Rh/SPO-WudaPhos-Catalyzed Asymmetric Hydrogenation of α-Substituted Ethenylphosphonic Acids via Noncovalent Ion-Pair Interaction.

Asymmetric hydrogenation of α-substituted ethenylphosphonic acids has been successfully achieved by Rh/ferrocenyl chiral bisphosphorus ligand (SPO-Wudaphos) through noncovalent ion-pair interaction between the substrate and catalyst under mild reaction conditions without base. A series of chiral phosphonic acids were obtained with excellent results (up to 98% ee, >99% conversion, 2000 TON). Moreover, the control experiments showed that the noncovalent ion-pair interaction was critical in this asymmetric hydrogenation.