Novel sultone based Br?nsted acidic ionic liquids with perchlorate counter-anion for one-pot synthesis of 2H?indazolo[2,1?b]phthalazine?triones

Article abstract of DOI:10.1016/j.molstruc.2020.129599

Three novel sultone based Br?nsted acidic ionic liquids are introduced. These ionic liquids were prepared in three similar two-steps reactions. The ring opening of 1,4-butane sultone was performed using 1,4-dimethyl piperazine or 1,10-phenantroline as nit

Full text of DOI:10.1016/j.molstruc.2020.129599

Journal Pre-proof
Novel Sultone Based Brønsted Acidic Ionic Liquids with Perchlorate
Counter-Anion for One-pot Synthesis of
2H–indazolo[2,1–b]phthalazine–triones
Fatemeh Arian , Mosadegh Keshavarz , Haleh Sanaeishoar ,
Neda Hasanzadeh
PII:
S0022-2860(20)31913-X
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.129599
MOLSTR 129599
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4 November 2020
4 November 2020
Please cite this article as: Fatemeh Arian , Mosadegh Keshavarz , Haleh Sanaeishoar ,
Neda Hasanzadeh , Novel Sultone Based Brønsted Acidic Ionic Liquids with Perchlorate Counter-
Anion for One-pot Synthesis of 2H–indazolo[2,1–b]phthalazine–triones, Journal of Molecular Structure
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Novel Sultone Based Brønsted Acidic Ionic Liquids with Perchlorate Counter-Anion for
One-pot Synthesis of 2H‑indazolo[2,1‑b]phthalazine‑triones
Fatemeh Arian1, Mosadegh Keshavarz2, Haleh Sanaeishoar1, Neda Hasanzadeh1
1Department of Chemistry, Ahwaz Branch, Islamic Azad University, Ahwaz, Iran
2Department of Applied Chemistry, Faculty of Gas and Petroleum, Yasouj University, Gachsaran,
Iran
Abstract
Three novel sultone based Brønsted acidic ionic liquids are introduced. These ionic liquids were
prepared in three similar two-steps reactions. The ring opening of 1,4-butane sultone was performed using
1,4-dimethyl piperazine or 1,10-phenantroline as nitrogen nucleophile sources to obtain zwitterions and
then followed by acidification by treatment with perchloric acid to give the introduced ionic liquids.
1
FTIR, HNMR, 13C-NMR, TGA and CHNS analysis techniques were used for the characterization of
these ionic liquids. These ionic liquids are completely water soluble and have good thermal stability.
Their catalytic efficiency was checked for the preparation of polycyclic 2H‑indazolo[2,1‑b]phthalazine‑
trione compounds. Small amount (3-7 mmol%) of the prepared acidic ionic liquid catalysts is required
and targeted products are obtained in short times (6-25 min) at high yields (86-96%). Moreover, the
introduced acidic ionic liquids are completely green, environmental benign and task specific and simply
recoverable up to six consecutive runs without significant decrease in their catalytic.
Keywords: Sultone, Brønsted Acidic Ionic Liquid, Task specific, Green Chemistry, Phthalazine-trione
 Correspond to Mosadegh Keshavarz; e-mail: chem.mosadegh@gmail.com; Zip-code: 75918-74831
1

1. Introduction
From the academic laboratories to chemical manufacturing plants, Brønsted acids have been
extensively used [1]. Solid acids are nonvolatile and environmental benign materials but they suffer from
high molecular weight/active-site ratios which rapid deactivation from coking limits their application to
some degree. On the other hand, mineral liquid acids have a greater effective surface area and efficient
catalysis but they also have some disadvantages such as corroding the equipment, not
recoverable/reusable, incomplete separation of this kind of acid catalysts from the final product, the need
for the neutralization of the used catalyst increases the economic costs and to some extent are noxious to
the environment [2].
Recently, water-stable room-temperature ionic liquids (RTILs) have been introduced as a powerful
alternative to traditional molecular organic solvents due to their particular properties, such as low vapor
pressure, wide liquid range, and ease of recovery and reuse that make RTILs a greener alternative to
volatile organic solvents [3-7]. The term “task-specific IL” refers to the non-solvent applications of the
ILs such as catalyst in the organic synthesis [8–12]. Probably, the most significant subcategory of the
task-specific ILs (TSILs) is referred to as Brønsted acidic ionic liquids (BAILs). BAILs have both
valuable characteristics of solid acids and mineral acids which are designed for replacement with
conventional mineral liquid acids, such as sulfuric acid and hydrochloric acid, in chemical processes [13-
17].
The first synthesized Brønsted acid functionalized ILs were reported by Cole and used as solvent
catalyst in esterification reaction. The prepared BAILs were reused for at least five times without
significant loss of activity in the synthesis of ethyl acetate [18]. The introduction of Brønsted acidic
functional groups into cationic or anionic parts of the ILs, especially SO3H-functional groups, has
obviously enhanced their acidity and water solubility, and gives great promise for using ILs as green
catalysts in many typical acid-catalyzed organic reactions with good catalytic activities [19-21].
Up to date, various SO3H-functional Brønsted acidic TSILs that bear an alkane sulfonic acid group in
an acyclic trialkanylammonium [22], cyclic aromatic [18] or none-aromatic compounds containing
nitrogen such as imidazolium [23], pyridinum or n-alkanyl pyrolidinum [24,25] and
triphenylphosphinium [26] cations with hydrogen sulfate counter anions have been synthesized and used
as TSILs in many organic transformations (Scheme 1).
Recently, we have prepared some new BAILs based on 1,4-dimethyl piperazinium and 1,10-
phenantrolinium cations with phosphotungstate anion counterparts as powerful acidic catalysts for the
synthesis of 3,3′-diaryloxindoles [27], 2H‑indazolo[2,1‑b]phthalazine-triones [28], esterification reaction
[29] and selective oxidation of alcohols [30]. In continuation to our attempts for the synthesis of new
BAILs, herein we wish to report three novel BAILs based on 1,4-dimethyl piperazinium and 1,10-
phenantrolinium cations with perchlorate anion as powerful recyclable and reusable acidic catalysts for
the synthesis of 2H‑indazolo[2,1‑b]phthalazine‑triones.
2

