Design, Synthesis, and Antioxidant Activity Screening of Some New Thiazole and Pyrazolo[5,1-c][1,2,4]triazole Derivatives

Thiazoles and pyrazolo[5,1-c][1,2,4]triazoles have attracted particular attention due to their reported biological and therapeutic effects, so the ultimate objective of the current research is to develop some novel heterocyclic ingredients with thiazole and pyrazolo[5,1-c][1,2,4]triazole constituents that have predicted biological effects. This can be achieved by combining 2-cyano-N-(5-methylthiazol-2-yl)acetamide (1) with cinnamaldehyde (2) to generate two different chemicals 3 or 4, depending on the catalyst employed. Compound 1 reacts also with furan-2-carbaldehyde (8), thiocarbohydrazide (10), acetylacetone 15 to afford the respective acrylamide deivative 9, pyrazolo[5,1-c][1,2,4]triazole-3-thione derivative 13, and oxopyridine-3-carbonitrile derivative 19. Also bromination of compound 1 can take place using N-bromosuccinimide (NBS) and ammonium acetate to provide 2-bromo-2-cyano-N-(5-methylthiazol-2-yl)acetamide (14). On the other hand, when ethyl cyanoacetate was combined with thiocarbohydrazide (10), it resulted in the dihydropyrazolo[5,1-c][1,2,4]triazole-3-thione derivative (21), which subsequently reacted with chloroacetic acid 22 and bromo-acetamide derivative 14 to achieve the equivalent pyrazolo[5,1-c][1,2,4]triazole derivatives 24 and 26. Compound 24 can potentially be employed as the precursor for the production of mercaptobut-2-en derivatives 28 and 31. Applying IR, 1H NMR, and mass spectroscopy, the molecular structure of each constructed product was verified. The antioxidant activity of some of the prepared compounds was assessed using the DPPH free radical scavenging assay in triplicate. Average values were taken into consideration, with ascorbic acid used as the reference standard, and all the investigated substances demonstrated antioxidant activity.