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13/5000 A new synthesis method of ethyl dichloronicotinate
Time：2019-6-28 17:53:42 Clicks：176
Ethyl chloronicotinate is an important intermediate in organic synthesis. In recent years, it has been used to synthesize prophylaxis and therapeutics for lowering blood glucose and inhibiting bronchial and vascular dilation, alkyl diamine derivatives for reducing tachycardia, and a series of derivatives of welfomycin as anti-vaccine. The only reported synthesis methods are: starting from diethyl acetone dicarboxylate, reacting with acetic anhydride and triethyl orthoformate, adding ammonia water to form dihydroxynicotinic acid ethyl ester, and finally reacting with phosphorus oxychloride to get dichloronicotinic acid ethyl ester. The raw materials of this method are expensive, difficult to get, and the yield is low.
Chloromethylpyridine nitrogen and oxygen compounds are easily deoxychlorinated by nucleophile. Taking chloromethylpyridine as raw material, dichloromethylpyridine is obtained through oxidation, nitrification and deoxychlorination, and then through carboxylation and esterification, ethyl dichloroniacin is obtained. The total yield is 53.8%. In the oxidation reaction, acetic anhydride replaces most acetic acid, increasing the oxidation of hydrogen peroxide. The high temperature decomposition of chloromethylpyridine oxide was avoided and the yield was increased by both of them. At the same time, the cheap concentrated sulfuric acid was used as catalyst to overcome the disadvantages of too long time and too much solvent in direct oxidation process. When nitrification reaction has little effect on yield, concentrated nitric acid is used instead of fuming nitric acid as nitrifying agent, which improves the safety factor of production, reduces the cost, and reduces the generation of by-products and environmental pollution. The deoxychlorination reaction system is the mixture of dichloromethylpyridine and nitromethylpyridine. Increasing the dropping temperature and reaction temperature is beneficial to the formation of chloromethylpyridine and improves the yield.
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