One-pot synthesis of l-dopa-functionalized water-dispersible magnetite nano-palladium catalyst and its application in the Suzuki and Heck reactions in water: A novel and highly active catalyst

Article abstract of DOI:10.1039/c4ra04189e

A palladium catalyst supported on water-dispersible magnetite nanoparticles end-functionalized with amino and carboxyl groups was successfully prepared by a facile one-pot template-free method combined with a metal adsorption-reduction procedure. It was characterized by TEM, XRD, XPS, FT-IR and VSM. This catalyst exhibits excellent catalytic activity for Suzuki and Heck reactions in water. Furthermore, the newly developed catalyst is easy to be recovered and recycled by magnetic separation from aqueous phase reactions. More importantly, the catalyst revealed high efficiency and high stability under the reaction conditions and during recycling stages. This catalyst can be used consecutively six times without significant loss in catalytic activity. the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra04189e

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One-pot synthesis of L-dopa-functionalized water-
dispersible magnetite nano-palladium catalyst and
its application in the Suzuki and Heck reactions in
water: a novel and highly active catalyst†
Cite this: RSC Adv., 2014, 4, 37761
a
b
a
a
a
*
Jianrui Niu, Fushan Wang, Xiaohang Zhu, Jiahui Zhao and Jiantai Ma
A palladium catalyst supported on water-dispersible magnetite nanoparticles end-functionalized with
amino and carboxyl groups was successfully prepared by a facile one-pot template-free method
combined with a metal adsorption–reduction procedure. It was characterized by TEM, XRD, XPS, FT-IR
and VSM. This catalyst exhibits excellent catalytic activity for Suzuki and Heck reactions in water.
Furthermore, the newly developed catalyst is easy to be recovered and recycled by magnetic separation
from aqueous phase reactions. More importantly, the catalyst revealed high efficiency and high stability
under the reaction conditions and during recycling stages. This catalyst can be used consecutively six
times without significant loss in catalytic activity.
Received 6th May 2014
Accepted 4th August 2014
DOI: 10.1039/c4ra04189e
www.rsc.org/advances
comply with the idea of green chemistry, many teams prefer to
carry out these two reactions in water to replace toxic organic
1 Introduction
solvents as the reaction medium since water is the safest
solvent.
It is well known that Pd-catalyzed Suzuki and Heck reactions are
signicantly important methods for C–C formation in modern
chemical transformations and industrial processes.1–3 One of
the most challenging tasks in inorganic chemistry today is to
design efficient and eco-friendly catalysts for C–C bond forma-
tion reactions.4 Homogeneous palladium catalysis possesses
many merits, such as high reaction rate, high turnover number,
and efficient selectivity.5,6 However, one of the great drawbacks
of such catalysis is that the products might be contaminated by
metal leaching.7 Moreover, homogenous Pd catalysts used in
these reactions need tedious and time-consuming work-up
procedures associated within efficient recycling. A heteroge-
neous Pd-catalyst can solve these problems very efficiently
because these heterogeneous systems are easy to handle,
recover and are “green” processes, and thus supported Pd-
catalysts can offer high activity and selectivity in the C–C
coupling reactions.8–11 Very recently, magnetic nanoparticles
have emerged as viable alternatives to conventional materials as
robust, readily available, high surface area heterogeneous
catalyst supports.12 On the other hand, the Heck and Suzuki
reactions are performed mostly in organic solvents. In order to
As it was difficult to use magnetic nanoparticles directly,
surface modication with active groups was usually required for
further applications.13 Carboxyl and primary amino groups are
the most attractive functional groups, which were especially
suitable for the immobilization of Pd nanoparticles. In partic-
ular, much attention has been focused on functionalized
magnetic nanoparticles since aer the functionalization the
magnetic nanoparticles can be against aggregation without
disturbing their desirable properties and also recognized to
increase their catalytic activity.14–20 Unfortunately, most of the
conventional functionalized methods require long reaction
times, toxic solvents and tedious synthetic steps. Therefore,
developing a simple and facile approach to obtain functional-
ized magnetic nanoparticles with a good dispersibility is highly
desirable.
