Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Poly (N-2-aminoethylacrylamide) grafted polystyrene–Cu (II) complex
catalyzed conversion of aldehydes into primary amides in water
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Deepak K. Kurhe, Radha V. Jayaram
Department of Chemistry, Institute of Chemical Technology, Matunga, Mumbai 400 019, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 April 2014
Received in revised form 21 July 2014
Accepted 22 July 2014
Available online 5 August 2014
Poly (N-2-aminoethylacrylamide) grafted polystyrene–Cu (II) complex was synthesized and characterized by
techniques such as FTIR spectroscopy, XRD, SEM–EDX, TGA and ICP-AES analysis. The catalyst exhibits an excel-
lent catalytic activity for the conversion of various aldehydes to corresponding amides in water. Also, the catalyst
could be recovered and reused five times without any significant loss in its activity.
© 2014 Elsevier B.V. All rights reserved.
Keywords:
Heterogeneous catalyst
Amide synthesis
1. Introduction
[11]. The most commonly used polymer supports are derived from
‘Merrifield resin’ — a cross-linked chloromethylated polystyrene resin.
The amide group is one of the most important functional groups
in chemistry and biology [1]. Amides can be prepared by the reaction
of carboxylic acids and derivatives of amines. However these methods
have drawbacks, such as the use of toxic materials, highly exothermic
reactions and complex reaction conditions [2]. Amides can also be syn-
thesized from aldoximes, but this conversion requires reagents in
stoichiometric amounts [3]. Hence one pot synthesis of amides from
corresponding aldehydes is a good alternative [4]. The homogeneously
catalyzed one pot conversion of aldehydes to corresponding amides is
explained in detail [5–7]. (See Schemes 1–4.)
Deigo J. Ramon et al. have successfully synthesized amides from
corresponding aldehydes, with copper acetate as a catalyst under
homogeneous reaction conditions. However, considering enhanced
environmental consciousness, efficient and recyclable heterogeneous
catalysts have gained much attention. Aldehydes are converted to corre-
sponding amides using bioglycerol based-carbon as a recyclable catalyst
[8].
Also, the conversion of aldehyde to amide with reusable choline
chloride based eutectic solvent is carried out [9]. Hence copper (II) cat-
alyzed conversion of aldehyde to amide under heterogeneous reaction
conditions is of considerable interest.
In the last few years, catalytically active supported metal complexes
have received much interest because of the possibility of easy separa-
tion and reuse of the catalyst [10]. Among various supports used to
anchor metal complexes, polymer matrices have received considerable
attention, since their physiochemical properties can be easily altered
Functional groups can be attached to this resin for desired applications
[12]. The resin in its various forms is widely in use [13,14]. However;
these crosslinked polystyrene resins are hydrophobic in nature and
swells in non-polar organic solvents. They also lack flexibility towards
anchoring ligands for complexation with metal ions [15]. Introduction
of hydrophilic units in these polystyrene based resins is a solution to
overcome this problem. Also polymer supports with flexible arms are
considered more useful than supports with rigid ligands [16,17].
Grafting is a suitable method for the introduction of hydrophilic
units in cross-linked polystyrene resins. A hydrophilic chain such as a
polyacrylamide has been successfully introduced into cross-linked poly-
styrene by grafting via gamma irradiation [18]. Graft copolymer matri-
ces are widely used in catalysis, biomedicine etc. considering their
modified surface structure and dispersion stability [19]. Linear polymers
grafted on cross-linked polystyrene offer both the advantages of flexi-
bility of the chains and insolubility of the resin [20] and provide
pseudo-homogenous reaction conditions and better access to functional
groups involved [21].
Thus it was intended to functionalize the hydrophilic polyacrylamide
grafted polystyrene with ethylene diamine to form a stable complex
with Cu (II) ion and use this complex as a catalyst for the conversion
of aldehydes to corresponding amides in heterogeneous manner.
2. Experimental
2.1. Reagents and instruments
All chemicals used in this study were of analytical grade and used
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Corresponding author at: Tel.: +91 22 3361 2607.
as received without further purification. The prepared catalyst was
1566-7367/© 2014 Elsevier B.V. All rights reserved.