Zirconium@guanine@MCM-41 nanoparticles: An efficient heterogeneous mesoporous nanocatalyst for one-pot, multi-component tandem Knoevenagel condensation–Michael addition–cyclization Reactions

Article abstract of DOI:10.1002/aoc.5704

MCM-41-supported nanoscale guanine bonded with Zr (IV) was prepared using sol–gel method and characterized by FT-IR, Raman, XRD, BET, TGA, EDX, ICP, AAS, X-Ray mapping, SEM and TEM techniques. This compound was employed as an efficient, chemoselectivity a

Full text of DOI:10.1002/aoc.5704

Received: 31 October 2019
DOI: 10.1002/aoc.5704
Revised: 4 March 2020
Accepted: 8 March 2020
F U L L P A P E R
Zirconium@guanine@MCM-41 nanoparticles: An efficient
heterogeneous mesoporous nanocatalyst for one-pot, multi-
component tandem Knoevenagel condensation–Michael
addition–cyclization Reactions
Mohsen Nikoorazm
| Masoud Mohammadi
| Maryam Khanmoradi
Department of Chemistry, Faculty of
Science, Ilam University, Ilam, Iran
MCM-41-supported nanoscale guanine bonded with Zr (IV) was prepared
using sol–gel method and characterized by FT-IR, Raman, XRD, BET, TGA,
EDX, ICP, AAS, X-Ray mapping, SEM and TEM techniques. This compound
was employed as an efficient, chemoselectivity and green heterogeneous
catalyst in order to prepare a series of benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine and spiro[benzo[a]benzo[6,7]chromeno[2,3-c] phenazine] deriva-
tives by one-pot, four-component domino reaction from the 2-hydroxy-1,-
4-naphthoquinone, benzene-1,2-diamines, 2-hydroxy-1,4-naphthoquinone and
Correspondence
Mohsen Nikoorazm, Department of
Chemistry, Faculty of Science, Ilam
University, Ilam, Iran.
Email: e_nikoorazm@yahoo.com
Funding information
Ilam University; Iran National Science
Foundation
ꢀ
carbonyl compounds in PEG, at 100 C and, also, Bis (pyrazolyl) methane
derivatives using aldehydes and 3-Methyl-1-phenyl-5-pyrazolone in ethanol
under reflux condition. Results indicated that all products were synthesized in
short reaction times and high yields in the ranges 78–99%. The Zr-guanine-
MCM-41 can be recycled four runs without any significant loss of its catalytic
activity. In addition, the stability of the catalyst was confirmed by metal
leaching, heterogeneity tests, SEM and FT-IR techniques.
K E Y W O R D S
benzo[a]benzo[6,7]chromeno[2,3-c]phenazines, Bis (pyrazolyl)methanes, Spiro[benzo[a]
benzo[6,7]chromeno[2,3-c] phenazine], Tandem Knoevenagel condensation–Michael addition–
cyclization, Zr-guanine-MCM-41
1 | INTRODUCTION
(MCRs) in combinatorial chemistry are highly regarded
in nature; as they are essential to life and minimize
Discovery of new chemical reactions which are able to
produce useful chemical products has been the subject
of much interest.[1–3] Traditional methods are
unsustainable to perform chemical synthesis from eco-
nomic and environmental points of view.[4,5] Multi-
component reactions (MCRs) have come out as a pow-
erful tool in modern synthetic organic chemistry and
the waste production, time, cost and labor.[10,11] These
reactions have become a strong synthetic methodology
for the rapid preparation of small-molecule libraries
that reduce the number of synthetic steps and can be
obtained in one pot with much fewer steps.[8,12–14] The
major advantages of multicomponent reactions are
one-pot synthesis, high atom economy and time-saving
without isolation of intermediates or generating by-
products.[14–19] In particular, Phenazines and chro-
menes have attracted increasing attention in drug
provide
a
solution to overcome the mentioned
disadvantages.[4,6–9] In this respect, it is significant to
note that the benefits of multi-component reactions
Appl Organomet Chem. 2020;e5704.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.5704

