Palladium nanoparticles supported on aminopropyl-functionalized clay as efficient catalysts for phosphine-free c-c bond formation via Mizoroki-Heck and Suzuki-Miyaura reactions

Article abstract of DOI:10.1246/bcsj.20100219

In this study, we have used palladium nanoparticles supported on aminopropyl-functionalized clay as an efficient catalyst for Mizoroki-Heck and Suzuki-Miyaura reactions. By using this catalyst, the reaction of iodo- and bromoarenes with n-butyl acrylate and styrene proceeded well and smoothly to produce the desired products in good to excellent yields under solvent-free conditions. The catalyst has been recycled for ten runs without much loss of its catalytic activity. SuzukiMiyaura reaction of structurally different aryl halides (I and Br) with phenylboronic acid by the aid of this catalyst in refluxing water or SDS micellar solution in the absence of any organic co-solvent was also performed well to give the desired biphenyl products in good to excellent yields. Production of the corresponding homocoupled products in negligible amounts was observed in these reactions. In comparison with many other reported palladium-catalyzed MizorokiHeck and SuzukiMiyaura reactions, the Pd-loading of this catalyst is one of the lowest. In the presence of this catalyst, all the reactions proceeded without using any external phosphorus ligands.

Full text of DOI:10.1246/bcsj.20100219

100
Bull. Chem. Soc. Jpn. Vol. 84, No. 1, 100–109 (2011)
© 2011 The Chemical Society of Japan
Palladium Nanoparticles Supported on Aminopropyl-Functionalized
Clay as Efficient Catalysts for Phosphine-Free C-C Bond Formation
via Mizoroki-Heck and Suzuki-Miyaura Reactions
Habib Firouzabadi,*1 Nasser Iranpoor,*1 Arash Ghaderi,1 Maryam Ghavami,1 and S. Jafar Hoseini2
1Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran
2Chemistry Department, College of Sciences, Yasouj University, Yasouj, Iran
Received August 9, 2010; E-mail: firouzabadi@chem.susc.ac.ir
In this study, we have used palladium nanoparticles supported on aminopropyl-functionalized clay as an efficient
catalyst for Mizoroki-Heck and Suzuki-Miyaura reactions. By using this catalyst, the reaction of iodo- and bromoarenes
with n-butyl acrylate and styrene proceeded well and smoothly to produce the desired products in good to excellent yields
under solvent-free conditions. The catalyst has been recycled for ten runs without much loss of its catalytic activity.
Suzuki-Miyaura reaction of structurally different aryl halides (I and Br) with phenylboronic acid by the aid of this catalyst
in refluxing water or SDS micellar solution in the absence of any organic co-solvent was also performed well to give the
desired biphenyl products in good to excellent yields. Production of the corresponding homocoupled products in
negligible amounts was observed in these reactions. In comparison with many other reported palladium-catalyzed
Mizoroki-Heck and Suzuki-Miyaura reactions, the Pd-loading of this catalyst is one of the lowest. In the presence of this
catalyst, all the reactions proceeded without using any external phosphorus ligands.
Construction of carbon-carbon bonds is one of the most
their size-dependent evolution properties.20 Investigators have
focused mainly on identifying new properties and applications
of such materials. Comparing to the corresponding bulk
materials, they can have different heat capacity, vapor pressure,
melting point, optical, magnetic, and electronic properties.20
Also owing to their high surface area, application of these
particles as catalysts results in high concentration of reactive
sites leading to higher reactivity and selectivity.2,21,22 There is
also evidence regarding the involvement of in situ generated Pd
nanoparticles in C-C bond forming reactions under phosphine-
free conditions.23
Palladium nanoparticles of different origins have been
utilized in the Mizoroki-Heck and Suzuki-Miyaura arylation
reactions with variable degrees of success.2,21,24-27 Moreover,
the immobilization of palladium onto clay28-30 and zeolites31,32
and their applications in the carbon-carbon bond formation
reactions have been reported. Some palladium catalysts which
are supported on carbon,33 carbon nanotubes,34 different metal
oxides,2,21 silica gel and modified silica gel,35 fluorous silica,27
molecular sieves,36 and so forth are also reported.
