Ring‐Opening Chlorination and Bromination of Pyrazolopyridines and Isoxazoles

Abstract We report the development of electrophilic ring‐opening chlorination and bromination reactions of pyrazoloazines and isoxazoles using chlorinating and brominating agents. These transformations proceed via selective cleavage of heteroaromatic N─N or N─O bonds, delivering structurally diverse tertiary halogenated compounds. Furthermore, treatment of formylated pyrazolopyridines with two equivalents of chlorinating or brominating agents afforded dihalogenated products in good yields. This strategy represents a valuable platform for constructing halogenated scaffolds from simple heteroaromatic precursors and broadens the synthetic utility of skeletal transformations in the functionalization of heteroaromatics.