Method for synthesizing pyraclostrobin intermediate

Abstract

The invention discloses a method for synthesizing a pyraclostrobin intermediate. The synthetic method comprises the following steps: preparing an intermediate 1-(4-chlorophenyl)-3-hydroxy-1-h-pyrazole from 4-chlorophenylhydrazine hydrochloride prepared with p-bromochlorobenzene and hydrazine hydrate as reaction raw materials; reacting o-nitrotoluene with chlorine in the presence of a catalyst so as to prepare o-nitrobenzyl chloride; and subjecting 1-(4-chlorophenyl)-3-hydroxy-1-h-pyrazole and o-nitrobenzyl chloride to an etherification reaction so as to obtain the pyraclostrobin intermediate, i.e., an etherification product 2[(N-4-chlorophenyl)-3-pyrazolyl-oxymethyl]nitrobenzene. The synthetic method provided by the invention can greatly reduce the amount of waste water produced in the synthesis process of 4-chlorophenylhydrazine hydrochloride; with 4-chlorophenylhydrazine hydrochloride as a raw material, the produced intermediate 1-(4-chlorophenyl)-3-hydroxy-1-h-pyrazole has HPLC content of no less than 98% and yield of no less than 90%; since chlorine is used for replacing bromine or hydrobromic acid to prepare o-nitrobenzyl bromide, production cost and environmental protection burden are controlled; and the etherification product with a content of no less than 98% and yield of no less than 90% is obtained.

Description

technical field [0001] The present invention is a method for synthesizing pyraclostrobin intermediate, in particular to pyraclostrobin intermediate 2-[(N-4-chlorophenyl)-3-pyrazolyloxymethyl]nitrobenzene The synthetic method of the invention belongs to the synthetic field of organic compounds. Background technique [0002] Pyraclostrobin is an effective broad-spectrum fungicide, and 2-[(N-4-chlorophenyl)-3-pyrazolyloxymethyl]nitrobenzene is used as an important synthetic intermediate in its synthesis process. The body can be prepared by reacting o-nitrobenzyl bromide with 1-(4-chlorophenyl)-3-pyrazolol. For example, as described in the patent document CN104592117A (a synthetic method of pyraclostrobin, 2015.05.06), p-chlorophenylhydrazine hydrochloride prepared from p-chloroaniline through diazotization, reduction and other steps , 1-(4-chlorophenyl)-3-pyrazolol is obtained by cyclization reaction and oxidation reaction, and then, o-nitrotoluene, bromination reagent, etc. ...

AI Technical Summary

Problems solved by technology

[0004] 1) p-Chlorophenylhydrazine hydrochloride is usually obtained by diazotization, sodium bisulfite reduction, and hydrolysis of p-chloroaniline. In the production process, a large amount of acid and sulfite will be used, and a huge amount of waste water will be generated There are potential safety hazards in the diazotization and reduction process. The concentration of diazonium salts cannot be high, otherwise the dangerous performance of production will be improved. The sulfite used in the reduction process will produce sulfur dioxide gas as a by-product. With the increasing awareness of green production and the increasing safety requirements, the problems of safety and three wastes have become the most restrictive conditions for the production of hydrazine by diazotization;

[0005] 2) In the existing synthesis methods of o-nitrobenzyl bromide, there are several important disadvantages, the most important of which are that bromine sources such as bromine or hydrobromic acid are expensive, inconvenient to transport, and there are environmental assessments such as the recovery of bromine sources skills requirement

There are two main synthetic methods: thermal chlorination method and illumination method ("Hubei Chemical Industry", No. 4, 1997, "New Technology for Synthesis of O-nitrobenzyl Chloride"). Among them, the thermal chlorination method has a low yield and generally Yield less than 5%

On the one hand, the light chlorination method is inconvenient to use light, and on the other hand, there are many by-products, and the reaction effect is not good. Therefore, at present, there is still no effective synthetic method with low cost and economic applicability for o-nitrobenzyl chloride.