ChenPhos: Highly Modular P-Stereogenic C1-Symmetric Diphosphine Ligands for the Efficient Asymmetric Hydrogenation of α-Substituted Cinnamic Acids

These cats are purrfectionists: The ChenPhos ligands (see structure) showed dramatically higher catalytic activity in the title reaction than their C2‐symmetric predecessor with two dimethylaminoethyl‐substituted ferrocenyl(phenyl)phosphanyl groups. The ready accessibility, extreme air stability, and high enantioselectivity, activity, and productivity of these ligands make them very promising for a wide range of practical applications.