An efficient one-pot, three-component synthesis of vinyl sulfones via iodide-catalyzed radical alkenylation

Article abstract of DOI:10.1016/j.tet.2015.07.043

An efficient one-pot, three-component synthesis of vinyl sulfones via iodide-catalyzed radical alkenylation using aryl diazonium salts, terminal alkenes and DABSO is reported. This protocol offers good yields and tolerates a broad range of functional groups. Based on the extensive control experiments, we propose a plausible radical mechanism.

Full text of DOI:10.1016/j.tet.2015.07.043

Accepted Manuscript
An Effeicient One-pot, Three-Component Synthesis of Vinyl Sulfones via Iodide-
catalyzed Radical Alkenylation
Weizheng Fan, Jiapeng Su, Dongyang Shi, Bainian Feng
PII:
S0040-4020(15)01088-1
10.1016/j.tet.2015.07.043
TET 26988
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 9 June 2015
Revised Date: 10 July 2015
Accepted Date: 14 July 2015
Please cite this article as: Fan W, Su J, Shi D, Feng B, An Effeicient One-pot, Three-Component
Synthesis of Vinyl Sulfones via Iodide-catalyzed Radical Alkenylation, Tetrahedron (2015), doi: 10.1016/
j.tet.2015.07.043.
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ACCEPTED MANUSCRIPT
Graphical Abstract
An Effeicient One-pot, Three-Component Synthesis of Vinyl
Sulfones via Iodide-catalyzed Radical Alkenylation
Weizheng Fan, Jiapeng Su, Dongyang Shi, Bainian Feng*
School of Pharmaceutical Science, Jiangnan University, Wuxi 214122, China
O
S
TABI(10 mol%)
TBHP (2 equiv)
R2
R1
DABCO (SO2)2
R1N2BF4
R2
CH3CN, 80 oC
O
2
DABSO
3
An efficient one-pot, three-component synthesis of vinyl sulfones via
iodide-catalyzed radical alkenylation using aryl diazonium salts, terminal alkenes and
DABSO is reported. This protocol offers good yields and tolerates a broad range of
functional groups. Based on the extensive control experiments, we propose a plausible
radical mechanism.

ACCEPTED MANUSCRIPT
An Effeicient One-pot, Three-Component Synthesis of Vinyl
Sulfones via Iodide-catalyzed Radical Alkenylation
Weizheng Fan, Jiapeng Su, Dongyang Shi, Bainian Feng*
School of Pharmaceutical Science, Jiangnan University, Wuxi 214122, China
*Corresponding author. E-mail: fengbainian@jiangnan.edu.cn,
A B S T R A C T
An efficient one-pot, three-component synthesis of vinyl sulfones via
iodide-catalyzed radical alkenylation using aryl diazonium salts, terminal alkenes and
DABSO is reported. This protocol offers good yields and tolerates a broad range of
functional groups. Based on the extensive control experiments, we propose a plausible
radical mechanism.
Keywords: Iodide-catalyzed, sulfones, alkenylation, radical mechanism
1. Introduction
Vinyl sulfones are an important organic structural motifs found in natural products
and biologically active molecules.1 They also exhibit interesting chemical properties
and are useful intermediates in organic synthesis.2 Thus, intense efforts have focused
on the development of these synthetic methods, including the oxidation of the
corresponding sulfides,3 condensation of aromatic aldehydes with sulfonylacetic
acids,4 and β-elimination of selenosulfones or halosulfones.5 Recently, an efficient
two-component coupling method is developed, which used sulfinate salts and
different vinyl sources, including vinyl halides,6a–c vinyl tosylates,6d vinyl triflates,6e
alkenylboronic acids,6f alkenes,6g cinnamic acids6h or alkynes6i in the presence of a
metal catalyst. Similarly, Lei’s group reported a radical oxidative alkenylation to
afford vinyl sulfones using sulfonyl hydrazides with simple alkenes.7 Besides, Li’s
group has also developed a selective method for the preparation of (E)-vinyl sulfones
via C–S cleavage.8
O
R
2
S
X
R
1
ONa
X = halides, tosylates,
triflates, boronic acids, H, COOH
Ref. 6a-6h
O
S
O
S
Ref. 7
R
2
DABCO (SO )
R N BF
4
2 2
R
1
1
2
R
2
R
1
R
NHNH
2
2
O
O
This work
Y= COOH, H
Ref. 6i
R
O
S
2
Y
R
ONa
1
Scheme 1. Coupling methods for the synthesis of vinyl sulfones

