Reaction of triarylphosphine radical cations generated from photoinduced electron transfer in the presence of oxygen.

[reaction: see text] The 9,10-dicyanoanthracene (DCA)-sensitized photoreaction of triarylphosphines (1) was carried out in acetonitrile under aerobic conditions. Phosphine 1 was oxidized to the corresponding phosphine oxide with no appreciable side reactions. Product analysis and laser flash photolysis experiments suggest that the radical cation of 1 formed by the electron transfer from 1 to DCA in the singlet excited state ((1)DCA) reacts with O(2) to eventually afford the phosphine oxide.