Study On The Synthesis Of Tefluthrin

The synthesis of tefluthrin, which is a pesticide, was studied in this paper. The synthetic technology of 4-methyl-2,3,5,6-tetrafluorobenzene methanol, an important intermediate of tefluthrin, was improved in this paper. 4-methyl-2,3,5,6-tetrafluoro-benzene methanol was synthesized by chlorination, acylation, fluorination, esterifica- tion, reduction, bromization, reduction from terephthalic acid. Tefluthrin was obtained from (Z)-(1RS,3RS)-3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl cycolpropa-necarboxylate acid by reacting with 4-methyl-2,3,5,6-tetrafluoro-benzene methanol. Tetrachloroterephthalic acid was prepared by chlorinating terephthalic acid, oleumsolvent and iodine catalyst. Tetrachloroterephthalic acid was acylated by sulphurous oxychloride in the presence of DMF to form tetrachloroterephthaloyl chloride. The acyl chloride product was fluorinated by potassium fluoride and esterified by methanol to synthesize dimethyl tetrafluoroterephthalate. The ester was reduced with potassium borohydride and lithium chloride to give tetrafluoroterephthalyl alcohol. The above product was bromated in the hydrobromic acid to obtain 4-bromomethyl-2,3,5,6-tetrafluoro-benzene methanol. 4-Methyl-2,3,5,-6-tetrafluorobenzene ethanol was obtained by reducing the bromide with magnesium. In the exist of DCC and DMAP, tefluthrin was got by the condensation reaction between 4-methyl-2,3,5,6-tetrafluoro-benzene methanol and (Z)-(1RS,3RS)- 3-(2- chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl cycolpropanecar-boxylate acid. The overall yield was 43.6%.The yield of reduce of ester was increased nearly one times than the past method because of KBH4-LiCl as the reducing agent instead of NaBH4. Changing the reaction conditions of bromization, the one-way yield enhanced 30%. The yield of reduce of the bromide was added by one times by improving the process. Tefluthrin was achieved by the catalytic esterification of DCC and DMAP. Thus, an appropriate industrializing route to synthesize tefluthrin was obtained.