Stable hemiaminals containing a triazole ring

Article abstract of DOI:10.1039/c0nj00346h

Reactions between 4-amino-1,2,4-triazole and nitro-substituted benzaldehydes in acetonitrile under neutral conditions afford stable hemiaminals, seven of which have been structurally and spectroscopically characterized. Two Schiff bases have also been obt

Full text of DOI:10.1039/c0nj00346h

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Stable hemiaminals containing a triazole ringw
´
Maciej Barys, Zbigniew Ciunik,* Krzysztof Drabent and Anna Kwiecien
Received (in Montpellier, France) 6th May 2010, Accepted 21st July 2010
DOI: 10.1039/c0nj00346h
Reactions between 4-amino-1,2,4-triazole and nitro-substituted benzaldehydes in acetonitrile
under neutral conditions afford stable hemiaminals, seven of which have been structurally
and spectroscopically characterized. Two Schiff bases have also been obtained after the
addition of hydrochloric acid to the reaction mixture. We describe a correlation between
the conformation and configuration of the hemiaminals, and conclude that the formation
of these species is determined by the substituents on the phenyl ring, as well as by the
presence of 4-amino-1,2,4-triazole.
of acid and with appropriate substrates). Crystals (1, 2, 3,
Introduction
4, 5, 6 and 7, Fig. 1) of seven stable hemiaminals were
obtained in the reaction of 4-amino-1,2,4-triazole with respec-
tive nitro-substituted benzaldehydes [2-nitrobenzaldehyde
(1), 3-nitrobenzaldehyde (2), 4-nitrobenzaldehyde (3),
2,4-dinitrobenzaldehyde (4), 2-chloro-6-nitrobenzaldehyde
(5) and 4-chloro-3-nitrobenzaldehyde (two polymorphic
forms: 6 and 7)] in a 1 : 1 molar ratio from an acetonitrile
solution.
It is well known that the formation of Schiff bases from
primary amines and aldehydes involves an unstable intermediate
with a tetrahedral carbon atom—a hemiaminal (also known as
carbinolamine).1 As a short-lived species, these intermediates
are typically observed only by spectroscopic methods at low
temperatures.2–5 To trap the hemiaminal intermediates, Rebek
et al.6,7 used a deep molecular cavitand. On the basis of NMR
measurements, the chemical half-lives of these compounds
were determined to vary from 30 min to over 100 h at ambient
temperature. On the other hand, Kawamichi et al.8 trapped a
hemiaminal intermediate in a porous coordination network
and determined its crystal structure. Dolotko et al.5 observed
the hemiaminal form as a short lived species in a solvent-free
reaction between o-vanillin and p-toluidine. Previously, the
first stable hemiaminal product was isolated as single crystals
from the condensation reaction of di-2-pyridyl ketone with
4-cyclohexyl-3-thiosemicarbazide.9
All of the new organic compounds obtained were charac-
terized by elemental analysis, ESI-MS, IR spectroscopy,
All the above-mentioned investigations have dealt with open-
chain hemiaminals. However, cyclic hemiaminals are also
known, for example, the naturally occurring echinocandins
have a reactive hemiaminal function due to the ornithine-
5-hydroxyl group, which is responsible for its instability.10
Moreover, some cyclic N-acyl hemiaminals,11 as well as cyclic
hemiaminals in a rhodium complex, have been reported.12
Hemiaminals, in which the nitrogen atom is a part of
an aromatic ring have also been observed, as in pyrrole
carbinols.13
The above-mentioned procedures are very sophisticated;
therefore, the original aim of our study was the syntheses
as well as the spectroscopic and single crystal X-ray diffrac-
tion studies of new stable hemiaminals synthesised in the
simplest manner (in an aprotic solvent without the addition
Faculty of Chemistry, University of Wroc!aw, 14 F. Joliot-Curie St.,
50-383 Wroc!aw, Poland. E-mail: ciunik@wchuwr.pl;
Fax: + 48 71 328 2348; Tel: + 48 71 375 7257
w Electronic supplementary information (ESI) available: Sample
preparation, additional structural information, including crystallo-
graphic experiments, crystal data, views of molecules and tables of
geometry parameters. CCDC 751216–751224. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/
c0nj00346h
Fig. 1 Molecular structures of stable hemiaminals 1–7, and Schiff
bases 2a and 4a.
c
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Fig. 2 General numbering scheme for the hemiaminals and Schiff
bases.
