A novel bisoxazoline/Pd composite microsphere: A highly active catalyst for Heck reactions

Article abstract of DOI:10.1039/c5ra16510e

A novel bisoxazoline/Pd microsphere catalyst was successfully prepared. The structure of the solid catalyst was characterized by SEM, TGA and FT-IR. The catalyst exhibits excellent activity for the Heck reaction. Moreover, the catalyst shows outstanding stability and reusability, can be recovered simply and effectively and reused six times without any activity decrease.

Full text of DOI:10.1039/c5ra16510e

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A novel bisoxazoline/Pd composite microsphere: a
highly active catalyst for Heck reactions†
Cite this: RSC Adv., 2015, 5, 76285
b
b
b
Junke Wang,a Yingxiao Zong,ab Guoren Yue, Yulai Hu and Xicun Wang
*
*
Received 16th August 2015
Accepted 2nd September 2015
DOI: 10.1039/c5ra16510e
www.rsc.org/advances
A
novel bisoxazoline/Pd microsphere catalyst was successfully development of an efficient heterogeneous catalyst for Heck-
prepared. The structure of the solid catalyst was characterized by SEM, type olenation is a challenging task.
TGA and FT-IR. The catalyst exhibits excellent activity for the Heck Metal–organic polymerization through the formation of “self-
reaction. Moreover, the catalyst shows outstanding stability and assembled” systems is a promising strategy to realize hetero-
reusability, can be recovered simply and effectively and reused six genization of the homogeneous catalysts or precursors.9
times without any activity decrease.
Compared with the other methods, the self-assembled strategy
can produce heterogeneous catalysts without using any supports
with high density of catalytically active units (Scheme 1).
The transition-metal-catalyzed C–C cross-coupling reaction is a
key step in the synthesis of organic building blocks, natural
products, pharmaceuticals, and agricultural derivatives.1
Certainly, Pd-catalyzed olenation of aryl halides (the Heck–
Mizoroki reaction) is one of the most powerful tools for the
construction of C–C bonds.2 In fact, the Pd-based catalytic
systems are highly efficient, and they generally offer excellent
product yields with good selectivity.3
In general, homogeneous palladium catalysts are mostly
used in the Heck reaction owing to their high efficiency.
However, the soluble palladium complexes suffer from draw-
backs associated with the catalyst separation and recovery aer
the reaction. A promising route to solve the problems is the
heterogenization of the homogeneous catalysts,4 and many
support materials have been explored to immobilize palladium
such as polymers, silica particles and metal oxides.5–8
In spite of their good catalytic activity in Heck coupling
reactions, the scope and functional group tolerance of these
catalytic systems are generally limited. More importantly, they
show less effectiveness in the Heck olenation of less-active
bromo- and chloroarenes. In addition, most of the catalytic
systems suffered from the use of higher metal loadings (typi-
cally 5–10 mol%) and poor reusability. Therefore, the
Most recently, metal–organic polymer (MOP) were found to
be an effective tool for the construction of C–C bonds.10 Bou-
chard et al.10a made the BDC-NH2 to be postmodied with sal-
icylic aldehyde to obtain the binding catalytically active Pd(II)
ions. The catalytic activity of the embedded Pd(II) ions was
tested via heterogeneous Heck coupling. They found that a
trade-off exists between the amount of metalation and pore
blocking during catalytic testing. Bagherzadeh et al.10b prepared
supported palladium nanoparticles on Mn-carboxylate coordi-
nation polymer (Pd/MnBDC) using solution impregnation
method. This catalyst can provide high activity and selectivity to
E-internal olens for the Mizoroki–Heck cross-coupling reac-
tion. However, bromo- and chloroarenes are less reactive.
Moreover, these metal–organic polymers (MOPs) contain two
kinds of metal and complicated ligands, which results in the
trouble of preparation and the high price, so that they cannot be
applied into the volume production. Hence, there is a contin-
uous exploration for a better heterogeneous Pd-based metal–
organic polymer (MOP) catalyst for the Heck coupling reaction.
According to Fujita et al.,11 the catalytically active center of the
metal–organic polymers is the metal ion for the construction of
metal–organic polymers, rather than the extra metal ion followed
by the post-modication. Thus, the leaching of the catalytically
aKey Laboratory of Hexi Corridor Resources Utilization of Gansu Universities, College
of Chemistry and Chemical Engineering, Hexi University, Zhangye 734000, China
bGansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical
Engineering, Northwest Normal University, Lanzhou 730070, China. E-mail:
wangjk@hxu.edu.cn; Fax: +86-936-8287080
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c5ra16510e
Scheme 1 The principle of self-supported catalysis.
