Selective synthesis of quinolines and indoles: Sulfur-assisted or selenium-catalyzed reaction of β-(2-nitrophenyl)-α, β-unsaturated ketones with carbon monoxide

Article abstract of DOI:10.1002/hc.21189

A simple and selective synthetic method of quinolines and indoles by the reaction of β- (2-nitrophenyl)-α,β-unsaturated ketones with carbon monoxide was developed. When β-(2-nitrophenyl)- α,β-unsaturated ketones were allowed to react with carbon monoxide and water in the presence of a stoichiometric amount of sulfur or a catalytic amount of selenium, the corresponding quinolines were produced in moderate-to-good yields. On the other hand, in the absence of water, the indoles were produced by the selenium-catalyzed reaction of the β-(2-nitrophenyl)- α,β-unsaturated ketones with carbon monoxide.

Full text of DOI:10.1002/hc.21189

Heteroatom Chemistry
Volume 25, Number 6, 2014
S
elective Synthesis of Quinolines and Indoles:
Sulfur-Assisted or Selenium-Catalyzed
Reaction of β-(2-Nitrophenyl)-α,
β-unsaturated Ketones with Carbon Monoxide
Rui Umeda, Hiroshi Kouno, Takayuki Kitagawa,
Tomohiro Okamoto, Keisuke Kawashima, Tsukasa Mashino,
and Yutaka Nishiyama
Department of Chemistry and Materials Engineering, Faculty of Chemistry, Materials and
Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan
Received 28 February 2014; revised 7 May 2014
INTRODUCTION
ABSTRACT: A simple and selective synthetic method
of quinolines and indoles by the reaction of β-
The quinoline derivatives have not only been widely
found in natural products with a biological activ-
ity, but have also been broadly used in medical, in-
dustrial, and organic synthetic chemistries [1]. Nu-
merous synthetic methods of quinoline including
the well-established methods such as the Combes,
Conrad–Limpach, Dobner–von Miller, Friedlander,
and Skraup quinoline syntheses have been reported
[1]. Even now, the development of new effective
strategies for the construction of the quinoline sys-
tem has received considerable attention in the phar-
maceutical, industrial, and organic chemistries [2].
Sonoda’s and our groups have recently shown
that the elemental selenium-catalyzed and sulfur-
assisted reductive N-heterocyclizations of o-nitro
substituted aromatic compounds with carbon
monoxide were efficient methods for the synthesis
of the N-heterocyclic aromatic compounds [3, 4].
Chinese chemists have also shown that elemental
selenium acts as a unique catalyst for the reduc-
tion or reductive carbonylation of aromatic nitro
compounds with carbon monoxide giving the cor-
responding nitrogen-containing compounds [5]. In
the continuous study of the use of carbon monoxide
for the synthesis of N-heterocyclic aromatic com-
pounds, we have now realized the selective synthetic
method of quinolines 2 and indoles 3 by the reaction
(
2-nitrophenyl)-α,β-unsaturated ketones with carbon
monoxide was developed. When β-(2-nitrophenyl)-
α,β-unsaturated ketones were allowed to react with
carbon monoxide and water in the presence of a stoi-
chiometric amount of sulfur or a catalytic amount of
selenium, the corresponding quinolines were produced
in moderate-to-good yields. On the other hand, in the
absence of water, the indoles were produced by the
selenium-catalyzed reaction of the β-(2-nitrophenyl)-
α,β-unsaturated ketones with carbon monoxide.
ꢀC
2
2014 Wiley Periodicals, Inc. Heteroatom Chem.
5:698–703, 2014; View this article online at wiley-
onlinelibrary.com. DOI 10.1002/hc.21189
Correspondence to: Yutaka Nishiyama; e-mail: nishiya@kansai-
u.ac.jp.
Dedicated to Professor Renji Okazaki on the occasion of his
7th birthday.
Contract grant sponsor: MEXT-Supported Program for the
7
Strategic Research Foundation at Private Universities.
