A rapid and efficient entry to synthesis of quino and chromenocarbazoles via Ullmann-Goldberg condensation

Article abstract of DOI:10.1016/j.tet.2009.05.061

An efficient two-step method for the preparation of quino and chromenocarbazoles via Ullmann-Goldberg condensation of 3-aminocarbazole and 3-hydroxy-9-ethylcarbazole with o-halobenzoic acids followed by cyclization with POCl₃ has been described

Full text of DOI:10.1016/j.tet.2009.05.061

Tetrahedron 65 (2009) 6050–6056
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A rapid and efficient entry to synthesis of quino and chromenocarbazoles
via Ullmann–Goldberg condensation
*
Ramu Meesala, Rajagopal Nagarajan
School of Chemistry, University of Hyderabad, Central University (P.O.), Hyderabad-500 046, India
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient two-step method for the preparation of quino and chromenocarbazoles via Ullmann–
Goldberg condensation of 3-aminocarbazole and 3-hydroxy-9-ethylcarbazole with o-halobenzoic acids
followed by cyclization with POCl3 has been described.
Received 27 January 2009
Received in revised form 11 May 2009
Accepted 22 May 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Available online 28 May 2009
CH3
1. Introduction
H3C
CH3
O
CH3
N
O
H3C
HO
Aryl and heteroarylcarbazoles are important classes of bi-
ologically active compounds that include notable alkaloids of
pharmaceutical interest1 are heteroaryl annulated derivatives of
carbazole. It is well established that the pyridocarbazole ring sys-
tem is an appropriate skeleton to design DNA intercalating drugs.2
For example, ellipticine3 and its natural analogues have received
a vast amount of attention because of their anticancer properties
due to the interaction with DNA. Pyranocarbazole alkaloids4 such as
glycoborinine and euchrestifoline are an important class of com-
pounds and glycoborinine, isolated from Glycosmis arborea, applied
against fever, liver complaints, and certain other diseases.5
As a result of their significant potential as therapeutics, interest
has grown in the development of methods for the efficient and
rapid synthesis of the derivatives of pyrido and pyranocarbazoles
especially because the current methods, which involve multi-step
reactions, lower yields, longer reaction times, and high cost of
palladium,1b,3b,i,k are unsatisfactory. Herein, therefore, we de-
scribed a simple, economical, and effective two-step procedure for
the synthesis of quino and chromenocarbazoles based on C–N and
C–O bond formation through Ullmann–Goldberg condensation6
followed by intramolecular Friedel–Crafts7 cyclization with POCl3.
Since the starting materials o-halobenzoic acids can be readily
prepared by diazotization of anthranilic acid8 derivatives and the
reagents CuI and POCl3 are relatively cheap, our synthetic meth-
odology for the preparation of quino and chromenocarbazoles is
simple and efficient.
CH3
CH3
N
H
N
H
N
H
CH3
O
Ellipticine
Glycoborinine
Euchrestifoline
2. Results and discussion
As shown in Scheme 1, we have carried out the condensation of
3-amino-9-ethylcarbazole 1 with various o-iodobenzoic acids 2a–e
in presence of CuI (0.1 equiv) and K2CO3 (2.0 equiv) without any
ligand in DMSO at 80 ꢀC. The reaction also works with 3-amino-
carbazole and the corresponding product 3a is obtained in 71%
yield. Facile reaction without any ligand is due to the activation of
halogens with the ortho carboxylic group.9 In the absence of CuI, no
condensation was observed. Outcome of the condensations is
presented in Table 1. The structure of 3b was also confirmed by the
single crystal X-ray analysis10 and Figure 1 shows the ORTEP dia-
gram of 3b. Due to the activation of the strong electron-with-
drawing nitro group, the time required for the formation of 3e was
comparatively reduced to half of the other iodobenzoic acids. Since
the order for ease of halogen displacement follows as I>Br>Cl, 2-
bromobenzoic acid has required longer reaction time.
Interestingly, diazocarbazole was obtained as a by product
(<5%) during the coupling between 3-amino-9-ethylcarbazole and
o-halobenzoic acids. The structure of diazocarbazole was also
confirmed by single crystal X-ray analysis.10 The aerobic oxidation
of CuI produces the active Cu(II) species, which oxidizes the ami-
nocarbazole to the corresponding diazocarbazole.11
The products 3a–e were subjected to cyclization with POCl3 as
shown in Scheme 1. At 60 ꢀC, 3a undergoes facile cyclization to give
* Corresponding author. Tel.: þ91 040 66794831; fax: þ91 040 23012460.
E-mail address: rnsc@uohyd.ernet.in (R. Nagarajan).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.05.061

R. Meesala, R. Nagarajan / Tetrahedron 65 (2009) 6050–6056
6051
R1
R1
NH2
+
X
COOH
O
COOH
NH
NH
CuI, K2CO3
POCl3
60 °C
N
R
DMSO, 80 °C
N
R
R1
N
R
1a-b
2a-e
3a-e
4a-e
POCl3
120 °C
R1
Cl
N
N
R1
+
N
R
N
R
Cl
6a-e
5a-e
Minor
Major
Scheme 1. Synthesis of quinocarbazoles.
Table 1
Synthesis of quinocarbazoles
products 6a–e (Scheme 1). These two isomers have been identified
from 1H NMR spectrum. The presence of two singlets at
8.85 and
d
7.96 ppm differentiate the regioisomer 6c from the other
regioisomer 5c in which two doublets are present in the same re-
gion. The structures of these two isomers were also confirmed by
the single crystal X-ray analysis10 (see Fig. 2).
The same method was successfully extended to 3-hydroxy-9-
ethylcarbazole. 3-Hydroxy-9-ethylcarbazole 7 condensed with o-
halobenzoic acids to provide the corresponding products 8a–d in
good yield and the results were summarized in Table 2. As shown in
Scheme 2, the condensed products 8a–d underwent cyclization to
the corresponding chromenocarbazoles after treating with excess
of POCl3. In this case, only one regioisomer 9a–d was formed at
60 ꢀC. The structure of 9a was also confirmed by single crystal X-ray
analysis10 as shown in Figure 3.
