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Wyświetlanie 1-3 z 3
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
Tytuł:
Karbeny N-heterocykliczne : synteza i zastosowanie
N-heterocyclic carbenes : synthesis and applications
Autorzy:
Malinowska, M.
Hryniewicka, A.
Powiązania:
https://bibliotekanauki.pl/articles/171528.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
karbeny N-heterocykliczne
sole imidazolidyniowe
katalizator metatezy
organokataliza
reakcja sprzęgania
N-heterocyclic carbenes
imidazolinium salts
methatesis catalysts
organocatalysis
coupling reactions
Opis:
N-Heterocyclic carbenes (NHCs) are powerful tools in organic chemistry, with numerous applications in academic and industrial laboratories. They are usually defined as singlet carbenes, in which the divalent carbonic centre is connected directly to at least one nitrogen atom in the heterocycle [1]. They have played an important role in organic chemistry ever since the first evidence of their existence. The isolation of stable, free 1,3‑diadamantylimidazol-2-ylidene (IAd, Fig. 1) by Arduengo et al. in 1991 was a milestone in the chemistry of carbenes [2]. From the beginnings as academic curiosities, N‑heterocyclic carbenes today are very useful compounds in a variety of organic transformations (Fig. 13). NHCs are neutral σ-donors, which form very strong bonds with the majority of transition metals (stronger than phosphines). These compounds are easy-to-make ligands with great potential in homogeneous catalysis (mainly ruthenium and palladium complexes) for large number of reactions, including the coupling reactions (Heck, Negishi, Stille, Suzuki or Sonogashira reactions) and olefin metathesis [3]. Moreover, they are very useful as organocatalysts used in the benzoin condensation, the Stetter reaction and ring-opening polymerization (ROP) or transesterification [4]. In this review, we aim to give an overview of the properties and applications of NHCs, which we expect will be a useful introduction for chemists interested in studying and applying these important compounds. The first part of this review is devoted to the main synthetic routes to NHCs, their properties and reactivity. In the second part we describe the metal complexes with NHCs as homogeneous catalysts and their applications in various types of reactions. At the end of this part of the paper the use of NHCs as organocatalysts is presented.
Źródło:
Wiadomości Chemiczne; 2015, 69, 3-4; 227-253
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ekonomiczne konsekwencje wichury w 2016 roku w Nadleśnictwie Supraśl
Economic consequences of the 2016 storm in the Supraśl Forest District
Autorzy:
Hryniewicka, A.
Mandziuk, A.
Powiązania:
https://bibliotekanauki.pl/articles/979028.pdf
Data publikacji:
2020
Wydawca:
Polskie Towarzystwo Leśne
Tematy:
extraordinary costs
timber price
value of stand
timber of disaster
Opis:
The purpose of the article is to determine the value of losses resulting from salvage cutting of stands and to estimate the amount of extraordinary costs and profits from the sale of removed wood in forests damaged by a wind−storm that occurred on June 17, 2016 in the Supraśl Forest District (NE Poland). We obtained the following data from the State Forests Information System: the size of disaster area, the volume and structure of harvested wood in the affected area, extraordinary costs as a result of damage caused by a wind−storm, average sales price of downed or broken wood separated into individual recipients and entrepreneurs. The renewal of the disaster area has not been completed as for June 5, 2019. To determine the value of losses due to salvage felling of stands, formulas included in the Regulation of the Minister of the Environment of 20 June 2002 on one−time compensation for salvage felling of stands were used. Tables of stand value indicators developed by the Forest Research Institute in 2013 were used for the calculations. The total area of forests damaged by a wind−storm in the Supraśl Forest District was 329 ha. The area in which harvesting was carried out using a clear−cutting method covered 284 ha, the removal of damage in the remaining area was performed in accidental cuts. The total extraordinary costs incurred by the Supraśl Forest District as a result of a wind−storm amounted to over PLN 10.9 million, the largest group were costs related to harvesting and skidding of trees in disaster areas (nearly PLN 9.5 million). The total value of sales of large− and medium−sized wood assortments to retail customers was approximately PLN 1.93 million and to entrepreneurs over PLN 44.7 million. The value of small−sized assortments was at the level of PLN 37.5 thousand for retail customers and PLN 39.8 thousand for entrepreneurs. The value of forests damaged by a wind−storm was estimated at over PLN 20.3 million. A comprehensive analysis of the economic effects of the natural disaster in the Supraśl Forest District has not been completed; it requires research conducted in subsequent years, as the consequences and related costs of the hurricane will be experienced in the near future.
Źródło:
Sylwan; 2020, 164, 04; 321-330
0039-7660
Pojawia się w:
Sylwan
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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