A general method for the synthesis of 5H-benzo[b]-,carbazolo[2,3-b]- and indolo[2,3-b]carbazole derivatives via copper(II) triflate-catalyzed heteroannulation

Article abstract of DOI:10.1002/adsc.201100887

A straightforward approach for the construction of 5H-benzo[b]-, carbazolo[2,3-b]- and indolo[2,3-b]carbazole derivatives has been developed by using copper(II) triflate-catalyzed heteroannulation. Copyright

Full text of DOI:10.1002/adsc.201100887

FULL PAPERS
DOI: 10.1002/adsc.201100887
A General Method for the Synthesis of 5H-Benzo[b]-,
Carbazolo
N
U
Copper(II) Triflate-Catalyzed Heteroannulation
K. S. Prakasha and Rajagopal Nagarajana,*
a
School of Chemistry, University of Hyderabad, Hyderabad – 500 046, India
Fax : (+91)-40-2301-2460; e-mail: rnsc@uohyd.ernet.in
Received: November 15, 2011; Revised: January 18, 2012; Published online: && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201100887.
Abstract: A straightforward approach for the con- oped by using copper(II) triflate-catalyzed heteroan-
struction of 5H-benzo[b]-, carbazolo
ACHTUNGERTN[NUNG 2,3-b]- and nulation.
indolo[2,3-b]carbazole derivatives has been devel-
ACHTUNGTRENNUNG
Keywords: carbazole derivatives; copper(II) triflate;
heteroannulation; heterocycles
Introduction
a halo[10] or a carbonyl or an imino group in an ortho
position by employing various catalysts.[11,12,15] Similar-
Over the past few years, carbazole and its fused aro- ly, Lewis acid-mediated domino reactions have been
matic systems were found to display a wide range of proven to be a powerful method in the synthesis of
attractive biological activities.[1] Of its fused aromatic
systems, syntheses of benzannulated and heteroannu-
lated carbazole analogues are vital as such com-
pounds are not found in abundance in natural sources.
They exhibit promising biological activities,[2] especial-
ly antitumor activity.[3] In particular, benzo[a]carba-
zole derivatives have been found to have binding af-
finities for the estrogen receptor, and inhibit the
mammary tumors of rats.[4a] Benzo[b]carbazole deriv-
atives 1 and 2 (Figure 1) show cytostatic activity
against leukemia type L 1210 cell culture[4b] and have
a potential bifunctional nucleic acid intercalating
property,[4c] respectively.
Ever since the first isolation of indolocarbazole in
1977, organic chemists have been interested in the
synthesis of indolocarbazole and its derivatives due to
their biological activities.[5] 6-Formylindolo
ACHTUNGTRENNUNG
bazole 3 and 6,12-diformylindoloACTHUNGTRENNNUG
(Figure 1) are reported to be highly efficient ligands
for the Ah receptor.[6] Carbazolocarbazole derivatives
are being explored in the field of organic electron-
ics,[7] anion binding studies[8] and organic dyes.[9] Al-
though the structure of carbazolocarbazole was first
reported in 1965, these derivatives did not receive
much attention and only a few reports were available
concerning their synthesis.[7–9]
In recent years, there has been an immense interest
Figure 1. Structures of important benzo-, indolo-, and carba-
in the cyclization of phenylacetylenes that have zolocarbazole derivatives.
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K. S. Prakash and Rajagopal Nagarajan
Table 1. Optimization of the reaction conditions.[a]
FULL PAPERS
a wide variety of polycyclic heterocycles.[14,19] Yama-
motoꢁs group described the iodine-mediated electro-
philic cyclization of 2-alkynyl-1-methylene azide,[13]
Lewis acid-catalyzed benzannulation of o-alkynyl-
ACHTUNGTRENNUNG
(oxo)benzenes with alkynes,[14a] alkenes[14b] and
enols.[14c] Barluenga et al. developed a new metal-free
À
À
protocol for consecutive C O and C C bond forma-
tion using IPy2·BF4.[15] Especially, Larock et al. report-
ed the reaction of alkynes having a tert-butylimino
group close to the carbon-carbon triple bond cata-
lyzed by copper,[16a–c] palladium;[16d,e] and cyclization
induced by electrophiles.[16f] Jana et al. developed an
intramolecular alkyne-carbonyl metathesis under
iron-catalyzed conditions.[17] Very recently, Cao and
colleagues have reported a Pd-catalyzed sequential
reaction for the synthesis of d-carbolines using
Larock heteroannulation/elimination/electrocycliza-
tion and oxidative aromatization.[18]
However, to the best of our knowledge, very few
reports have been published in the literature for the
annulation of indole and 2-ethynylbenzaldehyde,[20a,b]
and the reaction of heteroarylalkynylaldehyde with
indoles was unexplored. Thus, the development of
synthetic methods for annulated carbazoles is sure to
open up new opportunities to utilize these compounds
as organic materials as well as in new biological appli-
cations.
[a]
Reaction conditions: 6a (0.5 mmol), 7a (1.0 mmol), sol-
vent (5 mL), catalyst (15 mol%), 808C. NR: no reaction.
Isolated yields.
10 mol% catalyst was used.
Reaction was carried out at room temperature.
Reaction was carried out at 508C.
[b]
[c]
[d]
[e]
Here, we communicate a simple and facile strategy
for the synthesis of benzo[b]-, carbazolo
ACHTUNGTRENUN[NG 2,3-b]- and
indolo[2,3-b]carbazole derivatives via copper(II) tri-
ACHTUNGTRENNUNG
flate-catalyzed heteroannulation.
Result and Discussion
the acetylene (Scheme 1, 7a–e) could be handled
without any trouble and also gave the products in
We began our investigation by optimizing the reaction good yields. With arylalkynes bearing electron-with-
between 6a and 7a using various catalysts and sol- drawing groups (Scheme 1, 7f and 7g), we were
vents. The results are summarized in Table 1.
unable to separate the corresponding product due to
While using 10 mol% Cu(OTf)2, we got the product the complex mixtures as found in TLC. The structure
AHCTUNGTRENNUNG
8a with lower yield in longer reaction time (Table 1, of the product 8a was unambiguously confirmed by
entry 1). So, we increased the amount of catalyst to the single crystal X-ray diffraction analysis[21] and an
15 mol%. Under these conditions, the reaction pro- ORTEP diagram of 8a is shown in Figure 2.
ceeded smoothly and benzocarbazole 8a was obtained
Based on the reported literature,[14] a possible
in 92% yield (Table 1, entry 2). We also screened mechanism for the formation of benzocarbazole de-
other solvents, such as CH3CN, THF, toluene, etc. rivatives (8a–j) has been proposed in Scheme 2. As
(Table 1, entries 3, 4, and 5), however only inferior re- outlined in Scheme 2, CuACTHNUTRGEN(UNG OTf)2 coordinates with
sults were observed. Other catalysts gave the product triple bond of 6 to enhance the electrophilicity of the
in low yield (Table 1, entries 6–12). In the absence of alkyne. Subsequently, nucleophilic attack of the car-
a catalyst, no cyclization was observed (Table 1, bonyl oxygen followed by cycloaddition with alkyne
entry 13).
delivers the benzo[b]carbazole derivatives 8.
As shown in Table 1, we conclude that best result
We expected that a similar kind of cyclization could
was obtained with 15 mol% CuACTHNUTRGNEUNG(OTf)2 as a catalyst be done with 2-alkynylcarbazole-3-carbaldehydes (6a–
and dichloroethane as solvent at 808C. Employing the f) and indoles (9a–g) using the copper catalyst. As ex-
optimized reaction conditions, we successfully synthe- pected, we got the desired product 10a in good yield
sized various benzo[b]carbazole derivatives 8a–j.
