Alternating Current-Promoted Copper Catalysis for the Construction of Alkynyl Thioethers
Jiayi Yang1, Shabbir Muhammad1, Haoran Li1
1Institute for Advanced Studies (IAS), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, Hubei, P. R. China.
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Alkynyl thioethers are versatile intermediates in organic synthesis, and a synthetic strategy involving C-H/S-H oxidative cross-coupling is atom-economical and effective. However, the homocoupling of alkynes is hard to be prevented under aerobic conditions. Herein, we report an oxygen-free electrochemical oxidative coupling of terminal alkynes with thiophenols via an alternating current (AC) electrosynthesis. This approach stabilizes active Cu species and suppresses copper deposition via precisely controlling current, frequency, and duty ratio. The method affords up to 83% yields without external oxidants and ligands and minimizes undesired homocoupling and overoxidation. Mechanistic studies have confirmed that disulfide mediates the single-electron oxidation of the alkynyl copper intermediates.
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