One-pot synthesis of fused benzo[c]carbazoles by photochemical intramolecular annulation of 3-acyl-2-haloindoles with tethered styrenes

Article abstract of DOI:10.1002/ejoc.201100876

An efficient procedure for the synthesis of fused benzo[c]carbazoles has been achieved in moderate to high yields by the one-pot photochemical annulation of 3-acyl-2-haloindoles with tethered styrenes by photoinduced electron-transfer coupling, electrocyclic reactions, and deacylative aromatization in the presence of pyridine. Fused furo[2,3-c]carbazoles were also synthesized under the same conditions. 5,6-Dihydrobenzo[c]pyrrolo[1,2,3-lm] carbazoles were oxidized by DDQ to afford aromatic benzo[c]pyrrolo[1,2,3-lm] carbazole products in moderate to high yields.

Full text of DOI:10.1002/ejoc.201100876

FULL PAPER
DOI: 10.1002/ejoc.201100876
One-Pot Synthesis of Fused Benzo[c]carbazoles by Photochemical
Intramolecular Annulation of 3-Acyl-2-haloindoles with Tethered Styrenes
Shen-Ci Lu,[a] Shi-Chao Wei,[a] Wei-Xia Wang,[a] Wei Zhang,*[a] and Zhi-Feng Tu[a]
Keywords: Benzo[c]carbazoles / Photochemistry / C–C coupling / Aromatization / Styrenes / Halogens
An efficient procedure for the synthesis of fused benzo[c]-
carbazoles has been achieved in moderate to high yields by
the one-pot photochemical annulation of 3-acyl-2-haloind-
oles with tethered styrenes by photoinduced electron-trans-
fer coupling, electrocyclic reactions, and deacylative aroma-
tization in the presence of pyridine. Fused furo[2,3-c]carb-
azoles were also synthesized under the same conditions. 5,6-
Dihydrobenzo[c]pyrrolo[1,2,3-lm]carbazoles were oxidized
by DDQ to afford aromatic benzo[c]pyrrolo[1,2,3-lm]carb-
azole products in moderate to high yields.
Introduction
to dihydrophenanthrene (2b), that can be aromatized by the
action of a base (Scheme 1).[1,3]
The oxidative photocyclization of stilbenes (1) is the
most useful and versatile synthesis of phenanthrenes.[1] In
this reaction, the unstable intermediate dihydrophenan-
threne (2a) can be produced by photochemically allowed
conrotatory cyclization of (Z)-stilbene (1a) and then aroma-
tized in situ by an oxidant, leading to phenanthrene (3)
(Scheme 1). This reaction is equally useful for the synthesis
of phenanthrenoids, the heterocyclic analogues of phen-
anthrenes.[2]
Stilbenes are generally synthesized by several well-known
methods such as the Wittig reaction,[4] Heck reaction,[5] and
McMurry reaction.[6] Photochemical coupling of aryl ha-
lides with styrenes also supply another efficient route to
stilbenes. For example, Arnold reported the photochemical
coupling of 4-halobenzonitrile or 4-haloanisole with 1,1-di-
phenylethene to give 1-(4-cyanophenyl)-2,2-diphenylethene
or 1-(4-methoxyphenyl)-2,2-diphenylethene;[7a] Albini re-
ported the photochemical coupling of 4-bromo-N,N-di-
methylaniline with 1,1-diphenylethene to give 1-[4-(dimeth-
ylamino)phenyl]-2,2-diphenylethene;[7b] D’Auria reported
the photochemical coupling of 5-iodothiophene-2-carbal-
dehyde with styrene or 2-furylethene to afford 5-(2-phenyl-
ethenyl)thiophene-2-carbaldehyde or 5-[2-(2-furyl)ethenyl]-
thiophene-2-carbaldehyde.[7c] In all these reported reac-
tions, stilbenoids were generally formed by the deproton-
ation of the intermediate 1,2-diarylethyl cations derived
from the photoinduced electron-transfer reaction between
aryl halides with styrenes and the subsequent coupling of
the aryl radicals and the styrene radical cations or from the
addition of aryl cations to styrenes.
We have recently reported the photochemical coupling of
3-acyl-2-chloroindoles with styrenes and their subsequent
electrocyclic reaction and aromatization by deacylation by
a Norrish Type I reaction to afford benzo[c]carbazoles
(Scheme 2)[8a] and the photochemical intramolecular chlor-
ine atom transfer cyclization of 3-acyl-2-chloroindoles with
tethered alkenes.[8b]
Continuing our studies on the photoreactions of 3-acyl-
2-chloroheteroaromatics with olefins, especially the photo-
cyclization of stilbenoids produced in photoreactions and
the further aromatization of dihydrophenanthrenoids by de-
acylation, we report the combination of the above two reac-
tions to synthesize several fused benzo[c]carbazoles
(Scheme 3).
Scheme 1. Photocyclization of stilbenes.
The use of stilbenes containing a good leaving group at
one of the ortho positions of the aryl substituents (1b) al-
lows the operation of an interesting variant of the oxidative
photocyclization of stilbenes for the synthesis of phenan-
threnes. For example, the irradiation of stilbene (1b) leads
[a] State Key Laboratory of Applied Organic Chemistry,
Department of Chemistry, Lanzhou University,
Tianshui South Road 222, Lanzhou 730000, China
Fax: +86-931-8625657
E-mail: zhang_wei6275@yahoo.com
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201100876.
