Browsing by Author "Macquarrie, Duncan J."
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Item Catalysis of the Knoevenagel reaction by γ-aminopropylsilica(1997-12) Macquarrie, Duncan J.; Clark, James H.; Lambert, Arnold; Mdoe, James; Priest, AndrewThe Knoevenagel reaction can be catalysed by γ-aminopropylsilica. Reactions are rapid and essentially quantitative with small amounts of catalyst. A range of aldehydes and ketones can be reacted successfully, the only exceptions being very bulky ketones. The reaction is very dependent on the efficient removal of water, which leads to faster reaction rates and to much higher conversions. The choice of solvent is also extremely important, with nonpolar solvents such as cyclohexane being optimal. Less polar, higher boiling solvents are significantly less effective, even at much higher reaction temperatures. Catalyst poisoning is slow and appears to be due to amide formation on the surface.Item Michael Additions Catalyzed by N,N-Dimethyl-3-aminopropyl — Derivatized Amorphous Silica and Hexagonal Mesoporous Silica (HMS)(1998-06) Mdoe, James; Clark, James H.; Macquarrie, Duncan J.Solid bases prepared by derivatisation of amorphous silica and hexagonal mesoporous silica with dimethylaminopropyl groups are good catalysts for Michael addition reactions. Of the prepared catalysts, those based on hexagonal mesoporous silica show particularly high activities. The sol-gel method used in preparing the catalysts based on hexagonal mesoporous silica enables loading to be increased to more than twice that of those based on amorphous silica which are prepared by the post-modification method.Item Novel Supported Heterogeneous Palladium Catalysts for Carbon—Carbon Forming Reactions(Elsevier, 2000) Mubofu, Egid B.; Clark, James H.; Macquarrie, Duncan J.A novel palladium catalyst has been supported on chemically modified silica and tested for activity. The catalyst has high activity towards the Heck reaction of aryl iodides with olefins in acetonitrile solvent and has been reused several times without signicant loss of activity.Item A Novel Suzuki Reaction System Based on a Supported Palladium Catalyst(2001) Mubofu, Egid B.; Clark, James H.; Macquarrie, Duncan J.A range of supported palladium complex-catalysed Suzuki reactions is described with notable features including fast and efficient reactions, excellent catalyst recyclability, and total catalyst stability under the reaction conditions. We have achieved turnover numbers of several thousand based on ten re-use experiments from batch reactions in air. Our system not only solves the basic problems of catalyst separation and recovery but also avoids the use of phosphine ligands.Item Organomodified hexagonal mesoporous silicates(1999-01) Macquarrie, Duncan J.; Jackson, Dominic B.; Mdoe, James; Clark, James H.A neutral templating route to organically modified silicates with tightly controlled porosity is described. The materials prepared are characterised and compared to the corresponding organofunctionalised silicaItem Preparation of a Novel Silica-Supported Palladium Catalyst and Its Use in the Heck Reaction(2000) Clark, James H.; Macquarrie, Duncan J.; Mubofu, Egid B.A novel palladium catalyst supported on a chemically modified mesoporous silica gel has been prepared and exhibits high activity and stability in the Heck reaction of aryl iodides with olefins. The catalysts has been reused several times in reactions without significant loss of activity and selectivity.