ACCEPTED MANUSCRIPT
Although diverse successful synthesis of vinyl sulfones have been afforded, the
scope of arylsulfinate salts reported6 was limited due to their’s not commercially
available or pre-synthesized. So the development of one-pot and many-component
practical synthetic methods for vinyl sulfones with more simple starting marterials is
still needed. Recently, Willis developed a new convenient reagent DABSO
(DABCO·SO2, the combination of DABCO and sulfur dioxide), which can serve as a
surrogate of SO2 for the in situ formation of sulfinate salts in the synthesis of
sulfonamides and sulfamides.9 Since then, many synthesis of sulfones were reported
using DABSO.10 Inspired by these simplified synthesis, we attempted to employ the
same reagent of DABSO to achieve vinyl sulfones. Herein, we report an efficient
one-pot, three-component synthesis of vinyl sulfones via iodide-catalyzed radical
alkenylation using aryl diazonium salts, terminal alkenes and DABSO. The control
experiments suggested a radical mechanism.
2. Results and discussion
We initially chose phenyl diazonium salts (1a), phenylethylene (2a) and DABSO as
the substrates to test the reaction (Table 1). The well-established I–/TBHP radical
system7, 11 was chosen, in the presence of DABSO. We found that the combination of
KI and TBHP with CH3CN as solvent gave good yield of 3a (65%) at 80 oC (Table 1,
entry 1). On the contrary, the reactions did not work under the same conditions using
KBr or KCl as catalyst (Table 1, entries 2–3). When nBu4NI was used as catalyst
instead of KI, the yield of 3a increased to 82% (Table 1, entry 4). Other catalysts
containing an iodide anion, such as CuI, NaI and I2, gave no good results (SI-table 1).
Then, other oxidants such as H2O2, DTBP, BPO, DDQ and K2S2O8 were also
examined (Table entries 5–9). But no improvement was afforded. The use of other
solvents (Table 1, entries 10–13) or increasing the amount of loading catalyst or
oxidant, led no significant improvement on the yield (SI-table 1), nevertheless,
temperature influenced the reaction remarkably (Table 1, entry 14). 3a was not
afforded in the absence of nBu4NI or TBHP (Table 1, entries 15–16).
Table 1
Optimization of the reaction conditions
O
Catalyst, Oxidant
T, Solvent
Ph
S
Ph
DABCO
(SO )
PhN BF
2 2
Ph
2
4
O
3a
1a
2a
DABSO
Entrya Catalyst (10 mol%)
Oxidant (2 equiv)
TBHP
Sovlent /T (oC)
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
Yield (%)b
1
2
3
4
5
6
7
8
9
KI
65
0
KBr
TBHP
KCl
TBHP
0
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
TBHP
82
25
67
49
0
H2O2
DTBP
BPO
DDQ
K2S2O8
<5

