[Br:1][C:2]1[CH:3]=[C:4]([CH:18]=[CH:19][CH:20]=1)[C:5]([C:7]1[C:12]([O:13]COC)=[CH:11][CH:10]=[CH:9][N+:8]=1[O-:17])=[O:6].S(=O)(=O)(O)O.CC(C)=O.[OH-].[Na+]>O>[Br:1][C:2]1[CH:3]=[C:4]([CH:18]=[CH:19][CH:20]=1)[C:5]([C:7]1[C:12]([OH:13])=[CH:11][CH:10]=[CH:9][N+:8]=1[O-:17])=[O:6]
A mixture of 2-(3-bromobenzoyl)-3-methoxymethoxy pyridine 1-oxide (4.00 g), 3.6N-sulfuric acid (11 mL) and acetone (50 mL) was refluxed for 5 hours. The reaction mixture was poured into water, neutralized with an 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-bromobenzoyl)-3-hydroxypyridine 1-oxide (2.81 g). Physical properties and spectrum data of the product are shown below.
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