Using a Combination of Electrochemical and Photoelectron Transfer Reactions to Gain New Insights into Oxidative Cyclization Reactions

Radical cation initiated cyclization reactions can be triggered by the one electron oxidation of an electron-rich olefin using either electrochemistry or visible light and a photoredox catalyst. In principle, the two methods can be used to give complimentary products with the electrolysis leading to products derived from a net two electron oxidation and the photoelectron transfer method being compatible with the formation of products from a redox neutral process. However, we are finding an increasing number of oxidative cyclization reactions that require the rapid removal of a second electron in order to form high yields of the desired product. In those cases, the electrochemical method can provide a superior approach to accessing the necessary two electron oxidation pathway. With that said, it is a combination of the two methods that provides the mechanistic insight needed to understand when a reaction has this requirement, and we are finding that the use of photoredox catalysis in combination with electrochemical methods is changing our understanding of even the most successful anodic cyclization reactions run to date.