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Fig. 1 The comparison of 1H NMR spectra between the ligand (E) and
its palladium complex (F).
complex between ligand and palladium acetate was synthesized
without using any deprotonating base.
The catalyst has a high melting point of above 200 ꢀC, and it
was observed to be insoluble in the polar solvents, which enable
the catalyst to be a solid catalyst for the organic reactions.
The structure of the synthesized palladium complex was
characterized using different techniques such as 1H NMR, TGA,
IR, and SEM. 1H NMR spectra difference between the novel
oxazoline ligands and their metal complexes, is one the
important methods for characterization of complexes in the
literature.13,14 However, it is difficult to distinguish the 1H NMR
spectra difference because of their relative insolubility in
DMSO-D6. Therefore, we focused on the synthesis of N-(4,5-
dihydrooxazol-2-yl)benzamide (E), and prepared its Pd complex
(F) to conrm successful chelation of ligand to Pd (Scheme 3).
It is worth to note that, the 1H NMR spectra of the ligand (E)
in DMSO-D6 and its palladium complex (F) in DMSO-D6 is
similar, but the protons of oxazoline in the complex are shied
downeld relative to the protons of the ligand and the protons
of N–H in benzamide disappeared (Fig. 1). These facts
conrmed successful chelation to Pd. This result is accordant to
our previous work.12
Scheme
composite microsphere.
2 Preparation of the self-assembled bisoxazoline/Pd
active metal can be avoided, which may assure the reuses of the
catalyst many times. We presumed that it could also be concep-
tually possible to generate self-assembled catalysts or catalyst
precursors by using the self-assembled strategy. However, the
catalysts could be recovered heterogeneously. In this study, we
report the synthesis of a novel self-assembled bisoxazoline/Pd
composite microsphere, and investigate the catalytical property
for Mizoroki–Heck cross coupling reaction, reusability, and
stability of bisoxazoline/Pd composite microsphere.
As illustrated in Scheme 2, the synthesis of the ligand (C) is a
straightforward process starting from 4,40-oxybisbenzoyl chloride
and 2-aminoethanol, which are inexpensive.12 4,40-Oxybisbenzoyl
chloride (A) was treated with ammonium sulfocyanide in the
presence of polyethylene glycol 400 (PEG-400) in CH2Cl2, followed
by the addition of 2-aminoethanol, to obtain 4,40-oxybis(N-((2-
hydroxyethyl) carbamothioyl)benzamide) (B) in good yields
(85%). This intermediate can be used to implement the intra-
molecular cyclization in the present of DCC to obtain the corre-
sponding 4,40-oxybis(N-(4,5-dihydrooxazol-2-yl)benzamide) (C) as
the ligand in excellent yields (98%). By means of the self-
assembled coordination, Pd(OAc)2 was added into the solution
of the ligand in acetonitrile, and then the pale yellow powder was
obtained as the catalyst (D). Aer washing with solvent thor-
oughly and drying, the solid remains pale yellow. However, the
FT-IR was employed to give a detailed investigation of the
ligand (C) and palladium complex (D). As can be seen from
Fig. 2, the FT-IR spectra of the ligand shows that the strong peak
at 1638 cmꢁ1 could be due to the asymmetric and symmetric
stretching vibrations of C]O, and that the broad peak at
3310 cmꢁ1 could be due to N–H vibrations. However, there are
Scheme 3 Preparation of the N-(4,5-dihydrooxazol-2-yl)benzamide/
Pd (F).
Fig. 2 FT-IR spectra of the ligand (C) and palladium complex (D).
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results are those “maps” or images which indicate the distri-
bution of chemical elements in a sample (Fig. 5).
Following the successful preparation of bisoxazoline/Pd
microsphere, it was then applied to the Heck reaction of
various aryl halides and olens. In a model reaction of p-bro-
moacetophenone and methyl acrylate in DMF solvent, different
reaction parameters such as base, catalyst dosage and reaction
time were optimized. As shown in Table 1, the target products
were obtained when TEA and pyridine were used as base
(Table 1, entries 5 and 6). However, when inorganic bases like
K2CO3 or Na2CO3 were used (Table 1, entries 1 and 2), the iso-
lated yields were excellent. Under the same conditions, when
CH3COOK and CH3COONa was used as bases, the yield of the
cross-coupled product was considerably reduced (Table 1,
entries 3 and 4). Thus, K2CO3 has a pronounced effect on the
product yield. In order to show the efficiency of the catalyst, a
controlled experiment indicated that no cross-coupling product
was observed in the absence of the catalyst (Table 1, entries 7).
