Novel method for synthesis of unsymmetrical bis(indolyl)alkanes catalyzed by ceric ammonium nitrate (CAN) under ultrasonic irradiation

Article abstract of DOI:10.1016/j.tet.2005.08.040

The reaction of indole with (1H-indol-3-yl)(alkyl) methanol was catalyzed efficiently by ceric ammonium nitrate under ultrasonic irradiation to afford the unsymmetrical bis(indolyl)alkane in good to excellent yields.

Full text of DOI:10.1016/j.tet.2005.08.040

Tetrahedron 61 (2005) 10235–10241
Novel method for synthesis of unsymmetrical bis(indolyl)alkanes
catalyzed by ceric ammonium nitrate (CAN)
under ultrasonic irradiation
Xiao-Fei Zeng, Shun-Jun Ji and Shun-Yi Wang
*
Key Lab. of Organic Synthesis of Jiangsu Province, College of Chemistry and Chemical Engineering of Suzhou University,
Suzhou, 215006 China
Received 9 May 2005; revised 8 August 2005; accepted 11 August 2005
Abstract—The reaction of indole with (1H-indol-3-yl)(alkyl) methanol was catalyzed efficiently by ceric ammonium nitrate under
ultrasonic irradiation to afford the unsymmetrical bis(indolyl)alkane in good to excellent yields.
q 2005 Elsevier Ltd. All rights reserved.
1
. Introduction
In this report, as a continuous research of our previous
1
1
work, we wish to introduce a simple method for synthesis
of unsymmetrical BIAs. Using this method, various BIAs
can be obtained by changing different substrates (Scheme 1).
Indole derivatives are known to possess various biological
properties including antibacterial, cytotoxic, antioxidative
and insecticidal activities, many indole derivatives are used
1
as antibiotics in pharmaceuticals. Among them, bisindolyl-
2
alkanes (BIAs) are important class of bioactive metabolite.
With the continuing isolation of structurally more versatile
3
BIAs, the demand for efficient synthesis of BIAs become
4
an increasing interest in organic synthesis. In previous
reports concering synthesis of BIAs, most of them involve
the electrophilic substitution of indoles with various
5
aldehydes or ketones in the presence of either protic or
6
Lewis acids. Although the synthesis of symmetrical BIAs
has been studied extensively throughout the last century, the
synthesis of unsymmetrical BIAs is still highly sought-after
Scheme 1.
7
in synthetic community. To the best of our knowledge there
were only two general synthetic approaches for the
synthesis of unsymmetrical BIAs reported by Yannick
In recent years, ceric ammonium nitrate (CAN) has received
considerable attention as an inexpensive and easily
available catalyst for various organic reactions such as
oxidation, oxidative addition, nitration, photo-oxidation,
9
,10
8
and Chakrabarty. Yannick Vallee
9,10
Vallee
reported the synthesis of unsymmetrical BIAs, but the
firstly
8
operation was complicated. Chakrabarty reported that
12
deprotection, graft polymerization etc. CAN as a catalyst
to catalyze the reaction of indoles with carbonyl compounds
to afford the symmetrical BIAs has been reported by
through the Michael reactions of 3-(2-nitrovinyl)indole
with indoles, unsymmetrical BIAs also could be obtained,
however, the method was limited to 2,2-bis(3-indolyl)-
nitroethane derivatives. Furthermore, they were all suffered
from long reaction time, low yields and complex handling.
13
Biswanath Das and co-workers. However, the reaction
must be performed using the toxic CH CN as solvent under
3
the protection of N atmosphere and was only limited to the
2
synthesis of symmetrical BIAs.
Keywords: Indoles; CAN; Ultrasound irradiation; Unsymmetrical bis(indo-
lyl)methanes.
Ultrasonic irradiation was demonstrated to be an efficient
synthetic technique for activating various organic reactions
*
Corresponding author. Tel.: C86 512 65880086; fax: C86 512
5880089; e-mail: shunjun@suda.edu.cn
6
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.08.040

1
0236
X.-F. Zeng et al. / Tetrahedron 61 (2005) 10235–10241
Table 2. Lewis acid mediated reaction of 5-methyl-indole with (1H-indol-
proceeding via single electron transfer (SET) mechanism or
a
1
4
3
-yl)(phenyl)methanol 1a
radical route. Many organic transformations can be
accelerated by ultrasonic irradiation with fast reaction
rate, short reaction time, high yields and sometimes good
b
Entry
Lewis acid
CAN
Time (h)
Yield (%)
1
5
1
2
3
4
2.5
4.5
6.5
2.5
92
89
40
71
selectivity.
