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These reactions can be promoted by acids, bases, oxides, metals, organometallic complexes or enzymes.
While the primary areas of expertise of the members of the Center are heterogeneously and homogeneously catalyzed hydrogenations, oxidations, hydrogenolyses and hydroformylations, our staff is also familiar with most of the other types of catalytic reactions which are used for the synthesis of organic compounds. These include reactions such as isomerizations and the various carbon-carbon bond forming reactions which are catalyzed by metals, metal complexes, acids or bases. Most of our work has been concerned with developing reaction conditions for selective catalytic processes. In many cases this has involved an evaluation of the effect which changes in the reaction conditions have on the outcome of the reaction.
Most frequently this includes, at least, the use of different catalysts, reaction solvents, temperatures and pressures, but other factors such as the rate of agitation and the presence of catalyst modifiers are usually included in the study, as well. We have just concluded a thorough evaluation of the effect which reaction parameters have on the selectivity, reaction rate and productivity in the hydrogenation of nitrobenzene to p-amino-phenol.
Other hydrogenations for which optimal reaction conditions have been found include the stereoselective hydrogenation of cyclic vinylogous esters, amides and urethanes, the facile, stereoselective saturation of the double bond in cholesterol and the selective saturation of a substituted aromatic ring without the removal of a sensitive amine blocking group.
Conditions have been found for the hydrogenolysis of cyclopropane rings resulting in the selective introduction of a quaternary methyl group into a molecule. Similar selectivities in the hydrogenolysis of oxiranes and aziridines are used for the introduction of hydroxy or amine groups using an alkene precursor.
We have reported the first good example of the use of a supported catalyst for the acetoxylation of toluene. The heterogeneous nature of the catalyst makes it superior to the commonly used soluble species in ease of handling, facile separation from the reaction mixture and potential for reuse.
We have also developed catalysts to promote the hydroxylation of alkenes with hydrogen peroxide and the selective oxidation of primary alcohols to aldehydes. In the later reaction we have obtained 94% selectivity at 100% conversion with the reaction completed in a very short time.
Hydroformylations have been run using both homogeneous and heterogeneous catalysts, most recently with supported homogeneous species. In every instance, we seek to find appropriate catalysts and reaction conditions for optimum selectivity either for the formation of a linear aldehyde rather than the isomeric branched isomer or, through further reduction, for the corresponding alcohol.
Other reactions with which we have some experience include the various synthetically useful C-C bond formations. We have used supported Pd catalysts to promote both arylations and allylations and have employed solid base catalysts for use in selective aldol condensations.