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Copper-Catalyzed Three-Component Reaction to Imino-pyrrolines
S.-L. Cui, J. Wang, Y.-G. Wang*
Zhejiang University, Hangzhou, P. R. of China
23 January 2008 (online)
An efficient and general 3-component synthesis of 5-arylidene-2-imino-3-pyrrolines via a copper-catalyzed [2+3] cycloaddition of sulfonyl azides 1 with alkynes 2 followed by a reaction of the resulting ketenimines with aziridines 3 is described. Experiments using deuterated aziridine support the suggested mechanism involving triazolyl copper species and ketenimine as intermediates. The starting aziridines are conveniently available from chalcones (Y.-M. Shen et al. Angew. Chem. Int. Ed. 2006, 45, 8005; A. Armstrong et al. Org. Lett. 2007, 9, 351). Best yields and highest selectivity were obtained using acetonitrile as solvent and aromatic sulfonyl azide substrates.