Sulfonyl Hydrazones of Cyclic Amides and Quaternary Azo Sulfones of Heterocycles as Reagents in Azo Chemistry

Sulfonyl hydrazones of cyclic amides undergo oxidative coupling with phenols and reactive methylene components. The reaction proceeds via the azo sulfones, which may be used as such, and which, as ambident cations, enter into many reactions with nucleophiles and extend the scope of oxidative coupling. The reaction with phenols is a two-step process, in which the limiting cases k₁ ? k₂, k₁ ≈ k₂, and k₁ ? k₂ can be realized by slight variation of the reactants.