Sulfuric Acid → Methyl 1-(4-fluorophenyl)-6-hydroxy-4-oxo-1,4-dihydroquinoline-3-carboxylate

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Reaction Steps

Compound K (383 mg, 1.28 mmol, 1.00 eq) was dissolved in methanol (6.4 mL) and concentrated sulfuric acid (0.64 mL) was added dropwise. The reaction was heated to reflux for 3 hours at which point it was cooled and neutralized with a saturated solution of sodium bicarbonate. The mixture was extracted with a solution of 3:1 CHCl3:IPA (2×) and the combined organics were dried (MgSO4), filtered and concentrated in vacuo. Purification by flash chromatography on silica gel using 0-20% 89:10:1 DCM:methanol:NH40H afforded 296 mg (74%) of the title compound as yellow solid. 1H NMR (400 MHz, DMSO-d6) δ 10.03 (s, 1H), 8.36 (s, 1H), 7.72-7.68 (m, 2H), 7.61 (d, J=2.8 Hz, 1H), 7.49 (t, J=8.7 Hz, 2H), 7.11 (dd, J=9.0, 2.8 Hz, 1H), 6.84 (d, J=9.1 Hz, 1H), 3.71 (s, 3H); ES-MS [M+1]+: 314.2.

Provenance & Evidence