[CH2:1]([O:7][C:8]1[C:13]([F:14])=[C:12]([F:15])[CH:11]=[C:10]([F:16])[C:9]=1[F:17])[CH2:2][CH2:3][CH2:4][CH2:5][CH3:6].C([Li])CCC.CCCCCC.[C:29](=[O:31])=[O:30].Cl>C1COCC1>[CH2:1]([O:7][C:8]1[C:9]([F:17])=[C:10]([F:16])[C:11]([C:29]([OH:31])=[O:30])=[C:12]([F:15])[C:13]=1[F:14])[CH2:2][CH2:3][CH2:4][CH2:5][CH3:6]27.5 g of the compound (4) dissolved in 250 mL of THF were cooled at −78° C. in an argon atmosphere; thereto were then dripped 82 mL of a 1.6 M/L n-butyllithium/hexane solution, with stirring for 2 hours at the same temperature. After addition of a suitable amount of crushed dry ice, the temperature was raised to room temperature, followed by stirring overnight. 200 mL of 3N hydrochloric acid were then added under ice cooling, the organic layer was separated, and the aqueous layer was extracted with diethyl ether. The organic layers were combined, were washed with saturated brine, and were then dried over anhydrous magnesium sulfate. After evaporating the solvent, the organic layer was recrystallized from hexane to yield 25.9 g (88 mmol) of 4-hexyloxy-2,3,5,6-tetrafluorobenzoic acid (5).
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