Graphene Oxide as Metal-Free Catalyst in Oxidative Dehydrogenative C–N Coupling Leading to α-Ketoamides: Importance of Dual Catalytic Activity

Abstract

A heterogeneous, inexpensive, and environmentally friendly carbocatalyst, graphene oxide (GO) enables the formation of α-ketoamides from activated aldehydes and amines through a cross-dehydrogenative coupling pathway. The oxygenated functionalities (e.g., carboxyl, hydroxyl, ketonic, and epoxides) on the surface of graphene oxide impart acidic as well as oxidizing properties to the material. This dual catalytic property of graphene oxide is explored toward the generation of α-ketoamides where surface acidity of graphene oxide favors the initial formation of hemiaminal intermediate followed by oxidation leading to the desired final product. The hemiaminal intermediate could be isolated and confirmed by NMR and mass analysis. A few control experiments confirmed that both acidic and oxidizing catalytic activities of graphene oxide were instrumental in the coupling reaction. Use of benzoic acid and p-toluene sulfonic acid as catalysts resulted in the formation of only hemiaminal intermediate as the major prod...