Ultrasonic-assisted Cu-catalyzed multicomponent synthesis of furo[3,4-b]pyrazolo[4,3-f] quinolinones

Article abstract of DOI:10.1515/hc-2011-0086

A new series of 10-phenyl-7,9-dihydro-3 H-furo[3,4-b]pyrazolo[4,3-f] quinolin-9-one derivatives has been synthesized through an efficient multicomponent reaction of tetronic acid, 5-aminoindazole and various aromatic aldehydes catalyzed by copper(II) triflate under ultrasonic irradiation.

Full text of DOI:10.1515/hc-2011-0086

ꢁꢁꢁꢂ
DOI 10.1515/hc-2011-0086ꢀ ꢀHeterocycl. Commun. 2013; 19(2): 105–108
Saman Damavandi*, Reza Sandaroos and Ali Mohammadi
Ultrasonic-assisted Cu-catalyzed multicomponent
synthesis of furo[3,4-b]pyrazolo[4,3-f]
quinolinones
Abstract:
A
new series of 10-phenyl-7,9-dihydro- an important class of fused heterocyclic compounds, are
3H-furo[3,4-b]pyrazolo[4,3-f]quinolin-9-one derivatives antiviral [14] and antibacterial agents [15], acting as potent
has been synthesized through an efficient multicompo- remedies for treating atherosclerosis or restenosis [16],
nent reaction of tetronic acid, 5-aminoindazole and vari- inflammatory disorders, demyelinating disorders and
ous aromatic aldehydes catalyzed by copper(II) triflate cancers [17].
under ultrasonic irradiation.
Multicomponent reactions (MCRs) play a crucial role
in modern synthetic organic chemistry because they occur
Keywords: copper(II) triflate; furo[3,4-b]pyrazolo[4,3-f] in a single pot involving the simultaneous molecular
quinolinones; one-pot.
interaction of three or more components. They exhibit a
high atom economy and selectivity to furnish diverse com-
pounds [18, 19].
*Corresponding author: Saman Damavandi, Young Researchers
Club, Sarvestan Branch, Islamic Azad University, Sarvestan, Iran,
e-mail: saman_damavandi@yahoo.com
Reza Sandaroos: Faculty of Science, University of Birjand,
Department of Chemistry, Birjand, Iran
Ali Mohammadi: Young Researchers Club, Sarvestan Branch,
Islamic Azad University, Sarvestan, Iran
During the past few years, the outstanding potential
of a variety of metal triflates (trifluoromethylsulfonates)
has been realized, being widely used in organic synthe-
sis due to their low toxicity, low cost, high stability and
ease of handling [20]. Among the various metal triflates,
copper(II) triflate [Cu(OTf)2] plays an indispensable role
in the discovery of novel and improved reaction processes
[21]. In general, the triflate anion is both weakly nucleo-
philic and coordinating, rendering the metal counter ion
more cationic, thus providing a stronger Lewis acid.
Recently, the synthesis of pyrazolo[4,3-f]quinoline
derivatives has been reported by Shi and co-workers [22].
However, the synthesis of new heterocyclic compounds
containing the furopyrazoloquinolinone scaffold and the
development of more efficient entry to these heterocy-
cles are strongly desired. During the course of our studies
towards the development of new routes to the synthesis of
novel heterocycle compounds using triflate salts [23, 24],
herein, we wish to report a rapid and efficient synthesis
of a new series of furo[3,4-b]pyrazolo[4,3-f]quinolinones
via one-pot reaction of tetronic acid, aryl aldehydes and
5-aminoindazole under the influence of catalytic amount
of copper(II) triflate under ultrasonic irradiation.
