Selectivity adjustment of SBA-15 based tungstate catalyst in oxidation of sulfides by incorporating a hydrophobic organic group inside the mesochannels

Article abstract of DOI:10.1021/cs4003029

A novel heterogeneous catalyst system comprising tungstate ions embedded into the hydrophobic mesochannels of SBA-15 was found to exhibit significant selectivity enhancement in oxidation of sulfides in water or water/CH ₃CN using 30% H₂O₂. Our studies demonstrated that the presence of an n-octyl group in the interior of nanospaces of our catalyst system provides a hydrophobic/hydrophilic region in the mesochannels of the catalyst where the active tungstate species are located and in turn results in at least three distinct important features. First of all, the catalyst comprising the n-octyl group shows much better water tolerance than the catalysts not having hydrophobic organic moieties. Moreover, the nonproductive decomposition of H₂O₂ was significantly inhibited in the present catalyst system. The present catalyst system also offers an unprecedented selectivity changeover depending on the hydrophobic nature of the initial sulfides and/or the utilized solvent mixture. While high yields and excellent selectivities toward the corresponding sulfoxide were obtained in the oxidation of less hydrophobic sulfides in H₂O as a reaction solvent, the selectivity pattern was shifted toward sulfones in the case of using more hydrophobic sulfides as substrates. On the other hand, in CH₃CN/ H₂O (1:1) as the reaction solvent, almost all of the studied sulfides were selectively oxidized to the corresponding sulfoxide in high yields. On the basis of several compelling observations, we have proposed a synergistic model to explain the origin of the observed selectivities. The catalyst was respectively recovered and reused in five and seven successive reaction runs in water and water/CH₃CN, respectively, with only a slight decrease of reactivity.

Full text of DOI:10.1021/cs4003029

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Article
Selectivity Adjustment of SBA-15 Based Tungstate
Catalyst in Oxidation of Sulfides by Incorporating a
Hydrophobic Organic Group inside the Mesochannels
Babak Karimi, and Mojtaba Khorasani
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/cs4003029 • Publication Date (Web): 11 Jun 2013
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ACS Catalysis
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Selectivity Adjustment of SBA-15 Based Tungstate
Catalyst in Oxidation of Sulfides by Incorporating a
Hydrophobic Organic Group inside the Mesochannels
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BabakKarimi* and Mojtaba Khorasani
Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), PO-Box 45195-
1
159, Gava-zang, Zanjan 45137-6731, Iran
Fax: (+98-241-4214949)
Keywords: Supported Catalyst, SBA-15, Mesoporous Materials, Sulfoxides, Hydrogen Peroxideand
Tungstate.
ABSTRACT: A novel heterogeneous catalyst system comprising tungstate ions embedded into the
hydrophobic mesochannels of SBA-15 was found to exhibit significant selectivity enhancement in
oxidation of sulfides in water or water/CH CN using 30% H O . Our studies demonstrated that the
3
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2
presence of n-octyl group in the interior of nanospaces of our catalyst system provides a
hydrophobic/hydrophilic region in the mesochannels of the catalyst where the active tungstate species
are located and in turn results in at least three distinct important features. First of all, the catalyst
comprising n-octyl group shows much better water tolerance than the catalysts not having hydrophobic
organic moieties. Moreover, the non-productive decomposition of H O was significantly inhibited in
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2
the present catalyst system. The present catalyst system also offers an unprecedented selectivity
changeover depending to the hydrophobic nature of the initial sulfides and/or the utilized solvent
mixture. While high yields and excellent selectivities toward the corresponding sulfoxide were obtained
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in the oxidation of less hydrophobic sulfides in H O as reaction solvent, the selectivity pattern was
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shifted toward sulfones in the case of using more hydrophobic sulfides as substrates. On the other hand,
in CH CN/H O (1:1) as reaction solvent almost all of the studied sulfides were selectively oxidized to
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the corresponding sulfoxide in high yields. Based on several compelling observation we have proposed
a synergistic model to explain the origin of the observed selectivities. The catalyst was respectively
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recovered and reused in 5 and 7 successive reaction runs in water and water/CH CN, respectively, with
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only slight decrease of reactivity.
INTRODUCTION
1
Since the discovery of ordered mesoporous materials, a variety of inorganic-organic hybrid
mesoporous materials with high specific surface area, has been extensively used as adsorbent, catalyst,
2
and support in the chemical, biochemical and petrochemical applications. The distinct order of the
channels ranging from 2-50 nm as well as the ease with which pore size, pore structure, physical
properties, and chemical functionalities of these materials can be uniformly tailored, make them
promising platform in designing novel sophisticated materials possessing desired properties in a typical
application. In the catalyst design context, better understanding of the aforementioned characteristics
and their relationship to the reaction profile may effectively result in the possibility to enhance (or
adjust) the product selectivity whilst keeping high catalytic activity.
In particular, for the reactions in which a desired product could subject to further reaction on the catalyst
surface, its longer retention inside the nanospaces of such catalysts may drastically alter product
selectivity. On the other hand, considering the hydrophilic nature of mesoporous silica framework, for
the reactions which contain both aqueous phase and hydrophobic starting materials the major problem is
the mass transfer phenomena since the activity of these catalysts can often decline by physical
adsorption of water. Therefore, the hydrophobic/hydrophilic balance of the solid catalysts could
significantly influence on their catalytic performance, durability, and product selectivity.There are
several reports pointing to the design and applications of hydrophobic mesoporous silica in different
3
reactions such as esterification and biodiesel production, oxidation of alkyl benzenes, Pechmann
4
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ACS Catalysis
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coumarine synthesis and Strecker reactions and so on. It is also worthy of note that hydrophobic
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titanosilica based on MCM-41 has been also used for the efficient epoxidation of alkenes. It was well-
documented that the hydrophobization of nanospaces of the mesoporous support could markedly
influence the stability and/or the performance of a certain catalyst system especially in the reactions in
which water participates as one of the reaction partners.
