Metal-free, regio- and stereoselective S-methylation/phenylation of allyl halides using sulfoxides as sulfenylating agent

Article abstract of DOI:10.1016/j.tet.2017.05.088

A DCP promoted metal-free, regio and stereoselective S-methylation/phenylation of allyl halides using sulfoxides as sulfenylating agent is described. A variety of multifunctional allyl halides underwent S-methylation and S-phenylation by using dimethyl sulfoxide (DMSO) and diphenyl sulfoxide (DPSO) under the reaction conditions employed to provide the resulting thioethers in good to excellent yields.

Full text of DOI:10.1016/j.tet.2017.05.088

Accepted Manuscript
Metal-free, regio- and stereoselective S-methylation/phenylation of allyl halides using
sulfoxides as sulfenylating agent
Rakhee Choudhary, Rekha Bai, Pratibha Singh, Mahesh C. Sharma, Satpal Singh
Badsara
PII:
S0040-4020(17)30597-5
10.1016/j.tet.2017.05.088
TET 28754
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 10 March 2017
Revised Date: 25 May 2017
Accepted Date: 29 May 2017
Please cite this article as: Choudhary R, Bai R, Singh P, Sharma MC, Badsara SS, Metal-free, regio-
and stereoselective S-methylation/phenylation of allyl halides using sulfoxides as sulfenylating agent,
Tetrahedron (2017), doi: 10.1016/j.tet.2017.05.088.
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Graphical Abstract
Metal-free, regio- and stereoselective S-
methylation/phenylation of allyl halides
using sulfoxides as sulfenylating agent
Leave this area blank for abstract info.
Rakhee Choudhary, Rekha Bai, Pratibha Singh, Mahesh C. Sharma and Satpal Singh Badsara*
MFOS Laboratory, Department of Chemistry (Centre of Advanced Study),
University of Rajasthan, JLN Marg, Jaipur, Rajasthan-302004, India .

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Metal-free, regio- and stereoselective S-methylation/phenylation of allyl halides using
sulfoxides as sulfenylating agent
Rakhee Choudhary,† Rekha Bai,† Pratibha Singh,† Mahesh C. Sharma and Satpal Singh Badsara*
MFOS Laboratory, Department of Chemistry (Centre of Advanced Study), University of Rajasthan, JLN Marg, Jaipur, Rajasthan-302004, India.
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A DCP promoted metal-free, regio and stereoselective S-methylation/phenylation of allyl halides
using sulfoxides as sulfenylating agent is described. A variety of multifunctional allyl halides
underwent S-methylation and S-phenylation by using dimethyl sulfoxide (DMSO) and diphenyl
sulfoxide (DPSO) under the reaction conditions employed to provide the resulting thioethers in
good to excellent yields.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
S-methylation
S-phenylation
Allyl thioethers
Sulfoxides
Metal-free
1. Introduction
During our attempts towards the development of metal free C-
S bond formations between allyl bromide derivatives 1a and
diphenyl disulfide, we obtained unexpected and unprecedented
results. The C-S coupling reaction of 1a and diphenyl disulfide
under the influence of di-tert-butyl peroxide (DTBP) using
DMSO (2a) as a solvent could not yield into the desired allyl
phenyl thioether 3a instead allyl methyl thioether 4a was
obtained in 90% yield as shown in Scheme 1 (Table 1, entry 1).
Furthermore, it is important to note that a complete retention in
stereochemistry across the double bond was observed in the
product. The other possible products 3b and 3c were also not
obtained. Best of our knowledge,7d no example for the
preparation of allyl methyl thioethers in this fashion has appeared
so far. Intrigued by this interesting observation, we decided to
optimize the reaction conditions for methylthiolation of allyl
halides and herein report the metal-free, regio- and
stereoselective, peroxide promoted synthesis of allyl
methyl/phenyl thioethers by using sulfoxides as methyl or
phenylthiolation reagent for the first time.
Due to their important multidimensional applications in
organic synthesis, pharmaceutical industry and materials science,
development of synthetic routes for the synthesis of aryl
thioethers have gained much attention in recent years.1,2
Traditionally, the syntheses of thioethers have been carried out
via transition-metal-catalyzed C-S bond coupling reaction of
thiols with aryl halides and pseudo halides.1a-c,3 Various transition
metals such as Pd,4a-d Cu,4e-g Ni,4h,4i Fe,4j,4k In,4l Co,4m Au,4n Mg,4o
Ag4p etc. so far shown their catalytic efficiency in the C-S cross
coupling reactions. Due to environmental concerns and cost
issues, presently beside metal catalysis, metal-free C-S bond-
formation processes have received much attention.5
Being simple, cheap, and easy-to-handle, recently DMSO
emerged as a sustainable methylthiolation reagent.6 Various
transition metal catalytic systems such as Cu(OAc)2,6a CuF2-
K2S2O8,6b AgF-Cu(OAc)2,6c CuBr/CuI-ZnF2 have been so far
6d
used for the preparation of aryl methyl thioethers using DMSO as
a methylthiolation agent. However, these protocols often required
harsh reaction conditions and use of transition metals. Very
recently, DMSO has been used as a sulfenylating agent for
methylthiolation of alcohol containing indoles,7a in the synthesis
of 3-methylthiofurans from homopropargylic alcohols7b and in
methylthiolation of arylamines.7c
* Corresponding author. Tel.: +91-141-2702306
E-mail address: badsarass4@uniraj.ac.in; sattubhu2005@gmail.com (S. S.
