Reaction of 3,5-di-(tert-butyl)-o-benzoquinone with arylamines developing to the formation of a pentaheterocyclic 12Н-quinoxaline[2,3-b]phenoxazine system. A deeper insight into the reaction mechanism

Abstract Reaction between sterically crowded 3,5-di-( tert -butyl)- o -benzoquinone and aromatic amines occurring at the oxidative conditions and developing to the formation of compounds 8 , derivatives of the pentaheterocyclic 12Н-quinoxaline[2,3-b]phenoxazine system 2 was studied. The products obtained at the intermediate stages, including di-( tert -butyl) derivatives of the tricyclic 10H-phenoxazine system: ( E )-N-3Н-phenoxazin-3-ylidene-4-methoxyaniline 3 , N-(aryl)-3-arylimine-3Н-phenoxazine-2-amine 4 , 1-phenyl-10H-phenoxazine 5 and 1-phenyl-3H-phenoxazin-3-one 6 were preparatively isolated and their molecular structures determined by X-ray crystallography. A stable 1-phenyl-6,8-di-( tert -butyl)-10H-phenoxazine radical 7 , a primary product of oxidation of 5 was prepared and characterized by the ESR spectroscopy. Compounds 8 exhibit strong red luminescence distinguished by small Stokes shifts, short fluorescent lifetimes and high quantum yields.