5-Fluorouracil → 2,4-Dichloro-5-fluoropyrimidine

To a dry reaction flask equipped with a stir bar and a reflux condenser was placed 5-fluorouracil (0.65 g, 5 mmol) followed by phosphorus oxychloride (POCl3) (1.53 g, 10 mmol). The resultant mixture was heated at 110° C. for 8 hours under a nitrogen atmosphere. The reaction was cooled to room temperature, phosphorus pentachloride (PC15) (3.12 g, 15 mmol) was added and heated to 110° C. for a period of 12 hours. After cooling to room temperature, the mixture was poured into ice-water, saturated with sodium chloride and left for 1 hour at 0° C. to complete the decomposition of POCl3 and PC15. The solid of 2,4-dichloro-5-fluoropyrimidine was collected by rapid filtration, dried using blotting paper and stored at low temperature. 1H NMR (CDCl3): δ 8.47 (s, 1H); 13C NMR (CDCl3): δ 155.42, 151.87, 147.43 and 147.13; 19F NMR (CDCl3): −38149.