To address this problem, we introduce a simple and facile
one-pot solvothermal synthesis of highly water-dispersible
magnetic nanoparticles, end-functionalized with amino and
carboxyl groups. L-dopa was used both as a surfactant and an
interparticle linker, due to it being both economical and envi-
ronment-friendly.13 L-dopa is widely used in therapeutics;
therefore, they might be non-toxic and considered as excellent
candidates for synthesizing functionalization of magnetic
supporters. Herein, we report a one-pot, template-free synthesis
of an end-functionalized with amino and carboxyl groups,
magnetically recyclable and highly active Pd catalyst, and its
application in Suzuki and Heck reactions in water.
aState Key Laboratory of Applied Organic Chemistry, Gansu Provincial Engineering
Laboratory for Chemical Catalysis and College of Chemistry Chemical Engineering,
Lanzhou University, Lanzhou, 730000, P. R. China. E-mail: majiantai@lzu.edu.cn;
Fax: +86-0931-891-2582; Tel: +86-931-891-2311
bPetroChina, Lanzhou Perto Chemical Company, P. R. China. E-mail: wfshan@
petrochina.com.cn; Fax: +86-931-7561499; Tel: +86-931-7936028
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4ra04189e
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For the 1H NMR spectra, aer the organic fraction was dried
over MgSO4, the solvent was evaporated under reduced pres-
sure. The resultant residual was chromatographed on silica gel
(hexane/ethyl acetate) to give a pure product.21
2 Experimental
2.1 Characterization
XRD measurement was performed on a Rigaku D/max-2400
diffractometer using Cu-Ka radiation as the X-ray source in
the 2q range of 20ꢀ–90ꢀ. The size and morphology of the
magnetic nanoparticles were observed by a Tecnai G2 F30
transmission electron microscopy and samples were obtained
by placing a drop of a colloidal solution onto a copper grid and
evaporated in air at room temperature. Magnetic measurement
of Fe3O4, Fe3O4-L-dopa and Fe3O4-L-dopa-Pd0 was investigated
with a Quantum Design vibrating sample magnetometer (VSM)
at room temperature in an applied magnetic eld sweeping
from 15 to 15 kOe.
2.5 General procedure for Heck reaction in water
For the Heck coupling reactions, 0.5 mmol of the aryl halides,
0.75 mmol of styrene or acrylic acid, and 1.5 mmol of K2CO3
were taken into 5 mL of water. The amount of catalyst used in
each reaction was 1.5 mmol% (based on Aryl halide), and the
ꢀ
reaction mixture was at 90 C. The reaction process was moni-
tored by thin layer chromatography (TLC). Aer completion of
the reaction, the mixture was cooled to room temperature,
separated by magnetic decantation, the resultant residual
mixture diluted with 20 mL water, followed by extraction twice
(2 ꢁ 15 mL) with ethyl acetate (for the substrates containing
–COOH, the solution was diluted with water, acidied with 1
mol Lꢂ1 HCl and then extraction with ethyl acetate). The organic
fraction was dried over MgSO4, and an aliquot was taken with a
syringe and subjected to GC or GC-MS analysis. Yields were
calculated against the consumption of aryl halides.
2.2 Synthesis of the L-dopa modied magnetic nanoparticles
Typically, FeCl3 (0.973 g) was dissolved in ethylene glycol (30
mL) to form a clear solution, followed by the addition of NaOAc
(3.260 g) and L-dopa (0.2 g). The mixture was stirred vigorously
for 30 min, and then sealed in a Teon-lined stainless-steel
autoclave (50 mL capacity). Then, the autoclave was heated to
and maintained at 200 ꢀC for 12 h, and allowed to cool to room
temperature. The black products were washed several times
For the 1H NMR spectra, aer the organic fraction was dried
over MgSO4, the solvent was evaporated under reduced pres-
sure. Crude product was isolated and repeatedly re-crystallized
from ethyl acetate–hexane mixture to obtain compounds having
sufficient purity for further characterization purposes.22
ꢀ
with ethanol and dried at 50 C for 24 h.
