An efficient tandem oxidation of cyclohexanol to ε-caprolactone with peroxyacids and TEMPO catalyst in ionic liquids as solvents

The new one-pot tandem oxidation of cyclohexanol to -caprolactone with potassium peroxomonosulfate or m-chloroper-oxybenzoic acid as oxidation agents and ionic liquids as solvents is described. A 2,2,6,6-tetramethylpiperidine-1- oxyl radical with tetrabutylammonium bromide as the co-catalyst was used. A solution of KHSOin the ionic liquid 1-butyl-3-methylimidazolium tetra-fluoroborate [bmim]BFfacilitates the tandem oxidation of alcohol to lactone. In classic solvents, this reaction can only be carried out to the ketone formation step. This is most probably due to the ability of [bmim]BFto dissolve both alcohol and KHSO In the case of using m-chloroperoxybenzoic acid, ionic liquids provide an efficient medium for this reaction. This new method enables -caprolactone formation with high yields (75-80%).