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 groundbreaking 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.