Solvent-free, sonochemical, one-pot, four-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones and 1H-pyrazolo[1,2-b]phthalazine-diones catalyzed by Fe3O4@SiO2-imid-PMAn magnetic nanoparticles

Article abstract of DOI:10.1007/s11164-016-2462-6

A practical and green method for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones and 1H-pyrazolo[1,2-b]phthalazine-diones using Fe₃O₄@SiO₂-imid-PMAⁿ nanoparticles as an eco-friendly magnetic catalyst from the four-component condensation, solvent-free reaction of phthalic anhydride, hydrazinium hydroxide, 1,3-diketones, and aldehydes under thermal or ultrasound irradiation at room temperature is described. This new procedure has notable advantages such as operational simplicity, excellent yields, short reaction time, and absence of any tedious work-up or purification. In addition, thermal stability, easy preparation and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the catalyst can be easily recovered by a magnetic field and reused for eight consecutive reaction cycles without significant loss of activity.

Full text of DOI:10.1007/s11164-016-2462-6

Res Chem Intermed
DOI 10.1007/s11164-016-2462-6
Solvent-free, sonochemical, one-pot, four-component
synthesis of 2H-indazolo[2,1-b]phthalazine-triones
and 1H-pyrazolo[1,2-b]phthalazine-diones catalyzed
by Fe3O4@SiO2-imid-PMAn magnetic nanoparticles
Mohsen Esmaeilpour1 Jaber Javidi2,3
•
•
Fatemeh Nowroozi Dodeji2 Saeed Zahmatkesh4
•
Received: 2 January 2016 / Accepted: 26 January 2016
Ó Springer Science+Business Media Dordrecht 2016
Abstract A practical and green method for the synthesis of 2H-indazolo[2,1-
b]phthalazine-triones and 1H-pyrazolo[1,2-b]phthalazine-diones using Fe3O4@-
SiO2-imid-PMAn nanoparticles as an eco-friendly magnetic catalyst from the four-
component condensation, solvent-free reaction of phthalic anhydride, hydrazinium
hydroxide, 1,3-diketones, and aldehydes under thermal or ultrasound irradiation at
room temperature is described. This new procedure has notable advantages such as
operational simplicity, excellent yields, short reaction time, and absence of any
tedious work-up or purification. In addition, thermal stability, easy preparation and
separation of the catalyst make it a good heterogeneous system and a useful
alternative to other heterogeneous catalysts. Also, the catalyst can be easily
recovered by a magnetic field and reused for eight consecutive reaction cycles
without significant loss of activity.
Electronic supplementary material The online version of this article (doi:10.1007/s11164-016-2462-6)
contains supplementary material, which is available to authorized users.
&
&
Mohsen Esmaeilpour
m1250m551085@yahoo.com
Saeed Zahmatkesh
zahmatkesh1355@yahoo.com
1
2
Chemistry Department, College of Science, Shiraz University, Shiraz, Iran
Department of Pharmaceutics, School of Pharmacy, Shahid Beheshti University of Medical
Sciences, Tehran, Islamic Republic of Iran
3
4
Students Research Committee, School of Pharmacy, Shahid Beheshti University of Medical
Sciences, Tehran, Islamic Republic of Iran
Department of Science, Payame Noor University (PNU), Tehran, Islamic Republic of Iran
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M. Esmaeilpour et al.
Keywords Multi-component synthesis Á 2H-Indazolo[2,1-b]phthalazine-triones Á
1H-Pyrazolo[1,2-b]phthalazine-diones Á Solvent-free conditions Á Ultrasound
irradiation Á Heterogeneous magnetic catalyst
Introduction
Over the years, multicomponent reactions (MCRs) have received a great deal of
attention, most notably for the construction of heterocyclic compounds [1]. Such
reactions reduce the consumption of catalyst, solvent, time, labor, and energy,
thereby increasing waste compared to the corresponding series of individual
reactions [1]. Therefore, MCRs have been considered as an economic, practical and
green way to access diverse structures of complex products [2].
In the past decades, the synthesis of nitrogen-containing heterocyclic compounds
has gained regard as they are widespread in nature and their applications to
biologically active pharmaceuticals, agrochemical, and functional materials are
becoming increasingly wide-spread [3–5]. Among a large variety of heterocyclic
compounds, heterocycles containing phthalazine moieties have received consider-
able attention because they show some pharmacological and biological activities
and clinical applications [6, 7]. Furthermore, compounds with phthalazine moieties
are of paramount interest because of their cardiotonic [8], anticancer [9],
anticonvulsant [10], antiinflammatory [11], antifungal [12], hypolipidemic [13]
and vasorelaxant activities [14] together with unique electrical and optical
properties [15]. Fused phthalazine derivatives also have been found effective for
the selective binding of GABA receptor [16], inhibition of p38 MAP kinase [17],
high-affinity ligand to the a2d-1 subunit of calcium-channel [18], and new
luminescence or fluorescence probes [19]. Despite many methods being available
for the synthesis of phthalazine derivatives [20–23], their broad utility has
accentuated the need to develop new synthetic routes for these compounds.
The synthesis of indazolo[2,1-b]phthalazine-triones and pyrazolo[1,2-b]phtha-
lazine-diones can be carried out by four-component reaction of phthalic anhydride,
hydrazinium hydroxide, 1,3-diketones, and aromatic aldehydes or three-component
condensation of phthalhydrazide, 1,3-diketones, and aromatic aldehydes in the
presence of various catalysts such as heteropoly acids (HPAs) [24], silica supported
poly phosphoric acid [25], sulfuric acid-modified PEG-6000 (PEG-OSO3H) [26],
ionic liquid N,N,N,N-tetramethylguanidinium acetate [TMG][Ac] [27], 2-pyrroli-
donium hydrogensulfate ([Hnhp][HSO4]) [28], H2SO4 in water–ethanol or ionic
liquid [29], p-toluenesulfonic acid (p-TSA) [30], (S)-camphorsulfonic acid [31], wet
cyanuric chloride [32], 1-butyl-3-methylimidazolium bromide ([Bmim]Br) [33],
magnetic nanoparticle Fe3O4-supported guanidine [34], Ce(SO4)2Á4H2O [35], Ni
nanoparticles [36], and ZnO nanoparticles [37]. Although these methods are quite
satisfactory, many of the aforementioned methods suffer from serious drawbacks,
including the use of toxic organic solvents, harsh reaction conditions, unsatisfactory
yields, long reaction times, co-occurrence of several side products and employment
of corrosive and non-reusable acid catalysts, which lead to the creation of large
amounts of waste and difficult product separation. Therefore, due to the multiple
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Solvent-free, sonochemical, one-pot, four-component…
pharmacological and biological activities of these compounds, it seems that it is
necessary to design a simple, rapid, efficient, and clean catalytic system for their
synthesis.
In recent years, Brønsted acids such as Keggin-type heteropolyacids have been
used as efficient catalysts for a variety of organic reactions because of their redox
properties and superacidic, high thermal stability, ease of handling, high proton
mobility, stronger acidity than homogeneous acid catalysts, low toxicity, develop-
ment of clean technologies, low cost, water tolerance, recoverability, and reusability
[38]. Although HPAs are versatile compounds in their acidic form, their main
disadvantages are a high solubility in polar solvents and a low surface area (\10 m2/
g). Therefore, in a homogeneous reaction, the isolation of the products and the reuse
of the catalyst after reaction become difficult [39]. Therefore, in order to overcome
this problem, these materials disperse on supports (such as active carbon, silica,
acidic ion-exchange resins, etc.) which possess large surface areas. The use of
supports allows the heteropolyacids to be dispersed over a large surface area and
increases their catalytic activity [39, 40].
