Application of silica vanadic acid as a heterogeneous, selective and highly reusable catalyst for oxidation of sulfides at room temperature

Article abstract of DOI:10.1016/j.molcata.2012.12.015

Silica vanadic acid (vanadium has been supported on silica) is applied as an efficient, highly reusable and heterogeneous catalyst for the selective oxidation of sulfide to sulfoxide using hydrogen peroxide and in the acetonitrile as a solvent at room temperature. The catalyst can be easily recovered and reused for ten reaction cycles without considerable loss of activity. Also, some advantages of this method were applicable at large scales, high TON of catalyst, chemoselectivity, easy work-up and short reaction time.

Full text of DOI:10.1016/j.molcata.2012.12.015

Accepted Manuscript
Title: Application of Silica vanadic acid as a heterogeneous,
selective and highly reusable catalyst for oxidation of Sulfides
at room temperature
Authors: Mohammad Ali Zolfigol, Ardeshir Khazaei, Maliheh
Safaiee, Mohammad Mokhlesi, Rahele Rostamian, Mahsa
Bagheri, Morteza Shiri, Hendrik Gerhardus Kruger
PII:
DOI:
Reference:
S1381-1169(12)00421-9
doi:10.1016/j.molcata.2012.12.015
MOLCAA 8622
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
30-7-2011
13-12-2012
25-12-2012
Please cite this article as: M.A. Zolfigol, A. Khazaei, M. Safaiee, M. Mokhlesi,
R. Rostamian, M. Bagheri, M. Shiri, H.G. Kruger, Application of Silica vanadic
acid as a heterogeneous, selective and highly reusable catalyst for oxidation of
Sulfides at room temperature, Journal of Molecular Catalysis A: Chemical (2010),
doi:10.1016/j.molcata.2012.12.015
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Application of Silica vanadic acid as a heterogeneous, selective and highly
reusable catalyst for oxidation of Sulfides at room temperature
Mohammad Ali Zolfigola*, Ardeshir Khazaeia, Maliheh Safaieeb*, Mohammad Mokhlesic*,
Rahele Rostamiana and Mahsa Bagheria Morteza Shirid, Hendrik Gerhardus Krugere
a Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 6517838683, Hamedan, Iran
b College of Science, Islamic Azad University, Hamedan branch, Iran
c Fateh Sanat group Company, Nitelpars Co., Fateh Bldg., No32 , Aftab St., Khodami St., Vanak Sq., PC :
1994964743, Tehran, Iran.
d Department of Chemistry, College of Science, Alzahra University, Vanak, 1993893973, Tehran, Iran
e School of Chemistry, University of KwaZulu-Natal, Durban 4001, South Africa
Highlights
Application of supported transition metal oxides catalyst
Using catalyst in large scale
High reusable catalyst
Chemoselectivity and homoselectivity
High TON and TOF
Abstract
Silica vanadic acid (Vanadium has been supported on silica) is applied as an efficient, highly
reusable and heterogeneous catalyst for the selective oxidation of sulfide to sulfoxide using
hydrogen peroxide and in the acetonitrile as a solvent at room temperature. The catalyst can be
easily recovered and reused for ten reaction cycles without considerable loss of activity. Also,
1
Page 1 of 20

some advantages of this method were applicable at large scales, high TON of catalyst,
chemoselectivity, easy work-up and short reaction time.
Keywords: Silica vanadic acid, hydrogen peroxide, heterogeneous, large scales,
chemoselectivity, highly reusable catalyst.
1. Introduction
In recent years, considerable emphasis has been placed on improvement in the environmental
impact of industrial chemical processes. Thus, green chemistry has been defined as a set of
principles which reduce or eliminate the use or generation of hazardous substances and catalysts
throughout the entire life of chemical materials. The development of heterogeneous catalysts for
fine chemicals synthesis has become a major area of research. The inherent advantages of
heterogeneous catalyst system in liquid phase over their homogeneous counterparts lie mainly on
their easy separation and recycling ability as well as minimization of undesired toxic wastes.
These types of catalysts have used various support materials. One useful example of support
materials is Silica gel. This inorganic supporter has some advantageous properties such as
excellent stability, good accessibility and high surface area which will be beneficial to the
enhancement of loading amount and dispersion of catalytic active [1].
Oxidation over metal catalysts using eco-friendly oxidants such as hydrogen peroxide and
molecular oxygen are preferred for environmental and economical benefits. Along this line, the
design of soluble and heterogenized metal catalysts represents a rapidly growing field that has
been significantly applied in industry. Among the various transition metals, vanadium, an early
member of the3d transition metal series, exists on the surface of the earth more abundantly and
vanadium-based oxidants are effectively used for various oxidation reactions such as methanol
oxidation, carbon monoxide oxidation and partial oxidation of hydrocarbons. Also, supported
2
Page 2 of 20

