Synthesis of cis-1,2-dichlorovinylsulfones via Fe-catalyzed regio- and stereoselective addition of sulfonyl chlorides to aromatic chloroalkynes

Article abstract of DOI:10.1016/j.tetlet.2013.12.063

An iron-catalyzed regio- and stereoselective chlorosulfonylation of aryl chloroalkynes has been described, producing cis-1,2-dichlorovinylsulfones in satisfactory yields with good to excellent stereoselectivity (Z/E up to 95:5). A variety of functional groups such as F, NO₂, Cl, Br, OMe, and t-Bu are found to be compatible under the reaction conditions.

Full text of DOI:10.1016/j.tetlet.2013.12.063

Tetrahedron Letters 55 (2014) 1011–1013
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis of cis-1,2-dichlorovinylsulfones via Fe-catalyzed
regio- and stereoselective addition of sulfonyl chlorides to aromatic
chloroalkynes
a,b,
Lina Wang a, Hui Zhu b, Jianwei Che b, Yuanfa Yang a, , Gangguo Zhu
⇑
⇑
a Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, 688 Yingbin Road, Jinhua 321004, China
b Department of Chemistry, Zhejiang Normal University, 688 Yingbin Road, Jinhua 321004, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An iron-catalyzed regio- and stereoselective chlorosulfonylation of aryl chloroalkynes has been
described, producing cis-1,2-dichlorovinylsulfones in satisfactory yields with good to excellent stereose-
lectivity (Z/E up to 95:5). A variety of functional groups such as F, NO2, Cl, Br, OMe, and t-Bu are found to
be compatible under the reaction conditions.
Received 30 October 2013
Revised 7 December 2013
Accepted 17 December 2013
Available online 21 December 2013
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
1,2-Dihaloalkenes
Chloroalkynes
Iron
Sulfonyl chlorides
Stereoselectivity
Vinyl halides play a pivotal important role in organic chemistry,
and they have been widely exploited as the starting materials or
synthetic intermediates for natural product synthesis, material sci-
ence, and industrial chemicals.1 In this respect, 1,2-dihaloalkenes,
bearing two adjacent carbon–halide bonds, prove to be a class of
very attractive building blocks in organic synthesis, particularly
for assembling stereodefined multisubstituted olefins by the
cross-coupling reactions.2 As such, the interest in these motifs
has been long standing. Along this line, the halogenation of alkynes
appears to be the most straightforward and efficient method for
the preparation of 1,2-dihaloalkenes.3,4 For example, Ogilvie and
co-workers reported an effective synthesis of trans-1-chloro-2-
iodoalkenes by the stereoselective iodochlorination reaction using
n-Bu4NI and 1,2-dichloroethane (DCE).4 However, there are only
limited protocols for accessing the thermodynamic unfavorable
cis-1,2-dihaloalkenes, and consequently, the regio- and stereose-
lective synthesis of cis-1,2-dihaloalkenes is highly desirable.5
Recently, Jiang et al. described a novel trans-hydroiodination or
trans-hydrofluorination of haloalkynes, forming cis-1-halo-
2-iodoalkenes or cis-bromofluoroalkenes in a highly regio- and
transformations of alkynyl halides.7,8 Very recently, Nakamura dis-
covered an elegant Fe-catalyzed stereospecific chlorosulfonylation
of terminal alkynes, giving (E)-b-chlorovinylsulfones with perfect
regio- and stereocontrol.9 Inspired by this protocol, we wish to re-
port here a facile route to cis-1,2-dichloroalkenes via the Fe-cata-
lyzed regio- and stereoselective addition of sulfonyl chlorides to
aryl alkynyl chlorides.10,11
At the outset, phenylsulfonyl chloride (1a) and phenylethynyl
chloride (2a) were chosen for evaluating the reaction parameters.
