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

Abstract 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 …

Optimization Strategies for the Anodic Phenol‐Arene Cross‐Coupling Reaction

Large, Highly Modular Narrow-Gap Electrolytic Flow Cell and Application in Dehydrogenative Cross-Coupling of Phenols

The successive scale-up of electrochemical reactions is crucial with regard to the implementation of technical electro-organic syntheses. Therefore, we developed a scalable modular parallel-plate e...

Interfacial Domain Formation Enhances Electrochemical Synthesis.

The electroorganic C,C coupling of phenols to other aryl components is controlled by the fluoroalcohol-alcohol mixture solvents. Classical molecular dynamics and static density functional theory reveal that both kinds of solvents interact with the substrates, influencing the electronic structure of a phenoxyl radical intermediate in a cooperative manner to achieve maximal efficiency and selectivity. Simulations of the electrolyte-electrode interface showed that the substrates adsorb on the diamond surface in such a way that the repulsive fluorous-lipophilic interactions can be minimized and the attractive lipophilic-lipophilic interplay can be maximized, whereas the advantageous hydrogen bo…

Influence of the Nature of Boron‐Doped Diamond Anodes on the Dehydrogenative Phenol‐Phenol Cross‐Coupling

Mass‐Spectrometric Imaging of Electrode Surfaces—a View on Electrochemical Side Reactions

Abstract Electrochemical side reactions, often referred to as “electrode fouling”, are known to be a major challenge in electro‐organic synthesis and the functionality of modern batteries. Often, polymerization of one or more components is observed. When reaching their limit of solubility, those polymers tend to adsorb on the surface of the electrode, resulting in a passivation of the respective electrode area, which may impact electrochemical performance. Here, matrix‐assisted laser‐desorption/ionization mass spectrometry (MALDI‐MS) is presented as valuable imaging technique to visualize polymer deposition on electrode surfaces. Oligomer size distribution and its dependency on the contact …

3,4′,5,5′-Tetramethoxy-2′-methylbiphenyl-4-ol

The asymmetric unit of the title compound, C17H20O5, contains two independent molecules, A and B, with similar geometries [dihedral angles between the phenyl rings = 56.19 (8) and 54.98 (7)°, respectively]. Intramolecular O—H...O hydrogen bonds occur in both molecules. In the crystal, the A molecules form [1\overline{1}0] chains linked by O—H...O hydrogen bonds from the hydroxyl group to one of the methoxy O atoms. The B molecules form O—H...O hydrogen bonds to the hydroxyl O atoms of the A molecules and thus act as fixed spacers between the chains of molecule A. Some weak C—H...O contacts are also present.

Get into flow: Design of experiments as a key technique in the optimization of anodic dehydrogenative C,C cross-coupling reaction of phenols in flow electrolyzers

Abstract The optimization of electro-organic reactions poses a challenge due to the various parameters involved. Quite often those parameters are not independent from each other, leading the experimental scientist using linear approaches into an optimization loophole. We report a strategy for the optimization of the anodic oxidative dehydrogenative C,C cross-coupling reactions for the synthesis of biphenols based on Design of Experiments (DoE), which overcomes the drawbacks of linear optimization approaches. Using a fractional design, we increased the yield of a long-time investigated example reaction from 44% up to 85% and point out different suitable reaction conditions through to linear …

Electrosynthesis of 3,3′,5,5’-tetramethyl-2,2′-biphenol in flow

Abstract3,3′,5,5’-Tetramethyl-2,2′-biphenol is well known as an outstanding building block for ligands in transition-metal catalysis and is therefore of particular industrial interest. The electro-organic method is a powerful, sustainable, and efficient alternative to conventional synthetic approaches to obtain symmetric and non-symmetric biphenols. Here, we report the successive scale-up of the dehydrogenative anodic homocoupling of 2,4-dimethylphenol (4) from laboratory scale to the technically relevant scale in highly modular narrow gap flow electrolysis cells. The electrosynthesis was optimized in a manner that allows it to be easily adopted to different scales such as laboratory, semit…