Synthesis and Molecular Modeling Studies of SYNPHOS®, a New, Efficient Diphosphane Ligand For Ruthenium-Catalyzed Asymmetric Hydrogenation

A new, optically active, atropisomeric diphosphane ligand, (2,3,2′,3′‐tetrahydro‐5,5′‐bi(1,4‐benzodioxin)‐6,6′‐diyl)bis‐(diphenylphosphane) (SYNPHOS®), has been synthesized, characterized, and used in ruthenium‐catalyzed asymmetric hydrogenations. This new ligand has been compared with other atropisomeric diphosphanes (BINAP and MeO‐BIPHEP) with respect to their dihedral angles calculated by molecular modeling and the enantioselectivity of their ruthenium‐mediated hydrogenation reactions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)