Organic reactions in ionic liquids: A new method for the synthesis of alkyl aryl sulfones by alkylation of sodium arenesulfinates with unactivated alkyl chlorides

Article abstract of DOI:10.1081/SCC-200034831

A new method is reported for the synthesis of alkyl aryl sulfones by alkylation of sodium arenesulfinates with unactivated alkyl chlorides using ionic liquid based on 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF ₄) mixed with water (2:1) as reaction media. The ionic liquid can be reused and the procedure gives the sulfones in moderate yields.

Full text of DOI:10.1081/SCC-200034831

This article was downloaded by: [Case Western Reserve University]
On: 04 November 2014, At: 22:34
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T
3JH, UK
Synthetic Communications:
An International Journal
for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Organic Reactions in Ionic
Liquids: A New Method for
the Synthesis of Alkyl Aryl
Sulfones by Alkylation of
Sodium Arenesulfinates with
Unactivated Alkyl Chlorides
Yi Hu a b , Zhen‐Chu Chen a b , Zhang‐Gao Le a
Qin‐Guo Zheng c
&
a Ningbo Institute of Technology, Zhejiang
University , Ningbo, P. R. China
b Department of Chemistry , Zhejiang University ,
(Xi Xi Campus), Hangzhou, 310028, P. R. China
c Pharmaceutical Science Research Institute, Aston
University , Aston Triangle, Birmingham, UK
Published online: 12 Jan 2011.
To cite this article: Yi Hu , Zhen‐Chu Chen , Zhang‐Gao Le & Qin‐Guo Zheng (2004)
Organic Reactions in Ionic Liquids: A New Method for the Synthesis of Alkyl Aryl
Sulfones by Alkylation of Sodium Arenesulfinates with Unactivated Alkyl Chlorides,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 34:21, 4031-4035, DOI: 10.1081/SCC-200034831
To link to this article: http://dx.doi.org/10.1081/SCC-200034831

PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all
the information (the “Content”) contained in the publications on our
platform. However, Taylor & Francis, our agents, and our licensors
make no representations or warranties whatsoever as to the accuracy,
completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of
the authors, and are not the views of or endorsed by Taylor & Francis.
The accuracy of the Content should not be relied upon and should be
independently verified with primary sources of information. Taylor and
Francis shall not be liable for any losses, actions, claims, proceedings,
demands, costs, expenses, damages, and other liabilities whatsoever
or howsoever caused arising directly or indirectly in connection with, in
relation to or arising out of the use of the Content.
This article may be used for research, teaching, and private study
purposes. Any substantial or systematic reproduction, redistribution,
reselling, loan, sub-licensing, systematic supply, or distribution in any form
to anyone is expressly forbidden. Terms & Conditions of access and use
can be found at http://www.tandfonline.com/page/terms-and-conditions

SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 21, pp. 4031–4035, 2004
Organic Reactions in Ionic Liquids: A New
Method for the Synthesis of Alkyl Aryl
Sulfones by Alkylation of Sodium
Arenesulfinates with Unactivated
Alkyl Chlorides
1
Yi Hu,1,2 Zhen-Chu Chen,1,2, Zhang-Gao Le,
*
and Qin-Guo Zheng3
1Ningbo Institute of Technology, Zhejiang University,
Ningbo, P. R. China
2Department of Chemistry, Zhejiang University,
Hangzhou, P. R. China
3Pharmaceutical Science Research Institute, Aston University,
Aston Triangle, Birmingham, UK
ABSTRACT
A new method is reported for the synthesis of alkyl aryl sulfones by alky-
lation of sodium arenesulfinates with unactivated alkyl chlorides using
ionic liquid based on 1-butyl-3-methylimidazolium tetrafluoroborate
*
Correspondence: Zhen-Chu Chen, Department of Chemistry, Zhejiang University
(Xi Xi Campus), Hangzhou 310028, P. R. China; E-mail: humi1@sohu.com.
4031
DOI: 10.1081/SCC-200034831
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

4032
Hu et al.
(BmimBF4) mixed with water (2 : 1) as reaction media. The ionic liquid
can be reused and the procedure gives the sulfones in moderate yields.
Key Words: Alkylation; Alkylchlorides; Arenesulfinates; Ionic liquids;
Sulfones.
Alkyl aryl sulfones have been widely used as useful intermediates in
organic synthesis. Of particular interest are the applications of the sulfonyl
group as activating function that can be subsequently removed under mild
conditions. One important method for the preparation of alkyl aryl sulfones
involves the alkylation of arenesulfinates with alkyl halides.[1] To the best
of our knowledge the alkyl halides using this method are limited to alkyl
bromides, iodides, and activated halides; no desired product can be obtained
when unactivated alkyl chlorides are used.[2]
In recent years, room temperature ionic liquids (RTILs) have shown great
promise as an attractive alternative to conventional solvents for synthetic
organic chemistry.[3] In particular, there are many reports of great improve-
ments in the reaction yields and rates,[4] which prompted us to investigate
the alkylation of sodium arenesulfinates with unactivated alkyl chlorides in
ionic liquids. Such a reaction would provide a new method for the synthesis
of alkyl aryl sulfones.
For this study, BmimBF4 was synthesized according to the procedures
reported in the literature.[5] We found that the reaction of unactivated alkyl
chlorides with sodium arenesulfinates proceeded very slowly in BmimBF4
due to the poor solubility of sodium arenesulfinates in it and could not
occur in water. To increase the solubility of sodium arenesulfinates in
BmimBF4, we added some amount of water in the reaction mixture. In fact,
simple stirring of the sodium arenesulfinates (1) with the alkyl chlorides (2)
in BmimBF4 and water (v/v 2 : 1) at appropriate temperature gave after
workup the alkyl aryl sulfones (3) in moderate yields (Sch. 1). As summarized
Scheme 1.

