Synthesis of peri-annelated heterocyclic systems based on 3-substituted 1-aryl-4,6-dinitro-1H-indazoles

Article abstract of DOI:10.1023/A:1026056704860

A method for the synthesis of peri-annelated trinuclear heterocycles, including 14π-electron heteroaromatic systems, namely, 1H-thiopyrano[4,3,2- cd]indazoles and 1,5-dihydropyrazolo[3,4,5-de]cinnolines, from 3-R-1-aryl-4,6-dinitro-1H-indazoles was develo

Full text of DOI:10.1023/A:1026056704860

Russian Chemical Bulletin, International Edition, Vol. 52, No. 8, pp. 1777—1781, August, 2003
1777
Synthesis of periꢀannelated heterocyclic systems based on
3ꢀsubstituted 1ꢀarylꢀ4,6ꢀdinitroꢀ1Hꢀindazoles.
ꢀ
A. M. Starosotnikov, A. V. Lobach, V. M. Vinogradov, and S. A. Shevelev
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (095) 135 5328. Eꢀmail: shevelev@mail.ioc.ac.ru
A method for the synthesis of periꢀannelated trinuclear heterocycles, including 14π-elecꢀ
tron heteroaromatic systems, namely, 1Hꢀthiopyrano[4,3,2ꢀcd]indazoles and 1,5ꢀdihydroꢀ
pyrazolo[3,4,5ꢀde]cinnolines, from 3ꢀRꢀ1ꢀarylꢀ4,6ꢀdinitroꢀ1Hꢀindazoles was developed. The
method is based on the high mobility of the NO2 group in position 4 and consists of
either selective nucleophilic substitution of the 4ꢀNO2 group on treatment with the
HSCH2CO2Me—K2CO3 system followed by intramolecular cyclization of the resulting sulfide
(R = CHO) or the corresponding sulfone (R = CN) formed upon its oxidation or direct
intramolecular substitution of the 4ꢀNO2 group (R = CH=NNHPh).
Key words: 4,6ꢀdinitroꢀ1Hꢀindazoles, nucleophilic substitution, cyclization, periꢀannelated
trinuclear heterocycles, 14π-electron heteroaromatic systems, thiopyranoindazoles, dihydroꢀ
pyrazolocinnolines.
Previously, we developed methods for the synthesis of
3ꢀRꢀ1ꢀarylꢀ4,6ꢀdinitroꢀ1Hꢀindazoles (R = CHO (1)1,2
and CN (2)2) starting from 2,4,6ꢀtrinitrotoluene (TNT).
It was found that the nitro group in position 4 of 4,6ꢀdiꢀ
nitroindazoles 1 and 2, i.e., the group closest to the heteroꢀ
cyclic nucleus, is selectively substituted under mild conꢀ
ditions on treatment with anionic Sꢀ, Oꢀ, and Nꢀnucleoꢀ
philes.1,2 In this study, we employed the high mobility of
the 4ꢀNO2ꢀgroup in 4,6ꢀdinitroindazoles 1 and 2 to synꢀ
thesize periꢀannelated heterocyclic systems.
lated aromatic heterocycles, namely, 1,5ꢀdiarylꢀ7ꢀnitroꢀ
1,5ꢀdihydropyrazolo[3,4,5ꢀde]cinnolines 5a,b. It can be
assumed that the reaction proceeds via preliminary
deprotonation of phenylhydrazones 4a,b to give Nꢀanꢀ
ions B (see Scheme 1).
Thus, starting from 3ꢀformylꢀ4,6ꢀdinitroindazoles 1,
we synthesized representatives of two types of 14πꢀelecꢀ
tron periꢀannelated tricyclic heteroaromatic systems,
namely, 1Hꢀthiopyrano[4,3,2ꢀcd]indazoles and 1,5ꢀdiꢀ
hydropyrazolo[3,4,5ꢀde]cinnolines.
We have found that 1ꢀarylꢀ3ꢀformylꢀ4,6ꢀdinitroꢀ
1Hꢀindazoles (1) can be used to prepare 14πꢀelectron
periꢀannelated tricyclic heteroaromatic systems (for the
preliminary communication, see Ref. 3). Thus the reꢀ
action of 3ꢀformylꢀ4,6ꢀdinitroindazoles 1a,b with
methyl thioglycolate in Nꢀmethylpyrrolidone (NMP) or
DMF in the presence of solid K2CO3 gives the correꢀ
sponding periꢀannelated tricyclic heteroaromatic comꢀ
pounds, namely, methyl 1ꢀarylꢀ7ꢀnitroꢀ1Hꢀthiopyraꢀ
no[4,3,2ꢀcd]indazoleꢀ4ꢀcarboxylates 3a,b (Scheme 1).