Contract grant sponsor: Grant-in-Aid for Scientific Research.
Contract grant sponsor: Kansai University Research Grants:
Grant-in-Aid for Encouragement of Scientists.
ꢀC
2014 Wiley Periodicals, Inc.
698

Selective Synthesis of Quinolines and Indoles 699
TABLE 2 Sulfur-Assisted Synthesis of Quinolinesa
O
O
S or cat. Se
R2
S
+
CO
+
2
H O
O
R1
R2
N
R1
Et N
3
R1
NO
1
2
R2 + CO + H O
R1
2
2
3
benzene
R2
N
cat.
O
NO
2
1
Se
R2
2
+
CO
R2
N
H
R1
NO
2
R1
R1
R2
Yield (%)b
1
Entry
1
2
3
4
5
6
7
8
9
H
H
H
H
H
H
H
4-CH
3-CH
2-CH
3
3
3
C
C
C
6
6
6
H
H
H
4
4
4
2b
66
65
64
77
65
57
63
57
77
SCHEME 1
2c
2d
2e
2f
TABLE 1 Optimized Reaction Conditionsa
3 6 4
4-CH OC H
S
O
4-CIC
6
H
4
base
+
CO
+
2
H O
CH3
2-C10
Ph
2g
2h
2i
N
solvent
H
7
NO
2
CH
CI
3
O
2
a
1a
Ph
2j
CO
(atm)
Temperature Yield
aReaction conditions: 1 (0.5 mmol), S (0.5 mmol), Et3N (5.0 mmol),
H2O (20 mmol), and benzene (5.0 mL) under CO (50 atm) at 120°C
for 24 h.
o
b
Entry
Base
Solvent
( C)
(%)
1
Et
3
N
Benzene
50
120
94
b
Isolated yield.
(
76)
53
73
72
72
2
3
4
5
Et
3
Et
3
Et
3
Et
3
N
N
N
N
Toluene
THF
DMF
50
50
50
50
120
120
120
120
using N-methypyrrolidine, DBU, and K2CO3 instead
of triethylamine as the base, the yields of 2a de-
creased (entries 6–8). At 100 and 150°C, the yields
of 2a were almost the same as that at 120°C (entries
3
CH CN
6
NMe Benzene
50
120
45
9
and 10); however, at lower reaction temperature
7
8
9
1
1
1
1
1
DBU
C0
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
Benzene
50
50
50
50
50
50
30
50
120
120
150
100
80
50
120
80
46
58
87
90
78
44
78
82
(80 and 50°C) and lower pressure of CO (30 atm),
K
2
3
Et
3
Et
3
Et
3
Et
3
Et
3
Et
3
N
the yields of 2a were decreased (entries 11–13). On
the other hand, when the catalytic amount of sele-
nium instead of sulfur was used in the reaction, the
reaction smoothly proceeded under mild conditions
to give 2a in 82% yield (entry 14).
0
1
2
3
4
N
N
N
N
N
c
To elucidate the applicability of the sulfur-
assisted and selenium-catalyzed synthesis of
quinolones, the reaction of a variety of β-(2-nitro-
phenyl)-α,β-unsaturated ketones with carbon
monoxide and water was investigated. These results
are shown in Tables 2 and 3. In the case of 3-(2-nitro-
phenyl)-1-(4-methylphenyl)prop-2-en-1-one, 3-(2-
nitrophenyl)-1-(3-methylphenyl)prop-2-en-1-one,
and 3-(2-nitrophenyl)-1-(4-methoxyphenyl)prop-2-
en-1-one having electron-donating groups, the
reductive N-heterocyclization efficiently proceeded
to form the corresponding 2-aryl substituted quino-
lines in 66, 65, and 77% yields, respectively (entries
1, 2, and 4 in Table 2). Similarly, 3-(2-nitrophenyl)-
1-(4-chlorophenyl)prop-2-en-1-one, in which an
electron-withdrawing group was substituted on the
aromatic ring, was reductively N-heterocyclized
to give the 2-(4-chlorophenyl)quinoline in good
yield (entry 5). Even when 3-(2-nitrophenyl)-1-(2-
methylphenyl)prop-2-en-1-one, which has sterically
hindered group, was used as the β-(2-nitropheny)-
α,β-unsaturated ketone, the reaction smoothly
proceeded to give the corresponding quinoline
aReaction conditions: 1a (0.5 mmol), sulfur (0.5 mmol), H2O (20
mmol), base (5.0 mmol), and solvent (5.0 mL) for 24 h.
