Synthesis of cyclopentacarbazolones via palladium-catalyzed annulation of internal alkynes

Article abstract of DOI:10.1055/s-0031-1290807

A simple and efficient protocol for the synthesis of highly substituted cyclopentacarbazolones (50-82%) was developed by employing internal alkynes with 2-bromo-3-formylcarbazoles in the presence of palladium catalyst under ligand-free condition. High regioselectivity was observed for unsymmetrical (alkyl-, aryl-substituted) internal alkynes. Georg Thieme Verlag Stuttgart - New York.

Full text of DOI:10.1055/s-0031-1290807

1268
PAPER
Synthesis of Cyclopentacarbazolones via Palladium-Catalyzed Annulation of
Internal Alkynes
S
ynthesis of Cyclo
e
pentacarba
vzolones anga K. Sreenivas, Jatoth Sandhyarani, Rajagopal Nagarajan*
School of Chemistry, University of Hyderabad, Hyderabad 500046, India
Fax +91(40)23012460; E-mail: rnsc@uohyd.ernet.in
Received 8 December 2011; revised 28 January 2012
drugs, herein we wish to report a simple, and efficient pro-
tocol for the synthesis of various 2,3-disubstituted cyclo-
pentacarbazolones by the reaction of 2-bromo-3-
formylcarbazole with internal alkynes in the presence of
Abstract: A simple and efficient protocol for the synthesis of high-
ly substituted cyclopentacarbazolones (50–82%) was developed by
employing internal alkynes with 2-bromo-3-formylcarbazoles in
the presence of palladium catalyst under ligand-free condition. High
regioselectivity was observed for unsymmetrical (alkyl-, aryl- palladium catalyst under ligand-free conditions as shown
substituted) internal alkynes.
in Scheme 1.
Key words: estrogen receptors, palladium catalyst, annulations,
cyclopentacarbazolones, ligand-free synthesis
R4
R3
CHO
Br
O
Cyclopentadienones1 are members of a diverse class of at-
tractive molecules with demonstrated value and even
broader potential in synthesis, biology, materials science,
N
R1
R4
R3
R2
R6
Pd(OAc)2, K2CO3
+
R5
DMF, 100–140 °C
3–8 h
nanotechnology.2
Fused
and
substituted
R5
and
N
R1
R2
cyclopentadienones3 are also potentially useful building
blocks in organic, organometallic, and medicinal chemis-
try and also possess a broad range of biological activities
such as antiproliferative,4 antitumor,5 fungicidal,6 and
also act as estrogen binding receptors.7 Moreover, carba-
zole motif8 is a prominent structural unit discerned in var-
ious natural products and synthetic compounds with vital
medicinal values.9 Due to their significant pharmacologi-
cal importance, the development of facile strategies to ob-
tain such frameworks has become an attractive endeavor
in synthetic organic and medicinal chemistry. Therefore,
the synthesis of carbazole fused derivatives has become
an important research field and several methods have been
developed.10
R6
Scheme 1 Schematic representation of the present work
2-Bromo-9-ethyl-6-methyl-9H-carbazole-3-carbaldehyde13
and diphenylacetylene were used as model substrates for
optimizing the reaction conditions. The influences of cat-
alyst, ligand, additive, base, solvent, and temperature in
the reaction outcome were examined as shown in Table 1.
In the initial screenings in which various solvents were
tested for the reaction, DMF was found to be an efficient
media. Furthermore, different bases such as Cs2CO3,
Na2CO3, DABCO, KOAc, and K2CO3 were tested in the
reaction; it was found that K2CO3 was superior to other
bases. Ligand and additive had no effect on the reaction;
without ligand and additive the reaction proceeded well
within three hours (Table 1, entry 14). No reaction oc-
curred at or below 90 °C. By changing the catalyst loading
below 5 mol%, the reaction took more time to reach com-
pletion whereas when the catalyst loading was increased
(7.5–10 mol%), the reaction went to completion within
three hours with increased yield of the product. Based on
above findings, we concluded that the optimal conditions
for this reaction involved 1.0 equivalent of 1a, 1.0 equiv-
alent of 2a and 2.5 equivalents of K2CO3 in DMF with 7.5
mol% of Pd(OAc)2 at 140 °C. By using the optimized
condition the product 3a was obtained in good yield
(74%) within three hours. The product 3a was confirmed
by spectral data and single crystal X-ray analysis. The
ORTEP diagram is shown in Figure 1.14
In recent years, several methodologies have been reported
for the synthesis of cyclopentadienone fused with hetero-
cyclic based natural products.11 Palladium-catalyzed
annulation of internal alkynes by substituted ortho-ha-
lobenzaldehydes have been demonstrated to be a versatile
method to construct a wide range of complicated hetero-
and carbocycles. Significant work in this area was done by
Larock and co-workers who introduced the first catalytic
protocol for the efficient synthesis of indenones, even
though this catalytic system has some limitations in the
scope of the substrates.12 To the best of our knowledge, no
reports are available on the synthesis of carbazole fused
with substituted cyclopentadienone. Considering the bio-
logical as well as material importance of carbazole and
cyclopentadienone nuclei in various natural products and
SYNTHESIS 2012, 44, 1268–1278
x
x
.
x
x
.2
0
1
2
Advanced online publication: 27.03.2012
DOI: 10.1055/s-0031-1290807; Art ID: Z113711SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Synthesis of Cyclopentacarbazolones
1269
in moderate to good yields as shown in Table 2. After the
synthesis of 2,3-diphenylcyclopentacarbazolone deriva-
tives 3a–j, we noticed that the products with an electron-
withdrawing group in 5-position were formed in good
yields, for example, 3j (82%) and 3d (78%) (Table 2). In
the case of higher alkyl chain substitution present at 5-po-
sition such as 3b, 3c, 3g, and 3i moderate yields were ob-
tained. To check the versatility of this annulation, various
types of internal alkynes such as symmetrically and un-
symmetrically substituted alkyl- and arylalkynes were
tested. Symmetrical alkylacetylenes 2b,c afforded the
products 3k–n in moderate yields as shown in Table 3. In
the case of symmetrically substituted arylalkynes, the
products 3o and 3p were obtained in good yields (Table 4,
see below).