2.3 Loading of Pd on L-dopa functionalized magnetic
nanoparticles (Fe3O4-L-dopa-Pd0)
3 Result and discussions
Catalyst preparation and characterization
500 mg of as-synthesised Fe3O4 samples were rst dispersed in a
50 mL ethanol solution with ultrasonication for 0.5 h. The
formed black suspension was ultrasonically mixed with 3.0 mM
of a PdCl2 solution for 1 h, and then an excess of 0.01 M NaBH4
solution was slowly dropped into the above mixture with
vigorous stirring. Aer 6 h of reduction, the products were
obtained with the help of a magnet, washed thoroughly with
deionized water and then dried in a vacuum at room tempera-
ture overnight. The loading level of Pd in Fe3O4-L-dopa-Pd0
catalyst was measured to be 5.31% by AAS.
The process for the preparation of the catalyst Fe3O4-L-dopa-Pd0
is schematically described in Scheme 1. First, L-dopa-
functionalized magnetite nanoparticles were synthesized by a
facile one-pot solvothermal synthetic strategy. Second, Pd0
nanoparticles were immobilized on L-dopa-functionalized
magnetic nanoparticles through the reduction of PdCl2 by
NaBH4 with the assistance of intense agitation. Briey,
magnetite particles were rst prepared by a one-pot method and
then immobilized Pd0 on the surface of the magnetite nano-
particles (amine groups on the surface of nanoparticles act as a
2.4 General procedure for Suzuki reaction in water
In air, aryl halide (0.5 mmol), arylboronic acid (0.75 mmol), robust anchor and avoid Pd leaching).
K2CO3 (1.0 mmol), 5 mL of distilled water, the Fe3O4-L-dopa-Pd0
Fig. 1a shows the typical TEM image of Fe3O4-L-dopa nano-
catalyst (Pd 1 mol% based on Aryl halide) were combined in a 10 particles prepared by the versatile solvothermal reaction. As can
mL round-bottomed ask. The reaction mixture was magneti- be seen from the TEM (Fig. 1a and b) images indicated that the
cally stirred and the temperature was maintained at 80 ꢀC in an Fe3O4 modied with L-dopa were highly dispersed with a
oil bath. The reaction process was monitored by thin layer spherical shape and a nearly uniform size of approximately 350
chromatography (TLC). Aer completion of the reaction, the nm in diameter. The TEM image in Fig. 1c shows that the Fe3O4-
mixture was cooled to room temperature and separated by L-dopa-Pd0 catalyst did not change considerably aer attach-
magnetic decantation, the resultant residual mixture diluted ment of the palladium onto the surface of the magnetic nano-
with 10 mL ethyl acetate. The organic fraction was dried over particles. From Fig. 1d it can also be concluded that the
MgSO4, and an aliquot was taken with a syringe and subjected palladium particle sized is centered at 10 nm.
to GC or GC-MS analysis. Yields were calculated against the
Unambiguous evidence of palladium particles on Fe3O4-L-
consumption of aryl halides. Aer the rst cycle of the reaction, dopa is provided via X-ray powder diffraction analysis (XRD). In
the catalyst was recovered with the help of a magnet, succes- Fig. 2b, the characteristic diffraction peaks in the samples at 2q
sively rinsed with ethanol and distilled water (to remove excess of 30.2ꢀ, 35.5ꢀ, 43.3ꢀ, 53.8ꢀ, 57.2ꢀ, and 62.8ꢀ correspond to the
of base) and dried at room temperature ready for the next cycle. diffraction of (220), (311), (400), (422), (511), and (440) of the
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Fe3O4. All the diffraction peaks match with the magnetic cubic
structure of Fe3O4 (JCPDS 65-3107),23 and the sharp and strong
peaks conrm the products are well crystallized. Fig. 2a shows
that apart from the original peaks, the appearance of the new
peaks at 2q ¼ 40.1ꢀ, 46.5ꢀ and 68.0ꢀ are attributed to the Pd
species. The results from XRD indicate that the Pd nano-
particles have been successfully immobilized onto the surface
of the magnetic nanoparticles. According to the Debye–Scherrer
formula, the nanocrystal size of magnetite particles was calcu-
lated to be 10.1 nm, in good agreement with the TEM
observations.