The current challenge for developing palladium catalysts
which work in the presence of inexpensive and reusable ligands
or beds is a research area of much interest to chemists from
academia and industries. The role of supports and ligands is to
stabilize the zero-valent palladium and also to minimize the
aggregation of the naked palladium clusters37 which causes
inactivation of zero-valent palladium catalyst.38-40
Since the last decade, introduction of functional groups into
clays has been under attention. Very lately Chen et al. reported
a method for the preparation of nanoparticles of palladium into
montmorillonite modified with quaternary ammonium surfac-
demanding topics in organic synthesis.1-3 In general, transition-
metal-catalyzed cross-coupling reactions are accompanied with
higher yields and selectivity in comparison with many main-
group metals used as catalysts.4 Among the many procedures
reported in the literature, Mizoroki-Heck and Suzuki-Miyaura
reactions are of the most powerful tools for this purpose.5-8
In general, Mizoroki-Heck reaction has been performed
in different media such as organic solvents,9 ionic liquids,10
CO2,11 and water.12 However, less attention has been paid to
perform this reaction under solvent-free conditions,13,14 al-
though it is more environmentally friendly and economically
profitable. Very recently, a solvent-free Mizoroki-Heck reac-
tion has been reported in the presence of palladium catalyst
supported on 1,1,3,3-tetramethylguanidinium (TMG)-modified
molecular sieve Santa Barbara (SBA-15) or SBA-TMG at
140 °C. By the aid of this catalyst, only the reaction of aryl
iodides with olefins has been reported.15
Suzuki-Miyaura cross-coupling reaction is a highly practical
and simple method for the synthesis of biaryls, which are found
in natural products, pharmaceuticals, agrochemicals, etc.16 So,
improvement of the present methods is always welcome by
industries and academia. Recently, development of organic
synthesis in aqueous media has attracted a great deal of interest
due to the low cost, nontoxicity, abundance, safety, and
nonflammability of water and easy phase separation between
organic compounds and water are the advantages of using
water as the reaction media.17-19
Nowadays, attention has been paid to the use of nano-
particles in comparison with the corresponding bulk materials,
because of their potential applications in a variety of fields and
Published on the web January 1, 2011; doi:10.1246/bcsj.20100219

H. Firouzabadi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
101
Wavelength/nm
Wavelength/nm
(a)
(b)
Figure 1. UV-vis spectra of (a) Pd(II) before reduction and (b) Pd(0) after reduction with NaBH4.
tant which is used for aerobic oxidation of benzyl alcohol.41
Mann et al. reported the preparation of aminopropyl-function-
alized clay with unit cell composition of [H2N(CH2)3]8Si8-
Mg6O16(OH)4 and applied the clay for stabilization of some
biomolecules.42 Later, Rao reported the use of this amino-
functionalized clay as a support for stabilization of nano-
particles of Au, Ag, Pd, and Pt wrapped in exfoliated sheets of
the clay which can be easily dispersed in water.43
In continuation of our recent work on reactions under
solvent-free conditions and in aqueous media,12,44 we now
present the first report of catalytic use of this palladium
nanoparticles supported on aminoclay for carbon-carbon bond
formation via Mizoroki-Heck reaction under solvent-free
conditions and Suzuki-Miyaura reaction in aqueous media.
2θ/degree
Figure 2. XRD pattern of the Pd-aminoclay which shows
the peaks related to Pd(0) nanoparticles.
Results and Discussion
The Catalyst Characterization. For this study, first we
had to scale-up the preparation of the palladium nanoparticles
supported on aminoclay. For this purpose, a gram scale
preparation was developed and the characterization of the
produced palladium nanoparticles supported on aminoclay was
performed by different means. The UV-vis spectrum of the
resulting composite shows the complete conversion of Pd(II) to
Pd(0) by the absence of the peak at 420 nm (Figure 1).
