Nafion-H Catalyzed efficient and Greener Synthesis of Mannich Bases having Benzimidazole Moiety

Abstract

Derivatives of substituted Benzimidazole were prepared by condensation of o-phenylene diamine and substituted carboxylic acid in presence of zink diacetate as oxidant (1a-1e). These on nitration yields (2a-2e), further on treatment with 2-amino 4-phenyl 1, 3 thiazole in presence of Nafion-H affords corresponding Mannich bases (3a-3e). Last step reaction involves one pot, three component Mannich reactions of benzimidazole, formaldehyde and heterocyclic amines are efficiently catalyzed by heterogeneous Nafion-H at ambient temperature to give the mannich bases in good to excellent yields. The catalyst can be easily recovered and reused without any decrease of activity for at least five times.