An efficient method for the synthesis of benzo[f]quinoline and benzo[a]phenanthridine derivatives catalyzed by iodine by a three-component reaction of arenecarbaldehyde, naphthalen-2-amine, and cyclic ketone

Article abstract of DOI:10.1002/ejoc.200800287

A mild, efficient, and general method for the synthesis of benzo[f]quinoline and benzo[a]phenanthridine derivatives by a three-component reaction of arenecarbaldehyde, naphthalen-2-amine, and cyclic ketone using iodine as catalyst is described. A possible

Full text of DOI:10.1002/ejoc.200800287

FULL PAPER
DOI: 10.1002/ejoc.200800287
An Efficient Method for the Synthesis of Benzo[f]quinoline and
Benzo[a]phenanthridine Derivatives Catalyzed by Iodine by a Three-Component
Reaction of Arenecarbaldehyde, Naphthalen-2-amine, and Cyclic Ketone
Xiang-Shan Wang,*[a,b] Qing Li,[a] Chang-Sheng Yao,[a] and Shu-Jiang Tu[a,b]
Keywords: Benzo[f]quinoline / Benzo[a]phenanthridine / Iodine / Cycloketone / Multicomponent reactions / Heterocycles
A mild, efficient, and general method for the synthesis of
benzo[f]quinoline and benzo[a]phenanthridine derivatives
by a three-component reaction of arenecarbaldehyde, naph-
thalen-2-amine, and cyclic ketone using iodine as catalyst is
described. A possible reaction mechanism for the formation
of the product is proposed based on further experimental re-
sults.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
an efficient, mild, and high-yielding process for the prepara-
tion of biologically active benzo[f]quinoline derivatives ap-
peared interesting.
Introduction
Multicomponent reactions (MCRs) are of paramount
importance in the context of green chemistry. They offer a
convenient strategy for the rapid and convergent construc-
tion of complex organic molecules without the need to iso-
late and purify the intermediates, resulting in a substantial
minimization of waste, labor, time, and cost. Thus, MCRs
have become increasingly popular in the last decade.[1]
Benzo[f]quinoline and its derivatives are very useful com-
pounds in various fields of chemistry, including biological
and pharmacological chemistry. Some of these compounds
exhibit antibacterial activity,[2] UDP (uridine diphosphate)
glucuronosyl transferase activity,[3] inhibitory activity of re-
combinant human type 1 and 2 steroid 5a-reductase in vi-
tro,[4] antimicrobial activity,[5] antimalarial activity,[6] ago-
nistic activity at postjunctional α1-receptors,[7] antipsychotic
activity,[8] and peripheral dopaminergic activity in cat car-
dioaccelerator nerve assays.[9]
In view of the importance of benzo[f]quinoline and its
derivatives, several methods for the synthesis of benzo[f]-
quinoline and its derivatives have been developed by Kozlov
and co-workers[10] and other groups.[11] However, in spite of
their potential utility, many of these reported methods suf-
fer from drawbacks such as harsh reaction conditions, un-
satisfactory yields, prolonged reaction times, and cumber-
some procedures for product isolation. The development of
In recent years, the use of iodine in organic synthesis has
received considerable attention as an inexpensive, nontoxic,
readily available, mild Lewis acid catalyst for organic trans-
formations, such as the dehydration of tertiary alcohols to
alkenes,[12] the synthesis of alkyl benzyl ethers,[13] mixed
ethers under hydrogen pressure,[14] and biindoles,[15] the de-
protection of acetals,[16] esterification,[17] transesterifica-
tion,[18] Michael addition,[19] and many other transforma-
tions.[20,21]
To the best of our knowledge, the literature records only
a few reports describing the synthesis of benzo[f]quinolines
from arenecarbaldehyde, naphthalen-2-amine, and cyclic
ketone. Kozlov and Basalaeva[22] recently reported the for-
mation of benzo[a]phenanthridines by a multistep reaction;
arenecarbaldehyde and naphthalen-2-amine in EtOH were
first converted into the Schiff base, which then reacted with
cyclohexanone catalyzed by HCl to form benzo[f]quino-
lines. However, this protocol suffered from the disadvan-
tages of multistep reactions, including low yields, which
were obtained with cycloheptanone as the substrate in
1971[23a] and with methylcyclohexanone in 2004.[23b] The
work presented herein is part of our continuing drive to
prepare heterocyclic compounds by multicomponent reac-
tions.[24] Herein we report the successful three-component
reaction of arenecarbaldehyde, naphthalen-2-amine, and cy-
clic ketone catalyzed by iodine in THF without having to
isolate and purify the intermediates, affording benzo[f]quin-
olines or benzo[a]phenanthridines in good-to-high yields,
including benzo[f]cyclopenta[c]quinoline, benzo[a]phen-
anthridine, benzo[f]cyclohepta[c]quinoline, benzo[f]cyclo-
octa[c]quinoline, and benzo[f]cyclododeca[c]quinoline de-
rivatives.
