Polyaniline coated on celite, a heterogeneous support for palladium: Applications in catalytic Suzuki and one-pot Suzuki-aldol reactions

Article abstract of DOI:10.1039/c6nj02402e

Particles of celite were coated with polyaniline, characterized and used as a support for heterogenization of palladium metal ions. The prepared heterogeneous palladium catalysts were screened for Suzuki-Miyaura and one-pot Suzuki-aldol reactions with high conversions. The process of heterogenization on celite reduces the PANI consumption ten-fold when anchoring palladium ions onto the support. The recyclable catalyst was also used for the sunlight mediated Suzuki-Miyaura reaction with good conversion.

Full text of DOI:10.1039/c6nj02402e

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Polyaniline coated on Celite, a heterogeneous support for palladium:
Applications in catalytic Suzuki and one-pot Suzuki-aldol reactions
Heta A. Patel, Arun L. Patel* and Ashutosh V. Bedekar*
Department of Chemistry, Faculty of Science
M.S. University of Baroda, Vadodara 390 002, India
Tel. No. +91ꢀ265ꢀ2795552; Email: arunpatel_5376@yahoo.co.in; avbedekar@yahoo.co.in
Abstract:
Particles of celite were coated with polyaniline, characterized and used as support for
heterogenization of palladium metal ions. The prepared heterogeneous palladium catalysts were
screened for SuzukiꢀMiyaura and oneꢀpot Suzukiꢀaldol reactions with high conversions. The
process of heterogenization on celite reduces the consumption of PANI by ten folds during the
anchoring of palladium ions on to the support. The recyclable catalyst was also used for sunlight
mediated SuzukiꢀMiyaura reaction with good conversions.
aldol
O
Pd
Pd
Pd
Pd
Pd
Pd
Ar
Ar
Pd
Pd
Celite PANI Pd
Suzuki
(Catalyst)
72 to 79 % Y

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Introduction:
Synthesis of useful fine chemicals by various reactions utilizing heterogeneous catalysts has
been a well established option for contemporary chemists.1 Heterogeneous catalysis has several
distinct advantages over homogeneous systems such as recoverability, reusability, less
contamination of metal ions in the products, better activity in some cases etc. However, special care
is required to develop methods of anchoring metal ions to produce robust and stable systems of
heterogenization of metal ions while retaining their catalytic activity. This has been successfully
achieved by various methods of anchoring the metal ions by different modes of binding involving
chemical, physical and supramolecular forces. Metal ions may be loaded on inorganic supports2
like clays or zeolites,3 or materials like dendrimers4 and polymers.5 Amongst these approaches,
polymer supported metal catalysts are very important. The polymers which strongly bind with
metal ions can be designed and easily synthesized for this purpose.6 Polymers with amino
functional groups are ideal as they can form complexes or chelates with metal ions for diverse
catalytic applications.7
Many inorganic materials like celite and silica gel can be good candidates for appropriate
modifications to prepare solid reagents for useful chemical transformations. Recently some such
inorganicꢀorganic hybrid materials have been prepared and used for some transformations.8
Polyaniline (PANI) has electrical conducting properties and has been much studied in recent
decades.9 Many composite materials with PANI have been prepared and investigated for their
properties. Results indicate that in some cases incorporating PANI with inorganic materials like
silica can enhance some of the conducting properties.10 Recently some nanoparticles of composites
of PANI11 and micrometerꢀsize hollow particles12 have also been prepared and studied.
Heterogeneous polyaniline supported metal catalysts have been used to effect efficient organic
transformations. In recent decades several such reports have appeared in the literature where a wide

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variety of conversions, such as oxidations,13 Michael reactions,14 coupling reactions,15 acylations16
along with some miscellaneous reactions17 have been carried out with metal ion anchored on PANI
as catalysts.
The catalysts system of polyaniline loaded with metal ions or in some cases metal
complexes pose a practical difficulty of low solubility is some solvents, which do not make them
completely heterogeneous. This causes difficulty in recovering and recycling the catalyst in
efficient manner. Also the consumption of PANI for the synthesis of the product is quite high,
which is a matter of concern due to some aspects of its toxicity.18 Hence, to overcome some of the
problems, we have designed a strategy to heterogenize PANI over some solid material, and then
treat them with metal ions to prepare more robust heterogeneous catalysts. The prepared catalysts
would be then characterized and scanned to evaluate their efficacy in useful catalytic
transformation. Although there are few reports available on supporting PANI on silica gel, we have
chosen less acidic celite as solid inorganic support to its heterogenization. Due to our continuous
interest in PANI• palladium mediated chemical transformations15c we have presently focused on
this metal ion based catalysts, the Scheme 1 outlines the approach in brief.
Scheme 1 Schematic representation of anchoring palladium on heterogenized PANI on celite
Result and Discussion:
The standard preparation of PANI involves oxidative polymerization of aniline
hydrochloride with ammonium persulfate in aqueous medium.19 In the present study to load PANI

