Synthesis of Heterofunctionalized Multidentate Diphosphines

The synthesis of new chiral multidentate amino- and amidophosphine ligands bearing up to six potential coordination sites were synthesized starting from l-valine. Based on these compounds chiral Ru(II) complexes were prepared, characterized and tested in the asymmetric transfer hydrogenation of aryl–alkyl ketones. In all cases investigated the catalyst bearing additional hydroxy groups gave lower conversions than the complex without hydroxy groups. Highest enantioselectivity was achieved with isobutyrophenone as substrate (69%ee).