A reusable polymer supported copper catalyst for the C-N and C-O bond cross-coupling reaction of aryl halides as well as arylboronic acids

Article abstract of DOI:10.1016/j.jorganchem.2011.10.004

A simple and industrially viable protocol for C-N and C-O coupling was reported here. The polymer supported heterogeneous copper catalyst was prepared from chloromethyl polystyrene using a simple procedure. O-Arylation of substituted phenols with various aryl halides was achieved using this copper catalyst in DMSO medium. This heterogeneous copper catalyst, also efficiently works for the N-arylation of N-H heterocycles with aryboronic acids in methanol. This catalyst was also effective in amination reaction of primary amines with aryl halides as well as arylboronic acids in DMSO medium. The effects of solvent, base and temperature for the O-Arylation and amination reactions were reported. Further, the catalyst can be easily recovered quantitatively by simple filtration and reused up to several times without sufficient loss of its catalytic activity.

Full text of DOI:10.1016/j.jorganchem.2011.10.004

Journal of Organometallic Chemistry 696 (2012) 4264e4274
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A reusable polymer supported copper catalyst for the CeN and CeO bond
cross-coupling reaction of aryl halides as well as arylboronic acids
,
a
a
a
b
Sk.Manirul Islam a , Sanchita Mondal , Paramita Mondal , Anupam Singha Roy , K. Tuhina ,
*
Noor Salam a, Manir Mobarak a
a Dept. of Chemistry, University of Kalyani, Kalyani, Nadia 741235, W.B., India
b Dept. of Chemistry, B.S. College, S-24 PGS, 743329 W.B., India
a r t i c l e i n f o
a b s t r a c t
Article history:
A simple and industrially viable protocol for CeN and CeO coupling was reported here. The polymer
supported heterogeneous copper catalyst was prepared from chloromethyl polystyrene using a simple
procedure. O-Arylation of substituted phenols with various aryl halides was achieved using this copper
catalyst in DMSO medium. This heterogeneous copper catalyst, also efficiently works for the N-arylation
of NeH heterocycles with aryboronic acids in methanol. This catalyst was also effective in amination
reaction of primary amines with aryl halides as well as arylboronic acids in DMSO medium. The effects of
solvent, base and temperature for the O-Arylation and amination reactions were reported. Further, the
catalyst can be easily recovered quantitatively by simple filtration and reused up to several times without
sufficient loss of its catalytic activity.
Received 12 April 2011
Received in revised form
14 September 2011
Accepted 4 October 2011
Keywords:
Polymer supported copper catalyst
O-arylation
N-arylation
Amination
Ó 2011 Published by Elsevier B.V.
Reusable catalyst
1. Introduction
substituted aryl halide to the harsh reaction conditions applied.
Another major drawback of this protocol is the use of stoichio-
The formation of aryl-nitrogen and aryl-oxygen bonds via cross-
coupling reactions represent a powerful means for the preparation
of various compounds that are of biological, pharmaceutical and
material interest [1e3]. The development of a mild and highly
efficient method for synthesis of N-arylazoles over classical Ullman
type [4], or nucleophilic aromatic substitution reactions [5], or
coupling with organometallic reagents [6,7] has recently gained
considerable attention in synthetic chemistry [8]. Due to the
economic attractiveness of copper [9] and by using some special
ligands such as N,N- and N, O-bidentate compounds, many CuI-
catalyzed CeN [10,11], CeO [12,13], CeS [14,15], and CeC [16,17]
bond formation reactions have led to a resurgence of interest in
carbon-heteroatom coupling reactions, and their applications seem
to be of more and more importance [18,19]. The copper-mediated
Ullmann coupling reaction [20,21] is still the straightforward
method to form the requisite carbon-heteroatom bonds. However,
the synthetic scope of this reaction is strongly limited by the
insolubility of copper(I) salts in organic solvents, the high reaction
temperatures required (200 ꢀC) and the sensitivity of the
metric amounts of copper or copper salts, which results in the
production of large quantities of waste, making this method envi-
ronmentally unfriendly. Milder reactions using transmetallating
agents, such as triarylbismuth [22], aryl lead triacetates [7], aryl-
boronic acids [23,24] and hypervalent aryl siloxanes [6] have been
developed but these alternatives are limited since the preparation
of highly functionalized substrates usually requires multistep
sequences. Despite significant progress in the Cu-catalyzed N/O-
arylation reaction, only a few reports have appeared describing the
couplings of imidazoles and/or phenols with arylboronic acids/aryl
bromides or of functional substrates or of hindered substrates
[25,26] without the recovery of catalyst. Therefore, it is important
to develop more simple and efficient catalytic systems for the cross-
coupling methodology with an ability to utilize arylboronic acids/
aryl bromides [27,28] with reusability of catalyst. By using certain
copper precatalysts and ligands, successful N-arylation of anilines
[29,30], amides [31], hydrazides [32], oxazolidinones [33] and
various NeH heterocycles [34] with aryl halides as arylating
reagents was reported. However, only limited papers have
contributed to N-arylation of alkylamines (not chelating substrates)
and various NeH heterocycles in heterogeneous condition [35,36].
To date, few reports described reusable copper catalytic systems for
this CeO coupling that allowed the recycling of active metal,
* Corresponding author. Tel.: þ91 33 2582 8750; fax: þ91 33 2582 8282.
E-mail address: manir65@rediffmail.com (Sk.Manirul Islam).
0022-328X/$ e see front matter Ó 2011 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2011.10.004

Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
4265
nevertheless only some reported leaching measurements of metal
toxic residues in final products [37,38].
by column chromatography on silica gel to provide the desired
product.
Homogeneous catalysts have some disadvantages, such as they
may easily be destroyed during the course of the reaction and they
cannot be easily recovered after the reaction for reuse. These
disadvantages can be overcome by anchoring metal on suitable
supports which will allow easy separation and recyclability of the
catalyst with minimal amount of product contamination with
metal. These studies confirm that the anchoring of metal on solid
support not only exhibits improved catalyst activity, stability and
selectivity of the product but also enables easy recovery and reuse
of the catalyst.
Herein we report the synthesis of a polymer supported copper
catalyst and illustrate its application in a number of cross-coupling
reactions such as O-arylation, N-arylation and amination reactions.