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on the solid surface, the polymerization of aniline was performed in its aqueous solution in
hydrochloric acid in the presence of suspension of celite. The particles of celite were found to be
coated with a layer of PANI, which was separated by filtration. The solid material was treated in
aqueous ammonia solution to get its free base in emeraldine form. The excess of PANI, its
oligomers and excess of aniline were removed by proper washing with different solvents. The
material was vacuum dried till constant weight was observed. The free flowing dry powder of
Celite•PANI was characterized by usual techniques to establish its composition. For the present
study a sample was prepared with celite (5.0 g) and aniline (5.0 g), being referred as Celite•PANI.
The dry sample of Celite•PANI (1.0 g) was stirred with PdCl2 (three different quantities, 0.05 g,
0.10 g and 0.20 g) in acetonitrile for (24 h) and the material was filtered, washed and dried. Thus
the three samples of catalysts were prepared with different loading of palladium. The amount of
palladium present in each of the three catalysts was estimated by ICPꢀAES analysis (Table 1).20
Table 1 Three catalysts prepared with palladium loading
No
Catalyst Code
Amount of PdCl2 for
Celite•PANI (1.0 g)
Amount of Pd
(%) per gram of
catalysta
1
2
3
Celite•PANI•Pd•A
Celite•PANI•Pd•B
Celite•PANI•Pd•C
0.05 g
0.10 g
0.20 g
0.34
0.42
0. 50
aDetermined by ICPꢀAES analysis. 1.0 g Celite•PANI was treated with 0.05 g, 0.10 g and 0.20 g of PdCl2 for the
synthesis of Celite•PANI•Pd•A, Celite•PANI•Pd•B and Celite•PANI•Pd•C, respectively.
The materials were characterized by IR spectroscopy and compared with spectral features of
PANI to confirm the loading (Figure 1). The spectrum of pure PANI displays a broad band at 3,272
cm,ꢀ1 attributed to N–H stretching mode of aromatic amine, absorption bands at 1,587; 1,684 and
1495 cm,ꢀ1 could be due to the C=C stretching vibration of quinoid and benzenoid units of PANI
chain, band at 1,307 cmꢀ1 may be attributed to CꢀN stretching in aromatic amine. The spectrum of

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celite presents a strong and broad absorption band at 1,052 cm,ꢀ1 assigned to Si–O–Si symmetric
stretching vibrations. The spectrum of the CeliteꢀPANI composite contains contributions from both
components. The IR spectrum of Celite•PANI•Pd showed slight difference in the peaks, but no
major inference could be obtained which was in accordance with earlier studies.15a
Figure 1 Comparison of IR spectrum of Celite, PANI and Celite•PANI
The morphologies and composition of celite and Celite•PANI was studied by SEM and
EDX analysis. There is considerable change in the nature of the surface of celite after it is coated

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with PANI (Figure 2a & 2b). This demonstrates the successful incorporation of PANI onto the
surface of celite. The loading of palladium on Celite•PANI was further confirmed by SEM images
where Pd is seen as nanoꢀsized particles in the range of 50ꢀ170 nm (Figure 2c & 2d).
Figure 2 SEM images: (a) bare celite (top left); (b) Celite•PANI (top right); (c) Celite•PANI•Pd•B
(bottom left); (d) enlarged image of Celite•PANI•Pd•B (bottom right)
The presence of palladium is further conformed by EDS of a representative catalyst
Celite•PANI•Pd•B, recorded at random reference points on the surface (Figure 3). The EDS

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spectrum also confirms the presence of other ions attributing to celite as well as PANI, confirming
the composition of the catalyst.
cps/eV
5
4
K
Pd
3
Cl
N
C
O
Na
Al
Si
Cl Pd
K
2
1
0
1
2
3
keV
4
5
6
Figure 3 EDS spectrum of Celite•PANI•Pd•B.
The Xꢀray diffraction (XRD) analysis of the samples of Celite•PANI and its complex
confirmed the loading of palladium (Figure 4). The broad peak corresponding to 2 theta value 25
indicate the amorphous nature of Celite•PANI. The XRD analysis of Celite•PANI•Pd clearly
showed the two characteristic signals corresponding to 2 theta values at 40 and 46 which are
characteristic peaks for Pd.15c, 20
600
CeliteꢀPANI
CeliteꢀPANIꢀPd
500
400
300
200
100
10
20
30
40
50
60
2
theta