When the reaction was carried out with 10 mol % of FeCl2 and
P(4-tol)3 in toluene at reflux for 36 h under nitrogen atmosphere,
the desired 1,2-dichloroalkene 3aa was obtained in 62% GC yield,
albeit with a moderate stereoselectivity (Z/E = 74:26) (Table 1, en-
try 1). A brief survey of solvents was then conducted. Pleasingly,
we found that utilizing DCE instead of toluene provided 3aa in
75% isolated yield with better stereoselectivity (Z/E = 91:9) (Table 1,
entry 3).12 Other metal catalysts such as Fe(OTf)2, Fe(OAc)2,
Fe(acac)2, FeF2, CuCl, and CuCl2 were also tested; however, no sig-
nificant improvements were observed (Table 1, entries 4–10). On
the other hand, varying the ligands, including monodentate and
bidentate phosphine ligands, seemed to be ineffective (Table 1, en-
tries 11–18). Therefore, the best reaction conditions for chlorosulf-
onylation of alkynyl chlorides consisted of 10 mol % of FeCl2 and
10 mol % of P(4-tol)3 in DCE at reflux.13 The regio- and stereochem-
istry of this reaction was determined by the single X-ray analysis of
3aa.14
stereoselective manner.6 Meanwhile, we have developed
a
methodology for the efficient and stereocontrolled assembly of
cis- and trans-1,2-dihaloalkenes featuring the Pd-catalyzed
⇑
Corresponding authors. Tel.: +86 579 82283702; fax: +86 579 82282610.
E-mail addresses: sky688@zjnu.cn (Y. Yang), gangguo@zjnu.cn (G. Zhu).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.12.063

1012
L. Wang et al. / Tetrahedron Letters 55 (2014) 1011–1013
Table 1
Table 2
Screening of the reaction conditionsa
Scope of Fe-catalyzed chlorosulfonylation of alkynyl chloridesa
R2
Cl
SO2R1
Cl
FeCl2, P(4-tol)3
DCE, reflux
R1SO2Cl
+
R2
Cl
[M], ligand
solvent
SO2Ph
Cl
1
2
3
PhSO2Cl
+
Cl
R1 (1)
R2 (2)
Z/Eb
Yieldc (%)
Cl
1a
2a
Entry
3aa
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
Ph (1a)
4-Me–C6H4 (2a)
4-F–C6H4 (2b)
91:9
91:9
91:9
91:9
91:9
90:10
91:9
90:10
90:10
92:8
91:9
95:5
91:9
90:10
94:6
/
75 (3aa)
78 (3ab)
86 (3ac)
76 (3ad)
80 (3ae)
77 (3af)
85 (3ag)
83 (3ah)
84 (3ai)
75 (3aj)
81 (3ak)
84 (3al)
55 (3am)
74 (3an)
80 (3ao)
Messy
Entry
[M]
Ligand
Solvent
Z/Eb
Yieldb (%)
4-NO2–C6H4 (2c)
4-Cl–C6H4 (2d)
2-Cl–C6H4 (2e)
2,4-Cl2–C6H3 (2f)
4-Br–C6H4 (2g)
3-Br–C6H4 (2h)
Ph (2i)
4-t-Bu–C6H4 (2j)
4-OMe–C6H4 (2k)
3-OMe–C6H4 (2l)
3,4-(OMe)2–C6H3 (2m)
2-Naphthyl (2n)
1-Naphthyl (2o)
n-C8H17 (2p)
4-Me–C6H4 (2a)
4-Me–C6H4 (2a)
4-Me–C6H4 (2a)
4-Me–C6H4 (2a)
4-Me–C6H4 (2a)
4-Me–C6H4 (2a)
1
2
FeCl2
FeCl2
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(4-tol)3
P(2-tol)3
P(3-tol)3
PPh3
Toluene
THF
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
DCE
74:26
33:67
91:9
79:21
93:7
62
28
3
FeCl2
83 (75)c
25
4
FeCl3
5
6
7
8
Fe(OTf)2
Fe(OAc)2
Fe(acac)2
FeF2
40
52
30
61
58
28
63
68
52
47
89
80
66
60
81:19
81:19
76:24
49:51
62:28
86:14
85:15
83:17
76:24
82:18
77:23
82:18
82:18
9
CuCl
10
11
12
13
14
15
16
17
18
CuCl2
FeCl2
FeCl2
FeCl2
FeCl2
FeCl2
FeCl2
FeCl2
FeCl2
dppb
4-Me–C6H4 (1b)
4-F–C6H4 (1c)
4-Cl–C6H4 (1d)
4-Br–C6H4 (1e)
4-OMe–C6H4 (1f)
Me (1g)
90:10
95:5
94:6
90:10
90:10
86:14
67 (3ba)
81 (3ca)
71 (3da)
91 (3ea)
72 (3fa)
58 (3ga)
P(4-OMeC6H4)3
P(4-CF3C6H4)3
P(C6F5)3
Xphos
a
Reaction conditions: 1a (0.5 mmol), 2a (0.6 mmol), [M] (0.05 mmol), and ligand
(0.05 mmol) in 2 mL of solvent at reflux for 36 h under N2.
a
b
Reaction conditions: 1 (0.5 mmol), 2 (0.6 mmol), FeCl2 (10 mol %) and P(4-tol)3
Determined by GC analysis of the crude mixture.
c
(10 mol %) in 2 mL of DCE at reflux for 36 h.
