Preparation method of 2,3-dichloropyridine

Abstract

The invention discloses a preparation method of 2,3-dichloropyridine, and aims to solve the problems that a large amount of triethylamine hydrochloride is generated in a reaction process to wrap a palladium-carbon catalyst when a toluene solvent and triethylamine are used as acid binding agents during the preparation of 2,3-dichloropyridine by an existing 2,3,6-trichloropyridine catalytic dechlorination method, so that the activity of the catalyst is not high, the dosage of the catalyst is large, and the reaction selectivity is still not high. In the preparation method provided by the invention, methanol is used as a solvent, the palladium-carbon catalyst with a high water content has good dispersibility in methanol, and the dosage of the palladium-carbon catalyst can be effectively reduced; magnesium hydroxide is used as an acid binding agent, the generated magnesium chloride can be dissolved in methanol, a homogeneous system appears at the later stage of the reaction, and the problemof wrapping the catalyst is avoided; and formic acid is selected as a buffer agent to ensure that formic acid preferentially reacts with magnesium hydroxide to generate magnesium formate dissolved inmethanol, magnesium formate reacts with hydrogen chloride generated in the reaction to generate formic acid and magnesium chloride, and the formic acid realizes a catalytic cycle. The reaction selectivity in the preparation method provided by the invention reaches 85-90% and the yield reaches 87%.

Description

technical field [0001] The invention relates to the field of organic synthesis, in particular to a preparation method of 2,3-dichloropyridine. The present invention selects methanol as a solvent, uses magnesium hydroxide as an acid-binding agent, increases the reaction selectivity from 75-80% of the prior art to 85-90%, greatly improves the yield, and has higher application value and better performance. application prospects. Background technique [0002] 2,3-Dichloropyridine is an important fine chemical intermediate, which is mainly used in the preparation of chlorantraniliprole insecticides. The synthesis methods of 2,3-dichloropyridine mainly include: 1) chlorination of 3-aminopyridine after chlorination, and 2) dechlorination of 2,3,6-trichloropyridine. Because 2,3,6-trichloropyridine raw materials are easy to get, catalytic dechlorination to prepare 2,3-dichloropyridine atom economy is high; therefore, 2,3- Dichloropyridine has become a research hotspot and has attr...

AI Technical Summary

Problems solved by technology

It has been determined that the reaction selectivity of the present invention is as high as 85-90%. However, when the method of patent CN102153507A is used to prepare 2,3-dichloropyridine, a toluene solvent is used, and triethylamine is used as an acid-binding agent, and a large amount of triethylamine will be generated during the reaction. Ethylamine hydrochloride encapsulates the palladium carbon catalyst, resulting in low catalyst activity, large catalyst consumption, and still low reaction selectivity. A preparation method for 2,3-dichloropyridine is provided