S. no.
1
R
R1
H
X
I
Condensed
product
Time
(h)
Yield
(%)
Cyclized
product
Time
(h)
Yield
(%)
H
3a
3b
3c
3d
3e
3a
1
73
4a
5a
6a
4b
5b
6b
4c
5c
6c
4d
5d
6d
4e
5e
6e
4a
5a
6a
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
71
73
10
76
78
12
73
74
14
72
75
13
75
75
12
76
78
12
2
3
4
5
6
Et
Et
Et
Et
Et
H
I
1
73
72
70
74
64
Cl
I
1
Br
NO2
H
I
1
I
0.5
3
3. Conclusion
Br
In conclusion, we have developed a new, fast, and efficient route
to the synthesis of quino and chromenocarbazoles via Ullmann–
Goldberg condensation followed by intramolecular Friedel–Crafts
cyclization with POCl3.
the corresponding product 4a in good yield. The reaction works
well for other substituted o-halobenzoic acids (Scheme 1 and Table
1). The structure of 4c was also confirmed by the single crystal X-
ray analysis10 (see Fig. 2). When the reaction was performed at
120 ꢀC, two regioisomeric quinocarbazoles were formed. Com-
pounds 5a–e were formed as a major products along with minor
4. Experimental
4.1. General
The procedure does not require inert atmosphere. All the
products obtained were purified by column chromatography using
silica gel (100–200 mesh). Hexane was used as a co-eluent. 1H and
13C NMR were recorded in Brucker 400 and 100 MHz spectrome-
ters, respectively. The chemical shifts are reported in parts per
million downfield to TMS (
central CDCl3 resonance (
d
¼0) for 1H NMR and relative to the
d
¼77.0) for 13C NMR. We have observed
that the compounds 5a– and 6a– were converting to their corre-
sponding keto compounds 4a– in DMSO-d6. This may be due to the
presence of moisture in DMSO-d6. So, later we have recorded 1H
and 13C NMR of the compounds 4a–e and 6a– in CDCl3. LC–MS was
used for the mass spectral analysis. IR spectra were recorded on
a FT-IR spectrometer using KBr pellets. Elemental analysis was
carried out in CHN analyzer EA 1112, Thermo Finnigan. Elemental
Figure 1. ORTEP diagram of 3b.

6052
R. Meesala, R. Nagarajan / Tetrahedron 65 (2009) 6050–6056
Figure 2. ORTEP diagrams of 4c, 5c, and 6c.
Table 2
Synthesis of chromenocarbazoles
S. no.
R
X
Condensed
product
Time
(h)
Yield
(%)
Cyclized
product
Time
(h)
Yield
(%)
1
2
3
4
5
H
Cl
Br
NO2
H
I
I
I
I
8a
8b
8c
8d
8a
8
8
8
6
10
70
74
72
77
61
9a
9b
9c
9d
9a
2
2
2
2
2
73
75
73
71
73
Br
analysis was carried out at elemental analysis lab in School of
Chemistry, University of Hyderabad. Melting points were measured
in open capillary tubes and are uncorrected.
4.2. Preparation of 2-(9H-carbazolylamino)benzoic acid (3a)
A mixture of 3-amino-9H-carbazole (0.20 g, 1.0 mmol), 2-iodo-
benzoic acid (0.25 g, 1.0 mmol), CuI (19 mg, 0.1 mmol), and K2CO3
(0.276 g, 2 mmol) in DMSO was heated at 80 ꢀC for 1 h. Then the
reaction mixture was poured in water and extracted with ethyl-
acetate (3ꢁ20 mL). Then the solvent was evaporated under reduced
pressure and the crude material was purified by column chroma-
tography (15% ethylacetate/hexane). Rf (30% ethylacetate/hexane)
Figure 3. ORTEP diagram of 9a.
0.40. Mp 163–164 ꢀC; IR (KBr): 3387, 1649, 1575, 1493, 1238, 1126,
748 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 8.86 (1H, s), 8.19 (1H,
d, J¼4.0 Hz), 8.13 (1H, d, J¼8.0 Hz), 8.01 (1H, d, J¼8.0 Hz), 7.78 (1H, t,
J¼6.0 Hz), 7.64 (1H, t, J¼8.0 Hz), 7.48 (1H, d, J¼8.0 Hz), 7.37 (1H, t,
R
R
COOH
OH
X
O
O
COOH
O
CuI, K2CO3
+
POCl3
60 °C
DMSO, 80 °C
N
Et
N
Et
N
Et
9a-d
R
7
2a-d
8a-d
Scheme 2. Synthesis of chromenocarbazoles.

R. Meesala, R. Nagarajan / Tetrahedron 65 (2009) 6050–6056
6053
J¼8.0 Hz), 7.27–7.24 (2H, m), 7.06 (1H, d, J¼8.0 Hz), 6.99 (1H, d,
poured onto the crushed ice and then neutralized with 10% aq
NaOH solution. Then it was extracted with dichloromethane
(3ꢁ10 mL) and the solvent was evaporated and the crude material
was purified by column chromatography (30% ethylacetate/hexane)
to obtain the pure product 4a. Rf (40% ethylacetate/hexane) 0.50.
When the reaction was performed at 120 ꢀC, 5a and 6a were
obtained in major and minor quantities, respectively. Compounds
5a and 6a were purified by column chromatography (5% ethyl-
acetate/hexane). Rf (10% ethylacetate/hexane) 0.43.
J¼8.0 Hz); 13C NMR (100 MHz, TMS, CDCl3)
d: 168.8, 144.6, 142.9,
141.1,135.9,134.3,132.8,130.9,130.2,129.5,128.8,127.5,123.0,121.7,
120.8, 119.9, 117.1, 110.2, 109.1; LC–MS: m/z¼303 (MþHþ), positive
mode. Anal. Calcd for molecular formula C19H14N2O2: C, 75.48; H,
4.67; N, 9.27%. Found: C, 75.52; H, 4.61; N, 9.32%.
