title: An organocatalytic asymmetric Nazarov cyclization.
abstract: An organocatalytic asymmetric Nazarov cyclization of diketoesters that proceeds by means of a dual activation mechanism has been developed. Screening of a number of catalysts led to a new thiourea that incorporates a primary amino group. The method gives rise to cyclic products with two adjacent quaternary asymmetric carbon atoms, one of which is an all-carbon stereocenter, with complete or nearly complete diastereoselectivity and in high or very high enantiomeric excess. A brief and very convenient synthesis of the acyclic diketoester starting materials through nucleophilic addition to a ketene is also described.
authors.affiliation: Department of Chemistry, 2545 The Mall, University of Hawaii, Honolulu, Hawaii 96822, USA.
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Basak
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Shimada
authors.forename: William F
authors.initials: WF
authors.lastname: Bow
authors.forename: David A
authors.initials: DA
authors.lastname: Vicic
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Tius
mesh_terms: D002384:Catalysis; D003500:Cyclization; D004952:Esters; D009930:Organic Chemicals / Q000737:chemistry*
chemical_list: D004952:Esters; D009930:Organic Chemicals