Scheme
1 General reaction scheme of hemiaminal and imine
Table 1 Selected bond lengths for hemiaminals 1–7, and Schiff bases
2a and 4a
formation.
13C NMR spectroscopy, 1H NMR spectroscopy and X-ray
single crystal analysis.
Compound
N4–C14
N4–N3
C14–C1
C14–O14
1
2
3
4
1.469(2)
1.478(2)
1.467(2)
1.487(2)
1.412(2)
1.416(2)
1.411(2)
1.412(2)
1.525(2)
1.517(2)
1.515(2)
1.520(2)
1.408(2)
1.400(2)
1.406(2)
1.401(2)
A general procedure for the syntheses of hemiaminals and
Schiff bases is shown in Scheme 1.
5
Molecule A
Molecule B
6
7
2a
1.479(5)
1.472(5)
1.468(2)
1.474(2)
1.265(2)
1.412(4)
1.417(4)
1.412(2)
1.416(2)
1.392(2)
1.525(5)
1.529(5)
1.513(2)
1.514(2)
1.462(2)
1.404(5)
1.405(5)
1.408(2)
1.401(2)
—
Results
General remarks
Recently, we have studied the reaction between 4-amino-1,2,4-
triazole and X-substituted benzaldehydes in ethanolic solution
under neutral conditions.14–16 For X = Cl, Br, OH, CH3 and
OCH3, the appropriate Schiff bases were usually obtained. In
the case of X = NO2, a hemiaminal was unexpectedly detected
as the sole product, albeit in a low yield. However, the yield
increased considerably when the reaction was performed in an
acetonitrile solution. The reaction mixture was typically
stirred for 30 min at room temperature. The hemiaminals were
obtained as single crystals directly from the mother liquor. To
investigate the role of acidic conditions on the reaction outcome,
a few drops of hydrochloric acid were added to the reaction
mixture of a triazole and 3-nitrobenzaldehyde or 2,4-dinitro-
benzaldehyde. This resulted in the formation of the appropriate
Schiff base 2a and 4a (Fig. 1), respectively. A similar reaction has
been already performed by Kitaev et al.17
4a
Molecule A
Molecule B
1.258(2)
1.267(2)
1.383(2)
1.398(2)
1.469(3)
1.465(3)
—
—
Structure description
The molecular structures of compounds 1–7, as well as 2a and
4a, consist of phenyl and triazole rings directly linked through
the C1–C14–N4–N3 chain of atoms (Fig. 2). In the hemiaminals,
the N4 and C14 atoms have sp3 hybridization and both exhibit
stereogenic centers. Meanwhile, in the Schiff bases, the N4 and
C14 atoms are double-bonded. The respective bond lengths
are presented in Table 1.
Fig. 3 Twisted (6) and stretched (7) conformations, as well as the
numbering system used for the hemiaminals.
In the crystal structures of the title hemiaminals, two
molecular conformations—stretched and twisted—are observed
(Fig. 3). These conformations are determined by the
N3–N4–C14–C1 torsion angle (Table 2). For the stretched
molecule, this chain of atoms is antiperiplanar (ap) and both
rings are almost parallel. For twisted molecules, this chain
c
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Table 2 Selected torsion angles for hemiaminals 1–7, and Schiff bases
2a and 4a
In 4, the O–HÁ Á ÁN hydrogen bonds connect two molecules
with the same configuration into dimers (SR–SR and RS–RS).
All chains of molecules (in 1, 2, 3, 5, 6 and 7) as well as
dimers (in 4) are linked into a 3D network via N–HÁ Á ÁN/O
hydrogen bonds and C–HÁ Á ÁO/N weak interactions.
In both Schiff bases (2a and 4a), C–HÁ Á ÁN and C–HÁ Á ÁO
interactions are observed. These interactions join molecules
into 2D sheets. Stacking interactions are present between these
sheets (Fig. 7).
Compound
N3–N4–C14–C1
N3–N4–C14–O14
1
2
3
4
167.9(2)
164.1(2)
À64.3(2)
174.0(2)
À72.8(2)
À73.7(2)
60.1(2)
À65.4(2)
5
Molecule A
Molecule B
6
7
2a
À176.8(3)
À177.6(3)
À60.5(2)
168.2(2)
À54.0(5)
À55.6(5)
63.0(2)
À70.9(2)
—
Discussion
178.7(2)
4a
Molecule A
Molecule B
Hemiaminals can be obtained in a reaction of a primary amine
and an aldehyde, usually as a short-lived species. Recently,
highly sophisticated methods, like trapping the intermediate
product in a cavitand,6,7 a solvent-free reaction in the
solid state5 and stabilization of these hemiaminals at low
temperature in porous crystals have been used to identify
such products.7 The stabilization of the hemiaminal form
can be attributed to the intramolecular O–HÁ Á ÁN hydrogen
bond.9
177.2(2)
174.0(2)
—
—
is synclinal (sc) with both rings nearly perpendicular to
each other.
