Mechanistic study of lodenafil carbonate electrochemical reduction in acid medium

Abstract

The electrochemical reduction mechanism of lodenafil carbonate in acidic medium was studied using cyclic voltammetry, square wave voltammetry and chronoamperometry (sulfuric acid 0.1 mol L-1, potential controlled at -1.2 V). The formed product characterization was carried out by FT-IR spectroscopy combined with quantum calculations of the lodenafil molecular orbitals. Over the products IR spectrum, it was possible to note the presence of absorption bands corresponding to the aldehyde, amine and ethanol groups. These results, together with those obtained by electrochemical techniques and quantum calculations, allowed us to propose that the process of reducing lodenafil is dependent on protons and occurs in four irreversible steps, the first being the amide group reduction to an aldehyde and a primary amine. Then, the aldehyde is reduced to an alcohol, with the consumption of two electrons and two protons in each of these steps. Then, there is a reduction in two processes of one electron and one proton each, one of which by a radical way. In this last process, there are two possibilities: one is the sulfone group reduction and the other is the azomethine reduction adjacent to the amine group formed in the previous step.