Phosphorus oxychloride → 3-Benzenesulphonyl-7-chloro-5-methyl-pyrazolo[1,5-a]pyrimidine
Reaction equation
[C:1]1([S:7]([C:10]2[CH:11]=[N:12][N:13]3[CH:18]=[CH:17][C:16]([CH3:19])=[N:15][C:14]=23)(=[O:9])=[O:8])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.O=P(Cl)(Cl)[Cl:22]>>[C:1]1([S:7]([C:10]2[CH:11]=[N:12][N:13]3[C:18]([Cl:22])=[CH:17][C:16]([CH3:19])=[N:15][C:14]=23)(=[O:9])=[O:8])[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=1Participants
3
Procedure
A suspension of 0.91 g (3.14 mmol) of 3-benzenesulphonyl-5-methyl-pyrazolo[1,5-a]pyrimidine in 15 ml of POCl3 was heated at reflux for 1 hr. The reaction solution was cooled to RT and evaporated. The residue was treated with 30 ml of ice-water and the pH value of the solution was adjusted to 8 with sat. NaHCO3 solution. The aqueous phase was extracted three times with 20 ml of CH2Cl2, and the organic phases were dried (MgSO4), filtered and evaporated. Chromatography (SiO2, CH2Cl2/AcOEt 19:1) of the residue yielded 0.84 g (87%) of 3-benzenesulphonyl-7-chloro-5-methyl-pyrazolo[1,5-a]pyrimidine as a beige solid.