C([Li])[CH2:2][CH2:3][CH3:4].Br[C:7]1[CH:20]=[CH:19][C:10]2[O:11][C:12]([F:18])([F:17])[C:13]([F:16])([F:15])[O:14][C:9]=2[C:8]=1[CH3:21].[CH2:22]([O:24]CC)C.Cl>O>[F:17][C:12]1([F:18])[O:11][C:10]2[CH:19]=[CH:20][C:7]([CH:22]([OH:24])[CH:3]([CH3:2])[CH3:4])=[C:8]([CH3:21])[C:9]=2[O:14][C:13]1([F:16])[F:15]Under nitrogen atmosphere, 7.8 ml of n-butyllithium (1.57 M-n-hexane solution) was dropwise added at −50° C. to a mixture comprising 3.36 g of 6-bromo-2,2,3,3,-tetrafluoro-5-methyl-1,4-benzodioxane and 40.6 ml of ethyl ether, and then the mixture was stirred at the same temperature for 30 minutes. 0.89 g of isobutylaldehyde was dropwise added thereto at a temperature of at most −70° C., and the temperature was raised to room temperature followed by a reaction for 15 hours. After completion of the reaction, the reaction mixture was put into water, and then weakly acidified by an addition of hydrochloric acid. Then the mixture was extracted with ether, and the extract was washed with water and dried over magnesium sulfate, followed by concentration under reduced pressure. The obtained residue was purified by silica gel column chromatography (eluent: ethyl acetate/n-hexane=1/9) to obtain 1.90 g of oily 1-(2,2,3,3,-tetrafluoro-5-methyl-1,4-benzodioxan-6-yl)-2-methylpropanol. The NMR spectrum data of this product were as follows.
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