Pd-Catalyzed Allylic Substitution with Enantiomerically Pure Catalysts and Chiral Non-Racemic Substrates: A New Approach to Catalyst-Based Regiocontrol, Preliminary Communication

Abstract

Chiral, enantiomerically pure Pd-catalysts were used to control the regioselectivity of nucleophilic attack in allylic substitutions with optically active 1,3-disubstituted allyl acetates (Schemes 4 – 6). In contrast to reactions with achiral catalysts, where the regioselectivity is determined by the steric and electronic effects of the allylic substituents, chiral catalysts allow selective preparation of either one of the two regioisomeric products, depending on which enantiomer of the catalyst is employed. It is not necessary to start from an enantiomerically pure substrate, because the major and minor enantiomers are converted to different regioisomers (not to enantiomeric products; see Scheme 3), resulting in products of very high ee, even when the starting material is only of moderate enantiomer purity.