6-Benzyl-2,4-dichloro-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine

Preparation

6-Benzyl-2,4-dichloro-5,6,7,8-tetrahydropyrido[4,3-D]pyrimidine can be prepared by the following method:

6-Benzyl-5,6,7,8-tetrahydropyrido[4,3-d]pyrimidine-2,4(1H,3H)-diketone is dissolved in acetonitrile (50 mL), stirred at room temperature for 30 minutes, phosphorus oxychloride is added, the mixture is heated to reflux, and the reaction is carried out for 30 minutes. The reaction progress is detected by thin-layer chromatography.

After the reaction was complete, the heating was stopped, and the mixture was cooled to room temperature. It was then poured into ice water, stirred, and extracted with dichloromethane (50 mL × 3). The organic phase was washed with saturated sodium bicarbonate solution, decolorized with activated carbon, and dried over anhydrous sodium sulfate. After filtration and concentration, isopropanol (30 mL) was added, and the mixture was heated to dissolve and stirred. A white solid precipitated out. After standing for 2 hours, the mixture was filtered, and the filter cake was dried to obtain the target compound 6-benzyl-2,4-dichloro-5,6,7,8-tetrahydropyrido[4,3-D]pyrimidine.

References

[1] European Journal of Medicinal Chemistry, 2014, vol. 79, p. 399 - 412
[2] Patent: EP1537879, 2005, A1. Location in patent: Page/Page column 61
[3] Journal of Medicinal Chemistry, 2016, vol. 59, # 23, p. 10498 - 10519
[4] Patent: EP1547616, 2005, A1. Location in patent: Page/Page column 65
[5] Patent: WO2017/144633, 2017, A1. Location in patent: Page/Page column 112; 113