Our strategy was to attach a ligand to a polymer support and then
allow it to bind to copper through ligand exchange. The resulting
binding interaction also needs to be strong enough to prevent the
copper from dissociating from the polymer support under the
reaction conditions. Hence, using Cu(OAc)2 as the source of copper,
displacement of acetate would provide a copper-bound polymer-
supported catalyst.
2.2. General procedure for the N-arylation of NeH heterocycles
with arylboronic acids
In a 100 mL RB flask, polymer supported Cu(II) catalyst (50 mg,
0.0098 mmol), arylboronic acid (1 mmol), NeH heterocycles
(1.2 mmol), and 10 ml methanol were stirred under nitrogen
atmosphere, at 40 ꢀC. The reaction mixtures were collected at
different time intervals and identified by GCMS and quantified by
GC. After the completion of the reaction, the catalyst was filtered off
and washed with water followed by acetone and dried in oven. The
filtrate was extracted with ethyl acetate (3 ꢂ 20 mL) and the
combined organic layers were dried with anhydrous Na2SO4 by
vacuum. The filtrate was concentrated by vacuum and the resulting
residue was purified by column chromatography on silica gel to
provide the desired product.
2.3. General procedure for the amination of aromatic amines with
arylboronic acids
In a 100 mL RB flask, polymer supported Cu(II) catalyst (50 mg,
0.0098 mmol), arylboronic acid (1.5 mmol), aromatic amines
(1.2 mmol), K2CO3 (1 mmol), and 10 ml DMSO stirred under
nitrogen atmosphere, at 140 ꢀC. The reaction mixtures were
collected at different time intervals and identified by GCMS and
quantified by GC. After the completion of the reaction, the catalyst
was filtered off and washed with water followed by acetone and
dried in oven. The filtrate was extracted with ethyl acetate
(3 ꢂ 20 mL) and the combined organic layers were dried with
anhydrous Na2SO4 by vacuum. The filtrate was concentrated by
vacuum and the resulting residue was purified by column chro-
matography on silica gel to provide the desired product.
2. Experimental
Analytical grade reagents and freshly distilled solvents were
used throughout. All reagents and substrates were purchased from
Merck. Liquid substrates were predistilled and dried by molecular
sieve and solid substrates were recrystallized before use. Distilla-
tion, purification of the solvents and substrate were done by
standard procedures [39]. 5.5% crosslinked chloromethylated
polystyrene was purchased from Aldrich Chemical Company; U.S.A.
Copper acetate was procured from Merck and used without further
purification.
The FTeIR spectra of the samples were recorded from 400 to
4000 cmꢁ1 on a PerkineElmer FTeIR 783 spectrophotometer using
KBr pellets. UVeVis spectra were taken using a Shimadzu UV-
2401PC doubled beam spectrophotometer having an integrating
sphere attachment for solid samples. Thermogravimetric analysis
(TGA) was carried out using a Mettler Toledo TGA/DTA 851e.
Surface morphology of the samples was measured using a scanning
electron microscope (SEM) (ZEISS EVO40, England) equipped with
EDX facility. Copper content in the catalyst was determined using
a Varian AA240 atomic absorption spectrophotometer (AAS). The
reaction products were quantified (GC data) by Varian 3400 gas
chromatograph equipped with a 30 m CP-SIL8CB capillary column
and a flame ionization detector and identified by Trace DSQ II GC-
MS equipped with a 60 m TR-50MS capillary column.
2.4. General procedure for the amination of aromatic amines with
aryl halides
In an oven dried 100 mL RB flask, polymer supported Cu(II)
catalyst (50 mg, 0.0098 mmol), aryl halide (1 mmol), aromatic
amines (1.2 mmol), KOH (1 mmol), and 10 ml DMSO were stirred
under nitrogen atmosphere, at 140 ꢀC. The reaction mixtures were
collected at different time intervals and identified by GCMS and
quantified by GC. After the completion of the reaction, the catalyst
was filtered off and washed with water followed by acetone and
dried in oven. The filtrate was extracted with ethyl acetate
(3 ꢂ 20 mL) and the combined organic layers were dried with
anhydrous Na2SO4 by vacuum. The filtrate was concentrated by
vacuum and the resulting residue was purified by column chro-
matography on silica gel to provide the desired product.
2.1. General procedure for the O-arylation of phenol with aryl
halides
2.5. Synthesis of the metal complexes
Polymer supported Cu(II) catalyst (0.05 g, 0.0098 mmol) in
DMSO (5 mL) was taken in a 100 ml R.B flask and stirred at room
temperature for 10 min. Then aryl halide (1 mmol), phenol
(1 mmol), tetrabutylammonium bromide (tBu4NBr) (0.1 mmol),
Cs2CO3 (1 mmol) and DMSO (5 mL) were added to it. The final
reaction mixture was refluxed at 120 ꢀC under an open air condi-
tion. The reaction mixtures were collected at different time inter-
vals and identified by GCMS and quantified by GC. After the
completion of the reaction, the catalyst was filtered off and washed
with water followed by acetone and dried in oven. The filtrate was
extracted with ethyl acetate (3 ꢂ 20 ml) and the combined organic
layers were dried with anhydrous Na2SO4 by vacuum. The filtrate
was concentrated by vacuum and the resulting residue was purified
The preparation procedure followed to obtain the catalyst is
given in Scheme 1. Catalyst was readily prepared in two steps.
Firstly, the 2 g of chloromethylated polystyrene copolymer (2)
treated with 0.979 g of
b-alanine (1) to produce corresponding
polymer anchored ligand in the presence of sodium carbonate base
(0.759 g) in N,N-dimethylformamide solvent (DMF) at 100 ꢀC for
48 h to obtained a light brown polymer (L). The polymer was
washed thoroughly with DMF to remove excess b-alanine and then
with 1 M HCl to remove excess base. Finally, it was washed with
double distilled water, dried and stored at room temperature for
further use. This Polymer anchored
b-alanine ligand (1 g) in acetic
acid (20 mL) was treated with 5 mL 1% (w/v) acetic acid solution of

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Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
P
O
O
C
CH2
( )
CH2
/
DMF Na2CO3
C
O
CH2 CH2
NH2
P
100 0C/
NH2
P
HO
48 h
1
CH2
(L)
P
(2)
CH2Cl
CuI
ACN
O
Cu(OAc)2
AcOH
CuCl2
C
O
CH2
CH2
NH
P
Reflux
MeOH
CH2
P
O
Cu
O
I
C
O
CH2
CH2
P
C
O
CH2 CH2
P
CuLI
NH
P
CH2
CH2
NH
P
Cu
Cu
AcO
OAc
Cl
Cl
CuL(OAc)2
CuLCl2
Scheme 1. Synthesis of the polymer supported copper catalysts.
