Chitosan-attached nano-Fe3O4 as a superior and retrievable heterogeneous catalyst for the synthesis of benzopyranophenazines using chitosan-attached nano-Fe3O4

Article abstract of DOI:10.1515/znb-2019-0091

A simple and rapid method for the preparation of benzopyranophenazines is presented, involving a one-pot four-component reaction of hydroxynaphthoquinone, o-phenylenediamine, benzaldehydes, and malononitrile with nano-Fe₃O₄?chitosan

Full text of DOI:10.1515/znb-2019-0091

Z. Naturforsch. 2019; 74(10)b: 733–738
JCahvaidtoSasfaaeni--Gahtotmaic*,hMeadryanmaTnaova-zFoea3nOd4HaossseainsSuhaphebraizoi-rAlaavni d
retrievable heterogeneous catalyst for the synthesis of
benzopyranophenazines using chitosan-attached nano-Fe3O4
https://doi.org/10.1515/znb-2019-0091
thiourea-based organocatalysts [15], caffeine [16], theo-
phylline [17], l-proline [18], 1-butyl-3-methylimidazolium
hydroxide ([Bmim]OH) [19], Et3N [20], pyridine [21], and
oxalic acid [22]. However, some of the reported methods
suffer from drawbacks such as long reaction times, gen-
eration of a large amount of waste, unpleasant reaction
conditions, and use of toxic and nonreusable catalysts.
There remains a need, therefore, for new, efficient, and
mild approaches to obtain such products in high yields.
Magnetic materials have established themselves as a
special group of heterogeneous catalysts owing to their
diverse applications in syntheses and catalysis [23, 24]. To
overcome the drawback of the separation of the catalyst,
nanomagnetic materials have emerged as recoverable
and retrievable catalysts. The surface of magnetic nano-
particles (MNPs) can be functionalized simply through
convenient surface modifications to enable the loading
Received May 6, 2019; accepted August 12, 2019
Abstract: A simple and rapid method for the preparation
of benzopyranophenazines is presented, involving a one-
pot four-component reaction of hydroxynaphthoquinone,
o-phenylenediamine, benzaldehydes, and malononitrile
with nano-Fe3O4@chitosan as an efficient heterogeneous
solid acid catalyst under reflux conditions in ethanol.
The catalyst is characterized by powder X-ray diffraction
(XRD), scanning electron microscopy (SEM), magnetic
susceptibility measurements, energy-dispersive X-ray
spectroscopy (EDS), and Fourier transform infrared (FT-
IR) spectroscopy. Atom economy, high catalytic activity, a
wide range of products, excellent yields in short reaction
times, and low catalyst loading are some of the important
features of this method.
Keywords: catalytic activity; chitosan; nano-Fe3O4; one- of a variety of required functionalities [25–27]. Here we
pot reaction; pyranophenazines.
reported the use of nano-Fe3O4@chitosan as an efficient
catalyst for the preparation of benzopyranophenazines by
a one-pot four-component reaction of hydroxynaphtho-
quinone, o-phenylenediamine, benzaldehydes, and malo-
nonitrile under reflux conditions in ethanol (Scheme 1).
1 Introduction
Phenazines possess many important biological prop-
erties, including antitumor [1], antimicrobacterial [2],
antiproliferative [3], antibiotic [4], antifungal [5], and 2 Results and discussion
anti-inflammatory [6]. Some phenazines isolated from
Streptomyces (a marine bacterium) have been described Figure 1 shows the powder X-ray diffraction (XRD) pattern
with biological significance (Fig. 1) [7–10]. Finding effec- of nano-Fe3O4@chitosan. The pattern agrees well with the
tive methods for the synthesis of phenazines through reported pattern for Fe3O4 (JCPDS No. 75-0449). The crys-
multicomponent reactions (MCRs) is a significant area of tallite size of nano-Fe3O4@chitosan, as calculated by the
research in organic and medicinal chemistry. Recently, Scherrer equation, is 15–20 nm, which is in good agreement
there have been reports on the synthesis of phenazines with the results obtained by scanning electron microscopy
using p-TSA (para-toluenesulfonic acid) [11], glacial acetic (SEM; see below), which was used to determine the parti-
acid [12], 1,4-diazabicyclo[2.2.2]octane (DABCO) [13, 14], cle size and morphology. The statistics of the results from
the SEM images clearly demonstrate that the average size
of nano-Fe3O4@chitosan is 10–25 nm (Fig. 2).