b
GLC yield. The number in parenthesis shows the isolated yield.
A catalytic amount of selenium (0.1 mmol) instead of sulfur
c
(
0.5 mmol) was used.
of β-(2-nitrophenyl)-α,β-unsaturated ketones 1 with
carbon monoxide (Scheme 1) [6].
To determine the optimized reaction conditions,
3-(2-nitrophenyl)-1-phenylprop-2-en-1-one (1a) was
allowed to react with carbon monoxide and wa-
ter in the presence of a stoichiometric amount of
sulfur or a catalytic amount of selenium under vari-
ous reaction conditions. These results are shown in
Table 1. When 1a was treated with sulfur and H2O
in the presence of triethylamine as the base in
benzene under the pressurized CO (50 atm) at 120°C
for 24 h, the reductive N-heterocyclization of 1a ef-
ficiently occurred to give 2-phenylquinoline (2a) in
94% yield (entry 1). The use of other solvents, such
as toluene, THF, DMF, and acetonitrile, led to the
formation of 2a; however, benzene is the best sol-
vent for the reaction (entries 1–5). For the reaction
Heteroatom Chemistry DOI 10.1002/hc

700 Umeda et al.
TABLE 3 Selenium-Catalyzed Synthesis of Quinolinesa
itation of the reaction, various 3-(2-nitrophenyl)-
1-arylprop-2-en-1-ones 1 were treated with carbon
monoxide in the presence of a catalytic amount of
selenium and these results are shown in Table 4.
The 2-aroyl substituted 1H-indoles were synthesized
by the selenium-catalyzed reaction of 1 and carbon
monoxide in good yields [7].
Although the reaction pathway for the prepara-
tion of the quinolines and indoles by the reaction of
the β-(2-nitrophenyl)-α,β-unsaturated ketones with
carbon monoxide in the presence of a stoichio-
metric amount of sulfur or a catalytic amount of
selenium has not been fully clarified, the plausi-
ble reaction pathways are shown in Scheme 2. It
has already been reported that the aromatic ni-
tro compounds were reduced by the reaction of
carbon monoxide and water in the presence of sulfur
and the selenium catalyst [4, 8]. Thus, in the pres-
ence of H2O, we propose that the reaction starts
with the reduction of the nitro group with H2S or
cat.Se
Et N
3
O
Ar + CO + H O
2
benzene
N
Ar
NO2
1
2
Entry
Ar
Yield (%)b
1
2
3
4
5
4-CH
3-CH
2-CH
3
3
3
C
C
C
6
5
6
H
H
H
4
2b
2c
2d
2e
2f
86
79
83
83
88
4
4
3 6 4
4-CH OC H
4-CIC
6
H
4
aReaction conditions: (0.5 mmol), Se (0.1 mmol), Et3N (5.0 mmol),
and benzene (5.0 mL) under CO (50 atm) at 80°C for 24 h.
b
GLC yields.
TABLE 4 Selenium-Catalyzed Synthesis of Indolesa
cat.
