Selective oxygenation by electron transfer

Photocatalytic selective oxygenation reactions of aromatic compounds were achieved using an electron donor-acceptor linked dyad, 9-mesityl-1O- methylacridinium ion Acr -Mes as a photo- catalyst and molecular oxygen as an oxidant under visible light irradiation in homogeneous conditions. The oxygenation reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of acridinium moiety of Acr -Mes to afford an extremely long-lived electron-transfer state. The electron-transfer state can oxidize and reduce substrates and dioxygen, respectively, leading to selective oxygenation and halogenation of substrates. Photoinduced electron transfer from benzene to the singlet excited state of 3-cyano- quinolinium ion has enabled to oxidize benzene by dioxygen to yield phenol selectively. C C bond formation of substrates has also been made possible by using Acr -Mes as a photocatalyst.