Synthesis of 1-aryl-4,6-dinitro-1H-indazoyl-3-methylcarboxylates

Article abstract of DOI:10.1081/SCC-120002132

Synthesis of 1-aryl-4,6-dinitro-1H-indazoyl-3-methylcarboxylates from 2,4,6-trinitrotoluene derivatives is reported.

Full text of DOI:10.1081/SCC-120002132

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SYNTHESIS OF 1-ARYL-4,6-DINITRO-1H-INDAZOYL-3-
METHYLCARBOXYLATES
V. V. Rozhkov a , S. S. Vorob'ov a , A. V. Lobatch a , A. M. Kuvshinov a & S. A. Shevelev a
a N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky
prosp., 47, Moscow, 117913, Russia
Published online: 16 Aug 2006.
To cite this article: V. V. Rozhkov , S. S. Vorob'ov , A. V. Lobatch , A. M. Kuvshinov & S. A. Shevelev (2002) SYNTHESIS OF
1-ARYL-4,6-DINITRO-1H-INDAZOYL-3-METHYLCARBOXYLATES, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 32:3, 467-472
To link to this article: http://dx.doi.org/10.1081/SCC-120002132
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SYNTHETIC COMMUNICATIONS, 32(3), 467–472 (2002)
SYNTHESIS OF 1-ARYL-4,6-DINITRO-1H-
INDAZOYL-3-METHYLCARBOXYLATES
V. V. Rozhkov,* S. S. Vorob’ov, A. V. Lobatch,
A. M. Kuvshinov, and S. A. Shevelev
N. D. Zelinsky Institute of Organic Chemistry,
Russian Academy of Sciences, Leninsky prosp.,
47, 117913, Moscow, Russia
ABSTRACT
Synthesis of 1-aryl-4,6-dinitro-1H-indazoyl-3-methylcarboxyl-
ates from 2,4,6-trinitrotoluene derivatives is reported.
In our previous paper we described the synthesis of 2-aryl-4,6-dinitro-
2H-indazoles.1 Preparation of 1-aryl(hetaryl)-4,6-dinitro-1H-indazoles by
intermolecular cyclisation (with the displacement of the ortho-nitro group)
of 2,4,6-trinitrobenzaldehyde arylhydrazones has been reported before.2,3
In order to further modify 4,6-dinitroindazole by introduction of a
new substituent, we here report the facile synthesis of methyl esters of
1-aryl-4,6-dinitro-1H-indazolyl-3-carboxylic acids 6 from 2,4,6-trinitro-
toluene (TNT).
TNT can be easily converted into 2,4,6-trinitrophenylacetic acid (3)
according to Scheme 1 developed by Z. Bonecki and T. Urbansky.4
*Corresponding author. Current address: Department of Biochemistry and
Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, PA
19146, USA. Fax: þ1(215)573 3787; E-mail: rozhkov@mail.med.upenn.edu
467
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

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ROZHKOV ET AL.
Scheme 1.
The methyl ester was prepared by standard methodology, that is refluxing
picryl acetic acid with thionyl chloride in dry methanol.
We found that the ester 4 reacted with diazonium salts to form hydra-
zones 5, which undergo cyclisation in situ giving indazoles 6. The cyclisation
stepincludes an intermolecular substitution of the nitro group(Scheme 2)
and occurs under very mild conditions, at ꢀ10 to ꢀ5ꢁC. Most likely,
NaOAc, which is added to achieve the condensation of ester 4 with aryldia-
Scheme 2.
zonium salts, also promotes the cyclisation reaction.
1-Aryl-4,6-dinitroindazolyl-2-methylcarboxylates were obtained in
good yields (>80%) and the structures of the new indazoles 6 were estab-
1
lished by microanalyses, H and 13C NMR spectra.
EXPERIMENTAL
Melting points were measured using a Boetius apparatus and are
uncorrected. All reactions were monitored by TLC using Silufol (UV-254)

