Br[CH:2]1[CH:7]([Br:8])[C:6]2[CH:9]=[C:10]([C:13]([F:16])([F:15])[F:14])[CH:11]=[CH:12][C:5]=2[O:4][C:3]1([CH2:19][F:20])[CH2:17][F:18].[OH-].[Na+].Cl>O1CCOCC1>[Br:8][C:7]1[C:6]2[CH:9]=[C:10]([C:13]([F:16])([F:15])[F:14])[CH:11]=[CH:12][C:5]=2[O:4][C:3]([CH2:17][F:18])([CH2:19][F:20])[CH:2]=1A mixture of 3,4-dibromo-2,2-bis(fluoromethyl)-6-trifluoromethyl-3,4-dihydro-2H-1-benzopyran (10.72 g), a 2 N aqueous solution of sodium hydroxide (60 ml) and dioxane (100 ml) was stirred at room temperature for 2 hours. To the reaction mixture, 2 N HCl was added, followed by extraction with ethyl acetate; the resulting orgnaic layers were combined, washed with a saturated aqueous solution of sodium chloride, dried with anhydrous sodium sulfate and concentrated under reduced pressure; the resulting residue was subjected to silica gel column chromatography (eluent; hexane/ethyl acetate=10/1) to give 4-bromo-2,2-bis(fluoromethyl)-6-trifluoromethyl-2H-1-benzopyran (8.18 g).
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