In recent years, magnetic nanoparticles (MNPs) such as magnetite (Fe3O4) have
attracted great interest because of their magnetic and electrical properties, high
specific surface area, their unique catalytic activity, and their wide applications,
including drug delivery systems, targeted gene therapy, ion exchange separation,
magnetic resonance imaging, biological sensors, magnetic data storage, and
environmental remediation and catalysis [41–49]. For many applications, MNPs
are suitably chemically stable and uniform in size. But MNPs trend to aggregate due
to their nanoscale and strong interaction between each other. This problem can be
solved by coating of MNPs with a silica layer as the stabilizer, which prevents direct
contact between the nanoparticles. Furthermore, the abundant hydroxyl groups on
the surface of composite particles provide the opportunity to conjugate various
functional molecules for many special applications [50–52].
Recently, a number of functionalized Fe3O4 nanoparticles were employed in a
range of organic transformations, and the studies on immobilization of organocat-
alysts on silica-coated ironoxide nanoparticles have been reported [53, 54].
In previous work [55], we introduce a simple, repaid, inexpensive, and one-step
method (solvothermal) for synthesis of H3PMo12O4 nanoparticles (PMAn) from
H3PMo12O4 bulk particles (PMAb). Then, PMAn was supported on magnetic
Fe3O4@SiO2-imid nanoparticles [56]. Compared to other substrates (silica, acidic
ion-exchange resins, active carbon, and nano titania [57]), Fe3O4@SiO2-imid
nanoparticles have various advantages, such as a high loading capacity, low
leaching, and a simple and efficient recovery procedure. Figure 1 presents the
procedure for the preparation of Fe3O4@SiO2-imid-PMAn stepwise.
Therefore, as part of our continuing interest in developing newer methods for the
synthesis of useful compounds, we recently successfully developed Fe3O4@SiO2-
imid-PMAn as a recyclable catalyst for the green synthesis of 2H-indazolo[2,1-
b]phthalazine-triones and 1H-pyrazolo[1,2-b]phthalazine-diones via a novel, one-
pot, four-component condensation of phthalic anhydride, hydrazinium hydroxide,
aldehydes, and 1,3-diketones from simple and easily available starting materials
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M. Esmaeilpour et al.
Fig. 1 Process for preparation of immobilization of H3PMo12O40 nanoparticles (PMAn) on an imidazole-
functionalized Fe3O4@SiO2 nanoparticle
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Solvent-free, sonochemical, one-pot, four-component…
Scheme 1 One-pot, four-component synthesis of 2H-indazolo[1,2-b]phthalazine-triones and 1H-
pyrazolo[1,2-b]phthalazine-5,10-diones catalyzed by Fe3O4@SiO2-imid-PMAn
under solvent-free conditions at 80 °C and ultrasonic irradiation in excellent yields
(Scheme 1).
Experimental
General procedure
All chemicals were purchased from Merck or Fluka Chemical Companies. The
proton nuclear magnetic resonance ( 1HNMR; 500 MHz) and carbon 13 ( 13C) NMR
(125 MHz) were obtained at 500 MHz using a Bruker spectrometer in deuterated
chloroform (CDCl3 ) as the solvent and tetramethyl silane (TMS) as the internal
reference. Fourier transform infrared (FT-IR) spectra were recorded on a Shimadzu
FT-IR 8300 spectrometer using pressed KBr pellets. Dynamic light scattering (DLS)
images were recorded on an HORIBA-LB550. Scanning electron microscopy
(SEM) images were obtained on a Philips XL-30ESEM. The C, H, N, and S
elemental analyses were carried out by using a Thermofinigan Flash EA-1112
CHNSO rapid elemental analyzer. Sonication was performed using an ultrasound
cleaning bath (KQ-250B, China) with a frequency of 40 kHz and an output power of
200 W. Melting points were determined by an open capillary method and were
uncorrected. The progress of the reaction was monitored by thin layer chromatog-
raphy (TLC) and purification was achieved by recrystallized from ethanol.
1
Therefore, all the products were characterized by FT-IR, H NMR and 13C NMR,
and also by comparison with authentic samples.
Preparation of Fe3O4@SiO2 core–shell
The core–shell Fe3O4@SiO2 nanospheres were prepared by a modified Stober
method in our previous work [58]. In a typical procedure, the mixture of
FeCl3Á6H2O (1.3 g, 4.8 mmol) in water (15 mL) was added to the surfactant
solution [polyvinyl alcohol (PVA 15000)], and FeCl2Á4H2O (0.9 g, 4.5 mmol) in
water (15 mL), which was prepared by dissolving PVA in water followed by
addition of FeCl2Á4H2O. The resultant solution was stirred for 30 min in 80 °C.
Then, hexamethylentetraamine (HMTA; 1.0 mol/l) was added drop by drop with
vigorous stirring to produce a black solid product when the reaction pH reached 10.
The mixture was heated on water bath for 2 h at 60 °C and the black magnetite solid
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M. Esmaeilpour et al.
product was filtered and washed with ethanol three times and was then dried at
80 °C for 10 h. Then, Fe3O4 nanoparticles (0.50 g, 2.1 mmol) were dispersed in the
mixture of ethanol (50 mL), deionized water (5 mL), and tetraethoxysilane (TEOS;
0.20 mL), followed by the addition of 5.0 mL of NaOH (10 wt%). This solution
was stirred for 30 min at room temperature. Then, the product, Fe3O4@SiO2, was
separated by an external magnet, and was washed with deionized water and ethanol
three times and dried at 80 °C for 10 h.
Preparation of H3PW12O40 nanoparticles (PMAn)
PMAn nanoparticles were prepared in our previous work [59]. In a typical
procedure, 5 mmol of bulk H3PMo12O40 (PMAb) was dispersed in 50 mL of n-
octane, and the resulting dispersion was stirred vigorously for 30 min at room
temperature to form a homogeneous dispersion. This dispersion was transferred into
a Teflon-lined stainless autoclave filling to 80 % of the total volume. The autoclave
was sealed and maintained at 150 °C for 12 h. The autoclave was then cooled to
room temperature. Finally, the resulting powder was filtered and washed for several
times by octane, and dried in a vacuum at 80 °C for 12 h.
Preparation of Fe3O4@SiO2-imid-PMAn
Fe3O4@SiO2 (1 g) was added to the solution of 3-chlorotriethoxypropylsilane
(1 mmol, 0.241 g) and imidazole (1 mmol, 0.0680 g) in p-xylene (20 mL), and the
resultant mixture was under reflux for 24 h under nitrogen atmosphere. After
refluxing for about 24 h, the mixture was cooled to room temperature, filtered by an
external magnet, and the product was washed with xylene to remove no reacted
species and dried at 70 °C for 6 h. Fe3O4@SiO2-imid (1.0 g) was added to an
acetonitrile solution of PMAn (1.0 mmol) in 20 mL and was placed in a round-
bottom flask (Table 1). The mixture was refluxed for 24 h under nitrogen
atmosphere. After 24 h, the mixture was filtered by an external magnet, washed
with acetonitrile and dichloromethane, and dried at 70 °C for 6 h. Also, the same
method was used for the synthesis of Fe3O4@SiO2-imid-PMAb (PMAn = nano
H3PMo12O40, PMAb = H3PMo12O40) [59].