4.3. 2-(9-Ethyl-9H-carbazolylamino)benzoic acid (3b)
Mp 173–174 ꢀC; IR (KBr): 3343, 2986, 1666, 1580, 1447, 1242,
1159, 735 cmꢂ1; 1H NMR (400 MHz, TMS, DMSO-d6)
d: 9.63 (1H, br
4.8. 8,13-Dihydro-5H-indolo[3,2-a]acridin-13-one (4a)
s), 8.13 (1H, d, J¼7.6 Hz), 8.04 (1H, s), 7.87 (1H, d, J¼8.0 Hz), 7.62–
7.57 (2H, m), 7.43 (1H, t, J¼7.6 Hz), 7.35–7.27 (2H, m), 7.15 (1H, t,
J¼7.6 Hz), 6.94 (1H, d, J¼8.4 Hz), 6.66 (1H, t, J¼7.6 Hz), 4.43 (2H, q,
J¼7.2 Hz, N–CH2), 1.31 (3H, t, J¼7.2 Hz, CH3); 13C NMR (100 MHz,
Mp 296–298 ꢀC; IR (KBr): 3395, 2067, 1747, 1581, 1469, 1261,
1099, 804 cmꢂ1; 1H NMR (400 MHz, TMS, DMSO-d6)
d: 11.81 (1H, s,
NH), 11.71 (1H, s, NH), 9.81 (1H, d, J¼8.0 Hz), 8.38 (1H, d, J¼8.0 Hz),
8.00 (1H, d, J¼8.0 Hz), 7.69–7.63 (2H, m), 7.58–7.51 (2H, m), 7.38
(1H, t, J¼6.0 Hz), 7.25 (1H, t, J¼6.0 Hz), 7.15 (1H, t, J¼6.0 Hz); 13C
TMS, DMSO-d6) d: 170.7, 150.2, 140.5, 137.5, 134.7, 132.2, 132.0,
126.3, 123.8, 123.4, 122.4, 121.1, 119.0, 116.7, 116.4, 113.2, 111.4, 110.2,
109.5, 37.5, 14.1; LC–MS: m/z¼331 (MþHþ), positive mode; Anal.
Calcd for molecular formula C21H18N2O2: C, 76.34; H, 5.49; N, 8.48%.
Found: C, 76.18; H, 5.45; N, 8.37%.
NMR (100 MHz, TMS, DMSO-d6) d: 177.7, 140.4, 139.9, 137.9, 135.2,
132.6, 128.6, 126.6, 125.6, 123.6, 121.8, 120.9, 119.6, 118.2, 117.9, 117.2,
117.1, 116.6, 111.1; LC–MS: m/z¼285 (MþHþ), positive mode. Anal.
Calcd for molecular formula C19H12N2O: C, 80.27; H, 4.25; N, 9.85%.
Found: C, 80.15; H, 4.29; N, 9.96%.
4.4. 5-Chloro-2-(9-ethyl-9H-carbazolylamino)-
benzoic acid (3c)
4.9. 8-Ethyl-8,13-dihydro-5H-indolo[3,2-a]-
acridin-13-one (4b)
Mp 227–229 ꢀC; IR (KBr): 3341, 2967, 1668, 1572, 1435, 1227,
1140, 816, 717 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3þDMSO-d6)
d:
9.27 (1H, s), 7.62 (1H, d, J¼7.6 Hz), 7.55–7.53 (2H, m), 7.08–7.02 (3H,
m), 6.94–6.92 (1H, m), 6.81–6.75 (2H, m), 6.57 (1H, d, J¼9.2 Hz),
3.96 (2H, q, J¼7.2 Hz, N–CH2), 1.02 (3H, t, J¼7.2 Hz, CH3); 13C NMR
Mp 277–278 ꢀC; IR (KBr): 3266, 2930, 2072, 1738, 1584, 1474,
1150, 804, 557 cmꢂ1 1H NMR (400 MHz, TMS, DMSO-d6)
; d: 12.15
(1H, s, NH), 9.89 (1H, d, J¼8.0 Hz), 8.38 (1H, d, J¼8.0 Hz), 8.18 (1H, d,
J¼9.2 Hz), 7.76 (1H, d, J¼8.0 Hz), 7.69 (1H, d, J¼8.0 Hz), 7.65–7.61
(2H, m), 7.46 (1H, t, J¼7.3 Hz), 7.26 (1H, t, J¼8.0 Hz), 7.19 (1H, t,
J¼8.0 Hz) 4.56 (2H, q, J¼8.0 Hz, N–CH2), 1.32 (3H, t, J¼8.0 Hz, CH3);
(100 MHz, TMS, CDCl3þDMSO-d6)
d: 172.0,151.3,142.6,139.8,136.0,
134.4, 133.8, 133.4, 128.3, 126.0, 125.7, 124.6, 122.7, 121.1, 119.0, 117.0,
114.4, 111.6, 111.0, 39.8, 16.1; LC–MS: m/z¼364.5 (M), 366.5 (Mþ2).
Anal. Calcd for molecular formula C21H17ClN2O2: C, 69.14; H, 4.70;
N, 7.68%. Found: C, 69.14; H, 4.72; N, 7.93%.
13C NMR (100 MHz, TMS, DMSO-d6)
d: 180.1, 142.6, 142.5, 140.6,
137.4, 135.4, 131.5, 129.1, 128.4, 125.8, 124.3, 123.6, 120.9, 120.4,
120.2, 119.8, 119.6, 119.4, 111.7, 39.9, 17.0; LC–MS: m/z¼313 (MþHþ),
positive mode. Anal. Calcd for molecular formula C21H16N2O: C,
80.75; H, 5.16; N, 8.97%. Found: C, 80.61; H, 5.14; N, 9.00%.
4.5. 5-Bromo-2-(9-ethyl-9H-carbazolylamino)-
benzoic acid (3d)
Mp 181–183 ꢀC; IR (KBr): 3343, 2920, 1667, 1611, 1568, 1493,
4.10. 2-Chloro-8-ethyl-8,13-dihydro-5H-indolo-
[3,2-a]acridin-13-one (4c)
1377, 1229, 814, 744 cmꢂ1 1H NMR (400 MHz, TMS, DMSO-d6)
; d:
8.09 (1H, s), 7.99 (1H, s), 7.55 (2H, d, J¼5.2 Hz), 7.42 (2H, s), 7.28 (2H,
s), 7.13 (2H, s), 7.01 (2H, s), 4.40 (2H, s, N–CH2), 1.29 (3H, m, CH3);
Mp 315–317 ꢀC; IR (KBr): 3439, 2971, 2928,1632,1557,1474,1321,
13C NMR (100 MHz, TMS, CDCl3þDMSO-d6)
d
: 169.9, 149.1, 140.3,
1024, 812 cmꢂ1; 1H NMR (400 MHz, TMS, DMSO-d6)
d: 12.35 (1H, s,
137.6, 133.7, 131.6, 131.2, 125.9, 123.8, 123.5, 122.4, 120.4, 119.9, 118.7,
116.9, 114.6, 112.0, 109.1, 108.6, 37.6, 13.8; LC-MS: m/z¼408 (M), 410
(Mþ2); Anal. Calcd for molecular formula C21H17BrN2O2: C, 61.63;
H, 4.19; N, 6.84%. Found: C, 61.67; H, 4.18; N, 6.82%.
