Synthesis and nano-Pd catalyzed chemoselective oxidation of symmetrical and unsymmetrical sulfides

Article abstract of DOI:10.1039/c8ob03209b

A highly chemoselective, efficient and nano-Pd catalyzed protocol for the rapid construction of sulfoxides and sulfones via the oxidation of symmetrical and unsymmetrical sulfides using H₂O₂ as an oxidant has been developed, respectively. The ready availability of starting materials, easy recovery and reutilization of the catalyst, wide substrate scope, and high yields make this protocol an attractive alternative. The process also involves the metal-free and microwave-promoted synthesis of symmetrical diarylsulfides, and FeCl₃-mediated preparation of symmetrical diaryldisulfides through the reaction of arenediazonium tetrafluoroborates with Na₂S·9H₂O as a sulfur source. In addition, unsymmetrical sulfides were generated via the K₂CO₃-mediated reaction of arenediazonium tetrafluoroborates with symmetrical disulfides.

Full text of DOI:10.1039/c8ob03209b

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DOI: 10.1039/C8OB03209B
Organic & Biomolecular Chemistry
ARTICLE
Synthesis and Nano-Pd catalyzed chemoselective oxidation of
symmetrical and unsymmetrical sulfides
Xing Li,* Jia Du, Yongli Zhang, Honghong Chang, Wenchao Gao, Wenlong Wei
Received 00th January 20xx,
Accepted 00th January 20xx
A highly chemoselective, efficient and nano-Pd catalyzed protocol for the rapid construction of sulfoxides and sulfones via
the oxidation of symmetrical and unsymmetrical sulfides using H2O2 as an oxidant has been developed, respectively. The
ready availability of starting materials, easy recovery and reutilization of the catalyst, wide substrate scope, and high yields
make this protocol an attractive alternative. The process also involves the metal-free and microwave-promoted synthesis of
symmetrical diarylsulfides, and FeCl3-mediated preparation of symmetrical diaryldisulfides through the reaction of
arenediazonium tetrafluoroborates with Na2S·9H2O as a sulfur source. In addition, unsymmetrical sulfides were generated
via the K2CO3-mediated reaction of arenediazonium tetrafluoroborates with symmetrical disulfides.
DOI: 10.1039/x0xx00000x
www.rsc.org/
presence of an oxidant.5 However, readily oxidizable, foul-
smelling, and less available arenethiols were required in these
procedures. Although some homocouplings of sodium
Introduction
Aromatic organosulfur molecules such as thioethers, disulfides,
sulfoxides and sulfones are widely present in nature, and are
often found in biologically and pharmaceutically active
compounds, as well as organic materials. They commonly serve
as useful synthetic intermediates in organic reactions, too.
Therefore, the development of novel, efficient and
environmentally benign methodologies for the construction of
these molecules is very important.
Symmetrical diaryl thioethers are commonly prepared via
the metal-catalyzed reactions of aryl halides with different
sulfur surrogates in the presence of a base.1 However, these
methods typically require high temperature and are restricted
to the existence of a metal catalyst and base. An interesting
alternative synthesis of these compounds via the metal-
catalyzed deoxygenation reduction of sulfoxides was
documented.2 Recently, it has been demonstrated that thionyl
chloride (SOCl2) and triphenylphosphine (Ph3P) can also be used
to finish the reaction without the use of any metal.3 However,
the approach is limited to the use of stoichiometric amount of
SOCl2. Despite the value of these methods, it is highly appealing
to develop greener and simpler methods for constructing
various diaryl thioethers. Microwave irradiation has been
widely recognized as an efficient synthetic tool.4 To date,
nevertheless, no report was observed for the synthesis of
symmetrical diaryl thioethers involving the use of microwave.
The traditional method utilized to generate symmetrical
diaryl disulfides is the oxidative coupling of thiols in the
arenesulfinates have been disclosed, complex reaction system,
narrow substrate scope and low yields were unavoidable.6
Recently, some improvements have been directed to the use of
sulfur transfer reagents and aryl halides as coupling partner.7
Additionally, arenediazonium tetrafluoroborates could be
transferred into diary disulfides by employing CS2 as a sulfer
source,8 and the use of Na2S as an efficient sulfur transfer
reagent has also been observed for the synthesis of alkyl
disulfides.9 Despite these achievements, to the best of our
knowledge, a successful example for the synthesis of diaryl
disulfides through the reaction of arenediazonium
tetrafluoroborates with Na2S·9H2O remains unknown.
