Solvent-free synthesis of compounds containing chromene core catalyzed by novel Br?nsted acidic ionic liquids-ClO4

Article abstract of DOI:10.1002/jccs.202000449

A series of novel sulfonic acid-functionalized Br?nsted acidic ionic liquids (BAILs) with perchlorate counter anion are introduced. These ionic liquid catalysts were prepared through simple and eco-friendly procedures in high yields. Various analytical te

Full text of DOI:10.1002/jccs.202000449

Received: 10 October 2020
DOI: 10.1002/jccs.202000449
Revised: 16 January 2021
Accepted: 17 January 2021
A R T I C L E
Solvent-free synthesis of compounds containing chromene
core catalyzed by novel Brønsted acidic ionic liquids-ClO4
1
2
3
Layla A. Taib | Mosadegh Keshavarz
| Abolfath Parhami
1
Department of Chemistry, Faculty of
Abstract
Sciences, King Abdulaziz University,
Jeddah, Saudi Arabia
A series of novel sulfonic acid-functionalized Brønsted acidic ionic liquids
(BAILs) with perchlorate counter anion are introduced. These ionic liquid cat-
alysts were prepared through simple and eco-friendly procedures in high
2
Department of Applied Chemistry,
Faculty of Gas and Petroleum, Yasouj
University, Gachsaran, Iran
1
3
yields. Various analytical techniques such as Fourier transform infrared, H
Department of Chemistry, Payame Noor
13
University, Tehran, Iran
and C NMR, electro-spray ionization mass spectrometry, elemental analysis
CHNS), and thermogravimetric techniques were used for well characteriza-
(
Correspondence
tion of these catalysts. Next, the prepared BAILs were applied as efficient cata-
lysts with high yields under solvent-free conditions for the synthesis of
chromenes. The proposed method offers several superiorities, such as high
yields, decreased reaction times, cleaner reactions, and the lack of laborious
workup or purification procedures. The simplicity in operation, applicability,
and feasibility of this protocol for diverse substrates makes it an efficient alter-
native to conventional methods.
Mosadegh Keshavarz, Department of
Applied Chemistry, Faculty of Gas and
Petroleum, Yasouj University, Gachsaran,
Iran.
Email: chem.mosadegh@gmail.com
K E Y W O R D S
[
1 4 1 4 2 4 2
PhBs ]-ClO , [PipBs ]-ClO , [PipBs ]-(ClO ) , BAILs, chromenes, IL catalysts
1
| INTRODUCTION
liquids (BAILs) due to numerous abundant advantages
such as high thermal stability, high acidity, and simulta-
neously negligible release of hazardous gases, easy sepa-
ration, and the ability to recycle and reuse for several
times render the most important subset of task-specific
Nowadays, ionic liquids (ILs) constitute one of the most
widely used materials that have been exploited in many
different applications including reaction media, catalysts,
and reagents in organic reactions. Their great usefulness
is rooted in unique properties of these materials compris-
ing negligible vapor pressure, good thermal stability, high
ion conductivity, simple functionality, and ease of recov-
[
12]
ILs.
Recently, alkane sulfonic acid group functionalized
ILs have been introduced, proposing a new opportunity
for developing green acidic catalysts due to the combina-
tion of the advantages of mineral liquid acids and solid
acids, such as uniform acid sites, water and air resistant,
simple and fast separation, and reusability. In 2002, Cole
et al. first published an article about sulfonic acid group
[1,2]
ery/reuse processes.
It should be noted that there is
now a greater tendency toward non-solvent applications
of ILs since their use as the solvent requires large
amounts of ILs that are not cost-effective. On the other
hand, the occurrence of difficulties in the purification
phase for stripping the reaction wastes has caused their
use as the reaction media not to be satisfactory in all
[13]
functionalized ILs with strong Brønsted acidity.
The
prepared BAILs were reused at least five times without
significant loss of activity for the synthesis of ethyl ace-
[3–7]
+
aspects.
Therefore, non-solvent applications of ILs
tate. The fifth type of BAILs can have two or more H on
emerging in the statue of “task-specific ILs” are of partic-
the acidic functional groups and on the anion or cation
(Scheme 1).
[8–11]
ular importance.
Among them, Brønsted acidic ionic
J Chin Chem Soc. 2021;1–10.
http://www.jccs.wiley-vch.de
© 2021 The Chemical Society Located in Taipei & Wiley-VCH GmbH
1

2
TAIB ET AL.
There are a number of routes to synthesize this type
of BAILs with multiple acidic sites as shown in Scheme 1.
The research and application of various SO H
To circumvent these constraints, the evolution of
green and environmentally friendly methods by using
effective and achievable catalysts with high catalytic
activity and short reaction time for the preparation of
chromene is still of interest. Consequently, by consider-
ing unique catalytic properties of BAILs and in the fol-
lowing of our previous study to introduce novel sultone
3
functionalized strong BAILs have received much atten-
tion for their potential application in replacing conven-
tional homogeneous/heterogeneous acidic catalysts
because they are flexible, nonvolatile, noncorrosive, and
immiscible with many organic solvents and could be used
based BAILs with phosphotungstate anion (BAILs-
[14–20]
[21–24]
as dual solvents and catalysts.