Next, the effect of catalyst dosage was investigated (Table 1,
entries 8–10): when the amount of catalyst was raised from
0.05 mol% to 0.10 mol%, the isolated yields increased from
72% to 90%; using more catalyst did not improve the yield
further. Moreover, the reaction time were optimized (Table 1,
entries 11 and 12). Isolated yields rose from 90% to 98% as
reaction time rose from 2 h to 4 h. By prolonging reaction time
to 5 h, the yield did not increase any more (Table 1, entries 13),
which means that 4 h was sufficient for the present reaction.
With the optimum reaction conditions, a range of substituted
aryl halides and olens were investigated to check the feasibility
of this protocol whose results are tabulated in Table 2. In
general, the reaction afforded the desired products in good to
excellent isolated yields (82–98%) for aryl bromide and olens
(Table 2, entries 1–14). Generally, the reaction of aryl bromide
Fig. 3 TG pattern of the ligand (C) and palladium complex (D).
not absorption peaks of the C]O and N–H in palladium
complex. Thus, the above results indicate that the ligand was
successfully coordinated with palladium via coordination bond.
The stability of the ligand and palladium complex was
compared by the thermogravimetric (TG) analysis (Fig. 3). The
TG curve indicates that the decomposition temperature of the
ligand was about 246.3 ꢀC, which is lower than that of palla-
dium complex (291.1 ꢀC). This fact indicates the palladium
complex is not a physical mixture of the ligand with palladium,
but a metal complex.
Fig. 4 depicts the scanning electron microscopy (SEM)
images of the bisoxazoline/Pd composite microsphere catalyst,
the catalyst presents with a monodispersed, uniform spherical
morphology with the glabrate outer surface. The particle
diameter is ranging from 0.53 to 0.55 mm. EDAX analysis offers
both quantitative and qualitative information. The qualitative
Table 1 The effect of solvents and basesa
Entry
Catalyst (Pd mol%)
Base
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
0.05
0.05
0.05
0.05
0.05
0.05
0
0.075
0.10
0.15
0.10
0.10
0.10
Na2CO3
K2CO3
KOAc
NaOAc
TEA
Pyridine
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
2
2
2
2
2
2
2
2
2
2
3
4
5
56
72
40
30
21
14
0
80
90
90
94
98
98
Fig. 4 SEM of bisoxazoline/Pd composite microsphere catalyst (D).
9
10
11
12
13
a
Reaction conditions: bisoxazoline/Pd microsphere,
1
mmol of
p-bromoacetophenone, 1 mmol of methyl acrylate, 2 mmol of base,
5 ml of solvent, 80 ꢀC in air. b Isolated yield.
Fig. 5 EDAX spectrum of palladium complex (D).
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Table
2
Heck cross-coupling catalyzed by bisoxazoline/Pd Table 3 Recycling and reuse of bisoxazoline/Pd microsphere in Heck
reaction of bromoacetophenone and t-butyl acrylatea
microspherea
Entry
1 Run
98
2 Run
97
3 Run
97
4 Run
97
5 Run
96
6 Run
96
Yieldb (%)
a
Reaction conditions are the same as that of entry 1 in Table 2.
Isolated yields.
b
Entry
R
X
R0
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
–COCH3
–COCH3
–COCH3
–CHO
–CHO
–CHO
H
H
–CN
–CN
–CN
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
I
C6H5
4
4
4
4
4
4
4
4
4
4
4
4
4
4
2
2
4
4
96
98
98
95
95
97
93
94
99
97
93
96
92
82
98
96
–COOCH3
–COOtBu
–COOCH3
–COOtBu
–COOiBu
–COOCH3
–COOtBu
C6H5
–COOCH3
–COOtBu
–COOiBu
C6H5
9
10
11
12
13
14
15
16
17
18
–CN
H
–OCH3
–OCH3
H
–OCH3
–CHO
C6H5
C6H5
C6H5
C6H5
I
Cl
Cl
Trace
Trace
–COOCH3
Fig. 6 Comparison between the IR of bisoxazoline/Pd composite
Reaction conditions: bisoxazoline/Pd microsphere containing 0.10 microsphere (D0) after recycled eight times and the IR of the fresh
a
mol% Pd, 1.0 mmol of p-bromoacetophenone, 1.2 mmol of olens, 2
bisoxazoline/Pd composite microsphere (D).
