Ken-Ichiro Kanno

Introduction of various types of substituents onto oligosilane chains is important for not only synthesis scheme of functionalized oligosilanes but also modification and tuning of the unique photophysical and electronic properties. To explore further potentials of oligosilanes, development of their synthetic methods is essential. Since transition metal-based methodologies have contributed greatly to the remarkable progress in synthetic organic chemistry, application of similar strategies for the oligosilane synthesis is highly desirable. However, few such attempts have been reported so far, probably due to the intrinsic reactivity of the Si-Si bond toward transition metal species. We are trying to develop the transition metal-catalyzed reactions of oligosilanes without Si-Si bond cleavage. In this paper, titanium-catalyzed selective monoreduction of dichlorooligosilanes, ruthenium-catalyzed alkoxylation of hydrooligosilanes, and ruthenium-catalyzed regio- and stereoselective hydrosilylation reactions using hydrooligosilanes are described. By choosing appropriate catalysts, these reactions successfully provide a series of novel oligosilane derivatives with the Si-Si bond intact.

A series of novel 9,9‐dialkoxy‐9‐silafluorenes were synthesized, and their structures and reactivity were studied. Dehydrogenative alkoxylation of 9,9‐dihydro‐9‐silafluorene with various alcohols in the presence of PdCl₂ gave the corresponding dialkoxylated products in good yields. The structures of some of the novel 9,9‐dialkoxy‐9‐silafluorenes were analyzed by X‐ray crystallography. The 9,9‐dialkoxy‐9‐silafluorenes show remarkably high reactivity toward phenylmagnesium bromide to afford substitution products.

A series of unsymmetrically substituted oligosilanes were synthesized via stepwise introduction of different substituents to α-chloro-ω-hydrooligosilanes. The reactions of α-chloro-ω-hydrooligosilanes with organolithium or Grignard reagents gave hydrooligosilanes having various alkyl, alkenyl, alkynyl and aryl groups. Thus-obtained hydrooligosilanes were converted into alkoxyoligosilanes by ruthenium-catalyzed dehydrogenative alkoxylation with alcohols.