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 .
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
· (-)-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  while its analogue (R = H) on Rashig rings is a highly active recyclable catalyst , 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).
We have studied novel cross-metathesis reactions of electron deficient substrates: vinyl sulphones [15, 20, 42], azulenes  and chiral vinylphosphine oxides [21, 32].
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.
· 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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