Catalyst-free oxidation of sulfides to sulfoxides and diethylamine catalyzed oxidation of sulfides to sulfones using Oxone as an oxidant

Article abstract of DOI:10.1007/s11164-017-3026-0

Abstract: We describe here our journey from the failure of our attempts in controlled oxidation of sulfides to sulfoxides using an Oxone–KBr combination to our success in the development of a catalyst-free protocol for the oxidation of sulfides to sulfoxides using Oxone as an oxidant. We also describe the failure of our attempts at the oxidation of sulfides to sulfones using an excess of Oxone–KBr as well as Oxone, and our success towards the development of a rapid, scalable and chromatography-free protocol for the oxidation of sulfides to sulfones using diethylamine–Oxone as an unprecedented catalyst–oxidant combination.

Full text of DOI:10.1007/s11164-017-3026-0

Res Chem Intermed
DOI 10.1007/s11164-017-3026-0
Catalyst-free oxidation of sulfides to sulfoxides
and diethylamine-catalyzed oxidation of sulfides
to sulfones using Oxone as an oxidant
R. V. Kupwade1 S. S. khot1 U. P. Lad1
•
•
•
U. V. Desai1 P. P. Wadgaonkar2
•
Received: 19 March 2017 / Accepted: 26 June 2017
Ó Springer Science+Business Media B.V. 2017
Abstract We describe here our journey from the failure of our attempts in controlled
oxidation of sulfides to sulfoxides using an OxoneÒ–KBr combination to our success in
the development of a catalyst-free protocol for the oxidation of sulfides to sulfoxides
using Oxone as an oxidant. We also describe the failure of our attempts at the oxidation
of sulfides to sulfones using an excess of Oxone–KBr as well as Oxone, and our success
towards the development of a rapid, scalable and chromatography-free protocol for the
oxidation of sulfides to sulfones using diethylamine–Oxone as an unprecedented cata-
lyst–oxidant combination.
Graphical Abstract
Catalyst-free oxidation of sulfides to sulfoxides and diethylamine catalyzed oxidation of
sulfides to sulfones using Oxone as an oxidant: A journey from illogical failure to pursued
success
R. V. Kupwade, S. S. Khot, U. P. Lad, U. V. Desai,* P. P. Wadgaonkar
Electronic supplementary material The online version of this article (doi:10.1007/s11164-017-3026-0)
contains supplementary material, which is available to authorized users.
&
U. V. Desai
uvdchem2011@gmail.com; uprabhu_desai@rediffmail.com
1
2
Department of Chemistry, Shivaji University, Kolhapur, Maharashtra 416004, India
Polymer Science and Engineering Division, National Chemical Laboratory, Pune 416004, India
123

R. V. Kupwade et al.
Keywords Oxone Á Oxidation Á Sulfoxides Á Sulfones Á Organocatalysis Á
Diethylamine
Introduction
Modern chemistry has been invariably linked with sustainable chemistry, and, in an
over-polluted world, its implementation has become a practical need both from
socio and economic points of view. Consequently, in recent years, the development
of sustainable, atom-economical, operationally simple, scalable, and catalyst-free
protocols for the synthesis of pivotal intermediates useful in chemistry as well as
biology has become the focal point of research. However, when catalyst-free
conditions are unable to offer the aforesaid benefits, exploration of a commercially
available, inexpensive, environmentally benign and easy to handle catalyst in
organic synthesis is the most practical and logical alternative. Sulfoxides and
sulfones are two important classes of compounds which find wide applications as
intermediates in chemistry as well as biology. Among these, sulfoxides serve as
valuable synthons in C–C bond forming reactions, [1–4] Diels–Alder reactions,
[5, 6] as chiral auxiliaries [7], and in medicinal chemistry as anti-ulcer,
antihypertensive, cardiotonic agents, and CNS stimulants as well as vasodilators
[8]. They are also known to play an important role in enzyme activation [9], while a
few sulfoxides find application in the separation of radioactive and less common
metals [10]. Similarly sulfoxides and sulfones are also known to play a prominent
role in the field of organic synthesis, pharmaceuticals, and agrochemicals as well as
polymers [11–15].
Controlled and chemoselective oxidation of sulfides is one of the rational
pathways for the synthesis of sulfoxides and a great number of oxidizing agents,
such as halogens [16, 17], N2O4/PVP [18], TEMPO-linked metalloporphirines [19],
NaIO4, [20] hypervalent iodine reagents [21–23], H2O2 [24–33], TBHP [34],
OxoneÒ [35–38], etc., have been reported to effect the selective oxidation of sulfides
to sulfoxides. Our interest in studies on the oxidation of sulfides stems from our
earlier experiences in Oxone chemistry [39–42].
It is well known that Oxone is a stable 2:1:1 ternary composite of KHSO5, K2SO4
and KHSO4, and its use in various organic transformations is well documented [43].
We have reported earlier on the use of Oxone in oxidation of hydrazides to
diacylhydrazines [39], and have also demonstrated that Oxone–KBr combination
serves as an eco-safe source of bromonium ions. Thus, we exploited this oxidant–
reagent combination in the bromination of activated arenes, in the oxidation of
alkylcyanohydrazines to azo-bis-iso-butyronitriles, and in chemoselective depro-
tection of dithioacetals to carbonyls [40–42]. A literature survey within the
framework of the use of Oxone and an Oxone–KBr combination in the oxidation of
sulfides revealed that, Oxone supported on alumina or silica gel under the influence
of thermal or MW activation [35, 36], has been reported to effect oxidation of
sulfides to sulfoxides. However, the essentiality in the use of more than
stoichiometric amounts of Oxone, inorganic supports and the necessity of
123

