A short route to heteroarylcarbazoles: Synthesis of new pyrazolylcarbazoles and carbazolylquinolines

Article abstract of DOI:10.1055/s-2004-822353

A short synthesis of pyrazolylcarbazoles from 9-alkyl-carbazoles in three steps is reported. The acetylcarbazoles prepared by the acetylation of carbazoles with acetic anhydride catalyzed by BiCl₃ were converted into chloroaldehydes with Vilsmeier reagent. Condensation of chloroaldehydes with hydrazine followed by cyclization yield the pyrazolylcarbazoles. Carbazolyl chalcones were prepared by the condensation of carbazole-3-aldehyde with o-aminoacetophenone and cyclized to carbazolylquinolone using several catalysts. Cyclization of carbazolyl chalcones with the Vilsmeier reagent yields a mixture of carbazolylquinoline carbaldehydes.

Full text of DOI:10.1055/s-2004-822353

PAPER
1269
A Short Route to Heteroarylcarbazoles: Synthesis of New Pyrazolylcarbazoles
and Carbazolylquinolines
Synthesis of
N
ew
a
Pyrazolylc
j
arbazo
a
les and Ca
r
g
bazolylquino
o
line
s
pal Nagarajan, Paramasivan T. Perumal*
Organic Chemistry Division, Central Leather Research Institute, Adyar, Chennai - 600 020, India
Fax +91(44)24911589; E-mail: ptperumal@hotmail.com
Received 26 September 2003; revised 15 March 2004
strychnine-like activity. Based on the above facts a short
Abstract: A short synthesis of pyrazolylcarbazoles from 9-alkyl-
carbazoles in three steps is reported. The acetylcarbazoles prepared
by the acetylation of carbazoles with acetic anhydride catalyzed by
BiCl3 were converted into chloroaldehydes with Vilsmeier reagent.
and simple route to the synthesis of pyrazolylcarbazoles
was developed from 9-alkylcarbazoles. The first key step
involved in the synthesis is the acetylation of carbazoles
Condensation of chloroaldehydes with hydrazine followed by cy- with acetic anhydride catalyzed by BiCl3. The obtained
clization yield the pyrazolylcarbazoles. Carbazolyl chalcones were
prepared by the condensation of carbazole-3-aldehyde with o-ami-
noacetophenone and cyclized to carbazolylquinolone using several
densation of the conjugated aldehydes with hydrazine,
catalysts. Cyclization of carbazolyl chalcones with the Vilsmeier re-
agent yields a mixture of carbazolylquinoline carbaldehydes.
acetylcarbazoles were easily converted into the chlorovi-
nyl aldehydes by treatment with Vilsmeier reagent. Con-
followed by cyclization yielded the pyrazolylcarbazoles.
The acetylation of 9-ethylcarbazole with acetyl chloride
catalyzed by AlCl3 has been reported to give a mixture of
3- and 3,6-diacetyl derivatives3 together with large
amounts of tarry products due to high Lewis acidity of
AlCl3. Recently, BiCl3 has attracted much interest as a cat-
alyst due to its mild Lewis acidity and eco-friendly
nature4. The reaction was performed by addition of a 20
mol% of BiCl3 to a stirred solution of 9-ethylcarbazole in
excess acetic anhydride for 2 hours. Examination of the
TLC showed that only 3-acetylated product and no di-
acetylated carbazole had formed during the acetylation.
Also, minimal tarry products were formed when BiCl3
was used as a catalyst. The acetylcarbazole, on treatment
with Vilsmeier reagent at room temperature for 20 min-
utes, afforded the acrylaldehyde derivative 3a in 81%
yield. The 1H NMR spectrum of 3a exhibited the aldehyde
proton signal at d = 10.3 as a doublet with J = 6.8 Hz due
to coupling with the adjacent vinylic hydrogen atom. Sim-
ilar results were also obtained for other substituted acryl-
Key words: carbazoles, heterocycles, aldehydes, ring closure, con-
densation
The synthesis of substituted carbazoles1 has attracted con-
siderable attention in recent years, as this class of com-
pounds constitutes the structural framework of several
naturally occurring alkaloids with a wide range of biolog-
ical activity. Over the past years, the rapidly growing class
of heteroaryl-condensed carbazoles has attracted increas-
ing interest because of their broad spectrum of biological
activities.2
Most of the heteroarylcarbazoles reported in the literature
contain a heteroaryl ring fused to the carbazole ring but
the reports are scanty for heteroaryl ring substituted car-
bazoles.1 Carbazoles substituted with a quinoline moiety
were reported3 to enhance the physiological properties of
certain quinolines such as their antimalarial or their
Scheme 1 Reagents and conditions: (i) BiCl3 (20 mol%), Ac2O (3.0 equiv), CH2Cl2, r.t. 1a: 30 min, 59%, 1b: 35 min, 60%, 1c: 30 min, 62%;
(ii) DMF (excess), POCl3 (3.0 equiv), r.t. 2a: 20 min, 81%, 2b: 25 min, 86%, 2c: 30 min, 82%; (iii) N2H4·H2O (2.0 equiv), AcOH, 90 °C, 3 h.
