Synthesis, Characterization and biological activity of various substituted (E)-5-benzylidene-2-((4-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)methoxy)phenyl)amino)thiazol-4(5H)-one derivatives

2-(chloromethyl)-5-(4-nitrophenyl)-1,3,4-oxadiazole was synthesized via reaction of chloroacetic acid with 4-nitrobenzohydrazide in phosphonyl chloride(4). Compound 4 was treated with 4-aminophenol to form 4-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)methoxy)aniline(5) having free -NH2 group,which is reacted with chloroacetyl chloride to give 2-chloro-N-(4-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)methoxy)phenyl)acetamide(6). Compound 6 was cyclized by ammonium thiocyanate to form 2-((4-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)methoxy)phenyl)amino)thiazol-4(5H)-one(7) with thiazolone ring. Compound was reacted different aldehydes to form (E)-5-benzylidene -2-((4-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl) methoxy)phenyl) amino)thiazol-4(5H)-one derivatives(8a-j). In vitro antibacterial activity of the target compounds were investigated using two types of bacteria, Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). The results indicated that the newly synthesized (E)-5-benzylidene-2-((4-((5-(4-nitrophenyl)-1,3,4-oxadiazol-2-yl)methoxy) phenyl)amino)thiazol-4(5H)-one derivatives (compounds 8d and 8f) showed enhanced activity against Gram-negative bacteria when compared with that of the control drug (gentamycin).