Amination of 1‐Amino‐4‐Bromoanthraquinone‐2‐Sulfonic Acid Enabled by Alternating Current Electrolysis of Symmetrical Copper Electrodes

Amination of 1-amino-4-bromoanthraquinone-2-sulfonic acid (BAA), crucial for anthraquinone-type dyes production, relies on Cu⁺ catalysis. However, Cu⁺ disproportionation causes catalyst deactivation, requiring large amounts of Cu catalysts (e.g., CuSO₄ or CuCl) and reductants (e.g., FeSO₄), introducing heavy metals and increasing water consumption to remove byproducts and metals, raising both environmental and economic costs. To address these challenges, we introduce a innovative strategy for the in situ generation of Cu⁺ using symmetrical Cu electrodes under alternating current (AC) electrolysis. This method achieves 100% conversion of BAA in the amination with 3,5-diamino-2,4,6-trimethylbenzene sulfonic acid (M Acid) with 95% yield, while also providing a solution to the issue of Cu⁺ disproportionation without the need for any additional copper catalysts or reductants, demonstrating a broad substrate scope and significantly reducing water usage in post-treatment. Characterization techniques, including X-ray photoelectron spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy, reveal that the passive Cu₂O film formed on the symmetrical Cu electrodes under AC electrolysis continuously generates Cu⁺, which is crucial for the reaction. This approach is scalable, environmentally friendly, and holds great potential for industrial applications, offering substantial economic benefits while reducing environmental impact.