mmol of base, 5 ml of solvent, 80 ꢀC in air. b Isolated yield.
least until the six uses, with almost the excellent yield of product
in each run (Table 3). Furthermore, according to the IR shown
in Fig. 6 the used bisoxazoline/Pd microsphere catalyst can
retain its structure, indicating a good stability and durable
structure of bisoxazoline/Pd microsphere in liquid reaction.
Undoubtedly, this result is very promising and encouraging
from a practical point of view.
bearing electron-withdrawing group (–CN, –COOCH3, –COCH3)
with olens can afforded the coupling products in higher yields
than aryl bromide bearing electron donating group (–OCH3).
When this catalyst was applied to catalyze the Heck reaction
ꢀ
of aryl iodides and aryl chloride with t-butyl acrylate at 80 C
(Table 2, entries 15–18). 4-Iodoanisole and lodobenzene reacted
with styrene under the same conditions to give satisfying
conversion in 98 and 96% within 2 h.
Generally, a hot ltration test can determine if the catalysis
was derived from the bisoxazoline/Pd composite microsphere or
from leaching palladium.15 Thus, we chose 4-bromoanisole with
methyl acrylate as model reaction to investigate the fact. Aer the
reaction was carried out for 2 h (the conversion of 4-bromoani-
sole reached 73%, and the yield of the crude cross coupling
product is almost 70%), the catalyst was separated by a hot rapid
ltration. No further reaction was observed by GC analysis, and
no palladium could be detected in the hot liquid mixture by
atomic absorption spectrometry (AAS) (the detection limit of the
AAS experiment is 11 mg Lꢁ1). These results demonstrate that the
palladium atom remains into the ligand during the reaction.
The reusability of the catalysts is an important parameter for
practical application. Therefore, the reusability of bisoxazoline/
Pd composite microsphere for the Heck reaction of p-bromoa-
cetophenone and t-butyl acrylate was also investigated. In
detail, aer the reaction was completed, the catalyst particles
Conclusions
By the self-assembly of the bisoxazoline and Pd(AcO)2, a novel
and non-phosphine solid palladium catalyst, bisoxazoline/Pd
composite microsphere, was successfully prepared. The
synthesized bisoxazoline/Pd composite microsphere shown
high catalytic activity for Heck cross-coupling reactions of
various aryl bromides and olens even at catalyst loadings of
0.1 mol%. Moreover, the catalyst shows outstanding stability
and reusability, can be recovered simply and effectively and
reused six times without any activity decrease. Further investi-
gation of the detailed mechanism and application of this
chemistry are in progress in our lab.
Experimental section
General information
were collected simply and effectively by centrifugation and then Melting points were determined on a Perkin-Elmer differential
the recovered catalyst particles were reused in the next round of scanning calorimeter and were uncorrected. The IR spectra
reaction by mixing them with new substrate, base, and solvent. were run on a Nicolet spectrometer (KBr). NMR spectra were
It is noteworthy that the catalytic activity was maintained at recorded at 400 (1H) and 100 (13C) MHz, respectively, on a
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Varian Mercury plus-400 instrument using CDCl3 as solvent and catalyst is 20.01 wt% (1.8 mmol gꢁ1) measured by atomic
TMS as the internal standard. Scanning electron microscopy absorption spectroscopy (AAS).
(SEM) was performed on a FEI Quanta 450 FEG FESEM instru-
ment. High resolution mass spectra (HRMS) were obtained on
an Agilent LC-MSD-Trap-XCT spectrometer with micromass MS
General experimental procedures for Heck couplings
In a typical experiment, the bisoxazoline/Pd microsphere cata-
lyst (0.10 mmol of Pd) was added to a mixture of aryl halide
(1.0 mmol), olens (1.2 mmol), and K2CO3 (2.0 mmol) in DMF
(5.0 mL), and the reaction mixture was stirred at 80 ꢀC. Aer the
reaction was monitored to be complete by TLC analysis, the
catalyst was removed by ltration, washed with ethanol (3 ꢂ 3
mL), and dried under vacuum for the next run. The organic
fractions were then concentrated on a rotary evaporator to
afford the desired compound in excellent yield. The crude
products were puried by column chromatography on silica gel
using hexane/ethyl acetate. All of the products are known
compounds, and their 1H NMR data were identical to those
reported in literature.
soware using electrospray ionisation (ESI). All the solvents
used were strictly dried according to standard operation and
˚
stored on 4 A molecular sieves.
