Visible-Light-Induced Chemoselective Synthesis of α-Chloro and Vinyl Sulfones by Sulfonylation of Alkenes

Article abstract of DOI:10.1055/s-0036-1590925

Direct sulfonylation between alkenes and sulfonyl chloride was achieved at room temperature by a visible-light-induced photoredox process. This method allows the chemoselective synthesis of α-chloro and vinyl sulfone derivatives with moderate to high yields. The selectivity of the reaction was fully controlled by the electronic properties of the alkenes.

Full text of DOI:10.1055/s-0036-1590925

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Georg Thieme Verlag Stuttgart · New York
2017, 28, A–E
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Synlett
T.-f. Niu et al.
Letter
Visible-Light-Induced Chemoselective Synthesis of α-Chloro and
Vinyl Sulfones by Sulfonylation of Alkenes
Teng-fei Niu*
Dan Lin
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Lin-shuang Xue
Ding-yun Jiang
Bang-qing Ni*
School of Chemical and Material Engineering, Jiangnan University,
Wuxi 214122, Jiangsu Province, P. R. of China
niutf@jiangnan.edu.cn
byron_ni@yeah.net
Received: 28.07.2017
Accepted after revision: 11.09.2017
Published online: 20.10.2017
halogenated products especially under basic conditions
6
(Scheme 1, path II). Thus, achieving control of the selectiv-
DOI: 10.1055/s-0036-1590925; Art ID: st-2017-w0590-l
ity of visible-light-activated ATRA seems attractive.
Abstract Direct sulfonylation between alkenes and sulfonyl chloride
was achieved at room temperature by a visible-light-induced photo-
redox process. This method allows the chemoselective synthesis of α-
chloro and vinyl sulfone derivatives with moderate to high yields. The
selectivity of the reaction was fully controlled by the electronic proper-
ties of the alkenes.
ATRP process
R1
R
path I
X
hv
R1
R1
R
RX
R
X
base
R1
Key words visible-light-induced reaction, atom-transfer radical addi-
tion, sulfonylation of alkenes, chemoselectivity, α-Chloro sulfones, vinyl
sulfones
path II
R
H+
–
Scheme 1 General sequences for ATRA and dehalogenated process
Over the past decade, atom-transfer radical addition
Sulfone groups are prevalent structural motifs in natu-
ral products, pharmaceuticals, agrochemicals, and materi-
(
ATRA) has attracted much attention as a versatile tool in
1
7
organic synthesis. Typically, ATRA represents a practical
als. Despite some examples of transition-metal-catalyzed
8
synthetic path for difunctionalization of alkenes or alkynes
with activated halides in a highly atom-economic way, pro-
viding the corresponding alkyl or vinyl halides as important
ATRA processes, the manipulation of these valuable struc-
tures under visible-light conditions in a chemoselective
ATRA manner remains elusive.
2
intermediates for further transformation. With the com-
In 2012, the Stephenson group reported a visible-light-
induced ATRA of 4-toluenesulfonyl chloride (TsCl) to sty-
rene and norbornene, however, the substrate scopes of the
sulfonyl chlorides and the alkenes are limited (Scheme 2,
bined efforts of several research groups, various modes of
catalytic processes have been reported and applied in aca-
3
demic research laboratories and even in industry. Despite
4b
great progress, the development of more efficient, environ-
ment-friendly and sustainable methods for ATRA reactions
are still highly desirable.
a). On the other hand, Yu and co-workers described the
direct coupling of sulfonyl chlorides with enamides in the
9
presence of 1.5 equivalents of Na HPO (Scheme 2, b).
2
4
Recently, visible-light-induced processes have become a
powerful tool for the ATRA reaction due to their mild condi-
tions, high efficiency, and convenient workup. In principle,
Alternatively, the König group demonstrated a visible-light-
induced coupling of alkynes and aryl sulfinates with one
equivalent of nitrobenzene as the additive (Scheme 2, c).
