter of the Pd particles
was about 1–5 nm too, and nearly no evident aggregation was
found in the recycled Pd@PNP catalyst aer 5 reaction runs
(Fig. 1, right). The SEM image of the Pd@PNP showed that the
catalyst Pd@PNP contained irregularly shaped particles with
irregular pores (Fig. S1†). From nitrogen adsorption–desorption
analysis, the BET surface area of the catalyst Pd@PNP was about
48 m2 gꢁ1 (Fig. S2†). The average pore diameter of the catalyst
Pd@PNP was about 6.7 nm. The thermogravimetric analysis
(TGA) showed that the Pd@PNP was thermally stable up to 500
ꢀC. As shown in the TG curve (Fig. S3†), a sharp weight loss from
ꢀ
tube was heated to 150 C in an oil bath with stirring for 24 h.
Aer the reaction mixture cooled to room temperature, the
precipitated yellow powder was collected by centrifugation.
Aer washing with water and DMF 3 times, the powder was
dried under vacuum and stored in an argon atmosphere as the
Pd@PNP catalyst. The amount of Pd in the Pd@PNP catalyst
was found to be 1.81 wt% (determined by ICP-AES).
The Pd@PNP-1 was prepared similarly with 0.0229 g (0.025
mmol) of Pd2(dba)3 and 0.073 g (0.2 mmol) of tris(4-chlorophenyl)
phosphine added. The amount of Pd in the Pd@PNP-1 catalyst was
found to be 0.92 wt% (determined by ICP-AES).
The Pd@PNP-2 was synthesized with similar procedures
using 0.0224 g (0.1 mmol) of Pd(OAc)2 instead of Pd2(dba)3. The
amount of Pd in the Pd@PNP-2 catalyst was found to be 1.91
wt% (determined by ICP-AES).
The Pd@PN was synthesized using similar procedures using
tetrakis(triphenylphosphine)palladium instead of Pd2(dba)3
without the ligand tris(4-chlorophenyl)phosphine. 0.482 g (1.0
mmol) of tris(4-bromophenyl)amine, 0.2486 g (1.5 mmol) of
benzene-1,4-diboronic acid, 0.1156 g (0.1 mmol) of tetrakis
(triphenylphosphine)palladium and 0.2746 g (2.0 mmol) of
K2CO3 were added into a Schlenk tube with 30 mL of DMF
under argon. The amount of Pd in the Pd@PN catalyst was
found to be 1.92 wt% (determined by ICP-AES).
ꢀ
room temperature to 150 C occurred due to the loss of mois-
tureꢀand solventꢀ(DMF). There is no evident mass loss between
150 C and 500 C, which showed good thermostability of the
catalyst Pd@PNP. The catalyst Pd@PNP decomposed slowly
aer 500 ꢀC.
The X-ray diffraction patterns of Pd@PNP (Fig. S4†) exhibi-
ted broad peaks at 2q ¼ 40.016ꢀ, 46.664ꢀ, 68.378ꢀ and 82.199ꢀ
corresponding to Pd metal diffraction lines (111), (200), (220)
and (311) respectively. The diffraction peaks in this pattern
conrm that Pd was supported on solid N containing polymer.
The EDX elemental analyses of the Pd@PNP revealed the pres-
ence of C, N, P, Br and Pd (Fig. S5†). No Cl peak was found,
which may be because the amount of tris(4-chlorophenyl)
Typical procedure for Pd catalyzed Suzuki–Miyaura coupling
reaction of aryl halides with aryl boronic acid
Aryl chlorides (1.0 mmol), phenylboronic acid (1.2 mmol),
Pd@PNP catalyst (0.2–0.3% Pd), K2CO3 (2 mmol) and methanol
(2.0 mL) were added into a pressure tube underꢀAr. The pressure
tube was placed in an oil bath for 14 h at 80 C. The reaction
mixture was cooled to room temperature and the crude prod-
ucts were puried in a column with silica gel (eluting with ethyl
acetate/hexane).
The coupling reaction of aryl bromides with aryl boronic
acids was performed similarly, except with the addition of
Fig. 1 TEM images of Pd@PNP catalyst (left); the catalyst after five
a lower amount of catalyst Pd@PNP. The crude products were reaction runs (right); scale bar, 10 nm.
