Showing papers by "Shiro Hikichi published in 2003"
TL;DR: The effectiveness of this catalyst is evidenced by ≥99% selectivity to epoxide, ≥ 99% efficiency of H2O2 utilization, high stereospecificity, and easy recovery of the catalyst from the homogeneous reaction mixture.
Abstract: Epoxides are an important class of industrial chemicals that have been used as chemical intermediates. Catalytic epoxidation of olefins affords an interesting production technology. We found a widely usable green route to the production of epoxides: A silicotungstate compound, [gamma-SiW10O34(H2O)2]4-, is synthesized by protonation of a divacant, lacunary, Keggin-type polyoxometalate of [gamma-SiW10O36]8- and exhibits high catalytic performance for the epoxidation of various olefins, including propylene, with a hydrogen peroxide (H2O2) oxidant at 305 kelvin. The effectiveness of this catalyst is evidenced by >/=99% selectivity to epoxide, >/=99% efficiency of H2O2 utilization, high stereospecificity, and easy recovery of the catalyst from the homogeneous reaction mixture.
543 citations
TL;DR: In this article, a dinuclear peroxotungstate, K2[{W(O)(O2)2(H2O)}2(μ-O)]⋅2
Abstract: A dinuclear peroxotungstate, K2[{W(O)(O2)2(H2O)}2(μ-O)]⋅2 H2O, exhibits high catalytic performance for the epoxidation of various allylic alcohols with only one equivalent of hydrogen peroxide at 305 K in water solvent. The effectiveness of this system is evidenced by high chemo-, regio-, and diastereoselectivity, and stereospecificity for the epoxidation of allylic alcohols. Furthermore, products/catalyst separation can be easily carried out by simple extraction and the catalyst recovered can be reused with the maintenance of the catalytic performance.
53 citations
TL;DR: In this article, a mechanism involving a heterobimetallic di-μ-hydroxo intermediate formed via dehydrative condensation has been proposed for the oxidative dehydrogenation of a 3-isopropenyl-substituted TpiPr2 ligand.
Abstract: Treatment of hydroperoxopalladium complexes, (TpR)(py)Pd–OOH, with hydroxonickel complexes, [(μ-OH)NiTpR′]2, when either TpR or TpR′ is TpiPr2, results in dehydrogenation of an isopropyl group of the TpiPr2 ligand to give heterobimetallic di-μ-hydroxo complexes bearing the 3-isopropenyl-substituted Tp ligand [HB(pziPr2)2(pz3-isopropenyl-5-iPr). Similar dehydrogenation is observed for the reaction with the hydroxocobalt complex bearing the TpiPr2 ligand. The dehydrogenated products are characterized by spectroscopic and crystallographic methods and a mechanism involving a heterobimetallic μ-peroxo intermediate formed via dehydrative condensation has been proposed for the oxidative dehydrogenation.
11 citations
TL;DR: In this article, the reaction pathway (enolato formation vs. ester hydrolysis) is a combined result of various factors including the acidity of the CH moiety in 2, rigidity of the enolato skeleton, and relative thermodynamic stability of possible structures.
8 citations
TL;DR: In this article, a peroxochromium (V) complex was obtained by oxidative dehydrative condensation of the dimeric (dihydroxo)(aquo)chromium(III) complex, [TpiPr2Cr(OH)2(OH2)]2, with H2O2.
Abstract: Synthesis of a peroxochromium complex containing the TpiPr2
[hydrotris(3,5-diisopropylpyrazolyl)borato] ligand has been attempted by (i) dehydrative condensation between hydroxochromium complexes and H2O2 and (ii) oxidative addition to a Cr(II) species. As a result, a diperoxochromium(V) complex, TpiPr2Cr(O2)2, is obtained by oxidative dehydrative condensation of the dimeric (dihydroxo)(aquo)chromium(III) complex, [TpiPr2Cr(OH)2(OH2)]2, with H2O2, whereas O2-oxidative addition to Cr(II) species affords Cr(III) species or dinuclear TpiPr2Cr species bridged by chromate (CrO4) or dichromate ions (Cr2O7). The preparations of the starting complexes and oxidation reactions by the diperoxo complex are also described.
8 citations
TL;DR: In this paper, the methine moiety of an isopropyl group proximal to the metal center was peroxided to give a cyclic alkylperoxopalladium complex.
Abstract: Treatment of a hydroperoxopalladium complex, (TpiPr2)(py)Pd-OOH, with a catalytic amount of a Cu(II) species resulted in peroxidation of the methine moiety of an isopropyl group proximal to the metal center to give a cyclic alkylperoxopalladium complex.
8 citations
TL;DR: In this paper, a silicotungstate compound, [gamma-SiW10O34(H2O)2]4], is synthesized by protonation of a divacant, lacunary, Keggin-type polyoxometalate of [GammaSiW 10O36]8]8 and exhibits high catalytic performance for the epoxidation of various olefins, including propylene, with a hydrogen peroxide (H 2O2) oxidant at 305 kelvin.
Abstract: Epoxides are an important class of industrial chemicals that have been used as chemical intermediates. Catalytic epoxidation of olefins affords an interesting production technology. We found a widely usable green route to the production of epoxides: A silicotungstate compound, [gamma-SiW10O34(H2O)2]4-, is synthesized by protonation of a divacant, lacunary, Keggin-type polyoxometalate of [gamma-SiW10O36]8- and exhibits high catalytic performance for the epoxidation of various olefins, including propylene, with a hydrogen peroxide (H2O2) oxidant at 305 kelvin. The effectiveness of this catalyst is evidenced by >/=99% selectivity to epoxide, >/=99% efficiency of H2O2 utilization, high stereospecificity, and easy recovery of the catalyst from the homogeneous reaction mixture.
4 citations