Acridinium Betaine as a Single-Electron-Transfer Catalyst: Design and Application to Dimerization of Oxindoles

An intramolecular
ion-pairing acridinium phenoxide possessing a
redox-active component and a basic site within a single molecular
framework is developed. The potential of the acridinium betaine as
a chemical redox catalyst is demonstrated by its application to the
homodimerization of 3-aryl oxindoles, which proceeds through proton-coupled
electron-transfer pathway. Analysis of the kinetic profile has provided
important clues to understand the reaction mechanism.