The general procedure for the synthesis of 2,4-dichloro-5-fluoropyridine using 5-fluoropyrimidine-2,4(1H,3H)-dione as starting material is as follows:
Example 16: Preparation of N4-[(trans-4-aminocyclohexyl)methyl]-5-fluoro-N2-[2-(trifluoromethoxy)benzyl]pyrimidine-2,4-diamine
1. to a mixture of 5-fluorouracil (10.0 g, 76.9 mmol) and phosphorus trichloride (30 mL) was added phosphorus pentachloride (8.0 g, 38.4 mmol).
2. The reaction mixture was heated to reflux for 14 hours under nitrogen protection.
3. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently slowly poured into ice water.
4. the residue in the flask was dissolved in saturated sodium carbonate solution and poured into the ice-water mixture.
5. The mixture was extracted with ethyl acetate (3 times), the organic phases were combined and dried over anhydrous sodium sulfate.
6. The organic phase was concentrated under reduced pressure to give 5-fluoro-2,4-dichloropyridine (9.1 g, 71% yield) as a light yellow oil.
