Method for synthesizing 1-(2,4-dichlorophenyl)-3-methyl-4-difluoromethyl-1,2,4-triazole-5-ketone

Abstract

The invention discloses a method for synthesizing 1-(2,4-dichlorophenyl)-3-methyl-4-difluoromethyl-1,2,4-triazole-5-ketone. The method comprises the following steps: with o-chloroaniline as a raw material, carrying out diazotization, reduction and salification so as to synthesize o-chlorophenylhydrazine hydrochloride, carrying out alkali neutralization so as to prepare free o-chlorophenylhydrazine, subjecting o-chlorophenylhydrazine, acetaldehyde, sodium cyanate and sodium hypochlorite to condensation, cyclization and oxidation reactions so as to generate 1-o-chlorophenyl-3-methyl-1H-1,2,4-triazole-5-ketone, subjecting 1-o-chlorophenyl-3-methyl-1H-1,2,4-triazole-5-ketone to salification, potassium fluorination and chlorination reactions so as to obtain 1-(2,4-dichlorophenyl)-3-methyl-4-difluoromethyl-1,2,4-triazole-5-ketone (a sulfentrazone intermediate). The synthetic method provided by the invention uses o-chloroaniline as the raw material, can synthesize an intermediate with small steric hindrance and few impurities, improves the yield, has the advantages of easily-available and cheap raw materials, mild reaction, simple and convenient operation and high safety, and facilitatesindustrial production.

Description

technical field [0001] The invention relates to the technical field of herbicide preparation, specifically a method for synthesizing 1-(2,4-dichlorophenyl)-3-methyl-4-difluoromethyl-1,2,4-triazole-5- The keto approach. Background technique [0002] Sulfentrazone is a herbicide belonging to difluoromethyltriazolinones, which has the characteristics of high efficiency, low toxicity and broad spectrum. 1-(2,4-dichlorophenyl)-3-methyl- 4-Difluoromethyl-1,2,4-triazol-5-one is an important intermediate in the synthesis of sulfentrazone, and its chemical structure is as follows: [0003] [0004] At present, most manufacturers use phenylhydrazine as the starting material to synthesize 1-phenyl-3-methyl-4-difluoromethyl-1,2,4-triazol-5-one, and then in the benzene ring The above two chlorines generate intermediates, but this method requires secondary chlorination, the two chlorines on the benzene ring are more difficult, the impurities are high, and the yield is low; in additio...

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Problems solved by technology

The beneficial effects of the present invention are reflected in the use of o-chlorophenylhydrazine hydrochloride, which makes the steric hindrance of the intermediate product small and the yield high, but there are certain shortcomings in this method. The free o-chlorophenylhydrazine needs to be extracted with dichloromethane, and the The boiling point of methane is low, the recovery loss is large, and the cost is increased. The price of trimethyl orthoacetate and potassium cyanate used in cyclization is relatively high, and the chlorination reaction requires a composite catalyst, and the catalyst recovery operation is complicated.

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