All other chemicals (AR grade) were commercially available
and used without further purication.
Synthesis of bisacylthiourea B
To a solution of 4,40-oxybisbenzoyl chloride A (2 mmol) in
CH2Cl2 (10 mL) was added ammonium thiocyanate (2.6 mmol)
and PEG-400 (0.2 mmol). The mixture was then stirred at room
temperature for 60 min and cooled to 0 ꢀC, and the solution of
2-aminoethanol (1.8 mmol) in CH2Cl2 (2 mL) was added. The
mixture was continuously stirred for 60 min. Aer the comple-
tion of the reaction, the solvent was removed by distillation, and
water (10 mL) was added to obtain a white solid. The analytical
sample was produced by ash chromatography (acetone and
petroleum ether) to give a white solid B. Yield: 85%. Melting
point: 209–211 ꢀC. Spectral data: IR (KBr) (cmꢁ1): n 3337, 3225,
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (No. 21462016, 21262010), Natural Science
Foundation of Gansu Province and the Advanced Research
Fund of Jinchuan Group Co., Ltd.
1
2944, 1670, 1531. H NMR (400 MHz, DMSO) d 11.35 (s, 2H),
11.05 (s, 2H), 8.02 (d, J ¼ 8.8 Hz, 4H), 7.17 (d, J ¼ 8.8 Hz, 4H),
4.98 (s, 2H), 3.83–3.44 (m, 8H). 13C NMR (100 MHz, DMSO) d
180.71, 167.65, 159.87, 131.68, 128.22, 118.95, 58.75, 47.97,
40.38, 40.17, 39.96, 39.75, 39.54. HR-MS: m/z calcd for
Notes and references
C
20H21N2O5S2 [M + H]+: 433.0892; found: 433.0889.
1 (a) F. Diederich and P. J. Stang, Metal-Catalyzed Cross-
Coupling Reactions, Wiley-VCH, Weinheim, Germany, 1998;
(b) J. A. Baur and D. A. Sinclair, Nat. Rev. Drug Discovery,
2006, 5, 493.
Synthesis of bisoxazoline C
To a solution of compound B (1 mmol) in DMF (5 mL) was
added dicyclohexylcarbodiimide (DCC) (1 mꢀmol) and TEA (1
mmol). The mixture was stirred for 2 h at 80 C, and cooled to
room temperature. Aer the addition of water (5 mL), the white
solid was obtained by the ltration. This solid was added into
CH3CN (5 mL) to be dissolved, followed by the ltration and
concentration to afford the target compound C. Yield: 98%.
Melting point: 195–196 ꢀC. Spectral data: IR (KBr) (cmꢁ1): n
2 (a) I. P. Beletskaya and A. V. Cheprakov, Chem. Rev., 2000,
100, 3009; (b) N. J. Whitcombe, K. K. Hii and S. E. Gibson,
Tetrahedron, 2001, 57, 7449; (c) H. U. Blaser, A. Indolese,
F. Naud, U. Nettekoven and A. Schnyder, Adv. Synth. Catal.,
2004, 346, 1812; (d) K. H. Shaughnessy, P. Kim and
J. F. Hartwig, J. Am. Chem. Soc., 1999, 121, 2123; (e)
A. F. Littke and G. C. Fu, J. Am. Chem. Soc., 2001, 123, 6989.
3 (a) K. Okamoto, R. Akiyama, H. Yoshida, T. Yoshida and
S. J. Kobayashi, J. Am. Chem. Soc., 2005, 127, 2125; (b)
A. Dahan and M. Portnoy, Org. Lett., 2003, 5, 1197; (c)
Y. C. Yang and T. Y. Luh, J. Org. Chem., 2003, 68, 9870; (d)
J. C. Garcia-Martinez, R. Lezutekong and R. M. Crooks, J.
Am. Chem. Soc., 2005, 127, 5097; (e) V. Calo, A. Nacci,
A. Monopoli, A. Fornaro, L. Sabbatini, N. Cioffi and
N. Ditaranto, Organometallics, 2004, 23, 5154; (f) J. Huang,
T. Jiang, H. Gao, B. Han, Z. Liu, W. Wu, Y. Chang and
G. Zhao, Angew. Chem., Int. Ed., 2004, 43, 1397; (g)
A. Desforges, R. Backov, H. Deleuze and O. Mondain-
Monval, Adv. Funct. Mater., 2005, 15, 1689; (h) R. K. Arvela,
N. E. Leadbeater, M. S. Sangi, V. A. Williams, P. Granados
and R. D. Singer, J. Org. Chem., 2005, 70, 161; (i) W. Kleist,
Catal. Lett., 2008, 125, 197.
