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Chiral Anion Directed Asymmetric Carbocation-Catalyzed Diels-Alder Reactions
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
2016 (English)In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 9, p. 1708-1713Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

In recent years the carbocation has re-emerged as a highly efficient Lewis acid catalyst for a variety of organic transformations. However, the goal of asymmetric carbocation catalysis has so far been out of reach mainly as a result of difficulties associated with the preparation of stable chiral carbocations. Here, we describe developments towards asymmetric carbocation catalysis based on the concept of chiral-anion-directed catalysis. Chiral tritylium salts can be conveniently prepared in situ by mixing trityl chloride derivatives with chiral phosphonate, phosphoramide, bis(sulfonyl) amide, and bis(sulfuryl) amide silver or sodium salts. It is shown that the bis(sulfuryl) amide/tritylium ion salt catalyzes the Diels-Alder reaction with an up to 53 % enantiomeric excess.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2016. no 9, p. 1708-1713
Keywords [en]
Synthetic methods, Asymmetric catalysis, Cycloaddition, Carbocations, Trityl ion
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-186566DOI: 10.1002/ejoc.201501621ISI: 000374149600012Scopus ID: 2-s2.0-84959310716OAI: oai:DiVA.org:kth-186566DiVA, id: diva2:927996
Note

QC 20160513

Available from: 2016-05-13 Created: 2016-05-13 Last updated: 2018-09-26Bibliographically approved
In thesis
1. Carbocation Catalysis for Organic Synthesis
Open this publication in new window or tab >>Carbocation Catalysis for Organic Synthesis
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The most common view of carbocations in organic chemistry is that they are short-lived intermediates in several fundamental reactions, e.g. the classic SN1-reaction. However, carbocations that can delocalize their positive charge can be stable enough to be isolated and used as Lewis acid catalysts, phase transfer catalysts or oxidants in various reactions. The theme of this thesis concerns applying trityl cations as Lewis acid catalysts in different organic reactions. The first chapter presents a general introduction of the field of Lewis acids, the characteristics and applications of carbocations in different organic reactions, and the aims of this thesis. The second chapter describes the carbocation-catalyzed asymmetric Diels–Alder reactions assisted by chiral counteranions. The third chapter shows that carbocations can be utilized as catalysts in oxa-Diels–Alder reactions with unactivated aldehydes and dienes as substrates. The fourth chapter investigates the application of carbocation catalysis in bromination reactions for selective functionalization at the benzylic position and on the aromatic ring, respectively. The fifth chapter highlights that carbocation-catalyzed aldehyde–olefin metathesis reactions can be achieved in high yields by suppressing the decomposition of both starting materials and products.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 54
Series
TRITA-CBH-FOU ; 2018:44
Keywords
carbocation, trityl cation, Lewis acid catalyst, enantioselective, chiral counteranion, oxa-Diels–Alder, bromination, aldehyde–olefin metathesis
National Category
Organic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-235422 (URN)978-91-7729-966-0 (ISBN)
Public defence
2018-10-26, F3, Lindstedtsvägen 26, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20180926

Available from: 2018-09-26 Created: 2018-09-26 Last updated: 2018-09-26Bibliographically approved

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