Eur. J. Org. Chem. 2011, 5905–5910
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5905

S.-C. Lu, S.-C. Wei, W.-X. Wang, W. Zhang, Z.-F. Tu
FULL PAPER
aldehyde (5a, Table 1). It was found that 5a could react in
all selected solvents to afford the cyclization product 6a.
However, the conversion of 5a and the yield of 6a depended
on the solvents. In CH2Cl2, the conversion of 5a and the
yield of 6a were relatively low, because the solution became
Table 1. Photoreaction of 5a in different solvents and additives.[a]
Scheme 2. Photochemical reaction of 2-chloroindole-3-carbal-
dehyde with styrene.
Entry
Solvent
t [h] Conversion [%][b] Yield [%][c]
1
2
3
4
5
CH2Cl2
Me2CO
CH2Cl2/pyridine
Me2CO/pyridine
MeCN/pyridine
8
8
12
12
15
81
92
90
99
88
80
85
87
96
87
Scheme 3. Photochemical reactions of 3-acyl-2-halo-1-(ω-phenyl-
alkenyl)indoles.
[a] 5a (0.3 mmol) was dissolved in solvent (25 mL) or pyridine
(0.1 mL). The solution was irradiated at λ Ͼ 300 nm with a me-
dium-pressure mercury lamp (500 W) under argon at ambient tem-
perature. [b] Conversion was calculated on the basis of substrate.
Results and Discussion
We first investigated the effect of solvents on the photo-
reaction of 2-chloro-1-(5-phenylpent-4-enyl)indole-3-carb- [c] Yield of isolated products based on consumed substrate.
Table 2. Photoreaction of 3-acyl-2-halo-1-(ω-phenylalkenyl)indoles.[a]
Entry
Substrate
X
n
R1
R2
t [h]
Conversion [%][b]
Product
Yield [%][c]
1
2
3
4
5
6
7
8
5a
5b
5c
5d
5e
5f
5g
5h
5i
Cl
Br
I
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
4
1
1
1
1
1
1
1
1
H
H
H
H
H
H
H
H
H
CH3
CH3
CH3
H
H
H
CH3
H
H
CH3
H
CH3
H
H
H
H
CH3
OCH3
Cl
F
Cl
NO2
OCH3
Cl
F
H
Cl
F
F
H
H
H
12
12
30
12
12
12
12
12
24
16
16
16
18
18
18
24
48
12
18
18
24
36
36
12
16
99
96
76
96
94
98
98
96
0
92
94
96
90
92
92
92
90
94
90
92
90
92
91
94
92
6a
6a
6a
6d
6e
6f
6g
6f
6i
96
95
92
90
91
96
97
95
n.r.[d]
91
95
92
89
91
93
91
86
92
90
88
86
83
81
91
90
Cl
Cl
Cl
Cl
Br
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
5j
5k
5l
6e
6f
6g
6m
6n
6o
6o
6q
6r
6r
6t
5m
5n
5o
5p
5q
5r
5s
5t
5u
5v
5w
5x
5y
CH3
CH3
OCH3
OCH3
Cl
6t
6v
6v
6x
6x
CH3
H
CH3
Cl
[a] 5a–y (0.3 mmol) was dissolved in dry acetone (25 mL) containing pyridine (0.1 mL). The solution was irradiated at λ Ͼ 300 nm with
a medium-pressure mercury lamp (500 W) under argon at ambient temperature. [b] Conversion was calculated on the basis of substrate.
[c] Yield of isolated products based on consumed substrate. [d] No reaction.
5906
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One-Pot Synthesis of Fused Benzo[c]carbazoles
dark in a short time; whereas, in acetone a little improve-
ment was observed. This result may be derived from the
sensitization effect of acetone to 5a because the ET value of
acetone is 326 kJmol–1,[9a] which is higher than that of 2-
chloroindole-3-carbaldehyde (ET = 275 kJmol–1).[9b] How-
ever, the conversion of 5a and the yield of 6a were increased
by the addition of base, such as pyridine, because the solu-
tion could be irradiated for a much longer time without
becoming dark as pyridine retarded the oligomerization of
indole derivatives induced by HCl and light. Comparatively,
the reaction was more efficient in acetone with the addition
of pyridine than in other solvents as shown in Table 1.
Therefore, acetone with addition of pyridine was selected as
the medium for the investigation of the photoreactions of
all substrates.
In order to investigate the effects of the substrate struc-
tures on the photoreaction efficiency, other similar sub-
strates 5b–y with different substituents on both the indolyl
and phenyl groups and tethers were synthesized and exam-
ined under the same photoreaction conditions. All of the
substrates except 5i gave the corresponding cyclization
products 6 in moderate to high yields as shown in Table 2.
It was found that the substituents on both the indolyl and
phenyl rings and tethers all had a large influence on the
photoreaction efficiency and the yields of product 6. Com-
paratively, the conversion of the photoreaction of 2-chloro-
Figure 1. X-ray crystal structure of 6f.