Among the seven crystal structures of the hemiaminals
presented here, the twisted conformation was observed in only
two cases, 3 and 6. Moreover, for the hemiaminal synthesised
in a reaction of 4-amino-1,2,4-triazole and 4-chloro-3-nitro-
benzaldehyde, two polymorphic forms—6 and 7, with both
possible conformations—were found. This suggests that,
while both conformations can be isolated, the stretched con-
formation is more common than the twisted one.
The title hemiaminals were obtained at room temperature,
similar to the Schiff base formation reaction. Stable products
were isolated by slow crystallization. Finally, single crystal
X-ray analyses showed the presence of intermolecular hydrogen
bonds and the lack of intramolecular interactions that could
stabilize molecules. The parallel orientation of the column
axes and the shortest lattice vectors suggest that the O–HÁ Á ÁN
intermolecular hydrogen bond does not stabilize the hemiaminal
form but rather is a key factor in controlling crystal growth.
We conclude that the presence of both nitro group(s) in the
phenyl ring and the 1,2,4-triazole ring determine the stabiliza-
tion of the hemiaminals under study. To verify this, the
reaction of 2,4-dinitrobenzaldehyde and aniline was performed,
but only the appropriate Schiff base was synthesized.19 It is
well known that nitro groups are strongly deactivating
substituents in electrophilic aromatic substitution reactions.
Also, the electron-withdrawing substituents decrease the
electrophilicity of the carbonyl carbon atom.20 Furthermore,
Sayer and Jencks21 have shown that the equilibrium constants
for hemiaminal formation increase with the number of the
electron-withdrawing substituents on the benzaldehyde. Our
results confirm this conclusion and additionally show that the
presence of the electron-rich 1,2,4-triazole ring increases the
stability of intermediates.
As mentioned above, the hemiaminals studied here have two
stereogenic centers, at the N4 and C14 atoms, but only two of
the four possible enantiomers are observed for each con-
former. In the case of the stretched ones, only the RS and
SR exist in solid state, while only the RR and SS enantiomers
are observed for the twisted ones.
The crystal packing of the hemiaminals is determined
by a variety of intermolecular interactions, such as strong
O–HÁ Á ÁNtriazole, N–HÁ Á ÁNtriazole and N–HÁ Á ÁO hydrogen bonds,
weak C–HÁ Á ÁO and, in a few crystals, stacking interactions, all
with typical lengths and angles. Among these interactions, the
rather short and almost linear O–HÁ Á ÁNtriazole hydrogen bond
(with a HÁ Á ÁN distance in the range of 1.79–1.99 A) dominates
in all crystals. In 1, 2, 5 and 7, the connected molecules form
infinite chains (Fig. 4). Only in 4 does this interaction connect
two molecules into a dimer (Fig. 5).
In crystals of hemiaminals 1, 2, 5 and 7 with a stretched
conformation, the O–HÁ Á ÁN hydrogen bond links opposite
enantiomers into infinite chains (RS–SR–RS. . .). Additionally,
the parallel chains (except 1) interact with each other by
phenyl ring stacking. Such connected molecules form a 2D
network of zipper-like structure. The geometric parameters of
the stacking rings agree well with those observed by Janiak.18
All chains in 1, 2, 5 and 7 are oriented along the shortest lattice
vector in their crystals.
All the hemiaminals under study have two stereogenic
centers because the C14 and N4 atoms have sp3 hybridization
and four different substituents; the fourth substituent on N4 is
a lone electron pair. Geometrical analysis of both stereogenic
centers in all hemiaminals shows that this lone pair and a
hydroxyl group have an ap orientation. We have found
an analogous correlation in the geometrical analysis of the
hemiaminal obtained by Kurup et al.9 The main reason for
this observation lies in the repulsive stereoelectronic effect.