Presumably, first, the 4ꢀNO2 group is substituted on treatꢀ
ment with the thioglycolate—K2CO3 system to give interꢀ
mediate A. The formyl group in A undergoes baseꢀcataꢀ
lyzed intramolecular condensation with the active methꢀ
ylene fragment of the SCH2CO2Me substituent.
Note that 14πꢀelectron periꢀannelated heteroaromatic
systems consisting of two sixꢀmembered and one fiveꢀ
membered rings represent a relatively uncommon type of
heterocycles (see Refs. 4, 5). As regards the tricyclic sysꢀ
tems obtained in this work, we found no publications
describing their synthesis; only a collection of reports6
contains data on pharmacological properties of some
1Hꢀthiopyrano[4,3,2ꢀcd]indazoles with substituents other
that those considered in our study, but no synthetic proꢀ
cedures are reported.
We studied some transformations of thiopyranoꢀ
indazoles 3 using tricyclic derivative 3а as an example.
Compound 3а is easily and selectively oxidized on treatꢀ
ment with aqueous H2O2 in CF3COOH to afford the
corresponding sulfone 6; the same reaction in AcOH reꢀ
sults in sulfoxide 7 (Scheme 2). Alkaline hydrolysis of 3а
leads to the corresponding tricyclic carboxylic acid 8.
Previously we reported2 that the 4ꢀNO2 group in
3ꢀcyanoꢀ4,6ꢀdinitroꢀ1ꢀphenylꢀ1Hꢀindazole (2а) is reꢀ
placed in the reaction with methyl thioglycolate in the
Under standard conditions, 1ꢀarylꢀ3ꢀformylꢀ4,6ꢀdiꢀ
nitroindazoles 1a,b are converted into phenylhydrazones
4a,b, which undergo intramolecular cyclization with reꢀ
placement of the 4ꢀNO2 group on treatment with K2CO3
in NMP or DMF yielding the corresponding periꢀanneꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1686—1689, August, 2003.
1066ꢀ5285/03/5208ꢀ1777 $25.00 © 2003 Plenum Publishing Corporation

1778
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
Starosotnikov et al.
Scheme 1
Scheme 2
Reagents and conditions: i. 35% H2O2 (8 equiv.), CF3COOH,
20 °C, 0.5 h; ii. 35% H2O2 (120 equiv.), AcOH, 60 °C, 12 h;
iii. 10 equiv. NaOH, H2O, 100 °C, 20 h.
field shift of the NH2 signal (9.0 ppm). These data indiꢀ
cate a sizable contribution of structures 12´ and 12″ (see
Scheme 3). Indeed, such spectral data are quite inherent
in this type of pushꢀpull compounds. For example, in the
IR spectrum of derivatives of 3ꢀaminoꢀ2ꢀnitroacrylic esꢀ
ters, the absorption bands due to the ester group are loꢀ
cated in the 1650—1670 cm–1 region and the chemical
shifts of the NH2 protons reach 9.7 ppm (see Ref. 7).
It might be expected that 3ꢀformylꢀ4,6ꢀdinitroꢀ1ꢀpheꢀ
nylꢀ1Hꢀindazole oxime (13)2 can also be used to obtain a
tricyclic system. In particular, under the action of a base,
the arising oximate anion will enter into intramolecular
replacement of the 4ꢀNO2 group to form tricyclic comꢀ
pound 14. However, on treatment with K2CO3 in NMP,
oxime 13 is converted into 3ꢀcyanoꢀ4ꢀhydroxyꢀ6ꢀnitroꢀ
1ꢀphenylꢀ1Hꢀindazole (15) (Scheme 4).
In our opinion, tricyclic product 14 is formed iniꢀ
tially during the reaction but undergoes oxazine ring
opening under the action of a base present, being
thus converted into nitrile 15. This type of βꢀcleavage,
—ON=CH— → —OH + N≡C—, induced by bases is well
known for 3ꢀunsubstituted benzo[d]isoxazoles, which are
converted into 2ꢀhydroxybenzonitriles (see Refs. 8, 9),
and for Oꢀarylaldoximes containing electronꢀwithdrawꢀ
ing substitutes in the Oꢀaryl fragment, which give rise to
phenols and alkyl(aryl)nitriles (see Ref. 10).