PW),
a series of new BAILs with perchlorate anion
Recently, we have prepared some new BAILs with
acidic hydrogen-containing functional groups attached to
the cation based on 1,4-dimethyl piperazinium and
(BAIL-ClO ) based on sulfonic acid functionalized
4
1,10-phennantroline
and
1,4-dimethylpiperazine
(Scheme 2) are synthesized, characterized, and their
capability is investigated for the synthesis of structurally
diverse chromenes under solvent-free conditions
(Scheme 3).
1
,10-phenantrolinium cations with phosphotungstate
anion counterparts as powerful acidic catalysts for the
0
[21]
synthesis of 3,3 -diaryloxindoles,
2H-indazolo[2,1-b]
[22]
[23]
phthalazine-triones,
selective oxidation of alcohols.
esterification reaction , and
[24]
The “chromene” heterocyclic scaffolds represent a
privileged” structural motif that is extensively found in
nature, as they constitute structural components of diverse
2 | RESULTS AND DISCUSSION
2.1 | Preparation of [PhBs ]ClO ,
“
1
4
natural compounds with a broad spectrum of potent bio-
[PipBs ]ClO and [PipBs ](ClO ) catalysts
1
4
2
4 2
[
25]
[26]
logical activities that include antimicrobial,
antiviral,
[27]
[28]
[29]
antimalarial, antitumor, and anticancer.
The BAILs-ClO catalysts used in this study were pre-
4
The extensive biological and medicinal activities of
chromene have attracted great interest in developing
new synthetic routes for their preparation. Due to the
importance of the functionalized 4H-chromenes, espe-
cially in medicinal chemistry, several synthetic proto-
cols have been reported in the literature; that most of
them suffer from some disadvantages such as multiple
synthetic steps, boring reaction conditions, and expen-
pared from the method shown in Scheme 2. As shown
in Scheme 2, the synthetic pathway of these compounds
is performed in two steps, which include preliminary
quaternization of aliphatic and aromatic bis-amines
through nucleophilic ring-opening reaction with
1,4-butanesultone followed by addition of the obtained
[
30–38]
sive reagents.
SCHEME 1 Preparation of BAILs
4
SCHEME 2 Preparation of BAILs-ClO catalysts

TAIB ET AL.
3
4
SCHEME 3 BAILs-ClO catalyzed synthesis of 2-amino-4H-
chromenes
zwitterion salts to HClO acid. As is clear, the alkyl-
4
ation of aromatic bis-amine requires higher tempera-
ture. Moreover, the synthesis of bis-alkylated salts
proceeds at higher temperatures. Despite our effort, the
synthesis of bis-alkylated ammonium salt was not suc-
cessful in the case of 1,10-phenanthroline. This is prob-
ably due to increased steric hindrance as well as the
decreased nucleophilicity of nitrogen after the first
alkylation, which makes 1,10-phenanthroline resistant
to second alkylation.
FIGURE 1 FT-IR spectrum of pristine 1,10-phenanthroline
(a) and [PhBs ]-ClO catalyst (b)
1
4
2
2
.2 | Characterization of the catalysts
.2.1 | Fourier transform infrared
spectra
The Fourier transform infrared (FT-IR) technique is quite
useful to identify or confirm the structural and bonding
changes present in the prepared BAILs-ClO compared to
4
the nitrogen sources as starting materials. The FTIR spec-
tra of [PhBs ]ClO and pure 1,10-phenanthroline are
1
4
presented in Figure 1. The FTIR spectra of [PipBs ]ClO4
1
and [PipBs ](ClO ) with comparative depiction with
2
4 2
1
,4-dimetylpiperazine are shown in Figure 2. In the FTIR
spectrum of 1,10-phenanthroline, strong bands are
observed in two frequency regions, namely from 700 to
1
−1
9
00 cm− and from 1,400 to 1,650 cm . The strong bands
−1
at 738 and 854 cm have been assigned to the out of the
plane motion of the hydrogen atoms on the heterocyclic
rings, and to the hydrogen on the center ring, respec-
tively. Most intense and characteristic bands in the vibra-
tional spectrum of 1,10-phenanthroline appear in the
region 1,400–1,600 cm . All of these bands involve C C
and C N stretching vibrations. Four other bands can be
assigned to C C and C N vibrations, two of which give
rise to symmetric, and two anti-symmetric in plane ring
deformation frequencies (Figure 1a). The FTIR spectrum
−
1
of [PhBs ]ClO4 (Figure 1b), compared with the FTIR
1
spectrum of the pure 1,10-phenanthroline (Figure 1a),
shows two characteristic absorption bands at 1,080 and
FIGURE 2 The FT-IR spectrum of 1,4-dimethylPiperazine (a),
[PipBs ](ClO catalyst (b) and [PipBs ]ClO (c)
2
4
)
2
1
4

4
TAIB ET AL.
