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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.

Alkene Metathesis

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 [16].
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Hoveyda-type Ru metathesis catalysts

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.
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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].
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We have studied novel cross-metathesis reactions of α,β-unsaturated substrates: vinyl sulphones [15, 20, 42], vinyl azulenes [28] and chiral vinylphosphine oxides.
[21, 32].

Cross-Metathesis of vinyl sulfones and phosphine oxides

The cross-metathesis of α,β-unsaturated sulphones has been applied in the enantioselective synthesis of some natural products.
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Alkyne Metathesis

Alkyne Metathesis

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.

Stereoselective synthesis of Yuzu Lactone

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) [17].
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Metal Activation
High-surface alkali metals can be conveniently prepared via deposition of corresponding metals on various supports such as sodium chloride, polyethylene, polypropylene and cross-linked polystyrene from their solutions in liquid ammonia. Alkali metals deposited on polymeric supports can be stored in form of stable suspensions in inert solvents and used for the acyloin and Dieckmann condensations and for preparation of organolithiums. Addition of the suspension of supported alkali metal to a solution of zinc chloride gave an active zinc on polymeric support which can be used for the Reformatski and Barbier reactions [10,11].

Application of PS-Zn





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Last updated Saturday, 14-Aug-2010 11:43:46 CEST
(c) 1997-2017 Karol Grela (grela@icho.edu.pl)