Preparation of recoverable Fe3O4@PANI-PdII core/shell catalysts for Suzuki carbonylative cross-coupling reactions

Article abstract of DOI:10.1039/c4nj00697f

We report on the synthesis, characterization and catalytic performance of a palladium-based superparamagnetic catalyst of Fe₃O ₄@polyaniline core/shell microspheres (Fe₃O ₄@PANI-Pd^II). The material was characterized by TEM, FT-IR, vibrating sample magnetometry (VSM), XRD, and XPS. The catalyst showed high activity for the carbonylative cross-coupling reaction of aryl iodide with arylboronic acid. Moreover it could selectively reduce the formation of a direct-coupling product. The newly developed catalyst could be recovered from the liquid phase easily by magnetic separation and recycled 5 times without any significant loss of activity. the Partner Organisations 2014.

Full text of DOI:10.1039/c4nj00697f

NJC
View Article Online
View Journal | View Issue
PAPER
Preparation of recoverable Fe3O4@PANI–PdII
core/shell catalysts for Suzuki carbonylative
cross-coupling reactions†
Cite this: New J. Chem., 2014,
38, 4622
Xiaohang Zhu, Jianrui Niu, Fengwei Zhang, Jinghui Zhou, Xinzhe Li and Jiantai Ma*
We report on the synthesis, characterization and catalytic performance of
a palladium-based
superparamagnetic catalyst of Fe3O4@polyaniline core/shell microspheres (Fe3O4@PANI–PdII). The
material was characterized by TEM, FT-IR, vibrating sample magnetometry (VSM), XRD, and XPS. The
catalyst showed high activity for the carbonylative cross-coupling reaction of aryl iodide with
arylboronic acid. Moreover it could selectively reduce the formation of a direct-coupling product. The
newly developed catalyst could be recovered from the liquid phase easily by magnetic separation and
recycled 5 times without any significant loss of activity.
Received (in Porto Alegre, Brazil)
30th April 2014,
Accepted 8th July 2014
DOI: 10.1039/c4nj00697f
www.rsc.org/njc
palladium complexes as catalysts for Suzuki carbonylative coupling
Introduction
reactions. Cai et al. used MCM-41–2P–PdII (ref. 7) and MCM-41–
Synthesis of biaryl and heteroaryl carbonyl compounds has 2N–PdII (ref. 8) as catalysts for Suzuki carbonylative coupling
attracted considerable interest, as these compounds are important reactions. Bhanage et al.4b used Pd/C as a catalyst for Suzuki
moieties in many biologically active molecules, natural products, carbonylative coupling reactions. In order to improve recyclability,
and pharmaceuticals.1 One general approach for the synthesis of we have immobilized Pd complexes on silica-coated magnetic
biaryl ketones is the Friedel–Crafts acylation of substituted aromatic nanoparticles (Fe3O4@SiO2–SH–PdII) to catalyze Suzuki carbonylative
rings.2 However, Friedel–Crafts acylation has the disadvantage of coupling reactions, so that the catalyst (Fe3O4@SiO2–SH–PdII) could
using Lewis acid, which is reactive towards many functional be separated from the mother solutions by applying an external
groups, and the regioselectivity is untunable. Another direct and magnetic field.9
convenient approach is transition metal-catalyzed three-component
Core–shell structured superparamagnetic iron oxide hybrid
cross-coupling reaction among aryl metals (Mg, Al, Si, Sn, and Zn), nanoparticles have attracted increasing interest, as coatings can
carbon monoxide, and aryl electrophiles.3 But the generation of a stabilize magnetic nanoparticles, leading to better dispersion and
direct-coupling by-product without insertion of carbon monoxide is biocompatibility, and can also be further modified with functional
unavoidable. Among carbonylative cross-coupling reactions, Suzuki groups for diverse applications.10 Most of the magnetic core–shell
carbonylative coupling reaction is one of the most promising routes composite materials were prepared by coating Fe3O4 particles with
for the direct synthesis of biaryl ketones from carbon monoxide, as functional shells.11 Among these shell materials, polyaniline (PANI)
