Synthesis and Structure of Ladder Oligosilsesquioxanes: Tricyclic Ladder Oligomethylsilsesquioxanes

Novel tricyclic ladder oligomethylsilsesquioxanes were prepared by heterofunctional condensation of
cis-trans-cis-1,3,5,7-tetraisocyanato-1,3,5,7-tetramethylcyclotetrasiloxane with 1,3-di-tert-butoxy-1,3-dimethyldisiloxane-1,3-diol in the presence of triethylamine in THF. A mixture of stereoisomers of the
tricyclic oligomethylsilsesquioxanes was obtained. Two of the isomers were separated as white solids by
recycle-type high-performance liquid-phase chromatography. They were determined by X-ray crystallography to be tricyclic ladder oligomethylsilsesquioxanes consisting of three eight-membered rings
arranged in syn- and anti-configurations.