Oxaziridines: Versatile Reagents in Modern Organic Synthesis

Oxaziridines are three-membered heterocyclic compounds containing a carbon, an oxygen, and a nitrogen atom. Along with high regio-, chemo-, enantio-, and diastereoselectivity, oxaziridines have gained more interest in modern organic synthesis due to their unique structural and electronic features that allow O-atom and N-group/atom transfer reactions. The reactions of oxaziridines can be performed both stoichiometrically and catalytically. Their applications include selective α- and γ-hydroxylation/amination of carbonyl compounds, epoxidation of olefins and oxidation of thiols, sulfides and sulfoxides, etc. In addition, oxaziridines have been explored for ring-opening, rearrangement, and fragmentation, which produce amides, nitrones, imines, and other useful synthetic intermediates. Notably, oxaziridines undergo cycloaddition with alkenes, alkynes, ketenes, nitriles, etc., and offer structurally diverse heterocyclic frameworks such as isoxazolines, isoxazoles, oxadiazolines, oxadiazoles, etc. Among various oxaziridines, N-sulfonyl oxaziridines are known as Davis reagents, which are widely used for selective oxidations and synthesis of heterocycles. Chiral oxaziridines and oxaziridinium salts have found a broad spectrum of applications in asymmetric synthesis, enabling enantioselective oxygen-transfer reactions and the synthesis of complex molecules. This review collates the synthesis, structural features, mechanistic aspects, reactivity patterns, and synthetic applications of oxaziridines, including their roles in oxidation chemistry, cycloadditions, rearrangements, and synthesis of heterocyclics, natural products, and pharmaceutical drugs.