Schering Preis 2002
Dr. Simon Gessler
Chemistry Group, NOVALED GmbH, Dresden
Novel immobilised and homogeneous catalysts for the olefin metathesis reaction
The thesis covers several aspects of the design, synthesis and application of novel highly efficient catalysts for the olefin metathesis reaction in organic chemistry. This class of catalytic reactions involves the transformation and rearrangement of C-C-double (olefins) and triple bonds in small molecules. An organometallic entity is employed in catalytic amounts to cut these bonds into halves that are subsequently put together again in a different fashion. The resulting formal interchange of halves of double bonds can be utilised to build up complex organic molecules in only a view synthetic steps.
The reaction is in large parts dependent on the availability of suitable catalysts. They need to show a high activity and efficiency as well as a great stability. To meet these requirements, substantial improvements of the ligand sphere of the organometallic catalysts have been made during the thesis. The first chapter of the thesis shows new ways to immobilised olefin metathesis catalysts. The introduction of N-heterocyclic carbenes as replacement for the hitherto used phosphines in ruthenium alkylidene complexes has led to the development of permanently immobilised catalysts that can easily be filtered off after the reaction has taken place.
In a number of reactions no further purification of the product was necessary and the recovered catalyst could be reused up to four times in subsequent reactions. The second chapter deals with the design, synthesis and characterisation of entirely phosphine-free homogeneous ruthenium alkylidene catalysts. They possess an unprecedented stability against moisture and air and show a high activity and selectivity in olefin cross metathesis. The last chapter describes a new way for the introduction of chirality into N-heterocyclic carbene ligands. As a proof of concept, ruthenium alkylidene complexes bearing such chiral moieties have been synthesised, characterised and used in olefin metathesis reactions.