NH), 9.84 (1H, d, J¼8.4 Hz), 8.30 (1H, s), 8.20 (1H, d, J¼9.2 Hz), 7.76
(1H, d, J¼8.0 Hz), 7.72–7.63 (3H, m), 7.46 (1H, t, J¼8.0 Hz), 7.20 (1H, t,
J¼8.0 Hz), 4.56 (2H, q, J¼8.0 Hz, N–CH2), 1.31 (3H, t, J¼8.0 Hz, CH3);
13C NMR (100 MHz, TMS, DMSO-d6)
d: 176.4, 140.0, 138.5, 137.9,
135.0,132.8,128.8,126.0,125.4,125.3,124.1,123.1,122.4,119.8,118.5,
117.9, 117.6, 116.9, 109.2, 37.4, 14.5; LC–MS: m/z¼346.5 (M), 348.5
(Mþ2); Anal. Calcd for molecular formula C21H15ClN2O, C, 72.73; H,
4.36; N, 8.08%. Found: C, 72.69; H, 4.40; N, 8.10%.
4.6. 5-Nitro-2-(9-ethyl-9H-carbazolylamino)benzoic acid (3e)
Mp 177–178 ꢀC; IR (KBr): 3478, 2974, 2924, 1717, 1589, 1522,
1492, 1319, 1231, 1146, 928, 802 cmꢂ1 1H NMR (400 MHz, TMS,
;
CDCl3þDMSO-d6)
d
: 10.45 (1H, s), 8.77 (1H, s), 7.98–7.94 (4H, m),
4.11. 2-Bromo-8-ethyl-8,13-dihydro-5H-indolo-
[3,2-a]acridin-13-one (4d)
7.49 (1H, d, J¼8.0 Hz), 7.30 (2H, d, J¼8.0 Hz), 7.14 (2H, s), 6.89 (1H, d,
J¼8.0 Hz), 4.36 (2H, q, J¼6.0 Hz, N–CH2), 1.37 (3H, s, CH3); 13C NMR
(100 MHz, TMS, CDCl3þDMSO-d6)
d
: 169.5, 148.8, 140.1, 137.3, 133.5,
Mp 301–302 ꢀC; IR (KBr): 3271, 2967, 2924, 2864, 1628, 1578,
131.4,130.9, 125.8, 123.5, 123.2, 122.1, 120.2, 119.5,118.6,116.5,114.5,
111.9, 109.1, 108.6, 37.3, 13.6; LC–MS: m/z¼376 (MþHþ), positive
mode; Anal. Calcd for molecular formula C21H17N3O4: C, 67.19; H,
4.56; N, 11.19%. Found: C, 67.21; H, 4.52; N, 11.32%.
1557, 1022, 812 cmꢂ1; 1H NMR (400 MHz, TMS, DMSO-d6)
d: 12.35
(1H, s, NH), 9.84 (1H, d, J¼8.4 Hz), 8.45 (1H, d, J¼2.4 Hz), 8.19 (1H, d,
J¼8.8 Hz), 7.82–7.75 (2H, m), 7.64–7.61 (2H, m), 7.46 (1H, t,
J¼8.0 Hz), 7.20 (1H, t, J¼7.8 Hz), 4.55 (2H, q, J¼7.2 Hz, N–CH2), 1.31
(3H, t, J¼6.8 Hz, CH3); 13C NMR (100 MHz, TMS, DMSO-d6)
d: 178.9,
4.7. Preparation of 8,13-dihydro-5H-indolo[3,2-a]acridin-13-
one (4a) and 13-chloro-8H-indolo[3,2-a]acridine (5a)
142.6, 141.3, 140.5, 137.9, 137.6, 131.3, 131.1, 128.6, 125.6, 125.5, 122.5,
121.1, 120.5, 120.3, 119.6, 119.0, 115.7, 111.8, 39.9, 17.0; LC–MS: m/
z¼390 (M), 392 (Mþ2); Anal. Calcd for molecular formula
C21H15BrN2O: C, 64.46; H, 3.86; N, 7.16%. Found: C, 64.41; H, 3.84; N,
7.20%.
2-(9H-Carbazolylamino)benzoic acid (0.3 g, 1.0 mmol) in POCl3
(5 mL) was heated for 1 h at 60 ꢀC. Then the reaction mixture was

6054
R. Meesala, R. Nagarajan / Tetrahedron 65 (2009) 6050–6056
4.12. 2-Nitro-8-ethyl-8,13-dihydro-5H-indolo[3,2-a]-
acridin-13-one (4e)
m/z¼408.5 (M), 410.5 (Mþ2), 412.5 (Mþ4). Anal. Calcd for molec-
ular formula C21H14BrClN2: C, 61.56; H, 3.44; N, 6.84%. Found: C,
60.63; H, 3.10; N, 6.24%.
Mp 320–322 ꢀC; IR (KBr): 3418, 2924, 2857, 1616, 1555, 1516,
1460, 1331, 723 cmꢂ1; 1H NMR (400 MHz, TMS, DMSO-d6)
d
: 12.61
4.17. 2-Nitro-13-chloro-8-ethyl-8H-indolo[3,2-a]acridine (5e)
(1H, s, NH), 9.79 (1H, d, J¼12.0 Hz), 9.12 (1H, s), 8.38 (1H, dd,
J¼8.0 Hz), 8.24 (1H, d, J¼8.0 Hz), 7.76 (1H, d, J¼8.0 Hz), 7.71–7.66
(2H, m), 7.50 (1H, t, J¼4.0 Hz), 7.23 (1H, t, J¼4.0 Hz), 4.57 (2H, q,
J¼8.0 Hz, N–CH2), 1.33 (3H, t, J¼8.0 Hz, CH3); 13C NMR (100 MHz,
Mp 255–257 ꢀC; IR (KBr): 2962, 1708, 1575, 1421, 1337, 1256,
1069, 826, 647, 551 cmꢂ1 1H NMR (400 MHz, TMS, CDCl3)
; d: 9.44
(1H, s), 8.79 (1H, d, J¼8.28 Hz), 8.38 (1H, d, J¼7.6 Hz), 8.24 (1H, d,
J¼8.0 Hz), 8.09 (1H, d, J¼8.0 Hz), 8.03 (1H, d, J¼7.8 Hz), 7.57 (1H, d,
J¼7.3 Hz), 7.50 (1H, t, J¼7.7 Hz), 7.38 (1H, t, J¼8.0 Hz) 4.55 (2H, q,
J¼7.1 Hz, N–CH2), 1.52 (3H, t, J¼7.0 Hz, CH3); 13C NMR (100 MHz,
TMS, DMSO-d6) d: 179.8, 145.9, 143.4, 142.9, 140.0, 138.4, 131.2,
129.3, 126.6,125.4, 122.8, 121.3,120.8,120.5, 119.6,119.0,117.3,114.7,
111.9; 40.0, 17.0; LC–MS: m/z¼356 (MꢂHþ), negative mode. Anal.