[a] School of Chemistry and Chemical Engineering, Xuzhou Nor-
mal University,
Xuzhou Jiangsu 221116, P. R. China
Fax: +86-516-83500065
E-mail: xswang1974@yahoo.com
[b] The Key Laboratory of Biotechnology on Medical Plants,
Xuzhou, Jiangsu 221116, P. R. China
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2008, 3513–3518
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3513

X.-S. Wang, Q. Li, C.-S. Yao, S.-J. Tu
FULL PAPER
proceeded efficiently at reflux under mild conditions to af-
ford the corresponding benzo[f]cyclopenta[c]quinolines in
high yields. However, we failed to obtain the expected prod-
ucts when other amines such as naphthalen-1-amine or p-
toluidine were used. We think a possible reason for this is
that p-toluidine or naphthalen-1-amine are less reactive
than naphthalene-2-amine. All the products were charac-
Results and Discussion
The treatment of arenecarbaldehyde 1, naphthalen-2-
amine (2), and cyclopentanone (3) in THF in the presence
of 5 mol-% iodine at reflux afforded the corresponding
benzo[f]cyclopenta[c]quinoline derivatives 4 in high yields
(Scheme 1).
1
terized by H and 13C NMR and IR spectroscopy and ele-
mental analyses.
Table 2. I2-catalyzed reactions of benzaldehyde, naphthalen-2-
amine, and cyclopentanone in THF.[a]
Entry
Ar
Product Time [h]
Yield [%][b]
Scheme 1.
1
2
3
4
5
6
7
8
9
2-ClC6H4
2-thienyl
2,4-Cl2C6H3
3-ClC6H4
4-BrC6H4
4-FC6H4
4a
4b
4c
4d
4e
4f
7
8
8
9
9
8
8
8
6
91
82
88
87
88
96
87
89
90
86
84
In our initial study, the reaction of 2-chlorobenzaldehyde
(1a), naphthalen-2-amine (2), and cyclopentanone (3) was
used as a model reaction to optimize the conditions. The
reaction was first carried out in THF in the absence of I2.
No reaction occurred at room temperature and under reflux
conditions (Table 1, Entries 1 and 2). Similar reactions were
then attempted in the presence of 5, 10, and 20 mol-% of
I2. The results in Table 1 (Entries 5–7) show that the use of
5 mol-% of I2 at reflux in THF is sufficient to push the
reaction forward. Higher loading of the catalyst had no sig-
nificant influence on the reaction yield. To find the opti-
mum reaction temperature, the reaction was carried out
with 5 mol-% of I2 at room temperature, 50 °C, and at re-
flux temperature, which resulted in the isolation of 4a in a
trace amount and 80 and 91% yields (Table 1, Entries 3–5),
respectively. Thus, 5 mol-% of I2 and a reaction temperature
at reflux were the optimal conditions. In addition, CH3CN,
benzene, DMF, and ClCH2CH2Cl (Table 1, Entries 8–11)
were also tested as the solvents. In these cases, product 4a
was formed in slightly lower yields (Table 1, Entries 8–11).
3-BrC6H4
4-ClC6H4
2-O2NC6H4
2,3-(H3CO)2C6H3
4-H3CC6H4
4g
4h
4i
10
11
4j
12
10
4k
[a] Reagents and conditions: 1 (2 mmol), 2 (2 mmol, 0.286 g), 3
(2 mmol, 0.168 g), I2 (0.1 mmol, 0.026 g), THF (10 mL). [b] Iso-
lated yields.
As expected, the reaction could be extended to other cy-
clic ketones. Cyclohexanone, -heptanone, and -octanone
were also chosen to react with benzaldehyde and naph-
thalen-2-amine (Scheme 2) and were found to generate the
corresponding benzo[a]phenanthridines 5a–5k, benzo[f]cy-
clohepta[c]quinolines 6a–6k, and benzo[f]cycloocta[c]quin-
olines 7a–7d in good-to-high yields, respectively. Even with
cyclododecanone, the desired reaction took place success-
fully to afford benzo[f]cyclododeca[c]quinolines 8a,8b in
satisfactory yields. The results are summarized in Table 3.
Table 1. Synthesis of 4a under different reaction conditions.[a]
Entry Temp. [°C]
I2 [mol-%]
Solvent
Yield [%][b]
1
2
3
4
5
6
7
8
9
room temp.
reflux
room temp.
50
0
0
5
5
5
10
20
5
5
5
THF
THF
THF
THF
THF
THF
THF
CH3CN
benzene
DMF
0
0
trace
80
91
89
91
81
86
78
81
reflux
reflux
reflux
reflux
reflux
80
10
11
reflux
5
ClCH2CH2Cl
[a] Reagents and conditions: 1 (2 mmol), 2 (2 mmol, 0.286 g), 3
(2 mmol, 0.168 g), solvent (10 mL). [b] Isolated yields.
