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Wyszukujesz frazę "Enantioselectivity" wg kryterium: Temat


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Tytuł:
Katalizowane cynkiem asymetryczne hydrosililowanie ketonów i imin
Zinc-catalyzed asymmetric hydrosilylation of ketones and imines
Autorzy:
Gajewy, J.
Powiązania:
https://bibliotekanauki.pl/articles/172235.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
kataliza asymetryczna
hydrosililowanie
kompleksy cynku
enancjoselektywność
aktywacja asymetryczna
asymmetric catalysis
hydrosilylation
zinc complexes
enantioselectivity
asymmetric activation
Opis:
One of the fundamental research goals in modern chemistry is the development of efficient and selective procedures to access organic compounds. Among all of the methodologies developed so far, catalysis offers an efficient and economical approach to enantiomericaly pure substances. In particular, transition metal catalysts modified by ligands, usually phosphines, are one of most successful examples of practical catalysis. Unfortunately, most of the applied metals (e.g., Pd, Rh, Ru, Ir) are low abundant, toxic and expensive. For this reason, recent research is focusing on their replacement by cheaper and low toxic metals. For example, the use of zinc can be of great interest, due to its abundance (0.0076% in the earth crust), biological relevance and distinct abilities. In the last two decades many scientific group have been working on finding new, high efficient and inexpensive catalytic system based on zinc for enantioselective transformations. It has been found that many of important organic reactions (for example aldol, Diels-Alder, Friedel-Crafts, Henry reactions) in their asymmetric version can be catalyzed by zinc complexes. One of them is also asymmetric reduction of double carbon-heteroatom bonds through addition of hydride (from silane). Hydrosilylation reduction is a promising alternative for the catalytic transformation of organic molecules to other reduction methods such as: hydrogenation and transfer hydrogenation owing to its operational simplicity and mild conditions. This review will give a general overview of the possible applications of zinc-catalyzed hydrosilylation of carbonyl compounds and imines. Since the understanding of mechanism of reaction is crucial for rational planning of new and more efficient ligands, some part of this article was devoted for mechanical considerations.
Źródło:
Wiadomości Chemiczne; 2013, 67, 5-6; 521-562
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Production of (R)-styrene oxide by recombinant whole-cell biocatalyst in aqueous and biphasic system
Autorzy:
Xue, F.
Gao, J.
Powiązania:
https://bibliotekanauki.pl/articles/779547.pdf
Data publikacji:
2018
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
Kinetic resolution
Epoxide hydrolase
Enantioselectivity
(R)-styrene oxide
Opis:
The enantioselective resolution of racemic styrene oxide (rac-SO) to (R)-SO by whole cells of a recombinant Escherichia coli expressing epoxide hydrolase (EH) activity in aqueous and biphasic system were studied. Some parameters that may alter this bio-resolution, such as the concentration of recombinant cell, substrate and product were evaluated. The effect of the addition of different additives on the course of rac-SO biotransformation was also investigated. The results showed that the yield and the enantiomeric excess (ee) of (R)-SO were dependent on these variables. When the kinetic resolution was conducted with 350 mM of rac-SO, enantiopure (R)-SO with high (≥99%) ee was obtained with a yield of 38.2% yield at 12.2 h in the presence of 10% (v/v) Tween 80. An isooctane/aqueous system was developed to overcome the adverse factors in the aqueous phase, resulting in an improvement of yield from 38.2% to 42.9%. The results will provide a useful guidance for further application of this enzyme in the biocatalytic production of chiral synthons.
Źródło:
Polish Journal of Chemical Technology; 2018, 20, 2; 54-60
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
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