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

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.