Synthesis and antimicrobial activities of new 4,6-diaryl- 4,5-dihydro-3-hydroxy-2H-indazoles

Article abstract of DOI:10.1002/jhet.720

A series of new 4,6-diaryl-4,5-dihydro-3-hydroxy-2H-indazoles 5a-5k were synthesized by the cyclization of ethyl 2-oxo-4,6-diarylcyclohex-3-ene carboxylates 4a-4k. The compounds were characterized by IR, ¹H NMR, ¹³C NMR, 2D NMR, and elemental analysis. The synthesized compounds were evaluated for in vitro antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, Candida albicans, Aspergillus niger, Aspergillus flavus, and Rhizopus sp. Most of the compounds exhibited good activity against the tested organisms. Copyright

Full text of DOI:10.1002/jhet.720

428
Synthesis and Antimicrobial Activities of New 4,6-Diaryl-
4,5-dihydro-3-hydroxy-2H-indazoles
Vol 49
Parasuraman Amutha and Samuthira Nagarajan*
Department of Chemistry, Annamalai University, Annamalainagar 608 002, India
*E-mail: nagarajan.au@gmail.com
Received July 16, 2010
DOI 10.1002/jhet.720
Published online 19 December 2011 in Wiley Online Library (wileyonlinelibrary.com).
A series of new 4,6-diaryl-4,5-dihydro-3-hydroxy-2H-indazoles 5a–5k were synthesized by the cycli-
zation of ethyl 2-oxo-4,6-diarylcyclohex-3-ene carboxylates 4a–4k. The compounds were characterized
1
by IR, H NMR, 13C NMR, 2D NMR, and elemental analysis. The synthesized compounds were eval-
uated for in vitro antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli,
Salmonella typhimurium, Pseudomonas aeruginosa, Candida albicans, Aspergillus niger, Aspergillus
flavus, and Rhizopus sp. Most of the compounds exhibited good activity against the tested organisms.
J. Heterocyclic Chem., 49, 428 (2012).
INTRODUCTION
pounds 1,3-diarylprop-2-en-1-ones 3a–3k were prepared
by the reaction of 1-(2-naphthyl)ethanone/1-(4-isobutyl-
phenyl)ethanone with respective benzaldehydes in the
presence of sodium hydroxide. The precursors of 5a–5k
ethyl 2-oxo-4,6-diarylcyclohex-3-enecarboxylate 4a–4k
were obtained by Knoevenagel reaction of ethyl acetoac-
etate and 1,3-diarylprop-2-en-1-one. The compounds
4a–4k on treatment with hydrazine hydrate in ethanol
afforded the target compounds 4,6-diaryl-4,5-dihydro-3-
hydroxy-2H-indazoles 5a–5k.
The yield, melting point, molecular formula, and ele-
mental compositions of compounds 5a–5k are given in
Table I. The IR spectra of 5 displayed characteristic
absorption bands in the region 3123–3265 cmꢀ1 (NH),
3353–3429 cmꢀ1 (OH), 1606ꢀ1596 (C¼¼N). Thus, the
absence of C¼¼O stretching frequency and presence of OH
absorptions supports the formation of hydroxyindazoles.
In the 1H NMR spectra of 5 two double doublets
were observed in the region 4.2 ppm and 2.8–3.0 ppm
for H4 and H5b protons, respectively. The H5a proton
appears as a multiplet in the region 3.1–3.3 ppm instead
of expected double doublet. Similarly, H7 proton
appears as a doublet in the region 6.7–6.9 ppm instead
of expected singlet this may be due to long-range cou-
pling with H5a proton. In the 13C NMR spectra, the car-
bon resonance around 36 and 34 ppm was due to Cꢀ5
and Cꢀ4 carbons, respectively. The signal at around
114 ppm was attributed to Cꢀ7 carbon. The individual
assignments were further confirmed with the help of
The indazole ring is an important pharmacophore in
medicinal chemistry. During the last decade, consider-
able interest has been paid to chemistry of indazoles.
