Niu Wen-bo
2011
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Journal
Journal of Hebei University of Technology
Abstract
3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylic acid(Ⅴ) is an important intermediate of chlor-antraniliprole which is a new insecticide.3-Chloro-2-hydrazine pyridine(Ⅰ) was synthesized from 2,3-dichloropyridinevia nucleophilic substitution with aqueous hydrazine.2-(3-Chloro-2-pyridinyl)-5-oxo-3-pyrazolidine carboxylate(Ⅱ)was synthesized fromⅠvia cyclization with diethyl maleate.Ethyl 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylate(Ⅲ) was obtained from Ⅱ through bromination with phosphorus oxybromide.Ethyl 3-bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylate(Ⅳ) was obtained from Ⅲ through dehydrogenation with potassiumpersulfate.Ⅴ was obtained from Ⅳ via hydrolysis.The overall yield of product was 41.3%.The synthesis method withphosphorus oxybromide as bromination agent is better than that with 4-methyl benzene sulfonyl chloride and hydrogenbromide.Due to simple experimental operation and fast reaction,the impurities remain in aqueous layer via extraction,which helps improve the product yield and purity.The product and intermediates structure were characterized by 1H NMR spectrometry.