1
1
,032 cm− as new peaks that are assigned to the asym-
where pK(I)aq is the pKa value of the indicator
−
+
metric ClO4 stretching vibration. In the case of [PipBs1]
ClO , these absorption bands appear as new bands at
,070 and 1,025 cm (Figure 2c vs Figure 2a), and for
referred to an aqueous solution, IH is the protonated
+
form of indicator, and [I] and [IH ] are the molar
4
−
1
1
[
1
concentrations of unprotonated and protonated forms
of indicator in the BAILs, respectively (Figure 4).
PipBs ](ClO ) , absorption bands appear at 1,073 and
2
4 2
−
1
,027 cm , respectively (Figure 2b vs Figure 2a). Fur-
Moreover, 2,4-dichloro-6-nitroaniline (pK(I)aq
=
thermore, for all these three prepared BAILs, new bands
at nearly 600 cm− are attributed to symmetric stretching
−3.31) was chosen as the indicator base (I). The H0
1
value of BAILs was calculated by determining the
−1
+
vibration, and bands at 530–520 cm are referred to
[I]/[IH ] ratio from the measured absorbance.
−
bending vibration of ClO4 counterpart anion. The broad
Table 1 shows that [PipBs ](ClO ) has slightly stron-
2
4 2
−1
bands observed at 2,900–3,500 cm in the FT-IR spectra
ger acidity than [PipBs ]ClO , and [PhBs ]ClO is the
1 4 1 4
weakest acid among these BAILs.
of the BAILs catalysts are referred to OH groups. Finally,
the SO asymmetric vibrations of the BAILs are found at
2
−
1
around 1,470 and 1,200 cm .
2.3 | Optimization of the reaction
condition catalyzed by [PhBs ]-ClO ,
1
4
2.2.2 | Study of thermal stability
[PipBs ]-ClO and [PipBs ]-(ClO )
1
4
2
4 2
The thermal stability of the prepared BAILs was investi-
gated by thermogravimetric analysis (TGA). TGA curves
of all these BAILs are illustrated in Figure 3. Thermal
As a model to optimize the reaction conditions, the con-
densation reaction of 4-hydroxychomarine, benzalde-
hyde, and malononitrile was selected as a model
(Table 2). Originally, to determine the optimal condi-
tions, we employed the solvent-less process started at
ꢀ
degradations are started before 200 C for [PhBs ]ClO ,
1
4
ꢀ ꢀ
20 C for [PipBs ](ClO ) , and 240 C for [PipBs ]ClO ,
2 4 2 1 4
2
ꢀ
which are acceptable thermal stability for experimental
90 C in the presence of various amounts of each BAILs-
usage. The evaporation of adsorbed water lower than
ClO ([PhBs ]-ClO , [PipBs ]-ClO , and [PipBs ]-(ClO ) )
as the catalyst. As shown in Table 2, the highest yield
4
1
4
1
4
2
4 2
ꢀ
1
50 C is the reason for the slight weight loss at this tem-
perature range.
(96%) was achieved using 3 mol% (0.020 g) of [PipBs ]-
2
ꢀ
(
ClO ) catalyst in 20 min at 110 C (Table 2, entry 3).
4
2
2.2.3 | Acidities of the prepared BAILs
Hammett 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 (H ) is
0
defined as follows:
+
H0 = pKðIÞ + logð½Iꢁ=½IH ꢁÞ:
aq
FIGURE 4 Absorption spectra of 0.025 mg/ml 2,4-dichloro-
6-nitroaniline in ethanol (a) and in [PipBs
2
4 2
](ClO ) (b)
ꢀ
TABLE 1
BAILs
H
0
values of the BAILs at 110 C
+
[I] (%)
32
[HI ] (%)
H
0
[
[
[
PipBs
2
1
](ClO
4
)
2
68
60
55
−3.64
−3.47
−3.40
PipBs
]ClO
4
40
FIGURE 3 TGA of [PhBs
PipBs ]ClO (c)
1 4 2 4 2
]ClO (a), [PipBs ](ClO ) (b), and
PhBs
1
]ClO
4
45
[
1
4

TAIB ET AL.