Catalyst-free oxidation of sulfides to sulfoxides and…
thermal/MW activation make these protocols less attractive in practice. Yu et al.
have recently described a solvent-dependent protocol in the chemoselective
oxidation of sulfides to sulfoxides using Oxone as an oxidant [37]. This protocol
also suffers from the drawbacks of thermal activation (reflux in ethanol) and very
long reaction times (12 h). Hajipour et al. [38], on the other hand, have reported an
organic solvent-soluble derivative of Oxone, i.e., benzyltriphenylphosphonium
peroxymonosulfate (BTPP), in selective oxidation of sulfides to sulfoxides.
However, its very high molecular weight and consequently the cost of BTPP
restricts the practical applicability of the developed protocol in the synthesis of
sulfoxides. With this literature survey, with our experiences in Oxone chemistry,
and with our aim to make chemistry simple and easily adaptable, we set out to
develop an alternate pathway in the chemoselective oxidation of sulfides to
sulfoxides using Oxone as an oxidant. In this regard, taking recourse to our earlier
reported concept on the generation of Br? ions using the Oxone–KBr combination
[40–42], we surmised that sulfur, as a soft nucleophile, Br? generated in situ using
the Oxone–KBr combination would chemoselectively attack sulfur in thioether, 1,
to yield sulfenyl bromide, M, which on subsequent reaction with water would
furnish the corresponding sulfoxide, 2 (Scheme 1).
Results and discussion
To check the feasibility of the planned protocol, a model reaction was carried out
using thioanisole, Oxone and potassium bromide as the substrates. Thus, to an
equimolar solution of thioanisole, 1a, and potassium bromide (1 mmol, each) in
aqueous acetonitrile (3:1, 4 mL) was added dropwise an aqueous solution of Oxone
(1 equiv., 6 mL). It was noticed that oxidation of thioanisole to the corresponding
sulfoxide results in a very short time (10 min, TLC). However,the resulting
sulfoxide continues to undergo overoxidation to furnish the corresponding sulfone
as the major product (TLC, NMR) (Table 1, entry 1). In ordert to control the
reaction at the sulfoxide stage, the same reaction was then carried out at 273 K.
Scheme 1 Planned oxidation of
sulfides to sulfoxides using an
Oxone–KBr combination
K2SO4
+
HOBr
Br
R1
KHSO5
+
KBr
+
..
S
S
R
R1
HO Br
R
+
(M)
1
H2O
H
O+
O
S
H
Br
R1
R
R1
S
2
R
123

R. V. Kupwade et al.
Table 1 Optimization of reaction conditions for the controlled oxidation of thioanisole, 1a
O
S
S
Conditions
No.
Oxone:KBr (euivq.)
Time (min)
Yield (%)a
Sulfoxide
Sulfone
1
2b
1.0:1.0
1.0:1.0
0.75:1.0
0.50:1.0
1.0:0.75
1.0:0.5
1.0:0.2
1.0:-
10, 30, 90
10, 30, 90
15
70, 15, 15
60, 20, 20
60
30, 85, 85
40, 80, 80
30
3
4
15
50
30
5
10, 30
10, 30
15, 30
15, 60
15, 60
10, 60
60, 40
70, 50
90, 80
90, 70
92, 85
92, 90
40, 60
6
30, 50
7
10, 20
8
10, 30
9
0.8:-
Traces, 15
Traces, 10
10
0.7:-
a
Isolated yields
b
At 0 °C
However; we did not observe any pronounced change in the behavior of the
sulfoxide towards its overoxidation (Table 1, entry 2). These two interesting results
prompted us to pursue this reaction further.
A set of experiments were then carried out using the same model substrate and
different proportions of Oxone as well as potassium bromide. It was observed that,
even with the decrease in the proportion of Oxone, the reaction furnished a mixture
of sulfoxide and sulfone along with minor amounts of unreacted starting material
(TLC) (Table 1, entries 3, 4). It was further observed that, with the decrease in the
proportion of potassium bromide, oxidation of thioanisole to corresponding
sulfoxide requires nearly the same time period (10–15 min). However, its
overoxidation to sulfone needs a slightly longer time (Table 1, entries 5–7), and,
in the absence of potassium bromide, oxidation of the initially formed sulfoxide
takes an appreciably longer time (Table 1, entry 8). Further optimization of the
reaction conditions was focused on the proportion of Oxone. Interestingly, using
less than a stoichiometric amount of Oxone, conversion of sulfide to the
corresponding sulfoxide proceeds smoothly in nearly the same time span (Table 1,
entries 9, 10), and, happily enough, its overoxidation to sulfone requires a very long
time. This particular aspect of the reaction allows executing the chemoselective
oxidation of sulfide to the corresponding sulfoxide.
After establishing the correct reaction conditions, we next planned to explore the
generality as well as the scope of the reaction conditions. Initially, various
substituted thioethers bearing methyl, nitro, bromo, and iso-propyl as well as
123

