Biomass-Derived Cooperative Pyridinic/Pyrrolic-N Sites Enable Efficient Metal-Free N-Alkylation of Alcohols with Amines

Abstract

N-alkylamines serve as essential structural units in pharmaceuticals, agrochemicals, bioactive molecules, etc. Nevertheless, their conventional syntheses predominantly rely on metal-based catalysts, which frequently encounter challenges including metal leaching, easy poisoning, and poor recyclability. Herein, starting from the biomass resource chitosan, we engineered a series of chitosan carbon microspheres (CCMs) with high surface area and tunable N heteroatoms via sol−gel synthesis followed by facile calcination. Under relatively mild conditions, a metal-free catalytic system that achieved efficient N-alkylation of alcohols and amines using chitosan-derived N-doped carbon materials has been realized. The optimal CCM-800 exhibited activity advantages over many commercial and reported metal-based catalysts, along with high cycling stability (30 cycles) and broad substrate scope (103 compounds). Combined with theoretical calculations, it revealed that these cooperative pyridinic/pyrrolic-N sites enhanced their adsorption and activation capabilities for the key intermediate Ph-CH2OK in the rate-determining step (RDS) through their synergistic electronic structure and spatial configuration, thereby promoting the entire reaction. This work achieves efficient N-alkylation reaction using biomass-derived carbon materials under metal-free catalysis, providing a viable route for the efficient synthesis of N-alkylamines.