Benzenesulfonic Acid: A Versatile Catalyst for the Synthesis of Bis(indolyl)methanes as Antioxidants

Article abstract of DOI:10.1002/jhet.2873

The reaction of indoles with carbonyl compounds in the presence of 5?mol% benzenesulfonic acid in acetonitrile was performed to synthesize bis(indolyl)methane derivatives adopting conventional and ultrasonication methodologies. The reaction proceeded in s

Full text of DOI:10.1002/jhet.2873

Month 2017
Benzenesulfonic Acid: A Versatile Catalyst for the Synthesis of Bis
(indolyl)methanes as Antioxidants
Pulla Reddy Simha, Madhu Sekhar Mangali, Divya Kuppireddy Gari, Padmavathi Venkatapuram, and
*
Padmaja Adivireddy
Department of Chemistry, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh, India
*
E-mail: adivireddyp@yahoo.co.in
Additional Supporting Information may be found in the online version of this article.
Received November 14, 2016
DOI 10.1002/jhet.2873
Published online 00 Month 2017 in Wiley Online Library (wileyonlinelibrary.com).
The reaction of indoles with carbonyl compounds in the presence of 5 mol% benzenesulfonic acid in ace-
tonitrile was performed to synthesize bis(indolyl)methane derivatives adopting conventional and
ultrasonication methodologies. The reaction proceeded in shorter reaction time in ultrasonication methodol-
ogy leading to high yield of the products. All the synthesized compounds were tested for antioxidant activity.
Among all the tested compounds, 3k exhibited pronounced antioxidant activity.
J. Heterocyclic Chem., 00, 00 (2017).
INTRODUCTION
and inexpensive synthetic methodologies based on green
chemistry processes in organic synthesis. In the present
communication, we herein report the use of
benzenesulfonic acid as a catalyst for the synthesis of bis
(indolyl)methane derivatives and studied their antioxidant
properties.
Indole and their derivatives find important applications
in the field of pharmaceuticals, agrochemicals, and
materials science [1–3]. In fact bis(indolyl)alkanes
exhibit a wide spectrum of biological activities viz.,
cytotoxic [4,5], antitumor [6], antiviral [6], antimicrobial
[7], anti-inflammatory [8], and antioxidant [9,10].
The bis(indolyl)methane is also
scaffold in alkaloids including ramiflorine
a
privileged
and
RESULTS AND DISCUSSION
A
ramiflorine B, vibrindole A, streptindole, deoxytopsentin,
bromodeoxytopsentin, and sponges. Besides, these
compounds are the most active cruciferous substances for
promoting beneficial estrogen metabolism and preventing
cancer in human [11]. Some of the indole-based drugs are
indomethacin [12], tenidap [13], sumatriptan, frovatriptan,
and zolmitriptan [14]. Because of the unique
pharmacological activities and the prevalence of indole
moiety in many natural products, a great deal of interest
has been focused on the development of efficient
synthetic protocols for the preparation of bis(indolyl)
alkanes. A number of synthetic methods for their
preparation have been reported [15–19]. Among these
methods, the acid catalyzed electrophilic addition of
indole and carbonyl compounds is one of the most simple
and straightforward approaches [20]. However, the use of
toxic reagents, high temperature, and volatile organic
solvents are among the drawbacks of most of these
protocols [21]. Hence, there is a need for a new, efficient,
In recent years, benzenesulfonic acid has received
considerable attention as an inexpensive and easily
available catalyst for various organic reactions. In our
initial attempts, the reaction of indole (1) (2 mmol) with
4-nitrobenzaldehyde (2) (1 mmol) in tetrahydrofuran was
performed by using benzenesulfonic acid at room
temperature for 6 h, and after work up, the product was
obtained in 85% yield. Encouraged by these results, the
catalytic activity of different Lewis acids in acetonitrile
was examined in the reaction of compound 1 with
compound 2. Among the different catalysts, the reaction
was completed in 15 min in the presence of
benzenesulfonic acid (Table 1), which indicated its
highest catalytic activity.
Furthermore, the effect of solvent was carried out to
optimize the reaction conditions. The results presented in
Table 2 revealed that acetonitrile was the better one than
other solvents, and the reaction proceeded within 1 h at
room temperature in high yield.