Introduction
Heterocycles are used as scaffolds for creating pharmaco-
phores to yield potent and selective drugs. Pyrazole deriv-
atives are known for their various biological activities, for
example, pyrazolo[3,4-b]quinolines are potential antivi-
ral [1] and antimalarial agents [2], and they lower serum
cholesterol [3, 4]. Pyrazolo[3,4-c]pyrazoles are useful for
the treatment of esophageal and gastrointestinal mucosa
injury [5], brain injury [6] and are also immunostimula-
tory [7], antianginal and antitumor agents [8]. By contrast,
quinolines are important building blocks in synthetic
heterocyclic chemistry and their use in the preparation
of pyrazolo[3,4-b]quinolines and benzo[b][1,8]naphthy-
ridines derivatives has been reported recently [9–12]. In
addition, 1H-pyrazolo[3,4-b]quinoline compounds act as
sensors for the fluorescence detection of small inorganic
cations such as lithium, sodium, barium and magnesium Results and discussion
[13]. Furthermore, pyrazolo[3,4-f]quinoline derivatives
are a novel class of immunostimulant compounds with To choose the most appropriate medium in this heterocy-
potent in vivo effects in a murine infection model [5, 6]. clization reaction, we examined the Cu-catalyzed reaction
Moreover, pyrazolo[4,3-f]quinoline derivatives, which are oftetronicacid, 5-aminoindazoleand4-nitrobenzaldehyde
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106ꢀ ꢀS. Damavandi etꢃal.: Synthesis of furo[3,4-b]pyrazolo[4,3-fꢀ]quinolinones
Table 1ꢁInfluence of solvent on ultrasonic assisted, Cu-catalyzed (10
mol%) synthesis of 10-(4-nitrophenyl)-7,9-dihydro-3H-furo[3,4-b]
pyrazolo[4,3-f]quinolin-9-one (8).
as a model reaction to synthesize 10-(4-nitrophenyl)-
7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]quinolin-9-one in
varioussolventsat50°Cunderultrasonicirradiation(Table
1). The solvents examined were chloroform, ethanol, tet-
rahydrofuran, 1,2-dichloroethane and acetonitrile. The
reaction in ClCH2CH2Cl afforded the target product in
80% yield. When the reaction was carried out in CH3CN,
the reaction was faster and the product was obtained in
90% yield (Table 1, entry 1); it turned out to be the best
choice in terms of isolated yield. In the case of other sol-
vents such as CHCl3, THF and ethanol, the target product
8 was obtained in lower yields. Other copper salts includ-
ing CuCl, CuCN and Cu(OAc)2 were also employed for the
model reaction. As shown in Table 1, among the copper
salts screened, Cu(OTf)2 showed excellent activity in terms
of yield of the desired product and was more efficient
Entry Catalyst
Solvent
Reaction
time (min)
Yielda,b
(10 mol%)
1
2
3
4
5
6
7
8
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
CuCl
CH3CN
THF
10.5 90, 88, 88, 85, 80c
20
19
17
20
20
20
20
55
75
EtOH
ClCH2CH2Cl
CHCl3
CH3CN
CH3CN
CH3CN
80
55
Trace
32
CuCN
Cu(OAc)2
~10
aAll reactions were carried out at 50°C under ultrasonication.
bIsolated yields. cCatalyst was reused at least four times.
than other catalysts (Table 1, entries 6–8). The recyclabil- completed in minutes in the presence of a copper catalyst.
ity of Cu(OTf)2 was also investigated. The catalyst could It should be noted that in the absence of a catalyst no reac-
be reused without any significant loss of activity at least tion occurred after 6 h under otherwise similar conditions.
four times.
Various aromatic aldehydes were allowed to react
Subsequently, the effect of the amount of Cu(OTf)2 with tetronic acid and 5-aminoindazole, and all these
was examined. The optimum molar ratios of tetronic acid, reactions proceeded smoothly to give the corresponding
5-aminoindazole and 4-nitrobenzaldehyde to Cu(OTf)2 10-aryl-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]quinolin-
were found to be 1:1:1.1:0.1. Under optimized conditions, 9-one products 1–10 in good to excellent yields (Eq. 1). The
the reaction was conducted in acetonitrile under ultra- electronic nature of substituents on the aromatic alde-
sonication. As can be seen from Table 1, the reaction was hydes does not affect the reaction time significantly.
