1-Butyl-2-methylpipyridinium iodide ([BMPPY]I): novel ionic liquid for the synthesis of 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-ones under green solvent-free conditions

Article abstract of DOI:10.1007/s11164-019-03831-2

Abstract: In this article we reported preparation of 1-butyl-2-methylpipyridinium iodide ([BMPPY]I), as a novel ionic liquid (IL) through simple procedure. This newly prepared IL has been characterized by FT-IR, FESEM, EDX, TGA/DTG, ¹H NMR, ¹³C NMR, and Gc-mass techniques. The FESEM images revealed nano scale for the IL with the average diameter of 150–185?nm. Its efficacy examined for the synthesis of 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-ones via domino three-component reaction of isatin derivatives, isatoic anhydride, and indoles under solvent-free conditions at 100?°C. The results affirmed that ([BMPPY]I) possessed a dual catalytic/solvent role to promote this condensation. Non-flammability, thermal stability, non-toxicity and low cost of the IL that led to obtain pharmaceutically-active heterocycles though easy work-up procedure and short reaction times, are some highlighted features of this green protocol. Graphical abstract: [Figure not available: see fulltext.].

Full text of DOI:10.1007/s11164-019-03831-2

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-019-03831-2
1
‑Butyl‑2‑methylpipyridinium iodide ([BMPPY]I): novel
ionic liquid for the synthesis of 6‑hydroxy‑6‑(1H‑indol‑3‑yl)
indolo[2,1‑b]quinazolin‑12(6H)‑ones under green
solvent‑free conditions
1
1
Kobra Nikoofar · Seyedeh Shima Peyrovebaghi
Received: 19 January 2019 / Accepted: 9 April 2019
©
Springer Nature B.V. 2019
Abstract
In this article we reported preparation of 1-butyl-2-methylpipyridinium iodide
(
[BMPPY]I), as a novel ionic liquid (IL) through simple procedure. This newly pre-
1
pared IL has been characterized by FT-IR, FESEM, EDX, TGA/DTG, H NMR,
1
3
C NMR, and Gc-mass techniques. The FESEM images revealed nano scale for the
IL with the average diameter of 150–185 nm. Its eꢀcacy examined for the synthe-
sis of 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-ones via domino
three-component reaction of isatin derivatives, isatoic anhydride, and indoles under
solvent-free conditions at 100 °C. The results aꢀrmed that ([BMPPY]I) possessed a
dual catalytic/solvent role to promote this condensation. Non-ꢁammability, thermal
stability, non-toxicity and low cost of the IL that led to obtain pharmaceutically-
active heterocycles though easy work-up procedure and short reaction times, are
some highlighted features of this green protocol.
Keywords Ionic liquid · Domino reaction · Three-component reaction · Solvent-free
conditions · 6-Hydroxy-6-(1H-indol-3-yl)indoloquinazolinones · Green chemistry
Introduction
Ionic liquids (ILs) are organic or inorganic salts with the melting point usually below
1
00 °C (212 °F). They are preferably liquid at room temperature [1, 2] and they are
largely made of ions and short-lived ion pairs. These materials are variously called
liquid electrolytes, ionic ꢁuids, ionic melts, fused salts, liquid salts or ionic glasses
[
3, 4]. Ionic liquids possessed some highlighted properties such as poor electrical
conductivity, viscosity, high density, low vapor pressure, non-ꢁammability, thermal
*
Kobra Nikoofar
k.nikoofar@alzahra.ac.ir; kobranikoofar@yahoo.com
1
Department of Chemistry, Faculty of Physics and Chemistry, Alzahra University, Tehran, Iran
Vol.:(012
1
3456789)
3