So far, considerable efforts have been paid to develop
efficient synthetic strategies for the formation of
unsymmetrical arylsulfides10 such as deoxygenation of
sulfoxides11,
decarbonylative
thioetherification12
and
sulfenylation of organic reagents with arylsulfonyl chlorides or
sodium arylsulfinates13. Among them, the cross couplings of aryl
halides with thiols are proven to be more prominent.14
Especially, Pd, Cu, Ni, Co, Fe and Rh-based catalytic systems
have been extensively studied.15 However, these processes are
limited to the use of thiols, ligands or transition metals.
Although the coupling of two aromatic substrates is also proven
to be versatile in the presence of different sulfur-containing
reagents,16 most of them required the utilization of a transition
metal or lower yields were obtained. Recently, the cross
couplings of symmetrical diaryl disulfides with aromatic
reagents17 such as arylboronic acids,18 aryl halides19 and
arenediazonium tetrafluoroborates20 provided efficient access
to unsymmetrical arylsulfides. Despite these significant
advances, the development of novel alternative methods that
employs inexpensive reagents or promoters is highly desirable.
a X. Li, J. Du, Y. Zhang, H. Chang, W. Gao, W. Wei
College of Biomedical Engineering, Taiyuan University of Technology, 79 West Yingze
Street, Taiyuan 030024, People’s Republic of China.
E-mail: lixing@tyut.edu.cn
† Footnotes relating to the title and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [details of any supplementary
information available should be included here]. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
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In general, selective catalytic oxidation of sulfides to
Journal Name
Table 1 Optimization of reaction conditions under microwave irradiationa
View Article Online
DOI: 10.1039/C8OB03209B
sulfoxides is one of the most efficient approaches in the
presence of various oxidants.21 Such, the choice of oxidants and
catalysts is crucial. The use of hydrogen peroxide (H2O2) or
molecular O2 as an oxidant is more attractive because it is a
readily available, inexpensive, and environmentally friendly
oxidizing agent.22 In terms of catalysts, many metal-based
catalytic systems23 and metal-free catalysts24 have been well
reported. However, these available protocols still suffer from
one or more limitations, like high catalyst loading, the
requirement of a promoter or a co-catalyst, difficult recycle of
catalyst, relatively low yields, or high temperature. In addition,
the reaction can be carried out without any catalyst.25
Unfortunately, the complex operation and relatively low yields
were observed. Therefore, it is of current interest to explore a
more economic and environmental friendly method with the
use of greener catalyst to finish this reaction.
Among the methodologies reported26 such as DABSO-based
sulfone synthesis27, the preparation of arylsulfones from
arylsulfinic acid salts28 and promoter-mediated oxidation of
sulphides29, a reliable and straightforward route to sulfones
involves the selective catalytic oxidation of sulfides using H2O2
or molecular O2 as oxidant30. Although transition-metal
catalysts have been successfully reported,31 most procedures
required complicated ligands. Such, the development of
recyclable catalytic systems which utilized a recycled catalyst
and readily available ligand to facilitate the oxidation is still of
central importance. On the basis of the oxidation of sulfides to
sulfoxides, we want to further investigate the oxidation of
sulfides to sulfones. During several previous studies in our
research group, we reported an aluminum hydroxide-
supported nano-palladium catalyst which had been applied to
some cross couplings.32
S
N2BF4
T, Mw, Time
H2O
+
Na2S 9H2O
1a
3a
2
Entry
T (oC)
Power (W)
300
t (min)
30
Yield (%)b
1
2
3
4
5
6
7
8
80
67
60
89
80
85
81
90
62
90
300
30
100
100
100
100
100
100
300
30
200
30
400
30
300
10
300
20
300
40
a
Reaction conditions: 1a (38.5 mg, 0.2 mmol), 2 (53.2 mg, 0.22 mmol), H2O (1.0
mL). b Isolated yield.
