The Synthesis of 2-amino-4-chloro-benzothiazole

Abstract: 2-amino-4-chloro-benzothiazile is one of important intermediates in medicine, dyestuff, pesticide, herbicide and so on. Synthesis of this kind compounds are always been concerned. It is applied to the synthesizing of benazolin-ethyl in the herbicide field.This paper reviewed the status of herbicides at home and abroad, the research of benazolin-ethyl was introduced, and the synthesis process of 2-amino-4-chloro-benzothiazile was studied. the intermediate product 2-chloropheny-thiourea was synthesized from o-chloroaniline and ammonium thiocyanate. The target product 2- amino-4-chloro-benzothiazole was synthesized from 2-chloropheny-thiourea together with sodium bromide and concentrated sulfuric acid. Conditions like the ratio of raw materials, reaction temperature and time were investigated. In order to get higher yield, the optimization of the reactions was investigated.Therefore, the optimum conditions have been worked out, the period of 2-chloropheny-thiourea reation:n(o-chloroaniline): n(ammonium thiocyanate): n(hydrochloric acid): V(water)=1(mol): 1.25(mol): 1.2(mol):30(mL), reaction time and temperature is 2h(65℃)、4h(75℃)、6h(85℃), the average yield of 2-chloropheny-thiourea was 86.1%. the period of cyclization reaction : n(2-chloropheny-thiourea): n(concentrated sulfuric acid): n(sodium bromide)=1: 4.8(mol): 0.2(mol), reaction time is 5h at a 75℃temperature, the average yield of 2- amino-4-chloro-benzothiazole can reach 75.7%.
Key words: 2-amino-4-chloro-benzothiazole; 2-chloropheny-thiourea; synthesize process;

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