vanadium oxides constitute a very important group of catalysts that are industrially used for
sulfuric acid manufacture, oxidation of o-xylene to phthalic anhydride, ammoxidation of alkyl
aromatics to aromatic nitriles, and the selective catalytic reduction (SCR) of NOx emissions with
NH3 to N2 [2-5].
Sulfides oxidation is one of the most important organic processes, since the corresponding
sulfoxides are valuable synthetic intermediates for the synthesis of chemically and
biologicallyimportant molecules [5-7]. Sulfoxides are also valuable in the C–C bond-formation
[8] and molecular rearrangements [9,10]. Additionally, some of the biologically active sulfoxides
play important roles as therapeutic agents such as anti-ulcer [11,12], antibacterial [13] etc.
Although sulfides can be easily oxidized by wide variety of oxidizing reagents [14-24],
unfortunately, some of these reagents are not satisfactory for the selective oxidation of sulfides to
the sulfoxides because of several reasons such as over oxidation to sulfones, low selectivity, low
yields of products, long reaction time, high temperature, large amount of reagent and expensive
reagents or catalysts.
Aqueous hydrogen peroxide is a well known oxidant because it is a cheap, mild and
environmentally acceptable reagent with a high content of active oxygen and produces water as a
by-product [25]. Moreover, oxidation over metal support catalysts using eco-friendly oxidants
such as hydrogen peroxide and molecular oxygen is preferred now for environmental and
economical benefits [26].
In continuation of our ongoing research program on the applications of heterogeneous and silica
supported transition metal oxides catalysts for oxidation of organic functional groups [27-32], we
found that Aboelfetoh and Pietschnig react vanadiumoxytrichloride (I) with silica gel to give
silica vanadic acid (SVA) (III) during an easy and clean reaction [33]. VOCl3 (I) is a powerful
3
Page 3 of 20

oxidizing agent [34-36] but many of the reported methods in which it has been used as catalyst
or reagent are associated with one or more of the following drawbacks: (i) toxicity of VOCl3 (ii),
production of harmful HCl, (iii) by-products formation, (iv) harsh reaction conditions, and (v) no
agreement with the green chemistry protocols. However, when vanadiumoxytrichloride is
supported on a silica gel (silica vanadic acid), it is easy to be applied as a catalyst or reagent in
reactions (Figure 1).
O
Cl
O V O
Cl
OH
O V O
OH
n-Hexane
air
V
SiO2
SiO2
OH
+
SiO2
r.t
Cl
Cl
Cl
(I)
Silica Vanadic Acid (III
)
(II)
Scheme 1. Synthesis of Silica Vanadic Acid (SVA)
Figure 1. Vanadiumoxytrichloride (I), (B) silica-supported
vanadiumoxy dichloride (deep red) (II), (C) Silica Vanadic
Acid (deep green) (III).
Thus, in our present work, we were interested in using SVA to promote oxidation of sulfides
with H2O2 (Scheme 2).
OH
SiO2
O
V
O
O
S
OH
S
R
R'
H2O2/CH3CN/ r.t
R
R'
(1)
(2)
R, R' = Aryl, Alkyl
Scheme 2. Oxidation of sulfides using SVA/H2O2 in CH3CN as solvent at room temperature
4
Page 4 of 20

