Photoredox Enabled Cobalt Catalyzed Enantioselective C–H Activation and APEX Reaction for C–N Axially Chiral Heterocycles

Molecules with the C–N stereogenic axes have widespread applications, yet their asymmetric synthesis under mild and environmentally friendly conditions is increasingly challenging. Herein, we report the merger of inexpensive photoredox catalysis with cobalt-catalyzed asymmetric C–H activation/APEX strategy, enabling cascade annulation of (hetero)arenes and alkenes with α-aryl-allenyl acetates to deliver C–N axially chiral benzophenanthridinone and polycyclic quinolinone frameworks with very high yields and enantioselectivities at room temperature. This methodology leverages the multifaceted role of photocatalysis – facilitating the redox event of the cobalt catalyst and the formation of key intermediates that drive the APEX process. It also harnesses the α-aryl-allenyl acetate coupling partners as the formal arene precursors, which have been elusive thus far. The intricacy of the reaction mechanism and the rationale behind the stereoselective outcomes were also unraveled through controlled experiments and DFT studies.