Electricity-Driven Halogenation of α -Oxo Ketene Dithioacetals Using Lithium Halides as Dual-Function Electrolyte Reagents

Abstract Halogenation reactions are indispensable transformations in organic synthesis. However, they typically rely on toxic reagents or harsh conditions. Herein, we report an electrochemical method for the bromination and chlorination of α-oxo ketene dithioacetals using simple lithium halides as both the halogen source and supporting electrolyte under constant-current electrolysis. The protocol provides direct access to a broad range of brominated and chlorinated α-oxo ketene dithioacetals under additive-free conditions without external chemical oxidants. A total of 22 brominated and 6 chlorinated products were synthesized in up to 99% yield with excellent functional-group tolerance. The practicality of the protocol was further demonstrated through gram-scale electrolysis. Cyclic voltammetry, control experiments, and radical trapping studies suggest distinct anodic oxidation pathways for bromination and chlorination. This operationally simple protocol provides an efficient electrochemical strategy for the halogenation of α-oxo ketene dithioacetals using readily available lithium halides.