Synthesis Of Vitamin E Succinate Catalyzed By Supported 4-dimethylaminopryridine (DMAP)

Vitamin E succinate is widely used in medicine,food and cosmetics,which possessed the effect of antioxidant and inhibiting tumors of breast cancer,prostate cancer.Vitamin E succinate was usually synthesized by volatile organic amines catalyst.However,the method had the problems of separation,environmental pollution and product safety.In the study,the highly active acylation catalytic small molecule 4-dimethylaminopryridine?DMAP?was immobilized on silicon-based carriers,which successfully prepared supported DMAP under mild conditions.And synthesis of vitamin E succinate was catalyzed by supported DMAP,the heterogeneous catalyst could be easily recycled from reaction solvent after reaction,which achieved low cost,operational simplicity and no catalyst contamination of the product.In addition,low-toxicity hexane/acetone mixed solvent was studied to improve efficiency of multiphase reaction system.The conditions were systematically optimized in the heterogeneous mixed solvent.Firstly,NS-DMAP and NS-DMAP^e were prepared by nano-silica?NS?and different precursor,such as 4-methylaminopyridine?MAP?and N,N-dimethyl-N-?4-pyridyl?-1,2-ethanediamine?DMEAP?over N-alkylation,The prepared catalysts were characterized by Fourier Transform Infrared Spectroscopy?FT-IR?and Thermal Gravity Analysis?TG/DTG?.And they were employed to synthesize vitamin E succinate.The highest vitamin E succinate yield of 92%was achieved by NS-DMAP and the optimal experimental conditions were as followed:hexane/acetone?4:1 v/v?as mixed solvent,initial concentration of?-tocopherol of 32 mM,molar ratio of succinic anhydride to?-tocopherol of 3:1,the temperature of 55?,the amount of catalyst of 12 mmol-equ.DMAP/L and reaction time of 21 h.And vitamin E succinate yield of 75%was obtained by NS-DMAP^e,the optimal experimental conditions were as followed:hexane/acetone?4:1 v/v?as mixed solvent,molar ratio of succinic anhydride to?-tocopherol of3:1,the temperature of 55?,the amount of catalyst of 16 mmol-equ.DMAP/L and reaction time of 24 h.Besides,it was found that both NS-DMAP and NS-DMAP^e showed good stability,their initial catalytic activity had no significantly decrease after recycling 10 times.Next,the effect of different carriers on the activity of supported DMAP was investigated.The precursor was MAP described above,and carriers were nano-silica?NS?,silica gel?MSP?and MCM-41.The prepared catalysts were characterized by Fourier Transform Infrared Spectroscopy?FT-IR?and Thermal Gravity Analysis?TG/DTG?.And they were employed to synthesize vitamin E succinate.Under the same catalytic reaction conditions as NS-DMAP described above,the yield of vitamin E succinate catalyzed by MSP-DMAP and MCM-41-DMAP reached 88%and 83%when the amount of catalyst was 16 mmol-equ.DMAP/L and the optimal reaction time was 22 h and 28 h,separately.Similarly,their initial catalytic activity had no significantly decrease after recycling 10 times.Then,acylation of vitamin E was catalyzed by NS-DMAP.The reaction was carried out under the conditions of rection time of 22 h,reaction solvent of 250 mL and decrease of 50%amount of catalyst.The highest vitamin E succinate yield reached 92%,apparent catalytic activity of NS-DMAP was 0.223 h^-1,and catalytic activity of free DMAP was 0.627 h^-1.Therefore,supported DMAP remained the catalytic activity of DMAP.After reaction,supported DMAP was recovered by filtration,unreacted succinic anhydeide was removed by precipitation,and vitamin E succinate was purified in hexane by recrystallization.The excellent results make this technology become the promising candidate for the industrial production of vitamin E succinate.