CAN- and DDQ-Promoted Oxidation of Alkenyl Sulfides

Article abstract of DOI:10.1021/jo00103a033

Vinyl sulfides 1 react with CAN in acetonitrile at room temperature to give radical cations 2A in equilibrium with the thiiranyl radical cations 2B.The reaction products arise from nucleophilic attack of the nitrate counterion at either the sulfur atom of 2A or the trivalent carbon of 2B.The last reaction can proceed through 1,2-shift or displacement of the sulfide moiety.When α-methylenic protons are present in 2B, deprotonation occurs, leading to allyl radicals and, ultimately, to isomeric allyl alcohols.Reactions of 1 with DDQ in acetonitrile afford charge-transfer complexes and then zwitterionic electron-transfer (ET) complexes which can evolve rapidly through intramolecular proton transfer when trans methylenic protons are present.The resulting sulfur-oxygen ?-complexes are responcible for the reaction products mainly through either γ-elimination of DDQH2 or nucleophilic attack at the δ-vinilic carbon followed by displacement of DDQH(1-).