© 2017 Wiley Periodicals, Inc.

P. R. Simha, M. S. Mangali, D. Kuppireddy Gari, P. Venkatapuram, and P. Adivireddy
Vol 000
Table 1
The reaction of indole (1) with 4-nitrobenzaldehyde (2) in the presence of various catalysts.
Catalysta
C6H5SO3H
Cu(OTf)2
LiClO4
FeCl3
KHSO4
Sulphamic acid
Time (h)
0.25
95
3
90
12
30
12
59
13
60
10
67
Yield (%)b
a5 mol% of the catalyst was used.
bYields referred to the isolated yield.
Table 2
Effect of solvents in the reaction of indole (1) with 4-nitrobenzaldehyde (2) catalyzed by benzenesulfonic acid.
Solvents
H2O
MeOH
EtOH
THF
CH3CN
DCM
Toluene
Time (h)
16
48
19
60
22
65
6
85
01
95
18
53
24
40
Yield (%)a
THF, tetrahydrofuran; DCM, Dichloromethane.
aYields referred to the isolated yield.
Table 3
Apart from these, to determine the influence of the
catalyst concentration, the reaction of indole (1) and 4-
nitrobenzaldehyde (2) was carried out with different
concentrations of catalyst in acetonitrile at room
temperature. The results presented in Table 3 indicated
that 5 mol% of benzenesulfonic acid is optimum to
achieve high yield in shorter reaction time.
Effect of concentration of benzenesulfonic acid on the reaction of indole
(1) with 4-nitrobenzaldehyde (2).
Mole % of catalyst
1
2.5
5
10
15
Time (min)
Yield (%)a
45
41
30
69
15
95
15
95
15
95
aYields referred to the isolated yield.
Scheme 1. Synthesis of bis(indolyl)methane derivatives (3a-n).
Table 4
The preparation of compounds 3a-n catalyzed by benzenesulfonic acid in acetonitrile under conventional and ultrasound irradiation methods.
Conventional Ultrasound
Substituted
Indole
Carbonyl
compound
Time
(h)
Yield
(%)
Time
(min)
Yield
(%)
Entry
Product
3a
1.5
79
8
95
3b
1.0
86
17
90
(Continued)
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2017
Benzenesulfonic Acid: A Versatile Catalyst for the Synthesis of Bis(indolyl)
Methanes as Antioxidants
Table 4
(Continued)
Conventional
Ultrasound
Substituted
Indole
Carbonyl
compound
Time
(h)
Yield
(%)
Time
(min)
Yield
(%)
Entry
Product
3c
1.4
80
16
92
3d
2.0
85
05
95
3e
1.1
1.5
81
80
18
11
92
94
3f
3g
2.0
83
20
90
3h
1.6
76
12
93
(Continued)
Journal of Heterocyclic Chemistry
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P. R. Simha, M. S. Mangali, D. Kuppireddy Gari, P. Venkatapuram, and P. Adivireddy
Vol 000
Table 4
(Continued)
Conventional
Ultrasound
Substituted
Indole
Carbonyl
compound
Time
(h)
Yield
(%)
Time
(min)
Yield
(%)
Entry
Product
3i
1.4
68
10
95
3j
1.5
70
14
94
3k
1.3
84
10
90
3l
1.0
1.6
72
68
15
20
92
88
3m
3n
1.3
79
18
90
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Benzenesulfonic Acid: A Versatile Catalyst for the Synthesis of Bis(indolyl)
Methanes as Antioxidants
Table 5
ANTIOXIDANT ACTIVITY
The IC50 values of the compounds 3a-n in DPPH, H2O2, and NO
methods.
The compounds 3a-n were tested for antioxidant activity
by 2,2-diphenyl-1-picrylhydrazyl (DPPH) [22], nitric oxide
(NO) [23], and H2O2 [24] methods. Ascorbic acid was used
as standard control. This radical scavenging activity (RSA)
was calculated using the following equation.
IC50 values (μg/mL)
DPPH
method
H2O2
method
NO
method
Compound. No.