2. Experimental
2.1. Materials
All the sulfide substrates and VOCl3 were obtained from Aldrich, merck, alfa-aser and used as
received without any further purification.
2.2. Synthesis of silica vanadic acid
In a 100 ml round-bottomed flask, n-hexane (25 mL) and silica gel (4.0 g) were stirred for 10
min and then vanadiumoxytrichloride (4.0 g) was dissolved in n-hexane (25 mL) and added drop
wise to silica gel suspension (15-20 min). After addition of VOCl3, the red-brown mixture was
stirred for 10 hours. Then, solvent was evaporated and the residue (the red-brown powder (II)
obtained after the grafting process) was filtered, washed with dry n-hexane several times to
remove unreacted VOCl3, dried under vacuum, and stirred in the air for 72 hours to promote the
hydrolysis of V–O–Cl bonds [33, 37]. At this time, the red-brown powder changed to dark green
powder (III) slowly (Scheme 1). Typical loading of Vanadium was determined using X-ray
fluorescence (XRF) and shows a loading 8 ± 0.1 mmol g-1.
2.3. Catalyst characterization
X-ray diffraction (XRD) patterns of all catalysts were performed on a APD 2000, Ital structure
with Cu Ka radiation (k = 0.1542 nm) operating at 50 kV and 20 mA in a 2h range of 10–70o
with step size 0.01o and time step 1.0 s to assess the crystallinity of the vanadium oxide loading.
The vanadium concentration of the prepared catalysts was determined by XRF ARL8410.
Fourier transform-infrared spectra of the samples were recorded on a Perkin–Elmer FT-IR
spectrometer 17259 using KBr disks. Thermogravimetric analyses using a Perkin–Elmer TGA
were performed on both support materials (II and III) and all prepared catalysts. To evaluate the
overall amount of surface hydroxyl groups available for anchoring reactions, the weight loss
5
Page 5 of 20

between 300 and 600 0C was determined. A heating rate of 10 0C/min under argon was applied to
purge off-gasses from the TGA electronics and sample region. Semi-quantitative EDX (Ro¨ntec,
Quantax/QX2) analysis was used for the characterization of element concentration and vanadium
distribution within prepared catalysts. The SEM analyses were done with a TESCAN/VEGA
with a maximum acceleration voltage of the primary electrons between 10 and 15 kV.
The IR Spectra of catalyst showed some peaks in region of 471, 800, 1097, 1632 and 3415 cm-1.
The band of the V–O–Si rocking vibrations appears about 471 cm−1 [38]. The band at 800 cm-1 is
assigned to symmetric vibrations (Si–O–Si) and the band at 1097 cm-1 is assigned to the
asymmetric vibrations of (Si–O–Si) of silica vanadic acid [39]. The silica impregnated catalyst
with high V loading exhibit a very weak band at 973 cm-1, which indicates an asymmetric
stretching mode of Si–O–V [33].
Figure 2. IR Spectra of catalyst
The morphology of the silica vanadic acid was observed using an SEM. Typical SEM images are
shown in (Figure3).
6
Page 6 of 20

Figure 3. SEM image of catalyst
The XRD patterns of catalysts show partially amorphous nature of silica Fig. 4a. In the EDS
spectrum of the as-synthesized sample, the peaks of Si and V are obviously observed, and no other
impurities occur (Fig. 4b).
Figure 4. (a). XRD of catalyst, (b). EDS spectra of silica vanadic acid
Thermal analysis of the samples gives information about the stability of the –VO(OH)2 groups. In the
TG/DTG curve of catalyst, the weight loss below 120°C (<15%) is due to the desorption of water.
Analysis of these diagrams strongly proposed that silica vanadic acid structure was stable and
0
no further weight loss occurs below 210 C. Decomposition of the vanadic acid groups takes
place below 400°C (Fig.5).
7
Page 7 of 20

