Encapsulation of palladium chloride using 2-formylbenzoic acid supported by Fe3O4 nanoparticles modified with SiO2 and propylamine, its characterization and its application for Suzuki coupling reaction

Article abstract of DOI:10.1002/aoc.4384

A magnetically separable heterogeneous nanocatalyst, Fe₃O₄@SiO₂(CH₂)₃N―CH―Ar@Pd(0), was simply prepared and characterized using various techniques. The catalytic activity of this nanocatalyst was evaluated via the Suzuki–Miyaura cross-coupling reaction of aryl halides with phenylboronic acid under various experimental conditions such as kind of base, solvent and temperature. This nanocatalyst is completely magnetically recoverable because of the superparamagnetic behaviour of Fe and can be reused with sustained selectivity and activity.

Full text of DOI:10.1002/aoc.4384

Received: 8 December 2017
DOI: 10.1002/aoc.4384
Revised: 8 March 2018
Accepted: 9 March 2018
F U L L P A P E R
Encapsulation of palladium chloride using 2‐formylbenzoic
acid supported by Fe O nanoparticles modified with SiO
3
4
2
and propylamine, its characterization and its application for
Suzuki coupling reaction
Hamid Mostafavi | Mohammad Reza Islami
| Ahmad Momeni Tikdari
Chemistry Department, Shahid Bahonar
A
magnetically
separable
heterogeneous
nanocatalyst,
University of Kerman, Kerman 76169,
Iran
Fe O @SiO (CH ) N―CH―Ar@Pd(0), was simply prepared and characterized
3
4
2
2 3
using various techniques. The catalytic activity of this nanocatalyst was evalu-
ated via the Suzuki–Miyaura cross‐coupling reaction of aryl halides with
phenylboronic acid under various experimental conditions such as kind of
base, solvent and temperature. This nanocatalyst is completely magnetically
recoverable because of the superparamagnetic behaviour of Fe and can be
reused with sustained selectivity and activity.
Correspondence
Mohammad Reza Islami, Chemistry
Department, Shahid Bahonar University
of Kerman, Kerman 76169, Iran.
Email: mrislami@uk.ac.ir
KEYWORDS
aryl halides, biaryls, magnetic nanoparticles, nanocatalyst, phenylboronic acid
1
| INTRODUCTION
nanoparticles, and therefore such catalysts have appeared
as a bridge between homogeneous and heterogeneous
Catalysts can be classified into two general categories,
homogeneous and heterogeneous. Each category has its
advantages and disadvantages. Homogeneous catalysts
dissolve in the solvent of the reaction and form a uniform
layer with the reactants; therefore, interaction between
the substrate and the catalyst is greater than for
heterogeneous catalysts. This effect leads to significant
improvements in both activity and selectivity during the
corresponding reaction. Separation and recycling of
homogeneous catalysts are often very difficult.
Heterogeneous catalysts can be separated by filtration or
centrifugation and reused several times without signifi-
cant loss in their catalytic activities. Nanocatalysts have
high catalytic activities due to their high number of
surface atoms that increases with decreasing particle size,
as these surface atoms are the active sites for catalysis.
catalysts. In this context, the catalyst is covered with a
magnetic material such as magnetite (Fe O ), and, after
3
4
completion of the reaction, it is readily separated using
[3]
an external magnet without any tedious procedure.
Chemists believe that transition metals play an
important role in the synthesis of organic compounds as
either catalysts or reagents. One of the most important
transition metals is palladium or palladium salts. This
catalyst is used in many coupling reactions such as
[
4]
[5]
[6–8]
[9]
Suzuki–Miyaura,
Negishi,
Heck,
Stille,
Kumada,
[
10,11]
[12]
[13]
Hiyama
and Sonogashira.
Biaryls are useful building blocks for various poly-
mers, pharmaceuticals, agrochemicals and natural prod-
ucts including alkaloids, lignans, terpenes, flavonoids
and tannins, as well as polyketides, coumarins, peptides
and glycopeptides. For example, binaphthyl derivative is
found in the structure of gossypol as a natural pig-
[1,2]
They suffer from some drawbacks.
Nowadays, there
[
14,15]
are several ways to solve these problems. The separation
of homogeneous and heterogeneous catalysts from the
reaction mixture can be done using magnetic
ment.
The classical methods for synthesis of biaryls
[
16,17]
are the Ullmann reaction,
Hey reaction,
Gomberg–Bachmann–
[
18]
[19]
Pschorr cyclization
and Gatterman
Appl Organometal Chem. 2018;e4384.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
1 of 9
https://doi.org/10.1002/aoc.4384

