Rearrangements of 1,2,4-Oxadiazole: "One Ring to Rule Them All"

1,2,4-Oxadiazoles are heterocycles characterized by low aromaticity and the presence of a weak O-N bond and are widely studied due to their tendency to rearrange into more stable heterocyclic compounds. This review covers literature from the last fifteen years, highlighting the general features of 1,2,4-oxadiazoles and their applications. Regarding the reactivity, the development of classical reactions (thermal and photochemical rearrangements) is presented in terms of synthetic utility and mechanistic insight. Among the relevant rearrangement reactions, the Boulton-Katritzky Rearrangement (BKR), Migration - Nucleophilic Attack - Cyclization (MNAC), and Addition of the Nucleophile, Ring Opening, and Ring Closure (ANRORC) reactions are discussed, together with recent noteworthy syntheses and applications of the 1,2,4-oxadiazole ring.