Iron(II) Bromide-Catalyzed Synthesis of Benzimidazoles from Aryl Azides
作者:Meihua Shen、Tom G. Driver
DOI:10.1021/ol801227f
日期:2008.8.7
The identity of the ortho-substituent of an arylazide influences its reactivity toward transition metals. Substitution of a vinyl group with an imine disables rhodium(II)-mediated C-H amination and triggers a Lewis acid mechanism catalyzed by iron(II) bromide to facilitate benzimidazole formation.
N-[(2-Benzylideneamino)phenyl]-C-methylketenimines undergo intramolecular cyclization via two different reaction pathways, a [2+2] cycloaddition and a rare imino-ene reaction, to yield azeto[1,2-a]benznnidazoles and 2-(alpha-styryl)benzimidazoles, respectively. The results are interpreted in terms of a two-step mechanism involving two stereoisomeric conjugated betaines as intermediates. (C) 2002 Elsevier Science Ltd. All rights reserved.