3a
3b
3c
3d
63.22
52.45
–
72.40
61.83
–
68.90
54.70
–
%RSA ¼ ½ðAC ꢀ ASÞ=ACꢁꢂ100;
–
–
–
3e
3f
3g
3h
3i
3j
3k
3l
–
–
–
where AC is the absorbance of the control and AS is the
absorbance of the tested compound. The antioxidant
activity was also expressed as IC50 value that was defined
as the concentration (in μg/mL) of which compound at
which formation of DPPH, NO, and H2O2 radicals were
inhibited by 50%.
79.14
45.78
81.48
–
42.70
40.15
–
82.72
49.13
89.25
–
49.62
48.43
–
80.14
48.50
84.52
–
46.80
43.27
–
The compounds 3g, 3j, and 3k proved to exhibit potent
RSA; this may be due to the presence of electron donating
groups such as OH, OMe, and Me in phenyl ring of bis
3m
3n
67.50
54.18
33.50
73.30
61.83
39.97
70.45
60.02
37.56
Ascorbic Acid
DPPH, 2,2-diphenyl-1-picrylhydrazyl; NO, nitric oxide.
(indolyl)methane
derivatives
as
shown
in
Table and Figures 1–3. In all three methods
5
3,3″-((3,4-dimethoxyphenyl)methylene)bis(1H-indol-5-ol)
(3k) exhibited highest DPPH, NO, and H2O2 RSA with
IC50 as 40.15, 43.27, and 48.43 when compared with
other compounds. The compounds 3a, 3b, 3g, 3m, and
3n showed good to moderate antioxidant activity,
whereas the compounds 3f and 3h displayed least
Thus, the reaction of indole (1) with carbonyl
compounds (2) led to the formation of bis(indolyl)
methane derivatives (3a-n) (Scheme 1) under the
optimized reaction conditions in both conventional and
ultrasonication methodologies (Table 4).
Figure 1. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity IC50 values. [Color figure can be viewed in the online issue, which is
available at wileyonlinelibrary.com.]
Figure 2. H2O2 radical scavenging activity IC50 values. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

P. R. Simha, M. S. Mangali, D. Kuppireddy Gari, P. Venkatapuram, and P. Adivireddy
Vol 000
Figure 3. Nitric oxide (NO) radical scavenging activity IC50 values. [Color figure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
activity. However, the compounds 3c, 3d, 3e, 3i, and 3l
exhibited no activity.
elemental analyzer (Massachusetts, USA). The progress
of the reaction was monitored by TLC using silica gel
plates (silica gel 60 F254 0.25 mm), and components
were visualized by observation under ultraviolet (UV)
light (254 and 365 nm).The antioxidant activity is carried
out by measuring the absorbance of the test solution
using UV–visible spectrometer, Shimadzu UV-2450
(Shimadzu Corporation, California, USA).
CONCLUSIONS
The reaction of indole (1) with carbonyl compounds (2)
in the presence of 5 mol% benzenesulfonic acid as catalyst
in acetonitrile was carried out to obtain bis(indolyl)
methane derivatives (3a-n) adopting conventional and
ultrasonication methodologies. It was observed that the
reaction proceeded in shorter reaction times and in high
yield in ultrasonication methodology when compared with
conventional method. All the synthesized compounds
were tested for antioxidant activity. Among all the tested
compounds, 3k exhibited pronounced antioxidant activity.
General procedure for the synthesis of bis(indolyl)methane
derivatives (3a-n) under conventional method. To a stirred
solution of substituted indole (1) (2.0 mmol) and carbonyl
compound (2) (1.1 mmol) in acetonitrile (5 mL),
benzenesulfonic acid (0.05 mmol) was added and
continued the stirring at room temperature for 1–2.5 h.
After completion of the reaction (monitored by TLC), the
reaction mixture was extracted with dichloromethane.
The organic layer was washed with brine solution, dried
over an Na2SO4 and filtered. The solvent was removed
under vacuum, and resultant crude product was purified
by column chromatography (silica gel, 60–120 mesh)
using ethyl acetate-hexane (1:3) as an eluent.
EXPERIMENTAL
General.
All the chemicals were purchased from
commercial sources and used without further purification.
