Study On The Preparation Of The Herbicide Of Fluo-Substituted Diphenyl Ethers

(S)- 1-(ethoxycarbonyl)ethyl-5-(2-chloro-4-trifluoromethylphenoxy)-2-Chlorobenzoate(Ethoxyfen-ethyl for the trade name)is first prepared by BUDAPEST in 1988.As a diphenyl ether herbicide with trifluoromethyl group,it enjoys the following advantages:higher purity,higher yield,lower cost and the better safety,used in controlling or killing broadleaf in post-emergency for cereal crops.The traditional way to prepare (S)-1-(ethoxycarbonyl)ethyl-5-(2-chloro-4-trifluoromethylphenoxy)-2-chlorobenzoate, using 1,2-dichloro-4-(trifluoromethyl)benzene and 3-hydroxy benzoic acid as original material,was optimized.The effect of kinds of solvent,molar ratio of catalyst,reaction temperature and reaction time on chlorination reaction is investigated.The optimized reaction conditions are 1,2-dichloroethane as solvent and the ratio of catalyst AlCl₃ to FeCl₃ is 2.4:1,reaction temperature 50℃and reaction time 10h,the yield reaches 84.0%.The effect of different kinds of solvent,reaction temperature on acylation reaction is investigated.The optimized reaction conditions were: toluene as solvent and reaction time 2h.The highest yield is 95.0%.The effect of different kinds of acid absorbent,reaction time on esterification reaction is investigated.The optimized reaction conditions were:triethylamine as acid absorbent and reaction time 2h.The yield reaches 88.4%.All synthesized products and intermediates are characterized by ¹H-NMR and 1R.In our work,we investigate a new way to prepare ethoxyfen-ethyl,using 1,2-dichloro-4-trifluoromethylbenzene and 4-chloro-3-methylphenol as original materials.The new process of 5-(2-chloro-4-trifluoromethyl phenoxy)-2-chlorobenzoic acid is carried out using potassium permanganate as oxidant.High optical pure ethoxyfen-ethyl is obtained and each step is optimized.The new process of the preparation of ethoxyfen-ethyl includes:1) Using 1,2-dichloro-4-trifluoromethylbenzene and 4-chloro-3-methylphenol as original material,4-(2-chloro-4-trifluoro-methylphenoxy)-1-chloro-2-methylbenzene is obtained by condensation;2) 5-(2-chloro-4-trifluoromethylphenoxy)-2-chlorobenzoic acid is obtained from oxidizing 4-(2-chloro-4-(trifluoromethyl)phenoxy)-1-chloro-2-methylbenzene; 3)Ethoxyfen-ethyl is obtained by esterification.The effect of different ways of reaction,molar ratio of raw materials,and reaction temperature on the first step is investigated.The optimized reaction conditions are:1, 2-dichloroethane as solvent,toluene as water carrier,n(AlCl₃:FeCl₃)=2.4:1, reaction temperature 130-140℃and reaction time 10h.The yield reaches 90.7%.The effect of the different ways of oxidation,pH value,different solvent and catalysts,reaction temperature on the second step is investigated. The optimum reaction conditions are:KMnO₄ as oxidant,pH value of 7-8, V_H2O:V_C5H5N=1:1 and reaction time 2h,The yield reaches 40.1%.