Novel 1,4-diphosphanes with imidazolidin-2-one Backbones as chiral ligands: Highly enantioselective Rh-catalyzed hydrogenation of enamides

Abstract

Appropriate gauche steric interactions between the N-substituents and the phosphanylmethyl groups (see picture, top right) in the novel 1,4-diphosphane ligands 1 having an imidazolidin-2-one backbone affect the conformational flexibility of the seven-membered chelate ring formed by coordination to a metal atom. Thus, Rh complexes of 1 are excellent catalysts for enantioselective hydrogenation of enamides (bottom, cod= cyclooacta-1,5-diene).