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Alkene Metathesis --- Catalysts Design

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 important practical advantage of this system [16].

Hoveyda-type Ru metathesis catalysts

Our group is developing new ruthenium olefin metathesis catalysts of enhanced properties [18, 19, 23, 25, 26, 28-31, 33-41, 43-46]. We have found that changing the electron density at the Ru-chelating oxygen or nitrogen of Hoveyda or Grubbs type complexes has direct impact on the both catalyst activity and stability. The ruthenium catalysts 2-6 have found applications in target-oriented synthesis and polymerization.

Especially, the stable 5-nitro-substituted catalyst 2 [18, 23, 25], introduced in 2002, exhibits impressive activity in ring-closing (RCM), cross (CM) and enyne-metathesis. As a result, catalyst 2 has found many successful applications in target oriented syntheses and in the pharmaceutical industry.

Applications of the 'Nitro'-catalyst (2) in target oriented syntheses
Applications of the Nitro catalyst
· (-)-Sekurinine: T. Honda, H. Namiki, K. Kaneda, H. Mizutani, Org. Lett. 2004, 6, 87;
· (+)-Viroallosekurinine: T. Honda, H. Namiki, M. Watanabe, H. Mizutani, Tetrahedron Lett. 2004, 45, 5211;
· Hexacyclinic acid and (+)-FR182877: T. Stellfeld, U. Bhatt, M. Kalesse, Org. Lett. 2004, 6, 3889;
· (+)-FR901464: B. J. Albert, A. Sivaramakrishnan, T. Naka, K. Koide, J. Am. Chem. Soc. 2006, 128, 2792;
· BILN 2061 (Ciluprevirtm): Patent WO 2004/089974 A1 (2004, Boehringer Ingelheim International GmbH) and T. Nicola, M. Brenner, K. Donsbach, P. Kreye, Org. Proc. Res. Devel. 2005, 9, 513;
· Virydiofungine analogues: S. M. Goldup, C. J. Pilkington, A. J. P. White, A. Burton, A. G. M. Barrett, J. Org. Chem. 2006, 71, 6185;
· Porphyrin-fullerene dyad: S. Ostrowski, A. Mikus, Mol. Divers. 2003, 6, 315;
· Porphyrin building blocks: S. Ostrowski, A. Mikus, Heterocycles 2005, 65, 2339;
· Ruthenium polymerisation catalysts: J. O. Krause, O. Nuyken, M. R. Buchmeiser, Chem. Eur. J. 2004, 10, 2029;
· epi-Nor­panda­mari­lactonine-A: T. Honda, M. Ushiwata, H. Mizutani, Tetrahedron Lett. 2006, 47, 6251;

Various other EWG-activated Hoveyda catalysts have been later described, some are commercially available from Zannan Pharma and Strem Chemicals inc.

Moreover, we have proposed that substitution with 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 affinity to silica gel, enhanced solubility in chosen media, etc. The 'green angle' of Ru-catalysed olefin metathesis is extensively studied in our group [31, 36, 38, 39, 41, 45].

For example, complex 5 (R = Me) can be use in aqueous solutions [36] while its analogue (R = H) on Rashig rings is a highly active recyclable catalyst [41], particularly in cross metathesis reactions where it has been used in the preparation of a steroid precursor, inhibitor of 17β-hydroxysteroid dehydrogenase type 1 (Solvay AG).

Catalysts on Rashig rings

Alkene Metathesis --- New applications

We have studied novel cross-metathesis reactions of electron deficient substrates: vinyl sulphones [15, 20, 42], 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 successfully applied by Evans in a stereo­selective synthesis of (-)-maritolide and some other furanone natural products and by Pyne in a formal synthesis of (-)-swainsonine.

CM of vinyl sulfones
· Evans, P.; Leffray, M. Tetrahedron 2003, 59, 7973.
· Au, C. W. G.; Pyne S. G. J. Org. Chem. 2006, 71, 7097.

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Last updated Tuesday, 16-Sep-2008 23:28:20 CEST
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