Reaction of 1,3-dicarbonyl compounds with o-phenylenediamine or 3,3′-diaminobenzidine in water or under solvent-free conditions via microwave irradiation

Reaction of o-phenylenediamine with beta-diketones or beta-ketoesters in water formed 2-substituted benzimidazoles. Reaction of 3,3'-diaminobenzidine gave similar results. Under microwave irradiation conditions solvent-free reaction of o-phenylenediamine with beta-ketoesters afforded 1,5-benzodiazepin-2-one derivatives. An exception is the reaction of o-phenylenediamine with ethyl acetoacetate under microwave irradiation, which gave 2-methylbenzimidazole.