Chemical transformations of diazoles in the reactions of carboxylation, N-siloxycarbonylation, and transsilylation

Article abstract of DOI:10.1134/S1070363213070116

The behavior of 3,5-dimethylpyrazole, 3(5)-methylpyrazole, imidazole and their trimethyl-silyl derivatives in carboxylation, N-siloxycarbonylation, and transsilylation reactions was studied. A new Nsiloxycarbonylation reagent, diazole trimethylsilyl derivative-carbon dioxide, was found. This reagent makes it possible to obtain easily O-silylurethanes starting from primary, secondary amines and hydrazine derivatives, as well as to develop a convenient one pot synthesis method for trimethylsiloxycarbonyldiazoles.

Full text of DOI:10.1134/S1070363213070116

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 7, pp. 1365–1368. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © L.O. Belova, M.V. Pletnev, A.D. Kirilin, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 7, pp. 1113–1117.
Chemical Transformations of Diazoles in the Reactions
of Carboxylation, N-Siloxycarbonylation,
and Transsilylation
L. O. Belova, M. V. Pletnev, and A. D. Kirilin
Lomonosov Moscow State University of Fine Chemical Technology,
pr. Vernadskogo 86, Moscow, 119571 Russia
e-mail: lya17@mail.ru
Received July 9, 2012
Abstract—The behavior of 3,5-dimethylpyrazole, 3(5)-methylpyrazole, imidazole and their trimethyl-silyl
derivatives in carboxylation, N-siloxycarbonylation, and transsilylation reactions was studied. A new N-
siloxycarbonylation reagent, diazole trimethylsilyl derivative–carbon dioxide, was found. This reagent makes it
possible to obtain easily O-silylurethanes starting from primary, secondary amines and hydrazine derivatives,
as well as to develop a convenient one pot synthesis method for trimethylsiloxycarbonyldiazoles.
DOI: 10.1134/S1070363213070116
O
Previouslyit was shown that diazoles behaved un-
a
usually in N-siloxycarbonylation processes [1].
+
+
CO2
CO2
NCOSiMe3
I
N
N
N
This universal reaction did not yield O-
silylurethanes I: Always N-trimethylsilyl derivatives of
diazoles II were obtained as the end products.
SiMe3
+HN(SiMe3)2
O
+
HN(SiMe3)2
+
CO2
b
N
N
N
N
NCOH
N
O
H
H
+
NCOSiMe3
N
N
O
O
c
I
Et2NCOSiMe3
NCOSiMe3
N
N
N
_Et2NH
NSiMe3
I
H
II
silylating ability, allowed us discovering a new N-
Impossibility to obtain O-silylurethanes I by car-
boxylation (a) and N-siloxycarbonylation (b) reactions
was attributed to a low nucleophilicity of nitrogen
atoms of diazoles attacked with electrophilic carbon
atom of carbon dioxide.
siloxycarbonylating agent.
It was found that not only the known systems HN
(SiMe3)2/CO2 [3] and R3SiH/CO2 [4] have N-
siloxycarbonylating ability.
At the same time, these previously unavailable O-
silylurethanes I were obtained via transamination of
trimethylsilyl diethylcarbamate with diazoles (c) [2].
The system carbon dioxide–trimethylsilyl diazole
derivative was found to easily provide O-silylurethanes
from primary, secondary amines and hydrazine deri-
vatives. Most importantly, this approach reduces the
time of synthesis and increases the yield of the target
The inertness of N-trimethylsilyl-derived diazoles
in the carboxylation reaction (a), along with their high
1365

1366
BELOVA et al.
O
R1R2NH
+
+
CO2
R1R2NHCOSiMe3
+
N
N
N
N
SiMe3
N
H
Me
Me
=
N
N
Me
N
Me
N
N
N
N
N
N
a
c'
b
c
R1 = Et, Ph, Me2N; R2 = H, Et.
product (see the table).
method involves two successive reactions taking place
in one pot and excludes the need for intermediates isolation.