Figure.5 TGA and and DTG of catalyst.
2.4. Oxidation of benzyl phenyl sulfide to benzyl phenyl sulfoxide
A mixture of benzyl phenyl sulfide (1 g, 5.0 mmol), silica vanadic acid (5mg, 0.039 mmol of
V) and H2O2 30% (6 mmol) in CH3CN (3 mL) was stirred for 10 min. After completion of
the reaction, solvent was evaporated and the product was extracted with ether (2×10 mL),
dried with anhydrous Na2SO4, filtered and evaporated to afford the crude sulfoxide product.
Finally, the product was purified by column chromatography using ethyl acetate/hexane
(1.5:8.5) as eluent to give benzyl phenyl sulfoxide as a white solid in 93% yield.
2.5. General procedure for the oxidation of sulfide to sulfoxide in large scale
A mixture of sulfide (50 mmol), silica vanadic acid (50mg, 0.39 mmol of V) in CH3CN (30
mL) was stirred at room temperature for 5 min. Then, the solution of H2O2 30% (60 mmol)
was added dropwise (15-20 min). After completion of reaction, solvent was evaporated and
the product was extracted with ether (3×20 mL) dried with anhydrous Na2SO4, filtered and
evaporated to afford the crude sulfoxide product. Finally, the product was purified by column
chromatography using ethyl acetate/hexane (1.5:8.5) as eluent to give benzyl phenyl
sulfoxide as a white solid in 86% yield.
8
Page 8 of 20

3.
Result and discussion
3.1. Catalytic activity
In the beginning, conversion of benzyl phenyl sulfide into its corresponding benzyl phenyl
sulfoxide has been considered as a model reaction. Different reaction parameters such as
amount of catalyst, nature of solvent and type of oxidant are studied.
First of all, the reaction of benzyl phenyl sulfide was tested using different amounts of silica
vanadic acid at room temperature (Table 1). As it can be seen in table 1, the best amount of
the catalyst was 0.005 gr.
Solvent has a significant effect on the reaction even though the exact role of the solvent is not
very clear. We carried out the reaction with the same concentration of the reactants in H2O,
MeOH, THF, CH3CN and CH2Cl2. Both the yields and the reaction times listed in Table 1,
suggest that acetonitrile appears to be the most suitable solvent for the oxidation reaction
(Table 1, entries 4, 7-10). However, it is known that acetonitrile also activates H2O2 by
forming an intermediate which is a good oxygen transfer agent [40].
Table 1. The reaction of benzyl phenyl sulfide with Hydrogen peroxide using different amounts of catalyst in
various solventa
Entry
mmol of
sulfide
Solvent
Amount of Catalyst Mol%
(g)
Time(h) Yield(%)b
1
2
5 mmol
5 mmol
5 mmol
5 mmol
5 mmol
5 mmol
5 mmol
5 mmol
5 mmol
5 mmol
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
THF
H2O
CH2Cl2
CH3OH
---
5
5
sluggish
55
0.16 Mol%(0.001)
0.48 Mol%(0.003)
0.8 Mol%(0.005)
1.6 Mol%(0.01)
8 Mol%(0.05)
0.8 Mol%(0.005)
0.8 Mol%(0.005)
0.8 Mol%(0.005)
0.8 Mol%(0.005)
1.5
10(min)
10(min)
10(min)
88
94
92
93
75
25
3
4
5
6
7
8
9
10
5
5
5
1
50
c
-
a Reaction Condition: sulfide (5 mmol), H2O2 (6 mmol), solvent, room temperature, stir. b Isolated
Yields, c Mixture of sulfoxide and sulfone.
9
Page 9 of 20

In order to understand the preferred catalyst to other vanadium (V) compounds, benzyl phenyl
sulfide was treated with ammonium vanadate 5% and 10% under optimum reaction conditions
instead of SVA as a catalyst (Table 2). We found that in these circumstances the mixture of
sulfone and sulfoxide produced and the reaction time is increased. Therefore, these modified
silica gel catalysts enhance not only the conversion of organic sulfides but also the selectivity
towards the formation of sulfoxide.
Table 2. Catalytic activity of different vanadiume (V) oxide on the reaction of benzyl phenyl sulfide and H2O2
(30%) in acetonitrile at room temperature.
Catalyst
Catalyst
amount
(Mol%)
0.8
Time
(min)
Yield (%)
93a
Entry
Silica Vanadic Acid
NH4VO3
10
90
75
1
2
3
b
5
10
-
b
NH4VO3
-
a Isolated Yields, b mixture of sulfoxide and sulfone
3.2. The effect of different oxidant
In the next experiment, we examined the effect of various oxidants in the efficiency of the
reaction, carried out in the presence of hydrogen peroxide, urea hydrogen peroxide (UHP),
sodium perborate and sodium per carbonate as oxidant. In the absence of oxidant, the oxidation
reaction was failed. As shown in figure 6, a maximum conversion take as place for H2O2
followed by sodium per carbonate (Na2CO3. 1.5H2O2) whereas sodium perborate (NaBO3.4H2O)
and urea hydrogen peroxide (UHP) are not found to be effective for the oxidation even after 18
hours (Fig. 6). The conversion percentage of sodium per carbonate is almost similar to that of
hydrogen peroxide but the reaction with sodium per carbonate was completed after 16 hours
while reaction time in hydrogen peroxide was 10 minutes. At a higher concentration of hydrogen
10
Page 10 of 20