2
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MOSTAFAVI ET AL.
[20]
synthesis.
Among these methods, the palladium‐
in Figure 1. In the FT‐IR spectrum of Fe O @SiO
3
4
2
catalysed Suzuki–Miyaura cross‐coupling reaction is the
(Figure 1a) the absorption band of Fe―O was observed
−
1
best method for the synthesis of biaryls by the reaction
at 467 cm , and the absorption bands at 1094 and
[
14,21,22]
−1
of organic halides with phenylboronic acid.
800 cm were assigned to the asymmetric and symmetric
Organoboron reagents have some noticeable advantages
such as their high selectivity, less toxic nature and
negligible homocoupling of phenylboronic acid.
stretching of the Si―O―Si bond, respectively. As shown
in Figure 1(b–d), the C―H stretching band of the propyl
groups of catalysts C , C and C appeared in the range
3
−1
4
5
[23–30]
In the Suzuki coupling reaction,
Pd(0) is
2923 to 2929 cm . The C―N stretching bands of
immobilized using organic or inorganic compounds such
as silica, metal oxides, activated carbon and clays. These
materials are used as supports to prevent the agglomera-
catalysts C4 and C5 were observed at 1639.36 and
−
1
1633.7 cm respectively. The decrease of frequency in
−
1
Figure 1(d) (5.65 cm ) confirmed that palladium had
coordinated to N and O. The FT‐IR spectrum of recycled
catalyst is shown in Figure 1(e). This spectrum shows that
all catalyst absorption bands are identical to those of the
original catalyst.
[31–35]
tion of the magnetic nanoparticles.
Various
functional groups such as Schiff bases can be used for
anchoring the catalytic species on magnetic nanoparti-
[36]
cles.
Based on the considerations mentioned above,
herein we report a novel Pd(0) complex covalently anchor-
The particle morphology was investigated by SEM–
EDX, and the results are shown in Figure 2. The average
ing 2‐formylbenzoic acid supported by Fe O nanoparticles
3
4
modified with SiO and propylamine as a catalyst for the
synthesis of biphenyls via the Suzuki coupling reaction.
particle size of catalyst C was calculated using SEM. The
morphology of this catalyst was spherical in shape with a
rough surface (Figure 2a). The EDX spectrum of catalyst
2
5
[
37]
C is exhibited in Figure 2(b). This spectrum confirmed
5
2
| RESULTS AND DISCUSSION
the presence of elements such as Pd, Si and Fe in the
structure of catalyst C5.
First of all, as shown in Scheme 1, the new magnetic
nanocatalyst was prepared from FeCl and FeCl as pre-
The XRD patterns of Fe O @SiO (CH ) N―CH―Ar
3
4
2
2 3
and Fe O @SiO (CH ) N―CH―Ar@Pd(0) are shown in
2
3
3
4
2
2 3
cursors. The details of the total synthesis are given in
Section 3. The structure of the catalyst was confirmed
using several techniques, such as Fourier transform
infrared (FT‐IR) spectroscopy, scanning electron
microscopy (SEM) with energy dispersive X‐ray analysis
(Figure 2c). The XRD patterns of these compounds are
similar and diffraction peaks at around 2θ = 30.05°,
36.10°, 44.02°, 54.70°, 58.30°, 64.28° and 75.05° corre-
spond to the seven crystal faces (111), (220), (311),
(400), (422), (511) and (440), respectively. The magnetic
XRD peaks match well with these peaks, which is in
agreement with the standard pattern for crystalline mag-
(EDX), X‐ray diffraction (XRD), vibrating sample magne-
tometry (VSM) and thermogravimetric analysis (TGA).
[
38]
The FT‐IR spectra of the nanocatalyst (C –C ) are shown
netite (Fe O ) with an inverse spinel structure.
3 4
The six
2
5
SCHEME 1 Synthesis of
Fe @SiO (CH N═CH―Ar@Pd(0)
3
O
4
2
2 3
)