Catalyst-free oxidation of sulfides to sulfoxides and…
cyclopropyl groups were subjected to oxidation. In all the cases, the corresponding
sulfoxides were obtained in excellent yield ( Table 2, entries 2b–2f). We next turned
our attention to check the chemoselectivity in this oxidation process. Accordingly,
sulfides containing aldehyde and primary as well as secondary alcoholic groups
were selected as substrates. In all these cases, chemoselective oxidation of sulfide to
sulfoxide was observed (Table 2, entries 2g–2i). During oxidation of diallyl sulfide
and allyl phenyl sulfide, chemoselective oxidation of sulfides to corresponding
sulfoxides was also observed (Table 2, entries 2j, 2k). So as to explore the
functional group compatibility, sulfides containing nitrile and ester amide as well as
a keto group were subjected to oxidation under the established reaction conditions.
In all these cases, corresponding sulfoxides (Table 2, 2l–2o) resulted in excellent
isolated yields. Finally, the reaction was extended towards the oxidation of diaryl
and dibenzyl sulfides. In these cases too, corresponding sulfoxides (Table 2, 2p–2q)
were obtained in excellent yields. So as to check the practical utility of the
developed protocol, oxidation of dibenzyl sulfide was carried out on 50-mmol scales
when the corresponding sulfoxide was obtained as the sole product in excellent
yield (94%) in a very short time (10 min). Most gratifyingly, after isolation of the
product as a colorless solid, it did not require any further purification.
During optimization of the reaction conditions for the oxidation of sulfides to
sulfoxides, we had noticed that (1) with the choice of equimolar quantities of
thioanisole, Oxone and KBr, the initially formed sulfoxide continues to undergo
overoxidation to yield the corresponding sulfone as the major product; however,
even after prolonged stirring at room temperature, its oxidation to sulfone does not
go to completion, and, consequently, the final product is a mixture of sulfoxide and
sulfone, later being the major product (Table 1, entry 1,) and (2), with the choice of
more than the optimized amount of Oxone (Table 1, entry 8), the resulting oxidation
product is also a mixture of sulfoxide and sulfone. In this case, the former
compound is obtained as the major product. Based upon these two observations, we
surmised that, with the choice of either more than stoichiometric quantities of
Oxone–KBr or of Oxone, the oxidation of sulfide to sulfone could be easily
achieved. These two important observations prompted us to extend this oxidative
protocol towards the oxidation of sulfides to sulfones. A variety of reagents within
the range of the experimental conditions has recently been reported for the oxidation
of sulfides to sulfones [44–52]. However, we were interested in exploring the use of
Oxone or the Oxone–KBr combination in this oxidation. Thus, we initially
attempted the oxidation of thioanisole, 1a, to the corresponding sulfone, 3a, using
Oxone and KBr in different proportions (Table 3). However, the resultant product
was noticed to be a mixture of sulfoxide and sulfone (Table 3, entries 1–3). After
this failure, we undertook an uncatalyzed oxidation of thioanisole using different
proportions of Oxone (Table 3, entries 4–6). Once again, in all the cases, the
resultant product was noticed to be a mixture of sulfoxide, 2a, and sulfone, 3a, later
being obtained as the major but not the sole product. In the light of our earlier
studies (Table 1) on the oxidation of sulfides to sulfoxides, the results obtained
during these oxidation studies were surprising, and we do not have any logical
explanation for this behaviour. Hence, we became more determined to develop a
protocol for obtaining sulfone as the sole product using Oxone as an oxidant.
123

R. V. Kupwade et al.
Table 2 Chemoselective oxidation of sulfides to sulfoxides
O
S
Oxone
S
R1
R
R1
, RT
MeCN - H2O
R
1
2
O
S
O
S
O
S
O
2N
2a
15 / 92
2b
2c
15 / 90
15 / 95
O
S
O
S
O
S
Br
2d
15/ 92
2e
2f
15/ 90
15/ 89
O
O
OH
S
S
OH
S
OHC
O
2g
20 / 89
2h
2i
15 / 85
20 / 95
O
O
S
S
CN
S
O
2j
15 / 92
2k
2l
10 / 96
10 / 93
O
O
O
S
OCH3
NH2
S
S
O
O
O
2m
20 / 90
2n
20 / 90
2o
15 / 89
O
S
S
2q
O
(on 50 mmol scale)
2p
10 / 88
2q
10 / 92
10 / 94
Reaction conditions: Sulfide (1 mmol), acetonitrile - water (1:3, v / v, 4
mL), aqueous Oxone (0.7 mmol in 6 mL H2O), RT; b: all compounds
gave satisfactory spectral (IR, NMR) analysis
123