Table 1
Chemical composition of polymer anchored ligands and polymer supported Cu(II) catalyst.
Compound
Color
C%
H%
Cl%
N%
Cu%
(L)
CuL(OAc)2
CuLI
White
Yellowish Green
Green
71.11 (71.16)
66.89 (66.84)
65.93 (66.19)
66.19 (66.58)
7.14 (7.12)
6.63 (6.70)
6.39 (6.58)
6.47 (6.61)
3.49 (3.51)
3.12 (3.17)
3.15 (3.27)
6.34 (6.71)
5.54 (5.54)
5.06 (5.01)
5.22 (5.16)
5.27 (5.19)
e
3.36 (3.41) 3.34a
2.28 (2.34)
2.97 (3.06)
CuLCl2
Light green
Calculated values are given in parentheses.
a
Used catalyst.
copper acetate over a period of nearly 30 min under constant
stirring. Then the reaction mixture was refluxed for 24 h. The
greenish yellow copper complex thus formed was filtered and
washed thoroughly with ethanol and dried in room temperature
under vacuum.
copper iodide over a period of nearly 30 min under constant stir-
ring. Then the reaction mixture was refluxed for 24 h. The green
color copper complex (CuLI) thus formed was filtered and washed
thoroughly with ethanol and dried in room temperature under
vacuum.
The Polymer anchored
b
-alanine ligand (1 g) in acetonitrile
The Polymer anchored
b-alanine ligand (1 g) in methanol
(20 mL) was treated with 5 mL 1% (w/v) acetonitrile solution of
(20 mL) was treated with 5 mL 1% (w/v) methanolic solution of
Fig. 1. FTeIR Spectral data of polymer anchored ligand (L) (a), CuL(OAc)2 (b), CuLCl2 (c) and CuLI (d).

Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
4267
3. Result and discussion
3.1. Characterization of the polymer supported Cu(II) catalyst
Due to insolubilities of the polymer supported copper catalyst in
all common organic solvents, its structural investigation was
limited to its physicochemical properties, chemical analysis, SEM,
TGA, IR and UVeVis spectroscopic data. Table 1 provides the data of
elemental analysis of polymer supported ligand and the polymer
supported copper catalysts. Copper content in the catalysts deter-
mined by AAS suggests 3.36 wt % Cu in the catalyst.
The band at 676 cmꢁ1 for eCeCl stretching had disappeared in
the polymer anchored ligand. A few new bands appeared, e.g. those
at 3422 cmꢁ1 along with bands at 1641 cmꢁ1 showed the presence
of free eNH2 groups in the ligand. On complexation with copper,
the frequency of free eNH2 groups is reduced in intensity. In copper
catalyst (CuL(OAc)2)
a medium intensity band observed at
1319 cmꢁ1 suggests the monodentate coordination of the acetate
groups [40]. Monodentate acetate usually shows two bands at
1630 cmꢁ1 and 1310 cmꢁ1 due to antisymmetric and symmetric
stretching respectively [41]. The acetate oxygen involved in the
complexation with copper which is clearly evident from the
appearance of a new medium intensity band at 430 cmꢁ1 assign-
able to
n CueO in the IR spectra [41]. In addition, the bands at
528 cmꢁ1 may be assigned to the CueN [42] stretching vibration. In
FTeIR spectra of CuLCl2 and CuLI complexes, all bands were almost
same as CuL(OAc)2 complex. CuLCl2 shows a new one band at
354 cmꢁ1 for CueCl [43]. FTeIR spectra of the polymer supported
ligand and copper catalysts are given in Fig. 1.
Fig. 2. FEeSEM images of the polymer supported ligand (L) (A), CuL(OAc)2 (B), CuLCl2
(C) and CuLI (D).
The scanning electron micrographs (Fig. 2) of the polymer
supported ligand and supported copper catalysts clearly show the
morphological change which occurred on the surface of poly-
styrene after loading of metal on it. Energy dispersive spectroscopy
analysis of X-rays (EDAX) data for the polymer anchored ligand and
copper catalysts are given in Fig. 3. The EDX data also inform that
the attachment of copper metal on the surface of the polymer
matrix.
copper chloride over a period of nearly 30 min under constant
stirring. Then the reaction mixture was refluxed for 24 h. The light
green color copper complex (CuLCl2) thus formed was filtered and
washed thoroughly with ethanol and dried in room temperature
under vacuum.
Fig. 3. EDAX data of polymer supported ligand (L) (A) and copper catalysts CuL(OAc)2 (B), CuLCl2 (C) and CuLI (D).

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Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
The electronic spectrum (Fig. 4) of the polymer supported
copper catalyst (CuL(OAc)2) has been recorded in the diffuse
reflectance spectrum mode as MgCO3/BaSO4 disc due to its solu-
bility limitations in common organic solvents. In the catalyst four
bands at 310, 345, 370 and 410e435 nm are observed. The
absorption around 310 nm may be attributed to p/p* transition in
phenyl moiety. The bands at 345 nm and 370 nm arise due to LMCT.
In this complex, the bands around 410e435 nm are due to ded
transition [44].
Thermal stability of the complexes was investigated using TGA-
DTA at a heating rate of 10 ꢀC/min in air over a temperature range of
30e600 ꢀC. TGA-DTA curves of the polymer supported ligand and
supported copper catalysts are shown in Fig. 5. The ligand and
copper complexes were stable up to 350e370 ꢀC and above this
temperature they decomposed. Thermogravimetric study suggests
that the polymer supported copper complexes degrade at consid-
erably higher temperature.
(c)
(b)
(d)
(a)
3.2. Catalytic activity of the copper catalyst in O-arylation reaction
100
200
300
400
500
600
Temperature (0C)
Aryl ethers are an important class of ‘building blocks’ that are
widely employed in organic synthesis, materials science, and
pharmaceutical or agrochemical areas. To optimize the conditions
for the O-arylation reaction, we have chosen the reaction between
iodobenzene and phenol as a model reaction and various solvents
and bases were screened (Table 2). First of all, the optimal reaction
solvent was investigated. Table 2, entries 1e6 clearly show the
superiority of dimethylsulfoxide (DMSO) and N,N-dimethylforma-
mide (DMF) as reaction solvents for this reaction; other dia-
lkylamide solvents such as N,N-dimethylacetamide (DMA), or N-
methylpyrrolidinone (NMP) performed worse than DMF, whereas
in acetonitrile and 1,4-dioxane the complex was almost inactive.
