Photo-oxygenation of benzene derivatives by a novel derivative of the heterocyclic N-oxide, pyrimido[5,4-g]pteridine 5-oxide, involving a single-electron-transfer process

Abstract

1,3,7,9-Tetrabutylpyrimido[5,4-g]pteridine-2,4,6,8(1H,3H,7H,9H)-tetrone 5-oxide (1) efficiently oxygenates benzene (4a), toluene (4b), and anisole (4c) under photochemical conditions in a reaction mode different from that of 3-methylpyridazine 2-oxide (3) to give the corresponding phenols (5a–c) as major products. Experimental results clearly indicate that the photochemical oxygenation of (4a–c) by (1) involves a single-electron-transfer process followed by oxygen-atom transfer rather than interception of atomic oxygen generated from (1) in an excited state.