3a: 80%, 3b: 75%, 3c: 71%.
SYNTHESIS 2004, No. 8, pp 1269–1273
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Advanced online publication: 04.05.2004
DOI: 10.1055/s-2004-822353; Art ID: T10303SS
© Georg Thieme Verlag Stuttgart · New York

1270
R. Nagarajan, P. T. Perumal
PAPER
aldehydes. The general structure of acrylaldehydes was
also confirmed by single crystal X-ray analysis of 3c.5
Condensation of 3a with hydrazine, followed by cycliza-
tion with acetic acid, yielded the pyrazolylcarbazole 4a in
80% yield (Scheme 1).
Quinoline derivatives with a carbazole nucleus in the
2-position are known to have enhanced physiological
properties such as antimalarial or strychnine-like activity
when compared to their unsubstituted analogues.3 We
have prepared the carbazolylquinolones by the cyclization
of o-aminochalcone 6, obtained by the condensation
9-ethyl-9H-carbazole-3-carbaldehyde (5) with o-ami-
noacetophenone (Scheme 2). To a solution of 9-ethyl-9H-
carbazole-3-carbaldehyde (5) and o-aminoacetophenone
in methanol, solid KOH was added and refluxed for 1
hour. After workup, the chalcone 6 was obtained in 89%
yield. Cyclization of the aminochalcone 6 to carba-
zolylquinoline 7 was achieved with several catalysts
(Scheme 2).
Scheme 3
however the reaction led to a mixture of inseparable prod-
ucts and large amount of tarry products.
In conclusion we have shown that pyrazolylcarbazoles
can be synthesized from 9-alkylcarbazoles and carba-
zolylquinolines through cyclization of o-aminochalcone
by several catalysts. Similarly cyclization of chalcone
with Vilsmeier reagent afforded carbazolylquinoline car-
baldehydes. The methods adopted in this paper are simple,
inexpensive, give good yields and they are useful in con-
structing biologically important carbazole-substituted
heterocycles.
Mass spectra were recorded on Varian VG 70-70H mass spectrom-
eter. Melting points were measured in capillary tubes and are uncor-
rected. Analytical TLC was performed on precoated sheets of silica
gel G of 0.25 mm thickness containing PF 254 indicator (Merck,
Darmstadt). Column chromatography was performed with silica gel
(60–120 mesh, S.d Fine, Boisar). IR spectra were recorded as solids
Scheme 2 (i) Reagents and conditions: Montmorillonite K10 Clay,
MW, 2.5 min, 75%; (ii) InCl3 (20 mol%), 2.0 h, 49%; (iii) In(OTf)3
(20 mol%), 1.5 h, 55%; (iv) PPh3·HClO4 (20 mol%), 1.0 h, 41%; (v)
KHSO4 (30 mol%), 1.0 h, 49%.
1
in KBr pellets on a Perkin-Elmer FT-IR spectrometer. H NMR
spectra were recorded at 300 MHz on a Bruker spectrometer using
TMS as internal standard. 13C NMR spectra were recorded at 75
MHz in CDCl3 and chemical shifts are given in d relative to the sol-
vent peak (77.0). C, H, N analyses were carried out with Perkin-
Elmer 240C autoanalyser. Petroleum ether used had bp 60–80 °C.
Among the catalysts, the Montmorillonite K10 clay-sup-
ported cyclization under microwave irradiation was found
to give a high yield of the product in shorter reaction time.
Although, except for KHSO4, the other catalysts are well
known in organic synthesis6 they have not been explored
for this type of cyclization. Also for the first time, we re-
port that KHSO4 can catalyze this type of cyclization re-
action.
