Three-component synthesis of fused indenopyridines from aromatic aldehydes, 2-bromo-2H-indene-1,3-dione and aminouracil or aminopyrazole

Article abstract of DOI:10.1007/s13738-016-0876-0

Abstract: Three-component synthesis of fused indenopyridines containing pyrazole or uracil moiety by the reaction of benzaldehydes, 2-bromo-1H-indene-1,3(2H)-dione, and pyrazoles or uracil, catalyzed by ammonium acetate is reported. Graphical Abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s13738-016-0876-0

J IRAN CHEM SOC
DOI 10.1007/s13738-016-0876-0
ORIGINAL PAPER
Three‑component synthesis of fused indenopyridines
from aromatic aldehydes, 2‑bromo‑2H‑indene‑1,3‑dione
and aminouracil or aminopyrazole
Somayeh Ahadi1 · Ayoob Bazgir1
Received: 14 March 2016 / Accepted: 27 April 2016
© Iranian Chemical Society 2016
Abstract Three-component synthesis of fused indenop-
yridines containing pyrazole or uracil moiety by the reac-
tion of benzaldehydes, 2-bromo-1H-indene-1,3(2H)-dione,
and pyrazoles or uracil, catalyzed by ammonium acetate is
reported.
applications. These compounds have been reported to pos-
sess a wide spectrum of biologic activities such as anti‐
hyperglycemic, analgesic, anti‐inflammatory, antipyretic,
antibacterial, hypoglycemic, sedative‐hypnotic properties
[6–11]. In particular among heterocycle-fused pyrazoles,
Graphical Abstract
Keywords Indenopyridine · Pyrazole · Uracil · 2-Bromo-
1H-indene-1,3(2H)-dione
pyrazolopyridines are an important class of heterocycles
with broad pharmacological activities such as possible anti-
viral agent [12, 13], potent p38 kinase inhibitors [14], HIV
reverse transcriptase inhibitors [15].
Introduction
As a privileged scaffold, pyridine is a ubiquitous subu-
nit in various products with remarkable biological activities
such as antimicrobial [16–18], anticancer [19] anticonvul-
sant [20], antiviral [21], anti-HIV [22], antifungal, and anti-
mycobacterial [23]. Particularly, among of this category,
indenopyridines are attractive due to showing a wide range
of biological activities such as calcium antagonistic [24],
antioxidant [25], antihistamine, and antidepressant [26–
28], and also act as phosphodiesterase (PDE) inhibitors
[29], NK-1, and dopamine receptor ligands [30, 31].
Pyrazoles have gained more attention in recent years for
biological [1, 2], medicinal [3, 4], and agricultural [5]
* Ayoob Bazgir
a_bazgir@sbu.ac.ir
1
Department of Chemistry, Shahid Beheshti University,
General Campus, Tehran 1983963113, Iran
1 3

J IRAN CHEM SOC
Scheme 1 Synthesis of inde-
nopyridines containing pyrazole
or uracil 4
Very recently, we described a modified reaction for the
synthesis of spiro indenofuran-triones by the reaction of
1,3-dicarbonyl compounds, aldehydes, and cyclic α-halo
ketones [32–35]. As a continuation of our previous work
for heterocycles synthesis using cyclic α-halo ketones
[32–35], we herein investigate replacement of enamine
compounds instead of 1,3-dicarbonyl compounds in the
reaction. Notably, the expected product 5 was not obtained,
while indenopyridines containing pyrazole or uracil moiety
4 was isolated in good yields (Scheme 1).
(6H, m, H-Ar), 7.45–7.48 (1H, m, H-Ar), 7.59–7.74
(5H, m, H-Ar), 7.98–8.01 (1H, m, H-Ar), 8.33 (2H, d,
J = 7.6 Hz, H-Ar). MS (EI, 70 eV) m/z: 449 (M+). Anal.
Calcd. for C31H19N3O: C, 82.83; H, 4.26; N, 9.35. Found:
C, 82.76; H, 4.22; N, 9.26.
