Ionic liquid functionalized cellulose as an efficient heterogeneous catalyst for the facile and green synthesis of benzoxazine, pyrazine and quinoxaline derivatives in aqueous media

Article abstract of DOI:10.1007/s13738-016-0868-0

Immobilization of acidic ionic liquid, 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate on cellulose (Cell-[pmim]HSO₄) as an efficient heterogenous catalyst for the simple and environmentally benign synthesis of benzoxazine, pyrazine and quinoxaline derivatives in aqueous media at room temperature is described. The catalyst was characterized by FTIR spectroscopy and X-ray diffraction pattern. This method provides several advantages such as mild reaction conditions, environmentally friendly catalyst, good to excellent yields and simple work-up procedure.

Full text of DOI:10.1007/s13738-016-0868-0

J IRAN CHEM SOC
DOI 10.1007/s13738-016-0868-0
ORIGINAL PAPER
Ionic liquid functionalized cellulose as an efficient heterogeneous
catalyst for the facile and green synthesis of benzoxazine,
pyrazine and quinoxaline derivatives in aqueous media
Sevil Vaghefi Moghaddam1 · Hassan Valizadeh1
Received: 5 March 2016 / Accepted: 19 April 2016
© Iranian Chemical Society 2016
Abstract Immobilization of acidic ionic liquid, 1-methyl-
3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate
on cellulose (Cell-[pmim]HSO4) as an efficient heterog-
enous catalyst for the simple and environmentally benign
synthesis of benzoxazine, pyrazine and quinoxaline deriva-
tives in aqueous media at room temperature is described.
The catalyst was characterized by FTIR spectroscopy and
X-ray diffraction pattern. This method provides several
advantages such as mild reaction conditions, environmen-
tally friendly catalyst, good to excellent yields and simple
work-up procedure.
industry for their potential to inhibit the metal corrosion
[10, 11], the preparation of the porphyrins due to the simi-
larity of their structure to the chromophores, and also for
the preparation of electroluminescent materials [12–14]. In
view of the great importance of quinoxaline derivatives in
both industrial and medicinal field, a variety of protocols
have been developed for the synthesis of these compounds.
The condensation of o-arenediamines with 1,2-dicarbo-
nyl compounds in refluxing EtOH has been used as a use-
ful protocol for the synthesis of quinoxalines [15]. Several
catalysts, including acetic acid [16], oxalic acid [17], sul-
famic acid [18], H6P2W18O62·24H2O [19], KHSO4 [20],
CeCl3·7H2O [21], Ga(ClO4)3 [22], gold NPs supported with
cerium oxide [23], in situ generated iron sulfide from ele-
mental sulfur and ferric chloride [24], indium–acetic acid
or indium(III) chloride [25] and reduced graphene oxide
(rGO) [26] have been reported for this transformation. In
addition, other accomplished reported methods such as
Suzuki–Miyaura coupling reaction [27] and condensation
of 1,2-diamines with α-halo-β-ketoesters in ionic liquid
[28] have been reported for the synthesis of 2,3-disubsti-
tuted quinoxalines. However, most of the reported methods
suffer from drawbacks such as use of volatile organic sol-
vents, critical product isolation procedures, non-recovera-
ble catalysts, expensive and detrimental metal precursors
and harsh reaction conditions that limit their use in sustain-
able chemistry. Therefore, development of some new meth-
ods for the synthesis of quinoxaline derivatives is still a
desirable goal. Promoting of environmentally friendly route
is most apparent in the growth of green chemistry [29]. In
this regard, organic synthesis in aqueous media is rapidly
gaining importance since it avoids the use of many vola-
tile and toxic organic solvents spatially chlorinated hydro-
carbons which contribute to pollution. Biopolymers such
as, alginate [30], gelatine [31], starch [32] and chitosan
Keywords Benzoxazine · Pyrazine · Cell-[pmim]HSO4 ·
Quinoxalines · Aqueous media
Introduction
Quinoxaline and its derivatives are an important class of
nitrogen-containing fused heterocycles due to their bio-
logical and pharmaceutical activates such as anticancer [1],
antiviral [2], antibacterial [3–5] and kinase inhibition [6].
They have also significant applications such as using as
dyes [7], building blocks in the synthesis of organic semi-
conductors [8] and chemically controllable switches [9].
In addition, quinoxaline derivatives are important in the
Electronic supplementary material The online version of this
article (doi:10.1007/s13738-016-0868-0) contains supplementary
material, which is available to authorized users.
* Hassan Valizadeh
hvalizadeh2@yahoo.com
1
Department of Chemistry, Faculty of Sciences, Azarbaijan
Shahid Madani University, P.O. Box 53714-161, Tabriz, Iran
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J IRAN CHEM SOC
Scheme 1 Synthesis of benzo-
xazine, pyrazine and quinoxa-
lines in aqueous media using
Cell-[pmim]HSO4
NC
NC
NH2
NH2
N
N
Me
Me
NC
NC
3j
R
NH2
NH2
X= CH, N
R
X
N
R1
R1
O
O
R1
R1
Y= CH, N
X
R= H, Me, Cl, Br, NO2
Y
Cell-[pmim]HSO4
H2O
r.t
Y
N
3a-r
NH2
OH
N
Me
R1= Me, Ph
Me
OH
1
O
3o
2
+
N
N
-
HSO4
O
O
Si
O
Cell-[pmim]HSO4
=
O
O
HO
n
OH
derivatives [33] are appealing candidates that can be used
as supports for the catalytic applications. Cellulose is the
most abundant renewable bio-macromolecule in the nature
[34] which is widely produced in industrial scale. In both
pure and derivative forms, it has possible application in
electronics as a sensor material [35] in the pharmaceutical
[36] and in the cosmetic and packaging industries [37]. As
promising biopolymers of twenty-first century, cellulose
and its derivatives have some properties including biodeg-
radability and non-toxicity which make them superior sup-
ports for catalytic applications over conventional organic or
inorganic ones.
completely heterogeneous, the catalyst was washed with
toluene several times to remove any physisorbed ionic liq-
uid (Scheme 2).
The catalyst was characterized by XRD and FTIR spec-
troscopy. Powder XRD diffraction patterns of catalyst
and cellulose exhibited the characteristic peaks of both
cellulose and Cell-[pmim]HSO4; basically, the diffracto-
gram of cellulose showed peaks around 2θ = 16°, 22.5°,
34° assigned to (101), (002) and (040) planes [43]. Two
additional reflections were found in the XRD diffraction
patterns of catalyst around 2θ = 32°, 45° which could be
attributed to ionic liquid (Fig. 1).
In connection with our interest to develop environ-
mentally benign synthetic methods in organic chemistry
[38–42], we report herein an efficient and green protocol
for the synthesis of substituted quinoxalines, benzoxazine
and pyrazine using acidic ionic liquid immobilized on cel-
lulose (Cell-[pmim]HSO4) as a catalyst in aqueous media
(Scheme 1).
FTIR analysis of cellulose and Cell-[pmim]HSO4 is
shown in Fig. 2. The peak at 1576 cm−1 can be assigned
to the C=C band of the imidazolium ring attached to cel-
lulose. Additional bands at 3160 and 2927 cm−1 are due
to C–H stretching and deformation vibrations of imida-
zole moiety. The peak at 1163 cm−1 can be assigned to the
stretching mode of S=O. The band at 1034 cm−1 corre-
sponds to the Si–O. The S–O stretching mode of the func-
tional group of sulfuric acid is around 667 cm−1, confirmed
the successful preparation of the catalyst.
Results and discussion
For examination of the activity of catalyst for the syn-
thesis of quinoxaline derivatives, condensation of o-phe-
nylenediamine (1 mmol) and benzil (1 mmol) in water
at room temperature was chosen as a model reaction.
The reaction was carried out in the presence of different
amounts of catalyst. The results showed that the freshly
Catalyst, Cell-[pmim]HSO4, was prepared by stirring a mix-
ture of microcrystalline cellulose and ionic liquid 1-methyl-
3-(3-trimethoxysilylpropyl) imidazolium hydrogen sul-
fate in the presence of catalytic amount of (l)-tartaric acid
for 24 h at 70 °C. In order to make the reaction medium
1 3