Acetylation of Carbazoles 1; General Procedure
To a stirred mixture of carbazole 1 (0.5 g, 1 equiv) and Ac2O (3
equiv) in CH2Cl2 (10 mL), was added BiCl3 (20 mol%) and the mix-
ture was stirred for the time given in Scheme 1. H2O (50 mL) was
added, and the mixture was extracted with CH2Cl2 (3 × 10 mL) and
dried (Na2SO4). The solvent was distilled off and the residue was
chromatographed over silica gel, eluting with a mixture of EtOAc
The intramolecular cyclization of iminium species formed and petroleum ether (1:9) to give the acetylcarbazoles 2.
under Vilsmeier conditions is rapidly becoming an impor-
tant synthetic tool in organic chemistry, which provides a
3-Acetyl-9-methyl-9H-carbazole (2a)
Yield: 0.363 g (59%); colorless needles; mp 78–79 °C.
IR (KBr): 3055, 2926, 1667, 1593, 1430,1362, 1210, 824 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.60 (s, 1 H), 8.07 (m, 2 H), 7.47
(t, 1 H, J = 7.2 Hz), 7.33–7.22 (m, 3 H), 3.70 (s, 3 H), 2.66 (s, 3 H).
facile route to numerous heterocyclic systems from easily
accessible starting materials.7 The carbazolylquinolines
were prepared by the cyclization of o-aminochalcone with
Vilsmeier reagent. Thus, treatment of o-aminochalcone 6
in DMF as a solvent with six equivalents POCl3 at 90 °C
13C NMR (75 MHz, CDCl3): d = 197.7, 143.4, 141.5, 128.5, 126.4,
for 3 hours afforded the products 8 and 9 (Scheme 3). The 122.9, 122.3, 121.6, 120.4, 119.9, 108.9, 107.9, 29.1, 26.6.
MS: m/z = 223 (M+).
structure of 8 was also confirmed by single crystal X-ray
analysis.8 Based on the above facts, a possible mechanism
was proposed. The Vilsmeier reaction of carbazolylqui-
nolone 7 with Vilsmeier reagent was also carried out,
Anal. Calcd for C15H13NO: C, 80.69; H, 5.87; N, 6.27. Found: C,
80.86; H, 5.79; N, 6.36.
Synthesis 2004, No. 8, 1269–1273 © Thieme Stuttgart · New York

PAPER
Synthesis of New Pyrazolylcarbazoles and Carbazolylquinolines
1271
3-Acetyl-9-ethyl-9H-carbazole (2b)
Yield: 0.365 g (60%); colorless needles; mp 115–116 °C (Lit.3 mp
115 °C).
13C NMR (75 MHz, CDCl3): d = 191.6, 153.7, 141.9, 140.6, 126.7,
125.8, 124.8, 123.2, 122.7, 122.2, 120.7, 120.3, 120.0, 109.0, 108.6,
37.8, 13.8.
IR (KBr): 3046, 2921, 1667, 1593, 1495, 1351, 1170, 838 cm–1.
MS: m/z = 283 (M+), 285 (M + 2).
1H NMR (300 MHz, CDCl3): d = 8.75 (d, 1 H, J = 1.2 Hz), 8.18–
8.15 (m, 2 H), 7.50 (t, 1 H, J = 7.1 Hz), 7.46–7.26 (m, 3 H), 4.42 (q,
2 H, J = 7.2 Hz), 2.73 (s, 3 H), 1.46 (t, 3 H, J = 7.2 Hz).
Anal. Calcd for C17H14ClNO: C, 71.96; H, 4.97; N, 4.94. Found: C,
72.14; H, 4.81; N, 5.12.
(Z)-3-Chloro-3-(9-ethyl-6-methyl-9H-carbazol-3-yl)prop-2-
enal (3c)
Yield: 0.609 g (82%); yellow needles; mp 142–143 °C.
IR (KBr): 2921, 1664, 1671, 1582, 802 cm–1.
1H NMR (300 MHz, CDCl3): d = 10.25 (d, 1 H, J = 6.9 Hz), 8.51
(d, 1 H, J = 1.8 Hz), 7.93 (s, 1 H), 7.84 (dd, 1 H, J = 1.8, 8.7 Hz),
7.41–7.30 (m, 3 H), 6.78 (d, 1 H, J = 6.9 Hz), 4.37 (q, 2 H, J = 7.2
Hz), 2.55 (s, 3 H), 1.44 (t, 3 H, J = 7.2 Hz).
