Suzuki and sonogashira cross-coupling reactions in water medium with a reusable poly(N -vinylcarbazole)-anchored palladium(II) complex

Article abstract of DOI:10.1055/s-0029-1218776

Poly(3,6-dibenzaldimino-N-vinylcarbazole)-anchored palladium(II) complex has been synthesized and characterized by different physicochemical and spectroscopic techniques. The present complex shows excellent catalytic activities for Suzuki and Sonogashira coupling reactions under phosphine-free and copper-free reaction conditions in water medium. This immobilized catalyst can be easily separated and reused for further reactions for more than five times without noticeable loss in the catalytic activity. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0029-1218776

PAPER
2399
Suzuki and Sonogashira Cross-Coupling Reactions in Water Medium with a
Reusable Poly(N-vinylcarbazole)-Anchored Palladium(II) Complex
Manirul Islam,*a Paramita Mondal,a Anupam Singha Roy,a Kazi Tuhina b
a
Department of Chemistry, University of Kalyani, Kalyani 741235, WB, India
Department of Chemistry, Bankim Sadar College, South 24 Paraganas, Tangrakhali 743329, WB, India
b
E-mail: manir65@rediffmail.com
Received 1 February 2010; revised 25 March 2010
reuse of the catalyst are most important.6 Palladium as cat-
Abstract: Poly(3,6-dibenzaldimino-N-vinylcarbazole)-anchored
alyst plays an important role in organic synthesis.7 Palla-
dium exhibits good catalytic activity in carbon–carbon
bond-formation reactions. Various polymer-supported
palladium(II) complex has been synthesized and characterized by
different physicochemical and spectroscopic techniques. The
present complex shows excellent catalytic activities for Suzuki and
Sonogashira coupling reactions under phosphine-free and copper- palladium catalysts for the Suzuki and Sonogashira cross-
coupling reaction have been reported.8 However, most of
free reaction conditions in water medium. This immobilized cata-
lyst can be easily separated and reused for further reactions for more
them are related to the palladium(II) complexes in combi-
than five times without noticeable loss in the catalytic activity.
nation with phosphine ligand. Despite tertiary phosphines
are effective in controlling reactivity and selectivity in or-
ganometallic chemistry and heterogeneous catalysis, they
Key words: heterogeneous catalysis, Schiff base, palladium com-
plex, cross-coupling, biaryls
require air-free handling to prevent their oxidation. There-
fore, the development of phosphine-free heterogeneous
palladium catalysts having a high activity and good stabil-
ity is a topic of enormous importance.9
The Suzuki and Sonogashira cross-coupling reactions are
among the most important carbon–carbon bond-forming
processes in organic synthesis.1 It features applications
that range from the preparation of hydrocarbons and in-
dustrial production of pharmaceuticals to advanced syn-
thesis of natural products.2 The continuing depletion of
natural resources and growing environmental awareness
has necessitated changes in the practices of both the
chemical industry and academia. One strategy that ad-
dresses these issues is the replacement of deleterious mo-
lecular solvents with environmentally more benign,
reaction enhancing alternatives. Of the novel solvents that
have emerged, water has shown great promise.3 Actually,
water is an attractive alternative to traditional organic sol-
vents because it is inexpensive, nonflammable, nontoxic,
and environmentally sustainable by alleviating the prob-
lem of pollution by organic solvents. While a considerable
progress is being achieved in water medium, the vast ma-
jority of examples of catalytic reactions in aqueous medi-
um still use homogeneous catalysis.4 It is clear that green
chemistry not only requires the use of friendly solvents
but also it is very convenient to convert homogeneous ca-
talysis into heterogeneous catalysis in order to recover and
reuse the catalyst. Many immobilization methods and sup-
ported materials have been reported in literature,5 among
them charcoal, silicas, zeolites, hydrotalcites, and poly-
mers are widely exploited.
Here, we report the heterogeneous Suzuki coupling and
copper-free Sonogashira coupling reactions of aryl ha-
lides over a polymer-anchored palladium(II) Schiff base
complex catalyst in water medium under aerobic condi-
tion.
Preparation and Characterization of [Pd(C6H4CH=N–
P)(PhCN)Cl] Complex [P = poly(N-vinylcarbazole)]
Schematic illustration for the synthesis of the catalyst is
presented in Scheme 1. The functionalized poly(N-vinyl-
carbazole amine) 2 was prepared according to the method
of King and Sweet,10 which was converted to the polymer-
anchored ligand 3 by reaction with benzaldehyde in anhy-
drous toluene under reflux. The preparation of poly(N-vi-
nylcarbazole)-anchored palladium(II) complex 4 was
done by reaction of 3 with a methanolic solution of Pd(Ph-
CN)2Cl2.11 The catalyst 4 showed characteristic IR peaks
at 1620 cm–1 (C=N imine), 1590 cm–1 (C=C stretching, ar-
omatic), 720 cm–1 (orthometalation),12 2290 cm–1 (C≡N of
benzonitrile), 455 cm–1 (Pd–N),13 and 355 cm–1 (Pd–Cl),14
which support the formation of palladium(II) complex.