Badsara).
† Authors contributed equally.
Scheme 1. S-Methylation of allyl bromide 1a showing the possible products.

2
Tetrahedron
2. Results and Discussion
stereochemistry was found. However, the allyl bromide 1f could
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not provide the desired product (Table 2, entries 8 & 9).
Furthermore, it was observed that the allyl bromides provided the
superior results than that of allyl iodides (Table 2, entries 10-14).
For optimization, we have selected the allyl bromide 1a as
model substrate and treated it with diphenyl disulfide under the
influence of various oxidants using DMSO (2a) as solvent at 80
oC for 12 h (Table 1). As mentioned earlier, the DTBP provided
the allylmethyl thioether 4a in 90% yield (Table 1, entry 1).
Other oxidants such as H2O2, TBHP, BPO couldn’t provide
encouraging results (Table 1, entries 2-4) whereas K2S2O8 and
TBPB provided 4a in 86% and 30% yield respectively (Table 1,
entries 5 & 6). 5.0 equivalent of DCP provided the thioether 4a in
80% yield (Table 1, entry 7). Interestingly, deduction in the
amount of DCP from 5.0 to 1.0 equivalent provided the best
result with 96% yield of thioether 4a (Table 1, entry 8). When the
reaction was carried out at room temperature no product
formation was observed, although DMSO got converted into
dimethyl disulfide which was confirmed by GCMS (Table 1,
entry 9). Similarly, no desired product 4a was formed in absence
of diphenyl disulfide (Table 1, entry 10). It was found that higher
reaction temperature (Table 1, entry 11) and lower amount of
DMSO (Table 1, entry 12) diminished the yield of the product.
Table 2. Syntheses of thioethers 4 containing ester functionalitya
DCP (1.0 equvi.)
PhSSPh (0.5 equvi.)
O
CO2Me
CO2Me
SR
Ar
Ar
S
+
80 oC, 12 h
R
R
X
1
2
4
1a f 1g-i
X = Br ( - ); I ( )
Entry
1
Ar
4-MePh (1b)
R
Product Yield (%)b
Me
Me
Me
Me
Ph
4b
4c
4d
4e
4f
4g
4h
-
88
82
2
4-OMePh (1c)
3-ClPh (1d)
4-ClPh (1e)
Ph (1a)
3
91
4
90
5
88
6
4-MePh (1b)
4-ClPh (1e)
2-NO2Ph (1f)
2-NO2Ph (1f)
4-ClPh (1g)
4-ClPh (1g)
Ph (1h)
Ph
86
7
Ph
85
8
Me
Ph
N.R.
N.R.
55
9
-
10 c
11c
12c
13c
14c
Me
Ph
4e
4h
4a
4f
4g
Table 1. Optimization of the reaction conditionsa
51
Me
Ph
68
[Oxidant]
PhSSPh
O
S
CO2Me
SMe
CO2Me
Br
Ph (1h)
62
+
Me
Me
4-MePh (1i)
Ph
65
80 oC, time
a
4a
Reaction conditions: Allyl bromides/iodides 1 (2.0 mmol), diphenyl
2
1a
disulfide (1.0 mmol) and DCP (2.0 mmol) were reacted in DMSO (2.0
mL) or DPSO (1.0 g) at 80 oC for 12 h.
Entry
Oxidant (equiv.)
DTBP (5.0)
H2O2 (5.0)
TBHP (5.0)
BPO (5.0)
Time (h)
Yield (%)b
90
1
2
3c
4
12
24
24
24
24
24
12
12
12
12
12
12
b Isolated yields of 4 are based on allyl bromides/iodides 1.
N.R.
N.R.
N. R.
86
c Instead of allyl bromide, iodide was used.
Next, we have employed the allyl bromides/ iodides 5a-g
possessing nitrile functionality with E-stereochemistry for S-
methylation using phenyl disulfide and DMSO (2a) under the
influence of DCP following the optimized conditions which
provided resulting thioethers 6a-e in 48-91% yields with
complete retention in stereochemistry across the double bond i.e.
E-stereochemistry (Table 3, entries 1-5 & 8-10). Notably,
replacement of DMSO (2a) with DPSO (2b) in these reactions
provided the allyl phenyl thioethers 6f-g in 79-82% yield with
retention in stereochemistry around the double bond (Table 3,
entries 6-7, 10). In this case also bromides provided the superior
results than that of iodides (Table 3, entries 8-10).
