Palladium supported on modified magnetic nanoparticles: A phosphine-free and heterogeneous catalyst for Suzuki and Stille reactions

Article abstract of DOI:10.1002/aoc.3409

An efficient magnetic nanoparticle-supported palladium (Fe₃O₄/SiO₂-PAP-Pd) catalyst is reported for the Suzuki cross-coupling and Stille reactions. This method provides a novel and much improved modification of the Suzuki and Stille coupling reactions in terms of phosphine-free catalyst, short reaction time, clean reaction and small quantity of catalyst. Another important feature of this method is that the catalyst can be easily recovered from the reaction mixture and reused with no loss of its catalytic activity.

Full text of DOI:10.1002/aoc.3409

Full paper
Received: 26 August 2015
Revised: 22 October 2015
Accepted: 26 October 2015
Published online in Wiley Online Library: 28 December 2015
(wileyonlinelibrary.com) DOI 10.1002/aoc.3409
Palladium supported on modified magnetic
nanoparticles: a phosphine-free and
heterogeneous catalyst for Suzuki and
Stille reactions
Arash Ghorbani-Choghamarani* and Masoomeh Norouzi
3 4 2
An efficient magnetic nanoparticle-supported palladium (Fe O /SiO -PAP-Pd) catalyst is reported for the Suzuki cross-coupling
and Stille reactions. This method provides a novel and much improved modification of the Suzuki and Stille coupling reactions
in terms of phosphine-free catalyst, short reaction time, clean reaction and small quantity of catalyst. Another important feature
of this method is that the catalyst can be easily recovered from the reaction mixture and reused with no loss of its catalytic activity.
Copyright © 2015 John Wiley & Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web-site.
Keywords: magnetic nanoparticles; C–C coupling; biphenyl; heterogeneous catalysis
[
24]
[25]
[26]
carbene ligands, ionic liquids and so on. The Suzuki reac-
tion has continued to garner attention because of the many appli-
cations that result from its tolerance towards a wide range of
functional groups and because of the stability, low toxicity and
commercial availability of boronic acid and boronate ester reac-
tants. The Suzuki reaction has been used on an industrial scale for
the synthesis of the sartan family of hypertensive drugs and the
Introduction
Conventionally, heterogeneous catalysis is favoured over homoge-
neous catalysis because the former has more advantages, such as
the simplicity in recovery and regeneration.
synthesis, heterogeneous catalysts often suffer from lower effi-
ciency than their homogeneous counterparts. Nowadays, metal
nanoparticles are highly attractive tools for catalysis because of
[
1–8]
Despite their easy
[
9]
[
27,28]
fungicide boscalid.
lysts, new ligands and even ligand-free conditions, have been de-
veloped during the past two decades to render the Suzuki
reaction simple, mild and efficient.
As a part of our continuing interest in the development of effi-
Various modifications, such as new cata-
[
10]
their high surface-area-to-volume ratio.
[
11]
According to green chemistry principles, a ‘green’ catalyst is one
that can be simply removed from the reaction mixture and reused. In
this field, magnetic nanoparticles (MNPs) have been the focus of
[
29]
[12]
[30–33]
great attention as magnetically separable matrices for catalysts.
cient and new heterogeneous catalysts for organic synthesis,
Several approaches for the preparation of palladium catalysts on a
magnetically retrievable phase have been used. Chemical adsorption
of palladium salts on MNP surfaces with subsequent reduction and
herein we report a recoverable and efficient MNP-supported Pd
(Fe O /SiO -PAP-Pd) complex, which exhibits a high catalytic activ-
ity in the Suzuki and Stille cross-coupling reactions. In addition, the
catalyst can be easily recovered from the reaction mixture by sim-
ple filtration and reused at least five times without significant loss
of its catalytic activity.
3
4
2
[13,14]
formation of palladium nanoparticles is one of them.
These nanoparticles, because of their high surface area and
unique magnetic properties, have a broad range of potential uses
in disciplines including physics, biomedicine, biotechnology and
[15–19]
materials science and in catalysis support applications.