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Figure 4 XRD of Celite•PANI and Celite•PANI•Pd•B.
BrunauerꢀEmmetꢀTeller (BET) surface analysis of Celite•PANI and Celite•PANI•Pd•B
shows a type II isotherm (Figure S4 of SI). The specific area of Celite•PANI is 5.11 m2/g, which
increased to 6.02 m2/g in Celite•PANI•Pd•B. The average pore diameter are 204 Ao and 178 Ao for
Celite•PANI and Celite•PANI•Pd•B, respectively (Table 2). It can be assumed that pores are filled
with active phase which decreased the average pore diameter.
Table 2 BET analysis data for Celite•PANI and Celite•PANI•Pd•B
Sample
SBET
m2/g
Pore volume
cm3/g
Pore
Diameter
A0
CeliteꢀPANI
5.11
6.05
0.21
0.02
203
178
CeliteꢀPANIꢀPd
Thermogravimetric analysis (TGA) of the sample of Celite•PANI•Pd•B confirmed its
stability up to ~350 oC, which shows its suitability for the use as heterogeneous catalyst in standard
reaction parameters (Figure S5 of SI). The three systems were appropriate candidates for scanning
as heterogeneous catalysts in important transformations.
Synthesis of biaryls by palladium mediated coupling of aryl halides with arylboronic acids,
also known as SuzukiꢀMiyaura reaction is one of the most efficient and wellꢀstudied reactions in
contemporary chemistry.21 Although the reaction is well understood and optimized under
homogeneous conditions, there are several useful reports on the use of heterogeneous palladium
catalysts for this reaction.22 In our earlier report we have used palladium catalyst anchored on PANI
for MizorokiꢀHeck, SuzukiꢀMiyaura and their oneꢀpot combination with Wittig reaction15c with

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very good results. However, in the work in some cases we have observed some practical difficulty
due to partial solubility of PANI in some solvents at higher temperature. To address some of these
issues we now scan our present series of heterogenized Celite•PANI•Pd as catalysts for Suzukiꢀ
Miyaura reaction, and also extend the scope by performing its oneꢀpot combination with aldol
reaction.
The above catalysts were screened for testing their efficacy for the standard SuzukiꢀMiyaura
reaction with iodobenzene and phenylboronic acid 1 (Scheme 2), where the product biphenyl 2 was
isolated in very good yield.
catalyst (0.1 g)
K2CO3
I
B(OH)2
Ph
Ph
2
+
dioxane-water
90 oC, 4 h
(Table 1)
Ph
(0.1 g)
Ph
1
Scheme 2 SuzukiꢀMiyaura reaction
The results of the experiment with the three catalysts are summarized in Table 3, where the
data suggested effectiveness of all the three systems. The efficiency of any heterogeneous catalyst
system is also judged by the recyclability and reusability in subsequent cycles of the reaction. The
catalyst Celite•PANI•Pd•B recovered from the above reaction was washed with suitable solvents,
dried and used for five more cycles to check this property (Table 3). Reactions carried out under
identical conditions resulted in consistent conversions, establishing the recyclability of the catalyst
system.

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Table 3 Catalyst screening for synthesis of biphenyl 2
No
1
Catalyst
Yield (%)
TON
144
119
100
Celite•PANI•Pd•A
Celite•PANI•Pd•B
Celite•PANI•Pd•C
94
96
96
2
3
Recycle study with Celite•PANI•Pd•B
4
5
6
7
8
2nd Cycle
3rd Cycle
4th Cycle
5th Cycle
6th Cycle
93
90
91
90
89
115
112
113
112
111
Conditions: Aryl halide (1.0 equiv), K2CO3 (2.0 equiv), boronic acid (1.2 equiv), 90 oC, dioxaneꢀwater (1:1), 4 h
To study the leaching of Pd, standard SuzukiꢀMiyaura reaction with iodobenzene and
phenyl boronic acid was selected. Two sets of above reaction were carried out under optimized
condition (Figure 5). One set of reaction was quenched after one hour and product was isolated (35
% Yield). In other set, the catalyst was separated after one hour by filtration and the reaction was
allowed to continue for three hours, which resulted in almost no further conversion (37 % Yield)
The experimental results shows no significance change in the yield after catalyst separation which
clearly indicates very low leaching of palladium.
With catalyst
Without catalyst
100
90
80
70
60
50
40
30
20
10
1.0
1.5
2.0
2.5
3.0
3.5
4.0
TIME
Figure 5 Result of hot filtration test to study leaching of palladium

