Catalytic Epoxidation of Alkenes with Oxone

A practical, general and efficient protocol for the catalytic epoxidation of alkenes has been developed. The in situ generation of reactive dioxiranes capable of epoxidizing a variety of alkenes under biphasic conditions has been accomplished using phase transfer catalysts bearing a carbonyl group. Optimal epoxidation conditions employ 10 mol % of l-dodecyl-l-methyl-4-oxopiperidinium triflate (8d+OTf^-) in a CH₂CI₂/PH 7.5-8.0 biphase using potassium monoperoxosulfate (Oxone) as the oxidant. Optimization of the conditions identified (1) slow addition rate, (2) pH 7.5—8.0, (3) iV-dodecyl chain, and (4) the triflate salt as key experimental and structural variables. A selection of nine olefins was successfully oxidized to the corresponding epoxides in 83—96% yield.