Simple synthesis of sulfonyl chlorides from thiol precursors and derivatives by NaClO2-mediated oxidative chlorosulfonation

Article abstract of DOI:10.1055/s-0033-1339675

A simple method to synthesize diverse sulfonyl chlorides through NaClO ₂-mediated oxidative chlorosulfonation of S-alkyl isothiourea salts is presented. The approach features safe operation, environmental friendliness, convenient purification procedures, and delivers high yields of up to 96%. The procedure is also applicable to substrates such as thiols, disulfides, thioacetates, and xanthates. It is a versatile and convenient method for the synthesis of various sulfonyl chlorides from different thiol precursors and derivatives. Georg Thieme Verlag Stuttgart, New York.

Full text of DOI:10.1055/s-0033-1339675

LETTER
▌2165
lSetitemr ple Synthesis of Sulfonyl Chlorides from Thiol Precursors and Derivatives
by NaClO -Mediated Oxidative Chlorosulfonation
2
Synthesis of Sulfonyl Chlorides
Zhanhui Yang, Yongpeng Zheng, Jiaxi Xu*
State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, Faculty of Science, Beijing University of Chemical
Technology, Beijing 100029, P. R. of China
Fax +86(10)64435565; E-mail: jxxu@mail.buct.edu.cn
Received: 29.06.2013; Accepted after revision: 03.08.2013
With respect to their significant importance, sulfonyl
Abstract: A simple method to synthesize diverse sulfonyl chlorides
chlorides have received increasing interest during the past
through NaClO -mediated oxidative chlorosulfonation of S-alkyl
isothiourea salts is presented. The approach features safe operation,
2
centuries. Generally, the chlorination of sulfonic acids or
3
environmental friendliness, convenient purification procedures, and their salts, and oxidative chlorosulfonation of thiols and
4
delivers high yields of up to 96%. The procedure is also applicable their precursors or derivatives, are the two predominant
to substrates such as thiols, disulfides, thioacetates, and xanthates. methods for the synthesis of sulfonyl chlorides. The first
It is a versatile and convenient method for the synthesis of various
sulfonyl chlorides from different thiol precursors and derivatives.
method always suffers from the required use of reactive
3a
3b
3c
and hazardous reagents such as SOCl , PCl3, PCl5,
2
3
d
3e
3f
Key words: sulfonyl chloride, sodium chlorite, oxidative chloro-
sulfonation, synthetic methods, isothiourea
POCl , oxalyl chloride, or phosgene. Modified, mild
3
3g
chlorinating reagents such as PPh ·Cl
and cyanuric
3
2
3
h
chloride generate large amounts of byproducts. Com-
pared with the first methods, the second approach usually
gives the desired products in high yields in a single step
from thiols and their derivatives. Many relatively safe and
Sulfonyl chlorides are versatile building blocks for the
synthesis of sulfonic acid derivatives and are important
synthetic intermediates for the introduction of a sulfonyl
mild oxidative chlorosulfonating reagents have been de-
1
4
group. One representative type of sulfonic acid derivative
Most of the substrates
veloped to replace chlorine gas.
is the sulfonamide group, which is commonly used in an- employed in the above conditions are thiols or their deriv-
2
tibacterial medicines and enzyme inhibitors (Scheme 1).
The most efficient route toward the synthesis of sulfon-
amides is the coupling of sulfonyl chlorides and amines.
Sulfonyl chlorides have also been widely applied in the
atives, which are not friendly to workers or the environ-
ment because of their strong and repulsive odors.
Furthermore, compared with alkyl halides, thiols and their
5
derivatives are either not easily available or expensive.
production of fine chemicals, such as detergents, dyes, Thus, the preparation of sulfonyl chlorides in a simple and
and herbicides.1
b,c
environmentally friendly way is of ongoing concern in the
synthetic community.