In this
regard, MNP-supported catalysts have been efficiently employed as Experimental
heterogeneous catalysts. The main advantage of a catalytic system
Materials and instrumentation
based on MNPs is that the nanoparticles can be efficiently isolated
from the reaction mixture through a simple magnetic separation
Chemicals were purchased from Fisher and Merck. The reagents
and solvents used in this work were obtained from Sigma-Aldrich,
Fluka or Merck and utilized without further purification.
[
20]
process after completion of the reaction.
Over the past few decades, the Suzuki–Miyaura and Stille reac-
tions have emerged as powerful carbon–carbon bond forming
[21]
methodologies. The traditional Suzuki reaction usually proceeds
using phosphine-based palladium catalysts, and there has been
considerable recent interest in the development of new catalysts
that are environmentally benign and efficient. Some significant
advances have been made, including the use of water-soluble
* Correspondence to: Arash Ghorbani-Choghamarani, Department of Chemistry,
Ilam University, PO Box 69315516, Ilam, Iran. E-mail: arashghch58@yahoo.com;
a.ghorbani@mail.ilam.ac.ir
Department of Chemistry, Faculty of Science, Ilam University, PO Box 69315516,
Ilam, Iran
[
22]
[23]
phosphines as ligands,
microwave technology,
nucleophilic
Appl. Organometal. Chem. 2016, 30, 140–147
Copyright © 2015 John Wiley & Sons, Ltd.

Suzuki and Stille reactions catalysed by Fe O /SiO -PAP-Pd
3
4
2
The particle morphology was examined using SEM with a FESEM-
TESCAN MIRA3. Thermogravimetric analysis (TGA) curves were re-
corded using a PL-STA 1500 device (Thermal Sciences). The particle
size and morphology were investigated using a Zeiss-EM10C trans-
mission electron microscopy (TEM) instrument at an accelerating
voltage of 80 kV. Vibrating sample magnetometry measurements
were performed using an MDKFD magnetometer. The magnetiza-
tion measurements were carried out in an external field up to
General procedure for Suzuki reaction
To a stirred solution of aryl halide (1 mmol), Na
2
3
CO (0.424 g, 3 mmol)
and sodium tetraphenylborate (0.5 mmol) or phenylboronic acid
1 mmol) in poly(ethylene glycol) (PEG; 2 ml) was added Fe
SiO -PAP-Pd (4 mg), and the reaction mixture was stirred at
0 °C. Completion of the reaction was determined using TLC. Af-
(
3 4/
O
2
8
ter cooling the reaction mixture, the catalyst was separated
using an external magnet and reused in the next experiment.
The mixture was diluted with diethyl ether and water and the
15 kOe at several temperatures. Fourier transform infrared (FT-IR)
spectroscopic analyses were carried out with a Vertex 70 FT-IR spec-
ꢀ
1
organic layer was dried over Na
was evaporated and corresponding biphenyl was obtained in
0–98% yield.
2 4
SO (1.5 g). Finally the solvent
trophotometer (Bruker, Germany) in the range 400–4000 cm . The
amount of Pd in the catalyst was measured using an inductively
coupled plasma atomic emission spectrometer (Sare Kelasam,
PerkinElmer, Optima 8000).
4
General procedure for stille reaction
3 4
Preparation of Fe O MNPs
2 3
To a stirred solution of aryl halide (1mmol), Na CO (0.424 g,
A mixture of FeCl ꢁ6H O (5.838 g, 0.022 mol) and FeCl ꢁ4H O
3 mmol) and triphenyltin chloride (0.5mmol) in PEG (2mm) was
added Fe O SiO -PAP-Pd (4mg), and the reaction mixture was
3
2
2
2
(
2.147 g, 0.011 mol) was dissolved in 100 ml of deionized water in
3
4/
2
a three-necked round-bottom flask (250 ml) at 80 °C under nitrogen
stirred at 80 °C. Completion of the reaction was determined using
TLC. The reaction mixture was then cooled down and the catalyst
was separated using an external magnet and reused as such for
the next run. The mixture was diluted with diethyl ether and water
and the organic layer was dried over Na SO (1.5 g). Finally the sol-
atmosphere. Subsequently, 10 ml of aqueous NH solution (32%)
3
was added to the mixture within 30 min with vigorous mechanical
stirring. The black precipitate obtained was isolated by magnetic
decantation, washed with double-distilled water until neutrality,
and further washed twice with ethanol and dried at 80 °C in
vacuum.