Under the optimized conditions, various benzaldehydes
1 reacted with naphthalen-2-amine (2) and cyclopentanone
(3) to give 4-aryl-2,3-dihydro-1H-benzo[f]cyclopenta[c]-
quinolines 4 in high yields within a few hours. The results
are summarized in Table 2. It can be observed that the pro-
cess tolerates both electron-donating and -withdrawing sub-
stituents in the benzaldehydes. In all cases, the reactions Scheme 2.
3514
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3513–3518

Synthesis of Benzo[f]quinolines and Benzo[a]phenanthridines
Table 3. I2-catalyzed reactions of benzaldehyde, naphthalen-2- form intermediate II, which then undergoes an intramolec-
amine, and cyclic ketones in THF.[a]
ular Friedel–Crafts cyclization to give III. The subsequent
Product Time [h] Yield [%][b]
dehydration of III results in dihydroquinoline IV, which is
then oxidized by air to afford aromatized benzo[f]cyclo-
penta[c]quinoline 4.
Entry
Ar
n
1
2
3
4
5
6
7
8
3-ClC6H4
4-BrC6H4
3-BrC6H4
4-FC6H4
2-ClC6H4
2-thienyl
2,3-Cl2C6H3
4-ClC6H4
4-O2NC6H4
4-H3COC6H4
3-HOC6H4
3-ClC6H4
2,4-Cl2C6H3
3-BrC6H4
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
7
7
5a
5b
5c
5d
5e
5f
5g
5h
5i
8
9
10
8
8
10
8
10
8
12
14
8
86
89
92
90
96
87
90
84
86
84
78
89
90
86
85
86
86
88
82
79
85
79
76
72
80
71
73
76
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
5j
5k
6a
6b
6c
6d
6e
6f
6g
6h
6i
8
10
12
12
10
12
12
12
8
4-ClC6H4
4-BrC6H4
4-FC6H4
4-H3COC6H4
3,5-(H3CO)2C6H3
2,3-(H3CO)2C6H3
4-O2NC6H4
2-O2NC6H4
4-BrC6H4
6j
6k
7a
7b
7c
7d
8a
8b
8
16
20
18
16
18
20
3-BrC6H4
4-ClC6H4
3-ClC6H4
3-BrC6H4
4-ClC6H4
Scheme 4.
[a] Reagents and conditions: 1 (2 mmol), 2 (2 mmol, 0.286 g), 3
To verify the mechanism, we performed each step indi-
vidually. The Schiff base, N-arylidenenaphthalen-2-amine,
was obtained in 92% yield when 2-chlorobenzaldehyde (1,
Ar = 2-ClC6H4) was treated with naphthalen-2-amine in
THF at ambient temperature (Scheme 5). As expected, the
Schiff base reacted smoothly with cyclopentanone to give
the corresponding 4-(2-chlorophenyl)-2,3-dihydro-1H-
benzo[f]cyclopenta[c]quinoline (4a) at reflux in the presence
of 5 mol-% of iodine. This result indicates that the Schiff
base was formed during the reaction. However, the overall
yield was low (71%) in this multistep reaction, as men-
tioned above.
(2 mmol), I2 (0.1 mmol, 0.026 g), THF (10 mL). [b] Isolated yields.
In order to show the general scope of this iodine-cata-
lyzed reaction, we carried out the reaction with acetone or
propionaldehyde instead of cyclic ketone (Scheme 3). The
reaction proceeded smoothly as expected in high yields. The
results are summarized in Table 4.
Scheme 3.
Table 4. I2-catalyzed reactions of benzaldehyde, naphthalen-2-
amine, and acetone or propionaldehyde in THF.[a]
Scheme 5.
Entry
Ar
R
RЈ Product Time [h] Yield [%][b]
It should be noted that oxygen is important for the last
aromatization step. In order to gain more insight into the
reaction mechanism, we performed the three-component re-
action with 4-chlorobenzaldehyde, naphthalen-2-amine, and
cyclohexanone under dry N2 (Scheme 6): Unaromatized
1
2
3
4
2,3-Cl2C6H3 Me
H
H
9a
9b
9c
9d
8
8
6
6
92
90
84
86
2-FC6H4
3-O2NC6H4
4-H3COC6H4
Me
H
H
Me
Me
[a] Reagents and conditions: 1 (2 mmol), 2 (2 mmol, 0.286 g), ace-
tone or propionaldehyde (2.5 mmol), I2 (0.1 mmol, 0.026 g), THF
(10 mL). [b] Isolated yields.
In accord with the literature,[25] we think that iodine cata-
lyzes the reaction as a mild Lewis acid. The mechanism
proposed is shown in Scheme 4. In the presence of iodine,
cyclopentanone is in equilibrium with the enol form I. The
enol immediately attacks the iodine-activated Schiff base to Scheme 6.
Eur. J. Org. Chem. 2008, 3513–3518
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3515

X.-S. Wang, Q. Li, C.-S. Yao, S.-J. Tu
FULL PAPER
= 3054, 2939, 2860, 1595, 1561, 1475, 1446, 1433, 1410, 1342, 1318,
1255, 1134, 1077, 1044, 978, 884, 829, 799, 773, 747, 714, 700 cm–1.
