[F:1][C:2]([F:19])([F:18])[C:3]1[CH:4]=[C:5]2[C:10](=[O:11])[N:9]([CH2:12][CH:13]([CH3:15])[CH3:14])[C:7](=[O:8])[C:6]2=[CH:16][CH:17]=1.O>CO.[BH4-].[K+]>[F:18][C:2]([F:1])([F:19])[C:3]1[CH:4]=[C:5]2[C:6]([CH:7]([OH:8])[N:9]([CH2:12][CH:13]([CH3:14])[CH3:15])[C:10]2=[O:11])=[CH:16][CH:17]=1.[F:18][C:2]([F:1])([F:19])[C:3]1[CH:4]=[C:5]2[C:6](=[CH:16][CH:17]=1)[C:7](=[O:8])[N:9]([CH2:12][CH:13]([CH3:14])[CH3:15])[CH:10]2[OH:11]5-Trifluoromethyl-3-hydroxy-2-isobutyl-2,3-dihydroisoindol-1-one and 6-trifluoromethyl-3-hydroxy-2-isobutyl-2,3-dihydroisoindol-1-one are prepared as described in Example 1, starting with 14.9 g of 4-trifluoromethyl-N-isobutylphthalimide in 300 cm3 of methanol and 2.96 g of potassium borohydride. The reaction mixture is stirred at a temperature in the region of 20° C. for 16 hours and then cooled to a temperature in the region of 0° C. and 100 cm3 of distilled water are added dropwise. The methanol is then partially evaporated off under reduced pressure (2 kPa) at a temperature in the region of 40° C. The aqueous phase is extracted 3 times with 200 cm3 of ethyl acetate. The organic extracts are combined, washed with 300 cm3 of saturated sodium chloride solution, dried over magnesium sulfate, filtered and then concentrated to dryness under reduced pressure (2 kPa) at a temperature in the region of 40° C. 12.07 g of 5-trifluoromethyl-3-hydroxy-2-isobutyl-2,3-dihydroisoindol-1-one and 6-trifluoromethyl-3-hydroxy-2-isobutyl-2,3-dihydroisoindol-1-one are thus obtained in the form of a white powder. (Rf=0.64, thin layer chromatography on silica gel, eluent: cyclohexane/ethyl acetate (50/50 by volume)).
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