O
Se
Et N, MS3A
3
Ar
O
Ar + CO
benzene
H Se, which was generated by the elemental sul-
N
H
2
NO2
1
fur or selenium, carbon monoxide, and water in
3
the presence of the tertiary amine [7], forming the
corresponding β-(2-aminophenyl)-α,β-unsaturated
ketones. The intramolecular nucleophilic addition
of β-(2-aminophenyl)-α,β-unsaturated ketones fol-
lowed by dehydrolation efficiently proceeded to
produce the quinolines. Sonoda et al. also found
a convenient preparation method of carbonyl se-
lenide (SeCO), which involved the acid-catalyzed
decomposition of the ammonium salts of the se-
lenocarbamates generated by the reaction of elemen-
tal selenium with carbon monoxide and secondary
amine [9]. Therefore, in the absence of water, we
proposed that the reaction starts with the deoxygena-
tion of the nitro group of the β-(2-nitrophenyl)-α,β-
unsaturated ketones with SeCO prepared from ele-
mental selenium and carbon monoxide to generate
the corresponding short-lived nitrene or nitrenoid
species. The intramolecular insertion of the nitrene
or nitrenoid species, which was in situ generated
by the deoxygenation of the nitro group with SeCO,
into the vinyl C H bond at the o-position of the nitro
group efficiently proceeded to produce the indoles.
In summary, we have succeeded in the selec-
tive synthesis of quinolines by the reaction of β-(2-
nitrophenyl)-α,β-unsaturated ketones with carbon
monoxide and water in the presence of a stoichio-
metric amount of sulfur or a catalytic amount of
selenium. On the other hand, in the absence of wa-
ter, the indoles were selectively produced by the
selenium-catalyzed reaction of β-(2-nitrophenyl)-
α,β-unsaturated ketones and carbon monoxide. The
application of the reaction and the investigation of
the reaction mechanism are now in progress.
Yield (%)b
Entry
Ar
Ph
1
2
3
4
5
6
3a
3b
3c
3d
3e
3f
73
4-CH
3-CH
2-CH
3
3
3
C
C
C
6
6
6
H
H
H
4
4
4
91
78
84
86
79
3 6 4
4-CH OC H
4-CIC
6
H
4
aReaction conditions: 1 (0.5 mmol), Se (0.1 mmol), Et3N (5.0 mmol),
MS3A (150 mg), and benzene (5.0 mL) under CO (30 atm) at 140°C
for 48 h.
b
GLC yields.
in moderate yield (entry 3). The 2-methyl- and
2
-naphthylquinoline were also prepared by the
sulfur-assisted reductive N-heterocyclization of the
corresponding β-(2-nitropheny)-α,β-unsaturated
ketones with carbon monoxide and water (entries
and 7). The 2,6-disubstituted quinolines were
synthesized in moderate yields using this protocol
entries 8 and 9). Similarly, the transformation of the
β-(2-nitrophenyl)-α,β-unsaturated ketones to quino-
lines was successfully achieved by the selenium-
catalyzed reaction of the β-(2-nitrophenyl)-α,β-un-
saturated ketones with carbon monoxide and water
Table 3).
It is interesting to note that when the
selenium-catalyzed reaction of 3-(2-nitrophenyl)-1-
phenylprop-2-en-1-one (1a) with carbon monoxide
was carried out in the absence of water, 2-benzoyl-
6
(
(
1
H-indole (3a) was obtained in 73% yield with a
small amount of 2-phenylquinoline (2a) (8%) (en-
try 1 in Table 4). To determine the scope and lim-
Heteroatom Chemistry DOI 10.1002/hc

Selective Synthesis of Quinolines and Indoles 701
(
i) In the Presence of H O
2
S or Se + CO + H O
2
O
O
H S or H Se
2
2
Ar
Ar
N
Ar
NO2
NH2
(
ii) In the Absence of H O
2
Se + CO
O
O
O
SeCO
SeCO
O
Ar
Ar
Ar
Ar
N
H
NO2
NO
N
SCHEME 2 Plausible reaction paths.
EXPERIMENTAL
General
0.5 mmol), water (360 mg, 20 mmol), and triethy-
lamine (101 mg, 10 mmol), benzene (5 mL) was
added. The apparatus was then flushed several times
with carbon monoxide and fully charged with car-
bon monoxide (50 atm) at room temperature. The
reaction was carried out at 120°C for 24 h. The
reaction apparatus was then cooled to room tem-
perature. After the evacuation of the excess carbon
monoxide, the solution was then diluted with AcOEt.
