Unexpected high robustness of electrochemical cross-coupling for a broad range of current density.

Abstract

Electro-organic synthesis is a powerful technique for the sustainable preparation of compounds. However, many electrosynthetic reactions require complex equipment, are limited to a very narrow current density range, or have very long reaction times; some also involve nonselective transformations and bad scalability. The robust and selective synthesis of nonsymmetric biphenols and partially protected derivatives is established by anodic C-C cross-coupling. The setup is simple, involving constant current conditions and undivided cells. Its key is a unique electrolyte system based on fluorous alcohols and mixtures, particularly 1,1,1,3,3,3-hexafluoroisopropanol. This allows variations of the current density of more than two orders of magnitude without decreasing selectivity or product yield. This exceptional effect is unknown for electro-organic synthesis of products that have similar oxidation potentials as the starting materials. It potentially paves the way for industrial electrolyzers with variable current consumption, which could enable the flexible use of energy surplus in the electricity supply.