This is undoubtedly due to its broad variety of biologi-
cal activities [1,2]. Indazole subunits are frequently
found motifs in drug substances, for example, Benzdac
[3] and benzydamine [4] are commercially available
anti-inflammatory drugs. Apart from this, the range of
pharmacological effects of indazole derivatives include
nitric oxide synthase inhibition [5], analgesic [6], anti-
inflammatory [7], antiviral [8], HIV protease inhibitory
activity [9], anticancer [10], antitumor [11], YC1 gua-
nylyl cyclase activator [12], antimicrobial activities
[13,14], and antiproliferative activity [15], which
inspired the development of new synthesis and optimiza-
tion as well as functionalization of indazole ring. Being
involved in study of heterocyclic compounds, with the
purpose to perform a large program of biological screen-
ing, we focused our attention on synthesis of some py-
rimidine derivatives with antimicrobial activity [16]. In
continuation of our research work, we herein report the
synthesis and antimicrobial studies of series of 4,6-dia-
ryl-4,5-dihydro-3-hydroxy-2H-indazoles.
RESULTS AND DISCUSSION
The synthetic procedures adopted to obtain the target
compounds are depicted in Scheme 1. The starting com-
C
V
2011 HeteroCorporation

March 2012
Synthesis and Antimicrobial Activities of New 4,6-Diaryl-4,5-dihydro-
3-hydroxy-2H-indazoles
429
Scheme 1. Synthetic pathway to 5a–5k.
spectrum of 5g, the signal at 36.81 ppm has cross-peak
with signal for H5a and H5b protons. Similarly, the car-
bon signal at 33.80 ppm has correlation with signal for
H4 proton. Likewise the carbon resonance at 113.90
ppm has correlation with H7 proton.
Pharmacology. The antibacterial and antifungal
activities of compounds 5a–5k were assessed in compar-
ison with Ciprofloxacin and Amphotericin B, respec-
tively, against bacterial and fungal strains. The results
obtained are summarized in Tables II and III. The anti-
bacterial and antifungal data indicated that the com-
pounds 5a–5k have good activity against tested bacterial
and fungal strains. The naphthyl derivatives 5d and 5e
with 4-chloro and 4-fluoro substituents showed potent
activity than the rest of the compounds. Among the iso-
butyl derivatives also 5i and 5j with 4-fluoro and 4-
chloro substituted compounds are more effective than
the other compounds. Thus, the electron withdrawing
groups play a vital role in antimicrobial activity. The
importance of electron withdrawing groups in enhancing
the antimicrobial activity is supported by similar results
[14,17]. Rest of the compounds showed moderate to
good activity. The nature and position of the substituent
influence the extent of antibacterial and antifungal activ-
ity. From the analysis of the structures of most active
compounds 5e and 5j, it may be concluded that among
the electron withdrawing halo groups, the presence of a
4-fluorophenyl group improved the antimicrobial activ-
ity. The presence of isobutyl chain in the phenyl ring
not much influenced the antimicrobial activity of the
tested organisms.
1H-1H COSY and 1H-13C COSY spectra. In 1H-1H
COSY, the signal for H7 proton has cross-peak with H-
5a proton and vice versa this confirms that the multiplic-
ity of H5a proton instead of expected double doublet is
due to long-range coupling with H7 proton. In HSQC
EXPERIMENTAL
Melting points were determined in open capillaries and are
uncorrected. Infrared spectra were recorded on a NICOLET
AVATAR (FTIR-330) spectrophotometer in KBr pellets. 1H
and 13C NMR spectra were recorded in DMSO-d6 using
Table 1
Physical and analytical data for 5aꢀ5k.