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One of the objectives of the present study was to reduce the consumption of PANI for the
production of the coupling product. In our earlier study we have utilized palladium chloride loaded
on PANI for SuzukiꢀMiyaura reaction.15c Although the reaction was efficiently catalyzed by
PANI•Pd system, the consumption of PANI for the preparation of biphenyl was found to be quite
high (0.44 g PANI/ g of biphenyl). In the present work we are coating the particles of celite with a
thin layer of PANI to facilitate the adhering the metal ions to prepare the active heterogeneous
catalyst. A sample of the catalyst with known weight was taken in a porcelain crucible and
decomposed at high temperature (Bunsen burner). The process was repeated till constant weight of
the residue, subtracting from the original value we could estimate the amount of PANI present in
Celite•PANI. This was observed to be about 0.167 g PANI in 1.0 g of Celite•PANI, which was in
accordance with expected data based on increased weight of celite when coated with PANI. Based
on this information and the experimental yields of SuzukiꢀMiyaura reaction we estimated the
consumption of PANI for the production of biphenyl (Table 4). The optimization done with the
catalysts clearly indicate that by choosing Celite•PANI•Pd•C which has higher amount of
palladium loading, we could increase the conversion. These results indicate the possibility to reduce
the requirement of PANI by nearly ten folds as compared to our previous report of 0.44 g PANI/ g
of 2 (entry 5 & 6, Table 4). Besides the low use of PANI, this also offers advantages like more
stability due to less aggregation, effectively more surface area for efficient loading of palladium
metal for wider applications. The heterogeneous catalytic system becomes more robust by reducing
the quantity of the material (PANI) which has chance of being lesser stable under reaction
conditions. The particle size distribution was studied using dynamic light scattering (DLS) with a
BIC 90 Plus (Brookhaven) equipped with 35.0mW solid state lasers operating at 660 nm and an
avalanche photodiode detector. All measurements were made at 25 °C. The particle size of the
catalyst was also found to be much larger as compared to PANI•Pd, which opens up possibilities to
explore the use in continuous flow reactors. The particle size of PANI•Pd was observed in the

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ranges from 150 to 300 nm.15c The overall particle size for Celite•PANI•Pd•B was increased to
427.9 nm (Figure S6 of SI). The free flowing nature of the catalyst particles helps its easy filtration
and handling making it more practical for the synthetic applications.
Table 4 Estimation of consumption of PANI for the preparation of biphenyl
No PhI
[g]
Catalyst
[g]
Yield of 2
PANI
consumed
per g of 2
% [g]
1
2
3
4
5
6
0.1 Celite•PANI•Pd•A 94 [0.071]
[0.1]
0.237
0.233
0.233
0.119
0.059
0.040
0.1 Celite•PANI•Pd•B 96 [0.072]
[0.1]
0.1 Celite•PANI•Pd•C 96 [0.072]
[0.1]
0.2 Celite•PANI•Pd•C 93 [0.140]
[0.1]
0.4 Celite•PANI•Pd•C 93 [0.281]
[0.1]
0.4 Celite•PANI•Pd•C 68 [0.206]
[0.05]
o
Conditions: Aryl halide (1.0 equiv), K2CO3 (2 equiv), boronic acid (1.2 equiv), TBAB (10 %), 90 C, dioxaneꢀwater
(1:1), 4 h
Having established considerable advantages of the present series of the palladium catalysts
supported on the heterogeneous support of Celite•PANI and characterized them adequately we then
screened them for SuzukiꢀMiyaura coupling reaction (Scheme 3). The reactions were conducted
with the catalyst Celite•PANI•Pd•B as it has optimum quantity of palladium required for efficient
catalysis (Chart 1).
Celite PANI Pd B
K2CO3
I
Ar'
Ar'
+
Ar
Ar
(HO)2B
dioxane-water
90 oC, 4-12 h
(Chart 1)
(1.0 eq.)
(1.2 eq.)
1a, 1b
Scheme 3 Standardization of SuzukiꢀMiyaura reaction

