An efficient and facile synthesis of benzimidazo[1,2-a]benzimidazoles via copper-catalyzed domino addition/double cyclization

A copper-catalyzed synthesis of benzimidazo[1,2-a]benzimidazoles by domino addition/double cyclization of bis-(o-haloaryl)carbodiimides with primary amines was developed. A variety of the desired polycyclic benzimidazoles were efficiently and facilely assembled. Multibonds and polycyclic moieties were directly constructed in one pot. 2-Bromo-2′-iodo-diarylcarbodiimides gave good selectivity.