Elemental analysis (%)
H found (calculated)
Compound
m.p. (ꢁC)
Yield (%)
Molecular formula
C found (calculated)
N found (calculated)
5a
5b
5c
5d
5e
5f
5g
5h
5i
144–149
146–150
148–153
163–167
149–152
167–169
146–149
152–155
158–161
143–146
151–153
71
65
68
73
70
67
71
68
72
74
69
C23H18N2O
C24H20N2O
81.37 (81.63)
81.61 (81.79)
73.90 (74.09)
65.98 (66.20)
77.36 (77.51)
80.01 (80.20)
76.72 (76.98)
80.31 (80.41)
72.62 (72.91)
75.97 (76.22)
65.11 (65.25)
5.09 (5.36)
5.55 (5.72)
4.36 (4.60)
3.99 (4.11)
4.69 (4.81)
6.90 (7.02)
6.82 (7.00)
7.04 (7.31)
5.66 (6.12)
6.20 (6.40)
5.25 (5.48)
8.02 (8.28)
7.83 (7.95)
7.39 (7.51)
6.58 (6.71)
7.67 (7.86)
7.94 (8.13)
7.21 (7.48)
7.57 (7.81)
7.20 (7.39)
7.62 (7.73)
6.47 (6.62)
C23H17ClN2O
C23H17BrN2O
C23H17FN2O
C23H24N2O
C24H26N2O2
C24H26N2O
C23H23ClN2O
C23H23FN2O
C23H23BrN2O
5j
5k
Journal of Heterocyclic Chemistry
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430
P. Amutha and S. Nagarajan
Vol 49
Table 2
In vitro antimicrobial activity (zone of inhibition) values for 5aꢀ5k.
Diameter of zone of inhibition (mm)
Bacterial strains
Fungal strains
Compound S. aureus E. coli K. pneumoniae S. typhimurium P. aeruginosa C. albicans A. niger A. flavus Rhizopus sp.
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
Cip.
Amp. B
07
07
10
12
15
08
09
11
15
14
13
12
ꢀ
07
05
12
14
10
12
10
10
14
13
10
15
ꢀ
10
08
09
10
12
10
08
07
12
12
07
16
ꢀ
08
10
12
10
14
07
11
13
12
15
12
16
ꢀ
11
08
13
12
12
09
06
10
16
15
11
11
ꢀ
07
07
09
14
12
09
10
07
13
16
13
ꢀ
10
10
11
15
14
10
08
10
14
12
10
ꢀ
08
06
10
12
13
06
08
10
14
15
14
ꢀ
11
09
07
12
10
07
12
07
15
14
11
ꢀ
13
12
14
11
Cip., Ciprofloxacin; Amp. B, Amphotericin B.
Bruker AMX 500-MHz spectrometer. 13C NMR spectra were
recorded at an operating frequency of 125 MHz. The 2D NMR
spectra were recorded on DRX 500 NMR spectrometer. Chem-
ical shifts are expressed in parts per million using residual sol-
vent proton and carbon as internal standards.
Synthesis of 1,3-diarylprop-2-en-1-ones (3a–3k). A solu-
tion of substituted benzaldehyde (10 mmol) and 1-(2-naphthy-
lethanone) (10 mmol) in 65% aqueous ethanol (50 mL) con-
taining NaOH (12.5 mmol, 0.5 g) was heated over water bath
for 30 min. The solution was allowed to cool and poured into
crushed ice; the separated solid was filtered, washed with
water, and recrystallized from ethanol.
diarylprop-2-en-1-ones (0.01 mol) in absolute ethanol (20 mL)
was refluxed for 2 h on steam bath and then cooled. The sepa-
rated solid was filtered, washed with water, and recrystallized
from ethanol.
Synthesis of 4,6-diaryl-4,5-dihydro-3-hydroxy-2H-inda-
zoles (5a–5k). The ethyl 2-oxo-4,6-diarylcyclohex-3-enecar-
boxylate (0.1 mol) was dissolved in hot ethanol (25 mL), and
after addition of hydrazine hydrate (0.15 mol), the reaction
mixture was refluxed for 2–4 h. The hot solution was poured
into ice, and the separated solid was filtered and washed with
water. The crude product was recrystallized from ethanol. Fur-
ther the product was purified using column chromatography
(silica gel), eluent, benzene:ethylacetate (3:2).
Synthesis of ethyl 2-oxo-4,6-diarylcyclohex-3-enecarboxy-
lates (4a–4k). A mixture of sodium (2-g sodium in 60-mL dis-
tilled ethanol), distilled ethyl acetoacetate (0.01 mol), and 1,3-
4,5-Dihydro-6-(naphthalen-2-yl)-4-phenyl-2H-indazol-3-ol
(5a). IR (KBr) (cmꢀ1): 3402, 3205, 3055, 3019, 2924, 2854,
Table 3
In vitro antimicrobial activity (MIC) values for 5aꢀ5k.
