Photochemistry of quinoxaline 1-oxide and some of its derivatives

Abstract

The solvent and substituent effects on the photoisomerization of quinoxaline 1-oxide were investigated. Irradiation in water afforded the corresponding quinoxalones if there was a hydrogen atom in position 2 or 3. However from 2,3-dimethylquinozaline 1-oxide the hydrolysis product of 3,4-dimethyl-3,1,5-benzoxadiazepine was isolated. 3,1,5-Benzoxadiazepines were formed as the main products under irradiation in cyclohexane from all the methyl derivatives, while the parent compound and 2-methoxyquinoxaline 1-oxide gave 2-isocyanophenyl derivatives. Both ring enlargement products and open-chain compounds have to be considered as primary photoproducts.