Synthesis and structure of new ditopic ligands containing tetrazole and 3-nitro-1,2,4-triazole fragments

Article abstract of DOI:10.1134/S1070428014050200

Alkylation of 3-nitro-1,2,4-triazole with haloalkyltetrazoles has afforded in high yields previously unknown 1-[2-(3-nitro-1H-1,2,4-triazol-1-yl)ethyl]-1H- tetrazole and 2-tert-butyl-5-(3-nitro-1H-1,2,4-triazol-1-ylmethyl)-2H-tetrazole. The molecular and crystal structure of these compounds has been established by X-ray diffraction analysis (XRD).

Full text of DOI:10.1134/S1070428014050200

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2014, Vol. 50, No. 5, pp. 742–746. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © Yu.V. Grigor’ev, S.V. Voitekhovich, A.S. Lyakhov, L.S. Ivashkevich, A.F. Buglak, O.A. Ivashkevich, 2014, published in Zhurnal
Organicheskoi Khimii, 2014, Vol. 50, No. 5, pp. 752–756.
Synthesis and Structure of New Ditopic Ligands Containing
Tetrazole and 3-Nitro-1,2,4-triazole Fragments
Yu. V. Grigor’ev, S. V. Voitekhovich, A. S. Lyakhov, L. S. Ivashkevich,
A. F. Buglak, and O. A. Ivashkevich
Research Institute for Physical Chemical Problems of the Belarusian State University,
ul. Leningradskaya 14, Minsk, 220030 Belarus’
e-mail: azole@bsu.by
Received November 5, 2013
Abstract—Alkylation of 3-nitro-1,2,4-triazole with haloalkyltetrazoles has afforded in high yields previously
unknown 1-[2-(3-nitro-1H-1,2,4-triazol-1-yl)ethyl]-1H-tetrazole and 2-tert-butyl-5-(3-nitro-1H-1,2,4-triazol-1-
ylmethyl)-2H-tetrazole. The molecular and crystal structure of these compounds has been established by X-ray
diffraction analysis (XRD).
DOI: 10.1134/S1070428014050200
Derivatives of 1,2,4-triazole and tetrazole are used
in various fields of human activity: in special
technology, in industry, in agriculture as fungicides
and herbicides, in biochemistry and pharmacology
[1, 2]. In this connection compounds possessing in
their structure both azole fragments are very
interesting from the theoretical as well as practical
viewpoint. They may have a complex of useful
properties and the study of their behavior in various
chemical processes is of interest for the development
of the theory of heterocycles reactivity. Moreover
since these compounds are specimens of ditopic
ligands they are promising for designing hybrid
organic-inorganic homo- and heterometallic systems
possessing unique catalytic, adsorption, magnetic, and
other physicochemical characteristics [3–6].
by NMR spectroscopy that the alkylation occurred
prevailingly with the formation of 1-(2-aminoethyl)-3-
nitro-1,2,4-triazole (II). The oily substance was
contaminated with 2-(2-aminoethyl)-3-nitro-1,2,4-
triazole and also with initial azole I and 2-bromo-
ethylamine. Considering the intermediate character of
obtained amine II and the difficulties in its purification
from the above mentioned impurities we used in the
heterocyclization with triethyl orthoformate and
sodium azide unpurified azole II separated from the
reaction mixture after alkylation by filtration and
evaporation of the filtrate in a vacuum. As a result we
obtained in an overall yield of 20% 1-[2-(3-nitro-1H-
1,2,4-triazol-1-yl)ethyl]-1H-tetrazole (III) whose
molecule contained 3-nitro-1,2,4-triazol-1-yl and tetra-
zol-1-yl moieties connected by ethyl bridge (Scheme 1,
method a).
In extension of our research on functionalization of
3-nitro-1,2,4-triazole (I) [7–9] we showed in this study
the possibility to use the classic procedures of nitrogen
heterocycles functionalization for the synthesis of
compounds combining in their molecules 3-nitro-
1,2,4-triazol-1-yl with tetrazol-1-yl or tetrazol-5-yl
fragments.
Taking into account the relatively small yield of
compound III we developed an alternative method of
its preparation (Scheme 1, method b) including the
stages of the synthesis of 1-(2-bromoethyl)tetrazole
(IV) by heterocyclization of 2-bromoethylamine hyd-
robromide with triethyl orthoformate and sodium azide
followed by the alkylation with compound IV of azole
I. As a result compound III was obtained in over 90%
yield.
One of convenient methods of the preparation of 1-
substituted tetrazoles consists in the heterocyclization
of primary amines with triethyl orthoformate and
sodium azide [10, 11]. Therefore in order to introduce
into the molecule of azole I of an aminoethyl fragment
whose amino group might be transformed into a
tetrazole ring we have studied the alkylation of
substrate I with 2-bromoethylamine. It was established
Aiming at the preparation of a biheterocyclic
compound containing in the structure 3-nitro-1,2,4-
triazol-1-yl and tetrazol-5-yl fragments we studied the
alkylation of azole I with 2-tert-butyl-5-chloro-
methyltetrazole that in boiling acetonitrile in the
742

