Visible-Light-Driven α-C(sp)-H Carboxylation of Primary Benzylamines with CO to Access α-Amino Acids.

α-Amino acid motifs, serving as essential building blocks, are ubiquitous in natural products, bioactive molecules and drugs. Despite significant advances in the synthesis of α-amino acids (α-AAs) using CO as carboxyl source, the direct α-C(sp)-H carboxylation of primary amines, which are important organic chemical feedstocks, remains an attractive yet formidable challenge. Herein, we report the first visible-light-driven direct α-C(sp)-H carboxylation of primary benzylamines with CO, wherein CO acts dually as a transient protecting group and as the carboxyl source. This strategy enables efficient synthesis of diverse α-AAs under mild reaction conditions with a broad substrate scope and good functional group compatibility. Mechanistic studies indicate that an intermolecular hydrogen atom transfer (HAT) between the external HAT reagent and the carbamate intermediate, in situ-generated from primary amine and CO, is followed by reduction and carboxylation to furnish α-AAs. Moreover, a complementary protocol for carboxylation of α-C(sp)─H bonds in amides through an intramolecular 1,2-HAT pathway is also developed, obviating the need for an external HAT reagent and further expanding the synthetic utility of this methodology. These advances represent a versatile and practical platform for the synthesis of α-AAs from amine precursors using CO.