Copper-Catalyzed Domino Addition/Double Cyclization:an Approach To Polycyclic Benzimidazole Derivatives

An efficient and versatile method for the assembly of novel polycyclic benzimidazole derivatives has been developed by Cu-catalyzed domino addition/double cyclization reactions. A wide variety of polycyclic benzimidazole derivatives, which might be used as synthetic medicines and functional materials, were successfully assembled from bis-(o-haloaryl)carbodiimides with azoles. indoles, primary amines and active methylene compounds.Unexpected N-methylated benzo[4,5]imidazo[1,2-a]indoles can also be selectively assembled. Multi-bonds and polycyclic moieties were conveniently formed in one pot during these domino processes.Cu-mediated C-H functionalization and cross-coupling have been applied as powerful tools for the assembly of heterocycles via domino processes. Notably, although great achievements have been accomplished in the C-H functionalization using transition-metal catalysis, only limited domino approaches to N-heterocyles through Cu-catalyzed intramolecular direct sp2C-Harylation of azoles have been developed thus far. And to the best of our knowledge, there is no report about the one-pot multi-bond forming elaboration of benzo[4,5]imidazo[1,2-a]-indoles, azole-fused benzo[4,5]imidazo-[1,2-a]quinazolines and benzimidazo[1,2-a]benzimidazoles. As part of our ongoing efforts to assemble N-heterocycles using Cu-mediated domino protocols, we report on a novel Cu-catalyzed domino synthesis of the polycyclic benzimidazole derivatives from bis-(o-haloaryl)carbodiimides.