C,C cross-coupling reactions for the synthesis of nonsymmetrical biaryls represent one of the most significant transformations in contemporary organic chemistry. A variety of useful synthetic methods have been developed in recent decades, since nonsymmetrical biaryls play an evident role in natural product synthesis, as ligand systems in homogeneous catalysis and materials science. Transformation of simple arenes by direct C,H activation belongs to the cutting-edge strategies for creating biaryls; in particular the 2-fold C,H activation is of significant interest. However, in most examples very costly noble metal catalysts, ligand systems, and significant amount of waste-producing oxidants are required. Electrochemical procedures are considered as inherently "green" methods, because only electrons are required and therefore, no reagent waste is produced. Here, we report a metal-free electrochemical method for cross-coupling between phenols and arenes using boron-doped diamond (BDD) anodes in fluorinated media. Our sustainable approach requires no leaving functionalities. Employing water or methanol as mediator represents the key improvement for achieving nonsymmetrical biaryls with superb selectivity and synthetic attractive yields.

Particularly sustainable: The anodic cross‐coupling reaction between phenols and arenes can be performed on boron‐doped diamond electrodes. The arylated products are formed directly and obtained, in some cases, with high selectivity. Since only hydrogen atoms are sacrificed in the course of reaction this methodology opens the door to a novel concept for biaryl formation.

Enlarged scope by fluorinated mediators: Oxyl radicals are easily formed on boron-doped diamond (BDD) electrodes and can be exploited for the ortho-selective coupling to the corresponding biphenols (see scheme). At partial conversion, a clean transformation is achieved that can be applied to electron-rich as well as fluorinated phenols.

Besonders nachhaltig gelingt die anodische Kreuzkupplung zwischen Phenolen und Arenen an bordotierten Diamantelektroden. Die arylierten Produkte werden direkt gebildet und können in manchen Fällen vollständig selektiv erhalten werden. Dieses Konzept öffnet den Weg zu einem neuartigen Syntheseverfahren für Biaryle, bei dem nur Wasserstoffatome abgespalten werden.

The anodic treatment of guaiacol derivatives on boron-doped diamond electrodes (BDD) provides a direct access to nonsymmetrical biphenols, which would require a multistep sequence by conventional methods. Despite the destructive nature of BDD anodes they can be exploited for chemical synthesis.