Synthesis, spectroscopic studies, and antioxidant activities of novel thio/carbohydrazones and bis-isatin derivatives from terephthalaldehyde

Abstract

New bis(isatins-thio/carbohydrazones) based on Schiff bases were prepared from terephthalaldehyde biscarbohydrazone and 5-substituted isatins in the presence of a drop of sulfuric acid under reflux in ethanol. Terephthalaldehyde bis(thio/carbohydrazone) was synthesized by the reaction of (thio)/carbohydrazide and terephthalaldehyde inthe presence of a few drops of acetic acid under reflux in ethanol. The structures of these synthesized compounds weredetermined using IR, 1 H NMR, and 13 C NMR spectroscopy and elemental analysis. The in vitro antioxidant activityof all the compounds was determined by the 1,1-diphenyl-2-picryl hydrazyl (DPPH.) free radical scavenging method.Compound 2 showed the best antioxidant activity.