5
K2S2O8 (5.0)
TBPB (5.0)
DCP (5.0)
6
30
7
80
8
DCP (1.0)
DCP (1.0)
96
9d
10e
11f
12g
N.R.
N.R.
90
DCP (1.0)
DCP (1.0)
DCP (1.0)
94
a Reaction conditions: Allyl bromide 1a (2.0 mmol), diphenyl disulfide (1.0
mmol) and oxidant were reacted in DMSO (2.0 mL) at 80 oC.
b Isolated yields are based on 1a.
c TBHP solution in water.
d Room temperature.
Table 3 Syntheses of thioethers 6 containing nitrile functionalitya
O
S
DCP (1.0 equvi.)
PhSSPh (0.5 equvi.)
e Without phenyl disulfide.
f 120 oC.
X
Ar
+
Ar
R
R
SR
CN
5
80 oC, 12 h
2
NC
X = Br (5a-e); I (5f-g)
6
g
1.0 mL DMSO was used. (DTBP = di-tert-butyl peroxide, TBHP = tert-
Entry
Ar
Ph (5a)
R
Product Yield (%)b
butyl hydroperoxide, TBPB = tert-Butyl peroxybenzoate, BPO = benzoyl
peroxide, DCP = dicumyl peroxide).
1
2
Me
Me
Me
Me
Me
Ph
6a
6b
6c
6d
6e
6f
88
88
82
91
88
82
79
52
48
41
4-MePh (5b)
2-BrPh (5c)
3-ClPh (5d)
4-ClPh (5e)
Ph (5a)
Once, we have optimized conditions in hand, we then turned
our attention towards the study of substrate scope for this
fascinating methodology. For this, various allyl bromides/allyl
iodides derivatives (1 & 5) were synthesized from the Baylis-
Hillman alcohols following the literature procedures.8a,8b Firstly,
the allyl bromides (1b-1e) possessing ester functionality with Z-
stereochemistry were employed for S-methylation using phenyl
disulfide and DMSO (2a) reagent system under the influence of
DCP following the optimized reaction conditions which provided
the desired product 4b-e in 82-91% yields (Table 2, entries 1-4).
Similarly, allyl bromide 1a-b,e reacted with phenyl disulfide and
DPSO (2b) reagent system in presence of DCP to provide allyl
phenyl thioethers 4f-h in 85-88% yield (Table 2, entries 5-7). In
all these reactions complete retention in stero-chemistry i.e. Z-
3
4
5
6
7
4-MePh (5b)
Ph (5f)
Ph
6g
6a
6b
6g
8c
9c
10c
Me
Me
Ph
4-MePh (5g)
4-MePh (5g)
a
Reaction conditions: Allyl bromides/iodides 5 (2.0 mmol), diphenyl
disulfide (1.0 mmol) and DCP (2.0 mmol) were reacted in DMSO (2.0 mL) or
DPSO (1.0 g) at 80 oC for 12 h.
b Isolated yields of 6 are based on allyl bromides/iodides 5.

3
c Instead of allyl bromide, iodide was used.
multiplet. HRMS data were collected on Waters - Xevo G2S
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QTof with UPLC H-Class Ultra Performance Liquid
chromatography - mass spectrometry (LC-MS) facility. GCMS
data were collected on Thermo Scientific "TSQ 8000" Triple
quadrupole GC-MS-MS System with Pyrolyzer facility.
To find out the source of SMe group for these reactions, we
have carried out the reaction between allyl bromide 1a with
phenyl disulfide and DMSO-d6 under the influence of DCP
following the optimized conditions which provided the
deuterated thioether 4i confirmed by HRMS data analysis hence,
proved the DMSO as a source of S-methylation (Eq. 1).
4.2. General procedure for Table 1:
Synthesis of methyl (Z)-2-((methylthio)methyl)-3-phenylacrylate
(entry 8, 4a).10 To a stirred solution of allyl bromide 1a i.e.
methyl (2Z)-2-bromomethyl-3-phenylprop-2-enoate (2.0 mmol,
0.510 g) and diphenyl disulfide (1.0 mmol, 0.218 g) in DMSO
(2.0 mL) was added oxidant and then the reaction mixture was
stirred for 80 oC under nitrogen atmosphere. The reaction mixture
was then diluted with EtOAc (10 mL) and water (5.0 mL). After
usual workup, the organic layer was dried over anhydrous
Na2SO4, solvent was evaporated and the crude product thus
obtained was purified by column chromatography (silica gel, 2%
EtOAc in Hexanes) to provide the thioether 4a as pale yellow
DCP (1.0 equvi.)
O
CO2Me
CO2Me
SCD3
PhSSPh (0.5 equvi.)
80 oC, 12 h
CD3
Ph
Ph
4i
Eq. 1
S
+
D3C
Br
1a
2c
Mass: 224.9518
A plausible mechanism for obtaining allyl methyl thioethers is
presented in Scheme 2 taking 4a as a model case. Initially, in
presence of oxidant, the phenyl disulfide generated phenyl sulfide
radical which then coupled with allyl radical (generated from
allyl bromide 1a) to provide the thioether A. The thioether A then
instantly may get oxidized by DCP and DMSO into sulfone B.
