title: Lewis acids catalyze the addition of allylboronates to aldehydes by electrophilic activation of the dioxaborolane in a closed transition structure.
abstract: This study addressed the mechanism of the recently reported Lewis acid-catalyzed manifold for additions of allylboronates to aldehydes. A series of control experiments using various reagents and conditions, and kinetic studies by low-temperature NMR spectroscopy, were performed to investigate the origin of the activation provided by the best catalyst, Sc(OTf)3. The results obtained are strongly supportive of a mechanism involving electrophilic boron activation by coordination of the metal ion to one of the boronate oxygens in a closed bimolecular transition state.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada.
authors.forename: Vivek
authors.initials: V
authors.lastname: Rauniyar
authors.forename: Dennis G
authors.initials: DG
authors.lastname: Hall