Papers by Keyword: Silanol

Abstract: Recently we have reported the syntheses of a variety of silsesquioxanes including laddersiloxanes and cage silsesquioxanes. As a precursor of these compounds, cyclotetrasiloxanetetraols are very useful. Several groups reported the syntheses of alkyl-substituted all-cis-cyclotetrasiloxanesilanolate that can be converted to all-cis cyclotetrasiloxanetetraols. In addition, there was a report of the isomerization of phenyl-substituted all-cis-tetraphenylcyclotetrasiloxanetetraol by hydrochloric acid to give other three stereoisomers. With an aim to elucidate that the reaction is commonly applied or not to other cyclic silanols, we synthesized all-cis isobutyl cyclic silanol. With investigating the reaction condition, we could obtain this cyclic silanol in better yield than previously published methods. Additionally, stereoisomerization reaction with hydrochloric acid was investigated. With a slightly longer reaction time, isomerization reaction was observed to give other stereoisomers. This is the second example of the stereoisomerization of cyclic silanols.

Abstract: Recently we have been investigating solvent-free synthesis of siloxanes. Using no solvent gives less load to environment, and decreases cost in chemical industry. On the other hand, acidic or basic condition may not be applied to siloxanes bearing functional substituents. Therefore, the development of synthetic methods in neutral condition is desired. In this paper, we report the solvent-free thermal condensation of siloxane from silanol bearing vinyl group and strong electron-withdrawing 4-trifluoromethylphenyl group. Furthermore, we examined thermal properties of obtained vinyl-substituted silanol by TG-DTA measurement. With these results, we could determine the temperature of thermal condensation. We also elucidated the reaction pathway by tracing the reaction with GC-MS. Finally, we propose the possible reaction pathway from silanediol to cyclotrisiloxane (D₃) and cyclotetrasilxane (D₄).