This phenomenon is similar to the anomeric effect22 known
for compounds with a C–X–C–Y structural fragment, where
X = N, O or S, and Y = F, Cl, Br, O, N or S, but we did not
observe a shortening of the C–X (in our hemiaminals’
N4–C14) or an elongation of C–Y (in our hemiaminals’
In crystals of hemiaminals 3 and 6 with a twisted conforma-
tion, the O–HÁ Á ÁN hydrogen bond links the same enantiomers
to form infinite parallel chains (Fig. 6) of molecules
(SS–SS–SS... and RR–RR–RR...). Two such chains of opposite
chirality interact with each other by phenyl ring stacking, forming
single columns of zipper-like structure. These non-bonding inter-
actions link molecules along one of the two shortest lattice
vectors.
c
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Fig. 4 The O–HÁ Á ÁN hydrogen bonds in stretched hemiaminals that determine the packing motif of the crystal structures of compounds 1, 2, 5
and 7, connecting the molecules into zipper-like chains. Dashed lines indicate hydrogen bonds.
have an RS or SR configuration, while the twisted ones have
an RR or SS configuration.
Transformation of a stretched molecule into a twisted one
(Scheme 2) may be realized in the course of two low energetic
processes:23 rotation about the C–N single bond and inver-
sion of configuration on the N atom. During the possible
rotation about the C14–N4 bond (Fig. 8a), the lone electron
pair on the N4 atom approaches the hydroxyl group (Fig. 8b)
Fig. 5 Dimer formation in the crystal packing of 4 through O–HÁ Á ÁN
hydrogen bonds.
but the repulsion between them causes an inversion of configu-
ration on the nitrogen atom (Fig. 8c). The rotation and
inversion, both being low-energetic processes, must be highly
conjugated in order to cause the observed stereoelectronic
effect.
C14–O14) bond, which are typical for an anomeric effect. This
observation should be correlated with the conformation and
configuration of hemiaminals, in which stretched conformers
Fig. 6 Illustration of the O–HÁ Á ÁN hydrogen bonds in twisted hemiaminals 3 and 6, connecting aromatic rings into zipper-like chains.
c
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Fig. 8 Possible rotation about C14–N4 vs. configuration inversion on
nitrogen atom N4.
Aldrich and were used without further purification. NMR
spectra were recorded on a Bruker-500 spectrometer. Infrared
spectra were recorded using KBr pellets on a Bruker IFS66
FT-IR spectrometer. Elemental analyses were carried out at
the microanalytical laboratory of the University of Wroc"aw.
Fig. 7 Intermolecular C–HÁ Á ÁO/N and stacking interactions between
molecules of Schiff bases of 2a and 4a.
X-Ray crystallography
Single crystal X-ray diffraction data were collected on a Kuma
KM4CCD24 k-axis diffractometer with graphite mono-
chromated Mo-Ka radiation (l = 0.71073 A)24 at 100 K (1–7),
230 K (2a) and 295 K (4a) using an Oxford Cryosystem adapter.25
Data collection: CrysAlis CCD;26 data reduction: CrysAlis RED;
program used to solve the structures: SHELXS97;27 program
used to refine the structures: SHELXL97;27 software used to
prepare material for publication: SHELXL97; molecular graphics
software: DIAMOND.28
Scheme 2 Configurational and conformational changes resulting
from the inversion of configuration on nitrogen atom N4.
Conclusion
We have developed a new, general method for the efficient
preparation of stable hemiaminals via the reaction of nitro-
substituted benzaldehydes with 4-amino-1,2,4,-triazole. The
reaction mechanism can be considered as a multi-step process
with hemiaminal formation, protonation of a hydroxyl group,
dehydration and imine formation. It is well known that acidic
conditions influence the final product as much as the choice
of substrate does. Therefore, we used neutral solvent reac-
tion conditions and connected 4-amino-1,2,4-triazole with
benzaldehyde derivatives containing electron-withdrawing
substituents that decrease the electrophilicity of the carbonyl
carbon atom.
Syntheses
General procedure for syntheses of hemiaminals
A mixture of an appropriate nitrobenzaldehyde and 4-amino-
1,2,4-triazole (molar ratio 1 : 1) in acetonitrile or ethanol was
stirred at r.t. for 30 min. The crystals were filtered off, washed
with a small amount of acetonitrile and diethyl ether and then
dried in air.
General procedure for syntheses of Schiff bases
The crystal structures of the presented hemiaminals have
two stereogenic centers on both the C14 carbon atom and N4
nitrogen atom. The lone electron pair on the N4 nitrogen atom
and the hydroxyl group on the C14 carbon atom have an ap
orientation due to a repulsive stereoelectronic effect (similar
to an anomeric effect). Moreover, we have correlated this
observation with both the configuration and conformation
of the hemiaminals.
