A catalyst-free protocol for the green and efficient condensation of indoles with aldehydes in ionic liquids

Article abstract of DOI:10.1139/V08-172

Indoles are efficiently condensed with aromatic and aliphatic aldehydes in the absence of any catalyst in ionic liquid 1-butyl-3-methylimidazolium bromide {bmim]Br} under microwave irradiation to afford bis(indolyl)methanes in good to excellent yields and

Full text of DOI:10.1139/V08-172

416
A catalyst-free protocol for the green and efficient
condensation of indoles with aldehydes in ionic
liquids
Abdolkarim Zare, Abolfath Parhami, Ahmad Reza Moosavi-Zare,
Alireza Hasaninejad, Ali Khalafi-Nezhad, and Mohammad Hassan Beyzavi
Abstract: Indoles are efficiently condensed with aromatic and aliphatic aldehydes in the absence of any catalyst in ionic
liquid 1-butyl-3-methylimidazolium bromide {bmim]Br} under microwave irradiation to afford bis(indolyl)methanes in
good to excellent yields and in short reaction times.
Key words: catalyst-free, indole, aldehyde, ionic liquid, microwave, bis(indolyl)methane.
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Resume : Les indoles se condensent d’une maniere efficace avec les aldehydes aliphatiques et aromatiques, sans necessite
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de catalyseur, dans le liquide ionique bromure de 1-butyl-3-methylimidazolium {[bmim]Br} et sous irradiation par des mi-
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croondes et ces reactions conduisent, en un court laps de temps, a la formation de bis(indolyl)methanes avec des rende-
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ments allant de bons a excellents.
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Mots-cles : sans catalyseur, indole, aldehyde, liquide ionique, micro-onde, bis(indolyl)methane.
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[Traduit par la Redaction]
with aldehydes can be efficiently achieved without any cata-
lyst in neutral ionic liquids under microwave irradiation.
Currently, ionic liquids have been the subject of consider-
able interest as benign reaction media in organic synthesis
because of their unique properties such as non-volatility,
non-flammability, recyclability, and ability to dissolve a
wide range of materials.11 During the past decade, a variety
of ionic liquids have been demonstrated to be efficient and
practical alternatives to volatile organic solvents for many
important organic transformations.11 Together with the sub-
stitution of common molecular solvents, non-conventional
activation methods, mainly microwave irradiation, have
emerged as powerful techniques to decrease reaction times
and to enhance reaction rates.12
The condensation of indoles with carbonyl compounds is
of importance, because this reaction provides a simple route
to bis(indolyl)methanes synthesis.13 For this class of com-
pounds, different pharmacological and biological activities
have been reported.14 Several methods have been developed
for the preparation of bis(indolyl)methanes from indoles and
carbonyl compounds using catalysts such as silica sulfuric
acid,13a Ru (III),13b H3PMo12O40ÁxH2O,13c P2O5/SiO2,13d
silica chloride,13e ZrOCl2Á8H2O,13f PPh3-HClO4(TPP),13g
AlPW12O40,13h In(OTf)3,13i Dy(OTf)3,13j and La(PFO)3.13k
This transformation has been also carried out in H2O in the
presence of sodium dodecyl sulfate.13l Moreover, in this re-
port the same reaction has been performed in the absence of
catalyst in MeOH.13l In the mentioned paper, the results ob-
tained from a H2O/sodium dodecyl sulfate system are good;
however, the catalyst-free conditions have some drawbacks
including low yields, long reaction times, and no generali-
ty.13l To the best of our knowledge, there is no other report
on the condensation of indoles with aldehydes without cata-
lyst.