Isolated yield.
b
Determined by GC analysis of the crude mixture.
c
Isolated yield.
With the optimized reaction conditions in hand, the scope and
limitations of this reaction were then investigated by employing
different types of chloroalkynes as the substrates (Table 2). In gen-
eral, aryl chloroalkynes bearing either electron-withdrawing or
electron-donating groups in the benzene ring were converted into
cis-1,2-dichloroalkenes in satisfactory yields with excellent stere-
oselectivity (Z/E P 90:10). A wide range of functional groups,
including F, NO2, Cl, Br, OMe, and t-Bu were found to be well
tolerated. Moreover, 4-chlorophenyl, 2-chlorophenyl, and 2,4-
dichlorophenyl ethynylchlorides (2d–f) afforded the desired prod-
ucts 3ad–af in comparable yields and selectivity, indicating the
steric hindrance of alkynyl chlorides had little influence on the
reaction (Table 2, entries 4–6). In contrast, the alkyl substrate 2p
failed to produce the expected product under the same conditions
(Table 2, entry 16).
On the other hand, sulfonyl chlorides were also varied and the
results are included in Table 2. For instance, tosyl chloride (1b)
reacted with 2a to provide 3ba in 90% Z-selectivity, while 4-flur-
ophenylsulfonyl chloride (1c) and 4-chlorophenylsulfonyl chloride
(1d) furnished the corresponding cis-1,2-dichloroalkenes 3ca and
3da with a slightly higher stereoselectivity (Table 2, entries 17–
19). Besides aryl sulfonyl chlorides, the alkyl counterparts were
also investigated. When methylsulfonyl chloride (1g) was sub-
jected to the reaction conditions, 3ga was obtained in 58% yield
with decreased stereoselectivity (Z/E = 86:14) (Table 2, entry 22),
which may be attributed to the reduced stability of intermediate
A due to the lack of conjugation interactions in this case (see the
proposed mechanism). In contrast, both alkynyl bromides and sul-
fonyl bromides could not provide synthetic useful results so far.15
To explore the mechanism of this reaction, the coupling of 1a
with 2a was performed in the presence of 10 mol % of 2,2,6,6-
tetramethylpiperidinooxy (TEMPO), and consequently, only 11%
of 3aa was observed (Scheme 1). Running the reaction with
10 mol % of 1,1-diphenylethylene resulted in a significant decline
in the yield (19%), indicating that a radical mechanism might be in-
volved. Furthermore, replacing the FeCl2/P(4-tol)3 combination
conditions
1a
+
2a
3aa
yield
conditions
standard conditions + TEMPO (10 mol %)
standard conditions + 1,1-diphenylethylene (10 mol %) 19%
11%
Scheme 1. Preliminary mechanism study.
with common radical initiators such as BPO (benzoyl peroxide)
and AIBN (azobisisobutyronitrile) just led to low conversions
(<40%). As such, a possible mechanism of this iron-catalyzed chlo-
rosulfonylation reaction is proposed in Scheme 2. First, the electron
transfer between FeCl2 and sulfonyl chlorides 1 affords FeCl3 and a
radical sulfonyl species A.9,10 The addition of A with chloroalkynes
2 produces a vinyl radical intermediate B, followed by trapping
with FeCl3 to give cis-1,2-dichloroalkenes 3 and to regenerate the
FeCl2 catalyst (Scheme 2). Similar trans-addition of sulfonyl chlo-
rides across the C–C triple bonds has been well documented in
the previous reports.9,10 As shown in Scheme 2, the replacement
of Ar with alkyl group, such as n-C8H17, will lead to the failure of
this reaction due to the lack of stability caused by conjugation
effects.
In conclusion, we have realized an iron-catalyzed regio- and
stereoselective chlorosulfonylation of aromatic chloroalkynes,
1
3
1
R SO2Cl (
)
FeCl2
FeCl3
R1SO2
A
( )
Cl
Ar
Cl
SO2R1
2
Ar
B
Scheme 2. A possible mechanism.