The metal content of polymer-anchored palladium(II)
complex determined by AAS suggested 12.80 wt% metal
loading in the immobilized palladium complex.
Polymer-supported organotransition metal catalysts offer
several significant advantages in synthetic and industrial
chemistry; among these, the ease of separation of catalyst
from the desired reaction products and the recovery and
Suzuki Cross-Coupling Reactions
To explore the catalytic activity of the present catalyst,
initially the Suzuki coupling reaction15 of bromobenzene
with phenylboronic acid was studied as a model reaction
and the role of various solvents, temperatures, and bases
was screened using this catalyst (Scheme 2). Several sol-
SYNTHESIS 2010, No. 14, pp 2399–2406
x
x.
x
x
.
2
0
1
0
Advanced online publication: 05.05.2010
DOI: 10.1055/s-0029-1218776; Art ID: Z01910SS
© Georg Thieme Verlag Stuttgart · New York

2400
M. Islam et al.
PAPER
Table 1 Optimal Conditions for [Pd(C6H4CH=N–P)(PhCN)Cl]-
Catalyzed Suzuki Cross-Coupling Reactiona
O2N
NO2
SnCl2, HCl
HNO3, AcOH
N
N
NaOH
n
Entry Base
Solvent
DMF
MeCN
NMP
MeOH
DMSO
toluene
H2O
Time Temp (°C) Yield (%)
-CH-CH2-
n
-CH-CH2-
1
2
K2CO3
12
12
12
10
12
24
8
100
110
reflux
70
84
75
71
80
61
21
12
34
68
82
95
87
68
58
65
39
17
(1)
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
K3PO4·7H2O
NaOH
PhHC=N
N=CHPh
H2N
NH2
3
PhCHO
n
N
N
4
-CH-CH2-
-CH-CH2-
n
5
110
110
30
(2)
(3)
-CH-CH2-
N
6
7
Pd(PhCN)2Cl2
MeOH
N
N
Cl
Cl
Pd
Pd
8
H2O
8
40
PhCN
NCPh
9
H2O
8
50
(4)
n
10
11
12
13
14
15
16
17
H2O
8
60
Scheme
1
Synthesis of polymer-anchored [Pd(C6H4CH=N–
P)(PhCN)Cl] complex
H2O
8
70
H2O
8
70
vents such as DMF, MeCN, NMP, MeOH, DMSO, tolu-
ene, and water was investigated and it was found that
water was the best solvent for this coupling reactions us-
ing the present catalyst. With polar solvents like NMP,
MeCN, DMF, DMSO, and MeOH, yields were compara-
tively good (Table 1, entries 1–5). In contrast, the catalyt-
ic performance was not acceptable when a nonpolar
solvent toluene was employed (Table 1, entry 6). This
coupling reaction was found to be highly sensitive to the
reaction temperature. At lower temperatures (30–60 °C)
only low to moderate yield was obtained (Table 1 entries
7–10). A reaction temperature of 70 °C was found to be
optimal for the model reaction. The effect of base on the
reaction was also important, because the desired cross-
coupling products were not obtained in any noticeable
amounts in the absence of base. The addition of inorganic
carbonate base, K2CO3, resulted in excellent conversion
(95%, Table 1, entry 11); however, organic bases like
Et3N and piperidine gave lower conversion (Table 1, en-
tries 16, 17). The addition of other inorganic bases gave
moderate to low conversions of bromobenzene. The quan-
tity of K2CO3 was also found to be important. The base–
substrate molar ratio of 2:1 was found to be ideal for the
present catalytic system.
H2O
8
70
H2O
8
70
NaOAc
Et3N
H2O
8
70
H2O
8
70
piperidine
H2O
8
70
a Reaction conditions: bromobenzene (1.0 mmol), phenylboronic acid
(1.5 mmol), catalyst (1.0 mol% Pd), base (2.0 mmol), solvent (6 mL).