Figure 1 ORTEP diagram of 3a
With the optimized condition in hand, various derivatives
1a–j were treated with diphenylacetylene 2a, the reaction
proceeded well to afford the corresponding products 3a–j
Table 1 The Screening of Reaction Conditionsa
O
CHO
Ph
Ph
+
Br
Ph
N
N
Ph
Et
Et
1a
2a
3a
Entry
1
Catalyst
Pd/Cc
Ligand
Additive
Base
Solvent
DMF
toulene
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMA
DMSO
ODCB
DMF
DMF
DMF
TEG
Temp (°C)
120
Time (h) Yield (%)b
–
–
Et3N
24
24
28
24
8
NRd
22
2
Pd(PPh3)2Cl2
Pd(OAc)2
Pd(PPh3)4
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
–
TBAB
Cs2CO3
DABCO
Ag2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
KOAc
Cs2CO3
KOAc
K2CO3
K2CO3
K2CO3
KOAc
NaHCO3
120
3
–
–
130
30
4
–
–
140
NRd
62
5
Ph3P
TBAB
–
120
6
Ph3P
120
8
65
7
–
TBAB
LiCl
SDS
SDS
LiCl
TBAB
–
140
8
65
8
Cy3P
140
10
6
70
9
dppe
140
64
10
11
12
13
14
15
16
17
–
–
–
–
–
–
–
–
140
8
64
140
10
18
8
70
130
42
140
70
e
Pd(OAc)2
–
140
3
74
–
–
140
24
15
15
NRd
38
Pd(OAc)2
PdCl2
–
140
–
DMF
140
48
a Unless otherwise stated, all the reactions were carried at in a Schlenk tube by employing 0.05 equiv of catalyst, 0.2 equiv of ligand, 1.0 equiv
of additive, and 2.0 equiv of base. TBAB: Bu4NBr; SDS: sodium lauryl sulfate; ODCB: 1,2-dichlorobenzene; TEG: tetraethylene glycol.
b Isolated yields.
c Pd/C used: 10 mol%.
d NR: no reaction.
e Pd(OAc)2 used: 7.5 mol%.
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1268–1278

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D. K. Sreenivas et al.
PAPER
Table 2 Synthesis of 2,3-Diphenylcyclopentacarbazolonesa
O
R4
R3
R4
R3
CHO
Br
Ph
Ph
Pd(OAc)2
K2CO3
+
DMF
140 °C
3–6 h
Ph
N
R1
N
R1
R2
Ph
R2
1a–j
2a
3a–j
Entry
1
R1
Et
R2
R3
H
R4
Time (h)
Product
Yield (%)
74
O
Ph
H
H
Me
3
3a
Ph
N
Et
O
Ph
2
n-Bu
H
H
5
3b
65
Ph
N
n-Bu
O
Ph
3
4
5
6
7
8
n-C5H11
H
H
H
H
H
Br
H
Me
3c
3d
3e
3f
63
78
76
68
56
80
Ph
N
C5H11
O
Ph
Bn
H
H
4
4
4
6
3
Ph
O
N
Bn
Ph
Et
H
t-Bu
Ph
N
Et
O
Ph
Et
H
H
Ph
O
N
Et
Ph
n-Bu
H
H
3g
3h
Br
Ph
N
n-Bu
O
Ph
Et
Me
Me
Ph
N
Et
Synthesis 2012, 44, 1268–1278
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PAPER
Synthesis of Cyclopentacarbazolones
1271
Table 2 Synthesis of 2,3-Diphenylcyclopentacarbazolonesa (continued)
O
R4
R3
R4
R3
CHO
Br
Ph
Ph
Pd(OAc)2
K2CO3
+
DMF
140 °C
3–6 h
Ph
N
R1
N
R1
R2
Ph
R2
1a–j
2a
3a–j
Entry
9
R1
R2
R3
H
R4
H
Time (h)
Product
Yield (%)
65
O
Ph
n-C6H13
H
H
4
3i
Ph
N
C6H13
O
Ph
10
Bn
H
Me
4
3j
82
Ph
N
Bn
a Alkyne 2a used: 1.0 equiv.
When the unsymmetrical arylalkyne, chlorodiphenylacet- In the same manner, the products 3s, 3t, and 3u were ob-
ylene 2e was used, two regioisomers 3q and 3q¢ were ob- tained as shown in Table 4. The product 3s was also con-
tained in a ratio of 1:1 as shown in Table 4. The firmed by single crystal X-ray analysis and the ORTEP
substituents do not hinder sterically here, and as a result a diagram is shown in Figure 3.14
mixture of isomers in a 1:1 ratio were obtained. However,
in the case of alkynes with aryl and alkyl substituents such
as 2f–g, only one regioisomer was obtained in the range of
54–60% yield. This high regioselectivity is due to the
more sterically hindered group (phenyl) in the 3-position
of corresponding products 3r–u as the major product as
shown in Table 4. Further, from the 2D NOESY of the
product 3r it was confirmed that the ethyl group is adja-
cent to the carbonyl functional group. The structure of the
product 3r was also confirmed by single crystal X-ray
analysis. The ORTEP diagram is shown in Figure 2.14
Figure 3 ORTEP diagram of 3s
Based on the literature,12 the possible mechanism of annu-
lation is illustrated in Scheme 2 taking 3f as an example.
The oxidative addition of 1f to the active species of Pd(0),
which is formed by the reduction of Pd(OAc)2, leads to the
palladium(II) intermediate 1. Then, the insertion of inter-
nal alkyne 2a affords 3, which has a newly formed C–Pd
bond and it may undergo either an insertion or oxidative
addition pathway resulting in A and B, respectively. The
b-H elimination of A and the reductive elimination of B
would give the same desired product 3f and HPdBr spe-
cies, which would be converted to the active Pd(0) species
in the presence of base.
Figure 2 ORTEP diagram of 3r
© Thieme Stuttgart · New York
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D. K. Sreenivas et al.
