2503-56-2

24415-66-5

General procedure for the synthesis of 7-chloro-5-methyl-1,2,4-triazolo[1,5-α]pyrimidine from 7-hydroxy-5-methyl-1,3,4-tetraazaindolizine: to a solution of 7-hydroxy-5-methyl-1,3,4-tetraazaindolizine (1.60 g; 10.66 mmol) in dioxane (10 mL) was added sequentially phosphorous triclosulfate (2.5 mL; 26.65 mmol) and triethylamine (2.97 mL; 21.32 mmol). The reaction mixture was heated at 105 °C with stirring for 3 h. The reaction progress was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted slowly and dropwise by adding sodium bicarbonate solution to 8. Subsequently, dichloromethane (DCM) was added for phase separation. The aqueous phase was further extracted with dichloromethane. The organic phases were combined, dried with anhydrous magnesium sulfate and filtered. The solvent was removed by concentration under reduced pressure to give the crude product as an oil. The crude product was purified by column chromatography using a gradient elution from pure petroleum ether to 50% ethyl acetate/petroleum ether to afford 7-chloro-5-methyl-1,2,4-triazolo[1,5-alpha]pyrimidine (Compound 4) as a yellow solid (1.16 g, 65% yield).