Synthesis and spectral properties of 2-methyl-5-aryl-1,3,4-oxadiazoles

By heterocyclization of 1-acyl-2-aroylhydrazines under the influence of strong dehydrating substances, a series of 2-methyl-5-aryl-1,3,4-oxadiazoles has been synthesized and their UV, IR, and PMR spectra have been investigated. Through analysis of data on the influence of substituents on the position of the maximum in the electronic absorption spectrum, together with calculated data, it has been shown that the long-wave band of 2-methyl-5-phenyl-1,3,4-oxadiazole is due to an S0-S1 transition of the π-π* type and that it is a charge transfer band for transfer from the phenyl radical to the oxadiazole ring; the 1,3,4-oxadiazole ring as a substituent has an electron-acceptor character. ©1997 Plenum Publishing Corporation.