16900 | RSC Adv., 2016, 6, 16899–16903
This journal is © The Royal Society of Chemistry 2016

View Article Online
Communication
RSC Advances
phosphine added was low, and most of the Cl was removed via reaction. The solvents DMF, DMSO, toluene, ethanol, 1,4-
the reaction with benzene-1,4-diboronic acid. The existence of P dioxane and methanol were used, and methanol was found to
was in agreement with this deduction. The FT-IR spectra of the be the best solvent for the coupling reaction (Table 1, entries 5–
Pd@PNP catalyst is shown in Fig. S6.† The IR bands between 10). The bases Na2CO3, K3PO4, K2CO3, KOH and NaOH were
1500 cmꢁ1 and 500 cmꢁ1 are for the phenyl rings.
tested, and K2CO3 was the most suitable base for the coupling
reaction (Table 1, entries 11–13). Then, the added Pd amount
and reaction time were optimized, and 4-phenyltoluene was
obtained in 99% yield with 0.2 mol% of Pd in 14 hours (Table 1,
entries 14–17). The Pd@PNP stored in air for 1 week was used
for the coupling of 4-chloroluente with phenylboronic acid, and
4-phenyltoluene was obtained in 99% yield also, which showed
the Pd@PNP was not sensitive to air (Table 1, entry 18).
Suzuki–Miyaura coupling of 4-chlorotoluene with
phenylboronic acid
The catalyst Pd@PNP was studied for the Suzuki–Miyaura
coupling of 4-chlorotoluene with phenylboronic acid, and
reaction conditions were optimized. The catalysts Pd@PNP,
Pd@PNP-1, Pd@PNP-2 and Pd@PN were tested for comparison,
and the catalyst Pd@PNP was found to be more active than the
other catalysts for the coupling reaction (Table 1, entries 1–4).
The formation of the polymers was affected by the amount of Pd
added and the Pd source, as the polymerization was catalyzed by
the active Pd nanoparticles. Comparing Pd@PNP with
Pd@PNP-1, the decrease of added Pd2(dba)3 may slow down the
formation of polymers, and simultaneously lead to the aggre-
gation of Pd nanoparticles. In addition, the added Pd(Ac)2
needed to be reduced to active Pd(0) by benzene-1,4-diboronic
acid rst, which slowed down the formation of the polymers
and led to the aggregation of Pd nanoparticles. In Pd@PN, Pd
[P(C6H5)3]4 was used as a catalyst and Pd source. As the P(C6H5)3
cannot couple with benzene-1,4-diboronic acid, and Pd nano-
particles in the polymers were not stable enough, the aggre-
gated Pd particles were not quite active for the coupling
Suzuki–Miyaura coupling of aryl chlorides with aryl boronic
acids
With optimized reaction conditions, the catalyst Pd@PNP was
tested for Suzuki–Miyaura coupling reaction of aryl chlorides
with aryl boronic acids, and the results are presented in Table
2. The cross coupling of aryl chlorides with both electron
withdrawing substituents and electron donating substituents
afforded the corresponding biphenyl compounds in good to
excellent yields (Table 2, entries 1–8). The acyl, formyl, nitro
and nitrile groups were tolerated well in the reaction condi-
tions, and high yields of the corresponding products were ob-
tained (Table 2, entries 1–6). The coupling of deactivated aryl
chlorides, such as 4-chlorotoluene and 2-chloroanisole, gave
the corresponding products in high yields also (Table 2, entries
7 and 8). Moreover, phenylboronic acids with functional
groups, including methyl, methoxyl and nitrile groups, were
coupled well with chlorobenzene, and the corresponding
biphenyl products were obtained in 83% to 96% yields
(Table 2, entries 9–11).