Ar = Ph (a), 4ꢀClC6H4 (b)
Reagents and conditions: i.
2 equiv. K2CO3, NMP, 60 °C, 10 h; ii. 1 equiv. PhNHNH2•HCl,
EtOH, 78 °C, 3 h; iii. 1 equiv. K2CO3, NMP, 80 °C, 10 h.
1 equiv. HSCH2CO2CH3,
presence of K2CO3, giving rise to the corresponding sulꢀ
fide 9. An attempt to perform cyclization of sulfide 9
through the addition of the active methylene bridge to the
CN bond (in the presence of bases) to give tricyclic comꢀ
pound 10 (Scheme 3) failed, most likely, because of the
insufficient mobility of the hydrogen atoms in the methylꢀ
ene fragment of sulfide 9. In order to obtain a compound
with more reactive methylene bridge, sulfide 9 was oxiꢀ
dized with an aqueous H2O2—CF3COOH mixture to the
corresponding sulfone 11. Easy cyclization of this sulfone
on treatment with K2CO3 in NMP gave periꢀannelated
tricyclic amino derivative 12.
It should be noted that the position of the carbonyl
absorption band in the IR spectrum of derivative 12
(1668 cm–1) is unusual for an ester group. The H NMR
Thus, based on 1ꢀarylꢀ3ꢀformyl(3ꢀcyano)ꢀ4,6ꢀdinitroꢀ
1Hꢀindazoles and making use of the high mobility of
4ꢀNO2 group, one can obtain periꢀannelated trinuclear
1
spectrum of this compound exhibits a very strong downꢀ

Synthesis of periꢀannelated heterocycles
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
1779
Scheme 3
Reagents and conditions: i. H2O2, CF3COOH, 20 °C; ii. K2CO3, NMP, 80 °C.
Scheme 4
shifts (δ) are referred to Me4Si. The spinꢀspin coupling conꢀ
stants are given in Hz. IR spectra were measured using a Specord
Mꢀ80 instrument in KBr pellets. Mass spectra (EI, 70 eV) were
recorded using a Kratos MSꢀ30 mass spectrometer. The reacꢀ
tions were monitored and the compound purity was checked
using TLC on Silufol UVꢀ254 plates. The solvents were not
specially dried. Compounds 1, 9, and 13 were obtained accordꢀ
ing to known procedures.2
Preparation of thiopyranoindazoles 3а,b (general procedure).
Potassium carbonate (0.55 g, 4 mmol) was added to a solution
containing 3ꢀformylindazole 1а or 1b (2 mmol) and methyl
thioglycolate (0.18 mL, 2 mmol) in 7 mL of NMP, and the
mixture was stirred for 8 h at 60 °C. The reaction mixture was
cooled and poured in water, and the resulting mixture was acidiꢀ
fied to рH = 2. The precipitate was filtered off, washed with
acetone, and recrystallized from CHCl3.
Methyl 7ꢀnitroꢀ1ꢀphenylꢀ1Hꢀthiopyrano[4,3,2ꢀcd]indazoleꢀ
4ꢀcarboxylate (3а). M.p. 230—231 °C (CHCl3). Found (%):
C, 57.11; H, 3.39; S, 8.51. C17H11N3O4S. Calculated (%):
1
C, 57.78; H, 3.14; S, 9.07. H NMR (CDCl3), δ: 3.98 (s, 3 H,
i. K2CO3, NMP, 80 °C.
3
CH3); 7.45 (t, 1 H, Ph, JH,H = 7.2 Hz); 7.62 (t, 2 H, Ph,
3JH,H = 7.2 Hz); 7.70 (s, 1 H, H arom.); 7.75 (d, 2 H, Ph,
3JH,H = 7.2 Hz); 7.95 (s, 1 H, H arom.); 8.15 (s, 1 H, H arom.).
13C NMR (CDCl3), δ: 53.5, 103.4, 109.0, 121.6, 124.1, 127.5,
127.9, 130.0, 132.3, 132.9, 137.5, 139.2, 143.6, 150.1, 163.0.
MS, m/z: 353 [M]+, 307 [M – NO2]+. IR, ν/cm–1: 1720
(CO2Me), 1540, 1340 (NO2).
heterocycles, including representatives of new 14πꢀelecꢀ
tron heteroaromatic systems.
The structures and compositions of the compounds
obtained were proved by 1H NMR data, mass spectra (the
molecular ion is observed in all cases), IR spectra, and
elemental analysis.
