Datensatz

Zusammenfassung

This thesis describes studies on non-classical carbocations and enols in asymmetric catalysis. In the first part, a novel catalytic system based on asymmetric counteranion-directed Brønsted acid organocatalysis was developed, aiming for the enantiocontrol of highly reactive intermediates such as non-classical carbocations. This challenge led to the design and fine tuning of a new class of non-nucleophilic catalysts and culminated in the first proof of concept that these intermediates can indeed be controlled asymmetrically and good enantioselectivities were obtained. In the second part, a novel activation mode for organocatalysis is presented. Its key feature is the use of a chiral Brønsted acid to promote the enolization of carbonyl compounds and to overcome some intrinsic limitations of aminocatalysis. Successfully applied to asymmetric α-alkylations (Michael addition and α-allylation) and α-oxidation reactions of ketones, this concept opens versatile and highly enantioselective new routes towards synthetically challenging quaternary and tetrasubstituted chiral centers.