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General procedure for the synthesis of 2-chloro-5-(methylthio)pyrimidine from 5-bromo-2-chloropyrimidine and dimethyl disulfide: 1.00 g (5.17 mmol) of 5-bromo-2-chloropyrimidine and 551 μl (6.20 mmol) of dimethyl disulfide were dissolved in 26 ml of tetrahydrofuran and cooled to -78 °C. Under stirring, 1.89 ml (5.17 mmol) of 2.73N n-butyllithium/hexane solution was slowly added, keeping the reaction temperature at -78 °C, and stirring was continued for 2 hours. Upon completion of the reaction, the reaction was quenched by adding saturated aqueous ammonium chloride solution to the reaction mixture and the organic phase was extracted with ethyl acetate. The organic layers were combined, washed with saturated aqueous sodium chloride solution and dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure to give the crude product. Purification by silica gel column chromatography [eluent: n-hexane/ethyl acetate = 90/10 (V/V)], the fraction containing the target compound was collected and concentrated under reduced pressure to give 149 mg of 2-chloro-5-(methylthio)pyrimidine as a white solid (yield: 18%). The product was characterized by 1H-NMR (500 MHz, CDCl3): δ 8.49 (2H, s), 2.54 (3H, s).