Cobaloxime-Catalyzed Hydrogen Evolution in Photoredox-Facilitated Small-Molecule Functionalization

The development of efficient, mild, economical, and low-waste processes is a cornerstone of sustainable chemistry. One such synthetic strategy that exemplifies these characteristics is the use of catalytic dehydrogenation in small-molecule functionalization. This has been achieved in recent history through the use of photoredox catalysis in conjunction with cobaloximes, a class of catalysts that are capable of proton reduction. This has allowed for a variety of bond formations to be achieved with few to no stoichiometric additives while often producing hydrogen gas as the sole stoichiometric by-product. Herein, select advancements made in this area of sustainable chemistry and catalysis are detailed and the mechanistic insights this body of work has provided thus far are evaluated. As such, this review aims to aid in the further development and study of synthetic strategies involving photoredox-promoted hydrogen evolution.