Method for preparing 3,5,6-trichloropyridin-2-ol sodium by improved one pot process

Abstract

The invention discloses a method for preparing 3,5,6-trichloropyridin-2-ol sodium by an improved one pot process. The method comprises: undergoing a backflow reaction with trichloro-acetic chloride and vinyl cyanide in an inertia organic solvent, in the presence of a copper catalyst or a cuprous salt catalyst, when the content of butyryl chloride is detected to be the highest by gas spectrum, adding 2,2,4-trichloro-4-cyanobutanoyl chloride, simultaneously reducing the temperature, and undergoing a cyclization reaction for 2-5 h; and pumping and filtering to obtain a filtrate, reducing the temperature of the filtrate, adding sodium hydroxide solution to undergo an aromatization reaction, and reducing the temperature and pumping and filtering to obtain a crude product of sodium alkoxide. The method has the advantages of: adding a pure addition product obtained by a fractional step process in a later stage of the one pot process, catalyzing the cyclization reaction by HCl generated by the one pot process, and simultaneously reducing the temperature of the cyclization reaction, and allowing the process to be easily controlled. A substrate concentration is increased, the conventional cyclization yield is substantially improved, and thus the sodium alkoxide yield is improved.

Description

technical field [0001] The invention relates to a method for preparing sodium 3,5,6-trichloropyridin-2-alcohol. Background technique [0002] 3,5,6-trichloropyridin-2-ol sodium is an important intermediate in the synthesis of insecticides chlorpyrifos, chlorpyrifos-methyl and herbicide triclopyr. The synthesis reaction conditions of sodium alkoxide are harsh, the technical difficulty is high, and the production cost is high, which are the main factors affecting the production capacity and cost of downstream products. At present, the more economical and feasible route for industrially synthesizing sodium alkoxide is the trichloroacetyl chloride method. The main disadvantage of this method is that the sodium alkoxide content and the yield are not ideal, and the general yield is not more than 65%. [0003] The trichloroacetyl chloride method can be further divided into "one pot method" and step-by-step method. Chinese patent 02157262.3 adopts the "one pot method" to produce ...

AI Technical Summary

Problems solved by technology

Chinese patent 02157262.3 adopts "one pot method" to produce sodium alkoxide, the reaction process is short, but the content of by-product tetrachloropyridine is high and the yield of sodium alkoxide is only about 65%.

Dow’s patent 90102727.8 uses a step-by-step method to produce sodium alkoxide, which hardly produces tetrachloropyridine, but it needs to pressurize and feed HCl gas during the cyclization process, which corrodes the equipment and increases the difficulty of operation, which is not conducive to the health of personnel and industrial production

CN 200610038271.1 The pure addition product 2,2,4-trichloro-4-cyanobutyryl chloride can be obtained by a step-by-step method, and the cyclization reaction is carried out by adding HCl gas controlled release agent, but the process is violent and easy to flush , difficult to control, low operability