L. Wang et al. / Tetrahedron Letters 55 (2014) 1011–1013
1013
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furnishing cis-1,2-dichlorovinylsulfones in satisfactory yields with
good to excellent stereoselectivity. It provides a new effective
protocol for the synthesis of thermodynamically unfavorable
cis-1,2-dichloroalkenes. The tolerance of F, NO2, Cl, Br, OMe, t-Bu,
and other groups enables it a useful method for organic synthesis.
Further investigations on the reaction mechanism and the
synthetic utility of this reaction16 are currently undergoing in our
group.
Acknowledgments
We thank for the financial support from the Natural Science
Foundation of Zhejiang Province (LR12B02001), National Natural
Science Foundation of China (21172199) and Open Research Fund
of Key Laboratory of the Ministry of Education for Advanced Catal-
ysis Materials (ZJHX201310).
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Supplementary data
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12. The stereoselectivity of 3aa detected at different conversions (15%, 49% and
68%) was essentially same (Z/E = 90:10), implying that the stereoselectivity is
controlled by kinetic effects.
Supplementary data (experimental details, NMR spectra, and
analytical data of products 3) associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.tetlet.2013.12.063.
References and notes
13. Representative procedure for the Fe-catalyzed chlorosulfonylation of
chloroalkynes: To
(6.4 mg, 0.05 mmol) in 2 mL of DCE were added 2a (90.4 mg, 0.6 mmol) and
phenylsulfonyl chloride (1a) (64 L, 0.5 mmol) under nitrogen atmosphere.
a mixture of P(4-tol)3 (15.4 mg, 0.05 mmol) and FeCl2
1. Stavber, S.; Jereb, M.; Zupan, M. Synthesis 2008, 1487.
l
2. (a) Huynh, C.; Linstrumelle, G. Tetrahedron 1988, 44, 6337; (b) Wright, M. E.;
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Synthesis 2008, 2650; (g) Rajagopal, T.; Flynn, A. B.; Ogilvie, W. W. Tetrahedron
2010, 66, 8739; (h) Ngi, S. I.; Cherry, K.; Héran, V.; Commeiras, L.; Parrain, J.-L.;
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After stirring at reflux for 36 h, the reaction mixture was quenched with 5 mL
of water, extracted with ethyl acetate, washed with brine, dried over
anhydrous Na2SO4, and concentrated. Z/E = 91:9 (determined by GC). Column
chromatography on silica gel gave 3aa as a white solid (122 mg, 75% yield);
mp: 147–149 °C; 1H NMR (400 MHz, CDCl3): d 7.76–7.71 (m, 2H), 7.62–7.58
(m, 1H), 7.52–7.44 (m, 2H), 7.25 (d, J = 7.6 Hz, 2H), 7.21 (d, J = 8.0 Hz, 2H), 2.40
(s, 3H); 13C NMR (100 MHz, CDCl3): d 145.2, 140.8, 138.6, 134.1, 132.3, 131.8,
129.0, 128.8, 128.7, 128.7, 21.5; MS (EI, m/z): 330 (1), 328 (5), 326 (M+, 11), 173
(70), 150 (64); HRMS (EI) calcd for
325.9937.
C
15H12Cl2O2S (M+) 325.9935, found
14. Crystal data for 3aa (C15H12Cl2O2S, 327.21): monoclinic, space group P2(1)/c,
a = 13.1952(6) Å, b = 14.6121(6) Å, c = 7.9066(3) Å, U = 1496.80(11) Å3, Z = 4,
T = 296(2) K, absorption coefficient 0.570 mmÀ1, reflections collected 12404,
independent reflections 3389 [R(int) = 0.0305], refinement by full-matrix least-
squares on F2, data/restraints/parameters 3389:0:182, goodness-of-fit on
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F
2 = 1.083, final R indices [I > 2
r(I)] R1 = 0.0514, wR2 = 0.1301, R indices (all
data) R1 = 0.0812, wR2 = 0.1462, largest diff peak and hole 0.839 and
À0.723 e ÅÀ3. Crystallographic data for 3aa have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication no.
CCDC 968935. These data can be obtained from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
15. Oligomerization of bromoalkynes was observed under the reaction conditions,
while low conversions were obtained when sulfonyl bromides were employed
as the substrates.
16. Attempts to the synthesis of multifunctional alkenes via the cross-coupling of
two C–Cl bonds of 3 resulted in unsatisfactory results so far, due to the
formation of alkynyl sulfones via elimination reaction, for a related reference,
see: Ref. 2d.
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