Abstract

In this paper, a series of six dihydropyridine-fused coumarins were synthesized and electrochemically characterized in dimethylformamide (DMF). Dihydropyridine ring oxidation on glassy carbon electrode (GCE) for condensed heterocyclic compounds revealed a single anodic peak. Oxidation potential values correlated fairly well with substituent effects at 9-position. The overall oxidation mechanism involved 2-electrons and 2-protons as determined by chronoamperometry. Controlled-potential electrolysis followed by UV-Visible spectroscopy proves that dihydropyridine-fused coumarins are electrochemically oxidized in DMF giving rise to the aromatic pyridine derivative. ESA experimental spectra show a triplet, due to the C-centered dihydropyridyl radical trapped with N-tert-butylamine-alpha-phenylnitrone (PBN). Hyperfine coupling constant values (aN) of dihydropyridine-fused coumarins were higher than corresponding values for non-fused ones. These results could be due to the effect of the coupling of the dihydropyridine moiety with the coumarin ring over the splitting constant. (C) 2014 Elsevier Ltd. All rights reserved.