aryl halides and arylboronic acids with various functionalities can has received more attention for its application prospects in many
be tolerated on either partner and arylboronic acids are generally fields because of its high stability in air, solubility in various solvents,
nontoxic and thermally-, air- and moisture-stable.4
and its unique electrical properties.12 Recently, Fe3O4@PANI nano-
Many palladium-based homogeneous catalysts, such as composites have been developed intensively. Wan et al.13 reported a
5
Pd(tmhd)2/Pd(OAc)2,1a Pd2(dba)3,1b Pd(PPh3)4 and N-heterocyclic series of PANI composites containing nanomagnets prepared by
carbene palladium,6 showed good activity in carbonylative cross- chemical polymerization. Deng et al.14 reported the synthesis
coupling reactions. However, the problem is that homogeneous of PANI/Fe3O4 nanoparticles with core–shell structure via in situ
catalysts are difficult to separate from products and catalytic polymerization of aniline monomers in aqueous solution, which
media, which limits their commercial development and practical contained Fe3O4 nanoparticles and surfactants. The fabrication
use. Thus, much research interest is focused on heterogeneous of nanoscale ferromagnetic Fe3O4-cross-linked PANI by oxidative
polymerization of aniline with ammonium peroxodisulfate as
the oxidant was reported by Peng et al.12a All Fe3O4 nanoparticles
used in these studies have average diameters less than 10 nm.
College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou,
China. E-mail: majiantai@lzu.edu.cn
Unfortunately, these materials showed poor magnetic response
due to the relatively low mass fraction of Fe3O4.15
† Electronic supplementary information (ESI) available. See DOI: 10.1039/
c4nj00697f
4622 | New J. Chem., 2014, 38, 4622--4627
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
Paper
NJC
In this paper, we report on the synthesis of a high super- Loading of Pd on Fe3O4@PANI microspheres (Fe3O4@PANI–PdII)
paramagnetic catalyst Fe3O4@PANI–PdII with well-defined mor-
The as-synthesised Fe3O4@PANI microspheres (300 mg) were first
phology. The superparamagnetic Fe3O4@PANI microspheres have
dispersed in ethanol solution (100 mL) under ultrasonication for
been synthesised via a simple in situ surface polymerization
0.5 h. The formed black suspension was ultrasonically mixed with
method. PdII can adhere strongly and disperse uniformly on the
31 mg of PdCl2 (0.174 mmol) dispersed in deionized water. After
surface of Fe3O4@PANI microspheres due to the covalent bonding
the mixture was stirred at room temperature for 24 h, the resulting
between PdII and amino groups of PANI shells. Furthermore, the
precipitates were then thoroughly rinsed with deionized water and
ethanol, and then vacuum dried at 60 1C overnight. The weight
PANI shells improved the dispersibility of the microspheres in
percentage of Pd in Fe3O4@PANI–PdII, as determined by atomic
aromatic solution. Meanwhile, aromatic reactants can access active
sites easily because of the existence of p–p conjugation between the
absorption spectroscopic (AAS) analysis, was 4.8 wt%.
PANI shell and aromatic compounds. Fe3O4@PANI–PdII was used
to catalyze Suzuki carbonylative coupling reaction under mild
conditions.
Typical procedure for the Suzuki carbonylative coupling
reaction
A mixture of aryl iodide (0.5 mmol), arylboronic acid (0.6 mmol),
K2CO3 (1.5 mmol), and 1 mol% palladium catalyst in anisole
(5 mL) was stirred at 80 1C under 1 atm pressure of CO. After
the reaction, the mixture was cooled down to room tempera-
ture, separated by magnetic decantation, and the resultant
residual mixture was diluted with 10 mL of H2O, followed by
extraction with ethyl acetate (2 Â 10 mL). The organic fraction
was dried with MgSO4, the solvents were evaporated under
reduced pressure and the residue was redissolved in 5 mL of
ethanol. An aliquot was taken using a syringe and subjected to
GC analysis. Yields were calculated against the consumption of
the aryl iodides.
