Two new series of N-(4-acetyl-5-aryl-4,5-dihydro-1,3,4-thiadiazol-2-yl)acetamide and N-(4-acetyl-5-aryl-4,5-dihydro1,3,4-selenadiazol-2-yl)acetamide compounds (where aryl = 4-nitrophenyl, 4-hydroxy-3-methoxyphenyl, 3-ethoxy-4- hydroxyphenyl, 2-chloroquinolinyl, and 6-chloro-4-oxo-4H-chromenyl) were synthesized in good yields by heterocyclization of thiosemicarbazones (TSCs) and selenosemicarbazones (SSCs) with acetic anhydride, respectively. The new TSCs and SSCs compounds was prepared by condensation reaction of thiosemicarbazide and Selenosemicarbazide with aromatic aldehydes in acidic medium. The structures of newly synthesized 1,3,4-thiadiazoline (TDZs) and 1,3,4-selenadiazoline (SDZs) derivatives were characterized by the analytical and spectroscopic method such as IR, 1 H NMR, 13C NMR, mass spectra and elemental analysis. The purity of compound and evaluation of Rf value were determined by TLC. The toxicity of new compounds was assayed via the determination of their LD50 value by using Dixon’ s up and down method. The antibacterial activity of 1,3,4-thiadiazoline and 1,3,4-selenadiazoline compounds were tested in vitro against Staphylococcus aureus, Bacillus, Escherichia coli and Pseudomonas aeruginosa. Finally, antioxidant efficiency of all compounds were detected according to β-carotene bleaching method.

Several new and know 6-(4-substituted phenyl)-4-(4-substituted phenyl)-2-phenyl-6H-1,3-thiazine (or selenazine) (Z4B7, Z4D5, Z4B7' and Z4D5') were prepared by the 1,4-Michael addition reaction of chalcone derivatives with thiobenzamide or phenylselenocarboxamide in basic medium (where the chalcones was formed by Claisen-Schimidt condensation of aromatic aldehydes with 4-substituted acetophenone in presence of sodium hydroxide). These 6H-1,3-thia- or selenazine were used to a new series of cephem and selenacephem compounds (i.e. 7-chloro-4-(4-substituted phenyl)-2-(4-substituted phenyl)-6-phenyl-5-thia (or 5-selena)-1-azabicyclo[4.2.0]oct-2-en-8-one; AZ4B7, AZ4D5, AZ4B7' and AZ4D5'). All new compound derivatives were characterized by IR, 1H NMR, 13C NMR, mass spectroscopic techniques and elemental analysis. The toxicity of new compounds was assayed via the determination of their LD50 value by using Dixon's up and down method. The antibacterial activity of cephem and selenacephem compounds were tested in vitro against Staphylococcus aureus, Bacillus, Escherichia coli and Pseudomonas aeruginosa. Furthermore, the antioxidant, anticancer and DNA cleavage efficiency of compounds were evaluated.