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In this work, we try to address this issue by designing a novel catalyst system consisting tungstate ion
immobilized in the interior of hydrophobic nanospace of SBA-15 (Scheme 1) for selective oxidation of
sulfides using 30% H O to their corresponding sulfoxide or sulfones by choosing appropriate reaction
2
2
solvent.
Scheme 1. A schematic illustration of catalyst 5
The selective oxidation of sulfides into the correspondingsulfoxides is one of the most important
8
processes within both laboratory and industrial setting, since they are versatile intermediates and
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products in the synthesis of pharmaceuticals, agrochemicals and other fine chemicals. However,
frequently such oxidation reactions have traditionally been relied upon environmentally damaging
1
0
oxidant, many of which are extremely hazardous to use or toxic. Moreover, sulfoxides can often
undergo over-oxidation to their corresponding sulfones and therefore, it is very important that the
catalyst has a high selectivity toward sulfoxide and/or sulfone. In view of higher polarity of sulfoxides
in comparison with the pristine sulfides, we reasoned that designing a catalyst system having suitable
surface hydrophobicity might indeed provide a mean to expel the sulfoxide molecules as soon as they
formed from the catalyst surface, thus suppressing their further oxidation to the corresponding sulfones.
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Therefore we have chosen the oxidation of sulfide as a probe to exemplify whether it would be possible
to control the selectivity of this reaction by employing our novel hydrophobic SBA-15 immobilized
tungstate catalyst.
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RESULTS AND DISCUSSION
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The route for the preparation of the catalyst is schematically illustrated in Scheme 2. The pristine SBA-
15 was initially prepared by hydrolysis and condensation of (EtO) Si in the present of Pluronic P123
4
1d
under acidic condition according to the reported procedure with slight modification. The resulting
SBA-15 was then successively functionalized with terimethoxysilyl derivatives of 3-aminopropyl (AP)
and n-octyl (C ) moiety through two step silylation to yield the corresponding hydrophobic aminopropyl
8
=
SBA-15 denoted as C -AP@SBA-15 (3). The final catalyst which is denoted as C -AP-WO @SBA-15
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8
4
(5) was obtained by neutralization of amino groups in 3 with fresh CF SO H followed by ion-exchange
3
3
1
by tungstate ions according to our previously developed protocol. The process for preparing the
1
catalyst and its intermediates was first monitored by N adsorption-desorption analysis and the structural
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parameters for these materials are presented in Table 1. N sorption diagrams for all materials exhibited
2
type IV isotherms with relatively sharp hysteresis loop, which are characteristics of mesoporous
structure with narrow pore size distributions (Figure 1). It can be also clearly seen that the nitrogen gas
=
adsorption uptake decreased as the AP, C , and WO functions were successively incorporated into the
8
4
nanospaces of the parent SBA-15. Notably, a clear capillary condensation step was even observed for 5,
which provided clear evidence for the preservation of open-up mesopore structure, implying that the
channels and thus immobilized tungstate species are still accessible. According to BJH and BET plots,
specific surface area, pore size distributions and total pore volume of the materials were all decreased
after the post-grafting and tungstate ion immobilization stage (Table 1). TEM images of 5 along 001 and
1
10 directions also provided further evidence that the 2D-hexagonal mesostructures of the material were
well retained during the catalyst preparation processes, a result consistent with N sorption diagrams
2
(Figure 2).
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ACS Catalysis
Both elemental and thermogravimetric analysis (TGA) (Figure S2) were concomitantly employed in
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each stage to estimate the loading of individual organic groups in 5 (Table1). Finally, the amounts of
=
loaded WO in the catalyst were found to be 0.22 mmol/g using polarography a value which further
4
confirmed using inductively coupled plasma atomic emission spectroscopy (ICP-AES) of its acid
washed solution.
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OH
O
OH
OH
OH
OH
OH
O Si
O
NH2
(MeO) Si
3
NH2
(MeO) Si
3
P123
HCl
Si (OEt)4
OH
OH
OH
Toluene
reflux
Toluene
reflux
15h
15h
(1)
(2)
O
O
O
-O SCF
3 3
NH +
3
WO4=
O
O
O
O
Si
NH2
O Si
O
NH3+
O
O
Si
CF SO H
3
Na WO , 2H O
2 4 2
3
2
2
CH Cl2
deionized water
O
O
Si
O
O
Si
O Si
O
O
(3)
(4)
(5)
Scheme2. A schematic presentation for the preparation of catalyst 5
Figure 1.Nitrogen adsorption-desorption isotherms (left) and pore size distributions (right) of the
synthesized materials.
