Synthesis and characterization of 4,6-diaryl-4,5-dihydro-2H-indazol-3-ols and 4,6-diaryl-2-phenyl-4,5-dihydro-2H-indazol-3-ols - A new series of fused indazole derivatives

Article abstract of DOI:10.1007/s10593-008-0137-y

A novel class of 4,6-diaryl-4,5-dihydro-2H-indazol-3-ols and 4,6-diaryl-2-phenyl-4,5-dihydro-2H-indazol-3-ols is synthesized and characterized by melting point, elemental analysis, MS, FT-IR, ¹H and ¹³C NMR, D₂O exchanged ¹H NMR, and two-dimensional HSQC spectra.

Full text of DOI:10.1007/s10593-008-0137-y

Chemistry of Heterocyclic Compounds, Vol. 44, No. 8, 2008
SYNTHESIS AND CHARACTERIZATION
OF 4,6-DIARYL-4,5-DIHYDRO-2H-INDAZOL-
3-OLS AND 4,6-DIARYL-2-PHENYL-4,5-DIHYDRO-
2H-INDAZOL-3-OLS − A NEW SERIES OF FUSED
INDAZOLE DERIVATIVES
M. Gopalakrishnan, J. Thanusu, V. Kanagarajan
A novel class of 4,6-diaryl-4,5-dihydro-2H-indazol-3-ols and 4,6-diaryl-2-phenyl-4,5-dihydro-
2H-indazol-3-ols is synthesized and characterized by melting point, elemental analysis, MS, FT-IR,
1H and 13C NMR, D2O exchanged 1H NMR, and two-dimensional HSQC spectra.
Keywords: 3,5-diaryl-6-ethoxycarbonylcyclohex-2-en-1-ones, 4,6-diaryl-4,5-dihydro- 2H-indazol-3-ols,
4,6-diaryl-2-phenyl-4,5-dihydro-2H-indazol-3-ols, hydrazine hydrate, phenylhydrazine hydrochloride.
Various structurally diverse indazole derivatives have aroused great interest due to their wide variety of
biological properties such as antimicrobial activity [1], inhibition of protein kinase B/Akt [2], antiprotozaal [3],
antichagasic [3], leichmanocidal [3], and trypanocidal activities [3], inhibition of S-adenosyl homo-
cysteine/methylthioadenosine (SAH/MTA) nucleosidase [4], potent activation of nitric oxide receptors [5], and
inhibition of platelet aggregation [5].
R
2
1
O
O
N
N
3
OH
H2N–NHR
Me
Z
O
8
7
6
9
4
Y
Y
MeOH,
reflux 5-7 h
5
Z
X
X
1–8
9–24
9-16 R = H, 17-24 R = Ph; 9-13, 16-21, 24 X = H, 14, 22 X = Br, 15, 23 X = Me; 9-15,
17-23 Y = H, 16,24 Y = NO2; 9,14,15,17,22,23 Z = H, 10,18 Z = Me, 11,19 Z = Cl,
12,20 Z = NO2, 13,16,21,24 Z = OMe
__________________________________________________________________________________________
Synthetic Organic Chemistry Laboratory, Department of Chemistry, Annamalai University,
Annamalainagar-608 002, Tamil Nadu, India; e-mail: profmgk@yahoo.co.in Translated from Khimiya
Geterotsiklicheskikh Soedinenii, No. 8, pp. 1183-1188, August, 2008. Original article submitted Received
February 17, 2008.
950
0009-3122/08/4408-0950©2008 Springer Science+Business Media, Inc.

TABLE 1. Physical and Analytical Characteristics of Compounds 9-24
Found, %
——————
Calculated, %
m/z [M+.]
