title: Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent- and Metal-Free Anodic Cross-Coupling Reaction.
abstract: The oxidative cross-coupling of aromatic substrates without the necessity of leaving groups or catalysts is described. The selective formation of partially protected nonsymmetric 2,2'-biphenols via electroorganic synthesis was accomplished with a high yield of isolated product. Since electric current is employed as the terminal oxidant, the reaction is reagent-free; no reagent waste is generated as only electrons are involved. The reaction is conducted in an undivided cell, and is suitable for scale-up and inherently safe. The implementation of O-silyl-protected phenols in this transformation results in both significantly enhanced yields and higher selectivity for the desired nonsymmetric 2,2'-biphenols. The use of a bulky silyl group to block one hydroxyl moiety makes the final product less prone to oxidation. Furthermore, the partially silyl-protected 2,2'-biphenols are versatile building blocks that usually require tedious or low-yielding synthetic pathways. Additionally, this strategy facilitates a large variety of new substrate combinations for oxidative cross-coupling reactions.
authors.affiliation: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, 55128, Mainz, Germany.
authors.forename: Anton
authors.initials: A
authors.lastname: Wiebe
authors.affiliation: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, 55128, Mainz, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Schollmeyer
authors.affiliation: Evonik Performance Materials GmbH, Marl, Germany.
authors.forename: Katrin M
authors.initials: KM
authors.lastname: Dyballa
authors.affiliation: Evonik Performance Materials GmbH, Marl, Germany.|Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Franke
authors.affiliation: Institut für Organische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, 55128, Mainz, Germany. waldvogel@uni-mainz.de.
authors.forename: Siegfried R
authors.initials: SR
authors.lastname: Waldvogel
keywords: C-C coupling; C-H activation; biaryls; electrochemistry; protecting groups