Tetrahedron Letters
Pd/Cu-catalyzed facile approach to stilbenes: A novel diversity of TosMIC
as an aryl source
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Lingaswamy Kadari, Radha Krishna Palakodety
Organic Synthesis and Process Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Pd/Cu-catalyzed Heck type cross-coupling reaction of p-toluenesulfonylmethyl isocyanide (TosMIC) with
various styrenes to access stilbenes in DMSO solvent under mild conditions is developed. This efficient
and simple approach employs TosMIC as an aryl source for the first time and demonstrates the novel
diversity of TosMIC.
Received 27 May 2019
Revised 21 June 2019
Accepted 23 June 2019
Available online xxxx
Ó 2019 Elsevier Ltd. All rights reserved.
Keywords:
Pd/Cu-catalysts
Cross-coupling
TosMIC as an aryl source
CAC bond formation
Transition metal catalyzed reactions are most powerful tools for
incorporating CAC bond in organic synthesis and play important
role in both material science, fine chemicals and medicinal chem-
istry [1]. Among them, palladium and copper catalyzed reactions
are extensively used for the constructions of important organic
molecules including polymers [2], pharmaceuticals [3] and com-
modity chemicals [4]. The development of palladium and copper
catalysis has been intricately linked because both have been used
widely in the fabrications of similar type of CAC bond and C-hetero
bonds. Furthermore, advancement in and perception into copper
chemistry have often spurred advancements in palladium-cat-
alyzed processes, and vice versa, leading to a wide range of sturdy,
synthetically valuable and often complimentary synthetic methods.
Palladium catalyzed Heck reaction is most popular method for
preparation of vinyl benzenes. The Heck reaction has been demon-
strated to find wide utility in both synthesis of pharmaceuticals,
natural products and agrochemicals in industry [5]. The traditional
Heck reaction is palladium catalyzed coupling between aryl halide
and olefin in the presence of a base and aryl halides as an aryl
source. Other than aryl halides, a wide variety of aryl partners have
been used in Heck reaction such as aryltriflates [6], arylsulfonates
[7], arylcarboxylic acids derivatives [8], aryldiazonium salts [9],
arylsulfonyl halides [10], arylphosphonic acids [11], arylhydrazines
[12], arylsulfonic acids [13] and its sodium salts [14], carbazates
[15], aroylhydrazides [16] and arylsulfonyl hydrazides [17].
p-Toluenesulfonylmethyl isocyanide (TosMIC) has emerged as a
privileged reagent, multi-purpose synthetic tool and is prominent
for its diversity in organic synthesis [18]. The diversity of TosMIC
depends on reaction conditions. Amazingly, it has been used for
the synthesis of different products with same substrates by chang-
ing reaction conditions. In general, activated alkenes undergo cycli-
sation with TosMIC under base to afford pyrroles by the abolition
of tosyl group [19]. Our group reported the synthesis of oxazole
and pyrroles C-nucleosides as the first examples using TosMIC
[20]. Also recently, we reported functionalization of a variety of
olefins and alkynes and their acid derivatives in the presence of
iodine instead of base to access diverse vinyl, allyl and b-iodo
vinylsulfones employing TosMIC as sulfonylating agent (Scheme 1)
[21]. This is in complete contrast deportment of TosMIC to the pre-
vious report. This protocol details the Pd/Cu-catalyzed Heck type
cross-coupling reaction of TosMIC with various styrenes to access
stilbenes, signifying the diversity of TosMIC yet again.
Over the past decade, our group has been working on develop-
ment of novel diverse approaches to expand the synthetic horizon
of TosMIC [22]. In this context, we wish to investigate the diversity
of TosMIC by using transition metals as catalyst with the olefins.
Herein we report palladium and copper catalyst assisted Heck type
coupling between styrene and TosMIC to access stilbenes. To the
best of our knowledge, this is the first report on a novel disclosure
of TosMIC as an aryl source. The notable advantages of the present
protocol such as mild reaction conditions, cross-coupling, transi-
tion metals as catalyst, short reaction time, DMSO as solvent and
TosMIC as a rapid aryl source could make an effective compliment
of current method.
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Corresponding author.
0040-4039/Ó 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: L. Kadari and R. K. Palakodety, Pd/Cu-catalyzed facile approach to stilbenes: A novel diversity of TosMIC as an aryl source, Tetra-