ACCEPTED MANUSCRIPT
10
11
12
13
14
15
16
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
no
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
no
CH3OH/65
0
DCE/90
41
<5
0
Toluene/110
DMSO/120
CH3CN/60
CH3CN/80
CH3CN/80
49
0
nBu4NI
0
(a) Conditions: 1a (0.2 mmol), 2a (0.3 mmol), DABSO (0.25 mmol), Catalyst (10 mol%),
Oxidant (2 equiv), in 5 mL Solvent at proper temperature under Ar atmosphere for 12 h; (b)
isolated yield.
Encouraged by the preliminary results, we tried to explore the functional group
tolerance for the synthesis of vinyl sulfones. First of all, various substituted diazonium
salts were tried. The reaction showed a good tolerance to many functional groups,
including electron-donating and electron-withdrawing groups (Table 2, 3a–3h, e.g.,
OMe, Cl, Br, F, CF3, NO2). In addition, hetero-substitutes 3i and 3j also showed good
activity. Besides, alkyl diazonium salts (3k and 3l) were also employed well in this
process, affording the corresponding products in excellent yields. Next, various
alkenes were employed to synthesize alkenyl sulfones (3m–3r). Substrates with
electron-withdrawing groups on arenes rings (3m, 3n) afforded morderate yields.
However, hetero-alkene (3p), methyl acrylate (3q) and ethyl acrylate (3r) showed
good activity.
Table 2
Screening the substrates

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O
S
TBAI(10 mol%)
TBHP (2 equiv)
R2
R1
DABCO (SO2)2
R1N2BF4
R2
CH3CN, 80 oC
O
1
2
DABSO
3
O
S
O
S
O
S
Ph
Ph
Ph
H3CO
O
O
O
3c, 87%
3a, 82%
3b, 79%
O
S
O
S
O
S
Ph
Ph
Ph
Cl
F
Br
O
O
O
3d, 80%
3e, 73%
3f, 81%
O
O
S
O
S
S
Ph
Ph
F3C
O2N
Ph
O
O
O
O
3g, 65%
3h, 78%
3i, 84%
O
S
O
S
O
S
Ph
Ph
Ph
S
O
O
O
3j, 75%
3k, 88%
3l, 72%
O
O
O
S
S
S
Ph
Ph
Ph
O
O
O
CF3
NO2
3m, 69%
3n, 58%
3o, 75%
O
S
O
S
O
S
O
O
Ph
Ph
Ph
O
O
O
O
N
O
3p, 83%
3q, 71%
3r, 84%
Conditions: 1 (0.2 mmol), 2 (0.3 mmol), DABSO (0.25 mmol), TBAI (10 mol%), TBHP (2
equiv), in 5 mL CH3CN at 80 oC under Ar atmosphere for 12 h.
In order to study the mechanism for the synthesis of vinyl sulfones, control
experiments were employed as shown in Scheme 2. Firstly, the reaction ceased when
TEMPO (5 equiv) was employed under standard conditions and the TEMPO-radical
adduct of 3b’ was isolated in 43% yield, which implied that the reaction may be
proceeding through a radical intermediate. When radical inhibitor BHT
(2,6-di-tert-butyl-4-methylphenol) was introduced to the reaction mixture, the
formation of the desired product 3b was completely suppressed. Secondly, we found
that 3b was obtained in moderate yields (65%) when phenylethylene (2a) was allowed
to react with a freshly prepared p-toluenesulfonyl iodide (1b-I, yellowish solid).12
Finally, 1b reacted with DABSO in the presence of 1 equiv I2, affording

