(S)-Proline-derived new chiral ligands with phosphino, organosulfur or organoselenenyl functionality as an enantiocontrollable coordinating element

The synthesis of (S)-proline-derived chiral ligands bearing phosphino, orga nosulfur or selenenyl groups and their use as chiral ligands in palladium-c atalyzed asymmetric allylic alkylations has been accomplished. In particula r, the (S)-proline-derived phosphine ligands bearing alkylsulfenyl groups p rovided high enantioselectivity, and the degree of asymmetric induction was dependent upon the steric bulk of the alkyl substituents in sulfenyl group s. The stereochemical results are rationalized by a plausible mechanism inv olving the assistance of chelates formed by the participation of the two pr eferred heteroatoms involved. (C) 1999 Elsevier Science Ltd. All rights res erved.