[Li]CCCC.Br[C:7]1[C:15]([C:16]2[CH:21]=[CH:20][C:19]([F:22])=[CH:18][CH:17]=2)=[CH:14][C:10]2[O:11][CH2:12][O:13][C:9]=2[CH:8]=1.C[O:24][B:25](OC)[O:26]C.[OH-].[Na+]>C1COCC1>[F:22][C:19]1[CH:20]=[CH:21][C:16]([C:15]2[C:7]([B:25]([OH:26])[OH:24])=[CH:8][C:9]3[O:13][CH2:12][O:11][C:10]=3[CH:14]=2)=[CH:17][CH:18]=1
Under nitrogen, 6.3 mL (15.8 mmol) of n-BuLi (2.5 M in hexanes) was added to a stirred solution of 3.9 g (13.2 mmol) of 5-bromo-6-(4-fluorophenyl)-1,3-benzodioxole (Step 1) in 30 mL of anhydrous THF at −78° C. After 30 minutes, 4.5 mL (39.4 mol) of trimethylborate was added. The reaction was warmed to ambient temperature and stirred for 3 hours prior to the addition of 60 mL of 5% NaOH. The reaction was stirred for an additional 60 minutes, the THF removed in vacuo, and the pH adjusted to ca. 4. The residue was dissolved in ethyl acetate; the resulting solution was dried over Na2SO4 and concentrated in vacuo to give 1.7 g (50%) of [6-(4-fluorophenyl)-1,3-benzodioxol-5-yl]boronic acid as a pale yellow solid: NMR (CDCl3) δ 4.00 (br s, 2H), 6.06 (s, 2H), 6.75 (s, 1H), 7.08-7.17 (m, 2H), 7.26 (s, 1H), 7.31-7.39 (m, 2H).
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