[Li+].CC([N-]C(C)C)C.[NH2:9][C:10]1[C:22]([Br:23])=[CH:21][C:13]2[C:14]([C:17]([NH:19][CH3:20])=[O:18])=[CH:15][O:16][C:12]=2[CH:11]=1.[B:24](OC)([O:27]C)[O:25]C.[NH4+].[Cl-]>C1COCC1>[NH2:9][C:10]1[C:22]([Br:23])=[CH:21][C:13]2[C:14]([C:17](=[O:18])[NH:19][CH3:20])=[C:15]([B:24]([OH:27])[OH:25])[O:16][C:12]=2[CH:11]=1To a solution of LDA in THF (62.5 mmol, 70 mL, freshly prepared), 6-amino-5-bromo-N-methylbenzofuran-3-carboxamide (4 g, 14.86 mmol) in THF (60 mL) was added dropwise at −78° C. under N2. After the mixture was stirred for 1 hour, trimethyl borate (6.18 g, 59.5 mmol) was added dropwise at −78° C. After the mixture was stirred for 1 hour, NH4Cl (a.q.) was added, and the mixture was extracted with EtOAc (100 mL×3), dried over Na2SO4, filtrated and concentrated to give (6-amino-5-bromo-3-(methylcarbamoyl)benzofuran-2-yl)boronic acid (3.3 g, yield: 70%). 1H-NMR (DMSO-d6, 400 MHz) δ 9.56 (s, 2H), 8.46 (d, J=4.8 Hz, 1H), 8.00 (s, 1H), 6.95 (s, 1H), 5.20˜5.82 (br s, 2H), 2.87 (d, J=4.8 Hz, 3H). MS (M+H)+: 313/315.
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