Synthesis And Improvement On Process Of Tefluthrin

The synthesis of tefluthrin, which is a kind of pyrethroid pesticide, was studied in this paper. The synthetic process of the tefluthrin and the 4-methyl-2,3,5,6-tetrafluoro- benzyl alcohol, an important intermediate for tefluthrin, were improved. 4-Methyl- 2,3,5,6-tetrafluoro-benzyl alcohol was synthesized by acylation, fluorination, esterification, reduction, bromization and reduction from tetracloro-terephthalic acid. Tefluthrin was obtained from (Z)-(1RS, 3RS)-3-(2-chloro-3,3,3-trifluoro-1- propenyl)-2,2-dimethyl cycolpropanecarboxylate acid by reacting with 4-chlormethyl- 2,3,5,6-tetrafluorotoluol which was prepared from 4-methyl-2,3,5,6-tetrafluoro-benzyl alcohol.The reactions of bromization and reduction in the synthetic process were studied. Tetrafluoroterephthalyl alcohol was bromated in the hydro-bromic acid to obtain (4-(bromomethyl)-2,3,5,6-tetrafluorophenyl)methanol. With toluene sa solvent, the amount of hydrobromic acid decreased from ten times of the mol of tetrafluoroterephthalyl alcohol to five times and the yield increased from 88.13% to 90.07%. 4-Methyl-2,3,5,6-tetrafluoro-benzyl alcohol was obtained by reducing the bromide with magnesium and methanol. By replacing mathanol with dichloromethane as solvent, the amount of magnesium decreased to one fourth of that in former method and the yield increased from 78% to 96%.A new route of tefluthrin was designed. 4-Methyl-2,3,5,6-Tetrafluorobenzyl chloride was prepared from 4-methyl-2,3,5,6-tetrafluoro-benzyl alcohol and the yield was 91.86%. Then tefluthrin was achieved by the substituted reaction of 4-methyl-2,3,5,6- tetrafluoro-benzyl chloride and (Z)-(1RS,3RS)-3-(2-chloro-3,3,3-trifluoro-1-propenyl) -2,2-dimethyl cycolpro-panecarboxylate acid. The overall yield increased from 52.94% to 60.10%. Thus, an appropriate route to synthesize tefluthrin for industrializing was obtained.