Meanwhile, on heating, the DMSO generated MeSH and
HCHO.7b The bromide radical can generate methyl sulfide
radical. Since, the sulfones are reasonably good leaving group9
the methyl sulfide radical may substitute it to provide the desired
1
color oil. Yield: 0.426 g, 96%; Rf (6% EtOAc/hexanes) 0.31; H
NMR (400 MHz, CDCl3): δ 2.08 (s, 3 H), 3.62 (s, 2 H), 3.83 (s, 3
H), 7.32-7.41 (m, 3 H), 7.47 (d, J = 7.6 Hz, 2 H), 7.75 (s, 1 H);
13C NMR (100 MHz, CDCl3): δ 16.3, 30.6, 52.3, 128.7, 128.9,
129.4, 129.6, 135.0, 140.7, 168.0.
allyl methyl thioether 4a
.
4.3. General procedure for Table 2:
To a stirred solution of allyl bromide 1 (2.0 mmol) and
diphenyl disulfide (1.0 mmol, 0.218 g) in DMSO (2.0 mL) or
DPSO (1.0 g) was added DCP (2.0 mmol, 0.540 g) and then the
o
reaction mixture was stirred for 12 h at 80 C under nitrogen
atmosphere. The reaction mixture was then diluted with ethyl
acetate (10 mL) and water (5.0 mL). After usual workup the
organic layer was dried over anhydrous Na2SO4, solvent was
evaporated and the crude product thus obtained was purified by
column chromatography (silica gel, 1 or 2% EtOAc in hexanes)
to provide the thioether 4.
4.3.1. Synthesis of methyl (Z)-2-((methylthio)methyl)-3-(p-
tolyl)acrylate (entry 1, 4b). The title compound was prepared
following the general procedure for Table 2, using allyl bromide
1b i.e. methyl (2Z)-2-bromomethyl-3-(4-methylphenyl)prop-2-
enoate (2.0 mmol, 0.538 g), diphenyl disulfide (1.0 mmol, 0.218
g), DCP (2.0 mmol, 0.540 g) and DMSO (2.0 mL), providing 4b
as pale yellow oil. Yield: 0.415 g, 88%; Rf (6% EtOAc/hexanes)
0.28; 1H NMR (400 MHz, CDCl3): δ 2.10 (s, 3 H), 2.35 (s, 3 H),
3.64 (s, 2 H), 3.82 (s, 3 H), 7.20 (d, J = 8.0 Hz, 2 H), 7.39 (d, J =
8.0 Hz, 2 H), 7.73 (s, 1 H); 13C NMR (100 MHz, CDCl3): δ 16.2,
21.4, 30.6, 52.2, 128.4, 129.4, 129.8, 132.2, 139.2, 140.8, 168.1;
HRMS (ESI) exact mass calcd for C13H16O2S + K (M + K),
275.0508; Found: 275.0501.
Scheme 2. Plausible mechanism for synthesis of thioethers 4a
3. Conclusions
In conclusions, we have developed the metal free unexpected
and unprecedented regio- and stereoselective synthesis of allyl
methyl and allyl phenyl thioethers from allyl halides via the C-S
coupling reaction using sulfoxides as a sulfenylating agent for the
first time. In presence of phenyl disulfide and DCP, the DMSO
and DPSO resulted into in-situ formation of SMe and SPh group
respectively which underwent the C-S bond formation with allyl
halides to provide the thioethers in good to excellent yields.
During the reactions the stereochemistry around the double bond
found unchanged. Both the allyl bromides and iodides were
employed for this fascinating reactions and allyl bromides
provided the superior results over iodides.
4.3.2. Synthesis of methyl (Z)-3-(4-methoxyphenyl)-2-
((methylthio)methyl)acrylate (entry 2, 4c). The title compound
was prepared following the general procedure for Table 2, using
allyl bromide 1c i.e. methyl (Z)-2-(bromomethyl)-3-(4-
methoxyphenyl)acrylate (2.0 mmol, 0.570 g), diphenyl disulfide
(1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DMSO (2.0
mL), providing 4c as pale yellow oil. Yield: 0.413 g, 82%; Rf
4. Experimental section
4.1. General remarks
1
(6% EtOAc/hexanes) 0.19; H NMR (400 MHz, CDCl3): δ 2.07
(s, 3 H), 3.60 (s, 2 H), 3.75 (s, 3 H), 3.76 (s, 3 H), 6.87 (d, J = 8.8
Hz, 2 H), 7.43 (d, J = 8.8 Hz, 2 H), 7.65 (s, 1 H); 13C NMR (100
MHz, CDCl3): δ 16.2, 30.7, 52.2, 114.1, 126.8, 127.4, 131.7,
140.7, 160.3, 168.2; HRMS (ESI) exact mass calcd for
C13H16O3S + K (M + K), 291.0457; Found: 291.0462.
