A simple protocol for the regioselective N-arylation of the indole side chain of tryptophan using triarylbismuth reagents as the arylating agent is reported. The reaction is catalyzed by copper(II) acetate, operates in the presence of triethylamine or pyridine under air at 50 °C, allows the transfer of aryl groups bearing electron neutral, donating or withdrawing substituents at any position of the ring, shows high functional group tolerance and retains the integrity of the stereogenic center. The protocol was utilized to N-arylate tryptophan- containing di- and tripeptides.
Adrien Le Roch, Hwai-Chien Chan and Alexandre Gagnon