Palladium-Catalyzed Stereoselective Allylic Alkylation of Lithium Enolates

Significance

The allylic alkylation of unstabilized enolates remains an important task for organic chemists. This report nicely explains the optimization for the reaction of cyclohexanone enolate with allyl palladium species in the presence of a chiral ligand to give products with high enantioselectivity (90% ee). Unfortunately, the scope of ketone starting materials is not broad and much lower enantioselectivities are obtained for cylcopentanone and tetralone (64% and 66% ee, respectively). The addition of lithium chloride proved crucial for obtaining good enantioselectivities, presumably due to the influence of the aggregation state of the enolate or the transition-metal catalyst.