Redox-Neutral Cyclization of 2‑Isocyanobiaryls through Photoredox/PPh₃ Dual Catalysis

The photoredox/PPh₃-mediated cyclization of 2-isocyanobiaryls has been developed. A substantial range of functional-group-rich phenanthridine derivatives were synthesized at room temperature in a highly selective and atom-economic manner. Mechanistic studies suggested that the cyclization process is probably mediated both by Ph₃P radical cation with key 1,2-hydride transfer and hydrogen atom generated through O–H bond homolytic cleavage of Ph₃P–OH radical intermediate.