Modularly designed organocatalysts for asymmetric reactions
Organocatalysis is currently one of the fastest growing fields of research in organic chemistry. Catalysis by metal free organic molecules has been known in organic chemistry for more than 100 years, but its full potential was recognized only until the 21st century. Today, the most applications of organocatalysts are in asymmetric reactions. Development of new chiral catalysts is normally based on the structural tuning of known catalysts and on the synthesis of catalyst libraries. Catalyst development is a time consuming and complex process. The prediction of catalyst properties such as selectivity and reactivity is very difficult and the substrate scope of any given catalyst is usually narrow. Most of the reported organocatalysts have the reaction center and the stereocontrolling moiety in the same molecule connected by covalent bonds. This design is highly effective in achieving stereocontrol, but is disadvantageous for the modification and fine tuning of catalyst structures. The aim of the thesis is to bridge the gaps in the catalyst synthesis, which is suitable for high throughput screening. We designed target organocatalyst in a simplified way, it is synthesized in-situ from the self-assembly of the precatalyst modules (proteogenic á-aminoacids and cinchona alkaloid derivatives) through ionic interactions. Enantioselectivity and reactivity may be fine-tuned to a substrate or specific reaction by simply replacing the modules, without the need of synthesizing new chiral catalysts.