Table 3. Photoreaction of 3-acyl-2-chloro-1-(ω-furanylalkenyl)-
indoles.[a]
1-(5-phenylpent-4-enyl)indole-3-carbaldehyde
(5a),
2-
bromo-1-(5-phenylpent-4-enyl)indole-3-carbaldehyde (5b)
and 2-iodo-1-(5-phenylpent-4-enyl)indole-3-carbaldehyde
(5c) decreased gradually within the same irradiation time.
An electron-withdrawing group on the phenyl ring (e.g. Cl,
F) in 5f–g (Table 2, Entries 6 and 7) increased both the con-
version of 5f–g and the yields of 6f–g compared to those
with an electron-donating group on the phenyl ring (e.g.
CH3, OCH3) in 5d and 5e (Table 2, Entries 4 and 5). How-
ever, for the substrate with an NO2 group on the phenyl
ring (Table 2, Entry 9) no desired product was obtained.
The substrates with short tethers (5r and 5a, n = 1 and
2, respectively) reacted more easily to form five- and six-
membered rings (6r and 6a) than those with long tethers
(5m and 5q, n = 3 and 4, respectively) to form seven- and
eight-membered rings (6m and 6q). Despite all these differ-
ences, the photoreactions of all these substrates gave fused
benzo[c]carbazoles in high to excellent yields. The products
were fully identified by 1H and 13C NMR spectroscopy and
MS, and the structure of 6f was further confirmed by X-
ray crystallography (Figure 1).
Entry Substrate
n
R1
H
t
[h]
Conversion Product Yield
[%][b]
[%][c]
1
2
3
4
7a
7b
7c
7d
1
1
2
2
48
89
82
97
92
8a
8a
8c
8c
80
65
95
90
CH3 60
16
CH3 24
H
[a] 7a–d (0.3 mmol) was dissolved in dry acetone (25 mL) contain-
ing pyridine (0.1 mL). The solution was irradiated at λ Ͼ 300 nm
with a medium-pressure mercury lamp (500 W) under argon at am-
bient temperature. [b] Conversion was calculated on the basis of
substrate. [c] Yield of isolated products based on consumed sub-
strate.
Table 4. Aromatization of five-membered benzo[c]carbazoles 6r, 6t,
and 6x.[a]
Furthermore, to expand the scope of this reaction, we
investigated the photoreaction of 3-acyl-2-halo-1-(ω-furyl-
alkenyl)indoles. It was found that, under optimized condi-
tions, 7a–d were converted into the corresponding cycliza-
tion products 8a–c in moderate to good yields as depicted
in Table 3. Comparatively, the six-membered ring product
8c was more easily formed than the five-membered com-
pound 8a. The conversion of the photoreaction of 3-for-
mylindole derivatives (Table 3, Entries 1 and 3) was higher
than that of 3-acetylindole derivatives (Table 3, Entries 2
and 4).
Entry Substrate
R2
t
[h]
Conversion Product Yield
[%][b]
[%][c]
1
2
3
6r
6t
6x
H
CH3
Cl
12
12
12
98
82
96
9r
9t
9x
96
83
95
[a] 6r–x (0.3 mmol) was dissolved in dry CH2Cl2 (25 mL), and the
solution was stirred at room temperature. [b] Conversion was calcu-
lated on the basis of substrate. [c] Yield of isolated products based
on consumed substrate.
Eur. J. Org. Chem. 2011, 5905–5910
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S.-C. Lu, S.-C. Wei, W.-X. Wang, W. Zhang, Z.-F. Tu
FULL PAPER
123.5, 123.1, 122.5, 122.0, 121.8, 119.4, 112.3, 108.7, 41.3, 25.5,
22.6, 22.1 ppm. MS: m/z (%) = 271 (100), 254 (22.9), 149 (21.2),
121 (24.4), 40 (55.7). ESI-HRMS: calcd. for [C20H17N + H]+
272.1444; found 272.1442. C20H17N (271.36): calcd. C 88.52, H
6.31, N 5.16; found C 88.59, H 6.28, N 5.12.
We then tried the aromatization of the photoreaction
products 6r, 6t, and 6x by 2,3-dichloro-5,6-dicyanobenzo-
quinone (DDQ). The results showed that these five-mem-
bered ring-fused benzo[c]carbazoles were readily oxidized
by DDQ at room temperature to afford aromatic products
9r–x in moderate to high yields (Table 4).
7,8-Dihydro-12-methoxy-6H-benzo[c]pyrido[1,2,3-lm]carbazole (6e):
1
Colorless solid. M.p. 146–148 °C. H NMR (400 MHz, CDCl3): δ
= 8.45 (d, J = 8.0 Hz, 1 H), 7.99 (d, J = 2.4 Hz, 1 H), 7.82 (d, J =
8.8 Hz, 1 H), 7.45–7.51 (m, 3 H), 7.36 (t, J = 6.8 Hz, 1 H), 7.08
(dd, J = 8.8, 2.4 Hz, 1 H), 4.31 (t, J = 6.0 Hz, 2 H), 4.06 (s, 3 H),
3.15 (t, J = 6.0 Hz, 2 H), 2.30–2.36 (m, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 157.9, 138.7, 136.4, 130.1, 130.0, 124.3,
123.6, 123.4, 123.1, 121.6, 120.2, 119.4, 113.5, 112.2, 108.7, 103.2,
55.3, 41.2, 25.3, 22.6 ppm. MS: m/z (%) = 287 (100), 244 (44.7),
143 (20.8), 120 (14.9), 39 (4.2). ESI-HRMS: calcd. for [C20H17NO
+ H]+ 288.1383; found 288.1381. C20H17NO (287.36): calcd. C
83.59, H 5.96, N 4.87; found C 83.67, H 5.91, N 4.84.
