An efficient method has been developed for the catalysis of condensation of 1,2-phenylenediamines and 2-aminothiophenoles with different aldehydes into their corresponding 2-aryl-1H-benzimidazoles and 2-aryl-1H-benzothiazoles under mild condition. In this method, trans-3,5-dihydroperoxy-3,5-dimethyl-1,2-dioxolane (DHPDMDO)/HOAc/KI system was used as a novel and effective oxidant in water at room temperature with excellent results.