O
O
Ar
H2N
Cu(OTf)2
N
NH
O
N
O
(1)
ArCHO
CH3CN, reflux
N
H
N
H
O
1-10
1:
6:
Ar = Ph
Ar = 4-ClC6H4
7: Ar = 2-ClC6H4
8:
2: Ar = 4-MeOC6H4
3:
Ar = 4-MeC6H4
Ar = 4-NO2C6H4
4: Ar = 4-BrC6H4
5: Ar = 2-BrC6H4
9: Ar = 3-NO2C6H4
10: Ar = 2,4-Cl2C6H3
N
NH
N
O
O
NH
Ar
O
Cu(OTf)2
O
O
O
O
H2N
O
O
H
HN
Ar
H
Ar
-H2O
O
(TfO)2Cu
A
B
Cu(OTf)2
N
O
NH
O
Ar
Ar
N
NH
O
O
- Cu(OTf)2
-H2O
N
H
H2N
O
Cu(OTf)2
C
Scheme 1ꢀ
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S. Damavandi etꢃal.: Synthesis of furo[3,4-b]pyrazolo[4,3-fꢀ]quinolinonesꢀ
ꢀ107
J = 8 Hz, ArH), 5.60 (s, 1H, CH), 4.95–4.87 (m, 2H, CH2). Anal. Calcd for
A
plausible mechanism for the synthesis of
C18H13N3O2: C, 71.28; H, 4.32; N, 13.85. Found: C, 71.19; H, 4.24; N, 13.74.
pyrazolo[4,3-f]quinolinones is shown in Scheme 1. It can
be suggested that in the first step the Knoevenagel con-
densation generates an intermediate product A. Then,
Michael-type addition of 5-aminoindazole to A generates
10-(4-Methoxyphenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-
f]quinolin-9-one (2)ꢀAfer 13 min the yield was 85%; IR: ν 3355,
3183, 1710, 1633, 1545, 1406, 1361, 1233, 1166, 944 cm-1; 1H NMR: δ 11.46
another intermediate product B. Intramolecular cycliza- (s, 1H, NH), 10.10 (s, 1H, NH), 7.83 (s, 1H, ArH), 7.35–7.20 (m, 2H, ArH),
7.10–6.96 (m, 2H, ArH), 6.95–6.80 (m, 2H, ArH), 5.37 (s, 1H, CH), 4.94–
tion of B followed by dehydration furnishes the observed
product C.
4.88 (m, 2H, CH2), 3.62 (s, 3H, OCH3). Anal. Calcd for C19H15N3O3: C,
68.46; H, 4.54; N, 12.61. Found: C, 68.22; H, 4.48; N, 12.60.
10-(4-Methylphenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]
quinolin-9-one (3)ꢀAfer 12 min the yield was 86%; IR: ν 3314, 3109,
1721, 1657, 1577, 1488, 1372, 1201, 1089, 955 cm-1; 1H NMR: δ 12.73 (s, 1H,
Conclusion
NH), 10.32 (s, 1H, NH), 7.90 (s, 1H, ArH), 7.45–7.10 (m, 3H, ArH), 7.04–
6.96 (m, 3H, ArH), 5.43 (s, 1H, CH), 4.90–4.84 (m, 2H, CH2), 2.14 (s, 3H,
A rapid, direct and efficient synthetic route to 10-phenyl-
CH3). Anal. Calcd for C19H15N3O2: C, 71.91; H, 4.76; N, 13.24. Found: C,
7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]quinolin-9-one
71.68; H, 4.69; N, 13.12.
was developed. This class of compounds may prove to be
of interest for biomedical screening.