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NIKOORAZM ET AL.
discovery and medicinal chemistry which can be syn-
thesized by a one-pot two-steps procedure.[8,18–20] These
compounds have been reported as biological active spe-
phenazine and bis (pyrazolyl)methane derivatives via
the Knoevenagel condensation–Michael addition–
cyclization reactions of 2-hydroxy-1,4-naphthoquinone
(lawsone), benzene-1,2-diamine and carbonyl com-
pounds (aldehydes and ninhydrin and isatin as cyclic
ketones) and the Knoevenagel condensation–Michael
addition reactions of 3-Methyl-1-phenyl-5-pyrazolone
with aryl aldehydes. The main advantages of this syn-
thesis include simple workup, reusability of the cata-
lyst, easy recovery and fewer reaction steps without the
intermediates separation.
cies
which
involve
anticancer,
antifungal,
antiplasmodial, antimalarial, antibacterial, cancer che-
mopreventive, antiparasitic and antichagasagen activi-
ties.[19] Among the wide range of N-containing
heterocyclic compounds, the pyrazolones and bis-
pyrazolones were paid much attention for their various
biological activities, such as antitumor,[21] anti-
inflammatory,[22]
pesticides,[14]
antifilarial
selective
agents,[23]
COX-2
dyes,[24]
inhibitory,[25]
antibacterial[23] and fungicides.[15] Moreover, these
compounds were used as extracting agents for some
metal ions in analytical chemistry[26] and ligands in
coordination chemistry.[27]
2 | EXPERIMENTAL SECTION
2.1 | Materials
The development of new plans for catalytic stability
in reaction medium that minimizes the cost and toxic-
ity can result in important environmental and eco-
nomic interests.[4,28–32] The regular cylindrical
arrangement structure, heterogeneity and reusability of
MCM-41 (Mobil Composition of Matter No. 41) meso-
porous silica make it a great candidate as a heteroge-
neous solid catalyst, which can be functionalized by
reacting with organosilanes groups and the substitution
of metal complexes inside the mesoporous silica
framework.[33–35] MCM-41 with a hexagonal arrange-
ment and diameter of 2 nm to 10 nm and, also, owing
to a uniform open form structure, low cytotoxicity, low
cost, simple synthesis, biocompatibility, excellent stabil-
ity, uniform catalytic sites and large pore volume and
surface area can act as an excellent support which is
able to increase the catalytic activity.[36,37] Transitional
metal complexes have been greatly studied in the cata-
lyst field due to the solubility properties of transition
metal complexes in the aqueous phase and also in
drug discovery in accordance to their cytotoxic, antimi-
crobial and antitumor properties.[9,11,32,38] There is not
much information on zirconium (IV) complexes in the
synthesis of benzo[a]benzo[6,7]chromeno[2,3-c]phena-
zine derivatives. Therefore, in this work, the guanine
complex of zirconium ions supported on modified
MCM-41 nanoparticles has been synthesized and char-
acterized by FT-IR, Raman, XRD, BET, TGA, EDX,
ICP, AAS, X-Ray mapping, SEM and TEM techniques.
According to the structure of guanine, in several
models of metal complexes, the metal ions bind to the
guanine ring through carbonyl oxygen O (6) and/or
imidazolyl nitrogen, N (7) and/or N (1) position of
guanine).[38] Afterwards, they are used as an efficient
catalyst for the clean and facile one-pot domino syn-
Tetraethylorthosilicate (TEOS, 98%), cationic surfactant
cetyltrimethylammonium bromide (CTAB, 98%), guanine
(2-amino-1H-purin-6(9H)-one), Zr (IV) oxide chloride
(ZrO Cl2.8H2O), aromatic aldehydes, cyclic ketones,
2-hydroxy-1,4-naphthoquinone, benzene-1,2-diamines,
3-chloropropyl-triethoxysilane, solvents and other
reagents, that were employed in this work, were pur-
chased from Aldrich, Merck or Fluka chemical compa-
nies and used as received.
2.2 | Characterization techniques
Powder X-ray diffraction (PXRD) of Zr-guanine-MCM-
41 catalyst was recorded using a Holland Philips dif-
fractometer (Cu Kα, radiation at 40 kV and 30 mA).
The thermogravimetric analysis (TGA) curve was
obtained between 30 and 900 ꢀC in air at a heating
−1
ꢀ
rate of 10 C min using Shimadzu DTG-60 automatic
thermal analyzer. The infrared spectra (IR) of the sam-
ples were recorded in KBr disks using a NICOLET
impact 410 spectrometer. The particle size and mor-
phology were investigated by a JEOLJEM-2010 scan-
ning electron microscopy (SEM), on an accelerating
voltage of 200 kV. The transmission electron micros-
copy (TEM) images were recorded by a Philips CM10
microscope with operating voltage at 200 kV. The
products' component measurement was carried out by
the energy dispersive spectroscopy (EDX) using a
Tacnai TF20 high-resolution transmission electron
microscope. The Raman spectrum of the catalyst was
taken with a Jobin Yvon U1000 spectrometer. The con-
tent of Zr was measured by inductively coupled
plasma-optical emission spectrometry (ICP-OES) and
thesis
phenazine],
of
spiro[benzo[a]benzo[6,7]chromeno[2,3-c]
benzo[a]benzo[6,7]chromeno[2,3-c]
AAS analysis in
Germany device.
a
NovAA 400p Analyticaljena-

