Direct electrochemical oxidation of alcohols with hydrogen evolution in continuous-flow reactor

Abstract

Alcohol oxidation reactions are widely used for the preparation of aldehydes and ketones. The electrolysis of alcohols to carbonyl compounds have been underutilized owing to low efficiency. Herein, we report an electrochemical oxidation of various alcohols in a continuous-flow reactor without external oxidants, base or mediators. The robust electrochemical oxidation is performed for a variety of alcohols with good functional group tolerance, high efficiency and atom economy, whereas mechanistic studies support the benzylic radical intermediate formation and hydrogen evolution. The electrochemical oxidation proves viable on diols with excellent levels of selectivity for the benzylic position.

Electrocatalytic Deuteration of Halides with D2O as the Deuterium Source over a Copper Nanowire Arrays Cathode

“…Then, the carbon radicals coupled with the deuterium radicals produced via electrocatalytic D 2 O splitting to form the desired products. Both the carbon and hydrogen radicals were confirmed by the electron paramagnetic resonance (EPR) measurements using 5,5‐dimethyl‐1‐pyrroline‐ N ‐oxide (DMPO) as the trapping agent (Figure f) . A decreased conversion of the product after adding tertiary butanol ( t ‐BuOH), which could scavenge the hydrogen atoms, was observed, identifying the role of hydrogen radicals in this electrocatalytic reduction reaction (Supporting Information, Figure S7).…”

Prospects of Value‐Added Chemicals and Hydrogen via Electrolysis

“…However, the majority of organic oxidation reactions are performed at lower current densities, so increasing the yield of the anodic reaction is envisaged. In a recent study, high selectivity and high yields were observed for the conversion of a series of derived benzyl alcohols obtained in flow cells using a Ni cathode and a carbon anode, with currents up to 800 mA being applied to perform the reaction . Depending on the solubility of the generated product, the addition of acetonitrile or ionic surfactants was required in some cases to facilitate the homogeneity of the reaction environment.…”

“…Depending on the solubility of the generated product, the addition of acetonitrile or ionic surfactants was required in some cases to facilitate the homogeneity of the reaction environment. The selectivity of the reaction depends on the alcohol type, higher selectivity being reported for benzylic alcohols over the allylic ones . Complex CoCuN‐based electrodes having a hierarchical structure allowed also the conversion of benzylic alcohol to benzaldehyde with high selectivity …”

“…A continuous flow cell reactor was recently described for the electrochemical oxidation of various alcohols . The flow cell reactor, schematically shown in Figure a, uses carbon paper and a Ni plate as anode and cathode, respectively.…”

Photoelectrochemical Cells for Artificial Photosynthesis: Alternatives to Water Oxidation

“…In this context, we propose that a number of recent demonstrations that involve photoredox and electrochemically catalyzed/mediated oxidation reactions can be viable photoanodic processes to be combined with the concurrent generation of H 2 . For instance, there have been reports of C−N, C−P, C−S, and C−Se bond formation reactions, as well as the oxidation of alcohols to carbonyl compounds, all with H 2 produced at the cathode concomitantly. Similarly, C−C and S−S bond formation by dehydrogenative photoredox catalysis were also established.…”