(85%) by employing CuACTHNGUTER(NNUG OTf)2 (10 mol%) as a catalyst
As shown in Scheme 1, substrates containing sub- and dichloroethane as a solvent at 808C (Table 2,
stituents like phenyl, p-tolyl, diphenyl, and alkyl on entry 3).
2
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A General Method for the Synthesis of 5H-Benzo[b]-, CarbazoloACTHNUGTRENNUG[2,3-b]- and IndoloACHUTNGTREN[NUGN 2,3-b]carbazole
Scheme 1. Cu
ACHTUNGTRENNUNG(OTf)2-catalyzed cyclization of 2-(alkynyl)carbazole-3-carbaldehydes (6a–e) with different arylacetylenes
ACHTUNGTRENNUNG
6a–e (0.5 mmol) and 7a–g (1.0 mmol) in the presence of CuACHTUNTRGNE(NUG OTf)2 (15 mol%). Isolated yields after column chromatography
are given.
This result prompted us to optimize the reaction
conditions. When using CuBr2 as a catalyst, the yield next to the synthesis of indoloAHCNUTGTRENNUNG
Motivated by these results, we turned our attention
[2,3-b]carbazole deriva-
of the anticipated product was low with a trace tives using 2-alkynylindole-3-carbaldehyde and indole.
amount of inseparable by-products (Table 2, entry 7). Here again, we started our synthesis by screening var-
We could not improve the yield of the product while ious copper catalysts. Among them, 10 mol%
screening other copper catalysts. To extend this meth- Cu
odology further, we carried out the reaction of 2-alk- a solvent. After careful column chromatography,
ynylcarbazole-3-carbaldehydes (6a–f) with various in- indolo[2,3-b]carbazole 12a was isolated in moderate
doles (9a–g) in the presence of Cu(OTf)2 (10 mol%) yield. It was possible to slightly increase the yield of
under the optimized conditions. The scope of this re- the product as R1 was an electron-withdrawing sub-
ACHTUNGRTENN(UNG OTf)2 gave the expected product 12a in DCE as
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
action is outlined in Scheme 3.
stituent (Scheme 4, 12b–d).
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In order to understand the reaction pathway, we
trapped the intermediate 13 (Scheme 6) by perform-
ing a reaction between 2-alkynylcarbazole-3-carbalde-
hyde (6b) and indole (9a). Employing 10 mol%
CuACTHNUTRGEN(NUG OTf)2 in DCE as a solvent at room temperature
gave the intermediate 13 in trace amount. While heat-
ing, we were unable to trap the intermediate 13 be-
cause 10d was formed at faster rate. So, we changed
the reaction conditions (10 mol% PdCl2, DMSO as
a solvent at room temperature) to trap the intermedi-
ate 13. As shown in Scheme 6, the intermediate 13
was prepared in 78% yield and subjected to reaction
Figure 2. ORTEP diagram of 8a. Hydrogen atoms are omit-
ted for clarity.
under the standard conditions [10 mol% CuACHTUNGTRENNUNG(OTf)2
and 1,2-dichloroethane as a solvent], and this also
gave carbazolocarbazole 10d in good yield (85%).
In H NMR spectra of 12a–d, a singlet around d= These results clearly led to the conclusion that the
1
8.50–9.30 ppm which corresponds to the C-12 proton domino process proceeds through the trapped inter-
of the indoloACHTUNGTRENNUNG[2,3-b]carbazole derivatives clearly indi- mediate 13.
cate the formation of products (see the Supporting In-
formation). Reaction of 11a with indole did not
afford the desired product. The possible mechanism Conclusions
for the coupling of indole and 2-alkynylcarbazole-3-
carbaldehydes (6a–f), 2-alkynylindole-3-carbaldehydes In summary, we have demonstrated a simple and effi-
(11a–c) is depicted in Scheme 5 based on the litera- cient methodology for the synthesis of benzo[b]-,
ture.[14,20]
carbazolo
ACHUTGTNRENNUG[2,3-b]-, and indoloAHCTUNGTRNE[NUGN 2,3-b]carbazole deriva-
tives in moderate to good yields. The scope of this
Scheme 2. Possible mechanism for the formation of benzocarbazole derivatives.
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A General Method for the Synthesis of 5H-Benzo[b]-, CarbazoloACTHNUGTRENNUG[2,3-b]- and IndoloACHUTNGTREN[NUGN 2,3-b]carbazole
Table 2. Optimization of copper-catalyzed cyclization of 6a with indole.[a]
[a]
Reaction conditions: 6a (0.5 mmol), 9a (0.5 mmol), solvent (5 mL), catalyst
(10 mol%).
Isolated yields.
[b]
synthetic route is general. This process can be applica-
ble to wide range of functional groups, affording the
Ka fine-focus sealed tube (l=0.71073 ꢂ). Melting points
were measured in open capillary tubes and are uncorrected.
All the obtained products were purified by column chroma-
tography using silica gel (100–200 mesh). All reaction sol-
vents used were of GR grade and used without drying
unless mentioned. All other commercial reagents were used
as received.
2-Alkynylcarbazole-3-carbaldehydes (6a–f) were prepared
from 2-bromocarbazoles as methods developed from our
laboratory[22a,b] and 2-alkynylindole-3-carbaldehydes (11a–c)
were prepared according to reported literature meth-
ods.[16c,22c]
corresponding benzo[b]-, carbazolo
ACHTUNGTREN[NUNG 2,3-b]-, and
indolo[2,3-b]carbazole derivatives. With high conjuga-
ACHTUNGTRENNUNG
tion and functional groups like carbonyl near to the
free NH moiety, these molecules might be useful in
the field of biology and organic materials.
Experimental Section
General Information
1H and 13C NMR spectra were recorded at 400 and
100 MHz, respectively, or at 500 and 125 MHz, respectively.
Chemical shifts are calculated in ppm downfield from TMS
General Procedure for the Synthesis of Benzo[b]car-
bazole Derivatives
1
(d=0) for H NMR, and relative to the central CDCl3 reso-
nance (d=77.0) and DMSO-d6 (d=39.51) for 13C NMR.
Data are presented as follows: chemical shift, multiplicity
(bs=broad singlet, s=singlet, d=doublet, dd=doublet dou-
blet, t=triplet, q=quartet, m=multiplet), coupling constant
in Hertz (Hz) and integration. IR spectra were recorded on
a JASCO FT/IR-5300 instrument. Elemental analysis was
carried out in a Thermo Finnigan Flash EA 1112 analyzer in
the School of Chemistry, University of Hyderabad. X-ray
diffraction measurements were carried out at 298 K on an
automated diffractometer using graphite-monochromated
Mo-Ka (l=0.71073 ꢂ) radiation with CAD4 software or the
X-ray intensity data were measured at 298 K on an instru-
ment equipped with a graphite monochromator and a Mo-
An oven-dried 10-mL round-bottomed flask equipped with
a Teflon-coated magnetic stirring bar was charged with
0.5 mmol of 9-ethyl-2-(2-phenylethynyl)-9H-carbazole-3-car-
baldehyde (6a), 15 mol% of CuACHTNUGRTENUNG(OTf)2, 1.0 mmol of phenyla-
cetylene (7a) and 5 mL of dry 1,2-dichloroethane. The reac-
tion mixture was stirred at 808C. After 5 h, solvent and
excess of phenylacetylene were removed under reduced
pressure. The crude reaction mixture was then poured over
water and extracted with EtOAc (3ꢃ20 mL). The organic
layer was dried with anhydrous Na2SO4 and the solvent was
removed. The residue was purified by column chromatogra-
phy (10% ethyl acetate in hexanes) on silica gel to afford
the product 8a; yield: 92%. We followed the same proce-
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Scheme 3. Cu
wise noted, all the reactions were carried out in dichloroethane (5.0 mL) as a solvent at 808C using 6a–f (0.5 mmol) and 9a–f
(0.5 mmol) in the presence of Cu(OTf)2 (10 mol%). Isolated yields after column chromatography are given.