K. Nikoofar, S. S. Peyrovebaghi
stability, high polarity, high dielectric constant and non-volatility [5–7]. Nowadays
ILs utilized in diꢂerent area of sciences like sensors [8], fuel cells [9], batteries [10],
capacitors [11], lubricants [12], plastics [13], and ionic gels [14]. The special prop-
erties of ILs let them to be utilized as solvent and/or catalyst in diꢂerent kind of
transformations such as condensations [15], cyclization [16], 1,3-dipolar cycloaddi-
tions [17], domino Knoevenagel-Michael reaction [18], and Diels–Alder reactions
[
19].
Because of the versatile properties of ionic liquids, the number of publications
of these materials has increased quickly, especially in the last two decades. Room
temperature ionic liquids (RTILs) [20], task speciꢃc ionic liquids (TSILs) [21], and
nano ILs [22] are some special class of ionic liquids prepared in recent years with
wide range of applications.
Quinazolinone is an important heterocyclic moiety in organic compounds that
possessed diꢂerent pharmaceutical properties. As could be in Scheme 1, Raltitrexed
(
1) is an inhibitor of thymidylate synthase is widely used for the ꢃrst-line treatment
of advanced colorectal cancer [23], (3,4-dihydro-2-methyl-4-oxoquinazolin-6-yl)
methyl 4-(4-ꢁuorophenyl)piperazine-1-carbodithioate (2) with signiꢃcant antitumor
activity against human myelogenous leukemia K562 cells [24], Febrifugine (3) with
antimalarial properties [25], and Methaqualone (4) which is eꢂective for its seda-
tive-hypnotic eꢂects [26], are some examples of quinazolinones.
Besides quinazolinone derivatives are in great interest in medicinal and biologi-
cal ꢃelds because of various wide-range properties such as protein tyrosine kinase
inhibitory, cholecystokinin inhibitory, anti-microbial, anti-convulsant, hypotensive,
anti-depressant, anti-inꢁammatory, and anti-allergy, biofungicide, and diuretic activ-
ities [27, 28].
Due to the importance of quinazolinone core, diꢂerent heterocycles possessing
this moiety has been prepared [29–31].
In 2018 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b] quinazolin-12(6H)-ones, was
reported by Kumar et al. via a domino three-component reaction in the presence
of ZnO nanoparticles in ethanol at room temperature. In the ꢃrst step of the one-
pot procedure, isatins and isatoic anhydride mixed in order to obtain tryptanthrin
Scheme 1 Some pharmaceutical active compounds with quinazolinones building block
1
3

1‑Butyl‑2‑methylpipyridinium iodide ([BMPPY]I): novel…
intermediate. Then indolation of tryptanthrin yielded the corresponding products
32].
[
In continuation of our research group interest in utilizing novel nanostructures
as accelerators of multi-component reactions (MCRs) to obtain pharmaceutically
potent heterocycles [33–38], herein were report a novel green IL, 1-butyl-2-methyl-
pipyridinium iodide ([BMPPY]I, to promote preparation of 6-hydroxy-6-(1H-indol-
3
-yl)indolo[2,1-b]quinazolin-12(6H)-ones (5a–n) via the domino reaction of isat-
ins (1a–d), isatoic anhydride (2) and indoles (4a–e) under solvent-free conditions
at 100 °C (Scheme 2). The corresponding products 5a–n preparation contains of a
domino one-pot process consist of tryptanthrin intermediate (3) via C–N bond for-
mation–cyclization process followed by indolation of bioactive 3 intermediate.
Experimental
Materials and measurements
All materials and solvents were purchased commercially from Merck, Aldrich and
Alfa-Aesar and were used without puriꢃcation. The TLC plates containing an active
ꢁ
uorescent detector at 254 nm wavelengths were used by Merck to check the reac-
tion progress. The FT-IR spectra were recorded by the Bruker FT-IR infrared spec-
trometer Transor 27 model. KBr has been used to make tablets. Melting points was
determined by an Electro thermal 9200 instrument and uncorrected values have been
reported. Field Emission Scanning Electron microscope (FESEM) for the measure-
ment of the nanoparticles size was carried out on a model FESEM: VEGA\\TES-
CAN-LMU. The Energy dispersive X-ray spectroscopy (EDX) of the VEGA3 TES-
CAN model is used for elemental analysis and description and identiꢃcation. The
Scheme 2 Synthesis of 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-ones in the pres-
ence of [BMPPY]I
1
3

