Selenium-catalyzed reductive cyclization and carbocyclization of 2,2′-dinitrostilbenes with carbon monoxide: One-shot synthesis of indolo[1,2-c]quinazolinones

Article abstract of DOI:10.1002/hc.20685

When 2,2′-dinitrostilbene derivatives were allowed to react with carbon monoxide in the presence of a catalytic amount of selenium, reductive cyclization and carbocyclization proceeded to give indolo[1,2-c]quinazolin-6(5H) -ones, containing both indole an

Full text of DOI:10.1002/hc.20685

Heteroatom Chemistry
Volume 22, Number 3/4, 2011
Selenium-Catalyzed Reductive Cyclization and
ꢀ
Carbocyclization of 2,2 -Dinitrostilbenes with
Carbon Monoxide: One-Shot Synthesis of
Indolo[1,2-c]quinazolinones
Rui Umeda, Shigeru Morishita, and Yutaka Nishiyama
Department of Chemistry and Materials Engineering, Faculty of Chemistry,
Materials and Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan
Received 7 July 2010; revised 23 August 2010
with phosgene [2], (b) Pt-catalyzed cycliza-
ABSTRACT: When 2,2ꢀ-dinitrostilbene derivatives
tion of N-methoxy-Nꢀ-[2-(pent-1-ynyl)phenyl]-N-
were allowed to react with carbon monoxide in the
phenylurea derivative [3], (c) Pd-catalyzed cycliza-
presence of a catalytic amount of selenium, reduc-
tion of N-(2-bromophenyl)indole-1-carboxamides
tive cyclization and carbocyclization proceeded to give
[4], (d) aza-Wittig reaction of iminophosphrane with
indolo[1,2-c]quinazolin-6(5H)-ones, containing both
carbon dioxide [5], (e) acid-mediated cyclization
ꢁ
C
indole and cyclic urea units, in moderate yields. 2011
of spiro(imidazolidinoquinazolinone) derivative [6],
Wiley Periodicals, Inc. Heteroatom Chem 22:571–575,
and (f) addition/N-arylation/C-H activation sequen-
2011; View this article online at wileyonlinelibrary.com.
tial reaction of o-gem-dibromovinyl isocyanates with
DOI 10.1002/hc.20685
N-alkyl anilines [1a]. In addition, in these meth-
ods, there are several drawbacks, such as lengthy
sequences for their preparation, using expensive
transition metals, handling of toxic agent such as
phosgene, and limitation of the substrates. It is
INTRODUCTION
The development of the effective strategies for the
construction of polycyclic ring containing indole
unit has attracted much attention in the field of
pharmaceutical science, because various polycyclic
indole derivatives exhibit a wide range of biologi-
cal activity. In this connection, various synthetic ap-
proaches of polycyclic indole derivatives have been
disclosed [1]. However, examples of the synthe-
sis of indolo[1,2-c]quinazolinone derivatives, which
have both indole and cyclic urea structures, are
still rare; (a) reaction of 2-(o-aminophenyl)indoles
reported that some of pyrimido[1,6-a]indol-1(2H)-
one derivatives, which are structural analogues of
indolo[1,2-c]quinazolinone, have potential applica-
tions in both biology and material sciences [1a].
Thus, the development of practical and convenient
synthetic method for indolo[1,2-c]quinazolinone
derivatives became a challenging topic in organic
and pharmaceutical chemistry.
Recently, we have reported that the selenium-
catalyzed reaction of o-nitro substituted aromatic
compounds with carbon monoxide led to various N-
heterocyclic aromatic compounds via the reductive
deoxygenation or reductive carbonylation [7]. This
catalytic method is attractive in terms of the straight-
forward access to various N-heterocyclic aromatic
compounds from aromatic nitro compounds. On the
further application of this methodology, we found
Dedicated to Prof. Kin-ya Akiba on the occasion of his 75th
birthday.
