[Br:1][C:2]1[CH:3]=[C:4]([CH:17]=[CH:18][C:19]=1[F:20])[C:5]([C:7]1[C:12]([O:13]COC)=[CH:11][CH:10]=[CH:9][N:8]=1)=[O:6].S(=O)(=O)(O)O.CC(C)=O.[OH-].[Na+]>O>[Br:1][C:2]1[CH:3]=[C:4]([CH:17]=[CH:18][C:19]=1[F:20])[C:5]([C:7]1[C:12]([OH:13])=[CH:11][CH:10]=[CH:9][N:8]=1)=[O:6]A mixture of 2-(3-bromo-4-fluorobenzoyl)-3-methoxymethoxypyridine (5.68 g), 3.6N-sulfuric acid (6.0 mL) and acetone (30 mL) was refluxed for 3 hours. The reaction mixture was then poured into water, neutralized with a saturated aqueous solution of sodium hydroxide, and extracted with ethyl acetate. The extract was washed with water and a saturated aqueous saline solution, successively, and dried (sodium sulfate) and then concentrated. The concentrate was purified by means of a silica gel column (ethyl acetate--hexane) to afford 2-(3-bromo-4-fluorobenzoyl)-3-hydroxypyridine (4.51 g) (compound C-5). Physical properties and spectrum date of the product are shown in Table 5 and Table 6.
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