Nucleophilic addition of secondary phosphine sulfides to divinyl sulfoxide and divinyl sulfone

Secondary phosphine sulfides readily undergo addition to divinyl sulfoxide and divinyl sulfone in the presence of KOH (THF, 20–22°C, 1 h) with regiospecific formation of bis[2-(diorganylthiophosphoryl)-ethyl] sulfoxides and sulfones. A dramatic increase in the electrophilicity of the double bond in the monoadduct suggests transfer of the electron-acceptor effect of the thiophosphoryl group directly though space, due to its donor-acceptor interaction with the polarized S-O bond. It was demonstrated by the example of divinyl sulfoxide that, when performed with equimolar amounts of reactants and a weaker base (LiOH), the reaction can be stopped at the stage of formation of the monoadduct.