Experimental section
Materials
Ferric chloride hexahydrate (FeCl3Á6H2O), anhydrous sodium acetate,
ethylene glycol, aniline, ammonium peroxodisulfate (APS), poly-
(vinylpyrrolidone) (PVP), and 3-aminopropyltriethoxysilane (APTES)
were purchased from Sinopharm Chemical Reagent Co., Ltd. All
chemicals were of analytical grade and used as received without
further purification.
Synthesis and chemical modification of Fe3O4 particles
Characterization
The magnetic Fe3O4 particles were synthesized via solvothermal
reaction. Typically, FeCl3Á6H2O (1.35 g) and sodium acetate (3.6 g)
were dissolved in ethylene glycol (40 mL). The obtained homo-
geneous yellow solution was transferred to a Teflon-lined stainless-
steel autoclave and sealed to heat at 200 1C. After reaction for 8 h,
the autoclave was cooled to room temperature. The obtained black
magnetite particles were washed with ethanol six times and then
dried in a vacuum at 60 1C overnight. Then Fe3O4 particles (0.2 g)
and APTES (4 mL) were dissolved in anhydrous ethanol to give a
mixed solution (50 mL). The mixture was refluxed for 12 h under
dry nitrogen. The resulting modified Fe3O4 particles were separated
and then washed with ethanol. Finally, the product was dried in a
vacuum at 60 1C for 24 h and the amine-functionalized Fe3O4
particles (NH2–Fe3O4) were obtained.
Transmission electron microscopy (TEM) images were characterized
using a Tecnai G2 F30 transmission electron microscope. FT-IR
spectra were recorded using a Nicolet NEXUS 670. Magnetic
measurements of samples were performed using a vibrating
sample magnetometer (Lake Shore 7304) at room temperature.
X-ray-diffraction (PXRD) measurements were performed on a
Rigaku D/max-2400 diffractometer using Cu-Ka radiation as
the X-ray source in the 2y range of 101–801. X-ray photoelectron
spectroscopy (XPS) was recorded on a PHI-5702 instrument and
the C1S line at 292.1 eV was used as the binding energy reference.
Results and discussion
Catalyst preparation and characterization
The process of preparation of the catalyst Fe3O4@PANI–PdII is
schematically described in Scheme 1. Firstly, Fe3O4 particles
Synthesis of Fe3O4@PANI microspheres
The Fe3O4@PANI microspheres were prepared by the in situ surface were prepared by the method given in a previous report.17
polymerization method in the presence of PVP.16 Briefly, PVP (0.3 g) Secondly, Fe3O4 particles were modified with amine groups to
was dissolved in deionized water (600 mL), then the NH2–Fe3O4 enhance the growth of PANI. Afterwards, Fe3O4@PANI spheres
particles (0.09 g) were added. The mixture was ultrasonically dis- were prepared by in situ polymerization of aniline on the
persed. After that, aniline (0.12 mL) and HCl (0.6 mL) were added surface of Fe3O4 particles in the presence of PVP. Finally, PdCl2
into the mixture with vigorous stirring. After the mixture was stirred was anchored onto the surface of Fe3O4@PANI to afford the
for 30 min, an aqueous solution (120 mL) of APS (1.2 g) was added catalyst Fe3O4@PANI–PdII.
into the above mixture instantly to start the oxidative polymerization.
The typical TEM image of Fe3O4@PANI microspheres prepared
The reaction was performed under stirring for 3 h. The resulting by the in situ surface polymerization method at room temperature
precipitates were washed with deionized water and ethanol several is shown in Fig. 1a. The average diameter of the as-synthesized
times. Finally, the product was dried in a vacuum at 60 1C for 24 h to spherical particles was about 240 nm. A continuous layer of PANI
obtain the desired Fe3O4@PANI microspheres.
could be observed on the outer shell of the Fe3O4 microsphere
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 4622--4627 | 4623

View Article Online
NJC
Paper
Scheme 1 Preparation of Fe3O4@PANI–PdII.
