Addicions de Michael: catàlisi per fosfines, metalls de transició i estudis mecanístics

• Autores: Elisabet Pérez Vico
• Directores de la Tesis: Adelina Vallribera Massó (dir. tes.)
• Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2015
• Idioma: catalán
• Tribunal Calificador de la Tesis: Ramon Alibés Arqués (presid.), Alexandr Shafir (secret.), Caroline Marchi De la Pierre (voc.)
• Materias:
  • Química
    • Química inorgánica
      • Compuestos organometálicos
    • Química orgánica
      • Química de organofosforados
• Enlaces
  • Tesis en acceso abierto en:  TESEO  TDX 
• Resumen

  • Michael additions: catalysis by phosphines, transitions metals and mechanistic insights In recent years, the chemical community dedicated a lot of efforts to accomplish Michael additions under neutral and soft conditions in order to minimize side reactions. Our group has a wide experience in metal transition catalysis with metals such as Ni(II) and Cu(II) and also using phosphines as organocatalyst.

    In this work, quiral ß-dicarbonyl based nucleophiles have been synthesized and used in Michael additions catalyzed by PBu3. The diastereoselectivity depends on the substrates used and in general moderate diastereomeric excess and yields are obtained. The obtained quiral Michael adducts have hidden amino/acids functionalities that could be derivated to enantiomerical pure disubstituted amino acids and ¿-amino-ß-hydroxiacids, which are both important building blocks in organic chemistry. Nevertheless, the complete derivatisation to enantiomerically pure compounds hasn¿t been achieved.

    With the metal catalysis in view, we have synthesized different covalent copper and nickel catalyst from commercial reagents. The most effective catalyst is copper (II) bis-(5-tert-salicylaldehydate).The scope of this has been investigated using a wide range of electrophilic acceptors. The yields obtained are from moderate to good. The results obtained with non activated acceptors, such as acrylates and acrylonitriles, are remarkable; these poor acceptors usually show low activities when metal catalysts are used.

    The reaction mechanism of Michael addition catalyzed by species of Cu (II) has been studied using techniques such as ESI-MS, IR and UV-Vis spectroscopy and cyclic voltammetry. Kinetic studies have been also performed. All the evidences obtained show an enolate type coordination of ß-dicarbonilic compounds with the metal as intermediates of the reaction. The rate-determining step of Michael addition, in the cases studied, is the addition of the Michael acceptor to these intermediates.