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The reactions were run with ArꢀX (1.0 eq.), Ar’B(OH)2 (1.2 eq. per halogen), K2CO3 (2.0
eq. per halogen), TBAB (10 mol %), in dioxane or aqueous dioxane depending upon the solubility
or reagents. Aryl iodides (for 2, 3 & 12) and aryl bromides (for all other examples) were chosen as
starting materials, while aryl chlorides showed quite poor reactivity under these conditions. We
observed that when both bromine and chlorine are present, the reaction proceeds selectively
replacing the former (15). Generally the reactions were monitored by performing thin layer
chromatography (4 to 12 h), catalyst was simply separated by filtration and the products were
purified by column chromatography over silica gel. The yields mentioned in Table 5 refer to the
isolated yield and the products have been characterized by usual spectroscopic techniques. The
wide range of the aryl halides and different substituent indicates the generality of the catalyst
system.

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2, R = H
3, R = OCH3
4, R = NO2
5, R = CHO
6, R = COCH3
7, R = NHCOCH3
B(OH)2
R
Me
O2N
1a, R = H
1b, R = Me
R
8
R
R
R
R
R
R
13, R = H
14, R = Ph
15, R = Cl
9, R = H
10, R = CH3
11, R = H
12, R = OCH3
16
CN
Me
19
18
17
Chart 1 Examples of SuzukiꢀMiyaura reaction with Celite•PANI•Pd•B

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Table 5 SuzukiꢀMiyaura reaction with Celite•PANI•Pd•B
Entry Aryl halide
Product
Time
(h)
4
Isolated
Yield (%)
(see Chart 1)
1
2
Iodobenzene
96
94
91
85
93
90
90
71
73
78
80
84
73
83
87
60
80
2
3
1ꢀiodoꢀ4ꢀmethoxybenzene
4ꢀnitrobromobenzene
4ꢀbromobenzaldehyde
4ꢀbromoacetophenone
4ꢀbromoacetanilide
4
3
8
4
4
8
5
5
8
6
6
8
7
7
4ꢀnitrobromobenzenea
1,3,5ꢀtribromobenzene
1,3,5ꢀtribromobenzenea
1,4ꢀdibromobenzene
8
8
8
12
12
10
6
9
9
10
11
12
13
14
15
16
17
18
19
10
11
12
13
14
15
16
17
18
1,4ꢀdiiodoꢀ2,5ꢀdimethoxybenzene
9ꢀbromoanthracene
10
10
10
12
12
10
8
9,10ꢀdibromoanthracene
9ꢀbromoꢀ10ꢀchloroanthracene
2,7ꢀdibromonaphthalene
3,6ꢀdibromophenanthrene
1,3ꢀdibromoꢀ5ꢀmethylbenzene
2ꢀbromobenzonitrile
89
o
Conditions: ArX (1.0 equiv), K2CO3 (2 equiv), boronic acid (1.2 equiv), TBAB (10%), 90 C, 4ꢀ12 h, Dioxane:H2O
(1:1) for 2ꢀ4, 6ꢀ8, 12, 19, Dioxane for, 9ꢀ11, 13ꢀ18, Toluene for compound 5, ArI for 2, 3, 12 and ArBr for 4ꢀ11, 13ꢀ19.
aWith boronic acid 1b.
One of the twelve principles of “Green Chemistry” proposed by Anastas and Warner refer
to the use of energy efficient synthetic processes.23 The sixth principle says “the energy
requirements of chemical processes should be recognized for their environmental and economic

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impacts and should be minimized. The sunlight mediated chemical transformations have been
known for some time,24,25 but mostly it is used as a photon source for photochemical or
photothermal reactions, dimerisation26a or isomerisation of the conjugated compounds26b and the
related reactions. Beside these a few other sunlight mediated reactions have been developed over
the years and are summarized in recent articles.27,28 In our ongoing interest to develop useful
chemical transformations performed under the direct sunlight irradiation we have previously
developed homogeneous palladium catalyzed coupling reactions.29 We have scanned our present
heterogeneous catalyst system for the SuzukiꢀMiyaura reaction under the direct sunlight, as
outlined in Scheme 4.
Ar'
I
Celite PANI Pd B
Ar'
Ar
+
B(OH)2
Ar
K2CO3
dioxane-water
(Table 6)
(1.0 eq.) (1.2 eq.)
Scheme 4 Sunlight promoted SuzukiꢀMiyaura reaction
The reaction proceeds well with very good conversions, though the time required for
complete conversion is much longer (Table 6). The representative examples with comparable
conversions are presented here, establishing the efficacy of the procedure. The results of efficient
use of heterogeneous catalysis in sunlight promoted reaction are encouraging as most of such
reactions are performed in homogeneous conditions.29 The chemical yields of this reaction were
marginally better in some cases compared to our earlier study.29