A
wide range of substituted arenediazonium
tetrafluoroborates were then used to react with sodium sulfide
using this procedure. As shown in Scheme 1, good to excellent
yields were obtained for all examined substrates (3a-3q). It’s
obvious that the electronic nature of substituents on the phenyl
ring of arenediazonium salts had a significant effect
Scheme 1 Synthesis of symmetrical diaryl sulfides under microwave irradiationa, b
S
N2BF4
H2O, 100 o
C
+
R
Na2S 9H2O
R
R
Mw, 300 W
3
1
S
S
S
S
c
3d
3g
3b
3c
, 25 mins, 82%
3a
, 15 mins, 89%
, 15 mins, 81%
, 20 mins, 90%
Herein, we will report the microwave-assisted synthesis of
symmetrical diaryl sulfides via the coupling of arenediazonium
tetrafluoroborates with Na2S·9H2O without any catalyst in the
presence of H2O as a solvent, and FeCl3-promoted preparation
of symmetrical diaryl disulfides via the coupling of
arenediazonium tetrafluoroborates with Na2S·9H2O. K2CO3-
mediated cross-coupling of symmetrical disulfides with
arenediazonium salts for the construction of unsymmetrical
sulfides has been elucidated. More importantly, we report our
efforts in catalyst development for the nano-Pd catalyzed,
highly selective oxidation of sulfides to sulfoxides and sulfones
in the presence of H2O2 as an oxidant, respectively.
MeO
S
OMe
S
S
MeO
OMe
OMe
, 20 mins, 83%
OMe
, 25 mins, 79%
c
3f
3e
, 20 mins, 92%
S
NO2
S
O2N
S
O2N
NO2
O2N
NO2
, 15 mins, 73%
c
3j
, 25 mins, 71%
3h
, 10 mins, 77%
S
3i
F
F
S
S
F
F
F
F
3k
, 10 mins, 84%
3l
, 15 mins, 72%
3m
, 20 mins, 69%
Cl
Cl
S
S
S
Cl
Br
Cl
Br
Cl
3p
, 25 mins, 78%
Cl
Results and discussion
c
3n
, 10 mins, 83%
3o
, 15 mins, 77%
S
Our initial studies focused on the reaction of arenediazonium
tetrafluoroborates with Na2S·9H2O for synthesis of symmetrical
diaryl thioethers without any catalyst in the presence of H2O as
a solvent under microwave conditions. Optimization of reaction
conditions was performed to make this transformation more
efficient, as summarized in Table 1. Extensive screening showed
that the optimal reaction conditions were 0.2 mmol scale of 1a
with 1.0 equivalent of Na2S·9H2O under the power of 300 W in
1.0 mL H2O at 100 oC (Table 1, entry 7).
3q
, 15 mins, 76%
a
1
2
Reaction conditions: (0.2 mmol), (53.2 mg, 0.22 mmol), H2O (1.0 mL),
microwave (300 W), 100 oC. b Isolated yield. c 400 W and 25 min were adopted.
on the yield. For example, arenediazonium salts bearing
electron-donating groups (Me and MeO) provided good to
excellent yields, which were higher than those with electron-
2 | J. Name., 2012, 00, 1-3
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withdrawing groups (NO2, Br, Cl, and F) (3b-3g vs. 3h-3q). The than other aryldiazonium salts (5f and 5i). Moderate yields were
View Article Online
steric hindrance on the phenyl ring also played an important obtained
when
4-Cl-
and
4D-BOrI-:b1e0.n10z3e9n/eCd8iOaBz0o3n2i0u9mB
role on yields, which para-substituted arenediazonium salts tetrafluoroborates were used as substrates (5k and 5l).
afforded the corresponding products with higher yields than Furthermore, 2-naphthyldiazonium tetrafluoroborate could
ortho- and meta-substituted ones (3b vs. 3c and 3d, 3e vs. 3f offer 62% yield (5m). Subsequently, diaryl and dialkyl disulfides
and 3g, 3h vs. 3i and 3j, 3k vs. 3l and 3m, 3n vs. 3o and 3p).
were investigated using the reaction of symmetrical disulfides
Having identified the optimal conditions of the reaction of with benzenediazonium tetrafluoroborate, respectively. Diaryl
arenediazonium tetrafluoroborates with Na2S·9H2O leading to disulfides bearing an electron-rich group showed higher yields
symmetrical diaryldisulfides in the presence of FeCl3, we than that having an electron-poor group (5n and 5o vs. 5p and
investigated the scope and generality of arenediazonium 5q). 67% and 71% yields were provided with diethylsulfane and
tetrafluoroborates. As listed in Scheme 2, phenyldiazonium diallylsulfane, respectively (5r and 5s).
tetrafluoroborate could smoothly offer the 73% yield (4a).
a, b ,c
Scheme 3 Scope for unsymmetrical arylsulfides promoted by the K2CO3
Electron-donating groups such as Me and MeO were tolerated
S
N2BF4
in various positions on the phenyl ring, forming the
corresponding products 4b-4g in good yields. In terms of
electron-withdrawing groups such as F, Cl, Br, and NO2,
moderate to good yields could be obtained (4h-4q).
