One-pot, four-component synthesis of fully substituted 1,3,4-oxadiazole derivatives from N-isocyaniminotriphenylphosphorane (Ph3PNNC), a primary amine, a carboxylic acid and cinnamaldehyde

The imine intermediate generated by the addition of primary amine to the cinnamaldehyde is trapped by the N-isocyaniminotriphenylphosphorane (Ph3PNNC) and a carboxylic acid, and leads to the formation of the corresponding iminophosphorane intermediate. The 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were completed under neutral conditions at room temperature. The fully substituted 1,3,4-oxadiazole derivatives were produced in high yields. The method offers a mild, simple, and efficient route for the preparation of fully substituted 1,3,4-oxadiazols. The structures of the products were deduced from their IR, 1H NMR, 13C NMR spectra, and mass spectrometry.