Introduction
In recent years, catalyst-free reactions have attracted in-
creasing interest due to their ease of experimental procedure
as well as work-up, low cost, possibility of using acid- or
base-sensitive substrates, and their environmentally benign
nature.1–10 This useful technique has been used in several
chemical transformations, such as self-assembly of carbon
nanotubes, carbon nanowires, and carbon filaments,1 synthe-
sis of 2-aminothiazoles,2 N-benzyloxycarbonylation of
amines,3 synthesis of benzoic esters and benzyl esters,4
gem-bisallylation of carboxylic acid derivatives,5 synthesis
of polyorganosiloxanes,6 synthesis of dithiocarbamates,7 re-
gioselective conversion of epoxides to vicinal-halohydrins,8
transesterification of triglycerides,9 and Michael-type addi-
tion of amines to electron-deficient alkenes.10 As a part of
our continuing interest in developing efficient synthetic
methodologies in organic synthesis, we have initiated a pro-
gram to study useful organic transformations in the absence
of catalyst. Herein, we find that the condensation of indoles
Received 12 August 2008. Accepted 29 October 2008. Published
on the NRC Research Press Web site at canjchem.nrc.ca on
19 December 2008.
A. Zare,1 A. Parhami,2 and A.R. Moosavi-Zare. Department
of Chemistry, College of Sciences, Payame Noor University
(PNU), Iran.
A. Hasaninejad. Department of Chemistry, Faculty of Sciences,
Persian Gulf University, Bushehr 75169, Iran.
A. Khalafi-Nezhad and M.H. Beyzavi. Department of
Chemistry, College of Sciences, Shiraz University, Shiraz
71454, Iran.
1Corresponding author (e-mail: abdolkarimzare@yahoo.com).
2Corresponding author (e-mail: rezaparhami@yahoo.com).
Can. J. Chem. 87: 416–421 (2009)
doi:10.1139/V08-172
Published by NRC Research Press

Zare et al.
417
Scheme 1. The condensation of indole with benzaldehyde.
Table 1. The catalyst-free condensation of indole
with benzaldehyde under solvent-free conditions as
well as in ionic liquids promoted by microwave irra-
diation (400 W, max, 150 8C).
mechanism for the condensation of indoles with aldehydes
based on the activation of a carbonyl group of aldehydes
via hydrogen bond formation with solvent.13l According to
these observations, we suggest a mechanism for our reaction
(Scheme 2). In this mechanism, the [bmim]-based ionic
liquid has a dual activation role. Activation of the carbonyl
group occurs via hydrogen bond between 2-H of the [bmim]
moiety of the ionic liquid and oxygen of the carbonyl group.
Moreover, indole is activated when the bromide ion of the
ionic liquid removes the NH proton of the indole, since it
increases the nucleophilicity of the indole. We suggest that
firstly (3H-indol-3-yl)-phenyl-methanol (I) forms as a result
of nucleophilic attack of activated indole to electrophilic
carbon of activated carbonyl function of benzaldehyde.
Then, intermediate I eliminates a water molecule to convert
into 3-benzylidene-3H-indole (II). The electrophilicity of the
exocyclic double bond of intermediate II increases through
hydrogen bond formation between sp2 nitrogen of intermedi-
ate II and 2-H of [bmim] moiety. Finally, the activated in-
dole attacks the exocyclic double bond providing the
bis(indolyl)methane 1. Ionic liquids also stabilize charged
intermediates and enhance reaction rates.16 Moreover, these
polar solvents absorbs microwave irradiation and increase
reaction temperature rapidly.12a,12j
Entry
Solvent
Time (min)
Yielda (%)
1
2
3
4
Solvent-free
[bmim]Br
[bmim]Cl
[bmim]I
30
8
8
Trace
95
69
8
47
aIsolated yield.
In this study, we report a catalyst-free, efficient, green,
and simple method for the condensation of indoles with aro-
matic and aliphatic aldehydes in [bmim]Br under microwave
irradiation (Scheme 1).
Results and discussion
At first, we examined condensation of indole (2 mmol)
with benzaldehyde (1 mmol) in the absence of any catalyst
under solvent-free and microwave conditions at 400 W of
microwave power; but these conditions afforded the corre-
sponding bis(indolyl)methane 1 in trace yield after 30 min
(Table 1). Increasing the reaction time or microwave power
did not improve the yield. The yield increased to 95% when
the reaction was performed in ionic liquid [bmim]Br
(0.25 g) at 400 W (max 150 8C) (Table 1 and Scheme 1).
Moreover, the reaction of indole with benzaldehyde was ex-
amined in ionic liquids [bmim]Cl and [bmim]I (Table 1). As
Table 1 indicates, [bmim]Br afforded the best results.
