Mono or Di? A Potential-Controlled Electrochemical Halogenation of Anilines

In organic reactions, controlling the degree of substitution, such as monosubstitution or disubstitution, typically necessitates the use of varied reagents, reaction conditions, and temperatures, often leading to increased separation costs. Simplifying this complexity while developing more direct and efficient methods for controlling reaction outcomes remains a long-standing challenge. In this work, we present a novel and efficient electrochemical strategy that leverages the precise control of electrode potential to selectively halogenate aniline derivatives, offering a breakthrough in the reaction selectivity. By manipulating the electrode potential, we control the generation of different intermediates and, therefore, the reaction mechanisms. At a lower electrode potential (1.38 V vs SHE), the formation of X^• facilitates selective para-halogenation, whereas at a higher electrode potential (2.88 V vs SHE), the formation of X⁺ is the primary reason for obtaining dihalides. This method eliminates the need for oxidants, transition metals, or external bases, utilizing the unique ability of electrode activation to enhance the substrate reactivity and reaction efficiency. The approach provides an alternate perspective in organic or electrochemical synthesis.