The West Group
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Metallocarbenes/Ylide Chemistry

Research
Nazarov chemistry
Metallocarbenes
Photochemitry
Natural Products

Metallocarbenes and the cyclic ylides derived from their addition to pendant heteroatoms are two other classes of reactive intermediates that attract our interest as useful synthetic intermediates. Previous work in our research group has shown that spirocyclic ammonium ylides can undergo stereoselective rearrangements by the [1,2]-shift. Subjecting azetidinecarboxylate 1 to such conditions, the two natural Alkaloids, Turneforcidine and Platynecine could be obtained through an extremely short synthesis.

 

 

At the present several group members are investigating methodologies using oxonium, ammonium and sulfonium ylides in their work. They are developping novel synthetic protocols employing carbenoid pathways for the generation of heterocyclic frameworks, as well as for the total synthesis of various natural products.

 

By generating phenyl-iodonium ylides in situ (in the presence of a catalyst) these can undergo carbene transfer to give metallocarbene intermediates. When the substrates for this investigation were suitably functionalized, [2,3]- and [1,2]- rearrangements occurred upon onium-ylide formation.

 

 

Ring expansion through the generation and rearrangement of a intramolecular sulfonium ylide is also a stereoselective manner by which larger thio-bridged medium-sized ethers can be prepared .

 

 

The Stevens rearrangement of ammonium ylides is an efficient method for the synthesis of functionalized pyrrolidine and piperidine ring systems. These nitrogen-containing ring systems, common in numerous alkaloid natural products, are or great interest to our group.

 

 

 

Frederick G. West. Professor of Chemistry
Department of Chemistry, University of Alberta, W5-67 Gunning-Lemieux
Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada
Email: frederick.west@ualberta.ca