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Non-classical Carbocations and Enols in Asymmetric Catalysis


Pupo,  Gabriele
Research Department List, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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Pupo, G. (2017). Non-classical Carbocations and Enols in Asymmetric Catalysis. PhD Thesis, Universität zu Köln, Köln.

Cite as: http://hdl.handle.net/21.11116/0000-0001-1655-7
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.