Bimetallic [Co/K] hydrogen evolution catalyst for electrochemical terminal C-H functionalization

Discovering novel catalysts for hydrogen evolution reaction (HER) hold the potential to revolutionize the energy chemistry and unlock new tool for synthetic chemistry. Inspired by hydrogenases, we paired alkali metals with cobalt-Salen catalysts which allow the integration of ‘naked’ base site into bimetallic HER catalysts. Alkali metal incorporation significantly enhanced HER activity, and the [Co/K] system exhibited the highest HER catalytic efficiency (kobs ~ 31.4 s⁻¹), which was 9 times higher than the mononuclear analogue. Remarkably, this HER catalyst was repurposed for the terminal C(sp³)-H functionalization of N-allylimines with imine/aldehyde, a previously inaccessible transformation. Mechanistic studies revealed that the 'naked' base site enables selective C-H activation via proton relay, overriding the inherent preference for Pinacol coupling. This electrochemical protocol features exceptional functional group tolerance, and opens up a streamlined avenue for chiral pyrrolines, key precursors of the anti-cancer medicine Larotrectinib. More importantly, the alkali metal effect was rationalized through structural analysis, density functional theory (DFT) calculations, and control experiments.