A Facile Synthesis of α-Aryl α-Oxoheterocyclic Ketene N,N-Acetals Bearing an Electron-Rich Catechol Subunit-An Electrochemical Oxidative Approach

Heterocyclic ketene N,N-acetals are versatile building blocks for the synthesis of nitrogen-containing heterocyclic compounds. In the present work, the anodic oxidation of catechols 2a-f in the presence of alpha-oxoheterocychc ketene N,N-acetals 1a-d has been investigated using cyclic voltammetry and controlled-potential electrolysis methods. These results indicate that alpha-oxoheterocyclic ketene N,N-acetals could undergo Michael addition to the anodically generated o-benzo-quinones and produce alpha-carbon-arylated products in good yields. This approach provides effective and "green" access to the synthesis of alpha-aryl alpha-oxoheterocyclic ketene N,N-acetals containing an electron-rich aromatic ring. In addition, density functional theory calculations were performed to explain the exclusive formation of alpha-carbon-arylated products. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)