Water-involving transfer hydrogenation and dehydrogenation of N-heterocycles over a bifunctional MoNi4 electrode

A room-temperature electrochemical strategy for hydrogenation (deuteration) and reverse dehydrogenation of N -heterocycles over a bifunctional MoNi 4 electrode is developed, which includes the hydrogenation of quinoxaline using H 2 O as the hydrogen source with 80% Faradaic efficiency and the reverse dehydrogenation of hydrogen-rich 1,2,3,4-tetrahydroquinoxaline with up to 99% yield and selectivity. The in situ generated active hydrogen atom (H*) is plausibly involved in the hydrogenation of quinoxaline, where a consecutive hydrogen radical coupled electron transfer pathway is proposed. Notably, the MoNi 4 alloy exhibits efficient quinoxaline hydrogenation at an overpotential of only 50 mV, owing to its superior water dissociation ability to provide H* in alkaline media. In situ Raman tests indicate that the Ni II /Ni III redox couple can promote the dehydrogenation process, representing a promising anodic alternative to low-value oxygen evolution. Impressively, electrocatalytic deuteration is easily achieved with up to 99% deuteration ratios using D 2 O. This method is capable of producing a series of functionalized hydrogenated and deuterated quinoxalines. Water-involved transfer hydrogenation and dehydrogenation of N -heterocycles were developed by employing MoNi 4 as a bifunctional electrode. This method can be used to synthesize a series of functionalized hydrogenated and deuterated quinoxalines using H 2 O and D 2 O.