Chapter 6: Mediated Electron Transfer in Electrosynthesis: Concepts, Applications, and Recent Influences from Photoredox Catalysis

In organic electrosynthesis, mediators are often interposed between electrode and substrate when direct electron transfer does not proceed with the desired selectivity or when a specific reaction mechanism is to be induced to obtain a particular product. The mediated electron transfer occurs against a potential gradient, meaning that less positive (negative) potentials are required for oxidation (reduction) with respect to the potential needed for direct conversion, thus resulting in decreased energy consumption. In recent years, a large number of such indirect electrosyntheses have been reported. To understand the benefits and the mode of action, knowledge of a number of concepts and mechanisms is required. These are discussed in detail in this chapter using classic and recent examples. In addition, a section is devoted to combined photo- and electrochemical energy input, which has recently found its way into mediated organic electrochemistry.