Electrochemical oxidation of 1-phenylpyrazolidin-3-ones. Part 3. Reaction mechanism

Abstract

A cyclic voltammetric study of 1-phenylpyrazolidin-3-one and some typical substituted analogues has shown that the chemical step following the initial electron transfer involves deprotonation of the cation-radical at position 2 (NH). In the absence of added base and at substrate concentration > 2mM, the substrate itself deprotonates the cation-radical. In the presence of basic chloride ions oxidation occurs via the conjugate base of 1-phenylpyrazolidin-3-one. The lifetime of the cation-radical is relatively insensitive to the nature of the substituents at C(4) and C(5), but is increased markedly by substitution at N(2).