Change search
ReferencesLink to record
Permanent link

Direct link
Gold(I) Catalyzed Tandem Cyclization Reactions with Propargyl Acetals
Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, Department of Chemistry.
2013 (English)MasteroppgaveStudent thesis
Abstract [en]

The main goal of this thesis has been to further explore gold(I) catalyzed cyclization reactions including propargyl acetals. Gold(I) catalysts have a strong affinity to triple bonds, and alkyne-gold complexes are readily formed. Both propargyl esters and acetals have previously been investigated in gold(I) catalyzed reactions. These propargylic substrates undergo intramolecular rearrangements to form gold carbenoid intermediates IVa-b, which exhibit strong electrophilic character and are activated for nucleophillic attacks. Propargyl esters have previously proven to undergo gold(I) catalyzed [2+1] cyclization reactions with vinyl esters and amides while propargyl acetals have shown to undergo gold(I) catalyzed [3+2] cyclization reactions with the same substrates. The difference in chemoselectivity is due to the electronic properties of the OR-groups in the gold carbenoid intermediates IVa-b. Propargyl acetals have proven to be more reactive than propargyl esters and thus new reactions including these species were investigated further. Propargyl acetals 5a-c were synthesized in acid catalyzed reactions between propargyl alcohols 3a-c and 1-methoxy-2-propene. Non-commercial propargyl alcohols 3b-c were formed in a Grignard reaction with benzylic aldehydes 1a-b. 1-Phenylprop-1-yne 6 does not exhibit great nucleophilicity, but in the presence of gold(I) activated propargyl acetals, it has shown to readily undergo cyclization reactions. In this thesis, propargyl acetals 5a-d were treated with 1-phenylprop-1-yne 6 in gold(I) catalyzed reactions to readily form different cyclization products 7a-c, 8a-b and 10a-d by new tandem cyclization reactions. Propargyl acetals 5a and 5d provided approximately the same product compositions, respectively products 7a-c and 10b-d, with each fraction yielding 3-12%. Propargyl acetal 5d gave one additional product 10a which was isolated in 7% yield. Product 10a was generated by following a different reaction mechanism than for the formation of 10b-d. The reaction with propargyl acetal 5b was more regio- and stereospecific as it provided one major product 8a in 27% yield. Additionally, another stereoisomer 8b was obtained in 5% yield. Propargyl acetal 5c did not provide any tandem cyclization products, but by following a known [3+2] cycloaddition, product 9 was formed in 15% yield. Possible reaction mechanisms have been proposed for the formation of 7a-c, 8a-b, 10b-d and 10a respectively. All products 7-10 were characterized by 1D and 2D NMR experiments, IR and MS. NOESY experiments were of great importance when distinguishing diastereomers.

Place, publisher, year, edition, pages
Institutt for kjemi , 2013. , 147 p.
URN: urn:nbn:no:ntnu:diva-22559Local ID: ntnudaim:9743OAI: diva2:649804
Available from: 2013-09-19 Created: 2013-09-19 Last updated: 2013-09-19Bibliographically approved

Open Access in DiVA

fulltext(14673 kB)974 downloads
File information
File name FULLTEXT01.pdfFile size 14673 kBChecksum SHA-512
Type fulltextMimetype application/pdf
cover(184 kB)5 downloads
File information
File name COVER01.pdfFile size 184 kBChecksum SHA-512
Type coverMimetype application/pdf

By organisation
Department of Chemistry

Search outside of DiVA

GoogleGoogle Scholar
Total: 974 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: 89 hits
ReferencesLink to record
Permanent link

Direct link