K. Nikoofar, S. S. Peyrovebaghi
UNIVERSAL 320 centrifuge machine with 5000 rpm and 10,000 rpm was used for
the preparation of nanocatalyst. Thermal gravimetric analysis (TGA) TGA1 model
of METTLER TOLEDO was used to determine the thermal stability, moisture con-
tent and help identify the nanocayalysis structure. The mass spectra were recorded
by the mass spectrometer GC-Mass 5973 network mass GC 6690 Agilent, selective
detector. The BANDELIN electronic DT 255 H model ultrasonic bath was used in
the production of nanocatalyst process.
Preparation of 1‑butyl‑2‑methylpipyridinium iodide ([BMPPY]I)
In two-necked ꢁask to a mixture of butyl iodide (10 mmol) in 20 ml of ethyl acetate,
a mixture of 2-methylpipyridine (10 mmol) in ethyl acetate (20 ml), added dropwise
with dropping funnel while stirring with a magnetic stirrer. After stirring for 10 min
at room temperature, the obtained mixture heated at 110 °C for 13 h by magnetic
stirring. After cooling, the precipitate centrifuged and washed with ethyl acetate
(
2×10 ml) and then placed in an ultrasonic bath for 30 min. The resulting precipitate
air dried and washed with boiled absolute ethanol (20 ml). Subsequent washing with
ethyl acetate (2×10 ml), centrifugation, and drying in air gave the corresponding
1
[
BMPPY]I IL, as dusty powder, with a melting point of 181–184 °C. H NMR (300
MHZ, DMSO-d ) 8.94–8.76 (brm, 1H, NH), 3.3.2–3.34 (m, 1H, CH), 3.15–3.20 (m,
6
2
H, CH ), 2.97–3.15 (m, 2H, CH ), 1.48–1.72 (m, 8H, CH ), 1.25–1.38 (m, 5H,
2 2 2
1
3
CH ), 0.88 (t, J=6.73 Hz, 3H, Me). C NMR (75 MHz, DMSO-d ) 13.5, 17.37,
2
6
+
+
1
9.36, 21.35, 22.59, 24.25, 30.94, 33.16, 51.62, 58.15. m/z 283 [M ], 268 [M ]-Me,
+
+
+
2
67 [M ]-NH , 265 [M ]-C H , 155 [M ]-HI.
2
2
5
General procedure for synthesis of 6‑hydroxy‑6‑(1H‑indol‑3‑yl)indolo[2,1‑b]
quinazolin‑12(6H)‑ones (5a–n)
A mixture of isatoic anhydride 2 (1 mmol), isatin derivatives (1a–d) (0.8 mmol),
and [BMPPY]I (0.084 g) stirred magnetically at 100 °C within 45–135 min until
the intermediate 3 was obtained monored by TLC. Then indole derivatives (4a°e)
(
1 mmol) were added to the mixture and the reaction was performed in the same con-
dition for 80–230 min period. The reaction progress was followed by TLC (eluent:
petroleum ether/ethyl acetate, 3:2). After the reaction was completed the reaction
mixture was dissolved in small amount of methanol to reach a suitable concentra-
tion and the pure 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b] quinazolin-12(6H)-ones
(
5a–n) obtained form plate chromatography in 71–94%.
8
‑Bromo‑6‑(5‑chloro‑1H‑indol‑3‑yl)‑6‑hydroxyindolo[2,1‑b]
quinazolin‑12(6H)‑one (5f)
−1
Cream powder. Mp 356–358 °C. IR (KBr, cm ): 3673 (OH), 3367 (NH), 3118,
1
5
1
698 (C=O), 1616 (C=C), 1465 (C=C), 1241 (C–Br), 1056 (C–Br), 1383 (C–Cl),
1
54 (C–Cl), 1104 (C–O), 1169 (C–N), 685, 801. H NMR (300 MHz, DMSO-d ):
6
1.24 (S, 1H, NH), 10.86 (S, 1H, OH), 7.46–7.39 (m, 2H, Ar), 7.21 (m, 2H, Ar),
1
3

1‑Butyl‑2‑methylpipyridinium iodide ([BMPPY]I): novel…
Scheme 3 Synthetic pathway of [BMPPY]I IL
Fig. 1 The FT-IR spectra of
butyl iodide (a), 2-methylpi-
peridine (b), and the [BMPPY]
I IL (c)
7
3
1
.17 (m, 2H, Ar), 7.05 (d of d, J=8.62 Hz, J=1.69 Hz, 2H, Ar), 6.97–6.96 (m,
1
3
H, Ar). CNMR (75 MHz, DMSO-d ): 178.93, 140.53, 131.06, 127.38, 126.31,
6
26.26, 123.07, 121.19, 119.35, 113.43, 113.40, 113.07, 111.88, 52.30, 30.60.
Results and discussion
The schematic preparation procedure for the synthesis of 1-butyl-2-methylpipyridin-
ium iodide ([BMPPY]I), as a new IL, has been illustrated in Scheme 3.
In Fig. 1, the FT-IR spectra of the butyl iodide (a), 2-methylpiperidine (b) and the
[
BMPPY]I IL (c) shown respectively from top to down. As could be seen in Fig. 1a,
−
1
−1
the peaks in 2964 cm and 2878 cm are related to asymmetric vibrations of CH
3
−1
−1,
−1
and CH respectively. The bands at 1461 cm , 1381 cm and 594 cm based
2
on asymmetric bending of methyl and methylene groups of butyl iodide in addition
−1
−1
with the peaks in 594 cm and 1188 cm corresponds to stretching and bending
of C–I bond, are characteristic bands of the butyl iodide. Appearance of broad band
−1
in 3500–3206 cm related to NH group in addition with peaks at 1382, 1560, 1642
−1
and 1448 cm belong to NH bending scissors like, CH asymmetric bending, CH
3
3
symmetric bending and CH asymmetric bending vibration are some ꢃngerprint
2
−
1
of 2-methylpiperidine. Also the observed peak in 1117 cm is related to the CN
stretching bond. The Fig. 1c, contains all the mentioned peaks of the two substrates
that conꢃrms successful prepation of [BMPPY]I IL.
1
3