General procedure for the synthesis of 2H-indazolo[2,1-b]phthalazine-
triones by ultrasound irradiation
Dimedone (1 mmol), aldehyde (1 mmol), hydrazinium hydroxide (1.2 mmol), and
phthalic anhydride (1 mmol) were added to Fe3O4@SiO2-imid-PMAn catalyst
(0.015 g) in a 25-mL Pyrex flask. The mixture was continuously irradiated for the
appropriate time (Table 2) at room temperature (solid paste using a drop of
acetonitrile was prepared in case of solid aldehydes). The reactions were followed
by TLC using hexane/ethyl acetate (3:1). The temperature was controlled and fixed
at room temperature by pouring cold water in the bath in the case of any elevation of
temperature. After completion of the reaction, water (10 mL) was added and stirred
magnetically for 5 min. The Fe3O4@SiO2-imid-PMAn catalyst was recovered by an
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Solvent-free, sonochemical, one-pot, four-component…
external magnetic field and insoluble the crude products were filtered and
recrystallized from ethanol.
General procedure for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-
diones by ultrasound irradiation
To a thoroughly homogenized mixture of 1,3-diketone (1 mmol), aldehyde
(1 mmol), hydrazinium hydroxide (1.2 mmol), and phthalic anhydride (1 mmol),
Fe3O4@SiO2-imid-PMAn catalyst (0.015 g) was added. The reaction mixture was
subjected to ultrasound irradiation under solvent-free conditions at room temper-
ature (solid paste using a drop of acetonitrile was prepared in case of solid
aldehydes). Completion of the reaction was indicated by TLC [n-hexane/ethylac-
etate (3:1)]. The temperature was controlled and fixed at room temperature by
pouring cold water in the bath in the case of any elevation of temperature. After
completion of the reaction, water (10 mL) was added and stirred magnetically for
5 min and the catalyst was separated by an external magnet. The desired product
obtained was purified as mentioned above.
General procedure for the synthesis of 2H-indazolo[2,1-b]phthalazine-
triones under solvent-free conditions
A mixture of dimedone (1 mmol), aldehyde (1 mmol), hydrazinium hydroxide
(1.2 mmol), phthalic anhydride (1 mmol), and Fe3O4@SiO2-imid-PMAn catalyst
(0.015 g) was heated at 80 °C for the time indicated in Table 2. After completion of
the reaction as indicated by TLC, water (10 mL) was added and stirred magnetically
for 5 min and the catalyst was recovered by an external magnet. The crude product
(insoluble in water) was filtered and recrystallized from ethanol for more
purification.
General procedure for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-
diones under solvent free conditions
In a typical experiment, a mixture of aldehyde (1 mmol), 1,3-diketone (1 mmol),
hydrazinium hydroxide (1.2 mmol) and phthalic anhydride (1 mmol) in solvent-free
conditions was stirred for few minutes at 80 °C, in the presence of Fe3O4@SiO2-
imid-PMAn (0.015 g). After completion of the reaction (monitored by TLC), water
(10 mL) was added to the solidified mixture and stirred magnetically for 5 min and
the insoluble catalyst was separated by magnetic field. The desired product obtained
was purified as mentioned above.
Results and discussion
In continuation of our interest in the application of Fe3O4@SiO2-imid-PMAn
nanoparticles in organic synthesis [39, 59], we decided to explore the synthesis of
phthalazine derivatives in the presence of Fe3O4@SiO2-imid-PMAn catalyst under
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M. Esmaeilpour et al.
thermal solvent-free conditions and ultrasound irradiation at room temperature
(Scheme 1).
Initially the reaction between benzaldehyde (1 mmol), dimedone (1 mmol),
hydrazinium hydroxide (1.2 mmol), and phthalic anhydride (1 mmol) as the model
reaction was examined in the presence of 0.015 g of Fe3O4@SiO2-imid-PMAn
catalyst in various solvents and under neat conditions (Table 1). When the reaction
was performed solvent-free, the progress of the reaction was higher in comparison
with solvent conditions (Table 1, entry 10). Therefore, the solvent-free condition
was used for the synthesis of phthalazine derivatives. Then, the model reaction was
examined in the presence of various amounts of the catalyst (Table 1, entries
12–14). As it was shown in Table 1, the best result was obtained when we carried
out the model reaction in the presence of 0.015 g of catalyst. This condensation was
carried out with low amounts of Fe3O4@SiO2-imid-PMAn of 0.005 and 0.01 g, and
the corresponding products were obtained in 58 and 84 % yield, respectively
(Table 1, entries 12, 13). Use of a higher amount of catalyst did not improve the
yield (Table 1, entry 14). The results show clearly that catalyst is effective for this
transformation and in the absence of it, the reaction did not take place even after a
higher reaction time (Table 1, entry 11). The effect of temperature was also studied
by carrying out the model reaction in the presence of catalyst (0.015 g) under
solvent-free conditions (room temperature, 50, 60, 80, and 90 °C) and the best
results were obtained at 80 °C (Table 1, entries 10, 15–18).
Considering the ability of ultrasonic irradiation for the acceleration of organic
reactions, we examined the model reaction under solvent-free ultrasound irradiation
at room temperature and various amounts of catalyst. As it is clear from Table 1, the
best results were obtained in the presence of 0.015 g of catalyst (Table 1, entry 22).
However, synthesis of organic compounds under ultrasound irradiation has been
limited by the need for a specialized apparatus that may not be available in many
laboratories. Because of this limitation, herein we report both ultrasonic irradiation
under solvent-free conditions at room temperature and also solvent-free conditions
at 80 °C in the presence of 0.015 g of catalyst (Table 1, entries 10 and 22) for the
synthesis of phthalazine derivatives.
In the next step, other reactions were explored under the optimized conditions.
To investigate the nanocatalyst activity in this method, two reactions were carried
out in the presence of the same amount of Fe3O4@SiO2-imid-PMAn.
1. Synthesis of 2H-indazolo[2,1-b]phthalazine-triones
2. Synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones
Different aldehydes (2) were condensed with dimedone (4a) or 1,3-diketone (4b),
hydrazinium hydroxide (3), and phthalic anhydride (1) in the presence of
Fe3O4@SiO2-imid-PMAn catalyst under both solvent-free conditions at 80 °C and
ultrasonic irradiation. The results are displayed in Table 2.
The nature and electronic properties of the aldehyde substrates affect the
conversion rate and yield. Electron-deficient aldehydes furnished excellent yields of
the corresponding products in shorter reaction times (Table 2, entries 2–15, 32), but
the aromatic aldehydes with electron-donating substituents carried out the reaction
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Solvent-free, sonochemical, one-pot, four-component…
Scheme 2 Suggested mechanism for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones in the
presence of Fe3O4@SiO2-imid-PMAn catalyst
in longer reaction times in lower yields of the corresponding phthalazine derivatives
(Table 2, entries 16–22, 34). Beside this, our methodology has been used
successfully for heteroaromatic aldehydes, and corresponding products were
obtained in excellent yields and without any side product (Table 2, entries
25–27). Also, aromatic aldehydes (Table 2, entries 1–27, 31, 32, 34) react faster and
in higher yield than the aliphatic aldehydes (Table 2, entries 28–30, 33, 35).
We suggest a mechanism for this reaction in which the Fe3O4@SiO2-imid-PMAn
as an acid catalyst in situ generates H?, as shown in Scheme 2.
The mechanism contains two steps: initial formation of the phthalhydrazide(III)
by nucleophilic addition of hydrazinium hydroxide (II) to phthalic anhydride
(I) followed by dehydration occurs.
The second step involves initial formation of heterodiene (VI) by standard
Knoevenagel condensation of dimedone (V) and aldehyde (IV). Subsequent
Michael-type addition of the phthalhydrazide followed by cyclization affords the
corresponding product (IX).
A comparison among Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb
and the other catalysts, which were reported in the literature, in synthesis of 2H-
indazolo[2,1 b]phthalazine-1,6,11(13H)-trione (5a) revealed advantages of these
magnetic nanocatalysts over the most of them in terms of higher yields and shorter
reaction times (Table 3). As shown in Table 3, the described method in this article
occurred under mild and green reaction conditions. According to these findings,
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M. Esmaeilpour et al.