Yields refer to GC and GC-MS analysis using dodecane as internal
standard (average of two runs).
sults were obtained (Table 2). A control experiment indi-
cated that the coupling reaction did not occur in the
absence of catalyst. Aryl iodides containing electron-
donating and electron-withdrawing groups readily cou-
pled with phenylboronic acid in rather short time (Table 2,
entries 2 and 3). Although the reaction became slower,
bromobenzene gave 95% of biaryl products after eight
hours (Table 2, entry 4). The effect of substituents in bro-
mobenzene was also examined in this reaction (Table 2,
entries 5–11). The less active electron-rich 4-bromotolu-
ene and 4-bromoanisole produced moderate yield while
electron-deficient 4-bromoacetophenone and 4-bromoni-
trobenzene gave excellent yield of coupled products. Ster-
ic effects did not influence the yield significantly, for
example, in the reaction of o- and m- nitrobromobenzene
with phenylboronic acid, the corresponding coupled prod-
ucts were obtained in 90% and 94% yield, respectively
(Table 2, entries 10 and 11). Heteroaryl bromide, such as
2-bromopyridine, coupled effectively with phenylboronic
acid providing 94% biaryl product (Table 2, entry 12).
The reactivity pattern of bromobenzene with a variety of
substituted boronic acids was also examined (Table 2, en-
tries 13 and 14), which indicates that the electron-donat-
ing substituents increase the yield of the reactions. It is
R2
R2
X
(OH)2B
+
R1
R1
X = Cl, Br, I
R1 = H, NO2, COMe, OMe, Me, OH
R2 = H, COMe, Me
Scheme 2 Suzuki coupling reaction of aryl halides with arylboronic
acid
To examine the scope for this coupling reaction, a variety
of aryl halides, iodides, bromides, and chlorides, were
coupled with arylboronic acids under optimize reaction
conditions (K2CO3, H2O, 70 °C) and good to excellent re-
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York

PAPER
Suzuki and Sonogashira Cross-Coupling Reactions in Water Medium
2401
noteworthy that the water-soluble aryl bromide, 4-bro- phine-free and copper-free reaction condition (Scheme 3).
mophenol, gave good yields in only four hours (Table 2, Addition of a small amount of TBAB (tetrabutylammoni-
entry 9). We also tested the catalytic activity of the present um bromide) in the reaction medium enhanced the rate of
catalyst for the coupling of aryl chlorides. Aryl chlorides the reaction and increased the conversion. Model reaction
are generally unreactive in the coupling reactions. Less re- was carried out under different systems to optimize the re-
active chlorobenzene gave poorer conversion compared to action conditions (Table 3). Several solvents, such as
aryl bromides or iodides while electron-deficient 4-chlo- DMF, methanol, NMP, toluene, and H2O, were tested for
roacetophenone gave moderate yield of coupled product this coupling reaction and H2O was found to be the best
under these reaction conditions (Table 2, entries 15 and solvent based on conversion, reaction temperature, and re-
16).
action time (Table 3, entries 1–5). Next we examined the
effect of different bases for the Sonogashira coupling re-
actions. The reaction works very well when organic bases,
such as Et3N and piperidine, were used (Table 3, entries 5,
Sonogashira Cross-Coupling Reaction
We further extended the catalytic activity of the present 6), with the best result obtained in the case of Et3N as base
catalyst in copper-free Sonogashira cross-coupling reac- (Table 3, entry 5). Inorganic bases such as NaOAc,
tions.1c,16 In our initial experiments, we tested the K2CO3, and K3PO4·7H2O, were substantially less effec-
Sonogashira cross-coupling reaction of iodobenzene with tive and gave moderate to low conversion (Table 3, en-
phenylacetylene as model reaction in the presence of tries 7–9).
polymer-anchored palladium(II) catalyst 4 under a phos-
Table 2 Suzuki Cross-Coupling Reactions of Aryl Halides with Arylboronic Acids with [Pd(C6H4CH=N–P)(PhCN)Cl] Complex Catalysta
K2CO3, catalyst
R2
R2
+
X
(OH)2B
H2O, 70 °C
R1
R1
Entry
ArX
ArB(OH)2
Productb
Time (h)
5
Conv. (%)c Yield (%)
1
2
3
4
5
6
7
8
9
100
100
98
~100
~100
97
I
B(OH)2
1a
O2N
4
5
8
8
8
6
6
4
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
B(OH)2
I
O2N
1b
MeO
I
MeO
1c
95
95
Br
1a
MeO
1c
94
94
Br
MeO
94
94
Br
1d
O2N
98
97
Br
O2N
1b
MeOC
99
99
Br
MeOC
1e
HO
98
98
Br
HO
1f
O2N
O2N
10
6
96
94
B(OH)2
Br
1g
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York