Synthesis of Alkyl Aryl Sulfones by Alkylation of Sodium Arenesulfinates 4033
Table 1. Alkylation of sodium arenesulfinates with alkyl chlorides.
Entry
R2Cl
R1
Temp (8C)
Time (h)
Yielda (%)
1
2
3
4
5
6
7
8
9
n-Butyl chloride
n-Hexyl chloride
n-Octyl chloride
n-Butyl chloride
Iso-butyl chloride
n-Hexyl chloride
n-Hexyl chloride
n-Octyl chloride
Cyclohexyl
H
70
100
100
70
24
12
12
24
24
12
12
12
24
53
57
54
65
47
67
65b
63
45
H
H
CH3
CH3
CH3
CH3
CH3
CH3
70
100
100
100
100
chloride
aIsolated yields based on alkyl chlorides, purities were .98% by GC.
bBmimBF4 was reused three times.
in Table 1, all products were characterized by 1H NMR, IR that were consis-
tent with the literature data.
As delineated in Table 1, various unactivated primary and secondary
chlorides were examined and found to be generally applicable.
Moreover, the ionic liquid can be typically recovered and the recovered
ionic liquid could be reused with no appreciable decrease in yield and
reaction rate. Additionally, we haven’t detected the BmimBF4 which
was hydrolyzed by water under the reaction conditions. The PH of the
reaction mixture is about 6, which has not changed during the whole
reaction period.
In conclusion, we have presented a practical example for the synthesis of
alkyl aryl sulfones by alkylation of sodium arenesulfinate salts with unacti-
vated alkyl chlorides. The ionic liquid, BmimBF4 plays the dual roles of
solvent and promoter. Moreover, the present method has some obvious advan-
tages, including being environmentally more benign, the generality, the
simplicity of the methodology the ease of product isolation, and the potential
for recycling of ionic liquid.
EXPERIMENTAL
Melting points were determined on digital melting point apparatus and
were not corrected. Infrared spectra were recorded on a VECTOR-22 infrared
spectrophotometer. 1H NMR spectra were recorded on a BRUKER-400 MHz

4034
Hu et al.
spectrometer using CDCl3 as the solvent with TMS as an internal standard.
All materials are commercially available and were used without further
purification.
General Procedure for the Alkylation of
Sodium Arenesulfinates with Unactivated
Alkyl Chlorides
Sodium arenesulfinate (2.0 mmol), alkyl chloride (1 mmol) in BmimBF4
(2 mL), and H2O (1 mL), the mixture was stirred magnetically under reaction
conditions list in Table 1. After completion of the reaction, the reaction
mixture was extracted with diethyl ether (3 Â 10 mL), the ethereal solvent
was removed by evaporation, and the residue was purified by the preparative
thin-layer chromatography (silica gel, EtOAc-cyclohexane, v/v 1 : 3) to give
the pure product. After isolation of product, the remainder of the ionic liquid
can be typically recovered by drying for 4 h under vacuum at 508C and filter-
ing the suspension to remove residual sodium arenesulfinate and formed
sodium chloride.
REFERENCES
1. (a) Magnus, P.D. Recent developments in sulfone chemistry. Tetrahedron
1977, 33 (16), 2019–2045; (b) Trost, B.M.; Schmuff, N.R. Stereo-
chemistry of allyl sulfones: on the structure of metalated allyl sulfones
and their stereochemistry of alkylation. J. Am. Chem. Soc. 1985,
107 (2), 396–405; (c) Simpkins, N.-S. Sulfones in Organic
Synthesis. Baldwin, J.E., Magnus, P.D., Eds.; Tetrahedron Organic Chem-
istry Series; Pergamon Press: Oxford, 1993; Vol. 10; (d) Najera, C.;
Yus, M. Desulfonylation reactions: recent developments. Tetrahedron
1999, 55 (35), 10547–10658.
2. Crandall, J.K.; Pradat, C. Synthesis of sulfones by phase-transfer
alkylation of arenesulfinate salts. J. Org. Chem. 1985, 50 (8),
1327–1329.
3. (a) Welton, T. Room temperature ionic liquids. Solvent for synthesis and
catalysis. Chem. Rev. 1999, 99 (8), 2071–2083; (b) Wasserscheid, P.;
Keim, W. Ionic liquids-new “solutions” for transition metal catalysis.
Angew. Chem. Int. Edit. 2000, 39 (21), 3772–3789; (c) Sheldon, R.
Catalytic reactions in ionic liquids. Chem. Commun. 2001, 2399–2407;
(d) Jairton, D.; Robeerto, F.; Paulo, A.Z.S. Ionic liquids (molten salts)
phase organometallic catalysis. Chem. Rev. 2002, 102 (10),

Synthesis of Alkyl Aryl Sulfones by Alkylation of Sodium Arenesulfinates 4035
3667–3692; (e) Davis, J.H.; Fox, P.A. From curiosities to commodities:
ionic liquids begin the transition. Chem. Commum. 2003, (11),
1209–1212.
4. Wasserscheid, P.; Welton, T. Eds. Ionic Liquids in Synthesis; VCH
Wiley: Weinheim, Germany, 2002.
5. Owens, G.S.; Abu-Omer, M.M. Comparative kinetic investigations in
ionic liquids using the MTO/peroxide system. J. Mol. Catal. A: Chem.
2002, 187 (2), 215–225.
Received in Japan March 31, 2004