Table 1 Pd catalyzed Suzuki–Miyaura coupling of 4-chlorotoluene
with phenylboronic acid
Entry Catalyst
Base
Solvent
Pd (mol%) Yield (%)
Table 2 Suzuki–Miyaura coupling of aryl chlorides and arylboronic
1a
Pd@PNP
Pd@PNP-1 K2CO3
Pd@PNP-2 K2CO3
K2CO3
Methanol
Methanol
Methanol
Methanol
DMF
DMSO
Ethanol
Toluene
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
63
29
4
acidsa
2a
3a
4a
Pd@PN
K2CO3
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
K3PO4
5
5b
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
Pd@PNP
36
<1
15
2
6b
7b
Yieldb (%)
8b
Entry
R1
R2
9b
1,4-Dioxane 0.1
Methanol
28
38
61
15
11
99
86
99
95
99
1c
2
3
4
5
4-MeO
4-MeCO
4-CHO
4-NO2
2-CN
2-NO2
2-Me
2-MeO
H
H
H
H
H
H
H
H
H
96
96
94
93
70
94
95
95
83
95
96
10
11c
12c
13c
14
15d
16e
17f
18g
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.2
0.2
Na2CO3 Methanol
KOH
Methanol
Methanol
Methanol
Methanol
Methanol
Methanol
Methanol
NaOH
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
6c
7c
8c
9c
10c
11c
4-CN
4-CH3
4-MeO
H
H
a
Reaction conditions: 4-chlorotoluene, 1.0 mmol; phenylboronic acid,
1.2 mmol; base, K2CO3, 2 mmol; at 80 ꢀC; for 16 h; under argon.
b
c
a
K3PO4, 1.3 mmol; at 100 ꢀC. Na2CO3, 2.0 mmol; NaOH and KOH,
Reaction conditions: aryl chlorides, 1.0 mmol; phenylboronic acid 1.2
d
e
f
g
4.0 mmol. At 70 ꢀC. 14 h. 12 h. The catalyst Pd@PNP was mmol; Pd catalyst Pd@PNP, Pd, 0.2 mol%; K2CO3, 2 mmol; methanol, 2
b
exposed to the air for a week.
mL; at 80 ꢀC; 14 h; under argon. Isolated yield. c Pd, 0.3 mol%.
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 16899–16903 | 16901

View Article Online
RSC Advances
Communication
Suzuki–Miyaura coupling of aryl bromides with
phenylboronic acid
Aryl bromides were also examined for the Suzuki–Miyaura
coupling with phenylboronic acid, and the results are listed in
Table 3. As the C–Br bond (in aryl bromides) is weaker than the
C–Cl bond, Suzuki–Miyaura coupling of aryl bromides with
phenylboronic acid was performed with lower catalyst loading
(catalyst Pd@PNP, 0.02–0.05 mol% of Pd added). The Pd cata-
lyst Pd@PNP showed high efficiency for the cross coupling
reaction of aryl bromides with phenylboronic acid. The
coupling of aryl bromides with electron withdrawing or electron
donating groups gave the corresponding products in good to
excellent yields. The para-substituents in aryl bromides,
including methoxyl, nitrile, tert-butyl, acyl and formyl groups,
were well tolerated under the reaction conditions, and the
corresponding products were obtained in high yields (Table 3,
entries 1–5). The coupling reaction of ortho-substituted and 2,6-
dimethyl substituted bromobenzene afforded the correspond-
ing products in good yields also (Table 3, entries 6–10).
Fig.
2
Recycling of the Pd@PNP catalyst. Reaction conditions:
4-chlorotoluene, 1.0 mmol; phenylboronic acid, 1.2 mmol; Pd@PNP
Pd catalyst, Pd, 0.4 mol%; K2CO3, 2.0 mmol; methanol, 2 mL; at 80 ꢀC;
within 14 h; under argon.
cross-coupling of 4-chlorotoluene with phenylboronic acid aer
removal of the catalyst Pd@PNP, which indicated that the
catalyst Pd@PNP is a heterogeneous catalyst for Suzuki–
Miyaura reaction. There was no contamination (ligand or Pd)
found from the catalyst system, which is important for phar-
maceutical chemistry.
In a one-pot process, Pd with tris(4-chlorophenyl)phosphine
catalysed the coupling of tris(4-bromophenyl)amine with
benzene-1,4-diboronic acid to form the polymer, and the tris(4-
chlorophenyl)phosphine can also participate in the coupling
reaction with benzene-1,4-diboronic acid. And then the triphe-
nylphosphine (from tris(4-chlorophenyl)phosphine) was
anchored into the polymer. Furthermore, active Pd nano-
particles were trapped and immobilized into the polymer.
Evidently, active Pd nanoparticles were trapped and immobi-
lized into the polymer preferentially, as the polymerization was
catalyzed by the active Pd nanoparticles. Thus, highly active
Pd@PNP catalyst can be obtained in the one-pot process.
Catalyst reusability and discussion
The reusability of the catalyst Pd@PNP was tested for the cross-
coupling of 4-chlorotoluene with phenylboronic acid, and the
yields with recycled catalyst Pd@PNP are presented in Fig. 2.
