Synthesis of some novel 4-substituted coumarins having potential biological activity (Part III)

Various methyl substituted coumarin carboxaldehydes haw been condensed with aromatic amines to give Schiff bases. These Schiff bases have then been reacted with thioglycolic acid to give five membered cyclized products, 4-thiazolidinone substituted at 4-position of coumarins. 4-alkyl coumarin acetates have been reacted with semicarbazide or thiosemicarbazide in polyphosphoric acid to undergo condensation followed by in situ cyclization to form oxadiazoles and thiadiazoles. All the 4 - substituted coumarin heterocycles have been found to possess antibacterial activity.