2402
M. Islam et al.
PAPER
Table 2 Suzuki Cross-Coupling Reactions of Aryl Halides with Arylboronic Acids with [Pd(C6H4CH=N–P)(PhCN)Cl] Complex Catalysta
(continued)
K2CO3, catalyst
R2
R2
+
X
(OH)2B
H2O, 70 °C
R1
R1
Entry
ArX
ArB(OH)2
Productb
Time (h)
8
Conv. (%)c Yield (%)
Br
NO2
11
92
90
B(OH)2
NO2
1h
12
13
14
15
16
10
8
94
95
93
42
69
90
95
93
40
68
Br
B(OH)2
N
N
1i
Br
Br
Cl
B(OH)2
1d
MeOC
8
MeOC
B(OH)2
1e
16
16
B(OH)2
1a
MeOC
Cl
B(OH)2
MeOC
1e
a Reaction conditions: aryl halide (1.0 mmol), phenylboronic acid (1.5 mmol), catalyst (1.0 mol% Pd), K2CO3 (2.0 mmol), H2O (6 mL), 70 °C.
b Products were identified by comparison of their IR and 1H NMR spectral data with those reported in the literature.
c Conversion of reactant was determined by GC and GC-MS analysis using dodecane as internal standard.
present reaction conditions. Unfortunately, only a very
X
+
small amount of the cross-coupled product was isolated,
when aryl chlorides were coupled with phenylacetylene
under the same reaction conditions (Table 4, entries 14
and 15).
R
R
R = H, NO2, COMe, OMe, Me, CN
X = Cl, Br, I
Scheme 3 Sonogashira coupling reactions of aryl halides with phe-
nylacetylene
Table 3 Optimal Conditions for [Pd(C6H4CH=N–P)(PhCN)Cl]-
Catalyzed Sonogashira Cross-Coupling Reactiona
To examine the scope of this coupling reaction, phenyl-
acetylene was coupled with different aryl halides in H2O
in the presence of polymer-anchored palladium(II) cata-
lyst 4 at 70 °C (Scheme 3). The experimental results are
summarized in Table 4. As shown in Table 4, the elec-
tron-neutral, electron-rich and electron-poor aryl iodides
reacted with phenylacetylene very well to generate the
corresponding cross-coupling products in excellent yields
under the standard reaction conditions (Table 4, entries 1–
6). Trace amount of homocoupled product was detected in
the reaction medium. This cross-coupling was also toler-
ant of ortho substitution in aryl iodides and led to moder-
ate yields (Table 4, entry 6). Activated aryl bromides
reacted with phenylacetylene to generate the correspond-
ing products in good yields (Table 4, entries 8–10). For
electron-rich aryl bromides, relatively lower yield was ob-
tained under the present reaction conditions (Table 4, en-
tries 11 and 12). Heteroaromatic compound such as 2-
bromopyridine also reacted with palladium(II) catalyst to
give cross-coupling product in 78% yield (Table 4, entry
13). These results indicate that a variety of important
functional groups could be well tolerated under the
Entry Base
Solvent Time
Temp (°C) Yield (%)b
1
2
3
4
5
6
7
8
9
Et3N
DMF
MeOH
NMP
toluene
H2O
12
10
12
24
10
10
10
10
10
100
70
78
82
67
12
99
93
39
52
41
Et3N
Et3N
reflux
80
Et3N
Et3N
70
piperidine
NaOAc
K2CO3
H2O
70
H2O
70
H2O
70
K3PO4·7H2O H2O
70
a Reaction conditions: iodobenzene (1.0 mmol), phenylacetylene (2.0
mmol), catalyst (1.0 mol% Pd), base (2.0 mmol), TBAB (1.0 mmol),
solvent (6 mL).
b Yield refers to GC and GC-MS analysis using dodecane as internal
standard (average of two runs).
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York

PAPER
Suzuki and Sonogashira Cross-Coupling Reactions in Water Medium
2403
Table 4 Sonogashira Cross-Coupling Reactions of Aryl Halides with Phenylacetylene with [Pd(C6H4CH=N–P)(PhCN)Cl] Complex Catalysta
Et3N, catalyst
X
+
H
H2O, 70 °C
R
R
Entry
ArX
Productb
Time (H)
10
Conv. (%)c
100
Yield (%)
99
1
2
3
4
5
I
2a
O2N
2b
10
10
10
10
100
100
95
98
99
93
95
I
O2N
MeOC
I
MeOC
2c
MeO
MeO
I
2d
96
I
2e
NO2
NO2
6
12
86
83
I
2f
7
8
12
12
12
12
12
12
88
93
95
93
87
85
88
92
95
91
87
84
Br
2a
O2N
Br
O2N
MeOC
NC
2b
MeOC
9
Br
2c
NC
10
11
12
Br
2g
MeO
MeO
Br
2e
2f
Br
13
14
15
12
24
24
80
18
35
78
18
34
Br
Cl
N
N
2h
2a
MeOC
Cl
MeOC
2c
a Reaction conditions: aryl halide (1.0 mmol), phenylacetylene (2.0 mmol), catalyst (1.0 mol% Pd), Et3N (2.0 mmol), TBAB (1.0 mmol), H2O
(6 mL), 70 °C.
b Products were identified by comparison of their IR and 1H NMR spectral data those reported in the literature.
c Conversion of reactant was determined by GC and GC-MS analysis using dodecane as internal standard.