PAPER
Table 3 Synthesis of 2,3-Dialkylcyclopentacarbazolones
O
R4
CHO
R4
R3
R5
Pd(OAc)2
R6
K2CO3
R3
+
Br
DMF
100–140 °C
2–6 h
R5
N
R1
N
R1
3k–n
R2
R6
R2
1a–d
2b,c
R5, R6 = n-Pr, n-Bu
Entry
1
R1
Et
R2
R3
R4
Alkynea
Product
Yield (%)b
O
H
H
H
H
H
H
H
H
Me
2c
3k
3l
60
N
Et
O
2
3
4
n-Bu
H
2c
2c
2b
54
50
64
N
Bu
O
n-C5H11
Me
3m
3n
N
n-C5H11
O
Bn
H
N
Bn
a Alkyne used: 2.5 equiv.
b Isolated yield.
Table 4 Synthesis of Various 2,3-Disubstituted Cyclopentacarbazolones
O
R4
CHO
R4
R3
R5
R6
Pd(OAc)2, K2CO3
R3
Br
+
DMF, 100–140 °C
2–6 h
R5
N
R1
R2
R6
2d–g
N
R1
3o–u
R2
Entry Aldehyde
Alkynea
Time Temp Product
Yield
(%)b
(h)
(°C)
O
CHO
Br
1
3
140
80
N
N
2d
Et
Et
3o
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Synthesis of Cyclopentacarbazolones
1273
Table 4 Synthesis of Various 2,3-Disubstituted Cyclopentacarbazolones (continued)
O
R4
CHO
R4
R3
R5
R6
Pd(OAc)2, K2CO3
R3
Br
+
DMF, 100–140 °C
2–6 h
R5
N
R1
R2
R6
2d–g
N
R1
3o–u
R2
Entry Aldehyde
Alkynea
Time Temp Product
Yield
(%)b
(h)
(°C)
O
CHO
Br
Br
2
2d
5
140
58
Br
N
N
Bu
Bu
3p
O
Cl
CHO
Br
N
O
Cl
Et
3
6
140
55
1:1
3q
N
2e
Et
N
Et
3q′
Cl
O
CHO
Et
4
6
6
5
7
100
100
120
100
60
54
62
55
Br
N
N
2f
2f
Et
Et
3r
3s
3t
O
CHO
5
6
7
Br
N
N
Et
Et
O
CHO
Br
2f
N
N
Bn
Bn
O
CHO
Br
N
N
2g
Et
Et
3u
a Alkynes 2f–g used: 2.5 equiv.
b Isolated yield.
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1268–1278

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D. K. Sreenivas et al.
PAPER
Ph
insertion
H
Ph
CHO
Ph
CHO
2a
Pd-Br
Ph
Pd-Br
N
N
Et
3
Et
1
O-Pd-Br
Ph
CHO
oxidative addition
insertion
Br
Ph
N
N
Et
1f
Et
A
Pd(0)
Pd(OAc)2
O
base. HBr
Ph
Ph
base
N
Et
3f
O
H
Pd-Br
oxidative addition
H-Pd-Br
Ph
reductive elimination
N
Ph
Et
B
Scheme 2 Proposed mechanism for the annulation reaction
5-Ethyl-8-methyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-
one (3a); Typical Procedure
In conclusion, an efficient synthesis of 2,3-disubstituted
cyclopentacarbazolones has been developed by using pal-
ladium-catalyzed annulation of internal alkynes with var-
ious 2-bromo-3- formylcarbazoles. The reaction proceeds
well under relatively mild conditions with shorter reaction
times. For unsymmetrical (alkyl-, aryl-substituted)
alkynes, the one-pot annulation approach affords selec-
tively a single regioisomer.
A Schlenk tube was charged with 1a (0.10 g, 0.315 mmol) and
diphenylacetylene (2a; 0.056 g, 0.315 mmol) in DMF, and then
K2CO3 (0.10 g, 0.78 mmol) and Pd(OAc)2 (5.0 mg, 0.023 mmol)
were added. The mixture was heated in an oil bath till the comple-
tion of the reaction as indicated by TLC (eluent: EtOAc–hexanes,
7:93). The reaction mixture was cooled to r.t., poured into H2O (20
mL), and extracted with EtOAc (3  10 mL). The combined organic
layers were washed with H2O (3  10 mL) followed by brine (20
mL) and dried (Na2SO4). The solvent was evaporated under reduced
pressure and the crude product was purified by column chromatog-
raphy over silica gel (100–200 mesh) using 7% EtOAc in hexanes
as an eluent to afford 3a; yield: 0.096 g (74%); orange solid; Rf =
0.53; mp 170–172 °C (50% EtOAc in hexanes).
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. The 1H NMR and
13C NMR spectra were recorded at 500, 400 MHz and 125, 100
MHz, respectively. The chemical shifts are reported in ppm down-
field to TMS (d = 0.00 ppm) for 1H NMR and relative to the central
CDCl3 resonance (d = 77.0 ppm) and DMSO-d6 (d = 39.51 ppm) for
13C NMR spectroscopy. The coupling constants J are given in Hz.
IR spectra were recorded on FT/IR-5300 spectrophotometer. The
X-ray diffraction measurements were carried out at 298 K on an au-
tomated diffractometer using graphite monochromated Mo-Ka
(l = 0.71073 Å) radiation with CAD4 software or the X-ray inten-
sity data were measured at 298 K equipped with a graphite mono-
chromator and a Mo-Ka fine-focus sealed tube (l = 0.71073 Å).
Elemental analyses were recorded on a Thermo Finnigan Flash EA
1112 analyzer at the School of Chemistry, University of Hyderabad.
Mass spectra were recorded on either VG7070H mass spectrometer
using EI technique or Shimadzu-LCMS 2010A mass spectrometer.
Melting points were measured in open capillary tubes and are un-
corrected.
IR (KBr): 2922, 1682, 1589, 1481, 1327, 1244, 788, 509 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.24 (s, 1 H), 7.82 (s, 1 H),
7.44 (d, J = 3.5 Hz, 5 H), 7.30–7.23 (m, 7 H), 6.97 (s, 1 H), 4.26 (q,
J = 7.5 Hz, 2 H), 2.52 (s, 3 H), 1.37 (t, J = 7.0 Hz, 3 H).
13C NMR (125 MHz, CDCl3/TMS): d = 195.3, 154.6, 143.7, 142.9,
138.5, 134.6, 133.4, 131.2, 130.0, 129.9, 128.9, 127.9, 127.4, 127.2,
124.2, 122.9, 121.5, 120.2, 117.1, 108.9, 103.3, 37.8, 21.4, 14.0.
