EC-Backward-E Electrochemistry in Radical Cation Diels-Alder Reactions

Cascade processes, including electron transfer (E), chemical reaction (C), and backward electron transfer (E), are known as EC-backward-E mechanisms; however, they are rarely observed directly. Herein, we demonstrate that direct observation of EC-backward-E processes in radical cation Diels-Alder reactions is possible using cyclic voltammetry measurements. Formal expressions for the plausible reaction mechanisms provide a reasonable understanding of the processes, which are also supported by the highest occupied molecular orbitals and spin density distributions plotted from density functional theory calculations.