4
10
the addition of a halide ion to the radical intermediate is
the key step to generate the desired radical addition prod-
Although these methods provided the desired products in
attractive routes, the chemoselective synthesis of α-chloro
and vinyl sulfone derivatives without additives still has
4
a,d,f,i,j,5
uct (Scheme 1, path I).
However, these radical cations
are excellent hydrogen atom donors that can give rise to de-
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E

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Synlett
T.-f. Niu et al.
Letter
Cl
more, no desired product was achieved when the reaction
was carried out in the absence of a photocatalyst and visi-
ble light (Table 1, entries 14 and 15).
a
Ts
O
Cl
Ru(bpy)3Cl2
DMSO
S
+
or
O
or
visible light
Table 1 Screening of the Reaction Conditionsa
Ts
12–24h
Cl
O
O
b
c
Cl
photocatalyst
N , solvent
2
O
R2
S
O
S
S
R2
Ir(dtbbppy)(ppy)2PF6
visible light, base
O
R1
O +
R1
N
O
Cl
R
Cl
+
N
S
blue LED, rt
O
R
O2N
O2N
O
O
4
h
1a
2a
3aa
ONa
R2
R2
Entry
Photocatalyst (mol%)
Ru(bpy) Cl (2)
Solvent
Yield (%)
b
O
Eosin Y
PhNO2
S
S
+
R1
R1
O
1
2
3
3
2
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
DMF
86
O
visible light
R
18 h
R
Ir(ppy) (2)
63
3
Ir(dtbbppy)(ppy)
Eosin Y (2)
2
PF
6
(2)
80
this work
4
trace
trace
trace
trace
81
O
Ru(bpy)3Cl2
MeCN
O
EDG
5
Eosin B(2
R
S
Cl
+
EDG
S
R
O
visible light
O
6
Rhodamine B (2)
Cl
4
h
EDG: Ph-X: X = H, Cl, Me;
n-Pr, n-Oct, Cy,
naphthyl
7
Methylene blue hydrate (2)
8
Ru(bpy)
3
3
Cl
2
2
(1)
(1)
9
Ru(bpy)
Cl
trace
trace
53
O
S
Ru(bpy) Cl2
MeCN
3
O
R
Cl
EWG
10
11
Ru(bpy) Cl (1)
DMSO
acetone
DCM
+
EWG
3
3
3
2
2
2
S
O
visible light
R
O
4
h
Ru(bpy)
Ru(bpy)
Cl
Cl
(1)
(1)
EWG: Ph-X: X = CN, CO2Me;
CN,CONHPh, CON(Me)2,
CO2Me, CO2n-Bu
1
2
trace
48
13
Ru(bpy) Cl (1)
3
2
MeOH
MeCN
MeCN
MeCN
14c
Ru(bpy)
Cl
(1)
NRd
NR
Scheme 2 Visible-light-induced methods for the synthesis of α-chloro
and vinyl sulfone derivatives
3
2
15
1
6e
Ru(bpy)
3
Cl
2
(1)
NR
a
Reaction conditions: 1a (0.5 mmol), 2a (0.5 mmol), and photocatalyst in
been elusive. Herein, we report an electronic-property-con-
trolled visible-light-induced chemoselective sulfonylation
of alkenes to access these valuable structures.
indicated solvent (2 mL) were irradiated with a 5 W blue LED at rt for 4 h.
b
c
Isolated yield.
1.5 equiv of base such as Et
3 2 3 2 4
N, K CO , and Na HPO was added.
d
e
No reaction.
In the dark.
