Ultrafast Mechanochemical Epoxidation of Aldehydes and Ketones.

We report a mechanochemical Corey-Chaykovsky epoxidation that converts aldehydes and ketones to epoxides within minutes under an ambient atmosphere using sulfonium or sulfoxonium salts, KOH, and minimal liquid additives. The method accommodates a broad substrate scope, is readily scalable, and often enables simple extraction without chromatography. It further enables telescoped sulfonium generation-oxidation-epoxidation, tunable enone chemoselectivity, and direct conversion of imines to unstabilized aziridines. An unexpected dependence of reactivity on the ylide precursor halide reveals distinct mechanochemical reactivity from that under conventional solution-phase conditions.