The catalyst Pd@PNP can be reused 5 times at least, but slight
deactivation of the Pd@PNP catalyst was observed. The deacti-
vation may be due to the loss of the catalyst in the recycling
processes and the slight aggregation of the Pd nanoparticles.
And 4-phenyltoluene can be obtained in high yield also.
To test the leakage of Pd@PNP catalyst, the content of Pd was
measured by ICP-AES in the 5th reaction run solution, and no
Pd was detected in the solution (below detection limit, <7 ppb).
Moreover, no P (from the P ligand) was detected as having
leaked into the solution. The solution was not active for the
Conclusions
In summary, we demonstrated a highly active and reusable Pd
catalyst Pd@PNP for Suzuki–Miyaura reaction of aryl chlorides and
bromides with aryl boronic acids, and the corresponding biphenyl
compounds were obtained in good to excellent yields. The in situ
immobilized triphenylphosphine in the polymer support
enhanced the activity and the stability of the catalyst Pd@PNP, and
the catalyst Pd@PNP can be reused several times with good
activity. Moreover, the Pd@PNP catalyzed Suzuki–Miyaura reaction
was applicable widely, and various aryl chlorides and bromides
can be coupled with aryl boronic acids in high yields. Functional
groups, such as methoxyl, nitrile, tert-butyl, nitro, acyl and formyl
groups, were well tolerated under the reaction conditions, and the
corresponding products were obtained in high yields.
Table 3 Suzuki–Miyaura coupling of aryl bromides and phenylboronic
acida
Entry
R
Yieldb (%)
1
2
3
4
4-MeO
4-CN
99
98
80
99
99
86
94
95
98
93
4-tert-Butyl
4-CHO
4-MeCO
2-MeO
2-Me
2-NO2
2-CN
2,6-Di-Me
5
6c
7c
8c
9c
10c
Acknowledgements
This work was supported by the fund from the State Key Labo-
ratory of Materials-Oriented Chemical Engineering (grant
ZK201402), the National High Technology Research and
Development Program of China (No. 2012AA0 3A606) and the
Project of Priority Academic Program Development of Jiangsu
Higher Education Institutions.
a
Reaction conditions: aryl bromides, 5.0 mmol; phenylboronic acid,
6.0 mmol; Pd@PNP Pd catalyst, Pd, 0.02 mol%; K2CO3, 10.0 mmol;
b
c
methanol, 3 mL; at 70 ꢀC; 11 h; under argon. Isolated yield. Pd,
0.05 mol%.
16902 | RSC Adv., 2016, 6, 16899–16903
This journal is © The Royal Society of Chemistry 2016

View Article Online
Communication
RSC Advances
W. Li, L. Fu and H. Chen, Macromolecules, 2012, 45, 9004–
9009.
Notes and references
7 K. E. Balsane, R. S. Shelkar and J. M. Nagarkar, Catal. Lett.,
2015, 145, 1817–1824.
1 H. Juteau, Y. Gareau, M. Labelle, C. F. Sturino, N. Sawyer,
N. Tremblay, S. Lamontage, M. C. Carriere, D. Denis and
K. M. Metters, Bioorg. Med. Chem., 2001, 9, 1977–1984.
2 (a) N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95, 2457–
2483; (b) C. C. C. J. Seechurn, M. O. Kitching, T. J. Colacot
and V. Snieckus, Angew. Chem., Int. Ed., 2012, 51, 5062–
5085; (c) D. S. Surry and S. L. Buchwald, Chem. Sci., 2011,
2, 27–50.
3 (a) A. Zapf, A. Ehrentraut and M. Beller, Angew. Chem., Int.
Ed., 2000, 39, 4153–4155; (b) A. F. Littke and G. C. Fu,
Angew. Chem., Int. Ed., 2002, 41, 4176–4211; (c) A. Thakur,
K. Zhang and J. Louie, Chem. Commun., 2012, 48, 203–205;
(d) C. Liu, X. Li, Z. Gao, X. Wang and Z. Jin, Tetrahedron,
2015, 71, 3954–3959.
8 (a) M. L. Kantam, S. Roy, M. Roy, B. Sreedhar and
B. M. Choudary, Adv. Synth. Catal., 2005, 347, 2002–2008;
(b) S. Zhou, M. Johnson and J. G. C. Veinot, Chem.
