4-Fluoroaniline → Methyl 1-(4-fluorophenyl)-2-oxo-1,2-dihydropyridine-3-carboxylate

To a solution of methyl 2-oxo-2H-pyran-3-carboxylate (Aldrich, 2.31 g, 15 mmol) in THF (40 mL) and DMF (10 mL) at rt was added a solid of 4-fluoroaniline (1.67 g, 15 mmol), and the reaction mixture was stirred for 2.5 h. Solid precipitation was observed. To the 4-fluoroaniline adduct intermediate formed via Michael addition was added in situ EDCI.HCl (3.85 g, 20 mmol) and DMAP (120 mg) at rt. The reaction mixture was stirred at rt overnight. To the reaction mixture were added 1 N aq. HCl (50 mL) and EtOAc (150 mL). The EtOAc layer was separated, and the aqueous layer was washed with EtOAc (150 mL). The combined EtOAc layers were dried over MgSO4 and concentrated in vacuo to obtain a semi-solid material (˜4.4 g). To this crude product were added ether (100 mL) and methanol (15 mL). The mixture was stirred, and the solid was filtered to obtain the undesired solid product (870 mg). The filtrate solution was concentrated in vacuo to obtain a semi-solid crude desired product (2.95 g, crude 80%) which was sufficiently pure to use in the subsequent step without further purification. 1H NMR (DMSO-d6) δ 8.23 (dd, 1H, J=7.2, 2.2 Hz), 7.57 (dd, 1H, J=6.6, 1.7 Hz ), 7.32-7.34 (m, 2H), 7.17 (t, 2H, J=8.8 Hz), 6.32 (t, 1H, J=7.1 Hz), 3.89 (s, 3H); MS(ESI+) m/z 248.2 (M+H)+.