Enantioselective α-Allylation of Aryl Acetic Acid Esters via C1-Ammonium Enolate Nucleophiles: Identification of a Broadly Effective Palladium Catalyst for Electron-Deficient Electrophiles.

Abstract

We have identified a generally effective Pd catalyst for the highly enantioselective cooperative Lewis base/Pd-catalyzed α-allylation of aryl acetic esters using electron-deficient electrophiles. Changing between aldehyde, ketone, ester, and amide substituents at the terminus of intermediate cationic π-(allyl)Pd species affects both the efficiency of the reaction and, in the case of amides, control over the stereochemistry of the product alkene, as a function of the ligand. Tris[tri(2-thienyl)phosphino]Pd(0) serves as a broadly effective catalyst and overcomes these challenges to provide a general, high-yielding, and operationally simple C(sp3)-C(sp3) bond-forming method that gives products with high levels of enantioselectivity.