Electrocatalytic cyclic deracemization enabled by a chemically modified electrode

Abstract

Redox chemistry, which is frequently encountered in the formation of new bonds and stereocentres, relies on the compatibility of redox potentials. Despite recent advances, achieving a general electrocatalytic cyclic deracemization process without stoichiometric redox reagents remains a formidable challenge. Here we show that electrocatalytic cyclic deracemization of secondary alcohols can be accomplished through sequential iridium-catalysed enantioselective anodic dehydrogenation and rhodium-catalysed cathodic hydrogenation, utilizing metal hydride catalysis. A considerable hurdle arises as stronger hydride donors necessitate parent metal complexes to possess low reduction potentials, resulting in inherent redox potential incompatibility. Nonetheless, we overcame this incompatibility by leveraging a recyclable rhodium-catalyst-modified electrode as the cathode—an accomplishment that homogeneous rhodium catalysis could not achieve. Our approach enables chemoselective stereochemical editing of bioactive compounds with remarkable functional group tolerance. Surface characterization and mechanistic studies showcased the unique advantages conferred by the chemically modified electrode. Methods for electrocatalytic deracemization remained elusive. Now, electrocatalytic cyclic deracemization of alcohols is reported, involving sequential anodic dehydrogenation and cathodic hydrogenation using two distinct metal hydride catalysts and a chemically modified electrode to avoid redox incompatibility.