title: Intramolecular Chain Hydrosilylation of Alkynylphenylsilanes Using a Silyl Cation as a Chain Carrier.
abstract: Diorganyl[2-(trimethylsilylethynyl)phenyl]silanes 1a-c and methyl-substituted phenylsilanes 1d and 1e were treated with a small amount of trityl tetrakis(pentafluorophenyl)borate (TPFPB) as an initiator in benzene to afford the corresponding benzosiloles (2a-e) in moderate to good yields. However, no reaction was observed for the reaction using [2-(1-hexynyl)phenyl]diisopropylsilane lf. The methyl substituent was tolerated under the reaction conditions and increased the yield of the corresponding benzosilole depending on the substitution position. From the result using 1f, the current reaction was found to require the trimethylsilyl group, which can stabilize intermediary alkenyl carbocations by the β-silyl effect. The current reaction can be considered an intramolecular chain hydrosilylation of alkynylarylsilanes involving silyl cations as chain carriers. Therefore, the silyl cations generated by hydride abstraction from hydrosilanes 1 with the trityl cation causes intramolecular electrophilic addition to the C-C triple bond to form ethenyl cations, which abstract a hydride from 1 to afford benzosiloles 2 with the regeneration of the silyl cations.
authors.affiliation: Faculty of Education, University of Miyazaki, 1-1 Gakuen Kibanadai Nishi, Miyazaki, 889-2192 Miyazaki, Japan. hidekazu.arii@cc.miyazaki-u.ac.jp.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Arii
authors.affiliation: Faculty of Education, University of Miyazaki, 1-1 Gakuen Kibanadai Nishi, Miyazaki, 889-2192 Miyazaki, Japan. nakabys@cc.miyazaki-u.ac.jp.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nakabayashi
authors.affiliation: Department of Chemistry, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, 171-8588 Tokyo, Japan. kunio.mochida@gakushuin.ac.jp.
authors.forename: Kunio
authors.initials: K
authors.lastname: Mochida
authors.affiliation: Graduate School of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, 376-8515 Gunma, Japan. kawashima.t@gunma-u.ac.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawashima
mesh_terms: D002384:Catalysis; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012821:Silanes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D017646:Organosilicon Compounds; D012821:Silanes
keywords: benzosilole; hydrosilylation; metal free; silyl cation