peroxide (2.5 equiv.), the reaction took place at a shorter reaction time (5min) with over
oxidation and sulfone was formed.
Figure 6. Effect of the nature of the oxidant on benzyl
phenyl sulfide conversion to benzyl phenyl sulfoxide
(6 mmol oxidant. Other reaction conditions same as
that for table 1).
3.3. Generality, Chemoselectivity, Homoselectivity and catalyst reuse
To assess generality and efficacy of the method, different aromatic, linear and cyclic aliphatic
sulfides were reacted with hydrogen peroxide 30% in the presence of silica vanadic acid and
CH3CN as solvent under the optimized reaction conditions. The respective results are
summarized in Table 3. As it can be seen in Table 3, the protocol was general and efficient. All
reactions proceeded efficiently and the desired products were obtained in good to excellent
yields in relatively short reaction times. Also, to show the chemoselectivity of the described
system, three sulfides containing a hydroxy group were subjected to the sulfoxidation reaction,
but alcohol oxidation did not occur under the mentioned conditions, and primary hydroxyl group
remained intact in the course of the reaction (Table 3, 2f, 2g and 2h, Scheme 3).
11
Page 11 of 20

O
S
S
S
SVA, H2O2
CH3CN , rt
OH
OH
OH
O
+
91%
0%
O
SVA, H2O2
CH3CN , rt
S
S
S
O
+
OH
0%
90%
Scheme 3. Chemoselective sulfoxidation of 2-(phenylthio) ethanol and 2-(metylthio) ethanol.
It is of interest to note that the mentioned oxidizing system allowed the homoselective [41,42]
oxidation of bis-(methyl thio)-methane to their monosulfoxide derivatives (Scheme 4, Table 3,
2i).
O
S
O
S
O
S
SVA, H2O2
CH3CN , rt
S
S
S
+
0%
87%
Scheme 4. Homoselective oxidation of bis-(methyl thio)-methane to corresponding monosulfoxide derivative.
Table 3. Oxidation of sulfides 1 to the corresponding sulfoxides 2 using H2O2
(30%) and catalytic amounts of silica vanadic acid (III) in acetonitrile at room
temperaturea
12
Page 12 of 20

Time
(min)
Entry
Substrate (1)
Product (2)
Yield(%)b
O
S
S
a
b
c
10
13
5
93
91
94
O
S
S
O
S
S
Me
Me
O
S
S
d
e
40
20
88
89
O
S
S
O
S
S
OH
f
25
20
91c
90c
OH
O
S
S
g
OH
OH
a
S
S
OH
OH
h
i
25
30
93c
87c
Cl
Cl
O
S
S
S
S
O
O
j
15
25
92
94
S
S
O
O
S
S
OMe
OMe
k
O
O
Reaction Condition: sulfide (5 mmol), H2O2 (6 mmol), solvent, room temperature,
stir. b Isolated Yield. c Reaction Condition: sulfide (1 mmol) , H2O2 (1.2 mmol),
solvent (3 mL), room temperature, stir.
In order to recover the catalyst, CH3CN was evaporated under the reduced pressure and
removing the product by extracting with ether from the reaction mixture and charging the
reaction vessel with fresh substrate and H2O2 30% and then repeating the experiment. The
recovered catalyst was reused ten times in the oxidation of benzyl phenyl sulfide (1a) with H2O2,
and smooth loss of catalytic activity was observed from the 7th time of reuse (Fig. 7).
13
Page 13 of 20

