Sodium Hydroxide → 6-chloro-8-(5-chloro-1-pentynyl)-2-(trifluoromethyl)-2H-1-benzopyran-3-carboxylic acid

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The ester (Step 1) (0.500 g, 1.23 mmol) was dissolved in THF-ethanol-water (7:2:1; 10 mL). It was treated with sodium hydroxide (0.49 mL, 1.23 mmol of a 2.5 N solution), and stirred at room temperature for 18 hours. The solvent was evaporated and the residue was dissolved in water (10 mL). Diethyl ether (10 mL) was added and the mixture acidified with concentrated HCl. The organic layer was separated, and the aqueous phase was extracted with diethyl ether (2×10 mL). The combined extracts were dried over MgSO4, filtered, and evaporated to yield a yellow solid, which was recrystallized in diethyl ether-hexane to afford the title compound as a yellow solid (0.371 g, 80%): mp 154.4–156.4° C. 1H NMR (acetone-d6/300 MHz) 7.88 (s, 1H), 7.53 (d, 1H, J=2.4 Hz), 7.44 (d, 1H, J=2.4 Hz), 5.94 (q, 1H, J=7.1 Hz), 3.83 (t, 2H, J=6.5 Hz), 2.68 (t, 2H, J=6.8 Hz), 2.12–2.04 (m, 2H). ESLRMS m/z 377 (M−H). ESHRMS m/z 376.9930 (M−H, Calc'd. 376.9959). Anal. Calc'd. for C16H11Cl2F3O3+1.18% H2O: C, 5.0.08; H, 3.02; Cl, 18.48. Found: C, 50.11; H, 2.73; Cl, 18.28.

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