Fig. 3 presents XPS elemental survey scans of the surface of
theFe3O4-L-dopa-Pd0 catalyst. Peaks corresponding to oxygen,
carbon, nitrogen, palladium and iron are clearly observed. To
establish the oxidation state of Pd in Fe3O4-L-dopa-Pd, XPS
analysis was conducted, and the result is shown in Fig. 2b. The
binding energy of Pd 3d5/2 and 3d3/2 for the fresh Fe3O4-L-
dopa-Pd is found to be 336 and 341 eV (Fig. 2b), indicating that
the loaded palladium is in its 0 state.
Scheme
1 Preparation of Fe3O4-L-dopa functionalized magnetic
nanoparticles and Fe3O4-L-dopa-Pd0 catalyst.
The FT-IR spectra of (a) Fe3O4 (b) Fe3O4-L-dopa and (c) Fe3O4-
L-dopa-Pd0 are shown in Fig. 4. In Fig. 4, the band at 585 cmꢂ1
can be attributed to Fe–O stretching vibration. In Fig. 4b, the
absorption bands at 1617, 1469, and 878 cmꢂ1 associated with
amine and 1638, 1415 cmꢂ1 associated with carboxylate,
Fig. 1 TEM images of (a) Fe3O4-L-dopa (b) The HRTEM image of
Fe3O4-L-dopa (c) Fe3O4-L-dopa-Pd0 (d) The HRTEM image of Fe3O4-
L-dopa-Pd0.
Fig. 3 XPS spectrum of the Fe3O4-L-dopa-Pd showing Pd 3d5/2 and
Pd 3d3/2 binding energies.
Fig. 4 FT-IR spectra of (a) Fe3O4 (b) Fe3O4-L-dopa and (c) Fe3O4-L-
Fig. 2 XRD patterns of (a) Fe3O4-L-dopa-Pd0 and (b) Fe3O4-L-dopa.
dopa-Pd0.
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Table 1 Optimization of the reaction conditionsa
indicating that plenty of L-dopa molecules are immobilized on
the surface of the nanoparticles. The IR spectrum of the Fe3O4-L-
dopa-Pd0 catalyst (in Fig. 4c) demonstrates that almost no
change occurs aer immobilization of palladium on the
magnetite nanoparticle surface.
The magnetic property of magnetic nanoparticles were
investigated with a vibrating sample magnetometer (VSM) at
room temperature. The hysteresis loops of Fe3O4-L-dopa and
Fe3O4-L-dopa-Pd0. As shown in Fig. 5, magnetization curves
revealed the superparamagnetic behaviour of the magnetic
nanoparticles and the magnetic saturation values of these are
76 and 66 emu gꢂ1, respectively. The decrease of the saturation
magnetization suggests the presence of some palladium parti-
cles on the surface of the magnetic supports. Even with this
reduction in the saturation magnetization, the nanomaterials
still could be efficiently separated from the solution by placing a
magnet near the vessels (shown in the inset of Fig. 5).
