Visible-Light-Induced Organophotoredox-Catalyzed Phosphonylation of 2 H-Indazoles with Diphenylphosphine Oxide

A metal-free visible-light-induced phosphonylation of 2 H-indazoles with diphenylphosphine oxide has been developed using rose bengal as an organophotoredox catalyst under ambient air at room temperature. A library of diphenyl(2-phenyl-2 H-indazol-3-yl)phosphine oxide with broad functionalities has been synthesized in high yields. The experimental result suggests the radical pathway of the reaction.