Rh(I)-Catalyzed Enantioselective Hydrogenation of α‑Substituted Ethenylphosphonic Acids

A class of chiral Rh­(I) catalysts containing monodentate
phosphorous
acid diesters tautomerized from the corresponding secondary phosphine
oxides was discovered by serendipitous hydrolysis of phosphoramidite
ligands. The evolved catalysts demonstrated unprecedented enantioselectivities
(98–99% ee) and high catalytic activities (as low as 0.01 mol%
catalyst loading) in asymmetric hydrogenations of a wide variety of
α-aryl-/alkyl-substituted ethenylphosphonic acids, providing
a facile approach to the corresponding enantiopure phosphonic acids
with significant biological importance.