The mechanism and regioselectivity of 1,3-dipolar reaction of 2-azido-N-(4-diazenylphenyl) acetamide and an alkyne have been studied in gas phase and in DMSO using the B3LYP-GD3 functional and 6-31G(d,p) basis set. The reaction followed a one-step mechanism with asynchronous TSs. The calculated global reactivity indices calculated revealed, among other things, the nucleophile character of the 2-azido-N-(4-diazenylphenyl)acetamide and the electrophile character of the alkyne (4-bromo-2-chloro-1-ethynylbenzene), in addition to an electron transfer from the 4-bromo-2-chloro-1-ethynylbenzene towards the 2-azido-N-(4-diazenylphenyl) acetamide. The calculated local reactivity indices predicted the formation of the 1,4-triazole, with the most nucleophilic nitrogen and the most electrophilic carbon favoring its formation. However, analysis of the activation energies and thermochemistry parameters showed that the 1,5 triazole is energetically favorable and more stable under thermodynamic control. Bond order analysis coupled with bond formation evolution and the solvent effect was further investigated to support and highlight the asynchronicity in bond formation and the regioselectivity of the reaction, respectively.

A new series of 2-[3-(5-methyl-1-phenyl-1H-1,2,3-triazol-4-yl)-1-phenyl-1H-4-pyrazolyl]-3-aryl-1,3-thiazolan-4-one 5(a-i) have been designed, synthesized and evaluated for their in vitro antibacterial activity against Gram positive bacteria viz. Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 6538p), Micrococcus luteus (IFC 12708) and Gram negative bacteria viz. Proteus vulgaris (ATCC 3851), Salmonella typhimurium (ATCC 14028), Escherichia coli (ATCC 25922) the antifungal activity against Candida albicans (ATCC 10231), Aspergillus fumigatus (HIC 6094), Trichophyton rubrum (IFO 9185), Trichophyton mentagrophytes (IFO 40996). Antibacterial evaluation indicates that compounds containing 4-methoxyphenyl 5c, 4-fluorophenyl 5d and 2,5-difluorophenyl 5h groups on thiazolidinone ring showed significant activity equal to that of standard drug. The antifungal evaluation shows that compound 5c is highly active against A. fumigatus, compound 5d and 5h were also active against C. albicans and A. fumigatus.