Sequential Photoredox Catalysis for Cascade Aerobic Decarboxylative Povarov and Oxidative Dehydrogenation Reactions of N-Aryl alpha-Amino Acids

A visible-light-driven sequential photoredox catalysis to allow N-aryl alpha-amino acids to experience efficient cascade aerobic decarboxylative Povarov and oxidative dehydrogenation (ODH) reactions is described. With a dicyanopyrazine-derived chromophore (DPZ) as a photoredox catalyst in both transformations, two series of valuable azaarenes, i.e., 4-amino tetrahydroquinolines (THQs) and quinolines, were obtained in satisfactory yields featuring diverse 2- and 2,3-substituent patterns. To enable the ODH reaction of 4-amino THQs, a cooperative catalysis with N-hydroxyphthalimide was developed. Additionally, an unprecedented synthesis of chiral N-amino-2-methyl THQs with high enantioselectivities was realized.