NIKOORAZM ET AL.
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2.3 | Synthesis of MCM-41 modified with
(3-chloropropyl)-triethoxysilane
The mesoporous silica MCM-41 nanoparticles were pre-
pared by the coprecipitation technique as it was previ-
ously reported.[39] In order to produce the pure siliceous
MCM-41, cetyltrimethylammonium bromide (CTAB)
(1 g), which can be regarded as a cationic surfactant, was
added into a basic aqueous solution (3.5 ml of NaOH
(2 M) in 480 ml of deionized water. The chemicals were
stirred vigorously and heated up to 80 ꢀC until the
solution became uniform and, then,
5
ml
tetraethylorthosilicate (TEOS) was added dropwise to this
solution. Afterwards, the resulting solution was refluxed
for another 2 hr. After the reaction time, the heating was
stopped and the suspension was cooled down to room
temperature. Then, the solid particles were collected by
filtration, washed with ꢀdeionized water and dried over-
night in an oven at 70 C. Ultimately, the dried precipi-
SCHEME 1 Synthesis of Zr-guanine-MCM-41 nanostructure
2.6 | General procedure for the synthesis
of spiro[benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine] and benzo[a]benzo[6,7]
chromeno[2,3-c]phenazine derivatives
ꢀ
tate was calcined from room temperature to 550 C for
ꢀ
5 hr with the heating rate of 2 C/min. Afterwards, in
This One-pot, four-component, two-steps reaction was
applied according to the below procedure: first, the
2-hydroxy-1,4-naphthoquinone (1 mmol), benzene-1,-
2-diamines (1 mmol) and Zr- guanine-MCM-41
(0.30 mol%) were placed into a round bottom flask con-
taining 3 ml PEG-400 and, then, the obtained chemicals
order to synthesize CPTMS@MCM-41 in accordance to
the previously reported procedure,[40] a mixture of MCM-
41 and 3-chloropropyl-triethoxysilane (nPrCl), in a molar
ratio 1:1, was dissolved in n-hexane and refluxed for
20 hr under a nitrogen atmosphere. After the reaction
time, the precipitate was separated by simple filtration,
subsequently washed with n-hexane and, finally, dried
at 50 ꢀC.
ꢀ
were stirred and heated at 100 C until the compound A
is formed (10 min) (scheme 3). In the second step, the
reaction was followed by the addition of 2-hydroxy-1,-
4-naphthoquinone (1 mmol) and carbonyl compounds
(1 mmol) (aldehyde and cyclic ketones (ninhydrin and
isatin)) and, then, the resultant was heated further under
the same conditions for the times exhibited in Table 3.
The progress of the reaction was determined by TLC.
After the completion of the reaction, the resulting mix-
ture was decanted in water and ethyl acetate. The catalyst
was filtered, and the product was collected by evapora-
tion of ethyl acetate. For more purification, recrystalliza-
tion of the generated solid has been applied from hot
ethanol to the obtained pure product.
2.4 | Synthesis of guanine functionalized
MCM-41 mesoporous material (guanine-
MCM-41)
Firstly, 0.5 g of CPTMS@MCM-41 and 2-amino-1H-
purin-6(9H)-one (guanine) (1.2 mmol, 0.181 g), in 20 ml
toluene were refluxed under nitrogen atmosphere for
24 hr. The obtained white precipitate was filtered and
washed with ethanol and, finally, the solvent was
removed under vacuum.
2.7 | General pathway for the synthesis
of 4,40-(arylmethylene)-bis-(3-methyl-
1-phenyl-1H-pyrazol-5-ols)
2.5 | Synthesis of heterogeneous catalyst
(Zr-guanine-MCM-41)
In this step, guanine-MCM-41 (0.25 g) was mixed with Zr
(IV) oxide chloride (ZrO Cl2.8H2O) (0.5 mmol, 0.161 g) in
ethanol (20 ml) and refluxed for 20 hr. After the comple-
tion of the reaction, the chemicals were collected by fil-
tration, intensively washed by ethanol and, finally, dried
A mixture of aldehyde (1 mmol), 3-Methyl-1-phenyl-
5-pyrazolone (2 mmol) and Zr-gu-MCM-41 (0.25 mol%)
was dissolved in 3 ml of EtOH. Afterwards,ꢀthe flask was
sealed and stirred at reflux conditions (80 C). The pro-
gress of the reaction was monitored by TLC (n-hexa-
ne/ethyl acetate: 4/1). After completion of the reaction,
(the mixture was cooled down to room temperature,
ꢀ
at 50 C in order to give the Zr-guanine-MCM-41 com-
plex (Scheme 1).

4 of 20
NIKOORAZM ET AL.
filtered and, then, washed with hot EtOH to separate the
catalyst from other materials (the reaction mixture was
soluble in hot EtOH and the solid catalyst was insoluble).
Finally, the solvent removal was carried out and for fur-
ther purification to yield pure products, the crude prod-
uct was recrystallized by ethanol.
reaction of guanine-MCM-41with Zr (IV) oxide chloride
(Scheme 1).
3.2 | Catalyst characterizations
The as-prepared Zr-guanine-MCM-41catalyst was charac-
terized using FT-IR, Raman, XRD, BET, TGA, EDX, ICP,
AAS, X-Ray mapping, SEM and TEM techniques.
3 | RESULTS AND DISCUSSION
3.1 | Catalyst preparation
The selected vibrational frequencies for MCM-41,
nPrCl-MCM-41, guanine-MCM-41 ligand and Zr-gua-
nine-MCM-41 complex are prepared by FT-IR spectros-
copy as presented in Figure 1. The observation peaks at
1059, 962 cm−1 and 452 cm−1 are corresponding to the
asymmetric stretching and the symmetric stretching and
bending Si-O–Si vibrations respectively indicate the syn-
thesis of MCM-41 (Figure 1a). The FT-IR spectrum of the
modified MCM-41 (nPrCl-MCM-41) exhibits a broad
band at 3442 cm−1 duo to the hydrogen-bonding silanol
groups and the adsorbed water. Figure 1b confirmed that
the C–H stretching of CH2 vibrations was appeared at
about 2924 cm−1. In Figure 1c, the absence of this charac-
teristic band of C − H vibration and the presence of
In this research, Zr-guanine complex anchored onto the
MCM-41 mesoporous support (Zr-guanine-MCM-41) has
been introduced as
a
reusable zirconium based
nanocatalyst. Initially, the MCM-41 nanoparticles have
been easily prepared in water by the coprecipitation tech-
nique. Afterwards, it was modified using the immobiliza-
tion of nPrCl and, then, 2-amino-1H-purin-6(9H)-one
(guanine) supported into MCM-41 mesoporous (Zr-gua-
nine-MCM-41as a green ligand was grafted onto the mod-
ified MCM-41 mesoporous support in green conditions.
Finally, the Zr-guanine complex was synthesized by the
FIGURE 1 The FT-IR spectra for pure
MCM-41(a), nPrCl-MCM-41(b), guanine-MCM-
41 (c) and Zr-guanine-MCM-41 (d)

