Novel reactions to form an Si-O-Ge group

Full text of DOI:10.1007/s10593-006-0080-8

Chemistry of Heterocyclic Compounds, Vol. 42, No. 2, 2006
LETTERS TO THE EDITOR
NOVEL REACTIONS TO FORM AN Si–O–Ge GROUP
L. Ignatovich, V. Muravenko, S. Grinberga, and E. Lukevics
Keywords: alkoxygermanes, alkoxysilanes, hydrogermanes, hydrosilanes, siloxygermanes,
tris(pentafluorophenyl)borane.
In study of O-silylation of hydroxyl-containing compounds [1-3] and hydrosilylation of the carbonyl
group [3-6] in the presence of tris(pentafluorophenyl)borane [7], further reduction of the initially formed
alkoxysilanes by excess hydrosilane has been observed:
(1)
Si
H
Si
OR
Si
RH
+
O
Si
+
This reaction was suggested for preparative reduction of the carbonyl group to a methylene [8] or methyl
[3, 8, 9] group without preliminary separation of the intermediate alkoxysilanes.
Another group of researchers who were interested in organosilicon reaction products (1) suggested using
it for synthesis of new siloxanes and polysiloxanes [10, 11].
In a study of the mechanism of the reaction of hydrosilanes with alkoxysilanes in the presence of
B(C6F5)3, the following competing reaction was found involving exchange of substituents on the silicon atoms,
with formation of a new hydrosilane and a new alkoxysilane, which ultimately leads to formation of two
symmetric and one nonsymmetric disiloxane [12].
H
Si1
+
RO Si1
Si OR
Si
H
(2)
+
Alkylhydrosilanes [1-3, 5, 6, 9, 10, 12], arylhydrosilanes [4-6], alkylarylhydrosilanes [6, 10-12], and
hydrosiloxanes [8, 10] have been used in reactions (1) and (2).
We have shown that hetarylhydrosilanes, such as methyl(2-furyl)(2-thienyl)silane, also react with
alkoxysilanes in the presence of B(C6F5)3. Its reaction with methyltriethoxysilane occurs with stepwise
substitution of one and two ethoxy groups (Table 1, runs 6 and 7). With excess hydrosilane (run 8), we observe
formation of 1,3-di(2-furyl)-1,3-dimethyl-1,3-di(2-thienyl)disiloxane (via exchange according to reaction (2)).
Condensation of triethylsilane with 1-ethoxysilatrane (run 10), containing a five-coordinate silicon atom
in the ring, occurred with significantly more difficulty.
For the first time, we have established that alkoxygermanes (3) and hydrogermanes (4) enter into a
similar reaction, with formation of an Si–O–Ge group.
__________________________________________________________________________________________
Latvian Institute of Organic Synthesis, Riga LV-1006; e-mail: ign@osi.lv. Translated from Khimiya
Geterotsiklicheskikh Soedinenii, No. 2, pp. 299-302, February, 2006. Original article submitted January 20,
2006.
268
0009-3122/06/4202-0268©2006 Springer Science+Business Media, Inc.

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H
Si
Ge
Si
O
O
Ge OR
Si OR
RH
RH
Si
(3)
(4)
+
+
+
+
Ge
H
Ge
In this case, hydrogermanes proved to be less reactive than hydrosilanes. Thus triethylgermane reacted
with triethylethoxysilane more slowly than triethylsilane (runs 1 and 2), and only one ethoxy group was
substituted in methyltriethoxysilane (runs 4 and 5) under conditions where triethylsilane substituted two and
three ethoxy groups (run 3). Only one ethoxy group was substituted by the triethylsiloxy group in
2-thienyltriethoxygermane, when treated with triethylsilane (run 9).
The reactions were carried out in 8 ml toluene under a dry argon atmosphere with 1.4 mmol alkoxysilane
and 0.07 mmol B(C6F5)3; the products were analyzed by chromatography/mass spectrometry on an HP 6890
GC/MS spectrometer (70 eV) equipped with an HP-5 capillary column (30.0 m × 250 µm × 0.25 µm).
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