Diazenium cations. Part 2. Synthesis and mechanism of the ‘reduction’ of bicyclic cis-diazenium derivatives in alcoholic media

Abstract

Bicyclic cis-azo-compounds are protonated by mineral acids to give the corresponding diazenium ions in high yields. When refluxed in an alcohol bearing an α-hydrogen atom, the cations are transformed into mixtures of products difficult to separate, the major component of which is the corresponding hydrazinium species. All products have been characterized by independent synthesis. In an attempt to specify the mechanism of the ‘reduction,’ unsubstituted, N-isopropyl-, and N-t-butyl-diazenium salts with various counterions (Cl^–, Br^–, I^–, or CIO₄^–) have been prepared and their thermal properties investigated as a function of solvent and various additives. It is concluded that the unsubstituted diazenium cations react by alkylation, prototopic rearrangement, and subsequent hydrolysis. The mechanistic result has led to a new, high-yield synthesis of the N-t-butyldiazenium species.