Russian Journal of General Chemistry, Vol. 75, No. 5, 2005, pp. 827 828. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005,
pp. 875 876.
Original Russian Text Copyright
2005 by Gostevskii, Voronkov, Rakhlin, Mirskov.
LETTERS
TO THE EDITOR
Reactions of 1,1-Dimethyl-2,2-bis(trimethylsilyl)hydrazine
with Alcohols and Ketones:
A New Route to Trimethylsilyl Enol Ethers
B. A. Gostevskii, M. G. Voronkov, V. I. Rakhlin, and R. G. Mirskov
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, Russia
Received October 26, 2004
Proceeding with studies on the reactivity of
organosilicon derivatives of 1,1-dimethylhydrazine
[1, 2], we examined the reactions of 1,1-bis(trimethyl-
silyl)-2,2-dimethylhydrazine I with alcohols and
enolizing ketones. The reaction of I with excess
methanol leads to the cleavage of both N Si bonds
according to the following scheme:
hydrazine I in 5 ml of absolute methanol was placed
in an evacuated glass ampule and heated for 5 h at
95 C. A GLC analysis using references showed that
the reaction mixture contained dimethylhydrazine,
trimethylmethoxysilane, and an excess of methanol,
with compound I being completely consumed.
Reaction of 1,1-bis(trimethylsilyl)-2,2-dimethyl-
hydrazine I with acetophenone. A solution of 4.08 g
of I and 2.4 g of acetophenone in 20 ml of absolute
THF was stirred in an evacuated glass ampule with a
magnetic stirrer for 20 h at 90 C. Distillation of the
reaction mixture in a vacuum gave the starting com-
pounds in quantitative yields. Similar results were
obtained on adding 1.6 g of CsF or 0.5 g of KCN/18-
crown-6 complex to the reaction mixture.
Me2NN(SiMe3)2 + 2HOMe
Me2NNH2 + 2Me3SiOMe.
Hydrazine I did not react with acetophenone in
THF and methylene chloride in a sealed ampule at
90 C during a period of 20 h even in the presence of
the catalytic amounts of cesium fluoride or KCN/18-
crown-6 complex. However, on adding an equimolar
amount of methyl iodide into the above mixture,
1-phenyl-1-(trimethylsiloxy)ethene II readily formed
in 98% yield. The second reaction product was the
crystalline precipitate of 1,1,1-trimethyl-2-trimethyl-
silylhydrazinium iodide. Phenyl isopropyl ketone and
methyl tert-butyl ketone react with I similarly in the
presence of methyl iodide to form the corresponding
trimethylsilyl enol ethers III and IV in 72% and 86%
yields, respectively.
Reaction of I with acetophenone and methyl
iodide. A solution of 6.0 g of I, 3.5 g of acetophenone,
and 10 ml of methyl iodide in 20 ml of dry methylene
chloride was heated for 20 h at 90 C in an ampule.
The precipitate was filtered off and washed with two
10-ml portions of methylene chloride. Distillation
of the combined filtrates gave 5.5 g (98%) of
Ph(Me3SiO)CH=CH2, bp 75 C (5 mm Hg), nD20
1.5040. Published data [3]: bp 53 54 C (1 mm Hg),
n2D0 1.5040.
Me2NN(SiMe3)2 + RCOCHR2 + MeI
R(Me3SiO)C=CR + [Me3NHSiMe3]+I ,
According to GCL data, the product is highly pure,
and its retention time agrees with that of the specially
prepared reference.
2
R = Ph, R = H (II), Me (III); R = t-Bu, R = H (IV).
The precipitate (slightly yellowish crystals) is
The easiness of the process and the high yields of
trimethylsilyl enol ethers allowed this reaction to be
recommended as a preparative route to these com-
pounds. It is interesting that, in the absence of ketones,
hydrazine I does not react with methyl iodide even at
prolonged heating.
1,1,1-trimethyl-2-trimethylsilylhydrazinium
iodide
[Me3NNHSiMe3]+I , yield 6.4 g (81%), mp 158 C.
1H NMR spectrum (CD3CN, TMS), , ppm: 0.313 s
(9H, SiMe3); 3.50 s [9H, N+Me3]; 5.86 s (1H, NH).
29Si NMR spectrum (CD3CN, TMS), Si, ppm: 8.86.
Reaction of 1,1-dimethyl-2,2-bis(trimethylsilyl)-
hydrazine I with methanol. A solution of 4.08 g of
Reaction of I with phenyl isopropyl ketone and
methyl iodide. A solution of 3.0 g of I, 2.02 g of
1070-3632/05/7505-0827 2005 Pleiades Publishing, Inc.