Chiral 1,4-bis-diphosphine ligands from optically active (Z)-olefines

The catalytic asymmetric hydrogenation of prochiral ketones was carried out with Ru(II) complexes prepared from new chiral diphosphine ligands, cis (R,R)-2,5-bis[(diarylphosphino)]-3-hexenes.
These new ligands were prepared from optically pure (R,R) or (S,S)-Z-3-hexene-2,5 diol and enantiomeric excesses up to 85 % were obtained in the reduction of 2-benzamidomethyl-3-oxobutanoate, starting material for the synthesis of 4-acetoxy-2-azetidinone.