Solvent-free synthesis of arylsulfonyl cyanides using potassium hexacyanoferrate(II) as an ecofriendly cyanide source

Article abstract of DOI:10.1080/10426507.2013.819870

A solvent-free synthetic method for arylsulfonyl cyanides directly from corresponding sulfonyl chlorides using potassium hexacyanoferrate(II) as an ecofriendly cyanide source is described. The protocol has the advantages of no uses of highly toxic cyanating agent and volatile organic solvents, high yield, and simple work-up procedures.

Full text of DOI:10.1080/10426507.2013.819870

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Phosphorus, Sulfur, and Silicon and the
Related Elements
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Solvent-Free Synthesis of Arylsulfonyl
Cyanides Using Potassium
Hexacyanoferrate(II) as An Ecofriendly
Cyanide Source
Zheng Li a & Jun Xu a
a College of Chemistry and Chemical Engineering , Northwest Normal
University , Lanzhou , Gansu , 730070 , P.R. China
Accepted author version posted online: 02 Sep 2013.Published
online: 28 Jan 2014.
To cite this article: Zheng Li & Jun Xu (2014) Solvent-Free Synthesis of Arylsulfonyl Cyanides Using
Potassium Hexacyanoferrate(II) as An Ecofriendly Cyanide Source, Phosphorus, Sulfur, and Silicon and
the Related Elements, 189:3, 374-378, DOI: 10.1080/10426507.2013.819870
To link to this article: http://dx.doi.org/10.1080/10426507.2013.819870
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Phosphorus, Sulfur, and Silicon, 189:374–378, 2014
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2013.819870
SOLVENT-FREE SYNTHESIS OF ARYLSULFONYL
CYANIDES USING POTASSIUM HEXACYANOFERRATE(II)
AS AN ECOFRIENDLY CYANIDE SOURCE
Zheng Li and Jun Xu
College of Chemistry and Chemical Engineering, Northwest Normal University,
Lanzhou, Gansu 730070, P.R. China
GRAPHICAL ABSTRACT
Abstract A solvent-free synthetic method for arylsulfonyl cyanides directly from corresponding
sulfonyl chlorides using potassium hexacyanoferrate(II) as an ecofriendly cyanide source is
described. The protocol has the advantages of no uses of highly toxic cyanating agent and
volatile organic solvents, high yield, and simple work-up procedures.
Keywords Arylsulfonyl cyanide; potassium hexacyanoferrate(II); sulfonyl chloride; green
chemistry
INTRODUCTION
Sulfonyl cyanides have an activated cyano group and show many interesting re-
actions. Sulfonyl cyanides show (hetero)-Diels–Alder cycloadditions with dienes to give
important polycyclic compounds,1 and show 1,3-dipolar cycloadditions to produce some
heterocyclic compounds, such as 1,2,4-thiadiazoles,2 and tetrazoles.3 Sulfonyl cyanides
also exhibit electrophilic substitution reactions with metalated alkanes, alkenes, alkynes,4
arenes,5 or heteroarenes6 bearing various functional groups to afford polyfunctional ni-
triles, and exhibit electrophilic addition reactions with olefin to produce hydrocyanation
products.7 The photochemical reactions of sulfonyl cyanides can be efficiently transformed
C(sp3)–H bonds into C(sp3)–CN bonds.8 In addition, sulfonyl cyanides can also be utilized
as sulfinylation reagents for alkenes9 and alcohols.10
The general synthetic methods for arylsulfonyl cyanides include (1) the reactions
of sodium benzenesulfinate with cyanogen chloride,11 and (2) the oxidation of phenyl
Received 8 April 2013; accepted 24 June 2013.
The authors thank the National Natural Science Foundation of China (21162024) for the financial support
of this work.
Address correspondence to Zheng Li, College of Chemistry and Chemical Engineering, Northwest Normal
University, Lanzhou, Gansu 730070, P.R. China. E-mail: lizheng@nwnu.edu.cn
374