Calcd for molecular formula C21H15N3O3: C, 70.58; H, 4.23; N,
11.76%. Found: C, 7.60; H, 4.21; N, 11.73%.
TMS, CDCl3) d: 152.3, 149.1, 148.0, 141.4, 140.4, 140.2, 133.5, 131.4,
129.3, 127.2, 126.0, 125.9, 124.9, 124.3,122.5,121.8,114.1,112.1, 108.3,
40.6, 17.2; LC–MS: m/z¼375.5 (M), 377.5 (Mþ2). Anal. Calcd for
molecular formula C21H14ClN3O2: C, 67.12; H, 3.75; N,11.18%. Found:
C, 67.15; H, 3.77; N, 11.15%.
4.13. 13-Chloro-8H-indolo[3,2-a]acridine (5a)
Mp 207–208 ꢀC; IR (KBr): 2067, 1732, 1604, 1024, 1473, 1375,
1148, 1028, 817, 640, 551 cmꢂ1
;
1H NMR (400 MHz, TMS, CDCl3)
d:
4.18. 13-Chloro-11H-indolo[2,3-b]acridine (6a)
8.90 (1H, s), 8.63 (1H, d, J¼8.0 Hz), 8.45 (1H, d, J¼4.0 Hz), 8.15 (2H,
d, J¼13.0 Hz), 8.07 (1H, d, J¼8.0 Hz), 7.59 (2H, dd, J¼4.0 Hz), 7.54–
7.53 (1H, d, J¼4.0 Hz), 7.37 (1H, t, J¼8.0 Hz); 13C NMR (100 MHz,
Mp 167–169 ꢀC; IR (KBr): 2057,1789,1601,1452,1022,1160,1022,
806 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 8.96 (1H, s), 8.72 (1H,
TMS, CDCl3)
d
: 145.9, 142.3, 137.8, 135.2, 133.7, 131.0, 130.6, 130.0,
d, J¼8.0 Hz), 8.53 (1H, s), 8.28–8.16 (3H, m), 7.67–7.61 (2H, m), 7.40
128.6, 125.8, 125.6, 123.0, 122.7, 120.8, 120.6, 118.5, 115.5, 111.6,
110.3, LC–MS: m/z¼302.5 (M), 304.5 (Mþ2). Anal. Calcd for mo-
lecular formula C19H11ClN2: C, 75.38; H, 3.66; N, 9.25%. Found: C,
75.45; H, 3.68; N, 9.19%.
(2H, d, J¼8.0 Hz); 13C NMR (100 MHz, TMS, CDCl3)
d: 146.0, 142.2,
137.6,135.4,133.7,131.0,130.5,129.8,128.5,125.7,125.5,122.8,122.5,
120.8, 120.5, 117.5, 115.3, 111.6, 110.2, LC–MS: m/z¼302.5 (M), 304.5
(Mþ2). Anal. Calcd for molecular formula C19H11ClN2: C, 75.38; H,
3.66; N, 9.25%. Found: C, 75.45; H, 3.62; N, 9.32%.
4.14. 13-Chloro-8-ethyl-8H-indolo[3,2-a]acridine (5b)
4.19. 13-Chloro-11-ethyl-11H-indolo[2,3-b]acridine (6b)
Mp 219–220 ꢀC; IR (KBr): 2924, 1740, 1634, 1584, 1477, 1366,
1150, 1022, 804, 631, 557 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d:
Mp 129–130 ꢀC; IR (KBr): 2926, 1740, 1637, 1564, 1477, 1366,
8.89 (1H, d, J¼8.3 Hz), 8.65 (1H, d, J¼8.8 Hz), 8.48–8.44 (2H, m),
8.08 (1H, d, J¼9.2 Hz), 7.88 (1H, t, J¼7.0 Hz), 7.76 (1H, t, J¼7.2 Hz),
7.63 (1H, d, J¼8.2 Hz), 7.53 (1H, t, J¼7.2 Hz), 7.39 (1H, t, J¼7.8 Hz),
4.62 (2H, q, J¼6.9 Hz, N–CH2), 1.56 (3H, t, J¼7.2 Hz, CH3); 13C NMR
1148, 1020, 804, 634, 557 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d:
9.08 (1H, s), 8.46 (1H, d, J¼8.0 Hz), 8.42 (1H, d, J¼8.0 Hz), 8.23 (1H,
s), 8.20 (1H, d, J¼4.0 Hz), 7.86 (1H, t, J¼8.0 Hz), 7.74 (1H, t, J¼8.0 Hz),
7.64 (2H, t, J¼4.0 Hz), 7.32–7.28 (1H, m), 4.54 (2H, q, J¼8.0 Hz, N-
(100 MHz, TMS, CDCl3)
d: 145.4, 143.5, 138.8, 137.5, 130.3, 129.5,
CH2), 1.40 (3H, t, J¼8.0 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d:
127.4, 127.0, 126.9, 126.5, 124.9, 124.6, 123.4, 122.7, 119.7, 118.6, 111.7,
109.4, 107.7; 38.0, 14.6; LC–MS: m/z¼330.5 (M), 332.5 (Mþ2). Anal.
Calcd for molecular formula C21H15ClN2: C, 76.24; H, 4.57; N, 8.47%.
Found: C, 76.20; H, 4.55; N, 8.50%.