Catalyst-free oxidation of sulfides to sulfoxides and…
Table 3 Optimization of reaction conditions for oxidation of thioanisole, 1a, to the corresponding
sulfone, 3a
O
O
S
S
Oxone - KBr
or
Oxone, CH3CN - H2O
3a
1a
No.
Oxone (euqiv.)
KBr (equi.v)
Time (min)
Yield (%)a
Sulfoxide
Sulfone
1
2
3
4
5
6
a
1.5
2.0
2.0
1.5
2.0
2.5
1.5
2.0
1.0
–
90
90
90
90
90
90
10
10
20
15
10
10
90
90
80
85
90
90
–
–
Isolated yields
A literature survey as regards the use of Oxone inthe oxidation of sulfides to
sulfones revealed that there are only few earlier reports on this oxidative
transformation. Trost et al. and Morimoto et al. have reported, respectively, the
use of Oxone and a clay mineral–Oxone combination for this oxidation [53, 54].
However, apart from the mineral support, both these protocols require the use of
Oxone in excess. Yu et al. have reported an Oxone-mediated, catalyst-free
protocol for the oxidation of sulfides to sulfones [37]. However this protocol
suffers from drawbacks regarding the very long reaction times and elevated
temperature (reflux, 12 h). Web et al. have also reported the use of Oxone in the
direct oxidation of sulfides to sulfones [55]. Their protocol necessitates the use
Oxone as a solution in EDTA as solvent and the control of pH between 7.5–8.0 by
using sodium carbonate buffer. During the literature search, one report attracted
our attention: Ceccherelli et al. have reported the use of a base–Oxone
combination in an oxidative Nef reaction [56]. After this report, to our
knowledge, there are no reports on the use of a base–Oxone combination in
other oxidative transformations. This interesting observation coupled with our
continued interest in the development of ecobenign methodologies using basic
catalysts [57–62], meant that we became interested in investigating the use ofa
base–Oxone combination in the oxidation of sulfides.
A few model reactions were carried out initially. Thus, to a well-stirred mixture
of thioanisole, 1a (1 mmol), and a selected base catalyst (0.2 mmol) in acetonitrile
(2 mL) was added the solution of Oxone (2 mmol) in water (4 mL). Each reaction
was monitored by TLC. It was observed that, with the choice of inorganic base
catalysts, the oxidation of sulfide, 1a, to the corresponding sulfone, 3a, does not go
to completion (Table 4, entries 1, 2). On the other hand, with the choice of
organobasic catalysts like DBU, DABCO, piperidine, diethylamine, and DMAP, as
well as triethylamine, thioanisole directly undergoes oxidation to cthe orresponding
sulfone (Table 4, entries 3–8). Each model reaction was exothermic, fast and, most
123

R. V. Kupwade et al.
Table 4 Optimization of reaction conditions for base-catalyzed oxidation of thioanisole, 1a, to the
corresponding sulfone, 3a
O
O
S
S
Conditions
3a
1a
No.
Oxone (equiv.)
Catalyst (20 mol%)
Time (min)
Yield (%)a
Sulfoxide
Sulfone
1
2
3
4
5
6
7
8
9
a
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.5
K3PO4
K2CO3
DABCO
DBU
60
120
5
20
50
–
80
50
85
90
90
82
85
97
96b
5
–
Piperidine
Triethylamine
DMAP
DEA
5
–
30
30
5
–
–
–
DEA
5
–
Isolated yields; DEA diethylamine
interestingly, in none of the organic base catalyzed reactions did we notice the
presence of sulfoxide in the final product (TLC). Among the catalysts screened,
based upon the parameters of cost, commercial availability, ease of handling and
easy removal from the reaction mixture during work-up, diethylamine was noticed
to be the best-suited catalyst. During further optimization of the reaction conditions,
it was noticed that, with the use of 1.5 equiv. of Oxone, cthe onversion of
thioanisole to the corresponding sulfone takes place in nearly the same time and
yield (Table 4, entry 9).
Employing the optimized reaction conditions, initially, various substituted
thioanisoles were subjected to oxidation, when the corresponding sulfones were
obtained in almost quantitative yields (Table 5, entries 3a–3e). Subsequently, an
array of structurally diverse thioethers containing easily oxidizable substituents like
aldehyde as well as a secondary alcoholic group were subjected to oxidation under
the same reaction conditions. Once again, the corresponding sulfones resulted in
excellent yield (Table 5, entries 3h–3m). During screening of functional group
compatibility in this oxidation protocol, sulfides containing allyl, ester, and amide as
well as nitrile functions were subjected to oxidation. The protocol was noticed to be
functional grou- compatible (Table 5, 3n–3s). In most cases, the resultant sulfone
being a solid product and its isolation proved to be very easy. Thus, simply upon
dilution of the reaction mixture with water followed by filtration of the resultant
solid, the corresponding sulfone was obtained. Most gratifyingly,the resulting
sulfone did not require any further purification. On the other hand, when the sulfone
was obtained as a liquid, simple filtration through a short column of silica gel
yielded the pure product.
123

