Facile Synthesis of Pyrazole Encompassing Pyridyl Oxadiazoles Using Conventional and Microwave Techniques

In the present paper, novel compounds 1-(2-(3-(4-chlorophenyl)-1-phenyl-1H-pyrazol-4-yl)-5-(pyridin-4-yl)-1,3,4-oxadiazol- 3(2H)-yl)-3-(aryl)prop-2-en-1-ones 5a-m were synthesized via cyclization of hydrazone derivative 3 with acetic anhydride and further proceeded by Claisen Schmidt reaction with different aromatic aldehydes. Synthesis of title compounds 5a-m was achieved using both conventional and microwave irradiation techniques. The yields ranged between 79-91% using microwave method and between 59-66% using conventional method. All the novel compounds 5a-m were evaluated for their in vitro antibacterial and antifungal potency against Gram-positive, Gram-negative strains of bacteria as well as fungal strains respectively and in vitro cytotoxicity study (HeLa cell lines) using MTT colorimetric assay. Among the screened compounds, 5e, 5f, 5j, 5k and 5l showed most potent antibacterial activity, while compounds 5e, 5f, 5i, 5k and 5l demonstrated excellent antifungal activity. The structure activity relationship showed that occurrence of electron donating groups witnessed substantial improvement in the antimicrobial activity. While the outcome of MTT cytotoxicity studies on HeLa cells exposed that strong antimicrobial activity of 5e, 5f and 5i-l was escorted with low cytotoxicity