Copper Nitrate‐Mediated Selective Bond Cleavage of Alkynes: Diverse Synthesis of Isoxazoles†

Comprehensive Summary An unprecedented copper nitrate‐mediated bond cleavage of alkynes was developed for the modular synthesis of isoxazoles, where either C—S bond or C≡C triple bond was cleaved selectively. Substituents attached to the C≡C triple bonds could differentiate the chemical bonds cleavage and reaction pathways disparately. Various transformations of products illustrate promising applications of the given protocols.