A New and Facile Method for the Synthesis of Phenyldihydropyrimidines with its Substituted Derivatives and Their Microbial Evaluation

A green, simple, efficient, and cost-effective procedure has been developed for the synthesis of dihydropyrimidinones by a solvent-free and catalyst-free Biginelli’s condensation of 1,3-dicarbonyl compound, aldehyde, and urea. This approach of direct reaction in neat without solvent and catalyst shows a new direction in green synthesis. In a typical experimental procedure, a mixture of 1,3-icarbonyl compound, aldehyde, and urea was heated at 100-105 C without any solvent or catalyst. The reactions are completed in a hour, and the solid products were filtered and recrystallized. It has also been observed that under identical reaction conditions (without an acid catalyst) the reaction did not progress at all in refluxing dichloromethane, dichloroethane, THF, and toluene during 1 h. This indicates the special advantage of the solvent less reaction and the negative role of solvent at least in this case. A broad range of structurally diverse 1,3-dicarbonyl compounds, aldehydes, and urea are subjected under this procedure to produce the corresponding dihydropyrimidinones.