A mixture of the appropriate nitrobenzaldehyde and 4-amino-
1,2,4-triazole (molar ratio 1 : 1) and 3 drops of hydrochloric
acid in ethanol was stirred at r.t. for 4 h. The crystals were
filtered off, washed with a small amount of ethanol and diethyl
ether, and then dried in air.
(2-Nitrophenyl)(4H-1,2,4-triazole-4-ylamino)methanol (1)
In summary, the subtle connection of nitrobenzaldehyde
derivatives with 4-amino-1,2,4-triazole gave a new simple
route to stable hemiaminals with two chiral centers, and with
highly correlated conformations and configurations.
Upon standing of the reaction mixture for 3 h at room
temperature, yellow crystals of (2-nitrophenyl)(4H-1,2,4-tri-
azol-4-ylamino)methanol were deposited (0.89 g, 76%), mp
123–124 1C. Calculated: C 45.96, H 3.82, N 29.78%; found: C
1
46.13, H 3.60, N 30.06%. MS: (m/z) 236.1 [M]+. H NMR
(500 MHz, DMSO): d 8.25 (s, 2H), 7.94 (d, J = 8.0 Hz, 1H),
7.81 (d, J = 7.7 Hz, 1H), 7.72 (t, J = 7.6 Hz, 1H), 7.61 (t, J =
7.7 Hz, 1H), 7.46 (d, J = 7.2 Hz, 1H), 7.07 (d, J = 4.6 Hz,
1H), 6.05–5.93 (m, 1H). 13C NMR (125 MHz, DMSO): d 79.4,
124.1, 128.0, 129.7, 132.8, 133.0, 143.4, 148.3. IR (KBr, cmÀ1):
3445sh, 3194sh, 3089sh, 2996m, 2850m, 1557m, 1515vs,
Experimental
Materials and physical measurements
All reactions were performed using commercially available
reagents. All solvents were purchased from either POCh or
c
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1441w, 1338vs, 1254w, 1191s, 1067vs, 1039vs, 980m, 953w,
879m, 860s, 788s, 717vs, 639vs.
1H NMR (500 MHz, DMSO) d 8.41 (s, 2H), 8.24 (m, J = 8.7 Hz,
2H), 7.76 (m, J = 8.8 Hz, 2H), 7.48 (d, J = 6.6 Hz, 1H), 6.90
(d, J = 5.4 Hz, 1H), 5.65 (t, J = 6.0 Hz, 1H). 13C NMR
(125 MHz, DMSO): d 82.6, 123.2, 128.0, 143.9, 147.15, 147.24. IR
(KBr, cmÀ1): 3423sh, 3166sh, 3089sh, 2983sh, 2858sh, 2769sh,
1607m, 1569m, 1515vs, 1417w, 1349vs, 1291m, 1214w, 1199w,
1168m, 1107m, 1070s, 1050vs, 990m, 949s, 856vs, 755s, 739s,
688s, 630vs.
Crystal data: M = 235.21, crystal system: monoclinic, space
group: P21/c, a = 11.591(4), b = 10.437(4), c = 8.892(3) A,
b = 105.27(2)1, V = 1037.7(6) A3, Z = 4, crystal size:
0.23 Â 0.15 Â 0.12 mm, rc = 1.506 g cmÀ3, m = 0.117 mm,
ymax = 30.001, reflections: 13472, independent: 2995, Rint
0.0976, R1 = 0.0689, wR2 = 0.1450, GoF = 1.188.
=
Crystal data: M = 235.21, crystal system: monoclinic, space
group: Cc, a = 6.948(2), b = 20.546(6), c = 7.362(2) A,
b = 93.56(3)1, V = 1048.9(7) A3, Z = 4, crystal size: 0.38 Â
(3-Nitrophenyl)(4H-1,2,4-triazole-4-ylamino)methanol (2)
0.23 Â 0.12 mm, rc = 1.489 g cmÀ3, m = 0.116 mm, ymax
=
Upon standing of the reaction mixture for 2 d at room
temperature, yellow crystal plates of (3-nitrophenyl)(4H-1,2,4-
triazol-4-lamino)methanol were deposited (0.91 g, 78%), mp
141–143 1C. Calculated: C 45.96, H 3.82, N 29.78%; found: C
31.991, reflections: 6722, independent: 1791, Rint = 0.0210,
R1 = 0.0328, wR2 = 0.0870, GoF = 1.057.
