Abstract

Wurood S. Ahmed¹, Ammar A. Razzak Mahmood² and Redha I. Al-Bayati³

DOI : http://dx.doi.org/10.13005/ojc/340533

A series of disubstituted 1,3,4-oxadiazole derivatives, including imides and Schiff bases, was achieved from the starting material, ethyl-4-aminobenzoate, which was converted to the corresponding 4-aminobenzohydrazide (1), by its reaction with hydrazine hydrate in absolute ethanol. Two oxadiazole parent nuclei had been synthesized from (1), the first nucleus 5-(4-aminophenyl)-1,3,4-oxadiazol-2-amine(2), and the second is 5-(4-aminophenyl)-1,3,4-oxadiazole-2-thione (3). Compound (2) Obtained from stirring methanolic solution of (1) with cyanogen bromide (CNBr) and sodium bicarbonate (NaHCO₃) at RT. While compound  (3) was synthesized by refluxing of (1) with CS₂ in the presence of  (KOH), the produced potassium salt of hydrazide underwent cyclization by acidification with 10% HCl. Meanwhile, the cyclic imides derivatives (4-6) and (10-12) were synthesized by thermal fusion of (2) or (3) with acid anhydrides, While Schiffʼs bases derivatives (7-9) and (13-15) were  synthesized by a conventional method involved refluxing of  (2) or (3) with  different aromatic aldehydes, in acidic medium (using glacial acetic acid). The new derivatives had been tested against three Gram-positive bacteria (Staphylococcus aureus, Micrococcus luteus, and Bacillus pumilus), and two Gram-negative bacteria (Pseudomonas aeruginosa and  Escherichia coli),and two fungal species: (Saccharomyces cerevisiae and Candida albicans). Among the synthesized derivatives, compound (15) displayed a moderate to potent antibacterial activity, against different (Gram- positive and Gram- negative) bacteria, and also showed a slight to moderate antifungal activity.

Antimicrobial; Imides; Schiff base; Synthesis; 1,3,4-Oxadiazole derivatives

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