Ultrasonication was performed in a Bandelin Sonorex RK
102H (ProfiLab24 GmbH, Berlin, Germany) ultrasonic
bath operating at frequency of 35 KHz. Melting points
were determined in open capillaries on a Mel-Temp
apparatus and are uncorrected. The purity of the
compounds was checked by thin-layer chromatography
(TLC) (silica gel H, British Drug Houses (BDH), ethyl
acetate/hexane, 1:3). Infrared (IR) spectra were recorded
on a Thermo Nicolet IR 200 FT-IR spectrometer
(Shimadzu Corporation, Kyoto, Japan) as KBr pellets,
General procedure for the synthesis of bis(indolyl)methane
derivatives (3a-n) under ultrasound irradiation method. To
a solution of substituted indole (1) (2.0 mmol) and
carbonyl compound (2) (1.1 mmol) in acetonitrile (3 mL),
benzenesulfonic acid (0.05 mmol) was added and
subjected to ultrasound irradiation at a frequency of
35 KHz at room temperature for 5–20 min. The progress
of the reaction was monitored by TLC. After completion
of the reaction, the contents of the flasks were extracted
with dichloromethane. The dichloromethane layer was
washed with brine solution, dried, and filtered. Removal
of the solvent under reduced pressure gave crude product
which was purified by column chromatography (silica gel,
60–120 mesh) using ethyl acetate-hexane (1:3) as an eluent.
and the wave numbers are given in cmꢀ1 1H NMR
.
spectra were recorded in CDCl3/DMSO-d6 on a Varian
Mercury Plus spectrometer (Agilent Technology,
California, USA) at 400 MHz. 13C NMR spectra were
recorded in CDCl3/DMSO-d6 on Varian Gemini
spectrometer (Agilent Technology, California, USA) at
200 MHz. All chemical shifts are reported in δ (ppm)
using tetramethylsilane as an internal standard. Mass
spectra were recorded with PE Sciex model API 3000
spectrometer (Perkin Elmer, California, USA). The
microanalyses were performed on a Perkin-Elmer 240C
3,3″-(Phenylmethylene)bis(1H-indole) (3a).
Brick Red
solid, mp 126–127°C; IR (KBr cmꢀ1): 3364 (NH), 1625
1
(C = C); H NMR (400 MHz, DMSO-d6): δ 5.87 (s, 1H,
Ar-CH), 6.70–7.89 (m, 15H, Ar-H), 10.60 (bs, 2H, NH)
ppm; 13C NMR (200 MHz, DMSO-d6): δ 39.2 (Ar-CH),
112.4, 116.4, 120.3, 121.7, 123.6, 124.7, 125.4, 126.2,
130.4, 135.6, 138.2, 139.7 ppm (aromatic carbons). MS
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2017
Benzenesulfonic Acid: A Versatile Catalyst for the Synthesis of Bis(indolyl)
Methanes as Antioxidants
(ES): m/z 323.1473 [M + H]+. Anal. Calcd. for C23H18N2: C
1.23 (s, 9H, CH3), 5.78 (s, 1H, Ar-CH), 6.64–7.32 (m,
14H, Ar-H), 10.59 (bs, 2H, NH) ppm; 13C NMR
(200 MHz, DMSO-d6): δ 31.5 (Ar-CH3), 36.2 (C(CH3)3),
39.4 (Ar-CH), 102.3, 111.2, 111.4, 111.7 ,122.9 ,124.2,
126.9, 127.5, 131.2, 141.2, 146.2, 149.0 ppm (aromatic
carbons). MS (ES): m/z 379.2099 [M + H]+. Anal. Calcd.
for C27H26N2: C 85.68; H 6.92; N 7.40%. Found: C
85.79; H 6.90; N 7.61%.
85.68; H 5.63; N 8.69. Found: C 85.80; H 5.66; N 8.91%.