1
45.86, H 3.78, N 29.91%. MS: (m/z) 236.1 [M]+. H NMR
(2,4-Dinitrophenyl)(4H-1,2,4-triazole-4-amino)methanol (4)
(500 MHz, DMSO) d 8.43 (s, 2H), 8.34 (s, 1H), 8.20 (d, J =
8.1 Hz, 1H), 7.94 (d, J = 7.6 Hz, 1H), 7.68 (t, J = 7.9 Hz, 1H),
7.48 (d, J = 6.7 Hz, 1H), 6.92 (s, 1H), 5.67 (d, J = 6.6 Hz,
1H). 13C NMR (125 MHz, DMSO): d 82.5, 121.4, 123.0, 129.7,
133.4, 142.2, 143.9, 147.6. IR (KBr, cmÀ1): 3429sh, 3206sh,
3117sh, 2937sh, 2856sh, 2736sh, 1582w, 1520vs, 1481m,
1423w, 1353vs, 1309m, 1202m, 1096m, 1070vs, 1056vs,
979m, 953m, 927m, 882s, 759m, 729s, 674s, 636sh, 587sh.
Crystal data: M = 235.21, crystal system: monoclinic, space
group: P21/c, a = 12.316(4), b = 10.616(3), c = 7.863(3) A,
b = 92.39(3)1, V = 1027.2(6) A3, Z = 4, crystal size: 0.20 Â
Upon standing of the reaction mixture for 2 h at room
temperature, yellow crystals of (2,4-dinitrophenyl)(4H-1,2,4-
triazol-4-ylamino)methanol were deposited (1.17 g, 84%), mp
122–123 1C. Calculated: C 38.57, H 2.85, N 30.00%; found: C
1
38.93, H 2.66, N 30.12%. MS: (m/z) 281.1 [M]+. H NMR
(500 MHz, DMSO) d 8.73 (d, J = 2.3 Hz, 1H), 8.54 (dd, J =
8.6, 2.3 Hz, 1H), 8.27 (s, 2H), 8.04 (d, J = 8.6 Hz, 1H), 7.64
(d, J = 7.1 Hz, 1H), 7.39 (d, J = 5.5 Hz, 1H), 6.12–6.01
(m, 1H). 13C NMR (125 MHz, DMSO): d 79.1, 119.7, 127.1,
129.9, 139.3, 143.4, 147.5, 148.1. IR (KBr, cmÀ1): 3432sh,
3299sh, 3120sh, 2888sh, 2755sh, 1607s, 1532vs, 1496s, 1348vs,
1253w, 1189s, 1148m, 1078s, 1056vs, 978m, 908w, 803m, 716s,
632s, 569m.
0.13 Â 0.12 mm, rc = 1.521 g cmÀ3, m = 0.119 mm, ymax
=
30.001, reflections: 15102, independent: 2988, Rint = 0.0527,
R1 = 0.0482, wR2 = 0.1232, GoF = 1.099.
Crystal data: M = 280.21, crystal system: orthorhombic,
space group: Pccn, a = 14.202(4), b = 14.267(4), c =
11.223(3) A, V = 2274(1) A3, Z = 8, crystal size: 0.22 Â
0.15 Â 0.11 mm, rc = 1.637, m = 0.137 g cmÀ3, ymax = 29.501,
(N-(3-Nitrobenzylidene)-4H-1,2,4-triazole-4-amine) (2a)
Upon standing of the reaction mixture for 2 weeks at
room temperature, colorless crystals (needles) of (N-(3-nitro-
benzylidene)-4H-1,2,4-triazole-4-amine) were deposited (0.35 g,
54%), mp 240–241 1C. Calculated: C 49.76, H 3.23, N 32.26%;
found: C 49.58, H 3.15, N 32.25%. MS: (m/z) 218.1 [M]+.
1H NMR (500 MHz, DMSO) d 9.32 (s, 1H), 9.28 (d, J = 0.4 Hz,
2H), 8.64 (s, 1H), 8.43 (dd, J = 8.2, 2.2 Hz, 1H), 8.27 (d, J =
7.8 Hz, 1H), 7.88 (t, J = 8.0 Hz, 1H). 13C NMR (125 MHz,
DMSO): d 122.5, 126.4, 130.9, 133.8, 134.1, 139.0, 148.2, 156.0.
