title: Vicinal diboronates in high enantiomeric purity through tandem site-selective NHC-Cu-catalyzed boron-copper additions to terminal alkynes.
abstract: A Cu-catalyzed protocol for conversion of terminal alkynes to enantiomerically enriched diboronates is reported. In a single vessel, a site-selective hydroboration of an alkyne leads to the corresponding terminal vinylboronate, which undergoes a second site-selective and enantioselective hydroboration. Reactions proceed in the presence of 2 equiv of commercially available bis(pinacolato)diboron [B(2)(pin)(2)] and 5-7.5 mol % loading of a chiral bidentate imidazolinium salt, affording diboronates in 60-93% yield and up to 97.5:2.5 enantiomeric ratio (er). The enantiomerically enriched products can be functionalized to afford an assortment of versatile organic molecules. Enynes are converted to unsaturated diboronates with high chemo- (>98% reaction of alkyne; <2% at alkene) and enantioselectivity (e.g., 94.5:5.5 er).
authors.affiliation: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA.
authors.forename: Yunmi
authors.initials: Y
authors.lastname: Lee
authors.forename: Hwanjong
authors.initials: H
authors.lastname: Jang
authors.forename: Amir H
authors.initials: AH
authors.lastname: Hoveyda
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D001895:Boron / Q000737:chemistry; D001897:Boronic Acids / Q000138:chemical synthesis*; D002384:Catalysis; D003300:Copper / Q000737:chemistry; D008722:Methods; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D001897:Boronic Acids; D003300:Copper; D001895:Boron