Figure 7. The catalytic activity of SVA in ten cycles
for the reaction of benzyl phenyl sulfide (1a) with
Hydrogen peroxide.
3.4. Comparison with other reported methods
To assess the capability and efficiency of our catalyst with respect to the reported catalysts for
oxidation of sulfide, the results of the application of these catalysts for the preparation of some
sulfoxides are tabulated in Table 4. As shown in Table 4, higher yield and shorter reaction time
were obtained using silica vanadic acid. Furthermore, we calculated turn over numbers (TON)
and turn over frequencies (TOF) states on the effectiveness of these catalysts for the oxidation of
sulfide to sulfoxide (Table 4). The TON and TOF values showed that SVA is more effective than
another reported catalyst.
Table 4. Comparison of the oxidation of benzyl phenyl sulfide (1a) with H2O2 (30%) using the reported catalysts
versus Silica Vandic Acid.
14
Page 14 of 20

Entry
Catalyst
Mol%
H2O2
Time
Yield (%)a
TONb TOFc (min-1)
(mmol) ( min )
1
2
3
4
5
6
7
8
9
Silica Vandic Acid
Silica-Based Tungstate
ZrCl4
0.8
1
1.2
3
10
180
2
93 [This Work] 116.25
11.625
0.46
0.12
0.39
0.003
0.043
4.42
---
83[45]
96[44]
95[48]
91[43]
52[45]
84 [47]
94[50]
80 [49]
83
0.24
47.5
0.91
52
--f
2
14
5
Ta(Cl)5
120
300
1200
19
HCl
10
1
8
Cu(II)
10
8
Mn(III)
1
84
Ce(OTf)4·xH2O
TiO2
5e
2.5e
3d
2.5
360
160
---
---
---
a Isolated Yield, b Turn over number, c Turn over frequency, d H2O2 (50%), e mg, f Condition: ZrCl4 (4mmol),
sulfide 1 mmol.
3.5. Oxidation of sulfide to sulfoxide in large scale
In another study, to recognize the applicability of our method at large scales, we examined some
reactions in scales of 10 and 50 mmol. The results are summarized in Table 5. As shown in Table
5, the reactions were successfully performed at large scales without significant loss of the yields.
Table 5. The large scale oxidation of sulfides using SVA/H2O2/CH3CN at room
temperature
Amount of substrate/mmol
product
2b
Time (min)
Yield (%)a
5
10
50
5
10
50
5
10
50
5
13
20
25
5
10
15
40
50
85
20
91
90
86
94
92
90
88
85
81
89
2b
2b
2c
2c
2c
2d
2d
2d
2e
15
Page 15 of 20

10
50
2e
2e
25
35
88
85
a Isolated Yield
3.6. Reaction mechanism
Based on a variety of studies, a mechanism as depicted in Fig. 8 has been proposed [51]. The
catalytic cycle involves, as fundamental step, the formation in the active site of a
peroxovanadium species (IV) [49, 50, 51], which is a much stronger oxidant than H2O2 [52].
The peroxoderivative oxidizes the sulfides to sulfoxide [53, 54, 55].
H2O2
H2O
OH
V
OH
O
O
SiO2
(IV)
SiO2 V O
OH
OH
(III)
O
S
S
R
R'
R
R'
Figure 8. Proposed reaction mechanism
In conclusion, we have shown that the silica-based vanadium catalyst III can be easily prepared
from commercially available materials. This catalyst efficiently affects the selective oxidation of
a variety of sulfides to sulfoxides in room temperature with excellent yields without employing
any co-reductant or other additives. The catalyst (III) can be considered as a heterogeneous
version of VOCl3. Therefore it is possible to easily recover and reuse for several reaction cycles
without considerable loss of activity. The described method has many advantages, such as,
chemoselectivity, easy work-up, short reaction time, high TON of catalyst and applicability of
this method at large scales.
Acknowledgements
The authors gratefully acknowledge partial support of this work by the Research Affairs Office
of Bu-Ali Sina University (Grant number 32-1716 entitled development of chemical methods,
16
Page 16 of 20

