1,3,4-Oxadiazoles

This article describes progress in the chemistry and applications of 1,3,4-oxadiazoles over the period 2008–18. The main routes to the 1,3,4-oxadiazole skeleton involve oxidative cyclization of N-acylhydrazones, using a variety of oxidants such as molecular iodine, 2,3-dichloro-5,6-dicyanobenzoquinone, iodobenzene diacetate and others. Another convenient approach involves the cyclocondensation of 2-acyl-N-phenylhydrazinecarboxamidesin phosphorus(V) oxychloride heated at reflux, promoted by ultrasound or microwave irradiation. Of particular note are the impressive developments in medicinal chemistry based on 1,3,4-oxadiazoles, which exhibit broad bioactivity against various bio targets such as microorganisms, tumor cells and receptors. Huge progress has also been made in the application of 1,3,4-oxadiazole as luminescent compounds, dyes, and photosensitive materials.