Hydrochloric Acid → 3-Amino-5-(pyridin-4-yl)thiophene-2-carboxylic acid

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Reaction Steps

A mixture of methyl 3-amino-5-(pyridin-4-yl)thiophene-2-carboxylate (2.34 g, 10 mmol), sodium methoxide (1.62 g, 30 mmol), methanol (40 mL) and water (10 mL) was refluxed for 4 h. The mixture was allowed to cool to room temperature and stirring was continued overnight. The mixture was cooled under ice-bath, then conc. HCl (2.48 mL, 30 mmol) was added (pH was approx. 4). The resultant yellow precipitate was collected by filtration and washed with water and methanol to afford the title compound (2.02 g, 92%) as a yellow solid:

Provenance & Evidence