Asymmetric Hydrogenation of Dehydrodipeptides with Rhodium(I)–Chiral Diphosphinites. Selective (S,S)- and (R,R)-Product Formation by Double Asymmetric Induction

Abstract

Abstract In the hydrogenation of dehydrodipeptides, the effect of chiral center of the substrate ((S) or (R)) on the asymmetric induction was examined using the catalysts of Rh(I)–chiral diphosphinite containing pyrrolidine moiety (POP). The catalysts with POP’s having the ω-(dimethylamino)alkyl group indicated an extremely large double asymmetric induction to give (S,S)- or (R,R)-product in high stereoselectivities, depending on the chiral center of the substrates. This result was ascribed to the electrostatic interaction between the ligand and substrate. POP’s without ω-(dimethylamino)alkyl group gave (R,R)-product for (R)-substrate in a high stereoselectivity by the steric effect between the ligand and substrate, while for (S)-substrate, (S,S)-product was obtained in a low stereoselectivity.