General method: 6-methoxy-2-methylthio-4-chloropyrimidine (5 mmol), tetrabutylammonium bromide (0.16 g, 0.5 mmol, 10 mol%) were mixed with acetone (20 mL) at room temperature and stirred. An aqueous solution of Oxone (12.5 mmol, 2.5 eq.) was slowly added (20 mL) with vigorous stirring. After 4-6 hours of reaction, complete consumption of the feedstock was confirmed by TLC monitoring. The reaction mixture was filtered through a Brewer's funnel and the resulting solid product was washed with water and dried to give 4-chloro-6-methoxy-2-methylsulfonylpyrimidine. The yield, melting point and spectral data of the product are shown below.
[1] Synthetic Communications, 2018, vol. 48, # 6, p. 714 - 720
[2] Patent: US5599770, 1997, A
[3] Patent: US5723412, 1998, A