Minimum inhibitory concentration (lg/mL)
Bacterial strains
Fungal strains
Compound S. aureus E. coli K. pneumoniae S. typhimurium P. aeruginosa C. albicans A. niger A. flavus Rhizopus sp.
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
5k
Cip.
Amp. B
100
200
100
25
200
50
50
100
100
100
100
50
100
100
100
50
100
50
50
100
25
200
50
25
50
25
50
50
ꢀ
50
100
50
50
50
200
100
100
25
50
200
50
12.5
12.5
100
50
100
100
25
100
50
50
50
50
12.5
50
50
200
50
12.5
100
50
50
50
100
50
100
25
50
50
200
25
25
12.5
100
100
50
100
25
100
25
50
50
100
200
25
100
200
100
25
50
50
12.5
12.5
50
25
50
12.5
100
25
ꢀ
100
ꢀ
50
ꢀ
50
ꢀ
25
ꢀ
12.5
ꢀ
12.5
ꢀ
ꢀ
25
25
50
50
Cip., Ciprofloxacin; Amp. B, Amphotericin-B.
Journal of Heterocyclic Chemistry
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Synthesis and Antimicrobial Activities of New 4,6-Diaryl-4,5-dihydro-
3-hydroxy-2H-indazoles
431
1598, 1508, 746, 697; 1H NMR (d ppm): 3.09 (dd, 1H, H5b),
3.27–3.32 (m, 1H, H5a), 4.25 (dd, 1H, H4, J ¼ 8, 3.5 Hz), 6.97
(d, 1H, H7, J ¼ 2.0 Hz), 7.10–7.99 (m, 12H, ArꢀH); 13C
NMR (d ppm): 34.76 (Cꢀ4), 36.43 (Cꢀ5), 109.73 (Cꢀ9),
114.74 (Cꢀ7), 123.85–128.62 (ArꢀC), 132.77, 133.55, 136.27,
137.68, 145.82 (ipso carbons).
4,5-Dihydro-4-(4-methylphenyl)-6-(naphthalen-2-yl)-2H-inda-
zol-3-ol (5b). IR (KBr) (cmꢀ1): 3402, 3216, 3052, 3019, 2922,
2860, 1596, 1509, 814, 745; 1H NMR (d ppm): 2.19 (s, 3H,
CH3), 3.05 (dd, 1H, H5b, J ¼ 16.75, 4.25 Hz), 3.24–3.27 (m,
1H, H5a), 4.20 (dd, 1H, H4, J ¼ 9.5, 4.5 Hz), 6.95 (d, 1H, H7,
J ¼ 1.5 Hz), 7.00–7.98 (m, 11H, ArꢀH), 9.67 (s, 1H, NH),
11.56 (s, 1H, OH); 13C NMR (d ppm): 20.99 (CH3), 34.41
(Cꢀ4), 36.63 (Cꢀ5), 109.82 (Cꢀ9), 114.14 (Cꢀ7), 123.87–
129.08 (ArꢀC), 132.78, 133.56, 135.30, 136.24, 137.84,
142.77 (ipso carbons).
(Cꢀ9), 113.90 (Cꢀ7), 125.28–129.62 (ArꢀC), 136.57, 137.75,
141.06, 157.97 (ipso carbons).
