Catalytic α-Allylation of Unprotected Amino Acid Esters

Catalytic alpha-allylation of unprotected amino acid esters to produce alpha-quaternary alpha-allyl amino acid esters is reported. Catalytic loadings of picolinaldehyde and Ni(II) salts induce preferential reactivity at the enolizable alpha-carbon of amino acid esters over the free nitrogen with electrophilic palladium pi-allyl complexes. Fourteen examples are given. Additionally, the use of chiral ligands to access enantioenriched alpha-quaternary amino acid esters from racemic precursors is demonstrated by the enantioselective synthesis of alpha-allyl phenylalanine methyl ester from racemic phenylalanine methyl ester.