The general procedure for the synthesis of 5-bromo-2-(methylsulfonyl)pyrimidine from 5-bromo-2-methylmercaptopyrimidine was as follows: 5-bromo-2-methylthiopyrimidine (10.0 g, 48.8 mmol) was dissolved in methanol (195 mL), to which was subsequently added in batch and in an alternating addition pattern Oxone?(94.6 g, 154 mmol, 3.16 eq.) in an aqueous solution (500 mL) and 4N aqueous sodium hydroxide solution (40 mL, 160 mmol, 3.28 eq.), the temperature was controlled and the pH was maintained between 2 and 3 during the reaction. After the addition was completed, the reaction mixture was stirred at room temperature for 2 hours. Upon completion of the reaction, water (500 mL) was added to dilute and the mixture was extracted with ethyl acetate (2 x 500 mL). The aqueous layer was adjusted to pH 7 and extracted again with ethyl acetate. The organic layers were combined, dried with anhydrous magnesium sulfate and concentrated under reduced pressure to afford 9.23 g (80% yield) of the target product, 5-bromo-2-(methylsulfonyl)pyrimidine, which could be used in the subsequent reaction without further purification. The product was characterized by 1H-NMR (300 MHz, DMSO-d6) and mass spectrometry (ESI): 1H-NMR δ 9.28 (s, 2H), 3.37 (s, 3H); MS (ESI): m/z [M + H]+ 237 (79Br).