2
4
vent was evaporated and corresponding biphenyl product was
obtained.
3 4
Preparation of Fe O –(3-aminopropyl)triethoxysilane
Results and discussion
The obtained MNP powder (1.5 g) was dispersed in a mixture of eth-
anol and water (250ml, 1:1 by volume) using sonication for 30 min.
Then, (3-aminopropyl)triethoxysilane (99%, 3 ml) was added to the
mixture with mechanical stirring under nitrogen atmosphere at
room temperature for 8 h. The resulting product was redispersed
in ethanol using sonication. The final product was washed with
copious amounts of deionized water and ethanol, magnetically
decanted and dried under vacuum at room temperature overnight.
3 4 2
Characterization of Fe O /SiO -PAP-Pd
In order to immobilize the palladium complex, (3-aminopropyl)
triethoxysilane was first loaded on the surface of nanoparticles via
coordination bonding through hydroxyl group interaction, to
achieve amino-coated Fe
amino groups with acryloyl chloride led to acryloxyl group-
functionalized Fe MNPs. The Fe /SiO -PAP nanocatalyst was
3 4
O nanoparticles. Then, the reaction of
O
3 4
O
3 4
2
prepared by the Michael reaction of the acryloxyl groups with
piperazine. Ultimately, Fe O /SiO -PAP-Pd nanocatalyst was pre-
Preparation of Fe O /SiO -PAP
3
4
2
3
4
2
pared by reaction of Pd(OAc)
PAP) in ethanol. Piperazine was chosen as a ligand for chelating
palladium due to the fact that Pd–N bonding interactions are stable
2
with the resulting ligand (MNP–
The amino-functionalized MNPs (1g) were dispersed in dry CH Cl2
2
(3ml) in an ultrasonic bath for 10min, and the flask was cooled in
an ice–water bath. Triethylamine (3.2 ml) was added and stirred
for 30 min. Subsequently, acryloyl chloride (0.8ml, 9.84 mmol) was
added dropwise over a period of 30 min at room temperature.
The mixture was stirred at room temperature for 48 h. Then, the
Fe O /SiO -PAP nanoparticles were separated by magnetic decan-
3
4
2
tation and washed three times with acetone and deionized water
to remove the unattached substrates. The resulting material was
dispersed in methanol (10.0 ml), stirred with piperazine (2.0mmol,
0.172) and then stirred for a week at room temperature. The solids
were separated usinga magnetic field and washed with acetone.
The resulting product was dried under vacuum for 12 h.
3 4 2
Preparation of Fe O /SiO -PAP-Pd nanocatalyst
The Fe /SiO -PAP (0.5g) was added to a round-bottom flask
O
3 4
2
containing a solution of Pd(OAc) (0.25 g) in ethanol (20 ml). The
2
mixture was then stirred vigorously at reflux conditions for 20h.
The solid was separated by magnetic decantation. The magnetic
catalyst was washed with copious amounts of ethanol and dried
under vacuum at room temperature.
3 4 2
Scheme 1. Synthesis of Fe O /SiO -PAP-Pd.
Appl. Organometal. Chem. 2016, 30, 140–147
Copyright © 2015 John Wiley & Sons, Ltd.
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A. Ghorbani-Choghamarani and M. Norouzi
and inert towards cleavage. Scheme 1 illustrates the detailed
synthetic procedure for Fe /SiO -PAP-Pd nanoparticles.
