Change search
ReferencesLink to record
Permanent link

Direct link
Syntes och Applikationer av Kirala Karbokatjoner
KTH, School of Chemical Science and Engineering (CHE).
2015 (Swedish)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesisAlternative title
Synthesis and Application of Chiral Carbocations (English)
Abstract [en]

Asymmetric synthesis is most significant method to generate chiral compounds from prochiral substrates. It usually involves a chiral catalysis, which can be either metal based or organo-catalysis. Both of these systems have their own advantages and disadvantages. In recent times, organocatalysts are gathering widespread attention due to their low toxicity and inexpensive nature. Organocatalysts can replace traditional metal based Lewis acid catalysts in several useful organic transformations like the Diels-Alder reactions.

Carbocations are compounds with positively charged carbon atoms and they can activate the substrate by pulling its electrons thus making it more electrophilic. Though carbocations are well-known in literature, they are not well explored in catalysis despite their tremendous potential.

The aim of this project is to synthesize new chiral carbocations, derived from different chiral auxiliaries and substitution on aromatic moiety and to investigate them in asymmetric Diels- Alder reactions. We envisioned the final product to be enantio-enriched as the carbocations are chiral in nature.

We have synthesized several chiral secondary and tertiary alcohols as a precursor of carbenium salts. These alcohols were mainly synthesized by addition of Grignard reagent or organolithium reagents to the carbonyl compounds. Though, we have synthesized several chiral alcohols, only three carbocations could be isolated those having methoxy group in the aromatic ring. The methoxy group was found to be crucial for the stabilization of the carbocation.

All the isolated carbocations were able to catalyze the Diels-Alder reactions, however it was found that carbocation 4with BF4 as a counter ion was better reactive than others. Unfortunately, we could not get any chiral induction with the use of these catalysts. We believe that with better tuning in catalysts structure and the reaction conditions these carbocations might able to produce chiral induction in the product.

Place, publisher, year, edition, pages
2015. , 48 p.
Keyword [en]
Carbocation, Asymmetric catalysis, Lewis acid, Diels Alder, Organocatalys
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-170634OAI: diva2:839306
Available from: 2015-08-14 Created: 2015-07-02 Last updated: 2015-08-14Bibliographically approved

Open Access in DiVA

fulltext(1773 kB)120 downloads
File information
File name FULLTEXT01.pdfFile size 1773 kBChecksum SHA-512
Type fulltextMimetype application/pdf

By organisation
School of Chemical Science and Engineering (CHE)
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 120 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 36 hits
ReferencesLink to record
Permanent link

Direct link