During the cathodic phase, (hetero)arene reduction is taking place through direct SET. This mechanism is supported by the fact that the regioselectivity of 1,4-diene products corresponds to those in conventional Birch reduction products. Regarding chemoselectivity, it follows the reduction potential of the (hetero)arene and those of existing functionalities. Proton reduction, a pathway that normally competes to diminish reactivity towards arene reduction, is largely suppressed by applying rAP. In other words, cathodic limit of solvent electrochemical window is kinetically expanded by rAP. This effect also explains improved chemoselectivity under rAP conditions by removing side reactions promoted under a highly basic environment. During the anodic phase, DMS is presumably oxidized to generate α-ethoxy derivative. Analogous species 47 was detected in GC analysis of crude reaction mixture when heavier Et2S was used instead of DMS. A small amount of solvent oxidation may also take place during the anodic phase.