The condensation of indole with benzaldehyde was also
tested at different microwave powers (100–600 W, max.
150 8C). The reasonable results were obtained at 400 W.
To assess the generality and the scope of this catalyst-free
protocol, indoles were reacted with structurally diverse alde-
hydes. The results are summarized in Table 2. As can be
seen in Table 2, all reactions proceeded efficiently and the
desired products were produced in good to excellent yields
and in short reaction times. It must be mentioned that ali-
phatic and aromatic aldehydes possessing electron-releasing
substituents gave the corresponding bis(indolyl)methanes in
lower yields and in longer reaction times in comparison
with the others (Table 2, entries 7–10 and 17).
In summary, we have reported a new application of cata-
lyst-free protocol in organic synthesis. In this study, bis(in-
dolyl)methanes efficiently synthesized from indoles and
aldehydes in a ionic liquid under microwave conditions.
Experimental
All chemicals were purchased from Merck or Fluka
chemical companies. The ionic liquid was prepared accord-
ing to the reported methods.17 All reactions were carried out
using a laboratory microwave oven (MicroSYNTH, Mile-
1
stone Company, Italy). The H NMR (250 MHz) and 13C
NMR (62.5 MHz) were run on a Bruker Avance DPX-250
FT-NMR spectrometer, d in ppm. Mass spectra were re-
corded on a Shimadzu GC MS-QP 1000 EX apparatus. Mi-
croanalyses were performed on a PerkinElmer 240-B
microanalyzer. Melting points were recorded on a Bu¨chi B-
545 apparatus in open capillary tubes.
General procedure for the catalyst-free condensation of
indoles with aldehydes
One of the most interesting properties of ionic liquids is
their ease of recycling. For the reaction of indole with ben-
zaldehyde no significant loss of the product yield was ob-
served when [bmim]Br was reused, even after three
repeated uses.
It has long been studied that hydrogen bond formation can
occur between the solute and cationic or anionic counterpart
of ionic liquids.15 Moreover, Deb et al. have suggested a
To a mixture of indole (2 mmol, 0.234 g) and aldehyde
(1 mmol) in a microwave vessel was added [bmim]Br
(0.25 g), and the mixture was stirred carefully with a small
rod. The resulting mixture was irradiated in a microwave
oven at 400 W for the appropriate time (Table 2). The mi-
crowave was programmed to give a maximum internal tem-
perature of 150 8C. Afterward, the reaction mixture was
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418
Can. J. Chem. Vol. 87, 2009
Table 2. Catalyst-free condensation of indoles with aldehydes in [bmim]Br under microwave irradiation (400 W, max 150 8C).
Entry
1
X
H
CH3
H
H
H
CH3
H
H
H
CH3
H
H
H
H
R
C6H5
C6H5
Product
1
2
3
4
5
6
7
Time (min)
8
10
6
6
Yielda (%)
Mp 8C (Lit.)
95
89
97
96
96
92
88
85
83
86
97
85
90
82
80
140–142 (140–142)13d
246–248 (245–247)13e
216–218 (217–220)13l
220–222 (220–222)13d
99–101 (98–100)13d
240–242 (241–243)13e
94–96 (97–99)13a
2
3b
4b
5
p-NO2C6H4
m-NO2C6H4
m-CNC6H4
p-NO2C6H4
p-CH3C6H4
p-OMeC6H4
p-OHC6H4
p-CH3C6H4
p-ClC6H4
o-ClC6H4
4-Pyridyl
2-Furyl
7
8
6b
7
17
18
18
21
8
14
7
15
20
8
9
8
9
185–187 (178–181)13a
120–122 (119–121)13d
175–177 (174–175)13l
77–79 (76–77)13l
10
11
12
13
14
15
10
11
12
13
14
15
73–75 (70–71)13l
160–162 (161–163)13e
315–317 (>300)13l
H
161, dec. (162, dec.)13d
16
17c
H
H
E-C6H5CH=CH
CH3(CH2)3CH2
16
17
15
20
88
81
99–101 (98–99)13l
70–72 (71–73)13d
aIsolated yield.
bThis reaction was carried out at 300 W of microwave power (max 150 8C).
cThis reaction was performed in a sealed vessel.