J IRAN CHEM SOC
OMe
Si
MeO
MeO
MeO
MeO Si
MeO
neat
80-90 0C
3 days
+
Cl
N
Cl-
N
+
N
N
Acetone
rt
NaHSO4
48 h
OH
-
H
HSO4
O
+
N
N
O
HO
OH
n
OMe
MeO
(l )-tartaric acid
O
Si
Si
MeO
O
-
Touene/Methanol
70 0C
HSO4
+
O
N
N
H
O
24 h
O
HO
OH
n
Scheme 2 Preparation of Cell-[pmim]HSO4
Fig. 1 X-ray diffraction spectra
of microcrystalline cellulose
(Cell)
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J IRAN CHEM SOC
Fig. 2 Infrared (FTIR) spectra
of microcrystalline cellulose
(Cell) and Cell-[pmim]HSO4
prepared catalyst is more effective than other catalysts
in this procedure. In the absence of catalyst, the reaction
completed after 80 min and product 3a was prepared in
65 % yield (Table 1, entry 1). It was observed that upon
increasing the amount of Cell-[pmim]HSO4 from 100 to
200 and 300 mg, the yields enhanced from 70 to 80 and
98 % and the time decrease from 50 to 10 and 5, respec-
tively (Table 1, entry 2-4). Using of a higher amount of
catalyst has no more effect to improve the yield (Table 1,
entry 5). The effect of different solvents in the reaction was
also screened (Table 1, entry 6–10). As shown in Table 1,
it was found that water is a suitable solvent to produce
the target products in excellent yields and short reaction
time in comparison with other solvents. Therefore, it could
be concluded that 300 mg of Cell-[pmim]HSO4 at room
temperature for 5 min is the optimum amounts in this pro-
cedure. We examined this procedure on a 50 mmol scale
and found that they underwent a smooth transformation to
3a in good yields, suggesting that the present procedure is
amenable to scale up.
Table 1 Optimization of reaction conditions for the synthesis of 3a
using Cell-[pmim]HSO4
The scope and generality of the present method were
then further demonstrated by condensation of various
substituted o-diamines with 1,2-dicarbonyl compounds.
The results are presented in Table 2. As shown in Table 2,
in comparison with benzil, diacetyl was reacted in very
shorter reaction time and in higher yields in this pro-
cess. Reaction of 4-nitro-o-phenylenediamine with benzil
afforded to 2,3-diphenyl-6-nitroquinoxaline in 78 % yield
after 30 min. A slight increase in yield can be seen from
the reaction of diacetyl with o-phenylenediamines con-
taining electron donating groups in comparison with those
containing electron-withdrawing groups (Table 2, entries
6–9). However, significant differences were observed
from the reaction of benzil with o-phenylenediamines
containing electron donating groups in comparison with
those containing electron-withdrawing groups (Table 2,
entries 1–5).
Entry Solvent
Amount of catalyst
(mg)
Time (min) Yielda (%)
1
2
3
4
5
6
7
8
9
10
H2O
–
80
50
10
5
65
70
80
98
98
76
71
90
94
95
H2O
100
200
300
350
300
300
300
H2O
H2O
H2O
5
CH3Cl
CH3CN
EtOH
45
45
15
40
40
[bmim]Cl 300
[bmim]BF4 300
Reaction condition: o-phenylenediamine (1 mmol), benzyl (1 mmol),
Cell-[pmim]HSO4 (100, 200, 300, 350 mg) and water (3.0 mL)
a
Isolated yields after purification
1 3

