The highly chemo-, regio-, and diastereoselective and stereospecific epoxidn. of various allylic alcs. with only one equiv. of hydrogen peroxide in water can be efficiently catalyzed by the dinuclear peroxotungstate, K2[{W(=O)(O2)2(H2O)}2(ﾎｼ-O)]ﾂｷ 2H2O (I). The catalyst is easily recycled while maintaining its catalytic performance. The catalytic reaction mechanism including the exchange of the water ligand to form the tungsten-alcoholate species followed by the insertion of oxygen to the carbon-carbon double bond, and the regeneration of the dinuclear peroxotungstate with hydrogen peroxide is proposed. The reaction rate shows first-order dependence on the concns. of allylic alc. and dinuclear peroxotungstate and zero-order dependence on the concn. of hydrogen peroxide. These results, the kinetic data, the comparison of the catalytic rates with those for the stoichiometric reactions, and kinetic isotope effects indicate that the oxygen transfer from a dinuclear peroxotungstate to the double bond is the rate-limiting step for terminal allylic alcs. such as 2-propen-1-ol (1a). [on SciFinder(R)]
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