Study Of The Selective Oxidation Of2,5-dimethylpyrazine In The Presence Of Molecular Oxygen Catalyzed By Metalloporphyrines

5-Methylpyrazine-2-carboxylic acid is an important pharmaceutical intermediate.It is mainly used to synthesize the second generation sulfonylurea hypoglycemic agentglipizide, to synthesize new generation of long-term cholesterol-loweringdrugacipimox and PAE for anti-tuberaclosis. Firstly the article reviews the recent progressin applications and syntheses of5-Methylpyrazine-2-carboxylic acid. The articlemainly introduces three synthesis methods, the chemical synthesis, theelectrochemical synthesis, the microbial synthesis, at the same time advantages anddisadvantages of different synthesis processes were compared.Currently, the process of synthesis of5-Methylpyrazine-2-carboxylic acid consumes a large amount of catalysts and5-Methylpyrazine-2-carboxylic acid is difficult to be separated from the reaction system; the synthesis processe is conducted in an acidic medium, so there is a greater corrosion of the reaction vessel; besides, the reactionprocess is difficult to control, prone to deep oxidation and produces a large amount ofbyproducts. Metal porphyrins can simulate monooxygenase cytochrome P-450to cata-lytically activate molecular oxygen on mild conditions. Especially replaced metal porphyrins exhibit high catalytic activity and selectivity in the catalytic oxidation reaction. Thus,in mild condition, metal porphyrins can be used as catalyst and oxygen as the oxidant to catalytically oxidize2,5-dimethypyrazine.In this way, the method acquires5-methyl-pyrazine-2-carboxylic acid and achives satisfactory success.The paper introduces a method of oxidation of2,5-dimethylpyrazine catalyzedby different metalloporphyrins and the reaction process and the oxidation depth arecontrolled by green chemical processe. Thus reaction conversion rate and theselectivity of target product get improved.The paper mainly conducts a research onalkaline conditions, using metalloporphyrins catalytically to oxidize2,5-dimethylpyrazine to prepare5-methyl-pyrazin-2-carboxylic acid. The research is focused onporphyrin catalyst type and dosage, reaction temperature, alkali concentration, oxygenpressure, reaction time and other factors on the reaction yield and the target productacid selectivity. Through the analysis of the reaction mechanism we may understandthe essence relationship between the metalloporphyrins and sodium hydroxide, thesynergistic catalysis also explained the phenomenon that the catalytic oxidation can`toccur without sodium hydroxide.The results show that T(p-Cl)PPCoCl catalyst concentration:4.0×10-5mol/L ofcatalyst,0.375mol/L of alkali concentration, and100°C,1.5MPa of O2for8hours. Inthis conditions,2,5-dimethyl pyrazine conversion rate is21.69%, and the yield andthe selectivity of5-methyl-pyrazin-2-carboxylic acid are20.10%and92.68%.