1
3310, 2921, 1638, 1548. H NMR (400 MHz, DMSO) d 9.61 (s,
2H), 8.28–7.99 (m, 4H), 7.20–6.98 (m, 4H), 4.47 (t, J ¼ 8.6 Hz,
4H), 3.78 (t, J ¼ 8.6 Hz, 4H). 13C NMR (100 MHz, DMSO) d
180.71, 167.65, 159.87, 131.68, 128.22, 118.95, 58.75, 47.97,
40.59, 40.38, 40.17, 39.96, 39.75, 39.54, 39.33. HR-MS: m/z calcd
for C20H19N4O5 [M + H]+: 395.1355; found: 395.1395.
Synthesis of catalyst D
To the solution of Pd(AcO)2 (2 mmol) in CH3CN (5 mL) was
added dropwise into the obtained compound C (1.36 g, 6 mmol)
in CH3CN (2 mL), followed by the stirring for 10 h. On
completion, the ltration was conducted to a yellow solid.
Washing with commercial anhydrous CH3CN (3 ꢂ 5 mL) and
drying at 50 ꢀC overnight gave bisoxazoline/Pd microsphere as a
pale yellow powder (compound D). IR (KBr) (cmꢁ1): n 3443,
2907, 1592. The Pd content of the bisoxazoline/Pd microsphere
4 L. X. Yin and J. Liebscher, Chem. Rev., 2006, 107, 133.
´
5 M. Kralik and A. Biffis, J. Mol. Catal. A: Chem., 2001, 177, 113.
This journal is © The Royal Society of Chemistry 2015
RSC Adv., 2015, 5, 76285–76290 | 76289

View Article Online
RSC Advances
Communication
6 R. Bernini, S. Cacchi, G. Fabrizi, G. Forte, F. Petrucci, 10 (a) J. W. Brown, N. N. Jarenwattananon, T. Otto, J. L. Wang,
¨
A. Prastaro, S. Niembro, A. Shar and A. Vallribera, Green
Chem., 2010, 12, 150.
7 S. Zhou, M. Johnson and J. G. Veinot, Chem. Commun., 2010,
46, 2411.
S. Gloggler and L. Bouchard, Chem. Commun., 2015, 65, 105;
(b) M. Bagherzadeh, F. Ashouri, L. Hashemi and A. Morsali,
Inorg. Chem. Commun., 2014, 44, 10.
11 O. Ohmori and M. Fujita, Chem. Commun., 2004, 1586.
8 V. Polshettiwar, C. Len and A. Fihri, Coord. Chem. Rev., 2009, 12 J. Wang, Y. Zong, S. Weib and Y. Pan, Appl. Organomet.
253, 2599. Chem., 2014, 28, 351.
9 (a) M. A. Yoichi, S. M. S. Yamada and U. Yasuhiro, J. Am. 13 A. Sarkar, S. Bhattacharyya, S. K. Dey, S. Karmakar and
Chem. Soc., 2012, 134, 9285; (b) M. A. Yoichi, A. Mukherjee, New J. Chem., 2014, 38, 817.
S. M. S. Yamada and U. Yasuhiro, J. Am. Chem. Soc., 2012, 14 Y. M. Lee, E. S. Kim, H. J. Kim, H. J. Choi, Y. I. Kim,
134, 3190; (c) J. Gascon, A. Corma, F. Kapteijn and S. K. Kang and S. N. Choi, Dalton Trans., 2009, 126.
F. X. L. Xamena, ACS Catal., 2014, 4, 361; (d) Y. Liang, 15 S. Mohanty, D. Suresh, M. S. Balakrishna and J. T. Mague,
Q. Jing, X. Li, L. Shi and K. Ding, J. Am. Chem. Soc., 2005,
127, 7694.
Tetrahedron, 2008, 64, 240.
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