Development of Selective Oxidation Catalyst by Control of Multi-Nuclear Active Site of Transition Metal and Reaction Field

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We have developed the efficient oxidation catalysts such as the divacant lacunary polyoxotungstates and divanadium-substituted polyoxotungstate. The multi-nuclear active sites can activate H_2O_2 and substrates efficiently, resulting in the high catalytic performance for the epoxidation of olefins and Bayer-Villiger oxidation with H_2O_2. The novel selenium-containing dinuclear tungsten species shows the highest catalytic activity for H_2O_2-based epoxidation of homoallylic and allylic alcohols among selenium and tungsten complexes. The stabilization of the transition-state by the hydrogen bonding results in the high reactivity. We have also developed the dicopper-substituted γ-Keggin silicotungstate that can act as an effective homogeneous catalyst for the oxidative homocoupling of alkynes and regioselective 1,3-dipolar cycloaddition of organic azides to alkynes. The cooperative involvement of two copper centers in catalyzing the present reactions has been proposed.