Research into the oxidation of abietic acid-derived enone with atmospheric oxygen

This work presents results of methyl 7-oxoabiet-13(14)-en-18-oate (3) self-oxidation with air-oxygen in the presence of various bases such as triethylamine or sodium t-butoxide. While under aerobic conditions, the use of sodium t-butoxide as a base results in the formation of four isomeric alcohols, an addition of triethylamine into reaction medium directs the enone 3 oxidation to hydroperoxides. To clarify this base dependence and to obtain more in-depth information about this reaction additional studies with cyclohexenone as a reference enone have been undertaken. Their results demonstrated the predisposition of abietane hydroperoxides to oxidize α,β-unsaturated ketones to epoxides in the presence of t-butoxide while reducing the hydroperoxide group to hydroxyl. This ability of hydroperoxides to epoxidize conjugated double bonds and confirmed by the present study intermolecular course allowed proposing a plausible mechanism for this reaction.