4‑(4‑Nitrophenyl)‑1, 3‑diphenylindeno[1, 2‑b]
pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4b) Cream powder
(77 %); mp > 270 °C. IR (KBr) (νmax/cm−1): 1709, 1600,
1
1559. H NMR (300 MHz, DMSO-d6): δH 7.06–7.11 (4H,
m, H-Ar), 7.21–7.23 (1H, m, H-Ar), 7.46–7.70 (7H, m,
H-Ar), 7.77–7.82 (1H, m, H-Ar), 7.97–8.08 (3H, m, H-Ar),
8.34 (2H, d, J = 8.1 Hz, H-Ar). MS (EI, 70 eV) m/z: 494
(M+). Anal. Calcd. for C31H18N4O3: C, 75.29; H, 3.67; N,
11.33. Found: C, 75.34; H, 3.59; N, 11.24.
Experimental
Melting points were measured on an Electrothermal 9100
apparatus and are uncorrected. NMR spectra were recorded
on a BRUKER DRX-300 AVANCE spectrometer. NMR
spectra were obtained on solutions in DMSO-d6. IR spec-
tra were recorded using a BOMEM MB-Series. Elemental
analyses were performed using a Herecus CHN-O-Rapid
analyzer. The chemicals used in this work were obtained
from Fluka and Merck and were used without purification.
Due to very low solubility of the products 4, we cannot
report the 13C NMR date for these products.
4‑(4‑Bromophenyl)‑1,3‑diphenylindeno[1,2‑b]
pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4c) Yellow powder
(65 %); mp 245–247 °C. IR (KBr) (νmax/cm−1): 1709, 1603,
1
1554. H NMR (300 MHz, DMSO-d6): δH 7.01–7.07 (6H,
m, H-Ar), 7.18–7.27 (3H, m, H-Ar), 7.31–7.44 (2H, m,
H-Ar), 7.50–7.61 (5H, m, H-Ar), 7.96–798 (1H, m, H-Ar),
8.31 (2H, d, J = 6.9 Hz, H-Ar). MS (EI, 70 eV) m/z: 529
(M+ + 2), 527 (M+). Anal. Calcd. for C31H18BrN3O: C,
70.46; H, 3.43; N, 7.95. Found: C, 70.38; H, 3.37; N, 7.90.
Generalprocedureforpreparationof1,3‑diphenylindeno[1,2‑b]
pyrazolo[4,3‑e]pyridin‑5(1H)‑ones (4) A mixture of pyra-
zoles (1 mmol), aldehydes (1 mmol), 2-bromo-1H-indene-
1,3(2H)-dione (1 mmol) and NH4OAc (30 mol%) in refluxing
acetic acid (2 mL) was stirred for 24 h. After completion of the
reaction (confirmed by TLC), the reaction mixture was cooled
to room temperature. Then, the precipitate was filtered and
washed with methanol (5 mL) to afford the pure product 4.
4‑(4‑Methoxyphenyl)‑1,3‑diphenylindeno[1,2‑b]
pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4d) Yellow pow-
der (73 %); mp 205–207 °C. IR (KBr) (νmax/cm−1): 1710,
1607, 1558. 1H NMR (300 MHz, DMSO-d6): δH 3.71 (3H,
s, CH3), 6.62 (2H, d, J = 8.1 Hz, H-Ar), 6.98–7.22 (7H, m,
H-Ar), 7.44–7.70 (7H, m, H-Ar), 7.95 (1H, d, J = 6.9 Hz,
H-Ar), 7. (1H, m, H-Ar), 8.31 (2H, d, J = 7.8 Hz,
H-Ar). MS (EI, 70 eV) m/z: 479 (M+). Anal. Calcd. for
C32H21N3O2: C, 80.15; H, 4.41; N, 8.76. Found: C, 80.24;
H, 4.47; N, 8.38.
1,3,4‑Triphenylindeno[1,2‑b]pyrazolo[4,3‑e]pyri-
din‑5(1H)‑one (4a) Yellow powder (71 %); mp > 270 °C.
