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2) Preparation of intermediate 4,5-dichloro-6-methylpyrimidine: 50 mL of phosphorus oxychloride (POCl3) was slowly added dropwise to 50 mL of toluene solution containing 14.5 g (0.1 mol) of 5-chloro-6-methylpyrimidin-4(1H)-one. After completion of the dropwise addition, the reaction mixture was heated to reflux for 5-7 hours. The reaction process was monitored by thin layer chromatography (TLC). Upon completion of the reaction, toluene and excess TLC were removed by distillation under reduced pressure. Subsequently, the reaction mixture was carefully poured into ice water. The aqueous phase was extracted with ethyl acetate (3 x 50 mL), the organic phases were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. Finally, the residue was purified by silica gel column chromatography to afford 14.43 g of the target product 4,5-dichloro-6-methylpyrimidine as a yellow liquid in 88.5% yield.