Conclusions
An efficient procedure for the synthesis of fused benzo-
[c]carbazoles has been achieved in moderate to high yields
by a one-pot intramolecular photochemical annulation of
3-acyl-2-haloindoles with tethered styrenes in the presence
of pyridine. The fused benzo[c]carbazoles were formed by
two sequential photocyclization reactions, namely, intramo-
lecular photoinduced electron-transfer coupling of 3-acyl-
2-haloindoles with styrenes and deacylative 6π-electrocyclic
reactions.
12-Chloro-7,8-dihydro-6H-benzo[c]pyrido[1,2,3-lm]carbazole
(6f):
1
Colorless solid. M.p. 124–126 °C. H NMR (400 MHz, CDCl3): δ
= 8.57 (d, J = 2.0 Hz, 1 H), 8.45 (d, J = 8.0 Hz, 1 H), 7.80 (d, J =
8.0 Hz, 1 H), 7.47–7.48 (m, 3 H), 7.38 (td, J = 4.8, 3.2 Hz, 1 H),
7.34 (td, J = 8.8, 2.0 Hz, 1 H), 4.27 (t, J = 6.0 Hz, 2 H), 3.13 (t, J
= 6.0 Hz, 2 H), 2.28–2.34 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 138.7, 136.3, 131.5, 130.1, 129.6, 127.6, 124.0, 123.1,
123.1, 123.04, 122.9, 122.1, 121.8, 119.8, 111.9, 108.9, 41.2, 25.4,
22.4 ppm. MS: m/z (%) = 293 (33.5), 291 (100), 254 (17.9), 227
(7.6), 146 (11.6), 127 (24.3), 57 (17.0), 43 (26.2). ESI-HRMS: calcd.
for [C19H14ClN + H]+ 292.0888; found 292.0886. C19H14ClN
(291.78): calcd. C 78.21, H 4.84, N 4.80; found C 78.28, H 4.81, N
4.76. CCDC-784302 (for 6f) contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Experimental Section
General Procedure for Photochemical Reactions: Substrate 5a
(0.097 g, 0.3 mmol) was dissolved in dry acetone (25 mL) contain-
ing pyridine (0.1 mL). The solution was deaerated by bubbling Ar
for 30 min and irradiated at λ Ͼ 300 nm with a medium-pressure
mercury lamp (500 W) at ambient temperature. The progress of
reaction was monitored by TLC at regular intervals. After the sol-
vent had been removed under reduced pressure, the residue was
separated by column chromatography on silica gel eluted by hex-
ane/ethyl acetate, 20:1 (v/v) to afford product 6a.
General Procedure for the DDQ Oxidation of Five-Membered Fused
Benzo[c]carbazoles: To a solution of the substrate in CH2Cl2
(15 mL) was added DDQ, and the mixture was stirred at room
temperature for 12 h. An aqueous saturated NaHCO3 solution
(10 mL) was added, and the resulting mixture was extracted with
CH2Cl2 (3ϫ 10 mL). The combined organic layers were dried with
Na2SO4, filtered, and concentrated in vacuo. The reaction mixture
was purified by flash chromatography (hexane/EtOAc) to afford
the desired product.
12-Fluoro-7,8-dihydro-6H-benzo[c]pyrido[1,2,3-lm]carbazole
(6g):
1
Colorless solid. M.p. 123–124 °C. H NMR (400 MHz, CDCl3): δ
= 8.45 (d, J = 8.0 Hz, 1 H), 8.25 (d, J = 8.4 Hz, 1 H), 7.89 (dd, J
= 8.8, 6.4 Hz, 1 H), 7.47–7.54 (m, 3 H), 7.39 (td, J = 6.8, 1.6 Hz,
1 H), 7.17 (td, J = 8.8, 2.4 Hz, 1 H), 4.33 (t, J = 6.0 Hz, 2 H), 3.18
(t, J = 6.0 Hz, 2 H), 2.33–2.39 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 161.2 (d, J = 243.0 Hz), 138.7, 136.4, 130.7 (d, J =
10.0 Hz), 129.7 (d, J = 9.0 Hz), 126.2, 123.8, 123.3, 123.1, 122.0 (d,
J = 3.0 Hz), 121.6, 119.8, 112.4 (d, J = 5.0 Hz), 111.8 (d, J =
24.0 Hz), 108.9, 107.2 (d, J = 22.0 Hz), 41.3, 25.4, 22.5 ppm. MS:
m/z (%) = 275 (100), 149 (8.4), 137 (14.3), 126 (7.8), 40 (40.9).
ESI-HRMS: calcd. for C19H14FN + H]+ 276.1183; found 276.1186.
C19H14FN (275.32): calcd. C 82.89, H 5.13, N 5.09; found C 82.85,
H 5.15, N 5.12.