Scheme 1 Synthesis of various BAILs
2. Results and Discussion
2.1.Preparation of the introduced BAILs
The schematic routs for the preparation of three novel TSILs have been drawn in schemes 2 and 3. The
targeted TSILs were achieved in a two-steps reaction. At the first step, in a SN2 type reaction, the nitrogen
nucleophile from 1,10-phenantroline or 1,4-dimethyl piperazine attacked to C1 of 1,4-butane sultone led
to the ring opening of sultone which furnished the phenantrolinium butane sulfonate (2a) or piperazinium
butane sulfonate (3a and 3b) zwitterions.
Scheme 2 Preparation of novel [PhBs1]ClO4 BAIL
3

Scheme 3 Preparation of novel [PipBs1]ClO4 and [PipBs2](ClO4)2 BAIL
1
The H-NMR spectral analysis of these zwitterions revealed that when 1,10-phenantroline is reacted
with 1,4-butane sultone under various molar ratio and thermal conditions, only one of the two nitrogen
atoms is attacked and leads to the 1,10-phenantrolinium moiety bearing only one butyl sulfonate branch
(See the supplementary). We related this fail to the steric hindrance in double linkers structure and also
probably because of the disturbing effect of the enhanced positive charge on the ring aromaticity.
On the other hand, both mono and bis-substituted 1,4-dimethyl piperazinium salts (3a and 3b) were
prepared by changing the molar ratios and the reaction temperatures. The mono substituted piperazinium
salt was achieved when the equivalent molar ratios of 1,4-dimethyl piperazine and 1,4-butane sultone
were reacted at room temperature after 4 h while the bis-substituted piperzinium salt was prepared by the
reaction of 1:3 molar ratio of 1,4-dimethyl piperazine and 1,4-butane sultone at 60 ̊ C for 2 h. Next, the
completely dissolved phenantrolinium or piperazinium salts in water were reacted with equimolar ratio of
HClO4 at room temperature for 24 h. Finally, the evaporation of water solvent gave the targeted BAILs
([PhBs1]ClO4, [PipBs1]ClO4 and [PipBs2](ClO4)2) (Scheme 4 and Fig. 1).
4

Fig. 1 1H NMR (400 MHz, D2O) spectrum of PipBs1 (blue) and PipBs2 (green)
Scheme 4 The structural configuration of new introduced BAILs
5

2.2.FTIR characterization of the prepared novel BAILs
To confirm the successful preparation of these novel BAILs, The FTIR spectra of [PhBs1]ClO4 and
pure 1,10-phenantroline are presented in Fig. 2. The FTIR spectra of [PipBs1]ClO4 and [PipBs2](ClO4)2
with comparative depiction with 1,4-dimetylpiperazine have been shown in Fig. 3. As can be seen in Fig.
2 and 3, in comparison with starting material, the existence of sulfonic acid groups and perchlorate anions
has increased the number of vibration modes and has brought completely different FTIR spectra. The
FTIR spectrum of [PhBs1]ClO4 (Fig. 2b), in comparison with the FTIR spectrum of the pure 1,10-
phenantroline (Fig. 2a), shows two characteristic absorption bands at 1080 and 1032 cm-1 as new peaks
-
which are assigned to the asymmetric ClO4 stretching vibration.
Fig 2 FT-IR spectrum of 1,10-Phenantroline (2a) and [PhBs1]ClO4 catalyst (2b)
In the case of [PipBs1]ClO4 these absorption bands are appeared as new bands at 1070 and 1025 cm-1
(Fig. 3c vs 3a ) and for [PipBs2](ClO4)2 are appeared at 1073 and 1027 cm-1 respectively (Fig. 3b vs 3a).
6

Fig. 3 FT-IR spectrum of 1,4-dimethyl Piperazine (3a), [PipBs2](ClO4)2 catalyst (3b) and [PipBs1]ClO4
(3c)
7

Furthermore, for all these three prepared BAILs, new bands at nearly 600 cm-1 are attributed to
-
symmetric stretching vibration and bands at 530-520 cm-1 are referred to bending vibration of ClO4
counterpart anion. The broad bands observed at 2900-3500 cm-1 in the FT-IR spectra of the BAILs
catalysts are referred to OH groups. Finally, the SO2 asymmetric vibrations of the BAILs are found at
around 1470 and 1200 cm-1.
2.3.Study of thermal stability
The thermal stability of the prepared BAILs was investigated by TGA. For all these BAILs as depicted
for [PipBs2](ClO4)2 in Fig. 3, thermal degradation is started about 200
̊
experimental using. The evaporation of adsorbed water lower than 150
̊
weight loss at this temperature rang.
Fig 4 TGA of [PhBs1]ClO4(4a), [PipBs2](ClO4)2 (4b) and [PipBs1]ClO4 (4c)
2.4.Acidities of the prepared BAILs
Hammet equation was used to evaluate the acidity of the introduced BAILs. The Brønsted acidities of
the BAILs were measured using the Hammett method and UV–vis spectroscopy at 110◦C. The Hammett
function (H0) is defined as:
H0= PK(I)aq + log ([I]/[IH+])
where pK(I)aq is the pKa value of the indicator referred to an aqueous solution, IH+ is the protonated
form of indicator, and [I] and [IH+] are the molar concentrations of unprotonated and protonated form of
indicator in the BAILs, respectively (Fig. 5). Moreover, 2,4-dichloro-6-nitroaniline (pK(I)aq = −3.31) was
8