1H NMR ([D6]DMSO, 400 MHz): δ = 1.79–1.85 (m, 4 H, 2CH2),
2.82 (t, J = 6.4 Hz, 2 H, CH2), 3.59 (t, J = 5.6 Hz, 2 H, CH2),
7.51–7.54 (m, 3 H, ArH), 7.62 (s, 1 H, ArH), 7.70–7.73 (m, 2 H,
ArH), 7.83 (d, J = 8.8 Hz, 1 H, ArH), 8.04 (d, J = 8.4 Hz, 1 H,
ArH), 8.08–8.10 (m, 1 H, ArH), 8.83 (d, J = 8.8 Hz, 1 H, ArH)
ppm. 13C NMR (CDCl3, 100 MHz): δ = 22.2, 23.2, 28.4, 33.4,
125.1, 125.7, 126.4, 127.1, 128.1, 128.5, 128.8, 129.0, 129.06,
129.11, 129.7, 130.1, 130.3, 133.5, 134.3, 143.0, 145.5, 146.5,
157.7 ppm. C23H18ClN (343.85): calcd. C 80.34, H 5.28, N 4.07;
found C 80.45, H 5.29, N 4.00.
product 10 was obtained in 82% yield. Subsequent treat-
ment of intermediate 10 in THF at reflux in the absence of
I2 in air gave the corresponding aromatized compound 5h
in 80% yield.
Conclusion
We have found an efficient method for the synthesis of
benzo[f]quinoline and benzo[a]phenanthridine derivatives
by a three-component reaction of arenecarbaldehyde, naph-
thalen-2-amine, and cyclic ketone using 5 mol-% of iodine
as the catalyst. The features of this procedure are mild reac-
tion conditions, high yields, operational simplicity, and the
environmental friendlyness.
5-(2-Chlorophenyl)-1,2,3,4-tetrahydrobenzo[a]phenanthridine (5e):
Pale-yellow crystals (0.659 g, 96%), m.p. 168–170 °C. IR (KBr): ν
˜
= 3056, 2928, 2863, 1594, 1560, 1513, 1475, 1435, 1370, 1342, 1320,
1261, 1227, 1211, 1054, 1032, 1005, 967, 950, 872, 830, 750, 704,
681 cm–1. 1H NMR ([D6]DMSO, 400 MHz): δ = 1.71–1.86 (m, 4
H, 2CH2), 2.57–2.61 (m, 2 H, CH2), 3.54–3.67 (m, 2 H, CH2), 7.45–
7.54 (m, 3 H, ArH), 7.61–7.63 (m, 1 H, ArH), 7.72–7.74 (m, 2 H,
ArH), 7.83 (d, J = 8.8 Hz, 1 H, ArH), 8.05 (d, J = 9.2 Hz, 1 H,
ArH), 8.09–8.11 (m, 1 H, ArH), 8.05 (d, J = 9.2 Hz, 1 H, ArH)
ppm. 13C NMR (CDCl3, 100 MHz): δ = 22.1, 23.3, 27.5, 33.5,
125.4, 125.7, 126.3, 127.2, 128.5, 128.9, 129.2, 129.4, 129.6, 129.7,
130.1, 130.21, 130.24, 132.7, 133.5, 140.1, 145.1, 146.6, 157.3 ppm.
C23H18ClN (343.85): calcd. C 80.34, H 5.28, N 4.07; found C 80.30,
H 5.44, N 4.12.
Experimental Section
General: Melting points were determined in open capillaries and
are uncorrected. IR spectra were recorded with a TENSOR 27
spectrometer using KBr pellets. 1H and 13C NMR spectra were
obtained in [D6]DMSO or CDCl3 with Me4Si as the internal stan-
dard with a Bruker 400 spectrometer. Elemental analyses were car-
ried out with a Perkin-Elmer 2400 II analyzer.
General Procedure for the Synthesis of Benzo[f]quinolines 4, 6–8 and
Benzo[a]phenanthridines 5: A dry 50 mL flask was charged with ar-
enecarbaldehyde (2.0 mmol), naphthalen-2-amine (2.0 mmol,
0.286 g), cyclic ketone (2.0 mmol), I2 (0.1 mmol, 0.026 g), and THF
(10 mL). The reaction mixture was stirred at reflux for 6–20 h. Af-
ter completion of the reaction, as indicated by TLC, a little DMF
was added to the mixture until all the yellow solid had dissolved.
Crystals formed when the mixture was cooled to room temperature
and were collected by filtration to give 4, 5, 6, 7, or 8.