Initially, 4-nitrobenzenesulfonyl chloride 1a and sty-
rene 2a were chosen as the model substrates. The model re-
action was performed with 1a (0.5 mmol), 2a (0.5 mmol),
and a catalytic amount of Ru(bpy) Cl (2 mol%) in MeCN
Having determined the optimal reaction conditions, we
examined the scope and generality of the present method
(Scheme 3).11 To our delight, both aryl and aliphatic alkenes
reacted well with 4-nitrobenzenesulfonyl chloride 1a,
affording the corresponding products 3aa–al in good to ex-
cellent yield. The effects from steric hindrance for alkenes
were not significant, and para-, meta- or ortho-chlorinated
alkenes were converted into the corresponding products in
83%, 79% and 75% yield, respectively (3ab–ad). The internal
alkenes, such as β-methylstyrene and indene, afforded the
corresponding products in 65% and 72% yield, respectively
(Scheme 3, 3ah and 3ai). Different aromatic sulfonyl chlo-
3
2
(2 mL; Table 1, entry 1). The reaction mixture was stirred at
room temperature and irradiated using a blue LED (5 W)
under N atmosphere. After 4 h, the desired product 3a was
2
generated in 86% yield. Subsequently, various photocata-
lysts such as Ir(ppy) , Ir(dtbbppy)(ppy) PF , Eosin Y, Eosin
3
2
6
B, Rhodamine B, and methylene blue hydrate were exam-
ined (Table 1, entries 2–7). Ru(bpy) Cl was the most effec-
3
2
tive catalyst. Decreasing the amount of Ru(bpy) Cl to
3
2
1
1
mol% still led to a yield of 81% (Table 1, entry 8). Thus,
mol% of Ru(bpy) Cl was used as the photocatalyst. In the
3
2
solvent screening, MeCN provided the highest yield among
all (Table 1, entries 8–13). It is noteworthy that the reaction
was completely inhibited when a base (such as Et N, K CO ,
rides containing functional groups such as NO , Ph, CN, and
2
an ester were also well tolerated under the optimal condi-
tions, affording the desired products 3ba–da in moderate to
high yields. However, the aryl sulfinic chloride, bearing an
electron-donating group such as Me, is unsuitable for the
present reaction conditions. The halo substituents including
3
2
3
or Na HPO ) was added to the reaction mixture. Further-
2
4
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Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E

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T.-f. Niu et al.
Letter
F, Cl, and Br also did not survive the reaction conditions. Be-
sides, aliphatic sulfonyl chloride 1h was inert toward this
transformation. It is worth noting that substrate 2m with a
strong electron-withdrawing group (CN) provided a vinyl
product 4a (78%) under the standard conditions. We
assumed that the electronic property of the alkenes played
a vital role in the transformation, thereby providing a route
for the chemoselective synthesis of vinyl sulfone derivatives
using electron-poor alkenes.
The above results in Scheme 3 prompted us to explore
the applicability of this method for the preparation of vinyl
sulfone derivatives.12 Aryl alkenes containing strong elec-
tron-withdrawing groups such as CN and ester were toler-
ated, affording the corresponding products in high yields
(Scheme 4, 4a and 4b). Other electron-poor alkenes such as
acrylonitrile, α,β-unsaturated amide and α,β-unsaturated
ester also showed good compatibilities, affording the corre-
sponding products 4c–h in moderate to excellent yields.
O
O
Cl
Ru(bpy) Cl
N2, MeCN
R
3
2
S
S
O
+
R
O
Cl
O
blue LED, rt
R
R
1
2
3
Cl
Cl
O
O
S
S
S
O
Cl
O
Cl
O
Cl
O2N
O2N
2
O N
3
aa (81%)
Cl
3ab (83%)
3ac (79%)
O
O
S
O
S
S
O
Cl
O
O
Cl
Cl
O2N
O2N
O2N
3ad (75%)
3ae (85%)
3af (75%)
O
O
S
O
S
S
O
Cl
O
Cl
O
Cl
O2N
O2N
O2N
3ag (76%)
3ah (65%)
3ai (72%)
O
S
O
S
O
S
7
O
Cl
O
Cl
O
Cl
O2N
O2N
O2N
3aj (75%)
3ak (74%)
3al (77%)
O
S
O
S
O
S
O
Cl
O
Cl
O
Cl
EtO2C
Ph
NC
3ba (76%)
3ca (68%)
3da (83%)
O
S
O
S
Cl
Cl
O
Cl
O
O
S
O
X
X = F, Cl, Br
1e
NR
1f–g NR
1h NR
CN
O
O
Cl
Ru(bpy) Cl
N2, MeCN
3
2
S
S
O
+
O
blue LED, rt
O2N
NC
2
O N
1a
2m
4a (78% yield)
Scheme 3 Reaction scope for ATRA. Reagents and conditions: 1 (0.5 mmol), 2 (0.5 mmol), Ru(bpy) Cl ·6H O (1 mol%), and MeCN (2 mL), irradiated
3
2
2
with a 5 W blue LED at rt for 4 h under N atmosphere; isolated yield.