Entry
Base
Solvent
Time
T/ꢀC
Yieldb (%)
1
2
3
4
5
6
7
K2CO3
K2CO3
K2CO3
NaOAc
NaOH
KOH
Water
Water
Water
Water
Water
Water
Water
50 min
50 min
50 min
50 min
50 min
50 min
50 min
60
70
80
70
70
70
70
70
99
98
20
87
60
76
K3PO4
a
The reaction was carried out with 0.5 mmol of iodobenzene, 0.7 mmol
of phenylboronic acids, 1 mmol of K2CO3, 1 mol% of catalyst and water
(5 mL). b Determined by GC or GC-MS.
Aer the successful preparation of Fe3O4-L-dopa/Pd0, its
effectiveness for the Suzuki coupling reaction was examined
next. As is well known, the Suzuki reaction is largely effected by
the type of alkaline and the temperature. Therefore, rstly, the
reaction of iodobenzene with phenylboronic acid was used as a
model reaction for the screening of bases, and the results were
summarized in Table 1 (entry 2, 4–7). With the temperature
arylboronic acid, and the results are shown in Table 1. With
iodobenzene and 4-iodoacetophenone as the reactants, the
reaction nished within y minutes, the yields of the corre-
sponding coupling products were 99% and 97% (Table 2 entry 1
and 3). However, when the 2-iodoaniline reacted with phenyl-
boronic acids, the reaction time must be extended to 2 h, and
the yield was 96%. The substituted bromobenzenes, such as
4-NO2, 4-COCH3 also afforded satisfactory yields (90–99%) react
with phenylboronic acids or 4-methylphenylboronic acid (Table
2 entry 10–13) within a little time. Comparing the reactions
of bromobenzenes with strong electron-withdrawing, aryl
ꢀ
xed as 70 C, the reaction proceeded very well (yield is 99%)
when the inorganic base K2CO3 was used. By comparison,
NaOH, a stronger inorganic base, was less effective for the
reaction (entry 5). As K2CO3 was the most efficient base for the
present catalytic system, it was chosen for subsequent investi-
gations. Further experimentsꢀ showed that when the tempera-
ture increased from 60 to 70 C, the yield of product increased
from 70 to 99% (entry 1–2). On the other hand, when the
temperature was 80 ꢀC, the yield of product did not increase
(entry 3). Therefore, the optimized reaction conditions are: 70
ꢀC, water, and K2CO3.
Table 2 Suzuki coupling reaction of various aryl halide with arylbor-
onic acids in the presence of the Fe3O4/L-Dopa/Pd0 catalysta
With the optimized reaction conditions in hand, the scope of
the Fe3O4-L-dopa-Pd0 catalyzed Suzuki reactions was investi-
gated by employing various substituted aryl halides to react with
Entry
R1
X
R2
T
Yieldb (%)
1
2
3
4
5
6
7
8
H
I
I
I
H
H
H
H
H
H
H
H
H
H
H
CH3
H
50 min
2 h
15 min
9 h
9 h
9 h
9 h
9 h
9 h
9 h
60 min
75 min
60 min
75 min
20 h
99
96
97
97
60
90
85
88
51
98
99
98
94
90
77
o-NH2
4-COCH3
H
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Cl
2-NH2
4-CH3
m-CH3
4-OCH3
o-NO2
o-NO2
4-COCH3
4-COCH3
4-NO2
4-NO2
-H
9
9c
10
11
12
13
14
CH3
H
a
The reaction was carried out with 0.5 mmol of arylhalides, 0.7 mmol of
phenylboronic acids or 4-methylphenylboronic acid, 1 mmol of K2CO3,
1 mol% of catalyst and water (5 mL). b Determined by GC or GC-MS and
1H NMR. c TBAB (1 mmol).
Fig. 5 Room temperature magnetization curves of (a) Fe3O4-L-dopa
and (b) Fe3O4-L-dopa-Pd0.
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bromides bearing strong electron donating groups, such as 4-
CH3, 4-OCH3, needed a relatively longer time to obtain a
moderate yield (Table 2 entry 4, 6 and 8). The yield was a little
lower (60%) when 4-bromoaniline was used as the substrate
(entry 5). On the other hand, in the same time, 4-bromotoluene
(90%) afforded a higher yield than 3-bromotoluene (85%).
