Oxidation of Polynuclear Aromatic Hydrocarbons with Ceric Ammonium Sulfate: Preparation of Quinones and Lactones

The oxidation of polynuclear aromatic hydrocarbons with ceric ammonium sulfate (CAS) in sulfuric acid was investigated. Oxidation of benzo[κ]fluoranthene (1) gave a mixture of the 7,12- and 2,3-diones 3 and 4. The 2,3-dione (4) was used as the starting material for a facile synthesis of 2,3-dihydro-2,3-dihydroxybenzo[κ]fluoranthene (5) and the corresponding diol epoxide 6, which are potentially important metabolites of benzo[κ]fluoranthene. In a similar manner, 2,3-dihydro-2,3-dihydroxyfluoranthene (7) and its diol epoxide 8 were prepared from fluoranthene. Oxidation of benzo[b]fluoranthene (2) with CAS did not yield quinones, but instead gave benzo[d]fluoreno[2,1-b]pyran-5,13-dione (9), which was identified by its spectral properties and by reduction with LiAlH₄. The lactone 9 formed via initial A-region oxidation of 2. It was not formed from 1-hydroxybenzo- [5]fluoranthene (12), which gave benzo[b]fluoranthene-1,2-dione (13) upon CAS oxidation. CAS oxidation of benzo[a]pyrene (14) gave a mixture of the 1,6- and 3,6-quinones 17 and 18. Treatment of benz[a]anthracene (15) with CAS yielded 7-oxo-12-hydroxy-7,12-dihydrobenz[a]anthracene (19) and the 7,12-quinone 20. Oxidation of chrysene (16) with CAS gave 6H-benzo[d]naphtho[1,2-b]pyran-6-one (21) and the 5,6-quinone 22. The results of this study demonstrate that CAS oxidation is useful for the synthesis of certain PAH quinones or lactones, from polynuclear aromatic hydrocarbons, depending on the ring system.