chosen as indicator base (I). The H0 value of BAILs was calculated by determination of the [I]/[IH+] ratio
from the measured absorbance.
Fig. 5 Absorption spectra of 0.025 mg/ml 2,4-dichloro-6-nitroaniline in ethanol (a) and [PipBs2](ClO4)2 (b)
Table 1 H0 values of the BAILs at 110
̊
BAIL
[I] (%)
32
40
[HI+] (%)
H0
[PipBs2](ClO4)2
[PipBs1]ClO4
[PhBs1]ClO4
68
60
55
-3.64
-3.47
-3.40
45
Table 1 shows that [PipBs2](ClO4)2 has slightly stronger acidity that [PipBs1]ClO4 and [PhBs1]ClO4 is the
weakest acid among these BAILs.
2.5.One-pot synthesis and three‑component of 2H‑indazolo[2,1‑b]phthalazine‑trione derivatives
using the introduced BAILs
Using the novel synthesized BAILs in hand, the three-component condensation reaction of aromatic
aldehydes, dimedone (and or 1,3-cyclohexanedione), and phthalhydrazide was investigated to study the
catalytic activity of the introduced catalysts. At the first, the reaction of benzaldehyde, dimedone, and
phthalhydrazide was selected as a model. In order to provide greener procedure, the solvent-free was
selected as media condition of choice. The progress of the reaction using various amounts of the three
9

synthesized [PhBs]ClO4, [PipBs1]ClO4 and [PipBs2](ClO4)2 as catalysts at different thermal conditions
was checked by TLC.
The results with respect to the amount of used catalysts, temperature, reaction times and yields of the
product are summarized in table 2. It was found that the best thermal conditions is 110 ̊C and [PhBs1]ClO4
or [PipBs2](ClO4)2 gave better results than [PipBs1]ClO4. Moreover, [PipBs2](ClO4)2 as catalyst showed
slightly more efficiency than [PhBs]ClO4. However, all three catalysts, in comparison with previously
reported catalysts, showed comparative or even superior activity in most cases. The optimized used
amount of [PipBs2](ClO4)2 was 20 mg (3 mmol%, table 2, entry12), [PipBs1]ClO4 = 25 mg (7 mmol%,
table 2, entry 6) and [PhBs1]ClO4 = 30 mg (7 mmol%, table 2, entry 9).
Table 2 Optimization of the reaction conditions for the BAILs catalyzed 2H‑indazolo[2,1‑b]phthalazine‑
triones preparation
Entry
BAIL/ mg
T (
̊
Time(min)
Yield
(%)a
-
1
2
3
4
5
6
7
8
9
10
11
12
13
-
r.t
r.t
r.t
r.t
80
110
80
110
110
80
110
110
110
240
240
240
240
60
20
60
20
20
60
20
10
10
[PipBs1]ClO4/ 10 mg (3 mmol%)
[PipBs1]ClO4/ 20 mg (6 mmol%)
[PipBs1]ClO4/ 25 mg (7 mmol%)
[PipBs1]ClO4/ 25 mg (7 mmol%)
[PipBs1]ClO4/ 25 mg (7 mmol%)
[PhBs1]ClO4 / 20 mg (5 mmol%)
[PhBs1]ClO4 / 30 mg (7 mmol%)
[PhBs1]ClO4 / 30 mg (7 mmol%)
[PipBs2](ClO4)2/ 10 mg (1.5 mmol%)
[PipBs2](ClO4)2/ 15 mg (2 mmol%)
[PipBs2](ClO4)2/ 20 mg (3 mmol%)
[PipBs2](ClO4)2/ 25 mg (4 mmol%)
30
50
60
75
80
85
80
92
75
85
95
95
a Isolated Yield
After finding the optimum thermal condition and the best used amount of the BAIL catalysts, the
generality of the procedure and catalytic role applicability of the introduced BAILs were investigated and
the reaction was extended by using various substituted benzaldehydes under optimized condition (Scheme
5 and Table 3).
10