Com-
pound
Empirical
formula
mp,°C
Yield, %
C
H
N
9
C19H18N2O
C20H20N2O
C19H17Cl N2O
C19H17N3O3
C20H20N2O2
C19H17BrN2O
C20H20N2O
C20H19N3O4
C25H20N2O
C26H22N2O
C25H19Cl N2O
C25H19N3O3
C26H22N2O2
C25H19BrN2O
C26H22N2O
C26H21N3O4
291
305
326
336
321
370
305
366
364
378
398
409
394
443
378
439
78.55
78.59
78.88
78.92
70.21
70.26
68.01
68.05
74.63
74.98
61.76
61.80
78.89
78.92
65.70
65.74
82.35
82.39
82.47
82.51
75.22
75.28
73.31
73.34
79.11
79.16
67.69
67.73
82.46
82.51
71.01
71.06
6.21
6.25
6.59
6.62
5.26
5.28
5.07
5.11
6.27
6.29
4.61
4.64
6.59
6.62
5.20
5.24
5.49
5.53
5.82
5.86
4.78
4.80
4.65
4.68
5.58
5.62
4.28
4.32
5.81
5.86
4.79
4.82
9.61
9.65
9.17
9.20
8.58
8.62
12.50
12.53
8.71
8.74
7.56
7.59
9.17
9.20
11.46
11.50
7.64
7.69
7.36
7.40
6.98
7.02
10.23
10.26
7.06
7.10
6.29
6.32
7.36
7.40
9.51
9.56
226
230
234
212
204
232
225
210
237
242
251
224
219
238
239
205
73
70
68
72
70
69
60
68
80
75
76
78
70
65
60
75
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
In recent years there has been a great deal of interest in exploiting more than one proximal functional groups
for designing novel structures capable of performing a variety of functions. The present study describes the use of
3,5-diaryl-6-ethoxycarbonylcyclohex-2-en-1-one [6], an intermediate with three versatile functional groups, i.e.,
ketone, olefin, and ester, for the synthesis of fused indazole derivatives.
In continuation of our earlier work on the synthesis of various biologically active heterocyclic
compounds including biolabile piperidone, 1,2,3-selenadiazoles, 1,2,3-thiadiazoles, and 1,2,4,5-tetrazinanes
[7-11], we wish to report the development of fused indazoles based on 3,5-diaryl-6-ethoxycarbonylcyclohex-
2-en-1-one derivative, thus paving the way for a novel class of 4,6-diaryl-4,5-dihydro-2H-indazol-3-ols 9-16
and 4,6-diaryl-2-phenyl-4,5-dihydro-2H-indazol-3-ols 17−24.
The synthetic strategy for the formation of these fused indazole derivatives involves three steps, which is
described as follows. Condensation of the appropriate acetophenone and the appropriate benzaldehyde in the
presence of sodium hydroxide yields the respective 1,3-diarylprop-2-en-1-ones. Their reaction with ethyl
acetoacetate in the presence of sodium ethoxide gives 3,5-diaryl-6-ethoxycarbonylcyclohex-2-en-1-ones 1-8.
The formed ketones on treatment with hydrazine hydrate and phenylhydrazine hydrochloride/anhydrous
sodium acetate in refluxing methanol yield 4,6-diaryl-4,5-dihydro-2H-indazol-3-ols 9-16 or 4,6-diaryl-2-phenyl-
4,5-dihydro-2H-indazol-3-ols 17-24, respectively (Table 1).
The structures of the compounds are elucidated by melting points, elemental analysis, MS, FT-IR, 1H and 13C
NMR, D2O exchanged 1H NMR, and two-dimensional HSQC spectroscopic data.
951

EXPERIMENTAL
We used TLC to assess the reactions and the purity of the products. All the reported melting points were
determined in open capillaries and were uncorrected. IR spectra were recorded in KBr (pellet forms) on a
1
Nicolet-Avatar–330 FT-IR spectrophotometer, and noteworthy absorption values (cm−1) alone are listed. H,
1
D2O exchanged H and 13C NMR spectra were recorded at 400 and 100 MHz, respectively, on a Bruker AMX
400 NMR spectrometer using DMSO-d6 as a solvent. HSQC spectra were recorded at 500 MHz and on a Bruker
DRX 500 NMR spectrometer using DMSO-d6 as a solvent. The ESI + ve MS spectra were recorded on a Bruker
Daltonics LC-MS spectrometer. Satisfactory microanalysis was obtained on a Carlo Erba 1106 CHN analyzer.
By adopting the literature precedent, 1,3-diarylprop-2-en-1-ones [12−14] and 3,5-diaryl-6-ethoxycarbonyl-
cyclohex-2-en-1-ones 1-8 [6] were prepared.