IR (KBr) (νmax/cm−1): 1703, 1615, 1562. 1H NMR
(300 MHz, DMSO-d6): δH 7.03 (4H, m, H-Ar), 7.12–7.28
1 3

J IRAN CHEM SOC
1‑(4‑Methoxyphenyl)‑3,4‑diphenylindeno[1,2‑b]
pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4e) Yellow powder
for C31H17BrClN3O: C, 66.15; H, 3.04; N, 7.47. Found: C,
66.09; H, 3.10; N, 7.40.
1
(68 %); mp > 270 °C. IR (KBr) (νmax/cm−1): 1704. H
NMR (300 MHz, DMSO-d6): δH 3.86 (3H, s, CH3), 7.03–
7.32 (12H, m, H-Ar), 7.56–7.61 (2H, m, H-Ar), 7.66–7.77
(1H, m, H-Ar), 7.98 (1H, d, J = 7.5 Hz, H-Ar), 8.17 (2H,
d, J = 8.8 Hz, H-Ar). MS (EI, 70 eV) m/z: 449 (M+). Anal.
Calcd. for C32H21N3O2: C, 80.15; H, 4.41; N, 8.76. Found:
C, 80.08; H, 4.36; N, 8.70.
1‑(4‑Bromophenyl)‑3‑phenyl‑4‑(p‑tolyl)indeno[1,2‑b]
pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4j) Yellow pow-
der (70 %); mp 245–247 °C. IR (KBr) (νmax/cm−1): 1711,
1577, 1492. 1H NMR (300 MHz, DMSO-d6): δH 2.26 (3H,
s, CH3), 6.91–7.21 (8H, m, H-Ar), 7.58 (2H, bs, H-Ar),
7.80 (3H, m, H-Ar), 7.98 (1H, bs, H-Ar), 8.32 (2H, bs,
H-Ar). MS (EI, 70 eV) m/z: 543 (M+ + 2), 541 (M+).
Anal. Calcd. for C32H20BrN3O: C, 70.86; H, 3.72; N, 7.75.
Found: C, 70.78; H, 3.78; N, 7.84.
1‑(4‑Methoxyphenyl)‑4‑(4‑nitrophenyl)‑3‑phenylindeno[1,
2‑b]pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4f) Yellow pow-
der (69 %); mp 262–264 °C. IR (KBr) (νmax/cm−1): 1708,
1561, 1510. 1H NMR (300 MHz, DMSO-d6): δH 3.85
(3H, s, CH3), 6.97–7.08 (4H, m, H-Ar), 7.17–7.22 (3H,
m, H-Ar), 7.47–7.61 (4H, m, H-Ar), 7.71–7.76 (1H, m,
H-Ar), 7.93–7.98 (3H, m, H-Ar), 8.15 (2H, d, J = 8.8 Hz,
H-Ar). MS (EI, 70 eV) m/z: 524 (M+). Anal. Calcd. for
C32H20N4O4: C, 73.27; H, 3.84; N, 10.68. Found: C, 73.18;
H, 3.93; N, 10.72.
1‑(4‑Bromophenyl)‑3‑phenyl‑4‑(thiophen‑2‑yl)
indeno[1,2‑b]pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4k) Yel-
low powder (73 %); mp 267–269 °C. IR (KBr) (νmax
/
cm−1): 1706, 1558, 1492. H NMR (300 MHz, DMSO-
d6): δH 6.84–6.97 (2H, m, H-Ar), 7.12–7.28 (5H, m, H-Ar),
7.54–7.77 (7H, m, H-Ar), 7.87–7.91 (1H, m, H-Ar). MS
(EI, 70 eV) m/z: 535 (M+ + 2), 533 (M+). Anal. Calcd.
for C29H16BrN3OS: C, 65.17; H, 3.02; N, 7.86. Found: C,
65.08; H, 3.10; N, 7.81.