Scheme 5 Synthesis of 2H‑indazolo[2,1‑b]phthalazine‑triones catalyzed by introduced BAILs
Table 3 BAILs catalyzed the preparation of 2H‑indazolo[2,1‑b]phthalazine‑triones
Product
4a
4b
4c
4c
4c
4d
4d
4e
4e
4e
4f
Ar
C6H5
4-Me-C6H4
4-F-C6H4
4-F-C6H4
R
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
H
H
H
H
H
H
H
H
H
Time(min) Yield(%)a BAIL Catalyst
10
15
8
95
92
89
93
87
91
89
90
88
94
95
91
89
91
88
90
92
93
90
93
89
96
90
94
90
86
89
91
[PipBs2](ClO4)2
[PipBs2](ClO4)2
[PipBs2](ClO4)2
[PhBs]ClO4
12
15
15
20
10
10
7
10
20
25
25
15
10
15
20
6
10
12
10
10
15
10
15
15
10
4-F-C6H4
[PipBs1]ClO4
[PipBs2](ClO4)2
[PipBs1]ClO4
[PhBs]ClO4
[PipBs1]ClO4
[PipBs2](ClO4)2
[PhBs]ClO4
[PipBs2](ClO4)2
[PhBs]ClO4
[PipBs1]ClO4
[PipBs2](ClO4)2
[PipBs2](ClO4)2
[PhBs]ClO4
[PipBs1]ClO4
[PipBs2](ClO4)2
[PhBs]ClO4
[PipBs1]ClO4
[PipBs2](ClO4)2
[PhBs]ClO4
[PipBs1]ClO4
[PipBs2](ClO4)2
[PhBs]ClO4
[PipBs1]ClO4
[PipBs2](ClO4)2
2-Cl-C6H4
2-Cl-C6H4
4-Cl-C6H4
4-Cl-C6H4
4-Cl-C6H4
4-Br-C6H4
3-MeO-C6H4
3-MeO-C6H4
3-MeO-C6H4
2-Me-C6H4
2-Cl-C6H4
2-Cl-C6H4
2-Cl-C6H4
4-NO2-C6H4
4-NO2-C6H4
4-NO2-C6H4
4-OH-C6H4
4-OH-C6H4
4-OH-C6H4
3-Br-C6H4
3-Br-C6H4
3-Br-C6H4
4-Br-C6H4
4g
4g
4g
4h
4i
4i
4i
4j
4j
H
H
H
H
H
H
H
H
4j
4k
4k
4k
4l
4l
4l
4m
a Isolated Yield
11

In all the reactions, BAIL catalyst was simply separated and recovered. The prepared BAILs are
completely soluble in H2O and to some degree in EtOH but are not soluble in aprotic and non-polar
solvents. The filtrate precipitation was recrystallized in hot EtOH to give pure desired 2H‑indazolo[2,1‑
b]phthalazine‑trione. From table 2, all the three BAIL catalysts worked very well and in a one-pot three
component reaction type and gave target 2H‑indazolo[2,1‑b]phthalazine‑triones in short and completely
comparative times (6-25 min) at high to excellent yields (86-96%) in comparison with previous catalytic
method reports. It can be seen that the substituent on the phenyl ring of aromatic aldehyde could affect
the reaction time and/ or the yield of the product. The electron-withdrawing substituents usually lead to
shorter reaction times and also increase the yield of the product. Moreover, among the three introduced
BAILs, [PipBs2](ClO4)2 catalyst showed better catalytic activity than two others catalysts and is selected
as superior BAIL with respect of the optimized mol% amount of the catalyst, reaction time and yield of
the obtained product.
To show the catalytic activity of the introduced BAILs, we proposed a plausible mechanism for the
formation of 2H‑indazolo[2,1‑b]phthalazine‑triones from the reaction of aromatic aldehyde (1),
dimedone (2) and phthalhydrazide (3) catalyzed by BAIL catalysts. At the first, in the presence of BAIL,
the carbonyl group of aromatic aldehyde (1) is activated and dimedone (2) is converted to its enol form.
Then, the enol form is condensed with activated aldehyde to give intermediate (I) which after dehydration
lead to form the intermediate (II). In the next step, Michel type addition reaction of phthalhydrazide (3)
on the intermediate (II) followed by cyclization and dehydration in the presence of BAIL furnish the
desired 2H‑indazolo[2,1‑b]phthalazine‑trione product (4) (Scheme 6).
2.6.Reusability study
One of the most important properties for any catalyst is its simple recoverability and its ability to keep the
catalytic activity over several runs. To investigate this property for introduced novel BAILs, the
preparation reaction of 4a catalyzed by [PipBs2](ClO4)2 was selected as model. After completion of the
reaction, H2O was added to the mixture and then stirred for 5 min, the reaction mixture was filtered. The
H2O solvent of the filtered mixture was evaporated under reduced pressure to give the recovered BAIL as
precipitate which was washed several times with diethyl ether and n-hexane for further uses. The yield of
the product was calculated after recrystallization of filtrate precipitation in hot EtOH. The results
regarding the reaction times and yield of the product are graphically illustrated in Fig 6. The yield of the
product was not decreased during 4 consecutive runs while the reaction time was fixed on 10 minutes.
This observation means that the catalyst has been almost completely recovered and its efficiency has been
retained without any decrease.
12

Scheme 6 The proposed mechanism for the synthesis of 2H‑indazolo[2,1‑b]phthalazine‑triones
catalyzed by the introduced BAILs
13