13C NMR (75 MHz, CDCl3): d = 192.1, 154.3, 142.5, 139.3, 130.0,
128.4, 125.9, 125.1, 123.4, 122.5, 121.1, 120.8, 109.2, 108.9, 38.3,
21.8, 14.3.
13C NMR (75 MHz, CDCl3): d = 197.2, 142.2, 140.2, 128.3, 126.0,
122.8, 122.2, 121.4, 120.2, 119.5, 108.5, 107.6, 107.4, 37.3, 26.1,
13.3.
MS: m/z = 237 (M+).
Anal. Calcd for C16H15NO: C, 80.98; H, 6.37; N, 5.90. Found: C,
81.22; H, 6.48; N, 6.76.
6-Acetyl-9-ethyl-3-methyl-9H-carbazole (2c)
Yield: 0.372 g (62%); colorless crystals; mp 90–91 °C.
IR (KBr): 3049, 2976, 2922, 1629, 1596, 1448, 1353, 1302, 1244,
1161, 804 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.70 (d, 1 H, J = 1.2 Hz), 8.11 (dd,
1 H, J = 1.5, 8.4 Hz), 7.95 (s, 1 H), 7.38–7.32 (m, 3 H), 4.37 (q, 2
H, J = 7.2 Hz), 2.71 (s, 3 H), 2.55 (s, 3 H), 1.42 (t, 3 H, J = 7.2 Hz).
MS: m/z = 297 (M+), 299 (M + 2).
Anal. Calcd for C18H16ClNO: C, 72.60; H, 5.42; N, 4.70. Found: C,
72.47; H, 5.33; N, 4.87.
13 C NMR (75 MHz, CDCl3): d = 198.1, 143.3, 139.3, 129.8, 128.9,
128.1, 126.6, 123.8, 122.9, 122.3, 121.1, 109.1, 108.3, 38.2, 27.1,
21.8, 14.2.
9-Alkyl-3-(1H-pyrazole-5-yl)-9H-carbazoles 4; General Proce-
dure
To a solution of acrylaldehydes 3 (2.5 mmol) in AcOH (10 mL),
was added dropwise N2H4·H2O (0.37 mL, 7.5 mmol) and heated
over a water bath at 90 °C for 3 h. After the reaction was over, the
mixture was poured into H2O. The product formed was filtered,
dried and recrystallized from EtOAc–petroleum ether (1:1).
MS: m/z = 251(M+).
Anal. Calcd for C17H17NO: C, 81.24; H, 6.82, N, 5.57. Found: C,
81.54; H, 6.79; N, 5.36.
(Z)-3-(9-Alkyl-9H-carbazol-3-yl)-3-chloroprop-2-enals 3; Gen-
eral Procedure
9-Methyl-3-(1H-pyrazol-5-yl)-9H-carbazole (4a)
Yield: 0.494 g (80%); colorless solid; mp 211–212 °C.
IR (KBr): 3151, 2932, 1598, 1471, 1446, 1249, 753 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.50 (s, 1 H), 8.12 (d, 1 H, J = 7.7
Hz), 7.94–7.89 (m, 1 H), 7.59 (br s, 1 H, NH), 7.49 (s, 1 H), 7.46 (d,
2 H, J = 3.4 Hz), 7.21 (septet, J = 4.2, 3.9, 3.7 Hz, 2 H), 6.65 (s, 1
H), 3.87 (s, 3 H).
13C NMR (75 MHz, CDCl3): d = 148.1, 141.0, 140.2, 133.4, 125.8,
123.6, 123.4, 122.4, 122.3, 120.1, 118.9, 116.9, 108.7, 101.2, 29.0.
To a stirred ice-cold solution of acetylcarbazole 2 (2.5 mmol) in
DMF (10 mL), was added dropwise POCl3 (0.7 mL, 7.5 mmol). Af-
ter the addition, the reaction mixture was stirred at r.t. for the time
given in Scheme 1. After completion of the reaction as evidenced
by TLC, the mixture was poured over crushed ice and neutralized
with 10% NaOH solution. The precipitate was filtered, dried and re-
crystallized from EtOAc and petroleum ether mixture (3:7) to afford
acrylaldehydes 3 in good yield.
