Iron(II, III)-Catalyzed Oxidation of Limonene by Dioxygen

Labile iron(II) and iron(III) complexes {[FeII(bpy)22+]solv and [FeIII(bpy)23+]solv} in acetonitrile activate dioxygen for the oxidation of limonene to produce mainly carvone, carveol, limonene oxide, and perillaldehyde. Iron(III) complex is reduced by the substrate to iron(II) one, which activates dioxygen. Probably the catalyst interacts with substrate prior to the oxidation process. Perillaldehyde is likely formed directly from oxidation of methyl group (not via alcohol). However, the aldehyde is also reduced to perillyl alcohol by the reduced form of the catalyst.