145.5, 144.3, 139.0, 137.6, 130.4, 129.6, 127.5, 127.1, 127.0, 126.6,
125.0, 124.7, 123.5, 122.8, 119.8, 118.7, 111.8, 109.5, 107.8, 38.1, 14.8;
LC–MS: m/z¼330.5 (M), 332.5 (Mþ2). Anal. Calcd for molecular
formula C21H15ClN2: C, 76.24; H, 4.57; N, 8.47%. Found: C, 76.18; H,
4.60; N, 8.58%.
4.15. 2,13-Dichloro-8-ethyl-8H-indolo[3,2-a]acridine (5c)
4.20. 2,13-Dichloro-11-ethyl-11H-indolo[2,3-b]acridine (6c)
Mp 223–224 ꢀC; IR (KBr): 2963,1707,1584,1435,1337,1244,1078,
814, 636, 550 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 8.87 (1H, d,
Mp 140–141 ꢀC; IR (KBr): 2963, 1701, 1584, 1435, 1333, 1240,
J¼8.0 Hz), 8.60 (1H, d, J¼2.0 Hz), 8.20 (2H, dd, J¼8.0 Hz), 8.01 (1H, d,
J¼9.2 Hz), 7.72 (1H, dd, J¼7.2 Hz), 7.61 (1H, d, J¼8.0 Hz), 7.52 (1H, t,
J¼6.8 Hz), 7.39 (1H, t, J¼8.0 Hz), 4.60 (2H, q, J¼7.2 Hz, N–CH2), 1.56
1080, 814, 646, 550 cmꢂ1 1H NMR (400 MHz, TMS, CDCl3)
; d: 8.85
(1H, s), 8.36 (1H, d, J¼1.9 Hz), 8.25 (1H, d, J¼8.5 Hz), 8.17 (1H, d,
J¼9.1 Hz), 7.96 (1H, s), 7.64–7.59 (2H, m), 7.35–7.29 (2H, m), 4.38
(2H, q, J¼7.2 Hz, N–CH2), 1.52 (3H, t, J¼7.1 Hz, CH3); 13C NMR
(3H, t, J¼7.2 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d: 150.1,146.5,
141.3,140.5, 136.9,135.6, 133.2, 132.7, 131.4, 129.4, 128.0, 126.2,125.7,
125.6, 122.2, 120.1, 114.2, 111.9, 40.5, 17.2; LC–MS: m/z¼364 (M), 366
(Mþ2), 368 (Mþ4). Anal. Calcd for molecular formula C21H14Cl2N2: C,
69.05; H, 3.86; N, 7.67%. Found: C, 69.03; H, 3.82; N, 7.70%.
(100 MHz, TMS, CDCl3) d: 147.4, 146.5, 143.7, 139.2, 135.0, 134.9,
132.6, 132.0, 130.0, 129.4, 126.3, 125.1, 125.0, 124.6, 122.5, 122.3,
120.1, 111.0, 110.0, 40.3, 16.6; LC–MS: m/z¼364 (M), 366 (Mþ2), 368
(Mþ4). Anal. Calcd for molecular formula C21H14Cl2N2: C, 69.05; H,
3.86; N, 7.67%. Found: C, 69.12; H, 3.81; N, 7.71%.
4.16. 2-Bromo-13-chloro-8-ethyl-8H-indolo-
[3,2-a]acridine (5d)
4.21. 2-Bromo-13-chloro-11-ethyl-11H-indolo-
[2,3-b]acridine (6d)
Mp 266–267 ꢀC; IR (KBr): 2965, 1584, 1460, 1323, 1142, 1071,
953, 814, 781, 654 cmꢂ1
;
1H NMR (400 MHz, TMS, CDCl3)
d
: 8.85
Mp 151–152 ꢀC; IR (KBr): 2968, 1576,1460,1323,1139,1065, 953,
(1H, d, J¼8.4 Hz), 8.75 (1H, d, J¼1.6 Hz), 8.16–8.12 (2H, m), 7.98 (1H,
d, J¼9.2 Hz), 7.82 (1H, dd, J¼9.2 Hz), 7.59 (1H, d, J¼8.0 Hz), 7.51 (1H,
t, J¼7.6 Hz), 7.38 (1H, t, J¼7.2 Hz), 4.56 (2H, q, J¼8.0 Hz, N–CH2),1.54
814, 778, 654 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 8.87 (1H, s),
8.39 (1H, s), 8.25 (1H, d, J¼8.0 Hz), 8.18 (1H, d, J¼8.0 Hz), 7.90 (1H,
s), 7.64–7.60 (2H, m), 7.37–7.30 (2H, m), 4.41 (2H, q, J¼4.0 Hz, N–
CH2), 1.55 (3H, t, J¼10.0 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
(3H, t, J¼7.2 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d: 147.8,
145.2, 143.6, 138.8, 137.9, 132.6, 130.7, 128.9, 126.8, 126.6, 125.9,
124.3, 123.7, 123.0, 121.3, 119.7, 117.6,111.7, 109.4, 37.9, 14.6; LC–MS:
d: 147.8, 145.2, 143.6, 138.8, 137.9, 132.6, 130.7, 128.9, 126.8, 126.6,
125.9, 124.3, 123.7, 123.0, 121.3, 119.7, 117.6, 111.7, 109.4, 37.9, 14.6;

R. Meesala, R. Nagarajan / Tetrahedron 65 (2009) 6050–6056
6055
LC–MS: m/z¼408.5 (M), 410.5 (Mþ2), 412.5 (Mþ4). Anal. Calcd for
molecular formula C21H14BrClN2: C, 61.56; H, 3.44; N, 6.84%. Found:
C, 55.60; H, 3.08; N, 6.35%.
140.5, 139.6, 137.4, 127.9, 126.3, 123.6, 122.1, 122.0, 120.5, 118.9,
118.8, 116.7, 112.4, 109.6, 108.8, 37.6, 13.7; LC–MS: m/z¼376 (M).
Anal. Calcd for molecular formula C21H16N2O5: C, 67.02; H, 4.28; N,
7.44%. Found: C, 66.95; H, 4.24; N, 7.42%.
