Our research is mainly concerned with the development and improvement of organometallic reactions as well as their application to the synthesis of natural products and pharmaceutically relevant compounds. Current research is mainly focused on stereoselective organic synthesis mediated by transition metals with special emphasis on alkyne and alkene metathesis. Areas of investigation encompass the design of new userfriendly, supported or recyclable stable metathesis catalysts and extending the scope of the reaction itself.
We have designed a robust, stable and easy to use supported catalyst for olefin metathesis (1), which can be easily prepared in three steps from commercial butyldiethylsilyl polystyrene. The possibility of instant ruthenium determination renders an impotrant practical advantage of this system .
Recently, the group have developed new EWG- and EDG-substituted Hoveyda-type ruthenium complexes of enhanced properties [18, 19, 23, 25, 26, 28-31, 33-41, 43-46]. We have shown that changing the electron density on the Ru-chelating oxygen or nitrogen has direct impact on the both catalyst activity and stability.
The ruthenium catalysts 2-6 have found applications in target-oriented synthesis and polymerization.
Moreover, we have proposed that substitution with different functional groups can be used not only to fine-tune the catalyst activity but at the same time to introduce new physical properties, such as enhanced solubility in chosen media. This 'green angle' of Ru-catalysed olefin metathesis is currently studied in our group [31, 36, 38, 39, 41, 45].
We have studied novel cross-metathesis reactions of α,β-unsaturated substrates: vinyl sulphones [15, 20, 42], vinyl azulenes  and chiral vinylphosphine oxides.
The cross-metathesis of α,β-unsaturated sulphones has been applied in the enantioselective synthesis of some natural products.
During recent years, olefin metathesis has gained a position
of increasing significance. In particular, ring-closing olefin
metathesis (RCM) of dienes provides good access to various
carbo- and heterocycles of ring sizes >4. Among the
shortcomings that infringe upon the superb overall application
profile of RCM in the synthesis of medium- and
macrocyclic products, the lack of control over the stereo-
chemistry of the newly formed double bond is most
noteworthy. The products formed are usually obtained as
mixtures of the (E)- and (Z)-isomer. This constitutes a
significant drawback in target oriented synthesis, as can be
seen from many examples reported in the literature.
To circumvent this problem, an indirect but stereoselective approach to macrocyclic (E)- and (Z)-alkenes has been proposed, which comprises a ring-closing metathesis reaction of diynes (RCAM) followed by semireduction of the resulting cycloalkyne product.
We have described an improved "instant" catalyst for ring-closing alkyne metathesis reaction. Catalyst formed in situ from molybdenum hexacarbonyl and 2-fluorophenol can be used without exclusion of air and moisture and shows high activity in metathesis of functionalized diynes.
The high activity of the 2-fluorophenol-based system
can be clearly seen from the stereoselective synthesis of yuzu
lactone, the minty, camphor-like odored macrolide isolated
from the flesh and peel of the Japanese citrus tree Citrus
junos Tanaka (Yuzu) .
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Last updated Saturday, 14-Aug-2010 11:43:46 CEST
(c) 1997-2017 Karol Grela (email@example.com)