Correspondence to: Yutaka Nishiyama; e-mail: nishiya@
kansai-u.ac.jp.
c
ꢀ
2011 Wiley Periodicals, Inc.
571

572 Umeda, Morishita, and Nishiyama
SCHEME 1
SCHEME 2
a new synthetic method of indolo[1,2-c]quinazolin-
6(5H)-ones from trans-2,2ꢀ-dinitrostilbenes via dou-
ble cyclization involving both reductive deoxy-
genation and reductive carbonylation with carbon
monoxide (Scheme 1).
perature (80◦C) (entry 4). At higher reaction temper-
ature (120◦C), the almost same selectivity as that of
100◦C was observed (entry 5). On the reaction, the
total yield and selectivity were greatly influenced by
the solvent used. In the case of benzene, the reaction
did not proceed and the starting material was re-
covered (entry 6). Using DMF as a solvent provided
trans-2,2ꢀ-diaminostilbene (3) as the main product
(entry 7). In contrast, in DMA solvent, the selec-
tivity of indolo[1,2-c]quinazolin-6(5H)-one (1) was
dramatically increased and 1 was predominantly
formed (entry 8).
Next, we investigated the effect of bases in DMA
solvent and these results are shown in Table 2. The
reaction using organic amine such as Et3N led to
the complicated mixtures (entry 1). When other al-
kaline metal carbonates, Cs2CO3 and Na2CO3, were
used as a base, a higher selectivity of 1 compared
to that of K2CO3 was attained, but the total yield of
products was decreased (Table 1, entry 8; Table 2,
entries 2 and 5). It is interesting to note that the de-
creasing amount of their alkaline metal carbonates
to 1.0 equiv led to the increasing of both total yield
and selectivity of 1, and consequently, 1 was formed
RESULTS AND DISCUSSION
First, trans-2,2ꢀ-dinitrostilbene [8] was chosen as a
model compound and allowed to react with carbon
monoxide in the presence of selenium catalyst and
K2CO3 as a base. The effect of reaction temperature,
pressure of carbon monoxide, and solvents was eval-
uated, and these results are summarized in Table 1.
When the reaction was carried out in THF solvent
under low pressurized carbon monoxide (10 atm) at
100◦C for 5 h, mixtures of indolo[1,2-c]quinazolin-
6(5H)-one (1), 2-(o-aminophenyl)indole (2) [9], and
trans-2,2ꢀ-diaminostilbene (3) [10] were obtained
with low selectivity (entry 1). Increasing the pressure
of carbon monoxide (30 atm) led to the increasing
of total yield (entry 2); however, further increasing
the pressure of carbon monoxide (50 atm) caused
the diminishing selectivity (entry 3). The selectiv-
ity considerably decreased and 1, 2, and 3 were ob-
tained in almost same yield at lower reaction tem-
TABLE 1 Selenium-Catalyzed Reaction of trans-2,2ꢀ-Dinitrostilbene with Carbon Monoxide
Entry
CO/atom
Temp/ ◦C
Solvent
Total Yield/%a
Selectivity 1/2/3
1
2
3
4
5
6b
7
8
10
30
50
30
30
30
30
30
100
100
100
80
120
100
100
100
THF
THF
THF
THF
61
76
82
64
67
–
32/50/18
28/54/18
34/41/24
37/31/32
27/52/21
–
THF
Benzene
DMF
DMA
81
66
11/36/53
64/18/18
Reaction conditions: trans-2,2ꢀ-dinitrostilbene (0.5 mmol), Se (0.2 mmol), K2CO3 (1.5 mmol), and solvent (10 mL) for 5 h.
a1H NMR yields.
btrans-2,2ꢀ-Dinitrostilbene (65%) was recovered.
Heteroatom Chemistry DOI 10.1002/hc

Cyclization and Carbocyclization of 2,2ꢀ-Dinitrostilbenes with Carbon Monoxide: One-Shot Synthesis of Indolo[1,2-c]quinazolinones 573
TABLE 2 Effect of Bases on Selenium-Catalyzed Reaction of trans-2,2ꢀ-Dinitrostilbene with Carbon Monoxide
Entry
Base (mmol)
Total Yield/%a
Selectivity 1/2/3
1b
2
Et3N (1.5 mmol)
–
43
54
72
60
67 (60)
51
–
Cs2CO3 (1.5 mmol)
Cs2CO3 (1.0 mmol)
Cs2CO3 (1.0 mmol)
Na2CO3 (1.5 mmol)
Na2CO3 (1.0 mmol)
Na2CO3 (1.0 mmol)
81/0/19
100/0/0
0/23/77
93/0/7
100/0/0
100/0/0
3
4c
5
6
7d
Reaction conditions: trans-2,2ꢀ-dinitrostilbene (0.5 mmol), Se (0.2 mmol), DMA (10 mL), and carbon monoxide (30 atm) at 100◦C for 5 h.
a1H NMR yields. The number in parentheses shows the isolated yield.
bThe complicated mixture was obtained.
cH2O (5.0 mmol) was added.
dIsomeric mixtures of 2,2ꢀ-dinitrostilbene (cis/trans = 5/2) were used.
as the sole product (entries 3 and 6). Particularly, in
the case of Na2CO3, indolo[1,2-c]quinazolin-6(5H)-
one (1) was obtained in 67% yield (entry 6). When
water was added to the reaction solution, the selec-
tivity of products was dramatically changed, and di-
amine 3 was obtained with high selectivity (entry 4).
