158
O. Minge et al. · Triethoxysilane, Tetraethoxysilane and Hexaethoxydisiloxane
Silylation of organolithium compounds with hexaethoxy-
disiloxane (illustrated for 1,8-dilithionaphthalene)
196.9 Hz, 3J = 7.8 Hz); MS (EI, 70 eV): m/z = 150 (M+),
135 (M+-CH3), 120 (M+-SiH3), 105 (M+-SiH3-CH3);
C8H12Si (136.27):: calcd. C 70.51, H 8.88; found C 70.00,
H 8.98.
A solution of 0.73 g of the bis-tmeda adduct of 1,8-
dilithionaphthalene (1.96 mmol) in 10 ml of diethylether is
added rapidly to 1.0 g of hexaethoxydisiloxane (2.9 mmol,
1.5 eq.) at 0 ◦C.
3,4-Dimethyl-1-silyl-benzene (2): B. p.: 34 ◦C (1 Torr); 1H
NMR (270 MHz, C6D61): δ = 1.43 (s, 3H, CH3), 2.02 (s,
3H, CH3), 4.27 (d, 3H, J = 198.3 Hz, SiH3), 6.93 (d, 1H,
3J = 7.7 Hz, Ar), 7.21 (d, 1H, 3J = 7.7 Hz, Ar), 7.99 (s,
1H, Ar-2); 13C NMR (67.8 MHz, C6D6): δ = 14.40 (CH3),
32.14 (CH3), 124.8, 129.8, 133.9, 137.4, 142.7 (Ar); 29Si
NMR (coupled DEPT, 53.7 MHz, C6D6): δ = −60.16 (qdd
(qt)), 1J = 198.3 Hz, 3J = 6.7 Hz); IR (KBr): ν = 2146,
ν(Si-H), 726, ν(Si-C); MS (EI, 70 eV): m/z = 136 (M+),
121 (M+-CH3), 106 (M+-2 CH3), 91 (M+-SiH3-CH3);
C8H12Si (136.27): calcd. C 70.51, H 8.88; found C 71.50,
H 9.78.
After stirring for 2 h at r. t. the solvent is removed under
reduced pressure. The residue is taken up in 20 ml of hex-
ane, the solution filtered several times to remove precipitated
lithium salts, and the solvent evaporated. The residue is redis-
solved in ◦diethylether (10 ml) and the solution added drop-
wise at 0 C to a suspension of 0.12 g of LAH (3 mmol) in
10 ml of diethylether. The slurry is stirred at r. t. for another
10 h. The solvent is removed in vacuo, the residue taken up
in hexane (2×20 ml) and the solution filtered from insoluble
salts. Upon evaporation of the solvent, 1,8-disilylnaphthalene
remains as a colourless solid. Its physical constants
and spectroscopic data are in agreement with published
data [11a].
2,3-Dimethyl-1-silyl-benzene (3): B.p.: 30 ◦C (1 Torr); 1H
NMR (270 MHz, C6D61): δ = 1.43 (s, 3H, CH3), 2.13 (s,
3H, CH3), 4.28 (d, 3H, J = 198.6 Hz, SiH3), 6.98 (d, 1H,
3J = 7.0 Hz, Ar), 7.21 (d, 1H, 3J = 5.5 Hz, Ar), 8.58 (m,
1H, Ar); 13C NMR (67.8 MHz, C6D6): δ = 23.18 (CH3),
27.38 (CH3), 128.2, 132.6, 135.4, 136.2, 138.5 (Ar-C);
29Si NMR (coupled DEPT, 53.7 MHz, C6D6): δ = −62.28
(qd, 1J = 198.6 Hz, 3J = 6.7 Hz); IR (KBr): ν = 2147,
ν(Si-H), 726, ν(Si-C); MS (EI, 70 eV): m/z = 136 (M+),
121 (M+-CH3), 106 (M+-2 CH3), 91 (M+-SiH3-CH3);
C8H12Si (136.27): calcd. C 70.51, H 8.88; found C 70.50,
H 9.23.
