4-Chloro-2-methylthiopyrazolo[1,5-a]1,3,5-triazine

Synthesis

The general procedure for the synthesis of 4-chloro-2-(methylthio)pyrazolo[1,5-alpha][1,3,5]triazin-4(3H)-one from 2-(methylthio)pyrazolo[1,5-α][1,3,5]triazin-4(3H)-one was as follows: to a stirred suspension of 2-(methylthio)pyrazolo[1,5-alpha][1,3,5]triazin-4(3H)-one (2.0 g. 11 mmol) and a suspension of trichlorophosphorus (20 mL) was added to N,N-diethylaniline (0.7 mL). The reaction mixture was heated to reflux temperature. After 1.5 hours of reaction, the mixture was cooled to room temperature and concentrated under reduced pressure. The residue was dissolved in toluene and the organic layer was washed with brine and concentrated again under reduced pressure to give 4-chloro-2-(methylthio)pyrazolo[1,5-a][1,3,5]triazine (2.0 g, 91% yield).TLC Rf = 0.57 (ethyl acetate/hexane, 1/3); 1H NMR (300 MHz, CDCl3) δ 8.15 (d, J = 2.2Hz , 1H), 6.50 (d, J = 2.2 Hz, 1H), 2.60 (s, 3H).

References

[1] Bioorganic and Medicinal Chemistry, 2011, vol. 19, # 20, p. 5955 - 5966
[2] Patent: US2007/78136, 2007, A1. Location in patent: Page/Page column 50
[3] Patent: WO2011/31979, 2011, A1. Location in patent: Page/Page column 147
[4] Patent: US9303033, 2016, B2. Location in patent: Page/Page column 285; 286
[5] Patent: JP5802676, 2015, B2. Location in patent: Paragraph 0552