UPDATE
Ahmed Kamal, Gagan Chouhan
with ethyl acetate (5ꢀ20mL) and volatile materials was
evaporated under high vacuum to obtain the 1-n-butyl-3-meth-
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ylimidazolium bromide [b] as a brown-coloured liquid.
1
H NMR (200 MHz, CDCl ): d¼0.98 (t, 3H, J¼7.4 Hz), 1.30±
3
1
7
3
.50(m, 2H), 1.80±2. 00 (m, 2H), 4.20(s, 3H), 4.40(t, 2H,
J¼
.4 Hz), 7.60(s, 1H), 7.80(s, 1H), 10.40(s, 1H); IR (neat): n¼
[
6] a) A. Kamal, G. Chouhan, Tetrahedron Lett. 2002, 43,
347; b) A. Kamal, G. Chouhan, Synlett 2002, 474; c) A.
ꢁ
1
440, 3142, 3072, 2960, 2864, 1552, 1488, 800, 768, 624 cm
;
1
þ
FAB ( þve): m/z¼139 (MꢁBr) (100%), 357 (C H N ) Br
8
15
2 2
Kamal, G. Chouhan, Tetrahedron Lett. 2003, 44, 3337.
7] a) G. Centi, S. Perathoner, Catal. Today 2003, 77, 287;
b) P. T. Anastas, J. C. Warner, Green Chemistry; Theory
and Practice, Oxford University Press, New York, NY,
(
4%).
[
General Procedure for Thioacetalization of Carbonyl
Compounds in [bmim]Br
1
998; c) P. Tundo, P. T. Anastas, Green Chemistry; Theory
and Practice, Oxford University Press, New York, NY,
999.
1
To a stirred solution of the appropriate aldehyde (1 mmol) in
the ionic liquid [bmim]Br (1.5 mL) was added ethanethiol
[
8] For excellent reviews, see a) J. D. Holbrey, K. R. Seddon,
Clean. Prod. Process. 1999, 1, 223; b) T. Welton, Chem.
Rev. 1999, 99, 2071; c) P. Wasserscheid, W. Keim, Angew.
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gna, J. Mol. Catal. A. 2002, 182±183, 419; f) J. Dupont,
R. F. Desouza, P. A. Z. Suarez, Chem. Rev. 2002, 102,
3667.
(
2.5 mmol) or 1,2-ethandithiol (1.2 mmol) or 1,3-propanedi-
thiol (1.2 mmol) at room temperature. The reaction mixture
was stirred at room temperature for the appropriate time
(
see Table 1). After completion of the reaction as indicated
by TLC, ether (3ꢀ5 mL) was added to the reaction mixture
with vigorous stirring for 5 min. The mixture was allowed to
stand for further 5 min and the clear supernatant liquid was
decanted. The combined ether layers were concentrated Un-
der vacuum to obtain the crude product which was purified
by short silica gel column chromatography (eluent: ethyl ace-
tate/n-hexane) to furnish the corresponding thioacetal. The
ionic liquid layer was further washed with ether (2ꢀ3 mL),
volatile materials were evaporated under vacuum and the ionic
liquid recycled in subsequent runs. The products were charac-
terized by their NMR, IR, and MS analysis. The spectral data of
all the products were identical with those of authentic sam-
[
9] T. Fischer, A. Sethi, T. Welton, J. Woolf, Tetrahedron
Lett. 1999, 40, 793.
[
10] H. P. Zhu, F. Yang, J. Tang, M. Y. He, Green Chem. 2003,
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5
[
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4
4, 1835.
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Souza, J. Dupont, Polyhedron, 1996, 15,1217.
[2,3]
ples.
[
13] X. Lijin, W. Chen, J. Xiao, Organometallics 2000, 19,
1
123.
Acknowledgements
[
14] The ionic liquid was dissolved in water and to this was
added NaHCO in small amounts with vigorous stirring
3
One of the authors (G. C.)is thankful to CSIR (New Delhi)for
the award of senior research fellowship.
until no bubbling was observed from the ionic liquid wa-
ter mixture, then methanol was added to this mixture
and water was removed azeotropically at 808C under
high vacuum, later dichloromethane was added, the mix-
ture filtered and the filtrate dried on sodium sulfate, fi-
nally concentration under vacuum at 808C provided
the neutral ionic liquid.
References and Notes
[
1] a) T. W. Greene, P. G. M. Wuts, Protective Groups in Or-
ganic Synthesis, 3rd edn., Wiley, New York, 1999, p. 293;
b) P. J . Kocie n¬ ski, Protecting Groups, 3rd edn., Thieme,
Stuttgart, 2004, p. 77.
[
[
[
15] C. Thomazean, H. Olivier-Bourbigou, L. Magna, S. Luts,
B. Gilbert J. Am. Chem. Soc. 2003, 125, 5264.
16] J. S. Yadav, B. V. S. Reddy, S. K. Panday, Synlett 2001,
[
2] a) S. Muthusamy, S. Arulananda Babu, C. Gunanathan,
Tetrahedron Lett. 2001, 42, 359; b) H. Firouzabadi, N.
Iranpoor, H. Hazarkhani, J. Org. Chem. 2001, 66, 7527,
and references cited therein; c) H. Tani, K. Masumoto,
T. Inamasu, Tetrahedron Lett. 1991, 32, 2047.
2
38.
17] V. G. Saraswathy, S. Sankararaman, J. Org. Chem. 1994,
5
9, 4665.
582
¹ 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
Adv. Synth. Catal. 2004, 346, 579±582