Nitropyrazoles : 118. Synthesis and transformations of 5-amino-3,4- dinitropyrazole

Article abstract of DOI:10.1007/s11172-010-0287-9

A method of preparation of 5-amino-3,4-dinitropyrazole (1) from 3(5)-methyl-5(3)-nitro- and 3(5)-methyl-4,5(3)-dinitropyrazoles was developed, the key step of which was the Hofmann rearrengement of nitro- and dinitropyrazolecarboxamides. The protonation o

Full text of DOI:10.1007/s11172-010-0287-9

Russian Chemical Bulletin, International Edition, Vol. 59, No. 8, pp. 1631—1638, August, 2010
1631
Nitropyrazoles
18.* Synthesis and transformations of 5ꢀaminoꢀ3,4ꢀdinitropyrazole
I. L. Dalinger, I. A. Vatsadse, T. K. Shkineva, G. P. Popova, B. I. Ugrak, and S. A. Shevelev
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: dalinger@ioc.ac.ru
A method of preparation of 5ꢀaminoꢀ3,4ꢀdinitropyrazole (1) from 3(5)ꢀmethylꢀ5(3)ꢀnitroꢀ
and 3(5)ꢀmethylꢀ4,5(3)ꢀdinitropyrazoles was developed, the key step of which was the Hofmann
rearrengement of nitroꢀ and dinitropyrazolecarboxamides. The protonation of 5ꢀaminoꢀ
3,4ꢀdinitropyrazole was studied by spectral methods (UV spectroscopy, NMR spectroscopy).
In spite of low basicity of the amino group, compound 1 undergoes Nꢀarylation, Nꢀnitration,
and annulation reactions with formation of dinitropyrazolo[5,1ꢀa]pyrimidine derivatives and
hitherto unknown dinitroimidazo[1,2ꢀb]pyrazole derivatives. Diazotization of 1 leads to
5ꢀdiazoꢀ3,4ꢀdinitropyrazole (19), which exists in the form of the internal salt. Some reactions
of this compound were studied and the formation of the corresponding 5ꢀhalogeno(azido)ꢀ
3,4ꢀdinitropyrazoles under the action of the halide and azide ion was shown. Dinitropyrazoloꢀ
[5,1ꢀc][1,2,4]triazine and 7ꢀhydroxydinitroꢀ4,7ꢀdihydropyrazolo[5,1ꢀc][1,2,4]triazine derivaꢀ
tives were obtained by the action of active methylene compounds on the betaine 19.
Key words: pyrazole, dinitropyrazole, 5ꢀaminoꢀ3,4ꢀdinitropyrazole, 5ꢀdiazoꢀ3,4ꢀdinitroꢀ
pyrazole, the Hofmann rearrangement, Nꢀarylation, Nꢀnitration, annulation, imidazo[1,2ꢀb]ꢀ
pyrazole, pyrazolo[5,1ꢀa]pyrimidine, diazotization, active methylene compounds, pyrazoloꢀ
[5,1ꢀc][1,2,4]triazine, dihydropyrazolo[5,1ꢀc][1,2,4]triazine.
Earlier,2 we have reported on the preparation and some
properties of 5ꢀaminoꢀ3,4ꢀdinitropyrazole (1), which is
an important intermediate in the synthesis of pyrazole
nitro derivatives, however, experimental details have not
been given. Recently,3 we have published the synthesis
of pyrazole 1 based on the transformation of the product
of cineꢀsubstitution of an Nꢀnitro group in 1,3,4ꢀtrinitroꢀ
pyrazole by the azide ion, viz., 5ꢀazidoꢀ3,4ꢀdinitroꢀ
pyrazole. An alternative method for the synthesis of
pyrazole 1 and results of detailed study on its properties
and reactions are reported in the present study.
In our opinion, aminodinitropyrazole 1 can be obꢀ
tained using the developed earlier method for the syntheꢀ
sis of aminodinitropyrazoles4,5 the key step of which is
the Hofmann rearrangement of the corresponding nitroꢀ
pyrazolecarboxamides. Let us consider in detail the
method of synthesis based on the use of commercially
available 3ꢀmethylꢀ5ꢀnitropyrazole 2а (Scheme 1). Oxiꢀ
dation of the methyl group in pyrazole 2а smoothly proꢀ
ceeds under the action of sodium dichromate in concenꢀ
trated sulfuric acid at elevated temperature to afford
3ꢀnitropyrazoleꢀ5ꢀcarboxylic acid 3а in high yield. This
method of oxidation of the methyl group is general and
makes it possible to synthesize also 4ꢀhalogenoꢀsubstiꢀ
tuted nitropyrazolecarboxylic acids 3b,c obtained earlier
by other procedures, viz., by nitration of the correspondꢀ
ing 4ꢀhalogenopyrazoleꢀ3ꢀcarboxylic acids in oleum.6
It should be noted that nitropyrazolecarboxylic acids
3а—с are important intermediates for the synthesis, thereꢀ
from, of a number of compounds with various biological
activities.7,8 We developed a method of reduction of the
nitro group with hydrazine in water in the presence of
the Raney nickel resulting for the first time in amino acids
(4a,b) nonsubstituted at the nitrogen atom of the ring.
The classical methods of reduction using hydrazine in
ethanol do not lead to the desired product because of low
solubility of hydrazinium salts of compound 3 in ethanol.
The method of catalytic reduction over the Raney nickel
or Pd/C in various organic solvents is also inapplicable
because amines that formed are not soluble in the solvents
pointed and are adsorbed on the catalyst that leads to
considerable decrease in its activity.
Carboxylic acid 3а smoothly undergoes esterification
with methanol in the presence of thionyl chloride to give
methyl ester 5, which gives amide 6 in high yield under
the action of aqueous ammonia.
We studied the Hofmann rearrangement of amide 6.
It was found that upon the reaction in water a mixture of
* For Part 17, see Ref. 1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1589—1595, August, 2010.
1066ꢀ5285/10/5908ꢀ1631 © 2010 Springer Science+Business Media, Inc.

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Dalinger et al.
Yet another possible version of the synthesis of pyrazole
1 can be based on methylpyrazole containing two nitro
groups in the ring, viz., 3,4ꢀdinitroꢀ5ꢀmethylpyrazole
(9),10 as the starting compound (Scheme 2).
Scheme 1
Scheme 2
i. 1) KOH, KMnO4, 60 °C, 8 h, 2) H2SO4; ii. SOCl2, MeOH, Δ, 8 h;
iii. NH3•H2O, 25 °C, 8 h; iv. 1) NaOH, Br2, 50 °C, 2 h, 2) HCl.
