Studies On Wacker Oxidation Of Aromatic Olefins

The Wacker oxidation is an important method for the oxidation of olefins to give carbonyl compounds.The initially Wacker system,a method of great importance for the synthesis of acetaldehyde in industry,generally employs Pd(II)as catalyst and CuCl as oxidant under the air condition.With the development of environ-economics,there are many limitations with the traditional method,including the contamination by copper ions,chlorinated byproducts,inferior applicability,olefin isomerization and difficulties in catalyst recovery etc.Thus,it is of great practical significance to explore and develop new methods to realize the sustainable development of reactions.As a green oxidant,hydrogen peroxide has been applied to the Wacker oxidation of aromatic olefins,but there is a need to use complex palladium catalyst in the related reports.Thus,it is of great interest to discover a ligand-free palladium catalyst that will execute the Wacker oxidation of aromatic olefins.In this study,aromatic olefins could mildly transform into the corresponding methyl ketones in good selectivity and yield by the use of aqueous hydrogen peroxide in the presence of palladium acetate under acidic conditions in acetonitrile.The novel oxidation process effectively avoids the contamination of copper ions and the generation of chlorinated byproducts.Moreover,a heterogeneous catalyst involving palladium supported on carbon can be used in the catalytic reaction in the Wacker oxidation.A 93%yield of aromatic methyl ketones could be obtained from aromatic olefins with palladium supported on active carbon under optimal conditions.And the catalyst appeared to be regenerability.A plausible mechanism for the catalytic oxidation was discussed to guide the efficient and environmentally friendly Wacker oxidation.