Recent Advances in Asymmetric CC and C‐Heteroatom Bond Forming Reactions using Polymer‐Bound Catalysts

Bräse, Stefan; Lauterwasser, Frank; Ziegert, Robert E.

doi:10.1002/adsc.200202164

Cited by 107 publications

(22 citation statements)

References 378 publications

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“…The quest for new catalytic and highly enantioselective processes [1] is currently one of the primary challenges in chemical synthesis. In this context, chiral polyoxometalates (POMs) have recently become a topic of interest due to their potential applications in medicine and stereoselective catalysis.…”

Section: Introductionmentioning

confidence: 99%

Optically Active Tripodal Dendritic Polyoxometalates: Synthesis, Characterization and Their Use in Asymmetric Sulfide Oxidation with Hydrogen Peroxide

et al. 2011

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A series of structurally well-defined enantiopure tripodal allyl dendritic structures bearing three amine groups have been synthesized. The hydrogenation of the allyl groups in the presence of a Pd/C catalyst gave the corresponding enantiopure n-propyl counterparts. Treatment of these n-propyl amino dendrimers with heteropolyacid H3PW12O40 and excess H2O2 gave the enantiopure n-propyl {PO4[WO(O2)2]4}3– salts. Characterization of these dendritic POM hybrids in solution by NMR spectroscopy, elemental analysis, UV/Vis spectrophotometry, circular dichroism (CD), vibrational circular dichroism (VCD) and fluorimetry indicates the presence of POM–ligand interactions and confirms their optical and chiroptical properties. The hybrid compounds selectively oxidized sulfides to the corresponding chiral sulfoxides with up to 13 % enantiomeric excess (ee), highlighting the transfer of chirality from the dendritic wedges to the inorganic cluster. The properties of the POM anion, especially its solubility and regio- and stereoselectivity, are sensitive to the structure of the cation. The catalyst was recovered by precipitation without any discernible loss in activity, selectivity or enantioselectivity over three catalytic cycles at –50 °C. Interestingly, a dendritic effect was noted in the enantioselectivity as the dendritic-POM hybrids are more selective than their non-dendritic counterparts. The ee resulting from chirality transfer to the anionic POM unit is comparable to that obtained in our previous work with monopodal dendritic polyoxometalates (14 %) despite the polyvalency of the highly charged tripodal ligand, which is rationalized by different spectroscopic methods

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Section: Introductionmentioning

confidence: 99%

Optically Active Tripodal Dendritic Polyoxometalates: Synthesis, Characterization and Their Use in Asymmetric Sulfide Oxidation with Hydrogen Peroxide

et al. 2011

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“…The use of homogeneous catalysts bound to soluble polymeric supports [19] in continuously operating membrane reactors was pioneered by Wandrey and co-workers as well as Kragl and Dreisbach. The catalyst consists of a soluble polymeric support − a copolymer of 2-hydroxyethyl methacrylate and octadecyl methacrylate − combined with α,α- Figure 5.…”

Section: Selected Examples Of Continuous Homogeneous Catalysis 1) Polmentioning

confidence: 99%

Continuous Homogeneous Catalysis

2005

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This review article illustrates possible aspects for molecularweight enlargement and immobilisation of transition-metal complexes that have been developed for bridging the gap between homogeneous and heterogeneous catalysis. The recycling of homogeneous catalysts can be performed using different types of supports, such as dendrimers, hyperbranched polymers, nanostructured materials or stabilized nanoparticles in combination with suitable filtration methods

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“…[1][2][3][4] The use of heterogeneous catalysts under ambient conditions offers several advantages compared with their homogeneous counterparts, such as ease of recovery and recycling and enhanced stability. Distinct methodologies have been developed for the immobilization of homogeneous catalysts or the creation of heterogeneous catalysts.…”

Section: Introductionmentioning

confidence: 99%

Asymmetric heterogeneous carbene transfer catalyzed by optically active ruthenium spirobifluorenylporphyrin polymers

Ferrand

Poriel

Maux

et al. 2005

Tetrahedron: Asymmetry

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Recent Advances in Asymmetric CC and C‐Heteroatom Bond Forming Reactions using Polymer‐Bound Catalysts

Cited by 107 publications

References 378 publications

Optically Active Tripodal Dendritic Polyoxometalates: Synthesis, Characterization and Their Use in Asymmetric Sulfide Oxidation with Hydrogen Peroxide

Optically Active Tripodal Dendritic Polyoxometalates: Synthesis, Characterization and Their Use in Asymmetric Sulfide Oxidation with Hydrogen Peroxide

Continuous Homogeneous Catalysis

Asymmetric heterogeneous carbene transfer catalyzed by optically active ruthenium spirobifluorenylporphyrin polymers

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