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Figure2. TEM images of 5 along [001] (left) and [110] (right) directions
Table1.Textural properties and the loading of functionalized organic groups and tungstate in
the materials
a
b
c
d
d
SBET
2
m .g
Vt
3
m . g
DBJH
C
N
Loading of FunctionalGroups
-1
mmol. g
Material
-1
-1
nm
7.7
8.06
8.06
7.1
b)
%
%
1
2
3
5
a)
820
554
517
339
1.03
0.91
0.67
0.51
e
e
= f
6.5 1.2
0.86 (AP) , 0.35 (C ) , 0.22 (WO )
8 4
c)
SBET = specific surface area, V = total pore volume, DBJH = pore size distribution calculated
t
d)
from the adsorption branch using BJH methods, calculated from elemental (CHN) analysis,
e)
f)
Estimated by elemental (CHN) analysis and TGA, Determined using polarography and further
confirmed using ICP-AES of a sample of acid washed solution of 5
The catalytic activity of 5 was then examined in selective oxidation of sulfide using 30%
H O by emphasizing to preferably employ water as a green solvent. The reaction was first
2
2
tested in the oxidation of phenyl methyl sulfide at the ambient temperature (25-30 °C). In our
=
earlier study, we showed that silica-based tungstate catalyst (AP-WO @SiO 2-5 mol%) was
4
2
an effective catalyst for the selective oxidation of sulfides to the corresponding sulfoxides or
1
sulfones in CH OH/CH Cl solvent mixture. we found that this catalyst showed a
1
3
2
2
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completely disappointing catalytic activity and selectivity in aqueous media under otherwise
the some reaction condition (Table 2, entry 1). To our great delight, when as little as 1 mol%
of 5 and only 1 equivalent of 30% H O was employed, a significant yield improvement was
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observed affording phenyl methyl sulfoxide in 94% and remarkably excellent selectivity of
>97% (Table 2, entry 2).
Further studies also revealed that the use of a number of selected catalysts such as 4 alone and
=
in combination with un-supported Na WO (Table 2, entries 3 and 4), AP-WO @SBA-15
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4
(Table 2, entry 4) C -AP@SBA-15 (3) (Table 2, entry 6), AP@SBA-15 (2) (Table 2, entry 7)
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and SBA-15 (1) (Table 2, entry 8) under the same reaction conditions and with essentially the
=
same WO4 loading, if any, resulted in much inferior yields of phenyl methyl sulfoxides.
These data imply that the presence of both n-octyl groups and tungstate ion in immobilized
form is indispensable in attaining high activity in water by employing the present catalytic
system. In particular, the much prominent catalytic activity of 5 with regard to AP-
=
WO @SBA-15 may be attributed to appropriate hydrophilic-hydrophobic balance arising
4
from n-octyl unit inside the mesochannels of SBA-15, which would favor smooth diffusion of
both starting sulfide as well as H O into the nanospace of the catalyst and thus enhancing the
2
2
catalytic activity of 5. Encouraged by these promising results, we next proceeded to exemplify
further the scope and feature of our catalyst system by applying the given reaction condition
for the oxidation of various types of structurally divergent sulfides in water. The initial results
were rather interesting and revealed that the hydrophobic property of the sulfides has also
some marked effects on the reaction selectivity in water. Although high yield of 94% with
excellent selectivity (>97%) toward sulfoxide was obtained for the oxidation of thioanisole in
water (Table 3, entry1), the behavior of phenyl ethyl sulfide and phenyl n-butyl sulfide having
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a little bit more hydrophobic aliphatic part was completely different (Table 3, entries 2, 3). As
can be clearly seen by increasing the size of aliphatic part and thus to some extent the
hydrophobic property of the pristine sulfide, the selectivity pattern of the reaction was
gradually shifted toward the higher sulfone/sulfoxide ratio (Table 3, entries 2, 3). It is also
very important to note that in these cases both sulfoxide and sulfone were concomitantly
generated from the beginning of the reaction.
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Table2. The Oxidation of Phenyl Methyl Sulfide in the Presence of Various Possible Catalyst
Systems Including 1-5 using H O 30% in Water
2
2
a
A
a
B
b
Run
X
Solvent
TON
(
%)
-
(%)
=
AP-WO @SiO
1
2
3
4
5
6
7
8
9
H O
2
-
3
-
-
100
33
-
4
2
5
H O
2
94
4 +Na WO (1mol%)
2
H O
2
33
4
4
H O
2
17
-
=
AP-WO @SBA-15
H O
2
59
2
-
63
-
4
3
H O
2
5
2
H O
2
8
10
-
-
1
H O
2
-
-
Leaching test
H O
2
5
-
-
1
0
5
CH OH:CH Cl
3
51
-
51
2
2
a)
b)
GC
substrate/catalyst)×conversion (%).
yield
using
internal
standard
method.
TON
=
(
In light of the above finding and based on the observation that the catalyst system not
possessing n-octyl group exhibited much lower activity in water (Table 3, entry 4 and 5), it
appears that the presence of n-octyl group in the interior of nanospaces of 5 in the vicinity to
the catalytic center not only improved its water resistivity but it might also provide a means of
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longer retention of more hydrophobic organic substrates inside the mesochannels, thus
resulting in a gradual changeover of the product selectivity to sulfone. To our great delight in
two separated experiments when only two equivalents of 30% H O and 2 mol% of catalyst
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were employed for the oxidation of phenyl ethyl sulfide and phenyl butyl sulfide, a significant
selectivity refinement was observed in each case affording the corresponding sulfone within 4
h in 98% and 99% yields, respectively (Table 3, entries 6 and 7).
