Abstract:
In this work, the reaction mechanism of the electrochemical synthesis of
1,3,5-trisubstituted 1,2,4-triazoles by anodic oxidation of benzaldehyde
phenylhydrazones in the presence of benzonitrile was investigated. The redox
properties of hydrazones with various substituents were determined by cyclic
voltammetry and then related to the corresponding hydrazone structure. By digital
simulation (fitting of the simulation curves to the experimental ones) kinetic
parameters of the oxidation reaction of anisaldehyde phenylhydrazone (as representative
example for the hydrazones) were determined. The electrochemistry of anisaldehyde
phenylhydrazone in the presence of benzonitrile was investigated in neutral and
basic medium. The desired product (triazole) could only be observed in neutral
medium. Thus, the reaction path via a nitrilimine as intermediate - which
preferably would have occured in basic medium - could be excluded. Instead of this,
the direct attack of the nitrile on the primary oxidation product, the radical cation,
was postulated.