K. Nikoofar, S. S. Peyrovebaghi
The morphology of the obtained [BMPPY]I IL has been illustrated in Fig. 2.
As it is obvious, the uniform nano-scale couldn’t be observed, but some nanopar-
ticles with the average diameter of 150–185 nm obtained in the whole mass of the
IL.
The EDX analysis of the newly prepared IL is shown in Fig. 3. According to
the results [BMPPY]I contains 40.90% C, 10.57% N, and 48.53% I. The pattern
also proves that there is no other impurity related to the solvents and materials
used in the catalyst manufacturing steps.
The thermal stability of the novel IL has been calculated by TGA/DTG analy-
sis appeared in Fig. 4. The results indicates endothermic one-step degradation
process of [BMPPY]I in 260–350 °C. So, it is thermally stable up to 260 °C.
Fig. 2 FESEM spectrum for [BMPPY]I
1
3

1‑Butyl‑2‑methylpipyridinium iodide ([BMPPY]I): novel…
Fig. 3 EDX spectrum of [BMPPY]I
Fig. 4 TGA/DTG diagram of [BMPPY]I
In the next step, the catalytic activity of [BMPPY]I IL has been evaluated in
preparation of 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-ones.
For this purpose the reaction of isatin (1a), isatoic anhydride (2), and indole (4a)
chosen as the model reaction to screen the best reaction conditions. According to the
data in Table 1, the amount of the [BMPPY]I IL and temperature are two parameters
that has been investigated in the absence of solvent (entries 1–8). As could be seen
variety amounts of the catalyst in diꢂerent temperate has been examined. The best
results is due entry 7. Elevating the temperature up to 110 °C didn’t aꢂect the out-
put of the model reaction. It must be mentioned that all the entries performed in a
one-pot domino manner in which the isatin (1a) and isatoic anhydride (2) reacted to
obtain the intermediate 3, and then indole (4a) added to the reaction ꢁask to obtain
1
3

K. Nikoofar, S. S. Peyrovebaghi
Table 1 Screening optimized
conditions for the synthesis
of hydroxy-6-(1H-indol-3-yl)
indolo[2,1-b] quinazolin-
b
Entry
Conditions
Time (min)
Yield (%)
(
BMPPY)I (g)/temperature
(
°C)/solvent (5 ml)
1
2(6H)-one (5a)a
1
2
3
4
5
6
7
8
9
0.028/50/–
0.028/80/–
0.028/100/–
0.056/100/–
0.084/50/–
0.084/70/–
0.084/100/–
0.084/110/–
300
300
365
380
290
310
270
270
230
180
210
200
200
300
–
12
53
67
74
78
87
86
c
0.042/rt/H O
13
15
2
c
10
11
12
13
14
0.042/reꢁux/H O
2
0.084/rt/H O:EtOH (1:1)
41
63
62
–
2
0.056/reꢁux/EtOH
0.084/reꢁux/EtOH
–/100/–
a
Isatin 1a (0.8 mmol), isatoic anhydride 2 (1 mmol), indole 4a
(
1 mmol)
b
Isolated yield
Some by-products has been observed
c
the corresponding 5a product. The model reaction has also been examined in green
solvent like aqua, ethanol (entries 9–13). The results conꢃrmed that presentation of
solvent did not increased the reaction yield. It is noteworthy that doing the reaction
in aqueous media got some unknown by-products (entries 9 and 10). In order to
conꢃrm the eꢀcacy of the [BMPPY]I IL to promote the reaction, the model con-
densation has been performed in the absence of any catalyst. According to entry
1
4 of Table 1, no products observed. Therefore, according to the results, 0.084 g of
[
BMPPY]I at 100 °C under solvent-free conditions was considered as optimal situa-
tion (entry 7). The model reaction also accomplished in a one-pot one-step mode but
many by-products has been produced.
Obtaining the optimized reaction conditions, the eꢀcacy of the IL has been
extended through performing the one-pot domino reaction of various isatin deriva-
tives (1a–d), isatoic anhydride (2), and indoles (5a–e) to get the desired products
(5a–n). The results are summarized in Table 2.
As can be seen (entries 1–4), isatin and its derivatives performed the reaction well
with indole (4a). 5-choloroindole (4b) and 4-bromoindole (4c), as an electron-deꢃ-
cient candidates, has also done the condensation successfully with diꢂerent isatins
(
entries 5–10). 2-methyl indole (4d) was another candidate with electron-donating
sterically-hindered substituent also complete the reaction to obtain the desired prod-
ucts (entries 11–13). 5-Methoxyindole (4e) has also demonstrated good activity for
the preparation of 6-hydroxy-6-(5-methoxy-1H-indol-3-yl)indolo[2,1-b]quinazolin-
1
2(6H)-one (5) as reported in entry 14. There is no signiꢃcant relationship between
1
3

