Sodium Hydroxide → 4-oxo-5,6-dihydro-4H-cyclopenta[b]thiophene-2-carboxylic acid

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Reaction Steps

In a 500-mL round-bottomed flask equipped with a magnetic stirrer and reflux condenser, was charged with sodium hydroxide (3.34 g, 83.6 mmol) and water (65 mL). The solution was degassed with nitrogen for 15 min. 4 (7.19 g, 20.2 mmol) was added and the mixture was stirred at room temperature for 3 h. After this time, 1 M aqueous potassium phosphate monobasic was added to adjust the pH of the reaction mixture to 8.0, followed by water (200 mL). After heating at 50° C. for 16 h, the water was evaporated to 50 mL under reduced pressure, and 12 N hydrochloric acid was added to adjust the pH to 2.8 (pH meter). The resulting precipitate was collected by vacuum filtration, washed with water (5 mL) and dried for 16 h under vacuum at 50° C. to afford 5 in 37% yield (1.37 g) as a green solid: mp 195-196° C.; 1H NMR (500 MHz, DMSO-d6) δ 13.30 (br s, 1H), 7.64 (s, 1H), 3.23 (t, 2H, J=5.5 Hz), 2.76 (t, 2H, J=5.5 Hz); MS (APCI+) m/z 183.2 (M+H).

Provenance & Evidence