3,3″-((3,4-Dimethoxyphenyl)methylene)bis(1H-indole)
(3b). Red solid, mp 196–198°C; IR (KBr cmꢀ1): 3358
1
(NH), 1621 (C = C); H NMR (400 MHz, DMSO-d6): δ
3.64 (s, 3H, ꢀOCH3), 3.70 (s, 3H, ꢀOCH3), 5.77 (s, 1H,
Ar-CH), 6.80–7.38 (m, 13H, Ar-H), 10.76 (bs, 2H, NH)
ppm; 13C NMR (200 MHz, DMSO-d6): δ 40.2 (Ar-CH),
55.4 (Ar-OCH3), 111.3, 111.5, 112.5, 118.0, 118.3,
119.1, 120.1, 120.7, 123.4, 126.6, 136.5, 137.4, 146.8,
148.3 ppm (aromatic carbons). MS (ES): m/z 383.1672
[M + H]+. Anal. Calcd. for C25H22N2O2: C 78.51; H
5.56; N 7.32. Found: C 78.61; H 5.55; N 7.48%.
4-(Bis(5-hydroxy-1H-indol-3-yl)methyl)benzonitrile (3h).
Brick
red solid, mp 209–211°C; IR (KBr cmꢀ1): 3456 (OH),
3384 (NH), 1631 (C = C), 1574 (C = N); 1H NMR
(400 MHz, DMSO-d6): δ 5.69 (s, 1H, Ar-CH), 6.55–7.75
(m, 12H, Ar-H), 8.48 (s, 2H, OH), 10.54 (bs, 2H, NH)
ppm; 13C NMR (200 MHz, DMSO-d6): δ 40.6 (Ar-CH),
102.9, 108.4, 111.3, 111.7, 115.7, 119.0, 124.1, 127.0,
129.2, 131.1, 131.9, 150.0, 150.8 ppm (aromatic
carbons). MS (ES): m/z 380.1299 [M + H]+. Anal. Calcd.
for C24H17N3O2: C 75.97; H 4.52; N 11.08. Found: C
4-(Di(1H-indol-3-yl)methyl)benzonitrile
(3c).
Slight
brown solid, mp 205–207°C; IR (KBr cmꢀ1): 3374 (NH),
1
1633 (C = C); H NMR (400 MHz, CDCl3): δ 5.93 (s, 1H,
Ar-CH), 6.66–7.59 (m, 14H, Ar-H), 7.97 (bs, 2H, NH) ppm;
13C NMR (200 MHz, DMSO-d6): δ 38.7 (Ar-CH), 108.5,
111.4, 116.7, 118.3, 118.8, 118.9, 120.9, 123.7, 126.3,
129.2, 132.0, 136.5, 150.7 ppm (aromatic carbons). MS
(ES): m/z 348.1402 [M + H]+. Anal. Calcd. for C24H17N3: C
76.05; H 4.54; N 11.24%.
3,3″-((4-Nitrophenyl)methylene)bis(1H-indol-5-ol) (3i). Yellow
solid, mp 218–220°C; IR (KBr cmꢀ1): 3446 (OH), 3380
1
(NH), 1628 (C = C); H NMR (400 MHz, DMSO-d6): δ
82.97; H 4.93; N 12.10. Found: C 83.08; H 4.95; N 12.30%.
3,3″-((4-Nitrophenyl)methylene)bis(1H-indole) (3d). Yellow
5.77 (s, 1H, Ar-CH), 6.55–8.16 (m, 12H, Ar-H), 8.48 (s,
2H, OH), 10.59 (bs, 2H, NH) ppm; 13C NMR
(200 MHz, DMSO-d6): δ 41.0 (Ar-CH), 102.9, 111.3,
111.8, 115.6, 123.2, 124.2, 127.0, 129.3, 131.1, 145.6,
150.0, 153.0 ppm (aromatic carbons). MS (ES): m/z
400.1236 [M + H]+. Anal. Calcd. for C23H17N3O4: C
69.17; H 4.29; N 10.52. Found: C 69.27; H 4.32; N
solid, mp 217–219°C. IR (KBr cmꢀ1): 3372 (NH), 1629
1
(C = C); H NMR (400 MHz, DMSO-d6): δ 5.98 (s, 1H,
Ar-CH), 6.72–8.12 (m, 14H, Ar-H), 10.90 (bs, 2H, NH)
ppm; 13C NMR (200 MHz, DMSO-d6): δ 40.3 (Ar-CH),
111.5, 116.6, 118.3, 118.8, 121.0, 123.3, 123.9, 126.1,
129.4, 136.7, 145.6, 153.0 ppm (aromatic carbons). MS
(ES): m/z 368.1325 [M + H]+. Anal. Calcd. for
C23H17N3O2: C 75.91; H 4.66; N 11.44. Found: C 76.05;
H 4.70; N 11.61%.
