In this subsection, we introduce a method for protein modification using electrophilic species generated by electrochemical reactions as reactive anchors (Scheme 1A). By applying an appropriate potential specific to the anchor precursor, active anchor sites are oxidatively generated in the reaction system, while preserving the functional groups of the protein. These electrophilic anchor sites modify proteins via electrophilic aromatic substitution reactions at Tyr and Trp residues. The Tyr-ene reaction of 4-phenyl-3H-1,2,4-triazole-3,5(4H)diones (PTAD) and Tyr residues has been extensively studied by Barbas and co-workers, and is regarded as a promising approach for protein modification. However, the oxidative generation of PTAD from 4-phenylurazole in such systems is not orthogonal to the various functional groups of proteins. Furthermore, competing side reactions, such as hydrolysis of PTAD, restrict its applicability in a broad context. In 2018, Gouin and co-workers reported the first protein modification employing electrochemical techniques. This method exploits the low redox potential of 4-phenylurazole (+0.36 V vs. SCE), enabling rapid Tyr-ene reactions while generating active PTAD species in situ, without oxidizing the aromatic rings of the protein (>0.45 V, Scheme 1B). Another example comes from Heptinstall and coworkers, who reported modifications of protein Tyr residues via iodination or nitration. These modifications are achieved through the electrochemical oxidation of KI or NaNO2, which activates the reagents.