Waldvogel’s lab uses a variety of divided and undivided batch-type electrochemical cells (colored solutions added for visualization) for small-scale screening reactions and for prep-scale electrosynthesis.
GREEN CHEMISTRY
W
hen it comes to electrochemistry, the first things that pop into mind might be batteries and solar cells, or industrial processes like electroplating. Organic synthesis is not usually part of the conversation. Although electrochemical synthesis is well established, chemists have been reluctant to adopt the approach for common organic reactions, such as C–H activation or arene cross-couplings, believing it is too cumbersome or expensive. But the technology has been trending since 2015 and fully emerged this year. “Synthetic chemists have long viewed electrochemistry as an area where a few people do interesting reactions that are difficult for everyone else to repeat,” commented Kevin D. Moeller of Washington University in St. Louis. “That view is changing: The field is undergoing a dramatic uptick in popularity.” Electric current, when used as a surrogate reagent, offers the ability to avoid toxic or dangerous reagents, protecting groups, and catalysts typically used in organic synthesis. Moreover, electrosynthesis can reduce or eliminate the need to heat and cool reaction vessels, cutting energy consumption. Those advantages play right into the
C R E D I T: V E R BA N D D E R C H E MI S C H E I N D U STR I E /G E RA LD FU EST
Electrosynthesis got chemists charged up Using electrons as a reagent helped streamline organic reactions
hands of today’s synthetic organic chemist, who is faced with the challenge of creating increasingly complex molecules, but doing so in a greener, more sustainable, safer, and more cost-effective manner than before. In one example, Siegfried R. Waldvogel of Johannes Gutenberg University Mainz and his group in collaboration with researchers at Evonik Industries created a one-step electrochemical protocol for cross-coupling reactions to make biaryl diols and diamines, which are important chemical intermediates (C&EN, March 13, page 23). “This stuff is extraordinary,” Waldvogel told C&EN. “Electrosynthesis represents a disruptive technology and will be a game changer for industry.” Besides pushing to develop new electrochemically enabled reactions, academic research groups are helping develop user-friendly instrumentation specifically for the organic synthesis community. Last year, Waldvogel helped launch IKA’s labscale continuous-flow electrosynthesis system, called ElectraSyn Flow. And this year, Phil S. Baran of Scripps Research Institute California, whose group is turning more often to electrosynthesis for difficult steps in preparing terpene natural products, helped IKA launch ElectraSyn 2.0, a modernized version of the company’s electrochemical synthesis system. “This is incredibly impactful research,” Baran said. “The reemergence of electrochemistry deserves our attention.”—STEVE RITTER DECEMBER 11/18, 2017 | CEN.ACS.ORG | C&EN
21