LC-MS (positive mode): m/z = 414 (M + H)+.
Anal. Calcd for C30H23NO: C, 87.14; H, 5.61; N, 3.39. Found: C,
87.21; H, 5.58; N, 3.32.
5-Butyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-one (3b)
Yield: 0.083 g (65%); orange solid; mp 120–121 °C.
IR (KBr): 2926, 1691, 1585, 1365, 727 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.28 (s, 1 H), 8.03 (d,
J = 10.0 Hz, 1 H), 7.46–7.37 (m, 7 H), 7.31–7.23 (m, 6 H), 7.01 (s,
Synthesis 2012, 44, 1268–1278
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PAPER
Synthesis of Cyclopentacarbazolones
1275
1 H), 4.23 (t, J = 6.5 Hz, 2 H), 1.83–1.77 (m, 2 H), 1.38–1.32 (m, 2
H), 0.92 (t, J = 7.5 Hz, 3 H).
(m, 6 H), 7.04 (s, 1 H), 4.33 (q, J = 7.5 Hz, 2 H), 1.43 (t, J = 7.5 Hz,
3 H).
13C NMR (125 MHz, CDCl3/TMS): d = 195.3, 154.6, 143.8, 143.3,
140.7, 134.6, 133.3, 130.0, 129.0, 128.8, 128.6, 127.9, 127.5, 125.7,
124.0, 123.1, 121.6, 120.4, 120.3, 117.0, 109.5, 103.6, 42.9, 31.2,
20.3, 13.7.
13C NMR (125 MHz, CDCl3/TMS): d = 195.3, 154.6, 143.9, 142.8,
140.2, 134.6, 133.3, 131.2, 130.0, 129.0, 128.9, 128.6, 127.9, 127.5,
125.7, 124.1, 123.2, 121.7, 120.4, 117.1, 109.2, 103.3, 37.8, 14.0.
LC-MS (positive mode): m/z = 400 (M + H)+.
LC-MS (negative mode): m/z = 426 (M – H).
Anal. Calcd for C29H21NO: C, 87.19; H, 5.30; N, 3.51. Found: C,
87.09; H, 5.36; N, 3.48.
Anal. Calcd for C31H25NO: C, 87.09; H, 5.89; N, 3.28. Found: C,
87.22; H, 5.81; N, 3.19.
7-Bromo-5-butyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-one
8-Methyl-5-pentyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-
one (3c)
(3g)
Yield: 0.068 g (56%); red solid; mp 180 °C.
Yield: 0.080 g (63%); red solid; mp 168 °C.
IR (KBr): 2957, 1693, 1481, 1304, 1122, 794 cm–1.
IR (KBr): 2961, 2858, 1684, 1585, 1481, 1386, 1244, 1116, 1055,
896, 794, 698 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.24 (s, 1 H), 7.82 (s, 1 H),
7.45–7.43 (m, 5 H), 7.31–7.22 (m, 7 H), 6.98 (s, 1 H), 4.19 (t,
J = 7.2 Hz, 2 H), 2.52 (s, 3 H), 1.84–1.77 (m, 2 H), 1.33–1.27 (m, 4
H), 0.85 (t, J = 6.8 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 195.4, 154.6, 143.6, 139.0,
134.5, 133.3, 131.2, 130.0, 128.8, 128.6, 127.9, 127.1, 124.1, 122.9,
121.3, 120.1, 117.1, 109.2, 103.6, 43.2, 29.2, 28.8, 22.3, 21.4, 13.9.
1H NMR (500 MHz, CDCl3/TMS): d = 8.22 (s, 1 H), 7.87 (d, J = 8.0
Hz, 1 H), 7.52 (s, 1 H), 7.47–7.42 (m, 5 H), 7.37–7.35 (dd, J = 1.5,
1.5 Hz, 1 H), 7.30–7.23 (m, 5 H), 7.01 (s, 1 H), 4.19 (t, J = 7.5 Hz,
2 H), 1.82–1.76 (m, 2 H), 1.38–1.32 (m, 2 H), 0.93 (t, J = 7.5 Hz, 3
H).
13C NMR (125 MHz, CDCl3/TMS): d = 195.1, 154.5, 144.2, 143.5,
141.4, 134.7, 133.1, 133.0, 129.9, 129.1, 128.9, 128.5, 128.0, 127.6,
123.7, 123.6, 122.8, 121.4, 121.2, 119.3, 116.8, 112.6, 103.7, 43.1,
31.1, 20.3, 13.7.
LC-MS (positive mode): m/z = 456 (M + H)+.
Anal. Calcd for C33H29NO: C, 87.00; H, 6.42; N, 3.07. Found: C,
86.75; H, 6.35; N, 3.15.
LC-MS (positive mode): m/z = 507 (M + H)+, 509 (M + 2).
Anal. Calcd for C31H24BrNO: C, 73.52; H, 4.78; N, 2.77. Found: C,
73.45; H, 4.86; N, 2.71.
5-Benzyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-one (3d)
Yield: 0.098 g (78%); red solid; mp 192 °C.
5-Ethyl-6,8-dimethyl-2,3-diphenylcyclopenta[b]carbazol-
1(5H)-one (3h)
Yield: 0.103 g (80%); red solid; mp 187 °C.
IR (KBr): 1691, 1589, 1385, 1263, 1163, 1030, 787 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.30 (s, 1 H), 8.05 (d, J = 7.5
Hz, 1 H), 7.39 (d, J = 5.0 Hz, 4 H), 7.32 (d, J = 3.5 Hz, 3 H), 7.27–
7.22 (m, 9 H), 7.08 (d, J = 6.0 Hz, 2 H), 6.99 (s, 1 H), 5.44 (s, 2 H).
13C NMR (125 MHz, CDCl3/TMS): d = 195.3, 154.6, 144.0, 143.5,
140.9, 136.3, 134.5, 133.1, 131.1, 130.0, 129.0, 128.9, 128.8, 127.9,
127.7, 126.4, 126.0, 124.1, 123.6, 121.9, 120.8, 120.3, 117.0, 109.7,
103.9, 46.9.