The influence of bases on the yield of diaryl ether in the presence of
copper catalyst was also investigated (Table 2, entries 1 and 7e11).
It was found that Cs2CO3 was the most effective base, while the use
of other bases such as NaOMe, K3PO4, Et3N, K2CO3 and KOH resulted
in much lower or no yields. Cesium Carbonate was particularly
effective as a base in O-arylation reaction because cesium phen-
oxides are indeed more dissociated and more soluble in organic
solvents than their potassium and sodium counterparts [45].Next,
the reaction was carried out with different amounts of copper
catalysts over the range of 0.025e0.065 g and it was found that
0.05 g of copper catalyst was the most effective catalytic system
Fig. 5. Thermogravimetric weight loss plots for the polymer supported ligand (L) (a),
CuL(OAc)2 (b), CuLCl2 (c) and CuLI (d).
(Table 2, entries 12e14). This arylation was also found to be highly
sensitive to the reaction temperature and time. At lower temper-
atures (50 ꢀC) and with lower reaction time (5 h) only low to
moderate yield was obtained (Table 2, entries 15, 16). From Table 2,
it was found that, 0.05 g of copper catalyst, a reaction temperature
of 120 ꢀC and reaction time of 12 h were found to be optimal. From
the above discussions, it can be seen that the best yield was ob-
tained by using Cs2CO3 (1 mmol) in DMSO solvent at 120 ꢀC for 12 h
under open air.
Table 2
Effect of solvent, base, temperature, reaction time and catalyst amount on the O-
arylation reaction.a
OH
I
O
polymer supported
Cu(II) catalyst
+
>
1.2
1.0
0.8
0.6
0.4
0.2
Entry
Base
Solvent
Temperature
Time(h)
Yield(%)
1
2
3
4
5
6
7
8
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
K2CO3
K3PO4
Et3N
DMSO
DMF
DMA
1,4-dioxane
CAN
NMP
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
120 ꢀ C
130 ꢀ C
100 ꢀ C
90 ꢀ C
12
12
14
14
14
12
12
10
14
12
12
12
12
12
5
96
89
68
60
72
88
87
76
65
55
68
48
77
95
55
62
80 ꢀ C
140 ꢀ C
120 ꢀ C
130 ꢀ C
100 ꢀ C
120 ꢀ C
120 ꢀ C
120 ꢀ C
120 ꢀ C
120 ꢀ C
120 ꢀ C
50 ꢀ C
9
10
11
12b
13c
14d
15
16
KOH
NaOMe
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
12
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g, 0.026 mmol),
1 mmol of iodobenzene, 1 mmol of phenol, 1 mmol of base,0.1 mmol of tBu4NBr,
solvent (10 mL), 120 ꢀC, 12 h, open air. Yield determined by GC and GCMS analysis.
300
350
400
450
500
550
600
b
wavelength / nm
0.025 g of polymer supported Cu(II) catalyst.
0.04 g of polymer supported Cu(II) catalyst.
c
d
Fig. 4. DRSeUVevisible absorption spectra of the polymer supported copper catalyst.
0.065 g of polymer supported Cu(II) catalyst.

Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
4269
iodoarenes (entries 12, 13) was slightly difficult, and offered the
desired products with moderate to good yields. On the other hand,
the reaction was very sensitive to the steric effects of aryl iodides
(entries 14, 15). As shown in Table 3, the present catalytic system
was also effective for the coupling reaction of aryl bromides and
phenols. High yields were obtained for the aryl bromides with an
electron-withdrawing group such as nitro and cyano groups
(entries 17 and 18). The reaction of 4-methylphenyl bromide with
phenol which was a difficult case for classical Ullmann coupling
method, gave the coupling product in 56% (entry 19) yield.
Furthermore 4-cyanophenyl bromide successfully coupled with 4-
methoxyphenol with an excellent yield (entry 20). 4 Methox-
yphenol and 4-methylphenol were good substrates with bromo-
benzene at this reaction condition (entries 21, 22). Additionally, the
relatively lower yield for reaction of 2-methoxyphenyl bromide
with phenol implies that the steric hindrance of aryl bromides was
still disfavored for coupling reaction (entry 23). As can be seen from
Table 3, most of the tested substituted chlorobenzenes afforded the
corresponding diaryl ethers in good to excellent yields. Various
functionalized aryl chlorides, including those bearing electron-
donating and electron-withdrawing groups reacted at this reac-
tion conditions (entries 25e27).
For any supported catalyst, it was important to know its ease of
separation and possible reuse. Polymer anchored copper(II) catalyst
can be easily separated by filtration. For the recycling study O-
arylation reaction was performed with phenol and iodobenzene
maintaining the same reaction conditions using the recovered
catalyst. The catalyst was recycled twice to give isolated yields of
94, 92 (Table 3, entry 1). This showed that the catalyst retained
activity through recycling. It was necessary to carry out a control
experiment to confirm that the copper catalyst promoted the cross-
coupling reaction as opposed to leached copper in solution. After
suspending the copper catalyst in DMSO overnight and then
filtering off the catalyst, the cross-coupling reaction of iodobenzene
Scheme 2. Copper catalyzed O-arylation of phenols with aryl halides X ¼ I, Br, Cl;
R1 ¼ H, Me, OMe, NO2, Br; R2 ¼ H, Me, OMe, CN, NO2.
Under the optimized conditions, the coupling reaction between
a range of phenols and aryl halides was investigated to know about
the scope of our method (Scheme 2). The results are summarized in
Table 3. For phenols, electron-rich ones (Table 3, entries 2, 3) were
viable substrates, and offered the desired products in good to
excellent yields. The highest yield (quantitative yield) is obtained
when m-methoxyiodobenzene was reacted with p-cresol (entry 4).
