A facile one step synthesis of 1,6 -dihydro-7H-pyrazolo[4,3-d]-pyrimidin-7-ones

A general synthetic approach to pyrazolo[4,3-d]pyrimidines is reported. Aldehydes, arylideneanilines, carboxylic acids and orthoesters are used as one-carbon units for bridging the two amino functions of 4-amino-1-alkyl-3-propylpyrazole-5-carboxamides.