Simple aluminum salts activate hydrogen peroxide towards alpha,beta-unsaturated ketones, affording as major products alpha,beta-epoxyketones. The pathway of this reaction involves the interaction between [Al(H2O)(6)](3+) and H2O2, through hydrogen bonds, in the second-coordination sphere. This interaction enhances the proton exchange between non-coordinated water and hydrogen peroxide. as detected by H-1 NMR experiments. By this means, the hydroperoxide anion, formed as reactive intermediate in the proton exchange between H2O and H2O2, can be trapped by alpha,beta-unsaturated ketones. Surprisingly, this pathway is not followed when diethylmaleate is used as substrate. In this case, the radical addition of THF to the C=C bond of diethylmaleate takes place with high selectivity, affording 2-(THF)-derivatives with high yields. (C) 2009 Elsevier B.V. All rights reserved.