Table 3 Comparison of our results with previously reported methods
Entry Catalyst
Condition
Time (min) Yield (%)a References
1
PEG-OSO3Hc
PMA–SiOb2
TMSClb
Mg(HSO4)b2
p-TSAb
[TMG][Ac]c
PBBSb
Nano-alumina sulforic acidb Solvent-free/110 °C
Fe3O4-supported guanidineb Solvent-free/70 °C
H2SOb4
Solvent-free/80 °C
Solvent-free/80 °C
Reflux/CH3CN/DMF
Solvent-free/100 °C
Solvent-free/80 °C
Solvent-free/80 °C
Solvent-free/100 °C
13
30
30
10
10
15
25
14
35
30
35
35
25
6
87
85
86
85
86
92
65
85
93
88
91
88
85
78
94
94
93
92
90
87
90
91
94
92
[26]
2
[62, 63]
[64]
3
4
[65]
5
[30]
6
[27]
8
[61]
9
[66]
10
11
[34]
H2O-EtOH/Reflux
[bmim]BF4/80 °C
Solvent-free/100 °C
Solvent-free/80 °C
Solvent-free/125 °C
PEG 400/50 °C
Solvent-free/100 °C
Ultrasonic/r.t
[29]
[29]
12
13
14
15
16
17
18
19
Fe3O4@silica sulfuric acidb
Citric acidb
[67]
[68]
Ce(SO4)2Á4H2Oc
[35]
CANb
120
10
10
480
15
20
20
20
7
[69]
Boron sulfonic acidb
[Bmim]Brc
Hexafluoro-2-propanolb
(S)-Camphorsulfonic acidb
[70]
[33]
Solvent-free/55 °C
Solvent-free/80 °C
Ultrasonic/r.t
[71]
[31]
[31]
20
21
a
Fe3O4@SiO2-imid-PMAb
Fe3O4@SiO2-imid-PMAn
Solvent-free/80 °C
Ultrasonic/r.t
This work
This work
This work
This work
Solvent-free/80 °C
Ultrasonic/r.t
10
Yields refer to the isolated pure products
b
c
Based on the reaction of benzaldehyde, dimedone, and phthalhydrazide
Based on the reaction of benzaldehyde, dimedone, phthalic anhydride, and hydrazinium hydroxide
Fe3O4@SiO2-imid-PMAn and Fe3O4@SiO2-imid-PMAb led to the best result and
produced the maximum conversion in the shortest time under both solvent-free
conditions at 80 °C and ultrasonic irradiation (Table 3, entries 20, 21).
Fe3O4@SiO2-imid-PMAn magnetic catalyst can be easily separated by an
external magnetic field within several minutes without the need for a centrifugation
or filtration step or a tedious workup of the final reaction mixture (Fig. 2). However,
magnetic separation makes the nanoparticles more effective and convenient in
applications.
The reusability and recovery of the catalyst are important issues, especially when
the reactions use solid catalysts. Thus, the recovery and reusability of catalyst were
investigated for the preparation of 2,3,4,13-tetrahydro-3,3-dimethyl-13-phenyl-
indazolo[1,2-b]phthalazine-1,6,11-trione (5a) and 2-acetyl-3-methyl-1-phenyl-1H-
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Solvent-free, sonochemical, one-pot, four-component…
Fig. 2 Recoverability of the catalyst at the end of reactions by an external magnet
pyrazolo[1,2-b]phthalazine-5,10-dione (6a) under ultrasound irradiation at room
temperature and solvent-free conditions at 80 °C (Fig. 3a).
The catalyst was recovered by a magnetic field after each run, washed with hot
ethanol (2 9 10 mL), dried in an oven at 60 °C for 120 min prior to use and tested
for its activity in the subsequent run. The performance of the recycled catalyst in
reaction up to eight successive runs was shown in Fig. 3a. These bar diagrams
clearly suggest that the desired products were obtained in high yields without
distinct deterioration in catalytic activity.
Figure 3b shows the FT-IR spectra of the fresh and reused catalyst. The presence
of vibration bands in 556, 794, 864, 956, 1055, 1095, 1454, and 2790–2985 cm-1
which is due to the Fe–O, Mo–Oe–MO, Mo–Oc–MO, Mo–Ot, P–O, Si–O–Si,
C = N, and CH, respectively, demonstrates the existence of Fe3O4@SiO2-imid-
PMAn in the spectrum (Fig. 3b). This clearly indicated the presence of nano
H3PMo12O40 on the silica support even after the reaction.
Also, SEM and DLS images of the catalyst after the six recycle in the synthesis of
5a under solvent-free conditions at 80 °C have been represented in Fig. 3c, d. As
shown in Fig. 3c, Fe3O4@SiO2-imid-PMAn nanospheres had an average diameter of
75 nm, were of uniform size, and showed good dispersity. Additionally, the
hydrodynamic diameter of the catalyst was investigated by DLS technique
(Fig. 3d). This size distribution is centered at a value of 80 nm. Generally, the
size of catalysts will be increased after each cycle and leaching of H3PMo12O40
and increasing of catalyst size lead to a decrease in the yield.
,
To determine the degree of leaching of the PMAn from the heterogeneous
catalyst, the filtrate of the reaction between benzaldehyde, dimedone, hydrazinium
hydroxide, and phthalic anhydride after completion under solvent-free conditions at
80 °C was analyzed by the inductively coupled plasma (ICP) technique. The
123

M. Esmaeilpour et al.
Fig. 3 a Recyclability of Fe3O4@SiO2-imid-PMAn in the synthesis of 5a and 6a under the optimized
conditions; The FT-IR spectrum of the fresh and reused catalyst; c, d SEM and DLS images of
Fe3O4@SiO2-imid-PMAn nanoparticles after six reaction cycles. (a) Reaction conditions: benzaldehyde
(1 mmol), dimedone (1 mmol), hydrazinium hydroxide (1.2 mmol), phthalic anhydride (1 mmol),
Fe3O4@SiO2-imid-PMAn catalyst (0.015 g), solvent-free, 80 °C, 10 min. (b) Reaction conditions:
benzaldehyde (1 mmol), dimedone (1 mmol), hydrazinium hydroxide (1.2 mmol), phthalic anhydride
(1 mmol), Fe3O4@SiO2-imid-PMAn catalyst (0.015 g), ultrasonic irradiation (40 kHz), r.t, 10 min.
(c) Reaction condition: benzaldehyde (1 mmol), acetylacetone (1 mmol), hydrazinium hydroxide
(1.2 mmol), phthalic anhydride (1 mmol), Fe3O4@SiO2-imid-PMAn (0.015 g), solvent-free, 80 °C,
10 min. (d) Reaction condition: benzaldehyde (1 mmol), acetylacetone (1 mmol), hydrazinium hydroxide
(1.2 mmol), phthalic anhydride (1 mmol), Fe3O4@SiO2-imid-PMAn (0.015 g), ultrasonic irradiation
(40 kHz), r.t, 10 min
amount of molybdenum leaching after the first run was determined by ICP analysis
to be only 0.33 %, and after 8 repeated cycles, it was 4.86 %.
Conclusion
In summary, we have developed a simple, efficient, and one-pot, four-component
green protocol for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones and 1H-
pyrazolo[1,2-b]phthalazine-diones under solvent-free ultrasound irradiation at room
123

Solvent-free, sonochemical, one-pot, four-component…
temperature as well as solvent-free conditions at 80 °C using Fe3O4@SiO2-imid-
PMAn nanoparticles as a reusable magnetic catalyst.
