LAUSR

The Kolbe reaction forms carbon-carbon bonds through electrochemical decarboxylative coupling. Despite more than a century of study, the reaction has seen limited applications owing to extremely poor chemoselectivity and reliance on precious metal electrodes. In this work, we present a simple solution to this long-standing challenge: Switching the potential waveform from classical direct current to rapid alternating polarity renders various functional groups compatible and enables the reaction on sustainable carbon-based electrodes (amorphous carbon). This breakthrough enabled access to valuable molecules that range from useful unnatural amino acids to promising polymer building blocks from readily available carboxylic acids, including biomass-derived acids. Preliminary mechanistic studies implicate the role of waveform in modulating the local pH around the electrodes and the crucial role of acetone as an unconventional reaction solvent for Kolbe reaction. Description Alternate approach to Kolbe coupling Kolbe coupling is one of the very oldest reported reactions in organic chemistry. Essentially, an electrode oxidizes two carboxylic acids to release carbon dioxide and then couples the residual carbon fragments. Although direct and simple, the conventional reaction is incompatible with many common functionalities that can undergo competing oxidation. Hioki et al. now report that rapidly alternating the polarity of the electrochemical cell greatly expands the range of substituents compatible with the coupling (see the Perspective by Guo and Ye). This approach avoids pH lowering near the electrode that would otherwise slow down the decarboxylative oxidation at the expense of the side reactions. —JSY Rapid alternating polarity greatly expands the functional compatibility of a venerable electrochemical carbon–carbon coupling.