Typical Procedure for the Synthesis of 4,6-diphenyl-4,5-dihydro-2H-indazol-3-ols 9−16. A solution
of 6-ethoxycarbonyl-3,5-diphenylcyclohex-2-en-1-one 1 (0.1 mol) in methanol (40 ml) is treated with hydrazine
hydrate (0.15 mol) and refluxed for 5 h. The reaction mixture is cooled and then poured over crushed ice. The
crude product 9 is recrystallized twice using methanol as a solvent. IR, ν, cm−1: 3425, 3060, 2922, 2863, 1607,
1515, 1446, 1369, 758, 695. 1H NMR, δ, ppm (J, Hz): 2.90, 3.1−3.2 (2H, m, H-5); 4.19 (1H, dd, J = 11.8, J = 9.1,
H-4); 6.75 (1H, d, J = 7.6, H-7); 9.7 (1H, s, H-2); 11.53 (1H, s, OH); 7.10−7.48 (10H, m, H arom.). 13C NMR, δ,
ppm: 34.2 (C-4); 36.2 (C-5); 98.3 (C-9); 113.4 (C-7); 136.2 (C-8); 125.0−128.5 (C arom.); 140.2, 145.3 (ipso-
C’s); 157.2 (C-3). In the D2O exchanged 1H NMR spectrum, the broad peak at 11.53 ppm due to –OH proton at
C-3 and the broad peak at 9.74 ppm due to –NH proton at C-2 disappeared.
In the HSQC spectrum, one bond correlation (34.2/4.19) between C-4 and H-4a occurs. The 13C
resonance at 36.2 ppm has correlations with methylene protons H-5a (36.2/2.90; 36.2/3.20) and hence C-5
resonates at 36.2 ppm. The 13C resonance at 113.4 ppm has correlations with a doublet at 6.75 ppm. The doublet
at 6.75 ppm is conveniently assigned to H-7. The cross peak (113.4/6.75 ppm) confirms that the 13C resonance at
113.4 ppm is due to C-7. The 13C resonances at 98.3, 136.2, and 157.2 ppm have no correlations with protons
and hence it is due to quaternary carbons. Among the quaternary carbon resonances, the 13C resonance at 140.2
13
and 143.2 ppm is assigned to ipso carbons. The C resonances at 136.2 and 157.2 ppm are due to the C-8 and
C-3 carbons. The signal at 98.3 ppm is due to C-9 carbon and the C-6 carbon is merged with aromatic carbons.
Compounds 10−16 were synthesized similarly.
6-Phenyl-4-(p-tolyl)-4,5-dihydro-2H-indazol-3-ol (10). IR, ν, cm−1: 3419, 3060, 3062, 2919, 2858,
1593, 1516, 757, 695. 1H NMR, δ, ppm (J, Hz): 2.21 (3H, s, CH3 at phenyl ring); 2.87, 3.1-3.2 (2H, m, H-5); 4.14
(1H, dd, J = 12.3, J = 9.5, H-4); 6.75 (1H, d, J = 7.8, H-7); 8.30 (1H, s, H-2); 10.98 (1H, s, OH); 7.02−7.47 (9H, m,
H arom.). 13C NMR, δ, ppm: 20.5 CH3 at phenyl ring; 33.8 (C-4); 36.3 (C-5); 98.5 (C-9); 113.3 (C-7); 136.3
(C-8); 125.0-128.5 (C arom.); 134.8, 140.2, 141.1, 142.2 (ipso-C’s); 156.4 (C-3).
4-(4-Chlorophenyl)-6-phenyl-4,5-dihydro-2H-indazol-3-ol (11). IR, ν, cm−1: 3404, 3054, 2928, 1600,
1
1535, 1491, 757, 694. H NMR, δ ppm (J, Hz): 2.87; 3.1−3.2 (2H, m, H-5); 4.20 (1H, dd, J = 12.9, J = 8.6,
H-4); 6.76 (1H, d, J = 8.1, H-7); 8.35 (1H, s, H-2); 11.5 (1H, s, OH); 7.16−7.47 (9H, m, H arom.). 13C NMR, δ,
ppm: 33.7 (C-4); 36.1 (C-5); 97.8 (C-9); 113.4 (C-7); 136.2 (C-8); 125.1−128.5 (C arom.); 130.5, 140.1, 141.2,
144.2 (ipso-C’s); 156.3 (C-3).
4-(4-Nitrophenyl)-6-phenyl-4,5-dihydro-2H-indazol-3-ol (12). IR, ν, cm−1: 3422, 3076, 2924, 2847,
1
1599, 1515, 1437, 1345, 753, 695. H NMR, δ, ppm (J, Hz): 2.86, 3.20-3.25 (2H, m, H-5); 4.34 (1H, dd,
J =12.4, J = 8.2, H-4); 6.76 (1H, d, J = 7.9, H-7); 9.70 (1H, s, H-2); 11.70 (1H, s, OH); 7.25−8.11 (9H, m,
H arom.). 13C NMR, δ, ppm: 34.6 (C-4); 36.0 (C-5); 97.3 (C-9); 113.5 (C-7); 136.2 (C-8); 123.4−128.8 (C arom.);
140.1, 146.2 (ipso-C’s); 157.2 (C-3).
