4-oxadiazole

Coumarins are the family of benzopyrones, in which benzene ring amalgamated with the pyrone ring. Their versatile oxygen-containing heterocyclic structure and physicochemical characteristics are responsible to attract great attention from medicinal chemists and pharmacologists and for being a privileged scaffold in medicinal chemistry. In this study, 1, 3, 4 -oxadiazole incorporated a series of new coumarin derivatives have been synthesized. Structures of the newly synthesized compounds were established on the basis of FT-IR, 1H NMR spectroscopic techniques and elemental analysis. The synthesized compounds were screened for their in vitro antifungal activity against five pathogenic fungal strains: Aspergillus niger, Penicillium notatum, Saccharomyces cerevisiae, Penicillium chrysogenum and Neurospora crassa by disk-diffusion method. All the compounds were found to have significant antifungal activity against all the fungal strains.

The present communication deals with the synthesis of some N´-alkylidene/arylidene-2-(4-substituted-5-phenyl-1,3,4-oxadiazol-2-ylthio) aceto/arylhydrazides, their characterization and antimicrobial activity against medically important microbes. The final compounds were synthesized by reaction of 2-(4-substituted-5-phenyl-1,3,4-oxadiazol-2-ylthio) acetohydrazide with various aliphatic and aromatic aldehydes in presence of glacial acetic acid in ethanol. The structures of the synthesized compounds were established by IR, NMR and Mass spectral studies. The antimicrobial activity was studied against Staphylococcus aureus (MTCC 87), Bacillus subtilis (MTCC 121), Pseudomonas aeruginosa (MTCC 424), Escherichia coli (MTCC 40), Candida albicans (MTCC 183), Fusarium solani (MTCC 2935) using agar well diffusion method. Some of the tested compounds exhibited activity against all the microorganisms.  In particular, compounds 12, 19 and 22 were found to be active against all the tested bacterial strains and fungal strain Candida albicans. It was concluded that number and position of electron withdrawing substituents affects the activity.

5-(7-bromo-5-chloro-3-methylbenzofuran-2-yl)-1-phenyl-1H-pyrazole-3-carbohydrazide 1 underwent a series of hetero-cyclization reactions with different chemical reagents such as triethylorthoformate, acetic acid in phosphorous oxychloride, benzoic acid in phosphorous oxychloride,  N,N’carbonyldiimidazole in dioxane, carbon disulphide in pyridine to afford substituted 1,3,4-oxadiazoles 2, 3, 4, 5 and 6 respectively.  Extending the reaction of 6 with 4-(2-chloroethyl) morpholine hydrochloride afforded 7. The structures of the newly synthesized compounds were established on the basis of spectral analysis such as IR, 1H NMR, 13C NMR and Mass spectral data. The synthesized compounds were screened for their antimicrobial activity against two gram positive and gram negative bacteria and a fungus and found to possess good activity against selected strains.