Details

Autor(en) / Beteiligte

• Michrowska, Anna
• Bujok, Robert
• Harutyunyan, Syuzanna
• Sashuk, Volodymyr
• Dolgonos, Grigory
• Grela, Karol

Titel

Nitro-Substituted Hoveyda−Grubbs Ruthenium Carbenes:  Enhancement of Catalyst Activity through Electronic Activation

Ist Teil von

• Journal of the American Chemical Society, 2004-08, Vol.126 (30), p.9318-9325

Ort / Verlag

Washington, DC: American Chemical Society

Erscheinungsjahr

2004

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The design, synthesis, stability, and catalytic activity of nitro-substituted Hoveyda−Grubbs metathesis catalysts are described. The highly active and stable meta- and para-substituted complexes are attractive from a practical point of view. These catalysts operate in very mild conditions and can be successfully applied in various types of metathesis [ring-closing metathesis, cross-metathesis (CM), and enyne metathesis]. Although the presence of a NO2 group leads to catalysts that are dramatically more active than both the second-generation Grubbs's catalyst and the phosphine-free Hoveyda's carbene, enhancement of reactivity is somewhat lower than that observed for a sterically activated Hoveyda−Grubbs catalyst. Attempts to combine two modes of activation, steric and electronic, result in severely decreasing a catalyst's stability. The present findings illustrate that different Ru catalysts turned out to be optimal for different applications. Whereas phosphine-free carbenes are catalysts of choice for CM of various electron-deficient substrates, they exhibit lower reactivity in the formation of tetrasubstituted double bonds. This demonstrates that no single catalyst outperforms all others in all possible applications.