title: Boron carboxylate catalysis of homoallylboration.
abstract: Boron tris(trifluoroacetate) is identified as the first effective catalyst for the homoallyl- and homocrotylboration of aldehydes by cyclopropylcarbinylboronates. NMR spectroscopic studies and theoretical calculations of key intermediates and transition states both suggest that a ligand-exchange mechanism, akin to our previously reported PhBCl2-promoted homoallylations, is operative. Our experimental and theoretical results also suggest that the catalytic activity of boron tris(trifluoroacetate) might originate from more facile catalytic turnover of the trifluoroacetate ligands (in agreement with DFT calculations) or from a lower propensity for formation of off-pathway reservoir intermediates (as observed by (1)H NMR). This work shows that carboxylates are viable catalytic ligands for homoallyl- and homocrotylations of carbonyl compounds and opens the door to the development of catalytic asymmetric versions of this transformation.
authors.affiliation: Department of Chemistry, Brandeis University , Waltham, Massachusetts 02454-9110, United States.
authors.forename: Gabrielle J
authors.initials: GJ
authors.lastname: Dugas
authors.forename: Yu-hong
authors.initials: YH
authors.lastname: Lam
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.forename: Isaac J
authors.initials: IJ
authors.lastname: Krauss
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011789:Quantum Theory; D014269:Trifluoroacetic Acid / Q000737:chemistry*
chemical_list: D001896:Boron Compounds; D008024:Ligands; D014269:Trifluoroacetic Acid
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