Three-component difunctionalization of alkenes leading to β-acetamido sulfides and β-acetoxy sulfides

Article abstract of DOI:10.1039/c7ob00110j

A novel method for the synthesis of β-acetamido sulfides via NBS-mediated aminosulfenylation of alkenes with thiophenols and nitriles under metal-free conditions has been described. And β-acetamido sulfides were also synthesized with 1-(arylthio)pyrrolidine-2,5-diones as substrates and HBr as an additive. On the other hand, iodine-catalyzed 1,2-acetoxysulfenylation of alkenes by using (diacetoxyiodo)benzene as an oxygen source to synthesise various β-acetoxy sulfides was described as well.

Full text of DOI:10.1039/c7ob00110j

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Takeharu Haino et al.
Solvent-induced emission of organogels based on tris(phenylisoxazolyl)
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Three-component difunctionalization of alkenes leading to β‑
acetamido sulfides and β‑ acetoxy sulfides
Dingyi Wang,a Zhaohua Yan,a Qihuang Xie,a Rongxing Zhang,a Sen Lin*a and Yuanxing Wang*b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
A novel method for the synthesis of β‑acetamido sulfides via NBS-mediated aminosulfenylation of alkenes with
thiophenols and nitriles under metal-free conditions has been described. And β‑acetamido sulfides were also synthesized
with 1-(Arylthio) pyrrolidine-2, 5-diones as substrates and HBr as an additive. On the other hand, iodine-catalyzed 1,2-
acetoxysulfenylation of alkenes by using (Diacetoxyiodo)benzene as an oxygen source to synthesise various β‑ acetoxy
sulfides was described as well.
www.rsc.org/
Organosulfur compounds are useful chemical entities due to with nitriles and thiophenols as nucleophiles and sulfur
their application in multiple areas, including chemical synthesis, sources, respectively. Wang7 reported an efficient method for
materials science and the pharmaceutical industry.1 And over the selective synthesis of β-acetamido sulfide compounds by
the past several years, there have been many efficient and using thiophenols as well. There are only two reports
reliable procedures for the synthesis of sulfur-containing published in which diphenyl disulfides were used as sulfur
compounds, such as thiolation, sulfenylation, iodosulfonylation, sources via one-pot reaction. In 2006, Taniguchi8 disclosed that
thio etherification and so on.2 Among them, difunctionalization
β‑acetoxy sulfides were obtained by using CuI as a catalyst in
of unsaturated carbon− carbon bond is one of the most the presence of 2,2'-dipyridyl. In 2013, Kuhakarn9 reported
powerful tools for the introduction of sulphur-containing that PhI(OAc)2/KI promoted 1,2-acetoxysulfenylation of
functional groups into target compounds.3
alkenes with diphenyl disulfides to afford β
In this regard, preparation of organosulfur compounds The above protocols proved to be a convenient and flexible
through 1,2-difunctionalization of alkenes utilizing different procedure to synthesize β acetamido sulphides and β-acetoxy
‑acetoxy sulfides.
‑
thiolating reagents and various heteroatom nucleophiles is a sulfides. Nevertheless, direct, economic and efficient
O
hot topic. However, in contrast to the other addition reaction
Previous work
of alkenes, including alkoxythiolation, disulfidation and
HN
R2
[Pb], [Sb]
or [I] + [O]
acetoxythiolation, examples of hydroxysulfurization and
aminosulfenylation of alkenes are still rare. For the synthesis
of β-acetamido sulfide compounds, Denmark4 firstly reported
a novel method to produce the 1, 2-difunctionalized products
with high selectivity by using azide as a nucleophile. After that,
several groups5 reported that transition-metal-catalyzed
acetamidosulfidation of alkenes with nitriles by using
benzenesulfenanilides or disulfides as sulfur sources to give β-
acetamido sulphide derivatives. Chemists tried to improve the
reaction conditions utilizing non-metal reaction conditions due
to their widespread use and environmentally friendly effects.
Recently, Mao6 disclosed that aminosulfenylation of alkenes
R2CN
+
[S]
+
S
R1
R1
R3
OAc
[S] = ArSSAr; ArSH or ArNHSAr
[Cu] or [I]
S
PhI(OAc)2/AcOH
O
ArSSAr
+
+
R1
R1
Ar
N
S
Ar
This work
O
O
HN
R2
NBS
S
R2CN + H2O
R1
Ar
O
+
ArSH
metal-free
R1
O
I2 + DMSO
PhI(OAc)2
S
R1
Ar
Scheme 1. Methods for the Synthesis of β‑acetamido sulfides
or β- acetoxy sulphides.