Fig. 3 The magnetization curves of (a) Fe3O4, (b) Fe3O4@PANI, and
(c) Fe3O4@PANI–PdII.
Fe3O4@PANI–PdII (Fig. 2b) was similar to that of Fe3O4@PANI,
but the C–N stretching frequency shifted to a lower frequency
(around 1290 cmÀ1), which was probably caused by N bonded to
electron-deficient Pd to form the Pd complex.18
Fig. 1 TEM images of (a), (b) Fe3O4@PANI, and (c) Fe3O4@PANI–PdII.
cores and the thickness of the PANI shell was about 22 nm. The
resultant Fe3O4@PANI composites had good dispersibility and
spherical morphology. The TEM image of Fe3O4@PANI (Fig. 1b)
clearly showed that the magnetite particles were composed of
plentiful nanocrystals with the size of about 16 nm. From the
TEM image of Fe3O4@PANI–PdII (Fig. 1c), it could be seen that
the morphology of Fe3O4@PANI–PdII almost remained the
same after loading PdCl2 on Fe3O4@PANI microspheres.
We also measured the Fourier transform infrared (FT-IR)
spectra of Fe3O4@PANI and Fe3O4@PANI–PdII. In the FT-IR
spectrum of Fe3O4@PANI (Fig. 2a), the characteristic peaks at
1588 (CQC stretching deformation of the quinoid and benzenoid
ring, respectively), 1306 (C–N stretching of secondary aromatic
amine), 1150, and 827 cmÀ1 (out of plane deformation of C–H
in the 1,4-disubstituted benzene ring) showed that aniline was
successfully polymerized onto the Fe3O4 core. The bands at 574
and 3435 cmÀ1 corresponded to the characteristic band of Fe–O
vibration and –OH stretching vibration.11c The FT-IR spectrum of
Magnetic measurements were performed using a vibrating
sample magnetometer at room temperature. The magnetization
curves of Fe3O4, Fe3O4@PANI and Fe3O4@PANI–PdII are compared
in Fig. 3. There was no hysteresis in the magnetization for the three
types of particles. Additionally, neither coercivity nor remanence
could be observed, which suggested that the three particles were
superparamagnetic.19 The measured saturation magnetization
values were 71.8 emu gÀ1 for Fe3O4 particles, 46.5 emu gÀ1 for
Fe3O4@PANI and 42.6 emu gÀ1 for Fe3O4@PANI–PdII. The
saturation magnetization significantly decreased after aniline
was polymerized onto Fe3O4 particles, and further decreased
slightly after loading PdCl2 on Fe3O4@PANI microspheres. However,
the prepared Fe3O4@PANI–PdII microspheres still maintained good
magnetic properties and could be completely and quickly separated
from the aqueous solution when an external magnetic force was
applied.
The XRD patterns of Fe3O4@PANI and Fe3O4@PANI–PdII are
shown in Fig. 4. The main peaks of the Fe3O4@PANI–PdII
composite were similar to Fe3O4@PANI, which revealed that
immobilizing PdCl2 on the surface of Fe3O4@PANI did not
affect the structure of Fe3O4@PANI. Both the patterns showed
strong peaks, which confirmed that the products were crystal-
lized well after the coating process under acidic conditions and
the detected diffraction peaks in every pattern could be indexed
as cubic Fe3O4 (JCPDS card No. 82-1533). According to the
Debye–Scherrer formula, the nanocrystal size of magnetite
particles was calculated to be 16.3 nm, in good agreement with
the TEM observations.
The XPS elemental survey scans of the surface of the
Fe3O4@PANI–PdII catalyst are shown in Fig. 5. Peaks corres-
ponding to oxygen, carbon, nitrogen, palladium and iron were
clearly observed. To ascertain the oxidation state of Pd, X-ray
photoelectron spectroscopy (XPS) studies were carried out. In
Fig. 6, the Pd binding energy of Fe3O4@PANI–PdII exhibited two
strong peaks centered at 342.8 and 337.5 eV, which were
Fig. 2 FT-IR spectra of (a) Fe3O4@PANI and (b) Fe3O4@PANI–PdII.