To assess whether the aforementioned proposed model could be generalized or not, the
oxidation of a range of sulfides having different hydrophobic nature depending on their size
and/or additional functional groups has also been investigated under essentially identical
reaction conditions. As indicated by the two additional examples summarized in entries 8 and
9 of Table 3, similar to phenyl methyl sulfide (Table 3, entry 1), highly selective sulfoxide
formation can be also achieved in water in the case of aryl sulfides such as 4-
thiomethylbenzyl alchohol and 2-(phenylthio)ethanol that bear an additional polar hydroxyl
unit (Table 3, entries 8, 9). Interestingly, under identical reaction conditions, highly selective
oxidation of diallyl sulfide also proceeded smoothly within 1h and diallyl sulfoxide was
remarkably the only product detected in water (Table 3, entry 10). Neither over-oxidation to
diallyl sulfone nor epoxidation of double bonds was observed in this case even after
prolonged reaction time. To this end, if the observed high selectivities could be indeed related
to the hydrophobic/hydrophilic balance between the reaction partners and the solvent, it would
be a very important advance and thus we sought to further verify this issue. In order to better
probe how much the hydrophobic nature of starting sulfide could participate the selectivity
pattern of the described reaction, the oxidation reaction of a series of selected organic sulfide
with more hydrophobic character have been screened under our optimal reaction conditions.
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5
5
5
6
As can be clearly seen, these substrates were also oxidized effectively and affording the
corresponding sulfone in quantitative conversion and with excellent selectivities (Table 3,
entries 11-14). However, a slight decrease in the conversion (but not selectivity) was observed
in the case of 4-nitrodiphenyl sulfide, which may be caused by strong electron-withdrawing of
substitute nitro group on the aromatic ring (Table 3, entry 14).
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
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7
8
9
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1
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3
4
5
6
7
8
9
0
These results again imply that the hydrophobic nature of the starting sulfides might be mainly
contributed to the observed selectivities toward the corresponding sulfones. This
unprecedented observation offers the possibility of achieving high degree of selectivity to
either sulfoxide or sulfone by adjusting the polarity of initial sulfide.
Since the nature of solvent system could also effectively influence the retention of the reaction
products inside the system pores of our catalyst, we speculate that increase in partitioning of
the sulfoxide product into the reaction solvent will possibly decrease the over-oxidation
arising from extended sulfoxide residence on the catalyst surface, thus improving the
sulfoxide selectivities particularly in the case of more hydrophobic starting sulfide. Therefore,
we next planned to determine whether the product selectivities of the present oxidation
protocol using 5 might be affected by reaction solvent or not. Among different solvents and
solvent combinations we tested, it was proved that the use of a mixture of water and CH CN
3
(1:1) as reaction solvent resulted in the optimum catalyst performances in comparison with
those obtained using pure water (Table S1). Interestingly, we also found that the presence of
water was indispensable to ensure satisfactory conversion using this catalytic system. Once
again, our studies showed that among the materials listed in Table 2, 5 exhibited the highest
catalytic performance in water/CH CN (1:1) as it did the same in pure water (Table S2, entry
3
2).
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9
Table 3. Highly Selective Oxidation of Sulfide to Sulfoxide or Sulfones with 30% H O2
2
Catalyzed by 5 in Water
10
11
12
13
14
15
16
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18
19
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23
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32
33
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39
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41
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43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
H O Time
2
A
(h) (%) (%)
B
b
2
Run
1
Sulfide
n
1
1
a
a
TON
101
84
(eq)
1
S
1
93
60
4
S
2
1
1.5
12
44
S
3
4
5
6
7
1
1
1
2
2
1
1
1
2
2
2.5
2.5
2.5
4
18
-
106
-
S
c
-
S
d
59
2
2
63
S
98
102
100
S
4
-
>99
S
OH
S
e
e
8
9
1
1
1
2
2
1
2
1
1
1
2
2
2
4
1
1
94
97
6
106
103
103
100
100
200
86
e
e
3
HO
S
S
10
11
12
13
1
97
-
3
4
>99
>99
>99
S
4
-
S
S
2
-
e
14
10
-
86
2
O N
a)
b)
GC yield using internal standard method, TON = (substrate/catalyst)
c)
conversion (%). The reaction was performed in the presence of AP-
×
=
WO @SiO , 1mol%, The reaction was performed in the presence of
d)
4
2
=
AP-WO @SBA-15, 1mol%, Isolated yield.
e)
4
With these initial results in hand, we then started to investigate whether this new solvent
system could alter or influence the product selectivity in the oxidation of a relatively wide
range of sulfides. The results are collected in Table 4. As can be seen, the catalyst worked
well for various aryl alkyl sulfides by employing only 1 equivalent 30% H O , giving good to
2
2
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2
2
2
2
2
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5
6
excellent isolated yields of the sulfoxide product with excellent selectivities (Table 4, entry 1-
5). These results are remarkable since the quest for selective as well as economic oxidation of
1
sulfides using stoichiometric amount of H O remains a great challenge. In a similar way,
2
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
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8
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3
4
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8
9
0
even diaryl sulfides were converted to the corresponding sulfoxide in moderate yield and still
excellent selectivity up to 90% (Table 4, entries 6-7).
Interestingly, sulfides with additional functional groups susceptible to over oxidation such as
phenols (Table 4, Entry 6), alkenes (Table 4, entries 2 and 8) and alcohols (Table 4, entries 3-
4) were found to selectively afford the corresponding sulfoxide without affecting the sensitive
functionalities. Remarkably, no epoxidation of double bond and only a slight over-oxidation
of sulfoxide to their sulfone were observed during the oxidation of allylic sulfide (Table 4,
entries 2 and 8). Dibutyl sulfide as a model for dialkyl sulfides also underwent rapid oxidation
to selectively furnish dibutyl sulfoxide in excellent yield (Table 4, entry 5). Once again no
detectable sulfone products were ever seen in this case, a feature not observed for the
=
4
11
oxidation of the same substrate using our previously developed catalyst AP-WO @SiO .
