Russian Journal of General Chemistry, Vol. 71, No. 2, 2001, p. 316. Translated from Zhurnal Obshchei Khimii, Vol. 71, No. 2, 2001, p. 346.
Original Russian Text Copyright
2001 by Boyarkina, Mirskov, Voronkov, Rakhlin.
LETTERS
TO THE EDITOR
Unusual Desilanolysis
of 1,1-Dimethyl-1-(trimethylsiloxy)-3-phenylpropyne
E. V. Boyarkina, R. G. Mirskov, M. G. Voronkov, and V. I. Rakhlin
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
Received April 26, 2000
Proceeding with our studies on homolytic addition
to group 14 unsaturated derivatives [1, 2] we tried to
effect a photoinduced reaction of polyhaloalkanes
fluoroiodopropane in a sealed ampule was subjected
to UV irradiation for 50 h. Distillation of the reaction
mixture gave the starting heptafluoroiodopropane
(almost quantitative recovery) and 18.3 g (78%) of
2-methyl-4-phenylbut-1-en-3-yne (IV). bp 88 C
with trimethylsilyl ethers of phenylethynylcarbinols
1
of the general formula Me SiORR CC CPh, where
3
1
1
1
20
R = R = H (I); R = H, R = Me (II); and R = R =
Me (III). On UV irradiation of equimolar mixtures of
bromotrichloromethane or heptafluoroiodopropane
with compounds I or II we observed no reaction
within 50 h. This is evidently explained by steric
shielding of the triple bond, preventing attack of the
polyhaloalkyl radical. It was unexpectedly found that
irradiation of a mixture of heptafluoroiodopropane or
trifluoroiodomethane with ether III results in cleavage
of trimethylsilanol to give 2-methyl-4-phenylbut-1-
en-3-yne (IV). At the same time, the starting polyhalo-
alkane remains practically unchanged.
(3 mm), nD 1.5742 {published data [5]: bp 87 88 C
20
1
(
7 mm), nD 1.5750}. H NMR spectrum (CDCl ), ,
3
ppm: 7.29 m (5H, C H ); 5.36 d.q (1H, cis-HC=);
6
5
5
.26 d.q (1H, trans-HC=); 1.96 d.d [3H, CH ,
3
cis
trans
J(CH C=CH) 1.0 Hz,
J(CH C=CH) 1.6 Hz).
3
3
Reaction of ether III with iodotrimethylsilane.
A mixture of III and several drops of iodotrimethyl-
silane was placed in a two-necked flask equipped with
a reflux condenser with a calcium chloride tube and a
mechanical stirrer. After 2-h stirring, according to
GLC data, the starting compound almost completely
converted to 2-methyl-4-phenylbut-1-en-3-yne (IV).
The product was isolated by vacuum distillation in
Me SiOCMe C CPh + R I
3
2
F
8
9% yield.
CH =C(CH ) C CC H + Me SiOSiMe + H O.
2
3
6
5
3
3
2
1
The H NMR spectrum was recorded on a Bruker
This reaction is similar to the classical dehydra- DPX-400 spectrometer in CDCl3 against internal
tion of tertiary acetylenic alcohols under the action of
sulfuric acid, discovered by Favorskii [3, 4].
TMS. Gas chromatography was carried out on a Tsvet-
500 chromatograph, detector katharometer, glass
column (3000 4 mm), packing 10% of PMS-1000
on InertonSuper (0.120 0.150 mm).
We propose that on UV irradiation of a mixture of
the starting compounds, a small amount of iodotri-
methylsilane is formed, which induces the above-
mentioned reactions. This proposal is confirmed by
the fact that in the presence of catalytic amounts of
iodotrimethylisilane compound III converts to IV
within several hours at room temperature.
REFERENCES
1
2
3
4
. Voronkov, M.G., Rakhlin, V.I., and Mirskov, R.G.,
Adv. Organomet. Chem., 1985, pp. 196 216.
. Rakhlin, V.I., Mirskov, R.G., and Voronkov, M.G., Zh.
Org. Khim., 1996, vol. 32, no. 6, pp. 907 916.
. Favorskii, A.E., Zh. Russk. Khim. Obshch., 1906,
vol. 37, p. 643.
. Sbornik izbrannykh trudov akademika A.E.Favorskogo
(Collection of Selected Works of the Academician
A. E. Favorskii), Leningrad: Otd. Nauch.-Tekh. Inf.,
Me SiOCMe C CPh + Me SiI
3
2
3
Me SiOSiMe + ICMe C CPh,
3
3
2
ICMe C CPh
CH =CMeC CPh + HI,
2
2
Me SiOSiMe + HI
Me SiOH + Me SiI,
3
3
3
3
1
934, p. 151.
2
Me SiOH
Me SiOSiMe + H O.
3 3 2
3
5
. Attenburrow, I., Cameron, A.E.B., Chapman, I.H.,
Evans, R.M., Hems, B.H., Johnson, A.B.A., and Wal-
ker, T., J. Chem. Soc., 1952, p. 1094.
Reaction of ether III with heptafluoroiodopro-
pane. A mixture of 23.2 g of III and 26.9 g of hepta-
1
070-3632/01/7102-0316$25.00 2001 MAIK Nauka/Interperiodica