Hydrochloric Acid → 5,5-dimethyl-4H,5H,6H-cyclopenta[b]thiophene-2-carboxylic acid

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Reaction Conditions

Reaction Steps

In a 250-mL single-neck round-bottomed flask equipped with a magnetic stirrer and reflux condenser, 106b (4.00 g, 17.8 mmol) was dissolved in ethanol (50 mL). THF (50 mL), water (50 mL) and lithium hydroxide (854 mg, 35.6 mmol) were added, and the mixture was stirred at 60° C. for 4 h. After this time the reaction was cooled to room temperature and acidified with 2M hydrochloric acid to pH 1.5, and then extracted with ethyl acetate (2×200 mL). The organic layers were combined, washed with water (2×100 mL), followed by brine (100 ml) and dried over sodium sulfate. The drying agent was then separated by filtration. After evaporating the resulting filtrate, 106c was obtained in 91% yield (3.2 g) as a white solid: mp 170-172° C.; 1H NMR (300 MHz, CDCl3) δ 12.77 (s, 1H), 7.46 (s, 1H), 2.71 (s, 2H), 2.53 (s, 2H), 1.20 (s, 6H); MS (ESI−) m/z 195.0

Provenance & Evidence