New approaches for the using of chiral catalysts. Application in carbonylation reactions.
Nowadays the industrial interest of the carbonylated products has attracted the attention of scientists towards the development of new efficient catalytic systems. The alcoxycarbonylation of vinyl arenes has been considered an alternative route to obtain 2-aryl propionic acids, the most important class of non-steroidal anti-inflammatory drugs. Copolymers formed by carbon monoxide and alkenes are materials of industrial interest due to their potential application as engineering thermoplastics. The concept of atomic economy has influenced the development of industrial catalytic processes. The waste diminishing by the complete conversion of reagents into the desired product in a catalytic process introduce the homogeneous catalysis as an attractive sustainable technology. The knowledge of the carbonylation mechanisms is of great importance for the design of new highly efficient catalytic systems.
Based on these considerations, the first objective of this thesis was to develop new catalytic palladium systems and its application in the asymmetric methoxycarbonylation of vinyl arenes, in order to obtain high regio-and enantioselectivities simultaneously. The second objective was to synthesise new cationic palladium complexes and to study the activity in the copolymerisation reaction. To achieve the first objective, palladium complexes modified with monodentate and bidentate phosphine ligands were explored. In order to know more about the influence of the nature of the ligand on the mechanism, a mechanistic study under similar conditions to those used in the catalysis was performed. To achieve the second objective new cationic palladium complexes modified with diphosphine ligands derived from D-(+)-xylofuranose were synthesised. The new complexes were tested in the CO/ethene, CO/propene copolymerisation reaction, as well as in the CO/ethene/propene terpolymerisation process.
Chapter 2 Palladium complexes bearing monodentate ligands in asymmetric methoxycarbonylation of vinyl arenes shows the use of chiral monodentate cyclic phosphines, such as phosphetane, phospholane and binepine, in the palladium-catalysed asymmetric methoxycarbonylation of vinyl arenes. New neutral palladium complexes are synthesised and characterised by multinuclear NMR spectroscopy. This new complexes were showed a decreased in the catalytic activity when increased the number of the phosphorus membered ring.
Chapter 3 Palladium complexes bearing bidentate ligands in asymmetric methoxycarbonylation of vinyl arenes describes the synthesis of neutral and cationic complexes bearing bidentate ligands with different electronic and steric properties and its application in the methoxycarbonylation of vinyl arenes. In general terms, it was observed that the presence of electron withdrawing groups in the phenyl moiety of the ligand has an influence on the regioselectivity of the reaction to the branched ester.
Chapter 4 Mechanistic aspects of the methoxycarbonylation of styrene discusses mechanistic aspects of the methoxycarbonylation reaction. In situ studies are performed under similar conditions to those used in the catalytic studies. The studies are focuses in palladium systems modified with mono- and bidentate ligands, in order to establish comparison between them. The characterisation of some species by NMR spectroscopy is showed.
Finally in Chapter 5 Cationic palladium complexes bearing xylofuranose-derivative diphosphines in CO/ethene/propene co- and terpolymerisation reactions it was discussed the electronic effects of xylose-derivatives diphosphines ligands in the CO/ethene/propene co- and ter-polymerisation processes. The new diphosphines o-MeO-xylophos is synthesised. A series of new neutral and cationic palladium complexes bearing xylophos and o-MeO-xylophos were synthesised and fully characterised by multinuclear NMR techniques. The catalytic polymerisation reactions were performed in methanol using the cationic complexes and are compared to the reaction catalysed by analogous complexes bearing dppp and o-MeO-dppp to determine the electronic effects and the backbone rigidity on the perfectly alternating copolymerisation.
Advisor:Ruiz Manrique, Aurora; Claver Cabrero, Carmen
School:Universitat Rovira i Virgili
Source Type:Master's Thesis
Keywords:departament de química física i inorgànica
Date of Publication:11/16/2007