ACHTUNGTRENNUNG(OTf)2-catalyzed cyclization of 2-(alkynyl)carbazole-3-carbaldehydes (6a–f) with indoles (9a–g). Unless other-
AHCTUNGTRENNUNG
dure for the synthesis of other benzo[b]carbazole derivatives
(8b–8j).
(5-Ethyl-8-phenyl-5H-benzo[b]carbazol-7-yl)ACTHNUTRGNEUG(N phenyl)-
128.2, 128.1, 127.5, 127.2, 127.0, 125.6, 124.3, 122.5, 121.2,
119.2, 119.0, 108.3, 101.0 (aromatic C); 37.5, 13.1 (aliphatic
C); LC-MS (positive mode): m/z=426 (M+H+); anal.
calcd. for C31H23NO: C 87.50, H 5.45, N 3.29%; found: C
87.41, H 5.51, N 3.22%.
methanone (8a): Yield: 92%; mp 168–1708C; IR (KBr): n=
1
2910, 1720, 1590, 1060, 790 cmÀ1; H NMR (400 MHz, TMS,
(5-Ethyl-2-methyl-8-phenyl-5H-benzo[b]carbazol-7-yl)-
CDCl3): d=8.68 (s, 1H), 8.24 (t, J=8.4 Hz, 2H), 7.67 (d, J=
8.0 Hz, 2H), 7.61 (s, 1H), 7.55 (t, J=8.0 Hz, 1H), 7.49 (d,
J=8.4 Hz, 1H), 7.42–7.36 (m, 4H), 7.30–7.22 (m, 5H), 7.18–
7.16 (m, 1H), 4.27 (q, J=6.8 Hz, 2H), 1.33 (t, J=7.2 Hz,
3H); 13C NMR (100 MHz, TMS, CDCl3): d=200.8, 142.8,
140.9, 140.7, 138.5, 137.1, 134.3, 133.0, 130.3, 129.7, 129.6,
AHCTUNGTRENNUNG
;
(400 MHz, TMS, CDCl3): d=8.64 (s, 1H), 8.22 (d, J=
8.5 Hz, 1H), 8.08 (s, 1H), 7.67 (d, J=8.0 Hz, 2H), 7.58 (s,
1H), 7.49 (d, J=8.0 Hz, 1H), 7.41–7.37 (m, 4H), 7.28–7.23
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A General Method for the Synthesis of 5H-Benzo[b]-, CarbazoloACTHNUGTRENNUG[2,3-b]- and IndoloACHUTNGTREN[NUGN 2,3-b]carbazole
Scheme 4. Cu
wise noted, all the reactions were carried out in dichloroethane (5.0 mL) as a solvent at 808C using 11a–c (0.5 mmol) and 9a,
9d and 9g (0.5 mmol) in the presence of Cu(OTf)2 (10 mol%). Isolated yields after column chromatography are given.
ACHTUNGTRENNUNG(OTf)2-catalyzed cyclization of 2-alkynylindole-3-aldehydes (11a–c) with indoles (9a, 9d and 9g). Unless other-
AHCTUNGTRENNUNG
Scheme 5. Possible mechanism for the formation of indolo and carbazolocarbazole derivatives.
(m, 5H), 7.19 (t, J=7.0 Hz, 1H), 4.26 (q, J=7.0 Hz, 2H),
2.59 (s, 3H), 1.32 (t, J=7.0 Hz, 3H); 13C NMR (100 MHz,
TMS, CDCl3): d=200.6, 141.0, 140.9, 138.6, 137.0, 134.3,
132.9, 130.2, 129.7, 129.6, 129.5, 128.7, 128.5, 128.4, 128.2,
128.1, 127.2, 126.9, 125.5, 124.1, 122.6, 121.3, 118.9, 108.0,
100.9 (aromatic C); 37.5, 21.3, 13.1 (aliphatic C); LC-MS
(positive mode): m/z=440 (M+H+); anal. calcd. for
C32H25NO: C 87.44, H 5.73, N 3.19%; found: C 87.61, H
5.68, N 3.25%.
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Scheme 6. Formation of intermediate 13 and its cyclization. Reaction conditions: (i) 6b (0.5 mmol), 9a (0.5 mmol), 10 mol%
of PdCl2, 5 mL DMSO; (ii) 13 (0.3 mmol), 10 mol% of Cu(OTf)2, 4 mL DCE.
AHCTUNGTRENNUNG
Phenyl(2,4,5-trimethyl-8-phenyl-5H-benzo[b]carbazol-7-
yl)(phenyl)methanone (8c): Yield: 90%; mp 152–1548C; IR
(KBr): n=2928, 1722, 1490, 1070, 900 cmÀ1 1H NMR
143.8, 142.1, 141.1, 141.0, 140.9, 136.7, 136.0, 134.5, 130.0,
N
129.8, 129.6, 129.0, 128.9, 128.1, 127.1, 127.0, 125.8, 125.2,
124.2, 122.2, 118.9, 117.5, 107.8, 101.0 (aromatic C), 37.5,
34.7, 32.0, 21.6, 13.2 (aliphatic C); LC-MS (positive mode):
m/z=496 (M+H+); anal. calcd. for C36H33NO: C 87.24, H
6.71, N 2.83%; found: C 87.09, H 6.78, N 2.76%.
;
(400 MHz, TMS, CDCl3): d=8.58 (s, 1H), 8.20 (d, J=
8.4 Hz, 1H), 7.90 (s, 1H), 7.65 (d, J=8.0 Hz, 2H), 7.53 (s,
1H), 7.46 (d, J=8.8 Hz, 1H), 7.39–7.37 (m, 3H), 7.27–7.21
(m, 4H), 7.17 (d, J=7.2 Hz, 1H), 7.10 (s, 1H), 3.98 (s, 3H),
2.80 (s, 3H), 2.51 (s, 3H); 13C NMR (100 MHz, TMS,
CDCl3): d=200.8, 142.9, 140.9, 140.5, 138.4, 136.8, 134.4,
133.0, 132.2, 130.1, 129.7, 129.6, 128.7, 128.2, 128.1, 127.2,
127.0, 125.5, 124.1, 123.2, 119.9, 119.0, 118.5, 101.1 (aromatic
C); 32.6, 21.0, 20.1 (aliphatic C); LC-MS (positive mode):
m/z=440 (M+H+); anal. calcd. for C32H25NO: C 87.44, H
5.73, N 3.19%; found: C 87.32, H 5.68, N 3.25%.
