Synthesis and antimicrobial evaluation of 1,3,4-oxadiazole-based chalcone derivatives

A series of chalcones-bearing 1,3,4-oxadiazole derivatives was synthesized as novel bio-active antimicrobial agents against multidrug-resistant bacteria and fungi. The lead compounds (Z)-2-(5-(3-nitrophenyl)-1,3,4-oxadiazol-2-ylthio)-N-(4-(3-(aryl)acryloyl)phenyl)acetamides 5a–n were synthesized via acid-catalyzed aldol condensation (SOCl₂) by reacting N-(4-acetylphenyl)-2-(5-(3-nitrophenyl)-1,3,4-oxadiazol-2-ylthio)acetamide (4) with differently substituted aldehydes. Compound (4) was obtained by reacting 5-(3-nitrophenyl)-1,3,4-oxadiazole-2-thiol (2) with N-(4-acetylphenyl)-2-chloroacetamide (3) in the presence of K₂CO₃. The intermediates (2) and (3) were synthesized simultaneously from 3-nitrobenzohydrazide (1) and 4-aminoacetophenone, respectively. The formation of intermediates and targeted compounds were confirmed for their structure by means of various spectral–analytical techniques like IR, ¹H NMR, ¹³C NMR, elemental analysis, and mass spectra. Antimicrobial properties of all the synthesized compounds have been evaluated against broad panel of bacteria and fungi.