Designing Chiral Diphosphines For Asymmetric Homogeneous Catalysis

Chiral C2 and C1 symmetry diphosphines characterized by a heteroaryl atropisomeric backbone1, shown below in formulas 1 and 2, offer numerous advantages over traditional carbocyclic systems. More specifically, they are more easily accessible from a synthetic point of view, thanks to the regioselective metallation typical of five-membered heteroaromatic systems. From a structural point of view, they allow fine tuning of the electronic availability of phosphorus atoms2 either by variations in the supporting heterocyclic system or by changes in the position of the phosphorus atom on it. Discussed are the main synthetic strategies and the resolution of these diphosphines 1,3, their chemical and electrochemical characterization and their use as ligands of Rh(I) and Ru(II) to give efficient complexes in homogeneous stereoselective catalysis. Emphasis is placed on the influence of the steric and electronic properties of the ligand on the kinetic and stereoselective course of some hydrogenation reactions of the carbonyl function and of some Heck reactions4.