(2-tert-Butyl-5-ethyl-8-p-tolyl-5H-benzo[b]carbazol-7-yl)-
AHCTUNGTERG(NNUN p-tolyl)methanone (8f): Yield: 87%; mp 116–1188C; IR
1
(KBr): n=2910, 1720, 1470, 1580, 1080, 950 cmÀ1; H NMR
(400 MHz, TMS, CDCl3): d=8.67 (s, 1H), 8.28 (d, J=
1.6 Hz, 1H), 8.20 (d, J=8.4 Hz, 1H), 7.61 (m, 3H), 7.51 (s,
1H), 7.47 (d, J=8.4 Hz, 1H), 7.32 (m, 2H), 7.06 (m, 5H),
4.21 (q, J=7.2 Hz, 2H), 2.31 (s, 3H), 2.29 (s, 3H), 1.50 (s,
9H), 1.30 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, TMS,
CDCl3): d=200.5, 143.9, 142.1, 141.0, 140.9, 138.1, 137.5,
136.8, 136.6, 136.0, 134.3, 129.9, 129.4, 129.0, 128.9, 126.8,
125.7, 125.2, 124.4, 122.2, 120.7, 118.9, 117.5, 107.7, 100.9 (ar-
omatic C); 37.5, 34.7, 32.0, 21.7, 21.1, 13.2 (aliphatic C); LC-
MS (positive mode): m/z=510 (M+H+); anal. calcd. for
C37H35NO: C 87.19, H 6.92, N 2.75%; found: C 87.25, H
6.85, N 2.71%.
(2-tert-Butyl-5-ethyl-8-phenyl-5H-benzo[b]carbazol-7-yl)-
ACHTUNGTRENNUNG(phenyl)methanone (8d): Yield: 83%; mp 124–1268C; IR
1
(KBr): n=2920, 1722, 1585, 1290, 1060, 850 cmÀ1; H NMR
(400 MHz, TMS, CDCl3): d=8.69 (s, 1H), 8.28 (d, J=
1.8 Hz, 1H), 8.23 (d, J=8.8 Hz, 1H), 7.65 (m, 2H), 7.63 (dd,
J=8.8 & 2.0 Hz, 1H), 7.57 (s, 1H), 7.48 (d, J=8.8 Hz, 1H),
7.40–7.36 (m, 3H), 7.31 (d, J=8.4 Hz, 1H), 7.25–7.21 (m,
4H), 7.18 (d, J=7.2 Hz, 1H), 4.25 (q, J=7.2 Hz, 2H), 1.50
(s, 9H), 1.31 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, TMS,
CDCl3): d=200.7, 142.2, 141.1, 140.9, 138.6, 137.0, 134.3,
132.9, 130.2, 129.7, 129.6, 128.3, 128.2, 128.1, 127.2, 127.0,
125.9, 125.3, 124.1, 122.2, 118.9, 117.5, 107.8, 107.5, 100.9 (ar-
omatic C), 37.5, 34.7, 32.0, 13.2 (aliphatic C); LC-MS (posi-
tive mode): m/z=482 (M+H+); anal. calcd. for C35H31NO:
C 87.28, H 6.49, N 2.91%; found: C 87.14, H 6.38, N 3.05%.
(2-tert-Butyl-5-ethyl-8-phenyl-5H-benzo[b]carbazol-7-yl)-
(2-tert-Butyl-5-ethyl-8-pentyl-5H-benzo[b]carbazol-7-yl)-
AHCTUNGTERG(NNUN phenyl)methanone (8g): Yield: 72%; mp 104–1068C; IR
1
(KBr): n=2910, 1720, 1420, 1590, 1060, 850 cmÀ1; H NMR
(400 MHz, TMS, CDCl3): d=8.62 (s, 1H), 8.26 (d, J=
1.6 Hz, 1H), 8.11 (d, J=8.0 Hz, 1H), 7.92 (d, J=7.2 Hz,
2H), 7.62–7.57 (m, 2H), 7.45 (t, J=8.0 Hz, 2H), 7.35 (d, J=
8.8 Hz, 1H), 7.29–7.27 (m, 2H), 4.18 (q, J=7.2 Hz, 2H),
2.64 (t, J=8.0 Hz, 2H), 1.65 (m, 2H), 1.50 (s, 9H), 1.48–1.45
(m, 4H), 1.26 (m, 3H), 0.84 (t, J=6.8 Hz, 3H); 13C NMR
(100 MHz, TMS, CDCl3): d=201.3, 142.0, 140.7, 140.6,
138.3, 136.7, 134.2, 133.6, 129.9, 129.8, 129.7, 128.7, 126.3,
125.1, 125.0, 124.0, 122.3, 118.8, 117.4, 107.6, 100.6 (aromatic
C); 37.5, 34.7, 34.0, 32.0, 31.8, 31.0, 22.4, 13.9, 13.0 (aliphatic
C); LC-MS (positive mode): m/z=476 (M+H+); anal.
calcd. for C34H37NO: C 85.85, H 7.84, N 2.94%; found: C
85.68, H 7.91, N 2.85%.
ACHTUNGTRENNUNG
;
(400 MHz, TMS, CDCl3): d=8.70 (s, 1H), 8.31 (s, 1H), 8.24
(d, J=8.0 Hz, 1H), 7.64 (dd, J=8.0 & 2.0 Hz, 1H), 7.61 (d,
J=8.0 Hz, 2H), 7.57 (s, 1H), 7.50 (d, J=8.5 Hz, 1H), 7.45
(s, 1H), 7.43 (s, 1H), 7.32 (d, J=9.0 Hz, 1H), 7.29–7.26 (m,
2H), 7.20 (t, J=7.0 Hz, 1H), 7.05 (d, J=8.0 Hz, 2H), 4.26
(q, J=7.0 Hz, 2H), 2.31 (s, 3H), 1.52 (s, 9H), 1.34 (t, J=
7.0 Hz, 3H); 13C NMR (100 MHz, TMS, CDCl3): d=200.3,
(2-tert-Butyl-5-ethyl-8-hexyl-5H-benzo[b]carbazol-7-yl)-
AHCTUNGTREG(NNUN phenyl)methanone (8h): Yield: 73%; mp 102–1048C; IR
8
asc.wiley-vch.de
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

A General Method for the Synthesis of 5H-Benzo[b]-, Carbazolo
(KBr): n=2915, 1710, 1580, 1110, 650 cmÀ1 1H NMR
ACHUTGTNREN[UNG 2,3-b]- and IndoloACHTUNGTREN[NUNG 2,3-b]carbazole
;
(8-Ethyl-5,8-dihydrocarbazolo
yl)methanone (10a): Yield: 85%; mp 236–2388C; IR (KBr):
n=3395, 2950, 1688, 1633, 1555, 1222, 698 cmÀ1 1H NMR
ACHUTNGTRENNUG[2,3-b]carbazol-6-yl)ACHTUNGTRENNUNG(phen-
(400 MHz, TMS, CDCl3): d=8.61 (s, 1H), 8.25 (d, J=
2.0 Hz, 1H), 8.10 (d, J=8.4 Hz, 1H), 7.91 (d, J=7.2 Hz,
2H), 7.59 (m, 2H), 7.44 (t, J=7.6 Hz, 2H), 7.34 (d, J=
8.4 Hz, 1H), 7.26–7.29 (m, 2H), 4.91 (q, J=6.8 Hz, 2H),
2.63 (t, J=8.0 Hz, 2H), 1.63 (t, J=7.6 Hz, 2H), 1.49–1.47
(m, 11H), 1.24 (m, 7H), 0.85 (t, J=6.8 Hz, 3H); 13C NMR
(100 MHz, TMS, CDCl3): d=201.3, 142.0, 140.7, 140.6,
138.9, 136.7, 134.2, 133.6, 129.9, 129.7, 129.6, 128.7, 126.2,
125.1, 125.0, 124.0, 122.3, 118.8, 117.4, 107.6, 100.6 (aromatic
C); 37.5, 34.7, 34.0, 32.0, 31.5, 31.3, 29.3, 22.5, 14.1, 13.1 (ali-
phatic C); LC-MS (positive mode): m/z=490 (M+H+);
anal. calcd. for C35H39NO: C 85.84, H 8.03, N 2.86%; found:
C 85.92, H 8.12, N 2.75%.