The X-ray diffraction (XRD) pattern of the composite shows
that the bilayer arrangement of aminoclay has been maintained
in the large-scale preparation. The low angle reflection at d001 is
the strong evidence for this arrangement. The characteristic
bands for Pd(0) can be observed at (111), (200), (220), and
(311) crystallographic planes (Figure 2).12
Scanning electron microscopy (SEM) of the gram-scaled
prepared composite shows that the average size of the
nanoparticles is µ30 nm (Figure 3).
Figure 3. SEM picture of the immobilized palladium
nanoparticles on amino-functionalized clay which is
obtained by a gram-scale synthesis.
Atomic force microscopy (AFM) image of the composite
shows that the palladium nanoparticles are dispersed regularly
on the clay surface (Figure 4). According to the voltage profile
of the AFM, the average size of palladium nanoparticles (30 to
40 nm) was in accord with the information obtained by the
corresponding SEM image (Figure 3).
The palladium content of the aminoclay for the gram-scale
prepared composite was also obtained by induced coupled
plasma (ICP) to be 119 mg of palladium per kilogram of the
aminoclay support.
Application of the Palladium Nanoparticles Supported
on Aminoclay as a Catalyst in Mizoroki-Heck Reaction
under Solvent-Free Conditions. In order to optimize the
reaction conditions, first we studied the effect of media upon
the reaction. For this purpose, the reaction of iodobenzene
(1 mmol, 0.11 mL) with n-butyl acrylate (1.5 mmol, 0.21 mL) in
the presence of the supported palladium nanoparticles (0.01 g,
which contains 1.12 © 10¹3 mmol of Pd) in different solvents
and under solvent-free conditions was studied. Comparison of

102
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
C-C Bond Formation via Pd Nanoparticles
[−8.49V → −2.02V] −9.02V → −1.89V
(a)
(b)
(c)
Figure 4. AFM images (a) 3D image (b) 2D image (1 ¯m); (c) Voltage profile.
Table 1. Optimization Conditions in Mizoroki-Heck Reac-
tion between Iodobenzene and n-Butyl Acrylate in the
Presence of Pd Nanoparticles Supported on the Aminoclay
at 130 °C
Table 2. Reusability of the Catalyst in Reaction between
Iodobenzene and n-Butyl Acrylate in the Presence of
n-Pr3N and 0.01 g of the Catalyst
Run
1
2
3
4
5
6
7
8
9
10
Entry
Solvent
Time
Yield/%a)
Time for completion
of the reaction/min
25 25 25 45 45 45 50 80 95 120
1
2
3
4
5
H2O
Toluene
EtOH
NMP
Solvent-free
12 h
12 h
12 h
1.25 h
25 min
80b)
20b)
100b)
100
100
high coordinate N-methylpyrrolidone (NMP) solvent, for the
reaction of iodobenzene with n-butyl acrylate, the Pd-clay was
removed by hot filtration after 20% conversion of iodobenzene.
Continuation of the reaction under the same conditions gave
70% yield within 72 h reaction time showing that the amount of
leaching was low for this catalyst. Quantitative examination by
ICP analysis showed 7% leaching after the first run.
The catalyst was also recycled for the reaction of iodoben-
zene with n-butyl acrylate. We were able to recycle the catalyst
for 10 consecutive runs in order to complete the reaction within
25-120 min. This shows the catalytic activity of the catalyst
diminishes as the number of the runs increases. The results are
shown in Table 2.
Then in order to show the general applicability of the
catalyst we applied similar reaction conditions to structurally
different aryl iodides with styrene and n-butyl acrylate. The
reactions proceeded well with high isolated yields of the
desired products. This procedure is applicable for aryl iodides
carrying both electron-donating and electron-withdrawing
a) Refers to conversion yields. b) The reaction was carried out
in vacuum sealed tube.
the results shows that the reaction in the absence of solvent
proceeded much better than in solvents with excellent yield
and much shorter reaction time. The results of this study are
presented in Table 1.
Leaching of toxic palladium particles into the reaction
mixture gives rise to many problems such as contamination of
the final products with the residues of this metal.45a-45c This
problem gets more serious when the palladium catalyst is used
for pharmaceutical purposes and also for food products.