On the other hand, phenols bearing weak electron-withdrawing
group reacted smoothly (entry 5), while those bearing strong
electron-withdrawing groups seemed difficult to undergo the O-
arylation. For example, 4-nitrophenol and 4- cyanophenol (entries
6, 7) did not react at all, and the phenols were recovered. It was
noteworthy that the steric hindrance of phenols would not exert
a significant effect on this reaction since the reaction of 2-methyl
and 2-methoxy phenols (entries 8, 9) with iodobenzene could
give reasonable yields. This might be because the ortho-substituent
on the phenol, compared to that on the iodide (see below), was
a little farther away from copper center in the intermediate
complex formed in the catalytic cycle steps, and hence would
produce a smaller hindrance to formation of the complex. As for
iodoarenes, electron-deficient (entries 10, 11) ones were good
substrates for this reaction, providing the desired diaryl ethers in
good to excellent yields. But the reaction of electron-rich
Table 3
Polymer supported copper(II) catalyzed O-arylation reaction of aryl halides with phenols.a
Entry
Phenols
Aryl Halides
Productsb
Time(h)
Isolated Yield (%)
1
2
3
4
5
6
7
8
C6H5OH
C6H5I
C6H5I
C6H5I
m-CH3OC6H4I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
p-NO2C6H4I
p-CNC6H4I
p-CH3OC6H4I
p-CH3C6H4I
o-CH3OC6H4I
o-CH3C6H4I
C6H5Br
p-NO2C6H4Br
p-CNC6H4Br
p-CH3C6H4Br
p-CNC6H4Br
C6H5Br
C6H5Br
o-CH3OC6H4Br
C6H5Cl
p-NO2C6H4Cl
C6H5Cl
p-CNC6H4Cl
Diphenylether
12
10
10
14
16
20
20
14
14
10
10
14
14
16
16
14
12
12
16
10
12
12
16
14
14
14
12
95 (94)c, (92)d
p-CH3OC6H4OH
p-CH3C6H4OH
p- CH3C6H4OH
p-ClC6H4OH
p-NO2C6H4OH
p-CNC6H4OH
o-CH3OC6H4OH
o-CH3C6H4OH
C6H5OH
C6H5OH
C6H5OH
C6H5OH
C6H5OH
4-Methoxy-diphenylether
4-Methyl-diphenylether
4-Methyl-3-methoxy-diphenylether
4-Chloro-diphenylether
4-Nitro-diphenylether
4-Phenoxybenzonitrile
2-Methoxy-diphenylether
2-Methyl-diphenylether
4-Nitro-diphenylether
4-Phenoxybenzonitrile
4-Methoxy-diphenylether
4-Methyl-diphenylether
2-Methoxy-diphenylether
2-Methyl-diphenylether
Diphenylether
4-Nitro-diphenylether
4-Phenoxybenzonitrile
4-Methyl-diphenylether
4-cyano-4-methoxy-diphenylether
4-Methoxy-diphenylether
4-Methyl-diphenylether
2-Methoxy-diphenylether
Diphenylether
97
96
98
56
12
7
71
76
96
95
87
90
44
50
86
88
86
56
90
85
83
38
69
75
71
84
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
C6H5OH
C6H5OH
C6H5OH
C6H5OH
C6H5OH
p-CH3OC6H4OH
p-CH3OC6H4OH
p-CH3C6H4OH
C6H5OH
C6H5OH
C6H5OH
4-Nitro-diphenylether
4-Methoxy-diphenylether
4-cyano-4-methoxy-diphenylether
p-CH3OC6H4OH
p-CH3OC6H4OH
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g, 0.026 mmol), 1 mmol of aryl halides, 1 mmol of phenols, 1 mmol Cs2CO3, DMSO (10 mL), 0.1 mmol tBu4NBr,
120 ꢀC, open air. Isolated yield after column chromatography.
b
Products were identified by comparison of their IR, GC-MS and 1HNMR spectral data those reported in the literature.
Yields after 2nd cycle.
Yields after 3rd cycle.
c
d

4270
Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
Table 4
B(OH)2
Effect of copper source and solvent on the N-arylation reaction.a
polymer supported
Cu(II) catalyst
B(OH)2
Aryl-N-heterocycles
N(H)-heterocycles
methanol
,
N
40 0C
polymer supported
Cu(II) catalyst
N
N
R
N
H
Scheme 3. Copper catalyzed N-arylation of NeH heterocycles with arylboronic acids
R ¼ H, Me, OMe, Cl, F, CF3, NO2.
Entry
Copper source
Solvent
Yield (%)
occurrence of these structural units in biologically active inhibitors.
In an effort to evolve a better catalytic system, various catalysts
were screened for N-arylation of imidazole and phenylboronic acid
in methanol at 40 ꢀC. The results are summarized in Table 4. The
amount of copper catalyst (0.05 g) and the reaction time (10 h)
were the same for all experiments and were not further optimized.
The reaction temperature (40 ꢀC) was also set constant for all
reaction tests, since we wanted to evaluate the catalytic perfor-
mance of this catalyst at a comparatively low temperature.
Homogeneous Cu catalyst, CuCl2, Cu(OAc)2 and CuI, gave very low
yield (Table 4, entries 2e5). Polymer supported Cu(II) catalyst
afforded a very good yield (entry 6). However, no reaction occurred
in the absence of copper catalyst. As can be seen from Table 4,
polymer anchored Cu(II) catalysts were superior. Among polymer
supported Cu(II) catalysts, which were prepared from different
copper(II) sources, polymer supported Cu(II) catalyst from cop-
per(II) acetate was found to be the most effective one (entry 8). In
order to determine the best reaction medium, we tested different
solvents such as methanol, DMSO, acetonitrile, DMF and toluene
(entries 8e12). Methanol was found to be the best solvent for the
N-arylation of imidazole (98%). On the other hand, reaction in other
solvents gave trace amount of coupled product under identical
conditions. N-arylation reactions of NeH heterocycles with phe-
nylboronic acid were carried out in methanol with this copper
catalyst, without the need of any organic co-solvent, base or addi-
tives such as phase transfer catalysts. From the above discussions, it
can be seen that the best yield was obtained in the N-arylation
reaction of imidazole with phenylboronic acid in MeOH solvent at
40 ꢀC for 10 h without any base.
