title: Enantioselective synthesis of boron-substituted quaternary carbon stereogenic centers through NHC-catalyzed conjugate additions of (pinacolato)boron units to enones.
abstract: The first examples of Lewis base catalyzed enantioselective boryl conjugate additions (BCAs) that generate products containing boron-substituted quaternary carbon stereogenic centers are disclosed. Reactions are performed in the presence of 1.0-5.0 mol% of a readily accessible chiral accessible N-heterocyclic carbene (NHC) and commercially available bis(pinacolato)diboron; cyclic or linear α,β-unsaturated ketones can be used and rigorous exclusion of air or moisture is not necessary. The desired products are obtained in 63-95% yield and 91:9 to >99:1 enantiomeric ratio (e.r.). The special utility of the NHC-catalyzed approach is demonstrated in the context of an enantioselective synthesis of natural product antifungal (-)-crassinervic acid.
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, MA 02467 (USA).
authors.forename: Suttipol
authors.initials: S
authors.lastname: Radomkit
authors.forename: Amir H
authors.initials: AH
authors.lastname: Hoveyda
mesh_terms: D001895:Boron / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D020836:Protein Structure, Quaternary; D013237:Stereoisomerism
chemical_list: D002244:Carbon; D001895:Boron
keywords: N-heterocyclic carbenes; boron; conjugate additions; enantioselective synthesis; organic synthesis