MOSTAFAVI ET AL.
3 of 9
FIGURE 1 FT‐IR spectra of (a)
Fe
c) Fe
Fe
and (e) recycled
Fe @SiO (CH
3
O
4
@SiO
@SiO
@SiO (CH
2
, (b) Fe @SiO
3
O
4
2 2 3 2
(CH ) NH ,
(
3
O
4
2
(CH ) N―CH―Ar, (d)
2 3
3
O
4
2
2
2
)
)
3
3
N―CH―Ar@Pd(0)
N―CH―Ar@Pd(0)
3
O
4
2
peaks of Fe O @SiO (CH ) N―CH―Ar can also be seen
The TGA technique was used for measuring the
3
4
2
2 3
in the XRD pattern of the synthesized Fe O @SiO ‐
organic content of catalyst C . As shown in Figure 3
3
4
2
5
(
CH ) N―CH―Ar@Pd(0). This comparison shows that
(a), the weight loss of the catalyst occurred step by step
between 150 and 600°C. In the first stage, the reduction
in weight by 3.26% at 160–240°C can be attributed to
residual water loss in the sample. In the second and
third stages, the weight loss of 9.61% at 240 to 480°C is
attributed to the reduction of aromatic and propyl
groups of the catalyst. These results strongly confirm
the attachment of organic moieties on the surface of
2
3
the final catalyst does not have two different phases,
and the prepared Fe O nanoparticles in this stage are
pure with a spinel structure. Also, the observed diffrac-
tion peaks at 2θ = 40° and 46.5° correspond to two faces
3
4
(
111) and (200), respectively, indicating the presence of
[39]
Pd(0) in the nanocatalyst.
Figure 2(d) shows a plot of magnetization M versus
applied field H (VSM curve) for catalyst C . The lower
the Fe O @SiO
2
nanoparticles. The amount of
5
3
4
−
1
magnetization of the catalyst (14 emu g ) in comparison
palladium anchored to the fresh and recycled catalysts
was determined using the inductively coupled
plasma (ICP) technique, being7.12 and 5.20%,
respectively.
−
1
to that of Fe O @SiO (52.7 emu g ) and Fe O
3 4
3
1 [40]
4
2
−
(69.3 emu g )
is due to the existence of coated silica
layer and organic moieties on the surface of Fe O nano-
3
4
particles, but this decrease is small and the separation of
the catalyst using an external magnet is possible.
The
particle
size
of
Fe O @SiO (CH ) N―CH―Ar@Pd(0) (catalyst C ) was
3
4
2
2 3
5

4
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MOSTAFAVI ET AL.
FIGURE 3 (a) TGA of Fe
DLS measurement of Fe @SiO
visible spectra of PdCl and Fe
3
O
4
@SiO
(CH
@SiO
2
(CH
2
)
3
N―CH―Ar@Pd(0). (b)
O
3 4
2
2 3
) N―CH―Ar@Pd(0). (c) UV–
(CH N―CH―Ar@Pd(0)
2
3
O
4
2
2 3
)
The UV–visible spectrum of catalyst C was obtained,
5
which lacked an absorption band at about 419 nm,
indicating the presence of palladium in zero oxidation
state in the catalyst, which confirms the formation of
[41]
Fe O @SiO (CH ) N―CH―Ar@Pd(0) (Figure 3c).
3
4
2
2 3
The
catalytic
efficiency
of
Fe O @SiO (CH ) N―CH―Ar@Pd(0) (catalyst C ) was
3
4
2
2 3
5
investigated via the Suzuki–Miyaura cross‐coupling reac-
tion for the synthesis of biaryls. First, the reaction condi-
tions were optimized by the reaction of phenyl iodide
with phenylboronic acid. The results are summarized in
Table 1. Initially, the catalytic activity of catalysts C –C
FIGURE 2 (a) SEM image of Fe
b) EDX spectrum of Fe @SiO (CH
patterns of (c1) Fe @SiO (CH N―CH―Ar and (c2)
Fe @SiO (CH N―CH―Ar@Pd(0). (d) VSM curve of
Fe @SiO (CH N―CH―Ar@Pd(0)
3
O
4
@SiO
2 2 3
(CH ) N―CH―Ar@Pd(0).
(
3
O
4
2
2 3
) N―CH―Ar@Pd(0). (c) XRD
3
O
4
2
2 3
)
3
O
4
2
2 3
)
1
5
3
O
4
2
2 3
)
was compared by the reaction of phenyl iodide (1 mmol,
determined using the dynamic light scattering (DLS)
technique in aqueous solution (Figure 3b). The average
size of nanoparticles is 88 nm.
0.2040 g), phenylboronic acid (1 mmol, 0.1219 g), K CO
2
3
(2 mmol, 0.2764 g) as base, 10 ml of EtOH–H O (1:1) as
2
solvent and 10 mg of catalyst at 60°C (Table 1, entries

