Transition Metal Lewis Acids as Chiral Catalysts: Mechanistic and Synthetic Studies

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The development and application of chiral catalysts for asymmetric synthesis is of enormous interest for economical and ecological reasons. Biologically active chiral molecules can be synthesized without using stoichiometric amounts of optically pure compounds. Very good results for cycloaddition reactions with α,β unsaturated aldehydes have been obtained with remarkably stable and recoverable rutheniumbased Lewis acids bearing chiral perfluoroaryldiphosphinite ligands. Diels-Alder reactions were also successfully applied to α,β unsaturated ketones. This project aims at an understanding of mechanistic details of the catalysis and to develop further applications. Encouraged by preliminary results with α,β unsaturated ketones, the synthetic potential of these catalysts will be extended to conjugated addition reactions. A challenging aim is to apply α,β unsaturated aldehydes for Mukaiyama-Michael additions, as only one organocatalytic approach has been reported in this area. Furthermore, the versatility of the catalyst will be tested by performing reactions not involving coordination of a carbonyl compound. These are for example diastereo and enantioselective catalytic cyclopropanations and aziridinations.