title: Regioselective and Stereospecific Dehydrogenative Annulation Utilizing Silylium Ion-Activated Alkenes.
abstract: Treatment of dialkylbenzylsilanes (1) with trityl tetrakis(pentafluorophenyl)borate (TPFPB) afforded the corresponding silylium ions in equilibrium with their intra- or intermolecular π-complexes, which underwent dehydrogenative annulation with various alkenes to form 1,2,3,4-tetrahydro-2-silanaphthalenes (4) in up to 82% isolated yield. Sterically bulkier substituents on the silicon atom tended to increase the yield of cyclic products 4. The annulation products retained the stereochemistry in cases of the reactions using internal alkenes. The use of diisopropyl(1-naphthyl)silane (2) instead of 1 also resulted in annulation to obtain the 2,3-dihydro-1-sila-1H-phenalene derivatives 6. Electrophilic aromatic substitution at the 8-position was predominant, despite the two potentially reactive positions on the naphthyl group. The steric hindrance of the naphthyl group prevented addition of the cis-alkene to the silylium ion, which would considerably decrease yields of the desired products from 2 compared to those from 1.
authors.affiliation: Faculty of Education, University of Miyazaki , 1-1 Gakuen Kibanadai Nishi, Miyazaki, 889-2192 Miyazaki, Japan.
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.
authors.forename: Yuto
authors.initials: Y
authors.lastname: Yano
authors.affiliation: Faculty of Education, University of Miyazaki , 1-1 Gakuen Kibanadai Nishi, Miyazaki, 889-2192 Miyazaki, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Nakabayashi
authors.affiliation: Department of Materials Science and Biotechnology, Graduate School of Science and Engineering, Ehime University , 3 Bunkyo-cho, Matsuyama, 790-8577 Ehime, Japan.
authors.forename: Syuhei
authors.initials: S
authors.lastname: Yamaguchi
authors.affiliation: Graduate School of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, 305-8571 Ibaraki, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Yamamura
authors.affiliation: Department of Chemistry, Gakushuin University , 1-5-1 Mejiro, Toshima-ku, 171-8588 Tokyo, Japan.
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.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kawashima