*Corresponding author: Javad Safaei-Ghomi, Department of Organic
Chemistry, Faculty of Chemistry, University of Kashan, Kashan 51167,
IR Iran, Phone: +98 31 55912385, Fax: +98 31 55552935,
E-mail: safaei@kashanu.ac.ir
Maryam Tavazo and Hossein Shahbazi-Alavi: Department of Organic
Chemistry, Faculty of Chemistry, University of Kashan, Kashan 51167,
IR Iran
Figure S1 shows the Fourier transform infrared
(FT-IR) spectrum of nano-Fe3O4@chitosan. It displays
a broad band at about 3423 cm−1, which corresponds to
the stretching vibrations of O–H and N–H groups. Peaks
appearing at 2923 and 2855 cm−1 are characteristic of C–H
stretching vibrations. The band at 1590 cm−1 is assigned to
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ꢀꢀꢀꢁ
734ꢀ ꢀJ. Safaei-Ghomi et al.: Synthesis of benzopyranophenazines
Fig. 1:ꢀXRD patterns of nano-Fe3O4@chitosan.
O
N
Ar
O
nano-Fe3O4@chitosan
reflux, ethanol
H
OH
N
CN
H2N
CN
O
+
+
+
CN
Ar
NH2
H2N
O
Scheme 1:ꢀSynthesis of benzopyranophenazines using nano-Fe3O4@chitosan.
N–H bending vibration, and those at 1375–1450 cm−1 are
assigned to C–H bending vibration in chitosan. The bands
at 1069 and 628 cm−1 are assigned to the stretching vibra-
tions of C–O and Fe–O, respectively.
In order to investigate the size distribution of the
nanocatalysts, DLS (dynamic light scattering) measure-
ments of the nanoparticles were carried out (Fig. 3). The
dispersion for the DLS analysis (2.5 g nanocatalyst in
50 mL ethanol) was carried out using an ultrasonic bath
(60 W) for 30 min.
The magnetic properties of the nanoparticles were
characterized using a vibrating sample magnetometer
(VSM). Magnetic measurements show that nano-Fe3O4
and nano-Fe3O4@chitosan have saturation magnetization
values of 48.5 and 22.32 emu g−1, respectively (Fig. 4). These
results demonstrate that the magnetization decreases by
coating and functionalization.
The EDS (energy-dispersive X-ray spectroscopy) spec-
trum of nano-Fe3O4@chitosan (Fig. 5) shows that the ele-
mental composition consists of carbon, oxygen, iron, and
nitrogen.
Fig. 2:ꢀSEM photograph of nano-Fe3O4@chitosan.
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ꢁꢀꢀꢀ
J. Safaei-Ghomi et al.: Synthesis of benzopyranophenazinesꢂ
ꢂ735
Fig. 3:ꢀDLS of nano-Fe3O4@chitosan.
of
hydroxynaphthoquinone,
o-phenylenediamine,
4-chlorobenzaldehyde, and malononitrile as a model
reaction. To obtain the ideal reaction conditions for the
synthesis of compound 5b, we studied other catalysts
and solvents, as shown in Table 1. Screening of diverse
catalysts such as Et3N, imidazole, p-TSA, nano-Fe3O4, chi-
tosan, and nano-Fe3O4@chitosan revealed nano-Fe3O4@
chitosan as the most effective catalyst to perform this
reaction under reflux conditions in ethanol. From further
studies on the catalyst loading, we found that the yield
of compound 5b remained almost the same when 10 mg
of nano-Fe3O4@chitosan was used (Table 1). Using lower
catalyst loadings (8 mg) afforded 5b in 88% yield.
Fig. 4:ꢀVSM curve of (a) nano-Fe3O4 and (b) nano-Fe3O4@chitosan.
