2, 3-dichloropyridine preparation method

Abstract

The present invention discloses a 2, 3-dichloropyridine preparation method comprising the following steps: (1) 2,3-dimethylamide pyridine is dissolved in water, then a caustic soda aqueous solution and a sodium hypochlorite aqueous solution are successively added, after the addition is completed, the mixture is heated for full reaction, after the reaction is completed, the system is adjusted to be neutral or acidic by use of hydrochloric acid, and water is removed by distillation to obtain a 2,3-diaminopyridine crude product; (2) the 2,3-diaminopyridine crude product is dissolved in hydrochloric acid, a catalyst is added, then a sodium nitrite aqueous solution is added dropwise, after the addition is complete, the2,3-diaminopyridine crude product is completely reacted, and after the reaction is completed, a 2, 3-dichloropyridine crude product is obtained by distillation; and (3) the 2, 3-dichloropyridine crude product is added into an organic solvent for complete dissolving, then cooled for recrystallization, crystals are filtered off and dried to obtain a 2, 3-dichloropyridine finished product. The method avoids the problem of very low tendency for side effects of 2-site chlorination, the production process is simple, the reaction is smooth and steady, production cost is low, product yield is high, and product purity is high.

Description

Technical field [0001] The invention relates to a method for preparing 2,3-dichloropyridine. Background technique [0002] 2,3-Dichloropyridine is an important fine chemical intermediate, which is widely used in the fields of medicine and pesticide and has a large market demand. In recent years, there have been many studies on 2,3-dichloropyridine at home and abroad. The reported preparation methods of 2,3-dichloropyridine mainly include the following. [0003] The Chinese patent document with the publication number CN103570609A discloses that 3-carboxamide pyridine (nicotinamide) is used as the starting material and subjected to Hoffman degradation to obtain 3-aminopyridine, which is distilled to remove water, extracted with dichloromethane, and hydrochloric acid After back extraction, it reacts with hydrogen peroxide to obtain a hydrochloric acid solution of 2-chloro-3-aminopyridine, and then undergoes diazotization and Sandmeyer reaction to obtain 2,3-dichloropyridine. During ...

AI Technical Summary

Problems solved by technology

During the chlorination reaction of the 2-position of the pyridine ring by 3-aminopyridine and hydrogen peroxide, a side reaction of chlorination of the 6-position of the pyridine ring will occur. Exhaust emissions

Although the method disclosed in the Chinese patent document of CN102432528A has simple process and high yield, hydrogen gas is used in the reaction process, which has potential safety hazards, and the metal catalysts are mostly noble metals, and the cost is relatively high

Although the method of catalytic transfer hydrogenation in the Chinese patent document of CN103145609A has avoided the potential safety hazard caused by the use of hydrogen, and the process is simple and the yield is high, but the metal catalyst is palladium, and the cost is still relatively high