Sodium Hydroxide → 5-(Pyridin-2-yl)-4-(trifluoromethyl)isoxazole-3-carboxylic acid

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Reaction Steps

A solution of ethyl 5-(pyridin-2-yl)-4-(trifluoromethyl)isoxazole-3-carboxylate (138 mg, 0.482 mmol) and 1N aqueous sodium hydroxide (579 μL, 0.579 mmol) in ethanol (4.5 mL) was stirred at room temperature for 30 min. The reaction mixture was concentrated under reduced pressure, and the residue was diluted with water (0.5 mL) and acidified with a 1N aqueous solution of hydrochloric acid to a pH of ˜3.0. The solution was extracted with ethyl acetate (3×2 mL). The organic layer was washed with water (1 mL), washed with brine (1 mL), and dried over anhydrous sodium sulfate. Concentration under reduced pressure afforded 5-(pyridin-2-yl)-4-(trifluoromethyl)isoxazole-3-carboxylic acid (0.093, 0.361 mmol, 75% yield). The product had an HPLC retention. time=1.57 min.—Column: YMC S5 COMBISCREEN® 4.6×50 mm (4 min.); Solvent A=10% MeOH, 90% H2O, 0.1% TFA; Solvent B=90% MeOH, 10% H2O, 0.1% TFA. LC/MS M+1=259.0. 1H NMR (400 MHz, CD3OD) δ ppm 7.60-7.65 (m, 2H), 7.92 (d, J=8.03 Hz, 2H), 8.02-8.09 (m, 2H), and 8.78 (d, 2H).

Provenance & Evidence