Autoxidation of cycloalkenes by the system "molecular oxygen-bis(acetylacetonato) cobalt (II) complex-butyraldehyde"

Abstract

Oxidation of cycloalkenes with O2 promoted by heterogeneous bis(acetylacetonato) cobalt (II) complex catalyst which can be recycled has been performed under mild conditions. It was found that β-ionone, cyclohexene, 1-methylcyclohexene, and α-ionone were efficiently oxidized with O2 in the presence of Co (II) complex and butyraldehyde at 55 °C. A simple treatment of the resulting products led to epoxides as predominant products and a small amounts of allylic oxides, the chemoselectivity for the former being 82.1 - 90.8% with a 70.6 - 98.6% substrate conversion. On the other hand, oxidation of 1-phenylcyclohexene, 1-cyclohex-1-enylethan-1-one, α-pinene, and β-pinene gave allylic oxides as major products.