Enantioselective Rh-catalyzed hydrogenation of 3-aryl-4-phosphonobutenoates with a P-stereogenic BoPhoz-type ligand

A series of chiral 3-aryl-4-phosphonobutyric acid esters were synthesized in high enantioselectivities (93-98% ee) via the Rh-catalyzed asymmetric hydrogenation of the corresponding 3-aryl-4-phosphonobutenoates using a P-stereogenic BoPhoz-type phosphine-aminophosphine ligand. The methodology has been successfully applied to the asymmetric synthesis of a potential GABA(B) antagonist, (R)-phaclofen, in high enantioselectivity.