title: Formation of vinyl-, vinylhalide- or acyl-substituted quaternary carbon stereogenic centers through NHC-Cu-catalyzed enantioselective conjugate additions of Si-containing vinylaluminums to β-substituted cyclic enones.
abstract: A catalytic method for enantioselective conjugate addition (ECA) of Si-containing vinylaluminum reagents to β-substituted cyclopentenones and cyclohexenones is described. Reactions are promoted by 1.0-5.0 mol % of a bidentate NHC-Cu complex, which is prepared from air-stable CuCl(2)•2H(2)O and used in situ, and typically proceed to completion within 15-20 min. The requisite vinylmetals are generated efficiently by a site-selective hydroalumination of an alkyne with dibal-H. The desired products, containing a quaternary carbon stereogenic center, are obtained in 48-95% yield after purification and in 89:11 to >98:2 enantiomer ratio (er). The vinylsilane moiety within the products can be functionalized to afford acyl, vinyliodide, or desilylated alkenes in 67% to >98% yield and with >90% retention of the alkene's stereochemical identity. The utility of the catalytic process is illustrated in the context of a concise enantioselective synthesis of riccardiphenol B.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States.
authors.forename: Tricia L
authors.initials: TL
authors.lastname: May
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Dabrowski
authors.forename: Amir H
authors.initials: AH
authors.lastname: Hoveyda
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry; D002384:Catalysis; D003300:Copper / Q000737:chemistry; D006219:Halogens / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000475:Alkenes; D006219:Halogens; D007659:Ketones; D008670:Metals; D009942:Organometallic Compounds; C030011:carbene; D003300:Copper; D000535:Aluminum; D008697:Methane; D012825:Silicon