title: Cubic Siloxanes with Both Si-H and Si-OtBu Groups for Site-Selective Siloxane Bond Formation.
abstract: Cage-type siloxanes have attracted increasing attention as building blocks for silica-based nanomaterials as their corners can be modified with various functional groups. Cubic octasiloxanes incorporating both Si-H and Si-OtBu groups [(tBuO)nH8-nSi8O12; n=1, 2 or 7] have been synthesized by the reaction of octa(hydridosilsesquioxane) (H8Si8O12) and tert-butyl alcohol in the presence of a Et2NOH catalyst. The Si-H and Si-OtBu groups are useful for site-selective formation of Si-O-Si linkages without cage structure deterioration. The Si-H group can be selectively hydrolyzed to form a Si-OH group in the presence of Et2NOH, enabling the formation of the monosilanol compound (tBuO)7(HO)Si8O12. The Si-OH group can be used for either intermolecular condensation to form a dimeric cage compound or silylation to introduce new reaction sites. Additionally, the alkoxy groups of (tBuO)7HSi8O12can be treated with organochlorosilanes in the presence of a BiCl3catalyst to form Si-O-Si linkages, while the Si-H group remains intact. These results indicate that such bifunctional cage siloxanes allow for stepwise Si-O-Si bond formation to design new siloxane-based nanomaterials.
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Okubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Saito
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Okubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Yamasue
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Okubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Wada
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Okubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan. shimojima@waseda.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Shimojima
authors.affiliation: Department of Applied Chemistry, Faculty of Science and Engineering, Waseda University, Okubo-3, Shinjuku-ku, Tokyo, 169-8555, Japan. kuroda@waseda.jp.|Kagami Memorial Research Institute for Materials Science and Technology, Nishiwaseda-2, Shinjuku-ku, Tokyo, 169-0051, Japan. kuroda@waseda.jp.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Kuroda
keywords: cage compounds; hydrolysis; regioselectivity; siloxanes; silylation