Commun., 2010, 46, 2411–2413; (c) B. Sreedhar, D. Yada
and P. S. Reddy, Adv. Synth. Catal., 2011, 353, 2823–2836;
(d) H. Woo, K. Lee and K. H. Park, ChemCatChem, 2014, 6,
1635–1640; (e) R. S. Shelkar, S. H. Gund and
J. M. Nagarkar, RSC Adv., 2014, 4, 53387–53396.
9 (a) T. V. Magdesieva, O. M. Nikitin, O. A. Levitsky,
V. A. Zinovyeva, I. Bezverkhyy, E. V. Zolotukhina and
M. A. Vorotyntsev, J. Mol. Catal. A: Chem., 2012, 353, 50–57;
(b) Y. Zhou, C. Li, M. Lin, Y. Ding and Z. Zhan, Adv. Synth.
Catal., 2015, 357, 2503–2508; (c) Z. Ye, L. Xu, Z. Dong and
P. Xiang, Chem. Commun., 2013, 49, 6235–6255; (d) D. Astruc,
F. Lu and J. R. Aranzaes, Angew. Chem., Int. Ed., 2005, 44,
7852–7871; (e) C. Ornelas, A. K. Diallo, J. Ruiz and D. Astruc,
Adv. Synth. Catal., 2009, 351, 2147–2154; (f) S. Ogasawara and
S. Kato, J. Am. Chem. Soc., 2010, 132, 4608–4613; (g)
A. Modak, J. Mondal, M. Sasidharan and A. Bhaumik, Green
Chem., 2011, 13, 1317–1331; (h) C. Deraedt, L. Salmon, J. Ruiz
and D. Astruc, Adv. Synth. Catal., 2013, 355, 2992–3001.
10 Y. Li, F. Mao, T. Chen, Z. Zhou, Y. Wang and J. Huang, Adv.
Synth. Catal., 2015, 357, 2827–2832.
4 (a) X. Wu, P. Anbarasan, H. Neumann and M. Beller, Angew.
Chem., Int. Ed., 2010, 49, 9047–9050; (b) F. Saleem, G. K. Rao,
A. Kumar, S. Kumar and M. P. Singh, RSC Adv., 2014, 4,
56102–56111.
5 (a) R. Chinchilla and C. Najera, Chem. Rev., 2007, 107, 874–
922; (b) B. H. Lipshutz, D. W. Chung and B. Rich, Org.
Lett., 2008, 17, 3793–3796; (c) N. Liu, C. Liu, Q. Xu and
Z. Lin, Eur. J. Org. Chem., 2011, 4422–4428; (d) Y. Yong,
J. F. Y. Lim, X. Y. Chew, E. G. Robins, C. W. Johannes,
Y. H. Lim and H. Jong, Catal. Sci. Technol., 2015, 5, 3501–
3506; (e) C. Dai and G. C. Fu, J. Am. Chem. Soc., 2001, 123,
2719–2724; (f) C. Han and S. L. Buchwald, J. Am. Chem.
Soc., 2009, 131, 7532–7533; (g) H. Li, C. C. C. Johansson
Seechurn and T. J. Colacot, ACS Catal., 2012, 2, 1147–1164.
6 (a) T. Tagata and M. Nishida, J. Org. Chem., 2003, 68, 9412–
9415; (b) Y. Kitamura, S. Sako, T. Udzu, A. Tsutsui,
T. Maegawa, Y. Monguchi and H. Sajiki, Chem. Commun.,
2007, 5069–5071; (c) S. Liu, H. Li, M. Shi, H. Jiang, X. Hu,
11 Y. Yu, T. Hu, X. Chen, K. Xu, J. Zhang and J. Huang, Chem.
Commun., 2011, 47, 3592–3594.
12 (a) T. Hu, T. Schulz, C. Torborg, X. Chen, J. Wang, M. Beller
and J. Huang, Chem. Commun., 2009, 7330–7332; (b) T. Hu,
X. Chen, J. Wang and J. Huang, ChemCatChem, 2011, 3,
661–665; (c) J. Zhang, X. Chen, T. Hu, Y. Zhang, K. Xu and
Y. Yu, Catal. Lett., 2010, 139, 56–60.
This journal is © The Royal Society of Chemistry 2016
RSC Adv., 2016, 6, 16899–16903 | 16903