1
2
3
4
5
6
7
8
None
CuI
CuCl2
Cu(OAc)2
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
MeOH
DMSO
DMF
No reaction
44
59
73
78
81
84
98
57
54
60
36
98
82
Homogeneous copper catalyst
Polymer supported Cu(I)b catalyst
Polymer supported Cu(II)c catalyst
Polymer supported Cu(II)d catalyst
Polymer supported Cu(II)d catalyst
Polymer supported Cu(II)d catalyst
Polymer supported Cu(II)d catalyst
Polymer supported Cu(II)d catalyst
Polymer supported Cu(II)e catalyst
Polymer supported Cu(II)f catalyst
9
10
11
12
13
14
ACN
Toluene
MeOH
MeOH
a
Reaction conditions: copper catalyst (0.026 mmol), 1 mmol of arylboronic acid,
1.2 mmol of imidazole/benzimidazole, ` MeOH (10 ml), 40 ꢀC, 10 h, N2 atm. Yield
determined by GC and GCMS analysis.
b
Catalyst prepared from CuI.
Catalyst prepared from CuCl2.
Catalyst prepared from Cu(OAc)2.
Catalyst prepared with 2.5% crosslink polymer.
c
d
e
f
Catalyst prepared with 8% crosslink polymer.
and phenol was performed in the same reaction solvent. After 12 h,
no conversion to product was detected by gas chromatography (GC-
analysis). The copper catalyst was then added to the reaction
mixture, and 96% yield of the product was obtained within 12 h.
This illustrates that the cross-coupling reaction was indeed
promoted by the polymer supported copper catalyst.
3.3. Catalytic activity of the copper catalyst in N-arylation reaction
To check the generality and scope of the catalyst, we tried the N-
arylation of various NeH heterocycles with several other arylbor-
onic acids in MeOH without using any base at 40 ꢀC (Scheme 3). The
results are summarized in Table 5. Various arylboronic acids and
of NeH heterocycles with arylboronic acids
The synthesis of N-arylimidazoles and N-arylbenzaimadazoles
has attracted significant interest because of the frequent
Table 5
N-Arylation of NeH heterocycle with various arylboronic acids.a
Entry
NeH heterocycle
Aryl halides
Productsb
Time (h)
Isolated Yield(%)
1
2
3
4
5
6
7
8
Imidazole
Imidazole
Imidazole
Imidazole
Imidazole
Imidazole
Imidazole
Imidazole
C6H5eB(OH)2
1-Phenyl-1H-imidazole
10
12
12
16
18
18
18
20
20
16
18
18
20
12
12
12
98 (98, 96, 93, 93, 90)c
4-MeeC6H4B(OH)2
4-MeOeC6H4B(OH)2
2-MeeC6H4B(OH)2
3,4-MeOeC6H3B(OH)2
4-CleC6H4B(OH)2
4-FeC6H4B(OH)2
3-NO2eC6H4B(OH)2
4-CF3eC6H4B(OH)2
C6H5-B(OH)2
4-MeeC6H4B(OH)2
4-MeOeC6H4B(OH)2
C6H5eB(OH)2
C6H5eB(OH)2
4-MeeC6H4B(OH)2
C6H5eB(OH)2
1-(4-Methylphenyl)-1H-imidazole
1-(4-Methoxyphenyl)-1H-imidazole
1-(2-Methylphenyl)-1H-imidazole
1-(3,4-dimethoxyphenyl)-1H-imidazole
1-(4-Chlorophenyl)-1H-imidazole
1-(4-Fluorophenyl)-1H-imidazole
1-(3-nitrophenyl)-1H-imidazole
1-(4-Trifluoromethylphenyl)-1H-imidazole
1-phenyl-1H-benzimidazole
1-(4-Methylphenyl)-1H-benzimidazole
1-(4-Methoxyphenyl)-1H-benzimidazole
N-phenylsulfonamide
2-Phenylisoindoline-1,3-dione
2-p-Tolylisoindoline-1,3-dione
N-Phenylbenzamide
93
94
84
71
86
88
77
65
95
89
91
37
97
94
98
9
Imidazole
10
11
12
13
14
15
16
Benzimidazole
Benzimidazole
Benzimidazole
Sulfonamide
Phalimide
Phalimide
Benzamide
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g, 0.026 mmol), 1 mmol of arylboronic acid, 1.2 mmol of NeH heterocycle, MeOH (10 ml), 40 ꢀC, N2 atm.
Isolated yield after column chromatography.
b
Products were identified by comparison of their IR, GC-MS and 1HNMR spectral data those reported in the literature.
Yield after consecutive cycles.
c

Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
4271
Table 6
Effect of solvent, base, temperature, reaction time on the amination reaction of
aniline with phenylboronic acid.a
B(OH)2
NH2
H
N
polymer supported
Cu(II) catalyst
Scheme 4. Copper catalyzed amination of aniline with arylboronic acids R ¼ H, Me,
OMe, Cl, NO2.
Entry
Base
Solvent
Temperature
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
K2CO3
Na2CO3
Cs2CO3
K3PO4
Et3N
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
140 ꢀ C
140 ꢀ C
140 ꢀ C
140 ꢀ C
140 ꢀ C
140 ꢀ C
140 ꢀ C
130 ꢀ C
80 ꢀ C
12
12
12
14
14
12
14
12
16
16
16
12
16
12
12
6
86
61
59
52
56
45
57
71
55
48
53
68
45
38
44
42
50
phalimide under the generalized reaction conditions to afford the
corresponding products in excellent yields. However, the reaction
of benzamides with phenylboronic acid afforded the corresponding
products in good yields (entry 16).
NaOMe
KOH
For the recycling study N-arylation reaction was performed with
imidazole and phenylboronic acid maintaining the same reaction
conditions using the recovered catalyst. Each time after completion
of the reaction catalyst was recovered by simple filtration, washed
thoroughly with methanol to remove any excess reagents and dried
under vacuum and reused under the same reaction conditions as
for the initial run without any regeneration. The recycling efficiency
of the catalyst upto five successive runs were shown in (Table 5,
entry 1). From the results, it was shown that the catalyst retained its
high catalytic activity in these five repeating cycles.
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
9
EtOH
10
11
12
13
14
15
16
17
MeOH
CH3CN
THF
Toluene
DMSO
DMSO
DMSO
DMSO
80 ꢀ C
80 ꢀ C
100 ꢀ C
120 ꢀ C
50 ꢀ C
60 ꢀ C
140 ꢀ C
140 ꢀ C
8
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g, 0.026 mmol),
1.5 mmol of phenylboronic acid, 1.2 mmol of aniline, 1 mmol of base, solvent
(10 ml), N2 atm. Yield determined by GC and GCMS analysis.