All chemicals were purchased from commercial suppliers and
used without further purification. NMR spectra were recorded on
a JEOL Ressonanc-400 instrument using CDCl3/DMSO-d6 as
solvent. Chemical shifts are reported in parts per million (ppm)
and referenced to the residual solvent resonance. Coupling
constant (J) are reported in hertz (Hz). Standard abbreviations
indicating multiplicity were used as follows: s = singlet, d =
doublet, t = triplet, dd = double doublet, q = quartet, m =
4.3.3. Synthesis of methyl (Z)-3-(3-chlorophenyl)-2-
((methylthio)methyl)acrylate (entry 3, 4d). The title compound
was prepared following the general procedure for Table 2, using

4
Tetrahedron
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allyl bromide 1d i.e. methyl (Z)-2-(bromomethyl)-3-(3-
4.3.8. Synthesis of methyl (Z)-3-(4-chlorophenyl)-2-
chlorophenyl)acrylate (2.0 mmol, 0.579 g), diphenyl disulfide
(1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DMSO (2.0
mL), providing 4d as pale yellow oil. Yield: 0.467 g, 91%; Rf
((methylthio)methyl)acrylate (entry 10, 4e). The title compound
was prepared following the general procedure for Table 2, using
allyl iodide 1g i.e. methyl (Z)-3-(4-chlorophenyl)-2-
(iodomethyl)acrylate (2.0 mmol, 0.673 g), diphenyl disulfide (1.0
mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DMSO (2.0 mL),
providing 4e as pale yellow oil. Yield: 0.282 g, 55%. Spectral
data were found same as entry 4.
1
(6% EtOAc/hexanes) 0.25; H NMR (400 MHz, CDCl3): δ 2.07
(s, 3 H), 3.55 (s, 2 H), 3.81 (s, 3 H), 7.28-7.32 (m, 3 H), 7.44 (s, 1
H), 7.63 (s, 1 H); 13C NMR (100 MHz, CDCl3): δ 16.3, 29.7,
52.4, 127.6, 128.9, 129.5, 129.9, 130.7, 134.6, 136.8, 138.9,
167.1; HRMS (ESI) exact mass calcd for C12H13ClO2S + K (M +
K), 294.9962; Found: 294.9952.
4.3.9. Synthesis of methyl (Z)-3-(4-chlorophenyl)-2-
((phenylthio)methyl)acrylate (entry 11, 4h). The title compound
was prepared following the general procedure for Table 3, using
allyl iodide 1g i.e. methyl (Z)-2-(iodomethyl)-3-(4-
chlorophenyl)acrylate (2.0 mmol, 0.673 g), diphenyl disulfide
(1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DPSO (1.0
g), providing 4h as pale yellow oil. Yield: 0.325 g, 51%; Spectral
data were found same as entry 7.
4.3.4. Synthesis of methyl (Z)-3-(4-chlorophenyl)-2-
((methylthio)methyl)acrylate (entry 4, 4e). The title compound
was prepared following the general procedure for Table 2, using
allyl bromide 1e i.e. methyl (Z)-2-(bromomethyl)-3-(4-
chlorophenyl)acrylate (2.0 mmol, 0.579 g), diphenyl disulfide
(1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DMSO (2.0
mL), providing 4e as pale yellow oil. Yield: 0.462 g, 90%; Rf
(6% EtOAc/hexanes) 0.26; 1H NMR (400 MHz, CDCl3): δ 1.98
(s, 3 H), 3.51 (s, 2 H), 3.73 (s, 3 H), 7.43 (d, J = 8.8 Hz, 2 H),
7.51 (d, J = 8.8 Hz, 2 H), 7.59 (s, 1 H); 13C NMR (100 MHz,
DMSO-d6): δ 16.0, 30.4, 52.6, 129.2, 130.1, 131.8, 133.7, 134.4,
138.8, 167.4; HRMS (ESI) exact mass calcd for C12H13ClO2S +
K (M + K), 294.9962; Found: 294.9956.
4.3.10. Synthesis of methyl (Z)-2-((methylthio)methyl)-3-
phenylacrylate (entry 12, 4a).10 The title compound was prepared
following the general procedure for Table 3, using allyl iodide
1h i.e. methyl (2Z)-2-bromomethyl-3-phenylprop-2-enoate (2.0
mmol, 0.604 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP
(2.0 mmol, 0.540 g) and DMSO (2.0 mL), providing 4a as pale
yellow oil. Yield: 0.302 g, 68%. Spectral data were found same
as Table 1.
4.3.5.
Synthesis
of
methyl
(Z)-3-phenyl-2-
((phenylthio)methyl)acrylate (entry 5 , 4f). The title compound
was prepared following the general procedure for Table 3, using
allyl bromide 1a i.e. methyl (Z)-2-(bromomethyl)-3-
phenylacrylate (2.0 mmol, 0.510 g), diphenyl disulfide (1.0
mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DPSO (1.0 g),
providing 4f as pale yellow oil. Yield: 0.500 g, 88%; Rf (6%
4.3.11.