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Table 6 Sunlight promoted SuzukiꢀMiyaura reaction with Celite•PANI•Pd•Ba
No
Aryl Halide
Product
Timeb (h) Isolated
(see Chart 1)
Yield (%)
1
2
3
4
5
6
7
8
9
Iodobenzene
10
10
13
13
13
13
15
13
15
13
94
94
96
90
90
88
78
87
70
91
2
3
1ꢀiodoꢀ4ꢀmethoxybenzene
4ꢀnitrobromobenzene
4
4ꢀbromoacetophenone
4ꢀbromoacetanilide
6
7
4ꢀnitrobromobenzene
8
1,4ꢀdibromobenzene
11
12
18
19
1,4ꢀdiiodoꢀ2,5ꢀdimethoxybenzene
1,3ꢀdibromoꢀ5ꢀmethylbenzene
10 2ꢀbromobenzonitrile
aReactions were run with ArX (0.1 g, 1.0 eq.), ArB(OH)2 (1.2 eq. per number of halogens), catalyst (0.1 g), K2CO3 (2.0
b
eq. for each halogen), TBAB (10 mol %), in dioxaneꢀwater (1:1), under magnetic stirring in conical flask. Actual
sunlight exposure time.
The sunlight mediated coupling reaction probably involves a combination of photochemical
and photothermal effects.29 The photochemical cleavage of arylꢀhalogen bond may assists the
insertion of palladium as the initial step. Reaction performed in sunlight in a covered flask to cut off
the rays of light resulted in almost no conversion (tlc), clearly establishing the role of
photoirradiation.
Simultaneously, performing several chemical transformations offer many advantages. Such
procedures also referred as “oneꢀpot synthesis” offer advantages of lesser consumption of reagents,
easy workꢀup, can effectively reduce reaction time, may avoid purification of unstable, toxic, or
volatile intermediates, and generally follow the concept of green synthesis. Recently several
procedures have been developed for making useful molecules and intermediates by adopting oneꢀ
pot or domino or tandem synthetic schemes.30 As part of our interest in the synthesis of useful
molecules from readily available materials we have developed oneꢀpot dehydrohalogenationꢀHeck
or WittigꢀHeck,31 WittigꢀSuzuki,32 and oxidationꢀWittigꢀHeck33 reaction protocols.

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Base mediated aldol condensation reaction between an aldehyde and a ketone with acidic αꢀ
hydrogen is one of the most widely utilized carbonꢀcarbon bond forming reaction. Although there
are many oneꢀpot combinations involving this reaction are reported in the literature, there are not
many oneꢀpot methodologies involving aldol and SuzukiꢀMiyaura reaction known.34 Both the
reactions are compatible due to similar reaction conditions and hence we decided to extend our
methodology to explore this combination with our present catalysts. Accordingly, we started our
attempt by selecting 4ꢀbromobenzaldehye and substituted acetophenones as the aldol partners,
while performing the reaction under the SuzukiꢀMiyaura condition along with a boronic acid. The
base mediated aldol reaction of acetophenone with 4ꢀbromoaldehyde followed by dehydration can
give the chalcone unit while the bromine can couple with boronic acid to furnish an interesting
building block (Scheme 5). The reaction was performed with catalyst Celite•PANI•Pd•B in toluene
as the standard condition.
aldol
O
O
Celite PANI Pd B
K2CO3
CHO
+
+
toluene
100 oC, 12 h
(Chart 2)
B(OH)2
R
R
Br
Suzuki
Scheme 5 Oneꢀpot Suzukiꢀaldol reaction (Type A)
Several derivatives of acetophenone can be utilized to prepare the functionalized systems
(20ꢀ22, Chart 2), while αꢀtetralone can be substituted as the source of anion to produce compound
23, in good yields. All the compounds were separated by column chromatography over silica gel,
and the stereochemistry of the isolated major product was established to be E as expected in such
cases.