HOOC
O
O
S
N
Cl
H2N
H
Cl
Cl
HN
E7070
antitumor agent, ref. 2a
O
O
S
S
O
O
Cl
N
H
N
Efipladib
indole cPLA2α inhibitors
Ph
Ph
ref. 2b
NH2
O
O
S
N
N
X
N
N
O
N
N
O
F
N
X = Cl,
X = 4-MeC6H4
O
S
HN
Me
glucan synthase inhibitors
ref. 2c
immunomodulator
ref. 2d
F
Scheme 1 Representative important sulfonamides generated from sulfonyl chlorides as building blocks
SYNLETT 2013, 24, 2165–2169
Advanced online publication: 26.08.2013
0
9
3
6
-
5
2
1
4
1
4
3
7
-
2
0
9
6
DOI: 10.1055/s-0033-1339675; Art ID: ST-2013-W0601-L
Georg Thieme Verlag Stuttgart · New York
©

2166
Z. Yang et al.
LETTER
6
c
In our previous work, we modified the N-chlorosuccin- had little effect on the yield (Table 1, entries 4 and 5).
imide-mediated synthesis of sulfonyl chlorides from the However, when solid NaClO was replaced by its water
2
6
substrate aspect, by using more convenient S-alkyl iso- solution, the yield decreased from 82 to 62% (Table 1, en-
thiourea salts instead of malodorous thiols and their deriv- try 6). Prolonging the reaction time to two hours gave a
atives. In that procedure, however, organic waste yield of 71% (Table 1, entry 7).
succinimide was generated in large amount and, conse-
quently, contamination of the products, especially liquid
Under the optimized experimental conditions, starting
material 2a was almost completely consumed, and the by-
product urea and NaCl are quite soluble in water; howev-
products, was problematic. As an extension of our previ-
6
c
ous study, we wanted to solve that problem and find an
easily accessible and worker-safe oxidative chlorosulfo-
nating reagent, for which the reduction product does not
cause contamination of the desired products. After numer-
ous attempts, the commercially available, inexpensive re-
er, it was likely that there may be some sulfonic acid
generated from the hydrolysis of the sulfonyl chloride.
Since the sulfonic acid is strongly hydrophilic, we be-
lieved it would act like a surfactant and stay in the aqueous
phase during the purification. Based on these consider-
ations, we developed a convenient procedure with which
to quickly and easily purify the benzylsulfonyl chloride.
After completion of the reaction, water was added and the
resulting solution was evaporated at less than 20 °C in
vacuum to remove acetonitrile, upon which a large
amount of white solid ‘recrystallized’ from the solution.
Filtration of the solid and drying under infrared light af-
agent NaClO , which is a reagent widely applied in
2
7
Pinnick oxidation or Lindgren oxidation, was identified.
Herein, for the first time, we present the NaClO -mediated
2
oxidative chlorosulfonation of S-alkyl thiourea salts to
prepare and purify sulfonyl chlorides in a simple proce-
dure. The method can also be applied in the oxidative
chlorosulfonation of thiols and their derivatives.
Optimization of the conditions commenced by treating S- forded benzylsulfonyl chloride in analytical purity. This
benzyl isothiouronium chloride (2a) with solid NaClO2 procedure was found to be general for the purification of
(
2 equiv) and concentrated HCl (2 mL) in water, which is solid sulfonyl chlorides. The procedure for the purifica-
the most preferred solvent from the standpoint of green tion of liquid sulfonyl chlorides was also proposed as fol-
chemistry. However, since the yield was unsatisfactory lowing: after removal of acetonitrile in the same way, the
(
Table 1, entry 1), we replaced the water with acetonitrile, products could be obtained through a sequence of extrac-
which is also a usable solvent in green chemistry accord- tion with ethyl acetate (a preferred solvent in green chem-
8
ing to Pfizer solvent selection guide; use of this solvent istry), drying with Na SO , and removal of the solvent
2
4
dramatically improved the yield to 55% (Table 1, entry 2). under vacuum (Scheme 2). The applicability of this pro-
Further optimization by using NaClO (3 equiv) and con- cedure was confirmed in subsequent reactions.