8-(3-Chlorophenyl)-10,11,12,13-tetrahydro-9H-benzo[f]cyclohepta-
[c]quinoline (6a): Pale-yellow crystals (0.638 g, 89 %), m.p. 101–
102 °C. IR (KBr): ν = 3058, 2925, 2853, 1594, 1557, 1480, 1440,
˜
1416, 1384, 1368, 1338, 1256, 1234, 1216, 1165, 1091, 1076, 1045,
986, 891, 865, 832, 802, 785, 758, 740, 715, 700 cm–1. 1H NMR
([D6]DMSO, 400 MHz): δ = 1.74 (br., 2 H, CH2), 1.94 (br., 2 H,
CH2), 2.03 (br., 2 H, CH2), 2.89–2.91 (m, 2 H, CH2), 3.39–3.41 (m,
2 H, CH2), 7.41–7.43 (m, 1 H, ArH), 7.49 (d, J = 5.2 Hz, 2 H,
ArH), 7.56 (s, 1 H, ArH), 7.63–7.65 (m, 2 H, ArH), 7.72 (d, J =
8.8 Hz, 1 H, ArH), 7.94 (d, J = 9.2 Hz, 1 H, ArH), 7.99–8.01 (m,
1 H, ArH), 8.35–8.38 (m, 1 H, ArH) ppm. 13C NMR (CDCl3,
100 MHz): δ = 25.9, 27.4, 30.6, 31.7, 32.8, 124.7, 125.7, 126.6,
127.4, 127.9, 128.0, 128.6, 128.7, 129.4, 129.5, 129.8, 130.3, 133.2,
134.3, 135.2, 143.3, 146.7, 150.4, 156.2 ppm. C24H20ClN (357.88):
calcd. C 80.55, H 5.63, N 3.91; found C 80.68, H 5.70, N 3.80.
4-(2-Chlorophenyl)-2,3-dihydro-1H-benzo[f]cyclopenta[c]quinoline
(4a): Pale-yellow crystals (0.599 g, 91 %), m.p. 165–167 °C. IR
(KBr): ν = 3047, 2956, 2849, 1593, 1560, 1487, 1474, 1449, 1428,
˜
1371, 1296, 1281, 1260, 1124, 1086, 1051, 1036, 982, 861, 825, 789,
756, 739, 703, 673 cm–1. 1H NMR ([D6]DMSO, 400 MHz): δ =
2.21–2.27 (m, 2 H, CH2), 2.90 (t, J = 7.2 Hz, 2 H, CH2), 3.83 (t, J
= 7.2 Hz, 2 H, CH2), 7.51–7.56 (m, 3 H, ArH), 7.62–7.65 (m, 1 H,
ArH), 7.73–7.81 (m, 2 H, ArH), 7.95 (d, J = 9.2 Hz, 1 H, ArH),
8-(2,4-Dichlorophenyl)-10,11,12,13-tetrahydro-9H-benzo[f]cyclohep-
ta[c]quinoline (6b): Pale-yellow crystals (0.705 g, 90%), m.p. 161–
8.08–8.12 (m, 2 H, ArH), 8.78 (d, J = 8.0 Hz, 1 H, ArH) ppm. 13
C
163 °C. IR (KBr): ν = 3054, 2922, 2850, 1586, 1552, 1473, 1445,
˜
NMR (CDCl3, 100 MHz): δ = 25.2, 31.1, 37.5, 123.7, 126.5, 126.6,
126.8, 127.0, 128.8, 129.2, 129.6, 129.7, 130.2, 130.6, 130.8, 132.7,
132.8, 138.3, 139.2, 147.7, 150.1, 153.7 ppm. C22H16ClN (329.82):
calcd. C 80.11, H 4.89, N 4.25; found C 80.01, H 4.92, N 4.80.
1379, 1355, 1320, 1236, 1216, 1141, 1098, 1082, 1048, 1033, 988,
953, 905, 858, 832, 811, 780, 748 cm–1 1H NMR ([D6]DMSO,
.
400 MHz): δ = 1.70 (br., 2 H, CH2), 1.94–2.06 (m, 4 H, 2CH2),
2.78 (d, J = 6.4 Hz, 2 H, CH2), 3.41–3.46 (m, 1 H, CH), 3.55–3.59
(m, 1 H, CH), 7.50 (d, J = 8.4 Hz, 1 H, ArH), 7.58 (dd, J = 8.0,
1.6 Hz, 1 H, ArH), 7.69–7.79 (m, 4 H, ArH), 8.01 (d, J = 9.2 Hz,
1 H, ArH), 8.06–8.09 (m, 1 H, ArH), 8.47–8.49 (m, 1 H, ArH)
ppm. 13C NMR (CDCl3, 100 MHz): δ = 25.9, 27.3, 30.8, 31.9, 33.1,
125.4, 125.8, 126.7, 127.4, 127.9, 128.6, 128.7, 129.3, 129.8, 130.3,
2,3-Dihydro-4-(2-thienyl)-1H-benzo[f]cyclopenta[c]quinoline (4b):
Pale-yellow crystals (0.496 g, 82%), m.p. 176–178 °C. IR (KBr): ν
˜
= 3072, 2955, 2857, 1605, 1552, 1530, 1486, 1450, 1436, 1324, 1261,
1221, 1068, 983, 945, 864, 832, 749, 721, 675 cm–1. 1H NMR ([D6]-
DMSO, 400 MHz): δ = 2.27–2.34 (m, 2 H, CH2), 3.38 (t, J =
7.2 Hz, 2 H, CH2), 3.76 (t, J = 7.2 Hz, 2 H, CH2), 7.25–7.27 (m, 1 131.7, 133.2, 134.0, 134.5, 136.4, 139.0, 146.9, 150.2, 154.5 ppm.
