5-(Methylthio)pyrimidine-2,4(1H,3H)-dione (600 mg, 3.8 mmol) was used as a raw material and prepared according to the method described by Kopp F et al. in Organic Letters, 2007, 9, 1639-41. The raw material was dissolved in phosphoryl chloride (15 mL) and the reaction was stirred at 100 °C for 16 hours. Upon completion of the reaction, the reaction mixture was quenched by slowly pouring it into ice water. The mixture was subsequently extracted with dichloromethane (20 mL × 2), and the organic phases were combined, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was purified by column chromatography (eluent: dichloromethane/tetrahydrofuran = 100:100) to afford 2,4-dichloro-5-(methylthio)pyrimidine (520 mg, 70% yield) as a yellow oil.
