10.1002/anie.201705942
Angewandte Chemie International Edition
COMMUNICATION
groups has been achieved using this reaction. This approach is
a novel synthetic strategy of alkoxysiloxane oligomer using
designed precursors for siloxane-based
In conclusion, the leaving group ability of TMS groups in
oligosiloxanes was confirmed by reacting several oligosiloxanes
possessing TMS groups with alkoxychlorosilane in the presence
of BiCl3 as catalyst. The TMS groups of oligosiloxanes are
substituted with alkoxysilyl groups, and alkoxysiloxane oligomers
were
successfully
synthesized.
Trimethylsilyl-terminated
oligosiloxanes can be synthesized from natural and synthetic
silicates, and their siloxane structures are rich in diversity (linear,
branched, cyclic, and cubic). The expansion of this reaction’s
substrate scope by future studies will lead to a novel fruitful
synthetic method for alkoxysiloxane oligomers. The present
work demonstrates that the concept of protecting groups in
synthetic organic chemistry is applicable to siloxane-based
molecules. Further studies on the viability of this reaction will
contribute to a precise synthetic chemistry of siloxane-based
molecules.
Acknowledgements
We thank Dr. T. Shibue and Mr. N. Sugimura (Materials
Characterization Central Lab., Waseda University) for their help
with NMR and MS measurements. This work was supported in
part by JSPS Kakenhi (Grants-in-Aid for Scientific Research, B,
No. 15H03879).
Figure 1. 29Si NMR spectrum of the QM3Tvinyl/(MeO)2MeSiCl/BiCl3 reaction
system.
Keywords: Lewis acid • Nucleophilic substitution • Siloxane
oligomer • Trimethylsilyl group
materials.
†
Symbols Qn, Tn, Dn, and Mn denote the bonding state of Si atoms; Qn:
Si(OSi)n(OH, OR, or O–)4–n (n = 0, 1, 2, 3, or 4), Tn: R’Si(OSi)n(OH, OR, or O–
The substitution reaction of TMS groups is similar to the
alkoxysilylation of tert-butoxysilane with alkoxychlorosilane.[5d-f]
Leaving groups are substituted with alkoxysilyl groups in both
reactions. The difference of conversion in these two reactions
was investigated by reacting (MeO)2MeSiCl with QM4 or
Si(OtBu)4 under the same conditions (at room temperature for a
)
3–n (n = 0, 1, 2, or 3), Dn: R’2Si(OSi)n(OH, OR, or O–)2–n, (n = 0, 1, or 2) and Mn:
R’3Si(OSi)n(OH, OR, or O–)1–n (n = 0 or 1). In addition, the superscripts of
these symbols, such as TMe and TPh, denote the functional groups linked to the
Si atoms (R’) in this paper.
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day). The H, 13C, and 29Si NMR spectra show that all the Bu
groups are substituted with dimethoxy(methyl)silyl groups (Figs.
S33–S35). On the other hand, TMS groups partly remained after
the substitution reaction as mentioned above. This difference is
caused by the existence of the reverse reaction. As already
mentioned, the substitution of TMS groups progresses reversibly.
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