10-(4-Bromophenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]
quinolin-9-one (4)ꢀAfer 11.5 min the yield was 90%; IR: ν 3313,
3119, 1701, 1671, 1548, 1486, 1306, 1246, 1110, 973 cm-1; 1H NMR: δ 12.65
(s, 1H, NH), 10.80 (s, 1H, NH), 8.10 (s, 1H, ArH), 7.42–7.25 (m, 5H, ArH),
7.04 (d, 1H, J = 7.6 Hz, ArH), 5.70 (s, 1H, CH), 5.06–4.98 (m, 2H, CH2).
Anal. Calcd for C18H12BrN3O2: C, 56.56; H, 3.16; N, 10.99. Found: C,
56.77; H, 3.21; N, 11.09.
Experimental
The reagents were either prepared in our laboratories or purchased
from Merck, Fluka and Aldrich Chemical Companies. All yields re-
fer to isolated products. The IR spectra were recorded in KBr disks
on a Shimadzu-IR 470 spectrophotometer. The 1H NMR spectra were
recorded on a Bruker 100-MHz spectrometer in DMSO-d6. Flash col-
umn chromatography was performed with 300- and 400-mesh silica
gel, and analytical thin layer chromatography (TLC) was performed
on precoated silica gel plates (60F-254). Sonication was performed
in a Shanghai Branson-CQX ultrasonic cleaner with a frequency of
40 kHz and a nominal power of 100 W. Elemental analyses were per-
formed on a Thermo Finnigan EA1112 elemental analyzer.
10-(2-Bromophenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]
quinolin-9-one (5)ꢀAfer 15 min the yield was 90%; IR: ν 3302, 3109,
1711, 1663, 1567, 1371, 1263, 1217, 1108, 895 cm-1; 1H NMR: δ 12.15 (s, 1H,
NH), 10.24 (s, 1H, NH), 8.07 (s, 1H, ArH), 7.63 (d, 1H, J = 8.2 Hz, ArH),
7.50–7.25 (m, 4H, ArH), 7.05 (d, 1H, J = 8.7 Hz, ArH), 5.72 (s, 1H, CH),
4.90–4.85 (m, 2H, CH2). Anal. Calcd for C18H12BrN3O2: C, 56.56; H, 3.16;
N, 10.99. Found: C, 56.46; H, 3.09; N, 10.91.
10-(4-Chlorophenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]qui-
nolin-9-one (6)ꢀAfer 11.5 min the yield was 87%; IR: ν 3315, 3127, 1704,
1
1671, 1555, 1475, 1382, 1255, 1201, 1123, 924 cm-1; H NMR: δ 12.10 (s, 1H,
NH), 10.70 (s, 1H, NH), 8.13 (s, 1H, ArH), 7.52–7.35 (m, 4H, ArH), 7.15–6.97
(m, 2H, ArH), 5.55 (s, 1H, CH), 5.00–4.95 (m, 2H, CH2). Anal. Calcd for
C18H12ClN3O2: C, 64.01; H, 3.58; N, 12.44. Found: C, 63.87; H, 3.50; N, 12.37.
General procedure for the synthesis of
pyrazolo[4,3-f]quinolinone derivatives 1–10
10-(2-Chlorophenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]qui-
nolin-9-one (7)ꢀAfer 14.5 min the yield was 91%; IR: ν 3372, 3097, 1717,
1653, 1559, 1535, 1337, 1223, 1183, 1070, 956 cm-1; 1H NMR: δ 12.22 (s, 1H,
NH), 10.67 (s, 1H, NH), 8.05 (s, 1H, ArH), 7.60–7.25 (m, 4H, ArH), 7.25–7.12
(m, 2H, ArH), 5.48 (s, 1H, CH), 4.97–4.87 (m, 2H, CH2). Anal. Calcd for
C18H12ClN3O2: C, 64.01; H, 3.58; N, 12.44. Found: C, 63.86; H, 3.51; N, 12.35.
