Preparation Of Tetrafluorobenzoic Alcohol Derivative

Tetrafluorobenzoic alcohol derivatives such as 2,3,5,6-tetrafluoro-1,4-be -nzenedimethanol,2,3,5,6-tetrafluorobenzyl alcohol,2,3,5,6-tetrafluoro-4-met -hoxymethyl-benzenemethanol,2,3,5,6-tetrafluoro-4-methoxy-benzenemetha -nol which are key intermediate of fluorine containing pyrethroids have a broad application prospect and research value for that pyrethroids are one kind of effective synthetic pesticides, which have been widely used in agriculture and public health. Main conclusions made in this paper were listed as follows:1. 2,3,5,6-tetrafluoro-1,4-benzenedimethanol was prepared from 2,3,5,6-tetro -fluoroterepht halnitrile by hydrolyzation,(esterification),reduction. The system of sulfuric acid-acetic acid and sulfuric acid-water was studied separately.Through the study of single factor and orthogonal experiment, the optimum synthesis conditions were obtained: the density of sulfuric acid was 60%, reaction temperature was about 140℃and reaction time was about 7h, under which the yields of 2,3,5,6-tetrofluoroterephthalic acid could reach 87.4%. 2,3,5,6-tetrafluoro-1,4-benzenedimethanol was prepar -ed by reduction of 2,3,5,6-tetrafluoroterephthalic acid dimethyl ester with KBH4/PEG400. Moreover, the method that 2,3,5,6-tetrafluoro-1,4-benzene -dimethanol was prepared by reduction of 2,3,5,6-tetrafluoroterephthalic acid and reaction with dimethyl sulfate in 1,2-dimethoxyethane was also studied. The single crystals of 2,3,5,6-tetrachloroterephthalic acid were determined.2. 2,3,5,6-tetrafluoro-1,4-benzenedimethanol in the hydrobromic acid (hydrochloric acid)-toluene system gave 4-(bromomethyl)-2,3,5,6-tetrafluo -robezenemethanol(4-(chloromethyl)-2,3,5,6-tetrafluorobenzenemethanol), which were hydrogenolysis under the effect of catalyst, and to gained 4-methyl-2,3,5,6-tetrafluorobenzenemethanol. Through the study of single factor and orthotropic experiment, reactive temperature was about 95℃, the ratio of hydrobromic acid and 2,3,5,6-tetrafluoro-1,4-benzenedimeth -anol was 1.4 (mol ratio) and the catalysts were existed and the reaction time was about 6h, under which the yields of 4-methyl-2,3,5,6-tetra -fluorobenzenemethanol could reach 90%. The effects of all factors to reaction were studied and the yields of 4-methyl-2,3,5,6-tetrafluorobenzene -methanol could reach 80% under the optimum condition.3. 2,3,5,6-tetrafluorobenzyl alcohol was prepared from 2,3,5,6-tetrofluorotere -phthalonitrile by hydrolyzation, decarboxylation, reduction.The mechanic -sm of decarboxylation was studied Decarboxylation of 2,3,5,6-tetrafluoro -terephthalic acid in the presence of DMSO and water was studied separately. The effects of all factors to reaction were studied by single factor experiment.Furthermore, 2,3,5,6-tetrafluorobenzoic acid was prepar -ed from 2,3,5,6-tetrofluoroterephthalonitrile with sulfuric acid as catalyst. The result of the orthogonal experiment was analyzed by STATISTICA6.0. 2,3,5,6-tetrofluoroterephthalonitrile and water ( molar ratio: 0.002) reacted at 180℃for 7.0 h with 50.0% catalyst and the yield of 2,3,5,6-tetrafluoro -benzoic acid was above 98%. The method that 2,3,5,6-tetrafluorobenzyl -alcohol was prepared by reduction of 2,3,5,6-Tetrafluorobenzoic acid and reaction with dimethyl sulfate in 1,2-dimethoxyethane was also studied.4. 2,3,5,6-tetrafluoro-4-methoxymethyl-benzenemethanol was prepared from 2,3,5,6-tetrafluoro-1,4-benzenedimethanol by indirect etherification and direct etherification separately in good yield.5. According to the different solubility of raw material and product in toluene, added toluene into 2,3,5,6-tetrafluoro-1,4-benzenedimethanol/HBr system and 2,3,5,6-tetrafluoro-4-methoxymethyl-benzenemethanol/NaOH system to impel the reaction to carry on which has realized the opposition shift reaction.