IR (KBr): 2914, 1685, 1593, 1469, 1313, 1232, 846, 744, 582, 511
cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.19 (s, 1 H), 7.65 (s, 1 H),
7.47–7.41 (m, 5 H), 7.29–7.20 (m, 5 H), 6.97 (s, 1 H), 6.93 (s, 1 H),
4.43 (q, J = 7.0 Hz, 2 H), 2.71 (s, 3 H), 2.45 (s, 3 H), 1.35 (t, J = 7.5
Hz, 3 H).
13C NMR (125 MHz, CDCl3/TMS): d = 195.3, 154.7, 143.6, 143.5,
137.2, 134.5, 133.4, 1131.3, 130.7, 130.0, 128.9, 128.8, 127.9,
127.4, 125.2, 123.1, 121.8, 120.3, 118.0, 116.8, 103.4, 39.6, 21.0,
19.7, 15.8.
LC-MS (positive mode): m/z = 462 (M + H)+.
Anal. Calcd for C34H23NO: C, 88.48; H, 5.02; N, 3.07. Found: C,
88.32; H, 4.96; N, 3.12.
8-tert-Butyl-5-ethyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-
one (3e)
LC-MS (positive mode): m/z = 428 (M + H)+.
Yield: 0.096 g (76%); red solid; mp 185–187 °C.
IR (KBr): 2957, 1693, 1591, 1477, 1302, 1059, 1026, 744 cm–1.
Anal. Calcd for C31H25NO: C, 87.09; H, 5.89; N, 3.28. Found: C,
87.22; H, 5.81; N, 3.36.
1H NMR (500 MHz, CDCl3/TMS): d = 8.31 (s, 1 H), 8.05 (s, 1 H),
7.53–7.22 (m, 6 H), 7.33–7.22 (m, 6 H), 6.99 (s, 1 H), 4.27 (q,
J = 5.0 Hz, 2 H), 1.56 (s, 9 H), 1.39 (t, J = 10.0 Hz, 3 H).
13C NMR (125 MHz, CDCl3/TMS): d = 195.4, 154.6, 143.6, 143.1,
138.4, 134.5, 133.4, 131.2, 130.0, 128.9, 128.8, 128.6, 127.9, 127.4,
123.9, 123.8, 123.0, 121.9, 117.1, 116.4, 108.8, 103.3, 37.9, 31.8,
14.1.
5-Hexyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-one (3i)
Yield: 0.082 g (65%); red solid; mp 130 °C.
IR (KBr): 2924, 1687, 1589, 1468, 1251, 1161, 790 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.27 (s, 1 H), 8.02 (d, J = 8.0
Hz, 1 H), 7.45–7.41 (m, 6 H), 7.37 (d, J = 8.0 Hz, 1 H), 7.30 (d,
J = 6.5 Hz, 2 H), 7.26 (d, J = 8.0 Hz, 2 H), 7.23 (d, J = 8.5 Hz, 2 H),
7.00 (s, 1 H), 4.21 (t, J = 7.5 Hz, 2 H), 1.84–1.78 (m, 2 H), 1.33–
1.25 (m, 6 H), 0.84 (t, J = 7.0 Hz, 3 H).
LC-MS (positive mode): m/z = 456 (M + H)+.
13C NMR (125 MHz, CDCl3/TMS): d = 195.3, 154.6, 143.8, 143.3,
140.7, 134.6, 133.3, 131.2, 130.0, 129.0, 128.8, 127.9, 125.7, 124.0,
123.1, 121.6, 120.4, 117.0, 109.5, 103.6, 43.2, 31.4, 29.0, 26.7,
22.4, 13.9.
Anal. Calcd for C33H29NO: C, 87.00; H, 6.42; N, 3.07. Found: C,
86.91; H, 6.38; N, 3.15.
5-Ethyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-one (3f)
Yield: 0.089 g (68%); red solid; mp 220 °C.
LC-MS (positive mode): m/z = 456 (M + H)+.
IR (KBr): 2974, 2930, 1684, 1587, 1469, 1325, 1168, 841, 750, 694,
513 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.31 (s, 1 H), 8.07 (d, J = 8.0
Hz, 1 H), 7.51–7.45 (m, 6 H), 7.41 (d, J = 8.0 Hz, 1 H), 7.34–7.27
Anal. Calcd for C33H29NO: C, 87.00; H, 6.42; N, 3.07. Found: C,
87.19; H, 6.37; N, 3.15.
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1268–1278

1276
D. K. Sreenivas et al.
PAPER
5-Benzyl-8-methyl-2,3-diphenylcyclopenta[b]carbazol-1(5H)-
one (3j)
Yield: 0.102 g (82%); orange solid; mp 156–157 °C.
IR (KBr): 2922, 1685, 1481, 1302, 1149, 1026, 696 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.28 (s, 1 H), 7.85 (s, 1 H),
7.40–7.38 (m, 3 H), 7.33–7.31 (m, 2 H), 7.28–7.24 (m, 7 H), 7.23
(d, J = 2.0 Hz, 1 H), 7.20 (d, J = 0.8 Hz, 2 H), 7.08–7.06 (dd, J = 2.0,
1.2 Hz, 2 H), 6.97 (s, 1 H), 5.42 (s, 2 H), 2.52 (s, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 197.9, 156.4, 144.3, 143.5,
138.7, 137.1, 135.3, 133.2, 128.8, 127.7, 126.6, 119.9, 115.6, 108.9,
101.1, 43.2, 31.5, 30.6, 28.9, 25.8, 23.1, 23.0, 22.9, 22.7, 22.4, 21.4,
14.0, 13.9, 13.8.
LC-MS (positive mode): m/z = 416 (M + H)+.
Anal. Calcd for C29H37NO: C, 83.81; H, 8.97; N, 3.37. Found: C,
83.95; H, 8.91; N, 3.45.
5-Benzyl-2,3-dipropylcyclopenta[b]carbazol-1(5H)-one (3n)
Yield: 0.068 g (64%); red solid; mp 72 °C.
