4,4 ′ and 5,5 ′-DiamBINAP as a hydrosoluble chiral ligand: syntheses and use in Ru(II) asymmetric biphasic catalytic hydrogenation

Graphic 4,4 ′ and 5,5 ′-DiaminomethylBINAP were prepared in five steps from enantiomerically pure BINAP. Their synthesis involves, as key steps, the regioselective bromination of BINAP and the chemoselective efficient reduction of a dicyano, diphosphine oxide into the corresponding dicyano, diphosphine by a mixture of HSiCl 3/PhSiH 3. The ruthenium complexes of these new ligands were tested for the homogeneous and water/organic solvent biphasic asymmetric hydrogenation of β-ketoesters leading to 100% conversion with an enantiomeric excess greater than 97% in water. Catalysts can be recycled several times by extraction of the product with pentane.