ECOFRIENDLY SYNTHESIS OF ARYLSULFONYL CYANIDES
375
thiocyanate with m-chloroperbenzoic acid in benzene.12 However, these methods required
utilization of highly toxic and easily volatile cyanogen chloride as a cyanide source, or
required hazardous peroxides as oxidants and carcinogenic benzene as a solvent. Therefore,
there is a need to explore an ecofriendly method for the synthesis of arylsulfonyl cyanides.
Potassium hexacyanoferrate(II), K4[Fe(CN)6, is mainly used as carburizing agent in
the iron and steel industry. It is also used in the food industry for metal precipitation. In
addition, it has been described as an anti-agglutinating auxiliary for table salt (NaCl).13
K4[Fe(CN)6] is a by-product of the coal chemical industry and commercially available
on a ton scale, and it is even cheaper than KCN. Recently, K4[Fe(CN)6] has been used
as a cyanide source for some substitution reactions to synthesize benzonitriles,14 aroyl
cyanides,15 benzyl cyanides,16 and cinnamonitriles.17 Our research group also reported
some additional reactions for the compounds bearing C O, C N, and/or C C moieties
using K4[Fe(CN)6] as an ecofriendly cyanide source.18 In this work, we report an efficient
method for the synthesis of arylsulfonyl cyanides directly from corresponding sulfonyl
chlorides using K4[Fe(CN)6] as an ecofriendly cyanide source..
RESULTS AND DISCUSSION
Initially, benzenesulfonyl chloride was selected as a substrate to conduct the cyanation
reaction to synthesize benzenesulfonyl cyanide using potassium hexacyanoferrate(II) as an
ecofriendly cyanide source (Scheme 1, R H). The investigations were attempted under
different conditions including various solvents at different temperatures. However, it was
found that no corresponding product was observed in DMSO, DMF, EtOH, MeCN, THF, or
CH2Cl2 (Table 1, entries 1–6). In the later research, it was found that the reaction could be
processed under solvent-free conditions at different temperatures (Table 1, entries 7–10).
Among them the best yield was obtained at 170◦C (Table 1, entry 9). It was also found that
only 0.2 equiv of K4[Fe(CN)6] was needed for 1 equiv of benzenesulfonyl chloride, which
indicated that six CN− of K4[Fe(CN)6] could be fully utilized in this reaction. In addition, no
other by-products were observed in this reaction, which implied the high chemoselectivity
of the reaction.
Based on the above promising findings, a series of arylsulfonyl chlorides were exam-
ined for the direct cyanation reactions to synthesize arylsulfonyl cyanides under solvent-free
Table 1 The effect of reaction conditions on the yielda
Entry
Solvent
Condition
Reaction time (h)
Yield (%)b
1
2
3
4
5
6
7
8
9
DMSO
DMF
EtOH
MeCN
THF
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
150◦C
160◦C
170◦C
180◦C
24
24
24
24
24
24
2
2
2
2
0
0
0
0
0
CH2Cl2
0
Solvent-free
Solvent-free
Solvent-free
Solvent-free
18
45
86
58
10
a The reaction condition: K4[Fe(CN)6] (2 mmol) and benzenesulfonyl chloride (10 mmol).
b The isolated yield.

