Universität zu Köln

Singh, Vikas Kumar ORCID: 0000-0001-9858-0354 (2024). Taming Benzylic Cations via Asymmetric Counteranion Directed. PhD thesis, Universität zu Köln.

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Abstract

Reactions that proceed via carbocations play a big role in various chemical transformations for over a century. Their applications range from drug discovery, commercial compounds to petroleum industry. Despite their vast reactions in chemical synthesis, taming carbocations in asymmetric synthesis is rather limited. Hydrocarbon-based carbocations lack polarized bonds, which diminishes possible interactions with catalysts. The main objective of this thesis is reaction development, optimization, design and synthesis of enantiomerically pure Brønsted acids, which are capable of generating and stabilizing benzylic carbocations from the corresponding racemic sp3 starting materials. The developed methodology provides a general approach to the synthesis of chiral benzylic compounds with high enantioselectivity. The use of confined counteranions allows for the stabilization of the carbocation intermediate, which is crucial for achieving high enantioselectivity in the subsequent CC-, CO- and CN-bond forming reactions. The highly reactive cationic intermediate can be accessed from different precursors via Lewis- or Brønsted acid catalysis. In conclusion, this work represents a significant contribution to the field of asymmetric synthesis and has the potential to impact the development of new drugs and materials. The design and synthesis of enantiomerically pure Brønsted acids capable of generating and stabilizing benzylic carbocations has opened up new possibilities for the synthesis of enantioenriched benzylic compounds. The use of confined counteranions has proven to be a highly effective strategy for catalytic asymmetric reactions with excellent enantioselectivity. This research has significant implications for the development of new drugs and compounds in the pharmaceutical industry.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Singh, Vikas Kumar vikaskumar05071996@gmail.com orcid.org/0000-0001-9858-0354 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-727668
Date:	16 May 2024
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry
Subjects:	Natural sciences and mathematics
Uncontrolled Keywords:	Keywords Language Taming English Benzylic Carbocation English Asymmetric Counteranion-Directed Catalysis English
Date of oral exam:	12 March 2024
Referee:	Name Academic Title List, Benjamin Prof. Schmalz, Hans-Guenther Prof.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/72766