Synthesis and antibacterial activity of 5-aryl-2-[(alpha-chloro-alpha-phenylacetyl/alpha-bromopropionyl)amino]- 1,3,4-oxadiazoles and 2-[(5-aryl-1,3,4-oxadiazol-2-yl)imino]-5-phenyl/methyl-4-thiazolidinone s.

Reaction of 5-aryl-2-amino-1,3,4-oxadiazoles (BI-VI), obtained by the oxydative cyclization of aromatic aldehyde semicarbazones (AI-VI), with alpha-chloro-alpha-phenylacetyl chloride and alpha-bromopropionyl bromide yielded 5-aryl-2-[(alpha-chloro-alpha-phenylacetyl)amino]-1,3,4-oxadiazoles (Ia-VIa) and 5-aryl-2-[(alpha-bromopropionyl)amino]-1,3,4-oxadiazoles (VIIa-XIIa), respectively. Furthermore, Ia-XIIa were refluxed with ammonium thiocyanate to give 5-phenyl/methyl-2-[(5-aryl-1,3,4-oxadiazol-2-yl)imino]-4-thiazo lidinones (It-XIIt). All compounds were tested for antibacterial activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. They were all found to possess significant activity against S. aureus with MIC values ranging from 0.24 to 125 micrograms/ml. LD50 of compounds chosen as prototypes are estimated.