Oxidative Cross-Coupling of Two Different Phenols: An Efficient Route to Unsymmetrical Biphenols
摘要:
An efficient synthesis of unsymmetrical biphenols via the oxidative cross-coupling of two different phenols in the presence of K2S2O8 and Bu4N+.HSO3- (10 mol %) in CF3COOH at ambient conditions is described. 1:1 Cross-coupling of substituted phenols with naphthols and 1:2 cross-coupling of naphthols with phenol are also disclosed. By using Bu4N+.HSO3-, the homocoupling of phenols or naphthols was controlled. In these reactions, the ortho C-H bond of two different phenols and the ortho and para C-H bond of phenols were coupled together.
Metal‐ and Reagent‐Free Highly Selective Anodic Cross‐Coupling Reaction of Phenols
作者:Bernd Elsler、Dieter Schollmeyer、Katrin Marie Dyballa、Robert Franke、Siegfried R. Waldvogel
DOI:10.1002/anie.201400627
日期:2014.5.12
The direct oxidative cross‐coupling of phenols is a very challenging transformation, as homo‐coupling is usually strongly preferred. Electrochemical methods circumvent the use of oxidizing reagents or metal catalysts and are therefore highly attractive. Employing electrolytes with a high capacity for hydrogen bonding, such as methanol with formic acid or 1,1,1,3,3,3‐hexafluoro‐2‐propanol, a direct