Quinoline-2-carbohydrazide (2) obtained from quinaldic acid (1) was converted to the corresponding carbothioamide 3 and carboxamide 6 by treatment with benzyliso(thio) cyanate. The basic treatment of 3 and 6 yielded the corresponding 1,2,4-triazole derivatives 4 and 7. The synthesis of 5-(quinolin-2-yl)-1,3,4-oxadiazol-2-thiol (9) was performed from the reaction of 1 with CS2 in basic media. The Mannich reaction of compounds 4, 7, and 9 resulted in the formation of aminoalkylated derivatives 5a-c, 8, and 10a,b. The condensation of 1 with thiosemicarbazide, carbohydrazide, or thiocarbohydrazide gave the corresponding 1,2,4-triazole derivatives (11-13). The treatment of 4-amino-5-(quinolin-2-yl)-4H-1,2,4-triazole-3-thiol (13) with 4-chlorophenacyl bromide caused the formation of fused triazolothiadiazine 14. The condensation of 13 with 4-methoxybenzaldehyde generated the corresponding Schiff base 15.
The newly synthesized compounds were characterized by elemental analyses, IR, H-1-NMR, C-13-NMR, and mass spectra. The antimicrobial activity study revealed that some of the newly synthesized compounds showed good to moderate activity against a variety of microorganisms.