SYNTHESIS AND STRUCTURE OF NEW DITOPIC LIGANDS
743
Scheme 1.
NO2
NO2
H3N Br
N
K2CO3
HC(OEt)3
N
N
N
NO2
N
N
+
a
N
N
N
CH3CN
N
,
NaN3 AcOH
N
HN
N
Br
I
III
NH2
II
H3N Br
HC(OEt)3
N
I
b
N
N
Br
,
NaN3 AcOH
K2CO3, CH3CN
Br
N
IV
presence of potassium carbonate led to practically
selective formation of 2-tert-butyl-5-(3-nitro-1H-1,2,4-
triazol-1-ylmethyl)-2H-tetrazole (V) in 95% yield
(Scheme 2).
the atoms of rings from the least-squares plane of
0.0019(11) Å and 0.002(2) Å respectively.
The crystal structure of compound III contains
intermolecular non classical hydrogen bonds C–H···O
involving the C6 of the methylene group and C–H···N
The virtually selective formation of compounds III
and V in the studied conditions is well consistent with
published data indicating that the alkylation of azole I
with haloalkanes in the presence of bases affords in
high yields either exclusively the corresponding 1-
isomers [9, 12–15], or mixtures of 1- and 2-isomers
with the prevalence of 1-isomer [16].
C7
N9
N8
O2
C6
C10
C5
N1
N13
C12
N2
N11
The composition and structure of compounds III
and V were confirmed by the data of elemental
analysis, by NMR and IR spectra, and by XRD
analysis.
O1
N4
N3
Fig. 1. Structure of the molecule of 1-[2-(3-nitro-1H-1,2,4-
triazol-1-yl)-ethyl]-1H-tetrazole (III). Displacement ellip-
soids are shown at the 50% probability level.
According to XRD data compound III crystallized
in the monoclinic space group P21/c with the following
parameters of the unit cell: a 12.9269(5), b 5.4500(2),
c 14.4116(7) Å, β 120.231(2)º, Z 4. All atoms are
located in general positions (Fig. 1). In the tetrazole
ring the formally double bonds are the shortest: N2–N3
1.2883(19) Å and N4–C5 1.302(2) Å. The lengths of the
other bonds are in the range 1.3201(19)–1.346(2) Å. In
the triazole ring also the formally double bonds are the
shortest: N9–C10 1.3081(18) and N11–C12 1.319(2) Å.
The lengths of the other bonds are in the range
1.331(2)–1.3485(16) Å. The tetrazole and triazole
rings are nearly planar, with an average deviation of
a
c
0
Scheme 2.
N
N
Bu-t
Bu-t
N
N
I
N
N
Cl
N
N
N
N
Fig. 2. Crystal packing of molecules of 1-[2-(3-nitro-1H-
1,2,4-triazol-1-yl)ethyl]-1H-tetrazole (III). Hydrogen
bonds are shown by dashed lines.
K2CO3,
CH3CN
N
O2N
V
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 5 2014