4,5-Dihydro-6-(4-isobutylphenyl)-4-(4-methylphenyl)-2H-
indazol-3-ol (5h). IR (KBr) (cmꢀ1): 3353, 3205, 3013, 2954,
2922, 2865, 1598, 1511, 1460, 1020, 794; 1H NMR (d ppm):
0.84 (d, 6H, (CH3)2, J ¼ 8.5 Hz), 1.78–1.83 (m, 8H, ArꢀH),
2.20 (s, 3H, CH3), 2.41 (d, 2H, CH2, J ¼ 7.5 Hz), 2.86 (dd,
1H, H5b, J ¼ 16.75, 3.25), 3.10–3.15 (m, 1H, H5a), 4.12 (dd,
1H, H4, J ¼ 8.5, 3.5 Hz), 6.71 (d, 1H, H7, J ¼ 2.5 Hz), 6.99–
7.38 (m, 8H, ArꢀH); 13C NMR (d ppm): 21.61 (CH3), 22.62
[(CHꢀ3)2], 30.05 (CH), 34.23 (Cꢀ4), 36.74 (Cꢀ5), 44.67
(CH2), 102.23 (Cꢀ9), 113.38 (Cꢀ7), 125.27–129.61 (ArꢀC),
135.26, 136.56, 138.02, 141.06, 142.75 (ipso carbons).
4-(4-Chlorophenyl)-4,5-dihydro-6-(4-isobutylphenyl)-2H-inda-
zol-3-ol (5i). IR (KBr) (cmꢀ1): 3408, 3123, 3029, 2954, 2921,
2867, 1608, 1574, 1490, 1090, 794, 682; 1H NMR (d ppm):
0.84 (d, 6H, (CH3)2, J ¼ 6.5 Hz), 1.76–1.86 (m, 1H, CH), 2.42
(d, 2H, CH2, J ¼ 7.0 Hz), 2.86 (dd, 1H, H5b, J ¼ 16.75, 3.25
Hz), 3.11–3.17 (m, 1H, H5a), 4.18 (dd, 1H, H4, J ¼ 8.0, 3.5
Hz), 6.73 (d, 1H, H7, J ¼ 2.0 Hz), 7.13–7.39 (m, 8H, ArꢀH),
9.69 (s, 1H, NH), 11.65 (s, 1H, OH); 13C NMR (d ppm): 22.61
[(CH3)2], 30.05 (CH), 34.15 (Cꢀ4), 36.52 (Cꢀ5), 44.67 (CH2),
100.79 (Cꢀ9), 113.12 (Cꢀ7), 125.32–129.64 (ArꢀC), 130.95,
136.48, 137.86, 141.17, 144.74 (ipso carbons).
4,5-Dihydro-4-(4-fluorophenyl)-6-(4-isobutylphenyl)-2H-
indazol-3-ol (5j). IR (KBr) (cmꢀ1): 3391, 3206, 3128, 2955,
2923, 2866, 1601, 1507, 1460, 1224, 833; 1H NMR (d ppm):
0.85 (d, 6H, (CH3)2, J ¼ 6.5 Hz), 1.76ꢀ1.84 (m, 1H, CH),
2.42 (d, 2H, CH2, J ¼ 7.0 Hz), 2.87 (dd, 1H, H5b, J ¼ 17.0,
4.0 Hz), 3.11ꢀ3.16 (m, 1H, H5a), 4.18 (dd, 1H, H4, J ¼ 8.5,
3.5 Hz), 6.73 (d, 1H, H7, J ¼ 2.5 Hz), 7.01–7.39 (ArꢀH),
9.68 (s, 1H, NH), 11.58 (s, 1H, OH); 13C NMR (d ppm):
22.62 [(CH3)2], 30.04 (CH), 33.97 (Cꢀ4), 36.69 (Cꢀ5), 44.67
(CH2), 104.45 (Cꢀ9), 115.25 (Cꢀ7), 125.31–129.64 (ArꢀC),
136.51, 137.92, 141.15, 141.84 (ipso carbons).
4-(4-Chlorophenyl)-4,5-dihydro-6-(naphthalen-2-yl)-2H-inda-
zol-3-ol (5c). IR (KBr) (cmꢀ1): 3397, 3200, 3054, 2923, 2843,
1
1598, 1491, 817, 746; H NMR (d ppm): 3.06 (dd, 1H, H5b, J ¼
17.0, 4.0 Hz), 3.31–3.27 (m, 1H, H5a), 4.26 (dd, 1H, H4, J ¼
8.5, 4.0 Hz), 6.97 (d, 1H, H7, J ¼ 2Hz), 7.20–7.99 (m, 11H,
ArꢀH), 9.85 (s, 1H, NH), 11.49 (s, 1H, OH); 13C NMR (d
ppm): 34.34 (Cꢀ4), 36.40 (Cꢀ5), 114.00 (Cꢀ7), 123.86–131.00
(ArꢀC), 132.82, 133.53, 136.22, 137.62, 144.72 (ipso carbons).
