In situ Cu2+ complexation and H2O2 oxidation of a pyridine-2,6-dione dye is described.
Four products are isolated by treating this dye with Cu2+ and H2O2 in NH3·H2O/DMF.
A mechanism is proposed for hydroxyl-addition and ring-degradation products.
A method for preparing new dyes with an additional o-Ph-OH group is proposed.