Silyl, tris

An irreversible dyotropic rearrangement of fluoro-substituted tris(silyl)hydroxyl-amines (127) (128) has been reported and ab initio and density functional calculations for model compounds have confirmed the dyotropic course of this rearrangement. ... 

Iridium cationic complexes have recently been used as highly effective catalysts for the regioselective di- and tri-silylation of simple glycopyranosides with tert-butyldimethylsilane [76]. 

Recently, density functional calculations (B3LYP) on the thermal rearrangement of tris(silyl)hydroxylamines to silylamino disiloxane for model compounds concluded that the insertion of a silyl group into the N—O bond is energetically favoured if it occurs from the nitrogen atom. ... 

So far, no tris(silyl)-substituted cyclotetrasilazane is known. Starting with the isomeric unsymmetrically substituted cyclodisilazane, the next substituent R is bonded exocyclically at the four-membered ring yielding 25 (Scheme 33).31 56 63 64 66... 

Treatment of silyl ethers of sucrose with the Vilsmeier reagent gave various sucrose formates. When only one silyl protecting group was present, the reaction afforded the corresponding monoesters in high yields. However, when di- or tri-silylated sucroses were used as substrates, a mixture of mono- and di-formates were obtained (Scheme 26).301... 

Chlorosilane and chloromethylsilane both give the tris(silyl)amine with ammonia, while the disilazane is the only silicon-nitrogen product formed from chlorotrimethylsilane. Increasing the size of the silicon substituents impedes deamination, so both aminosilane and disilazane result and the amount of the latter increases on prolonged heating. 

Ring expansion occurs with the fourth substituent to give a six-membered ring (146). Also formed is the symmetrically substituted four-membered ring of 147. This means that the tris(silyl)-substituted unsymmetrical four-membered ring 143 forms in an interconversion reaction the tetrakis(silyl)-substituted symmetrical four-membered ring 147. The formation of 147 can be ascribed to an isomerization of the anion of the (silyl)-substituted ring, as described in Scheme 6. 

Nature of the solvent. For xerogels prepared from precursor 54, a high specific surface area with microporosity is obtained when prepared in methanol while non-porous material is obtained when prepared in THF97,98. This was also demonstrated in the case of xerogels of 40 and 73 of bis-silylated precursors and in the case of xerogels 73t of a tri-silylated precursor (Table 5)149,152,155... 

I. Tris(organyl)amine und Tris(silyl)amine. 102... 

Da die Phenoxysilane jedoch fiber Chlorsilane dargestellt werden mtissen, wird man sie nur in besonders gelagerten Fallen zur Gewinnung von Tris(silyl) aminen heranziehen (104,118). 

Es wird angenommen, daO bei der Reaktion primar gebildetes (SieHeJx mit freiwerdendem Ammoniak unter H2-Entwicklung zur Tris(silyl)-amin-Stufe XXXIV weiterreagiert. 

Tris(silyl)amine losen sich in der Regel gut in solchen organischen Lo-sungsmitteln, die Si—N-Bindungen oder funktionelle Gruppen am Si-Atom nicht angreifen, so in Benzol, Petrolather oder auch Dioxan. 

RaSi-Gruppen in Tris(silyl)aminen lassen sich nicht nur abspalten, son-dem innerhalb des Molekiils umgruppieren, wenn man es auf etwa 200 °C erhitzt (30, 63, 92). Diese hohe Beweglichkeit der RaSi-Gruppen ist in... 

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