In fact, we found that dinitropyrazole 9 can be
smoothly oxidized with potassium permanganate in water
to form dinitro acid 10. We synthesized the corresponding
dinitro ester 11 and amide 12 using the same procedures
as for mononitro ester 5 and amide 6. It turned out that
dinitro amide 12 is more appropriate compound for the
synthesis of the target aminopyrazole 1, since, in contrast
to mononitro amide 6, in this case the Hofmann rearꢀ
rangement proceeds in water with formation of aminoꢀ
pyrazole 1 in high yield and the alternative path via interꢀ
mediate dinitro carbamate 8 is not required.
X = H (a), Cl (b), Br (c)
i. Na2CrO7/H2SO4, 60 °C, 8 h; ii. SOCl2, MeOH, Δ, 8 h;
iii. N2H4/H2O, Ni Raney, 60 °C, 8 h; iv. NH3•H2O, 25 °C, 8 h;
v. 1) KOH, Br2, 1 h, 2) HCl; vi. H2SO4/HNO3, 25 °C, 2 h;
vii. 1) KOH/H2O, 60 °C, 8 h, 2) H2SO4.
Thus, we developed the general procedure for the
synthesis of aminonitroꢀ and aminodinitropyrazoles (see
also Refs 4, 5, 11), the key step of which is the Hofmann
rearrangement of nitroꢀ and dinitropyrazolecaboxamides.
The structures of all compounds mentioned were
established by IR and NMR spectroscopy and confirmed
by data from mass spectrometry and elemental analysis.
The presence of hydrogenꢀcontaining substituents folꢀ
compounds formed containing no 3(5)ꢀaminoꢀ5(3)ꢀ
nitropyrazole. Under milder conditions (in methanol,
at –30 °C), the formation of the carbamate group was
accompanied by simultaneous bromination at the free
position 4 of the pyrazole ring. Bromonitrocarbamate 7
undergoes nitrodebromination with a sulfuricꢀnitric acid
nitrating mixture under mild conditions with formation
of 3,4ꢀdinitrocarbamate 8 in moderate yield. The removal
of the methoxycarbonyl group was carried out by alkaline
hydrolysis using the procedure that was employed by us
for the synthesis of 4ꢀaminoꢀ3,5ꢀdinitropyrazole,9 which
is isomeric to dinitropyrazole 1.
1
lowed from the Н NMR spectra, whereas the structures
of nitrogenꢀcarbon framework were determined based on
the chemical shifts in the 13С, 14(15)N NMR spectra and
13С—1Н and 15N—1H coupling constants through differꢀ
ent number of bonds. The presence of one or several nitro
groups in the molecule leads to broadening of the signals

Properties of 5ꢀaminoꢀ3,4ꢀdinitropyrazoles
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1633
for carbon atoms bound to the nitro group in the 13С NMR
spectra due to the quadrupole effect of the 14N atom of
the nitro group. Therefore, the 13С NMR spectra were
recorded under the conditions of heteronuclear triple resoꢀ
nance 13С{1H,14N}, viz., the observation of 13С nuclei at
the broadband decoupling with 1Н and the selective
decoupling with 14N nuclei of the nitro groups.12,13 It
allowed us to observe a narrow signal for the carbon atom
C—NO2, longꢀrange 13С—1Н coupling constants and,
generally, to correlate the signal for the nitro group in the
14(15)N NMR spectrum with the signals for the carbon
atoms in the 13С NMR spectrum.
Scheme 3
Let us consider in detail the elucidation of the strucꢀ
ture of compound 1. Only one signal for the carbon atom
assigned to that bound to the NH2 group is observed at
δ 148.72 in the standard 13С NMR spectrum. The 13С{1H,14N}
NMR spectrum contained additionally two signals for the
carbon atoms bound to the NO2 groups at δ 150.21 and
109.08. It is known14,15 that in the 13С NMR spectra of
3(5),4ꢀdinitropyrazoles the order of the signals for carbon
atoms (C—NO2) is as follows: C(3) > C(5) > C(4). Therefore,
one can suppose that pyrazole 1 exists, at least in the soluꢀ
tion, mainly in the form of 5ꢀaminoꢀ3,4ꢀdinitropyrazole.
The protonation site of pyrazole 1 was established
using 15N NMR spectroscopy. Five signals at δ –22.05
(C(4)NO2), –23.30 (C(3)NO2), –108.32 (N(2)), –210.37
(N(1)), and –315.96 (t, NH2, J = 91.9 Hz) were observed
in the 15N NMR spectrum of compound 1. The signals
for the N(2) atom displaced to the greatest degree (by
84 ppm) upon addition of concentrated sulfuric acid
(δ –192.64, —193.25 (N(1), N(2))). This is evidence
of the protonation of the pyrazole ring, as in the case of
other 3(5)ꢀaminopyrazoles,16 rather than the amino group,
despite the presence of two nitro groups in the ring.
The acidity and basicity constants of pyrazole 1 in
water at 20 °C were determined spectrophotometrically.
The values obtained (рКа = 6.34, рКВН+ = –7.12) indicate
that pyrazole 1 as the NH acid is similar to carbonic acid
(рКа = 6.35) and, despite the presence of the amino
grou1p, is extremely weak base similar to 3,4ꢀdinitroꢀ
pyrazole (рКВН+ = –8.06). Since protonation of pyrazole
1 proceeds at the nitrogen atom of the ring, the "intrinsic"
basicity of the amino group is even lower in this comꢀ
pound.
R = Me (15,18), Ph (16), H (17)
i. HNO3/Ac2O, 0 °C, 2 h; ii. LiOMe/MeOH, picryl chloride,
25 °C, 2 h; iii. NaOH/DMF, BrCH2COR, Δ, 2—4 h;
iv. MeCO2H, CH2(COR)2, Δ, 8 h.
Arylation of the lithium salt of pyrazole 1 with picryl
chloride affords 5ꢀaminoꢀ3,4ꢀdinitroꢀ1ꢀpicrylpyrazole (14).
The presence of a vicinal NH fragment and the NH2
group in pyrazole 1 allows annulation of heterocycles.
Thus reaction of compound 1 with αꢀbromo ketones in
an alkaline medium results in hitherto unknown imidazoꢀ
[1,2ꢀb]pyrazole dinitroderivatives 15 and 16. Dinitroꢀ
pyrazole 1 also smoothly reacts with the simplest
βꢀdicarbonyl compounds, viz., malonaldehyde acetal and
acetylacetone, under conditions of acid catalysis to yield
pyrazole[5,1ꢀa]pyrimidine dinitroderivatives 17 and 18.
We succeeded in diazotization of aminodinitropyrazole
1 without application of special procedures despite low
basicity of the amino group. As in the case of 4ꢀaminoꢀ
3,5ꢀdinitropyrazole,9 which is isomeric to compound 1,
the corresponding diazodinitropyrazole 19 is formed as a
result of the treatment of pyrazole 1 with sodium nitrite in
20% H2SO4 at 0—5 °C; it occurs in the form of betaine
(Scheme 4). This is a quite stable compound, its decomꢀ
position begins at 110 °C.
Despite the reduced basicity of the amino group,
aminodinitropyrazole 1 smoothly undergoes nitration
under the action of acetyl nitrate in trifluoroacetic acid to
produce nitramine 13 (Scheme 3). This fact follows from
the 15N NMR spectrum: the signals at δ –40.57 and
–207.82 corresponding to the NН—NO2 fragment are
observed. Similar direction of the reaction toward the
nitration of the amino group has already been observed by
us in the case of nitration of 3(5)ꢀaminoꢀ4ꢀnitropyrazole.
Apparently, this is determined by the protonation of the
nitrogen ring atom of compound 1.5
Reactions of diazopyrazole 19 with nucleophiles, viz.,
the halide and azide ions and some carbanions, were studꢀ
ied by us in detail. Diazopyrazole 19 reacts with nucleoꢀ
philes in a conventional manner, viz., either azocoupling

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Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
Dalinger et al.
Scheme 4
R = Br (20), N3 (21), Cl (22)
i. 20% H2SO4/NaNO2, 0—5 °C, 2 h; ii. 20: 40% HBr/KBr, 0—5 °C, 1 h, 25 °C, 7 h; 21: NaN3/H2O, 0—5 °C, 1 h; 22: HCl/CuCl,
0—5 °C, 1 h, 25 °C, 7 h; iii. 1) NaCH(COMe)2/H2O, 25 °C, 10 h, 2) H2SO4; iv. 1) NaCH(CO2Et)COMe/H2O, 25 °C, 10 h,
2) H2SO4; v. NaC(CHO)2NO2/H2O, 25 °C, 10 h, 2) H2SO4; vi. 1) NaCH(CN)NO2/H2O, 25 °C, 2 h, 2) H2SO4.
Kratos MSꢀ30 and Finnigan MAT INCOS 50 mass spectrometers
or nucleophilic substitution of the diazo group takes place.
(direct sample inlet, electron impact, ionization energy of 70 eV).
Thus the corresponding dinitropyrazoles 20 and 21 are
The reaction course and purity of synthesized compounds were
formed under the action of the bromide and azide ions. In
monitored by TLC on Silufol UVꢀ254. Elemental analysis was
the case of the chloride ion, addition of CuCl is required
for the substitution of the diazo group (see Scheme 4).
carried out on a Perkin Elmer Series II 2400 instrument.
5ꢀAminoꢀ3,4ꢀdinitropyrazole (1). A. Carbamate 8 (10 g,
0.043 mol) was added to a solution of KOH (7.23 g, 0.13 mol)
Azocoupling of diazopyrazole 19 with active methylꢀ
ene carbonyl compounds resulted in dinitropyrazoloꢀ
[5,1ꢀc][1,2,4]triazines 23—27 (see Scheme 4). The forꢀ
mation of compounds 24 and 25 corresponding to two
directions of cyclization is observed. It should be noted
that under the reaction conditions aromatization of the
ring occurs not in all cases, which follows from the presꢀ
ence of the signals for both the ОН (δ 6.8—8.0), and NH
groups (δ 12—13) in the 1Н NMR spectrum. Mass spectra
shows intensive peaks of the ions [M+ – H2O] of the
corresponding aromatization products of compounds 23,
24, and 26.
in Н2О (100 mL). The reaction mixture was stirred for 7 h at
60—70 °C, cooled to ~20 °C, and acidified with 20% H2SO4 to
рН 2—3. It was extracted with ethyl acetate (3×50 mL), the
extract was dried with MgSO4, and the solvent was removed
in vacuo. The product was recrystallized from Н2О. The yield
was 5 g(67%).
B. Bromine (3.1 mL, 0.06 mol) was added dropwise to a
solution of NaOH (12 g, 0.3 mol) in Н2О (100 mL) at 0—5 °C,
then amide 12 (10 g, 0.05 mol) was added portionwise and the
reaction mixture was stirred for 40 min at 0—5 °C. Then it was
heated to 55—60 °C and kept for 2 h, cooled to 10 °C and
acidified with concentrated HCl to рН 2—3. The precipitate
that formed was filtered off, washed with water, and recrystallized
from Н2О. The yield was 5.4 g (62%). M.p. 197—199 °С (with
decomp.) (cf. Ref. 3). 13С NMR ((CD3)2CO) (cf. Ref. 3), δ:
109.80 (t, C(4), J = 4 Hz); 148.65 (C(5)); 150.21 (C(3)).
15N NMR ((CD3)2CO) (cf. Ref. 3), δ: –315.96 (t, NH2,
J = 91.9 Hz); –210.37 (N(1)); –108.32 (N(2)); –23.30 (С(3)NO2);
–22.05 (С(4)NO2). 15N NMR (H2SO4 (75%) + (CD3)2SO
(25%)), δ: –322.48 (NH2); –193.25, –192.64 (N(1), N(2));
–38.22 (С(3)NO2); –29.87 (С(4)NO2). UV, λ/nm (ε): H2O 356
(6290); NaOH 409 (5900); H2SO4 332 (2992).
Experimental
1Н and 13C NMR spectra were recorded on Bruker ACꢀ200,
Bruker WMꢀ250, Bruker ACꢀ300, and Bruker DRXꢀ500 instruꢀ
ments at 295 K (if other temperature is not pointed). The 1H and
13C chemical shifts are referred to SiMe4, the chemical shifts of
15N are referred to MeNO2, highꢀfield chemical shifts are given
with the minus sign. IR spectra were measured on a Specord Mꢀ80
instrument in KBr pellets, UV spectra were recorded on a
Specord UV—Vis instrument, mass spectra were obtained on
3ꢀNitropyrazoleꢀ5ꢀcarboxylic acids 3 (general procedure).
Nitropyrazole 2 (0.18 mol) was dissolved in concentrated H2SO4

Properties of 5ꢀaminoꢀ3,4ꢀdinitropyrazoles
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1635
(300 mL) and Na2Cr2O7•2H2O (53 g, 0.27 mol) was added
dropwise to this solution, temperature being maintained at
60—65 °C. The reaction mixture was kept at this temperature
for 8 h, poured into ice (1 kg), extracted with ethyl acetate
(3×250 mL). The organic layer was washed with water, dried
with MgSO4, the solvent was removed in vacuo, and the residue
was recrystallized from Н2О.
3ꢀNitropyrazoleꢀ5ꢀcarboxylic acid (3а). The yield was 25 g
(88%), m.p. 174—175 °С. Found (%): C, 30.88; H, 2.09;
N, 26.86. C4H3N3O4. Calculated (%): C, 30.58; H, 1.92; N, 26.75.
1Н NMR ((CD3)2SO), δ: 14.6 (br.s, 1 H, OH); 10.6 (br.s, 1 H,
NH); 7.25 (s, 1 H, H(4)). 13С NMR ((CD3)2SO), δ: 159.3 (CO);
156.2 (C(3)); 137.4 (C(5)); 104.5 (d, C(4), J = 188.97 Hz).
14N NMR ((CD3)2SO), δ: –19.54 (С(3)NO2). IR, ν/cm–1: 1696
(СО); 1536, 1336 (NO2). MS, m/z: 157 [M]+.
4ꢀChloroꢀ3ꢀnitropyrazoleꢀ5ꢀcarboxylic acid (3b). The yield
was 22.41 g (65%), m.p. 189—190 °С. Found (%): C, 25.24;
H, 1.10; Cl, 18.63; N, 22.05. C4H2ClN3O4. Calculated (%):
C, 25.08; H, 1.05; Cl, 18.51; N, 21.94. 13С NMR ((CD3)2SO),
δ: 158.52 (CO); 151.28 (C(3)); 134.61 (C(5)); 107.81 (C(4)).
IR, ν/cm–1: 1725 (CO); 1536, 1340 (NO2). MS, m/z: 193, 191
(1 : 3) [M]+.
4ꢀBromoꢀ3ꢀnitropyrazoleꢀ5ꢀcarboxylic acid (3с). The yield
was 24.21 g (57%), m.p. 201—202 °С. Found (%): C, 20.55;
H, 1.03; Br, 33.92; N, 17.97. C4H2BrN3O4. Calculated (%):
C, 20.36; H, 0.85; Br, 33.86; N, 17.81. 13С NMR ((CD3)2SO),
δ: 158.67 (CO); 153.17 (C(3)); 136.14 (C(5)); 92.29 (C(4)).
IR, ν/cm–1: 1708 (СО); 1560, 1296 (NO2). MS, m/z: 235, 237
(1 : 1) [M]+.
3ꢀAminopyrazoleꢀ5ꢀcarboxylic acids 4 (general procedure).
Hydrazine hydrate (10 g, 0.2 mol) was added to a solution of
nitro acid 3a,b (0.08 mol) in Н2О (200 mL), the solution was
heated to 60 °C, and freshly prepared Raney Ni was slowly
added over 3 h. The reaction mixture was kept at this temperature
for 3 h, then cooled, the solids were filtered off, and the solution
was acidified with conc. HCl to pH 4. The precipitate that
formed was filtered off, recrystallized from water, and dried at
100 °C for 4 h.
3ꢀAminopyrazoleꢀ5ꢀcarboxylic acid (4а). The yield was 7.6 g
(75%), m.p. 245—246 °С. Found (%): C, 38.00; H, 4.05; N,
33.23 C4H5N3O2. Calculated (%): C, 37.80; H, 3.97; N, 33.06.
13С NMR ((CD3)2SO) , δ: 162.15 (CO); 152.80; 138.29; 92.30.
IR, ν/cm–1: 1690 (СО); 1535, 1329 (NO2). MS, m/z: 127 [M]+.
3ꢀAminoꢀ4ꢀchloropyrazoleꢀ5ꢀcarboxylic acid (4b). The yield
was 8.43 g (55%), m.p. 287—288 °С. Found (%): C, 30.09;
H, 2.71; Cl, 22.25; N, 26.12. C4H4ClN3O2. Calculated (%):
C, 29.74; H, 2.50; Cl, 21.95; N, 26.01. 13С NMR ((CD3)2SO),
δ: 160.92 (CO); 151.22; 132.33; 95.45. IR, ν/cm–1: 1708 (СО);
1560, 1296 (NO2); 840 (ССl). MS, m/z: 163, 161 (1 : 3) [M]+.
Methyl nitropyrazoleꢀ5ꢀcarboxylates (general procedure).
Acid 4а (10) (0.10 mol) was dissolved in МеОН (100 mL) and
SOCl2 (8 mL, 0.11 mol) was added dropwise. The reaction
mixture was refluxed for 3 h, the solvent was removed in vacuo
and the products were used without additional purification for
subsequent tranformations.
(d, C(3), J = 5.1 Hz); 135.65 (d, C(5), J = 5.8 Hz); 104.47 (d,
C(4), J = 189.64 Hz); 52.48 (q, Me, J = 148.25 Hz). 14N NMR
((CD3)2SO), δ: –22.90 (С(3)NO2). IR, ν/cm–1: 1712 (СО);
1532, 1344 (NO2); 1232 (СООМе). MS, m/z: 171 [M]+.
Methyl 3,4ꢀdinitropyrazoleꢀ5ꢀcarboxylate (11). The yield was
19.66 g (91%), m.p. 59—60°С (Н2О). Found (%): C, 26.43; H,
2.57; N, 24.46. C5H4N4O6•0.5 Н2О. Calculated (%): C, 26.68;
H, 2.24; N, 24.89. 1Н NMR ((CD3)2СO), δ: 4.32 (s, 3 H, Me).
13С NMR ((CD3)2SO), δ: 156.24 (CO); 145.73 (C(3)); 130.34
(C(5)); 127.8 (C(4)), 53.48 (СН3). IR, ν/cm–1: 1720 (СО);
1525, 1328 (NO2). MS, m/z: 216 [M]+.
Nitropyrazoleꢀ5ꢀcarboxamides (general procedure). Ester 5
(11) (0.08 mol) was added to 25% aqueous ammonia (200 mL)
at 20 °C, the reaction mixture was stirred until complete
dissolution and kept for 24 h. The solvent was removed in vacuo,
the residue was suspended in Н2О (20 mL) and acidified with
20% H2SO4 to рН ~1. The suspension was stirred for an addiꢀ
tional 30 min, the precipitate was filtered off, washed with Н2О,
and dried in air.
3ꢀNitropyrazoleꢀ5ꢀcarboxamide (6). The yield was 10.61 g
(85%), m.p. 244 °С (Н2О). Found (%): C, 31.11; H, 2.84;
N, 36.02. C4H4N4O3. Calculated (%): C, 30.78; H, 2.58;
N, 35.86. 1Н NMR ((CD3)2SO), δ: 14.66 (br.s, 1 H, NH); 8.16
(s, 1 Н), 7.75 (s, 1 H, СОNH2); 7.56 (s, 1 H, H(4)). 13С NMR
((CD3)2SO), δ: 158.97 (CO); 155.86 (C(3)); 139.54 (C(5));
101.84 (d, C(4), J = 188.0 Hz). IR, ν/cm–1: 1690, 1672 (СО);
1525, 1350 (NO2). MS, m/z: 156 [M]+.
3,4ꢀDinitropyrazoleꢀ5ꢀcarboxamide (12). The yield was 14.47 g
(90%), m.p. 187—188 °С (EtOH). Found (%): C, 24.10;
H, 1.55; N, 34.90. C4H3N5O5. Calculated (%): C, 23.89;
H, 1.50; N, 34.83. 1Н NMR ((CD3)2SO), δ: 8.35 (br.s, 2 Н,
СОNH2). 13С NMR ((CD3)2SO), δ: 157.5 (CO); 147.3 (C(3));
137.5 (C(5)); 129.4 (C(4)). IR, ν/cm–1: 1690, 1672 (СО); 1535,
1340 (NO2). MS, m/z: 201 [M]+.
Methyl Nꢀ(4ꢀbromoꢀ3ꢀnitropyrazolꢀ5ꢀyl)carbamate (7).
Bromine (1.3 mL, 0.025 mol) was added dropwise to a solution
of KOH (5.25 g, 0.094 mol) in MeOH (50 mL) at –30 °C, then
amide 6 (2.1 g, 0.013 mol) was added portionwise, and the
mixture was stirred for 30 min at this temperature. Then it was
heated to 55 °C and kept for 1 h, cooled to ~20 °C, the solvent
was removed in vacuo, the residue was suspended in Н2О (15 mL)
and acidified with conc. HCl to рН ~3. The precipitate that
formed was filtered off, washed with Н2О, and dried in air. The
yield was 1.2 g (35%), m.p. 201 °С (MeOH). Found (%):
C, 22.90; H, 2.06; Br, 30.37; N, 21.36. C5H5BrN4O4. Calculꢀ
ated (%): C, 22.66; H, 1.90; Br, 30.15; N, 21.14. 1Н NMR
((CD3)2SO), δ: 14.0 (br.s, 1 H, NH); 9.5 (br.s, 1 Н, СОNH);
3.75 (s, 3 H, Me). 13С NMR ((CD3)2SO), δ: 154.25 (CO);
151.30 (C(3)); 138.81 (C(5)); 83.52 (C(4)); 52.69 (q, Me,
J = 147.65 Hz). IR, ν/cm–1: 1690 (CO); 1525, 1328 (NO2);
1208 (COOMe). MS, m/z: 264, 266 (1 : 1) [M]+.
Methyl Nꢀ(3,4ꢀdinitropyrazolꢀ5ꢀyl)carbamate (8). Nitric acid
(d = 1.5 g cm–3) (2 mL, 0.048 mol) was added to a solution of
carbamate 7 (2 g, 7.5 mmol) in 92.5% H2SO4 (d = 1.826 g cm–3
)
(15 mL, 0.24 mol) at 25—35 °C, and the mixture was stirred for
2 h at this temperature, then it was poured onto ice (60 g). The
precipitate that formed was filtered off, washed with water, and
dried in air. The yield was 1.2 g (69%), m.p. 188—190 °С (EtOH).
Found (%): C, 26.30; H, 2.26; N, 30.58. C5H5N5O6. Calculꢀ
ated (%): C, 25.98; H, 2.18; N, 30.30. 1Н NMR ((CD3)2SO), δ:
3.76 (s, 3 H, Me). 13С NMR ((CD3)2SO), δ: 153.35 (CO);
Methyl 3ꢀnitropyrazoleꢀ5ꢀcarboxylate (5). The yield was
16.42 g (96%), m.p. 135—136 °С (Н2О) (cf. Ref. 8: m.p. 138 °С).
Found (%): C, 35.21; H, 3.04; N, 24.77. C5H5N3O4. Calculꢀ
ated (%): C, 35.10; H, 2.95; N, 24.56. 1Н NMR ((CD3)2SO), δ:
14.83 (br.s, 1 H, NH); 7.35 (s, 1 H, H(4)); 3.88 (s, 3 H, Me).
13С NMR ((CD3)2SO), δ: 158.28 (q, CO, J = 4.2 Hz); 155.82

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Dalinger et al.
150.30 (C(3)); 149.25 (С(5); 130.20 (C(4)); 52.51 (q, Me,
J = 150.1 Hz). IR, ν/cm–1: 1700 (CO); 1560, 1360 (NO2); 1232
(COOMe). MS, m/z: 231 [M]+.
ated (%): C, 34.13; H, 2.39; N, 33.17. 1Н NMR ((CD3)2SO), δ:
12.40 (br.s, 1 H, NH); 7.58 (s, 1 H, H(3)); 2.48 (s, 3 Н, Me).
13С NMR ((CD3)2SO), δ: 150.10; 134.44; 122.22 (d, J = 200 Hz);
110.40 (dq, J = 11.4 Hz, J = 6.7 Hz); 106.96; 10.16 (q, Me,
J = 131.2 Hz). IR, ν/cm–1: 1516, 1344 (NO2). MS, m/z:
211 [M]+.
6,7ꢀDinitroꢀ2ꢀphenylimidazo[1,2ꢀb]pyrazole (16). The
yield was 1.61 g (59%), decomp. temp. 224 °С (DMF—Н2О).
Found (%): C, 48.60; H, 2.66; N, 25.95. C11H7N5O4. Calculꢀ
ated (%): C, 48.36; H, 2.58; N, 25.63. 1Н NMR ((CD3)2SO), δ:
13.85 (br.s, 1 H, NH); 8.58 (s, 1 H, H(3)); 7.90 (m, 2 Н, НPh);
7.48 (m, 3 H, НPh). 13С NMR ((CD3)2SO), δ: 150.14; 135.91;
135.00; 129.20 (d, J = 162.3 Hz); 128.84 (d, J = 161.3 Hz);
127.64; 125.96 (d, J = 160.6 Hz); 110.52; 106.73 (d, J = 205.3 Hz).
IR, ν/cm–1: 1520, 1340 (NO2). MS, m/z: 273 [M]+.
Dinitropyrazolo[1,5ꢀа]pyrimidines (general procedure).
Malonaldehyde bis(dimethyl acetal) or acetylacetone (3 mmol)
was added to a suspension of pyrazole 1 (3 mmol) in 2 М HCl (6 mL)
at 50—60 °С. The reaction mixture was kept at this temperature
for 1 h, then it was cooled to ~25 °C. the precipitate that formed
was filtered off, washed with Н2О, and dried over P2O5.
2,3ꢀDinitropyrazolo[1,5ꢀа]pyrimidine (17). The yield was
0.53 g (91%), m.p. 146 °С (МеОН). Found (%): C, 34.80;
H, 1.53; N, 33.71. C6H3N5O4. Calculated (%): C, 34.46;
H, 1.45; N, 33.49. 1Н NMR ((CD3)2SO), δ: 9.32 (dd, 1 H,
H(7), J = 7.1 Hz, J = 1.7 Hz); 9.21 (dd, 1 H, H(5), J = 4.3 Hz,
J = 1.7 Hz); 7.80 (dd, 1 H, H(6), J = 7.1 Hz, J = 4.3 Hz).
13С NMR ((CD3)2SO), δ: 159.09 (ddd, C(5), J = 185.6 Hz,
J = 6.0 Hz, J = 2.5 Hz); 153.42 (C(2)); 143.52 (C(3a)); 139.20
(ddd, C(7), J = 197.0 Hz, J = 4.5 Hz, J = 6.0 Hz); 115.81 (ddd,
C(6), J = 177.2 Hz, J = 9.4 Hz, J = 2.7 Hz); 113.40 (C(3)).
14N NMR ((CD3)2SO), δ: –25.5, –28.2 (С(2)NO2, С(3)NO2).
IR, ν/cm–1: 1520, 1350 (NO2). MS, m/z: 209 [M]+.
3,4ꢀDinitropyrazoleꢀ5ꢀcarboxylic acid (10). 3,4ꢀDinitroꢀ
5ꢀmethylpyrazole 9 (51.6 g, 0.3 mol) was added to a solution of
KOH (16.8 g, 0.3 mol) in Н2О (850 mL), the mixture obtained
was heated to 60 °C, KMnO4 (124 g, 0.78 mol) was added
portionwise at this temperature. Then the reaction mixture was
kept for an additional 5 h at 60 °C, cooled, acidified with 20%
H2SO4 to рН 2—3, extracted with ethyl acetate (4×100 mL). The
organic layer was dried with MgSO4, the solvent was removed
in vacuo, and the residue was recrystallized from 50% aqueous
ethanol. The yield was 47.3 g (78%), m.p. 194 °С (with decomp.).
Found (%): C, 23.64; H, 1.12; N, 27.81. C4H2N4O6. Calculꢀ
ated (%): C, 23.77; H, 1.00; N, 27.72. 13С NMR (CD3CN), δ:
155.20 (CO2H); 148.0 (C(3)); 130.10 (C(5)); 128.0 (C(4)).
IR, ν/cm–1: 3150 (NH); 1725 (CO); 1572, 1339 (NO2).
MS, m/z: 202 [M]+.
5ꢀNitraminoꢀ3,4ꢀdinitropyrazole (13). Nitric acid (d =
= 1.5 g cm–3) (3.3 mL, 0.08 mol) was added dropwise to a
suspension of compound 1 (0.79 g, 0.005 mol) in CF3CO2H
(5 mL) at 0 °C. Ас2О (1 mL, 0.01 mol) was added to the solution
that formed, this mixture was stirred for 2 h at 0—2 °C. The
precipitate that formed was filtered off, washed with water, and
dried in air. The yield was 0.7 g (69%), decomp. temp. 123 °С.
Found (%): C, 16.68; H, 1.10; N, 38.69. C3H2N6O6. Calculꢀ
ated (%): C, 16.52; H, 0.92; N, 38.54. 13С NMR ((CD3)2SO),
δ: 149.23 (C(3)); 135.03 (C(5)); 117.42 (C(4)). 15N NMR
((CD3)2SO), δ: –207.82, –187.42 (N(1)), NH—NO2); –40.57
(N—NO2); –27.37 (С(3)NO2, С(4)NO2). IR, ν/cm–1: 3152,
3132, 2940 (NH); 1560, 1376, 1344 (NO2). MS, m/z: 218 [M]+.
5ꢀAminoꢀ3,4ꢀdinitroꢀ1ꢀ(2,4,6ꢀtrinitrophenyl)pyrazole (14).
A solution of LiOMe in MeOH (1 М, 2.9 mL) and picryl chloride
(0.79 g, 3 mmol) were added to a solution of pyrazole 1 (0.5 g,
2.9 mmol) in МеОН (30 mL), the mixture obtained was kept for
24 h at ~20 °C. The organic solvent was removed in vacuo, the
residue was crystallized from 50% aqueous ethanol. The yield
was 0.8 g (72%), m.p. 168—169 °С. Found (%): C, 28.40;
H, 1.13; N, 29.34. C9H4N8O10. Calculated (%): C, 28.14;
H, 1.05; N, 29.17. 1Н NMR ((CD3)2CO), δ: 9.47 (s, 2 H, Н(3´),
H(5´)); 8.11 (br.s, 2 H, NH2). 13С ((CD3)2CO), δ: 151.88 (C(3));
150.40 (C(2´), C(6´)); 150.20 (C(4´)); 148.88 (C(5)); 127.52
(t, C(1´), J = 7.0 Hz); 126.40 (dd, (С(3´), C(5´), J = 160.0 Hz,
J = 5.0 Hz); 109.70 (t, C(4), J = 3.5 Hz). 15N NMR ((CD3)2CO),
δ: –312.43 (t, NH2, J = 93.2 Hz); –227.46 (N(1)); –109.47
(N(2)); –26.01, –25.0 (С(3)NO2, С(4)NO2); –23.07, –22.25
((NO2)Pic). IR, ν/cm–1: 3160, 3128 (NH); 1530, 1376, 1350
(NO2). MS, m/z: 384 [M]+.
5,7ꢀDimethylꢀ2,3ꢀdinitropyrazolo[1,5ꢀа]pyrimidine (18).
The yield was 0.42 g (63%), m.p. 138 °С (МеОН). Found (%):
C, 40.72; H, 3.09; N, 29.67. C8H7N5O4. Calculated (%):
1
C, 40.51; H, 2.97; N, 29.53. Н NMR ((CD3)2SO), δ: 7.53 (q,
1 H, H(6), J = 1.0 Hz); 2.85 (d, 3 H, C(7)Me, J = 1.0 Hz); 2.76
(s, 3 H, C(5)Me). 13С NMR ((CD3)2SO), δ: 169.59 (dq, C(5), J
= 2.2 Hz, J = 6.7 Hz); 153.14 (C(2)); 149.60 (dq, C(7),
J = 3.3 Hz, J = 6.6 Hz); 143.23 (C(3a)); 115.90 (dqq, C(6),
J = 172.0 Hz, J = 3.4 Hz, J = 3.4 Hz); 113.60 (C(3)); 25.39 (q,
C(5)CH3, J = 129.3 Hz); 16.45 (q.d, C(7)CH3, J = 131.2 Hz,
J = 3.2 Hz). 15N NMR ((CD3)2SO), δ: –168.10 (qd, N(8),
J = 4.7 Hz, J = 2.5 Hz); –122.80 (N(1)); –110.17 (q, N(4),
J = 3.2 Hz); –26.89 (С(3)NO2); –23.72 (С(2)NO2). IR, ν/cm–1
:
1520, 1350 (NO2). MS, m/z: 237 [M]+.
5ꢀDiazoꢀ3,4ꢀdinitropyrazole (19). A solution of NaNO2
(0.6 g, 9 mmol) in ice water (2 mL) was added dropwise with
stirring to a suspension of compound 1 (1.00 g, 6 mmol) in 20%
H2SO4 (12 mL) at 0—5 °C, the reaction mixture was kept at this
temperature for 2 h. The precipitate that formed was filtered
off, washed with cold water, and dried in vacuo over Р2О5. The
yield was 0.95 g (89%), decomp. temp. 110 °С. Found (%):
C, 19.73; N, 45.85. C3N6O4. Calculated (%): C, 19.58; N, 45.66.
13С NMR ((CD3)2CO), δ: 147.9 (СNO2); 129.6 (С(4)); 118.2
(СN2+). 14N NMR ((CD3)2CO), δ: –156.0 (ν1/2 = 70 Hz, N2+);
–32.9 (ν1/2 = 25 Hz, С(4)NO2), –27.2 (ν1/2 = 40 Hz, С(3)NO2).
Dinitroimidazo[1,2ꢀb]pyrazoles (general procedure). Sodium
hydroxide (0.42 g, 10.5 mmol) was added to a solution of pyrazole
1 (10 mmol) in methanol (30 mL), the mixture obtained was
stirred for 30 min, then the solvent was removed in vacuo. The
precipitate was dissolved in DMF (30 mL), and an αꢀbromoꢀ
ketone (12 mmol) was added to the solution. The mixture
was kept for 2 h at 140—145 °C, cooled and poured into water
(150 mL). It was extracted with ethyl acetate (3Ѕ40 mL), the
organic layer was washed with water, dried with MgSO4, and
the solvent was removed in vacuo.
+
2ꢀMethylꢀ6,7ꢀdinitroimidazo[1,2ꢀb]pyrazole (15). The
yield was 1.48 g (70%), decomp. temp. 201 °С (МеОН—Н2О).
Found (%): C, 34.30; H, 2.47; N, 33.31. C6H5N5O4. Calculꢀ
IR, ν/cm–1: 2250 (N2 ); 1525, 1350 (NO2). MS, m/z: 184 [M]+.
5ꢀBromoꢀ3,4ꢀdinitropyrazole (20). Potassium bromide
(1.19 g, 10 mmol) was added to a solution of compound 19

Properties of 5ꢀaminoꢀ3,4ꢀdinitropyrazoles
Russ.Chem.Bull., Int.Ed., Vol. 59, No. 8, August, 2010
1637
(0.93 g, 5 mmol) in 40% HBr (10 mL) at 0—5 °C, the reaction
mixture was stirred for 1 h. The temperature of the reaction
mixture was allowed to rise to ~25 °C spontaneously and kept
for an additional 7 h. It was extracted with ether (3×20 mL), the
organic layer was washed with water, and dried with MgSO4. The
solvent was removed in vacuo, the residue was recrystallized from
CCl4. The yield was 1.0 g (84%), m.p. 118—120 °С. Found (%):
C, 15.37; H, 0.51; Br, 34.04; N, 23.57. C3HBrN4O4. Calculꢀ
ated (%): C, 15.21; H, 0.43; Br, 33.72; N, 23.64. 13С NMR
((CD3)2CO), δ: 150.03 (C(3)); 126.94 (C(4)); 116.65 (C(5)).
14N NMR ((CD3)2CO), δ: –178.12 (N(1)); –29.53, –27.86
(С(3)NO2, С(4)NO2). IR, ν/cm–1: 1510, 1320 (NO2). MS,
m/z: 236, 238 (1 : 1) [M]+.
5ꢀAzidoꢀ3,4ꢀdinitropyrazole (21). A solution of NaN3 (0.64 g,
0.01 mol) in ice water (12 mL) was added dropwise with stirring
to a solution of compound 19 (0.93 g, 0.005 mol) in water
(10 mL) at 0—5 °C, the reaction mixture was kept at this
temperature for 1 h. The precipitate that formed was filtered
off, washed with cold water, and dried in vacuo over Р2О5.
It was recrystallized from dichloroethane. The yield was 0.65 g
(65%), decomp. temp. 125—126 °С (cf. Ref. 3: decomp. temp.
125 °C).
–26.56, –25.97 (С(2)NO2), С(3)NO2). IR, ν/cm–1: 3450 (NH);
3340 (ОН); 1690 (CO); 1525, 1352 (NO2). MS, m/z: 284 [M]+,
266 [M+ – H2O].
6ꢀAcetylꢀ7ꢀhydroxyꢀ2,3ꢀdinitropyrazolo[5,1ꢀc][1,2,4]ꢀ
triazine (24) and ethyl 7ꢀhydroxyꢀ7ꢀmethylꢀ2,3ꢀdinitroꢀ
4,7ꢀdihydropyrazolo[5,1ꢀc][1,2,4]triazineꢀ3ꢀcarboxylate (25).
The reaction was carried out with NaCH(CO2Et)COCH3. The
precipitate of compound 24 was filtered off, washed with cold
water, and dried over Р2О5. The yield of compound 24 was 0.5 g
(37%), m.p. 252—254 °С (dichloroethane). Found (%): C, 31.51;
H, 1.62; N, 31.48. C7H4N6O6. Calculated (%): C, 31.35;
H, 1.50; N, 31.34. 1Н NMR ((CD3)2SO), δ: 13.00 (br.s, 1 Н,
ОH); 2.60 (s, 3 Н, Me). 13С NMR ((CD3)2SO), δ: 192.85 (q,
СО, J = 6.2 Hz); 151.41 (C(2)); 144.75; 141.74; 139.61; 110.49
(С(3)); 27.74 (q, Me, J = 129.0 Hz). 14N NMR ((CD3)2SO), δ:
–28.64 (С(2)NO2), С(3)NO2). IR, ν/cm–1: 3230 (ОН); 1760
(CO); 1520, 1325 (NO2). MS, m/z: 268 [M]+.
The mother liquor was extracted with ether (3×10 mL), the
organic layer was washed with water, dried with MgSO4, and the
solvent was removed in vacuo. The yield of compound 25 was
0.6 g (38%), m.p. 176—178 °С (dichloroethane). Found (%):
C, 34.56; H, 3.30; N, 26.84. C9H10N6O7. Calculated (%):
C, 34.40; H, 3.21; N, 26.75. 1Н NMR ((CD3)2SO), δ: 12.10
(br.s, 1 Н, NH); 7.10 (br.s, 1 Н, ОН); 4.36 (q, 2 Н, СН2,
J = 7.0 Hz); 2.30 (s, 3 Н, Me); 1.35 (q, 3 Н, СН2СН3, J = 7.0 Hz).
13С NMR ((CD3)2SO), δ: 162.22 (t, СО, J = 3.1 Hz); 149.50
(C(2)); 138.20 (t, С(6), J = 3.4 Hz); 136.59 (d, С(3a), J = 10.8 Hz);
109.60 (С(3)), 81.07 (q, С(7), J = 4.6 Hz); 62.49 (tq, СН2,
J = 149.0 Hz, J = 4.4 Hz); 25.11 (q, Me, J = 131.0 Hz); 14.32
(q.t, СН2СН3, J = 128.2 Hz, J = 2.4 Hz). IR, ν/cm–1: 3400
(NH); 3250 (ОН); 1710 (CO); 1530, 1320 (NO2). MS, m/z:
314 [M]+, 296 [M+ – H2O].
4,7ꢀDihydroꢀ2,3,6ꢀtrinitropyrazolo[5,1ꢀc][1,2,4]triazinꢀ4ꢀol
(26). The reaction was carried out with NaC(CНО)2NO2. The
reaction mixture was extracted with ether (3×10 mL), the organic
layer was washed with water, and dried with MgSO4, the solvent
was removed in vacuo. The yield was 1.3 g (88%), m.p. 187 °С
(dichloroethane). Found (%): C, 22.13; H, 1.15; N, 36.02.
C5H3N7O7. Calculated (%): C, 21.99; H, 1.11; N, 35.90.
1Н NMR ((CD3)2SO), δ: 12.75 (br.s, 1 Н, NH); 8.02 (br.s, 1 Н,
ОН); 7.22 (s, 1 Н). 13С NMR ((CD3)2SO), δ: 149.72 (C(2));
144.97 (С(6)); 136.27 (С(3а)); 110.42 (С(3)); 72.88 (d, С(7),
J = 178.18 Hz). IR, ν/cm–1: 3350 (NH); 1530, 1340 (NO2).
MS, m/z: 273 [M]+, 255 [M+ – H2O].
7ꢀAminoꢀ2,3,6ꢀtrinitropyrazolo[5,1ꢀc][1,2,4]triazine (27).
The reaction was carried out with NaCH(CN)NO2. The preciꢀ
pitate that formed was filtered off, washed with cold water, and
dried over Р2О5. The yield was 1.27 g (95%), m.p. 242 °С
(CH3CN). Found (%): C, 22.39; H, 0.81; N, 42.05. C5H2N8O6.
Calculated (%): C, 22.23; H, 0.75; N, 41.89. 13С NMR ((CD3)2SO),
δ: 153.69; 144.47; 140.91; 140.01; 93.30. 15N NMR ((CD3)2SO),
δ: –184.68; –124.12; –64.35; –29.15 (С(6)NO2); –26.82
(С(3)NO2); –20.23 (С(2)NO2). IR, ν/cm–1: 3230 (ОН); 1520,
1325 (NO2). MS, m/z: 270 [M]+.
5ꢀChloroꢀ3,4ꢀdinitropyrazole (22). A solution of compound
19 (0.93 g, 0.005 mol) in conc. HCl (10 mL) was added with
stirring at 0—5 °C to a solution of CuCl (1 g, 0.01 mol) in conc.
HCl (4 mL), the reaction mixture was stirred for 1 h. The
temperature of the reaction mixture was allowed to rise to ~25 °C
spontaneously and kept for an additional 7 h. It was extracted
with ether (3×20 mL), the organic layer was washed with water,
and dried with MgSO4. The solvent was removed in vacuo, the
residue was recrystallized from CCl4. The yield was 0.8 g (83%),
m.p. 110—112 °С. Found (%): C, 18.90; H, 0.53; Cl, 19.04;
N, 29.28. C3HClN4O4. Calculated (%): C, 18.72; H, 0.52; Cl,
18.42; N, 29.10. 13С NMR ((CD3)2CO), δ: 149.62 (C(3)); 130.62
(C(5)); 124.21 (C(4)). 14N NMR ((CD3)2CO), δ: –178.43
(N(1)); –29.46, –27.32 (С(3)NO2, С(4)NO2). IR, ν/cm–1
:
1520, 1340 (NO2). MS, m/z: 194, 192 (1 : 3) [M]+.
Cyclization of betaine 19 with active methylene compounds
(general procedure). A suspension of betaine 19 (1 g, 5.4 mmol)
in Н2О (8 mL) was added at 5—10 °C to a solution of a salt of an
active methylene compound (11 mmol) in Н2О (5 mL). The
reaction mixture was kept at this temperature for 1 h, then the
temperature was allowed to rise to ~25 °C and the reaction
mixture was kept for an additional 12 h. The precipitate that
formed was filtered off, suspended in Н2О (15 mL) and acidified
with 10% H2SO4 to pH = 1.
6ꢀAcetylꢀ7ꢀhydroxyꢀ7ꢀmethylꢀ2,3ꢀdinitroꢀ4,7ꢀdihydroꢀ
pyrazolo[5,1ꢀc][1,2,4]triazine (23). The reaction was carried
out with NaCH(COCH3)2. The solution was extracted with ether
(3×10 mL), the organic layer was washed with water, and dried
with MgSO4, the solvent was removed in vacuo. The yield was
1.1 g (77%), m.p. 176—178 °С (dichloroethane). Found (%):
C, 34.41; H, 3.03; N, 29.68. C8H8N6O6. Calculated (%):
C, 33.81; H, 2.84; N, 29.57. 1Н NMR ((CD3)2SO), δ: 12.07
(br.s, 1 Н, NH); 6.81 (br.s, 1 Н, ОН); 2.44 (s, 3 Н, СОMe);
2.27 (s, 3 Н, С(7)Me). 13С NMR ((CD3)2SO), δ: 195.51 (q,
СО, J = 6.8 Hz); 149.20 (C(2)); 142.84 (q, С(6), J = 3.4 Hz);
136.37 (d, С(3a), J = 10.5 Hz); 108.99 (С(3)); 81.04 (q, С(7),
J = 4.8 Hz); 26.61 (q, Me, J = 129.9 Hz); 24.69 (q, С(7)СН3,
J = 131.6 Hz). 15N NMR ((CD3)2SO), δ: –244.07 (d, N(4),
J = 114.4 Hz); –198.75 (N(8)); –110.52 (N(1)); –59.67 (N(5));
References
1. A. A. Zaitsev, D. V. Zaiko, I. L. Dalinger, V. V. Kachala,
T. K. Shkineva, S. A. Shevelev, Izv. Akad. Nauk, Ser. Khim.,
2009, 2058 [Russ. Chem. Bull., Int. Ed., 2009, 58, 2122].

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Received April 12, 2010;
in revised form June17, 2010