1979-98-2

6299-25-8

Step b: Synthesis of 4,6-dichloro-2-methylthiopyrimidine (19b); 2-methylthiopyrimidine-4,6-diol (30.0 g, 189 mmol) was slowly added to phosphorochloride (350 mL) under cooling in an ice bath, followed by the slow addition of N,N-diethylaniline (52.5 mL) while maintaining cooling. The reaction mixture was gradually warmed to reflux and maintained at reflux for 2.5 hours. Upon completion of the reaction, the mixture was concentrated and subsequently poured into crushed ice for quenching. The aqueous phase was extracted three times with ethyl acetate, and the organic phases were combined and washed sequentially three times with water and once with brine, after which the organic phase was concentrated. The crude product was purified by silica gel column chromatography using hexane-ethyl acetate as eluent to afford 4,6-dichloro-2-methylthiopyrimidine (36 g, 97% yield).