2
centrated HCl (3 mL) gave a satisfactory yield of 82%
(
Table 1, entry 3). Changing the addition sequence of
filtration,
drying
NaClO and concentrated HCl, or increasing their amount
2
RSO2Cl
NaClO2, concd HCl,
MeCN, 10–20 °C
H2N
solid products
+
Table 1 Optimizing Reaction Conditionsa
NH X–
2
extraction,
drying,
concentration
R
S
+
add water,
remove MeCN
NH2 X
NaClO2, concd HCl
Cl
RSO Cl
2
Ph
S
Ph
S
NH2
solvent, 10–20 °C, 0.5 h
O
O
liquid products
3a
2a
Scheme 2 Procedure for the purification of solid and liquid sulfonyl
chlorides
Entry
NaClO2
equiv)
Concd HCl Solvent
(mL)
Yield
(%)
b
(
With the optimal conditions (Table 1, entry 3) and a con-
venient purification protocol established, we prepared
some significantly important sulfonyl chlorides; the re-
sults are presented in Table 2. All the halo-substituted
phenylmethanesulfonyl chlorides were prepared in good
to excellent yields (Table 2, entries 2–6), regardless of the
substituent positions (Table 2, entries 3–5). When strong
electron-withdrawing groups such as cyano or nitro were
introduced, the products were still afforded in 71 and 54%
yields, respectively (Table 2, entries 7 and 8). The de-
crease in the yields was presumably caused by reactions
1
2
2
3
3
4
3
3
2
2
3
3
4
3
3
H O
31
55
82
79
77
62
71
2
2
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
3
4c
5
6d
7e
a
Reaction conditions (5 mmol scale): To the solvent was sequentially of water with 3g and 3h either in the reaction mixture or
added solid NaClO , concd HCl, and then S-alkyl isothiourea salt 2a.
2
during workup. The presence of an electron-donating
group such as methyl at the para-position also led to the
corresponding sulfonyl chloride 3i in 65% yield (Table 2,
entry 9). 2-Phenylethanesulfonyl chloride (3j) was readily
b
c
d
e
Isolated yield after filtration.
NaClO solid was added after the addition of concd HCl.
An aqueous solution of NaClO (3 mL) was used instead of the solid.
Reaction conducted for 2 h.
2
2
Synlett 2013, 24, 2165–2169
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Sulfonyl Chlorides
2167
prepared in moderate yield (62%; Table 2, entry 10). To establish the versatility of our method, thiols, thiophe-
Since alkanesulfonyl chlorides with long chains are im- nol, and their derivatives, including disulfides, thioace-
portant intermediates in the field of surfactants, we tested tates, and xanthates, were directly subjected to the
our method in the synthesis of these compounds. Gratify- NaClO -mediated oxidative chlorosulfonation (Table 3).
2
ingly, the desired compounds with straight and branched To our delight, the reactions of thiols 4a and 4b and thio-
chains were generated in satisfactory to excellent yields phenol 4c proceeded smoothly, and the desired products
(
2
74 to 96%), regardless of the length of the chains (Table were obtained in satisfactory to good yields after purifica-
, entries 11–13). Surprisingly, butane-1,4-disulfonyl di- tion (Table 3, entries 1–3). Even the active ethanesulfonyl
chloride was also generated in excellent yield (94%; Table chloride (3s) was obtained in 46% yield from disulfide 4d
, entry 14). The β-functionalized sulfonyl chloride 3o in analytical purity (Table 3, entry 4). It is noteworthy that
was readily prepared in good yield (87%; Table 2, entry a one-pot procedure to synthesize sulfonyl chlorides was
2
5
1
5). The successful preparation of the latter compound in- also presented. Displacements of benzyl chloride with
dicates that the substrate scope of this method is not lim- nucleophiles KSAc and KSCSOEt afforded the corre-
ited to alkyl halides, with compounds containing other sponding thioacetate 4e and xanthate 4f. In the same pot,
good leaving groups such as mesylates also being suitable subsequent oxidative chlorosulfonation of 4e and 4f, me-
substrates.
