Synthesis of 1,5 and 2,5-disubstituted tetrazoles using NiO nanoparticles and their evaluation as antimicrobial agents

Treatments of tetrazolate salts prepared in situ from various aldehyde; malononitrile and sodium azide in the presence of NiO nanoparticles with benzyl bromide gave the corresponding 1,5- and 2,‌5-disubstituted tetrazoles. Reaction of tetrazolate salts with 2,4′-dibromoacetophenone in the presence of NiO nanoparticles provided the corresponding 2,5-disubstituted derivatives as an only isomer. The structures of the prepared tetrazoles were fully characterized by 1H and 13C NMR spectra, IR spectra, MS and elemental analysis. Use of simple and readily available starting materials, excellent yields, short reaction times, reusability of the catalyst, low amount of catalyst are some advantages of this protocol. Their antimicrobial activity has been tested in vitro against Gram negative bacteria; Gram positive bacteria and fungi. Four compounds have only moderate growth inhibitory effects against Gram positive bacteria. The antimicrobial screening suggests that compounds 5h; 6h; 5g and 6g have only moderate growth inhibitory effects against Gram positive bacteria. Among the newly synthesized compounds; good antimicrobial activity was observed for compound 6g against Staphylococcus epidermidis (MIC value 125 µg/ml).