title: NHC-mediated enantioselective formal [4 + 2] cycloadditions of alkylarylketenes and β,γ-unsaturated α-ketocarboxylic esters and amides.
abstract: Chiral N-heterocyclic carbenes (NHCs) promote the asymmetric formal [4 + 2] cycloaddition of alkylarylketenes with β,γ-unsaturated α-ketocarboxylic esters and amides. Divergent diastereoselectivity is observed in this process, with γ-aryl-β,γ-unsaturated α-ketocarboxylic esters and amides giving preferentially syn-dihydropyranones (up to 68 : 32 dr syn : anti, up to 98% ee), while γ-alkyl-derivatives generate anti-dihydropyranones (up to 18 : 82 dr syn : anti, up to 75% ee).
authors.affiliation: EaStCHEM, School of Chemistry, University of St Andrews, North Haugh, St Andrews, KY16 9ST, UK.
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Leckie
authors.forename: T Bruce
authors.initials: TB
authors.lastname: Brown
authors.forename: David
authors.initials: D
authors.lastname: Pryde
authors.forename: Tomas
authors.initials: T
authors.lastname: Lebl
authors.forename: Alexandra M Z
authors.initials: AM
authors.lastname: Slawin
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Smith
mesh_terms: D000577:Amides / Q000138:chemical synthesis* / Q000737:chemistry; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D003500:Cyclization; D004952:Esters / Q000138:chemical synthesis* / Q000737:chemistry; D005030:Ethylenes / Q000138:chemical synthesis* / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000577:Amides; D002264:Carboxylic Acids; D004952:Esters; D005030:Ethylenes; D006571:Heterocyclic Compounds; D007659:Ketones; C030011:carbene; C008223:ketene; D008697:Methane