4-(4-Methoxyphenyl)-6-phenyl-4,5-dihydro-2H-indazol-3-ol (13). IR, ν, cm−1: 3417, 3065, 3052, 2930,
2836, 1608, 1511, 1443, 1373, 760, 696. 1H NMR, δ, ppm (J, Hz): 2.85, 3.10−3.20 (2H, m, H-5); 3.64 (3H, s, OCH3
952

at phenyl ring); 4.11 (1H, dd, J = 11.1, J = 9.0, H-4); 6.73 (1H, d, J = 8.4, H-7,); 8.40 (1H, s, H-2); 10.70 (1H, s,
OH); 7.037.45 (9H, m, H arom.). 13C NMR, δ, ppm: 33.4 (C-4); 36.4 (C-5); 54.9 (OCH3 at phenyl ring); 98.7 (C-9);
113.4 (C-7); 136.2 (C-8); 125.0−128.5 (C arom.); 137.2, 140.3, 141.0, 157.5 (ipso-C's); 156.3 (C-3).
6-(4-Bromophenyl)-4-phenyl-4,5-dihydro-2H-indazol-3-ol (14). IR, ν, cm−1: 3402, 3093, 3000, 2927,
2830, 1608, 1526, 1439, 1349, 807, 736. 1H NMR, δ, ppm (J, Hz): 2.85, 3.10−3.20 (2H, m, H-5); 4.16 (1H, dd,
J = 11.6, J = 9.4, H-4); 6.76 (1H, d, J = 8.6, H-7); 9.70 (1H, s, H-2); 11.72 (1H, s, OH); 7.10−7.82 (9H, m,
H arom.). 13C NMR, δ, ppm: 34.4 (C-4); 36.1 (C-5); 97.8 (C-9); 113.3 (C-7); 135.2 (C-8); 126.0−129.7 (C arom.);
131.4, 131.9, 135.2, 139.2 (ipso-C’s); 157.5 (C-3).
6-(p-Tolyl)-4-phenyl-4,5-dihydro-2H-indazol-3-ol (15). IR, ν, cm−1: 3422, 3062, 3051, 2928, 2834,
1
1603, 1510, 1441, 1370, 764, 691. H NMR, δ, ppm (J, Hz): 2.81, 3.13−3.18 (2H, m, H-5); 2.24 (3H, s, CH3 at
phenyl ring); 4.08 (1H, dd, J = 10.8, J = 8.9, H-4); 6.70 (1H, d, J = 8.6, H-7); 8.38 (1H, s, H-2); 11.21 (1H, s, OH);
7.08−7.38 (9H, m, H arom.). 13C NMR, δ, ppm: 33.0 (C-4); 36.7 (C-5); 21.8 (CH3 at phenyl ring); 99.2 (C-9); 112.6
(C-7); 134.2 (C-8); 124.7−127.9 (C arom.); 137.0, 140.5, 141.5, 157.2 (ipso-C’s); 157.2 (C-3).
4,5-Dihydro-4-(4-methoxyphenyl)-6-(3-nitrophenyl)-2H-indazol-3-ol (16). IR, ν, cm−1: 3428, 3022,
1
2925, 2852, 1609, 1525, 1489, 1448, 818, 701. H NMR, δ, ppm (J, Hz): 2.85, 3.10−3.25 (2H, m, H-5); 4.16
(1H, dd, J = 12.3, J = 9.0, H-4); 6.77 (1H, d, J = 8.1, H-7); 9.82 (1H, s, H-2); 10.90 (1H, s, OH); 6.95−8.24 (8H,
m, H arom.). 13C NMR, δ, ppm: 33.4 (C-4); 36.3 (C-5); 99.0 (C-9); 113.5 (C-7); 137.0 (C-8); 116.0-131.4
(C arom.); 137.0, 141.9, 148.2, 157.6 (ipso-C’s); 156.1 (C-3).