Silylation of polymethylbromobenzenes with tetraethoxy-
silane (exemplified for the bromo-xylenes 1 – 5
in Scheme 1)
10
g of the corresponding bromo-dimethylbenzene
(54 mmol) is dissolved in 40 ml of THF, and about 10%
of this solution is added to a slurry of magnesium turnings
(1.7 g, 70 mmol, 1.3 eq.) and tetraethoxysilane (0.16 mol,
34 g, 3 eq.) in 50 ml of THF containing a small crystal of
iodine. The suspension is heated to reflux and the remainder
of the bromo-xylene solution is added via a dropping fun-
nel at such a rate, that the reaction mixture continues to re-
flux. Subsequently the mixture is kept at reflux for another
2 h. THF is then removed in vacuo at r. t. and the remaining
white solid taken up in pentane (2×50 ml) and filtered. Pen-
tane is evaporated to leave an oily, yellow liquid. Fractional
distillation yields the triethoxysilylated compound as a clear
colourless oil.
◦
2,4-Dimethyl-1-silyl-benzene (4): B. p.: 38 C (1 Torr);
1H NMR (400 MHz, C6D6): δ = 2.09 (s, 3H, CH3), 2.23
(s, 3H, CH3), 4.27 (d, 3H, 1J = 197.8 Hz, SiH3), 6.78 (s,
1H, Ar-3), 6.81 (d, 1H, 3J = 7.5 Hz, Ar), 7.39 (d, 1H, 3J =
7.5 Hz, Ar); 13C NMR (100 MHz, C6D6): δ = 14.30 (CH3),
23.06 (CH3), 126.5, 130.6, 137.5, 140.6, 144.4 (Ar-C);
29Si NMR (coupled DEPT, 79.4 MHz, C6D6): δ = −63.93
(qd, 1J = 197.8 Hz, 3J = 6.8 Hz); IR (KBr): ν = 2150,
ν(Si-H), 727, ν(Si-C); MS (EI, 70 eV): m/z = 136 (M+),
121 (M+-CH3), 106 (M+-2CH3), 91 (M+-SiH3-CH3);
C8H12Si (136.27): calcd. C 70.51, H 8.88; found C 69.30,
H 9.10.
This product is then dissolved in 30 ml of diethylether and
added to a slurry of LAH (1.5 eq.) in 50 ml of diethylether
with cooling to 0 ◦C. After stirring for◦about 10 h at r. t. the
solvent is removed in a vacuum at 0 C and the residue is
taken up in 100 ml of pentane and filtered from any pre-
cipitated salts. The solvent of the usually cloudy solution is
evaporated and the residue purified by short-path distillation.
Yield: 60 to 85%.
2,6-Dimethyl-1-silyl-benzene (5): B.p.: 37 ◦C (1 Torr); 1H
NMR (400 MHz, C6D6): δ = 2.27 (s, 6H, 2 CH3), 4.20 (d,
3H, 1J = 199.4 Hz, SiH3), 6.85 (d, 2H, 3J = 7.7 Hz, Ar-
3/5), 7.04 (t, 1H, 3J = 7.7 Hz, Ar-4); 13C NMR (100 MHz,
C6D6): δ = 21.32 (2 CH3), 124.3, 127.5, 130.1, 145.0 (Ar);
29Si NMR (coupled DEPT, 79.4 MHz, C6D6): δ = −77.47
(q, 1J = 199.4 Hz); IR (KBr): ν = 2146, ν(Si-H), 724, ν(Si-
C); MS (EI, 70 eV): m/z = 136 (M+), 121 (M+-CH3), 106
(M+-2 CH3), 91 (M+-SiH3-CH3); C8H12Si (136.27): calcd.
C 70.51, H 8.88; found C 69.44, H 9.00.
◦
2,5-Dimethyl-1-silyl-benzene (1): B.p.: 32 C (1 Torr);
1H NMR (400 MHz, C6D6): δ = 1.55 (s, 3H, CH3), 2.17
(s, 3H, CH3), 4.23 (d, 3H, 1J = 199.6 Hz, SiH3), 6.94 (d,
1H, Ar-3, 3J = 6.8 Hz), 7.07 (d, 1H, Ar-4, 3J = 6.8 Hz),
7.20 (s, 1H, Ar-6); 13C NMR (67.8 MHz, C6D6): δ =
◦
1-Silyl-2,4,5-trimethyl-benzene (6): B.p.: 44 C (1 Torr);
20.34, 21.81 (2 CH3), 130.8, 138.0, 141.1 (C-H); 29Si NMR 1H NMR (270 MHz, C6D6): δ = 1.41 (s, 3H, CH3), 2.00 (s,
(coupled DEPT, 53.6 MHz, C6D6): δ = −63.32 (qd, 1J = 3H, CH3), 2.25 (s, 3H, CH3), 4.30 (d, 3H, 1J = 196.0 Hz,
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