Endo/Exo-Controllable Photocyclization by EnT-SET-Switch

CBZ6, a redox-neutral non-donor-acceptor-type organo-photocatalyst, presents a strong reductive potential with an oxidative potential of -2.16 V (vs SCE). It can work as a photosensitizer for both single-electron transfer and triplet energy transfer processes. This feature enables site-selective control in the intramolecular hydroarylation of acrylamides. Both 5-exo-trig and 6-endo-trig cyclization products could be prepared regiospecfically under mild conditions. No transition metal, halogen-containing reagents, or additional reductant or oxidant is involved. This process provides a concise and environmentally sustainable access to a series of oxindoles and dihydroquinolinones.