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Abstract Using malononitrile as the raw material, a novel synthesis route of 2-amino-4,6-dimethoxypyrimidine (ADM) was put forward, in order to solve the instability in first step reaction of industrial synthesis. The influence of reactant ratio, temperature and time on product quality and yield was explored. The results showed that ADM was successfully prepared through acetyl chloride route, the yield was higher than that of industrial production process, and the process stability was good, with the product purity over 99%. Therefore, the new synthesis route is suitable for industrial production.
Keywords 2-amino-4,6-dimethoxypyrimidine (ADM); Pyrilamine
Compounds with pyrimidine ring, due to good biological activity, are widely used in the fields of pesticide, medicine, etc.[1-2]. As a derivative of pyrimidine, 2-amino-4,6-dimethoxypyrimidine (ADM) is an important intermediate of sulfonylurea herbicide featured by high activity, broad spectrum, low dosage, low toxicity and high selectivity[3_5l Besides, ADM can also be used to synthesize thiourea compounds with broad-spectrum antimicrobial and insecticidal properties, and has been extensively studied[6_8].
Currently, there are two synthetic routes of industrialized ADM. Firstly, 2-amino-4, 6-dihydroxypyrimidine is obtained through cyclization reaction of guanidine nitrate and diethyl malonate, then reacts with sodium methoxide and phosphorus trichloride to get 2-amino-4, 6-dichloropyrimidine which further reacts with sodium methanol solution to get ADM. Excessive phosphorus oxychloride used for chlorination in the process has safety risks in storage and use of phosphorus oxychloride when increasing byproducts. Moreover, the amount of process wastewater increases, and the difficulties in treatment increase as well. In recent years, some researchers have improved this route by directly using diazomethane[9], dimethyl carbonate^ and di-methyl sulfate[11] as methylation reagents to synthesize ADM in two steps after cyclization without chlorination, but industrial devices have not been formed for these routes. Secondly, 1,3-dimethylpropandiamidine dihydrochloride is obtained by reaction of malononitrile with methanol and hydrogen chloride, then reacts with sodium bicarbonate and cyan-amide to get 3-amino-3methoxy-N-nitrile-2-propamidine, and ADM is obtained by thermal cyclizationd 12 "14]. The synthesis route with malononitrile as the raw material has small discharge of three wastes, which will be the main route for industrial synthesis in the future. However, the synthesis process of 1,3dimethylpropandiamidine dihydrochloride in the first step requires anhydrous operation, which affects the stability of industrial synthesis.
The malononitrile process route was improved in the test. By...