NIKOORAZM ET AL.
5 of 20
signals at 1588 cm−1 (C=O) and 1673 cm−1 (C=N)
emphasize the presence of carboxyl and imine functional
groups of guanine (2-amino-1H-purin-6(9H)-one) ring
and, also, the successful removal of CTAB. The FT-IR
spectrum of the metal complex in Figure 1d indicates the
coordination of the metal to the guanine-MCM-41. The
Zr-guanine-MCM-41 complex showed the band at
3432 cm−1 while, in guanine-MCM-41, the mentioned
band appeared at 3449 cm−1. This chemical shift is attrib-
uted to the formation of zirconium complex.
Raman spectrum of Zr-guanine-MCM-41 is presented
in Figure 9. The band at around 879 cm−1 which is the
characteristic for the fourfold coordinated zirconium in
silicate structures also appears in the infrared spectrum
of Zr-guanine-MCM-41 at 877 cm−1 (Figure 1d) but not
in the IR (Figure 1c) or raman spectrum of MCM-41 sam-
ple.[44] There is a couple of wide and medium peaks, indi-
cating the stretching vibration of the aliphatic carbon
chains between 600 to 1300 cm−1, which comes from the
moieties of 3-amino propyl three ethoxy silane (3-APTES)
on the surface of MCM-41. Besides, the appearance peak
at around 560 cm−1 that is attributed to (Si-O-Si) shows
that 3-APTES has been successfully functionalized on the
MCM-41. The medium bending vibration peak of –CH2
FIGURE 3 XRD pattern of Zr-guanine-MCM-41
peaks corresponding to d100, d110 and, also, the decrease
in the intensity of the peak at d100 which can be regarded
as a strong evidence reveals that the well-grafting of zir-
conium complex into MCM-41 channels was occurred.
For further study, N2 adsorption–desorption of Zr-
guanine-MCM-41 was performed as the obtained infor-
mation is shown in Table 1. The BET curves that are
shown in Figure 4 indicate that the typical Type IV iso-
therms are related to the characteristics of mesoporous
materials with highly uniform size distributions.
According to the Table 1, we can observe that BET sur-
face area, pore volume and pore diameter of Zr-guanine-
MCM-41 are less than the MCM-41 calculated in the pre-
vious works.[49] These observations indicate that the Zr
complex has been successfully immobilized inside the
pore channels. The values of wall thickness of Zr-
function is from 1400–1470 cm−1 [44]
These observations
.
confirm the functionalization of the catalyst.
Figure 3 shows the low angle powder X-ray diffrac-
tion patterns of the Zr-guanine-MCM-41. As reported in
our previous works,[45–48] MCM-41 phase was identified
from the XRD patterns by the three characteristic peaks
related to the strong (100), smaller (110) and (200) reflec-
tions which confirm the hexagonal pore arrangement of
MCM-41. According to Figure 2,3, in the XRD patterns of
the Zr-guanine-MCM-41, there were no well-resolved
FIGURE 2 Raman spectra of Zr-guanine-MCM-41

6 of 20
NIKOORAZM ET AL.
TABLE 1
Surface properties of Zr-guanine-MCM-41
BET (m2/g)
Sample
S
Pore diam. (nm)
Pore vol. (cm3/g)
Wall thickness
MCM-41 [46]
Zr-guanine-MCM-41
1372.275
332.66
2.45
1.29
1.521
0.467
0.5
1.11
weight losses are also observed. The weight loss was
appeared in the temperature range of 200–350 ꢀC
(10.42%) which is related to the decomposition of organic
moieties.ꢀ Moreover, the major weight loss between
400–650 C is chiefly associated with the decomposition
of silanol groups and the organically modified
framework.[5,9,50]
Energy dispersive X-ray spectroscopy (EDX) analysis
of Zr-guanine-MCM-41 is carried out to indicate the
adsorption of zirconium on the surface of MCM-41
(Figure 6). In EDX image, the peaks associated with Zr
(1.84%), Si (24.48%), O (50.14%), C (6.56%) and N
(16.98%) can be observed. As expected, the amount of
nitrogen is a quarter than the amount of zirconium,
which is in good agreement with the structure of Zr-gua-
nine-MCM-41 in Scheme 1.
X-Ray map analysis was studied in order to explore
the dispersion of all elements of the catalyst structure.
The results shown in Figure 7 illustrate the good disper-
sion of all the elements on the surface of Zr-guanine-
MCM-41. In this sense, the results clearly confirmed the
results of EDS analysis.
FIGURE 4 Adsorption/Desorption isotherm Zr-guanine-
MCM-41
guanine-MCM-41, calculated by the below equation, has
been illustrated in Table 1.
Also, the amount of zirconium ions which was
obtained by ICP analysis was found to be
1.051 × 10−3 mol g−1 which is in good agreement with
AAS analysis illustrating 1.048 × 10−3 mol g−1of zirco-
nium in the Zr-guanine-MCM-41.
The Images on the scanning electron microscopy
(SEM) in Figure 8 showed the spherical particle morphol-
ogy with small and uniform nanoparticles and without
impurities for Zr-guanine-MCM-41 sample.
À
Á
Wall thickness : 2d100= √3 −DBJH
The thermal stability of Zr-guanine-MCM-41 was
studied by thermal gravimetric analysis (TGA) (Figure 5).
Zr-guanine-MCM-41 exhibits a one-step weight loss
below 100 ꢀC (~4%) due to the loss of the adsorbed water
ꢀ
and the organic solvent. But, at above 100 C, two other
FIGURE 5 TGA thermograms of Zr-
guanine-MCM-41