Interestingly, although the reaction using isomeric
mixtures of 2,2ꢀ-dinitrostilbene (cis/trans = 5/2), in
which cis isomer was contained predominantly, was
examined, reductive cyclization and carbocycliza-
tion of 2,2ꢀ-dinitrostilbene smoothly proceeded to
give 1 without the formation of 2 and 3 (entry 7).
This result indicates that conformation of carbon–
carbon double bond of 2,2ꢀ-dinitrostilbene does not
affect the selectivity of products.
were allowed to react with carbon monoxide un-
der same reaction conditions as entry 6 in Table 2
(Scheme 2). The reaction of dimethoxy substituted
stilbene derivative (cis/trans = 1/3) was smoothly
proceeded to give the corresponding indolo[1,2-
c]quinazolinone derivative in moderate yield (56%).
By contrast, in the case of a mixture of cis- and
trans-4,4ꢀ-dichloro-2,2ꢀ-dinitrostilbene (cis/trans =
1/4), the yield of the corresponding indolo[1,2-
c]quinazolinone derivative was low owing to the
formation of complicated products. On the re-
action of dichloro derivative, the corresponding
aminophenylindole and diaminostilbene derivatives
were not identified.
We cannot explain the reaction pathway in de-
tail, one of the reaction pathways was shown in
Scheme 3. At the first step, we proposed that a nitro
group of dinitrostilbene is reductive deoxygenated
To investigate the effect of the substituted groups
on the aromatic ring, the 2,2ꢀ-dinitrostilbenes substi-
tuted methoxy and chloro groups on aromatic ring
SCHEME 3 Plausible reaction pathway.
Heteroatom Chemistry DOI 10.1002/hc

574 Umeda, Morishita, and Nishiyama
by carbonyl selenide (SeCO), which is generated
by the reaction of elemental selenium with carbon
monoxide in the presence of base [7,11], to form
the corresponding nitrene or nitrenoid species I
(Scheme 3). For the transition metal-catalyzed N-
heterocyclization of nitro compounds, it was sug-
gested that the generation of the nitrene or nitrenoid
intermediate was the key step in the reaction [12].
The generated nitrene or nitrenoid species I is in-
serted into the vinylic C-H bond to form the indole
II. Next, reductive deoxygenation of nitro group of
II by SeCO followed by carbonylation with carbon
monoxide gives the isocyanate III. Finally, the in-
tramolecular addition of the N-H bond on isocyanate
affords the indoloquinazolinone.
etate = 4:1) to give the mixture of 1-(bromomethyl)-
4-chloro-2-nitrobenzene (4.0 mmol) and 3-chloro-
2-nitrotoluene (2.0 mmol) based on integration of
the 1H NMR spectra. 1-(Bromomethyl)-4-chloro-
2-nitrobenzene was used without further separation.
The above mixture was added to the solu-
tion of triphenylphosphine (1.15 g, 4.4 mmol)
in toluene (5 mL) and the reaction mixture
was heated at reflux for 1 h. After cooling to
room temperature, the precipitate was filtered off
and washed with toluene to give the 4-chloro-
2-nitrobenzyltriphenylphosphnium bromide in 33%
yield from 3-chloro-2-nitrotoluene.