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O
R
20, R = H (74 %)
21, R = NO2 (68 %)
22, R = CH3 (86 %)
O
23 (59 %)
Chart 2 Examples of oneꢀpot Suzukiꢀaldol reaction (Type A)
The derivatives of chalcone have many applications in medicinal, material and agro
chemistry.35 The two components of chalcone may have different substituent and a library of multi
substituted chalcone can be easily accessed. Similar to the above reaction we also developed
another combination where 4ꢀbromoacetophenone was chosen as aldol and Suzuki reaction partner,
while substituted benzaldehydes can complete the aldol reaction and provide another variation
(Scheme 6).
aldol
O
O
Celite PANI Pd B
K2CO3
OHC
+
+
toluene
100 oC, 12 h
(Chart 3)
B(OH)2
R
R
Br
Suzuki
Scheme 6 Oneꢀpot Suzukiꢀaldol reaction (Type B)
This reaction too was catalyzed by Celite•PANI•Pd•B in toluene under the standard
condition and a similar series of compounds were isolated in good yields (Chart 3). Both these
variants of oneꢀpot aldolꢀSuzuki reactions may offer different permutations and combinations and
may present an easy access to such compounds.

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O
R
24, R = H (85 %)
25, R = OCH3 (75 %)
26, R = Cl (85 %)
27, R = CH3 (84 %)
28, R = NO2 (60 %)
O
O
O
29 (66 %)
Chart 3 Examples of oneꢀpot Suzukiꢀaldol reaction (Type B)
In a variation we chose 4ꢀbromoacetophenone and 4ꢀbromobenzaldehyde for the aldol
reaction along with excess of phenylboronic acid 1a, under the same reaction parameters (scheme
7).The reaction involved a combination of an aldol condensation and double Suzuki reaction to
produce 4,4’ꢀdiphenyl chalcone 30, in good yield.
aldol
O
O
Celite PANI Pd B
K2CO3
OHC
+
+
toluene
100 oC, 12 h
B(OH)2
Br
Br
Suzuki
30 (71 %)
Scheme 7 Oneꢀpot SuzukiꢀaldolꢀSuzuki reaction (Type B)
All the compounds reported here were purified by column chromatography over silica gel
and the products obtained were adequately characterized by usual spectral and analytical methods.

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Experimental section:
Thin Layer Chromatography was performed on silica gel plates quoted on aluminium
sheets. The spots were visualized under UV light or with iodine vapor. All the compounds were
purified by column chromatography on silica gel (60ꢀ120 mesh). All reactions were carried out
under an inert atmosphere (nitrogen) unless other conditions are specified. NMR Spectra were
1
recorded on Bruker Avance 400 Spectrometer (400 MHz for H NMR, 100 MHz for 13C NMR)
with CDCl3 as solvent and TMS as internal standard. Mass spectra were recorded on Thermoꢀ
Fischer DSQ II GCMS instrument; IR spectra were recorded on a PerkinꢀElmer FTIR RXI
spectrometer as KBr pallets. Melting points were recorded in Thiele’s tube using paraffin oil and
are uncorrected.
Procedure for the synthesis of Celite•PANI:
Freshly distilled aniline (5 mL, 54.9 mmol) was dissolved in minimum amount of aqueous HCl (1.5
M). 5 g of celite was added and a solution of ammonium persulfate (6.27 g, 27.5 mmol) in HCl (1.5
M, 25 mL) was added to it at 0 °C. Since, aniline polymerization is strongly exothermic, the
oxidant must be added slowly over a period of 1 h. After the addition of the oxidant, the reaction
was stirred over night. The coated celiteꢀpolyaniline hydrochloride was separated by filtration and
washed consecutively with water (3x30 mL), methanol (2x25 mL), and diethyl ether (2x15 mL) to
remove the oligomers and the reaction side products. The polymer was then vacuumꢀdried until
constant mass. Deprotonation of polyaniline hydrochloride was achieved with aqueous ammonia (3
wt %). Deprotonated polymer was again washed with water, methanol, and diethyl ether and dried
until constant mass (5.962 g).
Procedure for the synthesis of Celite•PANI•Pd:
CeliteꢀPANI (5 g) was charged into a roundꢀbottomed flask containing an acetonitrile solution (150
mL) of palladium chloride and stirred under nitrogen atmosphere for 48 h. The resultant catalyst

