New and efficient technique for the synthesis of ε-caprolactone using KHSO₅ as an oxidising agent in the presence of a phase transfer catalyst

A new method for the synthesis of ε-caprolactone based on the Baeyer-Villiger oxidation of cyclohexanone was developed. In the proposed reaction, potassium peroxomonosulphate was used as an oxidising agent under phase transfer catalysis conditions. The effects of the reaction parameters, including the type of phase transfer catalyst, the concentration of the oxidising agent, the type of organic solvent and temperature, were investigated. When dichloromethane was used as an organic solvent and an adequate amount of water was added to the reaction mixture, the highest yield and selectivity for ε-caprolactone were achieved at 40 °C.