10.71%.
3,3″-((4-(Tert-butyl)phenyl)methylene)bis(1H-indol-5-ol)
(3j). Pink solid, mp 144–146°C; IR (KBr cmꢀ1): 3448
1
(OH), 3388 (NH), 1634 (C = C); H NMR (400 MHz,
3,3″-((3-Nitrophenyl)methylene)bis(1H-indole) (3e).
Brick
red solid, mp 154–156°C; IR (KBr cmꢀ1): 3378 (NH),
DMSO-d6): δ 1.25 (s, 9H, CH3), 5.52 (s, 1H, Ar-CH),
6.54–7.28 (m, 12H, Ar-H), 8.43 (s, 2H, OH) 10.40 (bs,
2H, NH) ppm; 13C NMR (200 MHz, DMSO-d6): δ 31.2
(CH3), 34.0 (C(CH3)3), 55.4 (Ar-CH), 103.1, 111.0,
111.5, 117.1, 123.8, 124.5, 127.2, 127.7, 131.0, 141.8,
147.6, 149.7 ppm (aromatic carbons). MS (ES): m/z
411.1997 [M + H]+. Anal. Calcd. for C27H26N2O2: C
79.00; H 6.38; N 6.82. Found: C 79.12; H 6.40; N
1
1635 (C = C); H NMR (400 MHz, CDCl3): δ 5.99 (s,
1H, Ar-CH), 7.98 (bs, 2H, NH), 6.68–8.21 (m, 14H, Ar-
H) ppm; 13C NMR (200 MHz, CDCl3): δ 39.9 (Ar-CH),
111.2, 118.1, 119.4, 121.3, 122.1, 123.4, 123.6, 126.5,
129.0, 134.8, 136.6, 146.3, 148.3 ppm (aromatic
carbons). MS (ES): m/z 368.1312 [M + H]+. Anal. Calcd.
for C23H17N3O2: C 75.91; H 4.66; N 11.44. Found: C
6.95%.
76.01; H 4.68; N 11.63%.
3,3″-((3,4-Dimethoxyphenyl)methylene)bis(1H-indol-5-ol)
3,3″-((4-Chlorophenyl)methylene)bis(1H-indole) (3f). Brownish
(3k). Brick red solid, mp 111–113°C; IR (KBr cmꢀ1):
red solid, mp 101–103°C; IR (KBr cmꢀ1): 3380 (NH),
3320 (NH), 1568 (C = N), 1633 (C = C); 1H NMR
(400 MHz, DMSO-d6): δ 3.60 (s, 3H, ꢀOCH3), 3.64
(s, 3H, ꢀOCH3), 5.72 (s, 1H, Ar-CH), 6.85–7.36 (m,
11H, Ar-H), 8.42 (s, 2H, OH) 10.72 (bs, 2H, NH)
ppm; 13C NMR (200 MHz, DMSO-d6): δ 40.1 (Ar-
CH), 55.5 (Ar-OCH3), 102.5, 111.8, 115.8, 120.1,
122.8, 123.8, 126.8, 129.7, 130.7, 137.2, 139.6, 144.9,
150.1, 153.5 ppm (aromatic carbons). MS (ES): m/z
415.1583 [M + H]+. Anal. Calcd. for C25H22N2O4: C
72.45; H 5.35; N 6.76. Found: C 72.41; H 5.34; N
6.81%.
1
1626 (C = C); H NMR (400 MHz, CDCl3): δ 5.86 (s,
1H, Ar-CH), 6.66–7.39 (m, 14H, Ar-H), 7.95 (bs, 2H,
NH) ppm; 13C NMR (200 MHz, DMSO-d6): δ 40.9 (Ar-
CH), 111.4, 117.4, 118.1, 118.9, 120.8, 123.5, 126.4,
127.8, 130.0, 130.1, 136.5, 143.9 ppm (aromatic
carbons). MS (ES): m/z 357.0977 [M + H]+. Anal. Calcd.
for C23H17ClN2: C 77.41; H 4.80; N 7.85. Found: C
77.54; H 4.83; N 8.10%.