IR (KBr): 2926, 1693, 1467, 1390, 1331 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.09 (s, 1 H), 8.00 (d, J = 8.0
Hz, 1 H), 7.35 (t, J = 7.5 Hz, 1 H), 7.30–7.22 (m, 5 H), 7.12 (d,
J = 7.0 Hz, 2 H), 6.9 (s, 1 H), 5.40 (s, 2 H), 2.49 (t, J = 10.0 Hz, 2
H), 2.25 (t, J = 10.0 Hz, 2 H), 1.64–1.58 (m, 2 H), 1.54–1.50 (m, 2
H), 1.00 (t, J = 7.5 Hz, 3 H), 0.95 (t, J = 7.5 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 195.3, 154.5, 143.8, 143.7,
139.2, 136.4, 134.5, 131.2, 130.3, 129.9, 128.8, 128.7, 128.5, 127.9,
127.7, 127.5, 127.4, 126.4, 124.3, 123.4, 121.7, 120.2, 117.0, 109.4,
103.9, 46.9, 21.4.
LC-MS (positive mode): m/z = 476 (M + H)+.
Anal. Calcd for C35H25NO: C, 88.39; H, 5.30; N, 2.95. Found: C,
88.25; H, 5.36; N, 2.87.
2,3-Dibutyl-5-ethyl-8-methylcyclopenta[b]carbazol-1(5H)-one
(3k)
Yield: 0.070 g (60%); viscous orange liquid.
13C NMR (125 MHz, CDCl3/TMS): d = 197.5, 156.5, 144.7, 143.6,
140.6, 137.2, 136.5, 128.9, 127.7, 126.3, 125.5, 124.2, 120.9, 120.5,
120.0, 115.6, 109.5, 101.5, 46.8, 29.6, 25.2, 22.6, 21.7, 14.4, 14.2.
IR (KBr): 2926, 1693, 1599, 1483, 1304, 1022, 794 cm–1.
LC-MS (positive mode): m/z = 394 (M + H)+.
1H NMR (400 MHz, CDCl3/TMS): d = 8.06 (s, 1 H), 7.79 (s, 1 H),
7.32 (d, J = 2.8 Hz, 1 H), 7.28 (d, J = 2.0 Hz, 1 H), 6.95 (s, 1 H),
4.36 (q, J = 5.6 Hz, 2 H), 2.26 (t, J = 6.4 Hz, 2 H), 2.53 (s, 3 H), 2.31
(t, J = 6.0 Hz, 2 H), 1.72–1.67 (m, 4 H), 1.55–1.49 (m, 4 H), 1.46 (t,
J = 5.6 Hz, 6 H), 1.03 (t, J = 6.0 Hz, 3 H).
Anal. Calcd for C28H27NO: C, 85.46; H, 6.92; N, 3.56. Found: C,
85.32; H, 7.06; N, 3.45.
5-Ethyl-2,3-(di-p-tolyl)cyclopenta[b]carbazol-1(5H)-one (3o)
Yield: 0.112 g (80%); red solid; mp 195 °C.
13C NMR (100 MHz, CDCl3/TMS): d = 197.5, 156.4, 144.4, 143.0,
138.2, 137.1, 129.6, 126.6, 123.4, 120.8, 120.0, 115.7, 108.7, 103.6,
100.8, 37.8, 31.5, 30.6, 25.8, 23.0, 22.9, 22.8, 21.3, 14.1, 14.0, 13.9.
IR (KBr): 2924, 2852, 1682, 1589, 1467, 1392, 1242, 1168, 1105,
817, 736 cm–1.
1H NMR (500 MHz, CDCl3/TMS): d = 8.29 (s, 1 H), 8.06 (d, J = 8.0
Hz, 1 H), 7.46 (t, J = 7.5 Hz, 1 H), 7.38 (q, J = 8.0 Hz, 3 H), 7.29 (t,
J = 7.5 Hz, 3 H), 7.24 (d, J = 8.0 Hz, 2 H), 7.11 (d, J = 7.5 Hz, 2 H),
7.05 (s, 1 H), 4.33 (q, J = 7.5 Hz, 2 H), 2.47 (s, 3 H), 2.35 (s, 3 H),
1.43 (t, J = 7.5 Hz, 3 H).
LC-MS (positive mode): m/z = 374 (M + H)+.
Anal. Calcd for C26H31NO: C, 83.60; H, 8.37; N, 3.75. Found: C,
83.45; H, 8.31; N, 3.82.
2,3,5-Tributylcyclopenta[b]carbazol-1(5H)-one (3l)
Yield: 0.063 g (54%); viscous orange liqid.
IR (KBr): 2957, 1693, 1467, 1331, 1209, 1016, 742 cm–1.
13C NMR (125 MHz, CDCl3/TMS): d = 195.6, 154.1, 144.2, 142.8,
140.1, 138.9, 137.2, 134.3, 130.5, 129.8, 129.5, 128.7, 128.5, 128.4,
125.6, 124.1, 123.4, 121.6, 120.4, 120.3, 116.9, 109.2, 103.2, 37.8,
21.5, 14.0.
1H NMR (500 MHz, CDCl3/TMS): d = 8.04 (s, 1 H), 7.96 (d, J = 7.5
Hz, 1 H), 7.39–7.33 (m, 2 H), 7.23–7.19 (m, 1 H), 6.93 (s, 1 H), 4.26
(t, J = 7.0 Hz, 2 H), 2.58 (t, J = 8.0 Hz, 2 H), 2.28 (t, J = 7.5 Hz, 2
H), 1.86–1.80 (m, 2 H), 1.70–1.62 (m, 2 H), 1.52–1.47 (m, 4 H),
1.41–1.37 (m, 4 H), 1.00 (t, J = 7.0 Hz, 3 H), 0.94 (t, J = 7.5 Hz, 6
H).
13C NMR (125 MHz, CDCl3/TMS): d = 197.5, 156.4, 144.5, 143.4,
140.3, 137.2, 125.2, 124.7, 124.1, 123.6, 121.0, 120.6, 120.1, 115.6,
109.3, 101.2, 31.5, 30.6, 25.8, 23.1, 23.0, 22.9, 20.4, 14.0, 13.9,
13.8.
LC-MS (positive mode): m/z = 428 (M + H)+.
Anal. Calcd for C31H25NO: C, 87.09; H, 5.89; N, 3.28. Found: C,
87.12; H, 6.36; N, 3.12.
