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Carbocations as Lewis Acid Catalysts: Scope and Reactivity
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.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
2015 (English)In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 357, no 1, 148-158 p.Article in journal (Refereed) Published
Abstract [en]

One class of potential Lewis acids that has received negligible attention as a catalyst is the carbocation. Here we show the potential of triarylmethylium ions as highly powerful Lewis acid catalysts for organic reactions. The Lewis acidity of the triarylmethylium ion can be easily tuned by variation of the electronic properties of the aromatic rings and the catalytic activity of the carbocation is shown to correlate directly to the level of stabilization of the empty p(C)-orbital at the cationic carbon. The versatility of triarylmethylium ions as efficient Lewis acid catalysts for organic reactions is demonstrated in Diels-Alder, aza-Diels-Alder, conjugate addition, halogenation, epoxide rearrangement and intramolecular hetro-ene reactions.

Place, publisher, year, edition, pages
2015. Vol. 357, no 1, 148-158 p.
Keyword [en]
carbocations, catalysis, Lewis acids, organocatalysis, trityl group
National Category
Organic Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-144522DOI: 10.1002/adsc.201400609ISI: 000347705400018Scopus ID: 2-s2.0-84920733647OAI: oai:DiVA.org:kth-144522DiVA: diva2:713894
Note

Updated from manuscript to article.

QC 20150306

Available from: 2014-04-24 Created: 2014-04-24 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Metal-Free Catalysis for Efficient Synthesis
Open this publication in new window or tab >>Metal-Free Catalysis for Efficient Synthesis
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The strength of efficient metal-free catalysis will be examined in this thesis. Efforts towards more sustainable processes will be demonstrated through implementation of strategies that meet several of the 12 principles of Green Chemistry.In the first part, a stereoselective total synthesis of multiple alkaloids from the Corynantheine and Ipecac families together with their non-natural analogues will be disclosed. A highly efficient, common synthetic strategy is applied leading to high overall yields starting from easily available starting material. Overall operational simplicity and sustainability have been the main focus. Time-consuming and waste-generating isolations and purifications of intermediates have been minimized, as well as the introduction of protection-group chemistry. Moreover, the first example of the total synthesis of Hydroxydihydrocorynantheol together with its non-natural epimer has been accomplished in multi-gram scale without protection groups and without a single isolation or purification step in high overall yield and diastereoselectivity.In the second part, carbocations will be presented as highly effective and versatile non-metal Lewis acid catalysts. Lewis acidity-tuning of carbocations will be introduced and applied in several reactions to suppress competing reactions. Finally, the broad scope of carbocation catalyzed transformations will be exposed.At large, evident progress has been made towards more sustainable chemistry.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2014. 69 p.
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2014:15
Keyword
Homogeneous c atalysi s, O rga nocatalysis, Green C hemistry, T o tal S ynthesis, A lkaloids, A symmetric S ynthesis, N on - metal Lewis acid s, C arbocations, Sustainability
National Category
Organic Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-144577 (URN)978-91-7595-110-2 (ISBN)
Public defence
2014-05-08, E3, Osquars Backe 14, 5 tr, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20140425

Available from: 2014-04-25 Created: 2014-04-24 Last updated: 2014-04-25Bibliographically approved

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