Overcoming the Limitations of Kolbe Coupling via Waveform-Controlled Electrosynthesis

The Kolbe reaction has seen limited applications owing to its extremely poor chemoselectivity and reliance on precious metal-based electrodes, despite its potential to be one of the workhorse reactions of organic synthesis for C–C bond formation in both discovery and process settings. Although hundreds of studies over a century aimed to improve its efficiency and selectivity, general solutions have yet to be found. Herein, an exceedingly simple solution to this long-standing challenge is presented by merely tuning the waveform employed. Thus, switching from classic direct current (DC) to rapid alternating polarity (rAP), a broad range of functional groups can now be tolerated using inexpensive and sustainable carbon-based electrodes. A variety of high-value molecules ranging from useful unnatural amino acids to promising polymer building blocks are now accessible from readily available carboxylic acids, including biomass-derived acids. The practicality of the rAP-Kolbe reaction enables facile implementation of large-scale reactions, realizing access to novel degradable polymers from biomass. Preliminary mechanistic studies implicate the role of waveform in modulating the local pH around electrodes, which in turn affects the underlying redox processes. The ease, efficiency, and chemoselectivity of the rAP-Kolbe reaction finally opens the door to the widespread mainstream adoption of this classic reaction.