Synthesis of 1,2-disubstitued benzimidazoles using SiO2/ZnCl2

A general and easy method for the synthesis of several 1,2-disubstituted benzimidazoles using SiO2/ZnCl2 and solvent-free conditions is described, This efficient and improved method furnishes selectively and in good yields the corresponding 1,2-bis(organyl)-benzimidazoles starting from o-phenylenediamine and aromatic or aliphatic aldehydes. The catalytic system was re-Used up three times and the use of focused microwaves accelerates the reaction. (C) 2009 Elsevier Ltd. All rights reserved.