The attractive features of this protocol are high catalytic activity, thermal
stability, easy preparation, heterogeneous nature and easy separation of the catalyst,
operational simplicity, cleaner reactions, reduced reaction times, eco-friendly
promising strategy, satisfactory yields of products, lower loading of catalyst
compared with the other methods, and avoidance of using hazardous organic
solvents that makes this method an instrumental alternative to the previous
methodologies for the scale up of these one-pot four-component reactions.
Furthermore, this easy removal and reusability of the catalyst make this method a
better choice for chemical industries from an economic and environmental point of
view. In addition, the catalyst could be successfully recovered by using a permanent
magnet and recycled at least for eight runs without significant loss in activity.
Selected spectral data
2,3,4,13-Tetrahydro-3,3-dimethyl-13-phenyl-indazolo[1,2-b]phthalazine-1,6,11-tri-
1
one (5a) Yellow powder, MP = 204–206 °C, H NMR (500 MHz, CDCl3) d:
1.23 (s, 6H), 2.36 (s, 2H), 3.27 (dd, 1H, J = 19.0, 2.1 Hz), 3.44 (d, 1H,
J = 19.0 Hz), 6.4 (s, 1H), 7.29–7.37 (m, 5H), 7.44 (d, 2H, J = 7.2 Hz), 7.86–7.87
(m, 2H), 8.28–8.36 (m, 2H); 13C NMR (125 MHz, CDCl3) d: 28.9, 29.1, 35.0, 38.4,
51.3, 95.4, 119.0, 127.5, 128.2, 128.4, 129.1, 129.4, 129.5, 133.9, 134.9, 136.8,
151.2, 154.7, 156.4, 192.5; IR (KBr, cm-1): 2952, 1667, 1578, 1356, 1304, 1271;
Anal. calcd. for C23H20N2O3: C, 74.18; H, 5.41; N, 7.52 %. Found: C, 74.22; H,
5.34; N, 7.47 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-bromophenyl)-indazolo[1,2-b]phthalazine-
1,6,11-trione (5b) White powder, MP = 264–266 °C, 1H NMR (500 MHz,
CDCl3) d: 1.23 (s, 6H), 2.36 (s, 2H), 3.26 (d, 1H, AB system, J = 19.0 Hz), 3.42
(d, 1H, AB system, J = 19.0 Hz), 6.42 (s, 1H), 7.29–7.4 (m, 4H), 7.8–8.3 (m, 4H);
13C NMR (125 MHz, CDCl3) d: 28.5, 28.7, 34.7, 38.0, 50.9, 64.4, 118.0, 122.8,
127.8, 128.1, 128.8, 128.9, 129.0, 131.9, 133.7, 134.7, 135.5, 151.1, 154.4, 156.0,
192.1; IR (KBr, cm-1): 2957, 1656, 1623, 1573, 1471, 1308, 1267; Anal. calcd. for
C23H19BrN2O3: C, 61.21; H, 4.24; N, 6.21 %. Found: C, 61.12; H, 4.14; N, 6.28 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-chlorophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5c) White powder, MP = 262–264 °C, 1H NMR (500 MHz,
CDCl3) d: 1.23 (s, 6H), 2.36 (s, 2H), 3.26 (d, 1H, AB system, J = 18.9 Hz), 3.43
(d, 1H, AB system, J = 18.8 Hz), 6.44 (s, 1H), 7.29–7.37 (m, 4H), 7.88–7.90 (m,
2H), 8.30–8.38 (m, 2H). 13C NMR (125 MHz, CDCl3) d: 28.5, 28.7, 34.7, 38.0,
50.9, 64.3, 118.1, 127.7, 128.1, 128.5, 128.8, 128.9, 129.0, 133.7, 134.5, 134.6,
134.9, 151.1, 154.3, 156.0, 192.2; IR (KBr, cm-1): 2960, 1665, 1628, 1361, 1313,
1264, 786; Anal. calcd. for C23H19ClN2O3: C, 67.90; H, 4.71; N, 6.89 %. Found: C,
67.85; H, 4.63; N, 6.79 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(3-chlorophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5d) White powder, MP = 204–206 °C, 1H NMR (500 MHz,
123

M. Esmaeilpour et al.
CDCl3) d: 1.21 (s, 6H), 2.34 (s, 2H), 3.21 (d, 1H, J = 19.1 Hz), 3. 41 (d, 1H,
J = 19.1 Hz), 6.40 (s, 1H), 7.24–7.38 (m, 4H), 7.86 (dd, 2H, J = 3.6 Hz), 8.27 (dd,
1H, J = 3.6, 5.3 Hz), 8.36 (t, 1H, J = 4.5 Hz); 13C NMR (125 MHz, CDCl3) d:
28.5, 28.6, 34.7, 38.0, 50.9, 64.3, 117.9, 125.8, 127.0, 127.7, 128.1, 128.9, 129.0,
130.0, 133.7, 134.6, 138.5, 151.2, 154.4, 156.0, 192.1; IR (KBr, cm-1):, 2952, 1659,
1620, 1467, 1363, 1307, 1268, 789; Anal. calcd. for C23H19ClN2O3: C, 67.90; H,
4.71; N, 6.89 %. Found: C, 67.84; H, 4.67; N 6.84 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(2-chlorophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5e) Yellow powder, MP = 266–268 °C, 1H NMR (500 MHz,
CDCl3) d: 1.23 (s, 6H), 2.34 (s, 2H), 3.26 (d, 1H, AB system, J = 19.0 Hz), 3.42 (d,
1H, AB system, J = 19.0 Hz), 6.7 (s, 1H), 7.24–7.50 (m, 4H), 7.87–8.39 (m, 4H);
13C NMR (125 MHz, CDCl3) d: 28.8, 29.2, 35.0, 38.4, 51.3, 64.4, 116.7, 127.6,
128.1, 128.4, 129.1, 129.4, 130.2, 130.9, 132.0, 133.0, 133.9, 134.9, 152.2, 154.6,
156.6, 192.4; IR (KBr, cm-1): 2957, 1661, 1622, 1467, 1472, 1359, 1311, 1267,
791; Anal. calcd. for C23H19ClN2O3: C, 67.90; H, 4.71; N, 6.89 %. Found: C, 67.81;
H, 4.78; N, 6.82 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(2,4-chlorophenyl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5f) Yellow powder, MP = 220–221 °C, 1H NMR
(500 MHz, CDCl3) d: 1.21 (s, 3H), 1.23 (s, 3H), 2.33 (s, 2H), 3.20–3.44 (2H, AB
system, J = 19.2 Hz), 6.64 (s, 1H), 7.26–8.42 (m, 7H); 13C NMR (125 MHz,
CDCl3) d: 28.4, 28.7, 34.6, 38.0, 50.8, 63.5, 118.1, 127.6, 127.7 (2C), 128.1, 128.6,
129.0, 131.1, 131.7, 133.2, 133.7, 134.6, 135.1, 152.0, 154.3, 156.1, 192.1; IR (KBr,
cm-1): 2967, 1664, 1627; 1473, 1369, 1253, 772; Anal. calcd. for C23H18Cl2N2O3:
C, 62.60; H, 4.10; N, 6.35 %. Found: C, 62.48; H, 4.02; N, 6.29 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(2,6-chlorophenyl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5g) MP = 262–264 °C, 1H NMR (500 MHz, CDCl3) d: 1.24
(s, 6H), 2.35 (s, 2H), 3.26 (d, 1H, AB system, J = 19.1 Hz), 3.39 (d, 1H, AB
system, J = 19.1 Hz), 7.47 (s, 1H), 7.19–7.32 (m, 3H), 7.88–7.90 (m, 2H),
8.27–8.36 (m, 2H).
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-fluorophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5i) Yellow powder, MP = 219–220 °C, 1H NMR (500 MHz,
CDCl3) d: 1.24 (s, 6H), 2.36 (s, 2H), 3.26 (dd, 1H, AB system, J = 19.1 Hz,
J = 2.2 Hz), 3.43 (dd, 1H, AB system, J = 19.3 Hz, J = 1.2 Hz), 6.46 (s, 1H),
7.02–7.06 (m, 2H), 7.40–7.44 (m, 2H), 7.86–7.89 (m, 2H), 8.27–8.39 (m, 2H); 13C
NMR (125 MHz, CDCl3) d: 28.8, 29.1, 35.1, 38.4, 51.3, 64.7, 116.0, 116.2 (d,
JC–F = 276 Hz), 118.6, 128.1, 128.4, 129.3, 129.4, 132.6, 134.0, 135.0, 151.4,
154.8, 156.4, 162.1, 164.1, 192.5; IR (KBr, cm-1): 2958, 2867, 1664, 1655, 1626;
1473, 1309; Anal. calcd. for C23H19FN2O3: C, 70.76; H, 4.91; N, 7.18 %. Found: C,
70.71; H, 4.84; N, 7.12 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(2-fluorophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5j) Yellow powder, MP = 268–270 °C, 1H NMR (500 MHz,
CDCl3) d: 1.18 (s, 3H), 1.22 (s, 3H), 2.31 (s, 2H), 3.41, 3.22 (2H, AB System,
123

Solvent-free, sonochemical, one-pot, four-component…
J = 19.1 Hz), 6.54 (s, 1H), 7.01 (t, 1H, J = 10.4 Hz), 7.14 (t, 1H, J = 7.6 Hz),
7.26–7.31 (q, 1H), 7.44 (t, 1H, J = 7.3 Hz), 7.87–7.89 (m, 2H), 8.19–8.21 (m, 1H),
8.33–8.35 (m, 1H); 13C NMR (125 MHz, CDCl3) d: 27.2, 28.0, 33.8, 37.1, 50.0,
59.7, 114.9, 115.9, 123.5, 126.5, 127.2, 127.9, 128.2, 129.4, 129.5, 132.8, 133.7,
150.8, 153.3, 155.0, 159.2, 191.1; IR (KBr, cm-1): 2951, 2868, 1665, 1621, 1354,
1311.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-bromo-2-fluorophenyl)-indazolo[2,1-b]ph-
thalazine-1,6,11-trione (5k) Yellow powder, MP = 279–280 °C, 1H NMR
(500 MHz, CDCl3) d: 1.18 (s, 3H), 1.21 (s, 3H), 2.32 (s, 2H), 3.21, 3.40 (2H, AB
system, J = 19.0 Hz), 6.48 (s, 1H), 7.18 (dd, 1H, J = 11.7, 1.4 Hz), 7.29 (d, 1H,
J = 8.4 Hz), 7.38 (t, 1H, J = 8.0 Hz), 7.85–7.87 (m, 2H), 8.23–8.26 (m, 1H),
8.34–8.37 (m, 1H); 13C NMR (125 MHz, CDCl3) d: 28.0, 28.8, 34.6, 37.9, 50.2,
60.8, 116.2, 119.6, 120.1, 122.8, 123.2, 127.8, 128.0, 128.6, 129.2, 131.3, 133.6,
134.5, 151.9, 154.4, 156.0, 192.0; IR (KBr, cm-1): 2956, 2880, 1655, 1355, 1283.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-nitrophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5l) Yellow powder, MP = 219–221 °C, 1H NMR (500 MHz,
CDCl3) d: 1.21 (s, 3H), 1.24 (s, 3H), 2.1 (s, 2H), 3.2 (dd, 1H, AB system,
J = 19.1 Hz, J = 2.2 Hz), 3.43 (d, 1H, AB system, J = 19.2 Hz), 6.53 (s, 1H),
7.61–7.64 (m, 2H), 7.90–7.91 (m, 2H), 8.20–8.41 (m, 4H); 13C NMR (125 MHz,
CDCl3) d: 28.8, 29.1, 31.3, 35.1, 38.4, 51.2, 64.5, 117.7, 128.2, 128.4, 128.6, 129.1,
129.3, 134.3, 135.2, 143.8, 148.3, 152.1, 154.9, 156.3, 192.4. %. IR (KBr, cm-1):
2973, 1697, 1617, 1660, 1525, 1368, 1148, 1102, 858, 701; Anal. calcd. for
C23H19N3O5: C, 66.18; H, 4.59; N, 10.07 %. Found: C, 66.25; H, 4.52; N, 10.01 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(3-nitrophenyl)-indazolo[2,1-b]phthalazine-
1H
1,6,11-trione
(5m) Yellow
powder,
MP = 271–273 °C,
NMR
(500 MHz,CDCl3) d: 1.2 (s, 6H), 2.38 (s, 2H), 3.30 (dd, 1H, AB system,
J = 19.1 Hz, J = 2.1 Hz), 3.46 (d, 1H, AB system, J = 19.2 Hz), 6.5 (s, 1H), 7.59
(t, 1H, J = 7.8 Hz), 7.89–7.93 (m, 3H), 8.19 (d, 2H, J = 8.7 Hz), 8.26–8.42 (m,
2H); 13C NMR (125 MHz, CDCl3) d: 28.8, 29.1, 35.1, 38.4, 51.2, 64.6, 117.6,
121.9, 124.1, 128.1, 128.7, 129.1, 129.4, 130.1, 134.3, 134.6, 135.2, 139.05, 152.2,
192.5. (KBr, cm-1): 2926, 1660, 1625, 1516, 1374, 1147, 1107, 867, 697; Anal.
calcd. for C23H19N3O5: C, 66.18; H, 4.59; N, 10.07 %. Found: C, 66.09; H, 4.50; N,
10.13 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(2-nitrophenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5n) Yellow powder, MP = 236–238 °C, 1H NMR (500 MHz,
CDCl3) d: 1.21 (s, 3H), 1.24 (s, 3H), 2.25 (s, 3H), 2.31–2.39 (m, 2H), 3.28 (dd, 1H,
AB system, J = 2.0 Hz, J = 19.1 Hz), 3.41 (d, 1H, AB system, J = 19.1 Hz), 7.2
(s, 1H), 7.45–7.59 (m, 3H), 7.87–7.96 (m, 3H), 8.27–8.4 (m, 3H); 13C NMR
(125 MHz, CDCl3) d: 28.9, 29.2, 34.9, 38.4, 51.2, 68.1, 115.3, 128, 128.5, 128.8,
129.5, 129.8, 130.1, 130.2, 133.4, 134.0, 134.9, 137.9, 153.3, 154.5, 156.7, 192.4.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-fluoro-3-nitrophenyl)-indazolo[2,1-b]ph-
thalazine-1,6,11-trione (5o) Yellow powder, MP = 224–226 °C, 1H NMR
123