4-(4-Bromophenyl)-4,5-dihydro-6-(naphthelen-2-yl)-2H-inda-
zol-3-ol (5d). IR (KBr) (cmꢀ1): 3422, 3265, 3052, 2923, 2853,
1605, 1534, 674; 1H NMR (d ppm): 3.05 (dd, 1H, H5b, J ¼
16.75, 5.25 Hz), 3.25–3.31 (m, 1H, H5a), 4.24 (dd, 1H, Hꢀ4, J
¼ 8.5, 4.0 Hz), 6.97 (d, 1H, H7, J ¼ 2.5 Hz), 7.14–7.98 (m,
11H, ArꢀH), 9.88 (s, 1H, NH), 11.55 (s, 1H, OH); 13C NMR
(d ppm): 34.38 (Cꢀ4), 36.34 (Cꢀ5), 109.63 (Cꢀ9), 113.96
(Cꢀ7), 123.85–129.75, 131.41, 132.81, 133.54, 136.23,
137.60, 145.17 (ipso carbons).
4,5-Dihydro-4-(4-fluorophenyl)-6-(naphthalen-2-yl)-2H-inda-
zol-3-ol (5e). IR (KBr) (cmꢀ1): 3424, 3221, 3056, 2924, 2843,
1
1600, 1507, 817, 746; H NMR (d ppm): 3.06 (dd, 1H, H5b, J
4-(4-Bromophenyl)-4,5-dihydro-6-(4-isobutylphenyl)-2H-inda-
zol-3-ol (5k). IR (KBr) (cmꢀ1): 3397, 3189, 3055, 2986, 2926,
¼ 17.0, 4.0 Hz), 3.26–3.31 (m, 1H, H5a), 4.27 (dd, 1H, H4, J
¼ 8.0, 4.0 Hz), 6.97 (d, 1H, H7, J ¼ 2.5 Hz), 7.02–7.99 (m,
11H, ArꢀH), 9.94 (s, 1H, NH), 11.16 (s, 1H, OH); 13C NMR
(d ppm): 34.17 (Cꢀ4), 36.57 (Cꢀ5), 108.36 (Cꢀ9), 115.26
(Cꢀ7), 123.87–129.19 (ArꢀC), 132.81, 133.56, 136.25,
137.67, 141.85 (ipso carbons).
1
2849, 1604, 1509, 1247, 818; H NMR (d ppm): 0.84 (d, 6H,
(CH3)2, J ¼ 6.5 Hz), 1.78–1.83 (m, 1H, CH), 2.42 (d, 2H, CH2,
J ¼ 7.5 Hz), 2.86 (dd, 1H, H5b, J ¼ 16.75, 3.75), 3.11–3.17 (m,
1H, H5a), 4.17 (dd, 1H, H4, J ¼ 8.5, 3.5 Hz), 6.73 (d, 1H, H7, J
¼ 2.0 Hz), 7.09–7.42 (m, 8H, ArꢀH); 13C NMR (d ppm):
22.61 [(CH3)2], 30.04 (CH), 34.23 (Cꢀ4), 36.47 (Cꢀ5), 44.68
(CH2), 104.96 (Cꢀ9), 119.42 (Cꢀ7), 125.32–129.71 (ArꢀC),
131.39, 136.47, 137.86, 141.17, 145.18 (ipso carbons).
