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The procedure was adapted from that reported in J. Med. Chem. 1976, 19, 1072. 6-Methylpyrimidine-2,4(1H,3H)-dione (7.0 g, 55.56 mmol) was added to concentrated sulfuric acid (26 mL) cooled in ice at such a rate that the internal temperature did not exceed 40°. To this mixture fuming nitric acid (5.2 mL) was added dropwise whilst maintaining the temperature below 15°. The cooling bath was removed and the mixture was stirred at room temperature for 30 min then dumped into 100 ml of crushed ice. After stirring for 10 min the solid was collected and washed with cold water then dried in vacuo over phosphorus pentoxide. A yellow-green solid of 6-methyl-5-nitropyrimidine-2,4(1H,3H)-dione was obtained (7.92 g, 83%).

1. temperaturecooled in ice at such a rate that the internal temperature
2. customdid not exceed 40°
3. temperaturewhilst maintaining the temperature below 15°
4. customThe cooling bath was removed
5. stirringAfter stirring for 10 min the solid
6. customwas collected
7. washwashed with cold water
8. dry with materialthen dried in vacuo over phosphorus pentoxide