Spectroelectrochemical study on the electrooxidation in aqueous medium of some 1,4-dihydropyridines: Effects of substitution in 1-position and 4-position

Abstract

Spectroelectrochemical and HPLC characterization of the electrochemical oxidation in aqueous medium of a series of six N-1 and C-4 substituted 1,4-dihydropyridines is presented. Based on the analysis of spectra obtained by in situ spectroscopic measurements it was possible to detect the generation of final oxidation products, which resulted in differences depending of the nature of the substitution on the nitrogen in the dihydropyridine ring. Controlled potential electrolysis (CPE) in aqueous medium was followed by the HPLC technique using EC and PDA detectors. This latter resulted adequately to follow the parent 1,4-DHP derivatives and their respective oxidation products. Electrochemical oxidation of parent N-H substituted 1,4-dihydropyridines generated the corresponding neutral pyridine derivative as final oxidation product. However, the N-ethyl substituted 1,4-dihydropyridine derivatives gave rise to the pyridinium salt derivatives.