Synthesis
of
methyl
(Z)-3-phenyl-2-
((phenylthio)methyl)acrylate (entry 13 , 4f). The title compound
was prepared following the general procedure for Table 3, using
allyl iodide 1h i.e. methyl (Z)-2-(iodomethyl)-3-phenylacrylate
(2.0 mmol, 0.604 g), diphenyl disulfide (1.0 mmol, 0.218 g),
DCP (2.0 mmol, 0.540 g) and DPSO (1.0 g), providing 4f as pale
yellow oil. Yield: 0.352 g, 62%; Spectral data were found same
as entry 5.
1
EtOAc/hexanes) 0.26; H NMR (400 MHz, CDCl3): δ 3.77 (s, 3
H), 4.05 (s, 2 H) 7.20-7.38 (m, 3 H), 7.40-7.42 (m, 7 H), 7.79 (s,
1 H); 13C NMR (100 MHz, CDCl3): δ 32.3, 52.3, 126.8, 128.2,
128.7, 129.0, 129.1, 129.6, 130.7, 134.8, 136.0, 141.6, 167.5;
HRMS (ESI) exact mass calcd for C17H16O2S + K (M + K),
323.0508; Found: 323.0502.
4.3.12. Synthesis of methyl (Z)-2-((phenylthio)methyl)-3-(p-
tolyl)acrylate (entry 14, 4g). The title compound was prepared
following the general procedure for Table 3, using allyl iodide 1i
i.e. methyl (Z)-2-(iodomethyl)-3-(p-tolyl)acrylate (2.0 mmol,
0.632 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP (2.0
mmol, 0.540 g) and DPSO (1.0 g), providing 4g as pale yellow
oil. Yield: 0.382 g, 65%; Spectral data were found same as entry
6.
4.3.6. Synthesis of methyl (Z)-2-((phenylthio)methyl)-3-(p-
tolyl)acrylate (entry 6, 4g). The title compound was prepared
following the general procedure for Table 3, using allyl bromide
1b i.e. methyl (Z)-2-(bromomethyl)-3-(p-tolyl)acrylate (2.0
mmol, 0.538 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP
(2.0 mmol, 0.540 g) and DPSO (1.0 g), providing 4g as pale
yellow oil. Yield: 0.513 g, 86%; Rf (6% EtOAc/hexanes) 0.25;
1H NMR (400 MHz, CDCl3): δ 2.37 (s, 3 H), 3.81 (s, 3 H), 4.09
(s, 2 H), 7.17-7.22 (m, 3 H), 7.25-7.29 (m, 2 H), 7.37-7.42 (m, 4
H), 7.80 (s, 1 H); 13C NMR (100 MHz, CDCl3): δ 21.5, 32.3,
52.3, 126.7, 127.2, 129.0, 129.5, 129.8, 130.6, 132.0, 136.3,
139.4, 141.9, 167.8; HRMS (ESI) exact mass calcd for
C18H18O2S + K (M + K), 337.0665; Found: 337.0661.
4.4. General procedure for Table 3:
To a stirred solution of allyl bromide 5 (2.0 mmol) and
diphenyl disulfide (1.0 mmol, 0.218 g) in DMSO (2.0 mL) or
DPSO (1.0 g) was added DCP (2.0 mmol, 0.540 g) and then the
o
reaction mixture was stirred for 12 h at 80 C under nitrogen
atmosphere. The reaction mixture was then diluted with ethyl
acetate (10 mL) and water (5.0 mL). After usual workup, the
organic layer was dried over anhydrous Na2SO4, solvent was
evaporated . The crude products thus obtained was purified by
column chromatography (silica gel, 2% EtOAc in Hexanes) to
provide the thioether 6.
4.3.7. Synthesis of methyl (Z)-3-(4-chlorophenyl)-2-
((phenylthio)methyl)acrylate (entry 7, 4h). The title compound
was prepared following the general procedure for Table 3, using
allyl bromide 1e i.e. methyl (Z)-2-(bromomethyl)-3-(4-
chlorophenyl)acrylate (2.0 mmol, 0.579 g), diphenyl disulfide
(1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and DPSO (1.0
g), providing 4h as pale yellow oil. Yield: 0.527 g, 85%; Rf (6%
4.4.1.
