Bis(cyclopentadienyl)zirkon‐verbindungen und aluminoxan als Ziegler‐Katalysatoren für die polymerisation und copolymerisation von olefinen

Kaminsky, Werner; Miri, Massoud J.; Sinn, Hansjörg; Woldt, Rüdiger

doi:10.1002/marc.1983.030040612

Cited by 301 publications

(61 citation statements)

References 5 publications

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“…3, Top). Considering that the rac-3-Cl 2 and Cp 2 ZrCl 2 complexes form highly isotactic and atactic polypropylenes (20), respectively, the existence of a single peak for each oligomer (Fig. 3, Bottom) implies that oligomerization took place in a highly diastereoselective manner with rac-3-Cl 2 .…”

Section: Optimization Of Reaction Conditions For Diastereoselective Pmentioning

confidence: 99%

One-step catalytic asymmetric synthesis of all- syn deoxypropionate motif from propylene: Total synthesis of (2 R ,4 R ,6 R ,8 R )-2,4,6,8-tetramethyldecanoic acid

Ota

Murayama

Nozaki

2016

Proc. Natl. Acad. Sci. U.S.A.

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In nature, many complex structures are assembled from simple molecules by a series of tailored enzyme-catalyzed reactions. One representative example is the deoxypropionate motif, an alternately methylated alkyl chain containing multiple stereogenic centers, which is biosynthesized by a series of enzymatic reactions from simple building blocks. In organic synthesis, however, the majority of the reported routes require the syntheses of complex building blocks. Furthermore, multistep reactions with individual purifications are required at each elongation. Here we show the construction of the deoxypropionate structure from propylene in a single step to achieve a three-step synthesis of (2R,4R,6R,8R)-2,4,6,8-tetramethyldecanoic acid, a major acid component of a preen-gland wax of the graylag goose. To realize this strategy, we focused on the coordinative chain transfer polymerization and optimized the reaction condition to afford a stereo-controlled oligomer, which is contrastive to the other synthetic strategies developed to date that require 3–6 steps per unit, with unavoidable byproduct generation. Furthermore, multiple oligomers with different number of deoxypropionate units were isolated from one batch, showing application to the construction of library. Our strategy opens the door for facile synthetic routes toward other natural products that share the deoxypropionate motif.

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Section: Optimization Of Reaction Conditions For Diastereoselective Pmentioning

confidence: 99%

One-step catalytic asymmetric synthesis of all- syn deoxypropionate motif from propylene: Total synthesis of (2 R ,4 R ,6 R ,8 R )-2,4,6,8-tetramethyldecanoic acid

Ota

Murayama

Nozaki

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The discovery by Kaminsky 1,2) in 1980 that homogeneous catalytic systems metallocene/MAO were able to produce highly linear and stereoregular polyolefins, represented an important breakthrough in alkene polymerization. Later, in 1986, Ishihara et al 3) discovered that similar catalytic systems based on group IV metal compounds like TiCl 4 and CpTiCl 3 combined with MAO could produce perfect syndiotactic polystyrene with high crystallinity.…”

Section: Introductionmentioning

confidence: 99%

Improvement of supported catalysts for syndiotactic polymerization of styrene

Pasquet¹,

Spitz

1999

Macromol. Chem. Phys.

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SUMMARY: The catalytic system Ti(OBu) 4 in combination with methylaluminoxane (MAO) was tested for the syndiospecific polymerization of styrene. A comparison was established between this homogeneous catalytic system and the same one supported on silica or alumina. An attempt was made to introduce a "tether" between the support and the active species to enhance both productivity and syndiospecificity. These tethers consisted of diols with different lengths. At last, the catalytic system Zr(OBu) 4 was supported on silica or alumina with MAO as a cocatalyst and was tested under the same conditions as other catalysts. This study reveals that Ti(OBu) 4 supported on silica enhances the productivity and leads to higher molecular weights, while the addition of a diol does not result in any enhancement compared to the silica-supported catalyst. On the contrary, alumina alone does not seem to be a good support for Ti(OBu) 4 , while introducing a short diol such as ethylene glycol leads to a great enhancement of both productivity and syndiospecificity. As reported in the literature, Zr(OBu) 4 always leads to much lower productivities than Ti(OBu) 4 .

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“…Polymethylaluminoxane is recognized as efficient co-catalyst of highly active homogeneous metallocene catalysts for the ethylene polymerization 1,2) . Polymethylyaluminoxane (or methylaluminoxane, MAO) is the key element determining the extremely high activity, as well as other kinetic peculiarities of these catalytic systems.…”

Section: Introductionmentioning

confidence: 99%

A DFT quantum-chemical study on the structures and active sites of polymethylaluminoxane

Захаров

Potapov

et al. 1999

Macromol. Theory Simul.

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SUMMARY:The electronic structure and geometry of polymethylaluminoxane (MAO) [ 1Al(CH 3 )O1 ] n with different size (n = 4 -12) have been studied using quantum-chemical DFT (density functional theory) calculations. It has been found: 1) Starting from n = 6, the three-dimensional oxo-bridged (cage) structure of MAO is more stable than the cyclic structure. 2) Both for cage structure and for cyclic structure the Lewis acidity

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Bis(cyclopentadienyl)zirkon‐verbindungen und aluminoxan als Ziegler‐Katalysatoren für die polymerisation und copolymerisation von olefinen

Cited by 301 publications

References 5 publications

One-step catalytic asymmetric synthesis of all- syn deoxypropionate motif from propylene: Total synthesis of (2 R ,4 R ,6 R ,8 R )-2,4,6,8-tetramethyldecanoic acid

One-step catalytic asymmetric synthesis of all- syn deoxypropionate motif from propylene: Total synthesis of (2 R ,4 R ,6 R ,8 R )-2,4,6,8-tetramethyldecanoic acid

Improvement of supported catalysts for syndiotactic polymerization of styrene

A DFT quantum-chemical study on the structures and active sites of polymethylaluminoxane

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