Unusual course of diazolees silylation and N-siloxycarbonylation

Article abstract of DOI:10.1134/S1070363211070140

The N-siloxycarbonylation and transamination reactions were studied by an example of diazoles. We found that because of insufficient nucleophilicity of the nitrogen atoms in the first case only the sililylation process occurs, in the second case the low-boiling amine is replaced by the higher boiling one and the process is completed by the formation of O-silyluretans. Pleiades Publishing, Ltd., 2011.

Full text of DOI:10.1134/S1070363211070140

ISSN 1070-3632, Russian Journal of General Chemistry, 2011, Vol. 81, No. 7, pp. 1493–1495. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © A.D. Kirilin, L.O. Belova, M.V. Pletneva, V.M. Panfilova, P.A. Storozhenko, V.D. Sheludyakov, 2011, published in Zhurnal
Obshchei Khimii, 2011, Vol. 81, No. 7, pp. 1145–1147.
Unusual Course of Diazolees Silylation
and N-Siloxycarbonylation
A. D. Kirilin, L. O. Belova, M. V. Pletneva,
V. M. Panfilova, P. A. Storozhenko, and V. D. Sheludyakov
Lomonosov Moscow State Academy of Fine Chemical Technology, pr. Vernadskogo 86, Moscow, 119571 Russia
e-mail: kirilinada@rambler.ru
Received June 22, 2010
Abstract—The N-siloxycarbonylation and transamination reactions were studied by an example of diazoles.
We found that because of insufficient nucleophilicity of the nitrogen atoms in the first case only the sililylation
process occurs, in the second case the low-boiling amine is replaced by the higher boiling one and the process
is completed by the formation of O-silyluretans.
DOI: 10.1134/S1070363211070140
Earlier it was shown [1–3] that the O-silyluretans
(I) can be obtained in the reactions of: (a) carbo-
xylation, (b) N-siloxycarbonylation, and (c) trans-
amination.
(a)
HN(SiMe3)2
CO2
RNHSiMe3
O
(b)
(c)
HN(SiMe3)2/CO2
RNHCOSiMe3
RNH2
I
Et2NC(O)OSiMe3
Synthesized by these routes compounds I are stable
and do not decompose at heating up to 70–80°C. The
analogous compounds of the Et2NC(O)OSiMe3 type
completely substituted at the nitrogen atom are stable
up to 108–113°C [4].
Only in the case of diazoles, which are formal
analogs of the secondary amines, the O-silyluretans II
by reactions (b) and (c), converting into the products of
silylation IV and V [5].
N
N
N
N
−CO2
N
N
N
H
(b), (c)
Me3SiO(O)C
Me3Si
II
IV
(1)
H
SiMe3
Me
N
C(O)OSiMe3
Me
N
N
N
N
−CO2
Me
Me
Me
Me
V
III
1493

1494
KIRILIN et al.
Since it is known that only thio analogs of O-
in the reaction (b) is not a consequence of elimination
of carbon dioxide. In this case the sililylation of dia-
zoles unexpectedly occurs faster than their N-siloxy-
carbonylation [reaction (2)]. The released ammonia
reacts with carbon dioxide to form ammonium carbamate,
which under the reaction conditions undergoes silyla-
tion resulting in the N,O-bis(trimethylsilyl)carbamate
VII by-product.
silyluretans are unstable substances [1], we decided to
study this process in detail. It turned out that the O-
silyluretans II and III do not violate the established
view of the thermal stability of these compounds. The
mistaken belief [reaction (1)] is caused by the incorrect
interpretation of the reaction results.
We found that the formation of products IV and V
N
N
N
N
Me3Si
H
HN(SiMe3)2/CO2
−NH3
IV
(2)
H
SiMe3
Me
N
N
N
N
O
Me
Me
Me
V
O
+HN(SiMe3)2
NH3 + CO2
H2NCONH4
Me3SiOCNHSiMe3
VII
VI
It is known that the reaction of N-siloxycarbonyla-
tion [2] proceeds through intermediate forma-tion of
carbamic acid (VIII), whose proton is released from
the carboxy group incomparably stronger than from the
NH group. This leads to acceleration of the formation of
O-silyluretanes and simultaneously reduces the impact of
electronic and steric factors. This enables the formation
of virtually any carbamates, even from aromatic amines.
HN(SiMe3)2
CO2
O
PhNHSiMe3
PhNH2
PhNHCOSiMe3
O
CO2
HN(SiMe3)2
[PhNHCOH]
VIII
Therefore, obtaining the products of silylation
rather than N-siloxycarbonylation in the reaction 2
suggests that this is caused by insufficient nucleo-
philicity of the diazole nitrogen atoms attacked by the
electrophilic carbon atoms of the CO2 molecule.
Being, in turn, weak bases, the diazoles easily enter
into silylation with hexamethyldisilazane, displacing
ammonia which is a weaker base. The silylation
process is accelerated due to the formation of
ammonium carbamate VI, which catalyzes this
process.
by release of carbon dioxide, and ends in the formation
of O-silyluretans II, III, and IX.
In this case the nucleophilicity of the nitrogen
atoms does not affect the course of process, since a
transamination reaction of O-silyuretans proceeds
accompanied by the displacement of low-boiling
amine by a high-boiling one.
EXPERIMENTAL
The IR spectra were recorded on a Specord IR-75
1
instrument. The H NMR spectra were recorded on a
Bruker WP-300 spectrometer with the operating
frequency 300 MHz, solvent and internal reference
trichloromethane-d.
Note in particular that the use of imidazole, 3,5-
dimethyl- and 3(5)-methylpyrazoles in transamination
reaction is not accompanied, as previously stated [5],
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 81 No. 7 2011

