[F:1][C:2]1[CH:22]=[CH:21][CH:20]=[C:19]([F:23])[C:3]=1[CH2:4][N:5]1[C:10]([CH3:11])=[CH:9][C:8](=[O:12])[C:7]([C:13]([O:15][CH2:16][CH3:17])=[O:14])=[C:6]1[CH3:18].[Br:24]Br>C(O)(=O)C>[F:1][C:2]1[CH:22]=[CH:21][CH:20]=[C:19]([F:23])[C:3]=1[CH2:4][N:5]1[C:6]([CH3:18])=[C:7]([C:13]([O:15][CH2:16][CH3:17])=[O:14])[C:8](=[O:12])[C:9]([Br:24])=[C:10]1[CH3:11]1-(2,6-Difluorobenzyl)-2,6-dimethyl-3-ethoxycarbonyl-4-pyridone (2.43 g, 7.6 mmol) was dissolved in glacial acetic acid (25 mL) and treated with bromine (490 μL, 9.5 mmol). The resulting mixture was stirred at room temperature for 8 hours and poured into ice/water. The product was extracted with dichloromethane, and the extracts were washed with 10% aqueous NaHCO3, 5% aqueous Na2S2O3 and brine. The organics were dried over anhydrous MgSO4, filtered and evaporated in vacuo. The residue was triturated with diethyl ether to give the product as a white solid (1.32 g, 3.3 mmol, 43%). 1H NMR (CDCl3, 300 MHz): 7.41-7.31 (m, 1H), 7.00-6.92 (m, 2H), 5.31 (s, 2H), 4.37 (q, J=6.9 Hz, 2H), 2.66 (s, 3H), 2.37 (s, 3H), 1.37 (t, J=6.9 Hz, 3H); LRMS m/z 400.1 (M+−1), 402.1 (M++1).
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