Photocatalytic Oxidative C(sp3)-H/N-H Cross-Dehydrogenative Coupling of Tertiary Anilines with Amides/Imides: Synthesis of N-Mannich Bases

A photocatalytic method for the synthesis of N-Mannich bases has been developed through the C(sp3)-H/N-H cross-dehydrogenative coupling of N,N-dimethylanilines with amides/imides. This process utilizes 2,4,6-triphenylpyrylium tetrafluoroborate (TPT) as the photocatalyst and is conducted at ambient temperature and atmospheric air. Various N,N-dimethylanilines and the aromatic, heteroaromatic and aliphatic (cyclic) amides, as well as imides were successfully employed, yielding moderate to good results. Preliminary mechanistic and isotope-labeling studies indicate that the reaction likely proceeds via a single electron transfer pathway and involves an alpha-aminoalkyl radical intermediate.