Direct Oxidative Amination of the Methyl C–H Bond in N-Heterocycles over Metal-Free Mesoporous Carbon
Xiangdong Long, Jia Wang, Guang Gao, Chao Nie, Peng Sun, Yongjie Xi, Fuwei Li
Abstract
Direct oxidative amination of the sp3 C–H bond is an attractive synthesis route to obtain amides. Conventional catalytic systems for this transformation are based on transition metals and complicated synthesis processes. Herein, direct and efficient oxidative amination of the methyl C–H bond in a wide range of N-heterocycles to access the corresponding amides over metal-free porous carbon is successfully developed. To understand the fundamental structure–activity relationships of carbon catalysts, the surface functional groups and the graphitization degree of porous carbon have been purposefully tailored through doping with nitrogen or phosphorus. The results of characterization, kinetic studies, liquid-phase adsorption experiments, and theoretical calculations indicate that the high activity of the carbon catalyst is attributed to the synergistic effect of surface acidic functional groups (hydroxyl/carboxylic acid/phosphate) and more graphene edge structures exposed on the surface of carbon materials with a high graphitization degree, in which the role of acidic functional groups is to adsorb the substrate molecule and the role of the graphene edge structure is to activate O2.