[Br:1][C:2]1[CH:3]=[CH:4][CH:5]=[C:6]2[C:10]=1[NH:9][C:8](=[O:11])[CH:7]2[C:12]1[C:20]([OH:21])=[CH:19][C:15]2[O:16][CH2:17][O:18][C:14]=2[CH:13]=1.[CH2:22]=[O:23].[OH-].[Na+].Cl>O>[Br:1][C:2]1[CH:3]=[CH:4][CH:5]=[C:6]2[C:10]=1[NH:9][C:8](=[O:11])[C:7]2([C:12]1[C:20]([OH:21])=[CH:19][C:15]2[O:16][CH2:17][O:18][C:14]=2[CH:13]=1)[CH2:22][OH:23]To a mixture of 7-bromo-3-(6-hydroxy-1,3-benzodioxol-5-yl)-1,3-dihydro-2H-indol-2-one (8.40 g, 24.1 mmol), para-formaldehyde (2.88 g, 96.0 mmol) and water (80 mL) was added sodium hydroxide (3.84 g, 96.0 mmol) at 0° C. The dark green solution was stirred at 0° C. for 4 h. The mixture was acidified with 3 N hydrochloride to pH 4 and extracted with ethyl acetate (3×100 mL). The combined ethyl acetate solution was washed with 25% ammonium chloride solution (50 mL) and brine (50 mL), dried over anhydrous sodium sulfate and concentrated in vacuo to dryness. The residue was treated with toluene (300 mL) to give an off white precipitate. The precipitate was filtered and dried under reduced pressure to give 7-bromo-3-(6-hydroxy-1,3-benzodioxol-5-yl)-3-(hydroxymethyl)-1,3-dihydro-2H-indol-2-one (4.80 g, 53%): 1H NMR (300 MHz, DMSO-d6) δ10.48 (s, 1H), 9.16 (s, 1H), 7.27 (dd, J=8.0, 1.0 Hz, 1H), 7.01 (s, 1H), 6.87-6.74 (m, 2H), 6.22 (s, 1H), 5.91 (s, 2H), 5.03 (br, 1H), 4.12 (d, J=10.0 Hz, 1H), 3.85 (d, J=10.0 Hz, 1H); MS (ES−) m/z 376 (M−1), 378 (M−1).
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