C–H functionalization via hydrogen atom transfer is an attractive method of decorating inert C–H bonds, yet it remains challenging so far. In such a reaction, the hydrogen abstractor generally plays a crucial role in determining the reactivity and selectivity. Among the various hydrogen abstractors developed, N-hydroxyphthalimide (NHPI) bearing an N-hydroxy group and two adjacent carbonyl groups has features including easy preparation, convenient modification, and a superior catalytic ability in many reactions. A large variety of electron-deficient N-hydroxy catalysts based on NHPI, including NHPI derivatives and analogues, have been successively developed and applied in a broad range of C–H functionalization reactions. This review comprehensively summarizes the development of N-hydroxy catalysts, with a special focus on the relationship between structure and performance.

N-Hydroxy benzimidazoles (NHBIs) have proved to be efficient hydrogen atom abstractors (HAAs), but their further application in catalysis has been rarely explored since the first report. Herein, we describe their...