The organic layer was dried over MgSO4. The result-
ing mixture was filtered and the filtrate was concen-
trated. Purification of the residue by silica gel col-
umn chromatography or preparative HPLC afforded
the quinolines. The structures of the products were
FT-IR spectra were recorded on a JASCO FT/IR-
100 instrument. 1H and C NMR spectra were
obtained on a JEOL AL400 or ECS400 (400 MHz,
00 MHz) instrument. Chemical shifts were reported
13
4
1
in parts per million relative to tetramethylsilane
or residual solvent as the internal standard. The
GLC mass spectral analyses were performed by a
Shimadzu GCMS-QP5050A with CBP-M25–025.
Preparative HPLC separation was undertaken using
a JAI LC-908 chromatograph equipped 600 mm × 20
mm JAIGEL-1H and 2H GPC columns and CHCl3 as
the eluent. Gas chromatography was carried out us-
ing a flame-ionizing detector equipped instrument
and a capillary column (0.25 mm × 1200 mm).
1
13
assigned by their H and C NMR and mass spec-
tra. The product was characterized by comparing its
spectral data with those of an authentic sample or
previous reports on 2a [10], 2b [11], 2c [12], 2d [12],
2
e [13], 2f [14], 2g [10], 2h [15], and 2i [16].
Reagents
1
2i: H NMR (400 MHz, CDCl3) δ 8.13 (d, J =
6
2
3
1
1
.7 Hz, 2H), 8.06 (d, J = 7.9 Hz, 2H), 7.69–7.64 (m,
The sulfur, selenium, and carbon monoxide were
commercially available and were used with-
out further purification. The β-(2-nitrophenyl)-
α,β-unsaturated ketones were synthesized by the
Aldol reaction of 2-nitrobenzaldehyde and car-
bonyl compounds. All other chemical agents were
commercially obtained. Solvents and triethylamine
were dried (drying agent in parentheses) and dis-
tilled prior to use: toluene (CaH2), benzene (CaH2),
CH3CN (MS 3A), THF (sodium/benzophenone),
DMF (MS 3A), and Et3N (KOH).
H), 7.52–7.42 (m, 4H), 7.16 (dd, J = 8.9, 2.6 Hz, 1H),
1
3
.94 (s, 3H). C NMR (100 MHz, CDCl3) δ 160.8,
57.5, 149.9, 139.8, 136.3, 129.1, 128.7, 128.4, 127.5,
22.3, 119.4, 116.8, 107.5, 55.4. MS (EI): m/z 235
+
(
M ).
General Procedure for the Selenium-Catalyzed
Reaction of β-(2-Nitrophenyl)-α,β-unsaturated
Ketones with Carbon Monoxide and Water
To an autoclave containing β-(2-nitrophenyl)-α,β-
unsaturated ketones (0.5 mmol), selenium (8 mg,
General Procedure for the Sulfur-Assisted
Reaction of β-(2-Nitrophenyl)-α,β-unsaturated
Ketones with Carbon Monoxide and Water
0.1 mmol), water (360 mg, 20 mmol), and
triethylamine (101 mg, 10 mmol), benzene (5 mL)
was added. The apparatus was then flushed several
times with carbon monoxide and fully charged with
carbon monoxide (50 atm) at room temperature. The
To an autoclave containing β-(2-nitrophenyl)-α,β-
unsaturated ketones (0.5 mmol), sulfur (16 mg,
Heteroatom Chemistry DOI 10.1002/hc

702 Umeda et al.
reaction was carried out at 80°C for 24 h. The reac-
tion apparatus was then cooled to room tempera-
ture. After the evacuation of the excess of carbon
monoxide, the solution was then diluted with AcOEt.
