Cobalt single-atom catalysts for domino reductive amination and amidation of levulinic acid and related molecules to N-heterocycles

Abstract

The development of single-atom-based catalysts (SACs), which bridge the traditional areas of homogeneous and heterogeneous catalysis, continues to be important for achieving organic synthesis in a more efficient and practical manner. Here, we report reusable cobalt-based SACs for the selective and general reductive amination of levulinic acid and related keto acids, which is of interest in the context of valorization of biomass. The optimal Co-SAC-based catalyst is prepared by pyrolysis (800°C) of cobalt-phenanthroline complexe on carbon and subsequent acid treatment. The resulting Co-SACs showed amazing activity compared with the corresponding Co-nanoparticles and displayed an excellent substrate scope for various reductive domino transformations including reactions of levulinic acid with nitro compounds and nitriles to produce various N-substituted pyrrolidones in good to excellent yields. Further, the synthesis of diverse isoindolinones from aromatic ketoacids and amines/nitro compounds was performed with the optimal catalyst system.