One-pot synthesis of sulfides by reaction of disulfides with alkyl halides in the presence of sodium dithionite

Article abstract of DOI:10.1080/10426500600892479

Sodium dithionite-promoted synthesis of unsymmetrical diorganyl sulfides by a reaction of diaryl disulfides with alkyl halides at r.t. has been developed. The advantages offered by this method are operational simplicity, a faster reaction, neutral and mild reaction conditions, and moderate to good yields of products.

Full text of DOI:10.1080/10426500600892479

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Phosphorus, Sulfur, and Silicon
and the Related Elements
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One-Pot Synthesis of Sulfides
by Reaction of Disulfides with
Alkyl Halides in the Presence of
Sodium Dithionite
Ri-Yuan Tang a , Ping Zhong a & Qiu-lian Lin a
a The School of Chemistry and Material Science ,
Wenzhou University , Wenzhou, P.R. China
Published online: 01 Feb 2007.
To cite this article: Ri-Yuan Tang , Ping Zhong & Qiu-lian Lin (2007) One-Pot Synthesis
of Sulfides by Reaction of Disulfides with Alkyl Halides in the Presence of Sodium
Dithionite, Phosphorus, Sulfur, and Silicon and the Related Elements, 182:1, 167-174,
DOI: 10.1080/10426500600892479
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Phosphorus, Sulfur, and Silicon, 182:167–174, 2007
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500600892479
One-Pot Synthesis of Sulfides by Reaction of Disulfides
with Alkyl Halides in the Presence of Sodium Dithionite
Ri-Yuan Tang
Ping Zhong
Qiu-lian Lin
The School of Chemistry and Material Science, Wenzhou University,
Wenzhou, P.R. China
Sodium dithionite-promoted synthesis of unsymmetrical diorganyl sulfides by a
reaction of diaryl disulfides with alkyl halides at r.t. has been developed. The ad-
vantages offered by this method are operational simplicity, a faster reaction, neutral
and mild reaction conditions, and moderate to good yields of products.
Keywords Disulfide; electron transfer; one-pot; sodium dithionite; sulfide
INTRODUCTION
Organic sulfides are useful chemical intermediates in organic
synthesis,1 and a C S bond can be found in many molecules that are
of biological, pharmaceutical, and materials interest.2 The formation
of a C S bond is usually achieved by the reaction of thiolate or thiol
with organic halides. However, these reactions require harsh reaction
conditions, and the yields and reaction conditions depend on the sol-
vent, strong basic catalyst, and acidity of thiol.3 Recently, Yin and
Pidgeon3c reported a high-yield method for the preparation of unsym-
metrical sulfides using very strong basic n-butyllithium. For developing
mild reaction conditions, Shah et al.4 reported a synthesis method of
thioethers using CsF–Celite in acetonitrile. Transition metal-mediated
alkylation has also been developed for the preparation of thioethers,5
which is a mild and efficient method. For example, a one-pot and
Received February 26, 2006; accepted June 6, 2006.
This project was supported by the National Natural Science Foundation of China
(No. 20572079) and the National Natural Science Foundation of Zhejiang Province
(Nos. Y205540 and Y404039). Supported by the Postgraduate Innovation Foundation
of Wenzhou University (No. YCX0514).
Address correspondence to Ping Zhong, The School of Chemistry and Material Science,
Wenzhou University, Wenzhou, P.R. China. E-mail: zhomgp0512@163.com
167

168
R.-Y. Tang et al.
RS
S
CN
CN
H2N
Cl
N
H2N
Cl
N
N
Na2S2O4/Na2HPO4
DMF,H2O r.t.
N
RBr
+
Cl
Cl
CF3
CF3
2
1
2
3
SCHEME 1
base-free conversion of disulfides to sulfides using an in-situ generated
organocobalt(III) reagent had been studied.6 A general and efficient Cu-
catalyzed carbon-sulfur bond formation under mild conditions has also
been reported.7 Indium(I) iodide-mediated cleavage of disulfides and
subsequent reaction with alkyl halides at r.t., and give high yields.8
Although these metal-mediated synthestic methods have made big
progress in the synthesis of thioether, the development of a one-step
synthetic method using commercial and cheaper reagents under neu-
tral conditions has attracted much attention. Recently we reported the
use of sodium dithionite9 for the synthesis of pyrazolyl alkyl sulfides 3
(Scheme 1).10 In this article, we demonstrate a further extension of this
work together with the application of sodium dithionite for the synthe-
sis of diorganyl sulfides 6 by a reaction of diaryl disulfides 4 with alkyl
halides (Scheme 2).
RESULTS AND DISCUSSION
The experimental procedure was very simple. A mixture of alkyl halide
and diaryl disulfide in dimethylformamide (DMF) as a 4:l cosolvent
with H2O was stirred in the presence of sodium dithionite at r.t. for a
certain period of time (TLC). Usual workup and extraction with ether
provided the product.
Na2S2O4/Na2HPO4
R
R`
S
R
R
+
R`X
S
S
DMF, H2O r.t.
4
5
6
4a: R=NO2
4b: R=Cl
SCHEME 2