Therefore, the amount of leaching is of vital importance. For
this aim, the quantity of leaching of palladium particles from
the aminoclay was determined by hot filtration test.45d
Typically, to check the amount of leaching of Pd particles into

H. Firouzabadi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
103
Table 3. Mizoroki-Heck Reaction of Aryl Halides (1 mmol) with n-Butyl Acrylate or Styrene (1.5 mmol) in the Presence of
Pd-Supported Nanoparticles on the Aminoclay under Solvent-Free Conditions
Catalyst
X
n-Pr3N (1.5 mmol)
R2
R2
+
Neat
130 °C
R1
R1
1
2
3
Catalyst/g;
Pd loading
/mol %
Isolated
yield/%
Entry
1
Aryl halide
Alkene
Product
Time
0.01;
1.12 © 10
25 min
95
90
86
¹3
1a
2a
2a
2a
3a
3b
0.01;
1.12 © 10
2
3
1 h
¹3
1b
1c
0.01;
1.12 © 10
2.15 h
¹3
3c
0.01;
1.12 © 10
4
5 days
80
¹3
2a
3d
1d
1e
0.01;
1.12 © 10
5
6
7
55 min
30 min
4.30 h
91
98
91
¹3
¹3
¹3
2a
2a
3e
3f
3f
0.01;
1.12 © 10
1f
0.02;
2.24 © 10
2a
1g
1h
0.02;
2.24 © 10
8
9
2.30 h
1.15 h
96
91
¹3
2a
2a
2b
3g
0.01;
1.12 © 10
¹3
1i
3h
3i
0.01;
1.12 © 10
10
1.15 h
71a)
¹3
1a
Continued on next page:

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Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
C-C Bond Formation via Pd Nanoparticles
Continued:
Catalyst/g;
Isolated
Entry
Aryl halide
Alkene
Product
Pd loading
/mol %
Time
yield/%
0.01;
1.12 © 10
11
6 h
77a)
¹3
2b
2b
2b
1b
3j
0.01;
1.12 © 10
12
13
6.20 h
9 h
79a)
¹3
1c
1f
3k
0.01;
1.12 © 10
80a)
¹3
3l
0.02;
2.24 © 10
14
15
3 days
6 h
76a)
82a)
¹3
2b
2b
1h
1i
3m
3n
0.01;
1.12 © 10
¹3
0.02;
2.24 © 10
16
31 h
81
¹3
2a
1j
3o
0.02;
2.24 © 10
17
18
8 days
3 days
74
¹3
2a
2a
1k
1l
3p
3a
0.03;
3.36 © 10
®
¹3
groups. The coupling reaction of sterically hindered aryl iodide
1d with n-butyl acrylate proceeded slowly within five days
producing the desired product in 80% isolated yield. The long
reaction time of this reaction shows the strong effect of steric
hindrance upon the rate of this reaction (Table 3, Entry 4).
This catalyst was also employed for the reaction of the less
reactive aryl bromides substituted with electron-donating and
electron-withdrawing groups with both n-butyl acrylate and
styrene. The reaction with aryl bromides substituted with
electron-donating groups did not proceed even after long
reaction times. However, the reaction of aryl bromides
substituted with electron-withdrawing groups proceeded
smoothly using higher amounts of the catalyst (0.02 g which
contains 2.24 © 10¹3 mmol of Pd) in longer reaction times with
lower yields in comparison with their corresponding iodides.
The results are tabulated in Table 3.
The reaction of heteroaryl bromides such as 3-bromopyri-
dine and 5-bromopyrimidine with n-butyl acrylate proceeded
well with the isolation of the desired products in good yields
(Table 3, Entries 16 and 17).
