Hydrogenation of "largely unfunctionalized" alkenes has been an active area of research for about a decade. Many catalysts have been prepared but we noticed that comparatively few substrates have been studied and none of these hydrogenations provided useful chirons for the organic synthesis area. That motivated us to investigate asymmetric hydrogenations of chiral acyclic alkenes, which are seldom used for hydrogenations and usually the reactions are fully substrate controlled. It emerged that such reactions could provide a concise entry points into chirons that can be used to prepare many natural products. Asymmetric hydrogenations of functionalized, but not coordinatively functionalized, alkenes have been used to prepare several chirons for syntheses ofpolyketide natural products using our N,carbene Crabtree's catalyst analog. Starting from optically active starting materials (eg Roche esters, lactic acid, glyceraldehyde dimethyl ketals, amino acids), highly optically active chiral alkenes can be made in several steps with high yield. With the iridium catalyzed asymmetric hydrogenations, chiral ethers, 1,3-hydroxymethyl chiron, alpha-methyl-beta-hydroxy-gamma-methyl chiron, alpha-methyl-gamma-alkyl-gamma-amino acid can be obtained with high stereoselectivities. With those well developed methodologies, (-)-dihydromyoporone, (-)-spongidepsin, (-)-invictolide have been prepared with high efficiency. Not like the vinyl acetate, which can be hydrogenated quite well with many Rh catalysts, the alkyl vinyl ether does not have a coordination functional group nearby, hence it is a difficult substrate for asymmetric hydrogenation and there are relatively few iv reports. Also the simple alkyl enol ether is quite acid sensitive and the Pfatlz's type N,PIr catalysts cannot hydrogenate the simple alkyl enol ethers well under the standard hydrogenation conditions. We explored many alkyl enol ethers and found some of them can be hydrogenated efficiently (50 bar H2, 1 mol percent N,carbene-Ir catalyst, 25 degree C) with high enantioselectivities (up to 98 percent ee). This study led us to suspect that more protons were produced when N,P-Ir catalyst precursors were used relative to the corresponding carbene catalyst since the former only gave complex mixture when being used. DF calculations and several other experiments supported this postulation.

The development of new, improved methods for forming carbon–carbon and carbon–heteroatom bonds is the basic goal in synthetic organic chemistry. In the Lautens group, many recent advances have been made using late transition metals such as rhodium and palladium. One such research project involves the synthesis of indoles through tandem C–N and C–C coupling reactions using gem-dibromoolefin starting materials, and this area serves as a starting point for the research described. Chapter 1 describes a method by which the tandem use of gem-dibromoolefins can be halted to give intramolecular monocoupling reactions, maintaining one of the carbon–bromine bonds which can serve as a useful handle for further functionalization. The use of copper as a catalyst is key to this reaction, as it features a unique mechanism for carbon–heteroatom bond formation. Benzofurans and benzothiophenes can be prepared by this method. Chapter 2 describes the synthesis of 2-bromoindoles using an intramolecular Buchwald–Hartwig amination of gem-dibromoolefins. It is found that the products are more reactive towards palladium(0) than the starting material, and the use of a bulky phosphine ligand which facilitates reversible oxidative addition is required. This represents one of the first catalytic applications of this step in synthesis. Chapter 3 further explores the concept of reversible oxidative addition in a novel carbohalogenation reaction of alkenes. Aryl iodides tethered to alkenes are treated with a palladium(0) catalysts, which can undergo the basic steps of oxidative addition, carbopalladation, and novel sp2 carbon–iodine reductive elimination. This process is remarkably simple in concept, and is a waste-free, atom economically method for preparing new carbon–carbon bonds. Chapter 4 discusses various limitations to the carbohalogenation methodology, and seeks to overcome these problems. The use of aryl bromide starting materials can be accomplished by adding an iodide source to the reaction, allowing halide exchange of palladium(II) intermediates to occur. Intermolecular and asymmetric variants are also explored. Computational studies are discussed which reveal useful mechanistic details of the catalytic cycle, and this information is used in the development of novel phosphine ligands.

This study armed at the development of an adequate process for the odor control of a gas vented from a plant for treating olefin-resin manufacturing wastewater.The gas contains various aromatic and olefin compounds, such as toluene, £\-methyl styrene, vinyl toluene, styrene, naphthalene, dicyclopentadiene, and indene.Primary tests showed that these odorous compounds could not be effectively eliminated by a biotrickling filter packed with fern chips.Instead, these compounds can easily be removed or eliminated by using sodium hypochlorite as an oxidant and followed by sodium thiosulfate as a reductant for removing the residual chlorine odor. Results indicate that by scrubbing the gas with sodium hypochlorite solution with an effective residual chlorine of 40-60 mg/L, pH of 7.9-9.8, and oxidation-reduction potential (ORP) of 500-760 mV, concentration of volatile organic compounds (VOCs) in the test gas could be removed from 250 ppm (expressed as methane) to 23 ppm.Trace olefin and chlorine odors in the oxidized gas could further be removed by scrubbing it with an aqueous solution of 270 mg/L Na2S2O3.The overall VOC removal was around 92%.

München, Techn. Univ., Diss., 2009

The development of new, improved methods for forming carbon–carbon and carbon–heteroatom bonds is the basic goal in synthetic organic chemistry. In the Lautens group, many recent advances have been made using late transition metals such as rhodium and palladium. One such research project involves the synthesis of indoles through tandem C–N and C–C coupling reactions using gem-dibromoolefin starting materials, and this area serves as a starting point for the research described. Chapter 1 describes a method by which the tandem use of gem-dibromoolefins can be halted to give intramolecular monocoupling reactions, maintaining one of the carbon–bromine bonds which can serve as a useful handle for further functionalization. The use of copper as a catalyst is key to this reaction, as it features a unique mechanism for carbon–heteroatom bond formation. Benzofurans and benzothiophenes can be prepared by this method. Chapter 2 describes the synthesis of 2-bromoindoles using an intramolecular Buchwald–Hartwig amination of gem-dibromoolefins. It is found that the products are more reactive towards palladium(0) than the starting material, and the use of a bulky phosphine ligand which facilitates reversible oxidative addition is required. This represents one of the first catalytic applications of this step in synthesis. Chapter 3 further explores the concept of reversible oxidative addition in a novel carbohalogenation reaction of alkenes. Aryl iodides tethered to alkenes are treated with a palladium(0) catalysts, which can undergo the basic steps of oxidative addition, carbopalladation, and novel sp2 carbon–iodine reductive elimination. This process is remarkably simple in concept, and is a waste-free, atom economically method for preparing new carbon–carbon bonds. Chapter 4 discusses various limitations to the carbohalogenation methodology, and seeks to overcome these problems. The use of aryl bromide starting materials can be accomplished by adding an iodide source to the reaction, allowing halide exchange of palladium(II) intermediates to occur. Intermolecular and asymmetric variants are also explored. Computational studies are discussed which reveal useful mechanistic details of the catalytic cycle, and this information is used in the development of novel phosphine ligands.

Zugl.: Dortmund, Techn. Universiẗat, Diss., 2008.

Thesis (doctoral)--Tübingen, 1982.

Zugl.: München, Techn. University, Diss., 2009.

Universiẗat, Diss., 2000--Dortmund. / Dateiformat: PDF.

Universiẗat, Diss., 1998--Konstanz.