Methyl
1ꢀ(4ꢀchlorophenyl)ꢀ7ꢀnitroꢀ1Hꢀthiopyraꢀ
no[4,3,2ꢀcd]indazoleꢀ4ꢀcarboxylate (3b). M.p. >300 °C (CHCl3).
Found (%): C, 52.69; Cl, 9.05; H, 2.85; S, 8.18. C17H10ClN3O4S.
1
Calculated (%): C, 52.65; Cl, 9.14; H, 2.60; S, 8.27. H NMR
Experimental
(CDCl3), δ: 3.95 (s, 3 H, CH3); 7.55 (d, 2 H, H arom., 3JH,H
8.8 Hz); 7.60 (d, 3 H, H arom., JH,H = 8.8 Hz); 7.95 (s, 1 H,
H arom.); 8.09 (s, 1 H, H arom.). MS, m/z: 387 [M]+, 341
[M – NO2]+. IR, ν/cm–1: 1712 (CO2Me), 1520, 1348 (NO2).
=
3
1
H and 13C NMR spectra were recorded on Bruker ACꢀ200
and Bruker AМꢀ300 instruments, respectively. The chemical

1780
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
Starosotnikov et al.
Preparation of 3ꢀformylindazole Nꢀphenylhydrazones 4a,b
(general procedure). PhNHNH2•HCl (0.93 g, 6.4 mmol) was
added to a suspension of compound 1а or 1b (6.4 mmol) in
30 mL of EtOH and the mixture was refluxed for 3 h. The
reaction mixture was cooled and the precipitate was filtered off,
washed with EtOH, and dried at 80 °C.
7.3 Hz); 8.05 (s, 1 H, CH); 8.60 (s, 1 H, H arom.); 8.90 (s, 1 H,
H arom.). IR, ν/cm–1: 1728 (CO2Me), 1536, 1336 (NO2),
1084 (S=O).
7ꢀNitroꢀ1ꢀphenylꢀ1Hꢀthiopyrano[4,3,2ꢀcd]indazoleꢀ4ꢀcarbꢀ
oxylic acid (8). A mixture of 2а (0.18 g, 0.5 mmol), NaOH
(0.2 g, 5 mmol), and 15 mL of water was refluxed for 24 h. After
cooling, the reaction mixture was acidified to рH = 2 and the
precipitate was filtered off, washed with water, dried, and reꢀ
crystallized from CHCl3 to give 0.14 g of compound 8. M.p.
4,6ꢀDinitroꢀ1ꢀphenylꢀ1Hꢀindazoleꢀ3ꢀcarboxaldehyde Nꢀpheꢀ
nylhydrazone (4а). M.p. 260—261 °C (EtOH). 1H NMR
3
(DMSOꢀd6), δ: 6.80 (t, 1 H, Ph, JH,H = 7.3 Hz); 7.00 (d, 2 H,
3
3
1
Ph, JH,H = 7.3 Hz); 7.20 (t, 2 H, Ph, JH,H = 7.3 Hz); 7.60 (t,
1 H, Ph, 3JH,H = 7.9 Hz); 7.70 (t, 2 H, Ph, 3JH,H = 7.8 Hz); 7.85
(d, 2 H, Ph, 3JH,H = 7.9 Hz); 8.20 (s, 1 H, CH=N); 8.55 (s, 1 H,
H arom.); 8.75 (s, 1 H, H arom.); 10.60 (s, 1 H, NH).
303—304 °C (CHCl3). H NMR (DMSOꢀd6), δ: 7.45 (t, 1 H,
Ph, 3JH,H = 6.7 Hz); 7.63 (t, 2 H, Ph, 3JH,H = 7.3 Hz); 7.80 (m,
3 H, Ph, CH); 8.08 (s, 1 H, H arom.); 8.25 (s, 1 H, H arom.).
13C NMR (DMSOꢀd6), δ: 103.2, 109.1, 121.4, 127.4, 130.1,
133.8, 137.2, 139.3, 144.2, 150.1, 163.9. MS, m/z: 339 [M]+,
293 [M – NO2]+. IR, ν/cm–1: 1700 (CO2H), 1530, 1350 (NO2).
