Alkynes Electrooxidation to α,α-Dichloroketones in Seawater with Natural Chlorine Participation via Competitive Reaction Inhibition and Tip-Enhanced Reagent Concentration

The traditional synthesis of α,α-dichloroketones usually requires corrosive chlorine, harsh reaction conditions, or excessive electrolytes. Here, we report an electrooxidation strategy of ethynylbenzenes to α,α-dichloroketones by directly utilizing seawater as the chlorine source and electrolyte solution without an additional supporting electrolyte. High-curvature NiCo2O4 nanocones are designed to inhibit competitive O2 and Cl2 evolution reactions and concentrate Cl– and OH– ions, accelerating α,α-dichloroketone electrosynthesis. NiCo2O4 nanocones produce 81% yield, 61% Faradaic efficiency, and 44.2 mmol gcat.–1 h–1 yield rate of α,α-dichloroketones, outperforming NiCo2O4 nanosheets. A Cl• radical triggered Cl• and OH• radical addition mechanism is revealed by a variety of radical-trapping and control experiments. The feasibility of a solar-powered electrosynthesis system, methodological universality, and extended synthesis of α,α-dichloroketone–drug blocks confirm its practical potential. This work may provide a sustainable solution to the electrocatalytic synthesis of α,α-dichloroketones via the utilization of seawater resources.