Zn(OTf)2/i-Pr2NEt promoted synthesis of tetraalkynylsilanes
Graphical abstract
Introduction
Tetraalkynylsilanes are of interest as building blocks for organic synthesis, in particular for the preparation of Si-containing heterocycles and spiro rings [1a]. Insecticidal activity [2] and photoluminescence [3] have also been described.
Most of the known methods for the synthesis of tetraalkynylsilanes are based on the reaction of silicon tetrachloride with metallated 1-alkynes, including lithium [1](a), [4], sodium [1a], and potassium [1a] alkynylides or alkynyl magnesium halides [5] (Scheme 1). Such an approach restricts the diversity of functional groups on the 1-alkyne due to the high reactivity of organometallic reagents.
Tetraalkynylsilanes have also been prepared via the reaction of Iotsich reagents with a hexacoordinated anionic silicon complex obtained from silica gel or tetramethoxysilane and pyrocatechol [6] (Scheme 2).
The numerous applications of alkynylsilanes in organic synthesis have resulted in increased interest in the development of different methods for Si-Csp bond formation. Halosilanes, being commercially available, are the most convenient reagents for the silylation of 1-alkynes [7]. Additionally, methods for the silylation of 1-alkynes with amino silanes [8], silyl triflates [9], and the Ruppert reagent [10], as well as various dehydrocondensation reactions [11] are known. A method for the preparation of alkynylsilanes via the catalytic decarboxylation of silyl alkynoates was recently developed [12]. However, none of these methods have been applied to the preparation of alkynylsilanes containing four alkynyl moieties on the silicon atom. At the same time, tetraalkynylsilanes are of potential interest as alkynylating reagents, offering an alternative to tetraalkynyltin [13].
Section snippets
Results and discussion
In order to develop a preparative-scale procedure for the synthesis of tetraalkynylsilanes, we first studied the model reaction of silicon tetrachloride with phenylacetylene in the presence of different amines and Lewis acids (Table 1). The reaction was initially carried out in the presence of 120 mol% phenylacetylene which provided the highest conversion of SiCl4, since the formation of partial alkynylation products can complicate the isolation of pure tetraalkynylsilanes. The use of zinc
Conclusion
An efficient method was developed to synthesize tetraalkynylsilanes from 1-alkynes and silicon tetrachloride in the presence of 125 mol% Zn(OTf)2/Hünig’s base, which complements earlier developed methods for the synthesis of tetraalkynylides of other group 14 elements from germanium [16] and tin tetrahalides [17].
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper
Acknowledgements
This publication was financially supported by the Russian Ministry of Education and Science (project no. FZEN-2020-0022). The reported study was funded by the RFBR and Krasnodar region according to the research project № 19-43-230009 and accomplished with the use of scientific equipment of the Collective Employment Centre «Ecoanalytical Centre», Kuban State University.
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