The above results show that the present catalytic
method is extendable to a wide variety of substrates to
Table 1:ꢀOptimization of the reaction conditions.a
Entryꢁ Solventꢁ Catalyst
(reflux)
ꢁ
Timeꢁ Yieldb
(min) (%)
1
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
H2O
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
–
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
600ꢃ Trace
400ꢃ 45
400ꢃ 40
200ꢃ 58
250ꢃ 48
200ꢃ 58
150ꢃ 68
150ꢃ 60
120ꢃ 75
80ꢃ 86
2
Et3N (10 mol.%)
3
Imidazole (10 mol.%)
p-TSA (10 mol.%)
Fe3O4 (8 mol.%)
Chitosan (12 mg)
Nano-Fe3O4@chitosan (8 mg)
Nano-Fe3O4@chitosan (8 mg)
5
6
7
8
9
CH2Cl2
10
11
12
13
CH3CN ꢃ Nano-Fe3O4@chitosan (8 mg)
EtOH
EtOH
EtOH
ꢃ
ꢃ
ꢃ
Nano-Fe3O4@chitosan (8 mg)
Nano-Fe3O4@chitosan (10 mg)ꢃ
Nano-Fe3O4@chitosan (12 mg)ꢃ
Fig. 5:ꢀEDS of nano-Fe3O4@chitosan.
80ꢃ 90
80ꢃ 90
Initially we studied and optimized the differ-
ent reaction parameters for the preparation of ben-
aReaction conditions: 2-hydroxynaphthalene-1,4-dione (1 mmol),
o-phenylenediamine (1 mmol), 4-chlorobenzaldehyde (1 mmol), and
zopyranophenazine by the condensation reaction malononitrile (1.5 mmol) as a model reaction. bIsolated yields.
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736ꢀ ꢀJ. Safaei-Ghomi et al.: Synthesis of benzopyranophenazines
create a wide library of benzopyranophenazines. From extent on each reuse (run 1, 90%; run 2, 90%; run 3, 90%;
the above observation, it is important to mention that run 4, 89%; run 5, 89%, run 6, 88%). After completion of
electron-withdrawing groups increase the reaction rate the reaction, the nanocatalyst could be easily separated
and give better yields than electron-donating groups using an external magnet. The catalyst was washed four
(Table 2).
times with ethanol and dried at room temperature for 24 h
We investigated the reusability of nano-Fe3O4@chi- before reuse.
tosan as the catalyst for the preparation of the product
A proposed mechanism for the synthesis of benzo-
5b. We found that product yields reduced only to a small pyranophenazines using nano-Fe3O4@chitosan is shown
in Scheme 2: (i) The initial condensation of hydrox-
ynaphthoquinone with o-phenylenediamine affords the
intermediate I. (ii) A Knoevenagel condensation of malon-
onitrile and benzaldehydes forms the intermediate II. (iii)
Table 2:ꢀSynthesis of benzopyranophenazine derivatives.
The Michael addition of intermediate I with intermediate
II gives the intermediate III, which in subsequent cycliza-
tion and tautomerism affords the corresponding product.
In this mechanism, the surface atoms of nano-Fe3O4@chi-
tosan activates the C=O and C≡N groups for better reac-
tion with the nucleophiles. This proposed mechanism is
supported by other reports in the literature [15, 19, 29].
Nanoparticles have good catalytic activity owing to their
large surface area and number of active sites. However,
the activity of the catalysts is also influenced by the
acid-base properties and many other factors such as the
geometric structure (particularly pore structure), the dis-
tribution of sites, and the polarity of the surface sites [30].
The free hydroxyl and amino groups distributed on the
surface of chitosan supported by nano-Fe3O4 are believed
to activate the substrates predominantly through hydro-
gen bonding [29].