The surface morphology of the Fe /SiO -PAP-Pd nanocatalyst
was characterized through SEM and TEM. SEM images of Fe
SiO -PAP-Pd (Figs. 1(a) and (b)) exhibit a cluster of aggregated
surface of the nanosolid is C = 19.61%, Fe= 57.00%, O = 15.02%
O
3 4
2
and Pd= 4.92%. The exact amount of palladium in Fe
3 4 2
O /SiO -
O
3 4
2
PAP-Pd was measured using inductively coupled plasma atomic
ꢀ
3
ꢀ1
3 4
O /
emission spectroscopy, and is found to be 1.9× 10 mol g .
2
Interpretations made on the basis of SEM images are further
supported by the TEM images shown in Figs. 2(a) and (b). The mean
diameter of Fe O /SiO -PAP-Pd is found to be around 5–20 nm.
3 4 2
Analysis of the TEM images shown in Figs. 2(a) and (b) indicates
that the diameter of each particle species is 11.59 ± 2 nm and
spherical particles with an average size of 5–20 nm. Energy disper-
sive X-ray spectroscopy (EDS) analysis provides local information
of various elements. EDS analysis of Fe O /SiO -PAP-Pd (Fig. 1(c))
3
4
2
shows that the distribution of elements (atomic percent) in the
2
0.0 ± 1.8 nm. The surface morphology of supported Fe O /
3 4
SiO -PAP-Pd displays spherical particles, which are surrounded
2
by rather uniform organic layers (Fig. 2(a)).
Dynamic laser scattering measurements of Fe O /SiO -PAP-Pd
3
4
2
are shown in Figs. 2(c) and (d). The hydrodynamic diameter of the
nanoparticles in water is found to be monodisperse with a mean
value of 25.5nm. Also, agglomeration of Fe O /SiO -PAP-Pd due
3
4
2
to the van der Waals force between the particles reduces after
surface modification.
The magnetic properties of Fe O and the catalyst were deter-
3
4
mined using vibrating sample magnetometry (Fig. 3), which shows
that the Fe O MNPs are ferromagnetic with a saturation magne-
3
4
ꢀ
1
tization of 78emu g , while the saturation magnetization of
ꢀ
1
Fe
3
O
4
/SiO
2
-PAP-Pd is 37.6 emug . The slight decrease observed
/SiO -PAP-Pd is due to
-PAP-Pd on the surface of Fe
in the saturation magnetization of Fe
O
3 4
2
the successful grafting of SiO
nanoparticles.
2
3 4
O
FT-IR spectra of Fe
O
3 4
MNPs, amino-functionalized MNPs, MNP–
acryloxyl and Fe /SiO
characteristic peaks around 580 and 3000–3500 cm
3
O
4
2
-PAP-Pd are shown in Fig. 4. In Fig. 4(a), the
ꢀ
1
can be
assigned to Fe–O and O–H stretching bonds, respectively. In the
spectrum of amino-functionalized MNPs (Fig. 4(b)), bands corre-
ꢀ
1
sponding to Si–O stretching appear at 1011 and 1001 cm . Fur-
thermore, characteristic peaks of C–H aliphatic bond are observed
ꢀ
1
ꢀ1
at 2854–2922 cm , and also a broad band appears at 3394 cm
which is related to the stretching vibration of NH groups. In the
spectrum of Fe –acryloxyl (Fig. 4(c)), absorption bands at 1710
and 1642 cm are attributed to C¼O and C¼C bonds and the peak
,
2
3 4
O
ꢀ
1
FeK
c
1
1
500
000
PdL
O K
FeL
5
00 C K
PdL
SiK
FeK
keV
0
0
5
10
3 4 2
Figure 1. (a, b) SEM images of Fe O /SiO -PAP-Pd at different
3 4 2
Figure 2. TEM images of Fe O /SiO -PAP-Pd at (a) × 63 000 and (b) × 100
magnifications. (c) EDS analysis.
000 magnification. (c, d) Dynamic laser scattering measurements.
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Appl. Organometal. Chem. 2016, 30, 140–147

Suzuki and Stille reactions catalysed by Fe O /SiO -PAP-Pd
3
4
2
ꢀ
1
observed at 3020 cm corresponds to the secondary amide group.