One-Pot Synthesis of Sulfides
169
TABLE I The Synthesis of Compounds 6a–l
Entry
R
RꢀX
m.p.(◦C)
Reaction Time (h) Isolated Yield (%)
6a
6b
6c
NO2
NO2
NO2
CH3I
C2H5Br
n-C3H7Br
71∼72
37∼38
Liquid
0.2
0.3
0.3
82
56
49
6d
6e
NO2
NO2
36∼37
0.25
0.25
68
73
Br
118∼119
CH2Br
O
6f
NO2
115∼116
0.3
71
CH2Br
6g
6h
6i
Cl
Cl
Cl
CH3I
C2H5Br
n-C3H7Br
18∼19
Liquid
Liquid
3
5
5
65
48
41
6j
Cl
Liquid
4
53
Br
CH2Br
6k
Cl
49∼50
4
57
O
6l
Cl
78∼79
5
51
CH2Br
Diverse alkyl halides underwent reactions with diaryl disulfides by
this procedure to produce the corresponding alkyl aryl sulfides, respec-
tively, in moderate to good yields. The results are presented in Table I.
As evident from Table I, alkyl, allylic, benzyl, benzyl bromides and
bromoaceto phenone and methyl iodides could participate in this re-
action to form the corresponding products. In general, the reaction of
4b took longer (3–5 h) than 4a (<30 min) by this procedure. However,
aryl halides and vinyl halides remained inactive in this reaction; on
the other hand, nonaromatic disulfides failed to undergo any reaction
by this reaction system. Proton and carbon-13 NMR data is presented
here. From the data, we found that the variation of the chemical shifts
on the CH2 connecting the sulfur atom were inagreement with the the-
oretic variation. When the CH2 bearing an alkyl, 1H, and 13C shift move
toward the lower magnetic field, while having the p-ꢀ conjugation ef-
fect, both shifts move toward the higher magnetic field. For example,
the shift change in compounds 6a–f is increasing.
We have speculated that sodium dithionite could serve as an electron
source for the cleavage of an S S bond or the dehalogenation of alkyl
halides. Therefore, two reaction pathways for the formation of alkyl

170
R.-Y. Tang et al.
Path 1
_
S2O42
_
.
SO2
.
e
+
2 SO2
_
ArSSAr+ e
ArS
_
+
ArS
RX
.
.
+ e
ArS
ArS
Path 2
ArSR
2 -
S 2 O 4
A r S S A r
R x
A r S R
R
SCHEME 3 Possible reaction pathways for the formation of sulfides.
phenyl sulfides are shown in Scheme 3. This reaction procedure might
involve Electronic Transfer (ET). Electron uptake by S S caused the
breaking of the S S bond to yield a radical (ArS·) and an anion (ArS-).
Therefore, the reactions were going through the intermediacy of a radi-
cal and an anion, which formed readily by the reaction of an electron re-
leased by sodium dithionite with diaryl disulfide. Then the anion (ArS-)
was alkylated with alkyl halide (Path 1). Another pathway including
the reaction of alkyl radicals, which was generated by the reduction of
alkyl halides with sodium dithionite, with aryl disulfides was suggested
(Path 2). It was said that sodium dithionite was capable of producing
the alkyl free radicals from alkyl halides.9m−q Moreover, the SO2 radical
anion, which can release an electron, was readily detected by electron
spin resonance in solutions of decomposing S2O4,2−11 so both pathways
would be possible.
Theoretical analysis about the reactions of disulfides involving ET
processes have been reported.12−15 S. Antonello et al.12 suggested that
with diaryl disulfides bearing electron-donating or mildly electron-
withdrawing groups, the inner reorganization is particularly large,
which reflects the significant stretching of the S S bond experienced by
the molecule upon ET. With electron-withdrawing groups, the extent of
delocalization of the SOMO (singly occupied MO) onto the aryl system
increases, leading to a decrease of the reorganization energy for radi-
cal anion formation. From the previous description, we should consider
that the stabilization of the formed radicals plays an important role
in the reaction. The ArS· radical-bearing electron-withdrawing groups
have higher stabilization than that of one bearing electron-donating
or mildly electron-withdrawing groups. It is well known that nitro is
strong electron-withdrawing group, while the chloro- is a mild one.
Thus, the formation of radical from 4a is much more easy than that
from 4b. That is why the reaction of 4a took much shorter time than 4b
by this procedure.

