A simple and efficient one pot biginelli condesation of pyrazolo[3,4-d]pyrimidine-ones/thiones

The synthesis of pyrazolo[5,4-d]pyrimidines from5-isopropyl-2,4-dihydro- 3H-pyrazol-3-one, substituted benzaldehydes and urea or thiourea in ethanol in the presence of catalytic amount of conc. acid as a one pot biginelli reaction involving iminium cation is described. The constitution of the product has been supported by FT-IR, 1H NMR and mass spectral data.