[F:1][C:2]1[CH:26]=[CH:25][CH:24]=[C:23]([F:27])[C:3]=1[C:4]([O:6][CH:7]([C:18]([O:20][CH2:21][CH3:22])=[O:19])[C:8]([C:10]1[CH:15]=[CH:14][C:13]([O:16][CH3:17])=[CH:12][CH:11]=1)=O)=O.C([O-])(=O)C.[NH4+:32]>C(O)(=O)C.O>[F:1][C:2]1[CH:26]=[CH:25][CH:24]=[C:23]([F:27])[C:3]=1[C:4]1[O:6][C:7]([C:18]([O:20][CH2:21][CH3:22])=[O:19])=[C:8]([C:10]2[CH:15]=[CH:14][C:13]([O:16][CH3:17])=[CH:12][CH:11]=2)[N:32]=1To a stirred solution of 3-ethoxy-1-(4-methoxyphenyl)-1,3-dioxopropan-2-yl 2,6-difluorobenzoate (0.082 g, 0.22 mmol) in acetic acid (3 mL) was added ammonium acetate (0.125 g, 1.62 mmol) and the reaction mixture heated to reflux for 3 hours. A further portion of ammonium acetate (0.017 g, 0.22 mmol) was added the reaction mixture heated to reflux for 1 hour. The reaction was diluted with water and extracted with EtOAc. The organic phase was washed with water and brine, dried over MgSO4 and the solvent removed in vacuo. The residue was purified by silica gel column chromatography using 15% EtOAc in hexanes as eluent to afford ethyl 2-(2,6-difluorophenyl)-4-(4-methoxyphenyl)oxazole-5-carboxylate (0.041 g, 0.11 mmol, 53%) as a white crystalline solid. 1H NMR (CDCl3) δ 1.41 (3H, t), 3.87 (3H, s), 4.43 (2H, q), 6.99 (2H, d), 7.07 (2H, t), 7.49 (1H, m), 8.15 (2H, d). LCMS (1) Rt: 2.46 min; m/z (ES+) 360.
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