;
(400 MHz, TMS, CDCl3): d=9.90 (bs, 1H), 8.90 (s, 1H),
8.73 (s, 1H), 8.21 (d, J=7.6 Hz, 2H), 7.77 (d, J=7.6 Hz,
2H), 7.58–7.42 (m, 7H), 7.34–7.24 (m, 3H), 3.95 (q, J=
7.2 Hz, 2H), 1.09 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz,
TMS, CDCl3): d=198.3, 142.8, 142.4, 141.7, 141.5, 140.0,
131.9, 130.7, 129.4, 128.7, 127.3, 127.0, 126.3, 123.7, 123.0,
122.6, 120.8, 120.6, 120.4, 120.3, 119.1, 111.1, 110.8, 108.0,
102.8 (aromatic C); 37.3, 13.1 (aliphatic C); LC-MS (positive
mode): m/z=439 (M+H+); anal. calcd. for C31H22N2O: C
84.91, H 5.06, N 6.39%; found: C 84.79, H 5.12, N 6.28%.
(11-tert-Butyl-8-ethyl-5,8-dihydrocarbazolo
zol-6-yl)(phenyl)methanone (10b): Yield: 83%; mp 186–
1888C; IR (KBr): n=3390, 2978, 1712, 1622, 1545, 1295,
840 cmÀ1 1H NMR (400 MHz, TMS, CDCl3): d=9.91 (bs,
ACHTUNGTREN[NUNG 2,3-b]carba-
(2-tert-Butyl-5-ethyl-8,9-dipentyl-5H-benzo[b]carbazol-7-
AHCTUNGTRENNUNG
yl)ACHTUNGTRENNUNG(phenyl)methanone (8i): Yield: 62%; mp 142–1448C; IR
1
(KBr): n=2915, 1720, 1590, 1469, 1060, 850 cmÀ1; H NMR
(400 MHz, TMS, CDCl3): d=9.14 (d, J=1.6 Hz, 1H), 7.74
(s, 1H), 7.71 (dd, J=8.8 & 2.0 Hz, 1H), 7.60–7.58 (m, 2H),
7.53 (s, 1H), 7.41–7.20 (m, 14H), 7.00 (t, J=7.2 Hz, 1H),
4.25 (q, J=8.0 Hz, 2H), 1.52 (s, 9H), 1.30 (t, J=8.0 Hz,
3H); 13C NMR (100 MHz, TMS, CDCl3): d=200.3, 142.2,
141.2, 141.1, 141.07, 138.4, 137.2, 136.6, 136.4, 133.0, 131.6,
130.3, 129.4, 129.3, 129.0, 128.3, 128.25, 128.1, 127.7, 126.8,
126.4, 126.1, 125.7, 125.2, 122.3, 120.8, 117.0, 107.5, 100.5 (ar-
omatic C); 37.6, 34.8, 32.0, 13.0 (aliphatic C); LC-MS (posi-
tive mode): m/z=558 (M+H+); anal. calcd. for C41H35NO:
C 88.29, H 6.33, N 2.51%; found: C 88.12, H 6.39, N 2.48%.
Phenyl(2,4,5-trimethyl-8,9-diphenyl-5H-benzo[b]carbazol-
7-yl)methanone (8j): Yield: 66%; mp 154–1568C; IR (KBr):
;
1H), 8.92 (s, 1H), 8.77 (s, 1H), 8.27 (d, J=2.0 Hz, 1H), 8.24
(d, J=7.6 Hz, 1H), 7.79–7.78 (m, 2H), 7.60–7.41 (m, 7H),
7.34 (t, J=7.2 Hz, 1H), 7.26 (m, 1H), 3.94 (q, J=7.2 Hz,
2H), 1.51 (s, 9H), 1.09 (t, J=7.2 Hz, 3H); 13C NMR
(100 MHz, TMS, CDCl3): d=198.3, 142.8, 142.2, 143.7,
141.5, 140.5, 140.4, 131.8, 130.6, 129.5, 128.6, 127.2, 126.3,
124.7, 123.6, 123.5, 123.3, 123.0, 122.3, 120.5, 120.2, 117.2,
111.1, 110.8, 107.5, 102.7 (aromatic C); 37.3, 34.7, 32.0, 13.2
(aliphatic C); LC-MS (positive mode): m/z=495 (M+H+);
anal. calcd. for C35H30N2O: C 84.99, H 6.11, N 5.66%;
found: C 84.91, H 6.15, N 5.58%.
(11-tert-Butyl-8-ethyl-5,8-dihydrocarbazolo
zol-6-yl)(p-tolyl)methanone (10c): Yield: 86%; mp 180–
1828C; IR (KBr): n=3400, 2985, 1675, 1628, 1535, 1295,
700 cmÀ1 1H NMR (400 MHz, TMS, CDCl3): d=9.72 (bs,
ACHTUNGTREN[NUNG 2,3-b]carba-
AHCTUNGTRENNUNG
n=2910, 1725, 1500, 1600, 1060, 850 cmÀ1
;
1H NMR
(500 MHz, TMS, CDCl3): d=8.62 (s, 1H), 8.22 (s, 1H), 8.16
(m, 1H), 7.95 (m, 1H), 7.92 (s, 1H), 7.60 (m, 3H), 7.49 (s,
1H), 7.38 (t, J=7.5 Hz, 1H), 7.25–7.15 (m, 8H), 7.11 (s,
1H), 6.74 (t, J=7.0 Hz, 1H), 4.00 (s, 3H), 2.82 (s, 3H), 2.53
(s, 3H); 13C NMR (125 MHz, TMS, CDCl3): d=200.7, 142.9,
141.3, 140.6, 138.9, 138.5, 136.4, 135.8, 132.8, 132.2, 131.1,
130.9, 130.1, 129.4, 128.8, 128.7, 128.6, 128.0, 127.6, 127.2,
126.6, 126.2, 125.9, 123.2, 119.9, 119.0, 118.6, 118.1, 100.8 (ar-
omatic C); 32.7, 21.0, 20.1 (aliphatic C); LC-MS (positive
mode): m/z=516 (M+H+); anal. calcd. for C38H29NO: C
88.51, H 5.67, N 2.72%; found: C 88.39, H 5.63, N 2.81%.
;
1H), 8.90 (s, 1H), 8.77 (s, 1H), 8.25 (d, J=1.6 Hz, 1H), 8.22
(d, J=7.6 Hz, 1H), 7.69 (d, J=8.4 Hz, 2H), 7.58 (dd, J=8.4
& 1.2 Hz, 1H), 7.51–7.40 (m, 3H), 7.32 (t, J=7.6 Hz, 1H),
7.25–7.22 (m, 3H), 3.98 (q, J=7.2 Hz, 2H), 2.42 (s, 3H),
1.49 (s, 9H), 1.11 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz,
TMS, CDCl3): d=198.1, 142.6, 142.4, 142.2, 141.7, 140.6,
140.4, 138.6, 130.6, 129.7, 129.3, 127.2, 125.8, 124.6, 123.6,
123.5, 123.3, 123.0, 122.3, 120.5, 120.2, 120.1, 117.2, 111.0,
110.7, 107.4, 102.5 (aromatic C); 37.3, 34.7, 32.0, 21.6, 13.0
(aliphatic C); LC-MS (positive mode): m/z=509 (M+H+);
anal. calcd. for C36H32N2O: C 85.01, H 6.34, N 5.51%;
found: C 85.15, H 6.29, N 5.63%.
