Study On Microwave-assisted Synthesis Of Ester Liquid Crystal Intermediates

As a heating method and transmitted medium, microwave has been widely used invarious fields. Compared with traditional heating, the microwave heating has greatadvantages such as high efficiency, environment benign and convenient operation.Since1986, when microwave irradiation was first applied towards organic synthesis,microwave-assisted organic synthesis has become increasingly popular for organicreactions and become a newly developed field.In the first part, we introduced the principle of microwave heating and thedevelopment of microwave-assisted synthesis of organic reaction, and summarized theresearch of ester liquid crystal.In the second part, the reactions for the synthesis of allylic bromide andp-hydroxyl benzoic acid were completed by microwave radiation heating and traditionaloil bath heating in the same temperature, with ethanol-water、glycol、DMF as solventrespectively. By parameter optimization, we obtained the optimum condition ofmicrowave irradiation. While the reaction temperature and reaction time were kept thesame, the reaction yields of each time point under the two different heating modes werecompared with the aid of HPLC. The experimental results showed that the yields ofmicrowave radiation heating were higher than traditional heating, and the higher thetemperature, the more obvious the yields of the microwave radiation heating. Theincrease of yields of the microwave radiation heating was more obvious when thetemperature was higher.The third part includes Chapter3. In this part, the reaction of allylic bromide andethyl p-hydroxybenzoate was researched. By comparing the yields of microwaveheating with traditional heating under different solvents (acetone/DMF/ethanol-water/glycol/DMF-water), we found that there was a little difference between the two heatingmodes.In the fourth part, we completed the reaction of p-hydroxyl benzoic acid andchloropropanols, the reaction conditions (temperature、 solvent、 power) of theetherification under microwave radiation were optimized and the comparison toconventional heating was made. We found that the higher the temperature, the moreobvious the yields of the microwave radiation heating. while the reaction conditionwere kept the same, the yields of microwave radiation heating were higher than conventional heating, the yields could be increased by4~18%, which showed thatmicrowave radiation could promote reactions.The fifth part includes Chapter5. In this part, the reaction of2-bromoethanol andp-hydroxyl benzoic acid was studied. At the reaction temperature of80℃, we comparedthe yields of microwave heating with traditional heating under differentsolvents(ethanol-water/glycol/DMF-water). In addition, we optimized the microwavereaction condition. The results showed that the yields of microwave radiation heatingwere higher than traditional heating. The reaction tendency of the two conditions wereapproximately identical, which indicated that the microwave didn’t change the reactionprocess. When glycol was used as solvent the yield was the highest under microwaveheating and was the most obvious comparing with conventional heating.