Radical-Radical Cross-Coupling Assisted N-S Bond Formation Using Alternating Current Protocol

Abstract

Alternating current (AC) electrolysis is a promising, yet challenging, and under-developed protocol in organic synthesis. To achieve as high an atom-efficiency as possible and avoid the use of external oxidant, electrochemistry has become a standard organic synthesis tool. Herein, an AC-based protocol is a superior option than its counterpart, direct current (DC), especially for those reactions that cannot be accomplished by DC. With an aim to achieve this objective, we have employed AC electrolysis successfully to deliver the unprecedented cross-coupling of sulfonyl- or acyl-substituted aniline derivatives with thiophenols/thiols under exogenous-oxidant- and catalyst-free conditions. Numerous N-S bond-containing compounds (40 in total) have been prepared at up to 93% yield and good selectivity. Interestingly, no reactivity has been noted using DC electrolysis or traditional chemical approaches under our reaction conditions. Mechanistic studies indicated that disulfide is the key intermediate in this AC-mediated radical-radical cross-coupling reaction. Therefore, the current work does not only provide an efficient method for N-S bond formation but also paves the way to new sustainable avenues for innovation in organic synthesis.