Method for preparing 2,6-dichloro benzoxazole

Abstract

The invention relates to a method for preparing 2, 6-dichlorobenzoxazole, adopting 6-chlorine-2-mercaptobenzoxazole and trichloromethyl chloroformate to synthesize 2, 6-dichlorobenzoxazole under the action of catalyst. The method comprises the following concrete steps that: the 6-chlorine-2-mercaptobenzoxazole, dimethylformamide as catalyst and toluene as medium solvent are added to a reaction vessel with the temperature controlled to be between 40 and 70 DEG C; trichlorome-thylchloroformate is added in drops for 4-8 hours; after drop adding is completed, the materials are heated to between 60 and 100 DEG C, react for 1-4 hours and are cooled, and then a toluene solution of the 2, 6-dichlorobenzoxazole is obtained. The method replaces gaseous phosgene, chlorine or phosphorus pentachloridewith the trichloromethyl chloroformate; during reaction, the trichloromethyl chloroformate is decomposed into single phosgene to participate in the reaction, and then the target object 2, 6-dichlorobenzoxazole is obtained through the reaction. The method does not need to separate the product from the solvent, is simple and convenient to operate, high in product yield, which can reach over 98 percent, pale in product color, excellent in product quality and low in equipment requirements, and does not need tail gas treatment.

Description

Technical field [0001] The invention relates to a synthesis method of an agricultural herbicide intermediate, in particular to a preparation method of 2,6-dichlorobenzoxazole. It belongs to the field of organic synthesis technology. Background technique [0002] Fenoxaprop-p-ethyl is a novel heterocyclic herbicide of phenoxycarboxylic acid. It has the characteristics of high efficiency, low toxicity and low environmental pollution. Fenoxaprop-p-ethyl has a good control effect on crops such as wheat, rye and other crops such as gramineous weeds, such as wheat nipples, wild oats, and setaria. 2,6-Dichlorobenzoxazole is an intermediate of fine oxadifen and also an important pesticide and pharmaceutical intermediate. Its English name is 2,6-DichLorobenzoXazo1e. The structural formula is: [0003] [0004] At present, the synthesis methods of this product mainly include: [0005] 1. The reaction between 6-chloro-2-mercaptobenzoxazole and phosgene, the reaction mechanism is: [0006] ...

AI Technical Summary

Problems solved by technology

[0010] The main defect of this method is: there are many side reactions, which will produce a chain reaction, thus forming Product yield is low, the highest can only reach 90%

[0013] The main disadvantages of this method are: phosphorus oxychloride by-products are produced, which increases the difficulty of separation, and the product needs to be distilled at high temperature and high vacuum, resulting in low product yield and high requirements for high vacuum equipment.

[0014] The above three methods all have the commonality of low product yield and low quality, and complicated operation

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