Interestingly, the Suzuki reaction of 1-bromo-2-nitrobenzene
with phenylboronic acid proceeded poorly under the same
conditions, and only 51% yield was obtained (entry 9). However,
when TBAB was added to the reaction mixture, a satisfactory
yield of 98% was achieved (entry 9c). It is noteworthy that
chlorobenzene could also react with phenylboronic acid by the
action of 1 mol% Fe3O4-L-dopa-Pd0 to afford the coupling
product in 77% yield (entry 14), although a longer time (20 h)
was required.
Fig. 6 Recycle efficiency of Fe3O4/L-Dopa/Pd0 in Suzuki coupling
reaction between iodobenzene and phenylboronic acid.
Encouraged by the exciting results with the Suzuki reactions,
the newly prepared catalyst was applied to the Heck reaction results show that substituted aryl bromides can be easily con-
next. For this purpose, 1.5 mol% of Fe3O4/L-Dopa/Pd0 was used verted to the corresponding coupling products in high yields
for the reaction of aryl halides and styrene or acrylic acid in and it also conforms to the law of electron-withdrawing
water. Table 3 lists the results of the Heck reaction. As shown in substituents enhance the coupling product formation, while
Table 3, the Heck reaction of various aryl iodides with hydro- electron-donating groups have a negative inuence on the
ꢀ
philic acrylic acid or styrene proceeded well in water at 90 C, reaction process.
resulting in the corresponding coupling Heck products in yields
The reaction was carried out with 0.5 mmol of iodobenzene,
of 83–99% (entry 1–8). The results show that electron- 0.7 mmol of phenylboronic acids, 1 mmol of K2CO3, 1 mol% of
withdrawing substituents enhance the coupling product catalyst and water (5 mL). The recyclability of Fe3O4-L-dopa/Pd0
formation, while electron-donating groups have a negative was further investigated because the recyclability of the
inuence on the reaction process. Bromobenzene did not react heterogeneous catalyst is one of the most important issues for
with hydrophobic styrene in H2O, but when a solvent of NMP practical applications. We therefore turned attention to the
was used, the reaction took place, and a satisfactory yield of reusability of our Pd catalyst. As shown in Fig. 6, the catalyst was
93% was achieved in 8 h (entry 9 and 9c). This protocol is also recycled in the Suzuki coupling of iodobenzene with phenyl-
applicable to substituted bromobenzenes, such as 4-CH3OC, 4- boronic acids. It is worth noting that the catalyst gave a
CH3 and 4-CH3O, react with acrylic acid (entry 10–12). The complete conversion of iodobenzene, and over 93% yield was
achieved within 50 min under each cycle and without a signif-
icant loss of activity. Furthermore, the catalyst could be easily
Table 3 Heck coupling reaction of various aryl halide with styrene or separated magnetically from the reaction mixture, washed three
acrylic acid in the presence of the Fe3O4/L-Dopa/Pd0 catalysta
times with ethanol and nally dried for the next run. The results
further conrmed the high recyclability of Fe3O4-L-dopa/Pd0.
The weight percentage of Pd in the HMMS-SH-Pd, as deter-
mined by atomic absorption spectroscopic (AAS) analysis, was
5.31 wt% before and 4.73% aer ve cycles.
