2-Aminophenol readily undergoes highly selective Co(salen) catalyzed oxygenation in methanol at room temperature resulting unexpectedly in the quantitative formation of 2-Aminophenoxazin-3-one. The oxygenation of substituted 2-aminophenols provides useful information to discuss the reaction path.
The catalytic oxidative cyclocondensation of the o-aminophenols 1a-f was investigated. The oxidants used were air/laccase, H2O2/horseradish peroxidase, H2O2/ebselen (3), and TBHP/diphenyl diselenide 4. The products obtained were 2-amino-3H-phenoxazin-3-one-questiomycin A, its derivative 2b, and cinnabarinic acid and actinocin (2c,d). Substrates with methyl groups at 4 and 5 positions of benzene ring were converted to different dihydrophenoxazinones 2g,h. Compounds having chlorine atoms at the same positions underwent oxidation to planar phenoxazinones 2e,f with elimination of one hydrochloride molecule.
v. Auwers; Deines, Fortschritte der Chemie, Physik und physikalischen Chemie, 1924, vol. 18, p. Heft 2, S. 28