One-Pot Two-Step Synthesis of Optically Active α-Amino Phosphonates by Palladium-Catalyzed Hydrogenation/Hydrogenolysis of α-Hydrazono Phosphonates.

An efficient and convenient one-pot procedure for the stereoselective catalytic synthesis of ring-substituted [amino(phenyl)methyl]phosphonates has been developed. The enantioselective hydrogenation of easily available diisopropyl ( Z)-[aryl(phenylhydrazono)methyl]phosphonates using palladium(II) acetate as a precatalyst, ( R)-2,2′-bis(diphenylphosphino)-5,5′-dichloro-6,6′-dimethoxy-1,1′-biphenyl [( R)-Cl-MeO-BIPHEP] as a ligand, and (1 S)-(+)-10-camphorsulfonic acid as an activator in a mixture of 2,2,2-trifluoroethanol and methylene chloride at ambient temperature results in the formation of corresponding [aryl(2-phenylhydrazino)methyl]phosphonates. The subsequent cleavage of the N−N bond has been accomplished with molecular hydrogen after the addition of palladium on carbon and methanol into crude reaction mixture to afford the optically active [amino(aryl)methyl]phosphonates. The method is operationally simple and provides an appreciable enantioselectivity up to 98 % ee. [ABSTRACT FROM AUTHOR]