Organic–inorganic hybrid material, dichloro N,N'-(1,2-phenylene)bis(2-aminobenzamide) cobalt(II)@Al-SBA-15: an environment friendly catalyst for the synthesis of 3-benzoxazol-2-yl-chromen-2-ones

Article abstract of DOI:10.1080/00958972.2019.1591618

A new organic-inorganic hybrid material, CoCl₂N,N'-(1,2-phenylene)bis(2-aminobenzamide)@Al-SBA-15, was synthesized by modification of Al-SBA-15 with (3-chloropropyl) trimethoxysilane (CPTMS), then the ligand was covalently attached to CPTMS@Al-SBA-15 and finally addition of CoCl₂ to form the complex. The mesoporous CoCl₂NN'PhBIA@Al-SBA-15 was an efficient catalyst in the preparation of 3-benzoxazol-2-yl-chromen-2-one derivatives through reaction of different coumarin-3-carboxylates and 2-aminophenol derivatives. The nanocatalyst increased rate and facility of the aforementioned reaction and had influence in the green synthesis of different 3-benzoxazol-2-yl-2H-chromen-2-one derivatives. The nanocatalyst was characterized by N₂ adsorption–desorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Some advantages of this procedure are mild reaction condition, high yields of 3-benzoxazol-2-yl-2H-chromen-2-one, short reaction times, environmentally benign, recoverability of the catalyst and reusability without significant loss of its catalytic performance.

Full text of DOI:10.1080/00958972.2019.1591618

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
Organic–inorganic hybrid material, dichloro
N,N'-(1,2-phenylene)bis(2-aminobenzamide)
cobalt(II)@Al-SBA-15: An environment friendly
catalyst for the synthesis of 3-benzoxazol-2-yl-
chromen-2-ones
Javad Safaei Ghomi, Zeinab Akbarzadeh & Atefeh Bakhtiari
To cite this article: Javad Safaei Ghomi, Zeinab Akbarzadeh & Atefeh Bakhtiari (2019):
Organic–inorganic hybrid material, dichloro N,N'-(1,2-phenylene)bis(2-aminobenzamide)
cobalt(II)@Al-SBA-15: An environment friendly catalyst for the synthesis of 3-benzoxazol-2-yl-
chromen-2-ones, Journal of Coordination Chemistry, DOI: 10.1080/00958972.2019.1591618
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Organic–inorganic hybrid material, dichloro N,N'-(1,2-phenylene)bis(2-
aminobenzamide) cobalt(II)@Al-SBA-15: An environment friendly catalyst
for the synthesis of 3-benzoxazol-2-yl-chromen-2-ones
JAVAD SAFAEI GHOMI*, ZEINAB AKBARZADEH and ATEFEH BAKHTIARI
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, 51167, I. R. Iran
A
new
organic-inorganic
hybrid
material,
CoCl2N,N'-(1,2-phenylene)bis(2-
aminobenzamide)@Al-SBA-15, was synthesized by modification of Al-SBA-15 with
(3-chloropropyl) trimethoxysilane (CPTMS), then the ligand was covalently attached to
CPTMS@Al-SBA-15 and finally addition of CoCl2 to form the complex. The mesoporous
CoCl2NN'PhBIA@Al-SBA-15 was an efficient catalyst in the preparation of 3-benzoxazol-2-yl-
chromen-2-one derivatives through reaction of different coumarin-3-carboxylates and
2-aminophenol derivatives. The nanocatalyst increased rate and facility of the aforementioned
reaction and had influence in the green synthesis of different 3-benzoxazol-2-yl-2H-chromen-2-
one derivatives. The nanocatalyst was characterized by N2 adsorption–desorption, Fourier
transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), powder X-ray diffraction (XRD) and energy dispersive
spectroscopy (EDS). Some advantages of this procedure are mild reaction condition, high yields
of 3-benzoxazol-2-yl-2H-chromen-2-one, short reaction times, environmentally benign,
recoverability of the catalyst and reusability without significant loss of its catalytic performance.
GRAPHICAL ABSTARCT
*Corresponding author. Email: safaei@kashanu.ac.ir
1

Keywords: Al-SBA-15; Mesoporous; 3-Benzoxazol-2-yl-chromen-2-one; Reusable catalyst;
Organic-inorganic hybrid
1. Introduction
Coumarins are found extensively in numerous natural or synthetic drugs and display a wide
range of pharmaceutical and biological properties comprising of anti-tumor, anti-HIV, anti-
hypertension, anti-inflammatory and anticoagulant behavior [1-5]. Coumarins have many
applications in perfumery [6], optical brightening agents, as fluorescent indicators [7], as dyes in
laser technology [8] and as donors of dye in dye-sensitized solar cells [9-11].
3-Benzoxazol-2-yl-chromen-2-ones have important biological activities (e.g.
chemotherapy [12] and antitumor [13]) and organic fluorescent dyes [14]. Generally,
3-benzoxazol-2-yl-chromen-2-ones are synthesized by 2-aminophenols and coumarin-3-
carboxylic acids in the presence of PPA at high temperature [15, 16]. Some limitations of this
2