M. Esmaeilpour et al.
(500 MHz, CDCl3) d: 1.22 (s, 6H), 2.35 (s, 2H), 3.42, 3.26 (2H, AB system,
J = 19.2 Hz), 6.46 (s, 1H), 7.30 (d, 1H, J = 8.5 Hz), 7.87–7.90 (m, 3H), 8.02 (dd,
1H, J = 9.2, 2.0 Hz), 8.23–8.26 (m, 1H), 8.36–8.38 (m, 1H); 13C NMR (125 MHz,
CDCl3) d: 28.4, 28.7, 34.7, 37.9, 50.7, 63.5, 116.7, 118.6, 118.8, 124.3, 127.6,
128.5, 128.9, 133.6, 133.9, 134.8, 135.2, 151.9, 154.7, 155.9, 192.1; IR (KBr,
cm-1): 2956, 2873, 1654, 1321, 1273.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-methylphenyl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5p) Yellow powder, MP = 228–230 °C, 1H NMR (500 MHz,
CDCl3) d: 1.17 (s, 6H), 2.25 (s, 3H), 2.28 (s, 2H), 3.18, 3.37 (s, 2H, AB system,
J = 18.8 Hz), 6.36 (s, 1H), 7.08–7.21 (m, 4H), 7.8 (m, 2H), 8.2–8.3 (m, 2H); 13C
NMR (125 MHz, CDCl3) d: 21.6, 28.8, 29.1,35.0, 38.4, 51.3, 65.1, 118.9, 127.4,
128.0, 128.3, 129.3, 129.5, 129.7, 133.8, 134.8, 138.8, 151.1, 154.6, 156.3, 192.5;
%; IR (KBr, cm-1): 2898, 1661, 1652, 1602, 1596, 1491, 1085, 825, 788, 685, 624,
493.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-methoxyphenyl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5r) Yellow powder, MP = 218–220 °C, 1H NMR
(500 MHz, CDCl3) d: 1.23 (s, 3 H), 1.24 (s, 3 H), 2.30 (s, 2 H), 3.21, 3.42 (2 H,
AB system, J = 18.9 Hz), 3.75 (s, 3 H), 6.38 (s, 1 H), 6.35–8.80 (m, 8H); 13C NMR
(125 MHz, CDCl3) d: 28.4, 28.7, 34.6, 38.1, 50.9, 55.1, 64.5, 114.1, 118.5, 127.6,
127.9, 128.3, 128.5, 128.9, 129.1, 133.4, 134.9, 1507, 154.2, 156.0, 159.6, 192.2; IR
(KBr, cm-1): 2957, 1665, 1627, 1602, 1511, 1467, 1427, 1360, 1314, 1266, 1243,
1170, 1101, 1029, 842, 799, 701.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-isopropylphenyl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5s) Yellow powder, MP = 225–227 °C, 1H NMR
(500 MHz, CDCl3) d: 1.22–1.25 (m, 12H), 2.37 (s, 2H), 2.9 (m, 1H), 3.26 (d,
1H, AB system, J = 19.0 Hz), 3.42 (d, 1H, AB system, J = 19.0 Hz), 6.47 (s, 1H),
7.19–7.36 (m, 4H), 7.86–7.88 (m, 2H), 8.3–8.4 (m, 2H); 13C NMR (125 MHz,
CDCl3) d: 24.2, 28.5, 29.0, 34.1, 35.3, 35.9, 51.9, 64.8, 111.3, 112.0, 114.6, 118.3,
119.2, 121.4, 123.0, 123.9, 127.2, 127.5, 128.3, 128.4, 132.2, 132.3, 135.5, 136.8,
156.4, 158.8, 191.3.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(4-(methylthio)phenyl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5t) Yellow powder, MP = 229–231 °C, 1H NMR
(500 MHz, CDCl3) d: 1.21 (s, 6H), 2.34 (s, 2H), 2.42 (s, 3H), 3.21–3.45 (2H, AB
system, J = 18.5 Hz), 6.4 (s, 1H), 7.10–7.35 (dd, 4H, J = 8.4 Hz), 7.84–7.88 (2H,
m), 8.25–8.37 (m, 2H); 13C NMR (125 MHz, CDCl3) d: 15.5, 28.4, 28.7, 34.6, 38.0,
50.9, 64.6, 118.3, 126.6 (2C), 127.6 (2C), 127.7, 127.9, 128.9, 129.0, 133.0, 133.5,
134.5, 139.2, 150.9, 154.3, 156.0, 192.1; IR (KBr, cm-1): 2955, 1663, 1629, 1364,
1271, 697; Anal. calcd. for C24H22N2O3S: C, 68.90; H, 5.30; N, 6.71 %. Found: C,
68.81; H, 5.24; N, 6.65 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(3,4,5-trimethoxyphenyl)-indazolo[2,1-b]ph-
1
thalazine-1,6,11-trione (5u) MP = 232–233 °C, H NMR (500 MHz, CDCl3) d:
1.23 (s, 3H), 1.24 (s, 3H), 2.36 (s, 2H), 3.21 (d, 1H, J = 19.1 Hz), 3.46 (d, 1H,
123

Solvent-free, sonochemical, one-pot, four-component…
J = 19.3 Hz), 3.80 (s, 3H), 3.83 (s, 6H), 6.40 (s, 1H), 6.63 (s, 2H), 7.87 (t, 2H,
J = 4.7 Hz), 8.30 (t, 1H, J = 4.4 Hz), 8.36 (t, 1H, J = 4.5 Hz); 13C NMR
(125 MHz, CDCl3) d: 28.1, 29.0, 34.6, 38.1, 51.0, 56.2, 60.7, 65.0, 104.6, 118.3,
127.7, 128.0, 128.9, 129.0, 131.8, 133.6, 134.6, 138.3, 150.9, 153.4, 154.5, 156.1,
192.2; IR (KBr, cm-1): 2965, 1657, 1626, 1598, 1506, 1466, 1422, 1360, 1312,
1267, 1125, 1002, 702; Anal. calcd. for C26H26N2O6: C, 67.52; H, 5.67; N, 6.06 %.
Found: C 67.46, H 5.62, N 5.98 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(naphthalen-2-yl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5w) MP = 251–253 °C, 1H NMR (500 MHz, CDCl3) d:
1.16 (s, 6H), 2.27 (s, 2H), 3.22 (d, 1H, J = 19.1 Hz), 3.41 (d, 1H, J = 19.1 Hz),
6.54 (s, 1H), 7.37–7.42 (m, 3H), 7.71–7.90 (m, 6H), 8.16–8.33 (m, 2H); 13C NMR
(125 MHz, CDCl3) d: 28.7, 29.0, 35.0, 38.4, 51.3, 65.4, 118.8, 124.6, 126.6, 126.7,
127.2, 128.0, 128.0, 128.3, 128.6, 129.0, 129.4, 133.5, 133.7, 133.9, 134.1, 134.9,
151.3, 154.7, 156.4, 192.4; IR (KBr, cm-1): 2954, 1665, 1617, 1578, 1470, 1265;
Anal. calcd. for C27H22N2O3: C, 76.76; H, 5.25; N, 6.63 %. Found: C, 76.52; H,
5.14; N, 6.49 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(naphthalen-1-yl)-indazolo[2,1-b]phtha-
lazine-1,6,11-trione (5x) Yellow powder, MP = 259–260 °C, 1H NMR
(500 MHz, CDCl3) d: 1.20 (s, 3H), 1.23 (s, 3H), 2.29 (s, 2H), 3.27–3.53 (2H, AB
system, J = 19.2 Hz), 7.10 (s, 1H), 7.38–7.87 (m, 7H) 8.18–8.41 (m, 4H); 13C
NMR (125 MHz, CDCl3) d: 28.4, 28.7, 34.6, 38.1, 50.9, 65.1, 119.9, 122.8, 125.1,
125.8, 126.5, 127.7 (2C), 128.0 (2C), 129.0, 129.6, 130.9, 133.5 (2C), 133.8, 134.5,
150.6, 154.1, 155.2, 156.2, 192.0; IR (KBr, cm-1): 2961, 1655, 1626; 1589, 1502,
1471, 1260; Anal. calcd. for C27H22N2O3: C, 76.76; H, 5.25; N, 6.63 %. Found: C,
76.58; H, 5.17; N, 6.54 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(thiophen-2-yl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5z) Yellow powder, MP = 218–220 °C, 1H NMR (500 MHz,
CDCl3) d: 1.22 (s, 6H), 2.34 (2H, AB system), 3.25 (1H, AB system, J = 18.5 Hz),
3.46 (1H, AB system, J = 18.0 Hz), 6.24 (s, 1H), 6.79 (d, 1H, J = 9.0 Hz), 6.98 (t,
1H, J = 9.0 Hz), 7.09 (d, 1H, J = 9.0 Hz), 7.68 (d, 2H, J = 8.2 Hz), 8.04 (d, 2H,
J = 8.2 Hz); 13C NMR (125 MHz, CDCl3) d: 24.4, 28.1, 29.3, 34.4, 35.0, 35.6,
51.9, 64.7, 116.0, 123.5, 125.6, 126.6, 127.0, 127.4, 128.5, 128.9, 132.1, 132.5,
135.7, 139.0, 155.4, 158.6, 191.3; IR (KBr, cm-1): 2958, 1661, 1575, 1470, 1258;
Anal. calcd. for C21H18N2O3S: C, 66.65; H, 4.79; N, 7.40 %. Found: C, 66.52; H,
4.83; N, 7.48 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(1H-indol-3-yl)-indazolo[2,1-b]phthalazine-
1,6,11-trione (5aa) Yellow powder, MP = 246–248 °C, 1H NMR (500 MHz,
CDCl3) d: 1.23 (s, 6H), 2.33 (2H, AB system), 3.24 (1H, AB system, J = 18.5 Hz),
3.43 (1H, AB system, J = 18.0 Hz), 6.43 (s, 1H), 7.32–8.46 (m, 9H), 9.87 (brs, 1H);
13C NMR (125 MHz, CDCl3) d: 24.2, 28.5, 29.0, 34.1, 35.3, 35.9, 51.9, 64.8, 111.3,
112.0, 114.6, 118.3, 119.2, 121.4, 123.0, 123.9, 127.2, 127.5, 128.35, 128.39,
132.21, 132.29, 135.5, 136.8, 156.4, 158.8, 191.3; Anal. calcd. for C25H21N3O3: C,
72.98; H, 5.14; N, 10.21 %. Found: C, 73.05; H, 5.09; N, 10.27 %.