H, ArH), 7.68–7.76 (m, 4 H, ArH), 7.89 (d, J = 9.2 Hz, 1 H, ArH),
C24H19Cl2N (392.32): calcd. C 73.47, H 4.88, N 3.57; found C
73.40, H 4.97, N 3.80.
8.04–8.07 (m, 2 H, ArH), 8.70 (d, J = 8.4 Hz, 1 H, ArH) ppm. 13
C
NMR (CDCl3, 100 MHz): δ = 25.2, 33.0, 37.1, 122.8, 126.37,
126.42, 126.6, 127.0, 127.9, 128.0, 128.8, 129.0, 130.2, 130.6, 132.5,
134.6, 145.6, 147.7, 148.1, 151.2 ppm. C20H15NS (301.40): calcd. C
79.70, H 5.02, N 4.65; found C 79.88, H 4.92, N 4.75.
8-(4-Bromophenyl)-9,10,11,12,13,14-hexahydrobenzo[f]cycloocta[c]-
quinoline (7a): Pale-yellow crystals (0.635 g, 76 %), m.p. 240–
242 °C. IR (KBr): ν = 3055, 2922, 2848, 1587, 1557, 1542, 1500,
˜
1476, 1436, 1392, 1362, 1327, 1269, 1253, 1176, 1102, 1085, 1067,
1005, 943, 862, 840, 805, 763, 744, 717 cm–1. 1H NMR (CDCl3,
400 MHz): δ = 1.55–1.58 (m, 2 H, CH2), 1.65–1.74 (m, 4 H, 2CH2),
5-(3-Chlorophenyl)-1,2,3,4-tetrahydrobenzo[a]phenanthridine (5a):
Pale-yellow crystals (0.593 g, 86%), m.p. 139–140 °C. IR (KBr): ν
˜
3516
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 3513–3518

Synthesis of Benzo[f]quinolines and Benzo[a]phenanthridines
2.27–2.30 (m, 2 H, CH2), 2.96–2.99 (m, 2 H, CH2), 3.64 (s, 2 H,
2870, 1681, 1606, 1578, 1549, 1485, 1446, 1412, 1387, 1353, 1254,
1
CH2), 7.41 (d, J = 8.0 Hz, 2 H, ArH), 7.64 (d, J = 8.4 Hz, 2 H, 1193, 1047, 1025, 866, 834, 794, 744, 708 cm–1. H NMR (CDCl3,
ArH), 7.67–7.72 (m, 2 H, ArH), 7.92–7.99 (m, 3 H, ArH), 8.85 (d,
400 MHz): δ = 3.20 (s, 3 H, CH3), 7.33–7.37 (m, 1 H, ArH), 7.56
J = 8.0 Hz, 1 H, ArH) ppm. 13C NMR (CDCl3, 100 MHz): δ = (dd, J = 8.0, 1.6 Hz, 1 H, ArH), 7.61 (dd, J = 7.6, 1.6 Hz, 1 H,
25.8, 27.3, 28.0, 30.7, 31.0, 31.1, 122.1, 124.8, 126.3, 126.4, 127.7,
129.3, 129.5, 130.1, 130.4, 130.6, 131.3, 132.9, 133.5, 141.2, 147.4,
ArH), 7.65–7.72 (m, 3 H, ArH), 7.97–8.01 (m, 2 H, ArH), 8.05 (d,
J = 8.8 Hz, 1 H, ArH), 8.87 (d, J = 8.0 Hz, 1 H, ArH) ppm. 13C
148.7, 158.3 ppm. C25H22BrN (416.35): calcd. C 72.12, H 5.33, N NMR (CDCl3, 100 MHz): δ = 26.9, 125.0, 126.3, 126.5, 126.7,
3.36; found C 72.25, H 5.20, N 3.55.
127.5, 127.7, 129.1, 129.3, 129.9, 130.5, 130.7, 131.1, 131.4, 133.1,
133.7, 141.5, 145.0, 149.5, 155.1 ppm. C20H13Cl2N (338.23): calcd.
C 71.02, H 3.87, N 4.14; found C 70.87, H 3.92, N 4.20.