NIKOORAZM ET AL.
7 of 20
reactions in order to synthesize benzo[a]benzo[6,7]chro-
meno[2,3-c]phenazines,spiro[benzo[a]benzo[6,7]
chromeno [2,3-c] phenazine], and Bis (pyrazolyl)methane
derivatives using Zr-guanine-MCM-41 as a heterogeneous
and efficient catalyst.
Initially, the catalytic properties of Zr-guanine-MCM-
41 were examined in the Synthesis of benzo[a]benzo[6,7]
chromeno[2,3-c]phenazines,spiro[benzo[a]benzo[6,7]
chromeno [2,3-c] phe-nazine].
In order to establish the feasibility of this protocol
and find the optimal conditions for the synthesis of
benzo[a]benzo[6,7]chromeno[2,3-c]phenazine
spiro[benzo[a]benzo[6,7]chromeno[2,3-c]
and
phenazine]
derivatives, we explored the reaction of 2-hydroxy-1,-
4-naphthoquinone, benzene-1,2-diamines, and
FIGURE 6 EDX spectrum of Zr-guanine-MCM-41
4-chlorobenzaldehyde as the model reaction. We also
aimed at investigating the effect of different reaction
parameters such as the amount of the catalyst, nature of
solvents and reaction temperature on the rate of the
chemical reaction and the yield of products (Scheme 2).
In order to establish the appropriate amount of the
catalyst, various loadings of the catalyst were studied
(Table 2, entries 5–12) and, consequently, 30 mol% of the
catalyst on the basis of Zr was found to be more effective
in terms of the best yield (Table 2, entry 11). In an
attempt to find the best solvent, the reaction was
explored using different solvents such as PEG-400, DMF,
EtOH and H2O (Table 2, entries 13–20). We found out
that the reaction in PEG-400 as the solvent was achieved
with 90 present yield of the desired product in 2 hr
TEM micrographs of Zr-guanine-MCM-41 sample
(Figure 9) confirm the well-ordered lattice of the hexago-
nal channels in the prepared mesoporous functionalized
catalyst. In addition, TEM images show a clear hexagonal
arrangement of pores with uniform size.
3.3 | Application of heterogeneous
catalysts
The present study investigates an efficient, facile, and
environmentally friendly procedure for one-pot tandem
Knoevenagel condensation–Michael addition–cyclization
FIGURE 7 Elemental mapping of (a) zirconium, (b) oxygen, (c) silica, (d) carbon and (e) nitrogen for Zr-guanine-MCM-41

8 of 20
NIKOORAZM ET AL.
FIGURE 8 SEM images of Zr-guanine-MCM-41
FIGURE 9 TEM images of Zr-guanine-MCM-41
SCHEME 2 Optimization of reaction conditions for the
preparation of 17-(4-chlorophenyl)-11H benzo[a]benzo[6,7]
chromeno[2,3-c]phenazine-11,16(17H)-dione

NIKOORAZM ET AL.
9 of 20
TABLE 2
Optimization of reaction conditions for the preparation of 17-(4-chlorophenyl)-11H benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine-11,16(17H)-dione
Entry
1
Catalyst
Amount of catalyst (mol%)
Solvent
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
EtOH
Temperature (ꢀC)
Time (h)
Yield (%)a
ZrO Cl2.8H2O
0.30
0.30
25 mg
25 mg
25 mg
-
100
100
100
100
100
100
100
100
100
100
100
100
100
70
2
27
2
Guanine
2
Trace
NRb
34
3
MCM-41
2
4
Zr- MCM-41
4
5
guanine-MCM-41
-
2
Trace
NRb
35
6
48
2
7
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
0.05
0.1
8
2
47
9
0.15
0.20
0.25
0.30
0.35
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
0.30
2
58
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
2
67
2
83
2
90
2
90
5
63
EtOH
reflux
reflux
100
100
100
reflux
reflux
110
100
100
100
100
5
76
H2O
2
b
DMF
10
4
54
DMSO
65
solvent-free
Dioxane
acetonitrile
PEG-400
PEG-400
PEG-400
PEG-400
PEG-400
6
58
18
12
2
trace
67
90
2
90
2
80
2
90
24
Trace
aIsolated yield.
bNo reaction.
(Table 2, entry 11). No product was formed in the
absence of the catalyst for 48 hr (Table 2, entry 5). There-
fore, in order to find the best temperature, we investi-
gated the reaction efficiency in various temperatures.
Besides, it was noted that the temperature played an
important role on the outcome of the reaction in the syn-
thesis of 17-(4-chlorophenyl)-11H-benzo[a]benzo[6,7]
chromeno[2,3-c]phenazine-11,16(17H)-dione. As a result,
100 ꢀC was selected as the best temperature for this reac-
tion (Table 2, entry 5).
After optimization of the reaction conditions, the
scope of the catalyst was further explored and various
aromatic aldehydes bearing electron-donating and
electron-withdrawing substituents and isatin or ninhy-
drin as cyclic ketones were studied for One-pot, four-
component domino synthesis of several benzo[a]
benzo[6,7]chromeno[2,3-c]phenazine (Table 3, entries
1–10) and spiro[benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine] (Table 3, entries 11, 12) derivatives using a
complex of Zr with 2-amino-1H-purin-6(9H)-one ligand
supported into MCM-41 mesoporous. As it can be
observed in Table 3, all aldehydes (containing electron-
withdrawing and electron-donating groups) produced the
desired derivative with good yields (Table 3). However, it
is worth mentioning that in a fixed time interval, the
aldehydes with electron-withdrawing groups show more
reactivity than the aldehydes with electron-donating
groups.
The mechanism for the synthesis of spiro[benzo[a]
benzo[6,7]chromeno[2,3-c] phenazine] and benzo[a]
benzo[6,7]chromeno[2,3-c]phenazine derivatives is pro-
posed in Scheme 3. According to this mechanism, after

