Journal of Organometallic Chemistry
Polystyrene supported thiopseudourea Pd(II) complex: Applications
for Sonogashira, Suzuki-Miyaura, Heck, Hiyama and Larock
heteroannulation reactions
Srinivas Keesara, Saiprathima Parvathaneni, Govardhan Dussa, Mohan Rao Mandapati*
I & PC Division, Indian Institute of Chemical Technology, Taranaka, Hyderabad 500607, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 November 2013
Received in revised form
A new polystyrene supported thiopseudourea palladium(II) complex (3) is found to be a highly active
catalyst for the copper-free Sonogashira, Suzuki, Heck, Hiyama and Larock heteroannulation reactions of
aryl halides. All the reactions proceeded well affording the corresponding cross-coupling products in
good to excellent yields. Further, the catalyst showed excellent recyclability without any significant loss
in its activity.
3
April 2014
Accepted 19 April 2014
Ó 2014 Elsevier B.V. All rights reserved.
Keywords:
Thiopseudourea
CeC coupling reactions
Larock indolization
Palladium
Introduction
view of this, several heterogeneous Pd-catalysts have been re-
ported [15]. However, polymer-supported palladium catalyst cata-
The palladium catalyzed Sonogashira [1], Suzuki-Miyaura [2],
Heck [3], Hiyama [4] and Larock heteroannulation [5] reactions
have emerged as powerful methods in organic synthesis. These
cross coupling reactions are having importance in the synthesis of
natural products and fine chemicals [6]. Most of the reported
Sonogashira [7], Suzuki [8], Heck [9], Hiyama [10] and Larock het-
eroannulation [11] reactions proceeded under homogeneous con-
ditions. However, many homogeneous systems cannot be
commercialized because of difficulties associated with the recovery
of the catalyst. In order to achieve environmentally benign condi-
tions, immobilization of homogeneous catalysts onto polymeric
organic or inorganic insoluble supports [12].
The immobilization of homogeneous catalysts is generally more
attractive from an industrial point of view and polystyrene-
supported palladium catalysts have successfully been used for a
variety of organic reactions [13]. C. Najera et al. have reported resin
supported and unsupported palladacycle oxime complexes for CeC
coupling reactions [14]. The development of efficient heteroge-
neous palladium catalyst systems that could be simultaneously
catalyzing the CeC coupling reactions and obtaining Pd-free pure
products is the most important for the pharmaceutical industry. In
lyzed Hiyama and Larock heteroannulation reactions have received
less attention. Very few efficient reusable palladium catalytic sys-
tems have been reported for Hiyama couplings [16]. C. L. Drian has
described very recently efficient reusable polystyrene-supported
palladium catalyst for Hiyama cross-coupling [17]. Laurent Djako-
vitch has reported heterogeneous Pd catalysts for different heter-
oannulation reactions [18]. Herein, we describe the synthesis and
application of polystyrene supported thiopseudourea palladium(II)
complex (3) [abbreviated as PS-tsu-Pd(II)] catalyst to CeC cross-
couplings (Sonogashira, Suzuki-Miyaura, Heck & Hiyama) and
Larock heteroannulation reactions.
Recently, we have reported homogeneous thiopseudourea pal-
ladium(II) complex (4) as catalysts for the above cross-coupling
reactions (Fig. 1) [19]. Although it showed significant catalytic ac-
tivity for all the cross-coupling reactions of aryl halides, the dis-
advantages associated with it are overwhelmed by our polymer
supported heterogeneous system.
Results and discussion
Synthesis and characterization of PS-tsu-Pd(II) complex
In Scheme 1, We have given the steps involved in the preparation
of a new polystyrene supported thiopseudourea palladium(II)
*
M.R. Mandapati).
(
complex 3.
A
1-(2-Picolyl)-3-(4-fluorobenzoyl)-2-benzyl-2-
022-328X/Ó 2014 Elsevier B.V. All rights reserved.
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