title: Conjugate umpolung of β,β-disubstituted enals by dual catalysis with an N-heterocyclic carbene and a Brønsted acid: facile construction of contiguous quaternary stereocenters.
abstract: A sterically hindered homoenolate has been generated by the NHC-catalyzed conjugate umpolung of β,β-disubstituted enals and successfully employed in a facile stereoselective annulation with isatins. The strategy provides efficient access to spirocyclic oxindoles bearing two highly congested contiguous quaternary carbon centers. The use of a Brønsted acid cocatalyst was found to be crucial for guaranteeing both excellent reactivity and high stereoselectivity.
authors.affiliation: Organisch-Chemisches Institut, NRW Graduate School of Chemistry, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster (Germany) http://www.uni-muenster.de/Chemie.oc/glorius/index.html.
authors.forename: Jun-Long
authors.initials: JL
authors.lastname: Li
authors.forename: Basudev
authors.initials: B
authors.lastname: Sahoo
authors.forename: Constantin-G
authors.initials: CG
authors.lastname: Daniliuc
authors.forename: Frank
authors.initials: F
authors.lastname: Glorius
mesh_terms: D000143:Acids / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D061565:Cycloaddition Reaction; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D000078183:Oxindoles; D013141:Spiro Compounds / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000143:Acids; D000447:Aldehydes; D006571:Heterocyclic Compounds; D007211:Indoles; D000078183:Oxindoles; D013141:Spiro Compounds; C022960:2-oxindole; C030011:carbene; D008697:Methane
keywords: carbenes; dual catalysis; quaternary centers; spiro compounds; umpolung