N, P co-doped porous biochar supported electron deficient Niδ+ for domino reductive amination and amidation of levulinic acid with nitroarenes to N-substituted pyrrolidones using methyl formate

Abstract

The synthesis of N-substituted pyrrolidones starting from biomass-derived levulinic acid (LA) and nitroarenes is a highly attractive route for LA valorization, but still faces challenges. Herein, we report an electron deficient Ni^δ+ catalyst (Ni₂P/NPCB-600) prepared by doping N and P into coffee biochar using a one-pot carbonization method. Ni₂P/NPCB-600 shows outperform catalytic performance compared with the corresponding metallic Ni catalysts (Ni/CB-600 and Ni/NPCB-600) in the domino reductive amination and amidation of LA with nitroarenes. Characterization and controlled experiments demonstrate that the high catalytic activity and selectivity of Ni₂P/NPCB-600 are mainly attributed to the formation of electron deficient Ni^δ+ (Ni₂^δ+-P^δ-), which could promote the decomposition of methyl formate, and the adsorption and activation of C=O bonds in LA during the domino reactions. Furthermore, Ni₂P/NPCB-600 also shows good substrate scope, various N-substituted pyrrolidones can be directly synthesized from LA and different nitroarenes with good to excellent yields (87.5–99 %). This study provides a potential pathway for efficiently producing N-substituted pyrrolidones by adjusting the electron density of Ni.