Entry
R1
X
R2
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
H
I
I
I
I
I
I
I
I
Br
Br
Br
Br
Br
Ph
Ph
Ph
Ph
COOH
COOH
COOH
COOH
Ph
12
10
12
12
12
12
12
12
12
8
97
>99
85
83
98
99
92
89
Trace
93
4-CH3CO
4-CH3
4-CH3O
H
4-CH3CO
4-CH3
4-CH3O
4-CH3CO
4-CH3CO
4-CH3CO
4-CH3
4 Conclusion
In summary, a nanosized water-dispersible heterogeneous Pd
catalyst has been developed by immobilizing Pd0 onto the
Fe3O4-L-dopo magnetic nanoparticles. In this system, the
magnetite nanomaterials play two important roles: one is in
increasing the stability and water-dispersible of the nano-
particles because of their surface amino and carboxyl groups,
and the other in supporting Pd by means of coordination. On
the basis of the above-mentioned reasons, the catalyst revealed
high efficiency and high stability under the reaction conditions
and during recycling stages. The newly prepared catalyst was
successfully applied to Suzuki and Heck reactions in water with
the fascinating nature of both a high activity and durability.
9
9c
10
11
12
Ph
COOH
COOH
COOH
12
12
12
95
85
82
4-CH3O
a
Reaction conditions: aryl halide (0.5 mmol), vinyl substrates (1 mmol),
Fe3O4/L-Dopa/Pd0 (1.5 mol%), K2CO3 (3 mmol), Water (5 mL) and argon
atmosphere. b Determined by GC or GC-MS and 1H NMR. c Reaction in
NMP.
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10 (a) N. Erathodiyil, S. Ooi, A. M. Seayad, Y. Han, S. S. Lee and
J. Y. Ying, Chem.–Eur. J., 2008, 14, 3118; (b) B. Karimi,
S. Abedi, J. H. Clark and V. Budarin, Angew. Chem., Int. Ed.,
2006, 45, 4776; (c) T. Mallat and A. Baiker, Chem. Rev.,
2004, 104, 3037; (d) H. Wu, Q. Zhang and Y. Wang, Adv.
Synth. Catal., 2005, 347, 1356.
Acknowledgements
The authors are grateful to the Key Laboratory of Nonferrous
Metals Chemistry and Resources Utilization, Gansu Province for
nancial support.
11 (a) T. Matsumoto, M. Ueno, N. Wang and S. Kobayashi,
Chem.–Asian J., 2008, 3, 196; (b) J. Shin, J. Bertoia,
K. R. Czerwinski and C. Bae, Green Chem., 2009, 11, 1576.
References
1 (a) M. M. Dell'Anna, M. Gagliardi, P. Mastrorilli,
G. P. Surannaand and C. F. Nobile, J. Mol. Catal. A: Chem.,
2000, 158, 515; (b) A. J. Amaliand and R. K. Rana, Chem.
Commun., 2008, 4165; (c) N. Erathodiyil, S. Ooi,
A. M. Seayad, Y. Han, S. S. Lee and J. Y. Ying, Chem.–Eur.
J., 2008, 14, 3118.
¨
12 (a) S. Shylesh, V. Schunemann and W. R. Thiel, Angew.
Chem., Int. Ed., 2010, 49, 3428; (b) U. Laska, C. G. Frost,
G. J. Price and P. K. Plucinski, J. Catal., 2009, 268, 318; (c)
R. B. Nasir Baig and R. S. Varma, Chem. Commun., 2012,
48, 2582.
2 (a) K. C. Nicolaou, A. L. Nold, R. R. Milburn, C. S. Schindler,
K. P. Cole and J. Yamaguchi, J. Am. Chem. Soc., 2007, 129,
1760; (b) F. Zhao, K. Murakami, M. Shirai and M. Arai, J.
Catal., 2000, 194, 479; (c) A. Biffis, M. Zecca and M. Basato,
J. Mol. Catal. A: Chem., 2001, 173–249; (d) L. Yin and
J. Liebscher, Chem. Rev., 2007, 107, 133.
13 H. Zhu, C. Hou, Y. J. Li, G. H. Zhao, X. Liu, K. Hou and
Y. F. Li, Chem.–Asian J., 2013, 8, 1447–1454.
14 (a) S. Mandal, D. Roy, R. V. Chaudhari and M. Sastry, Chem.