8-(3-Bromophenyl)-9,10,11,12,13,14-hexahydrobenzo[f]cycloocta[c]-
quinoline (7b): Pale-yellow crystals (0.600 g, 72 %), m.p. 142–
144 °C. IR (KBr): ν = 3063, 2922, 2856, 1594, 1556, 1545, 1492,
˜
2-Methyl-3-(3-nitrophenyl)benzo[f]quinoline (9c): Pale-yellow crys-
1474, 1449, 1435, 1405, 1376, 1348, 1269, 1255, 1232, 1070, 1011,
890, 848, 836, 806, 799, 767, 752, 722, 702, 678 cm–1. 1H NMR
(CDCl3, 400 MHz): δ = 1.53–1.55 (m, 2 H, CH2), 1.63–1.74 (m, 4
H, 2CH2), 2.23–2.29 (m, 2 H, CH2), 2.94–2.97 (m, 2 H, CH2), 3.61
(s, 2 H, CH2), 7.33–7.37 (m, 1 H, ArH), 7.43 (d, J = 7.6 Hz, 1 H,
ArH), 7.58 (d, J = 8.0 Hz, 1 H, ArH), 7.64–7.69 (m, 3 H, ArH),
7.89–7.97 (m, 3 H, ArH), 8.82 (d, J = 7.6 Hz, 1 H, ArH) ppm. 13C
NMR (CDCl3, 100 MHz): δ = 25.8, 27.3, 28.0, 30.7, 31.0, 31.1,
122.4, 124.8, 126.3, 126.5, 127.4, 127.8, 129.3, 129.5, 129.7, 130.1,
130.7, 130.9, 131.8, 132.9, 133.5, 144.2, 147.3, 148.8, 157.9 ppm.
C25H22BrN (416.35): calcd. C 72.12, H 5.33, N 3.36; found C 72.28,
H 5.30, N 3.50.
tals (0.528 g, 84%), m.p. 187–188 °C. IR (KBr): ν = 3085, 2960,
˜
1533, 1487, 1449, 1383, 1344, 1094, 1032, 895, 867, 828, 811, 749,
687 cm–1. 1H NMR (CDCl3, 400 MHz): δ = 2.61 (s, 3 H, CH3),
7.26–7.73 (m, 3 H, ArH), 7.93–8.04 (m, 4 H, ArH), 8.30–8.33 (m,
1 H, ArH), 8.57–8.58 (m, 1 H, ArH), 8.64 (d, J = 8.0 Hz, 1 H,
ArH), 8.84 (s, 1 H, ArH) ppm. 13C NMR (CDCl3, 100 MHz): δ =
20.7, 122.8, 123.1, 124.4, 125.0, 127.2, 127.5, 127.9, 128.77, 128.81,
129.1, 129.4, 130.7, 132.0, 132.9, 135.3, 142.3, 146.5, 148.3,
156.4 ppm. C20H14N2O2 (314.34): calcd. C 76.42, H 4.49, N 8.91;
found C 76.25, H 4.59, N 8.80.
General Procedure for the Synthesis of 5-(4-Chlorophenyl)-
1,2,3,4,5,6-hexahydrobenzo[a]phenanthridine (10):
flask was charged with 4-chlorobenzaldehyde (2.0 mmol, 0.281 g),
naphthalen-2-amine (2.0 mmol, 0.286 g), cyclohexanone
A dry 50 mL
8-(3-Bromophenyl)-9,10,11,12,13,14,15,16,17,18-decahydrobenzo-
[f]cyclododeca[c]quinoline (8a): Pale-yellow crystals (0.694 g, 73%),
m.p. 205–207 °C. IR (KBr): ν = 3057, 2927, 2905, 2863, 2841, 1557,
˜
(2.0 mmol), I2 (0.1 mmol, 0.026 g), and THF (10 mL). The reaction
mixture was stirred at reflux under dry N2 for 6 h. After completion
of the reaction, as indicated by TLC, pale-yellow crystals formed
when the mixture was cooled to room temperature and were col-
lected by filtration to give 10 (0.566 g, 82%), m.p. 166–168 °C. IR
1542, 1492, 1472, 1430, 1409, 1374, 1357, 1293, 1252, 1229, 1190,
1159, 1069, 996, 876, 844, 815, 783, 765, 753, 695, 685 cm–1. 1H
NMR (CDCl3, 400 MHz): δ = 1.35–1.68 (m, 14 H, 7CH2), 1.94–
1.96 (m, 2 H, CH2), 2.92–2.94 (m, 2 H, CH2), 3.55–3.59 (m, 2 H,
CH2), 7.33–7.37 (m, 1 H, ArH), 7.46 (d, J = 8.4 Hz, 1 H, ArH),
7.57 (d, J = 8.0 Hz, 1 H, ArH), 7.62–7.69 (m, 3 H, ArH), 7.87–
7.94 (m, 3 H, ArH), 8.77–8.79 (m, 1 H, ArH) ppm. 13C NMR
(CDCl3, 100 MHz): δ = 23.0, 23.4, 27.0, 27.1, 27.4, 27.9, 28.4, 28.9,
30.7, 122.4, 125.0, 126.2, 126.5, 127.1, 127.4, 129.2, 129.3, 129.7,
130.4, 130.6, 130.9, 131.9, 133.2, 133.3, 144.2, 147.1, 148.2,
158.3 ppm. C29H32BrN (474.48): calcd. C 83.41, H 6.80, N 2.95;
found C 73.53, H 6.70, N 2.81.