Reusability Study of [PipBs2](ClO4)2
95
95
100
80
60
40
20
0
94
92
90
91
Run 1
Run 2
Run 3
Run 4
Run 5
Run 6
Fig. 6 Reusability study of [PipBs2](ClO4)2 catalyst for the preparation of 4a product
3. Materials and Methods
NMR spectra were recorded at a Bruker Avance DPX 400 MHz (1H) and 100 MHz (13C) at 298 K using
tetramethylsilane (0 ppm) as the internal reference. NMR spectroscopic data were recorded in D2O,
1
DMSO(d6) and CDCl3 using as internal standards the residual nondeuteriated signal for H NMR and the
deuteriated solvent signal for 13C NMR spectroscopy. DEPT spectra were used for the assignment of
carbon signals. Chemical shifts (δ) are given in ppm, and coupling constants (J) are given in Hertz. The
following abbreviations are used for multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, dd =
doublet of doublets, and m = multiplet. Melting points were collected using a capillary melting point
apparatus and are uncorrected. UV-Vis spectra were recorded on Perkin-Elmer Lambda 365 UV–vis
spectrophotometer at room temperature. Fourier transform infrared (FT-IR) spectra were obtained as
potassium bromide pellets in the range 400–4000 cm-1 using an AVATAR 370 Thermo Nicolet
spectrophotometer. Elemental analyses (C, H, and N) were performed with a Heraeus CHN-O-Rapid
analyzer. The thermogravimetric (TG) analysis was performed on Netsch STA449c. The sample weight
was ca. 10 mg and was heated from room temperature up to 600 ̊ C with 10 ̊ C/min using alumina sample
holders.
3.1. Experimental
3.1.1. Preparation of 4-(1,4-dimethylpiperazin-1-ium-1-yl)butane-1-sulfonate (PipBs1)
A round bottom flask filled with 1,4-dimethylpiperazine (10 mmol) and 1,4-butane sultone (15 mmol)
was allowed to stir for 4 h at room temperature under inert atmosphere (N2 flow). The yielding white
14

precipitate (PipBs1) was separated through filtration followed by washing with diethyl ether (3×20 mL)
and then drying under vacuum. 95% yield of white solid product was obtained.
1H NMR (400 MHz, D2O, TMS): δ 1.65-1.80 (m, 2H), 1.81-1.97 (m, 2H), 2.28 (s, 3H), 2.66-2.86 (m,
4H), 2.88 (t, 3H, J= 6.8 Hz), 3.02 (s, 3H), 3.20-3.50 (m, 5 H). 13C NMR (100 MHz, D2O): δ 20.3, 22.1,
31.20, 46.7, 50.5, 54.0, 56.5, 58.1. Anal. Calcd for C10H22N2O3S: C, 47.98; H, 8.86; N, 11.19; S, 12.81.
Found: 47.95; H, 8.90; N, 11.21; S, 12.83.
3.1.2. Preparation of 1,4-dimethylPiperazinium-Butane sulfonate double-linkage (PipBs2)
A round-bottom flask containing a magnet was charged with 1,4-dimethylpiperazine (10 mmol) and
1,4-butane sultone (30 mmol) and stirred for 2 h under nitrogen atmosphere at 60 ̊C. The resulting white
precipitate was filtered and washed with diethyl ether and then dried in vacuum, and the resulting solid
was named 1,4-dimethylPiperazinium-Butane sulfonate double-linkage (PipBs2). A 90% yield of white
solid product was obtained [28-30].
1
The spectral H NMR, 13C NMR and elemental analysis data for the 1,4-DimethylPipirazinium-
1
Butane sulfonate double-linkage (PipBs2) were as follows: H NMR (400 MHz, D2O, TMS): δ 1.65-1.82
(m, 4H), 1.82-2.35 (m, 4H), 2.90 (t, 4H, J= 8 Hz), 3.22 (s, 3H), 2.24 (s, 3H), 3.30-4.50 (m, 12H). 13C
NMR (100 MHz, D2O, TMS): δ 20.2, 20.9, 22.3, 22.8, 35.7, 35.8, 47.1, 47.9, 49.7, 53.9, 54.6, 58.2, 58.8.
(ESI-MS) m/z Calcd for PipBs2: 386.15; Found: 306.12. Anal. Calcd for C14H30N2O6S2: C, 43.50; H,
7.82; N, 7.25; S, 16.59%. Found: C, 43.40; H, 7.88; N, 7.23; S, 16.63%
3.1.3. Preparation of Phenanthrolinum-butane sulfonate (PhBs1)
1,10-Phenanthroline (10 mmol) and 1,4-butane sultone (20 mmol) were dissolved in anhydrous
toluene (10 mL), with a stirring at 75 °C for 48 h under nitrogen atmosphere. The resulting white
precipitate (PhBS) was filtered and washed with diethyl ether and then dried in vacuum. A 87% yield of
white solid product was obtained []. Anal. Calcd for C16H16N2O3S (316.37): C, 60.74; H, 5.09; N, 8.86.
1
Found: C, 60.79; H 5.1; N, 8.91%. The spectral data for Phenanthrolinum-Butane solfonate (PhBs): H
NMR (400 MHz, DMSO, TMS): δ 1.16 (quintet, 2H, J=7.6 Hz), 2.16 (quintet, 2H, J=7.6 Hz), 2.46 (t, 2H,
J=7.6 Hz), 5.96 (t, 2H, J=7.6 Hz), 8.1 (m, 1H), 8.40–847 (m, 3H), 8.80-8.84 (m, 1H), 9.30-9.35 (m, 1H),
9.40-9.43 (m, 1H), 9.64-9.67 (m, 1H). 13C NMR (100 MHz, DMSO): δ 22.4, 27.7, 50.7, 51.9, 56.8, 121.1,
121.3, 124.2, 128.1, 128.4, 128.8, 136.3, 138.2, 143.2, 146.9, 150.2, 199.1.
3.1.4. Preparation of [PipBs1]ClO4, [PiPBs2](ClO4)2 and [PhBs1]ClO4
Three round-bottom flasks containing 10 ml of H2O and a magnet were prepared and an organic salt was
added to each of the flasks (20 mmol of PhBs1 was added to the first flask, 20 mmol of PipBs1 was added
to the second flask and 10 mmol of PipBs2 was added to the third flask). Then, the mixtures were stirred
to obtain a homogenous solution. After that, 20 mmol of HClO4 was added to each of the solutions.
15