GRIGOR’EV et al.
744
Table 1. Geometry of hydrogen bonds in the crystal structure of compounds III and V
Compound no.
D–H···A
D–H
H···A
D···A
Angle D–H···A, deg
C6–H6A···O2a
C12–H12···N4b
C10–H10B···N4c
C15–H15···N3c
0.963(15)
0.933(18)
0.962(14)
0.929(16)
2.518(16)
2.480(19)
2.564(14)
2.426(16)
3.405(2)
3.338(2)
153.0(12)
152.9(14)
164.5(11)
160.9(12)
III
3.5009(14)
3.3174(15)
V
Symmetry transformations: a –x, –y + 1, –z; b –x + 1, y + 1/2, –z + 1/2; c –x + 1/2, y + 1/2, –z + 1/2.
with the participation of the C–H group of the triazole
ring (see the table). The first type of hydrogen bonds
forms dimers which form layers normal to с axis
owing to the second type of hydrogen bonds (Fig. 2).
positions (Fig. 3). In the tetrazole ring the longest bond
is N4–C5 1.3437(14) Å, the other bond distances are in
the range 1.3183(12)–1.3298(12) Å. In the triazole ring
the longest bond is N11–N12 1.3533(12) Å, the other bond
distances are in the range 1.3134(13)–1.3380(14) Å. The
tetrazole and triazole rings are planar, with an average
deviation of the atoms of rings from the least-squares
plane of 0.0012(6) Å and 0.0011(7) Å respectively.
According to XRD data compound V crystallized in
the monoclinic space group P21/n [a 11.6380(2), b
7.17920(10), c 13.9321(3) Å, β 91.2580(10)º, V
1163.77(4) Å3, Z 4. All atoms are located in common
In the crystal structure of compound V only non-
classical hydrogen bonds C–H···N are present between
the hydrogen atoms of the methylene groups and the
C–H groups of the triazole rings (see the table). These
hydrogen bonds form polymer chains along the b axis
(Fig. 4).
C10
C15
N14
C13
N11
N4
C5
C8
N1
C6
C7
N2
N3
N12
N16
O2
C9
O1
Considering the presence in the structure of
compounds synthesized of two energetic heterocycles
it was interesting to investigate their thermal behavior.
The data of the complex thermal analysis* show that
compound III after melting at 136°C (endo effect
without mass loss) starts to decompose at the tempera-
ture around 180°C. The decomposition proceeds in
three stages, two of which are accompanied with exo
effects and correspond to the degradation of azole
heterocycles. It is therewith presumable basing on the
thermogravimetric data that in the first stage (exo
effect maximum at 229°C) the decomposition of the
tetrazole ring occurs with the ejection of the nitrogen
molecule, and in the second stage (exo effect
maximum at 315°C) the nitrotriazole ring is cleaved
with ejection of CNO2 fragment. Further the
thermolysis products burning takes place.
Fig. 3. Structure of the molecule of 2-tert-butyl-5-(3-nitro-
1H-1,2,4-triazol-1-ylmethyl)-2H-tetrazole (V). Displace-
ment ellipsoids are shown at the 50% probability level.
b
a
Compound V melts at 73°C (endo effect without
mass loss) and starts to decompose at the temperature
around 180°C. The decomposition proceeds in two
stages, one of which is accompanied with a pro-
nounced exo effect with the maximum at 282°C. The
c
Fig. 4. Polymer chain bound by hydrogen bonds in the
crystal structure of 2-tert-butyl-5-(3-nitro-1H-1,2,4-triazol-
1-ylmethyl)-2H-tetrazole (V). tert-Butyl groups are not
shown.
* The DSC and TGM curves are available from the authors by
email.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 50 No. 5 2014