2
At this point, one question arose: how could the observed product selectivities is related to the
matching between the surface physicochemical properties of our supported catalyst and the
hydrophobic character of the starting sulfide? Considering the reaction pathway profile of
sulfide oxidation using H O , it is obviously clear that during the reaction the reactants
2
2
(sulfide and H O ) should first diffuse into the mesopores of the catalyst where they got
2 2
reacted at available tungstate active site to produce the corresponding sulfoxide.
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Table 4. Highly Selective Oxidation of Sulfide to Sulfoxide with 30% H O Catalyzed by 5 in
2
2
water:CH CN Solvent System
3
10
11
12
13
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15
16
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50
51
52
53
54
55
56
57
58
59
60
Time
h)
A
(%)
B
(%)
b
Run
Sulfide
n
a
a
TON
(
S
1
2
3
1
1
1
1.5
1.5
1.5
93
84
3
6
99
96
95
S
S
OH
c
c
85
85
5
S
c
c
4
5
1
1
1.5
1
5
95
HO
S
97
2
101
S
c
c
6
2
5
60
55
10
45
HO
OH
S
S
d
c
c
7
4
2
6.5
2
5
16
8
9
84
93
5
47.5
S
2
2
2
2
4
50.5
42.5
S
c
c
10
77
70
5
5
Br
S
c
c
c
c
11
12
3
2
26.6
22
2
O N
S
3
2
4
57
5
S
13
2.5
90
9
54.5
TON
a)
b)
GC yield using internal standard method.
c)
substrate/catalyst)×conversion (%). Isolated yield. 3 eq 30% H O2
2
=
d)
(
was used
.
This should be followed by the departure of generated sulfoxide from the system pore which
leaves the reaction site for the next available reactant in order to attain high selectivity toward
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sulfoxide formation; otherwise it would further expose to the active site and thus over
oxidized to the corresponding sulfone. Considering the surface hydrophobic character of the
catalyst and based on the assumption that sulfide oxidation reduces their hydrophobicity, it
would be generally expected that the favorable interaction of the hydrophilic corona of the
0
1
2
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9
0
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0
sulfoxide molecules with water (or water/CH CN mixture) provides a driving force for its
3
faster departure from the hydrophobic mesopores of the catalyst, thus improving the
selectivity of process toward sulfoxide formation. However, when the starting materials
become more hydrophobic, the resulting sulfoxide would settle inside the hydrophobic pore
channels to a much greater extent, which inevitably can undergo further oxidation using H O2
2
at the available active site, thus yielding the corresponding sulfone as the final product. This
model may also explain the consistent higher selectivity toward sulfone in the oxidation of
more hydrophobic sulfides in water in comparison with those obtained in water/CH CN
3
solvent mixture. In fact, the use of organic co-solvent increases the departure rate of the
sulfoxides (preliminary oxidation product) as soon as they produce from the catalyst system
pore, thereby minimizing its over-oxidation arising from extended residence in the close
proximity to the active site. In the same way, the reason that sulfoxide formations are more
prominent in water in case of substrates bearing an additional polar hydroxyl substituent
(Table 4, entries 8-9) is possibly due to the more favorable hydrophilic-hydrophilic interaction
of the sulfoxide products and water, which facilitates their departure from the hydrophobic
catalyst nanospaces, thus strongly preventing their over-oxidation to the corresponding
sulfones. This proposed cooperative mechanism also emphasizes the critical role of grafted n-
octyl groups inside the nanospaces of the catalyst in attaining enhanced activity with
concomitant improved selectivities, since much inferior activity and selectivity have been
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8
9
=
observed by employing AP-WO @SBA-15 bearing any capped n-octyl group (Table 4, entry
4
=
). Once again, the lower activity of AP-WO @SBA-15 compared 5 may also be explained
4
4
in terms of rapid surface saturation of the former by the excess of water, which prevents non-
polar starting sulfide from diffusing into the pores and blocks the active site. Our studies also
showed that the presence of n-octyl functional groups has at least two additional advantages
beside the above-mentioned synergistic benefits. Obviously, the catalyst system having
hydrophobic n-octyl functionalized group shows much better water tolerance than both our
10
11
12
13
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59
60
6
previous silica based tungstate catalyst and AP-WO @SBA-15 which rapidly lose their
=
4
catalytic activity under our optimal aqueous conditions. Moreover, another advantage is that
the non-productive decomposition of H O was inhibited to a great extent in our catalyst
2
2
system. This can be clearly understood from the data embodied in Table 3 and 4. Almost in all
cases, the reactions proceeded well with 1 or 2 equivalents of H O with respect to the starting
2
2
sulfides, giving excellent yields of the corresponding sulfoxides or sulfones, respectively,
under the described optimal reaction conditions.
In order to explore the extent of recyclability of our catalyst system, the catalyst was
recovered by microfiltration from the oxidation of thioanisol in both water and water/CH CN
3
and reused in subsequent runs (Figure 3). The catalyst was found to retain its activity for a
minimum of five reaction cycles in water and seven reaction runs in water/CH CN and
3
displayed almost high catalytic performance with over 94% conversion of the substrate and
excellent selectivities all over the studied recycling experiment. It was found that the reason
for inferior recovery behavior of the catalyst in water is most likely owed to the slight loss of
th
the catalyst body during the recycling stages. TEM image of the recycled catalyst after the 7
reaction cycle in water/CH CN revealed that two dimensioned ordered mesoporous structures
3
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of the catalyst were mostly retained both catalysis and recycling step (Figure S5). N sorption
2
=
diagrams of the recycled catalyst which is denoted as Re-C -AP-WO @SBA-15 showed also
8
4
a distinct type IV isotherms with sharp hysteresis loop, further highlighting the notion that
ordered mesoporous structure were well preserved during the catalytic reactions and recycling
0
1
2
3
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9
0
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1
2
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6
7
8
9
0
stages (Figure S4). ICP analysis of the reaction solution in the first run revealed that the
=
leaching of WO was less than 10 ppb.
