General procedure for the synthesis of 4,6-dichloro-5-methylpyrimidine from 5-methylpyrimidine-4,6-diol: To a solution of POCl3 (1.9 mol, 174 mL) containing the pyrimidine derivative (0.38 mol, 1 eq.) was slowly added DMF (0.152 mol, 11.7 mL), noting that this process is exothermic. The reaction mixture was heated to reflux and maintained for 3 hours. Upon completion of the reaction, it was cooled to room temperature and the mixture was carefully poured into an ice/water mixture. The precipitated white solid product was collected by filtration, washed well with water and subsequently dried under vacuum to afford 4,6-dichloro-5-methylpyrimidine (1) in 90% yield.
