Direct Mechanochemical Oxidation: Sustainable Access to Azine <i>N</i> ‐Oxides

ABSTRACT A rapid, eco‐friendly mechanochemical protocol for direct oxidation of azines to N ‐oxides was developed. Using m CPBA—the common commercial oxidant—in a ball mill under solvent‐free conditions, the reaction completes in 1 h with yields up to 99%, much faster than traditional solution processes (typically 16–24 h). The protocol exhibits a broad substrate scope, accommodating a wide range of functionalized pyridines, quinolines, isoquinolines, and benzoquinolines bearing diverse substituents (e.g., ethers, halogens, carbonyls, and ureas). The corresponding N ‐oxides are generally obtained in good‐to‐excellent yields without the need for chromatographic purification. Thus, this mechanochemical approach opens a new sustainable avenue in the chemistry of heterocyclic compounds and heteroatom–oxygen bond formation, a field of great importance for medicinal chemistry and materials science.