4
Water: Acetonitrile
Water
1
00
90
80
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
1
2
3
4
5
6
7
Run
Figure 3. The reusability of catalyst (5) in oxidation of phenyl methyl sulfide to the corresponding
sulfoxide.
CONCLUSION
Although, many efforts have been devoted to the development of novel protocol for the
selective oxidation of sulfides to their corresponding sulfoxides and sulfones, to our
knowledge there has been no report regarding the influence of hydrophobic/hydrophilic
balance of reaction partners (starting sulfide, catalyst, and reaction solvent) on the selectivity
pattern of the reaction. We present, herein, the preparation and characterization of a novel
heterogeneous catalyst system comprising tungstate ions immobilized into the hydrophobic
nanospaces of SBA-15. The material was then successfully employed in the selective
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8
9
oxidation of sulfides in water or water/CH CN using 30% H O to their corresponding
3
2
2
sulfoxide or sulfone depending on either the nature of the substrate or solvent. Our studies
demonstrated that the presence of n-octyl group in the interior of mesochannels of our catalyst
system provides a hydrophobic/hydrophilic region where the active tungstate species are
located and in turn results in at least three distinct important features. First of all, the catalyst
comprising n-octyl group shows much better water tolerance than the catalysts not having
hydrophobic organic moieties. Moreover, the non-productive decomposition of H O was
10
11
12
13
14
15
16
17
18
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57
58
59
60
2
2
significantly inhibited in the present catalyst system. The present catalyst system also offers
an unprecedented selectivity changeover depending to the hydrophobic nature of the initial
sulfides and/or the utilized solvent mixture. While high yields and excellent selectivities
toward the corresponding sulfoxide were obtained in the oxidation of less hydrophobic
sulfides in H O as reaction solvent, the selectivity pattern was shifted toward sulfones in the
2
case of using more hydrophobic sulfides as substrates. On the other hand, in CH CN/H O
2
3
(1:1) as reaction solvent almost all of the studied sulfides were selectively oxidized to the
corresponding sulfoxide in high yields. Based on several compelling observation we have
proposed a synergistic model to explain the origin of the observed selectivities. The catalyst
was respectively recovered and reused in 5 and 7 successive reaction runs in water and
water/CH CN with only slight decrease of reactivity. It was found that the reason for inferior
3
recovery behavior of the catalyst in water is most likely owed to the slight loss of the catalyst
body during the recycling stages.
EXPERIMENTAL SECTION
1
d
Preparation of 1. Typically, 24 g Pluronic P123 (MW ≅ 5800, Aldrich) as structure
av
directing agent was dissolved in a solution containing 101 mL HCl (c) and 505 mL distilled
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1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
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4
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5
5
5
5
5
5
5
5
5
6
water. Then 54.2 ml TEOS was added and resulted mixture vigorously stirred at 35 °C for 18-
20h. Then, the resulting mixture was aged without stirring at 80 °C for 24h. The obtained
mesoporous silica with surfactant was filtered and washed with deionizer water, and dried at
room temperature. The surfactant was extracted from the SBA-15 channels by a Soxhlet
apparatus by using ethanol for 72h.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
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9
0
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2
3
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9
0
1
2
3
4
5
6
7
8
9
0
13
Preparation of 2. AP@SBA-15 (2) was synthesized according to literature procedure. In a
typical procedure, to a suspension of SBA-15 (2 g) in dry toluene, 3-aminoterimethoxy silan
(0.35 mL, 2 mmol) was added and the resulting mixture was refluxed for 15 h under inert
atmosphere. The resulted material was then filtered and unreacted 3-aminoterimethoxy silan
were washed using a Soxhlet apparatus overnight by employing ethanol. The material was
°
then dried at 80 C for 12h and used in the next stage.
1
Preparation of 3. n-octyl modified AP@SBA-15 (denote as C -AP@SBA-15, 3) was
3
8
prepared via a refluxing process, too. In a typical procedure, to a suspension of 2 (2 g) in dry
toluene, n-octylterimethoxysilan (3.3 mL, 10 mmol) was added and resulting mixture was
refluxed for 15 h under inert atmosphere. Then, the resulting material was filtered and
unreacted n-octylterimethoxysilan was washed with ethanol overnight using a Soxhlet
°
apparatus. The resulting material was then dried at 80 C for at least 12h and directly used in
the next step.
11
Preparation of 4. C -AP-OTf@SBA-15 (4) was synthesized according to our previously
8
reported protocol. Typically, 0.5 g of 3obtained from previous stage was dispersed in freshly
distilled CH Cl , and trifluoromethanesulfonic acid (CF SO H, 0.3 mL, 4 mmol) was added
2
2
3
3
and the resulting mixture stirred for 8 h. Finally, the material was filtered and was
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8
9
successively washed with ethanol (2×50 mL) and diethyl ether (2×25 mL). The resulted
material was dried at the room temperature in vacuum over P O .