10 of 20
NIKOORAZM ET AL.
TABLE 3
One-pot multi-component domino synthesis of benzo[a]benzo[6,7]chromeno[2,3-c]phenazine (entries 1–10) and
spiro[benzo[a]benzo[6,7]chromeno[2,3-c] phenazine] (entries 11, 12) derivatives using 25 mg Zr-guanine-MCM-41 as catalyst in PEG-400 at
100 ꢀC for 2 hr
M.p (ꢀC)
Entry
Product
Yield (%)a
Measured
Reported [Ref]
1
87
357–360[15]
359–361[41]
2
3
4
5
6
90
88
85
90
88
321–323
322–324[42]
330–332[41]
301–332[42]
270–272[42]
270–273[42]
331–333[15]
300–302[15]
274–275[15]
369–371

NIKOORAZM ET AL.
11 of 20
TABLE 3 (Continued)
M.p (ꢀC)
Entry
Product
Yield (%)a
Measured
Reported [Ref]
7
78
292–296
293–295[42]
8
92
332–33415
330–333[42]
9
89
90
92
341–343[15]
319–320[15]
289–291
340–342[42]
320–321[43]
289–291[42]
10
11
(Continues)

12 of 20
NIKOORAZM ET AL.
TABLE 3 (Continued)
M.p (ꢀC)
Entry
Product
Yield (%)a
Measured
Reported [Ref]
12
88
298–299[15]
297–299[43]
13
82
209–210[15]
210[43]
aIsolated yield.
tautomerization
of
4-hydroxy-1,2-naphthoquinone
to optimize the reaction conditions. Then, the effect of
various parameters were studied; including, the amount
of the catalyst, solvent and temperature on the reaction
efficiency (Table 3). Initially, the effect of different
amounts of the catalyst on the outcome of reaction was
investigated. Among the various catalyst loadings
(e.g., 0.05, 0. 1, 0.15, 0.20, 0.25 and 0.30 mol%), 0.25 mol%
of the catalyst on the basis of Zr was selected as the most
effective amount (Table 4, entry 6). Meanwhile, in the
absence of the catalyst, the reaction didn't proceed at all
even after 48 hr (Table 4, entry 5). Then, the influence of
the solvent on the outcome of the reaction was studied.
The obtained results revealed that ethanol is the most
effective solvent for this type of domino reaction. Subse-
quently, the effect of temperature was examined, the
results revealed that the highest yield of the product was
obtained at 80 ꢀC under reflux conditions. Eventually,
(lawsone), the Schiff base reaction between 2-hydroxy-1,-
4-naphthoquinone (1) and the benzene 1,2-diamine (2) in
the presence of Zr-guanine-MCM-41 was performed in
order to form the corresponding quinoxalinone
A. Knoevenagel condensation of carbonyl groups of alde-
hydes with 4-hydroxy-1,2-naphthoquinone forming the
olefin B. Finally, the Michael addition of the compound
A with the compound B in the presence of the catalyst
formed the intermediate C and, then, the inner molecular
ring occurred to be formed after a tautomeric proton shift
to generate spiro[benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine] and benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine derivatives.[5]
In the next part of this research project, the catalytic
activity of Zr-guanine-MCM-41 for the synthesis of 4,40-
(arylmethylene)bis(3-methyl-1H-pyrazol-5-ols) was inves-
tigated. For this purpose, the condensation of p-
Chlorobenzaldehyde (1 mmol) with, 3-Methyl-1-phenyl-
5-pyrazolone (2 mmol) was selected as a model reaction
ꢀ
EtOH at 80 C in the presence of Zr-guanine-MCM-41
(0.25 mol%) was found to be the best choice for the men-
tioned model reaction.

NIKOORAZM ET AL.
13 of 20
SCHEME 3 One-pot, domino,
multicomponent synthesis of benzo[a]
benzo[6,7]chromeno[2,3-c]phenazine (b) and
spiro[benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine] (c) derivatives in the presence of
Zr-guanine-MCM-41
SCHEME 4 Proposed mechanism for the
synthesis of benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine(E) and spiro[benzo[a]benzo[6,7]
chromeno[2,3-c] phenazine] (D) derivatives
SCHEME 5 Optimization of reaction conditions for the
synthesis of 4,40-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-
pyrazol-5-ols)
SCHEME 6 One-pot, domino,
multicomponent synthesis of 4,40-(arylmethylene)-
bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols) in the
presence of Zr-guanine-MCM-41

