Electrochemical Synthesis of Heterocyclic Compounds. 17. Anodic Oxidation of Hydrazones in the Presence of Heteroaromatic and Schiff Bases

Article abstract of DOI:10.1021/jo00256a033

Anodic oxidation of a series of hydrazones in the presence of heteroaromatic and Schiff bases were performed in acetonitrile-tetraethylammonium perchlorate electrolyte solution at platinum using controlled potentials.As a result of four-electron oxidation several s-triazolo<4,3-a>pyridinium perchlorates (1-9), s-triazolo<4,3-a>quinolinium perchlorate (10), s-triazolo<3,4-a>isoquinolinium perchlorate (11), and s-triazolo<4,3-a>benzoquinolinium perchlorate (12) were obtained in yields ranging from 30percent to 90percent.As a result of two-electron oxidation of -p-nitrophenylhydrazine (A) in the presence of imidazole and 1,2,4-triazole the azo derivatives 13 and 14 were obtained with high yields.As a result of two-electron oxidation of hydrazone A in the presence of Schiff bases the new Schiff bases 15-20 were obtained in high yields.On the bases of the electroanalytical and preparative results it is concluded that the electrochemical oxidation of hydrazone A in the presence of heteroaromatic and Schiff bases occurs through the formation of cation B, which is attacked by base as a nucleophile.This excludes the possibility of annelation of the heteroaromatics through nitrilimine as an intermediate.