Chemical oxidation of nitrated polycyclic aromatic hydrocarbons: hydroxylation with superoxide anion radical

Nitrated polycyclic aromatic hydrocarbon (nitroPAH) is a potent mutagen which is reductively and/or oxidatively metabolized. Biological oxidation of nitroPAH, such as hydroxylation and epoxidation, is known, but chemical oxidation has been reported in only a few papers. NitroPAH is barely oxidized by various chemical oxidants because of the electron deficient property of the aromatic ring with the nitro substituent. Nucleophilic reactivity of superoxide anion radical is known, and thus the oxidation of nitroPAH with the chemically generated superoxide anion radical was carried out in this study. When 1-nitropyrene was reacted with KO2/18-crown-6 in dimethylformamide, 5-, 6-, 8-, and 9-hydroxy-1-nitropyrenes and 1-hydroxypyrene were obtained in preparative yields. Three isomeric dinitropyrenes, 3-nitrofluoranthene, 6-nitrobenzo[a]pyrene, and 6-nitrochrysene, were oxidized to hydroxy derivatives, some of which correspond to the oxidative metabolite of nitroPAH. The oxidation of dinitropyrenes with trifluoroperacetic acid gave K-region oxidized products.