One-Pot Synthesis of Sulfides
171
It can be concluded that a one-pot procedure for the synthesis of alkyl
aryl sulfides has been developed. Although the result in this article is
not better than that carried out by transition metal,6,7c,8,16 this work
demonstrates the synthetic potential of sodium dithionite and develops
a free-base and free-metal synthestic method of aryl alkyl sulfides. The
significant advantages offered by this method are operational simplic-
ity, a faster reaction, neutral and mild (r.t.) reaction conditions, and
moderate to good yields of products.
EXPERIMENTAL
All melting points were determined with a Thomas-Hoover melting
1
point apparatus. The thermometer was not standardized. H spectra
were recorded at 300 MHz (1H) and 13C at 75 Mz on a (13C) spectrom-
eter using CDCl3 as a solvent with TMS as the internal standard. J
values are given in Hz. IR spectra were measured on a FTIR spectropho-
tometer as KBr disks. Silica gel 60 GF254 was used for analytical and
preparative TLC.
General Procedure for Synthesis of 6a–l
Aryl disulphide 4 (0.3 mmol) was dissolved in dimethylformamide
(8 mL); sodium hydrogen phosphate (0.15 g, 0.42 mmol) was dissolved
in water (2 mL). The dimethylformamide solution was then introduced
into a 50-mL glass reactor; alkyl halide 5 (0.72 mmol) was injected
into the mixture, followed by the aqueous solution. Sodium dithionite
(0.075 g, 0.42 mmol) was introduced in its turn with stirring. After a
certain period of time, water (50 mL) was then added, and this latter
mixture was subjected to a careful extraction with a portion of ethyl
ether (20 × 3 mL). The ether phase was separated off. The ether phase
was then eluted by water (20 × 2 mL). Finally, dehydrated MgSO4 and
the product were subjected to chromatography on a column of silica
gel, eluting with petroleum ether and ethyl acetate. The solution was
removed under reduced pressure, giving sulfide 6.
1
1-Methylthio-4-nitrobenzene 6a H NMR (300 MHz, CDCl3) δ 2.56
(3H, s, SCH ), 7.28 (2H, dd, JD 1.9, JD 9.0, ArH), 8.14 (2H, dd, JD
3
1.9, JD 9.0, ArH). 13C NMR (75 MHz, CDCl3) δ 14.8 (1C, SCH ), 123.9
3
(2C, Ar), 125.0 (2C, Ar), 144.7 (1C, Ar), 148.8 (1C, Ar). Anal. calcd. for
C7H7NO2S: C, 49.69; H, 4.17. Found: C, 49.51; H, 4.07.
1-Ethylthio-4-nitrobenzene 6b 1H NMR (300 MHz, CDCl3) δ 1.40 (3H,
t, JD 7.4, SCH2CH ), 2.56 (2H, q, JD 7.4, SCH2CH ), 7.31 (2H, dd, JD
3
3
1.9, JD 7.1, ArH), 8.12 (2H, dd, JD 1.9, JD 7.1, ArH). 13C NMR (75 MHz,
CDCl3) δ 13.7 (1C, SCH CH ), 26.0 (1C, SCH2CH3), 123.9 (2C, Ar), 126.0
2
3

