1. 450 mL (2.94 mol) of phosphorus trichloride was added to a 2-liter flask and 49.3 mL (0.39 mol) of N,N-dimethylaniline was added slowly while cooling and stirring.
2. 142 g (1 mol) of 1-methylpyrimidine-2,4,6(1H,3H,5H)-trione was added in a batch over 20 min and the reaction was exothermic.
3. the reaction mixture was heated to reflux and held for 5 hours until gas escape ceased.
4. the reaction suspension is slowly poured into water at a controlled temperature of 25°C to 30°C
5. Filter the aqueous suspension by suction and dissolve the filtrate in 250 mL of dichloromethane.
6. Filter the solution until clear and extract twice with 250 mL of ice water.
7. The organic phase was dried and concentrated by evaporation to give a crystalline residue.
8. the residue was dried under vacuum to give 126.7 g of 5-methyl-2,4,6-trichloropyrimidine crystals with a melting point of 67°C-68°C and a yield of 64.2% of the theoretical value.
