ortho-Nb2O5 as a recyclable heterogeneous catalyst for the synthesis of 2-substituted benzimidazoles and quinazolinones in an aqueous medium via oxidative dehydrogenative coupling

Abstract

Niobium pentoxide with deformed orthorhombic phase (ortho-Nb2O5) is found to be an efficient heterogeneous catalyst for the synthesis of N-heterocyclic compounds such as 2-substituted benzimidazoles and quinazolinones from primary alcohols via oxidative dehydrogenative coupling in an aqueous medium. The highlights of this environmentally benign method involve using bench-stable, heterogeneous, and biologically inert niobium metal-based catalyst, and the catalytic system is free of toxic metals, additives, oxidants, solvents, and byproducts. The catalyst is compatible with different substrates, and the desired benzimidazoles and quinazolinones were obtained with moderate to good yields. The catalyst is recyclable and used five times without much loss in activity.