172
R.-Y. Tang et al.
(2C, Ar), 144.9 (1C, Ar), 147.9 (1C, Ar). Anal. calcd. for C8H9NO2S: C,
52.44; H, 4.95. Found: C, 52.32; H, 4.80.
1
1-Propylthio-4-nitrobenzene 6c H NMR (300 MHz, CDCl3) δ 1.09
(3H, t, JD 7.3, SCH2CH2CH ), 1.76 (2H, m, SCH CH CH3), 3.01 (2H,
3
2
2
t, JD 7.3, SCH CH CH3), 7.31 (2H, dd, JD 1.8, JD 7.0, ArH), 8.12
2
2
(2H, dd, JD 1.8, JD 7.0, ArH). 13C NMR (75 MHz, CDCl3) δ 13.4
(1C, SCH2CH2CH ), 21.8 (1C, SCH2CH2CH3), 33.8 (1C, SCH2CH2CH3),
3
123.8 (2C, Ar), 125.9 (2C, Ar), 144.7 (1C, Ar), 148.0 (1C, Ar). Anal. calcd.
for C9H11NO2S: C, 54.80; H, 5.62. Found: C, 54.63; H, 5.51.
1
1-Nitro-4-((2-propenyl)thio)-benzene 6d H NMR (300 MHz, CDCl3)
δ 3.68 (2H, t, JD 6.5, SCH2CH CH2), 5.22 (1H, dd, JD 1.0, JD 10.5,
SCH2CH CH2), 5.33 (1H, dd, JD 1.0, JD 17.0, SCH2CH CH2), 5.85
(1H, m, SCH2CH CH2), 7.34 (2H, dd, JD 2.0, JD 7.0, ArH), 8.12 (2H,
dd, JD 2.0, JD 7.0, ArH). 13C NMR (75 MHz, CDCl3) δ 35.2 (1C,
SCH2CH CH2), 119.0 (1C, SCH2CH CH2), 123.8 (2C, Ar), 126.8 (2C,
Ar), 131.9 (1C, SCH2CH CH2), 145.2 (1C, Ar), 146.8 (1C, Ar). Anal.
calcd. for C9H9NO2S: C, 55.37; H, 4.65. Found: C, 55.16; H, 4.50.
1-Nitro-4-(phenylmethylthio)-benzene 6e 1H NMR (300 MHz, CDCl3)
δ 4.26 (2H, s, SCH2C6H5), 7.30 (5H, m, SCH2C6H5), 7.38 (2H, dd, JD
1.9, JD 7.5, ArH), 8.12 (2H, dd, JD 1.9, JD 7.5, ArH). 13C NMR (75 MHz,
CDCl3) δ 37.0 (1C, SCH2C6H5), 123.8 (2C, Ar), 126.8 (2C, Ar), 127.8 (1C,
Ar) 128.7 (2C, Ar) 128.9 (2C, Ar), 135.4 (1C, Ar), 145.2 (1C, Ar), 147.3
(1C, Ar). Anal. calcd. for C13H11NO2S: C, 63.65; H, 4.52. Found: C, 63.42;
H, 4.45.
2-[(4-Nitrophenyl)thio]-1-phenyl-1-ethanone 6f 1H NMR (300 MHz,
CDCl3) δ 4.46 (2H, s, SCH2COC6H5), 7.42 (2H, d, JD 8.9, ArH), 7.50
(2H, m, SCH2COC6H5), 7.63 (1H, d, JD 7.4, SCH2COC6H5), 8.00 (2H,
d, JD 7.5, SCH2COC6H5), 8.13 (2H, d, JD 8.9, ArH). 13C NMR (75 MHz,
CDCl3) δ 39.1 (1C, SCH2COC6H5), 124.0 (2C, Ar), 12H (2C, Ar), 128.6
3
(2C, Ar) 128.9 (2C, Ar) 134.0 (1C, Ar), 134.9 (1C, Ar), 145.3 (1C, Ar),
145.6 (1C, Ar), 192.7 (1C, C O). Anal. calcd. for C14H11NO3S: C, 61.53;
H, 4.06. Found: C, 61.22; H, 4.00.
1-Chloro-4-methylthiobenzene 6g 1H NMR (300 MHz, CDCl3) δ 2.47
(3H, s, SCH3), 7.18 (2H, dd, JD 1.9, JD 8.5, ArH), 7.26 (2H, dd, JD
1.9, JD 8.5, ArH). 13C NMR (75 MHz, CDCl3) δ 16.0 (1C, SCH3), 127.8
(2C, Ar), 128.9 (2C, Ar), 130.8 (1C, Ar), 137.0 (1C, Ar). Anal. calcd. for
C7H7ClS: C, 53.00; H, 4.45. Found: C, 52.85; H, 4.39.
1
1-Chloro-4-ethylthiobenzene 6h H NMR (300 MHz, CDCl3) δ 1.31
(3H, t, JD 7.4, SCH2CH3), 2.92 (2H, q, JD 7.4, SCH2CH3), 7.25 (4H,
s, ArH). 13C NMR (75 MHz, CDCl3) δ 14.2 (1C, SCH2CH3), 27.9 (1C,
SCH2CH3), 128.9 (2C, Ar), 130.3 (2C, Ar), 131.7 (1C, Ar), 135.1 (1C,
Ar). Anal. calcd. for C8H9ClS: C, 55.65; H, 5.25. Found: C, 55.48; H,
5.14.