Typical Procedure for the Synthesis of 2,4,6-diaryl-2-phenyl-4,5-dihydro-2H-indazol-3-ols 17-24. A
solution of 6-ethoxycarbonyl-3,5-diphenylcyclohex-2-en-1-one 1 (0.1 mol) in methanol (40 ml) is treated with
phenylhydrazine hydrochloride (0.15 mol) and anhydrous sodium acetate (0.15 mol) and refluxed for 7 h and
then poured over crushed ice. The crude product 17 is recrystallized twice using methanol as a solvent. IR, ν,
1
cm−1: 3425, 3062, 2921, 2862, 1605, 1514, 1445, 1367, 757, 705, 695. H NMR, δ, ppm (J, Hz): 2.98-3.13,
3.46-3.50 (2H, m, H-5); 4.34 (1H, dd, J = 12.0, J = 9.2, H-4); 6.86 (1H, d, J = 7.9, H-7); 11.73 (1H, s, OH);
7.20-7.58 (15H, m, H arom.). 13C NMR, δ, ppm: 34.4 (C-4); 37.2 (C-5); 99.2 (C-9); 114.5 (C-7); 136.6 (C-8);
1
125.6-128.6 (C arom.); 140.4, 142.2, 145.4 (ipso-C’s); 159.2 (C-3). In the D2O exchanged H NMR spectrum,
the broad peak at 11.73 ppm due to OH proton at C-3 disappeared.
In the HSQC spectrum, one bond correlation (34.4/4.34) between C-4 and H-4a occurs. The 13C
resonance at 37.2 ppm has correlations with methylene protons H-5a (37.2/2.98-3.13; 36.2/3.46−3.50) and hence
C-5 resonates at 37.2 ppm. The 13C resonance at 114.5 ppm correlates with a doublet at 6.86 ppm. The doublet at
6.86 ppm is conveniently assigned to H-7. The cross peak (114.5/6.86 ppm) confirms that the 13C resonance at
114.5 ppm is due to C-7. The 13C resonances at 99.2, 136.6, 159.2 ppm have no correlations with protons and
hence it is due to quaternary carbons. Among the quaternary carbon resonances, the 13C resonance at 140.4,
142.2, and 145.4 ppm are assigned to ipso carbons. The 13C resonances at 136.6 and 159.2 ppm are due to the
C-8 and C-3 carbons. The signal at 99.2 ppm is due to C-9 carbon and the C-6 carbon is merged with aromatic
carbons.
Compounds 18−24 were synthesized similarly.
2,6-Diphenyl-4-(p-tolyl)-4,5-dihydro-2H-indazol-3-ol (18). IR, ν, cm−1: 3419, 3062, 3065, 2917, 2857,
1592, 1514, 755, 708, 694. 1H NMR, δ, ppm (J, Hz): 2.34 (3H, s, CH3 at phenyl ring); 2.95−3.10, 3.33−3.69 (2H,
m, H-5); 4.01 (1H, dd, J = 12.4, J = 9.6, H-4); 6.87 (1H, d, J = 8.5, H-7); 11.35 (1H, s, OH); 7.02−7.57 (14H, m,
H arom.). 13C NMR, δ, ppm: 21.9 (CH3 at phenyl ring); 33.9 (C-4); 37.3 (C-5); 99.1 (C-9); 114.5 (C-7); 136.3
(C-8); 125.3−128.6 (C arom.); 140.2, 141.3, 142.3 (ipso-C’s); 159.4 (C-3).
4-(4-Chlorophenyl)-2,6-diphenyl-4,5-dihydro-2H-indazol-3-ol (19). IR, ν, cm−1: 3404, 3053, 2926,
1
1602, 1534, 1492, 756, 711, 695. H NMR, δ, ppm (J, Hz): 2.95−3.10, 3.26−3.40 (2H, m, H-5); 4.35 (1H, dd,
J =13.1, J = 8.7, H-4); 6.87 (1H, d, J = 8.0, H-7); 11.6 (1H, s, OH); 7.26−7.67 (14H, m, H arom.). 13C NMR, δ,
ppm: 34.5 (C-4); 37.4 (C-5); 99.3 (C-9); 114.7 (C-7); 136.2 (C-8); 125.1−128.8 (C arom.); 140.1, 141.2, 142.4,
144.2 (ipso-C’s); 159.3 (C-3).
