Flavyliumsalts and d-catechin condense oxidatively to yield crystalline 4-flavanylflavylium salts. Aerial oxidation is not involved in these condensation reactions. A 4-flavanylflavene is first formed and then oxidized by a second molecule of the flavylium salt, which is reduced to a monomeric flav-2-ene. This conclusion is supported by studies on the oxidation of model phenolic flav-2-enes. Disproportionation