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Table 1 Optimization of reaction conditionsa
Table 2 Three-component nitrosulfenylation of thiophenols with
styrene and acetonitrile a,b
Entry [Br] (equiv)
Solvent
neat
neat
neat
neat
Yieldc (%)
56
trace
trace
trace
trace
15
T (
℃)
O
O
O
1
2
3
4
NBS (1.0)
NaBr (1.0)
KBr (1.0)
TBAB (1.0)
Br2 (1.0)
100
100
100
100
100
100
100
100
100
100
100
100
80
HN
CH3
S
HN
CH3
S
HN
CH3
S
4c, 85%
4b, 73%
4a, 80%
OMe
O
O
O
5
neat
HN
CH3
S
6b
7b
8b
9b
10b
11b
12
13
NBS (1.0)
NBS (1.0)
NBS (1.0)
NBS (1.0)
NBS (1.0)
NBS (1.0)
NBS (2.0)
NBS (2.0)
Toluene
Dioxane
H2O
DMSO
DMF
DCE
HN
CH3
HN
CH3
S
S
27
4f, 72%
4d, 75%
4e
, 65%
Br
trace
trace
trace
16
80
62
Cl
O
O
O
HN
CH3
S
HN
CH3
S
HN
CH3
S
4g, 70%
4h, 75%
4i, 60%
Cl
neat
neat
Cl
F
O
O
O
aReaction conditions: 1a (0.60 mmol), 2a (0.30 mmol), 3a (1.0
HN
CH3
S
HN
CH3
HN
Cl
S
℃
, 15 h. b3a (0.1mL), solvent (2.0 mL)
S
mL), H2O (50μL), 100
cYield of isolated product.
4j, 56%
4l
c, 55%
4k
,78%
Br
O
O
O
methods to construct β
sulfides are still scarce. Herein, we present our results on the
generation of β acetamido sulfides or β- acetoxy sulfides using
thiophenols as sulfur-containing reagents under non-metallic
conditions. Besides, 1-(p-tolylthio) pyrrolidine-2, 5-dione was
‑acetamido sulphides and β- acetoxy
HN
HN
OMe
HN
S
S
S
‑
4o
, 66%
4nc,32%
4mc, 45%
CH3
O
O
HN
CH3
NH
also chosen as a sulfur source to synthesize β
sulphides.
‑acetamido
S
S
4q, trace
4p,52%
aReaction conditions:
NBS (0.60 mmol), H2O (50μL)
1
(0.60 mmol),
2
，100℃, 15 h. Yield of isolated
(0.30 mmol),
b
3
(1.0 mL)，
First of all, p-toluenethiol 1a, styrene 2a and acetonitrile 3a
were employed as initial substrates to investigate the reaction
conditions including additives, solvents and temperature. The
yield of target product 4a was 56% when the desired three-
product. C 3 (1g).
component reaction proceeded to give β
as single regioisomer by using
‑
acetamido sulfides
equiv of N-
generality of the process (Table 2). We found that aryl thiols
containing electron-rich or –poor groups on the aryl rings
could readily participate in the reactions, affording the
a
1
Bromosuccinimide (NBS) as an additive (Table 1, entry 1). Then
other bromides including NaBr, KBr, tetrabutylammonium
bromide (TBAB), and Br2 were investigated to increase the
production rate (Table 1, entries 2-5). It turned out that NBS
was the most effective catalyst among the above bromides
employed. Subsequently, we tested a variety of common
organic solvents for improving the yield. We found that the
yield decreased when the reaction was carried out in other
organic solvents (such as toluene, dioxane and so on) rather
than in substrate 3a as solvent (Table 1, entries 6-11). Under
the above mentioned experimental conditions, we changed
the addition amount of NBS and found that the yields reach
the maximum as the amount of NBS was increased up to 2.0
equivalents. (Table 1, entry 12). Finally, the yield decreased
dramatically when the reaction was run at lower temperatures
(Table 1, entry 13). On the basis of the results shown in Table 1,
that the reaction was carried out with 0.6 mmol of thiophenols,
0.3 mmol of styrenes, 1.0 mL of nitriles substrates and 0.6
mmol of DTBP at 100 °C for 15 h emerged as the optimized
reaction conditions for further research.
corresponding products in 65% to 85% yields (4a
different aryl thiols, it can be found that substrates
electron-rich groups on the benzene ring showed relatively
high reaction activity than those with electron-deficient groups.
From the Table 2, olefins containing electron-rich or –poor
groups on the aryl rings performed well and gave the desired
-
4f). For
1
with
products in moderate yields (4g-4k). And the reaction was
carried out by using cyclohexene as a substrate, the lower
yield was obtained (4p). While arylnitriles could serve as
suitable nitrogen, the target products were obtained in lower
yields under the standard conditions because of the steric
hindrance (4l-4n). Unfortunately, we could not found the
target product when butanethiol was selected as a sulfur
source. Therefore, aliphatic thiols were not suitable for this
reaction condition.