ACCEPTED MANUSCRIPT
p-toluenesulfonyl iodide (1b-I) in 59% yield.
O
S
N
N2BF4
Ph
5 equiv TEMPO
O
DABCO
(SO2)2
(1)
(2)
O
Standard conditions
2a
DABSO
1b
3b', 43%
O
O
S
Ph
S
I
Ph
O
O
2a
3b, 65%
O
1b-I
1b
N2BF4
S
O
1 equiv I2
DABSO
(3)
I
1b-I, 59%
Scheme 2. Control experiments
On the basis of the above results, a plausible mechanism for this radical
alkenylation is proposed, as shown in Scheme 3. First, TBHP decomposes to generate
the tert-butoxyl and hydroxyl radicals with the assistance of the iodide anion.13
Secondly, the decomposition of the diazonium salts in the presence of tBuO– forms
the phenyl radical.14 Subsequently the addition of DABSO affords sulfonyl radical.
After that, two paths may be involved. From path A, the addition of sulfonyl radical to
I2 formed intermediate I. Sulfonyl halides (I) easily generate corresponding sulfonyl
radicals and cause atom transfer radical additions to multiple bonds to form III.15
From path B, the addition of sulfonyl radical to 2a forms intermediate II.7 The radical
II reacts with in situ generated iodine to generate β-iodosulfone.7 Finally, elimination
of HI similar to the β-hydride elimination forms 3a to finish the catalytic cycle.7
1/2 I2
OH
OtBu
I
TBHP
PhN2
1a
Ph
O
S
3a
DABSO
I2
2a
PhSO2
Ph
Ph
II
I
III
Ph
Path A
Path B
I
O
S
O
O
Ph
I
Ph
I2
Ph
S
2a
DABSO
O
PhSO2
O
Ph
III
Scheme 3. Proposed formation mechanism
3. Conclusions
In summary, we present an efficient one-pot, three-component synthesis of vinyl
sulfones via iodide-catalyzed radical alkenylation using aryl diazonium salts, terminal
alkenes and DABSO. This synthesis is suitable for abroad range of substrates. The
control experiments suggested a possible radical mechanism. Further studies
concerning the detailed mechanism and the broader scope of substrates are currently
underway in our laboratory.
4. Experiment
4.1. General
Procedure for synthesis of 3a–3r: A mixture of 1 (0.2 mmol), 2 (0.3 mmol), DABSO

ACCEPTED MANUSCRIPT
(0.25 mmol), TBAI (10 mol%) and TBHP (2 equiv) in CH3CN (5 mL) was stirred at
o
80 C under Ar atmosphere for 12 h. After the reaction system was cooled to room
temperature, saturated NH4Cl solution (30 mL) and EtOAc (20 mL) were added. The
combined organic phases were dried over Na2SO4 and then concentrated to give crude
products. Further separation by column chromatography on silica gel (eluant with
EtOAc and n-hexane) gave the corresponding products (3a–3g,6i 3j–3n,6h 3p–3r,6h
3b’16).
4.2 Characterization Data
o
1
3h: (E)-1-Nitro-4-(styrylsulfonyl)benzene (78%) Yellow solid; mp 138–139 C; H
NMR (500 MHz, CDCl3): 8.14 (d, J = 8.6 Hz, 2H), 7.87 (d, J = 8.6 Hz, 2H), 7.71
(d, J = 14.8 Hz, 1H), 7.59 (d, J = 6.4 Hz, 2H), 7.45 (q, J =6.4 Hz, 3H), 6.89 (d, J
=14.8 Hz, 1H); 13C NMR (125 MHz, CDCl3): 148.1, 139.7, 134.6, 132.92, 131.5,
130.2, 129.1, 128.4, 126.5; HRMS (EI+) m/z calcd. for C14H11NO4S [M]+: 289.0409,
found 289.0412.
o
1
3i: (E)-2-(Styrylsulfonyl)oxole (84%) Pale yellow solid; mp 53–55 C; H NMR
(500 MHz, CDCl3): 7.75 (d, J = 3.0 Hz, 1H), 7.68–7.63 (m, 2H), 7.52 (d, J =15.2
Hz, 1H), 7.48 (d, J = 4.8 Hz, 1H), 7.44–7.39 (m, 3H), 7.14 (dd, J =4.8, 3.2 Hz,
1H), 6.92 (d, J =15.2 Hz, 1H); 13C NMR (125 MHz, CDCl3): 142.5, 141.9, 135.1,
134.8, 132.2, 131.0, 129.5, 128.7, 127.9, 127.5; HRMS (EI+) m/z calcd. for
C12H10O3S [M]+: 234.0351, found 234.0349.
1
3o: (E)-1-[2-(Phenylsulfonyl)vinyl]-4-(methyl)benzene (75%) mp 121-123 ºC; H
NMR (500 MHz, CDCl3): 8.02 (d, J = 8.2 Hz, 2H), 7.83 (d, J = 8.2 Hz, 2H), 7.65
13
(d, J = 15.0 Hz, 1H), 7.58 (m, 5H), 6.95 (d, J = 15.0 Hz, 1H), 2.45 (s, 3H); C
NMR (125 MHz, CDCl3): 145.7, 139.5, 138.9, 137.4, 133.1, 130.8, 129.7, 129.2,
127.5, 124.3, 21.8; HRMS (EI+) m/z calcd. for C15H14O2S [M]+: 258.0715, found
258.0718.
Acknowledgments
This work was supported financially by grants from the National Natural Science
Foundation of China (grants 21302066) and Young Program, SCF of Jiangsu
Province (BK20130129).
Supplementary material
Supplementary data associated with this article can be found, in the online
version, at http://dx.doi.org/
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Supporting Information
An Effeicient One-pot, Three-Component Synthesis of Vinyl
Sulfones via Iodide-catalyzed Radical Alkenylation
Weizheng Fan, Jiapeng Su, Dongyang Shi, Bainian Feng*
*School of Pharmaceutical Science, Jiangnan University, Wuxi 214122, China
E-Mail: fengbainian@jiangnan.edu.cn
I. General remarks
2
2
II. Experimental section
1. Optimization of the transformation from 1a to 3a
2. Supporting experiments for the proposed mechanism
3. Characterization data and the spectrum of new compounds
2
3
4
1