Synthesis
of
(E)-2-((methylthio)methyl)-3-
phenylacrylonitrile (entry 1, 6a). The title compound was
prepared following the general procedure for Table 3, using allyl
bromide 5a i.e. (E)-2-(bromomethyl)-3-phenylacrylonitrile (2.0
mmol, 0.444 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP
(2.0 mmol, 0.540 g) and DMSO (2.0 mL), providing 6a as pale
yellow oil. Yield: 0.332 g, 88%; Rf (6% EtOAc/hexanes) 0.14;
1H NMR (400 MHz, CDCl3): δ 2.09 (s, 3 H), 3.40 (s, 2 H), 6.97
(s, 1 H), 7.39-7.41 (m, 3 H), 7.73-7.76 (m, 2 H); 13C NMR (100
MHz, CDCl3): δ 14.9, 29.8, 108.0, 118.2, 128.9, 129.0, 130.6,
1
EtOAc/hexanes) 0.23; H NMR (400 MHz, CDCl3): δ 3.78 (s, 3
H), 3.98 (s, 2 H), 7.20-7.28 (m, 3 H), 7.34 (m, 4 H), 7.34-7.36
(m, 2 H), 7.67 (s, 1 H); 13C NMR (100 MHz, CDCl3): δ 32.3,
52.4, 127.0, 128.8, 128.9, 129.0, 130.8, 131.1, 133.2, 135.0,
135.6, 140.1, 167.4; HRMS (ESI) exact mass calcd for
C17H15ClO2S + K (M + K), 357.0118; Found: 357.0112.

5
133.0, 144.2; HRMS (ESI) exact mass calcd for C11H1 NS + K
(M + K), 228.0249; Found: 228.0241.
H), 6.65 (s, 1 H), 7.27-7.35 (m, 6 H), 7.44-7.46 (m, 2 H), 7.58-
ACCEPTED MANUSCRIPT
1
7.59 (m, 2 H); 13C NMR (100 MHz, CDCl3): δ 41.1, 107.7,
118.2, 128.1, 128.8, 128.9, 129.3, 130.5, 132.9, 133.1, 133.5,
144.9; HRMS (ESI) exact mass calcd for C16H13NS + K (M + K),
290.0406; Found: 290.0409.
4.4.2. Synthesis of (E)-2-((methylthio)methyl)-3-(p-
tolyl)acrylonitrile (entry 2, 6b). The title compound was prepared
following the general procedure for Table 3, using allyl bromide
5b i.e. (E)-2-(bromomethyl)-3-(p-tolyl)acrylonitrile (2.0 mmol,
0.472 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP (2.0
mmol, 0.540 g) and DMSO (2.0 mL), providing 6b as pale
yellow oil. Yield: 0.357 g, 88%; Rf (6% EtOAc/hexanes) 0.25;
1H NMR (400 MHz, CDCl3): δ 2.07 (s, 3 H), 2.34 (s, 3 H), 3.36
(s, 2 H), 6.92 (s, 1 H), 7.19 (d, J = 8.4 Hz, 2 H), 7.65 (d, J = 8.4
Hz, 2 H); 13C NMR (100 MHz, CDCl3): δ 14.8, 21.6, 29.8, 106.7,
118.4, 128.9, 129.7, 130.3, 141.0, 144.3, HRMS (ESI) exact
mass calcd for C12H13NS + K (M + K), 242.0406; Found:
242.0412.
4.4.7.
Synthesis
of
(E)-2-((phenylthio)methyl)-3-(p-
tolyl)acrylonitrile (entry 7, 6g). The title compound was prepared
following the general procedure for Table 3, using allyl bromide
5b i.e. (E)-2-(bromomethyl)-3-(p-tolyl)acrylonitrile (2.0 mmol,
0.472 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP (2.0
mmol, 0.540 g) and DPSO (1.0 g), providing 6g as pale yellow
oil. Yield: 0.420 g, 79%; Rf (6% EtOAc/hexanes) 0.21; 1H NMR
(400 MHz, CDCl3): δ 2.38 (s, 3 H), 4.19 (s, 2 H), 7.15 (s, 1 H),
7.22 (d, J = 8.0 Hz, 2 H), 7.26-7.46 (m, 5 H), 7.68 (d, J = 8.0 Hz,
2 H); 13C NMR (100 MHz, CDCl3): δ 21.7, 33.4, 106.6, 117.5,
125.7, 126.9, 128.0, 129.4, 129.8, 142.2, 146.7; HRMS (ESI)
exact mass calcd for C17H15NS + K (M + K), 304.0562; Found:
304.0556.
4.4.3.
Synthesis
of
(E)-3-(2-bromophenyl)-2-
((methylthio)methyl)acrylonitrile (entry 3, 6c). The title
compound was prepared following the general procedure for
Table 3, using allyl bromide 5c i.e. (E)-2-(bromomethyl)-3-(2-
bromophenyl)acrylonitrile (2.0 mmol, 0.601 g), diphenyl
disulfide (1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and
DMSO (2.0 mL), providing 6c as pale yellow oil. Yield: 0.439 g,
82%; Rf (6% EtOAc/hexanes) 0.22; 1H NMR (400 MHz,
CDCl3): δ 2.10 (s, 3 H), 3.40 (s, 2 H), 7.20-7.22 (m, 2 H), 7.23-
7.37 (m, 1 H), 7.58 (d, J = 7.2 Hz, 1 H), 7.87 (d, J = 8.0 Hz, 1 H);
13C NMR (100 MHz, CDCl3): δ 14.9, 38.7, 111.6, 117.3, 124.2,
127.9, 129.6, 131.5, 133.0, 133.5, 143.2; HRMS (ESI) exact
mass calcd for C11H10BrNS + K (M + K), 305.9354; Found:
305.9367.