diated by NaClO , gave rise to phenylmethanesulfonyl
2
Table 2 Preparation of Structurally Diverse Sulfonyl Chloridesa
H2N
NaClO2, concd HCl
SC(NH2)2
+
–
R
X
NH X
R
SO2Cl
MeCN, 10–20 °C, 0.5 h
EtOH, reflux
1
R
S
3
1
h
2
Entry
Substrate
1
Product
3
Yield (%)b
X
SO2Cl
R1
R1
1
1
1
2
3
4
5
6
7
8
9
R = H, X = Cl
1a
1b
1c
1d
1e
1f
R = H
3a
3b
3c
3d
3e
3f
82
75
92
91
96
90
71
54
65
1
1
R = 4-F, X = Cl
R = 4-F
1
1
R = 2-Cl, X = Cl
R = 2-Cl
1
1
R = 3-Cl, X = Cl
R = 3-Cl
1
1
R = 4-Cl, X = Cl
R = 4-Cl
1
1
R = 4-Br, X = Cl
R = 4-Br
1
1
R = 4-NC, X = Cl
1g
1h
1i
R = 4-NC
3g
3h
3i
1
1
R = 4-O N, X = Br
R = 4-O N
2
2
1
1
R = 4-Me, X = Cl
R = 4-Me
Br
SO Cl
2
1
1
0
1
1j
3j
62
74
Br
SO2Cl
1k
3k
Br
SO2Cl
n
n
1
1
2
n = 4
1l
n = 4
3l
96
96
3c
n = 14
1m
n = 14
3m
SO2Cl
1
4c,d
5
Br
Br
1n
1o
ClO S
2
3n
3o
94
87
2
3
OMs
SO2Cl
1
MeO
MeO
a
Reaction workup (5 mmol scale based on the alkyl halides or mesylate): compounds 3a–i, 3m–n were purified by filtration; others by con-
centration after extraction with ethyl acetate and drying with Na SO .
2
4
b
c
d
Isolated yield of two steps.
Reaction performed at 40–50 °C.
The amounts of thiourea, NaClO , concd HCl, and MeCN were doubled.
2
©
Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 2165–2169

2168
Z. Yang et al.
LETTER
Table 3 Synthesis of Sulfonyl Chlorides from Thiols and Deriva-
tives
A plausible mechanism for the NaClO -mediated oxida-
tive chlorosulfonation of S-alkyl isothiourea salts is de-
2
a
picted in Scheme 4. First, NaClO undergoes a redox
reaction with hydrochloric acid to generate a highly oxi-
dative species: hypochlorous acid (HOCl; Scheme 4, eq.
NaClO2, concd HCl
2
R1
R2
R1 SO2Cl
S
4
MeCN, 10–20 °C, 0.5 h
3
1
). Under acidic conditions, the hypochlorous acid initi-
Entry Substrate
4
Product
3
Yield
b
ates the oxidation of the S-alkyl isothiourea salt, leading
to the corresponding alkanesulfonyl methanimidamide
salt 5 after two consecutive oxidations. With the assis-
tance of water, intermediate 5 undergoes elimination of
urea to generate sulfinic acid 6, which is further oxidized
to the corresponding sulfonyl chloride 3 by another equiv-
alent of hypochlorous acid (Scheme 4, eq. 2). Alternative-
ly, chlorine could also be proposed as the highly oxidative
intermediate species. The mechanism is similar to that in-
volved in N-chlorosuccinimide-mediated oxidative chlo-
(%)
1
PhCH SH
4a
4b
4c
4d
4e
PhCH SO Cl
3a
3p
3q
3r
3a
3a
82
87
82
46
54e
73e
2
2
2
2
n-BuSH
PhSH
n-BuSO Cl
2
3
PhSO Cl
2
4c
5d
EtSSEt
EtSO Cl
2
PhCH SAc
PhCH SO Cl
2
2
2
6d
PhCH SCSOEt 4f
PhCH SO Cl
2 2
2
6c
rosulfonation.
a
Reaction workup (5 mmol scale, based on the substrate): Com-
pounds 3p–r were purified by concentration after extraction with eth-
yl acetate and drying over Na SO ; compound 3a was obtained by
In summary, a simple and reliable method for the prepara-
tion of sulfonyl chlorides has been developed. The meth-
od features NaClO -mediated oxidative chlorosulfonation
of S-alkyl isothiourea salts as well as thiols and their de-
rivatives, such as thioacetates, xanthates, and disulfides.
The use of S-alkyl isothiourea salts successfully circum-
vents problems caused by the strong and repulsive odors
of thiols and their derivatives, making our method envi-
9
2
4
filtration.
2
b
Isolated yield.
c
The amounts of NaClO , concd HCl, and MeCN were doubled.
One-pot procedure from benzyl chloride and KSAc or KSCSOEt.