R1
R1
S
K2CO3, CH3CN
R1
25 oC, N2
+
R
R
S
5
4
1
OMe
S
S
S
S
a, b
Scheme 2 Scope for symmetrical diaryldisulfides mediated by the FeCl3
MeO
N2BF4
d
d
FeCl3, CH3OH
S
5d
F
5b
5c
, 24 h, 74%
S
5a
, 24 h, 77%
S
, 28 h, 72%
S
, 24 h, 81%
S
R
+
Na2S 9H2O
0-25 oC, 24 h
S
R
F
R
2
4
1
F
d
e
d
5g
5e
5f
, 20 h, 71%
5h
, 28 h, 63%
, 28 h, 68%
S
, 18 h, 80%
O2N
S
S
S
S
S
S
S
S
S
S
4b
, 20 h, 81%
4a
4c, 20 h, 76%
4d
, 24 h, 72%
, 24 h, 73%
O2N
Br
Cl
MeO
OMe
d
5k
S
5i
, 24 h, 69%
, 24 h, 81%
S
5j
, 28 h, 75%
S
S
S
MeO
S
S
S
S
OMe
OMe
OMe
MeO
4g
, 24 h, 67%
d
5l
, 28 h, 63%
OMe
5m
, 30 h, 62%
5n
, 24 h, 82%
NO2
S
4e
4f
, 20 h, 75%
, 20 h, 82%
F
F
S
S
S
F
S
S
S
S
S
F
NO2
S
5r
, 30 h, 67%
5o
5p
, 24 h, 76%
S
, 28 h, 70%
5q
, 28 h, 64%
F
F
4i
, 30 h, 68%
4h
4j, 33 h, 67%
, 30 h, 73%
Cl
Br
S
S
S
Cl
S
S
5s
, 30 h, 71%
Br
S
Cl
a
1
4
All reactions were performed with ArN2BF4 (0.2 mmol), (ArS)2 (0.18 mmol)
Cl
and K2CO3 (27.7 mg, 0.2 mmol) in CH3CN (1.0 mL) under N2 atmosphere at 25
4l
4k
, 28 h, 70%
4n
, 28 h, 70%
b
oC.
The corresponding homocoupling products of arenediazonium
, 28 h, 75%
O2N
tetrafluoroborates were also detected during these reactions. c Isolated yield. d 35
oC was used. e 20 oC was used.
NO2
O2N
S
S
S
S
S
NO2
S
NO2
O2N
, 33 h, 59%
On the basis of the above-described synthesis of the
symmetrical and unsymmetrical sulfides, we started the
research on the oxidation of sulfides using 30% aqueous
hydrogen peroxide as an oxidant in the presence of nano-
palladium catalyst Cat. 1. First, the selective oxidation of
sulfides to sulfoxides was examined. Under the optimized
conditions, a series of symmetrical sulfides was subjected to the
oxidation, and the results are presented in Scheme 4. Diverse
sulfides proved to be amenable to the reaction conditions,
delivering the desired products 6a-6p in good to excellent
yields. The electronic properties of substituents on the phenyl
ring of sulfides had an obvious influence on the yield. Substrates
bearing electron-donating groups supplied excellent yields
which were higher than those with electron-withdrawing
groups (6a-6f and 6n-6o vs. 6g-6m). It was noteworthy that
ortho-substituted arylsulfides, which are sterically hindered,
4p
, 33 h, 66%
4q
4o
, 30 h, 71%
a
1
2
Reaction conditions: (0.2 mmol), (53.2 mg, 1.1 equiv), FeCl3 (39.1 mg, 1.2 equiv) in CH3OH (1.0
mL) at 0-25 oC. b Isolated yield.
Under the optimized experimental conditions, the results of
an examination of the scope of the cross-coupling reaction of a
series of arenediazonium tetrafluoroborates with symmetrical
disulfides are presented in Scheme 3. With regard to various
aryldiazonium salts, modest to good yields could be obtained. It
was noteworthy that steric hindrance of substituents on the
aromatic ring played an important role on the yield which para-
substituted substrates afforded the corresponding products
with higher yields than ortho- and meta-substituted ones (5b vs.
