A mild chemoselective method for S-arylation of cysteine has been developed in an open-flask procedure under metal-free conditions using arenediazoniumsalts in methanol.
generation of aminobiphenyl palladacycle pre‐catalyst “G3‐Xantphos” enables functionalization of peptides containing cysteine in high yields. The conjugation (bioconjugation) occurs chemoselectively at roomtemperature under biocompatible conditions. Extension of the method to protein functionalization allows selective bioconjugation of the trastuzumab antibody.