[CH2:1]([O:8][C:9]1[N:14]=[C:13]([O:15][CH3:16])[C:12]([F:17])=[CH:11][CH:10]=1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C1C(=O)N([Br:25])C(=O)C1>CN(C=O)C>[CH2:1]([O:8][C:9]1[N:14]=[C:13]([O:15][CH3:16])[C:12]([F:17])=[CH:11][C:10]=1[Br:25])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1step 3—A solution 142 (1 g, 4.29 mmol) in DMF (10 mL) was cooled in ice-bath and NBS (0.763 g, 4.29 mmol) was added. The colorless mixture was stirred for 2 h and then quenched with H2O. The mixture was extracted with EtOAc (2×50 mL). The combined extracts were washed sequentially with H2O and brine, dried (Na2SO4), filtered and concentrated in vacuo. The crude product was purified by SiO2 chromatography to afford 0.5 g of 6-benzyloxy-5-bromo-3-fluoro-2-methoxy-pyridine (144).
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