Microwave-Assisted Benzimidazole Cyclization by Bismuth Chloride

We have developed a multi-step, microwave-assisted method for the bismuth chloride catalyzed synthesis of 1,2-disubstituted benzimidazoles. Biologically interesting benzimidazoles were readily assembled using a SNAr reaction, reduction, and finally a bismuth(III)-mediated cyclization under microwave irradiation. The desired products were then liberated from the soluble matrix in excellent yield and purity after cleavage. Each step of the synthetic sequence was performed under microwave conditions.