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York

2404
M. Islam et al.
PAPER
Table 5 Comparison of Catalytic Activity of the Present Catalyst with Other Related Reported Systems
Entry Reaction type Catalyst Reaction conditions
Yield Refer-
(%) ence
1
Suzuki
[Pd(C6H4CH=N–P)(PhCN)Cl] cat. (1.0 mol%), K2CO3, H2O, 8 h, 70 °C
94
66
90
99
87
95
this work
17a
(4-bromotoluene + phenylboronic acid) chitosan-g-mPEG350Pd(0)
cat. (0.5 mol%), H2O, NaOH, 5 h, 150 °C
cat. (0.1 mol%), K2CO3,H2O, 12 h, 100 °C
–
–
17b
Pd-1/FSG
2
Sonogashira
[Pd(C6H4CH=N–P)(PhCN)Cl] cat. (1.0 mol%), Et3N,H2O, 10 h, 70 °C
this work
17c
(iodobenzene + phenylacetylene)
Pd-silica
Pd-salen
PdCl2
cat. (0.01 mmol), Et3N, H2O, 12 h, 70 °C
cat. (0.01 mmol), Cs2CO3, H2O, 9 h, 60 °C
–
17d
–
17e
cat. (1.0 mol%), H2O, pyrrolidine, 24 h, 50 °C 94
–
Comparison of Catalytic Activity with Other Reported
Systems
Table 5 provides a comparison of the results obtained for
our present catalytic system with those reported in the lit-
erature. The present catalyst exhibited higher conversions
and selectivities compared to the other reported systems.
Reactions conducted at lower temperature17a,b and shorter
reaction time17b,c,e were required in both the Suzuki and
Sonogashira coupling reactions.
Heterogeneity Tests
A hot-filtration test was performed in the Suzuki cross-
coupling reaction of 4-bromotoluene with phenylboronic
acid. After completion of the reaction, the solid catalyst
was filtered off and the filtrate was tested in another reac-
tion cycle. No conversion was detected in the filtrate, con-
firming the truly heterogeneous nature of the polymer-
supported catalyst.
Figure 1 Recycling activity of polymer-anchored palladium(II)
complex catalyst towards the Suzuki cross-coupling reaction of
4-bromotoluene with phenylboronic acid and Sonogashira cross-
coupling reaction of iodobenzene with phenylacetylene.
Catalyst Reuse
pable of performing well in neat water medium under
aerobic and phosphine-free conditions. This polymer-an-
chored catalyst is easy to make, air-stable, inexpensive,
and nonpolluting solid. The remarkable advantages with
the use of the catalyst are the ready accessibility of the cat-
alysts, its reusability, and storage. The high activity, broad
substrate scope, and the successful recycling of this cata-
lyst makes it a more economic and environmentally
friendly process for the synthesis of different fine chemi-
cals. Further studies of other coupling reactions catalyzed
by this system are currently in progress.
Catalyst lifetime and the ability to easily recycle the cata-
lyst are highly desirable for industrial applications. The
recycle efficiency of present polymer-anchored palladi-
um(II) complex 4 was investigated in the coupling reac-
tions of 4-bromotoluene with phenylboronic acid and
iodobenzene with phenylacetylene, respectively. After the
first run, the catalyst was separated by filtration, washed
thoroughly, and then dried under vacuum. The catalytic
run was repeated with further addition of substrates in ap-
propriate amount under optimum reaction conditions and
the nature and yield of the final products were comparable
to that of the original one. The catalytic results revealed
that the activity of the catalyst remained almost un-
changed over five reaction cycles (Figure 1).
Analytical grade reagents and freshly distilled solvents were used
throughout the experiment without further purification unless stated
otherwise. Poly(N-vinylcarbazole) (Art. No. 368350-5) was sup-
plied by Aldrich Chemical Company, U.S.A. Pd(PhCN)2Cl2 was
purchased from Arora Matthey and was used as such without fur-
ther purification. All other chemicals used in this investigation were
of analytical grade procured from E-Merck.