A mixture of tetronic acid (0.10 g, 1 mmol), 5-aminoindazole (0.13 g,
1 mmol), aldehyde (1 mmol) and Cu(OTf)2 (0.036 g, 0.1 mmol) in ace-
tonitrile (8 mL) was placed in a 100 mL conical flask and the mixture
was stirred at 50°C under ultrasonic irradiation. The course of the
reaction was followed by TLC. Upon completion of the reaction, the
mixture was extracted with ethyl acetate (20 mL) and the extract was
washed with dilute aqueous solution of NaHCO3 (2×10 mL). The aque-
ous layer containing the catalyst was separated and concentrated un-
der reduced pressure to afford the catalyst which was dried at 75°C
for 4 h before a subsequent reuse. The organic layer was dried over
anhydrous sodium sulfate and concentrated under reduced pressure
to give the crude product, which was purified by column chromatog-
raphy on silica gel using ethyl acetate-hexane (1:9) as eluent.
10-(4-Nitrophenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]
quinolin-9-one (8)ꢀAfer 10.5 min the yield was 92%; IR: ν 3311,
1
3106, 1722, 1660, 1561, 1551, 1339, 1263, 1160, 1083, 973 cm-1; H NMR:
δ 11.75 (s, 1H, NH), 10.34 (s, 1H, NH), 8.10 (s, 1H, ArH), 7.94 (d, 2H, J =
6.8 Hz, ArH), 7.55–7.45 (m, 2H, ArH), 7.30–7.10 (m, 2H, ArH), 5.55 (s, 1H,
CH), 4.87–4.80 (m, 2H, CH2). Anal. Calcd for C18H12N4O4: C, 62.07; H,
3.47; N, 16.09. Found: C, 61.93; H, 3.40; N, 15.96.
10-Phenyl-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]quinolin-
9-one (1)ꢀAfer 12 min the yield was 90%; IR: ν 3324, 3155, 1710,
1650, 1573, 1377, 1205, 1144, 1082, 930 cm-1; 1H NMR: δ 11.15 (s, 1H, NH),
9.85 (s, 1H, NH), 8.11 (s, 1H, ArH), 7.25–7.05 (m, 6H, ArH), 6.75 (d, 1H,
10-(3-Nitrophenyl)-7,9-dihydro-3H-furo[3,4-b]pyrazolo[4,3-f]
quinolin-9-one (9)ꢀAfer 12 min the yield was 88%; IR: ν 3312, 3097,
1
1717, 1653, 1559, 1535, 1337, 1223, 1183, 1070, 956 cm-1; H NMR: δ 12.83
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108ꢀ ꢀS. Damavandi etꢃal.: Synthesis of furo[3,4-b]pyrazolo[4,3-fꢀ]quinolinones
1H NMR: δ 11.65 (s, 1H, NH), 10.07 (s, 1H, NH), 8.03 (s, 1H, ArH), 7.63
(s, 1H, ArH), 7.44 (m, 3H, ArH), 6.95 (d, 1H, J = 7.8 Hz, ArH), 5.74 (s, 1H,
CH), 4.93–4.85 (m, 2H, CH2). Anal. Calcd for C18H11Cl2N3O2: C, 58.08; H,
2.98; N, 11.29. Found: C, 57.85; H, 2.93; N, 11.18.
(s, 1H, NH), 10.12 (s, 1H, NH), 8.15 (s, 1H, ArH), 8.05–7.90 (m, 2H, ArH),
7.70–7.65 (m, 2H, ArH), 7.35–7.17 (m, 2H, ArH), 5.65 (s, 1H, CH), 4.90–
4.82 (m, 2H, CH2). Anal. Calcd for C18H12N4O4: C, 62.07; H, 3.47; N, 16.09.
Found: C, 61.82; H, 3.39; N, 15.98.
10 -(2,6-Dichlorophenyl)-7,9- dihydro -3H-furo[3,4-b]
pyrazolo[4,3-f]quinolin-9-one (10)ꢀAfer 17 min the yield was
86%; IR: ν 3305, 3122, 1712, 1667, 1541, 1444, 1275, 1155, 1102, 965 cm-1;
Received October 4, 2011; accepted January 22, 2013; previously
published online March 14, 2013
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J. Chem. Sci. 2012, 124, 483–486.
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