Studies on Synthetic Utilities, Properties, and Functionalities of Novel Acylsilanes

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To know the synthetic utilities of acylpolysilanes, three novel types of acylpolysilanes were prepared and their thermal isomerization was studied and found that they may be useful precursors for linear conjugated silenes, as summarized bellow. In addition, it was found that the reactions of silaenolates prepared from acylpolysilanes with benzophenone readily produced dioxasilacyclopentane derivatives in good yields. These results clearly indicate that the acylpolysilanes are useful for the preparation of novel silicon reactive species as well as that of cyclic organosilicon compounds.1) It was found that the reactions of lithium silaenolates with phenyl-substituted acetylenes afforded acyl-(Z)-ethenyldisilane as the first example of α-functionalized acylpolysilanes. Acylethenyldisilanes thus obtained underwent unique isomerization at >100 degree C via 2-siladiene intermediates. This appears to be an important methodology to produce siladiene at rather low temperature.2) Thermal isomerization of a bis(acyl)disilane involving a 2,3-disiladiene intermediate, leading to the formation of a 1,2-disilacyclobuene derivative was investigated3) Thermal isomerization of compounds having two acyl groups linked by a cycloalkane bridge took place at >120 degree C to give the respective ring-enlarged products. This is the first observation of oxa-Cope rearrangement of silenes.