Ce(NO
Ce (C
Bi(NO
3
)
3
2
2
O
4
)
3
In this report, we described an ultrasound-accelerated
3 3
)
1
6
reaction of indoles with (1H-indol-3-yl) (alkyl)methanol
using a catalytic amount of CAN, which provided an
efficient route to the synthesis of unsymmetrical BIAs
Scheme 1).
a
All reactions were carried out using 10 mol% catalyst under sonic
irradiation.
Isolated yields.
1
b
(
2
. Results and discussion
The reactions were first carried out using 1:1 molar ratio of
1H-indol-3-yl)(phenyl)methanol 1a and 2b along with a
(
catalytic amount of CAN in different solvents under
ultrasonic irradiation. The results were summarized in
Table 1. It was observed that the reaction proceeded
efficiently in the presence of CAN (10 mol%) and
anhydrous alcohols (MeOH or EtOH, 2 mL) at room
temperature, giving the unsymmetrical BIAs 3b in excellent
yields (92–96%) (Table 1, entries 1–2), (Scheme 2).
Considering the lower toxicity of EtOH, thus we carried
out this reaction in anhydrous EtOH. In addition, it has also
been found that the same reaction did not progress well in
n-PrOH and aqueous EtOH media under identical con-
ditions, affording the product in 75 and 77% yields,
respectively (Table 1, entries 3–4).
Scheme 3.
entry 4), but the yield was relatively low (71%). Therefore,
CAN was found to be superior in terms of conversion and
reaction time (Scheme 3).
Prompted by this success, we extended the reaction of
(1H-indol-3-yl)(alkyl)methanol 1a with a wide range of
other substituted indole compounds under similar con-
ditions at room temperature, furnishing the unsymmetrical
BIAs in good to excellent yields (Table 3). Our findings
reflected the wide applicability and usefulness of this
method. In all cases, the reactions proceeded efficiently to
give the corresponding unsymmetrical BIAs in moderate to
excellent yields (75–96%). Even aliphatic substrates such
as 1-(1H-indol-3-yl)decan-1-ol 1b, (1H-indol-3-yl)metha-
nol 1d, 1-(1H-indol-3-yl)pentan-1-ol 1e, 1-(1H-indol-3-
yl)heptan-1-ol 1f and 1-(1H-indol-3-yl)nonan-1-ol 1gcould
also react with substituted indoles to afford the desired
products 3g, 3m–3s in good yields (80–96%, Table 3,
entries 7 and 14–20). The reactions were clean and the
products were obtained in moderate to excellent yields
without the formation of any by-products. However, the
reaction of 5-nitroindole 2i and phenyl(1-tosyl-1H-indol-3-
yl)methanol 1c did not occur under above conditions
Table 1. The solvent effect of reaction of 5-methyl-indole with (1H-indol-
3-yl)(phenyl)methanol 1a
a
b
Entry
Solvent
Time (h)
Yield (%)
1
2
3
4
MeOH
EtOH
n-PrOH
90% EtOH
3.5
2.5
4.5
5
96
92
75
77
a
All reactions were carried out using a catalytic amount of CAN (10 mol%)
at room temperature.
Isolated yields.
b
(
Table 3, entry 13), (Scheme 4).
3. Conclusions
Scheme 2.
In summary, we have developed a simple, novel and
efficient synthetic protocol for the synthesis of unsym-
metrical BIAs using a catalytic amount of CAN under
ultrasonic irradiation at room temperature. It is superior to
the existing synthetic routes to the synthesis of unsym-
metrical BIAs for a number of reasons, viz. (i) it is fast and
efficient, employs a cheap, non-toxic CAN as the catalyst
and involves a simple work-up; (ii) using this method, we
can obtain various BIAs simply by changing different
substrates.
The reaction of (1H-indol-3-yl)(phenyl)methanol 1a with
2
b was then carried out using different Lewis acids under
ultrasonic irradiation at room temperature. As shown in
Table 2, it was found that the other two ceric salts Ce(NO3)3
and Ce (C O ) (Table 2, entries 2–3) did not improve the
2
2 4 3
reaction under identical reaction conditions in comparison
to CAN. Furthermore, it was found that the reaction could
also be carried out using Lewis acid Bi(NO ) (Table 2,
3
3

X.-F. Zeng et al. / Tetrahedron 61 (2005) 10235–10241
10237
Yield
a
Table 3. Reaction of indoles with (1H-indol-3-yl)(phenyl)methanol 1a–d
Entry
1
2
Product (3)
Time
h)
b
(
(%)
1
1a
1a
2a
2b
3a
3b
2
93
92
2
2.5
3
1a
2c
3c
2.5
89
4
1a
1a
2d
3d
2.5
95
5
2e
3e
2.5
96
6
7
8
1a
1b
1c
2f
3f
2
89
90
75
2b
2d
3g
3h
2.5
3.5
9
1c
2a
3f
2.5
92

10238
X.-F. Zeng et al. / Tetrahedron 61 (2005) 10235–10241
Table 3 (continued)
Entry
1
2
Product (3)
Time
h)
Yield
b
(%)
(
10
11
12
13
1c
1c
1c
1c
2b
2g
2h
2i
3i
3.5
2.5
3
78
77
85
3j
3k
3l
c
nr
5
1
4
5
1d
1d
2h
2c
3m
3n
2.5
2.5
86
80
1
16
1e
2b
3o
2.5
96
1
1
1
7
8
9
1e
1f
2d
2b
2b
3p
3q
3r
2.5
2.5
2.5
84
82
80
1g
20
1g
2d
3s
2.5
86
a
b
c
All reactions were carried out in anhydrous ethanol at room temperature under ultrasound irridiation, employing 10 mol% CAN.
1
Isolated yields. All products are fully characterized by IR, HNMR, HRMS and mp etc.
No reaction.

X.-F. Zeng et al. / Tetrahedron 61 (2005) 10235–10241
10239
Scheme 4.
4
. Experimental
4.2.4. 3-((7-Methyl-1H-indol-3-yl)(phenyl)methyl)-1H-
indole, 3d. Brown powder; mp 145–147 8C; IR (KBr): n
K1
1
3
406, 3385, 2925, 2848 cm
;
H NMR (400 MHz,
CDCl ): d 2.36 (s, 3H), 5.87 (s, 1H), 6.61 (s, 1H), 6.66 (s,
4
.1. General
3
1
7
3
H), 7.00 (s, 1H), 7.01 (s, 1H), 7.06–7.35 (m, 6H), 7.37–
.40 (m, 4H), 7.82 (s, 1H), 7.90 (s, 1H), HRMS [found: m/z,
Melting points were recorded on an Electrothermal digital
melting point apparatus and uncorrected. H NMR
1
C
36.1613 (M ); calcd for C H N : M, 336.1626].
(
MHz spectrometer in CDCl . IR Spectra were obtained on a
400 MHz) spectra were recorded on a Varian Mercury
24 20 2
3
4.2.5. 3-((6-Methyl-1H-indol-3-yl)(phenyl)methyl)-1H-
indole, 3e. Pink powder; mp 91–93 8C; IR (KBr): n 3409,
Nicolet FT-IR500 spectrophotometer using KBr pellets.
High resolution mass spectra were obtained using GCT-
TOF instrument. Ultrasonic irradiation was performed in a
KQ-250E ultrasonic cleaner with a frequency of 40 KHz
and a normal power of 250 W. The reaction flask was
located in the water bath of the ultrasonic cleaner.
K1
918, 2956 cm ; H NMR (400 MHz, CDCl ): d 2.44 (s,
1
2
3
6
3
H), 5.87 (s, 1H), 6.58 (s, 1H), 6.66 (s, 1H), 6.61 (s, 1H),
.99 (s, 1H), 7.00–7.40 (m, 10H), 7.77 (s, 1H), 7.89 (s, 1H),
C
HRMS [found: m/z, 336.1609 (M ); calcd for C H N :
2
24 20
M, 336.1626].
4
.2. Typical experimental procedure
4.2.6. 3-((1H-Indol-3-yl)(phenyl)methyl)-1-tosyl-1H-
indole, 3f. Yellow solid; mp 196–198 8C; IR (KBr): n
A mixture of (1H-indol-3-yl)(phenyl)methanol 1a (0.112 g,
.5 mmol), 5-methylindole 2b (0.066 g, 0.5 mmol), CAN
0.028 g, 0.05 mmol) and anhydrous EtOH (2 mL) was
K1
430 cm ; H NMR (400 MHz, CDCl ): d 2.38 (s, 3H),
1
3
5
7
8
4
3
0
(
.73 (s, 1H), 6.57 (d, JZ7.2 Hz, 1H), 7.00–7.12 (m, 3H),
.20–7.30 (m, 16H), 7.39 (d, JZ7.6 Hz, 1H), 7.62 (d, JZ
.0 Hz, 1H), 7.98 (d, JZ7.6 Hz, 2H), HRMS [found: m/z,
irradiated under ultrasound in an open vessel at room
temperature until the disappearance of the starting material
C
76.1547 (M ); calcd for C H N O S: M, 476.1558].
3
0 24 2 2
(2.5 h, checked by TLC). After standing for 2 h, the reaction
mixture was poured into water and the precipitated solid
4.2.7. 3-(1-(2-Methyl-1H-indol-3-yl)decyl)-1H-indole, 3g.
Brown solid; mp: 105–107 8C; IR (KBr): n 3418, 2925,
was collected, washed with warm water (about 80 8C, 2!
1
0 mL). The crude mixture was purified by flash column
chromatography (EtOAc/petroleum ether 1:4) to afford the
pure product.
K1
1
2
853 cm ; H NMR (400 MHz, CDCl ): d 0.88 (t, JZ
3
4.6 Hz, 3H), 1.24–1.42 (m, 14H), 2.18–2.23 (m, 2H), 2.43
(s, 3H), 4.55 (t, JZ6.8 Hz, 1H), 6.90 (s, 2H), 6.95–7.06 (m,
3
8
1
3
H), 7.14 (t, JZ7.2 Hz, 1H), 7.19 (s, 1H), 7.28 (d, JZ
.0 Hz, 1H), 7.47 (d, JZ7.6 Hz, 1H), 7.60 (d, JZ8.0 Hz,
H), 7.71 (s, 1H), 7.76 (s, 1H), HRMS [found: m/z,
0
0
Brown powder; mp 142–144 8C; IR (KBr): n 3395,
4
.2.1. 1H, 1 H-3, 3 -Phenylmethanediyl-bis-indole, 3a.
K1
863 cm ; H NMR (400 MHz, CDCl ): d 5.90 (s, 1H),
1
2
6
2
C
3
86.2731 (M ); calcd for C H N : M, 386.2722].
26 32 2
.66 (s, 2H), 7.02 (t, JZ5.6 Hz, 2H), 7.18 (t, JZ7.2 Hz,
H), 7.23 (d, JZ7.2 Hz, 1H), 7.29 (t, JZ8.2 Hz, 3H), 7.36
(d, JZ8.0 Hz, 3H), 7.40 (d, JZ8.4 Hz, 2H), 7.89 (s, 2H),
HRMS [found: m/z, 322.1445 (M ); calcd for C H N :
4.2.8. 3-((7-Methyl-1H-indol-3-yl)(phenyl)methyl)-1-
tosyl-1H-indole, 3h. Yellow solid; mp 103–105 8C; IR
C
K1
KBr): n 3418, 2960, 2919 cm ; H NMR (400 MHz,
1
2
3 18 2
(
CDCl ): d 2.38 (s, 3H), 2.51 (s, 3H), 5.72 (s, 1H), 6.57 (s,
M, 322.1470].
3
1
H), 6.93–7.12 (m, 5H), 7.19–7.30 (m, 8H), 7.62 (d, JZ
.6 Hz, 2H), 7.92 (s, 1H), 7.98 (d, JZ7.2 Hz, 1H), HRMS
4.2.2. 3-((5-Methyl-1H-indol-3-yl)(phenyl)methyl)-1H-
indole, 3b. Brown solid; mp 87–89 8C; IR (KBr): n 3409,
7
C
found: m/z, 490.1698 (M ); calcd for C H N O S: M,
[
490.1715].
31 26 2 2
K1
960, 2842 cm ; H NMR (400 MHz, CDCl ): d 2.49 (s,
1
2
3
7
3
H), 5.89 (s, 1H), 6.66 (s, 2H), 6.92–7.03 (m, 3H), 7.16–
.30 (m, 5H), 7.35–7.41 (m, 4H), 7.83 (s, 1H), 7.90 (s, 1H),
4.2.9. 3-((5-Methyl-1H-indol-3-yl)(phenyl)methyl)-1-
tosyl-1H-indole, 3i. Pink powder; mp 245–247 8C; IR
C
HRMS [found: m/z, 336.1614 (M ); calcd for C H N :
2
4 20 2
K1 1
KBr): n 3430, 2919, 2858 cm ; H NMR (400 MHz,
M, 336.1626].
(
CDCl ): d 2.37 (s, 6H), 5.71 (s, 1H), 6.52 (s, 1H), 7.04 (s,
3
4.2.3. 3-((3-Methyl-1H-indol-2-yl)(phenyl)methyl)-1H-
indole, 3c. Black powder; mp 101–103 8C; IR (KBr): n
2H), 7.11 (d, JZ6.8 Hz, 2H), 7.20 (d, JZ8.4 Hz, 2H), 7.24–
7.29 (m, 8H), 7.64 (d, JZ8.0 Hz, 2H), 7.98 (d, JZ8.4 Hz,
1H), HRMS [found: m/z, 490.1673 (M ); calcd for
K1
407, 2960, 2853 cm ; H NMR (400 MHz, CDCl ): d
1
C
3
2
1
3
.27 (s, 3H), 5.95 (s, 1H), 6.70 (s, 1H), 7.00 (t, JZ5.6 Hz,
H), 7.11 (t, JZ2.8 Hz, 2H), 7.17–7.25 (m, 3H), 7.27–7.38
C H N O S: M, 490.1715].
31 26 2 2
(
7
(
m, 6H), 7.36 (d, JZ8.0 Hz, 2H), 7.58 (d, JZ4.8 Hz, 1H),
.67 (s, 1H), 8.05 (s, 1H), HRMS [found: m/z, 336.1610
4.2.10. 5-(Benzyloxy)-3-(phenyl(1-tosyl-1H-indol-3-yl)
methyl)-1H-indole, 3j. Yellow solid; mp 93–95 8C; IR
(KBr): n 1647, 1617 cm ; H NMR (400 MHz, CDCl ): d
3
C
M ); calcd for C H N : M, 336.1626].
K1 1
2
4
20
2

10240
X.-F. Zeng et al. / Tetrahedron 61 (2005) 10235–10241
K1
1
2
1
.19 (s, 3H), 4.90 (s, 2H), 5.67 (s, 1H), 6.54 (d, JZ1.6 Hz,
H), 6.84 (d, JZ2.4 Hz, 1H), 6.96–6.99 (m, 1H), 7.06–7.15
2951 cm ; H NMR (400 MHz, CDCl ): d 0.87 (t, JZ
3
8.4 Hz, 3H), 1.25–1.39 (m, 12H), 2.19–2.22 (m, 2H), 2.46
(s, 3H), 4.46 (t, JZ7.2 Hz, 1H), 6.95–7.05 (m, 5H), 7.14 (t,
JZ7.6 Hz, 1H), 7.32 (d, JZ8.0 Hz, 1H), 7.45–7.47 (m, 1H),
(
m, 4H), 7.23–7.41 (m, 8H), 7.62 (d, JZ8.0 Hz, 2H), 7.90
(
s, 1H), 7.97 (d, JZ8.8 Hz, 1H), HRMS [found: m/z,
C
82.1912 (M ); calcd for C H N O S: M, 582.1977].
5
7.59 (d, JZ7.6 Hz, 1H), 7.82 (s, 1H), 7.88 (s, 1H), HRMS
3
7 30 2 3
C
found: m/z, 372.2581 (M ); calcd for C H N : M,
[
372.2565].
26 32 2
4.2.11. 3-((2-Methyl-1H-indol-3-yl)(phenyl)methyl)-1-
tosyl-1H-indole, 3k. Pink powder; mp 235–237 8C; IR
K1
KBr): n 3433, 2929, 2860 cm ; H NMR (400 MHz,
1
(
CDCl ): d 2.33 (s, 3H), 2.45 (s, 3H), 5.73 (s, 1H), 6.55 (s,
4
.2.18. 3-(1-(7-Methyl-1H-indol-3-yl)nonyl)-1H-indole,
3s. Red powder; mp 95–97 8C; IR (KBr): n 3397, 3389,
3
K1
1
1
8
7
H), 7.01 (s, 2H), 7.11 (d, JZ7.2 Hz, 2H), 7.20 (d, JZ
.4 Hz, 2H), 7.22–7.27 (m, 8H), 7.64 (d, JZ8.4 Hz, 2H),
2
8
7
959 cm ; H NMR (400 MHz, CDCl ): d 0.85 (t, JZ
3
.0 Hz, 3H), 1.23–1.39 (m, 14H), 2.46 (s, 3H), 4.46 (t, JZ
.2 Hz, 1H), 6.95–7.04 (m, 5H), 7.14 (t, JZ8.0 Hz, 2H),
.95 (d, JZ8.0 Hz, 1H), HRMS [found: m/z, 490.1644
C
(
M ); calcd for C H N O S: M, 490.1715].
31 26 2 2
7.32 (d, JZ8.0 Hz, 1H), 7.60 (d, JZ8.0 Hz, 1H), 7.84 (s,
C
H), 7.91 (s, 1H), HRMS [found: m/z, 372.2581 (M );
1
calcd for C H N : M, 372.2565].
4
3
3
2
7
7
.2.12. 3-((2-Methyl-1H-indol-3-yl)methyl)-1H-indole,
m. Red powder; mp 131–134 8C; IR (KBr): n 3396,
2
6 32 2
K1
388, 2960 cm ; H NMR (400 MHz, CDCl ): d 4.25 (s,
1
3
H), 2.40 (s, 3H), 7.04 (s, 1H), 7.08–7.12 (m, 3H), 7.15–
.18 (m, 1H), 7.21–7.27 (m, 1H), 7.40 (d, JZ8.0 Hz, 1H),
.50–7.56 (m, 2H), 7.68 (s, 1H), 8.06 (s, 1H), HRMS
Acknowledgements
The work was partially supported by a research grant from
the Innovation Project for Graduate student of Jiangsu
Province, the Key Laboratory of Organic Synthesis of
Jiangsu Province (No. JSK008) and the National Science
Foundation of Jiangsu Province (No. BK2004038). This
work was also supported by the National Natural Science
Foundation of China (No. 20172039 and 20472062).
C
[
found: m/z, 260.1311 (M ); calcd for C H N O S: M,
31 26 2 2
2
60.1313].
4
3
2
2
1
.2.13. 3-((3-Methyl-1H-indol-3-yl)methyl)-1H-indole,
n. Red powder; mp 136–138 8C; IR (KBr): n 3399, 3389,
K1 1
958 cm ; H NMR (400 MHz, CDCl ): d 4.28 (s, 2H),
3
.34 (s, 3H), 7.07 (s, 1H), 7.09–7.15 (m, 3H), 7.18–7.19 (m,
H), 7.21–7.25 (m, 1H), 7.41 (d, JZ8.4 Hz, 1H), 7.50–7.56
(
2
m, 2H), 7.80 (s, 1H), 8.02 (s, 1H), HRMS [found: m/z,
60.1304 (M ); calcd for C H N O S: M, 260.1313].
31 26 2 2
C
References and notes
4
3
2
8
3
7
1
1
3
.2.14. 3-(1-(1H-Indol-3-yl)pentyl)-5-methyl-1H-indole,
o. Red powder; mp 67–69 8C; IR (KBr): n 3412, 3408,
1. (a) Sundberg, R. J. The Chemistry of Indoles; Academic: New
York, 1970. (b) Lounasmaa, M.; Tolvanen, A. Nat. Prod. Rep.
2000, 17, 175–183. (c) Hibino, S.; Chozi, T. Nat. Prod. Rep.
2001, 18, 66–71.
K1
1
958 cm ; H NMR (400 MHz, CDCl ): d 0.97 (t, JZ
3
.4 Hz, 3H), 1.29–1.33 (m, 4H), 1.39–1.41 (m, 2H), 2.47 (s,
H), 4.44 (t, JZ7.2 Hz, 1H), 6.92–6.98 (m, 3H), 7.03 (t, JZ
.6 Hz, 1H), 7.14 (t, JZ7.4 Hz, 1H), 7.21 (d, JZ8.0 Hz,
H), 7.32 (d, JZ8.0 Hz, 1H), 7.38 (s, 1H), 7.54–7.62 (m,
H), 7.80 (s, 1H), 7.89 (s, 1H), HRMS [found: m/z,
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16.1946 (M ); calcd for C H N : M, 316.1939].
22 24 2
4
3
2
8
3
7
1
1
3
.2.15. 3-(1-(1H-Indol-3-yl)pentyl)-7-methyl-1H-indole,
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.2 Hz, 1H), 7.16 (d, JZ7.6 Hz, 1H), 7.20 (d, JZ8.0 Hz,
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1
3
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22 24 2
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3
2
8
7
7
7
3
.2.16. 3-(1-(5-Methyl-1H-indol-3-yl)heptyl)-1H-indole,
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955 cm ; H NMR (400 MHz, CDCl ): d 1.01 (t, JZ
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.0 Hz, 3H), 1.45–1.60 (m, 10H), 2.43 (s, 3H), 4.46 (t, JZ
.2 Hz, 1H), 6.95–7.05 (m, 5H), 7.14 (t, JZ7.6 Hz, 1H),
.32 (d, JZ8.0 Hz, 1H), 7.45–7.47 (m, 1H), 7.59 (d, JZ
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