Catalyst-free oxidation of sulfides to sulfoxides and…
Table 5 Diethylamine catalyzed, chemoselective oxidation of sulfides to sulfones
O
O
Diethylamine - Oxone
CH3CN - H2 O, RT
S
1
R
R1
S
3
R
R1
Time (min.) / Yield (%)
O
O
S
O
S
S
O
O
O
F
3a
3b
3c
5 / 98
5 / 98
5 / 99
O
O
S
S
O
S
O
O
O
O2
N
3f
3d
3e
5 / 90
5 / 97
5 / 91
O
O
O
S
S
OH
O
S
O
O3g
5 / 98
OHC
3i
3h
10 / 88
O
5 / 88
O
O
OH
O
O
O
S
S
S
HO
HO
3l
3k
3j
15 / 90
15 / 95
10 / 90
O
S
O
S
O
O
O
O
S
HO
3m
Br
3n
3o
10 / 88
15 / 90
O
S
5 / 99
O
O
O
O
O
S
S
NH2
OCH 3
O
O
O
OC2H5
3p
10 / 96
O
3q
3r
10 / 90
10 / 99
O
S
3t
S
CN
O
O
(on 50 mmol scale)
10 / 94
3t
10 / 95
3s
5 / 97
Reaction conditions: sulfide (1 mmol), acetonitrile (1mL), diethylamine
(20 mol %), Oxone [1.5 mmol in water (4 mL)], RT;
123

R. V. Kupwade et al.
K
R
R
O
O
O
O
O
S
:
:
S
+
O
:
S
S
+
(i)
(Et)2 NH2
-O
O
O
H
O
R1
R1
K
NH
Et
Et
NH
2 KHSO4
+
2
Et
Et
K
R
O
O
O
O
O
O
(ii)
O
:
S
O
+
S
S
S
+
(Et)2 NH2
-O
R
R1
O
O
R1
H
O
K
NH
Et
Et
Scheme 2 Plausible mechanism for diethylamine-catalyzed oxidation of sulfides to sulfones
Encouraged by this success in the development of a high-yielding and
operationally simple protocol in the oxidation of sulfides to sulfones, we next
planned to explorethe scalability of the developed protocol. In this regard,
dibenzylsulfide was once a gain selected as a model substrate. Under the established
reaction conditions, the oxidation of dibenzylsulfide was performed on a 50-mmol
scale. Most gratifyingly, the corresponding sulfone, i.e., dibenzylsulfone, was
obtained as a colorless solid in almost quantitative yield and, after isolation, it did
not require any further purification.
Plausible mechanism of diethylamine catalyzed oxidation of sulfides to sulfones
is depicted in Scheme 2.
Conclusion
In conclusion, we have developed an ecobenign, catalyst-free, and scalable protocol
for the chemoselective oxidation of sulfides to sulfoxides using commercially
available Oxone as an oxidant. We have also developed a chemoselective,
chromatography-free and scalable protocol for the oxidation of sulfides to sulfones
using diethylamine–Oxone as a unique catalyst–oxidant combination. To the best of
our knowledge, the literature to date contains no precedent for such a simple,
energy-efficient and scalable protocol for the oxidation of sulfides to sulfoxides and
sulfones.
123

Catalyst-free oxidation of sulfides to sulfoxides and…
Experimental
General
Simple substituted thioethers were procured from commercial sources and were
used as received. Functionalized thioethers essential for the synthesis of
sulfoxides/sulfones (2l–2o/3p–3s) were prepared by potassium phosphate-cat-
alyzed Michael addition of thiols to acrylonitrile, methyl acrylate, acrylamide or
methyl vinyl ketone, respectively (see supplementary information). Thioethers,
essential for the synthesis of sulfoxide, 2i, and b-hydroxy sulfones (3j–3m) were
prepared by potassium phosphate-catalyzed, regioselective opening of respective
epoxides with thiol [63; see supplementary information]. Melting points were
recorded using a Kumar melting point apparatus. IR spectra were recorded using a
1
Perkin Elmer Spectrum 1 spectrometer. H and 13C NMR spectra were recorded
using a Bruker Avance-II (300 MHz) spectrometer. High-resolution mass spectra
(HRMS) were recorded using a Thermo-Scientific-Q-Exactive, Accela 1250 pump
instrument.
Representative procedure for the oxidation of sulfides to sulfoxides
To a well-stirred solution of thioether (1 mmol) in aqueous-acetonitrile (3:1, 4 mL)
was added dropwise a solution of Oxone (0.7 mmol) in water (6 mL). Stirring was
continued and the reaction was monitored by TLC. Upon completion of the reaction,
the mixture was diluted with chilled water. The resultant sulfoxide, if solid, was
filtered, washed with water and dried, or otherwise the reaction mixture was
extracted with ethyl acetate. The organic extract was washed with water, dried over
anhydrous sodium sulfate and the solvent was removed. The resultant residue was
filtered through a short column of silica gel. Elution with petroleum ether–ethyl
acetate (98:2%, v/v) afforded the pure sulfoxide.
Representative procedure for the oxidation of sulfides to sulfones
To a well-stirred solution of thioether (1 mmol) and diethylamine (0.2 mmol) in
acetonitrile (2 mL) was added the solution of Oxone (1.5 mmol) in water
(4 mL). Stirring was continued and the reaction was monitored by TLC. Upon
completion of the reaction, the mixture was diluted with chilled water. In most
of the cases, sulfones were obtained as pure solid products. Thus, they were
isolated by simple filtration. However, when the resulting sulfone was a liquid,
the product was extracted with ethyl acetate. The organic extract was washed
with water, dried over anhydrous sodium sulfate, and the solvent was removed.
The resultant residue on filtration through a short column of silica gel afforded
pure sulfone.
123