MOSTAFAVI ET AL.
5 of 9
a
TABLE 1 Characterization of Suzuki–Miyaura coupling reaction between aryl halide and phenylboronic acid
b
Entry
Catalyst
Base
Solvent
Temp. (°C)
Yield (%)
1
2
3
4
5
6
7
8
9
—
K
K
K
K
K
K
K
2
2
2
2
2
2
2
CO
CO
CO
CO
CO
CO
CO
3
3
3
3
3
3
3
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
EtOH–H
2
2
2
2
2
2
2
2
2
2
2
2
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (1:1)
O (2:1)
O (1:2)
60
60
60
60
60
60
75
75
75
75
75
75
0
90
0
C
C
C
C
C
C
C
C
C
C
C
5
4
3
2
1
5
5
5
5
5
5
0
0
40
98
70
95
10
95
92
KOH
Na CO
CaCO
2
3
1
1
1
0
1
2
3
K
K
2
2
CO
3
3
CO
a
Reaction conditions: phenyl iodide (1 mmol), phenylboronic acid (1 mmol), catalyst (10 mg).
C
5
:
Fe
3
O
4
@SiO
2
(CH
2
3 4
) N―CH―Ar@Pd(0); C :
Fe
3 4 2 2 3 3 3 4 2 2 3 2 2 3 4 2 1 3 4
O @SiO (CH ) N―CH―Ar; C : Fe O @SiO (CH ) NH ; C : Fe O @SiO ; C : Fe O .
b
Isolated yield.
1
–6). A high yield was obtained with catalyst C (Table 1,
(1:1), dried at 50°C and then used again for the next cycle.
As shown in Figure 4(a) the catalyst activity remained
virtually unchanged after five cycles. ICP, EDX, SEM
and XRD along with FT‐IR spectroscopy were also carried
out to characterize the recycled catalyst, which confirmed
the similarity of its structure to that of the initial catalyst
and the presence of Fe, Pd, Si elements in the recycled
catalyst structure (Figure 4b–d).
The mechanism of the reaction is not entirely clear
to us, but, according to what has been reported the liter-
ature, when the Suzuki reaction is carried out in aque-
ous media an organopalladium compound is formed
through a Pd(0)–Pd(II) catalytic cycle. Therefore, accord-
ing to this, a reasonable mechanism can be suggested.
On the basis of the reaction conditions, the first step of
the mechanism involves oxidative addition, in which
5
entry 2). To increase efficiency, the reaction was accom-
plished at 75°C and the product yield increased to 98%
(Table 1, entry 7). The reaction was then carried out in
the presence of various bases such as KOH, Na CO and
CaCO . As evident from Table 1, the use of potassium
carbonate as a base caused the product yield to increase
to 98% (Table 1, entries 7–10). In the final step of optimi-
zation, the reaction was performed in many solvents,
2
3
3
with EtOH–H O (1:1) being the best solvent for this reac-
tion (Table 1, entries 7, 11 and 12).
2
After the optimization of reaction conditions, we
synthesized several biaryls by the reaction of various
aryl halides with phenylboronic acid via the Suzuki–
Miyaura cross‐coupling reaction. The results are pre-
sented in Table 2. All products are known and the
structures of those have been characterized using FT‐
IR, H NMR and C NMR analyses.
that in these reactions aryl iodides and aryl bromides
are often used.
Aryl chlorides are less reactive in such reactions. So
we had to use compounds including iodine and
bromine atoms. The reusability of heterogeneous
catalysts is very important. Therefore the recyclability of
Fe O @SiO (CH ) N―CH―Ar@Pd(0) was investigated
for the reaction of phenyl iodide with phenylboronic acid
in five sequential cycles under the optimized reaction
conditions. After each cycle, the catalyst was separated
the Ar―X is attached to catalyst C , and forms an
5
1
13
[42–47]
It is noted
organopalladium compound through a Pd(0)–Pd(II) cat-
alytic cycle. In the next step transmetallation occurs
and the Ph group is transferred from the activated
phenylboronic acid to the palladium catalyst. In the
final step, reductive elimination occurs and biaryl is
[48]
[
49,50]
formed (Scheme 2).
Table 3 presents a comparison of the activity of the
synthesized nanocatalyst with those of other palladium
catalysts reported in the literature. The advantage of the
present protocol is that the Suzuki reaction is carried
out in less time and the reaction efficiency is higher, so
it is superior to other reported methods.
3
4
2
2 3
using an external magnet and washed with EtOH–H O
2

