Chemoselective electrochemical hydrogenation of α,β-unsaturated carbonyl compounds using methanol as a hydrogen source and a nail anode.

An electrochemical reductive hydrogenation of α,β-unsaturated carbonyl compounds has been developed using an undivided cell with a nail anode and a graphite rod cathode in CH3OH containing 0.1 M TBAPF6 at a constant current of 20 mA. The protocol accommodates a broad range of substrates, including chalcones, conjugated dienones, and alkynones, affording the corresponding saturated ketones in yields ranging from 73% to 96%. The reaction exhibits remarkable chemoselectivity toward CC and CC bonds over carbonyl groups and carbon-halogen bonds, as demonstrated by the complete retention of ketones and chloro, bromo, methoxy, and methyl substituents. Deuterium labeling experiments using CH3OD as the deuterium source confirm that the solvent serves as the exclusive hydrogen/deuterium source and provide a cost-effective route to deuterium-labeled ketones. Mechanistic insights from DFT calculations reveal that the LUMO energy levels and orbital distributions correlate well with the observed reactivity and regioselectivity trends, offering a rational basis for understanding the electrochemical reduction process.