Investigation of quinones

Naphtho2,3-f]quinoxaline-7,12-diones add a molecule of benzenesulfinic acid to give 5-phenylsulfonyl-7, 12-dihydroxynaphtho2,3-f]quinoxalines. The latter are oxidized to 5-phenylsulfonyl-substituted quinones, which add a molecule of benzenesulfinic acid to the oxygen atoms of the quinone grouping to give the O⁷-benzenesulfonate of 5-phenylsulfonyl-7, 12-dihydroxynaphtho2,3-f]quinoxaline. The protonated form of naphtho2,3-f]quinoxa-line-7, 12-dione, which is stabilized by an intramolecular hydrogen bond, as confirmed by the anomalously high basicity of angular naphtho2,3-f]quinoxaline-7,12-dione as compared with its linear isomer, which is inert in reactions with benzenesulfinic acid, undergoes reaction.