1‑Butyl‑2‑methylpipyridinium iodide ([BMPPY]I): novel…
Table 2 Synthesis of 6-hydroxy-6-(1H-indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-onesa
Time
Mp (°C)
190 [32]
Entry
Isatin
Indole
Product
Yield (%)
(
min)
1
270
87
4
a
1
a
5
a
2
11–213
2
4a
220
89
[
32]
1
b
5
b
2
1
11–213
32]
3
4a
4a
270
265
90
88
[
1
c
5
c
98–200
32]
4
[
1
d
5
d
2
3
11–213
32]
5
6
7
1a
1c
1a
275
210
73
84
75
[
4
b
5
e
56–358
New
4b
5
f
2
10–212
32]
285
[
4
c
5
g
1
3

K. Nikoofar, S. S. Peyrovebaghi
Table 2 (continued)
Time
Mp (°C)
Entry
Isatin
Indole
Product
Yield (%)
(
min)
2
2
19–221
32]
8
1b
4c
290
77
92
[
5
h
25–227
32]
9
1c
4c
225
[
5
i
2
2
13–215
32]
1
1
0
1
1d
4c
195
290
71
94
[
5
j
85–286
32]
1a
[
4
d
5
k
2
2
10–212
32]
1
2
3
1b
4d
320
290
86
93
[
5
l
91–294
32]
1
1d
4d
[
5
m
2
06–208
32]
1
4
1a
290
93
[
4
c
5
n
a
The reactions has been done isatins (0.8 mmol), isatoic anhydride (1 mmol), and indole (1 mmol), in the
presence of (BMPPY)I (0.084 g) at 100 °C
1
3

1‑Butyl‑2‑methylpipyridinium iodide ([BMPPY]I): novel…
Scheme 4 Proposed mechanism for the green synthesis of the products 5a–n
the substituent characteristic with the yield and time of the reactions not for isatins
nor with indole derivatives.
Although the reaction mechanist is not clear, but a proposed pathway has been
shown in Scheme 4. First the nucleophilic attack of isatin (1) to the activated car-
bonyl moiety of (2) followed by CO release gave the intermediate (A). Intramo-
2
lecular cyclization yielded B that undergoes a subsequent dehydration to get the
tryptamine 3. Nucleophilic attack of indole form its active site (C-3 positon) to the
carbonyl of intermediate 3 obtain the desired class of products 5.
Conclusions
Brieꢁy a novel, green and simple method for the synthesis of 6-hydroxy-6-(1H-
indol-3-yl)indolo[2,1-b]quinazolin-12(6H)-ones has been reported by domino three-
component reaction of isatin derivatives, isatoic anhydride and indoles under sol-
vent-free condition in the presence of catalytic amounts of (BMPPY)I at 100 °C.
This catalyst is also a newly prepared ionic liquid which has been obtained through
mixing the easily-available substrates simply and characterized with diꢂerent tech-
niques. Simple work-up, short reaction times, solvent-free conditions, good yields of
the products, and economical and environmentally friendly catalytic system usage
are some highlighted advantages of this protocol.
1
3

K. Nikoofar, S. S. Peyrovebaghi
Acknowledgements The authors thank Alzahra University for ꢃnancial support of this research.
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