Electrochemical reduction of the antitumour anthrapyrazole Cl-941: mechanism of formation and isolation of the leuco form

Abstract

The title compound undergoes two successive one-electron reductions in the aprotic solvent DMF and an apparent one-step two-electron reduction in the presence of proton donors. Both the leuco form, resulting from the addition of two electrons and two protons, and the product of its hydrolysis in acidic media, have been isolated. All of the observed reactions proceed according to thermodynamic and kinetic parameters (redox potentials, pK_as and rate constants) which are quantitatively analysed.