IR (KBr, cmÀ1): 3440sh, 3139m, 3085sh, 3058sh, 1611m, 1578w,
1524vs, 1470m, 1360vs, 1330m, 1287m, 1219m, 1168s, 1110w,
1081w, 1061vs, 978m, 929w, 870w, 848m, 807m, 736s, 679s,
621s, 596m.
reflections: 26651, independent: 3151, Rint = 0.0548, R1
0.0481, wR2 = 0.1141, GoF = 1.161.
=
(N-(2,4-Dinitrobenzylidene)-4H-1,2,4-triazole-4-amine) (4a)
The title compound crystallized directly from the solution to
afford (N-(2,4-dinitrobenzylidene)-4H-1,2,4-triazole-4-amine)
(0.47 g, 60%), mp 182–184 1C. Upon standing of reaction
mixture for 2 weeks at the room temperature, colorless crystals
(needles) were deposited. Calculated: C 41.22, H 2.29, N
32.06%; found: C 41.24, H 2.15, N 32.04%. MS: (m/z) 263.1
[M]+. 1H NMR (500 MHz, DMSO) d 9.42 (s, 1H), 9.26
(s, 2H), 8.87 (d, J = 2.3 Hz, 1H), 8.70 (dd, J = 8.6, 2.3 Hz,
1H), 8.30 (d, J = 8.6 Hz, 1H). 13C NMR (125 MHz, DMSO):
d 120.4, 128.3, 131.1, 131.8, 139.1, 148.5, 148.8, 152.4. IR
(KBr, cmÀ1): 3446sh, 3098sh, 3038sh, 1611m, 1593m, 1529vs,
1459s, 1344vs, 1219w, 1208w, 1197w, 1170m, 1157m, 1050s,
920m, 855m, 832m, 771m, 740m, 711m, 676w, 614m,
515w.
Crystal data: M = 217.20, crystal system: monoclinic, space
group: P21/c, a = 3.870(2), b = 10.917(4), c = 23.019(7) A,
b = 94.18(3)1, V = 969.7(7) A3, Z = 4, crystal size: 0.59 Â
0.13 Â 0.09 mm, rc = 1.487 g cmÀ3, m = 0.112 mm, ymax
=
28.771, reflections: 8490, independent: 2367, Rint = 0.0296,
R1 = 0.0422, wR2 = 0.1053, GoF = 0.966.
(4-Nitrophenyl)(4H-1,2,4-triazole-4-ylamino)methanol (3)
Crystal data: M = 262.20, crystal system: monoclinic, space
group: P21/c, a = 16.286(5), b = 7.007(2), c = 19.746(6) A,
b = 91.24(3)1, V = 2253(1) A3, Z = 8, crystal size: 0.19 Â
Upon standing of the reaction mixture for 4 d at room
temperature, yellow crystals (needles) of (4-nitrophenyl)-
(4H-1,2,4-triazol-4-lamino)methanol were deposited (0.81 g,
69%), mp 145–147 1C. Calculated: C 45.96, H 3.82, N 29.78%;
found: C 46.28, H 3.50, N 30.02%. MS: (m/z) 236.1 [M]+.
0.13 Â 0.10 mm, rc = 1.546 g cmÀ3, m = 0.126 mm, ymax
=
28.751, reflections: 31807, independent: 5577, Rint = 0.0578,
R1 = 0.0488, wR2 = 0.1308, GoF = 0.952.
c
2610 New J. Chem., 2010, 34, 2605–2611 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

View Article Online
(2-Chloro-6-nitrophenyl)(4H-1,2,4–triazole–4-amino)
ymax = 25.061, reflections: 11195, independent: 1985, Rint =
0.0259, R1 = 0.0286, wR2 = 0.0755, GoF = 1.052.
methanol (5)
Upon standing of the reaction mixture for 3 d at room tempera-
ture, yellow crystals (plates) of (2-chloro-6-nitrophenyl)-
References
(4H-1,2,4-triazole-4-ylamino)methanol
were
deposited
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pp. 1281.
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(0.93 g, 69%), mp 148–150 1C. Calculated: C 40.08, H 2.96,
N 25.98%; found: C 40.39, H 2.83, N 26.19%. MS: (m/z) 270.0
[M]+. 1H NMR (500 MHz, DMSO) d 8.28 (s, 2H), 8.03
(d, J = 8.6 Hz, 1H), 7.78 (d, J = 2.3 Hz, 1H), 7.72 (dd,
J = 8.6, 2.4 Hz, 1H), 7.53 (d, J = 7.3 Hz, 1H), 7.24 (d, J =
5.5 Hz, 1H), 6.07–5.91 (m, 1H). 13C NMR (125 MHz,
DMSO): d 82.0, 122.7, 130.0, 130.8, 132.9, 133.6, 143.7,
150.6. IR (KBr, cmÀ1): 3429sh, 3316sh, 3140sh, 3107sh,
2890sh, 2760sh, 1594w, 1530vs, 1442m, 1369s, 1295w,
1272w, 1215w, 1192m, 1087m, 1056s, 979m, 908w, 873m,
802m, 765m, 722m, 631s, 583w, 474w.
