Synthesis of phenylsilane doubly tritium-labeled in the benzene ring [8]

Full text of DOI:10.1023/B:RUGC.0000042444.01812.0d

Russian Journal of General Chemistry, Vol. 74, No. 6, 2004, pp. 973 974. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 6, 2004,
pp. 1053 1054.
Original Russian Text Copyright
2004 by Shishigin, Avrorin, Kochina, Sinotova.
LETTERS
TO THE EDITOR
Synthesis of Phenylsilane Doubly Tritium-labeled
in the Benzene Ring
E. A. Shishigin, V. V. Avrorin, T. A. Kochina, and E. N. Sinotova
Grebenshchikov Institute of Silicate Chemistry, Russian Academy of Sciences, St. Petersburg, Russia
St. Petersburg State University, St. Petersburg, Russia
Received November 4, 2003
Over many years we have performed a research
into ion-molecular reactions of carbenium and sili-
cenium ions [1 3] generated by the nuclear chemical
technique [4]. This technique has some unique
features, one of which is the possibility of generating
cations with a strictly fixed charge localization
defined exclusively by the position of tritium in the
source of the cations. To generate free cations by the
nuclear chemical technique, one should first syn-
thesize to a source of these cations. We have syn-
thesized phenylsilane tritium-labeled in the ortho and
para positions of the benzene ring to use it as a source
of silyl-substituted phenyl cations. The synthesis of
tritium-labeled phenylsilane I was based on catalytic
exchange of tritium for halogen in (2,4-dibromo-
phenyl)trimethoxysilane (II) followed by reduction of
methoxy derivative III with lithium aluminum
hydride [5]. The use of trimethoxy derivative II
instead of (2,4-dibromophenyl)silane as the starting
material was motivated by the necessity to avoid
replacement of the Si H hydrogen by tritium as a
result of the possible catalytic isotope exchange.
(2,4-Dibromophenyl)trimethoxysilane (II) was
prepared by the catalytic bromination of phenyltri-
chlorosilane (IV) with molecular bromine by the pro-
cedure [6]. Further (2,4-dibromophenyl)ttichlorosilane
(V) was subjected to methanolysis by a modified
procedure [7].
MeOH, Et3N
Br2, Fe
PhSiCl3
IV
2,4-Br2C6H3SiCl3
2,4-Br2C6H3Si(OMe)3,
C6H6
V
II
2T2, Pd/BaSO4, Et3N
Et2O, TBr
II
2,4-T2C6H3Si(OMe)3,
III
LiAlH4
III
2,4-T2C6H3SiH3.
Et2O
I
The structure and purity of the resulting com-
pounds were determined by means of NMR and IR
spectroscopy and GLC.
liquid nitrogen, evaculated, filled with molecular
tritium to 200 mm Hg, and sealed. The reaction was
performed at room temperature under vigorous stirring.
Reaction time 2 h. Unreacted tritium was removed in
a vacuum. The residual solution of labeled phenyltri-
methoxysilane III was transferred into a tube contain-
ing 0.2 ml of ethereal solution of 0.3 mg of lithium
aluminum hydride and 0.06 mg of aluminum bromide.
The reaction was complete within a few minutes, after
which the tube was evacuated, the ether was removed
2,4-Ditritiophenylsilane (I). A 2-ml ampule was
charged with 5 10 mg of catalyst (5% Pd on barium
sulfate) that was activated at 160 C for 1 h in a
3
vacuum (10 mm). Ethereal solution (200 l) of
1.4 l of dibromo derivative II and 2.2 l of triethyal-
amine was then added. The ampule was cooled with
1070-3632/04/7406-0973 2004 MAIK Nauka/Interperiodica

974
SHISHIGIN et al.
at 70 C, and labeled phenylsilane I was collected
into a receiver cooled with liquid nitrogen. Phenyl-
silane I was diluted with 1 ml of hexane, and the
concentration of the solution was determined by GLC.
The yield of compound I was 20 25% (per gaseous
tritium). The activity of an aliquot was measured in a
fluid-scintillation counter and quantified by the
internal calibration technique. The calculated specific
activity of the sample was 50 Ci/mmol, which cor-
responds to a 1.8 label multiplicity in the benzene ring.
REFERENCES
1. Kochina, T.A., Vrazhnov, D.V., Sinotova, E.N., Kat-
sap, M.Yu., and Shchegolev, B.F., Zh. Obshch. Khim.,
2001, vol. 71, no. 10, p. 1644.
2. Kochina, T.A., Shchukin, E.V., Nefedov, V.D., and Si-
notova, E.N., Zh. Obshch. Khim., 2001, vol. 70, no. 6,
p. 949.
3. Kochina, T.A., Vrazhnov, D.V., Sinotova, E.N., and
Shishigin, E.A., Zh. Obshch. Khim., 2004, vol. 74,
no. 2, p. 219.
The concentration of phenylsilane I was deter-
mined by GLC on a Tsvet-500 chromatograph (ther-
mal conductivity detector, column 2000 2 mm,
packing 5% Silicone SE-30 on Inerton-AW, carrier
gas helium). Activity measurements were performed
on a Beta-2 fluid analyzer (ZhS-8 scintillator), internal
reference labeled benzene.
4. Nefedov, V.D., Kochina, T.A., and Sinotova, E.N., Usp.
Khim., 1986, vol. 55, no. 5, p. 749.
5. Westermark, H., Acta Chem. Scand., 1954, vol. 8,
no. 10, p. 1830.
ACKNOWLEDGMENTS
6. Yakubovich, A.Ya. and Motsarev, G.V., Zh. Obshch.
Khim., 1953, vol. 23, no. 3, p. 412.
The work was financially supported by the Mi-
nistry of Education of the Russian Federation (project
no. A03-2.11-218).
7. Andrianov, K.A. and Gornets, L.V., Dokl. Akad. Nauk
SSSR, 1955, vol. 101, no. 2, p. 259.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 6 2004