Eco-Friendly and Efficient Synthesis of 2-Hydroxy-3-Hydrazono-Chromones Through α,β-C(sp2)–H Bond Difunctionalization/Chromone Annulation Reaction of o-Hydroxyaryl Enaminones, Water, and Aryldiazonium Salts

A novel, eco-friendly, and efficient method for constructing 2,3-disubstituted chromone skeletons from readily available water, <i>o</i>-hydroxyaryl enaminones (<i>o</i>-HPEs), and aryldiazonium salts has been developed under mild reaction conditions. This <i>α</i>,<i>β</i>-C(sp²)-H bond difunctionalization/chromone annulation reaction strategy is achieved by building two C(sp³)-O bonds and a C(sp²)-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.