Scheme 2. Suggested mechanism for the condensation of indoles with aldehydes.
cooled to room temperature and was extracted with Et2O
(2 Â 20 mL). The organic extracts were then combined and
washed with saturated solution of NaHSO3 (2 Â 20 mL) to
remove unreacted aldehyde and then with water (2 Â
20 mL). The organic layer was separated and dried with
CaCl2. The solvent was evaporated and the crude product
was purified by recrystallization from EtOAc/petroleum
ether (1:2) or plate chromatography on silica gel eluted
with EtOAc/petroleum ether (1:2). After isolation of the
product, the remaining Et2O in [bmim]Br was evaporated,
and it was used for the next run under identical reaction
conditions.
Published by NRC Research Press

Zare et al.
419
3-((1H-Indol-3-yl)(phenyl)methyl)-1H-indole (1)
2-Methyl-3-((2-methyl-1H-indol-3-yl)(4-
nitrophenyl)methyl)-1H-indole (6)
Recrystallization from EtOAc/petroleum ether (1:2) gave
pink solid; yield 0.306 g (95%); mp 140–142 8C (lit. 140–
142 8C).13d 1H NMR (CDCl3, ppm) d: 5.86 (s, 1H, ArCH),
6.66 (s, 2H), 7.11 (t, 2H, J = 6.9 Hz), 7.14–7.22 (m, 3H),
7.28–7.31 (m, 2H), 7.35–7.42 (m, 6H), 7.93 (br, 2H, NH).
13C NMR (CDCl3, ppm) d: 31.6, 110.9, 111.9, 118.4, 119.5,
121.2, 124.0, 126.3, 127.1, 128.5, 128.6, 137.0, 145.2. MS
m/z: 322 [M+]. Anal. calcd. for C23H18N2: C 85.68, H 5.63,
N 8.69; found: C 85.87, H 5.79, N 8.46.
Recrystallization from EtOAc/petroleum ether (1:2) gave
yellow solid; yield 0.365 g (92%); mp 240–242 8C (lit.
241–243 8C).13e 1H NMR (CDCl3, ppm) d: 2.13 (s, 6H),
5.96 (s, 1H), 6.71–6.96 (m, 6H), 7.21 (d, 2H, J = 8.0 Hz),
7.47 (d, 2H, J = 8.5 Hz), 8.00 (d, 2H, J = 8.5 Hz), 8.07 (br,
2H, NH). 13C NMR (CDCl3, ppm) d: 12.1, 39.0, 109.8,
111.9, 118.7, 119.1, 119.5, 121.5, 128.2, 129.4, 132.0,
135.0, 144.1, 152.4. MS m/z: 395 [M+]. Anal. calcd. for
C25H21N3O2: C 75.93, H 5.35, N 10.63; found: C 75.69, H
5.46, N 10.48.
2-Methyl-3-((2-methyl-1H-indol-3-yl)(phenyl)methyl)-1H-
indole (2)
3-((1H-Indol-3-yl)(p-tolyl)methyl)-1H-indole (7)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave pink solid; yield
0.312 g (89%); mp 246–248 8C (lit. 245–247 8C).13e 1H
NMR (CDCl3, ppm) d: 2.05 (s, 6H), 5.88 (s, 1H, ArCH),
6.78–7.01 (m, 6H), 7.14–7.22 (m, 5H), 7.28–7.31 (m, 2H),
8.02 (br, 2H, NH). 13C NMR (CDCl3, ppm) d: 13.4, 38.7,
109.6, 112.1, 118.9, 120.0, 121.4, 126.5, 128.4, 128.6,
129.1, 132.4, 135.7, 139.8. MS m/z: 350 [M+]. Anal. calcd.
for C25H22N2: C 85.68, H 6.33, N 7.99; found: C 85.47, H
6.48, N 7.86.
