Without any catalyst, a direct one-step synthesis of various benzimidazoles in methanol from aromatic aldehydes and 1,2-phenylenediamine was described using air as the oxidant. All reactions acquired good yield (≥69%), and the structures of all products were characterized by elemental analysis, IR and ¹H MNR spectra. Compared to the previous methods, this new protocol has the advantages of simple procedure, mild conditions, easy purification and environment friendliness.

Key words: benzimidazole, synthesis, aromatic aldehyde, 1,2-phenylenediamine, air oxidant