The first synthesis of O-silylurethanes I containing
diazole fragments via the transamination reactions using
trimethylsilyl diethylcarbamate and a discovery a new
N-siloxycarbonylating reagent (N-trimethylsilyl diazole
derivative–carbon dioxide) gave us an opportunity to
develop a new method for synthesis of compounds I. This
Since the trimethylsilyl derivatives of diazoles do
not absorb carbon dioxide (reaction a), in the first
stage the N-siloxycarbonylation reaction proceeds (d)
using the system carbon dioxide–trimethylsilyl diazole
derivative as the new N-siloxycarbonylating reagent to
O
d, 45_50оС
Et2NH
+
+
CO2
Et2NCOSiMe3
+
N
N
N
N
SiMe3
H
O
e, 85_90оС
_Et2NH
N N COSiMe3
Iа, Ib
afford trimethylsilyl diethylcarbamate and the
corresponding diazole.
the formation of trimethylsilyl-1H-imidazole-1-car-
boxylate Ia and trimethylsilyl-3,5-dimethyl-1H-pyra-
zole-1-carboxylate Ib in high yields.
The reaction temperature is 45–50°C, and the
reaction time is 6–8 h.
It should be noted that the proposed method excludes
the preliminary synthesis and subsequent isolation of tri-
methylsilyl diethylcarbamate by N-siloxycarbonyla-
tion of diethylamine using a mixture HN(SiMe3)2/CO2,
which reduces the reaction time almost two times.
The formation of trimethylsilyl diethylcarbamate
and diazole, the increase in the temperature to 85–90°
C and removing diethylamine from the reaction zone
favor the transamination process (e), which results in
Trimethylsilyl group of diazoles is transsilylated
Conditions of the synthesis of O-silylurethanes using a mixture of N-siloxycarbonylating mixture 3(5)-methyl-1-trimethyl-
silyl-1H-pyrazole–carbon dioxide
Yield, % with use
Temperature,
Time,
h
Yield,
%
О-Silylurethane
of a mixture
°С
HN(SiMe3)2–СО2
Et2NC(O)OSiMe3
50–55
60–65
55–60
1.5
2.5
2.5
97
93
95
87
41
75
PhNHC(O)OSiMe3
Me2NNHC(O)OSiMe3
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

CHEMICAL TRANSFORMATIONS OF DIAZOLES IN THE REACTIONS OF CARBOXYLATION
1367
+Me2SiCl2, kt
_Me3SiCl
Me
2
N
N
N
N
Si
N
N
+Me2Si(OMe)2, kt
Me
_Me3SiOMe
SiMe3
IIа, IIb
IIIа, IIIb
with organochloro- and organoalkoxysilanes, allowing
to obtain easily enough diazole-containing organo-
silicon products, like 1-[imidazol-1-yl(dimethyl)silyl]-
1H-imidazole IIIa and 1-[(3,5-dimethyl-1-pyrazol-1-
yl)dimethylsilyl]-3,5-dimethyl-1Н-pyrazole IIIb.
before use and thoroughly dried. Synthesis, isolation
and sampling for analysis were performed in dry
nitrogen atmosphere. Composition of the reaction
mixtures and purity of compounds were monitored by
GLC using a Shimadzu G-8 instrument (column
1500×3 mm, stainless steel, stationary phase SE-30 on
Chromaton N-AW, carrier gas helium).
At the same time, the use in this process of
methylphenyldimethoxy- and phenyltrichlorosilane results
in 1-[methoxy(methyl)phenylsilyl]-1H-imidazole IVa,
1-[methoxy(methyl)phenylsilyl]-3,5-dimethyl-1H-pyra-
zole IVb, 1-[dichloro(phenyl)silyl]-1H-imidazole Va
Trimethylsilyl-1H-imidazol-1-carboxylate (Ia).
