Synthesis Of Ethyl Carbonate Derivatives Of β-cyclodextrin And The Process Optimization

The ethyl carbonate derivatives of β-cyclodextrin are widely used as estershydrolysis catalysts, the chiral selectors and the good surfactants. The ethyl carbonatederivatives of β-cyclodextrin were generally obtained through the reaction of toxiccarbonyl imidazole compounds with β-cyclodextrin. In this thesis, the ethyl carbonatederivatives of β-cyclodextrin were synthesized using environment-friendly diethylcarbonate as carbonyl reagent, and the process was in-depth studied to find out thediscipline of the yield and average degree of substitution varying with processconditions. The new synthesis process is very simple with high yield, and there is noneed of protection and deprotection process.Firstly, Oil bath and microwave radiation were used as two different waysheating in the synthesis of ethyl carbonate derivatives of β-cyclodextrin, respectively.The effects of molar ratio of diethyl carbonate to β-cyclodextrin, reaction temperature,reaction time and amount of catalyst on the synthesis was investigated. The reactionswere monitored by TLC and the products were analyzed by HPLC. Then the productswere separated by semi-HPLC and characterized by FT-IR, MS,1H-NMR and13C-NMR spectroscopy. Finally, the process optimization model was set up based onresponse surface methodology to find out the optimum conditions to meet therequirements of the yield and the average degree of substitution.The results showed that the microwave radiation heating can greatly shorten thereaction time and reduce the reaction temperature, but the highest yield heating withmicrowave irradiation is88%，lower than that of98%heating with traditional oil bath.In addition, the results indicated that the molar ratio had a great effect while theamount of catalyst almost had no effect on the yield. FT-IR results showed that theproducts were the ethyl carbonate derivatives of β-cyclodextrin.13C-NMR and1H-NMR indicated that the substituted position was the C-6position. We confirmedthe average degree of substitution of the products under different process conditionsby MS. And the discipline of average degree of substitution variation with processconditions was obtained. In the response surface experiments, when the desired goalfor the operational conditions was defined as the maximum value for the yield, theoptimum conditions are as follows:10g β-cyclodextrin dissolved in80mL N, N-Dimethylformamide, n(diethyl carbonate)/n (β-cyclodextrin)=20.2/1, reactiontemperature126℃, reaction time8.5h and catalyst amount12%by weight ofβ-cyclodextrin. The yield of ethyl carbonate derivatives of β-cyclodextrin were98%under this condition. When the desired goal for the operational conditions was definedas the maximum value for the average degree of substitution, the optimum conditionsare as follows: n(diethyl carbonate)/n(β-cyclodextrin)=21/1, reaction temperature is115℃, reaction time is13h and catalyst of amount is16%. The average degree ofsubstitution reaches the maximum2.2.