2
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T.-f. Niu et al.
Letter
O
O
Cl
EWG
Ru(bpy)3Cl2
N2, MeCN
S
S
O
+
EWG
O
blue LED, rt
R
R
1
2
4
CN
CO2Me
O
CN
O
S
O
S
S
O
O
O
O2N
O2N
O2N
4a (78%)
4b (65%)
4c (79%)
O
O
O
O
O
S
O
S
S
N
N
O
H
O
O
O
O2N
O2N
O2N
4d (76%)
4e (77%)
4f (74%)
O
O
S
O
S
Cl
O
CN
S
O
O
O
O
X
NC
X = Cl, Br, Me
O2N
4g (70%)
4h (82%)
NR
Scheme 4 Photocatalyzed synthesis of vinyl sulfone derivatives. Reagents and conditions: 1 (0.5 mmol), 2 (0.5 mmol), Ru(bpy) Cl ·6H O (1 mol%) and
3
2
2
MeCN (2 mL), irradiated with a 5 W blue LED at rt for 4 h under N atmosphere; isolated yield.
2
Again, aryl sulfonyl chloride with halo and electron-donat-
ing group were still inert under the present reaction condi-
tions.
ble light irradiation generates the strongly reducing excited
2+
state *[Ru(bpy) ] , and subsequent single-electron transfer
3
(SET) between this species with sulfonyl chlorides 1 gener-
ates [Ru(bpy)3]3 and sulfonyl radical I. Next, addition of
sulfonyl radical I to alkene 2 affords the radical intermedi-
+
3+
ate II, which further undergoes SET with [Ru(bpy)3] com-
plex to deliver intermediate III. Finally, intermediate III
with an electron-donating group may undergo nucleophilic
–
trapping by Cl to afford the corresponding product 3 (path
A), while intermediate III containing an electron-withdraw-
ing group tends to generate product 4 via deprotonation
(path B). The direct formation of 3 through the Cl-atom
transfer from sulfonyl chloride 1 to radical intermediate II is
also the possible pathway (path C). In addition, due to the
electronic effect of the substituents, sulfinic chloride with
electron-donating groups such as p-TsCl and halo substitu-
ents cannot be easily activated at the initial SET process to
generate the sulfonyl radical in this system.
In conclusion, we have developed
a visible-light-
induced chemoselective process to access α-chloro and
vinyl sulfone derivatives without any additives. The selec-
tivity of the reaction is determined by the electronic prop-
erties of the alkenes. A series of substrates survived the re-
action conditions to give the corresponding products in
moderate to good yields. Notably, the prepared α-chloro
and vinyl sulfone derivatives can be further modified to ac-
cess other useful compounds.
Scheme 5 The proposed mechanism
According to our results and previous reports4b,9,10,13
plausible mechanism is depicted in Scheme 5. Initially, ex-
citement of the photoredox catalyst [Ru(bpy)3] under visi-
a
2+
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T.-f. Niu et al.
Letter
Funding Information
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The authors gratefully acknowledge the Natural Science Foundation
of Jiangsu Province, China (BK20160164) for financial support.