1
4‑(4‑Chlorophenyl)‑1‑(4‑methoxyphenyl)‑3‑phenylindeno
[1,2‑b]pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4g) Yellow pow-
der (66 %); mp 243–245 °C. IR (KBr) (νmax/cm−1): 1705,
1563, 1505. 1H NMR (300 MHz, DMSO-d6): δH 3.86 (3H, s,
CH3), 6.92 (1H, bs, H-Ar), 7.01–7.26 (10H, m, H-Ar), 7.56–
7.61 (2H, m, H-Ar), 7.71–7.75 (1H, m, H-Ar), 7.95 (1H, d,
J = 7.4 Hz, H-Ar), 8.15 (1H, d, J = 8.9 Hz, H-Ar). MS (EI,
70 eV) m/z: 513 (M+). Anal. Calcd. for C32H20ClN3O2: C,
74.78; H, 3.92; N, 8.18. Found: C, 74.73; H, 3.85; N, 8.27.
1,3‑Dimethyl‑5‑phenyl‑1H‑indeno[2′,1′:5,6]pyrido[2,3‑d]
pyrimidine‑2,4,6(3H)‑trione (4m) Cream powder (95 %);
mp > 270 °C. IR (KBr) (νmax/cm−1): 1701, 1685, 1604. 1H
NMR (300 MHz, DMSO-d6): δH 3.14 (3H, s, CH3), 3.75
(3H, s, CH3), 7.22–7.39 (4H, m, H-Ar), 7.49–7.66 (3H, m,
H-Ar), 7.75–7.80 (1H, m, H-Ar), 7.98 (1H, d, J = 7.1 Hz,
H-Ar). MS (EI, 70 eV) m/z: 369 (M+). Anal. Calcd. for
C22H15N3O3: C, 71.54; H, 4.09; N, 11.38. Found: C, 71.44;
H, 4.01; N, 11.30.
1‑(4‑Bromophenyl)‑4‑(4‑nitrophenyl)‑3‑phenylindeno
[1,2‑b]pyrazolo[4,3‑e]pyridin‑5(1H)‑one
(4h) Yel-
low powder (80 %); mp > 270 °C. IR (KBr) (νmax/cm−1):
1
1711, 1561, 1498. H NMR (300 MHz, DMSO-d6): δH
1,3‑Dimethyl‑5‑(4‑nitrophenyl)‑1H‑indeno[2′,1′:5,6]
pyrido[2,3‑d]pyrimidine‑2,4,6(3H)‑trione (4n) Yellow pow-
der (92 %); mp > 270 °C. IR (KBr) (νmax/cm−1): 1705,
1689, 1611. 1H NMR (300 MHz, DMSO-d6): δH 3.15 (3H,
s, CH3), 3.73 (3H, s, CH3), 7.53–7.66 (4H, m, H-Ar), 7.75–
7.80 (1H, m, H-Ar), 7.98 (1H, d, J = 7.3 Hz, H-Ar), 8.29
(2H, d, J = 8.5 Hz, H-Ar). MS (EI, 70 eV) m/z: 414 (M+).
Anal. Calcd. for C22H14N3O5: C, 63.77; H, 3.41; N, 13.52.
Found: C, 63.68; H, 3.33; N, 13.63.
7.04–7.09 (4H, m, H-Ar), 7.20–7.22 (1H, m, H-Ar), 7.48–
7.61 (4H, m, H-Ar), 7.74–7.83 (3H, m, H-Ar), 7.93–8.04
(3H, m, H-Ar), 8.34 (2H, d, J = 8.3 Hz, H-Ar). MS (EI,
70 eV) m/z: 574 (M+ + 2), 572 (M+). Anal. Calcd. for
C32H20ClN3O2: C, 64.93; H, 2.99; N, 9.77. Found: C,
64.83; H, 3.07; N, 9.72.
