Catalytic Oxidative Cyclocondensation of o‐Aminophenols to 2‐Amino‐3H‐phenoxazin‐3‐ones

Abstract

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 phenoxa-zinones 2e,f with elimination of one hydrochloride molecule.

Keywords:

• o‐aminophenols
• 2‐aminophenoxazin‐3‐ones
• enzymes
• hydroperoxides
• organoselenium compounds
• oxidation

Acknowledgments

The authors thank Ludwik Syper for the 3,3′‐ditrifluoromethyldiphenyl diselenide catalyst (4) used in this work. This work was supported by the Polish State Committee for Scientific Research (Grant No. 3T09A 003 27).