Design and synthesis of some new thiophene, thienopyrimidine and thienothiadiazine derivatives of antipyrine as potential antimicrobial agents.

4-acetamide Pyrazolone 2 was synthesized by acetylation of 4-amino antipyrine 1 in excellent yield. 4-acetamide pyrazolone 2 was exploited as a starting material for the syntheses of hitherto unknown different types of new heterocyclic compounds incorporating the antipyrine moiety which expect highly biological activity against various microorganisms. Thus, Claisen condensation of 4-acetamide pyrazolone 2 with diethyl oxalate have been utility to afford new 4-oxaloacetyl antipyrine 3, which upon hydrazinolysis of the ester function to obtain the acetohydrazide derivative 18 which used as starting material to synthesize 1,2,4-triazol 19 and hydrazone 20 derivatives. 4-aminothiophene carboxylate derivatives 6, 7 were synthesized by utility of Gewald reaction. On the other hand, Michael type addition of the enolate ion of acetyl functions in acetamide pyrazolone 2 to the activated double bond in arylidenemalonoester to furnish pyrane derivative 9 was done. Finally, 4-acetamide pyrazolone 2 was treated with aromatic substituted aldehyde to exhibit thiophenacrylamide derivative 10. Compound 6 gave characteristic reaction for enaminonitriles, thus, the behavior of o-aminoester of 4-aminothiophene carboxylate derivative 6 toward electrophilic reagent, one carbon donars, amide and acid was also investigated to afford the correspondence thiophene derivatives 11,12,13,15 and 16. In addition, treatment of carboxamide derivative 16 with thionyl chloride afforded the thienothiadiazine derivative 17. The characterization of all synthesized compounds was done by elemental analysis and spectral studies. Moreover, all the synthesized compounds were tested against antimicrobial activities by the disc diffusion method, which exhibited higher promising biological activities.