title: Dual catalysis in enantioselective oxidopyrylium-based [5 + 2] cycloadditions.
abstract: A new method for effecting catalytic enantioselective intramolecular [5 + 2] cycloadditions based on oxidopyrylium intermediates is reported. The dual catalyst system consists of a chiral primary aminothiourea and a second achiral thiourea. Experimental evidence points to a new type of cooperative catalysis with each species being necessary to generate a reactive pyrylium ion pair that undergoes subsequent cycloaddition with high enantioselectivity.
authors.affiliation: Department of Chemistry & Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Noah Z
authors.initials: NZ
authors.lastname: Burns
authors.forename: Michael R
authors.initials: MR
authors.lastname: Witten
authors.forename: Eric N
authors.initials: EN
authors.lastname: Jacobsen
mesh_terms: D002384:Catalysis; D003500:Cyclization; D006572:Heterocyclic Compounds, Bridged-Ring / Q000737:chemistry*; D013237:Stereoisomerism; D013890:Thiourea / Q000737:chemistry*
chemical_list: D006572:Heterocyclic Compounds, Bridged-Ring; D013890:Thiourea