R. V. Kupwade et al.
Spectral data of new compounds is summarized below (For original spectra
of all the synthesized compounds, please see supporting information)
1
(Prop-2-ene-1-sulfinyl) Benzene, (2l) Colorless oil; H-NMR (CDCl3, 300 MHz):
d = 7.55–7.53 (m, 2H, ArH), 7.52–7.42 (m, 3H, ArH), 5.60–5.50 (m, 1H, = CH),
5.27–5.23 (m, 1H, = CHH), 5.15–5.09 (m, 1H, = CHH), 3.55–3.40 (m, 2H,
SCH2); 13C- NMR (CDCl3, 75 MHz): d = 142.84, 131.06, 129.00, 125.21, 124.27,
123.80, 60.74 ppm.
3-[(4-methyl phenyl) sulfinyl] propane nitrile (2m) White solid; Mp 47–49 °C;
1H-NMR (DMSO, 300 MHz): d = 7.52 (d, 2H, J = 7.8 Hz, 2H, ArH), 7.31 (d,
J = 8.1 Hz, 2H, ArH), 3.32–3.23 (m, 1H, SCHH), 3.05–2.97 (m, 1H, SCHH),
2.89–2.79 (m, 1H, SCHH), 2.68–2.63 (m, 1H, SCHH), 2.29 (s, 3H, ArCH3); 13C-
NMR (DMSO, 75 MHz): d = 141.91, 138.99, 10.16, 130.29, 124.38, 118.50, 50.17,
21.36 ppm.
1
Methyl 3-[(4 methyl phenyl) sulfinyl] propanoate (2n) Pale yellow oil; H-NMR
(DMSO, 300 MHz): d = 7.46 (d, J = 7.5 Hz, 2H, ArH), 7.29 (d, J = 7.5 Hz, ArH),
3.66 (s, 3H, OCH3), 3.29–3.11 (m, 1H, SCHH), 2.96–2.87 (m, 1H, SCHH)),
2.71–2.63 (m, 1H, CHH)), 2.46–2.38 (m, 1H, CHH)), 2.33 (s, 3H, ArCH3); 13C-
NMR (DMSO, 75 MHz): d = 171.58, 141.49, 139.79, 130.07, 124.23, 52.01, 50.72,
25.88, 21.33 ppm.
3-[4-(Methylphenyl) sulfinyl] propanamide (2o) White solid; Mp 142–144 °C; 1H-
NMR (DMSO, 300 MHz): d = 7.56–7.45 (m, 2H, ArH), 7.37–7.31 (m, 2H, ArH),
6.90 (s, 1H, NH2), 3.14–3.04 (m, 1H, SCHH), 2.94–2.85 (m, 1H, SCHH),
2.51–2.37(m, 1H, CHH), 2.33(3H, s), 2.29–2.18 (m, 1H, SCHH); 13C- NMR
(DMSO, 75 MHz): d = 173.31, 142.05, 139.36, 130.39, 124.56, 51.46, 27.45,
21.28 ppm.
1-Phenyl-2-(phenyl sulfonyl) ethanol, (3j) White solid. Mp 108–110 °C; IR (KBr,
cm-1): 3365, 3094, 3085, 2962, 2944, 2935, 2922, 1690, 1463, 1431, 1338, 935,
960, 690; 1H-NMR (CDCl3, 300 MHz): 3.33–3.38 (1H, m), 3.49–3.57 (1H, m), 3.70
(1H, d), 5.28 (1H, d), 7.28–7.33 (5H, m), 7.61(2H, t, J = 8.1 Hz), 7.69–7.71
(1H,m), 7.79 (2H, d, J = 8.1 Hz); 13C-NMR (CDCl3, 75 MHz):63.97, 68.47,
125.66, 128.00, 128.38, 128.80, 129.49, 134.14, 139.21, 140.63; HRMS: mass
calculated for C14H15O3S (M ? H)?: 263.0736; Observed mass: 263.0733.
2-[4-(Bromophenyl) sulfonyl] Cyclohexanol (3m) White solid. Mp 138–141 °C,
IR (KBr, cm-1): 3345, 2990, 2966, 1478, 1461, 1307, 1203, 938, 730, 670, 590; 1H-
NMR (CDCl3, 300 MHz): d 1.23–1.38 (4H, m), 1.75 (2H, d, J = 6.0 Hz), 1.92 (1H,
d, J = 12.6 Hz), 2.36 (1H, t, J = 11.4 Hz), 2.95–3.03 (1H, m), 3.46 (1H, broad
doublet), 3.87–3.95 (1H, Sextet, J = 5.1 Hz), 7.73–7.76 (4H, d), 13C-NMR (CDCl3,
75 MHz):23.54, 24.52, 25.70, 34.23, 68.28, 69.13, 129.62, 130.52, 132.59, 135.98;
HRMS: mass calculated for C12H16O739BrS (M ? H)?: 318.9998; Observed mass:
318.9996.
123

