Oxidative Assemblies of Flavonoids Dimers - Synthesis of Dehydrodicatechin A

Catechin and quercetin were subjected to different oxidative conditions. Reagents such as silver oxide, potassium ferricyanide or PIDA (phenyliodine diacetate), as well as electrochemical and photocatalytic conditions were evaluated. From quercetin, the formation of a dimer resulting from an oxa-Diels-Alder has been systematically observed. From catechin, dehydrodicatechin A was obtained by the action of silver oxide in a toluene/acetone mixture. Complementary experiments in the presence of catechol gave information on the mechanisms of formation. Products resulting from these reactions have already been identified in plants and beverages made from plants and are supposed to result from the oxidation of flavonoids. This reactivity exploration provides a better understanding of the role of catechols in the formation of natural compounds arising from the dimerization of flavonoids during oxidative process. These results shed some light on the intrinsic reactivity of catechin and quercetin.