reagents and molecules), and Center of Excellence in Development of Chemical Method
(CEDCM), Hamedan, I.R. Iran.
References
[1] M.R. Maurya, A. Kumar, J.C. Pessoa, Coord. Chem. Rev. doi:10.1016/j.ccr.2011.01.050
In press.
[2] I.E. Wachs, Catalysis 13 (1997) 37.
[3] G. Deo, I.E.Wachs, J. Haber, Crit. Rev. Surf. Chem. 4 (1994) 141.
[4] M. Banares, X.T. Gao, J.L.G. Fierro, I.E. Wachs, Stud. Surf. Sci. Catal. 110 (1997) 295.
[5] A. Butler, Coord. Chem. Rev. 187(1999)17.
[6] M.J.Clague, N.N. Keder, A. Butler, Inorg. Chem. 32(1993)4754.
[7] V. Conte, F. DiFuria, G. Licini, Appl. Catal. A 157(1997)335.
[8] A.G.J. Ligtenbarg, R. Hage, B.L. Feringa, Coord. Chem. Rev. 237(2003)89-101.
[9] C. Bolm, Coord. Chem. Rev. 237(2003)245.
[10] K. Hiroi, Y. Suzuki, I. Abe, R. Kawagishi, Tetrahedron 56 (2000) 4701.
[11] M.C. Carreno, Chem. Rev. 95 (1995) 1717.
[12] I. Fernandez, N. Khiar, Chem. Rev. 103 (2003) 3651.
[13] T. Satoh, Y. Kuramochi, Y. Inoue, Tetrahedron Lett. 40 (1999) 8815.
[14] H. Kosugi, Y. Watanabe, H. Uda, Chem. Lett. (1989) 1865.
[15] V.C. Christov, I.K. Ivanov, Synth. Commun. 34 (2004) 3963.
[16] S. Okabe, K. Shimosako, J. Physiol. Pharmacol. 52 (2001) 639.
[17] C.M. Spencer, D. Faulds, Drugs 60 (2000) 321.
[18] E.N. Prilezhaeva, Russ. Chem. Rev. 70 (2001) 897.
[19] A.M. Al-Ajlouni, T.M. Daiafla, M. El-Khateeb, J. Mol. Catal. A-Chem. 275 (2007) 139.
[20] H. Egami, T. Katsuki, J. Am. Chem. Soc. 129 (2007) 8940.
17
Page 17 of 20

[21] F. Shirini, M.A. Zolfigol, A.-R.Abri, Chin. Chem. Lett. 19 (2008) 51.
[22] A. Shaabani, A.H. Rezayan, Catal. Commun. 8 (2007) 1112.
[23] M.M. Khodaei, K. Bahrami, M. Khedri, Can. J. Chem. 85 (2007) 7.
[24] D. Habibi, M.A. Zolfigol, M. Safaiee, A. Shamsian, A. Ghorbani-Choghamarani, Catal.
Commun. 10 (2009) 1257–1260.
[25] A. Dewan, T, Sarma, U. Bora, D.K. Kakati, Tetrahedron Lett. 52 (2011) 2563–2565
[26] U.R. Pillai, E. Sahle-Demessie App. Catal. A: Gen. 276 (2004) 139–144[27] M. Mokhlesi,
Synlett, Spothlight 318, (2010) 1574-1575.
[28] A. Ghorbani-Choghamarani, M.A. Zolfigol, M. Hajjami, S. Mallakpour, J. Iran. Chem. Soc.
7 (2010) 834-839.
[29] A. Ghorbani-Choghamarani, M.A. Zolfigol, M. Hajjami, S. Rastgoo, S. Mallakpour, Lett.
Org. Chem. 7 (2010) 249-254.
[30] A. Ghorbani-Choghamarani, M.A. Zolfigol, T. Rastegar, Chin. J. Catal. 30 (2009) 273-275.
[31] P. Salehi, M.A. Zolfigol, F. Shirini, M. Baghbanzadeh, Cur. Org. Chem. 10 (2006) 2171-
2189.
[32] M.A. Zolfigol, P. Salehi, A. Ghorbani-Choghamarani, M, Safaiee, M. Shahamirian, Synth.
Commun. 37 (2007) 1817–1823.
[33] E.F. Aboelfetoh, R. Pietschnig, Catal. Lett. 127 (2009) 83–94.
[34] Filipan-Litvic´, M.; Litvic´, M.; Vinkovic, V. Tetrahedron 64 (2008) 10912-10918.
[35] Carrick, W. L.; Karapinka, L.; Kwiatkowki, G. T. J. Org. Chem. 8 (1969) 2388-2390.
[36] Manning, T. D.; Parkin, I. P. Polyhedron 23 (2004) 3087-3095.
[37] I. Muylaert, M. Borgers, E. Bruneel, J. Schaubroeck, F. Verpoort, P. Van Der Voort, Chem.
Commun. (2008) 4475–4477.
18
Page 18 of 20

