title: Experimental and computational studies on interrupted Nazarov reactions: exploration of umpolung reactivity at the α-carbon of cyclopentanones.
abstract: A set of densely substituted, α-functionalized cyclopentanones can be generated by a two-component, domino reaction sequence entailing the Nazarov electrocyclization of divinyl ketones and nucleophilic addition of the resulting 2-oxidocyclopentenyl cations by selected trapping modalities. Bypassing the typical eliminative termination, Nazarov oxyallyl species can react with carbon π-nucleophiles through cycloadditions (or formal cycloadditions), in which bridged bicyclic systems are established, or nucleophilic trappings whereby one terminal carbon of the oxyallyl intermediate is subjected to carbon-carbon bond formation. A detailed investigation of reaction parameters to explicitly control the course of the "interrupted" Nazarov reactions is described. This methodology allows for facile installation of α-quaternary centers bearing allyl, alkynyl, and heteroaryl groups in an umpolung fashion. In addition, the trapping event of a Nazarov intermediate with furan was studied by DFT computations, in conjunction with experimental data, offering a rationale for the observed reaction pattern and diastereoselectivity.
authors.affiliation: X-ray Crystallography Lab, †Department of Chemistry, University of Alberta , E3-43 Gunning-Lemieux Chemistry Center, Edmonton, Alberta T6G 2G2, Canada.
authors.forename: Yen-Ku
authors.initials: YK
authors.lastname: Wu
authors.forename: Christine R
authors.initials: CR
authors.lastname: Dunbar
authors.forename: Robert
authors.initials: R
authors.lastname: McDonald
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ferguson
authors.forename: F G
authors.initials: FG
authors.lastname: West