Fe
and some have disappeared and new peaks are observed.
Significant decreases of bands of functional groups on Fe
3 4 2
O /SiO -PAP-Pd (Fig. 4(d)), there are some peaks that are shifted
ꢀ
1
The peaks at 1245 and 1164 cm can be assigned to C–N and C–O
stretching of ether groups, respectively. In the FT-IR spectrum of
3 4
O /
ꢀ
1
SiO
spond to C¼O and –C–C– stretching, respectively.
Figure 5 shows the thermal analysis of Fe and Fe
3 4
SiO -PAP-Pd nanoparticles. In the TGA curve of Fe O , weight loss
2
-PAP-Pd are detected at 1701 and 1155 cm , which corre-
3
O
4
3 4
O /
2
is mainly divided into two regions: below 200 °C and 200–600 °C.
Weight loss of about 3% below 200 °C is assigned to the loss of
physically adsorbed water and surface hydroxyl groups. The
weight loss of about 8% between 260 and 600 °C may be associ-
ated with the thermal crystal phase transformation from Fe O to
3
4
[
33]
γ-Fe O .
2
3
Differential thermal analysis (DTA; Fig. 5) shows an endothermic
peak at below 200 °C. The endothermic effect below 200 °C may
be due to removal of physically absorbed water and the endother-
mic effect at 246 °C is due to removal of structurally absorbed water.
The exothermic peak between 260 and 600 °C is due to recrystalli-
zation and phase transformation from Fe O to γ-Fe O .
3
4
2 3
There are two weight loss steps in the TGA curve of Fe O /
3
4
SiO -PAP-Pd (Fig. 5(b)). A small amount of loosely bound hy-
2
droxyl and water causes the weight loss (less than 4.9%) below
2
2
00 °C. This is followed by a weight loss of about 14.1% between
00 and 425 °C that is due to decomposition of organic moieties
of the complex.
3 4 3 4 2
Figure 3. Magnetization curves for (a) Fe O and (b) Fe O /SiO -PAP-Pd.
Figure 4. FT-IR spectra of (a) Fe MNPs, (b) amino-functionalized MNPs,
O
3 4
(
c) MNP–acryloxyl and (d) Fe /SiO -PAP-Pd.
3
O
4
2
3 4 3 4 2
Figure 5. TGA/DTA curves of (a) Fe O and (b) Fe O /SiO -PAP-Pd.
Appl. Organometal. Chem. 2016, 30, 140–147
Copyright © 2015 John Wiley & Sons, Ltd.
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A. Ghorbani-Choghamarani and M. Norouzi
Catalytic studies
Na CO
2 3
acts as an excellent base for this reaction (Table 1, entry 6).
Organic bases such as Et
Table 1, entries 7 and 8). In the presence of other bases, KOH, NaOH
and NaHCO , low to moderate yields are obtained (Table 1, entries
–11). As mentioned above, the Suzuki cross-coupling reaction is
considered in the presence of different bases including monobasic
KOH, NaOH), dibasic (Na CO ) and organic basic materials. The big-
gest difference between the monobasic (KOH, NaOH) and the bibasic
Na CO ) bases is that KOH and NaOH are the stronger bases, while
3
N and DMAP are substantially less effective
3 4 2
The catalytic activity of Fe O /SiO -PAP-Pd was evaluated in the
C–C coupling reaction of aryl halides with tetraphenylborate,
phenylboronic acid and triphenyltin chloride.
(
3
9
In our preliminary experiments, the reaction between 1-
bromo-4-nitrobenzene and sodium tetraphenylborate was inves-
tigated to optimize the reaction conditions, including catalyst
amount, base, solvent and temperature. The results are summa-
rized in Table 1.