953

4-(4-Nitrophenyl)-2,6-diphenyl-4,5-dihydro-2H-indazol-3-ol (20). IR, ν, cm−1: 3421, 3075, 2922,
1
2846, 1597, 1515, 1433, 1346, 752, 708, 693. H NMR, δ, ppm (J, Hz): 2.96−3.29, 3.40−3.55 (2H, m, H-5);
4.44 (1H, dd, J = 12.6, J = 8.4, H-4); 6.90 (1H, d, J = 8.2, H-7); 11.70 (1H, s, OH);7.35−7.56 (14H, m,
H arom.). 13C NMR, δ, ppm: 34.8 (C-4); 37.2 (C-5); 99.2 (C-9); 114.3 (C-7); 136.2 (C-8); 123.4−128.8 (C arom.);
140.1, 142.4, 146.2 (ipso-C’s); 159.2 (C-3).
4-(4-Methoxyphenyl)-2,6-diphenyl-4,5-dihydro-2H-indazol-3-ol (21). IR, ν, cm−1: 3416, 3064, 3051,
1
2932, 2835, 1606, 1511, 1441, 1372, 759, 712, 693. H NMR, δ, ppm (J, Hz): 2.94−3.20, 3.22−3.46 (2H, m,
H-5); 3.85 (3H, s, OCH3 at phenyl ring); 4.27 (1H, dd, J = 11.4, J = 9.1, H-4); 6.85 (1H, d, J = 8.6, H-7); 11.40
(1H, s, OH); 7.12-7.55 (14H, m, H arom.). 13C NMR, δ, ppm: 34.8 (C-4); 37.5 (C-5); 55.3 (OCH3 at phenyl
ring); 99.4 (C-9); 114.3 (C-7); 136.2 (C-8); 125.0-128.5 (C arom.); 137.2, 140.3, 141.0, 142.4 (ipso-C’s); 158.3
(C-3).
6-(4-Bromophenyl)-2,4-diphenyl-4,5-dihydro-2H-indazol-3-ol (22). IR, ν, cm−1: 3401, 3092, 2998,
2926, 2831, 1606, 1525, 1437, 1348, 805, 713, 735. 1H NMR, δ, ppm (J, Hz): 2.92-2.95, 2.96-3.17 (2H, m, H-5);
4.02 (1H, dd, J = 11.8, J = 9.5, H-4); 6.87 (1H, d, J = 8.8, H-7); 11.71 (1H, s, OH); 7.20-7.90 (14H, m, H arom.).
13C NMR, δ, ppm: 33.8 (C-4); 37.4 (C-5); 99.3 (C-9); 114.3 (C-7); 137.0 (C-8); 116.1-137.0 (C arom.); 142.1, 142.3,
149.0, 157.2 (ipso-C’s); 159.0 (C-3).
2,4-Diphenyl-6-(p-tolyl)-4,5-dihydro-2H-indazol-3-ol (23). IR, ν, cm−1: 3421, 3060, 3053, 2927, 2833,
1601, 1512, 1440, 1372, 763, 715, 690. 1H NMR, δ, ppm: 2.92−3.18, 3.20−3.44 (2H, m, H-5); 2.28 (3H, s, CH3 at
phenyl ring); 4.01 (1H, dd, J = 11.1, J = 8.8, H-4); 6.84 (1H, d, J = 8.4, H-7); 11.70 (1H, s, OH); 7.06−7.41 (14H, m,
H arom.). 13C NMR, δ, ppm: 33.9 (C-4); 38.7 (C-5); 22.1 (CH3 at phenyl ring); 99.4 (C-9); 112.7 (C-7); 134.1 (C-8);
123.7-127.7 (C arom.); 137.1, 140.6, 141.4, 157.3 (ipso-C’s); 159.2 (C-3).
4,5-Dihydro-4-(4-methoxyphenyl)-6-(3-nitrophenyl)-2-phenyl-2H-indazol-3-ol (24). IR, ν, cm−1:
3427, 3020, 2924, 2851, 1607, 1523, 1487, 1446, 819, 714, 703. 1H NMR, δ, ppm (J, Hz): 2.94−3.28, 3.30-3.44
(2H, m, H-5); 3.82 (3H, s, OCH3 at phenyl ring), 3.95 (1H, dd, J = 12.7, J = 9.2, H-4); 6.85 (1H, d, J = 8.2,
H-7); 11.82 (1H, s, OH); 7.00-8.44 (13H, m, H arom.). 13C NMR, δ, ppm: 34.4 (C-4); 37.8 (C-5); 99.5 (C-9);
114.2 (C-7); 135.2 (C-8); 126.0-129.7 (C arom.); 129.0, 131.4, 131.9, 139.2, 142.2 (ipso-C’s); 159.0 (C-3).
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