5
TABLE 2 Optimization study for
the preparation of 2-amino-4H-
4
chromenes using BAILs-ClO under
solvent-free condition at different
temperatures
Time
(min)
Yield
(%)
a
Entry
Catalyst (BAILClO
4
) (mol%/mg)
None
Conditions
ꢀ
1
2
3
4
5
6
7
8
9
None
Solvent-free 90 C
1 day
20
Trace
89
ꢀ
[PipBs
[PipBs
[PipBs
[PipBs
[PipBs
[PipBs
2
2
2
1
1
1
]-(ClO
]-(ClO
]-(ClO
4
4
4
)
)
)
2
2
2
3% (20 mg)
3% (20 mg)
5% (33 mg)
7% (25 mg)
5% (18 mg)
3% (11 mg)
7% (30 mg)
5% (21 mg)
9% (38 mg)
3% (20 mg)
3% (20 mg)
Solvent-free 100 C
ꢀ
Solvent-free 110 C
20
96
ꢀ
Solvent-free 110 C
20
93
ꢀ
]-ClO
]-ClO
]-ClO
4
Solvent-free 110 C
20
94
ꢀ
4
4
Solvent-free 110 C
30
90
ꢀ
Solvent-free 110 C
45
85
ꢀ
[PhBs
[PhBs
[PhBs
1
]-ClO
]-ClO
]-ClO
4
Solvent-free 110 C
20
94
ꢀ
1
1
4
4
Solvent-free 110 C
30
86
ꢀ
10
11
12
Solvent-free 110 C
30
87
ꢀ
[PipBs
[PipBs
2
2
]-(ClO
]-(ClO
4
4
)
)
2
2
Solvent-free 80 C
40
82
ꢀ
Solvent-free 120 C
40
89
a
Isolated yield.
Descending the temperature reduced the yield of the
product (82%) (Table 2, entry 11), while ascending the
temperature reduces the product yield even more
with either electron-donating or electron-withdrawing
groups smoothly underwent the reaction and gave the tar-
get products in good to excellent yields. However, as is
clear, [PipBs ]-(ClO ) is much more effective for this syn-
(Table 2, entries 12,13). The model reaction was also
2
4 2
examined in the absence of catalyst under solvent-free
thesis and affords higher yields of 2-amino-4H-chromene
products in shorter reaction times.
conditions, and the reaction did not proceed even after
ꢀ
1
day at 90 C (Table 2, entry 1). As is clear, [PipBs ]-
A proposed mechanism to demonstrate the role of the
catalyst is shown in Scheme 4. A Knoevenagel reaction,
Michael addition, and intra-molecular cyclization are
involved simultaneously in the synthesis of 2-amino-4H-
chromene derivatives. In the first step, the BAIL-ClO4
catalyst activates the carbonyl group by protonation, and
2
(
ClO ) is much more effective for this synthesis and
4 2
affords higher yields of 2-amino-4H-chromene products
in shorter reaction times.
2
.4 | Studying the scope and efficiency of
then the anionic form of BAIL-ClO abstracts a proton
4
the catalyst
from the active methylene group of malononitrile, lead-
ing to the formation of carbanion. The formed carbanion
of malononitrile makes a nucleophilic attack on the acti-
vated carbonyl of aromatic aldehyde, followed by loss of
a water molecule to form cyanocinnamonitrile intermedi-
Thus, in the next step, we explored the scope and effi-
ciency of the reaction. Therefore, different substituted
2
-amino-4H-chromenes were synthesized by three
BAILs-ClO catalysts under the discovered optimal condi-
ate. In the second step, BAIL-ClO catalyst reacts with
4
4
tions. From Table 3 and Scheme 3, under these optimized
conditions, the reaction of enol or enolizable ketones,
malononitrile, and various aromatic aldehydes was
dimedone and makes an enol form. Michael addition of
enol intermediate to Knoevenagel products, followed by
ring-closing and deprotonation, furnish 2-amino-4H-
chromene derivative.
explored using three BAILs-ClO catalysts. The catalytic
4
activities of [PhBs ]-ClO , [PipBs ]-ClO and [PipBs2]-
Although most of the previously reported
1
4
1
4
[
30–38]
(
ClO ) for the synthesis of 2-amino-4H-chromene deriva-
catalysts
have proper ability to advance the reac-
4
2
tives are presented comparatively in Table 3. All the
products were cleanly isolated and recrystallized from hot
ethanol. In all the cases, aromatic aldehydes substituted
tions with good yields, some of them require harsh condi-
tions, such as high reaction temperatures or long times,
and others suffer from a problem in separating the

6
TAIB ET AL.
4
TABLE 3 Solvent-free synthesis of 2-amino-4H-chromenes using BAILs-ClO as catalyst under thermal conditions
a
No.
Product
BAILs-ClO
4
Time (min)
Yield (%)
1
[PipBs
2
]-(ClO
4
)
)
)
2
2
2
25
30
25
96
95
93
[
[
PipBs
PhBs
1
]-ClO
4
1
]-ClO
4
2
3
[PipBs
2
]-(ClO
]-ClO
]-ClO
4
21
28
22
90
86
83
[
[
PipBs
1
4
PhBs
1
4
[PipBs
2
]-(ClO
]-ClO
]-ClO
4
31
40
34
93
90
86
[
[
PipBs
1
4
PhBs
1
4
4
5
[PipBs
2
]-(ClO
]-ClO
]-ClO
4
)
)
2
19
38
32
98
94
90
[
[
PipBs
1
4
PhBs
1
4
[PipBs
2
]-(ClO
]-ClO
]-ClO
4
2
16
36
30
99
97
94
[
[
PipBs
1
4
PhBs
1
4
6
7
[PipBs
2
]-(ClO
]-ClO
]-ClO
4
)
2
16
34
28
97
95
91
[
[
PipBs
1
4
PhBs
1
4
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
22
31
25
95
93
89
[
1
1
]-ClO
]-ClO
[
8
9
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
20
25
22
93
90
86
[
1
1
]-ClO
]-ClO
[
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
18
24
19
91
88
84
[
1
1
]-ClO
]-ClO
[
1
0
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
21
33
28
89
85
81
[
1
1
]-ClO
]-ClO
[

TAIB ET AL.
7
TABLE 3 (Continued)
a
No.
Product
BAILs-ClO
[PipBs ]-(ClO
PipBs
PhBs
4
Time (min)
Yield (%)
1
1
2
4
)
2
4
4
33
42
36
87
83
79
[
1
1
]-ClO
]-ClO
[
1
2
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
31
35
29
84
80
77
[
1
1
]-ClO
]-ClO
[
1
1
3
4
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
21
28
22
87
89
85
[
1
1
]-ClO
]-ClO
[
[PipBs
PipBs
PhBs
2
]-(ClO
4
)
2
4
4
28
27
22
93
91
88
[
1
1
]-ClO
]-ClO
[
a
Isolated yield.
catalyst from the reaction mixture and nonrecyclable cat-
alyst. The features of this method, which makes it more
preferable than other reported methods, are mild reaction
conditions, environmentally benign, easy recovery of
3 | EXPERIMENTAL
All necessary chemicals were provided commercially
from Sigma-Aldrich and Merck companies and used
without additional purification. Known products have
been identified by comparing spectral and physical
BAILs-ClO catalyst, reuse of the catalyst for six consecu-
4
tive times without loss of catalyst performance, high
yields of 2-amino-4H-chromene derivative products, and
short reaction times.
1
data with those reported in the papers. H NMR and
1
3
C NMR spectra were recorded on a Bruker Avance
spectrometer in DMSO-d , CDCl3 or D O solvents
The BAILs-ClO catalysts recoverability was inves-
4
6
2
tigated (Table 4). To investigate this property for the
introduced novel BAILs, the preparation reaction cat-
alyzed by [PipBs ](ClO ) was selected as the model.
with tetramethylsilane (TMS) as the internal standard.
UV–Vis spectra were recorded on Perkin-Elmer
Lambda 365 UV–Vis spectrophotometer at room tem-
perature. FT-IR spectra were obtained as potassium
bromide pellets in the range of 400–4000 cm− using
an AVATAR 370 Thermo Nicolet spectrophotometer.
Elemental analyses (C, H, and N) were performed
with a Heraeus CHN-O-Rapid analyzer. The TGA 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. The melting points are measured in open cap-
illary tubes in an electrothermal apparatus (Barnstead
IA 8103) and are uncorrected. The reaction was moni-
tored by TLC on PolyGram SILG/UV 254 silica gel
sheets.
2
4 2
After completion of the reaction, H O was added to
2
1
the mixture and then stirred for 5 min, the reaction
mixture was filtered. The H O solvent of the filtered
2
mixture was evaporated under reduced pressure to
give the recovered BAIL as precipitate, which was
washed several times with ethyl acetate (5 ml) to
ꢀ
remove the contaminants, dried in an oven at 80 C,
ꢀ
ꢀ
and used for the new run under similar reaction con-
ditions. The yield of the product was calculated after
recrystallization of filtrate precipitation in hot EtOH.
It was found that the catalyst could be reused for six
consecutive reactions with high yields and negligible
deterioration in catalytic activity.

8
TAIB ET AL.
ionization mass spectrometry—ESI-MS) m/z Calcd for
PhBs1: 316.37; Found: 316.08. Anal. Calcd for
C H N O S: C, 60.74; H, 5.09; N, 8.86. Found: C, 60.79;
16
16 2 3
H 5.1; N, 8.91%.
3
4
.2 | Preparation of
-(1,4-dimethylpiperazin-1-ium-1-yl)
butane-1-sulfonate (PipBs1)
A round bottom flask filled with 1,4-dimethylpiperazine
SCHEME 4 The proposed mechanism for BAILs-ClO
catalyzed formation of 2-amino-4H-chromenes
4
(
10 mmol) and 1,4-butane sultone (12 mmol) was allowed
to stir for 4 hr at room temperature under inert atmosphere
N flow). The yielding white precipitate (PipBs ) was sepa-
(
2
1
rated through filtration followed by washing with diethyl
ether (3 × 20 ml) and then drying under vacuum. White
solid product of 95% yield was obtained.
