Sodium Hydroxide → 5-Cyano-1-benzothiophene-7-carboxylic acid

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Reaction Steps

Ethyl 5-cyano-1-benzothiophene-7-carboxylate (5.6 g, 24.3 mmol) was dissolved THF (96 mL) and to the resultant solution was added an aqueous solution of NaOH (1.07 g of NaOH in 14 mL of water, 26.7 mmol) at 0° C. The mixture was stirred at room temperature overnight and then most of the solvent was removed by evaporation. The residue was dissolved in an aqueous solution of NaOH (0.1 M). The solution was washed thrice with chloroform, acidified with 2M HCl and then extracted with ethyl acetate. The organic solution was separated and the solvent was evaporated. The residue was flash chromatographed on silica gel (CH2Cl2-MeOH—NH4OH, 8:2:0.5). There was obtained 4.3 g (85%) of 5-cyano-1-benzothiophene-7-carboxylic acid as a tan solid. 1H NMR (500 MHz, DMSO-d6): 7.7 (d, 1H), 8.1 (d, 2H), 8.3 (d, 1H), 8.7 (s, 1H), 14 (b, 1H); LCMS: m/z 202 (M−1)−.

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