Photochemical Oxygenation of Cyclohexene through Reductive Quenching of Excited Tetraphenylporphyrinatoantimony(V) by Triphenylphosphine

Article abstract of DOI:10.1021/jo00103a032

When visible light (λ = 420 nm) was irradiated to a reaction mixture involving tetraphenylporphyrinatoantimony(V) 1 as a sensitizer, methylviologen as an electron acceptor and triphenylphosphine (PPh3) as an electron donor in acetonitrile-water (95:5) under the degassed condition, oxygenation reaction of cyclohexene 2 proceeded and 2-cyclohexenone and 3-cyclohexenone which were four electron oxidized products of 2 were mainly produced with rather high quantum yields of 0.14 and 0.04, respectively.Formation of cation radical of PPh3 (PPh3(1+.)) by an electron transfer from PPh3 to the excited triplet state of 1 upon visible light (λ = 420 nm) irradiation was the key step of the photooxygenation.Addition of PPh3(1+.) to 2 produced an adduct which suffered hydrolysis and further oxidation to afford the oxygenated products of 2.