2
5
1
1
=
Preparation of 5. C -AP-WO @SBA-15 (5) was prepared using a simple ion exchange
8
4
10
11
12
13
14
15
16
17
18
19
20
21
22
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6
technique according to our previously developed procedure with slight modification.
Typically, 4 (0.5g) was added to 20 mL of deionized water and sonicated for at least 10 min.
Na WO , 2H O (0.073 g, 0.21 mmol) was separately dissolved in deionized water (3 mL) and
2
4
2
gradually added to the above-mentioned suspension and stirred at room temperature for 24 h.
The resulted ion-exchanged solid was filtered and washed with acetonitrile (2×30 mL) and
acetone (2×40 mL), respectively. The material was then dried at room temperature under
vacuum over P O .
2
5
General Procedure for the Selective Oxidation of Sulfide to the Corresponding Sulfoxide
in Water/CH CN. To a solution of 0.5 mmol sulfide and 0.5-1.5 mmol H O (depending on
3
2
2
sulfide) in H O:CH CN (1:1), was added 0.023-0.092 g (depending on sulfide) 5 (1-4mol%)
2
3
and above solution was stirred at 30 °C for requisite time. The progress of the reactions was
monitored by TLC or GC. After completion of the reaction the product was first extracted
using CH Cl (2×25 mL), then evaporated solvent and purified product using column
2
2
chromatography (n-hexane: ethyl acetate (8:1)) if necessary.
General Procedure for the Selective Oxidation of Sulfide to the Corresponding Sulfoxide
and/or Sulfone in Water. To a solution of 0.5 mmol sulfide and 1-2 mmol30% H O2
2
(depending on sulfide) in H O, was added 0.023-0.046 g (depending on sulfide) 5 (1-4mol%)
2
and above solution stirred at 30 °C for requisite time. The progress of the reactions was
monitored by TLC or GC. After completion of the reaction the product was first extracted
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4
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5
5
5
6
using CH Cl (2×25 mL), then evaporated solvent and purifiedproduct usingcolumn
2
2
chromatography (n-hexane: ethyl acetate (8:1)) if necessary.
Typical Procedure for Recycling of 5 in Oxidation of Phenyl Methyl Sulfide to the
0
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Corresponding Sulfoxide. After the first reaction run, the catalyst was isolated with
centrifugation followed by washing with CH Cl (3 ×10 mL) and dried under vacuum for 12h
2
2
at room temperature. The recovered catalyst was used in the subsequent procedure in the same
manner as reported in the first run.
AUTHOR INFORMATION
Corresponding Author:
*E-mail :Karimi@iasbs.ac.ir
Present Address:
Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), PO-Box
45195-1159, Gava-zang, Zanjan 45137-6731, Iran Fax: (+98-241-4214949)
ACKNOWLEDGMENT
The authors thank the Institute for Advanced Studies in Basic Science (IASBS), and the Iran
National Science Foundation (INSF) for supporting this work.
REFERENCES
(1) (a) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K.
D.; Chu, C. T. W.; Olson, D. H.; Sheppard, E. W. J. Am. Chem. Soc.1992, 114, 10834.
(b) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S. Nature
20
ACS Paragon Plus Environment

Page 21 of 25
ACS Catalysis
1
2
3
4
5
6
7
8
9
1
992, 359, 710. (c) Zhao, D.; Feng, J.; Huo, Q.; Melosh, N.; Fredrickson, G. H.;
Chmelka, B. F.; Stucky, G. D. Science 1998, 279, 548. (d) Zhao, D.; Huo, Q.; Feng, J.;
Chmelka, B. F.; Stucky, G. D. J. Am. Chem. Soc. 1998, 120, 6024.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(
2) (a) Corma, A. Chem. Rev. 1997, 97, 2373. (b) De Vos, D. E.; Dams, M.; Sels, B. F.;
Jacobs, P. A. Chem. Rev. 2002, 102, 3615. (c) Wight, A. P.; Davis, M. E. Chem. Rev.
2
002, 102, 10, 3589. (d) Hoffmann, F.; Cornelius, M.; Morrel, J.; Fröba, M. Angew.
Chem., Int. Ed. 2006, 45, 3216 (e) Zamboulis, A.; Moitra, N.; Moreau, J. E.; Cattoën,
X.; Man, M. W. C. J. Mater. Chem. 2010, 20, 9322. (f) Shylesh, S.; Thiel, W. R.
ChemCatChem. 2011, 3, 278. (g) Aragay, G.; Pons, J.; Merkoçi, A. Chem. Rev. 2011,
1
11, 3433. (h) Aragay, G.; Pino, F.; Merkoçi, A. Chem. Rev. 2012, 112, 5317.
(3) (a) Mbaraka,I. K.; Shanks,B. H. J. Catal. 2005, 229, 365. (b) Dı ꢀa z, I.; Márquez-Alvarez,
C.; Mohino, F.; Pérez-Pariente, J.; Sastre, E. J. Catal. 2000, 193, 295. (c) Karimi, B.;
Mirzaei, H. M.; Mobaraki, A. Catal. Sci. Technol., 2012, 2, 828. (d) Karimi, B.;
Vafaeezadeh, M. Chem. Commun., 2012, 48, 3327.
(4) Ni, L.; Lv, Y.; Yang, P.; Cao, Y. Chem. Commun. 2009, 2171.
(5) Karimi, B.; Zareyee, D. Org. Lett. 2008, 10, 3989.
(6) Karimi, B.; Zareyee, D. J. Mater. Chem. 2009, 19, 8665.
(7) (a) Bhaumik, A.; Tatsumi, T. Catal. Lett. 2000, 66, 181. (b) Bhaumik, A.; Tatsumi. T. J.
