Noble-Metal-Free C-H Allylation of Tetrahydroisoquinolines Using a Cobalt- Organophotoredox Dual Catalyst System

Metallaphotoredox-catalyzed allylation represents an emerging synthetic methodology that enables allylic substitu-tion using nucleophilic radical species. The C-H allylation of N-aryl tetrahydroisoquinolines is an innovative example in this area and allows access to synthetically useful precur-sors for the further derivatization of tetrahydroisoquinolines. However, previous methods have required the use of noble metals, which has hampered their application due to concerns over their sustainability. Here we report the C-H allylation of N-aryl tetrahydroisoquinolines using a cobalt/organophotore-dox dual catalyst system. Based on precedent, control experi-ments and controlled irradiation experiments, a mechanism for the cobalt/photoredox-catalyzed allylation that involves a p-allyl cobalt complex is proposed.