Recrystallization from EtOAc/petroleum ether (1:2) gave
pink solid; yield 0.297 g (88%); mp 94–96 8C (lit. 97–
99 8C).13a 1H NMR (CDCl3, ppm) d: 2.33 (s, 3H, ArCH3),
5.87 (s, 1H, ArCH), 6.69 (s, 2H), 7.04 (t, 2H, J = 7.1 Hz),
7.12 (d, 2H, J = 7.1 Hz), 7.23–7.28 (m, 6H), 7.41 (d, 2H,
J = 7.2 Hz), 7.94 (br, 2H, NH). 13C NMR (CDCl3, ppm) d:
21.8, 39.4, 110.1, 111.8, 118.7, 119.6, 121.9, 123.4, 127.2,
129.4, 134.2, 135.1, 135.9. MS m/z: 336 [M+]. Anal. calcd.
for C24H20N2: C 85.68, H 5.99, N 8.33; found: C 85.46, H
6.13, N 8.51.
3-((1H-Indol-3-yl)(4-nitrophenyl)methyl)-1H-indole (3)
Recrystallization from EtOAc/petroleum ether (1:2) gave
yellow needles; yield 0.355 g (97%); mp 216–218 8C (lit.
217–220 8C).13l 1H NMR (CDCl3, ppm) d: 6.01 (s, 1H,
ArCH), 6.72 (s, 2H), 7.02–7.08 (m, 4H), 7.36 (d, 2H, J =
8.1 Hz), 7.41 (d, 2H, J = 8.1 Hz), 7.49 (d, 2H, J = 8.6 Hz),
8.05 (br, 2H, NH), 8.17 (d, 2H, J = 8.6 Hz). 13C NMR
(CDCl3, ppm) d: 40.2, 112.0, 113.1, 119.1, 120.4, 121.8,
122.1, 123.7, 127.4, 131.8, 136.1, 145.1, 153.5. MS m/z:
367 [M+]. Anal. calcd. for C23H17N3O2: C 75.19, H 4.66, N
11.44; found: C 75.36, H 4.51, N 11.31.
3-((1H-Indol-3-yl)(4-methoxyphenyl)methyl)-1H-indole
(8)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave brown solid; yield
0.298 g (85%); mp 185–187 8C (lit. 178–181 8C).13a 1H
NMR (CDCl3, ppm) d: 3.76 (s, 3H, OCH3), 5.85, (s, 1H,
ArCH), 6.68 (s, 2H), 6.91 (d, 2H, J = 8.2 Hz), 7.02 (t, 2H,
J = 7.3 Hz), 7.16 (t, 2H, J = 7.3 Hz), 7.20 (m, 2H), 7.35–
7.41 (m, 4H), 7.95 (br, 2H, NH). 13C NMR (CDCl3, ppm)
d: 38.6, 55.3, 110.6, 112.2, 115.0, 119.0, 119.8, 122.0,
123.9, 127.5, 130.2, 131.1, 136.4, 145.4. MS m/z: 352 [M+].
Anal. calcd. for C24H20N2O: C 81.79, H 5.72, N 7.95; found:
C 81.98, H 5.63, N 7.79.
3-((1H-Indol-3-yl)(3-nitrophenyl)methyl)-1H-indole (4)
Recrystallization from EtOAc/petroleum ether (1:2) gave
yellow solid; yield 0.352 g (96%); mp 220–222 8C (lit.
220–222 8C).13d 1H NMR (CDCl3, ppm) d: 6.23 (s, 1H,
ArCH), 7.01 (t, 2H, J = 7.3 Hz), 7.06 (s, 2H), 7.22 (t, 2H,
J = 7.0 Hz), 7.45 (d, 2H, J = 7.5 Hz), 7.53 (d, 2H, J =
8.0 Hz), 7.75 (m, 1H), 8.02 (d, 1H, J = 7.6 Hz), 8.26 (d,
1H, J = 7.7 Hz), 8.33 (s, 1H), 8.09 (br, 2H, NH). 13C NMR
(CDCl3, ppm) d: 38.7, 111.0, 112.6, 118.4, 119.0, 120.7,
121.9, 123.4, 125.3, 127.8, 129.5, 135.2, 136.8, 138.5,
148.0. MS m/z: 367 [M+]. Anal. calcd. for C23H17N3O2: C
75.19, H 4.66, N 11.44; found: C 75.38, H 4.50, N 11.57.
