Hydrochloric Acid → (2,3,4,5-Tetrafluoro-6-methylphenyl)methanol

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A solution of methyl bromide (9.6 g) in dry tetrahydrofuran (25 cm3) was added dropwise in a stirred mixture of magnesium turnings (5.0 g), dry tetrahydrofuran (50 cm3) and a small crystal of iodine at the ambient temperature (ca. 22° C.). When the addition was complete the mixture was stirred for a further 1 hour at the ambient temperature and the solution of methyl magnesium bromide thus formed was then added dropwise to a stirred solution to pentafluorobenzyl alcohol (17.8 g) in tetrahydrofuran (50 cm3) whilst the temperature was maintained at 30° C. When the addition was complete the mixture was stirred for a further 2 hours at the ambient temperature and for 3 hours at the reflux temperature. Water at 0° C. was added to the mixture, which was then acidified with dilute hydrochloric acid and extracted with diethyl ether (2×80 cm3). The extracts were combined, washed with water, dried over anhydrous magnesium sulphate and concentrated by evaporation of the solvent under reduced pressure. The residual oil (4.6 g) was shown by gas liquid chromatographic examination of a sample to consist of ca. 70% by weight of unreacted starting material and ca. 30% by weight of product. The oil was subjected to vigorous purification by column and thin-layer chromatography using a silica gel support and eluting with a mixture of diethyl ether and hexane (3:7 by volume), to obtain 2-methyl-3,4,5,6-tetrafluorobenzyl alcohol as a colourless oil.

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