Mesoporous CuMn2O4 nanoframework as an efficient catalyst for the synthesis of benzimidazole derivatives through air oxidative coupling in water

Abstract

Mixed-metal oxide (MMO) CuMn2O4 nanoframework with a mesoporous structure was synthesized. The advantages of this mesoporous MMO are its large specific surface area, uniform pore size, and various metal valence states. MMO CuMn2O4 nanoframework showed efficient catalytic activity in the oxidative coupling of 2-amino/hydroxy/mercaptoanilines with various alcohols in the preparation of benzimidazoles, benzoxazoles, and benzothiazoles using water as the sole solvent in high yields. The efficient catalytic activity is mainly attributed to large specific surface area, increased number of active sites, solvent reorganization between the pores of mesoporous CuMn2O4 nanoframework, and the various electronic states of the copper and manganese ions (Cu+, Cu2+, Mn3+, Mn4+) due to the Jahn-Teller effect. This research provides new insights into improving the catalytic performance of catalyst for the synthesis of nitrogen-containing five-membered ring compounds.