Study on the synthesis of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles and their acid-base interactions

A series of novel 5-substituted 2-[2-(pyridyl)ethenyl]-1,3,4-oxadiazoles were efficiently synthesized by cyclocondensation of the appropriate 3-(pyridyl)acrylohydrazides with triethyl orthoesters in the presence of glacial acetic acid. The products were identified by means of spectroscopic methods and their pK _A ionization constants were determined. The influence of substituents on the basicity of the pyridine system has been discussed. Graphical Abstract: [Figure not available: see fulltext.][Figure not available: see fulltext.]