Water → 5-Fluorothiophene-2-carboxylic acid

A mixture of the title product of Example 1 (1.5 g, 11.8 mmol) and 1.0 N NaOH (25 mL, 25 mmol) was refluxed for 3 hours. The mixture was poured into water (200 mL) and washed two times with 200 mL diethyl ether. The aqueous extract was acidified with 1N hydrochloric acid to pH 1, then extracted two times with 200 mL methylene chloride. The organic extracts were combined, washed with water (80 mL), dried (MgSO4) and concentrated in vacuo to give a solid. Trituration with hexanes afforded 1.2 g (82%) of the title product as a white solid, mp 140-2° C. 1H-NMR (d6 -DMSO): δ7.47 (m, 1H), 6.84 (m, 1H). Anal. Calcd. for C5H3O2SF: C, 41.10; H, 2.07. Found: C, 41.16; H, 1.98.