TABLE 4 Recyclability and reusability study of [PipBs
2
4 2
](ClO )
BAIL catalyst for the solvent-free synthesis of 2-amino-4H-
chromenes
3.2.1 | Characterization data for PipBs1
1
H NMR (400 MHz, D O, TMS): δ 1.65–1.80 (m, 2H),
2
1
3
.81–1.97 (m, 2H), 2.28 (s, 3H), 2.66–2.86 (m, 4H), 2.88 (t,
Run
1
2
3
4
5
6
13
H, J = 6.8 Hz), 3.02 (s, 3H), 3.20–3.50 (m, 5 H). CNMR
Time (min)
20
96
20
95
20
95
20
93
25
92
25
91
(100 MHz, D O): δ 20.3, 22.1, 31.20, 46.7, 50.5, 54.0, 56.5,
2
a
Yield (%)
58.1. Anal. Calcd for C H N O S: C, 47.98; H, 8.86; N,
10
22 2 3
11.19; S, 12.81. Found: 47.95; H, 8.90; N, 11.21; S, 12.83.
a
Isolated yield.
0
3
4
1
.1 | Preparation of
-(1,10-phenanthrolin-1-ium-1-yl)butane-
-sulfonate (PhBs1)
3.3 | Preparation of 4,4 -
(1,4-dimethylpiperazine-1,4-diium-1,4-diyl)
bis(butane-1-sulfonate) (PipBs2)
A
mixture of 1,10-Phenanthroline (10 mmol) and
A
round
bottom
flask
charged
with
1
,4-butane sultone (12 mmol) in anhydrous toluene
1,4-dimethylpiperazine (10 mmol) and 1,4-butane sultone
(30 mmol) was magnetically stirred for 2 hr at 60 C
ꢀ
ꢀ
(10 ml) was stirred for 24 hr at 75 C under inert atmo-
sphere (N flow). The yielding white precipitate (PhBs )
under inert atmosphere (N flow). The yielding white
2
1
2
was separated through filtration and rather purified by
multiple washing with diethyl ether (3 × 20 ml) followed
by drying under vacuum. White solid product of 97%
yield was obtained.
precipitate was separated through filtration and rather
purified by multiple washing with diethyl ether
(3 × 20 ml) followed by drying under vacuum.
3
.3.1 | Characterization data for PipBs2
3
.1.1 | Characterization data for PhBs1
1
H NMR (400 MHz, D O, TMS): δ 1.65–1.82 (m, 4H),
2
1
H NMR (400 MHz, DMSO-d , TMS): δ 1.16 (quintet, 2H,
1.82–2.35 (m, 4H), 2.90 (t, 4H, J = 8 Hz), 3.22 (s, 3H),
6
13
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
2.24 (s, 3H), 3.30–4.50 (m, 12H). CNMR (100 MHz,
D O, TMS): δ 20.2, 20.9, 22.3, 22.8, 35.7, 35.8, 47.1, 47.9,
2
(
(
m, 3H), 8.82 (m, 1H), 9.34 (m, 1H), 9.41 (m, 1H), 9.66
m, 1H). C NMR (100 MHz, DMSO-d ): δ 22.4, 27.7,
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 C H N O S : C,
13
6
14 30 2 6 2
5
1
0.7, 51.9, 56.8, 121.1, 121.3, 124.2, 128.1, 128.4, 128.8,
36.3, 138.2, 143.2, 146.9, 150.2, 199.1. (electro-spray
43.50; H, 7.82; N, 7.25; S, 16.59%. Found: C, 43.40; H,
7.88; N, 7.23; S, 16.63%.

TAIB ET AL.
9
3
.4 | Preparation of the [PhBs ]ClO ,
by TLC, the mixture was allowed to cool. Subsequently, the
reaction mixture was suspended in water (5 ml), and the
suspension was filtered to separate the crude product. The
crude product was dissolved in EtOH (5 ml), and crystal-
lized by dropwise addition of water (15 ml). The filtered
was evaporated under vacuum to precipitate the BAIL cata-
lyst. The recovered catalyst was washed several times with
dietylether, dried, and stored for further similar consecutive
runs. The products are known compounds and are charac-
terized by IR and NMR spectroscopy. Their melting points
1
4
[PipBs ]ClO and [PipBs ](ClO ) catalysts
1 4 2 4 2
A magnetically stirred aqueous solution of PhBs or
PipBs prepared by dissolving the corresponding solid
1
1
(
(
18 mmol) into distilled water in a round bottom flask
25 ml) and 18 mmol of HClO were added dropwise.
4
The resulting mixture was then allowed to react for
4 hr at room temperature. Evaporation of water in
2
reduced pressure afforded [PhBs ]ClO4 or [PipBs1]
ClO as a solid product. The same procedure was used
1
[30–38]
are compared with the reported values.
