General procedure for the synthesis of quinoline-6-carbohydrazide from methyl 6-quinolinecarboxylate: Methyl 6-quinolinecarboxylate (0.10 mol) was dissolved in ethanol (50 mL), 99% hydrazine hydrate (0.10 mol) was added, and the mixture was refluxed for 17 hours. Upon completion of the reaction, the reaction mixture was cooled and the resulting solid was collected by filtration and washed with a small amount of cold methanol to give quinoline-6-carbohydrazide. The reaction process was monitored by thin layer chromatography (TLC) with the unfolding agent being toluene: acetone (8:2, v/v). The product was a colorless solid in 89% yield, melting point 195-197 °C. IR (KBr, cm^-1): 3376, 3291 (NH2), 1689 (C=O, amide).1H NMR (400 MHz, DMSO-d6): δ 10.34 (br s, 1H, NH), 8.89 (dd, J = 1.7, 4.1 Hz, 1H) , 8.38-8.43 (m, 2H), 8.19 (dd, J = 1.6, 8.3 Hz, 1H), 7.97 (d, J = 7.7 Hz, 1H), 7.53 (dd, J = 4.1, 8.3 Hz, 1H), 4.71 (br s, 2H, NH2).