Application of the Palladium Nanoparticles Supported
on Aminoclay as a Catalyst in Suzuki-Miyaura Reaction in
Water. Based on the optimization studies for catalyst loading,
we realized that in the case of aryl iodides, 0.005 g of the
aminoclay catalyst which carries 5.6 © 10¹6 mmol of palla-
dium is sufficient to carry out the reactions in appropriate
reaction times (Table 4, Entries 7 and 8). This amount of the
catalyst is amongst the lowest loading catalysts reported for this
reaction in the literature.3,46-48 Primary studies to obtain the
optimum conditions for the reaction showed that solvent-free
condition was not suitable here, however the reactions occurs
efficiently in water (Table 4, Entries 2 and 6-13). This led us to

H. Firouzabadi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
105
Table 4. Optimization Conditions for the Reaction of 4-Iodotoluene (0.5 mmol), Phenylboronic Acid
(0.75 mmol), Pd Nanoparticles Supported on Aminoclay (0.005 g), Base and Solvent at 110 °C
Me
I
B(OH)2
Base (0.75mmol), Solvent (4 mL)
+
Me
Pd nanoparticles supported
on aminoclay (0.005 g)
5
T = 110 °C
Entry
Base
Solvent
Time/h
GC conversion yield/%
1
2
2
3
4a)
5
6
7
8b)
9
10
11
12
13a)
14c)
Tri(n-propyl)amine
Tri(n-propyl)amine
Tri(n-propyl)amine
(NH4)2CO3
(NH4)2CO3
(NH4)2CO3
Tri(n-propyl)amine
(NH4)2CO3
(NH4)2CO3
Cs2CO3
K2CO3
NMP
DMSO
none
DMSO
EtOH
1-Propanol
H2O
H2O
H2O
H2O
H2O
24
24
24
24
24
15
10
10
15
Trace
Trace
100
100
90
100
100
50
24
6
5.3
9.5
8.5
5.75
6.5
6
NaOH
N-Ethylmorpholine
(NH4)2CO3
H2O
H2O
H2O
H2O
65
60
10d)
10.5
24
(NH4)2CO3
a) The reaction was conducted at 80-85 °C. b) 0.0025 g of the catalyst was used. c) The reaction was
conducted in the presence of Pd-free aminoclay. d) 35% of biphenyl was obtained.
Table 5. The Effect of Surfactants on the Reaction of
Iodobenzene (0.5 mmol) with Phenylboronic Acid
(0.75 mmol) in Water
4-iodotoluene (0.5 mmol, 0.11 g), phenylboronic acid (0.75
mmol, 0.09 g), ammonium carbonate (0.75 mmol, 0.12 g) and
palladium nanoparticles supported aminoclay (0.005 g, con-
tains 5.6 © 10¹6 mmol of Pd nanoparticles) in neat water
(4 mL) at 110 °C (Table 4, Entry 7).
I
B(OH)2
(NH4)2CO3 (0.75 mmol)
+
H2O (4 mL) , Reflux
Similar reaction was also conducted in N-methylpyrrolidone
(NMP) and dimethyl sulfoxide (DMSO). In these solvents, the
reaction proceeded in only 15 and 10% respectively within 24 h
(Table 4, Entries 1 and 2). The use of refluxing ethanol and 1-
propanol was also examined. In these solvents, only trace
amounts of the product were obtained (Table 4, Entries 4 and
5). Therefore, we chose water as the appropriate solvent for this
reaction. To show the effect of different bases on the reaction,
we have examined a wide range of bases for the above model
reaction in water (Table 4).
Pd nano particles supported
on amino clay (0.005 g)
5
GC conversion
Entry
Surfactant
Time
yield/%
1
2
3
4
TBAB (0.5 mmol)
SDS (1 CMC)
SDS (3 CMC)
SDS (9 CMC)
1 h
2.5 h
1 h
45
78
97
94
1 h 20 min
The results indicated that ammonium carbonate was a
suitable base for the reaction under the chosen conditions
(Table 4, Entry 7). To ensure that the palladium nanoparticles
bear the main role in the reaction, we conducted a similar
reaction in the presence of palladium-free aminoclay under the
optimized conditions. The cross-coupling reaction proceeded
sluggishly giving only 10% of the desired product after 24 h,
whereas a substantial amount of the biphenyl product (35%
yield GC) was produced in the reaction mixture (Table 4,
Entry 14).
