Co-host: The Chemical Society of Japan, The Society of Synthetic Organic Chemistry, Japan (Cooperation)
Mechanistic investigation on the 9,10-dicyanoanthracene (DCA)-sensitized photoreaction of triarylphosphines in acetonitrile under aerobic conditions was carried out. Product analysis by GC shows that was oxidized to the corresponding phosphine oxide with no appreciable side reactions. Certainly, the reaction is initiated by electron transfer from triarylphosphine to DCA in the singlet excited state with the aid of co-sensitizer, biphenyl, giving the triarylphosphine radical cation. On the other hand, laser flash photolysis experiments reveals linear dependence of decay rate of the triarylphosphine radical cation on the concentration of molecular oxygen, suggesting that the radical cation reacts with the oxygen to eventually afford triarylphosphine oxide. Most likely, triarylphosphine radical cation undergoes radical-attack on oxygen in the ground state in this photoreaction.
