Diastereoselective Synthesis of P‐Chirogenic and Atropisomeric 2,2′‐Bisphosphino‐1,1′‐binaphthyls Enabled by Internal Phosphine Oxide Directing Groups

Diphosphine ligands that merge both axial and P-centered chirality may exhibit superior or unique properties. Herein we report the diastereoselective introduction of P-centered chirality at the 2-position of the axially chiral 2'-(phosphine oxide)-1,1'-binaphthyl scaffold. A lithium-bromide exchange reaction of a 2-bromo-2'-(phosphine oxide)-1,1'-binaphthyl and treatment with dichlorophosphines followed by a nucleophilic organometallic reagent afforded unsymmetrical 2-phosphino-2'-(phosphine oxide)-1,1'-binaphthyls with binaphthyl axial chirality and one or two phosphorus stereocenters with a variety of P substituents. The final diastereomerically pure 2,2'-bisphosphino-1,1'-binaphthyls were obtained by reduction of the phosphine oxide directing group. Preliminary results demonstrated that a ligand with this hybrid chirality could induce higher stereoselectivity in the metal-complex-catalyzed asymmetric hydrogenation of a dialkyl ketone.