Water → 3-Propyl-1,2-benzisoxazole-5-carboxylic acid

To a solution of methyl 3-propyl-1,2-benzisoxazole-5-carboxylate (90 mg, 0.4 mmol) in a 2:1:1 mixture of tetrahydrofuran, water, and methanol (4 mL) was added lithium hydroxide (50 mg, 1.2 mmol) and the resulting reaction mixture stirred at room temperature for 2.5 h. The reaction mixture was concentrated under reduced pressure, and partitioned between water and ethyl ether. The aqueous layer was washed twice with ether and acidified to pH 1 with 6 M hydrochloric acid. The resulting aqueous layer was extracted with ethyl acetate, dried (sodium sulfate), and concentrated under reduced pressure to afford 3-propyl-1,2-benzisoxazole-5-carboxylic acid (73 mg): 1H NMR (300 MHz, CD3OD): δ 8.28–8.27 (m, 1H), 8.09–8.06 (m, 1H), 7.64–7.61 (m, 1H), 2.99–2.94 (m, 2H), 1.96–1.86 (m, 2H), 1.08–1.02 (m, 3H).