Selective Autoxidation of Electron-Rich Substrates under Elevated Oxygen Pressures

Article abstract of DOI:10.1021/jo00243a018

We report here the observation of a novel autoxidation pathway which occurs with electron-rich substrates.Tertiary amines, dialkyl thioethers, olefins, and alkynes under high oxygen pressures (>20 bars of O2), in polar solvents, and at elevated temperatures (>90 deg C) yield in good to excellent selectivity amine oxides, sulfoxides, and site-specific olefin and alkyne cleavage products, respectively.The results of mechanistic studies, including high oxygen pressure electrochemical studies, are discussed.A mechanism for this novel oxygenation reaction pathway that is consistent with the observed results is proposed.It involves an initial unfavorable electron transfer from the electron-rich substrate to oxygen to yield superoxide and the radical cation, which reacts with triplet oxygen to yield the oxygenated radical cation intermediate, a suspected potent oxidant.Electron transfer to the oxygenated radical cation from additional substrate (chain reaction) or superoxide yields a zwitterionic intermediate.This intermediate either reacts with additional substrate (O-atom transfer) to yield product (sulfoxide and N-oxide, in the case of thioethers and tertiary amines) or is converted with unimolecular reactivity to dioxetane-like (in the case of alkenes) or dioxetene-like (in the case alkynes) derived products.