In conclusion, we have developed a highly active and eas-
ily recoverable poly(3,6-dibenzaldimino-N-vinylcarba-
zole) palladium(II) complex catalyst for the Suzuki and
Sonogashira cross-coupling reactions. The catalyst is ca-
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York

PAPER
Suzuki and Sonogashira Cross-Coupling Reactions in Water Medium
2405
The FTIR spectra were recorded on a Perkin-Elmer FTIR 783 spec-
trophotometer using KBr pellets. A Perkin-Elmer 2400C elemental
analyzer was used to collect microanalytical data (C, H, and N). The
metal loading in the polymer was analyzed using a Varian AA240
atomic absorption spectrophotometer (AAS). Morphology and par-
ticle size of different functionalized polystyrene samples were ana-
lyzed using a scanning electron microscope (SEM) (ZEISS EVO40,
England) equipped with EDX facility. The thermal stability of the
immobilized catalyst was determined using a Mettler Toledo TGA/
DTA 851. Diffuse reflectance UV-Vis spectra were taken using a
Shimadzu UV-2401PC doubled beam spectrophotometer having an
integrating sphere attachment for solid samples. The reaction prod-
ucts were analyzed by Varian 3400 gas chromatograph equipped
with a 30 m CP-SIL8CB capillary column and a frame ionization
detector and Trace DSQ II GC-MS equipped with a 60 m TR-50MS
capillary column. Flash chromatography was performed on silica
gel (230–400 mesh).
Sonogashira Cross-Coupling Reaction in Water Medium; Gen-
eral Procedure
To a suspension of the polymeric Pd(II) catalyst 4 (1.0 mol% of Pd)
in H2O (6.0 mL), aryl halide (1.0 mmol), phenylacetylene (2.0
mmol), TBAB (1.0 mmol), and Et3N (2.0 mmol) were added. The
reaction mixture was stirred at the prearranged temperature for ap-
propriate reaction time. Progress of the reaction was monitored by
GC analysis at different time interval of the reaction. After comple-
tion of the reaction, the reaction mixture was cooled to r.t., diluted
with H2O (10 mL), and extracted with CH2Cl2 (3 × 10 mL). The or-
ganic phase thus collected was dried (Na2SO4) and concentrated.
The crude material was purified by flash column chromatography
1
on silica gel. The product was analyzed by GC-MS and H NMR
spectroscopy. All prepared compounds are known and compared
with authentic samples (Table 4).
Reuse of the Catalyst
The Suzuki reaction was carried out with 4-bromotoluene (1.0
mmol), phenylboronic acid (1.5 mmol), K2CO3 (2.0 mmol) and Pd-
carbazole catalyst 4 (1.0 mol%) in H2O (6 mL). The Sonogashira re-
action was carried out with iodobenzene (1.0 mmol), phenylacety-
lene (2.0 mmol), Et3N (2.0 mmol), TBAB (1.0 mmol) and Pd-
carbazole catalyst 4 (1.0 mol%) in H2O (6 mL). Each reaction mix-
ture was stirred at 70 °C in air atmosphere. After completion of the
reaction, the mixture was cooled and the catalyst was separated
from the liquid mixture by filtration. The filtrate was analyzed by
gas chromatography to determine the yield of the product. The re-
covered catalyst was washed thoroughly with acetone and H2O, and
dried under vacuum. After that, the recovered catalyst was reused
for the next reaction under the same reaction conditions as men-
tioned above.
Poly(N-vinylcarbazole amine) (2)
Poly(N-vinylcarbazole) (5 g, 1.67 mmol) was taken in 1,2-dichloro-
ethane (100 mL). A mixture containing concd HNO3 (25 mL) and
50 mL of glacial AcOH (50 mL) was added dropwise at r.t. to the
above suspension with constant stirring and then the reaction mix-
ture was refluxed for 12 h. The resulting yellowish brown poly(3,6-
dinitro-N-vinylcarbazole) (1) was filtered, washed thoroughly with
AcOH, H2O, THF, and acetone in that order and then dried under
vacuum. A solution of SnCl2 (1.0 g, 5.27 mmol) in concd HCl (12
mL) was added to the suspension of yellowish brown 1 (5 g, 1.12
mmol) in AcOH (20 mL). The mixture was stirred at r.t. for 48 h.
The resulting yellow polymer was filtered, washed successively
with H2O, THF, MeOH, and acetone. The yellow polymer obtained
as the amine hydrochloride was dried under vacuum. Poly(N-vinyl-
carbazole-3,6-diamine) hydrochloride was treated with 5% alcohol-
ic NaOH solution for 6 h. The amine 2 thus obtained was filtered,
washed successively with H2O, MeOH, and finally dried under vac-
uum; yield: 4.2 g (84%).
Acknowledgment
We thank the Department of Chemistry, University of Calcutta, for
providing the instrumental support. One of the authors, K.T., is
thankful to the University Grants Commission (Eastern Region),
India, for financial support. We acknowledge the Department of
Science and Technology (DST), the Council of Scientific and Indu-
strial Research (CSIR), and the University Grant Commission
(UGC), New Delhi, India for funding. We also thank the DST and
UGC, New Delhi, India for providing instrumental support under
FIST and SAP program.