5c, 5d vs. 5e, 5f vs. 5g and 5h, 5i vs. 5j). Interestingly, substrates
bearing 4-F and 4-NO2 groups indicated obvious higher yields
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Journal Name
could give good yields (6d, 6f, 6i, 6l, and 6o). Interestingly,
dibenzyl sulfide was also a suitable substrate giving the dibenzyl
sulfoxide 6p in 99% yield.
Scheme 5 Nano-Pd-catalyzed selective oxidation of unsymmetrical sulfides to sulfoxides
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a, b
DOI: 10.1039/C8OB03209B
with H2O2
O
S
Nano-Pd (0.12 mol% Pd)
S
R3
R4
H2O2, CH3OH, 60 o
C
R3
R4
Scheme 4 Nano-Pd-catalyzed selective oxidation of symmetrical sulfides to sulfoxides
5
7
a, b
with H2O2
O
S
O
S
O
S
O
O
S
Nano-Pd (0.12 mol% Pd)
S
R2
R2
S
H2O2, CH3OH, 60 o
C
R2
R2
MeO
OMe
, 20 h, 93%
F
3
6
7d
7b
7c
, 24 h, 87%
7a
, 16 h, 92%
, 16 h, 95%
O
S
O
O
S
O
S
O
S
O
S
O
S
O
S
S
O2N
Cl
7g
, 16 h, 82%
7h
, 15 h, 99%
7e
7f
, 27 h, 76%
, 16 h, 86%
c
6d
, 20 h, 94%
O
6a
6c
, 18 h, 92%
OMe
, 16 h, 99%
6b
, 16 h, 95%
O
O
S
Br
O
S
O
S
O
S
O
S
S
O
S
Br
MeO
F
OMe
F
F
OMe
, 22 h, 90%
7l
, 16 h, 92%
7k
, 16 h, 96%
7i
, 15 h, 99%
7j
16 h, 99%
c
6g
, 22 h, 86%
6e
, 13 h, 96%
O
S
6f
O
O
O
S
F
O
S
Cl
S
S
S
O
O
7m
7n
, 15 h, 96%
, 15 h, 99%
Cl
Cl
F
Cl
a
F
5
Cat. 1
(4.1
All reactions were performed with sulfide (0.2 mmol), nano-pd catalyst
mg, 0.12 mol% Pd) and H2O2 (10 equiv) in MeOH (1.0 mL) at 60 oC. b Isolated yield.
6j
6k
, 21 h, 81%
6i
, 21 h, 87%
, 28 h, 78%
6h
, 24 h, 81%
O
S
O
S
Cl
O
S
Br
Br
HO
OH
Scheme 6 Nano-Pd-catalyzed selective oxidation of sulfides to sulfone with diphenyl
disulfides and H2O2
Cl
d
a, b
6l
6m
, 21 h, 84%
, 24 h, 79%
6n
, 16 h, 94%
NH2
O
S
NH2
Ph2S2 (10 mol%), Nano-Pd (0.12 mol% Pd)
S
O
R5
O
R6
S
R6
R5
S
H2O2, CH3OH (1.0 mL), 100 o
C
O
e
3
5
or
O
8
6p
, 16 h, 99%
6o
, 18 h, 87%
a
3
Cat. 1
O
O
All reactions were performed with sulfide (0.2 mmol), nano-Pd catalyst
O
O
O
S
S
(4.1 mg, 0.12 mol% Pd) and H2O2 (10 equiv) in MeOH (1.0 mL) at 60 oC. b Isolated
yield. c 0.08 mol% nano-Pd catalyst and 5 equiv. of H2O2 were used. d 15 equiv. of
H2O2 was utilized. e 5 equiv. H2O2 was used.
S
MeO
OMe
HO
Cl
OH
8c
, 6 h, 95%
8b
, 12 h, 87%
8a
, 6 h, 97%
O
O
O
O
O
O
S
S
S
Next, we turned our attention to unsymmetrical sulfides
under the same optimal conditions. This catalyst system also
exhibited a remarkably broad substrate scope, and equally good
results and a similar trend regarding the yield were also
observed. As summarized in Scheme 5, diary sulfides
underwent the reaction smoothly providing good to excellent
yields (7a–7g). Notably, extremely excellent yields could be
obtained for (hetero)aryl alkyl sulfides (7h–7l). Alkyl alkyl
sulfides also provided high yields (7m and 7n).
