文摘
New polydentate chiral ligands, containing the hydroxyl group, stereogenic sulfinyl group and enantiomeric prolinol moieties were synthesized and proved very efficient catalysts in the asymmetric diethylzinc addition to benzaldehyde, the asymmetric aldol condensation and the asymmetric Mannich reaction. Replacement of the central hydroxyl group with the second prolinol moiety of the same absolute configuration gave new ligands in which the sulfinyl group was not a stereogenic centre anymore, but which proved almost equally efficient as catalysts for the reactions investigated. The absolute configuration of the proline moiety exerted a decisive impact on the stereochemical outcome of these reactions, deciding about the absolute configuration of the products formed.