High frequency ultrasound as a tool for elucidating mechanistic elements of cis-cyclooctene epoxidation with aqueous hydrogen peroxide

•Cyclooctene epoxidation by H2O2/H2WO4/Aliquat 336 under high frequency ultrasound.•High frequency ultrasound proved the non-radical mechanism involved.•High frequency ultrasound allows step by step optimization of reaction parameters.•High Frequency ultrasound lead to enhanced selectivities. The use of high frequency ultrasound (800 kHz) highlights the non-radical character of the cis-cyclooctene epoxidation mediated by H2O2 and H2WO4. Combination of moderate mixing brought by the ultrasonic irradiation with precise thermoregulation of the double jacketed sonoreactor demonstrates the potential of this technique for studying and optimizing all the reaction parameters. The results not only reveal that the optimized ultrasonic conditions lead to excellent epoxidation outcomes with 96% yield and 98% selectivity but also to higher selectivities toward the epoxidation product compared with silent conditions.