1‑(4‑Bromophenyl)‑4‑(4‑chlorophenyl)‑3‑phenylindeno[1,
2‑b]pyrazolo[4,3‑e]pyridin‑5(1H)‑one (4i) Yellow pow-
der (50 %); mp 252–253 °C. IR (KBr) (νmax/cm−1): 1706,
1561, 1491. 1H NMR (300 MHz, DMSO-d6): δH 6.95–7.17
(9H, m, H-Ar), 7.44–7.64 (6H, m, H-Ar), 7.95 (1H, d,
J = 7.5 Hz, H-Ar), 8.27 (2H, d, J = 8.1 Hz, H-Ar). MS
(EI, 70 eV) m/z: 563 (M+ + 2), 561 (M+). Anal. Calcd.
5‑(4‑Methoxyphenyl)‑1,3‑dimethyl‑1H‑indeno[2′,1′:5,6]
pyrido[2,3‑d]pyrimidine‑2,4,6(3H)‑trione (4o) Cream pow-
1
der (87 %); mp > 270 °C. IR (KBr) (νmax/cm−1): 1706. H
NMR (300 MHz, DMSO-d6): δH 3.14 (3H, s, CH3), 3.74
(3H, s, CH3), 3.83 (3H, s, CH3), 6.93 (2H, d, J = 8.5 Hz,
1 3

J IRAN CHEM SOC
Table 1 Optimization of the
reaction
Entry
Solvent, reflux
Base (mol%)
Yield (%)a
1
CH3CN
EtOH
H2O
NH4OAc (30)
NH4OAc (30)
NH4OAc (30)
DBU (30)
45
40
2
3
43
4
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
70
5
K2CO3 (30)
CsCO3 (30)
NaOAc (30)
NH4OAc (30)
NH4OAc (20)
NH4OAc (40)
–
65
6
71
7
70
8
77
9
69
10
11
76
<30
Pyrazol-5-amine 1a (1 mmol), 4-nitrobenzaldehyde 2b (1 mmol) and indene-1,3(2H)-dione 3 (1 mmol)
a
Isolated yield
H-Ar), 7.17 (2H, d, J = 8.5 Hz, H-Ar), 7.61–7.79 (3H, m,
H-Ar), 7.97 (1H, d, J = 7.7 Hz, H-Ar). MS (EI, 70 eV) m/z:
399 (M+). Anal. Calcd. for C23H17N3O4: C, 69.17; H, 4.29;
N, 10.52. Found: C, 69.10; H, 4.23; N, 10.61.
providing indeno[1,2-b]pyrazolo[4,3-e]pyridin-5(1H)-one
4b in 77 % yield in the presence of 30 mol % of NH4OAc
(entry 8). It was found that when increasing the amount of
NH4OAc from 20 to 30 mol%, the isolated yield increased
from 69 to 77 %, respectively (entries 8 and 9), and more
amounts of the NH4OAc did not improve the yield (entry
10). It should be mentioned that when the reaction was car-
ried out in the absence of NH4OAc, the yield of the product
was low (entry 11). When this reaction was carried out with
other bases such as DBU, NaOAc, CsCO3, or K2CO3, the
yield of the expected product was reduced.
According to the optimized conditions, the three-com-
ponent condensation reaction of 1,3-diphenyl-1H-pyrazol-
5-amines 1a–c or uracil 1d, aldehydes 2, and 2-bromo-
1H-indene-1,3(2H)-dione 3 in the presence of NH4OAc
(30 mol%) proceeded in HOAc under reflux conditions to
afford indenopyridines containing pyrazole or uracil moi-
ety diones 4, in good yields after 24 h (Table 2). This proto-
col followed the GAP chemistry [36–39], which can avoid
traditional chromatography and recrystallization purifica-
tion methods. According GAP chemistry, pure products
were obtained simply by filtration and washing off the solid
with methanol.
1,3,4‑Triphenyl‑4,10‑dihydroindeno[1,2‑b]pyrazolo[4,3‑e]
pyridin‑5(1H)‑one (7) White powder (66 %); mp > 270 °C.
