Tetrahedron Letters
Polystyrene resin-supported CuI-cryptand 22 complex: a highly
efficient and reusable catalyst for the formation of aryl–sulfur bonds
in aqueous media
Nasrin Rezaei a,b, Barahman Movassagh a,
⇑
a
Department of Chemistry, K. N. Toosi University of Technology, PO Box 16315-1618, Tehran, Iran
Department of Chemistry, Razi University, PO Box 67149-67346, Kermanshah, Iran
b
a r t i c l e i n f o
a b s t r a c t
Article history:
The air and moisture stable polystyrene resin-supported copper(I) iodide-cryptand-22 complex (PS-C22-
CuI) behaves as an efficient and robust heterogeneous catalyst in the cross-coupling reaction of aryl
halides and thiols in aqueous media. Moreover, the heterogeneous catalyst can be easily recovered by
filtration and reused for five cycles without significant loss in activity.
Received 26 January 2016
Revised 26 February 2016
Accepted 2 March 2016
Available online 3 March 2016
Ó 2016 Elsevier Ltd. All rights reserved.
Keywords:
Heterogeneous catalysis
Polystyrene-based catalyst
Cryptand-22
Copper iodide
Carbon–sulfur bond formation
Introduction
ularly attractive because they represent an environmentally
friendly and cost-effective alternative to the aforementioned tran-
The formation of C–S bonds has received much attention from
the chemical community because various substituted aryl sulfides
sition metals. However, they suffer from inherent thermodynamic
instability, which results in their oxidation to Cu(II) and/or dispro-
portionation to Cu(0) and Cu(II). Previously, we have demonstrated
that complexes of Cu(I) and Pd(II) with the commercially available
diazacrown ether 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane
(KryptofixÒ 22 or cryptand 22) operate as active homogeneous cat-
1
,2
are of great significance to the pharmaceutical industry. Transi-
tion metal-catalyzed cross-coupling reactions for the formation
of Caryl–sulfur bonds are one of the most powerful organometallic
transformations applied to the synthesis of various aryl sulfides
and their derivatives. These compounds are of interest in pharma-
ceutical and material science.3–5 Among these, the coupling of aryl
halides with aryl- or alkyl thiols represents the most successful
method for the formation of aryl–sulfur bonds; however, harsh
reaction conditions such as high temperatures, polar solvents,
1
9–22
alysts under aerobic conditions.
We postulated that the
macrocyclic and chelating effect of such flexible N- and O-contain-
ing ligands may assist in stabilizing the reactive palladium and
copper intermediates allowing catalysis. In an effort to find an effi-
cient catalyst for the S-arylation reaction, we herein report the
cross-coupling between aryl halides and various thiols catalyzed
using the heterogeneous, reusable, heat-, and air-stable catalyst,
PS-C22-CuI. Anchoring homogeneous catalysts and converting
them into heterogeneous catalytic systems can have advantages,
such as increased surface area resulting in higher loading of the
6
and strong bases are often required.
Compared to the well-established methodologies for C–C, C–O,
and C–N bond formation, metal-catalyzed S-arylation has been less
explored due to the complications associated with thiols undergo-
ing oxidative coupling to disulfides; furthermore, organic sulfur
compounds have been shown to bind to transition metal catalysts,
active sites, simpler isolation of the reaction products, and recy-
7
23,24
leading to catalyst deactivation. Typical, Caryl–sulfur bond forma-
cling of the catalyst systems by filtration.
For the preparation
tion proceeds by cross-coupling between aryl halides and thiols in
of heterogeneous catalysts using precious metals, the complexes
of transition metals can be grafted on various inorganic and
7
,8
9
the presence of various transition metals, including Pd,
Ni,
1
0,11
12
13
14
15–18
25
26,27
Fe,
Co, Zn, In, and Cu.
Copper(I) catalysts are partic-
organic supports such as mesoporous silica, ionic liquids,
2
8,29
and polymer surfaces.
Polymer-supported catalysts offer many
advantages for industrial applications due to their versatile pro-
cessing capabilities and ease of separation and recycling. Among
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040-4039/Ó 2016 Elsevier Ltd. All rights reserved.
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