Entryꢁ
R
ꢁ
Productꢁ Time ꢁ Yielda
(min) (%)
ꢁ
m.p. (°C) found
(reportedb)
1
2
3
4
5
6
7
8
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
H
4-Cl
2-Cl
4-Br
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
5a
5b
5c
5d
5e
5f
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
ꢃ
90 ꢃ
80 ꢃ
85 ꢃ
80 ꢃ
80 ꢃ
86 ꢃ 297–300 (298–300)
90 ꢃ 290–292 (288–290)
88 ꢃ 299–302 (301–303)
90 ꢃ 282–284 (283–285)
92 ꢃ 273–276 (274–276)
90 ꢃ 277–281 (278–279)
94 ꢃ 280–282 (281–283)
4-F
3-NO2
4-NO2
4-CN
4-NMe2
4-Me
2-OMe
3-OMe
4-OMe
80 ꢃ
80 ꢃ
5g
5h
5i
5j
5k
5l
85 ꢃ
86
ꢃ
288–290
9
100 ꢃ
100 ꢃ
100 ꢃ
100 ꢃ
100 ꢃ
80 ꢃ
78 ꢃ 261–263 (261–263)
80 ꢃ 293–295 (293–294)
82 ꢃ 268–270 (270–272)
80 ꢃ 239–241 (240–242)
10
11
12
13
14
5m
78
ꢃ
268–269
2,4-Dichloroꢃ 5n
92 ꢃ 306–309 (308–310)
aIsolated yields. bAll reported values are from the literature [28].
CN
CN
O
Ar
CN
CN
nano-Fe3O4@chitosan
+
Ar
I
O
O
N
OH
H2N
H2N
N
nano-Fe3O4@chitosan
+
OH
II
N
Ar
O
nano-Fe3O4@chitosan
nano-Fe3O4@chitosan
I
N
II
Ar
+
CN
N
CN
N
C
NH2
N
OH
III
Scheme 2:ꢀProposed mechanism for the synthesis of benzopyranophenazines.
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ꢂ737
external permanent magnet. The solvent was evaporated
and the solid obtained was filtered and washed with EtOH
3 Experimental section
Reagent grade chemicals were purchased from Sigma- and water. The pure products were characterized by com-
1
Aldrich or Merck and were used without further puri- parison of their physical data (melting points, IR, and H
fication. Chitosan with an average molecular weight of NMR) with those of known compounds in the literature.
1
290 000 Da was purchased from Sigma-Aldrich. The prod- The FT-IR and H NMR spectra of selected compounds 5
ucts were isolated and characterized by physical and spec- are given as supplementary material (available online).
tral data. NMR spectra were obtained on a Bruker Avance
400 MHz spectrometer (1H NMR at 400 Hz, 13C NMR at
100 Hz) in DMSO-d6 using trimethylsilane (TMS) as the 3.2.1 3-Amino-1-(4-cyano-phenyl)-1H-benzo[a]
internal standard. Chemical shifts (δ) are given in ppm
and coupling constants (J) in hertz (Hz). FT-IR spectra
pyrano[2,3-c]phenazine-2-carbonitrile (5h)
were recorded with KBr pellets by a Nicolet Magna 550 Yellow solid. m.p. 288–290°C. FT-IR (KBr): ν (cm−1)ꢀ=ꢀ3322,
IR spectrometer. CHN compositions were measured using 3176, 3045, 2831, 2182, 2139, 1644, 1622, 1584, 1483, 1455,
1
a Carlo ERBA Model EA 1108 analyzer. Powder XRD was 1444, 1392, 1383, 1355, 1337, 1292, 1256, 1160. H NMR
carried out on a Philips X’pert diffractometer with mono- (400 MHz, DMSO-d6): δ (ppm)ꢀ=ꢀ5.42 (s, 1H, CH), 7.23 (s,
chromatized CuKα radiation (λꢀ=ꢀ1.5406 Å). The morphol- 2H, NH2), 7.38 (d, Jꢀ=ꢀ8.0 Hz, 2H, Ar-H), 7.42 (d, Jꢀ=ꢀ8.0 Hz,
ogy of the products was visualized by SEM (MIRA3). DLS 2H, Ar-H), 7.83–8.08 (m, 4H, Ar-H), 8.12–8.15 (m, 1H, Ar-H),
was accomplished with a Malvern instrument (Malvern 8.17–8.22 (m, 1H, Ar-H), 8.42 (d, 1H, Jꢀ=ꢀ7.6 Hz, Ar-H), 9.17
Zetasizer). Magnetic properties of the magnetite nano- (d, 1H, Jꢀ=ꢀ7.2 Hz, Ar-H). 13C NMR (100 MHz, DMSO-d6: δ
particles were measured using a VSM (Meghnatis Daghigh (ppm)ꢀ=ꢀ37.3, 57.9, 113.8, 115.3, 118.3, 122.1, 124.3, 125.5,
Kavir Co., Kashan Kavir, Iran) at room temperature.