Methyl 2ꢀ[(3ꢀcyanoꢀ6ꢀnitroꢀ1ꢀphenylꢀ1Hꢀindazolꢀ4ꢀyl)sulꢀ
fonyl]acetate (11). A 35% solution of H2O2 (1 mL) was added at
20 °C to a solution of compound 9 (0.4 g, 1.1 mmol) in 8 mL of
CF3COOH and the mixture was stirred for 1 h. The reaction
mixture was poured in water and the precipitate was filtered off,
washed with water and EtOH, and dried in vacuo to give
0.4 g (92%) of compound 11. M.p. 185—187 °C. 1H NMR
(DMSOꢀd6), δ: 3.67 (s, 3 H, OCH3); 4.98 (s, 2 H, CH2);
7.60—7.90 (m, 5 H, Ph); 8.70 (s, 1 H, H(5)); 8.90 (s, 1 H,
H(7)). 13C NMR (DMSOꢀd6), δ: 113.1, 115.5, 120.3, 123.0,
125.3, 130.9, 131.0, 132.8, 137.8, 140.1, 146.9, 163.5. IR,
ν/cm–1: 1724 (CO2Мe), 1540, 1340 (NO2), 1168 (SO2). MS,
m/z: 400 [M]+.
1ꢀ(4ꢀChlorophenyl)ꢀ4,6ꢀdinitroꢀ1Hꢀindazoleꢀ3ꢀcarboxaldeꢀ
hyde Nꢀphenylhydrazone (4b). M.p. 267—269 °C (EtOH).
1H NMR (DMSOꢀd6), δ: 6.88 (m, 1 H, Ph); 7.10—7.35 (m,
4 H, Ph); 7.64 (s, 1 H, CH=N); 7.78 (d, 2 H, H arom., 3JH,H
8.0 Hz); 8.05 (d, 2 H, H arom., JH,H = 8.0 Hz); 8.75 (s, 1 H,
H arom.); 8.90 (s, 1 H, H arom.); 11.75 (s, 1 H, NH).
=
3
Synthesis of pyrazolocinnolines 5а,b (general procedure). Poꢀ
tassium carbonate (0.21 g, 1.5 mmol) was added to a solution of
compound 4а or 4b (1.5 mmol) in 10 mL of NMP and the
mixture was stirred for 8 h at 90 °C. Then the reaction mixture
was cooled and poured in water and the precipitate was filtered
off, washed with acetone, and dried in air.
7ꢀNitroꢀ1,5ꢀdiphenylꢀ1,5ꢀdihydropyrazolо[3,4,5ꢀde]cinnoꢀ
line (5а). M.p. 257—259 °C. Found (%): C, 66.91; H, 3.95.
C20H13N5O2. Calculated (%): C, 67.60; H, 3.69. 1H NMR
(CDCl3), δ: 7.12 (s, 1 H, H arom.); 7.40—7.55 (m, 2 H, Ph);
7.55—7.65 (m, 6 H, Ph); 7.80 (d, 2 H, Ph, 3JH,H = 7.2); 7.92 (s,
1 H, H arom.); 8.09 (s, 1 H, CH=N). MS, m/z: 355 [M]+, 309
[M – NO2]+. IR, ν/cm–1: 1596 (C=N), 1544, 1340 (NO2).
1ꢀ(4ꢀChlorophenyl)ꢀ7ꢀnitroꢀ5ꢀphenylꢀ1,5ꢀdihydropyrazoꢀ
lo[3,4,5ꢀde]cinnoline (5b). M.p. 264—265 °C. Found (%):
C, 61.19; Cl, 9.50; H, 3.32. C20H12ClN5O2. Calculated (%):
Methyl 3ꢀaminoꢀ7ꢀnitroꢀ5,5ꢀdioxoꢀ1ꢀphenylꢀ1,5ꢀdihydroꢀ
5λ ꢀthiopyrano[4,3,2ꢀcd]indazoleꢀ4ꢀcarboxylate (12). Potassium
6
carbonate (0.21 g, 1.5 mmol) was added to a solution of comꢀ
pound 11 (0.6 g, 1.5 mmol) in 8 mL of NMP and the mixture
was stirred at 80 °C for 8 h. After cooling, the reaction mixture
was poured in water, the resulting mixture was acidified to
рH = 4, and the precipitate was filtered off, thoroughly washed
with CHCl3, and dried in air to give 0.33 g (55%) of comꢀ
pound 12. M.p. >300 °C. Found (%): C, 51.29; H, 2.74; S, 8.04.
C17H12N4O6S. Calculated (%): C, 51.00; H, 3.02; S, 8.01.