On the basis of the above study about the oxidation of
sulfides to sulfoxides, we then sought to investigate the
oxidation of sulfides to sulfones. It was found that the addition
of diphenyl disulfide to the catalytic system is essential, which
resulted in the formation of sulfones 8a with excellent yields. To
evaluate the scope of the oxidation reaction under the
optimized conditions, various sulfides were subjected to the
reaction and the results are shown in Scheme 6. Symmetrical
diaryl sulfides could be smoothly converted to sulfones 8a–8e
with high yields. Unsymmetrical diaryl sulfides having electron-
withdrawing groups (F) or electron-donating groups (OMe, Me)
on the phenyl ring were well tolerated and gave the desired
products 8g–8k in good to excellent yields. In addition, good
yields were achieved for aryl alkyl sulfides (8l and 8m). Alkyl
alkyl sulfide such as 3-(methylsulfonyl)prop-1-ene could also
offered 83% yield (8n).
OMe
8g
, 6 h, 91%
Cl
Br
O
Br
8d
, 6 h, 90%
8e
, 6 h, 86%
O
O
O
O
O
O
O
S
S
F
S
S
F
F
8j
8h, 6 h, 92%
8i, 12 h, 85%
, 15 h, 81% 8k
, 18 h, 80%
O
O
O
S
O
O
O
S
S
8l
, 6 h, 87%
8m
, 6 h, 85%
8n
, 6 h, 83%
a
3
5
Cat. 1
All reactions were performed with sulfide or (0.2 mmol), nano-pd catalyst
(4.1 mg, 0.12 mol% Pd), H2O2 (10 equiv) and (PhS)2 (10 mol%) in MeOH (1.0 mL) at
100 oC. b Isolated yield.
Conclusions
In conclusion, we have developed one green and efficient
approach for the synthesis of symmetrical diaryl sulfides and
symmetrical diaryl disulfides via the coupling of
arenediazonium tetrafluoroborates with sodium sulfide,
respectively. A variety of arenediazonium salts are well-
tolerated, affording the corresponding products in moderate to
good yields. Then we have also reported the reaction of
arenediazonium tetrafluoroborates with symmetrical disulfides
which could afford unsymmetrical sulfides in moderate to good
yields under mild conditions. More importantly, on the basis of
the above-described products, one highly effective and green
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purified by column chromatography on silica gel with ethyl acetate
methodology has been developed for the preparation of
symmetrical or unsymmetrical sulfoxides and sulfones in the
presence of H2O2 as an oxidant and nano-pd Cat. 1 as a catalyst,
respectively. The nano-Pd catalyst is highly active and highly
selective, is widely applicable to various sulfide substrates, is
capable of facile recycling, and the corresponding products are
provided with good to excellent yields.
and petroleum ether as eluents to afford the pure proVdieuwctAr6tiacl.e Online
DOI: 10.1039/C8OB03209B
2.6 General procedure for oxidation of asymmetric sulfides
to sulfoxides with H2O2
The mixture of nano Pd catalyst (4.1 mg, 0.12 mol% Pd), asymmetric
sulfide (0.2 mmol), 30% H2O2 (0.2 mL, 10 equiv.) in methanol (1.0 mL)
was stirred at 60 oC until the starting material was consumed which
was determined by TLC. After the solvent CH3OH was removed under
reduced pressure, the resulting mixture was purified by column
chromatography on silica gel with ethyl acetate and petroleum ether
as eluents to afford the pure product 7.
Experimental procedures
2.1 General procedure for the preparation of the nano-Pd
catalyst
2.7 General procedure for the symmetrical and asymmetric
sulfides to sulfones
A mixture of Pd(PPh3)4 (260 mg, 0.225 mmol), tetra(ethylene glycol)
(418 mg, 2.20 mmol), 1-butanol (3 mL, 32.7 mmol), and aluminum
The mixture of nano Pd catalyst (4.1 mg, 0.12 mol% Pd), diphenyl
disulfide (10 mol%) symmetric or asymmetric sulfide (0.2 mmol), 30%
o
tri-sec-butoxide (9.50 g, 38.5 mmol) was stirred at 110 C for 10 h.
Then water was dropwise added and the system was stirred at 110
oC for another 0.5 h to form a black gel. Subsequently, filtering,
washing with acetone, and drying the gel gave the nano-Pd catalyst
1 at room temperature as dark greyish-green powder.
o
H2O2 (0.2 mL, 10 equiv.) in methanol (1.0 mL) was stirred at 100 C
until the starting material was consumed which was determined by
TLC. After the solvent CH3OH was removed under reduced pressure,
the resulting mixture was purified by column chromatography on
silica gel with ethyl acetate and petroleum ether as eluents to afford
the pure product 8.