3,3″-((4-(Tert-butyl)phenyl)methylene)bis(1H-indole)
(3g). Yellow soild, mp 70-72°C; IR (KBr cmꢀ1): 3375
1
(NH), 1622 (C = C); H NMR (400 MHz, DMSO-d6): δ
Journal of Heterocyclic Chemistry
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P. R. Simha, M. S. Mangali, D. Kuppireddy Gari, P. Venkatapuram, and P. Adivireddy
Vol 000
REFERENCES AND NOTES
3,3″-(1-(4-Nitrophenyl)ethane-1,1-diyl)bis(1H-indole)
(3l). Yellow solid, mp 246–248°C; IR (KBr cmꢀ1): 3342
(NH), 1642 (C = C); H NMR (400 MHz, DMSO-d6): δ
[1] Murakatake, H.; Kumagami, H.; Natsume, M. Tetrahedron
1990, 46, 6351.
1
2.36 (s, 3H, CH3), 6.71–8.05 (m, 14H, Ar-H), 10.72 (bs,
2H, NH) ppm; 13C NMR (200 MHz, DMSO-d6): δ 28.8
(Ar-CH3), 39.4 (Ar-CH), 111.6, 118.1, 118.1, 120.6,
121.3, 122.8, 123.5, 125.6, 126.5 128.9, 137.0,
145.3 ppm (aromatic carbons). MS (ES): m/z 382.2473
[M + H]+. Anal. Calcd. for C24H19N3O2: C 75.57; H
5.02; N 11.02. Found: C 75.52; H 5.00; N 10.84%.
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Liu, P. Res Chem Intermed 2012, 38, 2501.
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Acta Part A 2011, 78, 726.
3,3″-(1-(m-Tolyl)ethane-1,1-diyl)bis(1H-indole) (3m).
White
solid, mp 160–162°C; IR (KBr cmꢀ1): 3330 (NH), 1635
1
(C = C); H NMR (400 MHz, DMSO-d6): δ 2.16 (s, 3H,
CH3), 2.21(s, 3H, Ar-CH3) 6.69–7.31 (m, 14H, Ar-H),
10.76 (bs, 2H, NH) ppm; 13C NMR (200 MHz,
DMSO-d6): δ 21.3 (Ar-CH3), 29.1 (Ar-CH3), 38.4 (Ar-
CH), 111.4, 117.7, 120.3, 120.9, 122.8, 123.2, 124.8,
125.3, 126.1, 127.2, 128.0, 129.3, 136.9, 148.1 ppm
(aromatic carbons). MS (ES): m/z 351.1789 [M + H]+.
Anal. Calcd. for C25H22N2: C 85.68; H 6.33; N 7.99%.
Found: C 85.75; H 6.35; N 8.14%.
3,3″-(1-(p-Tolyl)ethane-1,1-diyl)bis(1H-indole) (3n).
White
solid, mp 173–175°C; IR (KBr cmꢀ1): 3352 (NH), 1645
1
(C = C); H NMR (400 MHz, DMSO-d6): δ 2.25 (s, 3H,
CH3), 2.28 (s, 3H, Ar-CH3) 6.68–7.32 (m, 14H, Ar-H),
10.74 (bs, 2H, NH) ppm; 13C NMR (200 MHz, DMSO-d6):
δ 20.4 (Ar-CH3), 29.0 (Ar-CH3), 42.7 (Ar-CH), 111.2,
120.5, 121.4, 122.6, 123.5, 125.9, 127.4, 128.5, 129.6,
134.3, 136.2, 145.2 ppm (aromatic carbons). MS (ES): m/z
351.2785 [M + H]+. Anal. Calcd. for C25H22N2: C 85.68; H
6.33; N 7.99. Found: C 85.79; H 6.36; N 8.20%.
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Acknowledgments. The authors, M. Madhu Sekhar and K. Divya
are thankful to the University Grants Commission (UGC), New
Delhi for the sanction of UGC-SRF, UGC-BSR fellowships.
The authors are also thankful to Prof. T. Vijaya, Department of
Botany, S.V. University and Tirupati for providing necessary
facilities to carry out the antioxidant activity.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet