A Convenient Route to 1,3,4-Thiadiazoles,Thiazolidinone, Thiazoles,Pyridones, Coumarins,Triazolo[5,1-c]triazines,and Pyrazolo[5,1-c]triazines Incorporating Pyrazolone Moiety and Their Use as Antimicrobial Agents

Condensation of 4-acetyl-5-methyl-2-phenyl-2,4-dihydropyrazol-3-one (1) with hydrazine derivatives (2a–d) afforded hydrazone derivatives (3a–d), which reacted with alkyl halides 4a–c to give bis(alkylthio)methylene derivatives (5a–e). Also, 3a,b reacted with hydrazonyl halides 6a–d to give 1,3,4-thiadiazole (7a–d). Cyclization of 3c with ethyl bromoacetate and haloketones gave thiazolidinone and thiazole derivatives (8, 10a,b) respectively. Treatment of hydrazone (3d) with benzylidine malononitrile 13a,b gave pyridine (14a,b). In addition, cyclocondensation of 3d with phenolic aldehydes furnished coumarin derivatives (16a–c). Coupling of 3d with heterocyclic diazonium salts gave triazol5,1-c]triazine (20) and pyrazolo5,1-c]triazine (22). Some of the prepared products showed potent antimicrobial activity.