Practical by Ligand Design: A New Class of Monodentate Phosphoramidite Ligands for Rhodium‐Catalyzed Enantioselective Hydrogenations

Abstract

AbstractA new class of low‐cost and easy‐to‐prepare monodentate phosphoramidite ligands (CydamPhos) has been developed from readily accessible and cheap trans‐1,2‐diaminocyclohexane as starting material through a three‐step transformation. This type of ligands exhibited excellent enantioseletivities and high activities in rhodium(I)‐catalyzed asymmetric hydrogenations of dehydro‐α‐amino acid methyl esters 9 (ee: 96.2–99.8 %) and acetylenamides 11 (91.8–98.8 %). The remarkable substituent effects exhibited by the ligands on the enantioselective control of the catalysis are rationalized on the basis of molecular structure of the catalyst precursor.