Catalytic asymmetric Stetter reaction: intramolecular desymmetrization of cyclohexadienone and intermolecular reaction of glyoxamide
Date
2009
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Abstract
A series of cyclohexadienones were synthesized through dearomatization of phenols. The asymmetric intramolecular desymmetrizations of these substrates via Stetter reactions afford hydrobenzofuranones in good yields and excellent selectivities. Up to three contiguous stereocenters, as well as quaternary stereocenter, have been generated. An asymmetric intermolecular Stetter reaction of glyoxamides with alkylidenemalonates has been successfully developed. These reactions are catalyzed by a pyrrolidinone-derived carbene catalyst, and proceed in good yields with high asymmetric induction. When alkylidene ketoamides are employed, the reactions afford desired β-ketoamides in good yields, excellent enantioselectivities, and good diastereoselectivities. A carbene-catalyzed asymmetric redox reaction of ynal has been investigated. Cyclohexadienone-tethered ynal and alkylidenemalonate-tethered ynal were demonstrated as suitable substrates for the redox reaction. The desired products were obtained with moderate yields and modest selectivities.
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Subject
asymmetric Stetter reaction
carbenes
cyclohexadienone
desymmetrization
glyoxamide
organic chemistry