Finally, the reaction mixtures were stirred at room temperature for 24 h and then the water was removed
under reduced pressure. The remaining residues were dried at 50 C for 4 h. At the end, [PipBs1]ClO4
̊
[PiPBs2](ClO4)2 and [PhBs1]ClO4 BAILs were collected with 100% yield.
3.1.5. General procedure for novel introduced BAILs catalyzed synthesis of 2H‑indazolo[2,1‑
b]phthalazine‑triones
Aromatic aldehyde 1 (1 mmol), 5,5-dimethylcyclohexane-1,3-dione or cyclohexane-1,3-dione 2 (1 mmol)
and 2,3-dihydro-1,4-phthalazinedione 3 (1 mmol) were placed together in a 25 mL canonical flask and an
optimized amount of BAIL on the base of table 2 was added to the mixture (7 mmol% of [PhBs1]ClO4 or
[PipBs1]ClO4, 3 mmol% of [PiPBs2](ClO4)2 catalyst). The temperature was increased to 110 ̊ C, and then
the Mixture was magnetically stirred for appropriate time according to Table 3. After completion of the
reaction as monitored by TLC (n-hexane: ethyl acetate; 3:1), the mixture was cold to room temperature
and then 10 ml of H2O was added and stirred for 5 min. The mixture was filtered and the filtrate
precipitate was washed several times with hot water and then recrystallized from hot EtOH (2×25 mL)
to provide the pure crystals of 2H-indazolo[2,1-b]phthalazine-trione derivatives. The filtered was
evaporated under vacuum to precipitate the BAIL catalyst. The recovered catalyst was washed with ether,
dried and stored for further similar consecutive runs. The products are known compounds and are
characterized by IR and NMR spectroscopy and CHN data for new compounds. Their melting points are
compared with reported values [28].
3.2. Selected spectral data
3,4-Dihydro-3,3-dimethyl-13-phenyl-2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4a)
o

Yield: 0.37 g (97 %); M.P. = 210-212 C; IR (KBr): = 3031, 2961, 2873, 1668, 1630, 1605, 1361,
1314, 1270, 700 cm-1; 1H NMR (CDCl3, 400 MHz): δ = 1.22 (6H, s, 2CH3), 2.35 (2H, s, CH2), 3.26 (1H,
AB System, dd, 2JHH = 19.1 and 4JHH = 2.3 Hz, CH), 3.43 (1H, AB System, dd, 2JHH = 19.1 and 4JHH = 1.2
Hz, CH), 6.46 (1H, s, CH), 7.09-7.13 (1H, m, CH), 7.20-7.24 (1H, m, CH), 7.28-7.36 (1H, m, CH), 7.42-
7.44 (2H, m, 2CH), 7.83-7.87 (2H, m, 2CH), 8.26-8.28 (1H, m, CH), 8.34-8.39 (1H, m, CH) ppm; 13C
NMR (CDCl3, 100 MHz): δ = 28.7, 29.3, 34.9, 38.1, 50.7, 65, 118.6, 127.1, 127.7, 128.2, 127.9, 128.2,
128.4, 128.7, 129.1, 133.6, 134.5, 136.4, 150.9, 154.3, 156.1, 192.2 ppm; Anal. Calcd for C23H20N2O3
(372.41): C, 74.17; H, 5.41; N, 7.52. Found: C, 74.22; H, 5.40; N, 7.56 %.
3,3-dimethyl-13-p-tolyl-3,4-dihydro-1H-indazolo[2,1-b]phthalazine-1,6,11(2H,13H)-trione(C24H22N2O3,
4b)
1
Yellow powder; FT- IR: (KBr) ν(cm-1): 2957, 1666, 1630, 1359, 1313, 1269, 700. H NMR (400 MHz,
CDCl3): δ 8.36-8.8 (1H, m), 8.28-8.30 (1H, m), 7.85-7.87 (2H, m), 7.29-7.34 (2H, m), 7.15-7.17 (2H, m),
6.44 (1H, s), 3.23-3.46 (2H, AB system, J 19.2 Hz), 2.36 (2H, s), 2.32 (3H, s), 1.23 (6H, s). 13C NMR
(100 MHz, CDCl3): δ 192.2, 156.0, 154.2, 150.7, 138.5, 134.4,133.5, 133.4, 129.4, 129.1, 129.0, 127.9,
127.7, 127.0, 118.7, 114.1, 64.8, 50.9, 38.0, 34.6, 28.7, 28.5, 21.2. Anal. Calcd. for C24H22N2O3: C, 74.59;
H, 5.74; N, 7.25; Found: C, 74.70; H, 5.70; N, 7.30.
3,4-Dihydro-3,3-dimethyl-13-(4-fluorophenyl)-2H-indazolo[2,1-b]phthalazine-1,6,11 (13H)-trione (4c)
16

