Methanol → 6-Chloro-1,2-dihydro-2-(trifluoromethyl)-3-quinolinecarboxylic acid

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Reaction Steps

The ester from Step 2 (1.7 g, 5.6 mmol) and 2.5 N sodium hydroxide (4.4 mL, 11 mmol) were mixed in tetrahydrofuran (25 mL), methanol (10 mL), and water (25 mL). After stirring overnight, contents were concentrated in vacuo to remove the THF and methanol. The aqueous solution remaining was extracted with diethyl ether (2×100 mL). The resulting aqueous layer was acidified with 2 N HCl causing the precipitation of an oil. The oil was purified by flash chromatography on silica gel, eluting with ethyl acetate-hexanes (1:1). Fractions containing the desired product were combined, and concentrated in vacuo. The residue was triturated with dichloromethane, and filtered to afford the 6-chloro-1,2-dihydro-2-(trifluoromethyl)-3-quinolinecarboxylic acid as a yellow solid (0.645 g, 41%): mp 187.8–188.8° C. 1H NMR (acetone-d6, 300 MHz) 7.69 (s, 1H), 7.36 (s, 1H), 7.15 (d, 1H, J=8.0 Hz), 6.83 (d, 1H, J=8.0 Hz), 6.60 (brs, 1H), 5.20 (m, 1H). ESHRMS m/z 276.0040 (M−H, Calc'd 276.0039). Anal. Calc'd for C11H7NO2F3Cl+2.6% H2O: C, 46.39; H, 2.98; N, 4.92. Found: C, 45.99; H, 2.54; N, 4.85.

Provenance & Evidence