The solution of 1.2 M NaOEt in EtOH (9.0 mL,
11 mmol) was slowly added into the solution of 4-
chloro-2-nitrobenzyltriphenylphosphnium bromide
(1.59 g, 3.1 mmol) and 4-chloro-2-nitrobenzaldehyde
(0.52 g, 2.8 mmol) in EtOH (15 mL). After stir-
ring at room temperature for 24 h, water was
added to the reaction mixture to give the pre-
cipitate. The resulting precipitate was filtered off
and washed with EtOH to afford 4,4ꢀ-dichloro-2,2ꢀ-
dinitrostilbene (cis/trans = 1/4) in 60% yield as a pale
CONCLUSION
In conclusion, the practical and selective synthesis
of indolo[1,2-c]quinazolinone derivatives was suc-
cessfully achieved by the selenium-catalyzed reac-
tion of 2,2ꢀ-dinitrostilbene derivatives with carbon
monoxide. Preparation of asymmetric indolo[1,2-
c]quinazolinones from the corresponding 2,2ꢀ-
dinitrostilbenes and the investigation of the reaction
pathway are currently underway.
1
brown solid; H NMR (400 MHz, CDCl3) δ 6.95 (d,
J = 8.4 Hz, 2 H, trans), 7.05 (s, 2 H, trans), 7.33 (dd,
J = 8.2, 2.4 Hz, 2 H, trans), 7.51 (s, 0.5 H, cis), 7.65
(dd, J = 8.4, 2.4 Hz, 0.5 H, cis), 7.75 (d, J = 8.4 Hz,
0.5 H, cis), 8.06 (d, J = 1.6 Hz, 0.5 H, cis), 8.09 (d,
J = 2.0 Hz, 2H, trans); 13C NMR (100 MHz, CDCl3) δ
125.0, 128.4, 130.6, 133.4, 133.5, 134.5, 148.4 (Only
signals of trans isomer were shown because of low
intensity of those of cis isomer); IR (KBr) 3115, 1560,
1522, 1345, 1275, 1257, 1148, 1108, 965, 887, 842,
827, 796 cm−1; MS (EI):m/z 338 (M+).
EXPERIMENTAL
FT-IR spectra were recorded on a JASCO FT/-IR-
4100 instrument. 1H and 13C NMR spectra were
obtained on a JEOL AL400 (400 MHz, 100 MHz)
instrument. Chemical shifts were reported in ppm
relative to tetramethylsilane or residual solvent as
the internal standard. Mass spectra were obtained
on a JEOL JMS-700 spectrometer. All reagents were
obtained from commercial suppliers and used with-
out purification. Solvents were dried (drying agent
in parentheses) and distilled prior to use: THF (Na),
benzene (CaH2), DMF (MS 4A), DMA (MS 4A), Et3N
(KOH). K2CO3, Na2CO3, and Cs2CO3 were dried at
150◦C under vacuum (10 mmHg) for 1 h.
4,4ꢀ-Dimethoxy-2,2ꢀ-dinitrostilbene (cis/trans =
1/3): 1H NMR (400 MHz, CDCl3) δ 3.84 (s, 6 H,
trans), 3.91 (s, 2 H, cis), 6.86 (dd, J = 8.4, 2.8 Hz,
2 H, trans), 6.93 (d, J = 8.4 Hz, 2 H, trans), 6.96 (s,
2 H, trans), 7.19 (dd, J = 8.8, 2.8 Hz, 0.7 H, cis),
7.43 (s, 0.7 H, cis), 7.51 (d, J = 2.8 Hz, 0.7 H, cis),
7.56 (d, J = 2.8 Hz, 2 H, trans), 7.72 (d, J = 8.8 Hz,
0.7 H, cis); 13C NMR (100 MHz, CDCl3) δ 55.8, 55.9,
108.9, 109.1, 120.0, 120.4, 124.9, 126.9, 127.7, 129.8,
132.0, 132.1, 133.4, 148.7, 159.1, 159.5; IR (KBr)
3418, 3081, 2946, 1618, 1525, 1441, 1343, 1293, 1252,
1210, 1187, 1147, 1068, 1036, 946, 917, 880, 823, 795
cm−1; MS (EI): m/z 330 (M+).