Catalyst-free oxidation of sulfides to sulfoxides and…
3-(Phenyl sulfonyl) propanamide (3r) White solid; Mp 136–138 °C; IR (KBr,
cm-1): 3384, 3235, 2975, 2934, 2901,1635, 1312, 1104, 920, 750; 1H-NMR
(CDCl3, 300 MHz): d 2.75 (2H, t, J = 7.5 Hz), 3.47 (2H, t, J = 7.5 Hz), 5.62 (1H,
broad singlet), 5.89 (1H, broad singlet), 7.58–7.63 (2H, m), 7.67–7.72 (1H, m),
7.92–7.95 (2H, m); 13C-NMR (CDCl3, 75 MHz): 28.20, 51.74, 128.01, 129.44,
134.04, 138.80, 170.84; HRMS: mass calculated for C9H12O3NS (M ? H)?:
214.0532; Observed mass: 214.0531.
3-(Phenyl sulfonyl) propanenitrile (3s) White solid; yield: 193 mg (99%); Mp
1
93–94 °C; H-NMR (CDCl3, 300 MHz): d = 7.94 (d, J = 7.5 Hz, 2H, ArH), 7.74
(t, J = 7.2 Hz, 1H, ArH), 7.64 (t, J = 7.5 Hz, 2H, ArH), 3.41 (t, J = 7.5 Hz, 2H,
SCH2), 2.83 (t, J = 7.5 Hz, 2H, CH2); 13C-NMR (CDCl3, 300 MHz): d = 137.54,
134.71, 129.77, 128.25, 116.30, 50.98, 12.00; HRMS (ESI): m/z [M ? H] ? calcd
for C9H10O2NS: 196.0427; found mass: 196.0427.
Acknowledgements Authors UVD and SSK thank UGC New Delhi for the financial support [F. 43 -
221/2014 (SR)]. We are also grateful to the Department of Science & Technology (DST), New Delhi, for
financial assistance to the Department of Chemistry, Shivaji University Kolhapur, under the DST–FIST
program.
References
1. M.C. Carreno, Chem. Rev. 95, 1717–1760 (1995)
2. F. Colobert, A. Tito, N. Khiar, D. Denni, M.A. Media, M. Martin-Lomas, J.L. Ruano, G. Solladie, J.
Org. Chem. 63, 8918 (1998)
3. M.C. Carreno, M. Ribagodra, G.H. Posner, Angew. Chem. Int. Ed. 41, 2753 (2002)
4. S. Patai, H. Rappoport, J.J. Sterling, The chemistry of sulfones and sulfoxide (Wiley, New York,
1988)
5. N. Khiar, I. Fernandez, F. Alcudia, Tetrahedron Lett. 34, 123 (1993)
6. N. Kuneida, J. Nokami, M. Kinoshita, Bull. Chem. Soc. Jpn 49, 256 (1976)
7. I. Fernandez, N. Khiar, Chem. Rev. 103, 3651 (2003)
8. A. Atul Kumar, Tetrahedron Lett. 48, 7857 (2007). (references therein)
9. S.E. Martin, L.I. Rossi, Tetrahedron Lett. 42, 7147 (2001)
10. N.G. Afzaletdinova, E.R. Ibatova, YuI Murinov, Russ. J. Inorg. Chem. 51, 971 (2006)
11. N.S. Simpkins, Sulfones in organic synthesis (Pergamon Press, Oxford, 1993)
12. M. Madesclaire, Tetrahedron 42, 5459 (1986)
13. G. La Regina, A. Coluccia, A. Brancale, F. Piscitelli, V. Gatti, G. Maga, A. Samuele, C. Pan-
necouque, D. Schols, J. Balzarini, E. Novellino, R. Silvestri, J. Med. Chem. 54, 1587 (2011).
(references therein)
14. Y. Suzuki, T. Higashihara, S. Ando, M. Ueda, Macromolecules 45, 3402 (2012)
15. W. Xu, S. Yang, P. Bhadury, J. He, M. He, L. Gao, D. Hu, B. Song, Pestic. Biochem. Physiol. 101, 6
(2011)
16. I. Saikia, A.J. Borah, P. Phukan, Chem. Rev. 116, 6837 (2016)
17. A. Bravo, B. Dordi, F. Fontana, F. Minisci, J. Org. Chem. 66, 3232 (2001)
18. N. Iranpoor, H. Firouzabadi, A. Pourali, Tetrahedron 58, 5179 (2002)
19. J.-Y. Huang, S.-J. Li, Y.-G. Wang, Tetrahedron Lett. 47, 5637 (2006)
20. J. Nelson, C.R. Johnson, J. Org. Chem. 27, 282 (1962)
21. Z. Gross, A. Mahammed, J. Mol. Catal. A Chem. 142, 367 (1999)
22. Z. Li, C.-G. Xia, C.-Z. Xu, Tetrahedron Lett. 44, 9229 (2003)
23. V.G. Shukla, P.D. Salgaonkar, K.G. Akamanchi, J. Org. Chem. 68, 5422 (2003)
24. X.F. Wu, Tetrahedron Lett. 53, 4328 (2012)
25. A. Rostami, B. Tahmasbi, F. Abedi, A. Shokri, J. Mol. Cat. A Chem. 378, 200 (2013)
123

