Scalable electrochemical Clemmensen-type deoxygenation of aromatic aldehydes and ketones

Deoxygenation is an important approach for the conversion of abundant, oxygen-rich biomass-based compounds into higher value-added chemicals, typically performed under harsh reaction conditions producing excessive amounts of reagent waste. We report a mild, operationally simple electrochemical deoxygenation method based on the use of an inexpensive zinc cathode in a 2-electrode setup using formic acid as a green solvent and source of protons. This straightforward approach allowed efficient deoxygenation of a variety of aryl-substituted aldehydes and ketones, expanding the scope and efficiency of previously reported methods. Notable highlights in the scope are conversions of biogenic furfural, vanillin and syringaldehyde in good to excellent yields. The simple reaction conditions developed in batch were readily transferred to a more practically relevant flow setup and used for the preparative, multi-gram scale preparation of deoxygenated valueadded products. Systematic studies showed good reusability of all components of the reaction setup, like electrodes.