Enantioselective synthesis of optically active alkylphosphonates via Rh-catalyzed asymmetric hydrogenation of β-substituted α,β-unsaturated phosphonates

The Rh-catalyzed asymmetric hydrogenation of β-substituted α,β-unsaturated phosphonates using (Sc,Sp)-WalPhos as the chiral ligand is reported, in which a wide range of optically active β-substituted alkylphosphonates were obtained in good yields and with good to excellent enantioselectivities (86–98% ee). In contrast to the Rh/(Rc,Sa)-FAPhos system previously reported by us, the present catalytic system shows a wider substrate scope, and can perform the hydrogenation under milder reaction conditions.