One-Pot Synthesis of Sulfides
173
1
1-Chloro-4-propylthiobenzene 6i H NMR (300 MHz, CDCl3) δ 1.02
(3H, t, JD 7.5, SCH2CH2CH3), 1.62 (2H, m, SCH2CH2CH3), 2.85 (2H, t,
JD 6.5, SCH2CH2CH3), 7.22 (2H, d, JD 5.1, ArH), 7.26 (2H, d, JD 5.1,
ArH). 13C NMR (75 MHz, CDCl3) δ 13.3 (1C, SCH2CH2CH3), 22.4 (1C,
SCH2CH2CH3), 35.8 (1C, SCH2CH2CH3), 128.9 (2C, Ar), 130.3 (2C, Ar),
131.6 (1C, Ar), 135.4 (1C, Ar). Anal. calcd. for C9H11ClS: C, 57.90; H,
5.94. Found: C, 57.77; H, 5.73.
1
1-Chloro-4-[(2-propenyl)thio]benzene 6j H NMR (300 MHz, CDCl3)
δ 3.52 (2H, t, JD 6.9, SCH2CH CH2), 5.08 (1H, dd, JD 1.4, JD 7.2,
SCH2CH CH2), 5.12 (1H, dd, JD 1.4, JD 14.1, SCH2CH CH2) 5.85
(1H, m, SCH2CH CH2), 7.26 (2H, s, ArH), 7.27 (2H, s, ArH). 13C NMR
(75 MHz, CDCl3) δ 37.4 (1C, SCH2CH CH2), 117.9 (1C, SCH2CH CH2),
128.9 (2C, Ar), 131.3 (2C, Ar), 132.3 (1C, Ar), 133.2 (1C, SCH2CH CH2),
134.3 (1C, Ar). Anal. calcd. for C9H9ClS: C, 58.53; H, 4.91. Found: C,
58.36; H, 4.78.
1-Chloro-4-(phenylmethylthio)-benzene 6k 1H NMR (300 MHz,
CDCl3) δ 4.11 (2H, s, SCH2C6H5), 7.24 (4H, s, ArH), 7.31 (5H, m,
SCH2C6H5). 13C NMR (75 MHz, CDCl3) δ 39.2 (1C, SCH2C6H5), 127.2
(2C, Ar), 128.5 (2C, Ar), 128.7 (2C, Ar) 128.9 (2C, Ar) 131.3 (1C, Ar),
132.4 (1C, Ar), 134.6 (1C, Ar), 137.0 (1C, Ar). Anal. calcd. for C13H11ClS:
C, 66.52; H, 4.72. Found: C, 66.41; H, 4.55.
1
2-[(4-Chlorophenyl)thio]-1-phenyl-ethanone 6l H NMR (300 MHz,
CDCl3) δ 4.25 (2H, s, SCH2COC6H5), 7.24 (2H, dd, JD 2.0, JD 6.5, ArH),
7.31 (2H, dd, JD 2.0, JD 6.5, ArH), 7.48 (2H, m, SCH2COC6H5), 7.58 (1H,
d, JD 7.4, SCH2COC6H5), 7.94 (2H, d, JD 8.6, SCH2COC6H5). 13C NMR
(75 MHz, CDCl3) δ 41.2 (1C, SCH2COC6H5), 128.6 (2C, Ar), 128.7 (2C,
Ar), 129.2 (2C, Ar) 131.9 (2C, Ar) 133.1 (1C, Ar), 133.3 (1C, Ar), 133.6
(1C, Ar), 135.2 (1C, Ar), 193.7 (1C, C O). Anal. calcd. for C14H11ClOS:
C, 64.00; H, 4.22. Found: C, 63.85; H, 4.11.
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