376
Z. LI AND J. XU
Scheme 1 Synthesis of arylsulfonyl cyanides.
Table 2 Synthesis of arylsulfonyl cyanidesa
Entry
Product
Yield (%)b
mp (◦C, lit.)
1
2
3
4
5
6
7
8
9
C6H5SO2CN
4-CH3C6H4SO2CN
4-ClC6H4SO2CN
4-BrC6H4SO2CN
4-IC6H4SO2CN
4-CH3CH2C6H4SO2CN
4-(CH3)2CHC6H4SO2CN
4-CH3OC6H4SO2CN
4-CNC6H4SO2CN
4-NO2C6H4SO2CN
86
88
76
75
73
80
82
83
65
61
Oil (19–20)11b
48–50 (49.5–51)11b
56–57 (57.5–59)11b
97–98 (96–98)11a
35–37
58–60
67–69
65–67 (66–68)11b
122–124 (123–125)11b
121–123 (122–123.5)11b
10
The reaction condition: K4[Fe(CN)6] (2 mmol) and sulfonyl chloride (10 mmol) was stirred at 170◦C for 2 h.
The isolated yield.
condition using K4Fe(CN)6 as an ecofriendly cyanide source (Scheme 1). It was found that
arylsulfonyl chlorides bearing either electron-donating or electron-withdrawing groups on
aromatic rings could participate in the reactions. However, arylsulfonyl chlorides including
electron-donating groups on aromatic rings gave the corresponding products in higher yield
(Table 2, entries 2, 6–8). In contrast, arylsulfonyl chlorides including electron-withdrawing
groups on aromatic rings gave slightly lower yield (Table 2, entries 3–5, 9, 10). However,
the attempts to synthesize aliphatic sulfonyl cyanides using a similar method were unsuc-
cessful. The possible reason is that low boiling points of substrates often cause the large
loss of aliphatic sulfonyl chlorides at studied high temperature and atmospheric pressure.
CONCLUSION
In summary, an efficient method for the synthesis of arylsulfonyl cyanides from
corresponding sulfonyl chlorides using potassium hexacyanoferrate(II) as an ecofriendly
cyanide source under solvent-free condition was developed. The protocol avoided the use of
strong toxic cyanating agents and volatile organic solvents, therefore is an environmentally
benign alternative to the important building block, arylsulfonyl cyanides.
EXPERIMENTAL
IR spectra were recorded using KBr pellets on an Alpha Centauri FTIR spectropho-
tometer.1H NMR and 13C NMR spectra were recorded on a Mercury-400BB instrument
using CDCl3 as a solvent and Me4Si as an internal standard. Melting points were observed
in an electrothermal melting point apparatus. Potassium hexacyanoferrate(II) dried at 80◦C
under vacuum for 24 h and finely powdered prior to use.

ECOFRIENDLY SYNTHESIS OF ARYLSULFONYL CYANIDES
377
The General Procedure for the Synthesis of Arylsulfonyl Cyanides
The mixture of K4[Fe(CN)6] (2 mmol) and sulfonyl chloride (10 mmol) was stirred
at 170◦C for 2 h. The reaction progress was monitored by TLC. After the completion of the
reaction, the reaction system was cooled to room temperature, and the resulting mixture
was isolated by column chromatography using petroleum ether and ethyl acetate (80:1) as
an eluent to obtain pure product.
The Analytical Data for the Representative Products are as Follows
4-Iodobenzenesulfonyl Cyanide (Table 2, entry 5). Yellow solid. mp:
1
35–37◦C; IR (KBr): 2161, 1560, 1465 cm−1; H NMR (400 MHz, CDCl3): 7.76 (d, J =
8.0 Hz, 2H), 7.26 (d, J = 8.0 Hz, 2H); 13C NMR (100 MHz, CDCl3): 139.3, 128.7, 124.4,
109.7, 95.4. Anal. Calcd. for C7H4INO2S: C, 28.69; H, 1.38; N, 4.78. Found: C, 28.57; H,
1.37; N, 4.76.
4-Ethylbenzenesulfonyl Cyanide (Table 2, entry 6). Yellow solid. mp:
1
58–60◦C; IR (KBr): 2157, 1650, 1492 cm−1; H NMR (400 MHz, CDCl3): 7.58 (d, J =
7.6 Hz, 2H), 7.33 (d, J = 7.6 Hz, 2H), 2.62 (q, J = 8.0 Hz, 2H), 1.14 (t, J = 8.0 Hz, 3H);
13C NMR (100 MHz, CDCl3): 139.3, 131.8, 130.6, 119.8, 110.5, 30.6, 13.5. Anal. Calcd.
for C9H9NO2S: C, 55.37; H, 4.65; N, 7.17. Found: C, 55.45; H, 4.63; N, 7.14.
4-Isopropyllbenzenesulfonyl Cyanide (Table 2, entry 7). Yellow solid. mp:
1
67–69◦C; IR (KBr): 2158, 1596, 1492 cm−1; H NMR (400 MHz, CDCl3): 7.56 (d, J
= 8.0 Hz, 2H), 7.43 (d, J = 8.0 Hz, 2H), 2.76 (m, 1H), 1.18 (d, J = 8.4 Hz, 6H); 13C
NMR (100 MHz, CDCl3): 138.5, 131.5, 130.8, 123.7, 112.4, 32.9, 21.6. Anal. Calcd. for
C10H11NO2S: C, 57.40; H, 5.30; N, 6.69. Found: C, 57.56; H, 5.33; N, 6.66.
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