A new selective approach to unsymmetrical siloxanes and germasiloxanes via O-metalation of silanols with 2-methylallylsilanes and 2-methylallylgermanes
A scandium(III) trifluoromethanesulfonate-catalyzed O-metalation of silanols with 2-methylallylsilanes and 2-methylallylgermanes leading to siloxane or germasiloxane bond formation under mild conditions with evolution of isobutylene is described.
present a highly efficient method for the synthesis of functionalized silsesquioxanes mediated by scandium(III) triflate, which opens up the possibility of introducing a wide variety of functional groups into this class of organosilicon compounds under mild conditions with excellent yields. We also investigated the differences in the activity of the Lewisacid (Sc(OTf)3) and the hidden Brønsted acid (TfOH)
Sc(OTf)(3)-catalyzed coupling reaction of silanediols with 2-methylallylsilanes and germanes leading to SiO-Si or SiO-Ge bond formation with the evolution of isobutylene is described. Diisopropyl-substituted silanediols of the general formula HO(i-Pr)(2)Si[OSi(i-Pr)(2)](n)OH (n = 0,1) have been successfully functionalized by using 2-methylallylsilanes or 2-methylallylgermanes in the presence of scandium trifluoromethanesulfonate to yield new linear tri- and tetrasiloxanes or germasiloxanes under mild conditions. The reaction can be readily extended to the synthesis of high molecular weight polysiloxanes by using di(methylallyl)silane as a metalating agent. Unsaturated oligosiloxane products have been used as substrates for further functionalization via catalytic silylative coupling and hydrosilylation reactions:
O-Metalation of silanols and POSS silanols over Amberlyst-15 catalyst: A facile route to unsymmetrical siloxanes, borasiloxanes and germasiloxanes
作者:Krzysztof Kuciński、Grzegorz Hreczycho
DOI:10.1016/j.ica.2019.03.025
日期:2019.5
A simple and highly practical Amberlyst-catalyzed direct O-metalation of silanols, POSS silanols and alkoxy-silanes under mild conditions is proposed. This protocol can be applied to the synthesis of a wide range of important organosilicon derivatives such as siloxanes, germasiloxanes, borasiloxanes and functionalized silses-quioxanes. It is worth noting that Amberlyst-15 can be reused for further experiments and its catalytic activity in this process is well-preserved for several recycling steps.
An Efficient Catalytic Approach for the Synthesis of Unsymmetrical Siloxanes
作者:Grzegorz Hreczycho
DOI:10.1002/ejic.201402904
日期:2015.1
expanding the variety of catalytic methods for siloxane bond formation is explored. Alkoxysilanes react with methylallylsilanes in the presence of scandium(III) trifluoromethanesulfonate to yield disiloxanes and isobutene. The reaction proceeds through one-pot hydrolysis/O-silylation of alkoxysilanes with allylsilanes (via silanol intermediates) under mild conditions. Unsaturated siloxane products are used