Synthesis of new 3-(dialkoxyphosphoryl)butenoates and their enantioselective hydrogenation

(E)-3-Dialkoxyphosphorylbut-2-enoates, readily available by the dehydration of the 3-dialkoxyphosphoryl-3-hydroxybutyrates are converted to 3-dialkoxy phosphorylbut-3-enoates by Pd(II)-catalyzed photochemically assisted double bond migration. Hydrogenation of the latter catalyzed by chiral rhodium co mplexes affords 3-dialkoxyphosphorylbutyrates with higher rates and enantio selectivity (98% ee) than the hydrogenation of the (E)-3-dialkoxyphosphoryl but-2-enoates. The low activity of the rhodium complexes with bisphosphinit e ligands is caused by low affinity for complexation of the unsaturated pho sphonate.