Initially, the solvent effect was examined, and a significant sol-
vent effect is observed. We find that the nature of solvent signifi-
cantly affects the conversion of the coupling reaction. Among the
tested solvents, dimethylformamide (DMF) and dimethylsulfoxide
(
2
3
(
2
3
Na CO and NaHCO are weak bases, based on their known K
2
3
3
b
[34]
values. As previously reported by Knecht and co-workers,
for
KOH or NaOH, the amount of free and reactive hydroxide is higher
as compared to the Na CO and NaHCO systems, which results in
2
3
3
a strong combination with palladium species leading to a decrease
(
5
DMSO) lead to corresponding biphenyl product in 57 ± 9 and
9 ± 7% yields (Table 1, entries 1 and 2) in the presence of 4 mg
of Fe O /SiO -PAP-Pd. While in solvents such as water and EtOH,
in biphenyl yield. Also, organic bases such as Et N and DMAP are
3
not strong enough for this cross-coupling reaction. Based on these
results we find that a moderate base capacity is necessary to perform
the coupling reaction in the presence of a catalytic amount of Fe O /
3
4
2
trace amounts of product are obtained (Table 1, entries 3 and 4)
and in 1,4-dioxane no product is observed (Table 1, entry 5). In
the case of PEG-400 solvent the product is isolated in 98 ± 2%
yield (Table 1, entry 6). Consequently, PEG-400 was finally selected
as the best solvent for the coupling reaction based on product
yield.Our next studies focused on the effect of base in the model
reaction, with various bases (NaHCO , Na CO , KOH, NaOH, N,N-
3
4
SiO -PAP-Pd. Therefore, when Na CO and HNaCO are considered, a
2
2
3
3
different trend in reactivity is observed, with higher product yields as
compared to KOH, NaOH or organic bases. Based on this study,
Na CO was finally selected as the best base for this reaction.
2
3
This reaction is sensitive to temperature. Therefore the effect of
temperature on the outcome of the reaction was investigated. It
is found that higher temperatures can improve the reaction rate
and shorten the reaction time (Table 1, entries 13–16). Further stud-
ies reveal that the optimal reaction temperature is 80°C (Table 1,
entry 15).
3
2
3
dimethylpyridin-4-amine (DMAP) and Et N) being examined. The
3
reaction does not occur in the absence of base (Table 1, entry
12) and the presence of base has a significant effect in the Suzuki
coupling reaction. Among the examined bases, it is found that
The effect of the amount of sodium tetraphenylborate on the
yield was also investigated (Fig. 6). Reactions carried out in the
presence of 0.2, 0.3, 0.4 and 0.5 mmol of sodium tetraphenylborate
afford isolated yields of 52 ± 9, 74 ± 7, 83± 3 and 98 ± 2%, respec-
tively. It is found that 0.5mmol of sodium tetraphenylborate with
Table 1. C–C coupling of 1-bromo-4-nitrobenzene with sodium
tetraphenylborate in the presence of Fe
3 4 2
O /SiO -PAP-Pd under various
a
conditions
1
mmol of 1-bromo-4-nitrobenzene are the appropriate amounts
for the completion of the reaction.
Since the coupling reaction does not occur in the absence of
catalyst (Table 1, entry 19), the amount of palladium catalyst was
evaluated. It is found that 4 mg of Fe O /SiO -PAP-Pd is the optimal
3 4 2
amount, while when the amount of catalyst is decreased, lower
yield is achieved (Table 1, entry 17). Increasing the amount of
Entry
Solvent
Base Temperature Catalyst Time
Yield
(%)
b
(
mmol)
(°C)
(mg) (min)
1
2
3
4
5
6
7
8
9
DMF
Na
Na
Na
Na
1,4-Dioxane Na
2
CO
CO
CO
CO
CO
CO
3
80
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
3
5
—
35 57 ± 9
35 59 ± 7
35 Trace
35 Trace
DMSO
2
3
80
H
2
O
2
3
80
EtOH
2
3
Reflux
2
3
80
35
—
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
PEG
Na
Et
2
3
80
35 98 ± 2
35 Trace
35 Trace
35 60 ± 3
35 40 ± 6
35 74 ± 11
3
N
80
DMAP
KOH
80
80
10
11
12
13
14
15
16
17
18
19
NaOH
80
NaHCO
3
80
—
80
300
240
—
—
Na
Na
Na
Na
Na
Na
Na
2
CO
CO
CO
CO
CO
CO
CO
3
Room temp.