123

M. Esmaeilpour et al.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(ethyl)-indazolo[2,1-b]phthalazine-1,6,11-tri-
1
one (5ab) Yellow powder, MP = 144–146 °C, H NMR (500 MHz, CDCl3) d:
0.73–0.77 (t, 3H), 1.23 (s, 3H), 1.44 (s, 3H), 2.07–2.17 (m, 1H), 2.39 (m, 2H), 2.39
(s, 2H) 2.51–2.59 (m, 1H), 3.11–3.39 (2H, AB system, J = 18.0 Hz), 5.72–5.73 (m,
1H), 7.83–7.93 (m, 2H), 8.31–8.39 (m, 2H); 13C NMR (125 MHz, CDCl3) d: 7.2,
22.1, 28.3, 28.8, 34.4, 38.1, 51.0, 63.5, 117.6, 127.5, 127.8, 128.9, 129.0, 133.4,
134.4, 151.8, 155.3, 156.4, 193.0; IR (KBr, cm-1) 2961, 1664, 1622, 1571, 1471,
1421, 1369, 1251; Anal. calcd. for C19H20N2O3: C, 70.35; H, 6.21; N, 8.64 %.
Found: C, 70.21; H, 6.31; N, 8.52 %.
2,3,4,13-Tetrahydro-3,3-dimethyl-13-(hexyl)-indazolo[2,1-b]phthalazine-1,6,11-tri-
one (5ac) Yellow powder, MP = 80–82 °C, 1H NMR (500 MHz, CDCl3) d:
0.83–0.85 (t, 3H), 1.12–1.14 (m, 2H), 1.17–1.34 (m, 12H, 3CH2, 2CH3), 2.12–2.13
(m,1H), 2.44–2.46 (dd, 2H), 2.47–2.50 (m, 1H), 3.15–3.39 (2H, AB system,
J = 19.2 Hz), 5.73–5.74 (m, 1H), 7.88–7.93 (m, 2H), 8.37–8.41 (m, 2H); 13C NMR
(125 MHz, CDCl3) d: 14.3, 22.9, 23.7, 28.8, 29.2, 29.3, 29.7, 32.0, 34.9, 38.5, 51.4,
63.3, 117.7, 127.9, 128.3, 129.4, 133.8, 134.8, 152.0, 155.0, 156.5, 193.4; IR (KBr,
cm-1) 2960, 2927, 1656, 1625, 1574, 1473, 1419, 1362, 1255; Anal. calcd. for
C23H28N2O3: C, 72.60; H, 7.42; N, 7.36 %. Found: C, 72.47; H, 7.33; N, 7.34 %.
2-Acetyl-3-methyl-1-phenyl-1H-pyrazolo[1,2-b]phthalazine-5,10-dione
(6a)
1
Brown semisolid, H NMR (500 MHz, CDCl3) d: 2.06 (s, 3 H), 3.09 (s, 3 H),
6.47 (s, 1 H), 7.29–8.35 (m, 9H); 13C NMR (125 MHz, CDCl3) d: 14.4, 30.5, 66.1,
118.9, 127.2, 127.9, 128.2, 128.5, 128.7, 128.8, 129.1, 133.4, 134.1, 136.3, 146.1;
154.1, 156.2, 192.8; IR (KBr): 2926, 2853, 1687, 1654, 1603, 1492, 1467, 1353,
1281, 1202, 1134, 1107, 755, 698, 589.
2-Acetyl-3-methyl-1-(4-nitrophenyl)-1H-pyrazolo[1,2-b]phthalazine-5,10-dione
(6b) MP = 216–218 °C, 1H NMR (500 MHz, CDCl3) d: 2.23 (s, 3H), 3.09 (s, 3H),
6.55 (s, 1H, CH), 7.65 (d, 2H, J = 8.7 Hz), 7.83–7.86 (m, 2H), 8.21 (d, 3H,
J = 8.7 Hz), 8.35–8.38 (m, 1H); 13C NMR (125 MHz, CDCl3) d: 14.6, 30.5, 65.0,
119.1, 123.7, 127.0, 127.9, 128.0, 128.8, 129.1, 133.6, 134.3, 143.6, 146.0, 147.6,
153.9, 156.0, 192.0; IR (KBr, cm-1): 2925, 1660, 1618, 1519, 1350, 1312; Anal. calcd.
for C20H15N3O5: C, 63.66; H, 4.01; N 11.14 %. Found: C, 63.73; H, 4.08; N, 11.03 %.
2-Benzoyl-3-phenyl-1-p-tolyl-1H-pyrazolo[1,2-b]phthalazine-5,10-dione
(6d)
1
MP = 234–235 °C, H NMR (500 MHz, CDCl3) d: 2.27 (s, 3H), 6.83 (s, 1H),
7.02–7.07 (m, 2H), 7.13–7.21 (m, 6H), 7.31–7.35 (m, 4H), 7.44 (d, 2H,
J = 7.8 Hz), 7.75–7.84 (m, 2H), 8.22–8.28 (m, 2H); 13C NMR (125 MHz,
CDCl3) d: 21.2, 68.1, 123.2, 127.0, 127.4, 127.5, 127.7, 127.9, 128.5, 128.8,
129.6, 129.8, 130.0, 132.0, 133.4, 133.5, 134.0, 137.2, 138.6, 142.4, 154.7, 192.8;
IR (KBr, cm-1): 3044, 2928, 2856, 1741, 1661, 1413, 1339; Anal. calcd. for
C31H22N2O3: C, 79.13; H, 4.71; N 5.95 %. Found: C, 79.06; H, 4.79; N, 6.04 %.
Acknowledgments The authors are grateful to the council of Iran National Science Foundation and
University of Shiraz for their unending effort to provide financial support to undertake this work.
123

Solvent-free, sonochemical, one-pot, four-component…
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