Aerobic Palladium-Catalyzed Oxidations in the Upgrading of Biorenewables: Oxidation of β-Ionone and α-Ionone

alpha-Ionone and beta-ionone are natural products that are found in a variety of essential oils and are also produced synthetically on an industrial scale. Both ionones were selectively oxidized by molecular oxygen in the presence of chloride-free Pd(OAc)(2)/para-benzoquinone catalytic systems. Highly functionalized oxygenated terpenoids that were obtained in these new processes are potentially useful as ingredients in synthetic perfumes, cosmetics, and pharmaceuticals. beta-Ionone (known as rose ketone) was converted into a single major product, whereas alpha-ionone gave three isomeric products, all of which resulted from the allylic oxidation of their endocyclic double bonds. These processes operated with an efficient dioxygen-coupled catalytic turnover under 5-10 atm pressure, in the absence of conventionally used metal-redox-active cocatalysts. Alternatively, the reactions could be efficiently conducted under atmospheric pressure in the presence of copper acetate to assist in the regeneration of BQ by molecular oxygen.