4-(Di(1H-indol-3-yl)methyl)phenol (9)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave pink solid; yield
0.282 g (83%); mp 120–122 8C (lit. 119–121 8C).13d 1H
NMR (DMSO-d6, ppm) d: 5.74 (s, 1H), 6.63 (m, 4H), 6.87
(t, 2H, J = 7.5 Hz), 7.03 (t, 2H, J = 7.6 Hz), 7.13 (d, 2H,
J = 7.5 Hz), 7.34 (m, 4H), 8.58 (s, 1H, OH), 9.78 (br, 2H,
NH). 13C NMR (DMSO-d6, ppm) d: 43.6, 115.9, 119.6,
123.7, 124.8, 125.2, 126.9, 129.3, 131.9, 134.7, 140.5,
142.5, 160.2. MS m/z: 338 [M+]. Anal. calcd. for
C23H18N2O: C 81.63, H 5.36, N 8.28; found: C 81.38, H
5.48, N 8.16.
3-(Di(1H-indol-3-yl)methyl)benzonitrile (5)
Recrystallization from EtOAc/petroleum ether (1:2) gave
pink solid; yield 0.334 g (96%); mp 99–101 8C (lit. 98–
100 8C).13d 1H NMR (CDCl3, ppm) d: 6.09 (s, 1H, ArCH),
6.83 (s, 2H), 6.98–7.07 (m, 4H), 7.19 (d, 2H, J = 7.6 Hz),
7.42 (d, 2H, J = 7.6 Hz), 7.65–7.87 (m, 4H), 8.02 (br, 2H,
NH). 13C NMR (CDCl3, ppm) d: 39.2, 111.0, 111.9, 112.5,
116.8, 118.9, 119.4, 122.1, 123.7, 127.2, 129.7, 130.0,
133.8, 134.2, 136.2, 140.1. MS m/z: 347 [M+]. Anal. calcd.
for C24H17N3: C 82.97, H 4.93, N 12.10; found: C 82.74, H
5.04, N 11.98.
2-Methyl-3-((2-methyl-1H-indol-3-yl)(p-tolyl)methyl)-1H-
indole (10)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave pink solid; yield
0.312 g (86%); mp 175–177 8C (lit. 174–175 8C).13l 1H
NMR (CDCl3, ppm) d: 2.09 (s, 6H), 2.29 (s, 3H, ArCH3),
5.92 (s, 1H, ArCH), 6.71–6.96 (m, 6H), 7.00–7.09 (m, 4H),
7.18 (d, 2H, J = 7.7 Hz), 7.98 (br, 2H, NH). 13C NMR
(CDCl3, ppm) d: 14.0, 20.9, 38.7, 109.8, 111.8, 118.6,
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Can. J. Chem. Vol. 87, 2009
119.7, 121.5, 127.1, 129.3, 132.4, 133.8, 135.4, 136.1. MS
m/z: 364 [M+]. Anal. calcd. for C26H24N2: C 85.68, H 6.64,
N 7.69; found: C 85.87, H 6.55, N 7.72.
(E)-3-(1-(1H-Indol-3-yl)-3-phenylallyl)-1H-indole (16)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave pale yellow solid;
yield 0.306 g (88%); mp 99–101 8C (lit. 98–99 8C).13l 1H
NMR (CDCl3, ppm) d: 5.22 (m, 1H), 6.19 (m, 1H), 6.57 (d,
1H, J = 15.4 Hz), 6.89 (s, 2H), 7.02–7.09 (m, 4H), 7.26–
7.32 (m, 7H), 7.49 (d, 2H, J = 7.9 Hz), 7.92 (br, 2H, NH).
13C NMR (CDCl3, ppm) d: 43.1, 111.3, 117.4, 118.7, 120.0,
121.8, 122.3, 123.6, 126.8, 127.2, 128.4, 128.9, 129.3,
134.3, 136.7. MS m/z: 348 [M+]. Anal. calcd. for C25H20N2:
C 86.17, H 5.79, N 8.04; found: C 86.03, H 5.88, N 7.93.
3-((4-Chlorophenyl)(1H-indol-3-yl)methyl)-1H-indole (11)
Recrystallization from EtOAc/petroleum ether (1:2) gave
pink solid; yield 0.345 g (97%); mp 77–79 8C (lit. 76–
77 8C).13l 1H NMR (CDCl3, ppm) d: 5.86 (s, 1H, ArCH),
6.65 (s, 2H), 6.85–7.96 (m, 12H), 8.00 (br, 2H, NH). 13C
NMR (CDCl3, ppm) d: 37.9, 110.7, 111.7, 118.5, 119.3,
121.6, 123.5, 126.9, 128.1, 129.8, 130.2, 135.2, 135.8. MS
m/z: 356 [M+]. Anal. calcd. for C23H17ClN2: C 77.41, H
4.80, N 7.85; found: C 77.58, H 4.68, N 8.01.
3-(1-(1H-Indol-3-yl)hexyl)-1H-indole (17)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave colorless solid;
yield 0.257 g (81%); mp 70–72 8C (lit. 71–73 8C).13d 1H
NMR (CDCl3, ppm) d: 0.89 (t, 3H, J = 6.7 Hz), 1.27–1.33
(m, 6H), 1.52 (m, 2H), 4.79 (t, 1H, J = 6.6 Hz), 6.91 (s,
2H), 6.99–7.07 (m, 4H), 7.30 (d, 2H, J = 7.8 Hz), 7.55 (d,
2H, J = 7.8 Hz), 7.94 (br, 2H, NH). 13C NMR (CDCl3,
ppm) d: 13.8, 23.2, 25.9, 29.7, 31.5, 41.7, 110.8, 114.7,
118.6, 119.4, 121.9, 124.1, 127.5, 136.3. MS m/z: 316 [M+].
Anal. calcd. for C22H24N2: C 83.50, H 7.64, N 8.85; found:
C 83.69, H 7.54, N 8.99.
3-((2-Chlorophenyl)(1H-indol-3-yl)methyl)-1H-indole (12)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave pink solid; yield
0.305 g (85%); mp 73–75 8C (lit. 70–71 8C).13l 1H NMR
(CDCl3, ppm) d: 6.32 (s, 1H, ArCH), 6.67 (s, 2H), 7.02 (t,
2H, J = 7.8 Hz), 7.10–7.22 (m, 6H), 7.38–7.43 (m, 4H),
7.98 (br, 2H, NH). 13C NMR (CDCl3, ppm) d: 37.1, 110.4,
111.6, 119.2, 120.0, 122.4, 123.9, 126.8, 127.3, 128.5,
130.5, 131.4, 135.6, 136.8, 141.5. MS m/z: 356 [M+]. Anal.
calcd. for C23H17ClN2: C 77.41, H 4.80, N 7.85; found: C
77.26, H 4.91, N 7.98.
Acknowledgements
3-((1H-Indol-3-yl)(pyridin-4-yl)methyl)-1H-indole (13)
Purification by plate chromatography on silica gel, eluted
with EtOAc/petroleum ether (1:2), gave brown solid; yield
0.291 g (90%); mp 160–162 8C (lit. 161–163 8C).13e 1H
NMR (CDCl3, ppm) d: 5.96 (s, 1H, ArCH), 6.67 (s, 2H),
7.08–7.15 (m, 4H), 7.36 (d, 2H, J = 8.1 Hz), 7.43 (d, 2H, J
= 8.1 Hz), 7.37 (d, 2H, J = 7.9 Hz), 7.99 (br, 2H, NH), 8.34
(d, 2H, J = 7.9 Hz). 13C NMR (CDCl3, ppm) d: 40.1, 111.3,
112.2, 119.6, 120.8, 122.1, 122.7, 124.5, 126.7, 136.4,
148.7, 152.9. MS m/z: 323 [M+]. Anal. calcd. for C22H17N3:
C 81.71, H 5.30, N 12.99; found: C 81.49, H 5.17, N 12.86.
The authors appreciate Payame Noor University and Per-
sian Gulf University Research Councils for the financial
support of this work.
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