Synthesis of polycyclic fused heterocycles based on 4,6-dinitro-1-phenyl- 1H-indazole

Article abstract of DOI:10.1007/s11172-010-0025-3

Tricyclic heteroaromatic systems of the furoxan, vic-triazole, imidazole, and pyrazine series containing the annulated indazole fragment were synthesized based on substituted aminoindazoles prepared by the functionalization of 4-R-6-nitro-1-phenylindazole

Full text of DOI:10.1007/s11172-010-0025-3

Russian Chemical Bulletin, International Edition, Vol. 58, No. 2, pp. 414—420, February, 2009
414
Synthesis of polycyclic fused heterocycles
based on 4,6ꢀdinitroꢀ1ꢀphenylꢀ1Hꢀindazole*
M. A. Bastrakov,a A. M. Starosotnikov,a V. V. Kachala,a I. V. Glukhov,b and S. A. Sheveleva
aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: shevelev@ioc.ac.ru
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 6549. Eꢀmail: ivglukh@ineos.ac.ru
Tricyclic heteroaromatic systems of the furoxan, vicꢀtriazole, imidazole, and pyrazine
series containing the annulated indazole fragment were synthesized based on substituted
aminoindazoles prepared by the functionalization of 4ꢀRꢀ6ꢀnitroꢀ1ꢀphenylindazoles (R = NO2
or SO2Ph) at positions 6 and 7.
Key words: indazoles, nitro compounds, amination, amino group, diazotization, reduction,
polycyclic systems.
The present study is a continuation of investigations
Scheme 1
of 4,6ꢀdinitrobenzannulated aromatic fiveꢀmembered hetꢀ
erocycles, which became available via the transformaꢀ
tions of 2,4,6ꢀtrinitrotoluene, and is focused on the
functionalization of 4,6ꢀdinitroꢀ1ꢀphenylꢀ1Hꢀindazole
with the aim to allow the annulation of this compound
with additional hetetocyclic fragments.
Many natural and synthetic indazole derivatives have
diverse and useful biological activities. In particular, these
compounds can be used as drugs with antitumor1 and
antiꢀinflammatory activities,2 various antidepressants,3
analgesics, antipyretics,4 and substances exhibiting antiꢀ
HIV activity.5 The indazole moiety is present in many
other compounds with useful properties, such as herbiꢀ
cides, dyes,6 etc. In spite of a wide field of use, the chemꢀ
istry of indazole derivatives is less well studied compared
to other bicyclic heteroaromatic compounds, such as
indole and benzimidazole.
at position 7 aimed at preparing polycyclic systems as
potential biologically active compounds.
It is known that aromatic systems containing nitro
groups can be subjected to amination via the vicarious
A method for the synthesis of 4,6ꢀdinitroꢀ1ꢀphenylꢀ
1Hꢀindazole (1) based on 2,4,6ꢀtrinitrotoluene (TNT)
has been described previously.7,8
Scheme 2
The characteristic property of compound 1 is that the
nitro group at position 4 can be regioselectively substiꢀ
tuted with some anionic nucleophiles. This made it posꢀ
sible to synthesize a series of nitroindazoles containing
different substituents at position 4.8
The purpose of the present study was to perform the
functionalization of 4,6ꢀdinitroꢀ1ꢀphenylꢀ1Hꢀindazole
* On the occasion of the 75th anniversary of the foundation
of the N. D. Zelinsky Institute of Organic Chemistry of the
Russian Academy of Sciences.
Reagents and conditions: (CH3)3N+NH2I–, ButOK, DMSO, 20 °C.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 407—412, February, 2009.
1066ꢀ5285/09/5802ꢀ0414 © 2009 Springer Science+Business Media, Inc.

Fused polycyclic heterocycles
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
415
Scheme 3
used for the amination of 2ꢀarylꢀ4,6ꢀdinitroindoles giving
rise to orthoꢀnitroamine 2 (Scheme 2). The direction of
amination was established by 1H NMR spectroscopy
(2D NOESY).
The reduction of the nitro group at position 6 would
offer a convenient route to a synthon (A) for the annulaꢀ
tion of additional heterocyclic fragments (Scheme 3).
However, the reduction of compound 2 with standard
reducing agents (N2H4/RaꢀNi, (NH4)2S, SnCl2/HCl, or
Sn/HCl) is nonꢀselective and affords a mixture of reducꢀ
tion products at positions 4 and 6.
In this context, it seemed appropriate to replace the
nitro group at position 4 with another electronꢀwithdrawꢀ
ing substituent. We replaced the nitro group in compound
1 by the phenylthio moiety8 followed by the oxidation of
sulfide 3 to the corresponding sulfone 4 (Scheme 4). We
found that sulfone 4 is subjected to selective amination at
position 7 with TMHI in the presence of ButOK in DMSO
to form orthoꢀnitroamine 5. The reduction of the nitro
group in amine 5 with the N2H4•H2O + FeCl3•6H2O
system15 affords the expected diamine 6, which is a conꢀ
venient precursor for a wide range of fused polycyclic
systems (Scheme 4).
nucleophilic substitution at the ortho and para positions
with respect to the nitro group.9—13 The presence of two
nitro groups at the meta positions with respect to each
other facilitates this reaction, as has been exemplified
previously by the selective amination of 2ꢀarylꢀ4,6ꢀdinitroꢀ
indoles with 1,1,1ꢀtrimethylhydrazinium iodide (TMHI)
in the presence of ButOK.14
We studied the amination of dinitroindazole 1. It
appeared that this compound is subjected to selective
amination at position 7 under conditions similar to those
Scheme 5
Scheme 4
R = H (a), CH3 (b), CF3 (c).
Reagents and conditions: i, NaNO2, AcOH; ii, RC(O)RC(O),
MeCN, Δ; iii, RCO2H, HCl, Δ; iv, SOCl2, Δ, pyridine.
Reagents and conditions: i, PhSH, K2CO3, Nꢀmethylpyrrolidone,
90 °C; ii, H2O2, CF3CO2H; iii, (CH3)3N+NH2I–, ButOK, DMSO, 20 °C;
iv, N2H4•H2O, Cact, FeCl3•6H2O, MeOH, Δ.

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Bastrakov et al.
starting diamine 6 reacts with glyoxal derivatives to form
tricyclic systems of the pyrazine series 9 (Scheme 5). The
reaction of diamine 6 with SOCl2 produces thiadiazole
derivative 10, whose structure was established by Xꢀray
diffraction (Fig. 1, Table 1).
C(13)
C(12)
C(11)
C(14)
According to the Xꢀray diffraction data, the central
tricyclic fragment in compound 10 in the crystalline state
is planar (within 0.016 Å). The phenyl substituent at
the N(8) atom forms an angle of 49° with this plane. The
bond lengths in the thiadiazole fragment coincide within
experimental error with the published data. Thus, the
N(1)—S(2) and N(3)—S(2) bond lengths are 1.616(2)
and 1.620(2) Å, respectively, and the corresponding bond
lengths in the most closely related 5ꢀmethylimidazo[4,5ꢀd]ꢀ
benzoꢀ2,1,3ꢀthiadiazole are 1.615 and 1.625 Å.16 In the
crystal structure, the molecules are linked together to
C(10)
C(9)
O(2)
O(1)
S(3)
C(5A)
C(5)
C(6)
N(7)
C(4)
C(3A)
N(8)
C(8A)
C(1A)
...
form infinite chains via the S(2) N(7) interactions
...
(S(2) N(7), 3.205(2) Å).
N(3)
C(15)
C(16)
We studied the diazotization of amines 2 and 5. This
reaction was found to require nitrosylsulfuric acid. The
treatment of a solution of diazonium salts with an aqueꢀ
ous sodium azide solution affords azides 11 in good yields.
Azides 11 undergo intramolecular cyclization to give
furoxan derivatives 12 upon refluxing their solutions in
toluene.
C(20)
N(1)
S(2)
C(17)
C(18)
C(19)
The furoxan ring can undergo isomerization to anꢀ
other form containing the Nꢀoxide group on the opposite
side of the ring.17 However, the Xꢀray diffraction study
(Fig. 2, Table 2) showed that the isomerization does not
occur, and the position of the Nꢀoxide oxygen atom in
these compounds is described by the formulas 12a,b rather
than by 12´a,b.
Previously, we have reported the synthesis of a related
compound based on 2ꢀphenylꢀ4,6ꢀdinitroindole,18 to
which we assigned structure 13. In the present study, we
determined the structure of this furoxan by Xꢀray difꢀ
fraction and confirmed the previously proposed structure
(Fig. 3, Table 3).
Fig. 1. Xꢀray molecular structure of compound 10. Displaceꢀ
ment ellipsoids are drawn at the 50% probability level.
Table 1. Selected bond lengths (d) in thiadiazole 10
Bond
d/Å
Bond
d/Å
C(1A)—N(1)
C(1A)—C(8A)
C(1A)–(C3A)
N(1)—S(2)
1.339(3)
1.423(4)
1.432(4)
1.616(2)
S(2)—N(3)
N(3)—C(3A)
C(3A)—C(4)
1.620(2)
1.349(3)
1.421(4)
We found that diamine 6 can react with nitrous acid to
give the previously unknown tricyclic system of the triazole
series 7; the heating with carboxylic acids in the presence
of HCl as the catalyst affords imidazole derivatives 8. The
According to the Xꢀray diffraction data, the central
tricyclic fragment in compounds 12a and 13, like that in
Scheme 6
R = NO2 (11a, 12a), SO2Ph (11b, 12b).
Reagents and conditions: i, NOHSO4, AcOH + H2SO4; ii, NaN3; iii, toluene, Δ.

Fused polycyclic heterocycles
O(5)
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
417
compound 10, is planar (the average deviation of the
atoms from the mean plane is 0.036 and 0.008 Å for 12a
and 13, respectively). The phenyl substituent in 12a is
nearly coplanar with the central fragment (the angle
between the planes is 12°), whereas this angle in 13 is
34° due to steric repulsion between the phenyl group and
the methyl substituent at the N(8) atom. The structure of
the furoxan fragment is, on the whole, similar to that
published in the literature (see Tables 2 and 3). However,
it should be noted that the exocyclic N(3)—O(3) bond
(1.234(2) and 1.231(3) in furoxans 12a and 13, respecꢀ
tively) is one of the longest bonds found in this class of
compounds. For comparison, the corresponding bond
length in 4ꢀaminoꢀ5ꢀnitrobenzo[1,2ꢀc:3,4ꢀc´]bis[1,2,5]ꢀ
oxadiazole 3,8ꢀdioxide is 1.226 Å.19
C(6)
N(4)
N(7)
C(5A)
O(4)
C(5)
C(10)
C(9)
C(11)
C(4)
N(8)
C(8A)
C(12)
C(3A)
C(1A)
C(14)
C(13)
N(1)
N(3)
O(3)
O(2)
Fig. 2. Xꢀray molecular structure of compound 12a. Displaceꢀ
ment ellipsoids are drawn at the 50% probability level.
To sum up, we synthesized a convenient synthon for
the design of polycyclic structures based on 4ꢀRꢀ6ꢀnitroꢀ
1ꢀphenylindazoles (R = NO2 and SO2Ph) and prepared
representatives of tricyclic heteroaromatic systems of the
triazole, imidazole, thiadiazole, and pyrazine series, as
well as of the furoxan series with the previously unknown
combination of substituents.
Table 2. Selected bond lengths (d) in compound 12a
Bond
d/Å
Bond
d/Å
C(1A)—N(1)
C(1A)—C(3A)
C(1A)—C(8A)
N(1)—O(2)
1.322(2)
1.422(2)
1.432(2)
1.394(2)
O(2)—N(3)
N(3)—O(3)
N(3)—C(3A)
1.438(2)
1.234(2)
1.334(2)
Experimental
The 1H and 13C NMR spectra were recorded on a Bruker
AMꢀ300 instrument. The chemical shifts are given with respect
to SiMe4. All samples for NMR spectroscopy were prepared in
DMSOꢀd6. The IR spectra were measured on a SpecordꢀMꢀ80
instrument in KBr pellets. The EI mass spectra were obtained on
a Kratos MSꢀ30 instrument (70 eV). The course of the reactions
was monitored and the purity of the compounds was checked by
TLC on Silufol UVꢀ254 plates. The reactions were carried out
with the use of dry DMF and DMSO. The other solvents were
used without special drying. Indazoles 1 and 3 were synthesized
according to procedures described earlier.7,8 1,1,1ꢀTrimethylꢀ
hydrazinium iodide was prepared according to a known proꢀ
cedure.9
Xꢀray diffraction study of compounds 10, 12a, and 13 was
carried out on a threeꢀcircle Smart 1000 CCD diffractometer at
120 K (MoꢀKα radiation, graphite monochromator, ωꢀscanning
technique). The structures were solved by direct methods and
refined by the fullꢀmatrix leastꢀsquares method with anisotropic
thermal parameters for all nonhydrogen atoms (isotropic thermal
parameters for hydrogen atoms). The hydrogen atoms were
positioned geometrically. All calculations were carried out with
the use of the SHELXTL PLUS 5.0 program package. Principal
crystallographic parameters and the data collection and refineꢀ
ment statistics are given in Table 4.
13
O(5)
O(4)
C(5)
N(4)
C(5A)
C(10)
C(6)
C(7)
C(11)
C(12)
C(4)
C(3A)
C(9)
C(14)
O(3)
N(8)
C(8A)
C(1A)
C(13)
N(3)
O(2)
C(15)
N(1)
Fig. 3. Xꢀray molecular structure of compound 13. Displaceꢀ
ment ellipsoids are drawn at the 50% probability level.
7ꢀAminoꢀ4,6ꢀdinitroꢀ1ꢀphenylꢀ1Hꢀindazole (2). Potassium
tertꢀbutoxide (1.57 g, 14 mmol) was added to a solution of
indazole 1 (1.99 g, 7 mmol) and TMHI (2.83 g, 14 mmol)
in DMSO (30 mL). The reaction mixture was stirred at room
temperature for 30 min, poured into water, and acidified with
concentrated HCl to pH = 4—5. The precipitate that formed was
filtered off, washed with hot EtOH, and dried in air. Compound
2 was obtained in a yield of 1.76 g (84%). M.p. 213—215 °C.
Found (%): C, 52.37; H, 3.18; N, 23.23. C13H9N5O4. Calcuꢀ
Table 3. Selected bond lengths (d) in compound 13
Bond
d/Å
Bond
d/Å
C(1A)—N(1)
C(1A)—C(3A)
N(1)—O(2)
1.329(3)
1.415(4)
1.394(3)
O(2)—N(3)
N(3)—O(3)
N(3)—C(3A)
1.442(3)
1.231(3)
1.327(4)

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Bastrakov et al.
Table 4. Principal crystallographic parameters and the data collection and refinement statistics
Parameter
10
12a
13
Molecular formula
Molecular weight
Crystal system
Space group
C19H12N4O2S2
392.45
Orthorhombic
Pbca
C13H7N5O4
297.24
Monoclinic
P2(1)/n
4 (1)
C15H10N4O4
310.27
Orthorhombic
P2(1)2(1)2(1)
4 (1)
Z (Z´)
8 (1)
a/Å
b/Å
c/Å
α/deg
7.505(2)
18.134(5)
24.654(7)
90
9.3767(13)
5.9773(9)
20.729(3)
90
6.742(2)
9.446(3)
20.991(7)
90
β/deg
90
90
92.898(3)
90
1160.3(3)
1.702
90
90
γ/deg
V/Å3
3355.1(16)
1.554
1336.7(7)
1.542
1.16
dcalc/g cm–3
μ/cm–1
3.42
1.32
F(000)
1616
608
640
2θmax/deg
58
58
54
Number of measured reflections (Rint
Number of independent reflections
Number of refined parameters
Number of reflections with I > 2σ(I)
R1(I > 2σ(I))
)
15249 (0.071)
4378
12199 (0.062)
3094
5925 (0.044)
1693
244
2026
0.053
199
1564
0.043
209
1118
0.043
wR2
0.101
0.075
0.094
GOOF
1.007
0.997
1.027
Residual electron density/
0.414/–0.300
0.301/–0.235
0.242/–0.208
e Å–3, ρmax/ρ
min
lated (%): C, 52.18; H, 3.03; N, 23.40. 1H NMR, δ: 7.50 (s, 2 H,
NH2); 7.65—7.75 (m, 5 H, Ph); 8.71 (s, 1 H, CH); 8.88 (s, 1 H,
H). 13C NMR, δ: 113.29, 113.72, 119.57, 119.72, 123.47, 127.61,
128.55, 129.84, 130.14, 134.21, 138.13, 138.67.
1204, 1156, 1084, 1072, 936, 876, 772, 744, 720, 696, 688. MS,
m/z: 394 [M]+.
6,7ꢀDiaminoꢀ1ꢀphenylꢀ4ꢀ(phenylsulfonyl)ꢀ1Hꢀindazole
(6). Ferric trichloride hexahydrate FeCl3•6H2O (0.45 g)
and N2H4•H2O (3.7 mL) were added to a suspension of indazole
5 (3.8 g, 9.6 mmol) and activated carbon (5.0 g) in MeOH
(160 mL). Then the reaction mixture was refluxed for 48 h (TLC
monitoring). The hot reaction mixture was filtered off from the
carbon, the filtrate was cooled, and the precipitate that formed
was filtered off. The filtrate was concentrated to 70 mL, and the
residue was cooled, resulting in the precipitation of an addiꢀ
tional amount of the product. Compound 6 was obtained in a
yield of 2.55 g (73%) . M.p. 233—235 °C. Found (%): C, 62.39;
H, 4.50; N, 15.30. C19H16N4O2S. Calculated (%): C, 62.62;
H, 4.43; N, 15.37. 1H NMR, δ: 4.55 (s, 2 H, NH2.); 5.12 (s, 2 H,
NH2); 7.41—7.66 (m, 8 H, Ph, PhSO2, 1 H, CH); 7.97 (d,
2 H, Ph, 3J = 8.6 Hz); 8.32 (s, 1 H, CH). IR, ν/cm–1: 3456,
3376, 3340, 3296, 1656, 1624, 1596, 1564, 1528, 1496, 1448,
1412, 1372, 1332, 1292, 1272, 1228, 1148, 1080, 1012, 1000,
936, 904, 760, 732, 688, 620. MS, m/z: 364 [M]+.
6ꢀNitroꢀ1ꢀphenylꢀ4ꢀ(phenylsulfonyl)ꢀ1Hꢀindazole (4). A 30%
H2O2 solution (4.0 mL) was added dropwise to a solution
of sulfide 3 (2.86 g, 1.3 mmol) in CF3CO2H (30 mL). The
reaction mixture was stirred at 20 °C for 1 h and poured into
water (150 mL). The precipitate that formed was filtered off,
washed with water, and dried in air. Compound 4 was obtained
in a yield of 3.0 g (96%). M.p. 175—179 °C. Found (%):
C, 60.33; H, 3.52; N, 11.02. C19H13N3O4S. Calculated (%):
C, 60.15; H, 3.45; N, 11.08; S, 8.45. 1H NMR, δ: 7.52—7.88 (m,
3
8 H, Ph, PhSO2); 8.25 (d, 2 H, Ph, J = 7.6 Hz); 8.61 (s, 1 H,
CH); 8.73 (s, 1 H, CH); 8.95 (s, 1 H, CH).
7ꢀAminoꢀ6ꢀnitroꢀ1ꢀphenylꢀ4ꢀ(phenylsulfonyl)ꢀ1Hꢀindazole
(5). Potassium tertꢀbutoxide (2.24 g, 20 mmol) was added
to a solution of sulfone 4 (3.79 g, 10 mmol) and TMHI (4.0 g,
20 mmol) in DMSO (70 mL). The reaction mixture was stirred
at room temperature for 30 min, poured into water, and acidiꢀ
fied. The precipitate that formed was filtered off, washed with
water, and dried in air. Compound 7 was obtained in a yield of
3.84 g (97%). M.p. 280—285 °C. Found (%): C, 57.57; H, 3.88;
N, 14.33. C19H14N4O4S. Calculated (%): C, 57.86; H, 3.58;
8ꢀPhenylꢀ5ꢀ(phenylsulfonyl)ꢀ3,8ꢀdihydro[1,2,3]triazoloꢀ
[4,5ꢀg]indazole (7). A solution of NaNO2 (0.07 g) in H2O
(2 mL) was added to a solution of diamine 6 (0.3 g, 0.8 mmol)
in AcOH (5 mL). The reaction mixture was stirred at 20 °C for
2 h and poured into water (25 mL). The precipitate that formed
was filtered off, washed with water, and dried in air. Compound
7 was obtained in a yield of 0.24 g (77%). M.p. 228—232 °C.
Found (%): C, 60.49; H, 3.73; N, 18.23. C19H13N5O2S. Calcuꢀ
1
N, 14.21. H NMR, δ: 7.21 (s, 2 H, NH2); 7.64—7.72 (m, 8 H,
3
Ph, PhSO2); 8.12 (d, 2 H, Ph, J = 7.4 Hz); 8.52 (c 1 H, CH);
8.54 (s, 1 H, CH). 13C NMR, δ: 117.38, 118.62, 121.75, 122.51,
123.44, 126.12, 127.63, 128.39, 129.73, 129.83, 130.00, 133.44,
133.55, 137.67, 138.28, 140.79. IR, ν/cm–1: 3440, 3328, 1616,
1572, 1520, 1496, 1460, 1448, 1404, 1380, 1324, 1300, 1264,
1
lated (%): C, 60.79; H, 3.49; N, 18.66. H NMR, δ: 4.52 (br.s,
N(3)H + H2O); 7.45—7.83 (m, 6 H, Ph, PhSO2); 8.05 (d, 2 H,

Fused polycyclic heterocycles
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 2, February, 2009
419
3
3
Рh, J = 8.1 Hz); 8.20 (d, 2 H, Рh, J = 8.8 Hz); 8.49 (s, 1 H,
CH); 8.73 (s, 1 H, CH). MS, m/z: 375 [M]+.
0.115 g (36%). M.p. 101—105 °C. Found (%): C, 57.95; H, 3.29;
N, 14.53. C19H12N4O2S2. Calculated (%): C, 58.15; H, 3.08;
N, 14.28. 1H NMR, δ: 7.57—7.74 (m, 6 H, Ph, PhSO2); 7.85 (d,
Synthesis of imidazoles (general procedure). A solution of
diamine 6 (0.3 g, 0.8 mmol) in a mixture of the corresponding
acid (HCO2H for 8a, AcOH for 8b, and CF3CO2H for 8c) (7 mL)
and HCl (0.5 mL) (in the case of imidazole 8c, the reaction was
carried out in the absence of HCl) was refluxed for 2—8 h (TLC
monitoring). Then the reaction mixture was cooled and poured
into water (25 mL). The precipitate that formed was filtered off
and dried in air.
3
2 H, Рh, J = 7.7 Hz); 8.27 (d, 2 H, Рh, 3J = 7.7 Hz); 8.55 (s,
1 H, CH); 8.73 (s, 1 H, CH). IR, ν/cm–1: 1500, 1448, 1324,
1152, 1108, 1084, 968, 920, 876, 852, 764, 732, 692, 684.
MS, m/z: 392 [M]+.
Synthesis of azides 11a,b (general procedure). Amine 2
(1 mmol) was suspended in a 1 : 1 mixture of AcOH and H2SO4
(20 mL). Then a solution of NaNO2 (0.14 g, 2 mmol) in H2O
(7 mL) was added dropwise to the reaction mixture at 0—5 °C.
The resulting solution of the diazonium salt was stirred at
this temperature for 1 h and then poured into a solution of
NaN3 (0.26 g, 4 mmol) and AcONa•3H2O (50 g) in ice water
(20 mL). The reaction mixture was stirred for 30 min. The
precipitate that formed was filtered off, washed with water, and
dried in air.
1ꢀPhenylꢀ4ꢀphenylsulfonylꢀ1,6ꢀdihydroimidazo[4,5ꢀg]ꢀ
indazole (8a). The yield was 0.19 g (74%). M.p. 239—242 °C.
Found (%): C, 64.08; H, 4.03; N, 14.63. C20H14N4O2S. Calcuꢀ
1
lated (%): C, 64.16; H, 3.77; N, 14.96. H NMR, δ: 3.71 (br.s,
N(6)H + H2O); 7.26—7.42 (m, 6 H, Ph, PhSO2); 8.01 (d, 2 H,
3
3
Рh, J = 7.4 Hz); 8.12 (d, 2 H, Рh, J = 6.7 Hz); 8.25 (s, 1 H,
CH); 8.48 (s, 1 H, CH); 8.65 (s, 1 H, CH). MS, m/z: 374 [M]+.
7ꢀMethylꢀ1ꢀphenylꢀ4ꢀphenylsulfonylꢀ1,6ꢀdihydroimidazoꢀ
[4,5ꢀg]indazole (8b). The yield was 0.25 g (78%). M.p. 268—270 °C.
Found (%): C, 64.77; H, 4.39; N, 14.37. C21H16N4O2S. Calcuꢀ
lated (%): C, 64.93; H, 4.15; N, 14.42. 1H NMR, δ: 2.50 (s, 3 H,
Me); 7.41—7.64 (m, 6 H, Ph, PhSO2); 7.98 (d, 2 H, Рh, 3J = 7.6 Hz);
8.11 (d, 2 H, Рh, 3J = 8.7 Hz); 8.13 (s, 1 H, CH); 8.63 (s, 1 H);
13.22 (br.s, N(6)H). MS, m/z: 388 [M]+.
7ꢀAzidoꢀ4,6ꢀdinitroꢀ1ꢀphenylꢀ1Hꢀindazole (11a). The yield of
compound 11a was 0.25 g (77%). M.p. 127—132 °C. Found (%):
C, 48.25; H, 2.37; N, 30.55. C13H7N7O4. Calculated (%):
C, 48.01; H, 2.17; N, 30.15. 1H NMR, δ: 7.52—7.79 (m, 5 H,
Ph, PhSO2); 8.77 (s, 1 H, CH); 8.90 (s, 1 H, CH). IR, ν/cm–1
:
2148, 1600, 1576, 1532, 1496, 1472, 1412, 1332, 1204, 1148,
1100, 960, 896, 816, 800, 768, 700.
1ꢀPhenylꢀ4ꢀphenylsulfonylꢀ7ꢀtrifluoromethylꢀ1,6ꢀdihydroꢀ
imidazo[4,5ꢀg]indazole (8c). The yield was 0.29 g (80%).
M.p. 129—132 °C. Found (%): C, 56.87; H, 3.12; N, 12.71.
C21H13F3N4O2S. Calculated (%): C, 57.01; H, 2.96; N, 12.66.
1H NMR, δ: 7.39—7.79 (m, 6 H, Ph, PhSO2); 7.99 (d, 2 H, Рh,
3J = 8.3 Hz); 8.09 (d, 2 H, Рh, 3J = 6.6 Hz); 8.17 (s, 1 H, CH);
8.75 (s, 1 H, CH); 14.95 (br.s, N(6)H). MS, m/z: 442 [M]+.
1ꢀPhenylꢀ4ꢀ(phenylsulfonyl)ꢀ1Hꢀpyrazolo[3,4ꢀf]quinoxaline
(9a). A 40% glyoxal solution (0.3 mL) was added to a suspension
of diamine 6 (0.3 g, 0.8 mmol) in CH3CN (15 mL). The reacꢀ
tion mixture was refluxed for 3 h, cooled, poured into water
(50 mL), and acidified with concentrated HCl to pH 5. The
precipitate that formed was filtered off, washed with water, and
dried in air. Compound 9a was obtained in a yield of 0.28 g
(86%). M.p. 242—246 °C. Found (%): C, 65.32; H, 3.59;
N, 14.48. C21H14N4O2S. Calculated (%): C, 65.27; H, 3.65;
N, 14.50. 1H NMR, δ: 7.43—7.85 (m, 8 H, Ph, PhSO2); 8.28 (d,
2 H, Рh, 3J = 9.8 Hz); 8.47 (s, 1 H, CH); 8.80 (s, 1 H, CH); 8.87
(s, 1 H, CH); 9.11 (s, 1 H, H(5)). MS, m/z: 386 [M]+.
7,8ꢀDimethylꢀ1ꢀphenylꢀ4ꢀ(phenylsulfonyl)ꢀ1Hꢀpyrazoloꢀ
[3,4ꢀf]quinoxaline (9b). Diacetyl (0.17 mL, 0.2 mmol) was added
to a suspension of diamine 6 (0.3 g, 0.8 mmol) in EtOH (5 mL).
The reaction mixture was refluxed for 3 h, cooled, poured into
water (50 mL), and acidified with concentrated HCl to pH 5.
The precipitate that formed was filtered off and recrystallized
from EtOH. Compound 9b was obtained in a yield of 0.25 g
(73%). M.p. 191—195 °C. Found (%): C, 66.78; H, 4.53;
N, 13.33. C23H18N4O2S. Calculated (%): 66.65; H, 4.38;
N, 13.52. 1H NMR, δ: 2.39 (s, 3 H, Me); 2.68 (s, 3 H, Me);
7.44—7.81 (m, 8 H, Ph, PhSO2); 8.22 (d, 2 H, Рh, 3J = 10.8 Hz);
8.31 (s, 1 H, CH); 8.74 (s, 1 H, CH).
7ꢀAzidoꢀ6ꢀnitroꢀ1ꢀphenylꢀ4ꢀ(phenylsulfonyl)ꢀ1Hꢀindaꢀ
zole (11b). The yield of compound 11b was 0.36 g (96%).
M.p. 97—100 °C. Found (%): C, 54.19; H, 2.96; N, 19.75,
S, 7.55. C19H12N6O4S. Calculated (%): C, 54.28; H, 2.88;
N, 19.99; S, 7.63. 1H NMR, δ: 7.57—7.73 (m, 8 H, Ph, PhSO2);
3
8.22 (d, 2 H, Рh, J = 7.6 Hz); 8.52 (s, 1 H, CH); 8.83 (s, 1 H,
CH). IR, ν/cm–1: 2144, 1616, 1596, 1572, 1532, 1500, 1476,
1448, 1356, 1328, 1160, 1148, 1088, 1068,932, 884, 760, 732,
720, 692.
Synthesis of furoxans 12a,b (general procedure). A solution
of azides 11 (1.2 mmol) in toluene (15 mL) was refluxed for 6 h.
Then the solvent was largely evaporated, and the residue was
diluted with hexane. The precipitate that formed was chromatoꢀ
graphed on a column (SiO2/toluene).
5ꢀNitroꢀ8ꢀphenylꢀ8Hꢀ[1,2,5]oxadiazolo[3,4ꢀg]indazole
3ꢀoxide (12a). The yield of compound 12a was 0.06 g (25%).
M.p. 150—154 °C. Found (%): C, 52.45; H, 2.42; N, 23.63.
C13H7N5O4. Calculated (%): C, 52.53; H, 2.37; N, 23.56.
1H NMR, δ: 7.80—7.98 (m, 5 H, Ph); 8.39 (s, 1 H, CH); 8.80 (s,
1 H, CH). IR, ν/cm–1: 1608, 1544, 1496, 1486, 1388, 1340,
1196, 1056, 960, 868, 760, 712, 688, 668. MS, m/z: 297 [M]+.
8ꢀPhenylꢀ5ꢀ(phenylsulfonyl)ꢀ8Hꢀ[1,2,5]oxadiazolo[3,4ꢀg]ꢀ
indazole 3ꢀoxide (12b). The yield of compound 12b was 0.11 g
(34%). M.p. 150—154 °C. Found (%): C, 58.07; H, 3.01;
N, 14.45. C19H12N4O4S. Calculated (%): C, 58.16; H, 3.08;
N, 14.28; S, 8.17. 1H NMR, δ: 7.52—7.84 (m, 8 H, Ph, PhSO2);
3
7.99 (s, 1 H, CH); 8.26 (d, 2 H, Рh, J = 7.5 Hz); 8.70 (s, 1 H,
CH). IR, ν/cm–1: 1620, 1536, 1512, 1496, 1460, 1436, 1316,
1152, 1076, 1016, 960, 912, 856, 760, 740, 724, 688, 628. MS,
m/z: 392 [M]+.
This study was financially supported by the Russian
Foundation for Basic Research (Project No. 07ꢀ03ꢀ00414),
the Council on Grants at the President of the Russian
Federation (Program for State Support of Young Scienꢀ
tists, Grant MKꢀ1293.2008.3), and the International
Science and Technology Center (ISTC, Grant 3197r).
8ꢀPhenylꢀ5ꢀ(phenylsulfonyl)ꢀ8Hꢀ[1,2,5]thiadiazolo[3,4ꢀg]ꢀ
indazole (10). A solution of diamine 6 (0.3 g) in a mixture of
SOCl2 (5 mL) and pyridine (5 mL) was refluxed for 1 h. Then
the reaction mixture was cooled and poured onto ice (50 g). The
precipitate was filtered off and washed with acetone, The filtrate
was concentrated. Compound 10 was obtained in a yield of

420
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Bastrakov et al.
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Received June 4, 2008;
in revised form September 17, 2008