Eco-Friendly and Efficient Synthesis of 2-Hydroxy-3-Hydrazono-Chromones Through ,-C(sp)-H Bond Difunctionalization/Chromone Annulation Reaction of -Hydroxyaryl Enaminones, Water, and Aryldiazonium Salts.

A novel, eco-friendly, and efficient method for constructing 2,3-disubstituted chromone skeletons from readily available water, -hydroxyaryl enaminones (-HPEs), and aryldiazonium salts has been developed under mild reaction conditions. This ,-C(sp)-H bond difunctionalization/chromone annulation reaction strategy is achieved by building two C(sp)-O bonds and a C(sp)-N bond, which provides a practical pathway for the preparation of 2-hydroxy-3-hydrazono-chromones in moderate to excellent yields, enabling broad substrate scope and good functional group tolerance, as well as gram-scale synthesis. This protocol offers a valuable tool for synthesizing diverse functionalized chromones with potential applications in drug discovery and industrial synthesis.