Microwave-Assisted Rapid Synthesis of Pyrido[2,3-d:6,5-d]dipyrimidine-2,4,6,8-tetraones over Sulfonic Acid Functionalized Imidazolium Salts under Solvent-Free Condition

Seven numbers of sulfonic acid functionalized imidazolium salts (ionic liquids) have been tested for the synthesis of pyrido[2,3-d:6,5-d]dipyrimidine-2,4,6,8-tetrone derivative with completely aromatic pyridine ring. [Dsim]Cl is found to be the best among them to carry out the synthesis via condensation of 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione with aromatic aldehydes within minutes under microwave irradiation, paving the way for an excellent methodology towards the synthesis of a series of pyrido[2,3-d:6,5-d]dipyrimidine-2,4,6,8-tetrone. The catalyst can easily be recovered and reproduced, and the reproduced catalyst is found to be equally effective as the fresh one for the purpose. The methodology is quite simple, fast and general. In comparison to already described methodologies, it enjoys additional advantage of being carried out under solvent-free condition. The synthesized compounds are found to possess remarkable activity against S. aureus and K. pneumonia among the tested bacterial strains.