Crystal data: M = 269.65, crystal system: monoclinic, space
group: P21/c, a = 12.882(4), b = 8.440(3), c = 21.129(7) A,
b = 100.04(3)1, V = 2262(1) A3, Z = 8, crystal size: 0.18 Â
0.12 Â 0.10 mm, rc = 1.584 g cmÀ3, m = 0.347 mm, ymax
=
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´
12 R. El Mail, M. A. Garralda, R. Hernandez, L. Ibarlucea, E. Pinilla
30.001, reflections: 25378, independent: 6273, Rint = 0.1096,
R1 = 0.0789, wR2 = 0.1660, GoF = 1.103.
(4-Chloro-3-nitrophenyl)(4H-1,2,4-triazole-4-ylamino)
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methanol (6 and 7)
Upon standing of the reaction mixture for 2 weeks at room
temperature, yellow crystals (needles) of (4-chloro-3-nitro-
phenyl)(4H-1,2,4-triazole-4-ylamino)methanol were deposited
(0.85 g, 63%), mp 133–134 1C. Calculated: C 40.08, H 2.96, N
25.98%; found: C 40.14, H 2.88, N 26.06%. MS: (m/z) 270.0
[M]+. 1H NMR (500 MHz, DMSO) d 8.44 (s, 2H), 8.13
(s, 1H), 7.80 (s, 2H), 7.49 (d, J = 6.6 Hz, 1H), 6.98 (d, J =
5.5 Hz, 1H), 5.63 (t, J = 6.0 Hz, 1H). 13C NMR (125 MHz,
DMSO): d 81.9, 123.7, 124.5, 131.4, 132.1, 141.0, 143.8, 147.1.
IR (KBr, cmÀ1): 3141sh, 3085sh, 2979sh, 2868sh, 1693w,
1606m, 1528vs, 1476m, 1449w, 1393m, 1346vs, 1321s,
1285m, 1204w, 1177w, 1124w, 1066vs, 986m, 946s, 893m,
860s, 822m, 754m, 671m, 923vs, 555m.
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24 Kuma KM4CCD,
: Z. Galdecki, D. Kucharczyk; M. Meyer,
Crystal data 6: M = 269.65, crystal system: monoclinic,
space group: P21/n, a = 7.143(2), b = 21.329(6), c = 7.429(2) A,
b = 94.31(3)1, V = 1128.6(5) A3, Z = 4, crystal size: 0.24 Â
A. Kowalski, KM4CCD. A Novel 4-Circle Diffractometer with Large
Area CCD Detector: User’s Manual, Kuma Diffraction Ltd., Wroc"aw,
Poland, 1997; Kuma KM4, : Kuma KM4 Software: User’s Guide, ver
3.1, Kuma Diffraction Ltd., Wroc"aw, Poland, 1989.
25 600 Series Cryostream Cooler: Operation & Instruction Guide ver.
4.2, Oxford Cryosystems, Oxford, UK, 1998.
26 CrysAlis CCD and CrysAlis RED ver. 1.171, Oxford Diffraction
Poland, Wroc"aw, Poland, 1995–2003.
27 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr.,
2008, 64, 112.
0.14 Â 0.12 mm, rc = 1.587 g cmÀ3, m = 0.348 mm, ymax
=
28.641, reflections: 7678, independent: 2699, Rint = 0.0195, R1 =
0.0350, wR2 = 0.0954, GoF = 1.103.
Crystal data 7: M = 269.65, crystal system: monoclinic,
space group: P21/c, a = 12.386(4), b = 10.764(3), c = 8.407(3) A,
b = 93.08(2)1, V = 1119.2(6) A3, Z = 4, crystal size:
0.20 Â 0.15 Â 0.10 mm, rc = 1.600 g cmÀ3, m = 0.351 mm,
28 K. Brandenburg, DIAMOND, Crystal Impact GbR, Bonn, Germany,
2007.
c
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010 New J. Chem., 2010, 34, 2605–2611 2611