Cyclization of o-phenylenediamines by CO2 in the presence of H2 for the synthesis of benzimidazoles

The cyclization of o-phenylenediamines by CO2 in the presence of H-2 was presented to directly synthesize benzimidazoles, and a series of benzimidazoles were obtained in excellent yields using RuCl2(dppe)(2) as the catalyst.