4624 | New J. Chem., 2014, 38, 4622--4627
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
Paper
NJC
The Suzuki carbonylative coupling reaction
The carbonylative cross-coupling reaction of phenylboronic
acid with 4-iodoacetophenone under an atmospheric pressure
of carbon monoxide was chosen as the model reaction, to
optimize temperature, solvent and base applied in the reaction.
The results are summarized in Table 1. At 40 and 60 1C, the
yield of the desired product was low (Table 1, entries 1 and 2).
Increasing the temperature up to 80 1C, high yield of the
desired product (95%) was obtained (Table 1, entry 3). However,
when the temperature increased to 100 1C, the yield of the
desired product (94%) did not increase (Table 1, entry 4).
Therefore, the optimum reaction temperature was 80 1C.
According to the evaluated results of solvents, anisole was
found to be the best (Table 1, entry 3). As less polar solvents,
such as anisole, dioxane, and toluene, were used in the reac-
tion, a relatively good yield of the carbonylative cross-coupling
product, 4-methoxybenzophenone, could be obtained. How-
ever, the yield of the carbonylative cross-coupling product was
relatively low in polar solvent, such as DMF, as a significant
amount of the direct coupling product, 4-methoxybiphenyl
(72%), was produced (Table 1, entry 7). The inorganic bases
used in the carbonylative Suzuki coupling reaction (Na2CO3,
K2CO3, Cs2CO3, and K3PO4) could affect the selectivity of the
products. Cs2CO3 and K3PO4 had a strong tendency to produce
the direct coupling product (Table 1, entries 9 and 10). Unfor-
tunately, Na2CO3 showed the lowest activity compared to the
other three inorganic bases (Table 1, entry 8). As a result, K2CO3
was the most efficient base. Therefore, the optimized reaction
conditions are: 80 1C, anisole, and K2CO3.
Fig. 4 XRD patterns of (a) Fe3O4@PANI and (b) Fe3O4@PANI–PdII.
To investigate the substrate scope of this carbonylative
cross-coupling reaction, a variety of arylboronic acids and aryl
iodides were investigated under optimized reaction conditions.
As shown in Table 2, the carbonylative cross-coupling reaction
could proceed smoothly under mild conditions to afford the
corresponding carbonylative coupling products in high yields,
whether using arylboronic acids and aryl iodides containing
either electron-withdrawing groups or electron-donating
Fig. 5 XPS spectrum of the elemental survey scan of Fe3O4@PANI–PdII.
Table 1 The carbonylative cross-coupling of phenylboronic acid with
4-iodoacetophenone under different conditionsa
Yieldb (%)
Entry
Solvent
Base
Temp./1C
1
2
1
2
3
4
5
6
7
8
9
10
Anisole
Anisole
Anisole
Anisole
Toluene
Dioxane
DMF
Anisole
Anisole
Anisole
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
Cs2CO3
K3PO4
40
60
80
100
80
80
80
80
80
80
21
66
95
94
55
76
24
21
48
46
21
10
2
5
8
5
72
5
23
43
Fig. 6 XPS spectrum of Fe3O4@PANI–PdII, which shows the Pd 3d5/2 and
Pd 3d3/2 binding energies.
