<i>ortho</i> -Nb ₂ O ₅ as a recyclable heterogeneous catalyst for the synthesis of 2-substituted benzimidazoles and quinazolinones in an aqueous medium <i>via</i> oxidative dehydrogenative coupling

Niobium pentoxide with a deformed orthorhombic phase (<i>ortho</i>-Nb₂O₅) was found to be an efficient heterogeneous catalyst for the synthesis of N-heterocyclic compounds such as 2-substituted benzimidazoles and quinazolinones from primary alcohols <i>via</i> oxidative dehydrogenative coupling in an aqueous medium. This environmentally benign method uses a 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 in moderate to good yields. It is recyclable and can be used five times without significant loss in activity.