[Br-].[K+].BrBr.[CH3:5][O:6][C:7]1[CH:15]=[CH:14][CH:13]=[C:12]2[C:8]=1[CH:9]=[CH:10][N:11]2[CH3:16].C(=O)(O)[O-:18].[Na+]>O.[Pd].C(O)(C)(C)C>[CH3:5][O:6][C:7]1[CH:15]=[CH:14][CH:13]=[C:12]2[C:8]=1[CH2:9][C:10](=[O:18])[N:11]2[CH3:16]
To a solution of potassium bromide (3986 mg, 33.5 mmol) in water (26.5 ml) was added bromine (0.863 ml, 16.75 mmol). A separate flask containing 4-methoxy-1-methyl-1H-indole (900 mg, 5.58 mmol) was charged with t-butanol (20.00 ml) and water (20.0 ml). To this flask was added 22.5 mL of bromine solution dropwise. The mixture was permitted to stir for approximately 30 minutes and then was neutralized with saturated aqueous sodium bicarbonate and quenched with saturated aqueous sodium thiosulfate. The reaction was then diluted with dichloromethane and saturated aqueous sodium bicarbonate and the layers were separated. The aqueous layer was extracted two additional times with dichloromethane and the organic layers were combined, dried over anhydrous sodium sulfate, filtered, and concentrated. The resulting residue was dissolved in 50 mL EtOH and 5 mL of AcOH. The solution was then charged with 10% palladium on carbon (1.2 g, 1.13 mmol). The atmosphere over the reaction mixture was evacuated and the reaction was placed under an atmosphere of hydrogen gas via a balloon. The reaction was stirred for 18 hours. The reaction mixture was then filtered through a plug of Celite® and the filtrate was then concentrated to approximately 25% of its original volume. The reaction was then diluted with dichloromethane and saturated aqueous sodium bicarbonate and the layers were separated. The aqueous layer was extracted two additional times with dichloromethane and the organic layers were combined, dried over anhydrous sodium sulfate, filtered, and concentrated. The resulting residue was purified by silica gel flash chromatography (ethyl acetate-heptane, 0 to 60%) to afford 4-methoxy-1-methyl-1,3-dihydro-indol-2-one; MS: (ES+) m/z 178.0 (M+H)+.
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