Abstract Lithium dimethyldiphenylphosphonium diylide reacts with electrophiles such as Ph 2 PCl, Ph 2 P(O)Cl or Ph 2 P(S)Cl to give monoylide intermediates allowing by reaction with benzaldehyde the synthesis of the styrylphosphines or the corresponding oxides or sulfides. This efficient one-pot method permits at choice the selective synthesis of each isomer Z or E and corroborates further the isomeric identification of the styrylphosphines.