26567-10-2Relevant articles and documents
Selective and Scalable Dehydrogenative Electrochemical Synthesis of 3,3,5,5-Tetramethyl-2,2-biphenol
Franke, Robert,Mentizi, Stamo,Schollmeyer, Dieter,Selt, Maximilian,Waldvogel, Siegfried R.
, p. 2062 - 2067 (2019)
3,3,5,5-Tetramethyl-2,2-biphenol is a compound of high technical significance, as it exhibits superior properties as building block for ligands in the transition-metal catalysis. However, side reactions and overoxidation are challenging issues in the conventional synthesis of this particular biphenol. Here, an electrochemical method is presented as powerful and sustainable alternative to conventional chemical strategies, which gives good yields up to 51percent. Despite using inexpensive and well-available bromide-containing supporting electrolytes, the issue of bromination and general byproduct formation is effectively suppressed by adding water to the electrolyte. Additionally, the scalability of this method was demonstrated by conducting the electrolysis on a 122 g scale.
Unexpected highly chemoselective anodic ortho-coupling reaction of 2,4-dimethylphenol on boron-doped diamond electrodes
Malkowsky, Itamar M.,Griesbach, Ulrich,Puetter, Hermann,Waldvogel, Siegfried R.
, p. 4569 - 4572 (2006)
Anodic conversion of 2,4-dimethylphenol on boron-doped diamond (BDD) electrodes under solvent-free conditions results in an unusual highly selective formation of the desired 2,2′-biphenol, representing the best electrochemical synthesis for this particular compound. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
Supporting-Electrolyte-Free and Scalable Flow Process for the Electrochemical Synthesis of 3,3′,5,5′-Tetramethyl-2,2′-biphenol
Franke, Robert,Selt, Maximilian,Waldvogel, Siegfried R.
, p. 2347 - 2355 (2020)
The most efficient electrochemical synthesis of 3,3′,5,5′-tetramethyl-2,2′-biphenol by dehydrogenative coupling is reported. The electrolysis is performed supporting-electrolyte-free in 1,1,1,3,3,3-hexafluoroisopropanol and at carbon electrodes, whereby glassy carbon electrodes turned out to be superior. To provide sufficient conductivity, pyridine is added, and it can easily be recovered by evaporation and reused. This facilitates the downstream process tremendously, making it simple, economical, and technically viable. The scalability was proven by establishing a flow electrolysis in differently sized narrow-gap flow electrolyzers. Carrying out a multistep cascade electrolysis enabled the challenging hydrogen evolution to be successfully addressed. The scaled-up electrolysis provided an isolated yield of 59% biphenol.
Oxidative photocatalytic homo- And cross-coupling of phenols: Nonenzymatic, catalytic method for coupling tyrosine
Niederer, Kyle A.,Gilmartin, Philip H.,Kozlowski, Marisa C.
, p. 14615 - 14623 (2020/12/23)
An oxidative photocatalytic method for phenol? phenol homo- and cross-coupling is described, and isolated yields of 16?97% are obtained. Measured oxidation potentials and computed nucleophilicity parameters support a mechanism of nucleophilic attack of one partner onto the oxidized neutral radical form of the other partner. Our understanding of this model permitted the development of cross-coupling reactions between nucleophilic phenols/arenes and easily oxidized phenols with high selectivity and efficiency. A highlight of this method is that one equivalent of each coupling partner is utilized. Building on these findings, a nonenzymatic, catalytic method for coupling tyrosine was also developed.
Selective, Catalytic, and Metal-Free Coupling of Electron-Rich Phenols and Anilides Using Molecular Oxygen as Terminal Oxidant
Bering, Luis,Vogt, Melina,Paulussen, Felix M.,Antonchick, Andrey P.
supporting information, p. 4077 - 4080 (2018/07/15)
Selective oxidative homo- and cross-coupling of electron-rich phenols and anilides was developed using nitrosonium tetrafluoroborate as a catalyst. Oxidative coupling of phenols revealed unusual selectivities, which translated into the unprecedented synthesis of inverse Pummerer-type ketones. Mechanistic studies suggest that oxidative coupling of phenols and anilides shares a common pathway via homolytical heteroatom-hydrogen bond cleavage. Nitrosonium salt catalysis was applied for cross-dehydrogenative coupling initiated by generation of heteroatom-centered radicals.
