title: Stereospecific asymmetric N-heterocyclic carbene (NHC)-catalyzed redox synthesis of trifluoromethyl dihydropyranones and mechanistic insights.
abstract: N-heterocyclic carbene (NHC)-catalyzed redox asymmetric hetero-Diels-Alder reactions of α-aroyloxyaldehydes with β-trifluoromethyl enones generates synthetically useful dihydropyranones containing a stereogenic trifluoromethyl substituent in good yields (up to 81%) and excellent diastereoselectivity and enantioselectivity (up to >95:5 dr and >99% ee). The process is stereospecific, with use of either (E)- or (Z)-β-trifluoromethyl enones forming syn- or anti-dihydropyranone products, respectively. Mechanistic studies through in situ kinetic analysis of the reaction reveal key differences in reactivity between chiral NHC precursor 1 and an achiral NHC precursor.
authors: EaStCHEM, School of Chemistry, University of St Andrews , North Haugh, St Andrews KY16 9ST, United Kingdom.
authors: Alyn T
authors: AT
authors: Davies
authors: James E
authors: JE
authors: Taylor
authors: James
authors: J
authors: Douglas
authors: Christopher J
authors: CJ
authors: Collett
authors: Louis C
authors: LC
authors: Morrill
authors: Charlene
authors: C
authors: Fallan
authors: Alexandra M Z
authors: AM
authors: Slawin
authors: Gwydion
authors: G
authors: Churchill
authors: Andrew D
authors: AD
authors: Smith
mesh_terms: D002384:Catalysis; D006571:Heterocyclic Compounds / Q000737:chemistry*; D006845:Hydrocarbons, Fluorinated / Q000138:chemical synthesis* / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011753:Pyrones / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D006571:Heterocyclic Compounds; D006845:Hydrocarbons, Fluorinated; D011753:Pyrones; C030011:carbene; D008697:Methane