The organic layer was dried over MgSO4. The result-
ing mixture was filtered and the filtrate was concen-
trated. Purification of the residue by silica gel col-
umn chromatography or preparative HPLC afforded
the quinolines. The structures of the products were
Jones, G. In Comprehensive Heterocyclic Chemistry
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Pergamon: Oxford, UK, 1996, Vol. 5, p. 167; (g) Jones,
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General Procedure for the Selenium-Assisted
Reaction of β-(2-Nitrophenyl)-α,β-unsaturated
Ketones with Carbon Monoxide
To an autoclave containing, β-(2-nitrophenyl)-α,β-
unsaturated ketones (0.5 mmol), selenium (8 mg,
0.1 mmol), MS3A (150 mg), and triethylamine
(101 mg, 10 mmol), benzene (5 mL) was added.
[
4] (a) Miyata, T.; Mizuno, T.; Nagahama, Y.; Nishiguchi,
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The apparatus was then flushed several times with
carbon monoxide and fully charged with carbon
monoxide (30 atm) at room temperature. The reac-
tion was carried out at 140°C for 48 h. The reaction
apparatus was then cooled to room temperature. Af-
ter the evacuation of the excess carbon monoxide,
the solution was then was then diluted with AcOEt.
The organic layer was dried over MgSO4. The re-
sulting mixture was filtered and the filtrate was con-
centrated. Purification of the residue by silica gel col-
umn chromatography or preparative HPLC afforded
the indoles. The structures of the products were as-
1
991, 2, 473; (b) Miyata, T.; Kambe, N.; Murai, S.;
Sonoda, N.; Nishiguchi, I.; Hirashima, T. Nippon Ka-
gakukaishi 1987, 1332.
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535; (j) Chen, J.; Ling, G.; Yu, Z.; Wu, S.; Zhao, X.;
1
13
signed by their H and C NMR and mass spec-
tra. The product was characterized by comparing its
spectral data with those of an authentic sample or
previous reports on 3a [17], 3b [17], 3c [17], 3e [18],
1
Wu, X.; Lu, S. Adv Synth Catal 2004, 346, 1267; (k)
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9
2
1
2
3
29; (l) Liu, X.; Liu, Q.; Lu, S. Cuihua Xuebao 2004,
5, 597; (m) Liu, X.; Lu, S. J Mol Catal A 2004, 212,
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21; (p) Chen, J.; Ling, G.; Lu, S. Tetrahedron 2003,
and 3f [18].
1
3
d: H NMR (400 MHz, CDCl3) δ 9.78 (s, 1H),
7
1
8
7
.66 (dd, J = 8.0, 0.8, 1H), 7.61 (dd, J = 8.0, 1.2 Hz,
H), 7.50 (dd, J = 7.6, 0.8 Hz, 1H), 7.43 (dt, J =
.0, 1.2 Hz, 1H), 7.38–7.30 (m, 2H), 7.14 (dt, J =
.6, 0.8 Hz, 1H), 6.91 (dd, J = 8.0, 0.8 Hz, 1H), 2.47
59, 8251; (q) Mei, J.; Lu, S. Huaxue Jinzhan 2002,
1
3
2
4
4, 433; (r) Xue, Y.; Lu, S. Chihua Xuebao 2001, 22,
87; (s) Yang, Y.; Lu, S. Chihua Xuebao 1999, 20,
24; (t) Yang, Y.; Lu, S. Tetrahedron Lett 1999, 40,
845.
1
3
(
s, 3H). C NMR (100 MHz, CDCl3) δ 189.7, 138.0,
1
1
2
37.9, 137.0, 125.5, 131.1, 130.5, 128.7, 127.5, 126.6,
[
6] (a) Cenini, S.; Bettettini, E.; Fedele, M.; Tollari, S. J.
Mol Cata A: Chemical 1996, 111, 37; (b) Akazome, M.;
Kondo, T.; Watanabe, Y. J Org Chem 1994, 59, 3375;
25.1, 123.2, 121.0, 113.7, 112.3, 19.8. MS (EI): m/z
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