Yield over two steps.
2
d
e
chloride in 54 and 73% yield, respectively, over two steps. ronment- and worker-friendly. We achieved the synthesis
The purification procedures described above worked well of various sulfonyl chlorides in satisfactory to excellent
in the workup of all the reactions.
yields by this simple procedure, which involves conve-
nient operation and straightforward purification.
The ability to scale up this method was confirmed by the
preparation of (4-chlorophenyl)methanesulfonyl chloride
(
3e) on a 50-mmol scale (Scheme 3). In the large-scale
Acknowledgment
production, oxidative chlorosulfonation proceeded
smoothly to give the desired product in excellent yield
The project was supported by The National Basic Research Pro-
gram of China (No. 2013CB328900) and The National Natural Sci-
ence Foundation of China (Nos. 21172017 and 20092013).
(90%) and analytical purity after filtration and drying.
1
. SC(NH2)2, EtOH, reflux, 1 h
. NaClO2, concd HCl, MeCN,
2
SO Cl
Cl
Supporting Information for this article is available online at
2
http://www.thieme-connect.com/ejournals/toc/synlett. SnuIpofoipmngr irtSatnoIuipfog
r
t
iornat
Cl
Cl
10–20 °C, 0.5 h
1e
3e
on 50-mmol scale,
yield: 10.17 g, 90%
References and Notes
Scheme 3 Large-scale synthesis of (4-chlorophenyl)methanesulfo-
nyl chloride
(1) (a) Hoyle, J. The Chemistry of Sulfonic Acids, Esters and
their Derivatives, In The Chemistry of Functional Groups;
NaClO2 + 2HCl
2HOCl + NaCl
Cl
(1)
O
+
R
S
H , HOCl
S+
+NH2 X–
H2O
R
S
+NH2 X–
+NH2 X–
R
+
H2N
–
H2O
– H , – HCl
H2N
NH2
O
O
O
S
O
H+
– OC(NH2)2, – H+
+
R
S
H O
1
2
. H , HOCl, – H2O
2
R
NH2
OH
+NH2 X–
+
– HX
. H2O, – H , – HCl
H2N
H2N
5
O
O
O
HOCl
H2O
S
R
S
OH
(2)
R
Cl
–
6
3
Scheme 4 Plausible mechanism for NaClO -mediated oxidative chlorosulfonation of S-akyl isothiourea salts
2
Synlett 2013, 24, 2165–2169
© Georg Thieme Verlag Stuttgart · New York

LETTER
Synthesis of Sulfonyl Chlorides
2169
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Synthesis 1992, 1203. (g) Nishiguchi, A.; Maeda, K.; Miki,
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T.; Panja, C.; Olah, G. A. J. Org. Chem. 2007, 72, 5847.
temperature below 20 °C. After the addition, the resulting
mixture was stirred for another 30 min, then H O (25 mL)
2
was added, and the resultant mixture was evaporated in
(i) Bahrami, K.; Khodaei, M. M.; Soheilizad, M. J. Org.
vacuum at 15 °C to remove MeCN. After addition of H O
2
Chem. 2009, 74, 9287. (j) Bahrami, K.; Khodaei, M. M.;
Soheilizad, M. Synlett 2009, 2773. (k) Sohmiya, H.; Kimura,
T.; Fujita, M.; Ando, T. Tetrahedron 1998, 54, 13737.
(100 mL), filtration on a Büchner funnel and drying under an
infrared lamp, 3e was afforded as colorless crystals. Yield:
6
c
1
1.080 g (96%); mp 91–93 °C (Lit. 90–92 °C). H NMR
(
2
l) Massah, A. R.; Sayadi, S.; Ebrahimi, S. RSC Adv. 2012,
, 6606. (m) Joyard, Y.; Papamicael, C.; Bohn, P.; Bischoff,
L. Org. Lett. 2013, 15, 2294. (n) Veisi, H.; Ghorbani-
(400 MHz, CDCl ): δ = 7.46–7.41 (m, 4 H), 4.83 (s, 2 H);
3
1
3
C NMR (101 MHz, CDCl ): δ = 136.8, 132.6, 129.5, 124.6,
3
70.0.
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Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 2165–2169

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