4.22. 2-Nitro-13-chloro-11-ethyl-11H-indolo-
[2,3-b]acridine (6e)
4.27. 8-Ethyl-8,13-dihydrochromeno[2,3-c]-
carbazol-13-one (9a)
Mp 172–173 ꢀC; IR (KBr): 2962,1708,1573,1419,1330,1252,1069,
826, 644, 551 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 9.62 (1H, s),
Mp 187–189 ꢀC; IR (KBr): 2963, 2926, 1719, 1645, 1611, 1578,
1443,1323,1149,1022, 891, 748, 619 cmꢂ1; 1H NMR (400 MHz, TMS,
8.87 (1H, d, J¼8.0 Hz), 8.52 (1H, d, J¼8.0 Hz), 8.38 (1H, d, J¼8.0 Hz),
8.22 (1H, d, J¼8.0 Hz), 8.15 (1H, s), 7.66 (1H, d, J¼8.0 Hz), 7.57 (1H, t,
J¼8.0 Hz), 7.44 (1H, t, J¼8.0 Hz) 4.51 (2H, q, J¼7.6 Hz, N–CH2), 1.55
CDCl3)
d
: 9.84 (1H, d, J¼8.4 Hz), 8.48 (1H, dd, J¼6.8 Hz), 7.79 (1H, d,
J¼8.8 Hz), 7.73–7.68 (1H, m), 7.59–7.34 (6H, m), 4.42 (2H, q,
(3H, t, J¼7.0 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d: 150.0,147.1,
J¼7.2 Hz, N–CH2), 1.42 (3H, t, J¼7.2 Hz, CH3); 13C NMR (100 MHz,
146.7, 140.1, 139.0, 138.0, 137.9, 131.1, 129.0, 127.0, 125.0, 123.6, 122.5,
121.8, 120.1, 119.4, 116.3, 114.1, 109.7, 38.1, 14.7; LC–MS: m/z¼375.5
(M), 377.5 (Mþ2). Anal. Calcd for molecular formula C21H14ClN3O2: C,
67.12; H, 3.75; N, 11.18%. Found: C, 67.22; H, 3.72; N, 11.25%.
TMS, CDCl3) d: 177.9, 155.2, 152.5, 140.7, 135.9, 133.8, 128.5, 126.7,
126.5, 123.4, 122.9, 122.5, 119.0, 118.7, 117.7, 117.4, 115.9, 115.8, 108.1,
37.4, 13.9; LC–MS: m/z¼314 (MþHþ), positive mode. Anal. Calcd for
molecular formula C21H15NO2: C, 80.49; H, 4.82; N, 4.47%. Found: C,
80.53; H, 4.79; N, 4.45%.
4.23. 2-(9-Ethyl-9H-carbazolyloxy)benzoic acid (8a)
4.28. 2-Chloro-8-ethyl-8,13-dihydrochromeno[2,3-c]carbazol-
13-one (9b)
Mp 187–186 ꢀC; IR (KBr): 3445, 2972, 2924, 1736, 1697, 1488,
1321, 1256, 1219,1149, 789 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d:
8.18 (1H, d, J¼8.0 Hz), 8.03 (1H, d, J¼7.8 Hz), 7.87 (1H, d, J¼4.0 Hz),
7.53–7.49 (2H, m), 7.46–7.41 (2H, m), 7.27–7.24 (2H, m), 7.18–7.15
(1H, m), 6.83 (1H, d, J¼8.0 Hz), 4.47 (2H, q, J¼8.0 Hz, N–CH2), 1.41
Mp 158–159 ꢀC; IR (KBr): 3414, 2922, 2857, 1713, 1634, 1312,
1020, 806, 741, 621 cmꢂ1 1H NMR (400 MHz, TMS, CDCl3)
; d: 9.75
(1H, d, J¼7.4 Hz), 8.39 (1H, s), 7.78 (1H, d, J¼9.2 Hz), 7.60–7.53 (3H,
(3H, t, J¼4.0 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d: 172.3,
m), 7.45–7.35 (3H, m), 4.42 (2H, q, J¼8.0 Hz, N–CH2), 1.43 (3H, t,
163.1, 156.6, 153.9, 145.3, 141.5, 138.0, 136.6, 130.9, 128.2, 127.1,
126.9, 125.3, 123.5, 123.4, 122.9, 116.1, 114.2, 113.6, 42.3, 18.6; LC–
MS: m/z¼330 (MꢂHþ), negative mode. Anal. Calcd for molecular
formula C21H17NO3: C, 76.12; H, 5.17; N, 4.23%. Found: C, 76.17; H,
5.13; N, 4.19%.
J¼4.0 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d: 176.6, 1553.4,
155.1,140.7,135.9,133.8,128.5,126.7,125.9,123.2,122.7,119.4,119.0,
118.6, 117.2, 116.1, 115.6, 108.9, 108.1, 37.4, 14.0; LC–MS: m/z¼347.5
(M), 349.5 (Mþ2). Anal. Calcd for molecular formula C21H14ClNO2:
C, 72.52; H, 4.06; N, 4.03%. Found: C, 72.74; H, 3.93; N, 4.09%.
4.24. 5-Chloro-2-(9-ethyl-9H-carbazolyloxy)benzoic acid (8b)
4.29. 2-Bromo-8-ethyl-8,13-dihydrochromeno[2,3-c]-
carbazol-13-one (9c)
Mp 171–172 ꢀC; IR (KBr): 3046, 2972, 2876,1736,1626,1458,1379,
1256, 1148, 745 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 8.20 (1H, d,
Mp 177–178 ꢀC; IR (KBr): 3419, 2915, 2868, 1711, 1619, 1322,
J¼2.8 Hz), 8.05 (1H, d, J¼8.0 Hz), 7.85 (1H, d, J¼2.0 Hz), 7.52 (1H, t,
J¼7.6 Hz), 7.45–7.42 (2H, m), 7.35 (2H, dd, J¼6.4 Hz), 7.27–7.24 (2H,
m), 6.77 (1H, d, J¼9.2 Hz), 4.39 (2H, q, J¼7.2 Hz, N–CH2), 1.46 (3H, t,
1016, 809, 768, 617 cmꢂ1 1H NMR (400 MHz, TMS, CDCl3)
; d: 9.74
(1H, s), 8.54 (1H, s), 7.73–7.70 (2H, m), 7.57–7.52 (3H, m), 7.35–7.32
(3H, m), 4.40 (2H, q, J¼8.0 Hz, N–CH2), 1.48 (3H, s, CH3); 13C NMR
J¼7.2 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d
: 165.0,157.5,146.4,
(100 MHz, TMS, CDCl3) d: 176.4, 155.2, 153.9, 140.8, 137.1, 136.6,
140.7, 137.7, 134.5, 132.8, 128.2, 126.6, 123.9, 122.2, 120.7, 119.9, 119.2,
118.6, 117.9, 112.5, 109.7, 108.9, 37.8, 13.8; LC–MS: m/z¼365.5 (M),
367.5 (Mþ2). Anal. Calcd for molecular formula C21H16ClNO3: C,
68.95; H, 4.41; N, 3.83%. Found: C, 68.89; H, 4.47; N, 3.85%.
