4-Aminopyrimidine-5-carboxylic acid (1.0 g, 7.2 mmol) was used as raw material and mixed with 15 mL of ethanol and 1 mL of concentrated sulfuric acid. The suspension was stirred under reflux conditions for 72 hours. After completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was poured on ice and stirred for 1 hour and subsequently neutralized with saturated sodium carbonate solution. The product was extracted with chloroform (3 x 70 mL) and the combined organic layers were washed with brine and dried with anhydrous sodium sulfate. Finally, the organic phase was concentrated under reduced pressure to give ethyl 4-aminopyrimidine-5-carboxylate (0.76 g, 63% yield).