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MODIFICATION OF 4,6-DINITROINDAZOLES
469
precoated aluminium plates. NMR spectra were recorded on a Bruker
AC 200 spectrometer in DMSO-d6. Chemical shifts are reported in ppm
downfield from TMS, coupling constants are reported in hertz. Organic
solvents and reagents were purified by accepted literature procedures. A
column chromatography was run on silica gel Chemapol 5/40.
Picrylethanol (1) was obtained by condensation of TNT with formaldehyde
according to the known procedure5 and its NMR spectra are given in Lit.6
1-Picrylethyl Acetate (2)
Yield 90%; mp98–99 ꢁC (from PriOH); lit.4 yield 78%; mp98 ꢁC;
1H NMR d 1.19 (s, 3H, Me), 3.35 (t, 2H, CH2, 3J ¼ 5.8), 4.27 (t, 2H,
OCH2, 3J ¼5.8), 9.05 (s, 2H, Harom). 13C NMR d 20.44, 26.59, 62.63,
123.12, 132.33, 146.48, 151.18, 170.00.
Picrylacetic Acid (3)
ꢁ
ꢁ
1
Yield 72%; mp164–165 C; lit.4 yield 77%; mp163–165 C; H NMR
(MeOD) d 4.18 (s, 2H, CH2), 9.0 (s, 2H, Harom). 13C NMR d 35.02, 132.51,
131.80, 148.25, 152.62, 170.98.
Methyl Picrylacetate (4)
To a stirred solution of 5 g (18.5 mmol) of picrylacetic acid (3) in
50 mL of dry MeOH 22 g (185 mmol) of SOCl2 was added dropwise at
0ꢁC. The mixture was refluxed for 2 h and poured into 100 g of ice. The
precipitated solid was collected by filtration, washed with water until neutral
reaction and passed through 100 g silica gel using benzene as eluent. Yield
ꢁ
1
85%; mp54–56 C (PriOH); H NMR d 3.70 (s, 3H, OCH3), 4.25 (s, 2H,
CH2), 9.10 (s, 2H, Harom). 13C NMR d 33.89, 52.52, 128.34, 129.69, 146.68,
150.63, 168.31. Calcd for C9H7N3O8: C, 37.91; H, 2.47; N, 14.74. Found: C,
37.95; H, 2.57; N, 14.68.
Synthesis of Indazoles 6. General Procedure
Methyl picrylacetate 4 0.14 g (0.5 mmol) was dissolved in the mixture
of 15 mL of EtOH and 15 mL of pyridine. To this solution was added 0.67 g
(8 mmol) of NaOAc. The obtained suspension was left at ꢀ10 to ꢀ5ꢁC and a

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rigorously stirred solution of 0.48 mmol of aryldiazonium salt in 5 mL of
15% HCl was added dropwise. The mixture was kept at this temperature for
6 h and then poured into 100 mL 10% HCl. The precipitated solid was
collected by filtration, dried on air and crystallized from PriOH.
1
Yields, mp, H and 13C NMR Spectra of Compounds 6
Methyl 1-Phenyl-4,6-dinitro-1H-indazoyl-3-carboxylate (6a)
ꢁ
1
Yield 85%; mp179–180 C; H NMR d 3.95 (s, 3H, MeO), 7.72 (m,
2H, ABB0CC0 spectrum, Ph), 7.79 (m, 2H, ABB0CC0 spectrum, Ph), 8.79 (d,
1H, Harom, 4J ¼ 1.6), 8.81 (d, 1H, Harom, 4J ¼ 1.6). 13C NMR d 52.76, 113.30,
114.39, 115.88, 124.35, 129.65, 130.13, 136.04, 137.13, 139.97, 141.31,
145.96, 161.26. Calcd for C15H10N4O6: C, 52.64; H, 2.94; N, 16.37.
Found: C, 52.68; H, 3.01; N, 16.42.
Methyl 1-( p-Methylphenyl)-4,6-dinitro-1H-indazoyl-3-carboxylate (6b)
Yield 82%; mp202–203 ꢁC; 1H NMR d 2.45 (s, 3H, Me), 3.94 (s,
3H, MeO), 7.51 (m, 2H, AA0BB0 spectrum, p-MePh), 7.73 (m, 2H,
AA0BB0 spectrum, p-MePh), 8.76 (d, 1H, Harom
H
130.52, 134.70, 135.80, 139.57, 140.00, 141.31, 145.89, 161.29. Calcd
for C16H12N4O6: C, 53.94; H, 3.39; N, 15.73. Found: C, 53.90; H, 3.45;
N, 15.72.
,
4J ¼ 1.6), 8.77 (d, 1H,
4
arom, J ¼ 1.6). 13C NMR d 20.73, 52.77, 113.29, 114.33, 115.78, 124.22,
Methyl 1-( p-Methoxyphenyl)-4,6-dinitro-1H-indazoyl-3-carboxylate (6c)
Yield 87%; mp178–179 ꢁC; 1H NMR d 3.89 (s, 3H, MeO), 3.93
(s, 3H, MeO), 7.24 (m, 2H, AA0BB0 spectrum, p-MeOPh), 7.78 (m, 2H,
AA0BB0 spectrum, p-MeOPh), 8.71 (d, 1H, Harom, J ¼ 1.6), 8.78 (d, 1H,
4
4
H
arom, J ¼ 1.6). 13C NMR d 52.74, 55.67, 113.23, 114.26, 115.18, 115.60,
126.23, 129.96, 135.53, 140.31, 141.33, 145.84, 160.05, 161.35. Calcd
for C16H12N4O7: C, 51.62; H, 3.25; N, 15.05. Found: C, 51.66; H, 3.21;
N, 15.09.

