title: Solvent-Dependent Reaction Pathways Operating in Copper(II) Tetrafluoroborate Promoted Oxidative Ring-Opening Reactions of Cyclopropyl Silyl Ethers.
abstract: Oxidative ring-opening reactions of benzene-fused bicyclic cyclopropyl silyl ethers, promoted by copper(II) tetrafluoroborate, were investigated. The regioselectivity of cyclopropane ring-opening as well as product distributions were found to be highly dependent on the nature of the solvent. In alcohols, dimeric substances arising from external bond cleavage are major products. Radical rearrangement products are also formed in solvents such as ether and ethyl acetate. On the contrary, nucleophile addition to carbocation intermediates, generated by internal bond cleavage, occurs mainly in reactions taking place in acetonitrile. It is proposed that the observed solvent effects that govern the reaction pathways followed are a consequence of varying solvation of copper intermediates, which governs their reactivity and redox properties. In addition, the influence of counteranions of the copper salts, organonitriles, cyclic dienes, and substrate structures on the pathways followed in these reactions was also examined.
authors.affiliation: Department of Chemistry, Faculty of Science, Niigata University , 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Eietsu
authors.initials: E
authors.lastname: Hasegawa
authors.affiliation: Department of Chemistry, Faculty of Science, Niigata University , 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nemoto
authors.affiliation: Department of Chemistry, Faculty of Science, Niigata University , 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Nagumo
authors.affiliation: Department of Chemistry, Faculty of Science, Niigata University , 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Tayama
authors.affiliation: Department of Chemistry, Faculty of Science, Niigata University , 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Iwamoto