Oxygen-implanted MoS2 nanosheets promoting quinoline synthesis from nitroarenes and aliphatic alcohols via an integrated oxidation transfer hydrogenation–cyclization mechanism

Abstract

We herein report that MoS₂ with oxygen-implanting modification (O-MoS₂) can work as a multifunctional catalyst to achieve the one-pot quinoline synthesis from basic nitroarenes and aliphatic alcohols. Different from common knowledge that the application of MoS₂-based catalysts and above quinoline synthesis need anaerobic conditions, we conduct the heterogeneous catalysis under an unusual air atmosphere. Catalyst characterization and experimental results indicate that the MoO_x clusters implanted in the MoS₂ skeleton, not the coordinatively unsaturated Mo sites (CUS Mo), dominate the generation of quinolines. By overturning the catalysis perception that O₂ adsorption on MoS_x can deactivate the MoS₂-based catalysts using an efficient method for in situ healing of the MoO_x structure in O-MoS₂ and protecting the O-MoS₂ catalyst by inhibiting unwanted MoO_x elimination with extra H*, we innovatively introduce O₂ into the quinoline synthesis. The robust O-MoS₂ can be consecutively used ten times without regeneration and it offers 69–75% yields of 2-methylquinoline from nitrobenzene and ethanol. Furthermore, different from the traditional transfer hydrogenation–condensation mechanism, an integrated oxidation–transfer hydrogenation–cyclization mechanism is proposed over the O-MoS₂ catalyst.