Synthesis of a Water‐Soluble Cationic Chiral Diamine Ligand Bearing a Diguanidinium and Application in Asymmetric Transfer Hydrogenation.

Abstract A novel water-soluble cationic N-monosulfonated chiral diamine ligand diguanidinium 1c was easily prepared from (R,R)-DPEN and its rhodium complex and was successfully applied in the asymmetric transfer hydrogenation of prochiral ketones and imines in water by using sodium formate and formic acid as co-hydrogen donors. Various substrates were reduced with high yields and good to excellent enantioselectivities (up to >99% ee).