Mater., 2004, 16, 3714; (b) M. A. White, J. A. Johnson,
J. T. Koberstein and N. J. Turro, J. Am. Chem. Soc., 2006,
128, 11356.
3 (a) A. Fihri, M. bouhrara, B. Nekoueisharki, J. M. Basset and
V. Polshettiwar, Chem. Soc. Rev., 2011, 40, 5181; (b)
15 (a) D. Guin, B. Baruwati and S. V. Manorama, Org. Lett., 2007,
9, 1419; (b) L. N. Lewis, Chem. Rev., 1993, 93, 2693.
16 (a) J. Alvarez, J. Liu, E. Roman and A. E. Kaifer, Chem.
Commun., 2000, 1151; (b) R. M. Crooks, M. Q. Zhao,
L. Sun, V. Chechik and L. K. Yeung, Acc. Chem. Res., 2001,
34, 181.
´
A. Molnar, Chem. Rev., 2011, 111, 2251–2320; (c) A. Balanta,
C. Godard and C. Claver, Chem. Soc. Rev., 2011, 40, 4973–4985.
4 A. Modak, J. Mondal, M. Sasidharan and A. Bhaumik, Green
Chem., 2011, 13, 1317.
5 (a) M. Beller, Chem. Ing. Tech., 2006, 78, 1061; (b) N. Selander
17 (a) R. S. Underhill and G. J. Liu, Chem. Mater., 2000, 12, 3633;
(b) D. K. Yi, S. S. Lee and J. Y. Ying, Chem. Mater., 2006, 18,
2459.
18 (a) Y. Li and M. A. El-Sayed, J. Phys. Chem. B, 2001, 105, 8938.
19 (a) R. Abu-Reziq, D. Wang, M. Post and H. Alper, Chem.
Mater., 2008, 20, 2544.
¨
and K. J. Szabo, Chem. Rev., 2011, 111, 2048.
6 (a) C. E. Tucker and J. G. De Vries, Top. Catal., 2002, 19, 111;
(b) B. M. Bhanage and M. Arai, Catal. Rev.: Sci. Eng., 2001, 43,
315.
7 M. Cao, Y. Wei, S. Y. Gao and R. Cao, Catal. Sci. Technol.,
2012, 2, 156–163.
¨
¨
20 (a) A. F. Thunemann, D. Schutt, L. Kaufner, U. Pison and
´
´
´
8 (a) A. Corma, P. Concepcion, I. Domınguez, V. Forne and
M. J. Sabater, J. Catal., 2007, 251, 39; (b) B. M. Choudary,
S. Madhi, N. S. Chowdari, M. L. Kantam and B. Sreedhar, J.
Am. Chem. Soc., 2002, 124, 14127; (c) M. J. Jacinto,
O. H. C. F. Santos, R. F. Jardim, R. Landers and
L. M. Rossi, Appl. Catal., A, 2009, 2, 117.
¨
H. Mohwald, Langmuir, 2006, 22, 2351; (b) A. J. Amali and
R. K. Rana, Chem. Commun., 2008, 4165.
21 J. H. Yang, D. F. Wang, W. D. Liu, X. Zhang, F. L. Bian and
W. Yu, Green Chem., 2013, 15, 3429–3437.
22 A. Modak, J. Mondal, M. Sasidharan and A. Bhaumik, Green
Chem., 2011, 13, 1317.
9 (a) G. Wei, W. Zhang, F. Wen, Y. Wang and M. Zhang, J. Phys.
Chem. C, 2008, 112, 10827; (b) N. Jamwal, M. Gupta and
S. Paul, Green Chem., 2008, 10, 999; (c) H. Yang, L. Zhang,
P. Wang, Q. Yang and C. Li, Green Chem., 2009, 11, 257.
23 J.-Q. Wan, W. Cai, J.-T. Feng, X.-X. Meng and E.-Z. Liu, J.
Mater. Chem., 2007, 17, 1188–1192.
37766 | RSC Adv., 2014, 4, 37761–37766
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