[Br:1][C:2]1[CH:19]=[CH:18][C:5]([N:6]([CH2:8][CH2:9][CH2:10][C:11]([O:13][C:14]([CH3:17])([CH3:16])[CH3:15])=[O:12])[CH3:7])=[C:4]([CH:20]=O)[CH:3]=1.C(O[K])(C)(C)C.O>C(O)(C)(C)C>[Br:1][C:2]1[CH:19]=[CH:18][C:5]2[N:6]([CH3:7])[CH2:8][CH2:9][C:10]([C:11]([O:13][C:14]([CH3:17])([CH3:16])[CH3:15])=[O:12])=[CH:20][C:4]=2[CH:3]=1.[Br:1][C:2]1[CH:19]=[CH:18][C:5]2[N:6]([CH3:7])[CH2:8][CH2:9][C:10]([C:11]([OH:13])=[O:12])=[CH:20][C:4]=2[CH:3]=1
In tert-butanol (250 ml) was dissolved tert-butyl 4-(4-bromo-2-formyl-N-methylanilino)butyrate (4.54 g) and tert-butoxy potassium (1.43 g), and the mixture was refluxed for 1 hour and cooled. To the mixture was added water (500 ml), and the mixture was extracted with ethyl acetate (500 ml×2). The aqueous layer was made weakly acidic with 1N hydrochloric acid (about 12.5 ml), and the mixture was extracted with ethyl acetate (500 ml). Both of these organic layer was washed with saturated brine (250 ml) and dried with anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was purified with silica gel column chromatography (200 g, hexane:ethyl acetate=10:1→1:1) to give tert-butyl 7-bromo-1-methyl-2,3-dihydro-1-benzoazepine-4-carboxylate (3.33 g, 77%) and 7-bromo-1-methyl-2,3-dihydro-1H-1-benzoazepine-4-carboxylic acid (0.60 g, 17%). tert-butyl 7-bromo-1-methyl-2,3-dihydro-1-benzoazepine-4-carboxylate;
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