Transition Metal Catalysis for Selective Synthesis and Sustainable Chemistry

This thesis discusses the preparation and use of transition-metal catalysts for selective organic chemical reactions. Specifically, two different matters have been studied; the asymmetric hydrogenation of carbon-carbon double bonds using N,P-ligated iridium catalysts and the metal-catalyzed transfer of small molecules from biomass to synthetic intermediates. In the first part of this thesis, chiral N,P-ligands were synthesized and evaluated in iridium catalysts for the asymmetric hydrogenation of non- and weakly functionalized alkenes (Papers I & II). The new catalysts were prepared via chiral-pool strategies and exhibited superior properties for the reduction of certain types of alkenes. In particular, some of the catalysts showed excellent activity and selectivity in the enantioselective reduction of terminal alkenes, and the preparation of a modular catalyst library allowed the asymmetric hydrogenation of a wide range of 1,1-disubstituted alkenes with unprecedented efficiency and enantioselectivity (Paper III). Methods for the selective preparation of chiral hetero- and carbocyclic fragments using iridium-catalyzed asymmetric hydrogenation as an enantiodetermining key step were also developed. A range of elusive chiral building blocks that have applications in pharmaceutical and natural-product chemistry could thus be conveniently prepared (Papers IV & V). The second part of this thesis deals with the catalytic decomposition of polysaccharides into sugar alcohols and the incorporation of their decomposition products into alkene substrates. Iridium-catalyzed dehydrogenative decarbonylation was found to decompose polyols into CO:H2 mixtures that could be used immediately in the ex situ low-pressure hydroformylation of styrene (Paper VI). The net process was thus the hydroformylation of alkenes with biomass-derived synthesis gas

Transition Metal Catalysis for Selective Synthesis and Sustainable Chemistry

This thesis discusses the preparation and use of transition-metal catalysts for selective organic chemical reactions. Specifically, two different matters have been studied; the asymmetric hydrogenation of carbon-carbon double bonds using N,P-ligated iridium catalysts and the metal-catalyzed transfer of small molecules from biomass to synthetic intermediates. In the first part of this thesis, chiral N,P-ligands were synthesized and evaluated in iridium catalysts for the asymmetric hydrogenation of non- and weakly functionalized alkenes (Papers I & II). The new catalysts were prepared via chiral-pool strategies and exhibited superior properties for the reduction of certain types of alkenes. In particular, some of the catalysts showed excellent activity and selectivity in the enantioselective reduction of terminal alkenes, and the preparation of a modular catalyst library allowed the asymmetric hydrogenation of a wide range of 1,1-disubstituted alkenes with unprecedented efficiency and enantioselectivity (Paper III). Methods for the selective preparation of chiral hetero- and carbocyclic fragments using iridium-catalyzed asymmetric hydrogenation as an enantiodetermining key step were also developed. A range of elusive chiral building blocks that have applications in pharmaceutical and natural-product chemistry could thus be conveniently prepared (Papers IV & V). The second part of this thesis deals with the catalytic decomposition of polysaccharides into sugar alcohols and the incorporation of their decomposition products into alkene substrates. Iridium-catalyzed dehydrogenative decarbonylation was found to decompose polyols into CO:H2 mixtures that could be used immediately in the ex situ low-pressure hydroformylation of styrene (Paper VI). The net process was thus the hydroformylation of alkenes with biomass-derived synthesis gas

Transition Metal Catalysis for Selective Synthesis and Sustainable Chemistry

This thesis discusses the preparation and use of transition-metal catalysts for selective organic chemical reactions. Specifically, two different matters have been studied; the asymmetric hydrogenation of carbon-carbon double bonds using N,P-ligated iridium catalysts and the metal-catalyzed transfer of small molecules from biomass to synthetic intermediates. In the first part of this thesis, chiral N,P-ligands were synthesized and evaluated in iridium catalysts for the asymmetric hydrogenation of non- and weakly functionalized alkenes (Papers I & II). The new catalysts were prepared via chiral-pool strategies and exhibited superior properties for the reduction of certain types of alkenes. In particular, some of the catalysts showed excellent activity and selectivity in the enantioselective reduction of terminal alkenes, and the preparation of a modular catalyst library allowed the asymmetric hydrogenation of a wide range of 1,1-disubstituted alkenes with unprecedented efficiency and enantioselectivity (Paper III). Methods for the selective preparation of chiral hetero- and carbocyclic fragments using iridium-catalyzed asymmetric hydrogenation as an enantiodetermining key step were also developed. A range of elusive chiral building blocks that have applications in pharmaceutical and natural-product chemistry could thus be conveniently prepared (Papers IV & V). The second part of this thesis deals with the catalytic decomposition of polysaccharides into sugar alcohols and the incorporation of their decomposition products into alkene substrates. Iridium-catalyzed dehydrogenative decarbonylation was found to decompose polyols into CO:H2 mixtures that could be used immediately in the ex situ low-pressure hydroformylation of styrene (Paper VI). The net process was thus the hydroformylation of alkenes with biomass-derived synthesis gas