7,8-Dihydro-6H-benzo[c]pyrido[1,2,3-lm]carbazole (6a): Colorless
1
solid. M.p. 93–94 °C. H NMR (400 MHz, CDCl3): δ = 8.66 (d, J
= 8.0 Hz, 1 H), 8.51 (d, J = 8.0 Hz, 1 H), 7.90 (d, J = 8.0 Hz, 1
H), 7.67 (t, J = 8.0 Hz, 1 H), 7.51 (s, 1 H), 7.44–7.46 (m, 2 H), 7.40
(t, J = 7.2 Hz, 1 H), 7.33–7.38 (m, 1 H), 4.23 (t, J = 6.0 Hz, 2 H),
3.11 (t, J = 6.0 Hz, 2 H), 2.24–2.30 (m, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 138.6, 135.8, 129.4, 128.9, 128.7, 125.7,
123.6, 123.4, 123.2, 122.94, 122.90, 122.4, 122.0, 119.5, 112.6,
108.8, 41.1, 25.5, 22.5 ppm. MS: m/z (%) = 257 (100), 241 (7.0),
228 (9.1), 128 (16.9), 114 (7.6), 100 (6.9), 39 (9.5). ESI-HRMS:
calcd. for [C19H15N + H]+ 258.1277; found 258.1276. C19H15N
(257.33): calcd. C 88.68, H 5.88, N 5.44; found C 88.74, H 5.84, N
5.42.
6,7,8,9-Tetrahydrobenzo[c]azepino[1,2,3-lm]carbazole (6m): Color-
less solid. M.p. 123–125 °C. 1H NMR (400 MHz, CDCl3): δ = 8.74
(d, J = 8.0 Hz, 1 H), 8.57 (d, J = 8.0 Hz, 1 H), 7.90 (d, J = 8.0 Hz,
1 H), 7.63 (td, J = 7.6, 0.8 Hz, 1 H), 7.53–7.56 (m, 2 H), 7.48 (t, J
= 7.6 Hz, 1 H), 7.42 (t, J = 7.2 Hz, 1 H), 7.36 (t, J = 7.2 Hz, 1 H),
4.55 (t, J = 5.2 Hz, 2 H), 3.36 (t, J = 5.2 Hz, 2 H), 2.21–2.30 (m,
4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 140.3, 139.4, 129.3,
128.9, 128.3, 128.1, 126.02, 126.01, 123.8, 123.7, 122.9, 122.8,
122.0, 119.6, 115.6, 109.3, 43.6, 31.8, 27.9, 26.2 ppm. MS: m/z (%)
= 271 (100), 254 (12.2), 242 (13.8), 136 (14.1), 127 (13.1), 41 (16.7).
ESI-HRMS: calcd. for [C20H17N + H]+ 272.1434; found 272.1432.
C20H17N (271.36): calcd. C 88.52, H 6.31, N 5.16; found C 88.59,
H 6.28, N 5.12.
7,8-Dihydro-12-methyl-6H-benzo[c]pyrido[1,2,3-lm]carbazole (6d):
1
Colorless solid. M.p. 133–134 °C. H NMR (400 MHz, CDCl3): δ
= 8.55 (d, J = 8.0 Hz, 1 H), 8.45 (s, 1 H), 7.82 (d, J = 8.4 Hz, 1
H), 7.44–7.52 (m, 3 H), 7.36 (t, J = 7.2 Hz, 1 H), 7.25 (t, J =
5.6 Hz, 1 H), 4.32 (t, J = 6.0 Hz, 2 H), 3.17 (t, J = 6.0 Hz, 2 H),
2.65 (s, 3 H), 2.32–2.38 (m, 2 H) ppm. 13C NMR (100 MHz, 13-Chloro-6,7,8,9-tetrahydrobenzo[c]azepino[1,2,3-lm]carbazole
CDCl3): δ = 138.7, 136.1, 135.5, 129.2, 128.6, 127.5, 124.5, 123.6,
(6n): Colorless solid. M.p. 92–95 °C. 1H NMR (400 MHz, CDCl3):
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 5905–5910

One-Pot Synthesis of Fused Benzo[c]carbazoles
δ = 8.66 (s, 1 H), 8.50 (d, J = 8.0 Hz, 1 H), 7.80 (d, J = 8.0 Hz, 1
H), 7.48–7.54 (m, 3 H), 7.34–7.39 (m, 2 H), 4.53 (t, J = 5.6 Hz, 2
= 8.31 (d, J = 8.0 Hz, 1 H), 7.83 (d, J = 9.2 Hz, 1 H), 7.81 (s, 1
H), 7.47–7.49 (m, 2 H), 7.41 (t, J = 7.2 Hz, 1 H), 7.33 (t, J =
H), 3.32 (t, J = 5.6 Hz, 2 H), 2.19–2.28 (m, 4 H) ppm. 13C NMR 7.2 Hz, 1 H), 7.05 (dd, J = 8.8, 2.4 Hz, 1 H), 4.61 (t, J = 7.2 Hz, 2
(100 MHz, CDCl3): δ = 140.2, 139.8, 131.7, 129.6, 129.4, 128.3, H), 4.05 (s, 3 H), 3.89 (t, J = 7.2 Hz, 2 H) ppm. 13C NMR
127.5, 125.6, 124.1, 123.5, 123.3, 122.0, 121.7, 119.9, 114.8, 109.4,
43.5, 31.7, 27.8, 26.1 ppm. MS: m/z (%) = 307 (32.5), 305 (100),
254 (9.2), 241 (16.6), 152 (7.1), 127 (13.8), 41 (14.1). ESI-HRMS:
calcd. for [C20H16ClN + H]+ 306.1044; found 306.1047. C20H16ClN
(305.81): calcd. C 78.55, H 5.27, N 4.58; found C 78.52, H 5.28, N
4.55.