2.2 General procedure for the synthesis of symmetrical
sulfides under microwave
The mixture of phenyl diazonium tetreafluoroborate (38.5 mg, 0.2
mmol), and Na2S·9H2O (53.2 mg, 0.22 mmol) in water (1.0 mL) was
heated under microwave irradiation (300 W, 100 oC) until the starting
material was consumed which was determined by TLC. The reaction
system was then extracted with ethyl acetate (3 × 10 mL), and the
combined organic phase was dried over anhydrous Na2SO4. At last,
the organic extracts were concentrated in vacuum and the resulting
mixture was purified by column chromatography on silica gel with
petroleum ether as an eluent to afford the pure product 3a.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
We appreciate gratefully the Natural Science Foundation of
Shanxi Province (No. 201601D011028) for financial support.
2.3 General procedure for the synthesis of symmetrical
disulfides promoted by FeCl3
To the mixture system of phenyl diazonium tetrafluoroborate (38.5
mg, 0.2 mmol) and FeCl3 (39.1 mg, 0.24 mmol, 1.2 equiv) in CH3OH
Notes and references
o
(1.0 mL) was added Na2S·9H2O (53.2 mg, 1.1 equiv.) slowly at 0 C.
1
Selected examples: a) A. Ghorbani-Choghamarani and Z.
Taherinia, New. J. Chem., 2017, 41, 9414; b) F. Ke, Y.-Y. Qu, Z.-
Q. Jiang, Z.-K. Li, D. Wu and X.-Z. Zhou, Org. Lett., 2011, 13,
454; c) H.-Y. Chen, W.-T. Peng, Y.-H. Lee, Y.-L. Chang, Y.-J.
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a) N. García, P. García-García, M. A. Fernández-Rodríguez, D.
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2013, 15, 999; b) S. C. A. Sousa, J. R. Bernardo, M. Wolff, B.
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6328.
The reaction mixture was then stirred, and the temperature rose to
room temperature naturally. The stirring continued until no
substrate could be detected by TLC. After the solvent CH3OH was
removed under reduced pressure, the residue was purified by
column chromatography on silica gel with petroleum ether as an
eluent to afford the direct cross-coupling product diphenyl disulfide
4a.
2.4 General procedure for the synthesis of asymmetrical
sulfides via the cross-coupling of disulfides with aryl
diazonium tetrafluoroborate
To the mixture system of p-MeO-phenyl diazonium
tetrafluoroborate (44.5 mg, 0.2 mmol) and K2CO3 (27.7 mg 0.2 mmol)
in CH3CN (1.0 mL) was added diphenyl disulfide (39.3 mg, 0.18 mmol)
under N2 atmosphere at 25 oC. The reaction mixture was then stirred
until no substrate could be detected by TLC. The resulting mixture
was purified by column chromatography on silica gel with petroleum
ether as an eluent to afford the direct cross-coupling product (4-
methoxyphenyl)(phenyl)sulfide 5a.
2
3
4
5
C. Gonzalez-Arellano, R. Luque and D. J. Macquarrie, Chem.
Commun., 2009, 40, 1410.
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19, 4061; b) S. C. Banfield, A. T. Omori, H. Leisch and T.
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J. Org. Chem., 2002, 67, 8666; f) M. Oba, K. Tanaka, K.
2.5 General procedure for oxidation of symmetric sulfides to
sulfoxides with H2O2
The mixture of nano Pd catalyst (4.1 mg, 0.12 mol% Pd), symmetric
diphenyl sulfide (0.2 mmol) and 30% H2O2 (0.2 mL, 10 equiv.) in
methanol (1.0 mL) was stirred at 60 oC until the starting material was
consumed which was determined by TLC. After the solvent CH3OH
was removed under reduced pressure, the resulting product was
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ARTICLE
Nishiyama and W. Ando, J. Org. Chem., 2011, 76, 4173; g) X.-
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8
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10 The synthesis of aryl sulfides from aryl comounds and
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18 N. Taniguchi, J. Org. Chem., 2007, 72, 1241.