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I. General remarks
All starting materials and reagents were purchased from commercial sources and used
as received unless otherwise noted. Analytical thin layer chromatography (TLC) was
performed on silica gel 60 F254 plates. Flash column chromatography was undertaken
1
P
on silica gel (200–300 mesh).
P
H NMR was recorded on Bruker DRX 500 and
chemical shifts were referenced to the appropriate solvent peak or 7.24 ppm for
13
P
residual d–chloroform.
P
C NMR was recorded on 125 MHz and fully decoupled by
broad band proton decoupling. Chemical shifts were reported in ppm referenced to the
center line of a triplet at 77.0 ppm of d–chloroform. High resolution mass spectra
were measured on Agilent-G6540 UHD Accurate-MassQ-TOF.
II. Experimental section
1. Optimization of the transformation from 1a to 3a
SI-Table 1. Optimization the catalysts and oxidants for the transformation
O
Catalyst, Oxidant
T, Solvent
Ph
S
Ph
DABCO
(SO )
PhN BF
2 2
Ph
2
4
O
3a
1a
2a
DABSO
Entrya
Catalyst (10 mol%)
KI
Oxidant (2 equiv)
TBHP
Sovlent /T (oC)
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
Yield (%)h
1
65
0
2
KBr
TBHP
3
KCl
TBHP
0
4
NaI
TBHP
41
<5
50
82
25
67
49
0
5
CuI
TBHP
6
I2
TBHP
7
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
TBHP
8
H2O2
9
DTBP
10
11
12
13
BPO
DDQ
K2S2O8
O2 (1 atm)
<5
<5
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14
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
nBu4NI
no
BQ
CH3CN/80
0
15
PhI(OAc)2
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
TBHP
no
CH3CN/80
CH3OH/65
DCE/90
0
16
0
17
41
<5
0
18
Toluene/110
DMSO/120
CH2Cl2/35
CH3CN/60
CH3CN/40
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
CH3CN/80
19
20
0
21
49
<5
0
22
23
24
nBu4NI
nBu4NI (20)
nBu4NI (5)
nBu4NI
nBu4NI
nBu4NI
nBu4NI
0
25b
26c
27d
28e
29f
29g
TBHP
TBHP
TBHP (2.5)
TBHP (1.5)
TBHP
TBHP
85
47
80
58
78
65
(a) 1a (0.2 mmol), 2a (0.3 mmol), DABSO (0.25 mmol), Catalyst (10 mol%), Oxidant (2 equiv),
in 5 mL Solvent at proper temperature under Ar atmosphere for 12 h; (b) Catalyst (20 mol%); (c)
Catalyst (5 mol%); (d) Oxidant (2.5 equiv); (e) Oxidant (1.5 equiv); (f) DABSO (0.3 mmol); (g)
DABSO (0.2 mmol); (h) isolated yield.
2. Supporting experiments for the proposed mechanism
O
N
S
N BF
Ph
2
4
