Aspects of Immobilisation of Catalysts on Polymeric Supports

Dioos, Bart; Vankelecom, Ivo F.J.; Jacobs, Pierre

doi:10.1002/adsc.200606202

Cited by 227 publications

(100 citation statements)

References 190 publications

(269 reference statements)

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“…[98] Ein wichtiges Forschungsgebiet ist die Immobilisierung von Homogenkatalysatoren, um sie heterogen einsetzen zu können und so leicht und schnell zurückzugewinnen. [104,105] Mehrere Arbeitsgruppen haben Phosphoramidit-Liganden an Polystyrol-und Merrifield-Harzen immobilisiert. [106][107][108] Allerdings wurde häufig beobachtet, dass bei einer Immobilisierung des chiralen Homogenkatalysators die Enantioselektivität der Testreaktionen abnahm.…”

Section: Phosphoramidite: Struktur Synthese Und Eigenschaftenunclassified

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

2010

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Die asymmetrische Katalyse mit Übergangsmetallkomplexen ist die Grundlage unzähliger stereoselektiver Umwandlungen und hat damit das Bild der modernen Synthesechemie gewandelt. Der Schlüssel zum Erfolg war die Entwicklung chiraler Liganden zur Kontrolle der Regio‐, Diastereo‐ und Enantioselektivität. Dabei haben sich Phosphoramidite als eine äußerst vielseitige und leicht zugängliche Klasse von chiralen Liganden erwiesen. Ihre modulare Struktur ermöglicht die Herstellung von Ligandenbibliotheken und erleichtert die Feinabstimmung für eine bestimmte katalytische Reaktion. Phosphoramidite bewirken oft außerordentlich hohe Stereoselektivitäten, und ihre einzähnige Natur ist in der kombinatorischen Katalyse, die gemischte Liganden verwendet, unverzichtbar. In diesem Aufsatz werden neue Entwicklungen in der asymmetrischen Katalyse mit Phosphoramiditen diskutiert, wobei der Schwerpunkt auf der Bildung von Kohlenstoff‐ Kohlenstoff‐ und Kohlenstoff‐Heteroatom‐Bindungen liegt.

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Section: Phosphoramidite: Struktur Synthese Und Eigenschaftenunclassified

Phosphoramidite: privilegierte Liganden in der asymmetrischen Katalyse

2010

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“…In general, the presence of functional groups in the polymer structure is fundamental to promote chemical interactions between the catalyst and the support. 5 However, direct attachment of transition metals to the functional groups has negative effects on the performance of polymer-supported ZieglerNatta catalysts. Magnesium compounds are often used to modify the polymer supports with an aim to optimize the performance of polymer-supported catalyst.…”

Section: Introductionmentioning

confidence: 99%

Synthesis mechanisms of poly[styrene‐co‐(acrylic acid)]‐supported TiCl₄ catalysts modified by magnesium compounds

Wang

et al. 2011

J of Applied Polymer Sci

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Soluble poly[styrene‐co‐(acrylic acid)] (PSA) modified by magnesium compounds was used to support TiCl4. For ethylene polymerization, four catalysts were synthesized, namely PSA/TiCl4, PSA/MgCl2/TiCl4, PSA/(n‐Bu)MgCl/TiCl4, and PSA/(n‐Bu)2Mg/TiCl4. The catalysts were characterized by a set of complementary techniques including X‐ray photoelectron spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy, and element analysis. Synthesis mechanisms of polymer‐supported TiCl4 catalysts were proposed according to their chemical environments and physical structures. The binding energy of Ti 2p in PSA/TiCl4 was extremely low as TiCl4 attracted excessive electrons from COOH groups. Furthermore, the chain structure of PSA was destroyed because of intensive reactions taking place in PSA/TiCl4. With addition of (n‐Bu)MgCl or (n‐Bu)2Mg, COOH became COOMg‐ which then reacted with TiCl4 in synthesis of PSA/(n‐Bu)MgCl/TiCl4 and PSA/(n‐Bu)2Mg/TiCl4. Although MgCl2 coordinated with COOH first, TiCl4 would substitute MgCl2 to coordinate with COOH in PSA/MgCl2/TiCl4. Due to the different synthesis mechanisms, the four polymer‐supported catalysts correspondingly showed various particle morphologies. Furthermore, the polymer‐supported catalyst activity was enhanced by magnesium compounds in the following order: MgCl2 > (n‐Bu)MgCl > (n‐Bu)2Mg > no modifier. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

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“…[58] From the examples described here, it is clear that asymmetric catalysis using helical biopolymers has started to emerge as an attractive new approach. This is mainly due to the fact that these helical polymers can provide a chiral microenvironment for a catalyst that is analogous to an enzyme active site, which can be used to direct the catalyzed reaction towards the selective formation of one enantiomer of a product.…”

Section: Discussionmentioning

confidence: 99%