(8-Ethyl-11-methyl-5,8-dihydrocarbazolo
yl)(phenyl)methanone (10d): Yield: 84%; mp 212–2148C;
IR (KBr): n=3397, 2980, 1688, 1638, 1527, 1292, 700 cmÀ1
ACHTUNGTREN[NUNG 2,3-b]carbazol-6-
General Procedure for the Synthesis of Carbazolo-
ACHTUNGTRENNUNG[2,3-b]carbazole Derivatives
AHCTUNGTRENNUNG
;
1H NMR (400 MHz, TMS, CDCl3): d=9.91 (bs, 1H), 8.88 (s,
1H), 8.69 (s, 1H), 8.22 (d, J=7.6 Hz, 1H), 8.03 (s, 1H), 7.78
(m, 2H), 7.59–7.44 (m, 5H), 7.39 (s, 1H), 7.35–7.31 (m, 2H),
7.20 (d, J=8.4 Hz, 1H), 3.92 (q, J=7.2 Hz, 2H), 2.59 (s,
3H), 1.08 (t, J=7.2 Hz, 3H) ; 13C NMR (100 MHz, TMS,
CDCl3): d=198.3, 142.8, 141.7, 141.6, 140.6, 140.2, 131.8,
130.7, 129.4, 128.7, 128.4, 128.1, 127.2, 126.3, 123.6, 123.5,
123.0, 122.9, 122.7, 121.0, 120.5, 120.3, 120.25, 111.0, 110.8,
107.7, 102.6 (aromatic C); 37.3, 21.4, 13.1 (aliphatic C); LC-
MS (negative mode): m/z=452 (M+); anal. calcd. for
C32H24N2O: C 84.93, H 5.35, N 6.19%; found: C 85.12, H
5.31, N 6.25%.
An oven-dried 10-mL round-bottomed flask equipped with
a Teflon-coated magnetic stirring bar was charged with
0.5 mmol 9-ethyl-2-(2-phenylethynyl)-9H-carbazole-3-carbal-
dehyde (6a), 10 mol% of CuACHTNUTRGENNG(U OTf)2, and 5 mL of dry 1,2-di-
chloroethane. To this 0.5 mmol of indole (9a) was added.
Then the reaction mixture was stirred at 808C. After 1 h,
solvent was removed under reduced pressure. The crude re-
action mixture was then poured over water and extracted
with EtOAc (3ꢃ20 mL). The organic layer was dried with
anhydrous Na2SO4 and the solvent was removed. The resi-
due was purified by column chromatography using silica gel
with hexanes-ethyl acetate mixture (eluent: 15% ethyl ace-
tate in hexanes) to afford the product 10a; yield: 85%. We
followed the same procedure for the synthesis of other
Phenyl(8,9,11-trimethyl-5,8-dihydrocarbazoloACTHNUTRGNE[NUG 2,3-b]carba-
zol-6-yl)methanone (10e): Yield: 83%; mp 218–2208C; IR
1
carbazolo
G
N
(KBr): n=3384, 2987, 1688, 1527, 1292, 700 cmÀ1; H NMR
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
9
ÞÞ
These are not the final page numbers!

K. S. Prakash and Rajagopal Nagarajan
FULL PAPERS
(400 MHz, TMS, CDCl3): d=9.84 (bs, 1H), 8.87 (s, 1H),
8.63 (s, 1H), 8.22 (d, J=7.6 Hz, 1H), 7.86 (s, 1H), 7.78 (m,
2H), 7.58 (t, J=7.6 Hz, 1H), 7.52–7.44 (m, 4H), 7.34–7.33
(m, 2H), 7.05 (s, 1H), 3.63 (s, 3H), 2.76 (s, 3H), 2.53 (s,
3H); 13C NMR (100 MHz, TMS, CDCl3): d=198.2, 142.7,
142.2, 141.7, 141.6, 140.1, 131.8, 131.6, 130.3, 129.4, 128.7,
128.6, 127.2, 126.1, 123.7, 123.5, 123.4, 123.0, 120.5, 120.2,
119.7, 119.6, 118.7, 111.1, 110.7, 102.6 (aromatic C); 31.9,
21.1, 20.0 (aliphatic C); LC-MS (negative mode): m/z=452
(M+); anal. calcd. for C32H24N2O: C 84.93, H 5.35, N 6.19%;
found: C 84.85, H 5.31, N 6.25%.
7.51 (t, J=7.6 Hz, 2H), 7.30 (d, J=8.4 Hz, 1H), 7.26 (s,
1H), 7.03 (s, 1H), 6.92 (d, J=7.6 Hz, 1H), 3.69 (s, 3H), 2.71
(s, 3H), 2.43 (s, 3H); 13C NMR (100 MHz, TMS, DMSO-
d6 +CDCl3): d=197.6, 151.6, 142.1, 140.5, 140.1, 139.7, 136.5,
133.4, 131.9, 129.9, 129.86, 129.3, 128.4, 124.0, 123.8, 123.2,
122.9, 122.6, 120.2, 120.1, 118.9, 116.2, 112.1, 112.0, 106.4,
100.5 (aromatic C); 32.2, 21.1, 19.9 (aliphatic C); LC-MS
(positive mode): m/z=469 (M+H+); anal. calcd. for
C32H24N2O: C 82.03, H 5.16, N 5.98%; found: C 82.12, H,
5.22, N 6.07%.
Due to limited solubility, 13C NMR spectra of the follow-
ing three compounds (10j, 10k, 10l) could not be taken.
1-(8,9,11-Trimethyl-5,8-dihydrocarbazoloACTHNUGRTENUNG[2,3-b]carbazol-
Phenyl(5,8,9,11-tetramethyl-5,8-dihydrocarbazolo
carbazol-6-yl)methanone (10j): Yield: 85%; mp 208–2108C;
IR (KBr): n=2970, 1658, 1630, 1505, 1287, 870 cmÀ1
ACHTUNGTRENN[UNG 2,3-b]-
6-yl)hexan-1-one (10f): Yield: 79%; mp 196–1988C; IR
1
(KBr): n=3387, 2980, 1710, 1527, 1292, 800 cmÀ1; H NMR
;
(400 MHz, TMS, CDCl3): d=10.50 (bs, 1H), 8.80 (s, 1H),
8.70 (s, 1H), 8.17 (d, J=7.2 Hz, 1H), 7.95 (s, 1H), 7.89 (s,
1H), 7.46 (m, 2H), 7.29 (m, 1H), 7.10 (s, 1H), 4.13 (s, 3H),
3.38 (m, 2H), 2.85 (s, 3H), 2.55 (s, 3H), 2.01 (m, 2H), 1.42
(m, 4H), 0.93 (t, J=7.2 Hz, 3H); 13C NMR (100 MHz, TMS,
CDCl3): d=204.9, 143.1, 142.1, 141.7, 140.1, 131.7, 130.0,
128.9, 127.2, 126.3, 123.7, 123.6, 123.4, 122.9, 122.8, 120.6,
120.5, 120.2, 119.8, 118.7, 113.5, 110.8, 100.7 (aromatic C);
44.1, 32.5, 31.8, 25.8, 22.7, 21.1, 20.1, 14.0 (aliphatic C); LC-
MS (positive mode): m/z=447 (M+H+); anal. calcd. for
C31H30N2O: C 83.37, H 6.77, N 6.27%; found: C 83.25, H
6.71, N 6.35%.
