Deep reduction in electrosynthesis

Electrochemical reduction is solidifying its role as an increasingly important and practical alternative to the use of conventional stoichiometric chemical reductants. Not only can this technique be sustainable, safe and scalable, but it provides a facile approach to accessing deep reduction potentials (approximately <-2.5 V versus Fc⁺/Fc) that may be inaccessible using common reductants or accessible only using highly reactive and potentially unsafe reagents. Hence, over recent years substantial efforts have been made to develop electrochemical deep reduction to enable safer access to new areas of chemical space. While hazardous reagents have been replaced and novel transformations have been invented, the technique also comes with its challenges. In this review, we provide context to the issues that can arise when applying very reducing potentials and offer examples of mitigating strategies by describing selected transformations that are enabled or improved by deep electrochemical reduction.