4.4.8.
Synthesis
of
(E)-2-((methylthio)methyl)-3-
phenylacrylonitrile (entry 8, 6a). The title compound was
prepared following the general procedure for Table 3, using allyl
iodide 5f i.e. (E)-2-(iodomethyl)-3-phenylacrylonitrile (2.0
mmol, 0.538 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP
(2.0 mmol, 0.540 g) and DMSO (2.0 mL), providing 6a as pale
yellow oil. Yield: 0.196 g, 52%; Spectral data were found same
as entry 1.
4.4.9.
Synthesis
of
(E)-2-((methylthio)methyl)-3-(p-
tolyl)acrylonitrile (entry 9, 6b). The title compound was prepared
following the general procedure for Table 3, using allyl iodide 5g
i.e. (E)-2-(iodomethyl)-3-(p-tolyl)acrylonitrile (2.0 mmol, 0.566
g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP (2.0 mmol,
0.540 g) and DMSO (2.0 mL), providing 6b as pale yellow oil.
Yield: 0.194 g, 48%; Spectral data were found same as entry 2.
4.4.4.
Synthesis
of
(E)-3-(3-chlorophenyl)-2-
((methylthio)methyl)acrylonitrile (entry 4, 6d). The title
compound was prepared following the general procedure for
Table 3, using allyl bromide 5d i.e. (E)-2-(bromomethyl)-3-(3-
chlorophenyl)acrylonitrile (2.0 mmol, 0.513 g), diphenyl
disulfide (1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and
DMSO (2.0 mL), providing 6d as pale yellow oil. Yield: 0.405 g,
91%; Rf (6% EtOAc/hexanes) 0.21; 1H NMR (400 MHz,
CDCl3): δ 2.10 (s, 3 H), 3.40 (s, 2 H), 6.92 (s, 1H), 7.35-7.36 (m,
2 H), 7.65 (s, 1 H),7.68-7.70 (m, 1 H); 13C NMR (100 MHz,
CDCl3): δ 15.0, 39.2, 110.0, 117.6, 126.6, 128.5, 129.0, 130.5,
134.7, 134.9, 142.4; HRMS (ESI) exact mass calcd for
C11H10ClNS + K (M + K), 261.9860; Found: 261.9859.
4.4.10.
Synthesis
of
(E)-2-((phenylthio)methyl)-3-(p-
tolyl)acrylonitrile (entry 10, 6g). The title compound was
prepared following the general procedure for Table 3, using allyl
iodide 5g i.e. (E)-2-(iodomethyl)-3-(p-tolyl)acrylonitrile (2.0
mmol, 0.566 g), diphenyl disulfide (1.0 mmol, 0.218 g), DCP
(2.0 mmol) and DPSO (1.0 g), providing 6g as pale yellow oil.
Yield: 0.217g, 41%; Spectral data were found same as entry 7.
Acknowledgement:
SERB-DST,
New
Delhi
(YSS/2015/001870) and UGC-India (Start-up grant) are
gratefully acknowledged for financial support. P.S. thanks the
UGC and R.B. thanks the SERB-DST for their fellowships.
S.S.B. is DST INSPIRE Faculty (IFA-2014/CH-167), DST-India.
We thank MRC-MNIT Jaipur for NMR and USIC-University of
Rajasthan, Jaipur for HRMS & GCMS data collection.
4.4.5.
Synthesis
of
(E)-3-(4-chlorophenyl)-2-
((methylthio)methyl)acrylonitrile (entry 5, 6e). The title
compound was prepared following the general procedure for
Table 3, using allyl bromide 5e i.e. ((E)-2-(bromomethyl)-3-(4-
chlorophenyl)acrylonitrile (2.0 mmol, 0.513 g), diphenyl
disulfide (1.0 mmol, 0.218 g), DCP (2.0 mmol, 0.540 g) and
DMSO (2.0 mL), providing 6e as pale yellow oil. Yield: 0.402 g,
88%; Rf (6% EtOAc/hexanes) 0.20; 1H NMR (400 MHz,
CDCl3): δ 2.04 (s, 3 H), 3.35 (s, 2 H), 6.88 (s, 1 H), 7.30 (d, J =
8.8 Hz, 2 H), 7.63 (d, J = 8.8 Hz, 2 H); 13C NMR (100 MHz,
CDCl3): δ 14.9, 29.7, 108.8, 117.9, 129.1, 130.1, 131.5, 136.3,
142.6; HRMS (ESI) exact mass calcd for C11H10ClNS + K (M +
K), 261.9860; Found: 261.9851.
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Synthesis
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(E)-3-phenyl-2-
((phenylthio)methyl)acrylonitrile (entry 6, 6f). The title
compound was prepared following the general procedure for
Table 3, using allyl bromide 5a i.e. (E)-2-(bromomethyl)-3-
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1
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6
Tetrahedron
ACCEPTED MANUSCRIPT
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