Various 3,5-diaryl-1-phenyl-2-pyrazolines were synthesized, and their thermal oxidation to their corresponding 2-pyrazoles was investigated using tetrabutylammonium peroxydisulfate in acetonitrile solution. Compared to the reported oxidative methods, this oxidizing agent provides a clean and non-expensive oxidative reaction in a short reaction time. Based on the proposed reaction mechanism, the extent of co-planarity of the C3-aryl ring toward C3=N2 double bond of the heterocyclic ring affects the electron-donating ability of the heterocyclic ring and decreases the time of oxidative reaction. The experimental results are supported by cyclic voltammetric measurements.
Keywords: 2-Pyrazolines; Electron transfer; Oxidation; Peroxydisulfates; Substituent effects.