Redox-Neutral Cyclization of 2-Isocyanobiaryls through Photoredox/PPh 3 Dual Catalysis.

The photoredox/PPh 3 -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 Ph 3 P radical cation with key 1,2-hydride transfer and hydrogen atom generated through O-H bond homolytic cleavage of Ph 3 P-OH radical intermediate.