1H NMR (500 MHz, TMS, DMSO-d6): d=8.88 (s, 1H), 8.73
(s, 1H), 8.25 (d, J=7.5 Hz, 1H), 7.93 (d, J=7.0 Hz, 1H),
7.87 (s, 1H), 7.79 (m, 3H), 7.63 (t, J=7.5 Hz, 1H), 7.49 (m,
2H), 7.33 (s, 1H), 7.29 (t, J=7.5 Hz, 1H), 7.04 (s, 1H), 3.89
(s, 3H), 3.55 (s, 3H), 2.78 (s, 3H), 2.50 (s, 3H); LC-MS (pos-
itive mode): m/z=467 (M+H+); anal. calcd. for C33H26N2O:
C 84.95, H 5.62, N 6.00%; found: C 84.85, H 5.56, N 6.08%.
(2-Fluoro-8,9,11-trimethyl-5,8-dihydrocarbazolo
ACHTUNGTRENUN[NG 2,3-b]car-
bazol-6-yl)(phenyl)methanone (10k): Yield: 84%; mp 226–
AHCTUNGTRENNUNG
2288C; IR (KBr): n=3405, 2850, 1648, 1610, 1507, 1315,
1
750 cmÀ1; H NMR (500 MHz, TMS, DMSO-d6): d=11.07 (s,
1H), 9.09 (s, 1H), 8.84 (s, 1H), 8.30 (s, 1H), 8.16 (d, J=
7.0 Hz, 1H), 7.95 (s, 1H), 7.77 (dd, J=7.0 & 1.5 Hz, 2H),
7.68 (t, J=7.0 Hz, 1H), 7.54–7.45 (m, 2H), 7.29 (m, 2H),
7.06 (s, 1H), 3.73 (s, 3H), 2.73 (s, 3H), 2.45 (s, 3H); LC-MS
(positive mode): m/z=471 (M+H+); anal. calcd. for
C32H23FN2O: C 81.68, H 4.93, N 5.95%; found: C 81.52, H
4.89, N 5.88%.
(2-Bromo-8,9,11-trimethyl-5,8-dihydrocarbazolo
bazol-6-yl)(phenyl)methanone (10g): Yield: 87%; mp 232–
2348C; IR (KBr): n=3399, 2976, 1670, 1537, 1292, 860 cmÀ1
ACHTUNGTRENUN[NG 2,3-b]car-
ACHTUNGTRENNUNG
;
1H NMR (400 MHz, TMS, CDCl3): d=9.81 (bs, 1H), 8.77 (s,
1H), 8.59 (s, 1H), 8.28 (d, J=2.0 Hz, 1H), 7.86 (s, 1H), 7.76
(m, 2H), 7.55 (m, 2H), 7.45 (t, J=8.0 Hz, 2H), 7.29 (m,
2H), 7.05 (s, 1H), 3.62 (s, 3H), 2.75 (s, 3H), 2.53 (s, 3H);
13C NMR (100 MHz, TMS, CDCl3): d=198.2, 142.6, 142.4,
141.4, 140.3, 140.1, 131.9, 131.8, 130.8, 129.7, 129.4, 128.8,
128.6, 126.4, 124.9, 123.7, 123.3, 123.2, 122.2, 119.7, 118.7,
112.8, 112.0, 111.3, 102.6 (aromatic C); 31.9, 21.0, 20.0 (ali-
phatic C); LC-MS (negative mode): m/z=530 (M+), 532
(M+2); anal. calcd. for C32H23BrN2O: C 72.32, H 4.36, N
5.27%; found: C 72.45, H 4.41, N 5.18%.
Methyl 6-benzoyl-8,9,11-trimethyl-5,8-dihydrocarbazolo-
AHCTUNGTRENNUNG
;
DMSO-d6): d=11.36 (s, 1H), 9.08 (s, 1H), 8.88 (s, 1H), 8.78
(s, 1H), 8.15 (t, J=7.0 Hz, 1H), 7.95–7.49 (m, 7H), 7.27 (s,
1H), 7.02 (s, 1H), 3.94 (s, 3H), 3.74 (s, 3H), 2.74 (s, 3H),
2.45 (s, 3H); LC-MS (negative mode): m/z=486 (MÀH+);
anal. calcd. for C34H26N2O3: C 79.98, H 5.13, N 5.49%;
found: C 79.85, H 5.21, N 5.56%.
(2-Methoxy-8,9,11-trimethyl-5,8-dihydrocarbazolo
ACHTUNGTRENN[UNG 2,3-b]-
carbazol-6-yl)(phenyl)methanone (10h): Yield: 90%; mp
ACHTUNGTRENNUNG
228–2308C; IR (KBr): n=3388, 2980, 1705, 1638, 1527,
1
1292, 700 cmÀ1; H NMR (400 MHz, TMS, CDCl3): d=9.77
(bs, 1H), 8.80 (s, 1H), 8.60 (s, 1H), 7.85 (s, 1H), 7.76 (d, J=
7.2 Hz, 2H), 7.71 (d, J=2.0 Hz, 1H), 7.58 (t, J=7.2 Hz,
1H), 7.45 (t, J=8.0 Hz, 2H), 7.35–7.30 (m, 2H), 7.12 (dd,
J=8.4 & 2.4 Hz, 1H), 7.04 (s, 1H), 3.99 (s, 3H), 3.61 (s,
3H), 2.74 (s, 3H), 2.52 (s, 3H); 13C NMR (100 MHz, TMS,
CDCl3): d=198.1, 154.5, 143.4, 142.2, 141.7, 136.3, 131.7,
131.6, 130.8, 129.4, 128.7, 128.6, 126.3, 123.6, 123.5, 123.4,
123.3, 122.8, 119.7, 119.6, 118.6, 115.2, 111.3, 110.9, 104.5,
102.6 (aromatic C); 56.2, 31.9, 21.0, 20.0 (aliphatic C); LC-
MS (positive mode): m/z=483 (M+H+); anal. calcd. for
C33H26N2O2: C 82.13, H 5.43, N 5.81%; found: C 82.23, H
5.48, N 5.76%.
General Procedure for the Synthesis of Indolo
carbazole Derivatives
ACHTUNGTRENN[UNG 2,3-b]-
An oven-dried 10-mL round-bottomed flask equipped with
a Teflon-coated magnetic stirring bar was charged with
0.5 mmol of 1-methyl-2-(2-phenylethynyl)-1H-indole-3-car-
baldehyde (11b), 10 mol% of CuACHTNUTRGNEUNG(OTf)2, and 5 mL of dry
1,2-dichloroethane. To this 0.5 mmol of indole (9a) was
added. Then, the reaction mixture was stirred at 808C for
2 h. Then, solvent was removed under reduced pressure.
The crude reaction mixture was then poured over water and
extracted with EtOAc (3ꢃ20 mL). The organic layer was
dried over anhydrous Na2SO4 and the solvent was removed.