5 equiv TEMPO
O
DABCO
(SO )
2 2
(1)
(2)
O
Standard conditions
2a
DABSO
1b
3b', 43%
O
O
S
Ph
S
I
Ph
O
O
2a
3b, 65%
1b-I
1b
O
N BF
2
4
S
O
1 equiv I
2
DABSO
(3)
I
1b-I, 59%
A. Firstly, the reaction ceased when TEMPO (5 equiv) was employed under standard
conditions and the TEMPO-radical adduct of 3b’ was isolated in 43% yield, which
implied that the reaction may be proceeding through a radical intermediate. When
radical inhibitor BHT (2,6-di-tert-butyl-4-methylphenol) was introduced to the
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reaction mixture, the formation of the desired product 3b was completely suppressed.
B. Secondly, we found that 3b was obtained in moderate yields (65%) when
phenylethylene (2a) was allowed to react with a freshly prepared p-toluenesulfonyl
iodide (yellowish solid).
C. Finally, 1b reacted with DABSO in the presence of 1 equiv I2, affording
p-toluenesulfonyl iodide in 59% yield.
3. Characterization data and the spectrum of new compounds
o
1
3h: (E)-1-Nitro-4-(styrylsulfonyl)benzene (78%) Yellow solid; mp 138–139 C; H
NMR (500 MHz, CDCl3): 8.14 (d, J = 8.6 Hz, 2H), 7.87 (d, J = 8.6 Hz, 2H), 7.71
(d, J = 14.8 Hz, 1H), 7.59 (d, J = 6.4 Hz, 2H), 7.45 (q, J =6.4 Hz, 3H), 6.89 (d, J
=14.8 Hz, 1H); 13C NMR (125 MHz, CDCl3): 148.1, 139.7, 134.6, 132.92, 131.5,
130.2, 129.1, 128.4, 126.5; HRMS (EI+) m/z calcd. for C14H11NO4S [M]+: 289.0409,
found 289.0412.
o
1
3i: (E)-2-(Styrylsulfonyl)oxole (84%) Pale yellow solid; mp 53–55 C; H NMR
(500 MHz, CDCl3): 7.75 (d, J = 3.0 Hz, 1H), 7.68–7.63 (m, 2H), 7.52 (d, J =15.2
Hz, 1H), 7.48 (d, J = 4.8 Hz, 1H), 7.44–7.39 (m, 3H), 7.14 (dd, J =4.8, 3.2 Hz,
1H), 6.92 (d, J =15.2 Hz, 1H); 13C NMR (125 MHz, CDCl3): 142.5, 141.9, 135.1,
134.8, 132.2, 131.0, 129.5, 128.7, 127.9, 127.5; HRMS (EI+) m/z calcd. for
C12H10O3S [M]+: 234.0351, found 234.0349.
1
3o: (E)-1-[2-(Phenylsulfonyl)vinyl]-4-(methyl)benzene (75%) mp 121-123 ºC; H
NMR (500 MHz, CDCl3): 8.02 (d, J = 8.2 Hz, 2H), 7.83 (d, J = 8.2 Hz, 2H), 7.65
13
(d, J = 15.0 Hz, 1H), 7.58 (m, 5H), 6.95 (d, J = 15.0 Hz, 1H), 2.45 (s, 3H); C
NMR (125 MHz, CDCl3): 145.7, 139.5, 138.9, 137.4, 133.1, 130.8, 129.7, 129.2,
127.5, 124.3, 21.8; HRMS (EI+) m/z calcd. for C15H14O2S [M]+: 258.0715, found
258.0718.
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