Catalysis Communications
Short Communication
Supported iron oxide nanoparticles: Recoverable and efficient catalyst
for oxidative S-S coupling of thiols to disulfides
Fatemeh Rajabi a, , Tayeb Kakeshpour b,1, Mohammad Reza Saidi b,1
⁎
a
Department of Science, Payame Noor University, P. O. Box 19395-4697, Tehran, Iran
Department of Chemistry, Sharif University of Technology, P. O. Box 11365-9516, Tehran, Iran
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Supported iron oxide nanoparticles are found to be efficient and recoverable catalyst in the selective oxidation of
thiols to their corresponding disulfides using hydrogen peroxide as green oxidant at room temperature. The
protocol features an easy work-up, simplicity and the utilizing mild reaction conditions, as well as high selectivity
toward disulfides, are highly advantageous compared to alternative reported methodologies. The supported iron
oxide nanoparticles could be easily recovered and reused several times without any loss of activity. ICP-MS results
prove that there is no metal leaching observed, and demonstrating the stability of the catalyst under the reaction
conditions.
Received 8 March 2013
Received in revised form 10 May 2013
Accepted 15 May 2013
Available online 28 May 2013
Keywords:
Iron oxide nanoparticle
Oxidation
© 2013 Elsevier B.V. All rights reserved.
Disulfide
Thiol
1. Introduction
Disulfides are valuable intermediates for production of sulfenyls [18]
and sulfinyls [19,20] in synthetic chemistry. They also have industrial
Application of transition metal nanoparticles (NPs) to catalyze or-
ganic reactions constitutes one of the most powerful strategies in de-
velopment of readily available, cheaper and more efficient catalysts as
alternatives to traditionally employed metal catalysts [1–3]. Among
the various NPs in recent years, iron oxide NPs catalysts emerged as
green alternative catalysts, due to their low toxicity, abundance and
interesting activities which allow the utilization of mild reaction con-
ditions [4]. Iron oxide NPs catalysts have shown applications in di-
verse organic transformations such as oxidations [5,6], C-C and
C-heteroatom couplings [7], alkylations [8], and Fischer–Tropsch re-
action [9]. Their stabilization onto supports for the design of well dis-
persed, small size nanoparticles with enhanced catalytic applications
is highly desirable from both environmental and economic view-
points [10]. Another important aspect of supported iron oxide NPs is
the ease of its separation and recovery.
application as vulcanizing agents and elastomers [21,22]. Along this
line, various reagents and oxidants such as halogens and their deriv-
atives [23–26], transition metal salts [27–30] and peroxides [31,32]
have been introduced to be active in oxidative coupling of thiols to
the corresponding disulfides. Despite considerable progress in the
field of thiol oxidation, the selective disulfide synthesis has consid-
ered a major challenge due to over oxidation drawbacks, the need
for excess and/or expensive reagents, poor activity and selectivity, long
reaction time, hazardous oxidants or reagents, tedious work-up protocols,
and harsh reaction conditions.
Thus, from both economic and eco-friendly standpoint, development
of a simple environmentally benign oxidation catalysts and oxidants such
as H2O2 or O2, which promotes oxidation of thiols to corresponding
disulfides at room temperature without any contamination by over
oxidation, has long been a challenge in this transformation.
The selective oxidation of thiols to their corresponding disulfides
has gained significant importance in chemical industry and biological
processes [11–13]. Disulfide bonds play a special role in the structures
of many proteins by forming covalent links between parts of a polypep-
tide molecule or between two different polypeptide chains. In proteins,
disulfide bonds are the principal entities to stabilize secondary or tertia-
ry structure [14]. In disulfide-containing peptides such as oxytocin, va-
sopressin, and somatostatin, the disulfide has proportionally greater
importance in maintaining a biologically active conformation [15–17].
In continuation of our ongoing efforts to look for environmentally
friendly and reusable catalysts for developing of heterogeneously
catalyzed methodologies based on the use of supported iron oxide
nanoparticles [33,34], herein we describe a simple and efficient meth-
odology for chemoselective oxidation of thiols to disulfides at room
temperature conditions with H2O2 as a green oxidant.
2. Experimental section
2.1. General information
⁎
Corrresponding author. Tel.: +98 281 3336366; fax: +98 281 3344081.
Tel.: +98 21 6600 5718; fax: +98 21 6601 2983.
All reagents and solvents were purchased from common commer-
cial sources used without further purification. Melting points were
1
1566-7367/$ – see front matter © 2013 Elsevier B.V. All rights reserved.