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471
Methyl 1-( p-Bromphenyl)-4,6-dinitro-1H-indazoyl-3-carboxylate (6d)
ꢁ
1
Yield 88%; mp184–185 C; H NMR d 3.93 (s, 3H, MeO), 7.83 (m,
2H, AA0BB0 spectrum, p-BrPh), 7.91 (m, 2H, AA0BB0 spectrum, p-BrPh),
4
4
8.79 (d, 1H, Harom, J ¼ 2.1), 8.87 (d, 1H, Harom, J ¼ 2.1). 13C NMR d
52.84, 113.45, 114.53, 115.99, 122.62, 126.35, 133.06, 136.33, 136.42,
140.00, 141.28, 146.08, 161.18. Calcd for C15H9BrN4O6: C, 42.78; H, 2.15;
N, 13.30. Found: C, 42.75; H, 2.20; N, 13.33.
Methyl 1-( p-Acetylphenyl)-4,6-dinitro-1H-indazoyl-3-carboxylate (6e)
Yield 81%; mp187–188 ꢁC; 1H NMR d 2.69 (s, 3H, MeCO), 3.94 (s, 3H,
MeO), 8.03 (m, 2H, AA0BB0 spectrum, p-MeCOPh), 8.24 (m, 2H, AA0BB0
4
spectrum, p-MeCOPh), 8.81 (d, 1H, Harom, J ¼ 1.6), 8.92 (d, 1H, Harom
,
4J ¼ 1.6). 13C NMR d 26.95, 52.95, 113.64, 114.76, 116.29, 124.15, 130.15,
136.78, 136.95, 139.97, 140.58, 141.35, 146.26, 161.24, 197.12. Calcd
for C17H12N4O7: C, 53.13; H, 3.15; N, 14.58. Found: C, 53.15; H, 3.20;
N, 14.54.
Methyl 1-(3-Pyridyl)-4,6-dinitro-1H-indazoyl-3-carboxylate (6f)
Yield 81%; mp193–194 ꢁC; 1H NMR d 3.96 (s, 3H, MeO), 7.78
(m, ABCD spectrum, Py), 8.36 (m, ABCD spectrum, Py), 8.83 (d, 1H,
Harom
,
4J ¼ 2.1), 8.84 (m, ABCD spectrum, Py), 8.96 (d, 1H, Harom
,
4J ¼ 2.1), 9.10 (m, ABCD spectrum, Py). 13C NMR d 52.87, 113.59,
114.64, 115.99, 124.80, 132.45, 136.81, 140.48, 141.26, 145.33, 146.20,
150.47, 161.19. Calcd for C14H9N5O6: C, 48.99; H, 2.64; N, 20.40. Found:
C, 48.95; H, 2.69; N, 20.42.
ACKNOWLEDGMENT
We thank the International Science and Technology Center (Project
#419) for financial support.

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ROZHKOV ET AL.
REFERENCES
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Int. 2000, 32, 94.
Received in the USA March 19, 2001

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