3.4. Catalytic activity of the copper catalyst in amination reaction
of primary amines with arylboronic acids
NeH heterocycles reacted to give the corresponding N-arylated
products under mild reaction conditions. We found that arylbor-
onic acids containing electron releasing groups as well as electron-
withdrawing groups reacted with imidazole to give corresponding
N-arylated imidazoles. Presence of electron releasing groups such
as methyl and methoxy groups on arylboronic acid at para position
increased the yield of the coupling reaction whereas an electron-
withdrawing group such as chloro and fluoro groups on boronic
acid decreased reaction yield for the N-arylation reaction (entries
2e9). The coupling of 3-nitroboronic acid which is a difficult
substrate also proceeded smoothly under the present conditions
(entry 6). Similar observation was made when benzimidazole was
used in place of imidazole to obtain the corresponding N-arylben-
zimidazoles, but the reactions took longer time compared to that in
the reactions of imidazole (entry 10e12). In an endeavor to expand
the scope of the above methodology, the catalytic system was also
applied to imides, amides and sulfonamides. Such coupling was
found to give the desired N-arylation products in moderate yields,
as shown in Table 5, except for sulfonamide, which afforded the
corresponding products in lower yield (entry 13). A series of
substituted arylboronic acids (entries 14, 15) were coupled with
The synthesis of N-aryl amines is an active area in organic
synthesis due to their occurrence in biologically important natural
products, pharmaceuticals and their applications in materials
research. Preliminary experiments were carried out by taking
phenylboronic acid as a test molecule for the amination reaction of
aniline. The results are summarized in Table 6. The amount of
copper catalyst (0.05 g) was the same for all experiments and was
not further optimized. We tested several different bases for the
amination reactions catalyzed by the polymer supported Cu(II)
catalyst in DMSO at 140 ꢀC K2CO3 was found to be the most effec-
tive. Other bases such as Na2CO3, Cs2CO3, K3PO4, KOAc, triethyl-
amine and piperidine were substantially less effective (Table 6,
entries 1e7). We then turned our attention to investigate the effect
of solvent on the coupling reaction using K2CO3 as base. When the
reactions were conducted in DMF and DMSO, good to excellent
yields (71% and 86%, respectively) of products were obtained. Good
to moderate desired cross-coupling product was observed during
reactions in EtOH, MeOH, THF, CH3CN, and toluene (Table 6, entries
1, 8e13). The amination reaction catalyzed by copper catalyst was
performed at higher temperature (140 ꢀC) and higher reaction time
Table 7
Amination reaction of aniline with various arylboronic acids.a
Entry
Arylboronic acids
Aryl amines
Productsb
Time (h)
Isolated Yield (%)
1
2
3
4
5
6
C6H5eB(OH)2
C6H5NH2
C6H5NH2
C6H5NH2
C6H5NH2
C6H5NH2
C6H5CH2NH2
N-(Phenyl)aniline
12
15
15
16
18
12
86 (85)c, (82)d
4-MeeC6H4B(OH)2
4-MeOeC6H4B(OH)2
4-CleC6H4B(OH)2
3-NO2eC6H4B(OH)2
C6H5eB(OH)2
N-(4-Methylphenyl)aniline
N-(4-Methoxyphenyl)aniline
N-(4-Chlorophenyl)aniline
N-(3-nitrophenyl) aniline
N-Phenylbenzylamine
91
89
64
58
75
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g 0.026 mmol), 1.5 mmol of arylboronic acid, 1.2 mmol of aniline, K2CO3 (1 mmol), DMSO (10 ml), 140 ꢀC,
N2 atm. Isolated yield after column chromatography.
b
Products were identified by comparison of their IR, GC-MS and 1HNMR spectral data those reported in the literature.
Yields after 2nd cycle.
Yields after 4th cycle.
c
d

4272
Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
Table 8
Effect of solvent, base, temperature, reaction time on the amination reaction of
aniline with iodobenzene.a
I
H
N
NH2
polymer supported
Cu(II) catalyst
Entry
Base
Solvent
Temperature
Time (h)
Yield (%)
Scheme 5. Copper catalyzed amination reaction of aromatic amines with aryl iodides
R1 ¼ H, Me, OMe; R2 ¼ H, Me.
1
2
3
4
5
6
7
8
9
KOH
KOH
KOH
KOH
KOH
KOH
K3PO4
K2CO3
Cs2CO3
DMSO
DMA
DMF
Toluene
1,4 dioxane
NMP
DMSO
DMSO
DMSO
140 ꢀ C
120 ꢀ C
130 ꢀ C
140 ꢀ C
90 ꢀ C
16
16
16
18
18
16
18
16
16
82
77
80
32
26
75
52
47
49
the amination reaction, we have chosen the reaction between
iodobenzene and aniline as a model reaction and various solvents
and bases were screened. The results are shown in Table 8. The
amount of copper catalyst (0.05 g) was the same for all experiments
and was not further optimized. The solvents also play an important
role in the amination reaction. Polar solvents, such as DMSO, DMA,
and DMF were found to be highly suited for this reaction, while the
less polar solvents, such as toluene, afforded the product only in
very poor yields (Table 8, entry 1e4). The results in Table 8 indicate
that the reaction performs better in more polar solvents, optimum
results being observed in dimethylsulfoxide (DMSO). Although the
reaction did proceed in 1,4-dioxane, the yield of reaction product
was much lower (Table 8, entry 5). N-methylpyrrolidinone (NMP)
also proved to be effective solvents (Table 8, entry 6). The influence
of bases on the yields of diphenylamine in the presence of copper
catalyst was investigated to find that KOH was the most effective
and using milder bases such as K3PO4, K2CO3, and Cs2CO3 signifi-
cantly resulted in low yields (Table 8, entries 1, 7e9). This reaction
140 ꢀ C
140 ꢀ C
140 ꢀ C
140 ꢀ C
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g, 0.026 mmol),
1 mmol of, 1.2 mmol of aromatic amine, 1 mmol base, solvent (10 ml), 140 ꢀC,
N2 atm. Yield determined by GC and GCMS analysis.