(Z)-3-Chloro-3-(9-methly-9H-carbazol-3-yl)prop-2-enal (3a)
Yield: 0.545 g (81%); brown needles; mp 119–120 °C.
MS: m/z = 247 (M+).
Anal. Calcd for C16H13N3: C, 77.71; H, 5.30; N, 16.99. Found: C,
77.56; H, 5.39; N, 17.09.
IR (KBr): 1651, 1574, 1378, 1135, 797 cm–1.
1H NMR (300 MHz, CDCl3): d = 10.30 (d, 1 H, J = 6.8 Hz), 8.58 (s,
1 H), 8.18, (d, 1 H, J = 7.3 Hz), 7.93 (dd, 1 H, J = 2.0, 8.8 Hz),
7.62–7.32 (m, 4 H), 6.85 (d, 1 H, J = 7.3 Hz), 3.91 (s, 3 H).
9-Ethyl-3-(1H-pyrazol-5-yl)-9H-carbazole (4b)
Yield: 0.489 g (75%); colorless solid; mp 139–140 °C.
13C NMR (75 MHz, CDCl3): d = 191.6, 153.7, 142.9, 141.6, 126.7,
125.8, 124.7, 123.0, 122.5, 122.2, 120.5, 120.2, 120.1,109.0, 108.6,
29.3.
IR (KBr): 3139, 2973, 1602, 1444, 1470, 1231, 748 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.45 (d, 1 H, J = 1.2 Hz), 8.29 (br
s, 1 H), 8.07 (d, 1 H, J = 7.8 Hz), 7.84 (dd, 1 H, J = 1.5, 8.4 Hz),
7.68 (d, 1 H, J = 2.1 Hz), 7.49–7.18 (m, 4 H), 6.67 (d, 1 H, J = 2.1
Hz), 4.28 (q, 2 H, J = 7.2 Hz), 1.42 (t, 3 H, J = 7.2 Hz).
13C NMR (75 MHz, CDCl3): d = 149.7, 140.7, 140.2, 134.7, 126.3,
124.3, 123.6, 123.3, 123.2, 121.0, 119.4, 118.3, 109.1, 108.9, 102.6,
37.9, 14.2.
MS: m/z = 269 (M+), 271 (M + 2).
Anal. Calcd for C16H12ClNO: C, 71.25; H, 4.48; N, 5.19. Found: C,
71.05; H, 4.38; N, 5.02.
(Z)-3-Chloro-3-(9-ethyl-9H-carbazol-3-yl)prop-2-enal (3b)
Yield: 0.608 g (86%); yellow solid; mp 71–72 °C.
IR (KBr): 1662, 1582, 1385, 1196, 749 cm–1.
1H NMR (300 MHz, CDCl3): d = 10.25 (d, 1 H, J = 6.8 Hz), 8.53 (d,
1 H, J = 2.0 Hz), 8.13 (d, 1 H, J = 7.8 Hz), 7.85 (dd, 1 H, J = 2.0,
8.8 Hz), 7.54–7.25 (m, 4 H), 6.78 (d, 1 H, J = 6.8 Hz), 4.37 (q, 2 H,
J = 7.3 Hz), 1.44 (t, 3 H, J = 7.3 Hz).
MS: m/z = 261 (M+).
Anal. Calcd for C17H15N3: C, 78.13; H, 5.79; N, 16.08. Found: C,
78.29; H, 5.58; N, 15.91.
9-Ethyl-3-methyl-6-(1H-pyrazol-5-yl)-9H-carbazole (4c)
Yield: 0.488 g (71%); light brown solid; mp 89–90 °C.
IR (KBr): 3138, 2925, 1605, 1483, 1231, 796 cm–1.
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R. Nagarajan, P. T. Perumal
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1H NMR (300 MHz, CDCl3): d = 8.40 (d, 1 H, J = 1.3 Hz), 7.88 (s,
1 H), 7.82 (dd, 1 H, J = 1.5, 8.5 Hz), 7.66 (d, 1 H, J = 2.0 Hz), 7.34–
7.22 (m, 3 H), 7.14 (s, 1 H, NH), 6.66 (d, 1 H, J = 1.9 Hz), 4.28 (q,
2 H, J = 7.2 Hz), 2.52 (s, 3 H), 1.37 (t, 3 H, J = 7.2 Hz).
13C NMR (75 MHz, CDCl3): d = 149.1, 140.0, 138.6, 134.2, 128.3,
127.2, 123.6, 123.0, 122.1, 120.6, 117.8, 108.6, 108.3, 102.2, 37.6,
21.4, 13.8.
