1-Methyl-3-propyl-1H-pyrazole-5-carboxylic acid (3) was exclusively brominated at the 4-position by bromine in the dark. Brominated product 8 was then converted into 1-methyl-3-propyl-1H-pyrazole-5-carboxamide 9 by successive treatment with thionyl chloride and ammonium hydroxide. Carboxamide 9 was treated with various aroyl amides under microwave (MW) irradiation to afford 4-aroylamino-1-methyl-3-propyl-1H-pyrazole-5-carboxamides 10-22 and 5-aryl-1-methyl-3-propyl-1,6-dihydro-1H-pyrazolo [4,3-d]pyrimidin-7-ones 23-35. The 1H-pyrazole-5-carboxamides 10-22 were also converted to pyrimidinones 23-35 either by conventional heating or by MW irradiation. However, MW irradiation method gives excellent yields in very short time.