Chemo- and regiospecific monoaddition of secondary phosphine sulfides to 1-acyl-2-phenylacetylenes

Secondary phosphine sulfides react with 1-acyl-2-phenylacetylenes under mild conditions (KOH, THF, r.t.) to afford chemo-and regiospecifically 3-diorganophosphorothioyl-1-R-3-phenyl-2-propen-1-ones in high yield, with the E-isomers being formed exclusively (R = Ph and 2-thienyl) or predominantly (60%, R = Me).