Divinyl-Functionalized 10-8-10 Fused Tricyclic Laddersiloxanes: Synthesis and Reactivity

We report the synthesis and reactivity of divinyl-functionalized syn-type tricyclic laddersiloxanes featuring enlarged 10-8-10 fused frameworks. The reaction of a silanol precursor with dichloromethylvinylsilane afforded methyl-substituted derivative 2 in an excellent yield (96%), whereas the bulkier phenyl analog 3 was obtained in a moderate yield (38%) under intensified conditions. Both compounds were formed as mixtures of three isomers and exhibited relatively high thermal stability. Post-functionalization studies revealed a pronounced steric effect on the reactivity. While both derivatives underwent efficient platinum-catalyzed hydrosilylation with dimethylphenylsilane, the increased bulk of the silane significantly reduced or suppressed the conversion, particularly for the phenyl-substituted system. In addition, the thiol-ene reaction of 2 enabled the incorporation of hydroxyl functionality. These results expand the structural toolbox of functional bat siloxanes and demonstrate their potential as versatile precursors for siloxane-based architectures.