(Chemical Equation Presented) We report here domestic microwave-induced perchloric acid-catalyzed solvent-free synthesis of various 4-aryl-3,4- dihydropyrimidones for the first time. In all the cases the yields are excellent and the mechanism follows a simple Biginelli condensation to produce the dihydropyrimidones in a few seconds. This procedure has been successfully employed to synthesize the mitotic kinesin EG5 inhibitor Monastrol (Figure I).