The effect of surfactants such as tetra-n-butylammonium
boromide (TBAB) and sodium dodecyl sulfate (SDS) on the
reaction rate of iodobenzene with phenylboronic acid in water
was also studied. Our findings show that the reaction in the
presence of TBAB proceeded in only 45% yield after 1 h, while
similar reaction in SDS micellar solution (3 CMC) worked well
with higher yield (97%, GC) after 1 h (Table 5, Entries 1 and
3). We have also tested the lower concentration of SDS (1
CMC) in the reaction which causes the reaction to proceed just
78% after 2:30 (Table 5, Entry 2). Higher concentration of
SDS (9 CMC) did not have considerable impact on the reaction
(Table 5, Entry 4).
In order to show the general application of SDS micellar
media, we have studied the reaction of different aryl halides
carrying electron-donating and electron-withdrawing groups
with phenylboronic acid. Shorter reaction times and higher
yields are the general trend for the reaction of different
substrates we have studied in this situation. The results in neat
water and micellar media are compared in Table 6. Therefore,
we can conclude that SDS micellar medium is a more suitable
media than using neat water for the reactions conducted in

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Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
C-C Bond Formation via Pd Nanoparticles
Table 6. Suzuki-Miyaura Reaction between Aryl Halides and Phenylboronic Acid in the Presence of
Pd Nanoparticles
(NH4)2CO3 (0.75 mmol)
X
B(OH)2
H2O or SDS (3 CMC)(4 mL)
Reflux
R
R
+
X=I
Pd nano particles supported
on amino clay 0.005g
X=Br Pd nano particles supported
on amino clay 0.015g
5
1
6
Time/h;
Time/h;
Entry
1
Substrate
Product
Yield/%a)
Yield/%b)
3.5; 94
5.3; 91
1; 95
6a
6b
1a
2
5.5; 92
1b
3c)
10; 88
12; 78
6.5; 85
10; 75
6c
1c
4
6d
1m
5c)
6c)
7
9; 86
6.5; 90
48; 78
18; 82
1i
1f
6e
6f
64; 76
30; 75
6g
6a
1c
8
9
4; 87
3.5; 93
9; 95
1n
10; 91
21; 87
7; 72
6b
6c
6d
6f
1o
1p
1q
10
11
6; 92
10; 92
12c)
13c)
48; trace
10.5; 90
72; 75
7.5; 94
1g
1h
6h
Continued on next page:

H. Firouzabadi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
107
Continued:
Time/h;
Time/h;
Entry
14c)
Substrate
Product
Yield/%a)
Yield/%b)
13; 75
10; 88
7; 89
6i
6j
1j
15
16
14.5; 88
1r
48; 42
25; 89
1s
6k
17
30; 58
13; 65
60; 15
1k
1t
6l
18d)
48; trace
6b
a) All yields refer to the isolated products and the reactions are conducted in neat water. b) All yields refer
to the isolated products and the reactions are conducted in SDS micellar solution (3 CMC). c) The reaction
was conducted in a sealed tube. d) Pd catalyst (0.1 g) was used, the reaction was conducted in a vacuum
sealed tube at 130 °C and the yield is referred to GC conversion yield.
the presence of this catalyst. The results of this study are
summarized in Table 6.
For aryl bromides and heteroaryl bromides the optimum
amount of the catalyst was 0.015 g (contains 1.68 © 10¹5 mmol
of Pd nanoparticles) which is three times more than the amount
used for aryl iodides.
Unfortunately, aryl chlorides were not reactive in the
reaction with phenylboronic acid by the aid of this catalyst in
a sealed tube at 130 °C (Table 6, Entry 18).
suspension, a solution of PdCl2 in water (100 mL, 1 mM) was
added followed by the dropwise addition of NaBH4 solution
(100 mL, 0.1 M), within 15 min (fast addition of the reducing
agent results formation of larger particles). Then ethanol
(100 mL) was added to the resulting mixture to precipitate the
desired palladium nanoparticles supported on aminoclay. The
precipitates were isolated by centrifugation and dried at 40 °C
under vacuum.
