Dynamic Kinetic Resolution Based Asymmetric Transfer Hydrogenation of α‑Alkoxy-β-Ketophosphonates. Diastereo- and Enantioselective Synthesis of Monoprotected 1,2-Dihydroxyphosphonates

Dynamic kinetic resolution driven, asymmetric transfer hydrogenation reactions of a wide range of 2-substituted α-alkoxy-β-ketophosphonates 3 were observed to proceed efficiently to give the corresponding 2-substituted α-alkoxy-β-hydroxy phosphonates 4 with excellent levels of diastereo- and enantioselectivity. These processes are promoted by using well-defined, commercially available, chiral transition metal catalysts and a 0.2:1 mixture of formic acid and triethylamine as the hydrogen source and solvent.