(KBr): ν = 3419, 3387, 3054, 2934, 2855, 2830, 1633, 1611, 1517,
˜
1480, 1409, 1386, 1338, 1316, 1294, 1274, 1239, 1208, 1182, 1143,
1117, 1104, 1084, 1012, 917, 831, 812, 748, 696 cm–1. 1H NMR
([D6]DMSO, 400 MHz): δ = 1.09–1.17 (m, 1 H, CH), 1.46–1.51 (m,
2 H, CH2), 1.68–1.72 (m, 1 H, CH2), 2.16–2.21 (m, 1 H, CH), 2.37–
2.42 (m, 1 H, CH), 2.47–2.50 (m, 1 H, CH2), 4.27 (d, J = 10.8 Hz,
1 H, CH), 6.25 (s, 1 H, CH), 6.50 (s, 1 H, NH), 6.91 (d, J = 8.4 Hz,
1 H, ArH), 7.07–7.11 (m, 1 H, ArH), 7.29–7.32 (m, 1 H, ArH),
7.45–7.48 (m, 5 H, ArH), 7.63 (d, J = 8.0 Hz, 1 H, ArH), 8.19 (d,
J = 8.4 Hz, 1 H, ArH) ppm. 13C NMR ([D6]DMSO, 100 MHz): δ
= 20.0, 26.2, 26.3, 37.5, 62.7, 111.0, 117.5, 120.7, 123.1, 125.1,
126.1, 127.7, 128.0, 128.48, 128.54, 130.0, 131.4, 132.2, 141.9,
142.2 ppm. C23H20ClN (345.86): calcd. C 79.87, H 5.83, N 4.05;
found C 79.99, H 5.92, N 3.92.
8-(4-Chlorophenyl)-9,10,11,12,13,14,15,16,17,18-decahydrobenzo-
[f]cyclododeca[c]quinoline (8b): Pale-yellow crystals (0.653 g, 76%),
m.p. 218–220 °C. IR (KBr): ν = 2919, 2854, 1594, 1557, 1544, 1490,
˜
1467, 1436, 1394, 1380, 1335, 1263, 1234, 1089, 1014, 949, 867,
1
841, 828, 748, 725, 706, 688 cm–1. H NMR (CDCl3, 400 MHz): δ
= 1.34–1.68 (m, 14 H, 7CH2), 1.94–1.97 (m, 2 H, CH2), 2.89–2.96
(m, 2 H, CH2), 3.55–3.60 (m, 2 H, CH2), 7.47 (s, 4 H, ArH), 7.62–
7.65 (m, 2 H, ArH), 7.87–7.94 (m, 3 H, ArH), 8.78 (d, J = 8.4 Hz,
1 H, ArH) ppm. 13C NMR (CDCl3, 100 MHz): δ = 23.0, 23.4, 27.0,
27.1, 27.4, 27.9, 28.4, 28.8, 30.7, 124.9, 126.2, 126.4, 127.1, 128.4,
129.2, 129.3, 130.2, 130.4, 130.5, 133.27, 133.30, 133.8, 140.6,
147.1, 148.1, 158.7 ppm. C29H32ClN (430.02): calcd. C 81.00, H
7.50, N 3.26; found C 80.79, H 7.55, N 3.40.
Supporting Information (see footnote on the first page of this arti-
cle): Detailed experimental procedures, melting points, elemental
analyses, and spectroscopic data (1H and 13C NMR, IR) for 4c–
4k, 5b–5d, 5f–5k, 6c–6k, 7c–7d, 9b, and 9d.
Acknowledgments
General Procedure for the Synthesis of Benzo[f]quinolines 9: A dry
50 mL flask was charged with arenecarbaldehyde (2.0 mmol),
naphthalen-2-amine (2.0 mmol, 0.286 g), acetone or propionalde-
hyde (2.5 mmol), I2 (0.1 mmol, 0.026 g), and THF (10 mL). The
reaction mixture was stirred at 50 °C for 6–8 h. After completion
of the reaction, as indicated by TLC, a little DMF was added to
the mixture until all the yellow solid had dissolved. Crystals formed
when the mixture was cooled to room temperature and were col-
lected by filtration to give 9.
We are grateful to the Natural Science Foundation of Xuzhou Nor-
mal University (Nos. 06AXL10 and 06PYL04) and the Natural
Science Foundation of the Education Committee of Jiangsu Prov-
ince (No. 04KJB150139) for financial support.
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˜
Eur. J. Org. Chem. 2008, 3513–3518
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3517

X.-S. Wang, Q. Li, C.-S. Yao, S.-J. Tu
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Received: March 18, 2008
Published Online: May 26, 2008
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Eur. J. Org. Chem. 2008, 3513–3518