[38] Handke, M.; Mozgawa, W. J. Mol. Struct. 348 (1995) 341–344.
[39] George, J.; Shylesh, S.; Singh, A. P. App. Catal. A: Gen. 290 (2005) 148–158.
[40] U.R. Pillai, E. Sahle-Demessie, R.S. Varma, Tetrahedron Lett. 43 (2002) 2909.
[41] M.A. Zolfigol, K. Amani, M. Hajjami, A. Ghorbani-Choghamarani, R. Ayazi-Nasrabadi, S.
Jafari, Catal. Commun. 9 (2008) 1739.
[42] M.A. Zolfigol, K. Amani, A. Ghorbani-Choghamarani, M. Hajjami, Monatsh. Chem.140
(2009) 65.
[43] H. Firouzabadi, N. Iranpoor, A. Jafari, A. Adv. Synth. Catal. 348 (2006) 434-438
[44] K. Bahrami, Tetrahedron Lett. 47 (2006) 2009-2012
[45] B. Karimi, M. Ghoreishi-Nezhad, J.H. Clark, Org. Lett. 7 (2005) 625-628
[46] S. Velusamy, A.V. Kumar, R. Saini, T. Punniyamurthy, Tetrahedron Lett. 46 (2005) 3819–
3822.
[47] F. Hosseinpoor, H. Golchoubian, Tetrahedron Lett. 47 (2006) 5195-5197.
[48] M. Kirihara, J. Yamamot, T. Noguchi, Y. Hirai, Tetrahedron Lett. 50 (2009) 1180–1183.
[49] M. Rahimizadeh, G. Rajabzadeh, S-M. Khatami, H. Eshghi, A. Shiri, J. Mol. Catal. A,
Chem. 323 (2010) 59–64.
[50] B.R. Raju, S. Sarkar, U.Ch. Reddy, A.K. Saikia, J. Mol. Catal. A, Chem. 308 (2009) 169-
173.
[51] A.G.J. Ligtenbarg, R. Hage, B.L. Feringa, Coord. Chem. Rev. 237 (2003) 89-101.
[52] V. Conte, A. Coletti, B. Floris, G. Licini, C. OZonta, Coord. Chem. Rev. (2011)
[53] O. Bortolini, V. Conte, J. Inorg. Biochem. 99 (2005) 1549–1557
[54] V. Conte, B. Floris, Inorg. Chim. Acta, 363 (2010) 1935–1946
[55]A. Kozlov, A. Kozlova, K. Asakura, Y. Iwasawa, J. Mol. Catal. A, Chem. 137 (1999) 223.
19
Page 19 of 20

Graphical Abstract
Application of Silica vanadic acid as a heterogeneous, selective and highly
reusable catalyst for oxidation of Sulfides at room temperature
Mohammad Ali Zolfigol, Ardeshir Khazaei, Maliheh Safaiee, Mohammad Mokhlesi, Rahele
Rostamian and Mahsa Bagheri
H2O2
H2O
OH
V
OH
O
O
SiO2
(IV)
SiO2 V O
OH
OH
(III)
O
S
S
R
R'
R
R'
20
Page 20 of 20