14 of 20
NIKOORAZM ET AL.
TABLE 4
Screening of the reaction parameters for the synthesis of 4,40-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols)
Entry
1
Catalyst
Amount of Catalyst (mol%)
Solvent
EtOH
Temperature (ꢀC)
Time (min)
48 h
48 h
48 h
2 h
48 h
48 h
15
Yield (%)a
Trace
NRb
NRb
63
NRb
NRb
39
ZrO Cl2.8H2O
0.25
0.25
25 mg
25 mg
25 mg
-
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
80
2
guanine
EtOH
3
MCM-41
EtOH
4
Zr-MCM-41
EtOH
5
guanine-MCM-41
-
EtOH
6
EtOH
7
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
Zr-guanine-MCM-41
0.05
0.10
0.15
0.20
0.25
0.30
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
EtOH
8
EtOH
15
67
9
EtOH
15
83
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
EtOH
15
91
EtOH
15
98
EtOH
15
98
Acetonitrile
PEG-400
acetone
n-Hexane
DMF
15
83
80
15
80
Reflux
Reflux
80
15
53
15
Trace
63
15
DMSO
Dioxane
H2O
80
15
72
Reflux
80
15
38
15
63
solvent-free
acetonitrile
acetonitrile
EtOH
80
15
Trace
10
25
15
70
15
75
NRb
25
15
EtOH
40
15
37
EtOH
50
15
59
EtOH
60
15
79
EtOH
65
15
87
EtOH
70
15
91
aIsolated yield.
bNo reaction.
In order to investigate the scope and generality of this
procedure, different electron-withdrawing or electron-
donating groups, such as OCH3, NO2, and CH3, were
selected to react 3-Methyl-1-phenyl-5-pyrazolone under
the optimized reaction conditions. The results are sum-
marized in Table 5. The experimental results show that
various aromatic aldehydes having both electron-
withdrawing and electron-donating groups (such as Cl,
Br, OH, OCH3, NO2, and CH3) produced their
corresponding derivatives in good to excellent yields.
However, it is worth mentioning that the reaction time of
the aryl aldehydes with electron-donating groups on the
aromatic ring was longer than aryl aldehydes with
electron-withdrawing groups. In order to show the
chemoselectivity of this new catalytic system, the reac-
tion of terephthaldehyde was also investigated in which
the NMR investigations show that, both of the aldehyde
Substituents on aromatic ring showed good reactivity and
the corresponding 40,400,400‘-(1,4-Phenylenebis (met-
hanetriyl))tetrakis (3-methyl-1-phenyl-1H-pyrazol-5-ol)
product was obtained in 83% yield (Tables 5 entry 10).
The suggested reaction mechanism for the described
combination via tandem Knoevenagel–Michael reaction
in the presence of Zr-guanine-MCM-41 nanocatalyst has
been depicted in Scheme 7 based on the previously
reported reaction pathway.[51] Initially, intermediate III
formed from the Knoevenagel condensation of aldehyde
and Pyrazolone in the presence of Zr-guanine-MCM-41

NIKOORAZM ET AL.
15 of 20
TABLE 5
Preparation of 4,40-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-5-ols) derivatives catalyzed by Zr-guanine-MCM-41
M.P. (ꢀC)
Entry
Product
Time (min)
Yield (%)a
Measured
Reported [Ref]
1
20
99
170–173
170–172[20]
2
3
1
15
10
98
98
212–214
198–200
213–215[11]
198–200[19]
4
25
97
201–203
202–204[20]
5
30
90
173–175
173–175[11]
6
25
88
153–155
153–155[11]
7
45
95
195–197
194–196[11]
(Continues)

16 of 20
NIKOORAZM ET AL.
TABLE 5 (Continued)
M.P. (ꢀC)
Measured
Entry
Product
Time (min)
Yield (%)a
Reported [Ref]
8
10
92
224–226
225–227[19]
9
15
91
150–152
151–153[12]
10
60
83
214–216
214–216[19]
aIsolated yield.
nanocatalyst. Sequentially, a possible intermediate IV
was formed via Michael addition of the second mol of
Pyrazolone with intermediate III to give bis (pyrazolyl)
methanes.
11H-benzo[a]benzo[6,7]chromeno[2,3-c]phenazine-
11,16(17H)-dione and 4,40-((4-chlorophenyl)methylene)
bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) under the opti-
mized reaction conditions (the amount of the reactants
and catalyst was tripled). After completion of the reac-
tion, the chemicals were placed in a separatory funnel
and, then, separated into an organic and aqueous layer.
The catalyst was separated by simple filtration, washed
with hot EtOH and acetone to remove the residual prod-
uct and reused in the subsequent runs. This result
showed that the catalyst is robust and has fine running
cycling performance (Figure 10).
3.4 | Catalyst reusability
The reusability of the catalyst is an important benefit
especially for industrial and commercial applications.
Thus, the recovery and reusability of the nanocatalyst
were investigated in the synthesis of 17-(4-chlorophenyl)-

NIKOORAZM ET AL.
17 of 20
SCHEME 7 Proposed mechanism for the synthesis of
4,40-(arylmethylene)-bis-(3-methyl-1-phenyl-1H-pyrazol-
5-ols)
Moreover, in order to examine the stability of the cat-
alyst after the recycling, the recycled catalyst has been
characterized by SEM, TEM and FT-IR techniques. These
characterizations confirmed that the recovered catalyst is
in good agreement with the fresh catalyst. These charac-
terizations are strong evidences for the high stability of
Zr-guanine-MCM-41 after recycling.
The SEM image of the recycled catalyst is shown in
Figure 11 in which particles of the recovered catalyst
were observed between 15–20 nm with homogeneous size
and morphology. In addition, The SEM image also
showed some evidences of slight aggregation and fusing.
FT-IR spectrums of the recycled catalyst are shown in
Figure 12. The results show that a good agreement was
observed for FT-IR of the fresh Zr-guanine-MCM-41
(Figure 12a) and the recycled catalyst (Figure 12b).
Therefore, Figure 12 illustrates the good stability of Zr-
guanine-MCM-41 after recycling.
3.5 | Hot filtration test
Moreover, hot filtration test was performed in order to
prove that the metal was not leaching out from the solid
catalyst during the reactions. For this purpose, the reac-
tion of 2-hydroxy-1,4-naphthoquinone (1 mmol) and the
benzene 1,2-diamine (1 mmol) in the presence of Zr-gua-
nine-MCM-41 (25 mg) was performed in the first step
and
the
condensation
between
2-hydroxy-1,-
4-naphthoquinone (1 mmol) with 4-chlorobenzaldehyde
(1 mmol) in the second step in PEG-400 at 100 ꢀC. When
about 50% of the reaction was done, the catalyst was
FIGURE 10 Reusability of Zr-guanine-
MCM-41 nanocatalyst for the synthesis of
17-(4-chlorophenyl)-11H-benzo[a]benzo[6,7]
chromeno[2,3-c]phenazine-11,16(17H)-dione
(series 1) and 4,40-((4-chlorophenyl)methylene)
bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (series 2)
reactions

