One-pot ultrasonication assisted synthesis of biologically active 1, 3, 4- oxadiazole derivatives catalyzed by TiO2 nanoparticles

Abstract

A novel approach was adopted in the one-pot synthesis of 2-phenyl-5-aryl substituted-1, 3, 4-oxadiazole derivatives through ultrasonication. Substituted carboxylic acids (1a-l) underwent condensation with benzohydrazide (13) in the presence of ortho- (benzotriazol-1-yl)-N, N, Nʹ, Nʹ-tetramethyluronium tetrafluoroborate (TBTU) to form diacylhydrazine derivatives (3a-l). In the next step, the derivatives 3a-l were subjected to cyclodehydration in the presence of titanium dioxide (TiO2) nanoparticles (NPs) in the presence of dichloromethane (DCM) solvent, at room temperature through which excellent pure yields of substutitued 1, 3, 4- oxadiazoles (4a-l) were obtained. These synthesized derivatives were characterized by spectral techniques like 1HNMR, 13CNMR, Mass spectrophotometers and the respective elemental analysis was determined. The reaction scheme was also performed with other metal oxides NPs (CuO, ZnO, NiO) and the results have shown that TiO2 NPs were most effective in forming the best yields of the derivatives. Their biological applicability was investigated by conducting anti-bacterial studies against gram-negative Escherichia coli and grampositive Staphylococcus aurues. In these studies, almost majority of the derivatives have shown positive results in deactivating the micro-organisms.