(100 MHz, CDCl3): δ = 158.1, 150.3, 138.3, 130.9, 130.8, 128.6,
127.0, 123.4, 123.1, 122.2, 120.5, 119.3, 112.6, 110.5, 107.3, 104.2,
55.4, 47.8, 33.1 ppm. MS: m/z (%) = 273 (100), 242 (85.7), 120
(29.2), 106 (8.6), 93 (14.6), 51 (9.2). ESI-HRMS: calcd. for
[C19H15NO + H]+ 274.1227; found 274.1229. C19H15NO (273.33):
calcd. C 83.49, H 5.53, N 5.12; found C 83.46, H 5.55, N 5.10.
13-Fluoro-6,7,8,9-tetrahydrobenzo[c]azepino[1,2,3-lm]carbazole (6o):
11-Chloro-6,7-dihydrobenzo[c]pyrrolo[1,2,3-lm]carbazole (6x): Col-
1
Colorless solid. M.p. 124–126 °C. H NMR (400 MHz, CDCl3): δ orless solid. M.p. 165–167 °C. 1H NMR (400 MHz, CDCl3): δ =
= 8.47 (d, J = 8.0 Hz, 1 H), 8.31 (dd, J = 11.2, 2.4 Hz, 1 H), 7.86 8.35 (d, J = 2.0 Hz, 1 H), 8.30 (d, J = 8.0 Hz, 1 H), 7.81 (d, J =
(dd, J = 8.8, 6.0 Hz, 1 H), 7.52–7.55 (m, 2 H), 7.49 (td, J = 7.2,
1.2 Hz, 1 H), 7.37 (td, J = 8.0, 0.8 Hz, 1 H), 7.18 (td, J = 8.4,
2.4 Hz, 1 H), 4.55 (t, J = 6.0 Hz, 2 H), 3.34 (t, J = 6.0 Hz, 2 H),
2.21–2.29 (m, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 161.2
(d, J = 243.0 Hz), 140.2, 139.9, 132.4 (d, J = 30.0 Hz), 130.3 (d, J
= 9.0 Hz), 127.1, 126.1, 125.7, 124.0, 123.5, 121.5, 119.9, 113.4 (d,
8.8 Hz, 1 H), 7.40–7.47 (m, 3 H), 7.30–7.36 (m, 2 H), 4.57 (t, J =
7.2 Hz, 2 H), 3.86 (t, J = 7.2 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 149.9, 138.1, 131.6, 130.8, 130.4, 130.3, 128.1, 126.2,
123.6, 122.6, 122.42, 122.41, 120.2, 119.6, 110.6, 106.8, 47.7,
33.2 ppm. MS: m/z (%) = 279 (33.2), 277 (100), 242 (95.5), 120
(39.2), 106 (10.6), 51 (4.2). ESI-HRMS: calcd. for [C18H12ClN +
J = 5.0 Hz), 112.3 (d, J = 24.0 Hz), 109.4, 107.1 (d, J = 21.0 Hz), H]+ 278.0731; found 278.0735. C18H12ClN (277.75): calcd. C 77.84,
43.6, 31.7, 27.9, 26.2 ppm. MS: m/z (%) = 289 (100), 274 (15.9),
149 (16.4), 127 (19.5), 40 (66.7). ESI-HRMS: calcd. for [C20H16FN
+ H]+ 290.1340; found 290.1345. C20H16FN (289.35): calcd. C
83.02, H 5.57, N 4.84; found C 83.05, H 5.56, N 4.81.
H 4.35, N 5.04; found C 77.86, H 4.37, N 5.01.
