1072895-86-3

1,3-Dimethyl-1,7-dihydro-pyrazolo[3,4-d]pyrimidine-4,6-dione (1 g, 5.56 mmol) was used as starting material and mixed with phosphorus pentachloride (3.47 g, 3 equiv.) in phosphorus trichloride (20 mL). The reaction mixture was heated to reflux for 18 hours. Upon completion of the reaction, the excess phosphorous trichloride was removed by distillation under reduced pressure. The residue was carefully poured onto ice and extracted with dichloromethane (3 x 20 mL). The organic phases were combined and purified by column chromatography to give 4,6-dichloro-1,3-dimethyl-1H-pyrazolo[3,4-d]pyrimidine (680 mg, 63% yield) as a final product as a beige solid.

[1] Patent: WO2009/97446, 2009, A1. Location in patent: Page/Page column 65; 66
[2] Tetrahedron Letters, 2008, vol. 49, # 42, p. 6081 - 6083