ChemInform Abstract: ASYMMETRIC HYDROGENATION WITH RHODIUM(I)-CHIRAL DIPHOSPHINITES. THE EFFECT OF THE DIMETHYLAMINO GROUP OF THE LIGAND ON THE ASYMMETRIC INDUCTION

Abstract

New chiral diphosphinites were prepared starting from (+)-diethyl tartrate. The asymmetric hydrogenation of dehydroamino acids, itaconic acid and dehydrodipeptides was studied using Rh(I)-diphosphinite catalysts. In the hydrogenation of dehydroamino acid derivatives, an introducion of ω-(dimethylamino)alkyl group in the ligands did not raise the optical yield. By the use of Rh(I)-diphosphinite having 3-(dimethylamino)propyl group, the inversion of the preferred product was observed. Itaconic acid can be hydrogenated in a good optical yield (76% e.e.) by use of the diphosphinite having 2-(dimethylamino)ethyl group. The diphosphinites having ω-dimethylamino group gave high optical yields in the case of dehydrodipeptides with a chiral center. Especially Rh(I)-catalysts coordinated by diphosphinites with 4-methyl or 4-methoxyl group on the phenyl ring of the ligand gave excellent stereoselectivities (more than 98% d.e.) in the case of Ac–ΔPhe–(S)-Phe–OH. The effect of these new chiral diphosphinites on the as...