(12 h). At lower temperatures (50 ꢀC and 60 ꢀC) and reaction times
(6 h and 8 h), no significant amount of product was formed (Table 6,
entries 14e17). From the above discussions, it can be seen that the
best yield was obtained in the amination reaction of aniline with
phenylboronic acid by using K2CO3 in DMSO solvent at 140 ꢀC for
12 h.
Our method proved useful for the coupling of aniline with
a range of different arylboronic acids (Scheme 4) and the results are
shown in Table 7. The highest yield (91%) was obtained with an
electron releasing eCH3 substituent at the para position of the
boronic acid (Table 7, entry 2). Introduction of an electron releasing
methoxy group at the para position resulted in a similar yield of
89% (Table 7, entry 3). The meta nitro analog, however, only
resulted in a 58% yield (Table 7, entry 5). Reaction of benzylamine
with phenylboronic acid under the same reaction condition resul-
ted in a 75% yield (Table 7, entry 6). This Cu(II) catalyst was
recovered quantitatively by simple filtration and was reused
several times, with consistent activity even after the fourth cycle
(Table 7, entry 1). The absence of copper in the filtrate was
confirmed by atomic absorption spectroscopy, which confirms no
leaching of copper during the reaction and provides evidence for
heterogeneity throughout the reaction.
using polymer supported Cu(II) catalyst was also performed at
ꢀ
higher temperature (140 C) and higher reaction time (16 h).From
the above discussions, it can be seen that the best yield was ob-
tained in the amination reaction of aniline with iodobenzene by
using KOH in DMSO solvent at 140 ꢀC for 16 h.
The scope of this polymer supported Cu(II) catalyst for the ami-
nation of aryl halide was explored bycoupling reaction of aryl iodide
with primary amines using KOH as base in solvent DMSO at 140 ꢀC
(Scheme 5). The results are shown in Table 9. Methyl and methoxy
groups at the para position were tolerated on the aryl iodide
component (Table 9, entries 2, 3). Both p-toluidine (Table 9, entry 4)
and benzylamine (Table 9, entry 5) were also reacted to a consider-
able extent. The system also permits the use of sterically hindered
amine such as o-toluidine (Table 9, entry 6), which gave good yield.
Here also the catalyst was recovered by simple filtration and reused
for several cycles with consistent activity (Table 9, entry 1).
3.5. Catalytic activity of the copper catalyst in amination reaction
of primary amines with aryl iodides
3.6. Comparison with other reported system
After achieving excellent results with aryboronic acids, we
further applied this catalytic system for the amination reaction of
aromatic amines with aryl halides. To optimize the conditions for
Table 10 provides a comparison of the results obtained for our
present catalytic system with those reported in the literature. From
Table 9
Amination reaction of primary amines with various aryl halides.a
Entry
Aryl halides
Aryl amines
Productsb
Time (h)
Isolated Yield (%)
1
2
3
4
5
6
C6H5I
C6H5NH2
C6H5NH2
C6H5NH2
p-CH3C6H5NH2
C6H5CH2NH2
C6H5NH2
N-(Phenyl)aniline
16
14
14
14
16
22
82 (77)c
80
81
78
70
p-CH3C6H4I
p-CH3OC6H4I
C6H5I
C6H5I
o-CH3C6H4I
N-(4-Methylphenyl)aniline
N-(4-Methoxyphenyl)aniline
N-(4-Methylphenyl)aniline
N-Phenylbenzylamine
N-(2-Methylphenyl)aniline
63
a
Reaction conditions: polymer supported Cu(II) catalyst (0.05 g 0.026 mmol), 1 mmol of aryl halide, 1.2 mmol of aromatic amine, 1 mmol KOH, catalyst (50 mg,0.0129 mmol)
DMSO (10 ml), 140 ꢀC, N2 atm. Isolated yield after column chromatography.
b
Products were identified by comparison of their IR, GC-MS and 1HNMR spectral data those reported in the literature.
Yields after 5th cycle.
c

Sk.Manirul Islam et al. / Journal of Organometallic Chemistry 696 (2012) 4264e4274
4273
Table 10
Comparison of activity of different catalysts in the O-arylation, N-arylation and amination reaction.
Reaction
Catalyst
Reaction conditions
Yield (%)
Reference
O-Arylation (iodobenzene þ phenol)
CuL(OAc)2
Cs2CO3, DMSO, 120 ꢀC, 12 h
KF, DMSO, 130 ꢀC, 16 h
DMF, K3PO4, 90 ꢀC, 24 h
MeOH, 40 ꢀC, 10 h
95
92
85
98
88
82
95
86
71
This study
[45]
[46]
This study
[35]
This study
[47]
silica-supported Cu catalyst
Cu(bpy)2BF4
CuL(OAc)2
CueFAP
CuL(OAc)2
CuO nanoparticles
CuL(OAc)2
Cu(OAc)2
N-Arylation (imidazole þ phenylboronic acid)
Amination (aniline þ iodobenzene)
MeOH, 5 h, rt.
DMSO, KOH, 140 ꢀC, 16 h
DMSO, KOH, 140 ꢀC, 16 h
DMSO, 140 ꢀC, K2CO3, 12 h
DCM, Et3N/Py, rt, 2 h
Amination (aniline þ phenylboronic acid)
This study
[2]
its successful application for the O-arylation reaction of various aryl
halides with substituted phenols, N-arylation of various arylboronic
acids with nitrogen containing heterocycles and amination reac-
tions of primary amines with arylboronic acids as well as aryl
halides. The present system is highly air and moisture stable and
the catalyst can be synthesized readily from inexpensive and
commercially available starting materials. Moreover the catalyst
was reused for several consecutive cycles with consistent catalytic
activity. Further work is in progress to broaden the scope of this
catalytic system for other organic transformation.
100
90
80
70
60
50
Usual reaction
Acknowledgments
Reaction of filtrate after
removal of catalyst
40
30
20
We thank the Department of chemistry, University of Calcutta,
for providing us the instrumental support. We gratefully
acknowledge DST, New Delhi, for award of grant under its FIST
program to the Department of Chemistry, University of Kalyani. PM
acknowledges CSIR, New Delhi, India for fellowship. SMI
acknowledge the following agencies for funding: DST, CSIR and
UGC, New Delhi, India.
0
2
4
6
8
10
Time (h)
Fig. 6. Time conversion curve for the hot-filtration test.
References
Table 10, it is seen that present catalyst exhibited higher conver-
sions and yields compared to the other reported system [46e48].
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