SYNTHESIS AND STRUCTURE OF NEW DITOPIC LIGANDS
745
1
weight loss at this thermolysis stage reached over 75%,
indicating the materially simultaneous decomposition
of both heterocycles present in the molecule.
needle crystals, mp 135–136°С. Н NMR spectrum, δ,
ppm: 4.88 t (2Н, СН2), 5.02 t (2Н, СН2), 8.74 s (1Н,
СHtriazole), 9.31 s (1Н, СHtetrazole). 13С NMR spectrum,
δ, ppm: 46.6 (СН2), 49.7 (СН2), 144.4 (СHtetrazole),
147.4 (СHtriazole), 162.2 (CNO2). Found, %: C 28.69; H
2.71; N 53.49. C5H6N8О2. Calculated, %: C 28.57; H
2.86; N 53.33.
EXPERIMENTAL
NMR spectra were registered on a spectrometer
Bruker Avance-500 in DMSO-d6 at operating frequen-
cies 500.13 (1Н) and 125.76 МHz (13C).
b. To a heated to boiling stirred slurry of 0.775 g
(6.8 mmol) of azole I and 0.94 g (6.8 mmol) of K2CO3
in 30 mL of acetonitrile was slowly added a solution of
1.2 g (6.8 mmol) of 1-[(2-bromoethyl)]tetrazole (II) in
20 mL of acetonitrile. The reaction mixture was stirred
at reflux for 20 h, cooled to room temperature, filtered,
the precipitate on the filter was washed with 10 mL of
acetonitrile, and the filtrate was evaporated in a
vacuum. The residue was dissolved in acetone, the
solution was filtered, and the filtrate was evaporated in
a vacuum. Thus a spectrally pure compound III was
obtained as oily substance that crystallized within 24 h.
Yield 1.35 g (95%). After recrystallization from water
or from a mixture ethanol–2-propanol, 1 : 10, mp 135–
136°С.
XRD data were obtained on a diffractometer Smart
Apex II [17] [MoKα radiation, graphite mono-
chromator, λ 0.71073 Å, temperature 296 K for com-
pound III, 100 K for compound V]. Crystal structures
were solved by direct methods using program SIR2004
[18] and refined in the full-matrix least-squares
method with respect to F2 using SHELXL-97 software
[19]. The molecular graphics was performed with the
use of program packages ORTEP-3 for Windows [20]
and PLATON [21]. The crystallo-graphic data on
compounds III and V are deposited in Cambridge
Crystallographic Data Center and are available by the
numbers CCDC 940230 and 940231 respectively [22].
Differential thermal analysis was carried out on a
thermal analyzer STA 449 (Netzsch) in a nitrogen
atmosphere.
2-tert-Butyl-5-(3-nitro-1H-1,2,4-triazol-1-ylmet-
hyl)-2H-tetrazole (V). To a heated to boiling stirred
slurry of 0.69 g (6 mmol) of azole I and 0.9 g (6.5 mmol) of
K2CO3 in 30 mL of acetonitrile was slowly added a
solution of 1.1 g (6.2 mmol) of 2-tert-butyl-5-
chloromethyltetrazole in 20 mL of acetonitrile. The
reaction mixture was stirred at reflux for 20 h, cooled
to room temperature, filtered, the precipitate on the
filter was washed with 10 mL of acetonitrile, and the
filtrate was evaporated in a vacuum. The residue was
dissolved in ethyl acetate, the solution was filtered, and
the filtrate was evaporated in a vacuum. Yellow oily
substance slowly crystallized on storage. Yield 1.44 g
(95%). After recrystallization from water mp 71–73°С.
1Н NMR spectrum, δ, ppm: 1.68 s [9Н, С(СН3)3], 5.99
s (2Н, СН2), 9.08 s (1Н, СHtriazole). 13С NMR spectrum,
δ, ppm: 28.7 (СН3), 45.2 (СН2), 64.4 [С(СН3)3], 147.5
(СHtriazole), 159.7 (Сtetrazole), 162.2 (CNO2). Found, %:
C 40.81; H 5.13; N 41.29. C8H12N7О2. Calculated, %:
C 40.34; H 5.04; N 41.18.
3-Nitro-1,2,4-triazole (I) was obtained from 3-
amino-1,2,4-triazole and sodium nitrite in acid
environment by the method [23]. 2-tert-Butyl-5-
chloromethyltetrazole was obtained by the alkylation
of 5-(chloromethyl)tetrazole with t-BuOH in sulfuric
acid [24], 1-[2-(bromoethyl)]tetrazole (II) was
prepared by heterocyclization of 2-bromoethylamine
with triethyl orthoformate and sodium azide [25].
1-[2-(3-Nitro-1H-1,2,4-triazol-1-yl)ethyl]-1H-tetra-
zole (III). a. A mixture of 1.14 g (10 mmol) of azole I,
2.35 g (12 mmol) of bromoethylamine hydrobromide,
and 3.45 g (25 mmol) of K2CO3 in 50 mL of
acetonitrile was stirred at reflux for 20 h. Then the
reaction mixture was cooled to room temperature,
filtered, the precipitate on the filter was washed with
10 mL of acetonitrile, and the filtrate was evaporated
in a vacuum. To the residue was added 0.715 g (11 mmol) of
NaN3, 4.38 g (30 mmol) of triethyl orthoformate, and
at stirring was added 6.0 g (100 mmol) of glacial acetic
acid. The mixture was stirred for 3 h at 100ºC, cooled,
2 mL of conc. HCl was added, the reaction mixture
was filtered, and the filtrate was evaporated in a
vacuum. The residue was recrystallized from a mixture
ethanol–2-propanol, 1 : 10, yield 0.42 g (20%), yellowish
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