Polymer-Anchored Ligand 3
The polymer-anchored ligand 3 was prepared by the reaction of 2 (3
g, 0.9 mmol) with benzaldehyde (10 mL) in anhyd toluene (30 mL)
under reflux condition for 72 h under N2; yield: 2.7 g (90%).
Poly(N-vinylcarbazole)-Anchored Palladium(II) Complex 4
For the preparation of poly(N-vinylcarbazole)-anchored palladi-
um(II) complex 4, a methanolic solution (25 mL) of Pd(PhCN)2Cl2
(0.7 g, 1.82 mmol) was mixed with 3 (2 g, 0.5 mmol) and the reac-
tion mixture was first stirred for 24 h at r.t. and then refluxed in a
water bath for 12 h; yield: 1.6 g (80%).
References
(1) (a) Stetter, J.; Lieb, F. Angew. Chem. Int. Ed. 2000, 39,
1724. (b) Negishi, E.; Anastasia, L. Chem. Rev. 2003, 103,
1979. (c) Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Angew.
Chem. Int. Ed. 2005, 44, 4442.
Suzuki Cross-Coupling Reaction in Water Medium; General
Procedure
(2) (a) Chinchilla, R.; Nájera, C. Chem. Rev. 2007, 107, 874.
(b) Nicolaou, K. C.; Boddy, C. N. C.; Brase, S.; Winssinger,
N. Angew. Chem. Int. Ed. 1999, 38, 2096. (c) Baudoin, O.;
Cesario, M.; Guenard, D.; Gueritte, F. J. Org. Chem. 2002,
67, 1199. (d) Tsuji, J. Palladium Reagents and Catalysts;
Wiley: New York, 1995. (e) Paterson, I.; Davies, R. D. M.;
Marquez, R. Angew. Chem. Int. Ed. 2001, 40, 603.
(f) Mongin, O.; Porres, L.; Moreaux, L.; Mertz, J.;
Blanchard-Desce, M. Org. Lett. 2002, 4, 719.
(3) (a) Shaughnessy, K. H. Eur. J. Org. Chem. 2006, 1827.
(b) Li, C. J. Chem. Rev. 1993, 93, 2023. (c) Li, C. J. Chem.
Rev. 2005, 105, 3095. (d) Guan, J. T.; Weng, T. Q.; Yu, G.;
Liu, S. H. Tetrahedron Lett. 2007, 48, 7129. (e) Wan, Y.;
Wang, H.; Zhao, Q.; Klingstedt, M.; Terasaki, O.; Zhao, D.
J. Am. Chem. Soc. 2009, 131, 4541.
A mixture of aryl halide (1.0 mmol), phenylboronic acid (1.5
mmol), K2CO3 (2.0 mmol), H2O (6.0 mL) and 1.0 mol% of Pd cat-
alyst 4 was stirred at 70 °C under air. To study the progress of the
reaction, the reaction mixtures were collected at different time inter-
val and quantified by GC analysis. At the end of the reaction, the
catalyst was separated by simple filtration. The filtrate was extract-
ed with CH2Cl2 (3 × 10 mL) and passed through a pad of silica gel.
The organic phase thus collected was dried (Na2SO4), filtered, con-
centrated, and the residue was purified by flash chromatography on
silica gel. The product was analyzed by GC-MS and 1H NMR spec-
troscopy. All prepared compounds are known and compared with
authentic samples (Table 2).
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York

2406
M. Islam et al.
PAPER
(4) (a) Zhao, F. Y.; Bhanage, B. M.; Shirai, M.; Arai, M. J. Mol.
Catal. A: Chem. 1999, 142, 383. (b) Reetz, M. T.; de Vries,
J. G. Chem. Commun. 2004, 1559. (c) Komáromi, A.;
Tolnai, G. L.; Novák, Z. Tetrahedron Lett. 2008, 49, 7294.
(d) Bakherad, M.; Keivanloo, A.; Bahramian, B.; Hashemi,
M. Tetrahedron Lett. 2009, 50, 1557.
(8) (a) Cai, M.; Sha, J.; Xu, Q. J. Mol. Catal. A: Chem. 2007,
268, 82. (b) Wolf, C.; Lerebours, R. Org. Biomol. Chem.
2004, 2, 2161. (c) Zhao, H.; Wang, Y.; Sha, J.; Sheng, S.;
Cai, M. Tetrahedron 2008, 64, 7517. (d) Uozumi, Y.;
Danjo, H.; Hayashi, T. Tetrahedron Lett. 1998, 39, 8303.
