3-溴-1-(3-氯-2-吡啶基)-1H-吡唑-5-甲酸(V)是合成新型杀虫剂氯虫苯甲酰胺的重要中间体.以2,3-二氯吡啶为起始原料,与水合肼亲核取代制得3-氯-2-肼基吡啶(Ⅰ),Ⅰ与马来酸二乙酯环合制得2-(3-氯-2-吡啶基)-5-氧-3-吡唑烷甲酸乙酯(Ⅱ),Ⅱ经三溴氧磷溴代制得3-溴-1-(3-氯-2-吡啶基)-4,5-二氢-1H-吡唑-5-甲酸乙酯(Ⅲ),Ⅲ经过硫酸钾脱氢制得3-溴-1-(3-氯-2-吡啶基)-1H-吡唑-5-甲酸乙酯(Ⅳ),Ⅳ经水解制得目标物V,总收率41.3％.以三溴氧磷作为溴代试剂,实验操作简单,反应迅速,后处理萃取操作可以将杂质全部留在水相,大大提高产品收率和纯度,优于以对甲基苯磺酰氯酯化和溴化氢溴化的制备方法.产品及中间体经1HNMR确证.%3-Bromo-1- (3-chloro-2-pyridinyl) -1H-pyrazole-5-carboxylic acid (V) is an important intermediate of chlorantraniliprole which is a new insecticide. 3-Chloro-2-hydrazine pyridine (I) was synthesized from 2,3-dichloropyri-dine via nucleophilic substitution with aqueous hydrazine. 2- (3-Chloro-2-pyridinyl) -5-oxo-3-pyrazolidinecarboxylate (II) was synthesized from I via cyclization with diethyl maleate. Ethyl 3-bromo-l- (3-chloro-2-pyridinyl) -4,5-di-hydro-1H-pyrazole-5-carboxylate (III) was obtained from II through bromination with phosphorus oxybromide. Ethyl 3-bromo-l- (3-chloro-2-pyridinyl) -1H-pyrazole-5-carboxylate (IV) was obtained from HI through dehydrogenation with potassium persulfate. V was obtained from IV via hydrolysis. The overall yield of product was 41.3%. The synthesis method with phosphorus oxybromide as bromination agent is better than that with 4-methyl benzene sulfonyl chloride and hydrogen bromide. 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.
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