11 Selected examples: a) Y. Kuwahara, Y. Yoshimura, K. 19 a) N. Taniguchi, J. Org. Chem., 2004, 69, 6904; b) S. Kumar and
Haematsu and H. Yamashita, J. Am. Chem. Soc., 2018, 140,
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78, 6328 and internal documents; c) N. Iranpoor, H.
Firouzabadi and H. R. Shaterian, J. Org. Chem., 2002, 67, 2826
and internal documents; d) A. S. Touchy, S. M. A. H. Siddiki, W.
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2554; e) T. Mitsudome, Y. Takahashi, T. Mizugaki, K. Jitsukawa
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Martinek, M. Korf and J. Srogl, Chem. Commun., 2010, 46,
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Ni, M. Hu and T. Tang, Chem. Commun., 2015, 51, 5890; f) N.
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Movassagh and Z. Hosseinzadeh, Synlett, 2016, 27, 777.
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2012, 354, 321.
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Green Chem., 2012, 14, 2024.
21 Selected examples: a) I. Fernandez and N. Khiar, Chem. Rev.,
2003, 103, 3651; b) J. Legros, J. R. Dehli and C. Bolm, Adv.
Synth. Catal., 2005, 347, 19; c) N. Fukuda and T. Ikemoto, J.
Org. Chem., 2010, 75, 4629; d) R. S. Varma and K. P. Naicker,
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K. G. Akamanchi, J. Org. Chem., 2003, 68, 5422; f) Y. X. Zhang,
Z. R. Wong, X. X. Wu, S. J. L. Lauw, X. Huang, R. D. Webstera
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12 a) C. Liu and M. Szostak, Chem. Commun., 2018, 54, 2130; b)
N. Ichiishi, C. A. Malapit, Ł. Woźniak and M. S. Sanford, Org.
Lett., 2018, 20, 44; c) L. Guo and M. Rueping, Acc. Chem. Res.,
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K.-H. Wang and D. Huang, RSC Adv., 2017, 7, 6018; c) D. Wang,
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d) D. Wang, S. Guo, R. Zhang, S. Lin and Z. Yan, RSC Adv., 2016,
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Bolm, Angew. Chem., Int. Ed., 2004, 43, 4225; f) C. Drago, L.
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14 Selected examples: a) R. B. N. Baig and R. S. Varma, Chem.
Commun., 2012, 48, 2582; b) V. P. Reddy, K. Swapna, A. V.
Kumar and K. R. Rao, J. Org. Chem., 2009, 74, 3189; c) K. D.
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Chem. Res., 2008, 41, 1534; f) G. T. Venkanna, H. D. Arman
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15 Selected examples: a) C.-K. Chen, Y.-W. Chen, C.-H. Lin, H.-P. 23 Selected examples: a) T. Yamaguchi, K. Matsumoto, B. Saito
Lin and C.-F. Lee, Chem. Commun., 2010, 46, 282; b) J.-R. Wu,
and T. Katsuki, Angew. Chem., Int. Ed., 2007, 46, 4729; b) A.
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Casado-Sánchez, R. Gómez-Ballesteros, F. Tato, F. J. Soriano,
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24 Selected examples: a) E. N. Kadnikova and N. M. Kostic, J. Org.
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25 S. M. Bonesi, S. Crespi, D. Merli, I. Manet and A. Albini, J. Org.
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26 a) S. Patai, Z. Rappoport, C. J. M. Stirling, Eds. The Chemistry
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27 a) C. C. Chen and J. Waser, Org. Lett., 2015, 17, 736; b) A. S.
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28 Selected examples: a) K. Luo, L. Zhang, J. Ma, Q. Sha and L.
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Bandgar, S. V. Bettigeri and J. Phopase, Org. Lett., 2004, 6,
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A. Kar, I. A. Sayyed, W. F. Lo, H. M. Kaiser, M. Beller and M. K.
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Manolikakes, Org. Lett., 2013, 15, 188; h) G. Manolikakes and
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Org. Chem., 2005, 70, 2696.
29 K. Bahrami, M. M. Khodaei and M. S. Arabi, J. Org. Chem.,
2010, 75, 6208.
30 a) A.-N. R. Alba, X. Companyó and R. Rios, Chem. Soc. Rev.,
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Heindl, T. Schirmeister, M. L. Calabrò and M. Zappalà,
ChemMedChem, 2011, 6, 1228; c) M. Kirihara, J. Yamamoto,
T. Noguchi, A. Itou, S. Naito and Y. Hirai, Tetrahedron, 2009,
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