6
of 9
MOSTAFAVI ET AL.
a
TABLE 2 Suzuki–Miyaura cross‐coupling of aryl halides with phenylboronic acid catalysed by Fe
3
O
4
@SiO
2
(CH
2
)
3
N―CH―Ar@Pd(0)
b
Entry
Ar―X
Yield (%)
M.p. (°C)
1
98
68–70
2
3
4
5
6
94
40
87
76
87
68–70
68–70
85–88
85–88
Oil
7
8
9
78
Oil
c
83
153–155
100
89
116–119
84–86
46–47
—
10
11
12
72
Trace
1
3
76
111–113
a
Reaction conditions: aryl benzene (1 mmol), phenylboronic acid (1 mmol, 0.1219 g), K
10 mg), reaction time = 20 min, 75 °C.
2 3 2
CO (2 mmol, 0.2764 g), solvent EtOH–H O (1:1) (10 ml), catalyst
(
b
Isolated yield.
c
Yield after 12 h.
3
| EXPERIMENTAL
alternating gradient force magnetometer. TGA was carried
out with a thermal analyser under argon flow at a heating
−
1
3.1 | Chemicals and Methods
rate of 10°C min in the range 25–600°C. ICP analysis
was performed by an ICP‐OES simultaneous model Arcos
EOP spectrometer. The UV–visible analysis of the
nanocatalyst was carried out with a Cary Conc spectro-
photometer. The particle size of the nanocatalyst was
All the materials used in this work were of analytical
grade. The solvents were distilled before use. The FT‐IR
spectra were recorded as KBr pellets with a Nicolet IR
1
1
00 instrument. The SEM–EDX analyses were conducted
determined using the DLS technique. H NMR spectra of
with Philips XL 30 and S‐4160 instruments with samples
being coated with gold. The XRD patterns were obtained
with a Philips X‐Pert 1710 diffractometer using Co Kα (λ
products were recorded with a Bruker INOVA 400 (MHz).
3
.2 | Preparation of Silica‐Coated
=
1.78897 Å) at a voltage of 40 kV and current of 40 mA.
Magnetic Nanoparticles (Fe O @SiO )
3
4
2
The data were collected from 10° to 90° (2θ) with a scan
−
1
speed of 0.02° s . The magnetic measurement of the cata-
lyst was conducted using a vibrating magnetometer/
The preparation strategy for the nanocatalyst was a multi‐
step procedure as shown in Scheme 1. First, magnetic

MOSTAFAVI ET AL.
7 of 9
SCHEME 2 Plausible mechanism for synthesis of biaryls via
Suzuki–Miyaura cross‐coupling reaction
nanoparticles (Fe O ) were synthesized via a simple co‐
3
4
[
37]
precipitation method,
in which FeCl ⋅4H O (10 mmol,
2
2
1
.99 g) and FeCl ⋅6H O (20 mmol, 5.4 g) were separately
3
2
dissolved in 25 ml of deionized water. An aqueous ammo-
nia solution (30 ml, 25% w/w) was added dropwise to the
stirring mixture of ferric and ferrous ions to increase the
reaction pH to about 12. Fe O was formed immediately,
3
4
and then the reaction mixture was stirred at room
temperature for 1 h. The resulting mixture was refluxed
at 100°C for 1 h. After cooling, 80 ml of EtOH was added
to the reaction mixture and allowed to stir for 1 h at room
temperature. Subsequently, 20 ml of tetraethyl
orthosilicate was added into the reaction vessel, and the
reaction mixture was continuously stirred at 40°C for
24 h. The silica‐coated magnetic nanoparticles were
separated from the reaction mixture using an external
magnet and washed with 25 ml of ethanol and 25 ml of
diethyl ether, consecutively, and dried at 60°C for 12 h
to give Fe O @SiO .
3
4
2
3
.3 | Synthesis of 3‐Aminopropyl
Covalently Attached onto the Surface of
Fe O @SiO (Fe O @SiO (CH ) NH ;
3
4
2
3
4
2
2 3
2
Catalyst C3)
An amount of 2 g of Fe O @SiO and 1.15 g of 3‐
3
4
2
aminopropyltriethoxysilane were added to 150 ml of dry
toluene, and the reaction mixture was refluxed and
stirred for 48 h at 100°C. The product was isolated with
an external magnet and washed with ethanol and diethyl
ether, consecutively, and dried at 50°C for 12 h.
3
.4 | Synthesis of
Fe O @SiO (CH ) N―CH―Ar (Catalyst C )
3
4
2
2 3
4
FIGURE 4 (a) Recyclability of catalyst, and (b) EDX spectrum,
(
c) SEM image and (d) XRD pattern of recycled
2‐Formylbenzoic acid (1.5 mmol, 0.225 g) in 5 ml of
Fe @SiO (CH N―CH―Ar@Pd(0)
3
O
4
2
2
)
3
methanol was added dropwise to a suspension of

