Study On The Methylation Of 1,3-dimethyl Xanthine

The target product of caffeine was obtained by methylation reaction of 1,3-dimethylxanthine(theopHylline).This was the last step of the synthesis on caffeine,and it was a key step to realize green production[1-4].At present,dimethyl sulfate was a mainly methylation reagent onsynthesisof coffee in the industry,and the technology was already quite mature.however,dimethyl sulfate toxicity was stronger,and a mass of waste water wasproduced in the process.So there was a lot of negative effect to the production and living[4-5].Therefore,itwas particularly important to seek a green and efficient methylation process.There were a series of experimental studies about the feasibility of theopHylline sodium and dimethyl carbonate instead ofdimethyl sulfate as methylatingreagent,which reacted withtheopHylline sodiumto synthesise caffeine.AlthoughtheopHylline sodium was low toxicity,theyield of target product(caffeine)was low withtheopHylline sodium asmethylatin greagent,and a lot of sodium hydroxide was needed in post-processing.Therefore,for many reasons,this process can't meet therequirements of standard industrial production,and more studies are requied.The effect of catalyst,molar ratio,reaction time,reaction temperature and times of mother liquor cycles on the yield was investigated.The optimum reaction conditions were as follows: reaction temperature 130?,NaY used as catalyst,emulsion of containing most of water used as a solvent(m(water): m(DMC): m(OP-10)=14:1:1),turkey red oil used as emulsifier,molar ratio of theopHylline sodium and DMC 1:1.30,reaction time 3 h.Under this condition,the yield of the target product caffeine reached 97.84%.In addition,the separation and purification of by-products were studied in the work,and its content and structure were confirmed by HPLC,LC-MS and 13 CNMR.This was why the process referred to as green process that dimethyl carbonate was nontoxic and harmless.What's more,the by-products of the process were harmless.And it was possible to realize the continuous production by using recycling mother liquor.Therefore,no matter from environment or production efficiency point,it's all possible that the dimethyl carbonat instead of dimethyl sulfate as methylating reagen torealize green industrial production.