4
for the preparation of [PipBs ](ClO ) using 36 mmol
2
4 2
of HClO instead. The remaining residues were dried
4
ꢀ
at 50 C for 4 hr. At the end, [PipBs ]ClO [PiPBs ]
(
4 | CONCLUSIONS
1
4
2
ClO ) and [PhBs ]ClO BAILs were collected with
4 2 1 4
1
00% yield.
In conclusion, a series of new recyclable BAILs-ClO cata-
4
lysts are reported to be green and efficient catalysts for
the synthesis of 2-amino-4H-chromenes under solvent-
free conditions. Moreover, this method is successfully
extended to a wide variety of enol or enolizable ketones,
malononitrile, and various aromatic aldehydes. Further-
more, the developed method has numerous benefits, com-
prising efficiency, generality, simple work-up procedure,
mild reaction conditions, green and clean process, easy
recycling, and reusability of BAILs up to six runs with
simple extraction from the organic phase by dissolving in
water, excellent yields of chromene derivatives, and short
reaction times.
3
.5 | Determination of acidity using UV–
Vis spectrophotometer
The UV spectra were recorded on a Perkin-Elmer
Lambda 365 UV–Vis spectrophotometer at room temper-
ature. The freshly prepared BAILs are viscous colorless
liquids and then gradually solidify at room temperature.
Since they melt at 90–95 C, the experiments were per-
formed at 110 C in order to obtain comparable acidity
results, temperature, indicator concentration, and water
content of BAILs were chosen almost same in all runs.
Consequently, BAILs were heated to 110 C to form liquid
ꢀ
ꢀ
ꢀ
ACKNOWLEDGMENTS
with good fluidity. Then, a solution of indicator dissolved
in EtOH (indicator concentration: 0.025 mg/ml) was
The authors gratefully acknowledge the Research Coun-
cil of King Abdulaziz and Yasouj Universities for finan-
cial support of this work.
added into the BAIL, and the mixture was stirred for
ꢀ
2
0 min to form the solution at 110 C. The concentration
ORCID
of the indicator in the BAIL was located within the scale
of the calibration curve. The UV spectra were recorded at
room temperature and the calibration curves with linear-
ity higher than 0.999 for the indicator in the
unprotonated form were shaped by means of their etha-
nol solutions.
Mosadegh Keshavarz https://orcid.org/0000-0001-8869-
3451
REFERENCES
[
[
1] M. Petkovic, K. R. Seddon, L. P. N. Rebelo, C. S. Pereira,
Chem. Soc. Rev. 2011, 40, 1383.
2] N. Isambert, M. M. S. Duque, J. C. Plaquevent, J. Rodriguez, T.
Constantieux, Chem. Soc. Rev. 2011, 40, 1347.
3
.6 | General procedure for BAILs-ClO4
[3] R. Tayebee, M. Jomei, B. Maleki, M. Kargar Razi, H. Veisi, M.
Bakherad, J. Mol. Liq. 2015, 206, 119.
accelerated synthesis of 2-amino-4H-
chromenes
[4] M. A. H. Hassan, A. B. Mohamed, K. M. Shaima, E. A. El-
Sharkawy, A. A. Emad, J. Mol. Liq. 2017, 236, 385.
[
[
5] Y. Zhang, Z. Zhou, L. Zou, R. Chi, J. Mol. Liq. 2019, 275, 136.
6] M. Keshavarz, B. Karami, A. Zarei Ahmady, A. Ghaedi, H.
Vafaei, C. R. Chim. 2014, 17, 570.
ß-naphthol or enolizable compound (1 mmol), aldehyde
(1 mmol), and malononitrile (1 mmol) were placed
together in a round-bottom flask containing BAILs-ClO4
[
7] M. Keshavarz, A. Zarei Ahmady, A. Mostoufi, N. Mohtasham,
(
7 mmol% for [PhBs ]-ClO and [PipBs ]-ClO and 3 mmol
1 4 1 4
Molecules 2017, 22, 1385.
%
for [PipBs ]-(ClO ) , and the mixture was heated in an
2 4 2
[8] C. Li, M. Wang, X. Lu, L. Zhang, J. Jiang, L. Zhang, ACS Sus-
tain. Chem. Eng. 2020, 8, 11.
[9] F. Rajabi, C. Wilhelm, W. R. Thiel, Green Chem. 2020, 22, 14.
ꢀ
oil bath at 110 C for suitable period of time indicated in
Table 3. Following completion of the reaction as confirmed

10
TAIB ET AL.
[
[
10] M. Li, F. Wu, Y. Gu, Chin. J. Catal. 2019, 40, 8.
11] A. Zarei, M. Yarie, M. A. Zolfigol, K. Niknam, J. Chin. Chem.
Soc. 2020, 67, 1120.
12] V. I. Parvulescu, C. Hardacre, Chem. Rev. 2007, 107, 2615.