18 of 20
NIKOORAZM ET AL.
filtered off at the reaction temperature and the experi-
ment was continued without the catalyst for another half
reaction time. The observation indicated that there was
no detectable progress in the reaction.
3.6 | Leaching test
In order to consider the leaching of Zr into reaction
media, ICP-AES analysis was performed, the Zirconium
content in reaction media in the synthesis of
17-(4-chlorophenyl)-11H-benzo[a]benzo[6,7]chro-
meno[2,3-c]phenazine-11,16(17H)-dione
and
4,40-
((4-chlorophenyl)methylene)bis(3-methyl-1-phenyl-1H-
pyrazol-5-ol) was found to be 0.39 and 0.47% respectively.
The results show that the leaching of Zr into reaction
media is negligible.
3.7 | Comparison
The efficiency of this catalytic system was demonstrated
by comparing our results on the synthesis of
FIGURE 11 SEM image of recycled Zr-guanine-MCM-41
FIGURE 12 FT-IR spectrums of Zr-
guanine-MCM-41(a) and recovered Zr-guanine-
MCM-41

NIKOORAZM ET AL.
19 of 20
TABLE 6
Comparison of Zr-guanine-MCM-41for the synthesis of 17-(4-Methyl)-11H–benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine-11,16 (17H)-dione and 4,40-((4-chlorophenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) with previously reported
procedures
Entry
Substrate
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-Cl C6H4
4-Cl C6H4
4-Cl C6H4
4-Cl C6H4
Catalyst
Catalyst nature
Homogeneous
Heterogeneous
Heterogeneous
Heterogeneous
Heterogeneous
Heterogeneous
Heterogeneous
Heterogeneous
Time (min)
Yield (%)a
Ref
[46]
[47]
[15]
1
2
3
4
5
6
7
8
p-toluenesulfonic acid
Ni-Gly-isatin@boehmite
γ-Fe2O3@SiO2-SCH2CO2H
Zr-guanine-MCM-41
Na+-MMT-[pmim]HSO4
Nanocrystalline Cu–ZnO
CuFe2O4 MNPs
120
420
180
120
10
87
80
89
92
92
93
89
98
This work
[52]
90
[53]
15
[54]
Zr-guanine-MCM-41
15
This work
aIsolated yield.
17-(4-Methyl)-11H–benzo[a]benzo[6,7]chromeno[2,3-c]
phenazine-11,16 (17H)-dione (Table 6 entry 1–4) and
4,40-((4-chlorophenyl)methylene)bis(3-methyl-1-phenyl-
1H-pyrazol-5-ol) with some recent reported catalytic sys-
tems in the literatures (Table 6 entry 5–8). The summa-
rized results in Table 6 obviously show that the present
protocol provides better results in terms of the reaction
time and product yield. Besides, this catalyst is compara-
ble in terms of price, non-toxicity, stability and easy
separation.
more economic and environment friendly because of its
low Zr leaching. This recoverable catalyst, Zr (IV) oxide
chloride, has been synthesized and characterized using
TGA, XRD, BET, ICP, AAS, SEM, TEM, Raman, EDX
and FT-IR spectroscopy. Moreover, the recovery test con-
firms that the synthesized catalyst can be reused for sev-
eral times. In addition, the recovered catalyst was
characterized by SEM and FT-IR techniques.
ACKNOWLEDGMENTS
This work was supported by the Iran National Science
Foundation and research facilities of Ilam University,
Ilam, Iran.
4 | CONCLUSIONS
Finally, we have introduced an efficient Zr-guanine-
MCM-41 catalyzed, one-pot multicomponent tandem
Knoevenagel condensation–Michael addition–cyclization
reactions for the selective synthesis of benzo[a]benzo[6,7]
ORCID
Mohsen Nikoorazm https://orcid.org/0000-0002-4013-
0868
Masoud Mohammadi https://orcid.org/0000-0002-
1043-3470
chromeno[2,3-c]phenazine,
spiro[benzo[a]benzo[6,7]
chromeno[2,3-c] phenazine] and Bis (pyrazolyl)methane
derivatives (which could be of biological significance)
under green conditions. The catalyst was prepared by the
immobilization of Zr@2-amino-1H-purin-6(9H)-one
supported into MCM-41 mesoporous (Zr-guanine-MCM-
41) by covalent cross-linking. The structure of the pre-
pared Zr nanocatalyst was characterized by FT-IR,
Raman, XRD, BET, TGA, EDX, ICP, AAS, X-Ray map-
ping, SEM and TEM techniques. The product required a
minimum of time, cost, labor, and waste production and
was obtained in good to excellent yields. High-yielding of
the products in pure form was the fundamental charac-
teristic of this protocol. Operational simplicity, ease of
the catalyst recovery and its good performance under
mild reaction conditions are the other advantages of this
methodology. Furthermore, catalytic activity of Zr-gua-
nine-MCM-41catalyst was compared to the previously
reported ones. Additionally, the Zr-guanine-MCM-41 is
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