Metal-free decarboxylative oxygenation of α-amino acids to amide compounds via photoredox catalysis

Abstract

A strategy for the photocatalytic conversion of α-amino acids into corresponding amides was developed. A series of carbon nitride samples were prepared as the catalyst. Various characterizations of the catalyst indicated that effective photocatalytic activity and low recombination efficiency of photo-generated carriers were significant for the high activity of the catalyst. Reaction conditions for the photocatalytic decarboxylation of α-amino acids were optimized, alongside an investigation into the potential mechanism through controlled experiments and DFT computations. Mechanism studies unveiled that photo-generated electrons activated O₂ to reactive oxygen species, while photo-generated holes induced the decarboxylation reactions by activating the carboxylic acid groups, generating carbon radicals that ultimately lead to the formation of corresponding amides under the influence of reactive oxygen species. Moreover, the photocatalytic decarboxylation of different alpha amino acids was also discussed, providing new strategies for the formation of amides and lactams.