7-Bromo-5-butyl-2,3-di(p-tolyl)cyclopenta[b]carbazol-1(5H)-
one (3p)
Yield: 0.075 g (58%); red solid; mp 167–167 °C.
IR (KBr): 2924, 1693, 1595, 1464, 1388, 1016, 819 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.23 (s, 1 H), 7.88 (d, J = 8.5
Hz, 1 H), 7.54 (s, 1 H), 7.37 (t, J = 7.5 Hz, 3 H), 7.28 (d, J = 4.0 Hz,
3 H), 7.23 (d, J = 8.0 Hz, 1 H), 7.11 (d, J = 8.0 Hz, 2 H), 7.05 (s, 1
H), 4.21 (t, J = 7.0 Hz, 2 H), 2.47 (s, 3 H), 2.35 (s, 3 H), 1.87–1.89
(m, 2 H), 1.39–1.33 (m, 2 H), 0.96 (t, J = 6.0 Hz, 3 H).
LC-MS (positive mode): m/z = 388 (M + H)+.
Anal. Calcd for C27H33NO: C, 83.68; H, 8.58; N, 3.61. Found: C,
83.55; H, 8.51; N, 3.68.
2,3-Dibutyl-8-methyl-5-pentylcyclopenta[b]carbazol-1(5H)-one
(3m)
Yield: 0.057 g (50%); viscous liquid.
IR (KBr): 2957, 1693, 1601, 1466, 1259, 1022, 794 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.02 (s, 1 H), 7.76 (s, 1 H),
7.40 (d, J = 2.0 Hz, 1 H), 7.24 (d, J = 0.8 Hz, 1 H), 6.91 (s, 1 H),
4.25 (t, J = 7.2 Hz, 2 H), 2.58 (t, J = 8.0 Hz, 2 H), 2.50 (s, 3 H), 2.28
(t, J = 7.6 Hz, 2 H), 1.87–1.83 (m, 2 H), 1.67–1.62 (m, 2 H), 1.52–
1.45 (m, 6 H), 1.36–1.32 (m, 4 H), 0.99 (t, J = 7.6 Hz, 3 H), 0.93 (t,
J = 7.2 Hz, 6 H).
13C NMR (100 MHz, CDCl3/TMS): d = 195.4, 154.0, 144.4, 143.5,
141.4, 139.1, 137.4, 134.4, 130.2, 129.8, 129.5, 128.7, 128.5, 125.6,
123.5, 121.3, 119.2, 116.6, 112.5, 103.5, 43.1, 31.1, 21.4, 21.3,
20.3, 13.7.
LC-MS (positive mode): m/z = 535 (M + H)+, 537 (M + 2).
Anal. Calcd for C33H28BrNO: C, 74.16; H, 5.28; N, 2.62. Found: C,
74.31; H, 5.32; N, 2.58.
2-(4-Chlorophenyl)-5-ethyl-3-phenylcyclopenta[b]carbazol-
1(5H)-one (3q)
Yield: 0.039 g (50%); red solid; mp 206–208 °C.
Synthesis 2012, 44, 1268–1278
© Thieme Stuttgart · New York

PAPER
Synthesis of Cyclopentacarbazolones
IR (KBr): 2962, 1685, 1470, 1229, 792 cm–1.
1277
IR (KBr): 2908, 1676, 1450, 1014 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.30 (s, 1 H), 8.06 (d, J = 8.0
Hz, 1 H), 7.52–7.48 (m, 3 H), 7.45 (d, J = 8.0 Hz, 3 H), 7.41 (d, J =
8.0 Hz, 1 H), 7.31–7.24 (m, 5 H), 7.02 (s, 1 H), 4.33 (q, J = 8.0 Hz,
2 H), 1.42 (t, J = 8.0 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 195.6, 155.3, 143.6, 140.2,
133.5, 133.0, 131.2, 129.6, 129.0, 128.5, 128.2, 125.9, 124.0, 123.0,
121.9, 120.5, 117.3, 109.3, 103.5, 39.7, 14.1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.23 (s, 1 H), 8.06 (d, J = 7.6
Hz, 1 H), 7.55–7.48 (m, 3 H), 7.45–7.43 (m, 2 H), 7.39–7.37 (dd,
J = 1.2, 1.0 Hz, 1 H), 7.34–7.27 (m, 5 H), 7.10–7.08 (dd, J = 2.8, 1.6
Hz, 2 H), 6.91 (s, 1 H), 5.45 (s, 2 H), 2.39 (q, J = 7.6 Hz, 2 H), 1.15
(t, J = 7.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 197.1, 153.8, 144.7, 143.5,
140.6, 139.1, 136.3, 133.1, 128.9, 128.8, 127.9, 127.7, 126.4, 125.7,
124.1, 123.8, 121.2, 120.6, 120.1, 116.5, 109.7, 103.3, 46.7, 16.9,
14.0.
LC-MS (positive mode): m/z = 433 (M + H)+, 434 (M + 1).
Anal. Calcd for C29H20ClNO: C, 80.27; H, 4.65; N, 3.23. Found: C,
80.36; H, 4.98; N, 3.07.
LC-MS (positive mode): m/z = 414 (M + H)+.
Anal. Calcd for C30H23NO: C, 85.43; H, 5.68; N, 4.15. Found: C,
85.32; H, 5.62; N, 4.21.
3-(4-Chlorophenyl)-5-ethyl-2-phenylcyclopenta[b]carbazol-
1(5H)-one (3q¢)
Yield: 0.039 g (50%); red solid; mp >280 °C.
5-Ethyl-2-methyl-3-phenyl-2,3-dihydrocyclopenta[b]carbazol-
1(5H)-one (3u)
Yield: 0.061 g (55%); orange solid; mp 189–190 °C.
IR (KBr): 1687, 1469, 1339, 785 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.21 (s, 1 H), 8.02 (d, J = 7.6
Hz, 1 H), 7.62–7.50 (m, 5 H), 7.44–7.38 (m, 2 H), 7.28 (t, J = 8.0
Hz, 1 H), 6.97 (s, 1 H), 4.31 (q, J = 7.2 Hz, 2 H), 1.97 (s, 3 H), 1.41
(t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 197.2, 153.9, 144.5, 142.7,
140.0, 133.6, 133.2, 128.9, 128.8, 128.1, 125.4, 124.1, 123.4, 120.9,
120.3, 120.2, 116.7, 109.1, 102.6, 37.8, 14.1, 8.89.