1H NMR (DMSOꢀd6), δ: 3.90 (s, 3 H, OCH3); 7.60—7.80 (m,
3 H, Ph); 8.00 (d, 2 H, Ph, 3JH,H = 7.3 Hz); 8.51 (s, 1 H, H(5));
8.90 (s, 1 H, H(7)); 9.00 (br.s, 2 H, NH2). IR, ν/cm–1: 1668
(CO2Me), 1548, 1336 (NO2), 1260 (SO2). MS, m/z: 400 [M]+,
354 [M – NO2]+.
1
C, 61.63; Cl, 9.10; H, 3.10. H NMR (DMSOꢀd6) δ: 6.95 (s,
1 H, H arom.); 7.50 (m, 1 H, Ph); 7.60 (m, 6 H, Ph); 8.90 (m,
3 H, Ph, H arom.); 8.22 (s, 1 H, CH=N). MS, m/z: 389 [M]+,
343 [M – NO2]+. IR, ν/cm–1: 1596 (C=N), 1532, 1340 (NO2).
6
Methyl 7ꢀnitroꢀ5,5ꢀdioxoꢀ1ꢀphenylꢀ1,5ꢀdihydroꢀ5λ ꢀthioꢀ
pyrano[4,3,2ꢀcd]indazoleꢀ4ꢀcarboxylate (6). A 35% solution of
H2O2 (3 mL) was added at 20 °C to a solution of 2а (0.45 g,
1.28 mmol) in 20 mL of CF3COOH and the mixture was stirred
for 20 min. The reaction mixture was poured in water and the
precipitate was filtered off, dried at 100 °C, and recrystallized
from CHCl3 to give 0.4 g of compound 6. M.p. 218—220 °C
(CHCl3). Found (%): C, 52.99; H, 3.06; S, 8.04. C17H11N3O6S.
Calculated (%): C, 52.99; H, 2.88; S, 8.32. 1H NMR (DMSOꢀd6)
δ: 3.97 (s, 3 H, OCH3); 7.54—7.76 (m, 3 H, Ph); 7.91 (d, 2 H,
Ph, 3JH,H = 7.9 Hz); 8.55 (s, 1 H, CH); 8.75 (s, 1 H, H arom.);
8.91 (s, 1 H, H arom.). MS, m/z: 385 [M]+, 308 [M – Ph]+. IR,
ν/cm–1: 1720 (CO2Me); 1544, 1344 (NO2); 1320 (SO2).
3ꢀCyanoꢀ4ꢀhydroxyꢀ6ꢀnitroꢀ1ꢀphenylꢀ1Hꢀindazole (15). Poꢀ
tassium carbonate (0.09 g, 0.6 mmol) was added to a solution of
compound 13 (0.2 g, 0.6 mmol) in 6 mL of NMP and the
mixture was stirred at 80 to 90 °C for 6 h. The reaction mixture
was cooled and poured in water. The resulting mixture was
acidified to рH = 2 and extracted with AcOEt (3×15 mL). The
solvent was evaporated and the residue was purified by column
chromatography (SiO2/CHCl3). Evaporation of the eluent gave
1
0.1 g of compound 15. M.p. 238—240 °C (CHCl3). H NMR
4
Methyl 7ꢀnitroꢀ5ꢀoxoꢀ1ꢀphenylꢀ1,5ꢀdihydroꢀ5λ ꢀthiopyraꢀ
(DMSOꢀd6), δ: 7.48 (s, 1 H, H(5)); 7.50—7.80 (m, 5 H, Ph);
8.01 (s, 1 H, H(7)); 11.90 (br.s, 1 H, OH). MS, m/z: 280 [M]+,
234 [M – NO2]+. IR, ν/cm–1: 2250 (CN), 1660 (C=N), 1540,
1345 (NO2).
no[4,3,2ꢀcd]indazoleꢀ4ꢀcarboxylate (7). A 35% solution of H2O2
(5×3 mL, every 2 h) was added at 60 °C to 2а (0.45 g, 1.28 mmol)
in 20 mL of AcOH. After cooling the reaction mixture, the
precipitate was filtered off, washed with water, dried at 100 °C,
and recrystallized from CHCl3 to give 0.13 g of compound 7.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 01ꢀ03ꢀ
32261).
1
M.p. 224—225 °C (CHCl3). H NMR (DMSOꢀd6), δ: 3.98 (s,
3 H, OCH3); 7.60—7.80 (m, 3 H, Ph); 7.87 (d, 2 H, Ph, 3JH,H
=

Synthesis of periꢀannelated heterocycles
Russ.Chem.Bull., Int.Ed., Vol. 52, No. 8, August, 2003
1781
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Received April 7, 2003