Tailored trisubstituted chiral CpxRhIII catalysts for kinetic resolutions of phosphinic amides

Abstract

A trisubstituted chiral Cp^x ligand family is introduced. Based on the disubstituted atropchiral Cp^x ligand scaffold, the introduction of a bulky third substituent at the central position of the Cp ring leads to substantially increased selectivities for rhodium(III)-catalyzed kinetic resolutions and allowed for s-factors of up to 50. Their superiority is demonstrated by kinetic resolutions of phosphinic amides providing access to compounds with stereogenic phosphorus(V) atoms. The unreacted acyclic phosphinic amide and the cyclized product are both obtained in good yields and enantioselectivities. The ligand synthesis capitalizes on a late stage modification and expands the accessible ligand Cp^x ligand portfolio.