a
The reactions were carried out using 4-iodoacetophenone (0.5 mmol),
arylboronic acid (0.6 mmol), CO (1 atm), base (1.5 mmol), solvent
assigned to Pd 3d 3/2 and Pd 3d 5/2, respectively. These values
agreed with the PdII binding energy of PdCl2.20
b
(5 mL), and 1 mol% palladium catalyst. Determined by GC.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 4622--4627 | 4625

View Article Online
NJC
Paper
Table 2 The synthesis of unsymmetrical biaryl ketonesa
Table 3 The carbonylative cross-coupling of phenylboronic acid with
4-iodoacetophenone using different catalystsa
Yieldb (%)
1
Catalyst
amount (mol%)
Time/ Temp./ Yield
Entry
R1
R2
t/h
2
Entry Catalyst
h
1C
(%)
1
2
3
4
5
6
7
8
4-CH3CO
4-CH3CO
4-CH3CO
2-NO2
2-NO2
2-NO2
H
H
6
6
6
6
6
6
8
8
8
8
8
8
8
8
8
12
12
12
95
90
92
98
97
97
97
94
97
95
92
88
95
90
87
96
98
97
2
5
3
0.7
2
0.3
3
5
1
3
4
2
2
2
2
1
1
0.6
1
2
3
4
5
6
Fe3O4@PANI–PdII
1
2
2
2
1
2
6
5
8
6
6
8
80
95
85
85
86
92
76
MCM-41–2P–PdII
Pd/Cb
80
100
80
80
100
4-CH3
4-Cl
H
4-CH3
4-Cl
H
4-CH3
4-Cl
H
4-CH3
4-Cl
H
4-CH3
4-Cl
H
4-CH3
4-Cl
MCM-41–2N–PdII
Fe3O4@SiO2–SH–PdII
ImmPd–ILc
a
b
Reaction conditions: CO (1 atm), anisole. Reaction conditions: CO
H
H
c
(200 psi), anisole. Reaction conditions: CO (1 MPa), toluene.
9
10
11
12
13
14
15
16
17
18
4-CH3
4-CH3
4-CH3
4-CH3O
4-CH3O
4-CH3O
2-NH2
2-NH2
2-NH2
The catalytic activities of heterogeneous catalysts, MCM-41–
2P–PdII,7 Pd/C,4b MCM-41–2N–PdII,8 Fe3O4@SiO2–SH–PdII,9
and ImmPd–IL,21 for Suzuki carbonylative coupling reaction
in literature are also shown in Table 3. Compared with those
heterogeneous catalysts, Fe3O4@PANI–PdII showed the highest
activity. There are two possible reasons for the high activity:
firstly, the covalent bonding between PdII and amino groups of
PANI can make PdII adhere strongly and disperse uniformly on
the surfaces of supports. Secondly, there existed p–p conjuga-
tion between the PANI shell and aromatic compounds, so
Fe3O4@PANI–PdII has good dispersibility in anisole and aro-
matic reactants can access active sites easily. The main draw-
back of Suzuki carbonylative coupling reaction is the formation
of a lot of direct-coupling products. The carbonylative cross-
coupling reaction catalyzed by Fe3O4@PANI–PdII produced only
little amounts of direct coupling product (Table 2). The route of
transmetalation without migratory insertion of carbon mon-
oxide and direct reductive elimination should account for the
formation of the direct coupling product (step 3). The p–p
conjugation between the PANI shell and the aromatic substrate
would lead to a lower reaction rate of reductive elimination. In
this case, carbon monoxide insertion occurring after transme-
talation was promoted (step 4), so only a small amount of direct
coupling products was produced.
a
The reactions were carried out using aryl iodide (0.5 mmol), arylboronic
acid (0.6 mmol), CO (1 atm), K2CO3 (1.5 mmol) and 1 mol% palladium
b
catalyst in anisole (5 mL) at 80 1C. Determined by GC.
groups (Table 2, entries 1–18). Aryl iodides substituted with
electron-withdrawing groups, such as 4-CH3CO and 2-NO2
(Table 2, entries 1–6), were found to be the most active reagents
in carbonylative cross-coupling, as high yields were obtained in
the shortest time (6 h). According to the proposed reaction
mechanism (Scheme 2), the existence of electron-withdrawing
groups could promote the oxidative addition of the organic
halide to palladium(0) (step 1). Comparing the reaction using aryl
boronic acid with the same substituent (Table 2, entries 1–18), we
found that changing the electronic properties of boronic acid would
affect the selectivity for the direct coupling products. It could be
seen that aryl boronic acid containing the electron-attracting group,
–Cl, produced the lowest yields of the direct coupling product. In
contrast, aryl boronic acid containing the electron-donating
group, –CH3, gave the highest yields of the direct coupling
product. Since transmetalation (step 2) was slow with aryl
boronic acid containing the electron-attracting group, direct
coupling was hindered. In contrast, aryl boronic acid containing
the electron-donating group could promote direct coupling.5a
Unfortunately, the derivatives of bromobenzene and bromobenzene
can not react with phenylboronic acid.