Through a mixture of 15 g of diethylamine and 28.77 g
of 1-trimethylsilyl-1H-imidazole was bubbled carbon
dioxide within 6 h at a temperature of 45–50°C. The
mixture was then heated at 85–90°C for 5 h until the
evolution of diethylamine completed. The target
compound was isolated by fractionation. Yield 34.76 g
(92% relative to the starting diethylamine), bp 100–
102°C (2 mm Hg), nD20 1.4462 {published data [2]: bp
101–102°C (2 mm Hg), nD20 1.4463}.
Ph
Ph
kt
2
N
N
+ MeOH
N
Si
N
OMe
Si
OMe
Me
Me
SiMe3
IIа, IIb
IVа, IVb
Ph
Ph
Si
Trimethylsilyl-3,5-dimethyl-1H-pyrazole-1-car-
boxylate (Ib) was prepared similarly from 15 g of
diethylamine and 34.51 g of trimethylsilyl-1H-3,5-
dimethylpyrazole. Yield 40.93 g (94% relative to the
starting diethylamine), bp 140–141°C (1 mm Hg), nD20
1.4485 {published data [2]: bp 140–142°C (1 mm Hg),
nD20 1.4483}.
kt
3
N
N
N
N
+ Cl
Si
Cl
Cl
Cl
Cl
SiMe3
IIа, IIb
Vа, Vb
and 1-[dichloro(phenyl) silyl]-3,5-dimethyl-1H-pyra-
zole Vb, i. e., in the reaction course only one chlorine
atom or methoxy group is transsilylated.
1-[Imidazol-1-yl(dimethyl)silyl]-1H-imidazole
(IIIa). A mixture of 18 g of trimethylsilyl-1H-imida-
zole IIa and 15.44 g of dimethyldimethoxysilane was
heated in the presence of catalytic amounts of alu-
minum isopropoxide in a flask equipped with a full
condensation distilling head until the evolution of
trimethylmethoxysilane completed. The target com-
pound was isolated by fractionation. Yield 16.29 g
(81.2%), bp 107–109°C (1 mm Hg), nD20 1.4825. IR
It should be noted that attempts to carry out an
exhaustive transsilylation of alkoxysilanes IVa, IVb
with the corresponding initial trimethylsilyl derivatives
of diazoles IIa, IIb were not successful. In all cases,
only starting compounds were isolated. Apparently,
this is due to steric hindrances of phenyl substituent.
1
spectrum, ν, cm–1: 3080 (C=CH), 1520 (C=N). H
EXPERIMENTAL
NMR spectrum, δ, ppm: 0.47 s (6Н, SiCH3), 7.04 s
(4Н, СН), 7.61 s (2Н, СН). Found, %: C 49.69; H
6.02; N 28.91. C8H12N4Si. Calculated, %: C 49.97; H
6.29; N 29.14.
The IR spectra were recorded on a Specord IR-75
1
instrument. The H NMR spectra were taken on a
Bruker WP-300 spectrometer operating at 300 MHz in
CDCl3 solution using the residual proton signals as
internal reference.
1-[(3,5-Dimethyl-1-pyrazol-1-yl)dimethylsilyl]-3,5-
dimethyl-1Н-pyrazole (IIIb) was prepared similarly
All starting materials and solvents were purified
from 11.80
g of trimethylsilyl-1H-3,5-dimethyl-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1368
BELOVA et al.
pyrazole IIb and 9.03 g of dimethyldichlorosilane.
SnCl4 was used instead of aluminum isopropoxide.
Yield 13.6 g (78.3%), bp 120–121°C (1 mm Hg), nD20
1.4943. IR spectrum, ν, cm–1: 3140 (C=CH), 1540
(C=N). 1H NMR spectrum, δ, ppm: 0.92 s (6H, SiCH3),
2.24 s and 2.26 s (12H, СCH3), 5.86 s (2H, CH).
Found, %: C 57.84; H 8.17; N 22.48. C12H20N4Si.
Calculated, %: C 58.02; H 8.12; N 22.56.
