| To resolve the existed problems of the traditional peroxy acid Baeyer-Villiger oxidation such as needing a lot of acid, the corrosion equipment, many by-products, difficult separation and pollution of the environment, in this paper, three kinds of heteropolyacid ionic liquids are designed and synthesized. The structures of these ionic liquids are characterized by infrared spectroscopy(IR), H atom nuclear magnetic resonance(1H NMR) and thermogravimetric characterization(TG-DTG). These ionic liquids have been used for catalyzing Baeyer-Villiger oxidation of cyclic ketones. Three green Baeyer-Villiger catalytic systems are designed and developed including(1) Lewis acid-functionalized ionic liquids catalyzed Baeyer-Villiger oxidation of cyclic ketones,(2) Br?nsted-Lewis acid-functionalized ionic liquids catalyzed Baeyer-Villiger oxidation of cyclic ketones,(3) Br?nsted acid-functionalized ionic liquids catalyzed Baeyer-Villiger oxidation of cyclic ketones.With N-methyl imidazole, chlorinated n-butane, anhydrous AlCl3, anhydrous FeCl3, anhydrous ZnCl2 as raw materials, a series of Lewis acidic ionic liquids are synthesized, and used for catalyzing cyclohexanone Baeyer-Villiger oxidation reaction. It not only shows good catalytic activity but also has better performance of recyclability. Among these prepared Lewis acidic functionalized ionic liquids, [BMIM]-Zn3Cl7 exhibits the best catalytic activity for the model cyclohexanone Baeyer-Villiger oxidation reaction. The effects of the dosage of the catalyst, the dosage of the H2O2, reaction temperature, and reaction time on the cyclohexanone Baeyer-Villiger oxidation reaction catalyzed by [BMIM]-Zn3Cl7 have been fully investigated. The selected optimal conditions are as follows: the molar ratio of cyclohexanone to the catalyst 4:1, the molar ratio of cyclohexanone to H2O2 1:5, reaction temperature 50 °C, and reaction time 6 h. Under the optimal conditions, the cyclohexanone conversion rate can reach 67.9%, ε-caprolactone yield reaches 44.5%, and the reaction selectivity is up to 65.5%. After the reaction, the upper oil is removed, and the lower Lewis acidic ionic liquids can be directly recycled after drying. Under the above selected reaction conditions, the catalytic activity of the catalyst [BMIM]-Zn3Cl7 for the cyclohexanone Baeyer-Villiger oxidation reaction nearly remains unchanged during 6 recycles. After nine times, the reaction conversion is down to 52.1%. The catalytic activities of the catalyst [BMIM]-Zn3Cl7 of Baeyer-Villiger oxidation for the other cyclic ketones(cyclobutanone, cyclopentanone, 2-methyl cyclohexanone, 4-methyl cyclohexanone, cycloheptanone and 2-adamantanone) have been fully investigated, and the results show that these cyclic ketones can be well converted to the corresponding lactones by [BMIM]-Zn3Cl7 catalyst.With N-methyl imidazole, pyridine, triethylamine, chlorinated n-butane, 1,3-propanesultone, metal salts, phosphotungstic acid as raw materials, a series of Br?nsted-Lewis double acidic ionic liquids are synthesized, and used for catalyzing cyclohexanone Baeyer-Villiger oxidation reaction. Among these prepared Br?nsted-Lewis acidic ionic liquids, Al0.5[Py-PS]0.5HPW12O40 exhibits the best catalytic activity for the model cyclohexanone Baeyer-Villiger oxidation reaction. The effects of the dosage of the catalyst, the dosage of the H2O2, reaction temperature, and reaction time on the cyclohexanone Baeyer-Villiger oxidation reaction catalyzed by Al0.5[Py-PS]0.5HPW12O40 have been fully investigated. The selected optimal conditions are as follows: the molar ratio of cyclohexanone to the catalyst 100:1, the molar ratio of cyclohexanone to H2O2 1:6, reaction temperature 50 °C, and reaction time 1 h. Under the optimal conditions, the cyclohexanone conversion rate reaches 46.7%, ε-caprolactone yield reaches 38.8%, and the reaction selectivity is up to 83.1%. Under the above selected reaction conditions, the catalytic activity of the catalyst Al0.5[Py-PS]0.5HPW12O40 for cyclohexanone Baeyer-Villiger oxidation reaction nearly remains unchanged during 7 recycles. However, after nine times recycles, the reaction conversion is down to 39.7%. Under the above selected reaction conditions, the catalytic activities of the catalyst Al0.5[Py-PS]0.5HPW12O40 of Baeyer-Villiger oxidation for the other cyclic ketones(cyclobutanone, cyclopentanone, 2-methyl cyclohexanone, 4-methyl cyclohexanone, cycloheptanone and 2-adamantanone) have been investigated, and the results show that these cyclic ketones all can be converted to the corresponding lactones by Al0.5[Py-PS]0.5HPW12O40.With N-methyl imidazole, pyridine, triethylamine, chlorinated n-butane, 1,3-propanesultone, chloroacetic acid, dichloroacetic acid, 2,3-dichloropropionic acid phosphotungstic acid as raw materials, a series of Br?nsted acidic ionic liquids are synthesized, and used for catalyzing cyclohexanone Baeyer-Villiger oxidation reaction. Among these prepared Br?nsted acidic ionic liquids, [MIM-CH2CHClCOOH]3PW12O40 exhibits the best catalytic activity for the model cyclohexanone Baeyer-Villiger oxidation reaction. The effects of the dosage of the catalyst, the dosage of the H2O2, reaction temperature, and reaction time on the reaction catalyzed by [MIM-CH2CHClCOOH]3PW12O40 have been fully investigated. The selected optimal conditions are as follows: the molar ratio of cyclohexanone to the catalyst 25:1, the molar ratio of cyclohexanone to H2O2 1:5, reaction temperature 40 °C, and reaction time 5 min. Under the optimal conditions, the cyclohexanone conversion rate can reach 61.2%, ε-caprolactone yield reaches 46.5%, and the reaction selectivity is up to 76.0%. Under the above selected reaction conditions, the catalytic activity of the catalyst [MIM-CH2CHClCOOH]3PW12O40 for the cyclohexanone Baeyer-Villiger oxidation reaction nearly remains unchanged during 7 recycles. However, after 9 recycles, the reaction conversion is down to 42.1%. The catalytic activities of the catalyst [MIM-CH2CHClCOOH]3PW12O40 of Baeyer-Villiger oxidation for the other cyclic ketones(cyclobutanone, cyclopentanone, 2-methyl cyclohexanone, 4-methyl cyclohexanone, cycloheptanone and 2-adamantanone) have been investigated, and the results show that these cyclic ketones can be well converted to the corresponding lactones by [MIM-CH2CHClCOOH]3PW12O40.This paper has successfully established three kinds of Baeyer-Villiger catalytic oxidation systems. Many cyclic ketones can be well converted to the corresponding lactones in these catalytic systems, and the catalysts can achieve efficient separation and recycling. The paper provides a new science basis for the application of acidfunctionalized ionic liquids in Baeyer-Villiger oxidation reaction. |
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