Amine‐Directed Palladium‐Catalyzed C−H Halogenation of Phenylalanine Derivatives

An efficient primary‐amine‐directed, palladium‐catalyzed C−H halogenation (X=I, Br, Cl) of phenylalanine derivatives is reported on a range of quaternary amino acid (AA) derivatives thanks to suitable conditions employing trifluoroacetic acid as additive. The extension of this original native functionality‐directed ortho‐selective halogenation was even demonstrated with the more challenging native phenylalanine as tertiary AA. A site‐selective, primary amine (as a native NH2 functionality)‐directed, palladium‐catalyzed C(sp2)−H halogenation (X=I, Br, Cl) of phenylalanine platforms is demonstrated. Efficient and versatile, this strategy paves the way to constructing a large array of original halogenated phenylalanine derivatives as nonproteinogenic AAs.