The residue was purified by column chromatography using
silica gel (eluent: 15% ethyl acetate in hexane). The product
12a was eluted as a light yellow solid; yield: 31%. We fol-
lowed the same procedure for the synthesis of the other
(2-Hydroxy-8,9,11-trimethyl-5,8-dihydrocarbazolo
ACHTUNGTRENN[UNG 2,3-b]-
carbazol-6-yl)(phenyl)methanone (10i): Yield: 88%; mp
ACHTUNGTRENNUNG
242–2448C; IR (KBr): n=3390, 3300, 2916, 1660, 1638,
1
1527, 1292, 700 cmÀ1; H NMR (400 MHz, TMS, DMSO-d6 +
CDCl3): d=10.73 (s, 1H), 9.12 (s, 1H), 8.95 (s, 1H), 8.82 (s,
1H), 7.89 (s, 1H), 7.75 (d, J=7.2 Hz, 2H), 7.65 (m, 2H),
indoloACTHNUTRGENUG[N 2,3-b]carbazole derivatives (12b–12d)
10
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A General Method for the Synthesis of 5H-Benzo[b]-, CarbazoloACTHNUGTRENNUG[2,3-b]- and IndoloACHUTNGTREN[NUGN 2,3-b]carbazole
(5-Methyl-5,7-dihydroindolo
yl)methanone (12a): Yield: 31%; mp 266–2688C; IR (KBr):
n=3435, 2968, 1518, 1455, 1010, 805 cmÀ1 1H NMR
G
E
0.5 mmol of 9-ethyl-6-methyl-2-(2-phenylethynyl)-9H-carba-
zole-3-carbaldehyde (6b), 10 mol% of PdCl2, and 5 mL of
DMSO. To this 0.5 mmol of indole (9a) was added. Then,
the reaction mixture was stirred at room temperature. After
completion of the reaction as monitored by TLC, the crude
reaction mixture was poured over water and extracted with
dichloromethane (3ꢃ20 mL). The organic layer was dried
over anhydrous Na2SO4 and the solvent was removed under
reduced pressure. The residue was purified by column chro-
matography using silica gel (eluent: 20% ethyl acetate in
hexanes). The product 13 was eluted as a viscous liquid;
yield: 78%. IR (neat): n=3056, 2965, 2912, 1457, 1045, 1035,
(400 MHz, TMS, CDCl3): d=9.58 (bs, 1H), 8.90 (s, 1H),
8.21–8.17 (m, 2H), 7.75 (d, J=7.6 Hz, 2H), 7.55 (t, J=
7.2 Hz, 1H), 7.44–7.39 (m, 5H), 7.34–7.29 (m, 2H), 7.23 (d,
J=8.0 Hz, 1H), 3.19 (s, 3H); 13C NMR (100 MHz, TMS,
CDCl3): d=195.6, 142.6, 140.8, 140.2, 139.8, 133.0, 129.5,
125.4, 125.2, 123.8, 123.4, 120.2, 120.0, 119.6, 119.3, 118.7,
118.4, 116.7, 110.8, 109.1, 103.4 (aromatic C); 35.1 (aliphatic
C); LC-MS (positive mode): m/z=375 (M+H+); anal.
calcd. for C26H18N2O: C 83.40, H 4.85, N 7.48%; found: C
83.31, H 4.81, N 7.56%.
769 cmÀ1 1H NMR (500 MHz, TMS, CDCl3): d=8.03 (bs,
;
Phenyl{5-(benzenesulfonyl)-5,7-dihydroindolo
[2,3-b]car-
1H), 7.92 (d, J=8.0 Hz, 1H), 7.71–7.69 (m, 3H), 7.66 (s,
1H), 7.37 (d, J=8.0 Hz, 1H), 7.29–7.28 (m, 3H), 7.27 (s,
1H), 7.23–7.20 (m, 2H), 7.18–7.16 (m, 2H), 6.87 (s, 1H),
6.85 (d, J=2.5 Hz, 1H), 6.67 (s, 1H), 4.35 (q, J=7.0 Hz,
2H), 2.46 (s, 3H), 1.45 (t, J=7.0 Hz, 3H); 13C NMR
(125 MHz, TMS, CDCl3): d=152.3, 140.4, 138.5, 136.6,
135.1, 130.3, 128.4, 128.2, 128.1, 126.7, 126.5, 125.3, 125.0,
123.4, 122.3, 122.2, 121.2, 120.3, 120.1, 120.0, 117.1, 116.4,
111.2, 108.1, 103.2, 102.0 (aromatic C); 74.8, 37.7, 21.3, 13.9
(aliphatic C); LC-MS (negative mode): m/z=453 (MÀH+),
454 (M+); anal. calcd. for C32H26N2O: C 84.55, H 5.77, N
6.16%; found: C 84.41, H 5.71, N 6.25%.
bazol-6-yl}methanone (12b): Yield: 42%; mp 254–2568C; IR
(KBr): n=3415, 2970, 1718, 1650, 1628, 1537, 1292,
908 cmÀ1 1H NMR (400 MHz, TMS, DMSO-d6 +CDCl3):
;
d=10.80 (s, 1H), 8.60 (s, 1H), 8.08 (d, J=7.6 Hz, 1H), 7.90
(m, 1H), 7.82 (m, 1H), 7.66–7.60 (m, 4H), 7.47 (t, J=
7.2 Hz, 1H), 7.39–7.31 (m, 4H), 7.20 (m, 2H), 7.00–6.95 (m,
4H); 13C NMR (100 MHz, TMS, DMSO-d6 +CDCl3): d=
193.3, 141.2, 139.6, 139.1, 138.1, 135.4, 134.4, 133.4, 132.1,
129.3, 129.1, 128.0, 127.9, 126.3, 125.9, 125.5, 123.2, 121.7,
121.5, 119.8, 119.5, 119.1, 117.9, 114.1, 111.8, 111.2, 110.7 (ar-
omatic C); LC-MS (positive mode): m/z=501 (M+H+);
anal. calcd. for C31H20N2O3S: C 74.38, H 4.03, N 5.60%;
found: C 74.26, H 4.10, N 5.52%.
{2-Hydroxy-7-(benzenesulfonyl)-5,7-dihydroindolo
carbazol-6-yl}
242–2448C; IR (KBr): n=3418, 3320, 2990, 1728, 1670,
1638, 1437, 1382, 710 cmÀ1 1H NMR (400 MHz, TMS,
DMSO-d6): d=11.15 (s, 1H), 9.17 (bs, 1H), 8.92 (s, 1H),
8.31 (s, 1H), 8.05–7.93 (m, 2H), 7.62–7.43 (m, 9H), 7.17–
6.97 (m, 5H); 13C NMR (100 MHz, TMS, DMSO-d6): d=
193.2, 151.8, 151.8, 139.8, 138.5, 135.7, 135.5, 134.7, 133.1,
129.7, 129.3, 129.1, 128.9, 126.7, 126.4, 123.6, 122.9, 121.1,
120.2, 119.7, 118.3, 116.6, 115.6, 113.2, 112.7, 111.5, 105.4 (ar-
omatic C); LC-MS (negative mode): m/z=515 (MÀH+);
anal. calcd. for C31H20N2O4S: C 72.08, H 3.90, N 5.42%;
found: C 72.15, H 3.95, N 5.36%.
ACHTUNGTRENN[UNG 2,3-b]-
(phenyl)methanone (12c): Yield: 48%; mp Acknowledgements
;
We thank DST (Project number: SR/S1/OC-70/2008) for fi-
nancial assistance and for the single-crystal X-ray diffractom-
eter facility in our school. K. S. P. thanks UGC for a Junior
Research Fellowship.
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Procedure for the Synthesis of 6-Ethyl-1,6-dihydro-1-
(1H-indol-3-yl)-9-methyl-3-phenylpyranoACHTNUTRGNE[UNG 4,3-b]car-
bazole (13)
An oven-dried 10-mL round-bottomed flask equipped with
a Teflon-coated magnetic stirring bar was charged with
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K. S. Prakash and Rajagopal Nagarajan
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A General Method for the Synthesis of 5H-Benzo[b]-, CarbazoloACTHNUGTRENNUG[2,3-b]- and IndoloACHUTNGTREN[NUGN 2,3-b]carbazole
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FULL PAPERS
14 A General Method for the Synthesis of 5H-Benzo[b]-,
CarbazoloACHTUNGTRENNUNG[2,3-b]- and IndoloCAHTUNGTRENN[UGN 2,3-b]carbazole Derivatives
via Copper(II) Triflate-Catalyzed Heteroannulation
Adv. Synth. Catal. 2012, 354, 1 – 14
K. S. Prakash, Rajagopal Nagarajan*
14
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