Addition of secondary amines to alkynylphosphonates

Addition of secondary amines to alkynylphosphonates catalyzed by Cu(I) salts proceeds regio- and stereospecifically to form (E)-2-(dialkylamino)alkenylphosphonates. The E-configuration was proved by analysis of 13C–31P vicinal spin–spin coupling constants in the NMR spectra of the products and authentic model compounds. The 3JPC constants in the model compounds fall in the range of 6–12 Hz for the cis arrangement of the coupled nuclei and are equal to or higher than 16 Hz for the trans configuration. Related coupling constants in the addition products are around 5 Hz, that is, corresponding to cis coupling.