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(
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A 10 mL reaction vessel with a magnetic stirring bar was
equipped with 4-nitrobenzenesulfonyl chloride (100 mg, 0.5
mmol), styrene (52 mg, 0.5 mmol), Ru(bpy) Cl ·6H O (7.5 mg,
3
2
2
4910. (f) Wang, Y.-. Q.; He, Y.-T.; Zhang, L.-L.; Wu, X.-X.; Liu, X.-
1
mol%), and MeCN (2 mL). The mixture was irradiated with a
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C. G.; Su, Y. M.; Li, Y.; Lan, Q.; Wang, X. S. Org. Lett. 2016, 18,
blue LED (5 W) and stirred at rt in an air atmosphere for 4 h. The
distance of the reaction vial from the light source was about 2
cm. After the reaction, the solvent was removed under reduced
pressure. Purification of the crude product was achieved by
flash column chromatography using PE/EtOAc (6:1) as eluent;
yield 132 mg (81%). H NMR (400 MHz, CDCl ): δ = 8.27–8.21
4806.
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.24 (d, J = 8.8 Hz, 1 H), 5.39 (t, J = 7.1 Hz, 1 H), 4.10–4.05 (m, 1
13
H), 4.00–3.94 (m, 1 H). C NMR (101 MHz, CDCl ): δ = 150.7,
1
MS: m/z = 326 [M+1] . Anal. Calcd for C14H12ClNO S: C, 51.62; H,
3
3
44.8, 137.8, 129.7,129.5, 129.1, 127.2, 124.1, 64.2, 54.9. ESI-
1
(
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+
4
.71; N, 4.30. Found: C, 51.75; H, 3.83; N, 4.17.
(
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Masson, G. Synthesis 2015, 47, 2439. (i) Tang, X.-J.; Dolbier, W. R.
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Typical Procedure
A
10 mL reaction vessel with
was equipped with 4-nitrobenzenesulfonyl chloride (110 mg,
.5 mmol), 4-vinylbenzonitrile (65 mg, 0.5 mmol), Ru(bpy) Cl ·6H O
a magnetic stirring bar
0
3
2
2
(
7. 5 mg, 1 mol%), and MeCN (2 mL). The mixture was irradiated
with a blue LED (5 W) and stirred at rt in an air atmosphere for
h. The distance of the reaction vial from the light source was
4
about 2 cm. After the reaction, the solvent was removed under
reduced pressure. Purification of the crude product was
achieved by flash column chromatography using PE/EtOAc (6:1)
as eluent; yield 123 mg (78%). H NMR (400 MHz, DMSO): δ =
8
(5) (a) Iqbal, N.; Jung, J.; Park, S.; Cho, E. J. Angew. Chem. Int. Ed.
1
2
2
014, 53, 539. (b) Cao, M.-Y.; Ren, X.; Lu, Z. Tetrahedron Lett.
015, 56, 3732. (c) Yoshioka, E.; Kohtani, S.; Jichu, T.; Fukazawa,
.50–8.45 (m, 2 H), 8.24–8.19 (m, 2 H), 7.96 (m, 5 H), 7.87 (s, 1
13
H). C NMR (101 MHz, DMSO): δ = 151.0, 146.0, 142.5, 137.1,
T.; Nagai, T.; Kawashima, A.; Takemoto, Y.; Miyabe, H. J. Org.
Chem. 2016, 81, 7217. (d) Wang, K.; Meng, L. G.; Wang, L. J. Org.
Chem. 2016, 81, 7080. (e) Huan, F.; Chen, Q. Y.; Guo, Y. J. Org.
Chem. 2016, 81, 7051.
1
3
8
33.3, 130.7, 130.3, 129.5, 125.4, 118.8, 113.8. ESI-MS: m/z =
+
15 [M+1] . Anal. Calcd for C15H10N O S: C, 57.32; H, 3.21; N,
2
4
.91. Found: C, 57.14; H, 3.36; N, 8.83.
(
13) Jiang, H.; Cheng, Y.; Zhang, Y.; Yu, S. Eur. J. Org. Chem. 2013,
5485.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E