Recyclability of Fe3O4@PANI–PdII
After the first cycle of the reaction, the catalyst was recovered
successively by placing a magnet near the reaction vessel and
washed with distilled water and ethanol several times and then
dried at room temperature. As shown in Table 4, the catalyst
Table 4 The carbonylative cross-coupling reaction of 4-iodoaceto-
phenone with phenylboronic acid catalyzed by the recycled catalysta
Recycle
Catalyst cycle
Yield (%)
1
5
1
5
95
92
a
The reactions were carried out using 4-iodoacetophenone (0.5 mmol),
PhB(OH)2 (0.6 mmol), CO (1 atm), K2CO3 (1.5 mmol), and the Pd
catalyst (1 mol%) in anisole (5 mL) at 80 1C.
Scheme 2 Catalytic cycles of carbonylative cross-coupling reaction.
4626 | New J. Chem., 2014, 38, 4622--4627
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
Paper
NJC
4 (a) T. Ishiyama, H. Kizaki, T. Hayashi, A. Suzuki and N. Miyaura,
J. Org. Chem., 1998, 63, 4726–4731; (b) M. V. Khedkar,
P. J. Tambade, Z. S. Qureshi and B. M. Bhanage, Eur. J. Org.
Chem., 2010, 6981–6986.
5 (a) M. Medio-Simon, C. Mollar, N. Rodriguez and
G. Asensio, Org. Lett., 2005, 7, 4669–4672; (b) P. Prediqer,
A. V. Moro, C. W. Noqueira, L. Saveqnaqo, P. H. Menezes,
J. B. Rocha and G. Zeni, J. Org. Chem., 2006, 71, 3786–3792.
6 B. M. Okeefe, N. Simmons and S. F. Martin, Org. Lett., 2008,
10, 5301–5304.
was recycled in the carbonylative cross-coupling reactions of
4-iodoacetophenone with phenylboronic acid. Fe3O4@PANI–PdII
still maintained high activity and selectivity after being reused
for five runs. The weight percentage of Pd in the reused catalyst,
as determined by atomic absorption spectroscopic (AAS) anal-
ysis, was 3.9 wt%.
Conclusions
In summary, we have developed a novel and practical hetero-
geneous catalyst for the Suzuki carbonylative coupling reaction
under mild reaction conditions. This novel Pd catalyst exhibits
higher activity for the Suzuki carbonylative coupling reaction
than many other heterogeneous catalysts, such as MCM-41–2P–PdII,
Pd/C, MCM-41–2N–PdII, Fe3O4@SiO2–SH–PdII, and ImmPd–IL,
reported in literature. Furthermore, a significant reduction in
the formation of the direct coupling product could be observed
when Fe3O4@PANI–PdII was used to catalyze the Suzuki carbonyla-
tive coupling reaction. This catalyst can be reused five times without
significant loss in catalytic activity. In addition, the Fe3O4@PANI–PdII
catalyst avoids the use of phosphine ligands, which makes it more
environmentally friendly.
7 M. Z. Cai, G. M. Zheng, L. F. Zha and J. Peng, Eur. J. Org.
Chem., 2009, 1585–1591.
8 M. Z. Cai, J. Peng, W. Y. Hao and G. D. Ding, Green Chem.,
2011, 13, 190–196.
9 J. R. Niu, X. Huo, F. W. Zhang, H. B. Wang, P. Zhao,
W. Q. Hu, J. T. Ma and R. Li, ChemCatChem, 2013, 5, 349–354.
10 L. L. Zhou, J. Y. Yuan and Y. Wei, J. Mater. Chem., 2011, 21,
2823–2840.
