Silanes alkenyloxy

The most simple molecular topology of such systems reported so far is a tetrahedral supermolecule obtained by reacting tetrakis(dimethylsiloxy)-silane with alkenyloxy-cyanobiphenyls (Fig. 22), as discussed previously. Such tetramers exhibit smectic A liquid crystal phases [179]. For such end-on materials, microsegregation at the molecular level favors the formation of the smectic A phases in preference to the nematic phase exhibited by the mesogenic monomers themselves. The use of different polyhedral silox-ane systems (Fig. 24) or the Ceo polyhedron as the template for multi- and polypedal hexakis(methano)fullerenes (Fig. 70) substituted with a large number of terminally attached mesogenic groups confirm the same tendency to the formation of smectic A phases (vide supra). 

Analogously, intramolecular hydrosilation reactions have been carried out with alkenes cyclization of alkenyloxy-silanes catalyzed by thiols <1998J(P1)467> and by Pt <1996TL827> has been described. In addition, intramolecular temporary silicon-tethered rhodium-catalyzed [4- -2- -2]-cycloisomerization reactions have been carried out by Evans and Bawn (Equation 50) <2004JA11150>. 

Fig. 21 Transition temperatures (°C) for the tetramers of alkenyloxy-cyanobiphenyls substituted tetrakis-( dimethylsiloxy) silane...

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