2
3
50
80
240 25 ± 6
35 98 ± 2
35 98 ± 2
150 72 ± 8
35 98 ± 1
2
3
2
3
100
80
2
3
2
3
80
2
3
80
1440
—
a
Reaction conditions: 1-bromo-4-nitrobenzene (1 mmol), NaPh
4
B
(
0.5 mmol), base (3 mmol), solvent (2 ml).
b
Figure 6. Effect of amount of sodium tetraphenylborate on outcome of
reaction.
Isolated yield.
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Copyright © 2015 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2016, 30, 140–147

Suzuki and Stille reactions catalysed by Fe O /SiO -PAP-Pd
3
4
2
Table 2. Suzuki-type C–C coupling reaction of aryl halides with sodium tetraphenylborate in the presence of catalytic amounts of Fe
Pd
3
O
4
/SiO
2
-PAP-
a
Entry
R
X
Time
Yield
(%)
M.p. (°C)
TOF
b
ꢀ1 c
(
min)
(h
)
Found
Reported
[
26]
1
2
3
4
5
6
7
8
9
H
I
20
60
98
92
95
97
96
92
97
96
95
93
98
95
89
98
86
60
40
52
67–68
107–109
44–47
84–85
44–47
67–68
82–83
56–58
162–163
105–106
113–115
52–54
219–223
Oil
68–70
3722
1165
2405
3932
5189
2084
2126
1730
3851
3016
2270
2568
722
[35]
2-CO
2
H
I
111–113
[
26]
4-CH
4-OCH
3
I
30
44–46
[
26]
26]
26]
29]
28]
3
I
20
88–90
[
4-CH
H
3
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
15
44–46
[
35
68–70
[
4-CN
4-CHO
4-OH
4-SH
37
85–86
[
45
54–56
[29]
20
163–164
[36]
10
11
12
13
14
15
16
17
18
25
110–111
[26]
4-NO
4-NH
4-CO
2-CH
2
35
112–114
[28]
2
30
50–53
[35]
2
H
100
70
224–228
[
37]
2
OH
Oil
1135
1162
34
[
38]
3-CHO
60
46–48
Oil
53–54
[
29]
2-Br-naphthalene
4-CHO
1440
1200
1440
Oil
[28]
57–58
219–223
54–56
27
[39]
4-CO
2
H
224–228
29
a
4 3 4 2
Reaction conditions: aryl halide (1 mmol), NaPh B (0.5 mmol), base (3 mmol), Fe O /SiO -PAP-Pd (4 mg), PEG-400 (3 ml).
b
Isolated yield.
c
Turnover frequency.
a
Table 3. Suzuki-type C–C coupling reaction of aryl halides with phenylboronic acid in the presence of catalytic amounts of Fe
3 4 2
O /SiO -PAP-Pd
Entry
R
X
Time
Yield
(%)
M.p. (°C)
TOF
b
ꢀ1 c
(
min)
(h
)
Found
Reported
[
26]
1
2
3
4
5
6
7
8
9
H
I
I
I
I
8
25
98
94
97
93
99
93
99
98
98
70
97
97
90
95
96
83
67–68
107–109
44–47
68–70
9932
3049
5243
7540
6689
4436
2006
2649
5297
2270
5618
4369
1459
2201
54
[35]
2-CO
4-CH
4-OCH
4-CH
2
H
111–113
[
26]
3
15
44–46
[
26]
26]
26]
29]
28]
3
10
84–85
88–90
[
3
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Cl
12
44–47
44–46
[
H
17
67–68
68–70
[
4-CN
4-CHO
4-OH
4-SH
40
82–83
85–86
[
30
56–58
54–56
[29]
15
162–163
105–106
113–115
52–54
163–164
[36]
10
11
12
13
14
15
16
25
110–111
[26]
4-NO
4-NH
4-CO
3-CHO
2
14
112–114
[28]
2
18
50–53
[39]
2
H
50
219–223
46–48
224–228
[
38]
35
53–54
[
29]
2-Br-naphthalene
4-CHO
1440
1440
Oil
Oil
[28]
57–58
54–56
47
a
3 4 2
Reaction conditions: aryl halide (1 mmol), PhB(OH) (1 mmol), base (3 mmol), Fe O /SiO -PAP-Pd (4 mg), PEG-400 (3 ml).
