Green photocatalytic N-debenzylations with molecular oxygen catalyzed by recyclable metal-free tubular carbon nitride

Abstract

Debenzylations are widely used in fields such as pharmaceuticals and fine chemicals. In this study, metal-free tubular carbon nitride (CN-T) was prepared and used in photocatalytic debenzylations with molecular oxygen as the sole oxidant, affording 44 kinds of debenzylated amines in yields up to 93%. The average yield of 88% and catalyst recovery rate of 97% were obtained in the 6 cycle recovery and amplification experiments. Both experiments and DFT calculations were conducted to reveal the detailed reaction mechanism. The in situ generated Cl· radicals from HCl play an important role in the HAT process for debenzylations of tertiary amines. ¹O₂ could promote the debenzylations of primary/secondary amines by simultaneously extracting hydrogen atoms from N–H and benzylic C–H groups to form imines, which readily undergo hydrolysis. The utilization of CN-T offers a convenient pathway for catalyst recovery and reuse.