Ruthenium/1,1′-Bis(diphenylphosphino)ferrocene-Catalysed Oppenauer Oxidation of Alcohols and Lactonisation of α,ω-Diols using Methyl Isobutyl Ketone as Oxidant

A number of ruthenium catalysts, made in situ from [Ru(p-cymene)Cl-2](2) and various monodentate and bidentate phosphorus ligands were screened in the double Oppenauer oxidation of 1,6-hexanediol to caprolactone using methyl isobutyl ketone as oxidant and potassium carbonate as base. The catalyst based on 1,1-bis(diphenylphosphinyl)ferrocene gave this lactone in excellent yield. The same catalyst was evaluated for the oxidation of other diols to their lactones, of primary alcohols to the corresponding aldehydes and of secondary alcohols to the ketones under the same reaction conditions. The products were obtained in moderate to excellent yields.