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Wyszukujesz frazę "olefin metathesis" wg kryterium: Temat


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Tytuł:
Katalizatory metatezy olefin, modyfikacje liganda NHC
Olefin metathesis catalysts, modifications on the NHC ligand
Autorzy:
Retajczyk, M.
Wróblewska, A.
Powiązania:
https://bibliotekanauki.pl/articles/172547.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
metateza olefin
ligand NHC
katalizatory Grubbsa
katalizator Hoveydy-Grubbsa
olefin metathesis
Grubbs catalyst
Hoveyda-Grubbs catalyst
Opis:
Olefin metathesis is one of the most important synthetic tools, both in organic and olefin chemistry. Olefin metathesis allows to shorten production time of organic compounds and it is characterized by a smaller amount of by-products and waste in comparison with the classical ways of the synthesis of these compounds. Simultaneously, the conditions at which metathesis is performed are environmentally friendly. This method allows obtaining very valuable compounds, such as: anti-inflammatory agents, fungicides and many others. This causes that olefin metathesis has an important place in the organic synthesis and develops constantly. The first catalysts had undefined structure, therefore, it was difficult to predict the mechanism of their action. Big development metathesis came with the synthesis of catalysts with a clearly defined structure. This article explains what olefin metathesis is and shows applications of olefin metathesis. This work presents catalysts, which possess transition metal in the structure, such as: ruthenium, molybdenum or tungsten. It also shows the comparison of catalysts possess ruthenium (Grubbs catalyst first and second generation and Hoveyda-Grubbs catalyst) taking into account their structure and properties. This work describe carbenes, which improve thermal stability of catalysts compare with complexes containing phosphine. Researchers receive new compounds through modifications on the NHC ligand. In this work are presented modifications of the NHC ligand complexes of ruthenium described in the literature and their influence on such catalytic properties as: activity, selectivity, and efficiency. Modifications concern: heteroatoms, bulky groups and groups, which change electron density. Despite many studies and receiving large amounts of catalysts for this reaction, still a problem is the obtaining of an universal catalyst for all types transitions, that would have a high activity, high efficiency and which could be easily recovered after the reaction.
Źródło:
Wiadomości Chemiczne; 2017, 71, 5-6; 323-347
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synteza i zastosowanie nowych katalizatorów metatezy olefin
Synthesis and application of new olefin metathesis catalysts
Autorzy:
Hryniewicka, A.
Powiązania:
https://bibliotekanauki.pl/articles/172521.pdf
Data publikacji:
2014
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
metateza olefin
katalizatory rutenowe
pochodne chromanu
sole imidazolidyniowe
glikokoniugaty
olefin metathesis
ruthenium catalysts
chromane derivatives
imidazolinium salts
glycoconjugates
Opis:
Olefin metathesis has emerged as a powerful tool for the formation of carboncarbon double bonds. The success of this methodology has spurred the intense investigation of new catalysts showing a better application profile. The syntheses and the application profiles of the seven new ruthenium metathesis catalysts have been described. Five of them were modified in benzylidene part with 6-hydroxychromane- and 2H-3,4-chromenemethylidene moiety. In chromanol – α-tocopherol model compound, some specific stereoelectronic effects have been observed. Introduction of this ligand to the catalyst may provide new advantageous properties. The other new catalysts contained modified N-heterocyclic carbene ligand (NHC), in which N,N’-mesityl substituents of NHC system were linked with diethylene glycol chain as a “clamping ring”. This ring would contribute to a steric shield of the NHC and ruthenium coordination center. Probably it may inforce a proper orientation of substituents in metallacyclobutane (all-cis), leading to Z-olefin formation. The obtained catalysts were investigated in model reactions: ring closing metathesis, cross metathesis and enyne metathesis. The experiments proved they efficiency. In many reactions the catalysts showed activity comparable or superior to that of commercially available Grubbs and Hoveyda 2nd generation complexes. Stereochemistry Z/E of the cross-metathesis products obtained using new and known complexes were similar as well. The catalysts were applied in the synthesis of a new type of α-tocopherol glycoconjugates. An efficient method of the synthesis Hoveyda 2nd type complexes starting from ruthenium trichloride was developed. It is possible to circumvent using special laboratory equipment and expensive reagents. Hoveyda type complexes can be achieved with very good yield in gram scale. Keywords:
Źródło:
Wiadomości Chemiczne; 2014, 68, 11-12; 961-980
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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