b
Isolated yield.
c
Turnover frequency.
Appl. Organometal. Chem. 2016, 30, 140–147
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

A. Ghorbani-Choghamarani and M. Norouzi
Table 4. Stille-type C–C coupling reaction of aryl halides with
triphenyltin chloride in the presence of catalytic amounts of Fe
SiO -PAP-Pd
2
of 4 mg of catalyst in PEG-400 (2ml) as solvent were studied. The re-
sults are summarized in Table 3. The Suzuki cross-coupling reac-
tions of phenylboronic acid with aryl iodides bearing electron-
donating or electron-withdrawing groups at their meta-positions
or ortho-positions all give the corresponding biphenyl in high
yields.
3 4
O /
a
3 4 2
The Fe O /SiO -PAP-Pd catalyst also shows a high activity for the
Stille reaction in PEG solvent using organostannane (Ph SnCl,
Entry
R
X
Time Yield
M.p. (°C)
Found Reported
TOF
3
b
ꢀ1 c
(min) (%)
(h
)
0.5 mmol). As evident from Table 4, the results are similar to those
for the Suzuki reaction. Aryl iodides and aryl bromides give better
results than aryl chlorides.
[
26]
26]
26]
26]
26]
29]
28]
26]
1
2
3
4
5
6
7
8
9
H
I
I
I
20 95
120 96
60 40
60 93
35 94
50 98
180 91
55 89
67–68
44–47
84–85
44–47
67–68
82–83
56–58
70–71
68–70
3851
649
[
For practical purposes, easy recyclability of a catalyst is highly de-
sirable. To investigate this issue, the recyclability of the catalyst was
examined for the reaction of 1-bromo-4-nitrobenzene and sodium
tetraphenylborate. We find that this catalyst demonstrates excel-
lent reusability. After completion of the reaction, the catalyst is eas-
ily and rapidly separated from the reaction mixture using an
external magnet and decantation of the reaction solution. The re-
maining magnetic nanocatalyst was washed with ethyl acetate to
remove residual product. Then, the reaction vessel was charged
with fresh substrate and subjected to the next run. As shown in
Fig. 7, the catalyst can be recycled for up to five runs without any
significant loss of its catalytic activity.
4-CH
4-OCH
3
44–46
[
3
88–90
540
[
4-CH
H
3
Br
Br
Br
44–46
1257
2178
1589
410
[
68–70
[
4-CN
85–86
[
4-CHO Br
54–56
[
4-Cl
4-OH
H
Br
Br
Cl
77–79
1312
1540
172
[29]
50 95 162–163 163–164
[26]
10
240 51
70–71
68–70
a
Reaction conditions: aryl halide (1 mmol), Ph
3
SnCl (0.5 mmol), base
(
3 mmol), Fe /SiO -PAP-Pd (4 mg), PEG-400 (3 ml).
3
O
4
2
b
c
Isolated yield.
Turnover frequency.
Conclusions
In summary, we have successfully developed a novel, efficient and
practical method for the synthesis of biphenyl derivatives through
the reaction of aryl halides with sodium tetraphenylborate,
phenylboronic acid or triphenyltin chloride using Fe
PAP-Pd as catalyst under mild reaction conditions.
3 4 2
O /SiO -
Acknowledgments
The authors are grateful to the research facilities of Ilam University,
Ilam, Iran, for financial support of this research project.
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Copyright © 2015 John Wiley & Sons, Ltd.
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