Visible-light promoted allylation of N-substituted tetrahydroisoquinoline using riboflavin tetra-acetate as photocatalyst

Riboflavin (RF) and relative derivatives are important coenzyme of some redox enzymes controlling the growing development of plants by harvesting light. The unique isoalloxazine structure unit with special photoredox capacity makes it applicable to induce single electron transfer (SET) oxidation of organic molecules. We report here that riboflavin tetra-acetate (RFTA) catalyzed the oxidation of N-phenyl tetrahydroisoquinoline to α-amino C-radical which subsequently undergoes radical type Michael addition to CC double bond of allylsulfone to access 1-allylated N-phenyl tetrahydroisoquinoline.