Electrochemical oxidative dynamic kinetic resolution of phosphines using chiral supporting electrolytes

The synthesis of enantiopure compounds is a central focus in organic chemistry owing to the prevalence of chiral centers in biological systems and the impact of homochirality on molecular properties. With growing recognition of electrochemistry as a powerful tool to improve the scope and sustainability of organic synthesis, increasing efforts have been directed toward developing asymmetric electrocatalytic reactions to access challenging chiral molecules. However, many useful electrochemical reactions rely on direct electrolysis without a catalyst, making them inherently difficult to render enantioselective. Supporting electrolytes are integral to electrochemical systems and, in addition to ensuring sufficient solution conductivity, they can influence the rate and selectivity of electrochemical transformations. Chiral supporting electrolytes can mediate asymmetric reactions via direct electrolysis, but their use in organic electrosynthesis remains largely unexplored. Here, we describe the use of substoichiometric chiral phosphate salts as supporting electrolytes to facilitate the oxidation of racemic trivalent phosphines to afford enantioenriched phosphine oxides. Our approach relies on a dynamic kinetic resolution (DKR) strategy that exploits the rapid pyramidal inversion of an anodically generated phosphoniumyl radical cation, while a high concentration of chiral phosphate at the electrode–electrolyte interface enhances enantioselective control during rate-limiting nucleophilic addition. Our results highlight the promise of chiral supporting electrolytes for promoting radical ion-mediated asymmetric transformations.