IR (KBr): 2922, 1682, 1464, 1323, 1086, 750 cm–1.
1H NMR (400 MHz, CDCl3/TMS): d = 8.31 (s, 1 H), 8.06 (d, J = 7.6
Hz, 1 H), 7.48–7.45 (m, 3 H), 7.42–7.49 (m, 3 H), 7.30–7.26 (m, 6
H), 6.98 (s, 1 H), 4.34 (q, J = 7.32 Hz, 2 H), 1.43 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 195.1, 153.2, 143.5, 142.8,
140.2, 134.9, 131.7, 130.8, 129.9, 129.3, 128.1, 127.7, 125.9, 124.0,
122.9, 121.8, 120.5, 120.4, 117.3, 109.3, 103.1, 37.9, 14.1.
LC-MS (positive mode): m/z = 433 (M + H)+, 434 (M + 1).
Anal. Calcd for C29H20ClNO: C, 80.27; H, 4.65; N, 3.23. Found: C,
80.52; H, 4.85; N, 3.18.
LC-MS (positive mode): m/z = 338 (M + H)+.
2,5-Diethyl-8-methyl-3-phenylcyclopenta[b]carbazol-1(5H)-
one (3r)
Anal. Calcd for C24H19NO: C, 85.43; H, 5.68; N, 4.15. Found: C,
85.32; H, 5.62; N, 4.21.
Yield: 0.069 g (60%); orange solid; mp 106–108 °C.
IR (KBr): 2966, 2920, 1689, 1597, 1375, 1238, 1022, 704 cm–1.
Supporting Information for this article is available online at
1H NMR (400 MHz, CDCl3/TMS): d = 8.17 (s, 1 H), 7.82 (s, 1 H),
7.68–7.50 (m, 5 H), 7.27 (dd, J = 2.0, 1.2 Hz, 2 H), 6.89 (s, 1 H),
4.26 (q, J = 7.2 Hz, 2 H), 2.54 (s, 3 H), 2.40 (q, J = 7.2 Hz, 2 H),
1.38 (t, J = 7.2 Hz, 3 H), 1.16 (t, J = 7.2 Hz, 3 H).
http://www.thieme-connect.com/ejournals/toc/synthesis. Included
1
are spectroscopic data of all synthesized compounds 3a–u: H
NMR, 13C NMR, DEPT, LC-MS, and elemental analysis, and 2D
NOESY of 3r.
13C NMR (100 MHz, CDCl3/TMS): d = 197.1, 153.8, 144.4, 142.8,
139.1, 138.3, 133.3, 129.8, 128.8, 127.9, 126.0, 123.1, 120.7, 120.0,
116.6, 108.9, 102.7, 37.8, 21.4, 16.9, 14.1, 14.0.
Acknowledgment
We gratefully acknowledge DST for financial assistance (project
number SR/S1/OC-70/2008) and providing a single-crystal X-ray
diffractometer facility in our school. D.K.S. thanks CSIR for a Se-
nior Research Fellowship. D.K.S. also thanks Rambabu for helping
with crystal studies.
LC-MS (positive mode): m/z = 367 (M + H)+.
Anal. Calcd for C26H23NO: C, 85.45; H, 6.34; N, 3.83. Found: C,
85.32; H, 6.41; N, 3.79.
2,5-Diethyl-3-phenylcyclopenta[b]carbazol-1(5H)-one (3s)
Yield: 0.066 g (54%); orange solid; mp 178–180 °C (CDCl3).
IR (KBr): 2976, 1687, 1593, 1392, 1331, 1016, 785 cm–1.
References
1H NMR (400 MHz, CDCl3/TMS): d = 8.20 (s, 1 H), 8.03 (d, J = 8.0
Hz, 1 H), 7.62–7.52 (m, 5 H), 7.46–7.38 (m, 2 H), 7.29–7.25 (m, 1
H), 6.91 (s, 1 H), 4.30 (q, J = 7.2 Hz, 2 H), 2.40 (q, J = 7.2 Hz, 2 H),
1.40 (t, J = 7.2 Hz, 3 H), 1.16 (t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3/TMS): d = 197.1, 153.9, 144.6, 142.7,
140.0, 139.2, 133.3, 128.8, 127.9, 125.4, 124.1, 123.4, 121.0, 120.3,
120.2, 116.6, 109.1, 102.7, 37.8, 16.9, 14.1.
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LC-MS (positive mode): m/z = 351 (M + H)+.
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Anal. Calcd for C25H21NO: C, 85.44; H, 6.02; N, 3.99. Found: C,
85.36; H, 6.08; N, 3.86.
5-Benzyl-2-ethyl-3-phenylcyclopenta[b]carbazol-1(5H)-one (3t)
Yield: 0.070 g (62%); orange solid; mp 98–99 °C.
Thielemans, J.; Viaene, L.; Cotlet, M.; Hofkens, J.; Weil, T.;
© Thieme Stuttgart · New York
Synthesis 2012, 44, 1268–1278

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(14) X-ray crystallographic data for 3a: Formula: C30H23N1O1.
Unit cell parameters: a = 9.0690(13), b = 10.359(2),
c = 13.357(2), a = 85.794(15), b = 72.369(13),
g = 70.831(16), space group P1. X-ray crystallographic data
for 3r: Formula: C26H23N1O1. Unit cell parameters:
a = 8.3997(16), b = 10.227(2), c = 12.402(2), a = 76.514(3),
b = 78.141(3), g = 75.769(3), space group P1. X-ray
crystallographic data for 3s: Formula: C25H21N1O1. Unit cell
parameters: a = 7.9184(6), b = 10.4371(7), c = 12.1136(10),
a = 76.338(6), b = 83.212(7), g = 77.905(6), space group P1.
The CCDC deposition numbers of compounds 3a,r,s are
840023, 840025, and 840024, respectively. Further data can
be obtained free of charge at www.ccdc.cam.ac.uk/conts/
retrieving.html [or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
+44(1223)336033, E-mail: deposit@ccdc.cam.ac.uk].
Synthesis 2012, 44, 1268–1278
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