Radical mechanism in the photoreaction of organic N-oxides: oxygen transfer from photoexcited paradiazine di-N-oxides to amines

摘要: Abstract Photolysis of paradiazine di-N-oxides in solution leads to the production N-hydroxy-N′-oxyl radicals via hydrogen abstraction. For example, a chloroform 2-methyl-3-acetylquinoxaline 1,4-dioxide gives radical 1-hydroxy-2-methyl-3-acetylquinoxalinyl-4-oxyl. In presence amines, photoinduced oxygen transfer has been observed and electron spin resonance studies have indicated that reaction formation amine-derived nitroxide systems involving triethylamine secondary amines. Thus, two typical cyclic nitroxides pyrrolidinyl-1-oxyl 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl are generated through photolysis solutions containing corresponding The evidence presented suggests active oxygenating species lowest triplet states N-oxides by photolysis. Exciplexes formed collision T1 state with amines may be intermediates oxygen-transfer processes. Amine-derived from exciplexes further ON bond α cleavage amine moiety.