IR (KBr) (νmax/cm−1): 1704, 1601, 1543. 1H NMR
(300 MHz, DMSO-d6): δH 5.67(1H, s, CH), 7.09 (1H,
m, H-Ar), 7.24–7.43 (5H, m, H-Ar), 7.52–7.65 (7H, m,
H-Ar),), 7.77 (3H, m, H-Ar),), 7.99–8.01 (3H, m, H-Ar),
11.05 (1H, s, NH). MS (EI, 70 eV) m/z: 451 (M+). Anal.
Calcd. for C31H21N3O: C, 82.46; H, 4.69; N, 9.31. Found:
C, 82.40; H, 4.62; N, 9.25.
Results and discussion
To achieve suitable conditions for the synthesis of inde-
nopyridines 4, various reaction conditions and bases have
been investigated in the reaction of pyrazol-5-amine 1a,
4-nitrobenzaldehyde 2b, and indene-1,3(2H)-dione 3 as a
model reaction (Table 1). Screening of the solvent revealed
that acetic acid is the most suitable reaction media,
To demonstrate the key role of 2-bromo-1H-indene-
1,3(2H)-dione 3 in the reaction, we investigated the reac-
tion of 1,3-indandion 6 with 1H-pyrazol-5-amine 1a and
1 3

J IRAN CHEM SOC
Table 2 Indenopyridines
consist of pyrazole or uracil 4
Product
X
y
Yield (%)
4a
4b
4c
4d
4e
4f
H
H
71
77
65
73
68
69
66
80
50
70
73
95
92
87
H
NO2
Br
H
H
OMe
H
OMe
OMe
OMe
Br
Br
Br
Br
_
NO2
Cl
4g
4h
4i
NO2
Cl
4g
4k
4m
4n
4o
Me
Thiophene
H
_
NO2
OMe
_
4-nitrobenzaldehyde 2b in the same reaction conditions
(Scheme 2). The indenopyrazolopyridin-5(1H)-one 4a was
not detected at all, while 4-(4-nitrophenyl)-1,3-diphenyl-
4,10-dihydroindeno[1,2-b]pyrazolo[4,3-e]pyridin-5(1H)-
one 7 was obtained in 66 % yield. In the HNMR spec-
trum of 7, the benzylic proton is observed as a singlet at
5.67 ppm which confirms the proposed structure of 7.
Although the exact mechanism of the reaction is not very
clear, a plausible mechanism for the formation of product
4 is proposed in Scheme 3. Initially, nulleophilic reaction
of aminopyrazole 1 to iminium salt 8 (formed in situ by
the reaction of amine and aldehyde), followd by acid–base
reaction produced intermediate 9. Then, nucleophilic reac-
tion of 2-bromo-1H-indene-1,3(2H)-dione 3 to intermedi-
ate 9 followed by intracyclization afforded intermediate 10.
Eventually, elimination of HBr and H2O from 10 produced
the corresponding product 4.
Finally, in situ generation of 2-bromo-1H-indene-
1,3(2H)-dione 3 by the reaction of 1,3-indandion 6 and
bromine was investigated in the reaction. Therefore, the
reaction of 1,3-diphenyl-1H-pyrazol-5-amine 1a, 4-nitro
aldehyde 2b, 1,3-indandion 6 and bromine under same
reaction conditions afforded the same product 4 in 65 %
yield after 24 h (Scheme 4).
Conclusion
In this paper, 2-bromo-1H-indene-1,3(2H)-dione as a
cyclic α-halo compound was used for the synthesis of
1 3

J IRAN CHEM SOC
Scheme 2 Reaction of
1,3-indandion, aldehyde and
aminopyrazole
Scheme 3 Proposed mechanism
Scheme 4 In situ generation of 2-bromoindene-dione 3 in the reaction
1 3

J IRAN CHEM SOC
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indenopyridines containing densely pyrazole or uracil in
good yields via multi-component coupling reactions. Prom-
inent among the advantages of this new method are novelty,
operational simplicity, good yields, and easy work-up pro-
cedures employed.
Acknowledgments We gratefully acknowledge financial support
from the Research Council of Shahid Beheshti University.
22. T.J. Tucker, J.T. Sisko, R.M. Tynebor, T.M. Williams, P.J.
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