J IRAN CHEM SOC
Table 2 Synthesis of benzoxazine, pyrazine and quinoxaline derivatives catalyzed by Cell-[pmim]HSO4
Entry Diamine
Diketone Product
Time (min) Yielda (%) Melting point (°C)
Founded Reported
NH2
NH2
O
Ph
N
N
Ph
Ph
1
5
98
124–127 126–127 [44]
O
O
Ph
Ph
3a
NH2
N
N
Ph
Ph
2
20
15
7
83
85
90
121–123 120–122 [45]
122–124 122–122.7 [46]
O
O
Ph
Ph
Br
Br
NH2
3b
NH2
N
Ph
3
O
O
Ph
Ph
Cl
N
Ph
Ph
Cl
NH2
3c
NH2
N
4
114–117 115.7–116.9
[46]
O
O
Ph
Ph
Me
N
Ph
Me
NH2
3d
NH2
N
Ph
Ph
5
30
3
78
99
98
182–184 184.7–185.5
[46]
O
Ph
O2N
N
O2N
NH2
3e
O
Me
N
Me
NH2
6
106–107 102–104 [47]
N
Me
O
O
Me
Me
NH2
3f
NH2
NH2
N
Me
7
3
89–91
88–89 [48]
Cl
N
Me
O
O
Me
Me
Cl
3g
N
Me
NH2
8
1
5
98
96
101–104 90–92 [47]
O
O
Me
Me
Me
N
Me
Me
NH2
NH2
3h
N
Me
9
132–133 130–132 [47]
O
O
Me
Me
O2N
NH2
O2N
N
Me
3i
Me
NC
NC
NH2
CN
N
N
10
11
7
95
90
165–167 160–162 [47]
116–118 113–115 [48]
O
O
Me
Me
CN
Me
NH2
3j
NH2
Me
10
Me
NH2
N
N
N
O
Me
3k
N
O
O
Ph
Ph
NH2
Ph
12
15
87
174–176 172–173 [48]
Ph
NH2
N
N
N
3l
N
1 3

