(S)-Proline-Derived New Chiral Ligands with Phosphino, Organosulfur or Organoselenenyl Functionality as an Enantiocontrollable Coordinating Element.

Abstract The synthesis of ( S )-proline-derived chiral ligands bearing phosphino, organosulfur or selenenyl groups and their use as chiral ligands in palladium-catalyzed asymmetric allylic alkylations has been accomplished. In particular, the ( S )-proline-derived phosphine ligands bearing alkylsulfenyl groups provided high enantioselectivity, and the degree of asymmetric induction was dependent upon the steric bulk of the alkyl substituents in sulfenyl groups. The stereochemical results are rationalized by a plausible mechanism involving the assistance of chelates formed by the participation of the two preferred heteroatoms involved.