Base-Mediated Cascade Substitution–Cyclization of 2H‑Azirines: Access to Highly Substituted Oxazoles

A novel strategy to synthesize highly functionalized oxazoles has been successfully developed via a base-mediated intermolecular substitution between 2-acyloxy-2H-azirines and N-nucleophile or O-nucleophile with a subsequent ring expansion of a 2H-azirine intermediate. This method provides straightforward access to highly substituted oxazoles with high efficiency and excellent functional group compatibility under metal-free reaction conditions.