(e) Uozumi, Y.; Danjo, H.; Hayashi, T. J. Org. Chem. 1999,
64, 3384. (f) Uozumi, Y.; Nakai, Y. Org. Lett. 2002, 4,
2997. (g) Uozumi, Y.; Kikuchi, M. Synlett 2005, 1775.
(9) (a) Phan, N. T. S.; Styring, P. Green Chem. 2008, 10, 1055.
(b) Mohanty, S.; Suresh, D.; Balakrishna, M. S.; Mague, J.
T. J. Organomet. Chem. 2009, 694, 2114.
(10) King, R. B.; Sweet, E. M. J. Org. Chem. 1979, 44, 385.
(11) Kharasch, M. S.; Seyler, R. C.; Mayo, F. R. J. Am. Chem.
Soc. 1983, 60, 822.
(12) Onue, H.; Moritani, I. J. Organomet. Chem. 1972, 43, 431.
(13) Durig, J. R.; Layton, R.; Sink, D. W.; Mitchell, B. R.
Spectrochim. Acta 1965, 21, 1367.
(5) (a) Mora, M.; Jiménez-Sanchidrián, C.; Ruiz, J. R. J. Mol.
Catal. A: Chem. 2008, 285, 79. (b) Shimizu, K.; Maruyama,
R.; Komai, S.; Kodama, T.; Kitayama, Y. J. Catal. 2004,
227, 202. (c) Reddy, E. A.; Barange, D. K.; Islam, A.;
Mukkanti, V.; Pal, M. Tetrahedron. 2008, 64, 7143.
(d) Jana, S.; Dutta, B.; Bera, R.; Koner, S. Inorg. Chem.
2008, 47, 5512. (e) Crudden, C. M.; Sateesh, M.; Lewis, R.
J. Am. Chem. Soc. 2005, 127, 10045. (f) Kang, C.; Huang,
J.; He, W.; Zhang, F. J. Organomet. Chem. 2010, 695, 120.
(g) Mayr, M.; Mayr, B.; Buchmeiser, M. R. Angew. Chem.
Int. Ed. 2001, 40, 3839. (h) Byun, J. W.; Lee, Y. S.
Tetrahedron Lett. 2004, 45, 1837. (i) Kim, J. H.; Jun, B. H.;
Byun, J. W.; Lee, Y. S. Tetrahedron Lett. 2004, 45, 5827.
(6) (a) Kim, J. W.; Kim, J. H.; Lee, D.; Lee, Y. Tetrahedron Lett.
2006, 47, 4745. (b) Uozumi, Y. Top. Curr. Chem. 2004,
242, 77. (c) Guino, M.; Hii, K. K. M. Chem. Soc. Rev. 2007,
36, 608.
(14) Santra, P. K.; Sagar, P. J. Mol. Catal. A: Chem. 2003, 197,
37.
(15) (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
(b) Suzuki, A. J. Organomet. Chem. 1999, 576, 147.
(c) Suzuki, A. J. Organomet. Chem. 2002, 653, 83.
(d) Miyaura, N. Top. Curr. Chem. 2002, 11. (e)Miyaura, N.
Metal-Catalyzed Cross-Coupling Reactions, 2nd ed., Vol. 1;
de Meijere, A.; Diederich, F., Eds.; Wiley-VCH: Weinheim,
2004, 41–124.
(16) (a) Sonogashira, K. J. Organomet. Chem. 2002, 653, 46.
(b) Negishi, E.; Anastasia, L. Chem. Rev. 2003, 103, 1979.
(17) (a) Sin, E.; Yi, S.; Lee, Y. J. Mol. Catal. A: Chem. 2010, 315,
99. (b) Wang, L.; Cai, C. J. Mol. Catal. A: Chem. 2009, 306,
97. (c) Bandini, M.; Luque, R.; Budarin, V.; Macquarrie, D.
J. Tetrahedron 2005, 61, 9860. (d) Bakherad, M.;
Keivanloo, A.; Bahramian, B.; Hashemi, M. Tetrahedron
Lett. 2009, 50, 1557. (e) Liang, B.; Dai, M.; Chen, J.; Yang,
Z. J. Org. Chem. 2005, 70, 391.
(7) (a) Wang, S.; Zhang, Z.; Hu, Z.; Wang, Y.; Lei, P.; Chi, H.
J. Environ. Sci. 2009, 21, S124. (b) Pelagatti, P.; Carcelli,
M.; Costa, M.; Ianelli, S.; Pelizzi, C.; Rogolino, D. J. Mol.
Catal. A: Chem. 2005, 226, 107. (c) Kang, Y. K.; Kim, D.
Y. Tetrahedron Lett. 2006, 27, 4565.
Synthesis 2010, No. 14, 2399–2406 © Thieme Stuttgart · New York