Calculated, %: C 63.37; H 7.36; N 11.37.
1-[Dichloro(phenyl)silyl]-1H-imidazole (Va) was
prepared similarly from 16.83 g of trimethylsilyl-1H-
imidazole IIa and 8.47 g of phenyltrichlorosilane.
SnCl4 was used instead of aluminum isopropoxide.
Yield 7.78 g (80%), mp 130–132°C. IR spectrum, ν,
1
cm–1: 3110 (C=CH), 1560 (C=N). H NMR spectrum,
δ, ppm: 7.29 s, 7.31 s, 8.79 s (3H, СН), 7.38 t (1H,
CH), 7.33 t (2H, CH), 8.01 t (2H, CH). Found, %: C
44.39; H 3.12; N 11.44. C9H8Cl2N2Si. Calculated, %:
C 44.45; H 3.32; N 11.52.
1-[Methoxy(methyl)phenylsilyl]-1H-imidazole (IVa)
was prepared similarly from 16 g of trimethylsilyl-1H-
imidazole IIa and 10.39 g of methylphenyldi-
methoxysilane. Yield 10.67 g (85.7%), bp 94–96°C
(2 mm Hg), nD20 1.5350. IR spectrum, ν, cm–1: 3100
1-[Dichloro(phenyl)silyl]-3,5-dimethyl-1H-pyra-
zole (Vb) was prepared similarly from 20 g of tri-
methylsilyl-1H-3,5-dimethylpyrazole IIb and 8.38 g of
phenyltrichlorosilane. SnCl4 was used instead of alu-
minum isopropoxide. Yield 8.15 g (76%), bp 136–
138°C (10 mm Hg), nD20 1.5482. IR spectrum, ν, cm–1:
1
(C=CH), 1560 (C=N). H NMR spectrum, δ, ppm:
0.75 s (3H, SiCH3), 3.56 s (3H, ОCH3), 8.13 s, 7.39 s,
7.54 s (3H, СН), 7.47 t (1H, CH), 7.53 t (2H, CH),
8.01 t (2H, CH). Found, %: C 60.57; H 6.88; N 12.28.
C11H14N2OSi. Calculated, %: C 60.51; H 6.46; N
12.83.
1
3120 (C=CH), 1590 (C=N). H NMR spectrum, δ,
ppm: 2.32 s and 2.38 s (6H, СCH3), 6.01 s (1H, CH),
7.57 t (1H, CH), 7.59 t (2H, CH), 7.86 t (2Н, СН).
Found, %: C 48.57; H 4.41; N 10.24. C11H12Cl2N2Si.
Calculated, %: C 48.71; H 4.46; N 10.33.
1-[Methoxy(methyl)phenylsilyl]-3,5-dimethyl-1H-
pyrazole (IVb) was prepared similarly from 15 g of
trimethylsilyl-1H-3,5-dimethylpyrazole IIb and 9.74 g
of methylphenyldimethoxysilane. Yield 10.6
g
(84.4%), bp 128–130°C (2 mm Hg), nD20 1.5050. IR
REFERENCES
spectrum ν, cm–1: 3110 (C=CH), 1540 (C=N). H
1
1. Sheludyakov, V.D., Kirilina, N.I., and Kirilin, A.D.,
NMR spectrum, δ, ppm: 0.41 s (3H, SiCH3), 2.28 s
(6H, СCH3), 3.58 s (3H, OCH3), 5.52 m (1H, CH),
7.41 t (1H, CH), 7.55 t (2H, CH) and 8.06 t (2Н, СН).
Found, %: C 63.18; H 7.31; N 11.29. C13H18N2OSi.
Russ. J. Gen. Chem.,1980, vol. 50, no. 2.
2. Kirilin, A.D., Belova, L.O., Pletneva, M.V., Panfilo-
va, V.M., Storozenko, P.A., and Sheludyakov, V.D.,
Russ. J. Gen. Chem.,2011, vol. 81, no. 7, p. 1493.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013