Anal. Calcd for C23H20N2O: C, 81.15; H, 5.92; N, 8.23. Found: C,
81.02; H, 6.14; N, 8.35.
4-Chloro-2-(9-ethyl-9H-carbazol-3-yl)-1(2H)-quinolinecarbal-
dehyde (8) and 4-Chloro-2-(9-ethyl-9H-carbazol-3-yl)-1,3(2H)-
quinolinedicarbaldehyde (9)
To a stirred ice-cold solution of 6 (0.85 g, 2.5 mmol) in DMF (10
mL), was added dropwise POCl3 (0.7 mL, 7.5 mmol) and the mix-
ture was heated over a water bath for 3 h. After completion of reac-
tion as evidenced by TLC, the mixture was poured over crushed ice
and neutralized with aq 10% NaOH solution, and extracted with
EtOAc (3 × 10 mL). The combined organic layers were washed
with H2O, brine, dried (Na2SO4), filtered and the solvent was evap-
orated. The residue was purified by column chromatography eluting
with EtOAc–petroleum ether (1:1) to afford quinoline carbalde-
hydes 8 and 9.
MS: m/z = 275 (M+).
Anal. Calcd for C18H17N3: C, 78.52; H, 6.22; N, 15.26. Found: C,
78.72; H, 6.14; N, 15.47.
1-(2-Aminophenyl)-3-(9-ethyl-9H-carbazol-3-yl)prop-2-en-1-
one (6)
To a solution of 9-ethyl-9H-carbazole-3-carbaldehyde (5; 0.558 g,
2.5 mmol) and o-aminoacetophenone (0.371 g, 2.75 mmol) in
MeOH (20 mL), was added KOH (0.7 g, 12.5 mmol) and the mix-
ture was refluxed for 3 h. After the reaction was over, excess MeOH
was distilled off and the residue was poured onto ice-cooled H2O.
The residue was extracted with CH2Cl2 (3 × 10 mL) and washed
with H2O, brine, dried (Na2SO4) and the solvent was distilled under
reduced pressure. The crude product was used without further puri-
fication in the next step; yield: 0.756 g (89%); yellow solid; mp 71–
72 °C.
8
Yield: 0.0567 g (10%); colorless solid; mp 188–189 °C.
IR (KBr): 2922, 1676, 1487, 753 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.70 (s, 1 H, NCHO), 8.03 (d, 1
H, J = 8.0 Hz), 7.80 (s, 1 H), 7.78–7.25 (m, 8 H), 7.04 (s, 1 H), 6.66
(d, 1 H, J = 7.4 Hz), 6.44 (d, 1 H, J = 6.3 Hz), 4.31 (q, 2 H, J = 7.3
Hz), 1.37 (t, 3 H, J = 7.3 Hz).
13C NMR (75 MHz, CDCl3): d = 161.7, 140.9, 140.3, 134.8, 130.1,
126.0, 125.9, 125.8, 125.7, 125.4, 120.7, 119.8, 119.0, 118.2, 108.8,
108.6, 53.3, 37.6, 13.9.
IR (KBr): 3436, 1637, 1570, 967, 745 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.37 (s, 1 H), 8.16 (d, 1 H, J = 7.4
Hz), 8.01 (s, 1 H), 7.97–7.95 (m, 1 H), 7.69 (s, 1 H), 7.66 (s, 1 H),
7.52–7.40 (m, 5 H), 6.75–6.71 (m, 2 H), 6.34 (br s, 2 H, NH2), 4.39
(q, 2 H, J = 7.4 Hz), 1.47 (t, 3 H, J = 7.4 Hz).
MS: m/z = 386 (M+), 388 (M + 2).
Anal. Calcd for C24H19ClN2O: C, 74.51; H, 4.95; N, 7.24. Found: C,
74.78; H, 5.10; N, 7.45.
13C NMR (75 MHz, CDCl3): d = 192.0, 150.9, 144.7, 134.1, 131.1,
126.3, 121.4, 120.7, 120.1, 119.7, 117.4, 116.0, 109.0, 108.9, 37.9,
13.9.