To expand three-component difunctionalization of alkenes,
we next tried to synthesize β‑ acetoxysulfides by using NBS as
an additive. First, we chose p-toluenethiol 1a and styrene 2a as
representative reactants in the presence of iodobenzene
diacetate (PIA) in the presence of NBS. Unfortunately, we
couldn’t find the target compound by GC-MS. Then we
reinvestigated the effects of additives utilizing thiophenols as a
After optimized reaction conditions were obtained, a range
of thiophenols 1, olefins 2 and nitriles 3 were used as
substrates in this transformation to explore the scope and
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Table 3 Optimization of reaction conditionsa
Table 4 1, 2-acetoxysulfenylation of alkenes with phenylthiols and
Iodobenzene diacetate a, b
Entry catalyst PhI(OAc)2 DMSO
Solvent Yieldb
(mol%)
NBS
TBAI (20) 1.0
(equiv)
1.0
(equiv)
-
(mL)
DCE
DCE
DCE
DCE
H2O
DMSO
THF
CH3CN
DME
DMF
DCE
DCE
DCE
DCE
DCE
DCE
DCE
(%)
trace
21
trace
58
12
trace
17
26
1
2
3
4
5
6
7
8
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
1.0
3.0
2.0
NH4I
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.5
2.0
1.5
1.5
1.5
1.5
1.5
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (20)
I2 (30)
I2 (40)
I2 (30)
I2 (30)
I2 (30)
9
16
10
11
12
13
14
15
16
17c
trace
67
65
86
84
65
85
52
aReaction conditions:
mmoL), DCE (2.0 mL), 85
1
(0.45 mmol), 2 (0.30 mmol), PIA (0.45
, 12 h. bYield of isolated product.
℃
aReaction conditions: 1a (0.45 mmol), 2a (0.30 mmol), solvent
(2.0 mL). 85
℃
, 12 h. bYield of isolated product. c At rt
acetoxysulfides. To our
sulfur source for the formation of β
‑
delight, we found that the corresponding compound 5a was
obtained when iodine was employed as a catalyst in the
presence of DMSO. The optimum yield of the target product
6a was obtained by screening the effect of iodides, solvents
and other conditions. (Table 3). The most suitable reaction
condition was obtained by using 1.5 equiv of 1, 1 equiv of 2
and 1.5 equiv of PIA as substrates, 30 mol% of iodine as a
catalyst, in DCE, at 85 °C, and 12 h reaction time.
Scheme 3. Reaction of p-toluenethiol with 1-Hexene or
[Bis(trifluoroacetoxy)iodo]benzene.
Under the above optimized conditions, a range of arylthiols
and terminal olefins 2 were employed in the transformation
1
to study the scope and universality of this procedure (Table 4).
The arylthiols with electron-withdrawing and electron-
donating groups reacted with 2a to yield the corresponding β
‑
acetoxy sulfides in moderate to excellent yields smoothly. This
method could tolerate various functional groups such as
halogen and methoxy group (5c-5e), which provided the
possibility for further functionalization. Furthermore, a series
of olefins were subjected to the transformation, and the
corresponding compounds were produced in moderate to
good yields. To our delight, non-aromatic alkenes were also
applicable to this reaction system and the good yield was
obtained, in the case of 5i by using cyclohexene as a substrate.
However, difunctionalization of 1-Hexene with p-toluenethiol
1a in the presence of styrene 2a gave a 3 : 1 mixture of β-
alkoxy sulfides 5j1 and 5j2 (Scheme 3). Meanwhile, the
corresponding product could not be found when we use
[Bis(trifluoroacetoxy)-iodo]benzene as a nucleophile (Scheme
3).
Scheme 4. Control experiments.
acetamido sulfides or β‑acetoxy sulfides via direct difunctiona-
lization of olefins with thiophenols as sulfur sources (Scheme
4). The reaction was completed by using 1-(p-Tolylthio)
pyrrolidine-2, 5-dione 6a instead of p-toluenethiol 1a under
different conditions. The best result was obtained when HBr
was selected as additive to complete this transformation.
To gain further insight into the mechanism, several control
experiments were carried out under different reaction
conditions depicted in Scheme 4 for the generation of β
‑
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Unfortunately, only small quantity of 4a was detected when disulphide 7a in the presence of iodine. Then, 7a reacts with
the above reaction was performed without any additives. iodine to yield electrophilic species 10a which was introduced
Meanwhile, referring to Fu’s report10b, we reason that the to styrene 2a to get thiiranium ion 11a. And PIA reacts with
thiiranium ion intermediate 11a to produce the target product
5a. In these steps, iodine has been converted to AcOI and HI,
and the two of which react with DMSO to regenerate iodine to
continue the catalytic cycle with the release of water and
dimethyl sulphide.
formation of β
formation of intermediate 1-(arylthio)-pyrrolidine-2,5-dione
6a). Under the standard conditions without olefin and PIA as
shown in Table 4, p-tolyl disulphide 7a was given in 92%. For
the generation of β
‑acetoxy sulfides presumably underwent the
(
Scheme 5. Three-component nitrosulfenylation of 6a with
styrene and acetonitrile.