J IRAN CHEM SOC
Table 2 continued
Entry Diamine
Diketone Product
Time (min) Yielda (%) Melting point (°C)
Founded Reported
120–123
O
Me
Me
O
O
13
5
97
–
N
N
Me
Me
NH2
NH2
O
3m
O
Ph
O
O
14
10
97
139–141 139–140 [49]
NH2
NH2
N
Ph
O
Ph
N
Ph
3n
O
Me
NH2
N
Me
Me
OH
15
16
5
95
90
166–168
–
O
OH
O
Me
3o
NH2
NH2
O
Ph
N
N
Ph
10
160–161 154–156 [47]
O
Ph
Ph
3p
All of the reactions are run at room temperature in H2O and in the presence of 300 mg Cell-[pmim]HSO4
a
Isolated yields after purification
-
HSO4
Plausible mechanism for the generation of quinoxa-
lines from o-diaminobenzenes and 1,2-diketons is depicted
+
N
N
in Scheme 3. In this process, Cell-[pmim]HSO4 acts as a
Brønsted acid and plays a significant role in increasing the
nucleophilic character of carbonyl groups. The reaction
is initiated with the protonation of carbonyl groups in the
presence of catalyst. Then, they are readily attacked by the
nitrogens of amines to afford the intermediate 4 which is
underwent dehydration to obtain quinoxaline derivatives 5.
O
O
O
O
Ph
Ph
Si
O
H
O
O
HO
n
OH
1
Ph
N
N
-2 H2O
Experimental
General
Ph
HO
HO
Ph
5
2
4
OH
OH
H
Ph
Ph
Ph
N
All reagents were purchased from Merck Company and
used without further purification. Infrared spectra were
recorded on a Perkin-Elmer FTIR spectrometer using KBr
N
H
H2N
H2N
pellets, νmax in cm−1. H NMR spectra were recorded on
1
a Bruker Avance (300 or 400 MHz) spectrometer. Chemi-
cal shifts are reported in ppm from tetramethylsilane with
the solvent resonance resulting from incomplete deuterium
incorporation as the internal standard (CDCl3: δ 7.26 ppm).
13C NMR spectra were recorded on a Bruker Avance (75 or
100 MHz) spectrometer with complete proton decoupling.
Chemical shifts are reported in ppm from tetramethyl-
silane with the solvent resonance as the internal standard
(CDCl3: δ 77.16 ppm). Elemental analyses were conducted
3
Scheme 3 Plausible mechanism for the formation of quinoxaline
derivatives
using the Euro EA 3000 elemental analyzer. All melting
points measured in open glass capillaries using Stuart melt-
ing point apparatus. XRD studies were carried out using a
1 3

J IRAN CHEM SOC
D8 advance diffractometer (Bruker, AXS model) equipped
with Cu–Kα (λ = 1.54 Å) radiation as an X-ray source
operating.
Conclusion
In summary, the present work demonstrates the efficiency
of 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium
hydrogen sulfate immobilized on cellulose as an effective
catalyst for one-pot synthesis of benzoxazine, pyrazine and
quinoxaline derivatives via the condensation of the repre-
sentative 1,2-diketones with 2-aminophenol or o-diamines
at room temperature. Ambient conditions, easy work-up
procedure, very good yields in short reaction times, and
avoiding volatile and hazardous solvents are the significant
advantages of our environmentally friendly protocol.
Preparation of 1‑methyl‑3‑(3‑trimethoxysilylpropyl)
imidazolium hydrogen sulfate
1-Methyl-3-(3-trimethoxysilylpropyl) imidazolium chlo-
ride was prepared as in our previously reported work [39].
As a typical procedure, 1-methylimidazole (4 g, 50 mmol,
1.0 equiv.) and (3-chloropropyl) trimethoxysilane (10 g,
50 mmol, 1.0 equiv.) were refluxed at 80 °C for 3 days
in the absence of any catalyst and solvent. The unre-
acted materials were washed by diethyl ether (3 × 8 mL).
Sodium hydrogen sulfate (2.4 g, 20 mmol, 1.3 equiv.) was
added to the acetone (10 mL) solution of the freshly pre-
pared ionic liquid (4 g, 15 mmol, 1.0 equiv.) and stirred for
48 h at room temperature. The suspension was filtered to
remove the precipitated sodium chloride salt. The solvent
was removed under reduced pressure at room temperature
followed by heating under vacuum to yield a yellowish vis-
cous liquid.
Acknowledgments The partial financial assistance from the
Research Vice Chancellor of Azarbaijan Shahid Madani University is
gratefully acknowledged.
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