13] A. C. Cole, J. L. Jensen, I. Ntai, K. L. T. Tran, K. J. Weaver,
D. C. Forbes, J. H. Davis, J. Am. Chem. Soc. 2002, 124, 5962.
14] F. Han, L. Yang, Z. Li, Y. Zhao, C. Xia, Adv. Synth. Catal.
[27] V. F. De Andrade-Neto, M. O. F. Goulart, J. F. D. S. Filho, M. J.
Da Silva, M. D. C. F. R. Pinto, A. V. Pinto, M. G. Zalis, L. H.
Carvalho, A. U. Krettli, Bioorg. Med. Chem. Lett. 2004, 14, 1145.
[28] D. R. Anderson, S. Hegde, E. Reinhard, L. Gomez, W. F.
Vernier, L. Lee, S. Liu, A. Sambandam, P. A. Sinder, L. Masih,
Bioorg. Med. Chem. Lett. 2005, 15, 1587.
[
[
[
[29] P. S. Elisa, E. B. Ana, A. G. Ravelo, D. J. Yapu, A. G. Turba,
Chem. Biodivers. 2005, 2, 264.
2
014, 356, 11.
[
[
15] K. V. Wagh, B. M. Bhanage, Green Chem. 2015, 17, 4446.
16] J. Gui, X. Cong, D. Liu, X. Zhang, Z. Hu, Z. Sun, Catal.
Commun. 2004, 5, 473.
[30] L. Yu, J. F. Gao, L. H. Cao, J. Chin. Chem. Soc. 2009, 56, 1175.
[31] J. Sheng, M.-M. Zhang, H. Jiang, X.-S. Wang, J. Chin. Chem.
Soc. 2012, 59, 650.
[
17] Q. Yang, Z. Wei, H. Xing, Q. Ren, Catal. Commun. 2008, 9,
[32] M. Kangani, N. Hazeri, A. Yazdani-Elah-Abadi, M.-T.
Maghsoodlou, J. Chin. Chem. Soc. 2017, 64, 1259.
[33] H. Ghavidel, B. Mirza, S. Soleimani-Amiri, M. Manafi, J. Chin.
Chem. Soc. 2020, 67, 1856.
1
307.
[
18] S. Mahato, S. Santra, R. Chatterjee, G. V. Zyryanov, A. Hajra,
A. Majee, Green Chem. 2017, 19, 14.
[
[
19] S. Liu, X. Liu, C. Wang, Ind. Eng. Chem. Res. 2013, 52, 47.
20] F. Arian, M. Keshavarz, H. Sanaeishoar, N. Hasanzadeh,
J. Mol. Struct. 2020. https://doi.org/10.1016/j.molstruc.2020.
[34] K. Bhuvaneswari, P. Sivaguru, A. Lalitha, J. Chin. Chem. Soc.
2020, 67, 1877.
[35] A. Khazaei, E. Bashirian, A. Ranjbaran, M. Khazaei, A. R.
Moosavi-Zare, J. Chin. Chem. Soc. 2017, 64, 757.
1
29599.
[
21] M. Keshavarz, M. Tabatabaee, M. Shahabi, E. Yazdankish,
[36] M. Aghajani, N. Monadi, J. Chin. Chem. Soc. 2019, 66, 775.
[37] M. M. Heravi, B. Baghernejad, H. A. Oskooie, J. Chin. Chem.
Soc. 2008, 55, 659.
[38] M. Keshavarz, N. Irvani, M. H. Ahmadi Azghandi, S. Nazari,
Res. Chem. Intermed. 2016, 42, 4591.
Polycycl. Aromat. Compd. 2019, 1. https://doi.org/10.1080/
1
0406638.2019.1593864.
22] N. Iravani, M. Keshavarz, A. Parhami, Res. Chem. Intermed.
019, 45, 5045.
23] M. Keshavarz, N. Iravani, A. Parhami, J. Mol. Struct. 2019,
189, 272.
24] M. Shahabi, M. Tabatabaee, M. Keshavarz, Catal. Commun.
019, 131, 105748.
[
[
[
[
[
2
1
2
How to cite this article: Taib LA, Keshavarz M,
Parhami A. Solvent-free synthesis of compounds
containing chromene core catalyzed by novel
25] M. M. Khafagy, A. H. F. A. El-Wahas, F. A. Eid, A. M. El-
Agrody, Farmacoterapia 2002, 57, 715.
26] P. W. Smith, S. L. Sollis, P. D. Howes, P. C. Cherry, I. D.
Starkey, K. N. Cobley, H. Weston, J. Scicinski, A. Merritt, A.
Whittington, P. Wyatt, N. Taylor, D. Green, R. Bethell, S.
Madar, R. J. Fenton, P. J. Morley, T. Pateman, A. Beresford,
J. Med. Chem. 1998, 41, 787.
Brønsted acidic ionic liquids-ClO . J Chin Chem
4
Soc. 2021;1–10. https://doi.org/10.1002/jccs.
202000449