5,6-Dihydrofuro[2,3-c]pyrrolo[1,2,3-lm]carbazole (8a): Colorless so-
1
lid. M.p. 145–146 °C. H NMR (400 MHz, CDCl3): δ = 8.12 (d, J
= 8.0 Hz, 1 H); 7.76 (s, 1 H), 7.40–7.44 (m, 3 H), 7.25 (d, J =
9.6 Hz, 1 H), 7.17 (s, 1 H), 4.63 (t, J = 7.2 Hz, 2 H), 3.93 (t, J =
6,7,8,9-Tetrahydro-10H-benzo[c]azocino[1,2,3-lm]carbazole
(6q):
1
Colorless solid. M.p. 162–163 °C. H NMR (400 MHz, CDCl3): δ 7.2 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 152.5, 148.0,
= 8.81 (d, J = 8.4 Hz, 1 H), 8.63 (d, J = 8.0 Hz, 1 H), 7.92 (d, J =
8.0 Hz, 1 H), 7.66 (td, J = 8.0, 0.8 Hz, 1 H), 7.57 (s, 1 H), 7.44–
7.55 (m, 3 H), 7.39 (t, J = 6.8 Hz, 1 H), 4.82 (br., 2 H), 3.51 (br.,
144.3, 139.2, 127.4, 124.0, 122.4, 121.0, 119.0, 118.5, 110.3, 106.6,
105.6, 105.4, 48.3, 33.7 ppm. MS: m/z (%) = 233 (100), 204 (15.0),
176 (9.3), 149 (4.3), 108 (11.1), 39 (11.2). ESI-HRMS: calcd. for
2 H), 2.01–2.09 (m, 4 H), 1.41 (br., 2 H) ppm. 13C NMR (100 MHz, [C16H11NO + H]+ 234.0914; found 234.0917. C16H11NO (233.27):
CDCl3): δ = 139.4, 139.1, 129.2, 129.1, 128.3, 128.2, 126.1, 126.0,
123.7, 123.2, 122.8, 122.7, 121.9, 119.5, 114.6, 108.5, 43.0, 33.4,
29.77, 29.73, 21.5 ppm. MS: m/z (%) = 285 (100), 254 (12.8), 241
(8.4), 230 (12.7), 127 (5.5). ESI-HRMS: calcd. for [C21H19N + H]
+: 286.1590; found 286.1593. C21H19N (285.39): calcd. C 88.38, H
6.71, N 4.91; found C 88.45, H 6.67, N 4.88.
calcd. C 82.38, H 4.75, N 6.00; found C 82.35, H 4.76, N 6.03.
5,6-Dihydro-7H-furo[2,3-c]pyrido[1,2,3-lm]carbazole (8c): Colorless
1
solid. M.p. 78–80 °C. H NMR (400 MHz, CDCl3): δ = 8.18 (d, J
= 8.0 Hz, 1 H); 7.75 (d, J = 2.0 Hz, 1 H), 7.43–7.48 (m, 2 H), 7.39
(s, 1 H), 7.24–7.29 (m, 2 H), 4.30 (t, J = 6.0 Hz, 2 H), 3.17 (t, J =
6.0 Hz, 2 H), 2.31–2.37 (m, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 150.5, 144.2, 139.3, 134.0, 124.4, 122.3, 121.4, 118.5,
6,7-Dihydrobenzo[c]pyrrolo[1,2,3-lm]carbazole (6r): Colorless solid.
M.p. 157–158 °C. 1H NMR (400 MHz, CDCl3): δ = 8.45 (d, J = 118.4, 118.2, 111.9, 108.3, 107.2, 105.3, 41.2, 25.6, 22.7 ppm. MS:
8.0 Hz, 1 H), 8.35 (d, J = 8.0 Hz, 1 H), 7.91 (d, J = 8.0 Hz, 1 H), m/z (%) = 247 (100), 218 (15.0), 190 (7.3), 163 (7.3), 108 (11.1), 39
7.60 (td, J = 8.0, 1.2 Hz, 1 H), 7.36–7.46 (m, 4 H), 7.32 (td, J =
8.0, 1.2 Hz, 1 H), 4.51 (t, J = 7.2 Hz, 2 H), 3.83 (t, J = 7.2 Hz, 2 248.1074. C17H13NO (247.30): calcd. C 82.57, H 5.30, N 5.66;
(11.2). ESI-HRMS: calcd. for [C17H13NO + H]+ 248.1070; found
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 149.6, 138.2, 132.3,
129.7, 129.6, 128.5, 125.9, 125.8, 123.26, 123.25, 122.5, 122.2,
120.5, 119.3, 110.56, 107.5, 47.6, 33.2 ppm. MS: m/z (%) = 243
(100), 213 (5.5), 120 (19.2), 106 (8.6), 93 (4.6), 51 (4.2). ESI-HRMS:
calcd. for [C18H13N + H]+ 244.1121; found 244.1125. C18H13N
(243.31): calcd. C 88.86, H 5.39, N 5.76; found C 88.89, H 5.40, N
5.72.
found C 82.54, H 5.32, N 5.69.
Benzo[c]pyrrolo[1,2,3-lm]carbazole (9r): Colorless solid. M.p. 69–
70 °C. 1H NMR (400 MHz, CDCl3): δ = 8.65 (d, J = 8.4 Hz, 1 H),
8.42 (d, J = 7.6 Hz, 1 H), 8.28 (s, 1 H), 8.25 (d, J = 8.4 Hz, 1 H),
7.92 (d, J = 3.2 Hz, 1 H), 7.77 (d, J = 8.0 Hz, 1 H), 7.72 (td, J =
6.8, 1.2 Hz, 1 H), 7.54 (td, J = 6.8, 1.2 Hz, 1 H), 7.49 (td, J = 7.6,
1.2 Hz, 1 H), 7.42 (td, J = 7.6, 1.2 Hz, 1 H), 6.95 (d, J = 3.2 Hz, 1
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 140.5, 137.8, 133.0,
6,7-Dihydro-11-methylbenzo[c]pyrrolo[1,2,3-lm]carbazole (6t): Col-
orless solid. M.p. 185–186 °C. 1H NMR (400 MHz, CDCl3): δ = 131.11, 131.10, 130.8, 127.8, 126.3, 126.1, 125.1, 123.9, 123.5,
8.36 (d, J = 7.6 Hz, 1 H), 8.22 (s, 1 H), 7.80 (d, J = 8.4 Hz, 1 H),
7.43–7.45 (m, 2 H), 7.39 (td, J = 8.0, 1.2 Hz, 1 H), 7.32 (td, J =
122.8, 122.7, 122.0, 121.9, 111.5, 109.4 ppm. MS: m/z (%) = 241
(100), 225 (9.1), 128 (36.9), 114 (7.6), 100 (6.9), 39 (9.5). ESI-
8.0, 0.8 Hz, 1 H), 7.21 (dd, J = 8.4, 1.6 Hz, 1 H), 4.53 (t, J = HRMS: calcd. for [C18H11N + H]+ 242.0966; found 242.0968.
