VCl3-catalyzed selective oxidation of sulfides to sulfoxides using H2O2 as oxidant

Article abstract of DOI:10.1080/00397910600947882

VCl₃ is an effective catalyst for the catalytic oxidation of sulfides to afford sulfoxides in good yields using hydrogen peroxide as an oxidant. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600947882

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VCl3‐Catalyzed Selective Oxidation of Sulfides
to Sulfoxides Using H2O2 as Oxidant
R. Trivedi a & P. Lalitha a
a Inorganic and Physical Chemistry Division , Indian Institute of Chemical
Technology , Hyderabad, India
Published online: 01 Dec 2006.
To cite this article: R. Trivedi & P. Lalitha (2006) VCl3‐Catalyzed Selective Oxidation of Sulfides to Sulfoxides
Using H2O2 as Oxidant, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 36:24, 3777-3782, DOI: 10.1080/00397910600947882
To link to this article: http://dx.doi.org/10.1080/00397910600947882
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Synthetic Communicationsw, 36: 3777–3782, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600947882
VCl3-Catalyzed Selective Oxidation
of Sulfides to Sulfoxides Using H2O2
as Oxidant
R. Trivedi and P. Lalitha
Inorganic and Physical Chemistry Division, Indian Institute
of Chemical Technology, Hyderabad, India
Abstract: VCl3 is an effective catalyst for the catalytic oxidation of sulfides to afford
sulfoxides in good yields using hydrogen peroxide as an oxidant.
Keywords: Hydrogen peroxide, sulfides, sulfoxides, VCl3
INTRODUCTION
A number of synthetic procedures are available for the oxidation of sulfides to
chiral/achiral sulfoxides or sulfones.[1] The standard practice for carrying out
such reactions involves oxidation of sulfides with various oxidizing reagents
such as nitric acid,[2] KMnO4,[3] m-chloroperbenzoic acid,[4] sodium
periodate,[5] bromine,[6] nitrogentetraoxide,[7] oxaziridine,[8] benzeneseleninic
peracid,[9] tert-butyl hydroperoxide,[10] sulfinyl peroxy compounds,[11] and
4-methylmorpholine N-oxide with osmium tetraoxide[12]. Most of these
reagents perform unsatisfactorily for medium- to large-scale synthesis
because of low effective oxygen content, leading to the formation of environ-
mentally unfavorable by-products and high cost. Apart from these reagents,
singlet oxygen or molecular oxygen combined with 2-methylpropanal and
Co(II) complexes[13,14] have also been used. Aqueous hydrogen peroxide
(30%) is an ideal oxidant in view of its high effective oxygen content (as
high as 47%), cleanliness (it produces only water as a by-product), safety in
Received in India May 5, 2006
Address correspondence to R. Trivedi, Inorganic and Physical Chemistry Division,
Indian Institute of Chemical Technology, Hyderabad 500007, India. E-mail: trivedi@
iict.res.in or trivedi@iictnet.org
3777

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R. Trivedi and P. Lalitha
storage and operation, and low cost of production and transportation.[15]
Recently, Karimi et al. have reported highly efficient synthesis of sulfoxide
with a recoverable silica-based tungstate interphase catalyst using hydrogen
peroxide.[16] Selective synthesis of sulfoxides remains a challenging task
and constitutes an active area of research on its own.
Vanadium trichloride and its complexes are gaining importance as mild
Lewis acid catalysts to perform a plethora of organic transformations such
as ring opening of epoxides, Biginelli condensation and deprotection of
acetonide,[17] synthesis of bis-indoles and a-amino phosphonates,[18] and
pinacol coupling.[19]
RESULTS AND DISCUSSION
In this communication, we disclose a simple, efficient sulfoxidation using 30%
hydrogen peroxide as an oxidizing agent with a catalytic amount of VCl3
(Scheme 1).
Several solvent systems were studied for the preparation of sulfoxides. The
solvent has a pronounced effect on these reactions, in which water and dichlor-
omethane afforded lower yields, whereas acetone and acetonitrile gave moderate
yields, and methanol and tetrahydrofuran (THF) proved to be good solvents in
selective oxidation of sulfides. The reaction was found to be complete within
few minutes in THF at room temperature.
The controlled reaction conducted under identical conditions devoid of
catalyst showed no oxidized product formation within the stipulated
reaction time. Various structurally diverse sulfides underwent selective
oxidation to give the corresponding sulfoxides with good to excellent yields
with trace quantities of sulfones as confirmed by gas chromatography (GC)
1
and H NMR of the crude reaction mixture.
EXPERIMENTAL SECTION
Typical Procedure for the Oxidation of Sulfides
To the stirred solution of the sulfide (124 mg, 1 mmol) and VCl3 catalyst (6 mg,
5 mol%) in THF (5 ml), an aqueous solution of 30% (w/w) hydrogen
Scheme 1. VCl3-catalyzed synthesis of sulfoxide.

Oxidation of Sulfides to Sulfoxides
3779
Table 1. Vanadium(III)-catalyzed selective oxidation of sulfides to sulfoxides with
a
30% H2O2
Time Yieldb
Entry
1
Substrate
Sulfoxide
(min)
(%)
5
98
2
3
4
5
5
5
95
93
96
94
8
10
6
7
10
10
92
95
(continued)

3780
R. Trivedi and P. Lalitha
Table 1. Continued
Time Yieldb
Entry
8
Substrate
Sulfoxide
(min)
(%)
15
90
9
12
93
10
11
15
15
90
90
12
35
83
aReaction conditions: sulfide (1 mmol), H2O2 (1 mmol), VCl3 (5 mol%), and THF
(4 mL).
bIsolated yields.
peroxide (0.1 ml, 1 mmol) was added dropwise at room temperature. After
completion of the reaction (as monitored by thin-layer chromatography,
TLC), the reaction mixture was extracted with ethyl acetate (2 Â 10 ml).
The organic phase was separated, dried over anhydrous sodium sulfate, and
concentrated to afford the sulfoxide after silica-gel chromatography. All the
products were characterized by 1H NMR, mass, IR spectroscopy, and
elemental analysis.
ACKNOWLEDGMENTS
We thank CSIR for providing the financial support through Task Force Project
CMM-0006. P. L. thanks IICT for financial support.

Oxidation of Sulfides to Sulfoxides
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