‑acetoxy sulfides, the target product was detected in 66%
Scheme 7. Plausible mechanism for β‑ acetoxy sulfides
yield utilizing p-tolyl disulfide as a sulfur source. Finally, we
tried to take advantage of ESI-MS analysis on the model
reaction of 4a to further probe the reaction pathway. When Conclusions
the reaction was completed under the standard conditions
In conclusion, two novel and efficient protocols were developed
shown in Table 1, we took a few samples from the reaction
mixture and directly analyzed by ESI-MS in positive ion mode.
m/z signals characterized for cationic intermediates (Tol-S+)
was observed.
to synthesise β‑acetamido sulfides and β‑acetoxy sulfides. The
difunctionalization of alkenes proceeded with good regioselectivity,
and no regioisomers were observed in the present reaction system.
There is a reason to believe that those two synthetic technologies
can be directly applied in the syntheses of organic and medicinal
compounds and can also be transformed into a series of other
useful functionalized sulfocompounds. Besides, 1-(p-Tolylthio)
pyrrolidine-2, 5-dione has also been employed in this
1-(Arylthio) pyrrolidine-2, 5-diones are important sulfur
sources because of their stability, readily availability, low
toxicity and so on. Therefore, different olefins 2, 1-(p-Tolylthio)
pyrrolidine-2, 5-dione 6a, and acetonitrile were also employed
in this transformation to explore the scope and generality of transformation for β‑acetamido sulphides.
this procedure (Scheme 5).
General Procedure for the Synthesis of β‑acetamido sulphides
Based on our research results described above and
descriptions in published literatures,6,7,10 a plausible reaction
pathway was thus proposed in Scheme 6 for β‑acetamido
sulphides. Firstly, p-toluenethiol 1a reacted with NBS to
produce intermediate 6a with the release of HBr. Then 6a
reacts with HBr to give intermediate 8a which was introduced
in olefins 2a to give thiiranium ion intermediate 9a. Ring-
opening of thiiranium ion 9a with nitrile 3a, followed by
with thiophenols
NBS (0.60 mmol) was added to a solution of thiophenol 1 (0.60
mmol), phenylethylene 2 (0.3 mmol) and H2O (50 μL) in Nitrile 3
(1.0 mL), and the reaction mixture was stirred at 100 °C for 15 h.
The solvent was evaporated in vacuo, and the residue was
subjected to column chromatography using ethyl acetate in
petroleum ether as the eluent to afford the pure target product 4.
hydrolysis (Rittertype reaction) results in the generation of β
acetamido sulphides 4a with the release of succinimide.
‑
General Procedure for the Synthesis of β‑ acetoxysulfides
I2 (0.03 mmol) was added to a solution of thiophenol 1 (0.45 mmol),
phenylethylene 2 (0.3 mmol), PhI(OAc)2 (0.45 mmol) and DMSO (0.6
mmol) in DCE (2.0 mL), and the reaction mixture was stirred at 85 °C
for 12 h. After completion of the reaction, the reaction mixture was
diluted with ethyl acetate, and quenched with saturated sodium
thiosulfate solution and extracted twice with ethyl acetate (2 × 15
mL). The organic layer was washed with water and dried over anhyd.
sodium sulfate. The solvent was evaporated in vacuo, and the
residue was subjected to column chromatography using ethyl
acetate in petroleum ether as the eluent to afford the pure target
product 5.
General Procedure for the Synthesis of β‑acetamido sulphides
with 1-(p-Tolylthio) pyrrolidine-2, 5-dione
Scheme 6. Plausible mechanism for β‑acetamido sulfides .
HBr (0.36 mmol, 40% aqueous) was added to a solution of 6a (0.36
mmol), phenylethylene 2 (0.3 mmol) and H2O (50 μL) in acetonitrile
(1.0 mL), and the reaction mixture was stirred at 100 °C for 12 h.The
In the meantime, we have also proposed a plausible
mechanism for the generation of β acetoxy sulfides (Scheme
7). Initially, p-toluenethiol 1a was oxidized into p-tolyl
‑
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solvent was evaporated in vacuo, and the residue was subjected to
column chromatography using ethyl acetate in petroleum ether as
the eluent to afford the pure target product 4.
Acknowledgements
We are grateful for the financial support from the National Natural
Science Foundation of China (21362022) .
Notes and references
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