7.2 Hz, 2 H), 3.83 (t, J = 7.2 Hz, 2 H), 2.62 (s, 3 H) ppm. 13C C18H11N (241.29): calcd. C 89.60, H 4.60, N 5.81; found C 89.64,
NMR (100 MHz, CDCl3): δ = 149.8, 138.2, 135.6, 130.3, 129.8,
129.4, 128.6, 124.9, 124.1, 123.1, 122.9, 122.5, 120.4, 119.2, 110.4,
107.2, 47.7, 33.2, 21.9 ppm. MS: m/z (%) = 257 (100), 227 (35.5),
120 (49.6), 106 (10.6), 93 (24.3), 51 (4.2). ESI-HRMS: calcd. for
[C19H15N + H]+ 258.1277; found 258.1274. C19H15N (257.33):
calcd. C 88.68, H 5.88, N 5.44; found C 88.64, H 5.89, N 5.47.
H 4.59, N 5.78.
11-Methylbenzo[c]pyrrolo[1,2,3-lm]carbazole (9t): Colorless solid.
M.p. 122–123 °C. 1H NMR (400 MHz, CDCl3): δ = 8.44 (d, J =
7.2 Hz, 1 H), 8.41 (s, 1 H), 8.24 (s, 1 H), 8.14 (d, J = 8.4 Hz, 1 H),
7.90 (d, J = 3.2 Hz, 1 H), 7.77 (d, J = 7.6 Hz, 1 H), 7.48 (td, J =
7.6, 1.2 Hz, 1 H), 7.42 (td, J = 7.6, 1.2 Hz, 1 H), 7.37 (dd, J = 8.4,
1.6 Hz, 1 H), 6.93 (d, J = 3.2 Hz, 1 H), 2.69 (s, 3 H) ppm. 13C
6,7-Dihydro-11-methoxybenzo[c]pyrrolo[1,2,3-lm]carbazole
(6v):
1
Colorless solid. M.p. 162–163 °C. H NMR (400 MHz, CDCl3): δ NMR (100 MHz, CDCl3): δ = 140.6, 137.7, 136.1, 131.2, 130.8,
Eur. J. Org. Chem. 2011, 5905–5910
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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S.-C. Lu, S.-C. Wei, W.-X. Wang, W. Zhang, Z.-F. Tu
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128.7, 128.1, 125.9, 125.1, 124.8, 123.5, 123.1, 122.0, 121.8, 121.7,
111.4, 110.8, 109.4, 22.2 ppm. MS: m/z (%) = 255 (100), 239 (11.1),
128 (46.9), 114 (9.6), 100 (12.9), 39 (11.5). ESI-HRMS: calcd. for
[C19H13N + H]+ 256.1121; found 256.1123. C19H13N (255.32):
calcd. C 89.38, H 5.13, N 5.49; found C 89.35, H 5.11, N 5.53.
11-Chlorobenzo[c]pyrrolo[1,2,3-lm]carbazole (9x): Colorless solid.
M.p. 185–186 °C. 1H NMR (400 MHz, CDCl3): δ = 8.56 (d, J =
2.0 Hz, 1 H), 8.37 (d, J = 7.6 Hz, 1 H), 8.23 (s, 1 H), 8.15 (d, J =
8.8 Hz, 1 H), 7.91 (d, J = 3.2 Hz, 1 H), 7.76 (d, J = 8.0 Hz, 1 H),
7.41–7.52 (m, 3 H), 6.93 (d, J = 3.2 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 140.7, 137.8, 132.3, 132.3, 132.0, 131.1,
130.3, 128.1, 126.6, 125.4, 123.6, 123.4, 122.9, 122.2, 121.8, 111.5,
110.9, 109.5 ppm. MS: m/z (%) = 277 (32.3), 275 (100), 128 (36.9),
114 (7.6), 100 (6.9), 39 (9.5). ESI-HRMS: calcd. for [C18H10ClN +
H]+ 276.0575; found 276.0578. C18H10ClN (275.74): calcd. C 78.41,
H 3.66, N 5.08; found C 78.44, H 3.63, N 5.05.
[4]
[5]
[6]
Supporting Information (see footnote on the first page of this arti-
cle): General procedures for the preparation of the photoreaction
1
substrates and copies of the H and 13C NMR spectra for all new
compounds.
Acknowledgments
We are grateful to the National Nature Science Foundation of
China (Grant Nos. 20872056 and J0730425) and the “Young
Scholar of Distinction of Lanzhou University” award for financial
support.
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Org. Chem. 2010, 75, 6764.
Received: June 15, 2011
Published Online: August 17, 2011
5910
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 5905–5910