R. V. Kupwade et al.
26. A.M. Kulkarni, U.V. Desai, K.S. Pandit, M.A. Kulkarni, P.P. Wadgaonkar, RSC Adv. 4, 36702
(2014)
27. K. Jeyakumar, D.K. Chand, Tetrahedron Lett. 47, 4573 (2006)
28. D.H. Koo, M. Kim, S. Chang, Org. Lett. 7, 5015 (2005)
29. M. Rahimizadeh, G. Rajabzadeh, S.-M. Khatami, H. Eshghi, A. Shiri, J. Mol. Catal. 323, 59 (2010)
30. K. Bahrami, M.M. Khodaei, S. Sohrabnezhad, Tetrahedron Lett. 52, 6420 (2011)
31. A. Rostami, J.A. Akradi, Tetrahedron Lett. 51, 3501 (2010)
32. S. Hussain, S.K. Bharadwaj, R. Pandey, M.K. Chaudhari, Eur. J. Org. Chem. 20, 3319 (2009)
33. W. Zhao, C. Yang, Z. Cheng, Z. Zhang, Green Chem. 18, 995 (2016)
34. N. Komatsu, M. Hashizume, T. Sugita, S. Uemura, J. Org. Chem. 58, 4529 (1993)
35. P.J. Kropp, J.W. Breton, J.D. Fields, J.C. Tung, B.R. Loomis, J. Am. Chem. Soc. 122, 4280 (2000)
36. R.P. Greenhalgh, Synlett. 36, 235–236 (1992)
37. B. Yu, A.-H. Liu, L.-N. He, B. Li, Z.-F. Diao, Y.-N. Li, Green Chem. 14, 957 (2012)
38. A.R. Hajipour, S. Mallakapoor, H. Adibi, J. Org. Chem. 67, 8666 (2002)
39. P.P. Kulkarni, A.J. Kadam, U.V. Desai, R.B. Mane P.P. Wadgaonkar, J. Chem. Res, 184 (2000)
40. B.V. Tamhankar, U.V. Desai, R.B. Mane, P.P. Wadgaonkar, A.V. Bedekar, Synth. Commun. 31,
2021 (2001)
41. B.V. Tamhankar, U.V. Desai, R.B. Mane, P.P. Kulkarni, P.P. Wadgaonkar, Synth. Commun. 32,
3643 (2002)
42. U.V. Desai, D.M. Pore, B.V. Tamhankar, S.A. Jadhav, P.P. Wadgaonkar, Tetrahedron Lett. 47, 8559
(2006)
43. H. Hussain, I.R. Green, I. Ahmed, Chem. Rev. 113, 3329 (2013)
44. C.K. Jin, Y.M.A. Yamada, Y. Uozumi, Bull. Korean Chem. Soc. 31, 547 (2010)
45. S. Doherty, J.G. Knight, M.A. Carroll, J.R. Ellison, S.J. Hobson, S. Stevens, C. Hardacre, P.
Goodrich, Green Chem. 17, 1559 (2015)
46. S. Ahammed, D. Kundu, M.N. Siddiqui, B.C. Ranu, Tetrahedron Lett. 56, 335 (2015)
47. G.K. Surya Prakash, A. Shakhmin, K.E. Glinton, S. Rao, T. Mathew, G.A. Olah, Green Chem. 16,
3616 (2014)
48. B. Maleki, S. Hemmati, A. Sedrpoushan, S.S. Ashrafia, H. Veisid, RSC Adv. 4, 40505 (2014)
49. M. Kirihara, A. Itou, T. Noguchi, J. Yamamoto, Synlett. 10, 1557 (2010)
50. S.P. Das, J.J. Boruah, N. Sharma, N.N.S. Islam, J. Mol. Catal. A Chem. 356, 36 (2012)
51. Q. Xue, Z. Mao, Y. Shi, H. Mao, Y. Cheng, C. Zhu, Tetrahedron Lett. 53, 1851 (2012)
52. M. Jereb, Green Chem. 14, 3047 (2012)
53. B.M. Trost, D.P. Curran, Tetrahedron Lett. 22, 1287 (1981)
54. T. Morimoto, J. Tomaru, M. Hirano, Chem. Lett. 523 (1991)
55. K.S. Web, Tetrahedron Lett. 35, 3457 (1994)
56. P. Ceccherelli, M. Curini, M.C. Marcotullio, F. Epifano, O. Rosati, Synth. Commun. 28, 3057 (1998)
57. K.S. Pandit, R.V. Kupwade, P.V. Chavan, U.V. Desai, P.P. Wadgaonkar, ACS Sustain. Chem. Eng.
4, 3450 (2016)
58. R.V. Kupwade, K.S. Pandit, U.V. Desai, M.A. Kulkarni, P.P. Wadgaonkar, Res. Chem. Intermed. 42,
6313 (2016)
59. K.S. Pandit, P.V. Chavan, M.A. Kulkarni, U.V. Desai, P.P. Wadgaonkar, New J. Chem. 39, 4452
(2015)
60. U.V. Desai, M.A. Kulkarni, K.S. Pandit, P.P. Wadgaonkar, Green Chem. Lett. Rev. 7, 228 (2014)
61. M.A. Kulkarni, V.R. Pandurangi, U.V. Desai, P.P. Wadgaonkar, C. R. Chim. 15, 745 (2012)
62. M.A. Kulkarni, K.S. Pandit, U.V. Desai, U.P. Lad, P.P. Wadgaonkar, C. R. Chim. 16, 689 (2013)
63. Unpublished work from Ph. D. thesis of Dr. U. P. Lad, submitted to Shivaji university, Kolhapur,
India (2010)
123