The Process Research Of2,6-dimethyl-γ-Pyranon Synthetized By Ethyl Ecetoacetate

2,6-dimethyl-gamma-pyrone is one of the γ-pyrone derivatives, which is widelyused in the pharmaceutical and chemical industry, such as promoting and inhibitingmany enzyme systems. And it is usually used for synthesis of light emittingmaterial, fragrances, dyes and other substances. There are the problems about lowyield, too much byproduct, difficult to separation products on the method for thesynthesis of2,6-dimethyl-gamma-pyrone in current. This paper studied the synthesisconditions, separation and analytical methodologies.Dehydroacetic acid was synthesized by ethyl acetoacetate first and then toproduce2,6-dimethyl-gamma-pyrone. The effects of the catalyst, reactiontemperature and time as well as the separation and purification methods on the yieldwere discussed. The optimum conditions as follows: the1ststep, Na2CO3&NaHCO3(molar ratio1:1) as catalyst, amount was0.03g/100g ethyl acetoacetate,internal temperature180℃～220℃, top temperature60℃～75℃, reaction time6h;the2ndstep, hydrochloric acid(mass concentration37.5%) as the reactionmedium, H4PW11VO40as catalyst, m（dehydroacetic acid）：m（H4PW11VO40）=5.5:1, reaction time6h, oil temperature95℃. The product wasextracted bychloroform and then sublimated under85℃. Under the optimum conditions, theyield was49.4%and the quality content was above99.5%.The molecular structure of2,6-dimethyl-gamma-pyrone was checked by IRand NMR. The result was the same with the expect. The method of separationand detection of2,6-dimethyl-gamma-pyrone and its reaction system’sintermediate analysis was built through HPLC. The optimum separation anddetection conditions was: Agilent HC-C18column (250mm×4.6mm,5μm),methanol-water(5:95,V/V,including0.3%Ammonium acetate pH=6.0adjustedby acetic acid), column temperature35℃, velocity of flow0.5mL/min, injectionvolume5μL, ultraviolet wavelength249nm. The correlation coefficient of2,6-dimethyl-gamma-pyrone and ethyl acetoacetate was0.9992~0.9995within thelinear range; and the relative standard deviations were less than1.0%, the spikedrecoveries were98.5%～101.3%.The yield was improved greatly and reactants was easy availability as well as thereaction conditions were mild by this new method. The operation for separation and purification was simple, the recovery was high and the products was very pure. Theanalysis method of HPLC was reliable and effective, which could separate anddetect the2,6-dimethyl-gamma-pyrone and the ethyl acetoacetate rapidly. Thismethod is useful for optimization the process conditions as it could track theprogress of the reaction, detection the raw material conversion rate andselectivity at any time.