Typical Synthesis of 4,4ꢀ-Dichloro-2,2ꢀ-
dinitrostilbene
To the solution of 3-chloro-2-nitrotoluene (1.20 g,
7.0 mmol) and N-bromosuccinimide (NBS) (1.00 g,
5.6 mmol) in benzene (15 mL) was added a cat-
alytic amount of benzoyl peroxide (BPO). After stir-
ring at reflux for 24 h, the reaction mixture was
cooled to room temperature and filtered off and
washed with CHCl3. The filtrate was concentrated
under reduced pressure and the residue was purified
by chromatography over silica gel (hexane:ethyl ac-
Typical Synthesis of Indolo[1,2-c]quinazolin-
6(5H)-one (1)
To an autoclave containing trans-2,2ꢀ-dinitrostilbene
[8] (135 mg, 0.50 mmol), Na2CO3 (106 mg,
1.0 mmol), and Se (16 mg, 0.20 mmol) was added
DMA (10 mL). The apparatus was then flushed
Heteroatom Chemistry DOI 10.1002/hc

Cyclization and Carbocyclization of 2,2ꢀ-Dinitrostilbenes with Carbon Monoxide: One-Shot Synthesis of Indolo[1,2-c]quinazolinones 575
several times with carbon monoxide and fully
charged with carbon monoxide (30 atm) at room
temperature. The reaction was carried out at 100◦C
for 5 h. The reaction apparatus was cooled to room
temperature. After the evacuation of the excess car-
bon monoxide at room temperature, the deposited
selenium and salt was filtrated off and washed with
THF. The filtrate was concentrated under reduced
pressure. The residue was washed with benzene to
give indolo[1,2-c]quinazolin-6(5H)-one (1) in 60%
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1
yield as a white solid; H NMR (400 MHz, DMSO-
d6) δ 7.23–7.29 (m, 2H), 7.34–7.39 (m, 3H), 7.42–7.46
(m, 1H), 7.75–7.77 (m, 1H), 8.11 (dd, J = 7.6, 0.8 Hz,
1H), 8.56–8.58 (m, 1H), 11.38 (s, 1H); 13C NMR (100
MHz, DMSO-d6) δ 98.2, 113.6, 115.3, 115.5, 120.2,
123.0, 123.5, 123.7, 129.4, 129.6, 133.3, 134.1, 134.3,
147.1 (one signal is missing due to overlap); IR (KBr)
3053, 2928, 1702, 1598, 1488, 1447, 1400, 1340, 1149,
1011, 800 cm−1; MS (EI): m/z 234 (M+); HRMS (EI)
calcd. for C15H10N2O1: 234.0793. found: 234.0786.
3,9-Dichloroindolo[1,2-c]quinazolin-6(5H)-one:
1H NMR (400 MHz, DMSO-d6) δ 7.25–7.30 (m, 2H),
7.37–7.41 (m, 3H), 7.76 (d, J = 8.8 Hz, 1H), 8.11 (d,
J = 8.0 Hz, 1H), 8.52 (d, J = 1.6 Hz, 1H); 13C NMR
(100 MHz, DMSO-d6) δ 98.6, 112.5, 114.9, 115.0,
121.6, 123.0, 123.8, 125.5, 127.5, 128.3, 133.47,
133.54, 134.1, 135.5, 146.7; IR (KBr) 3114, 1703,
1593, 1435, 1391, 1331, 1228, 1090, 931, 860, 809
cm−1; MS (EI): m/z 302 (M+); HRMS (EI) calcd.
for C15H8N2O315Cl2 and C15H8N2O317Cl2: 302.0014 and
305.9986. found: 301.9986 and 305.9984.
3, 9 - Dimethoxyindolo[1, 2 - c]quinazolin - 6(5H) -
1
one: H NMR (400 MHz, DMSO-d6) δ 6.78 (s, 1H),
6.82–6.84 (m, 1H), 6.98–7.00 (m, 1H), 7.09 (s, 1H),
7.58 (d, J = 8.4 Hz, 1H), 7.93 (d, J = 8.4 Hz, 1H),
8.10 (s, 1H), 11.19 (s, 1H); 13C NMR (100 MHz,
DMSO-d6) δ 55.3, 55.4, 96.3, 99.3, 99.4, 107.3, 110.3,
112.8, 120.3, 123.8, 124.6, 133.1, 134.0, 135.4, 147.4,
155.9, 159.9; IR (KBr) 2932, 2834, 2359, 1707, 1625,
1599, 1524, 1492, 1442, 1401, 1311, 1286, 1271, 1238,
1204, 1173, 1048, 1031, 955, 843, 818 cm−1; MS (EI):
m/z 294 (M+); HRMS (EI) calcd. for C17H14N2O3:
294.1004. found: 294.1000.
ACKNOWLEDGMENTS
This research was supported by a Grant-in-Aid for
Science Research, and Strategic Project to Support
the Formation of Research Bases at Private Universi-
ties from the Ministry of Education, Culture Sports,
and Science and Technology of Japan.
Heteroatom Chemistry DOI 10.1002/hc