4,6-Dichloro-5-nitropyrimidine (9.7 g, 50 mmol) was used as starting material and dissolved in tetrahydrofuran (100 mL). To this solution ammonia (100 mL) and sodium bicarbonate (4.6 g, 55 mmol) were added sequentially. The reaction mixture was heated to 55°C and stirred at this temperature overnight. Upon completion of the reaction, the mixture was cooled to room temperature and the organic solvent was subsequently evaporated under reduced pressure. The residue was filtered and purified by fast column chromatography (eluent ratio of dichloromethane: methanol = 100:1) to give the final target product 4-amino-6-chloro-5-nitropyrimidine (6-chloro-5-nitropyrimidin-4-amine, 8.1 g, 93% yield).
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