Antimicrobial activity. All the compounds have been
screened for antibacterial and antifungal activities using disc-
diffusion and twofold serial dilution method. Ciprofloxacin and
Amphotericin B were used as standard drugs for antibacterial
and antifungal activities. The compounds were screened for
antibacterial activity against Staphylococcus aureus, Esche-
richia coli, Klebsiella pneumoniae, Salmonella typhimurium,
and Pseudomonas aeruginosa in nutrient agar medium and for
antifungal activity against Candida albicans, Aspergillus niger,
Aspergillus flavus, and Rhizopus sp. in Sabouraud’s dextrose
agar medium. The sterilized agar medium was poured into pet-
ridishes and allowed to solidify. On the surface of the media,
microbial suspensions were spread with the help of sterilized
glass spreader. Whatmann paper discs of 5-mm diameter were
impregnated in test compounds dissolved in dimethyl sulfoxide
(DMSO; 200 lg/mL) for 30 min. Commercially available drug
4,5-Dihydro-6-(4-isobutylphenyl)-4-phenyl-2H-indazol-3-ol
(5f). IR (KBr) (cmꢀ1): 3402, 3194, 3112, 3084, 2954, 2922,
2867, 1599, 1507, 795, 751; 1H NMR (d ppm): 0.84 (d, 6H,
(CH3)2, J ¼ 8.5 Hz), 1.76–1.84 (m, 1H, CH), 2.41 (d, 2H,
CH2, J ¼ 7.0 Hz), 2.90 (dd, 1H, H5b, J ¼ 17.0, 3.5 Hz), 3.13–
3.18 (m, 1H, H5a), 4.18 (dd, 1H, H4, J ¼ 9.0, 3.5 Hz), 6.73 (s,
1H, H7, J ¼ 2.0 Hz), 7.11–7.39 (m, 9H, ArꢀH); 13C NMR (d
ppm): 22.61 [(CH3)2], 30.04 (CH), 36.59 (Cꢀ5), 34.63 (Cꢀ4),
44.68 (CH2), 99.03 (Cꢀ9), 112.93 (Cꢀ7), 125.29–129.62
(ArꢀC), 136.61, 137.97, 141.10, 145.83 (ipso carbons).
4,5-Dihydro-6-(4-isobutylphenyl)-4-(4-methoxyphenyl)-2H-
indazol-3-ol (5g). IR (KBr) (cmꢀ1): 3194, 3024, 2997, 2953,
2931, 2867, 1606, 1509, 1246, 831, 795; 1H NMR (d ppm): 0.84 (d,
6H, (CH3)2, J ¼ 7.0 Hz), 1.76–1.84 (m, 1H, CH), 2.42 (d, 2H, CH2,
J ¼ 7.0 Hz), 2.86 (dd, 1H, H5b, J ¼ 16.75, 3.25), 3.09–3.14 (m, 1H,
H5a), 3.66 (s, 3H, OCH3), 4.12 (dd, 1H, H4, J ¼ 8.5, 3.5 Hz), 6.72
(d, 1H, H7, J ¼ 3 Hz), 6.75–7.39 (m, 8H, ArꢀH), 9.87 (s, 1H, NH),
11.37 (s, 1H, OH); 13C NMR (d ppm): 22.62 [(CH3)2], 30.05 (CH),
33.80 (Cꢀ4), 36.81 (Cꢀ5), 44.68 (CH2), 55.37 (OCH3), 101.04
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

432
P. Amutha and S. Nagarajan
Vol 49
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was used as positive reference standard. The discs were placed
on the inoculated agar plates and incubated at 37 6 1ꢁC for
about 18–24 h. Antibacterial activity was evaluated by meas-
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A twofold serial dilution of the compounds and reference
drug were dissolved in DMSO. The test compounds were
taken at different concentration ranging from 200, 100, 50, 25,
12.5, 6.25, and 3.13 lg/mL for minimum inhibitory concentra-
tion (MIC) by using seeded broth dilution. Similarly, the
standard solutions of drugs were prepared at concentration of
200, 100, 50, 25, 12.5, 6.25, and 3.13 lg/mL with sterile dis-
tilled water and DMSO was maintained throughout the experi-
ment simultaneously as control. The MIC was the lowest con-
centration of the tested compound that resulted in no visible
growth of the organism. To ensure that the solvent had no
effect on bacterial growth, a control test was also performed
with test medium supplemented with DMSO at same dilutions
as used in the experiment.
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Acknowledgments. The authors are thankful to the SAIF IIT
Madras for NMR spectral measurements. P. Amutha is thankful
to UGC-SAP for research fellowship.
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet