Novel synthesis of 6,12-dihydroindolo[3,2-b]carbazoles catalysed by p-toluenesulfonic acid

Article abstract of DOI:10.3184/030823409X424858

An efficient and straightforward procedure for the synthesis of 6,12-dihydroindolo[3,2-b]carbazoles has been achieved through the one-pot reaction of indole with aromatic aldehydes in the presence of p-toluenesulfonic acid (pTSA) as the catalyst.

Full text of DOI:10.3184/030823409X424858

JOURNAL OF CHEMICAL RESEARCH 2009
MARCH, 191-194
RESEARCH
PAPER
191
Novel synthesis of 6,12-dihydroindolo[3,2-b]carbazoles
p-toluenesulfonic acid
catalysed by
Can Jin, 80 Zhang, Chuanming Yu and Weike SU*
Key Laboratory of Pharmaceutical
Engineering of Ministry of Education, College of Pharmaceutical
Sciences, Zhejiang University
of Technology, Hangzhou 310014, P.R. China
An efficient and straightforward
achieved through the one-pot reaction of indole with aromatic aldehydes in the presence of p-toluenesulfonic
procedure for the synthesis of 6,12-dihydroindolo[3,2-blcarbazoles
has been
acid
(pTSA) as the catalyst.
Keywords:
6,12-dihydroindolo[3,2-b]carbazole,
one-step reaction,p-toluenesulfonic
acid, aromatic aldehyde, indole
Several methods for the synthesis of 6,12-dihydroindolo
Yb(OTfh
CU(OTf)2, CaCI2, BF3,TfDNH3Ph,
NaHS04,
[3,2-b]carbazoles
cyclodimerisation
by hydrochloric
benzaldehyde
have
of
been
reported
including
catalysed
of indole and
conditions,2 (3)
(1)
CH3COOH, HCl and pTSA. In the course of the study it
was found that only HCl and pTSA gave the desired product
3-(1-phenylvinyl)indole
acid,! (2) dimerisation
under strongly acidic
in 60% and 86% yield respectively.
Most Lewis acids or
CH3COOH only afforded the 3,3'-bis(indolyl)methanes
2a
reaction of 2-hydroxybenzylideneaniline
with indole,3 (4)
of l-(l-benzotriazol-
(Scheme 1, Table 1) in moderate to good yield. Compound
2a could be easily converted to 3a when treated with pTSA
Lewis acid catalysed
l-yl-alkyl)indoles,4,5
dimerisation
(5) reaction
of 4,6-dimethoxyindole
chloride,6 (6) acid-
(Scheme
1). The solvent effect was also examined
by
with aryl aldehydes
catalysed dimerisation
and phosphoryl
of 2-(3'-hydroxy-3'-methyl-E-but-1'-
the model reaction of benzaldehyde
(2 mmol) and indole
(1 mmol) in the presence of pTSA (0.02 mmol) under reflux
(Table 2). Although the reaction proceeded in other organic
enyl)indole,7 (7) reaction of 2,3'-bis(indolyl)methanes
aromatic aldehydes under acidic conditions,S and (8) dimeric
condensation of 2-(I-hydroxyethyl)-I-methylindole.
with
solvents
such as alcohol and chloroform,
the yield of
was lower
9
the desired 6,12-dihydroindolo[3,2-b]carbazole
However,
more disadvantages
materials, prolonged
solvents, requirement for excess reagents or catalyst, special
apparatus, harsh reaction conditions and poor yield of
the desired product and selectivity. Thus, there is need
for the development of an alternative route to construct
dihydroindolo [3,2-b]carbazole derivatives.
We now report an efficient and convenient method for the
synthesis of 6,12-dihydroindolo[3,2-b]carbazoles involving
one-step condensation of indole and aromatic aldehydes in the
presence of p-toluenesulfonic acid (PTSA) as the catalyst.
In an initial study to examine the catalytic activity of
different catalysts, we examined the model reaction of
these methodologies
suffered
from one or
than in CH3CN. Hence pTSA was chosen as the optimal
such as inaccessibility
of the starting
reaction time, use of toxic organic
Table 1 Reaction of benzaldehyde (1 mmo!) and indole (1 mmo!)
in the presence of various catalysts (0.02mmo!) in acetonitrile
a
Entry
Catalyst
Time/min
Yield/Yo" of 3a
a
1
2
3
4
5
6
7
8
9
pTSA
HCI
20
20
60
60
60
60
60
60
60
60
60
86
60
0
0
0
0
0
0
0
CH
3
COOH
AICI
3
ZnCI2
Yb(OTfh
Cu(OTfh
CaCI2
SF
3
10
11
TfONHPh
NaHS04
benzaldehyde with indole (Scheme 1, Table 1) in acetonitrile
(5 mL) for 20 minutes under reflux conditions in the presence
of different catalyst (0.02 equiv) including AICI3, ZnClb
0
0
"Isolated yield based on aldehydes.
Ph
Lewis acid or AcOH
MeCN, reflux
~
~
N
H
N
H
V l l
H
2a
1a
j
pTSA (2mol%)
MeCN,
reflux,
20min
_
Ph
H
pTSA (2mol%)
MeCN, reflux,20min
q¢rb
H
Ph
3a
Scheme 1
* Correspondent. E-mail: suweike@zjut.edu.cn

192 JOURNAL OF CHEMICAL RESEARCH 2009
Table 2 Reaction of benzaldehyde (1 mmo!) and indole
(1 mmo!) in the presence of pTSA (0.02 mmo!) in different
refluxing solvents
Table 3 Synthesis of 6,12-dihydroindolo[3,2-blcarbazoles
from indole (1 mmo!) and aromatic aldehydes (1 mmol)
catalysed by pTSA"
Entry
Solvent
Time/min
Entry
R
Time/min Prduct Yield/%b
Yield/%"
1
2
3
4
5
6
CH
CH
CH
CH
3
3
3
3
CN
20
20
60
60
60
60
86
80
77
60
50
35
1
2
C
6
H
5
20
10
15
15
15
15
15
50
50
90
90
60
86
90
90
92
94
92
88
65
75
60
72
75
3a
3b
3c
3d
3e
3f
3g
3h
3i
NOz
CHzOH
0H
2-HO-C
4-HO-C
4-CH O-C
2,4-(CH
4-HO-3-CH
3,4-CH -C
6
H
4
3
6
H4
4
3
6
H
4
3
O}z-C
6
H
3
5
CICHzCHzCI
CHCI
3
6
3
O-C
6
H
3
3
6
H
3
7
"Isolated yield based on aldehydes.
8
3-CI-C
6
H
4
9
4-CI-C
6
H
4
catalyst and CH3CN was used as the best solvent for the
purpose of this reaction.
3-Br-C
6
H
4
10
11
12
3j
3k
31
4-Br-C
6
H
4
3- OzN-C
6
H
4
In our reaction strategy, indole and aromatic aldehydes with
a catalytic amount of pTSA in refluxing acetonitrile for 10-90
minutes afforded dihydroindolo[3,2-b]carbazoles 3 in good
yields (Scheme 2). Thus in a simple experimental procedure
when indole and the aromatic aldehyde la were heated in
the presence of a catalytic amount of pTSA (2 mol%), in
refluxing acetonitrile for 20 minutes dihydroindolo[3,2-b]
carbazole 3a was obtained in 86% yield (Table 3).
The product was isolated simply by filtration and purified by
washing with solvent. The structure of the compound was
determined from spectroscopic data. Our observations are
recorded in Table 3. No dehydrogenated product was detected
by IH NMR spectroscopy. These dihydro compounds seemed
to be stable in air at room temperature for months without
dehydrogenation.
13
15
3m
92
rb-
"Allreactions were performed on a 1 mmol scale using 2 mol%
of pTSA
blsolated yield based on aldehydes.
even for 5 h only gave the 3, 3'-bis(indolyl)methane derivates
2, which were rather stable and did not form the dihydroindolo
[3, 2-b]carbazoles. It should be pointed out that steric effects
were not observed, hindered benzaldehydes such as 2, 4-
dimethoxybenzaldehyde and 2-hydroxybenzaldehyde reacted
with indole faster and in higher yields than benzaldehyde
under the present reaction condition.
It was found that all substituted benzaldehydes with an
electron-donating group reacted with indole completely and
afforded the corresponding products 3 in high yields. In
contrast, aldehydes with an electron-withdrawing group were
less active and the reaction proceeded relatively slowly and
the yield was lower. Thus the common aromatic aldehydes
were acceptable substrates in the protocol. Aliphatic aldehydes
and some aromatic aldehydes having strong electron-
withdrawing substituents such as 4-fluorobenzaldehyde, and
picolinaldehyde when treated under these reaction conditions
Although the yield of products in the reaction were not very
high in some cases, there was a selective formation of the
dihydroindolo[3,2-b]carbazole. In many reported methods,
both the indolo[3,2-b]carbazoles and indolo[2,3-b]carbazoles
were formed which were difficult to separate due to their
insolubility. In the present case, there was no formation of the
dihydroindolo[2,3-b]carbazole isomer in refluxing acetonitrile.
Interestingly (Scheme 3), the reaction at room
temperature gave dihydroindolo[3,2-b ]carbazoles 3a and
dihydroindolo[2,3-b ]carbazoles 4a in fair yields (3a/4a = 4: 3),
_
R
H
pTSA(2mol%)
RCHO+~ ~l
•
MeCN,reflux,20min
q¢b
H
R
1a-m
3a-m
Scheme 2
~o
~
+ ~N~
~l
_P_TS_A_(2_mC_Qo¢t_bIr;':_)\ Ph \ MIf
~
+ ~#
I Ph I ~ Ii
MeCN,
N
N
H
N
H
r.t.,20min
H
Ph
-
Ph
H
(4:3)
3a
4a
J
pTSA(10mol%)
MeCNr,eflux,2h
pTSA(2mol%)
3a + 4a (3:1)
MeCN6, 0°C,20min
,~ pTSA(20mol%)
'1MeCN,reflux,5h
3a + 4a (100:0)
pTSA(2mol%)
MeCNr,eflux2,0min
Scheme 3

JOURNAL OF CHEMICAL RESEARCH 2009
193
6.12-bis(phenyl)-6.12-dihydroindolo[3.2-b}carbazole (3a): White
as observed in the 1H NMR and MS. The ratio of 3a and 4a
solid. M.p. 350-352°C (Lit.2 M.p. 353-355°C). IR (em"): 3393
(NH). 'H NMR (500 MHz, DMSO-~) 8: 5.70 (s, 2H), 6.79 (d, 2H,
J= 7.0 Hz), 6.93-6.95 (m, 2H), 7.08 (d, 2H, J= 7.5 Hz), 7.20 (d, 2H,
J= 7.0 Hz), 7.24 (d, 2H, J= 8.5 Hz), 7.29 (d, 4H, J= 8.5 Hz), 7.34
(d, 4H, J= 8.5 Hz),10.70 (s, 2H, NH). l3C NMR (100 MHz, DMSO-
d6) 8: 109.8, 111.0, 118.1, 118.4, 120.5, 125.6, 126.3, 128.2, 128.4,
136.6, 137.1, 144.1. MS(ESI): m/z = 410.5 (M+).
varied depending on the reaction temperature
it was 3: 1. The dihydroindolo[2,3-b]carbazoles
and at 60°C
4a could
partly be converted
to dihydroindolo[3,2-b
]carbazoles
3a
in refluxing acetonitrile in the presence of pTSA as catalyst
until the ratio of 3a/4a achieved 3: 1. The reaction at O°C
formed an insoluble and unknown complex. In the light of our
experimental results, a plausible reaction mechanism is shown
in Scheme 4.
6.12 -bis(2-hydroxylphenyl)-6.12-dihydroindolo[3.
2-b} carbazole
(3b): White solid. M.p. 349-351 °C (Lit.3 M.p. >300°C). IR (em"):
3542 (ArOH), 3395 (NH). 'H NMR (400 MHz, DMSO-d6) 8: 6.10
(s, 2H, CH), 6.51-6.59 (m, 4 H), 6.79 (t, 2H, J= 7.6 Hz), 6.91-6.99
In summary, we have reported a very simple, mild, and highly
efficient method for the synthesis of dihydroindolo[3,2-b]
(m, 6H), 7.24 (t, 4H, J
= 8.4 Hz), 9.89 (s, 2H, OH), 10A3 (s, 2H,
NH). l3C NMR (l00 MHz, DMSO-~) 8: 110.8,111.0,115.3,117.9,
118.3, 119.1, 120.2, 125.7, 126.9, 129.4, 130.2, 136.8, 136.9, 155.4.
MS(ESI): m/z = 442.4 (M+).
carbazoles
from indole and aromatic
aldehydes
in the
presence of pTSA as catalyst. This very simple, mild, and
effective method is a valuable addition to the chemistry of
dihydroindolo [3,2-b]carbazoles.
6.12 -bis( 4-hydroxylphenyl)-6.12-dihydroindolo[3.
2-b} carbazole
(3c): Pink solid. M.p. 334-335°C. IR (em"): 3474 (ArOH), 3413
(NH). 'H NMR (400 MHz, DMSO-d6) 8: 5.53 (s, 2H, CH), 6.65 (d,
4H,J= 8.4 Hz), 6.78 (t, 2H, J= 7.6 Hz), 6.93 (t, 2H, J= 7.4 Hz), 7.08
(t, 6H, J= 8.4 Hz), 7.23 (d, 2H, J= 8.4 Hz), 9.18 (s, 2H, OH), 10.56
(s, 2H, NH). l3C NMR (100 MHz, DMSO-d6) 8: 110.0, 110.9, 115.0,
118.0, 118.5, 120.3, 125.8, 129.3, 134.4, 137.0, 155.8. HRMS(EI):
Calcd for C30H22N202442.1681 (M+). Found 442.1687.
Experimental
Melting points were measured on a Biichi B-540 apparatus and
are uncorrected. IR spectra were recorded on a Nicolet Avatar-370
instrument. 'H NMR and l3CNMR spectra were recorded on a Varian
400 MHz or Bruker Avance III (500 MHz) instrument in CDCI3 or
DMSO-d6 as the solvent, and chemical shifts were expressed in parts
per million (ppm) using TMS as an internal standard. Mass spectra
were measured with a Trace Fiunigan DSQ. High resolution mass
spectral (HRMS) analyses were measured on an Agilent 6210 TOF
LC/MS.
6. 12-bis( 4-methoxylphenyl)-6.12-dihydroindolo[3.2-b}
carbazole
(3d): Light yellow solid. M.p. 343-345°C. IR (em"): 3413 (NH),
1247 (ArOCH3). 'H NMR (400 MHz, DMSO-d6) 8: 3.70 (s, 6H,
OCH3), 5.61 (s, 2H, CH), 6.78 (t, 2H, J
J, 2.0, J2 6.8 Hz), 6.94 (td, 2H, J,
2H, J 7.6 HZ),7.22 (dd, 6H, J, 2.0, J2 =
=
7.6 Hz), 6.83 (dd, 4H,
1.2, J2 7.6 Hz), 7.07 (d,
6.8 Hz), 10.67 (s, 2H,
=
=
=
=
=
=
NH). l3C NMR (100 MHz, DMSO-d6) 8: 54.92,109.9,111.0,113.6,
114.6, 118.0, 118.4, 120.4, 125.7, 129.3, 136.1, 136.9, 137.0, 155.8.
HRMS(EI): Calcd for C32H26N202470.1994 (M+). Found 470.1999.
6. 12-bis(2. 4-dimethoxyphenyl)-6.12-dihydroindolo[3.2-b}
carbazole (3e): Pink solid. M.p. 326-328°C. IR (em"): 3386 (NH),
1206 (ArOCH3). 'H NMR (400 MHz, DMSO-d6) 8: 3.69 (s, 6H,
OCH3),4.08 (s, 6H, OCH3), 6.03 (s, 2H, CH), 6.27 (dd, 2H, J, = 2.4,
Typical procedure
p-To1uene sulfonic acid (0.02 mmo1) was added to a solution of
indole (1.0 mmo1) and the appropriate aldehyde (la, 1.0 mmo1) in
CH3CN (5 mL), and the reaction mixture was refluxed for 20 min.
The precipitate which formed was filtered off, washed with EtOH
and carefully dried to constant weight to yield 3a (0.176 g, 86%). The
filtrate was concentrated, then purified by column chromatography
and eluted with ethyl acetate-petroleum ether (1:4) to afford 2a
(0.008 g, 5%). The structure of the compound obtained was identified
from spectroscopic data.
J2
= 8.4 Hz,), 6.53(s, 2H), 6.72 (d, 2H, J = 2.4 Hz), 6.79 (t, 2H,
J= 7.6 Hz), 6.93 (t, 2H, J= 7.6 Hz), 7.05 (t, 2H, J= 7.6 Hz), 7.23 (d,
2H,J= 8.0 Hz), 10.36 (s, 2H, NH). l3C NMR (l00 MHz, DMSO-d6)
8: 55.0, 55.9, 98.2, 105.3, 110.5, 111.0, 118.1, 120.3, 124.2, 125.7,
129.8, 136.9, 137.1, 157.4, 158.8. HRMS(EI): Calcd for C34H30N204
530.2206 (M+). Found 530.2217.
3.3'-bis(indolyl)phenylmethane (2a): Red solid. M.p.125-126°C
(Lit.IOM.p.125-126°C).
CDC13) 8: 5.89 (s, lH, CH), 6.66 (d, 2H, J
8.0 Hz), 7.15-7.18 (m, 2H), 7.19-7.22 (m, lH), 7.25-7.29 (m,
IR (em"): 3408 (NH). 'H NMR (500 Mz,
6. 12-bis( 4-hydroxyl-3-methoxyphenyl)-6.12-dihydroindolo[3.
2-b}
=
2.5 Hz), 7.00 (t, 2H,
carbazole (3f): Light yellow solid. M.p. 368-370°C. IR (em"): 3506
(ArOH), 3357 (NH), 1227 (ArOCH3). 'H NMR (400 MHz, DMSO-
d6) 8: 3.72 (s, 6H, OCH3), 5.55 (s, 2H, CH), 6.58 (dd, 2H, J, = 2.0,
J
=
2H), 7.34-7.36 (m, 4H), 7.39 (d, 2H, J= 8.5 Hz), 7.90 (s, 2H, NH).
l3C NMR (l00 MHz, CDC13) 8: 40.1, 111.0, 119.1, 119.6, 119.8,
121.8, 123.6, 126.1, 127.0, 128.2, 128.7, 136.6, 144.0. MS(ESI):
m/z = 322.3 (M+).
J2
= 8.0 Hz), 6.64 (d, 2H, J = 8.0 Hz), 6.79 (t, 2H, J = 7.6 Hz),
6.92-6.98 (m, 4H), 7.09 (d, 2H, J = 8.0 HZ),7.24 (d, 2H, J = 8.0 Hz),
8.72 (s, 2H, OH), 10.54 (s, 2H, NH). l3CNMR (100 MHz, DMSO-d6)
R
f'--;c1l1
'=<..1 t.~
N
N
H
H
_
R
H
_
R
H
Aromatisation
~N~
~N~
Wb
H R
R
Scheme
4

194 JOURNAL OF CHEMICAL RESEARCH 2009
8: 55.7,109.8,110.9,113.0,115.4,118.0,118.7,120.3,120.6,125.9,
135.0, 137.0, 137.2, 145.0, 147.2. HRMS(EI): Calcd for C32H26N204
502.1893 (M+). Found 502.1909.
6,12-bis(3, 4-dimethylphenyl)-6, 12-dihydroindolo[3,2-b }carbazole
(3g): Pale yellow solid. M.p. >400°C. IR (em"): 3406 (NH).
'H NMR (400 MHz, DMSO-d6) 8: 2.13 (s, 6H, CH3), 2.15 (s, 6H,
CH3), 5.59 (s, 2H, CH), 6.78 (t, 2H, J = 7.4 Hz), 6.93 (t, 2H, J= 7.6 Hz),
6,12-bis(3-nitrophenyl)-6, 12-dihydroindolo[3,2-b }carbazole (31):
Yellow solid. M.p. >400°C. IR (em"): 3408 (NH). 'H NMR (400
MHz, DMSO-d6) 8: 6.04 (s, 2H, CH),6.83 (t, 2H, J= 7.8 Hz), 6.99
(t, 2H, J= 7.4 Hz), 7.10 (d, 2H, J= 8.4 Hz), 7.25 (d, 2H, J= 8.4 Hz),
7.58 (t, 2H, J
= 8.0 Hz), 7.74 (d, 2H, J = 8.4 Hz), 8.10 (dd, 2H,
J, = 2.8, J2 = 8.4 Hz), 8.28 (s, 2H), 10.98 (s, 2H, NH). l3CNMR (100
MHz, DMSO-d6) 8: 109.3, 111.30, 118.4, 118.7, 121.1, 121.8, 123.0,
125.2, 130.0, 135.3, 136.0, 137.2, 146.2, 147.8. HRMS(EI): Calcd
for C30H20N404500.1485 (M+). Found 500.1509.
6, 12-di(benzo[ d}[1,3}dioxol-5-yl)-6, 12-dihydroindolo[3,2-b}
carbazole (3m): White or pink solid. M.p. 351-352°C. IR (em"):
3417 (NH), 1245 (ArOCHP). 'H NMR (400 MHz, DMSO-~) 8:
5.62 (s, 2H, CH), 5.93 (d, 4H, ArOCH20, J= 6.8 Hz), 6.70 (s, 2H),
6.80-6.84 (m, 4H), 6.89 (dd, 2H, J, = 2.0, J2 = 8.0 Hz), 6.96 (td, 2H,
7.02-7.08 (m, 8 H), 7.22 (d, 2H, J
= 8.0 Hz), 10.57 (s, 2H, NH).
l3C NMR (100 MHz, DMSO-d6) 8: 18.9, 19.5, 109.8, 111.0, 118.0,
118.5, 120.4, 125.8, 125.9, 129.4, 134.0, 135.8, 136.8, 137.0, 141.5.
HRMS(EI): Calcd for C34H30N2466.2409 (M+). Found 466.2415.
6, 12-bis(3-chlorophenyl)-6,
12-dihydroindolo[3,2-b }carbazole
(3h): White solid. M.p. 291-293°C. IR (em"): 3417 (NH). 'H NMR
(400 MHz, DMSO-d6) 8: 5.67 (s, 2H, CH), 6.86 (t, 2H, J= 7.6 Hz),
7.02 (t, 2H, J
= 7.6 Hz), 7.13 (d, 2H, J = 7.6 Hz), 7.29-7.33 (m,
J,
= 1.2,J2 = 8.4 Hz), 7.11 (d, 2H,J= 8.0 HZ),7.25 (d, 2H,J= 8.0 Hz),
4H),7.39 (t, 2H, J= 7.8 Hz), 7.45-7.47 (m, 4H), 11.00 (s, 2H, NH).
l3C NMR (l00 MHz, DMSO-d6) 8: 108.8, 111.3, 118.3, 118.6,
121.0, 125.4, 126.6, 127.1, 128.1, 130.3, 133.1, 136.2, 137.1, 146.1.
HRMS(EI): Calcd for C30H2oN2C14278.1004 (M+). Found 478.1001.
6,12-bis( 4-chlorophenyl)-6, 12-dihydroindolo[3,2-b }carbazole (3i):
Light yellow solid. M.p. >400°C. IR (em"): 3385 (NH). 'H NMR
10.66 (s, 2H, NH). HRMS(EI): Calcd for C32H22NP4 498.1580 (M+).
Found 498.1597.
We are grateful to the National Natural Science Foundation
of China (No. 20676123 and 20876147) and for financial
support.
(400 MHz, DMSO-~) 8: 5.23 (s, 2H, CH), 6.82 (td, 2H, J,
= 0.8,
J2
=
7.6 Hz), 6.97 (td, 2H, J, 1.2, J2 8.4 Hz), 7.08 (d, 2H,
=
=
J= 7.6 Hz), 7.24 (d, 2H, J= 7.6 Hz), 7.34 (s, 8H), 10.75 (s, 2H, NH).
HRMS(EI): Calcd for C30H2oN2C14278.1004 (M+). Found 478.1003.
Received 13 January 2009; accepted 7 February 2009
Paper 09/0388 doi: 10.3184/030823409X424858
Published online: 6 April 2009
6, 12-bis(3-bromophenyl)-6,
12-dihydroindolo[3,2-b}carbazole
(3j): White solid. M.p. 275-277°C. IR (em"): 3415 (NH). 'H NMR
(400 MHz, DMSO-d6) 8: 5.66 (s, 2H,CH),6.87 (t, 2H, J= 7.2 Hz),
References
7.02 (t, 2H, J
= 7.6 Hz), 7.14 (d, 2H, J = 7.6 Hz), 7.30-7.35 (m,
4H),7.45 (dt, 2H, J, = 0.8, J2 = 7.2 Hz), 7.52 (d, 2H, J = 7.6 Hz), 7.57
(s, 2H), 11.00 (s, 2H, NH). '3CNMR (100 MHz, DMSO-~) 8: 108.9,
111.3, 118.3, 118.6, 121.0, 121.8, 125.4, 127.5, 129.5, 130.6, 130.9,
136.2, 137.1, 146.3. HRMS(EI): Calcd for C30H20N2Br2565.9993
(M+). Found 565.9972.
6, 12-bis( 4-bromophenyl)-6, 12-dihydroindolo[3,2-b}carbazole
(3k): Light yellow solid. M.p. 343-345°C. IR (em"): 3384 (NH).
'H NMR (400 MHz, DMSO-~) 8: 5.71 (s, 2H, CH), 6.82 (td, 2H,
1
2
W.E. Noland and M.R. Yenkiteswaranib, J Org. Chern., 1961,26,4203.
J. Bergman, S. Hogberg and J.O. Lindstrom, Tetrahedron, 1970, 26,
3347.
3
J. Banerji, R. Charkrabarti, A.K. Das and U.K. Pandit, Indian
Sect. B: Org. Chern. Incl. Med. Chern., 1986, 25B, 1204.
J Chern.,
4
5
6
7
A.R. Katritzky, J.Q. Li and C.Y. Stevens,J. Org. Chern., 1995, 60, 3401.
J. TholanderandJ. Bergman, Tetrahedron, 1999,55,12577.
D.s. Black, A.J. Ivory and N. Kumar, Tetrahedron, 1995,51,11801.
Y. Lee, M.K. Cheung, W.T. Wong andK.F. Cheng, Tetrahedron, 1996, 52,
9455.
J. TholanderandJ. Bergman, Tetrahedron, 1999,55,6243.
S.C. Lin, F.D. Yang, J.S. Shiue, S.M. Yang and J.M. Fang, J Org. Chern.,
1998,63,2909.
J,
=
1.2, J2 = 7.6 Hz), 6.97 (td, 2H, J,
=
1.2, J2 = 7.6 Hz), 7.09 (d, 2H,
J= 8.0 Hz), 7.23-7.29 (m, 6H), 7.47 (dd, 4H, J,
=
2.0, J2 7.6 Hz),
=
8
9
10.77 (s, 2H, NH). l3C NMR (100 MHz, DMSO-d6) 8: 109.5, 111.1,
118.4, 119.4, 120.8, 125.4, 130.7, 131.1, 132.3, 136.2, 137.1, 143.4.
HRMS(EI): Calcd for C30H20N2Br2565.9993 (M+). Found 565.9950.
10 R. Nagarajan and P.T. Perumal, Tetrahedron, 2002, 58, 1229.