Oxidation of flavonols with Cu(II), Fe(II) and Fe(III) in aqueous media

Reactions of flavonols, 3-methoxyflavones, and flavones with Cu2+, Fe3+, and Fe2+ in acidic aqueous solutions with three different organic modifiers are investigated. Complexation may be followed by an oxidation of flavonols, yielding additional peaks in HPLC chromatograms of the reaction mixtures. The products are synthesized with high yields and isolated in mg amounts. They are characterized as 2-(hydroxybenzoyl)-2-hydroxybenzofuran-3(2H)-ones, using two-dimensional NMR techniques and PBI-NCI and -EI-MS. The electrochemical behaviour of the compounds is further investigated with cyclic voltammetry.