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was filtered off and washed with acetonitrile followed by acetone. The residue was dried in air for
24 h to afford the grey colored powder of Celite•PANI•Pd.
General procedure for SuzukiꢀMiyaura reaction (Scheme 3):
To an ovenꢀdried two necked round bottom flask equipped with a stirrer bar was charged
iodobenzene (0.2 g, 0.98 mmol), potassium carbonate (0.27 g, 1.96 mmol), Celite•PANI•Pd•B (0.2
g, 0.0079 mmol of Pd) in dioxane:water (1:1).To the reaction mixture phenyl boronic acid (0.14 g,
o
1.17 mmol) was added and heated at 95 C for 4 h. The reaction mixture was quenched with water
and extracted with ethyl acetate (3x25 mL).The combined organic phase was washed with water
and dried over anhydrous sodium sulfate. Solvent was removed in vacuum and crude product was
purified by column chromatography on silica gel to afford biphenyl 2 as white solid. (0.145 g, 96
%). M.p. 71 oC [Lit.36 71 oC] 1HꢀNMR (CDCl3, 400 MHz): δ 7.41 (t, J= 7.2 Hz, 1H), 7.51 (t, J=7.6
Hz, 2H), 7.66 (d, J=7.2 Hz , 2H). IR [KBr]: υ 3059, 3032, 1596, 1568, 1477, 1427, 1375, 730, 695
cm.ꢀ1
General procedure for sunlight promoted SuzukiꢀMiyaura reaction (Scheme 4):
To an ovenꢀdried flat bottom flask equipped with a stirrer bar was charged iodobenzene (0.2 g, 0.98
mmol), potassium carbonate (0.27 g, 1.96 mmol), Celite•PANI•Pd•B (0.2 g, 0.0079 mmol of Pd) in
dioxane:water. To the reaction mixture phenyl boronic acid (0.14 g, 1.17 mmol) was added and
kept in sunlight for 10 h. The reaction mixture was quenched with water and extracted with ethyl
acetate (3x25 mL).The combined organic phase was washed with water and dried over anhydrous
sodium sulfate. Solvent was removed in vacuum and crude product was purified by column
chromatography on silica gel to afford biphenyl 2 as white solid. (0.142 g, 94 %).
General procedure for Oneꢀpot Suzukiꢀaldol reaction Type A & Type B (Scheme 5 and 6):

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To an ovenꢀdried two necked round bottom flask equipped with a stirrer bar was charged 4ꢀ
bromobenzaldehyde (0.2 g, 1.08 mmol), acetophenone (0.13 g, 1.08 mmol), potassium carbonate
(0.60 g, 4.32 mmol), Celite•PANI•Pd•B (0.2 g, 0.0079 mmol of Pd), phenyl boronic acid (0.14 g,
o
1.17 mmol) in toluene were added and heated at 100 C for 12 h. Excess of toluene was distilled
under vacuum and then reaction mixture was quenched with water and extracted with ethyl acetate
(3x25 mL). The combined organic phase was washed with water and dried over anhydrous sodium
sulfate. Solvent was removed in vacuum and crude product was purified by column
chromatography on silica gel to afford (E)ꢀ3ꢀ([1,1'ꢀbiphenyl]ꢀ4ꢀyl)ꢀ1ꢀphenylpropꢀ2ꢀenꢀ1ꢀone 20.
as white solid. (0.23g, 74 %).118ꢀ120 oC [Lit.34b 119ꢀ121 oC] 1HꢀNMR (CDCl3, 400 MHz): δ 7.42ꢀ
7.43(m, 1H), 7.48ꢀ7.59(m, 5H), 7.61ꢀ7.70(m, 6H), 7.75ꢀ7.77(m, 2H), 7.891(d, J=15.6 Hz, 1H),
8.06ꢀ8.08(m, 2H). IR [KBr]: υ 3055, 3032, 1690, 1601, 1459, 1446, 1216, 834, 690, 758 cm.ꢀ1
Mass (EI): 284(41), 283(100), 207(41), 178(53), 77(30)
Conclusions:
In this paper we present preparation of celite supported PANI particles and their complex with
palladium ions. These Celite•PANI•Pd heterogeneous catalysts were scanned for SuzukiꢀMiyaura
reaction under thermal and sunlight irradiation and developed their applications in oneꢀpot Suzukiꢀ
aldol reactions. The resultant heterogenized PANI•Pd works well as a robust, recyclable catalyst
system with tenfold reduction of the consumption of polymeric material for the synthesis of
biphenyl.
Acknowledgments:

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We thank University Grants Commission (UGC), New Delhi for the financial support and a
research fellowship to HAP. We are also grateful to Dr. S. Sahoo of Sun Pharma Pvt. Ltd. for some
of the analysis for this work and to Prof. P. Padmaja and Dr. H.P. Soni for useful discussions.
Supporting Information: Detail analytical data and the copies of the spectral charts of some
representative compounds are available as the supporting information.
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