Photoinduced Hydrophosphination of Terminal Alkynes with Tri( o -tolyl)phosphine: Synthesis of Alkenylphosphonium Salts.

Herein reported is a photoinduced hydrophosphination reaction of terminal alkynes with tri( o -tolyl)phosphine to form alkenylphosphonium salts. The reaction is more sustainable than conventional methods since it dispenses with the need for elaborated starting materials and precious transition metals. The o -methyl groups of tri( o -tolyl)phosphine play two important roles: (1) to guide the phosphorus radical to add onto the terminal sp carbon and (2) to donate a hydrogen atom onto the developing sp 2 carbon radical intramolecularly.