8
of 9
MOSTAFAVI ET AL.
TABLE 3 Comparison of catalytic activity of Fe
3
O
4
@SiO
2
(CH
2
)
3
N―CH―Ar@Pd(0) with that of other Pd catalysts previously reported in
the literature
Yield
(%)
Reaction time
(min)
Temperature
(°C)
Catalyst
Aryl halide
Ref.
[
[
[
[
[
[
50]
26]
51]
52]
49]
53]
Pd‐NPs@S. lavandulifolia
Pd/C–C catalyst
Iodobenzene
Iodobenzene
Iodobenzene
Iodobenzene
Iodobenzene
Iodobenzene
Iodobenzene
98
90
95
91
80
92
98
60
60
60
60
Pd NPs@Hibiscus sabadariffa L.
Palladacycle complex
120
90
80 °C
120
78
Pd0@CMC/Fe
Pd‐SBTU@Fe
Fe @SiO (CH
3
O
4
30
3
O
4
420
20
80
3
O
4
2
2
)
3
N―CH―Ar@Pd(0)
75
Present work
Fe O @SiO (CH ) NH (1 g) in 25 ml of methanol for
which was employed for the synthesis of biaryls via the
Suzuki–Miyaura cross‐coupling reaction. Biaryls were
derived in good to excellent yields. The catalyst was
removed from the reaction mixture using an external
magnet, and was used several times without significant
loss of its catalytic activity.
3
4
2
2 3
2
5
min. Then the reaction mixture was refluxed and stirred
for 6 h at 60°C. Subsequently, the product was isolated
with an external magnet, washed with 25 ml of ethanol
and then dried for 10 h at 50°C.
3
.5 | Preparation of
ACKNOWLEDGEMENT
Fe O @SiO (CH ) N―CH―Ar@Pd(0)
3
4
2
2 3
(Catalyst C )
5
We are grateful to the Shahid Bahonar University of
Kerman for the financial support of this research.
Catalyst C (0.5 g) and PdCl (1 mmol) were added into a
4
2
flask containing 25 ml of acetonitrile, and stirred for 24 h
at room temperature. The product was separated with an
external magnet, washed with ethanol and then dried for
ORCID
Mohammad Reza Islami http://orcid.org/0000-0003-0884-
1
0 h at 50°C.
1245
3
.6 | General Procedure for Synthesis of
REFERENCES
Biaryls
[
1] Y. Piao, Y. Jang, M. Shokouhimehr, I. S. Lee, T. Hyeon, Small
007, 3, 255.
2] D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. Int. Ed. 2005,
4, 7852.
An amount of 10 mg of catalyst C was added to a solu-
tion of aryl halide (1 mmol), phenylboronic acid (1 mmol)
and K CO (2 mmol) in EtOH–H O (1:1, 8 ml). The
mixture was heated and stirred at 75°C for 25 min. The
5
2
[
2
3
2
4
[
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[
2
5 min, the nanoparticles were separated from the
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2
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2
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The solvent was removed under reduced pressure to give
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4
| CONCLUSIONS
In summary, we synthesized a new heterogeneous
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