Selective, metal-catalyzed transfer of H2 and CO from polyols to alkenes

Induction motors are widely applied in industry. Their performance strongly depends on relative power supply quality, such as voltage sags, harmonics, voltage unbalance and voltage fluctuations. This paper investigates the impact of voltage fluctuations on induction motor performance, particularly the stator and rotor current variation characteristics. An induction motor steady state analysis method is proposed when the motor is subjected to regular voltage fluctuations. The dynamic model of an induction motor is used in order to represent the induction motor instantaneous response. Furthermore, the correlative simulation and experiment work are presented in order to illustrate the impact of voltage fluctuations. The stator and rotor RMS current magnitudes of the motor increase dramatically and this effect keeps deteriorating with modulation frequency and voltage change increases. The increase in RMS current will increase losses, resulting in motor winding temperature rise, subsequently accelerating the ageing process

Evaluation of Oxidation Stability of Refined Mineral Oil Enriched with Carotenoids from Carrot Using Supercritical Carbon Dioxide Extraction

Refined mineral oil, intended for various technical applications, was enriched with carotenoids by supercritical carbon dioxide extraction using the oil itself as cosolvent. It was envisioned that the carotenoids could function as renewable oil additives, adding chemical functionality to the end product such as enhanced resistance to oxidation. In order to investigate such possible antioxidant activity, a testing protocol was developed in which oil samples were thermally aged in the presence of a controlled amount of oxygen, and the time-dependent hydroperoxide and keto functionality concentration was monitored. An indication of antioxidant activity was indeed found, and further experiments were undertaken in order to investigate whether this was caused by the main carotenoid found in carrots, beta-carotene. This was not found to be the case, and other possible explanations for the observed oxidative behavior, still to be investigated, are discussed

Asymmetric Hydrogenation of Olefins Using Chiral Crabtree-type Catalysts : Scope and Limitations

AuthorCount:4;Other funders:Nordic Energy Research (N-INNER II); Spanish Government CTQ2010-15835;  Catalan Government 2009SGR116 ICREA; Foundation through the ICREA Academia awards  </p

High Yields of Bio Oils from Hydrothermal Processing of Thin Black Liquor without the Use of Catalysts or Capping Agents

Black liquor (BL) from the kraft pulping process has been treated at elevated temperatures (380 °C) in a batch reactor to give high yields of a bio oil comprising monomeric phenolic compounds that were soluble in organic solvents and mineral oil and a water fraction with inorganic salts. The metal content in the product was <20 ppm after a simple extraction step. A correlation between concentration, temperature, and reaction time with respect to yield of desired product was found. At optimal reaction conditions (treating BL with 16 wt % dry substance at 380 °C for 20 min), the yield of extractable organics was around 80% of the original lignin with less than 7% of char. The product was analyzed by gel permeable chromatography, mass spectroscopy, nuclear magnetic resonance, elemental analysis, and inductively coupled plasma. It was found that a large fraction composed of mainly cresols, xylenols, and mesitols. This process provides a pathway to convert a major waste stream from a pulp mill into a refinery feed for fuel or chemical production, whereas at the same time the inorganic chemicals are recovered and can be returned back to the pulp mill

Tame and wild coordinates of ℤ[x,y]

Algorithms to decide whether a polynomial is a coordinates (tame coordinate, respectively) of ℤ[x,y] are given. Moreover, if a polynomial p∈Z[x,y] is a coordinate (tame coordinate, respectively), the algorithms effectively construct a concrete automorphism of ℤ[x,y] that sends x to p. The algorithm to determine tame coordinate is applicable to R[x,y] where R is an Euclidean domain; while the algorithm to determine coordinate is applicable to D[x.y] where D is a unique factorization domain. © 2004 Published by Elsevier Inc.link_to_subscribed_fulltex