Reaction of Iodobenzene with n-Butyl Acrylate under
Solvent-Free Conditions as
Mizoroki-Heck Reaction. Iodobenzene (1 mmol, 0.11 mL)
and n-butyl acrylate (1.5 mmol, 0.21 mL) were added to a flask
a Typical Procedure for
Experimental
General. NMR spectra were recorded on a Bruker Avance
DPX-250 spectrometer (1H NMR 250 MHz and 13C NMR
62.9 MHz) in CDCl3 and TMS as the internal standard. UV-
vis spectra were recorded on Perkin-Elmer, Lambda 25, UV-
vis spectrometer which shows the complete conversion of
Pd(II) to Pd(0). Scanning electron micrographs were obtained
by SEM (SEM, XL-30 FEG SEM, Philips, at 20 KV). X-ray
diffraction (XRD, D8, Advance, Bruker, axs) spectra were used
to characterize the catalyst. Atomic force microscope, AFM
(DME, Dual ScopeTM DS 95-200-E) was also used to obtain
AFM image for the size of the nanoparticles. The amount of
palladium supported on the aminoclay was determined by ICP
analyzer (Varian, Vista-pro).
¹5
containing the catalyst (0.01 g of the catalyst, 1.12 © 10
mmol of palladium) and n-Pr3N (1.5 mmol, 0.29 mL) in the
absence of solvent. The mixture was stirred at 130 °C in air.
After completion of the reaction (monitored by TLC), chloro-
form (15 mL) was added to the reaction vessel. The catalyst
was separated by simple filtration. Dilute HCl (2 M, 1 © 10
mL) solution was added to the chloroform phase and decanted.
Then the organic phase was washed with water (10 mL) and
dried over anhydrous Na2SO4. Evaporation of the solvent gave
the desired n-butyl cinnamate 3a in 95% isolated yield
(Table 3).
Reusability of the Catalyst in Mizoroki-Heck Reaction.
After completion of the reaction in the first run, chloroform
(5 mL) was added to the reaction mixture to extract the organic
compounds. The chloroform solution was removed by a
syringe and the catalyst was dried under nitrogen flow. After
complete drying, the catalyst was charged again into the vessel
Modified Gram-Scale Preparation of Palladium Nano-
particles Supported on Aminopropyl-Functionalized Clay.
The aminoclay was prepared according to a reported proce-
dure,42 which was first exfoliated by dispersing it (1 g) in
distilled water (100 mL) by sonication for 3 min. To this

108
Bull. Chem. Soc. Jpn. Vol. 84, No. 1 (2011)
C-C Bond Formation via Pd Nanoparticles
2
3
A. J. Amali, R. K. Rana, Green Chem. 2009, 11, 1781.
J. J. Dong, J. Roger, F. Požgan, H. Doucet, Green Chem.
containing the reacting substrates and the reaction was
performed under similar conditions, as mentioned in the
preceding section. This recycling was repeated for ten consec-
utive runs (Table 2).
2009, 11, 1832.
4
F. Schneider, A. Stolle, B. Ondruschka, H. Hopf, Org.
Process Res. Dev. 2009, 13, 44.
Reaction of Iodobenzene with Phenylboronic Acid in
Neat Water Using Palladium Nanoparticles Supported on
Aminoclay as a Typical Procedure for Suzuki-Miyaura
Reaction. Iodobenzene (0.5 mmol, 0.055 mL) and phenyl-
boronic acid (0.75 mmol, 0.09 g) were added to a flask
5
3009.
6
I. P. Beletskaya, A. V. Cheprakov, Chem. Rev. 2000, 100,
K. C. Nicolaou, P. G. Bulger, D. Sarlah, Angew. Chem., Int.
Ed. 2005, 44, 4442.
7
V. Polshettiwar, A. Molnár, Tetrahedron 2007, 63, 6949.
F. Alonso, I. P. Beletskaya, M. Yus, Tetrahedron 2005, 61,
¹6
containing the catalyst (0.005 g of the catalyst, 5.6 © 10
8
11771.