126.3, 127.8, 128.2, 128.6, 129.0, 129.2, 130.1, 130.3, 130.6,
130.8, 139.9, 140.1, 140.7, 141.4, 145.6, 146.5, 159.5. Analysis
for C27H15N5O: calcd. C76.22, H 3.55, N 16.46; found C 76.18,
H 3.43, N 16.35.
3.1 Preparation of nano-Fe3O4@chitosan
Our purpose was to synthesize a magnetic nanocatalyst
with a mass ratio of chitosan to nano-Fe3O4 (g/g)ꢀ=ꢀ2:1. In 3.2.2 3-Amino-1-(4-methoxy-phenyl)-1H-benzo[a]
order to achieve this, 1 g of chitosan and 0.43 g (2.1 mmol)
of FeCl2·4H2O and 1.17 g of FeCl3·6 H2O (2ꢀ×ꢀ2.1 mmol) were
pyrano[2,3-c]phenazine-2-carbonitrile (5m)
placed in a 100-mL round bottom flask, and 40 mL of Yellow solid. m.p. 268–269°C. IR (KBr): ν (cm−1)ꢀ=ꢀ3315,
0.4 m HCl was added to them under stirring at room tem- 3174, 3048, 2829, 2180, 1652, 1620, 1585, 1487, 1465, 1450,
perature. The mixture was stirred until complete dissolu- 1394, 1384, 1350, 1330, 1293, 1258, 1163. 1H NMR (400 MHz,
tion. Then 400 mL of NH3 (0.7 m) was added to the mixture DMSO-d6): δ (ppm)ꢀ=ꢀ3.84 (s, 3H, OCH3), 5.83 (s, 1H, CH),
under argon gas for 20 min. The formed nanocatalyst was 6.65 (d, 2H, Jꢀ=ꢀ7.6 Hz, Ar–H), 6.90 (d, 2H, Jꢀ=ꢀ7.6 Hz, Ar–H),
filtered and washed with H2O and dried in an oven at 70°C. 7.35 (s, 2H, NH2), 7.85–7.93 (m, 4H, Ar-H), 7.98–8.40 (m, 3H),
13
9.10 (d, 1H, Jꢀ=ꢀ8.0 Hz, Ar-H). C NMR (100 MHz, DMSO-
d6): δ (ppm)ꢀ=ꢀ37.5, 55.2, 58.3, 112.1, 115.2, 115.5, 120.2, 120.4,
3.2 General procedure for the synthesis of
benzopyranophenazines
121.4, 125.2, 127.0, 129.1, 129.3, 129.7, 130.1, 130.5, 130.8,
130.9, 140.3, 141.2, 141.9, 146.4, 147.3, 159.4, 160.5. Analysis
for C27H18N4O2: calcd. C 75.34, H 4.21, N 13.02; found C 75.25,
Nano-Fe3O4@chitosan (10 mg) was added to a mixture H 4.15, N 12.93.
of hydroxynaphthoquinone (1 mmol) and o-phenylen-
ediamine (1 mmol) in EtOH (5 mL) at room temperature
under stirring. After 5 min, the aldehydes (1 mmol) and 4 Conclusion
malononitrile (1.5 mmol) were added and the mixture was
refluxed for the appropriate amount of time (Table 2). The We have developed a straightforward and efficient
progress of the reaction was monitored by thin-layer chro- method for the preparation of benzopyranophenazines
matography (TLC; EtOAc/n-hexane 2:1), and the mixture using nano-Fe3O4@chitosan as an efficient, heteroge-
was cooled to room temperature. After completion of the neous, acidic, solid catalyst. The method offers several
reaction, the nanocatalyst was easily separated using an advantages including the rapid synthesis of potentially
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738ꢀ ꢀJ. Safaei-Ghomi et al.: Synthesis of benzopyranophenazines
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The FT-IR spectrum of nano-Fe3O4@chitosan (Fig. S1) as
well as copies of the FT-IR and 1H NMR spectra of selected
compounds 5 are given as supplementary material avail-
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