o

Yield: 0.38 g (97 %); M.P. = 222-224 C; IR (KBr): = 3073, 2961, 2877, 1668, 1630, 1604, 1510,
1469, 1360, 1313, 1270, 700 cm-1; H NMR (CDCl3, 400 MHz): δ = 1.23 (6H, s, 2CH3), 2.36 (2H, s,
CH2), 3.25 (1H, AB System, dd, JHH = 19.1 and JHH = 2.3 Hz, CH), 3.43 (1H, AB System, dd, JHH
19.1 and 4JHH = 1.2 Hz, CH), 6.45 (1H, s, CH), 7.03 (2H, t, 3JHH = 8.6 Hz, 2CH), 7.4-7.43 (2H, m, 2CH),
1
2
4
2
=
13
7.85-7.89 (2H, m, 2CH), 8.25-8.30 (1H, m, CH), 8.34-8.39 (1H, m, CH) ppm; C NMR (CDCl3, 100
MHz): δ = 28.4, 28.7, 37.9, 38, 50.8, 64.4, 115.6, 115.9, 118.2, 127.7, 128, 128.9, 129, 132.3, 133.6,
1
134.6, 151, 154.4, 156, 162.7 (d, JFC = 264 Hz), 192.2 ppm; Anal. Calcd for C23H19FN2O3 (390.4): C,
70.76; H, 4.91; N, 7.18; F, 4.87. Found: C, 70.81; H, 4.88; N, 7.28; F, 4.90 %.
3,4-Dihydro-3,3-dimethyl-13-(2-chlorophenyl)-2H-indazolo[2,1-b]phthalazine-1,6,11 (13H)-trione (4d
8b)
o
Yield: 0.36 g (88 %); M.P. = 262-264 C; IR (KBr): = 2958, 1666, 1469, 1360, 1314, 1270, 704 cm-1;

1H NMR (CDCl3, 400 MHz): δ = 1.22 (3H, s, CH3), 1.23 (3H, s, CH3), 2.34 (2H, s, CH2), 3.26 (1H, AB
System, dd, 2JHH = 19.1 and 4JHH = 2.3 Hz, CH), 3.42 (1H, AB System, dd, 2JHH = 19.1 and 4JHH = 1.1 Hz,
CH), 6.69 (1H, s, CH), 7.23-7.35 (3H, m, 3CH), 7.49-7.50 (1H, m, CH), 7.84-7.89 (2H, m, 2CH), 8.25-
8.28 (1H, m, CH), 8.37-8.39 (1H, m, CH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 28.4, 28.8, 34.6, 38,
50.8, 64.1, 116.7, 127.7, 128, 128.7, 129.1, 129.9, 130.2, 130.5, 132.6, 133, 133.6, 134.5, 151.8, 154.2,
156.2, 192.1 ppm; Anal. Calcd for C23H19ClN2O3 (406.86): C, 67.89; H, 4.71; N, 6.89; Cl, 8.72. Found: C,
67.82; H, 4.76; N, 6.94; Cl, 8.68 %.
3,4-Dihydro-3,3-dimethyl-13-(4-bromophenyl)-2H-indazolo[2,1-b]phthalazine-1,6,11 (13H)-trione (4f,
8i)
o
1
Yield: 0.40 g (87 %); M.P. = 261-263 C; IR (KBr): = 2959, 1660, 1363, 1313, 1270, 697 cm-1; H
NMR (CDCl3, 400 MHz): δ = 1.22 (3H, s, CH3), 1.23 (3H, s, CH3), 2.36 (2H, s, CH2), 3.26 (1H, AB
System, dd, 2JHH = 19.1 and 4JHH = 2.3 Hz, CH), 3.42 (1H, AB System, dd, 2JHH = 19.1 and 4JHH = 1.2 Hz,
CH), 6.44 (1H, s, CH), 7.32 (2H, d, 3JHH = 8.6 Hz, 2CH), 7.38 (2H, d, 3JHH = 8.6 Hz, 2CH), 7.86-7.91(2H,
m, 2CH), 8.28-8.3 (1H, m, CH), 8.37-8.39 (1H, m, CH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 28.5,
28.7, 34.7, 38.1, 50.9, 64.4, 118.1, 127.8, 128.1, 128.5, 128.9, 133.7, 134.5, 134.6, 134.9, 151.1, 154.4,
156, 192.1 ppm; Anal. Calcd for C23H19BrN2O3 (451.32): C, 61.21; H, 4.24; N, 6.21; Br, 17.71. Found: C,
61.28; H, 4.2; N, 6.18; Br, 17.65 %.

3,4-Dihydro-13-(2-chlorophenyl)-2H-indazolo[2,1-b]phthalazine-1,6,11(13H)-trione (4i, 8n)
o

Yield: 0.32 g (83 %); M.P. = 226-228 C; IR (KBr): = 3059, 2956, 2872, 1664, 1471, 1425, 1368,
1306, 1285, 1178, 703 cm-1; 1H NMR (CDCl3, 400 MHz): δ = 1.96-2.07 (1H, m, CH), 2.23-2.39 (1H, m,
CH), 2.46-2.49 (1H, m, CH), 2.52-2.67 (1H, m, CH), 3.35-3.42 (1H, m, CH), 3.51-3.57 (1H, m, CH), 6.69
(1H, s, CH), 7.06-7.52 (4H, m, 4CH), 7.86-7.88 (2H, m, 2CH), 8.26-8.28 (1H, m, CH), 8.37-8.39 (1H, m,
CH) ppm; 13C NMR (CDCl3, 100 MHz): δ = 22.3, 24.5, 36.9, 64.2, 117.7, 127.7, 128.1, 128.8, 129, 129.9,
130.2, 130.5, 132.7, 132.9, 133.3, 133.6, 134.5, 153.3, 154.2, 156.2, 192.4 ppm; Anal. Calcd for
C21H15ClN2O3 (378.81): C, 66.60; H, 3.99; N, 7.40; Cl, 9.36. Found: C, 66.65; H, 3.94; N, 7.44; Cl, 9.31
%.
17