9
MS: m/z = 340 (M+).
Yield: 0.152 g (25%); colorless solid; mp 206–207 °C.
IR (KBr): 2926, 1676, 1592, 1488, 1267, 765 cm–1.
Anal. Calcd for C23H20N2O: C, 81.15; H, 5.92; N, 8.23. Found: C,
81.32; H, 5.78; N, 8.09.
1H NMR (300 MHz, CDCl3): d = 10.04 (s, 1 H, CHO), 8.71 (s, 1 H,
NCHO), 8.52 (s, 1 H), 8.02 (d, 1 H, J = 1.8 Hz), 7.97 (dd, 1 H,
J = 1.8, 8.6 Hz), 7.80–7.78 (m, 1 H), 7.51–7.27 (m, 5 H), 7.05–7.00
(m, 1 H), 6.64 (d, 1 H, J = 6.3 Hz), 6.44 (d, 1 H, J = 6.3 Hz), 4.32
(q, 2 H, J = 7.4 Hz), 1.39 (t, 3 H, J = 7.4 Hz).
13C NMR (75 MHz, CDCl3): d = 191.9, 161.7, 143.9, 140.6, 134.8,
130.2, 128.8, 128.7, 126.6, 125.9, 125.3, 120.0, 118.2, 109.6, 108.9,
53.0, 38.1, 13.9.
2-(9-Ethyl-9H-carbazol-3-yl)-2,3-dihydroquinolin-4-(1H)-one
(7)
The slurry of 6 (0.85 g, 2.5 mmol) supported in montmorillonite K10
clay (2.5 g) (prepared by adding clay to a solution of aminochalcone
6 in CH2Cl2 and evaporating the solvent) was irradiated in a domes-
tic microwave oven for 2.5 min (90% power). After the reaction was
over, the slurry was washed with CH2Cl2 (3 × 10 mL) and the com-
bined organic layers were washed with H2O, brine, dried (Na2SO4),
filtered and the solvent was evaporated. For the other catalysts, a so-
lution of aminochalcone 6 in MeOH (10 mL), InCl3 (20 mol%) or
In(OTf)3 (20 mol%) or PPh3·HClO4 (20 mol%) or KHSO4 (30
mol%) was added and stirred at r.t. for the appropriate time. After
the reaction was over, the mixture was poured into H2O and extract-
ed with CH2Cl2 (3 × 10 mL). The combined organic layers were
washed with H2O, brine, dried (Na2SO4), filtered and the solvent
was evaporated. The residue was purified by column chromatogra-
phy eluting with EtOAc–petroleum ether (1:1) to afford the qui-
nolone; yield: 0.638 g (75%); pale yellow solid; mp 179–180 °C.
MS: m/z = 414 (M+), 416 (M + 2).
Anal. Calcd for C25H19ClN2O2: C, 72.37; H, 4.62; N, 6.75. Found:
C, 72.52; H, 4.78; N, 6.89.
Acknowledgment
We thank the Council of Scientific and Industrial Research, New
Delhi, India for financial support.
References
IR (KBr): 3353, 1657, 1604, 751 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.20 (s, 1 H), 8.11 (d, 1 H, J = 7.4
Hz), 7.92 (d, 1 H, J = 6.3 Hz), 7.50–7.26 (m, 6 H), 6.82 (t, 1 H), 6.74
(d, 1 H, J = 8.6 Hz), 4.94 (d, 1 H, J = 10.9 Hz), 4.62 (br s, 1 H, NH),
4.38 (q, 2 H, J = 7.4 Hz), 3.04–2.87 (m, 2 H), 1.45 (t, 3 H, J = 7.4
Hz).
13C NMR (75 MHz, CDCl3): d = 193.9, 151.8, 135.5, 127.8, 126.2,
124.4, 123.2, 122.7, 120.6, 119.2, 118.7, 118.4, 116.0, 108.9, 108.8,
59.1, 47.3, 37.8, 13.9.
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MS: m/z = 340 (M+).
Synthesis 2004, No. 8, 1269–1273 © Thieme Stuttgart · New York

PAPER
Synthesis of New Pyrazolylcarbazoles and Carbazolylquinolines
1273
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Synthesis 2004, No. 8, 1269–1273 © Thieme Stuttgart · New York