UNUSUAL COURSE OF DIAZOLEES SILYLATION
1495
N
II
N
H
O
H
N
N
N
N
(c) −Et2NCOSiMe3
−Et2NH
III
Me
Me
Me
H
N
NC(O)OSiMe3
Me
IX
All starting compounds and solvents were carefully
purified and dried before use. Synthetic procedures and
sampling for analysis of all the substances were carried
out in the dry nitrogen atmosphere. The composition of
reaction mixtures and pure compounds was monitored
by GLC on a Shimadzu G-8 device (column 1500×3 mm
of stainless steel, stationary phase SE-30 on
Chromaton N-AW, carrier gas helium).
3,5-Dimethyl-1-(trimethylsilyl)-1H-pyrazole (V).
Through a mixture of 15 g of 3,5-dimethylpyrazole
and 16.23 g of hexamethyldisilazane was passed
carbon dioxide for 20 h at a temperature of 50–55°C.
By fractionation 19.14 g (85%) of compound V was
isolated, bp 77–78°C (10 mm Hg), nD20 1.4719 [5].
Trimethylsilyl-3(5)-methyl-1H-pyrazole-1-carbo-
xylate (IX). A mixture of 20 g of 3(5)-methylpyrazole
and 46.16 g of trimethylsilyl diethylcarbamate was
heated at a complete reflux to the end of diethylamine
release. By fractionation 44.47 g (92%) of compound
IX was isolated, bp 93–95°C (10 mm Hg), nD20 1.4552.
IR spectrum, ν, cm–1: 3120 (C=CH), 1690 (C=O),
Trimethylsilyl 1H-imidazole-1-carboxylate (II).
A mixture of 15 g of imidazole and 41.66 g of tri-
methylsilyl diethylcarbamate was heated at a complete
reflux to complete release of diethylamine. By frac-
tionation compound was isolated II, 36.88 g (91%), bp
100–101°C (2 mm Hg), nD20 1.4463. IR spectrum, ν,
1
1
cm–1: 3080 (C=CH), 1660 (C=O), 1520 (C=N). H
1520 (C=N). H NMR spectrum, δ, ppm: 0.41 s (9H,
SiCH3), 2.29 s (6H, CCH3), 6.01 s and 6.07 s (1H,
CH), 7.43 s and 7.45 s (1H, CH). Found, %: C 48.65;
H 7.23; N 14.41. C8H4N3O2Si. Calculated, %: C 48.46;
H 7.12; N 14.13.
NMR spectrum, δ, ppm: 0.37 s (9H, SiCH3), 6.95 s
(2H, NCH), 7.6 s (1H, NCHN). Found, %: C 45.32; H
6.37; N 15.34. C7H12N2O2Si. Calculated, %: C 45.63;
H 6.56; N 15.20.
Trimethylsilyl 3,5-dimethyl-1H-pyrazole-1-carbo-
xylate (III). A mixture of 15g of 3,5-dimethylpyrazole
and 29.56 g trimethylsilyl diethylcarbamate was heated
at a complete reflux to the end of diethylamine release.
By fractionation 30.81 g (93% ) of compound III was
isolated, bp 140–142°C (1 mm Hg), nD20 1.4483. IR
spectrum, ν, cm–1: 3180 (C=CH), 1690 (C=O), 1520
(C=N). 1H NMR spectrum, δ, ppm: 0.44 s (9H,
SiCH3), 2.23 s (6H, CCH3), 5.81 s (1H, CH). Found,
%: C 50.92; H 7.55; N 13.31. C9H16N2O2Si.
Calculated, %: C 50.91; H 7.60; N 13.19.
REFERENCES
1. Breederveld, H., Rec. Trav. Chim., 1962, vol. 81,
p. 276.
2. Sheludyakov, V.D., Kirilin, A.D., and Mironov, V.F.,
Zh. Obshch. Khim., 1975, vol. 45, no. 2, p. 479.
3. Sheludyakov, VD, Kirilin, A.D., and Mironov, V.F., Zh.
Obshch. Khim., 1977, vol. 47, no. 7, p. 1515.
4. Shmyreva, G.O., Shmakov, V.G., Golosova, R.M.,
Kostrukov, V.N., Sheludyakov, V.D., and Kirilin, A.D.,
Termodinamika organicheskikh soedinenii (Thermo-
dynamics of Organic Compounds), Gorkii: Gork. Gos.
Univ.. 1978, no. 7, p. 85.
1-Trimethylsilyl-1H-imidazole (IV). Through a
mixture of 15 g of imidazole and 19.20 g of hexa-
methyldisilazane was passed carbon dioxide for 20 h at
70°C. By fractionation 25.35 g (82%) of compound IV
was isolated, bp 92–93°C (10 mm Hg), nD20 1.4745 [5].
5. Sheludyakov, V.D., Kirilina, N.I., and Kirilin, A.D., Zh.
Obshch. Khim., 1976, vol. 50, no. 2, p. 472.
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