N–O Bond Cleavage and Skeletal Reorganization of Isoxazoles Enabled by Earth-Abundant Transition Metal Catalysis

The readily accessible isoxazoles have played an important role in facilitating organic transformations and accelerating the discovery of new drugs. In recent years, remarkable advances have been made in the N-O bond cleavage and skeletal reorganization of isoxazoles under precious metal catalysis. In comparison, the use of earth-abundant metals is appealing and in accordance with the principle of sustainable development due to their low cost, favorable biocompatibility, and distinctive reactivity patterns. This perspective summarizes recent developments in the selective functionalization of isoxazoles and anthranils via N-O bond cleavage using earth-abundant transition metal catalysts, including Cu, Fe, Ni, Ti, and Co. By selecting representative examples from the past five years, we introduce not only versatile reaction types and substrate scope but also a comprehensive interpretation of the plausible mechanistic pathways. We anticipate that this review will inspire synthetic organic chemists to cultivate novel transformations involving ring cleavage of heterocycles and facilitate the practical application of these methodologies in medicinal chemistry.