LETTER
Dehydrogenation of 2-Imidazolines with Trichloroisocyanuric Acid
2805
(11) (a) Luca, L. D.; Giacomelli, G.; Porcheddu, A. Org. Lett.
2001, 3, 3041. (b) Xiong, Z.-X.; Huang, N.-P.; Zhong, P.
Synth. Commun. 2001, 31, 245. (c) Firouzabadi, H.;
Iranpoor, N.; Hazarkhani, H. Synlett 2001, 1641.
(d) Tilstam, U.; Harre, M.; Heckrodt, T.; Weinmann, H.
Tetrahedron Lett. 2001, 42, 5385. (e) Zolfigol, M. A.;
Madrakian, E.; Ghaemi, E.; Mallakpour, S. Synlett 2002,
1633. (f) Zolfigol, M. A.; Madrakian, E.; Ghaemi, E. Synlett
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(12) Typical Experimental Procedure: 2-(4-Methyl-
phenyl)imidazoline (1b, 2.0 mmol) was dissolved in MeCN
(40 mL) and DBU (0.54 g, 3.6 mmol) was added. The
solution was cooled to –15 °C and a solution of TCCA
(0.185 g, 0.8 mmol) in MeCN (10 mL) was added dropwise.
The reaction mixture was stirred for 3 min. After completion
of the reaction (as monitored by TLC), the mixture was
allowed to warm up to r.t. and passed through a short pad of
alumina. The solvent was evaporated and the resulting crude
material was purified by column chromatography on
alumina with appropriate eluent to afford the pure 2-(4-
methylphenyl)imidazole (2b, 94%), mp 218–220 °C (lit.9
mp 223 ºC). IR (KBr): 3435, 3150, 2985, 1658, 1610, 1575,
1514, 1435, 1100, 815, 725 cm–1. 1H NMR (500 MHz,
DMSO-d6): d = 2.31 (s, 3 H), 6.99 (br s, 1 H), 7.18 (br s, 1
H), 7.23 (d, J = 7.5 Hz, 2 H), 7.81 (d, J = 8 Hz, 2 H), 12.39
(s, 1 H).
Acknowledgment
We are thankful to the Isfahan University Research Council for
partial support of this work.
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Synlett 2004, No. 15, 2803–2805 © Thieme Stuttgart · New York