129.0, 128.4, 126.8, 123.1, 121.9, 121.3, 119.4, 119.2, 117.4, 116.5, 115.7,
108.9, 108.2, 37.5, 14.0; LC–MS: m/z¼393 (M), 395 (Mþ2). Anal.
Calcd for molecular formula C21H14BrNO2: C, 64.30; H, 3.60; N,
3.57%. Found: C, 64.31; H, 3.67; N, 3.56%.
4.25. 5-Bromo-2-(9-ethyl-9H-carbazolyloxy)benzoic acid (8c)
4.30. 2-Nitro-8-ethyl-8,13-dihydrochromeno[2,3-c]carbazol-
13-one (9d)
Mp 179–180 ꢀC; IR (KBr): 3039, 2967, 2776, 1726, 1646, 1459,
1369, 1255, 1132, 749 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d
: 8.23
Mp 167–168 ꢀC; IR (KBr): 3298, 2930, 2863, 1657, 1462, 1343,
(1H, s), 8.03 (1H, s), 7.86 (1H, s), 7.52 (1H, d, J¼8.0 Hz), 7.51–7.42
1261, 1099, 804, 746 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d: 9.64
(2H, m), 7.40–7.34 (3H, m), 6.78 (1H, s), 4.41 (2H, q, J¼8.0 Hz, N–
(1H, d, J¼8.0 Hz), 9.13 (1H, s), 8.33 (1H, d, J¼8.0 Hz), 7.88 (1H, d,
J¼8.0 Hz), 7.66–7.57 (2H, m), 7.46–7.44 (2H, m), 7.34 (1H, m), 4.43
(2H, q, J¼7.6 Hz, N-CH2), 1.46 (3H, t, J¼8.0 Hz, CH3); 13C NMR
CH2), 1.47 (3H, t, J¼8.0 Hz, CH3); 13C NMR (100 MHz, TMS, CDCl3)
d:
177.9.0, 155.2, 152.5, 140.7, 135.9, 133.8, 128.5, 126.7, 126.5, 123.4,
122.9, 122.5, 119.0, 118.7, 117.7, 117.4, 115.9, 115.8, 108.1, 37.4, 13.9;
LC–MS: m/z¼411 (MþHþ), positive mode. Anal. Calcd for molecular
formula C21H16BrNO3: C, 61.48; H, 3.93; N, 3.41%. Found: C, 61.50; H,
3.84; N, 3.29%.
(100 MHz, TMS, CDCl3) d: 176.2, 167.6, 158.3, 150.2, 143.2, 140.5,
135.5, 128.2, 127.8, 127.2, 123.5, 122.3, 121.7, 119.4, 118.8, 116.6, 115.6,
108.3, 106.5, 37.5, 14.0; LC–MS: m/z¼358 (M). Anal. Calcd for mo-
lecular formula C21H14N2O4: C, 70.39; H, 3.94; N, 7.82%. Found: C,
70.54; H, 3.95; N, 8.09%.
4.26. 5-Nitro-2-(9-ethyl-9H-carbazolyloxy)benzoic acid (8d)
4.31. (9-Ethyl-9H-3-carbazolyl)-9-ethyl-9H-azocarbazole
Mp 167–168 ꢀC; IR (KBr): 3468, 2969, 2361, 1709, 1613, 1516,
1472, 1379, 1259, 1149, 1070, 922, 837 cmꢂ1
;
1H NMR (400 MHz,
Mp 202–203 ꢀC; IR (KBr): 2984, 2926, 1525, 1522, 1472, 1323,
TMS, CDCl3)
d
: 8.67 (1H, d, J¼4.0 Hz), 7.99 (1H, d, J¼8.0 Hz), 7.68
1231, 1135, 933, 802 cmꢂ1; 1H NMR (400 MHz, TMS, CDCl3)
d
: 8.78
(2H, s), 8.23 (4H, s), 7.51–7.46 (6H, m), 7.32 (2H, s), 4.40 (4H, s, N–
CH2), 1.49 (6H, s, CH3); 13C NMR (100 MHz, TMS, CDCl3)
: 149.1,
143.8, 143.3, 128.7, 126.2, 125.9, 123.4, 123.3, 122.1, 118.6, 111.5, 111.2,
(1H, d, J¼4.0 Hz), 7.35–7.30 (3H, m), 7.07 (2H, d, J¼4.0 Hz), 6.72 (1H,
t, J¼4.0 Hz), 4.26 (2H, q, J¼4.0 Hz, N–CH2), 1.30 (3H, t, J¼4.0 Hz,
d
CH3); 13C NMR (100 MHz, TMS, CDCl3)
d: 165.7, 163.8, 147.0, 141.2,

6056
R. Meesala, R. Nagarajan / Tetrahedron 65 (2009) 6050–6056
40.4, 16.4; LC–MS: m/z¼417 (MþHþ), positive mode. Anal. Calcd for
molecular formula C28H24N4: C, 80.74; H, 5.81; N, 13.45%. Found: C,
80.52; H, 5.88; N, 13.52%.
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Acknowledgements
We thank Department of Science and Technology (DST), India
for providing financial assistance (Project number: SR/S1/OC-70/
2008) and for providing single crystal X-ray spectrometer in our
school. R.M. thanks CSIR for providing Senior Research fellowship.
We thank referees for their valuable suggestions.
Supplementary data
1H and 13C spectra of all compounds. Mass spectrums and ele-
mental analysis reports of 3b, 3c, 4b, 5d, 8a, and 9a. ORTEP dia-
grams of 5e, 6b, 3d, and diazocarbazole. Supplementary data
associated with this article can be found in the online version, at
doi:10.1016/j.tet.2009.05.061.
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