Electrode “Cocktail Effect” Enables Charge Selective C─C Bond Cleavage of Acetonitrile for Aryl Halide Methylation

ABSTRACT The introduction of a single methyl group onto aromatic frameworks can profoundly alter molecular properties and biological activity. However, controllable aromatic methylation using simple and inexpensive acetonitrile remains challenging due to the difficulty of selectively cleaving the C─C bond and stabilizing the resulting methyl species without organometallic catalysts. Herein, we report an electrode‐controlled electrochemical methylation strategy enabled by a stainless steel cathode, in which a multi‐metallic “cocktail effect” arising from the cooperative interaction of charge‐differentiated Cr, Fe, and Ni sites promotes acetonitrile polarization, selective C─C bond cleavage, and stabilization of surface‐adsorbed methyl radicals. Fluorene is employed as a single electron transfer mediator to selectively activate aryl halides and generate aryl radicals, which subsequently attack the electrode‐stabilized methyl radicals to afford the methylated products. This cooperative electrode‐mediator system enables selective coupling of substrates with diverse properties and provides a general platform for controlled radical transformations.