Developments in the dehydrogenative electrochemical synthesis of 3,3′,5,5′-tetramethyl-2,2′-biphenol

The symmetric biphenol 3,3′,5,5′‐tetramethyl‐2,2′‐biphenol is a well‐known ligand building block and is used in transition‐metal catalysis. In the literature, there are several synthetic routes for the preparation of this exceptional molecule. Herein, the focus is on the sustainable electrochemical synthesis of 3,3′,5,5′‐tetramethyl‐2,2′‐biphenol. A brief overview of the developmental history of this inconspicuous molecule, which is of great interest for technical applications, but has many challenges for its synthesis, is provided. The electro‐organic method is a powerful, sustainable, and efficient alternative to conventional synthesis to obtain this symmetric biphenol up to the kilogram scale. Another section of this article is devoted to different process management strategies in batch‐type and flow electrolysis and their respective advantages.
Sustainable scale‐up: Investigations into the electrochemical synthesis of 3,3′,5,5′‐tetramethyl‐2,2′‐biphenol in recent decades are reviewed. An overview of different sustainable synthetic approaches, with a focus on the anodic dehydrogenative homocoupling of 2,4‐dimethylphenol, is provided. Due to technical interest in this outstanding molecule as a ligand building block for transition‐metal catalysis, the scale‐up of electrochemical processes is surveyed, for both batch‐type and continuous‐flow processes up to the technical scale.