11 (a) S. H. Xuan, Y. X. J. Wang, J. C. Yu and K. C. F. Leung,
Langmuir, 2009, 25, 11835–11843; (b) Y. H. Deng, Y. Cai,
Z. K. Sun, J. Liu, C. Liu, J. Wei, W. Li, C. Liu, Y. Wang and
D. Y. Zhao, J. Am. Chem. Soc., 2010, 132, 8466–8473; (c) Y. Lu,
Y. Yin, B. T. Mayers and Y. Xia, Nano Lett., 2002, 2, 183–186.
12 (a) J. Deng, X. Ding, W. Zhang, Y. Peng, J. Wang, X. Long, P. Li
and A. S. C. Chan, Polymer, 2002, 43, 2179–2184; (b) D. P. He,
C. Zeng, C. Xu, N. C. Cheng, H. G. Li, S. C. Mu and M. Pan,
Langmuir, 2011, 27, 5582–5588; (c) F. Wu, J. Chen, L. Li, T. Zhao
and R. Chen, J. Phys. Chem. C, 2011, 115, 24411–24417.
13 M. X. Wan and W. G. Li, J. Polym. Sci., Part A: Polym. Chem.,
1997, 35, 2129–2136.
Acknowledgements
The authors are grateful to the Key Laboratory of Nonferrous
Metals Chemistry and Resources Utilization, Gansu Province,
for financial support.
14 J. G. Deng, C. L. He, Y. X. Peng, J. H. Wang, X. P. Long, P. Li
and A. S. C. Chan, Synth. Met., 2003, 139, 295–299.
Notes and references
1 (a) P. J. Tambade, Y. P. Patil, A. G. Panda and B. M. Bhanage, 15 Y. H. Deng, D. W. Qi, C. H. Deng, X. G. Zhang and
Eur. J. Org. Chem., 2009, 3022–3025; (b) H. L. Li, M. Yang, D. Y. Zhao, J. Am. Chem. Soc., 2008, 130, 28–29.
Y. X. Qi and J. J. Xue, Eur. J. Org. Chem., 2011, 2662–2667; 16 S. H. Xuan, Y. X. J. Wang, K. C.-F. Leung and K. Y. Shu,
(c) N. De Kimpe, M. Keppens and G. Froncg, Chem. Com-
mun., 1996, 635–636.
2 (a) C. E. Song, W. H. Shim, E. J. Roh and J. H. Choi, Chem.
J. Phys. Chem. C, 2008, 112, 18804–18809.
17 H. Deng, X. L. Li, Q. Peng, X. Wang, J. P. Chen and Y. D. Li,
Angew. Chem., Int. Ed., 2005, 117, 2842–2845.
Commun., 2000, 1695–1696; (b) S. Gmouh, H. Yang and 18 S. Y. Wei, Z. Y. Ma, P. Wang, Z. P. Dong and J. T. Ma, J. Mol.
M. Vaultier, Org. Lett., 2003, 5, 2219–2222; (c) A. Furstner, Catal. A: Chem., 2013, 370, 175–181.
D. Voigtlander, W. Schrader, D. Giebel and M. T. Reetz, Org. 19 S. H. Xuan, L. Y. Hao, W. Q. Jiang, X. L. Gong, Y. Hu and
Lett., 2001, 3, 417–420. Z. Y. Chen, J. Magn. Magn. Mater., 2007, 308, 210–213.
3 (a) B. M. O’Keefe, N. Simmons and S. F. Martin, Tetrahedron, 20 M. Ranjbar, S. Fardindoost, S. M. Mahdavi, A. Iraji zad and
2011, 67, 4344–4351; (b) X. F. Wu, H. Neumann and M. Beller,
Adv. Synth. Catal., 2011, 353, 788–792; (c) M. Dai, B. Liang,
N. Tah-masebi Garavand, Sol. Energy Mater. Sol. Cells, 2011,
95, 2335–2340.
C. H. Wang, Z. J. You, J. Xiang, G. B. Dong, J. H. Chen and 21 M. V. Khedkar, T. Sasaki and B. M. Bhanage, RSC Adv., 2013,
Z. Yang, Adv. Synth. Catal., 2004, 346, 1669–1673. 3, 7791–7797.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 4622--4627 | 4627