Catal. 2000, 189, 31.
21
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ACS Catalysis
Page 22 of 25
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
8) (a) Varma, R. S.; Naicker, K. P. Org. Lett. 1999, 1, 189. (b) Imada, Y.; Iida, H.; Ono, S.;
Murahashi, S.-I. J. Am. Chem. Soc. 2003, 125, 2868. (c) Koo, D. H.; Kim, M.; Chang, S.
Org. Lett. 2005, 7, 5015. (d) Bordoloi, A.; Vinu, A.; Halligudi, S. B. Chem. Commun.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
007, 4806. (e) Mba, M.; Prins, L. J.; Licini, G. Org. Lett. 2007, 9, 21. (f) Bigi, F.;
Cradini, A.; Quarantelli, C.; Sartori, G. J. Catal. 2007, 255, 222. (g) Shi, F.; Tse, M. K.;
Kaiser, H. M.; Beller, M. Adv. Synth. Catal. 2007, 349, 2425. (h) Gamelas, C. A.;
Lourenço, T.; Costa, A. P.; Simplício, A. L.; Royo, B.; Romão, C. C.; Tetrahedron Lett.
2008, 49, 4708. (i) Sreedhar, B.; Radhika, P.; Neelima, B.; Hebalkar, N.; Mishra, A. K.
Catal. Commun. 2008, 10, 39. (j) Shi, X. -Y.; Wei, J. -F. J. Mol. Catal. A: Chem. 2008,
2
80, 142. (k) Gregori, F.; Nobili, I.; Bigi, F.; Maggia, R.; Predieri, G. Sartori. G.; J. Mol.
Catal. A: Chem. 2008, 286. 124. (l) Noguchi, T.; Hirai, Y.; Kirihara, M. Chem.
Commun. 2008, 3040. (m) Raju, B. R.; Sarkar, S.; Reddy, U. C.; Saikia, A. K. J. Mol.
Catal. A: Chem.2009, 308, 169. (n) Das, R.; Chakraborty. D. Tetrahedron Lett. 2010,
5
1, 6255. (o) Panda, K. P.;Shaikh, M. M.; Ghosh, P. Dalton Trans. 2010, 39, 2428. (p)
Maggi, R.; Chitsaz, S.; Loebbecke, S.; Piscopo, C. G.; Sartori, G.; Schwarzer, M. Green
Chem. 2011, 13, 1121 (q) Bahrami, K.; Khodaei, M. M.; Fattahpour, P. Catal. Sci.
Technol. 2011, 1, 389. (r) Tang, N.; Zhang, Y.; Lin, F.; Lü, H.; Jiang, Z.; Li, C. Chem.
Commun. 2012, 48, 11647. (s) Zhang, P.; Wang, Y.; Li, H.; Antonietti, M. Green Chem.
2012, 14, 1904. (t) Li, B.; Liu, A. -H.; He, L. -H.; Yang, Z. -Z.; Gao, J.; Chen, K. -H.
Green Chem. 2012, 14, 130. (u) Jereb, M. Green Chem. 2012, 14, 3047. (v) Shi, X.; Ma,
W.; Ou, H.; Han, X.; Lu, C.; Chen, Y.; Wei, J. J. Braz. Chem. Soc. 2012, 23, 1536.
(9) (a) Kotelanski, B.; Grozmann, R. J.; Cohn, J. N. Clin. Pharmacol. Ther. 1973, 14, 427.
b) Block, E. Reaction of Organosulfur Compounds; Academic Press: New York, 1978.
(
22
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Page 23 of 25
ACS Catalysis
1
2
3
4
5
6
7
8
9
(
c) Focke, M.; Feld, A.; Lichtenthaler, K. FEBS Lett. 1990, 12, 106. (d) Carreno, M. C.
Chem. Rev. 1995, 95, 1717. (e) Agarwal, K. C. Med. Res. 1996, 16, 111. (f) Merino, G.;
Molina, A. J.; Garcia, J. L.; Pulido, M. M.; Prieto, J. G.; Alvarez, A. I. J. Pharm.
Pharmacol. 2003, 55, 757. (g) Sovova, M.; Sova, P. CeskaSlov. Farm. 2003, 52, 82.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(
10) (a) Bordwell,F. G.; Boutan, P. J. Am. Chem. Soc. 1957, 79, 717. (b) Leonard, N. J.;
Johnson, C. R. J. Org. Chem.1962, 27, 282. (c) Durst, T. J. Am. Chem. Soc.1969, 91,
1
034. (d) Drabowicz, J.; Midura, W.; Kolajczyk, M. Synthesis 1979, 39. (e) Gokel, G.
W.; Gerdes, H. M.; Dishong, D. M. J. Org. Chem., 1980, 45, 3634. (f) Khurana, J. M.;
Panda, A. K.; Ray, A.; Gogia, A. Org. Prep. Proced. Int., 1996, 28, 234.
(11) Karimi,B.; Ghoreishi-Nezhad, M.; Clark, J. H. Org. Lett. 2005, 7, 625.
(
12) (a) Shi, S.; Tse, M. K.; Kaisar, H. M.; Beller, M. Adv. Synth. Catal. 2007, 349, 2425. (b)
Kamata, K.; Hirano, T.; Mizuno, N. Chem. Commun. 2009, 3958.
(13) Inumaru, K.; Ishihara, T.; Kamiya, Y.; Okuhara, T.; Yamanaka, S. Angew. Chem., Int.
Ed. 2007, 46, 7625.
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