9
mmol of palladium) and (NH4)2CO3 (0.75 mmol, 0.12 g) in
water (4 mL). The mixture was stirred in an oil bath under
reflux conditions. After completion of the reaction (monitored
by TLC), the reaction mixture was cooled down to room
temperature and then, dichloromethane (3 © 10 mL) was added
to the reaction vessel. The organic phase was separated and
dried over anhydrous Na2SO4. Evaporation of the solvent gave
the pure desired biphenyl 6a in 94% isolated yield (Table 6).
The reaction in the SDS micellar solution is similar to the
reaction in water, except, we added SDS micellar solution (3
CMC) instead of water.
Y. Han, H. V. Huynh, L. L. Koh, J. Organomet. Chem.
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11 M. A. Carroll, A. B. Holmes, Chem. Commun. 1998, 1395.
12 H. Firouzabadi, N. Iranpoor, M. Gholinejad, Tetrahedron
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13 N. E. Leadbeater, V. A. Williams, T. M. Barnard, M. J.
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14 A. Díaz-Ortiz, P. Prieto, E. Vázquez, Synlett 1997, 269.
15 X. Ma, Y. Zhou, J. Zhang, A. Zhu, T. Jiang, B. Han, Green
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Conclusion
16 X.-M. Zhao, X.-Q. Hao, K.-L. Wang, J.-R. Liu, M.-P. Song,
Y.-J. Wu, Transition Met. Chem. (Dordrecht, Neth.) 2009, 34, 683.
17 a) C.-J. Li, T. H. Chan, Organic Reactions in Water:
Principles, Strategies and Applications, ed. by M. Lindström,
Blackwell Publishing, New York, 1997. b) B. Feng, Z. Hou, X.
Wang, Y. Hu, H. Li, Y. Qiao, Green Chem. 2009, 11, 1446. c)
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& Professional, Glasgow, 1998.
18 R. B. DeVasher, L. R. Moore, K. H. Shaughnessy, J. Org.
Chem. 2004, 69, 7919.
19 H. Firouzabadi, N. Iranpoor, A. Garzan, Adv. Synth. Catal.
2005, 347, 1925.
20 a) A. Fukuoka, H. Araki, J. Kimura, Y. Sakamoto, T.
Higuchi, N. Sugimoto, S. Inagaki, M. Ichikawa, J. Mater. Chem.
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21 K. Chattopadhyay, R. Dey, B. C. Ranu, Tetrahedron Lett.
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In conclusion, in this article, we have reported a gram-scale
preparation of palladium nanoparticles supported on amino-
propyl-functionalized clay. The structure of the gram-scale
prepared nanoparticles was determined by UV-vis, XRD,
SEM, and AFM images. The amount of palladium supported
on the aminoclay has been determined by ICP analysis. We
have used these highly dispersed palladium nanoparticles
supported on aminoclay with the average size of the nano-
particles to be µ30-40 nm as a highly efficient catalyst for the
Mizoroki-Heck arylation under solvent-free conditions. In the
presence of this catalyst, the reaction of aryl iodides and aryl
bromides with n-butyl acrylate and styrene proceeded well
giving the desired products in high yields. The catalyst is
reusable and has been recycled for the reaction of iodobenzene
with n-butyl acrylate for ten consecutive runs. Also, this
palladium-supported aminoclay has been successfully applied
as a catalyst for Suzuki-Miyaura reactions in neat water and
also in SDS micellar solution in the absence of any organic co-
solvent. The positive effect of the micellar solution is general
and shows its outcome upon the reaction of aryl halides with
phenylboronic acid reaction. The other benefit of using this
catalyst is the low loading of palladium which can render the
reactions without addition of any phosphorus ligands.
23 a) M. T. Reetz, E. Westermann, Angew. Chem., Int. Ed.
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The authors are grateful to TWAS Chapter of Iran based at
ISMO and Shiraz University Research Council for their
supports.
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Supporting Information
1H NMR and 13C NMR spectra of all compounds. This
material is available free of charge on the web at http://
www.csj.jp/journals/bcsj/.
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