13-(4-chlorophenyl)-3,3-dimethyl-3,4-dihydro-1H-indazolo[2,1-b]phthalazine-1,6,11(2H,13H)-
trione(C23H19ClN2O3, 4e).
Yellow powder; FT- IR: (KBr) ν(cm-1): 2958, 1654, 1624, 1371, 1311, 269, 697. 1H NMR (400 MHz,
CDCl3): δ 8.36-8.39 (1H, m), 8.27-8.30 (1H, m), 7.87-7.89 (2H, m), 7.29-7.34 (4H, m), 6.43 (1H, s),
3.23-3.45 (2H, AB system, J 19.2 Hz), 2.36 (2H, s), 1.23 (6H, s). 13C NMR (100 MHz, CDCl3): δ 192.1,
156.0, 154.4, 151.1, 134.9, 134.6, 134.5, 133.7, 129.0, 128.9, 128.9, 128.5, 128.0, 127.7, 118.0, 64.3,
50.9, 38.0, 34.7, 28.7, 28.4. Anal. Calcd. for C23H19ClN2O3: C, 67.90; H, 4.71; N, 6.89; Found: C, 68.09;
H, 4.65; N, 6.94.
Conclusion
Three new BAILs are introduced as task specific IL for the preparation of polycyclic 2H‑indazolo[2,1‑
b]phthalazine‑trione derivatives under solvent-free conditions at 110
were obtained in short times (6min-25 min) at high yields (86%-96%). These BAILs are thermally stable
up to 200 C which is reasonable and satisfactory for laboratories application. These are easy to handle
̊C and in all cases desired products
̊
powerful acidic catalysts with no corrosive properties. Hammett method and UV–vis spectroscopy were
used to study their acidity and it was found that that [PipBs2](ClO4)2 has slightly stronger acidity that
[PipBs1]ClO4 and [PhBs1]ClO4 is the weakest acid among these BAILs. Moreover, the introduced BAILs
are completely green and water soluble. These catalysts can be simply separated from the organic
products with high recoverability/reusability ability that makes this procedure to be cost-effective and
time saving method. The reusability study of the prepared BAILs showed that these task-specific ILs can
be recovered and reused up to at least 6 consecutive runs without significant decrease in their efficiency.
It was found that among the introduced BAILs, [PipBs2](ClO4)2 is more superior and has better catalytic
efficiency. These BAILs could be considered as green catalysts added to previously reported catalysts.
List of abbreviations
BAIL: Brønsted Acidic Ionic Liquid
PhBs1: 4-(1,10-phenanthrolin-1-ium-1-yl)butane-1-sulfonate
PipBs1: 4-(1,4-dimethylpiperazin-1-ium-1-yl)butane-1-sulfonate
PipBs2: 1,4-dimethylpiperazine-1,4-diium-1,4-diyl)bis(butane-1-sulfonate)
BAILs-ClO4: Brønsted acidic ionic liquids with perchlorate anion
-
[PhBs1]-ClO4: [4-(1,10-phenanthrolium-1-yl)butane-1-sulfonic]ClO4
-
[PipBs1]ClO4: [4-(1,4-dimethylpiperazin-1-ium-1-yl)butane-1-sulfonic]ClO4
-
[PipBs2](ClO4)2: [1,4-dimethylpiperazine-1,4-diium-1,4-diyl)bis(butane-1-sulfonic)]( ClO4 ) 2
18

Acknowledgement
The authors gratefully acknowledge to the Research Council of Ahvaz Branch, Islamic Azad University
for financial support of this work.
Credit author statement
Fatemeh Arian: experimental
Haleh Sanaeishoar: experimental and measure the acdity function
Neda Hasanzadeh: characterization and interpretation of spectra, preparation of the manuscript draft
Mosadegh Keshavarz:
Design the work and revise the draft
Declaration of research interest
We have focused our attention on multi-component reactions specially click reaction. Moreover, we are
trying to design new BAILs and solid acids using new supports. We also interested in heterogenization of
organocatalysts.
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21

Scheme Captions
Scheme 1 Synthesis of various BAILs
Scheme 2 Preparation of novel [PhBs1]ClO4 BAIL
Scheme 3 Preparation of novel [PipBs1]ClO4 and [PipBs2](ClO4)2 BAIL
Scheme 4 The structural configuration of new introduced BAILs
Scheme 5 Synthesis of 2H‑indazolo[2,1‑b]phthalazine‑triones catalyzed by introduced BAILs
Scheme 6 The proposed mechanism for the synthesis of 2H‑indazolo[2,1‑b]phthalazine‑triones
catalyzed by the introduced BAILs
Figure Captions
Fig. 1 1H NMR (400 MHz, D2O) spectrum of PipBs1 (blue) and PipBs2 (green)
Fig 2 FT-IR spectrum of 1,10-Phenantroline (2a) and [PhBs1]ClO4 catalyst (2b)
Fig. 3 FT-IR spectrum of 1,4-dimethyl Piperazine (3a), [PipBs2](ClO4)2 catalyst (3b) and [PipBs1]ClO4
(3c)
Fig. 4 TGA of [PhBs1]ClO4(4a), [PipBs2](ClO4)2 (4b) and [PipBs1]ClO4 (4c)
Fig. 5 Absorption spectra of 0.025 mg/ml 2,4-dichloro-6-nitroaniline in ethanol (a) and [PipBs2](ClO4)2 (b).
Fig. 6 Reusability study of [PipBs2](ClO4)2 catalyst for the preparation of 4a product
22

Graphical abstract
23