method are harsh conditions, low chemical yield, difficult and toxic procedures for separation of
product from reaction mixture.
Because of the significance of these compounds in many fields, especially dye-sensitized
solar cells, it is important to develop methods for the preparation of 3-benzoxazol-2-yl-chromen-
2-ones. The aim of this study is to minimize problems for the synthesis of 3-benzoxazol-2-yl-
chromen-2-ones by functionalized mesoporous silica nanocatalyst.
Ordered mesoporous silicas such as M41S, SBA-n and MSU-X discovered in the early
1990s are a promising class of materials for catalysis and separation [17, 18]. SBA-15 has
attracted attention owing to excellent mechanical and thermal stabilities, large pore sizes, high
specific surface area, uniform-sized pores and defined surface acidity [19-24]. Substituents such
as aluminium, zirconium and titanium can be incorporated into the silica framework to gain
materials for applications in catalysis and ion exchange. Among the metal-substituted
mesoporous materials, aluminium-incorporated mesoporous materials have potential in
moderating acid-catalyzed reactions for large molecules [25-27]. A number of research groups
have followed new approaches to incorporating multiple organic-inorganic functional groups
onto heterogeneous catalysts for organic reactions [28, 29]. Multifunctional organic-inorganic
hybrid catalysts include many active sites that play significant roles in chemical processes [30].
These materials show important applications in catalysis, biomedicine, drug delivery and
biotechnology [31-33].
Organic-inorganic hybrid catalysts on mesoporous materials have been applied to
accelerate organic reactions by providing high surface area, environmentally mild reaction
conditions, efficient recovery from reactions by filtration and reusability [34, 35].
In our ongoing research, CoCl2N,N'-(1,2-phenylene)bis(2-aminobenzamide)@Al-
SBA-15 (CoCl2NN'PhBIA@Al-SBA-15) was synthesized, characterized and applied as an
efficient catalyst in the preparation of 3-benzoxazol-2-yl-chromen-2-one derivatives through
condensation of different coumarin-3-carboxylates and 2-aminophenols (scheme 1). This
approach provides several advantages containing environmentally benign, moderate reaction
conditions, simple removal of the nanocatalyst by filteration, recoverability and reusability of the
nanocatalyst.
3

R2
N
O
R1
O
O
Scheme 1. Structure of 3-benzoxazol-2-yl-chromen-2-ones.
2. Experimental
2.1. Chemicals and apparatus
Ethyl coumarin-3-carboxylate was synthesized according to the procedure reported in our
previous research [36]. Other chemicals were purchased from Sigma-Aldrich and Merck
companies and were applied without additional purification. Melting points of products were
determined by means of an Electro thermal 9200. FT-IR measurements were recorded on Magna
550 apparatus using KBr plates. NMR spectra were recorded on a Bruker Avance-400 MHz
spectrometer in the presence of tetramethylsilane as internal standard. The XRD patterns were
obtained by an X-ray diffractometer (PHILIPS, PW 1510, Netherlands) using Cu-Kα radiation
(λ = 0.154056 nm) from 2θ = 0.8-10°. Microscopic morphology of the nanocatalysts were
visualized by scanning electron microscopy (SEM) using a Model FESEM (MIRA 3 TESCAN).
The particle size and structure were observed using a Philips CM10 transmission electron
microscope (TEM) operating at 30 kV. Energy-dispersive X-ray spectroscopy (EDS) of the
CoCl2NN'PhBIA@Al-SBA-15 imaged by a Sigma ZEISS, Oxford Instruments Field Emission.
The N2 adsorption/desorption analyses (BET) were performed at 120 °C using an automated gas
adsorption analyzer (BEL SORP mini II).
2.2. Preparation of 2-amino-N-{2-[(2-aminobenzoyl)amino]phenyl}benzamide
To a solution of 1,2-phenylenediamine (1 mmol, 0.108 g) in hot water (10 ml), 2 mmol of isatoic
anhydride (0.326 g) was added. The solution was stirred at 60 °C for 3 h. Heating on a water
bath was continued until CO2 gas evolution stopped. The reaction mixture was allowed to stand
overnight and the product was recrystallized from methanol to yield white NN'PhBIA. The
ligand was characterized by IR and NMR spectroscopies as follows: FT-IR (KBr): 3463 (N-H),
3352 and 3268 (NH2), 1636 (C=O), 1611 and 1577 (C=C aromatic), 1517, 1441, 1255 (C-N),
1
1160, 1031, 746 cm-1. H NMR (400 MHz, DMSO-d6): δ (ppm) 9.73 (s, 2H, NH), 7.59 (m, 4H,
4

Ar-H), 7.26 (m, 2H, Ar-H), 7.18 (t, 2H, J= 7.6 Hz, Ar-H), 6.74 (d, 2H, J= 8.4 Hz, Ar-H), 6.53 (t,
2H, J= 7.6 Hz, Ar-H), 6.44 (s, 4H, NH2).
2.3. Preparation of Al-SBA-15
Al-SBA-15 was prepared by the following procedure. In a classic procedure 2 g of pluronic P123
was dissolved in 75 ml hydrochloric acid solution (pH=1.5). The solution was stirred at 40 °C for
6 h. A second solution was made by adding 3.2 ml of tetraethylorthosilicate (TEOS) and 5 ml of
hydrochloric acid solution of pH 1.5 to 0.22 g of aluminum triisopropoxide. This suspension was
vigorously stirred in a closed flask for 1.5 h to become clear. The TEOS solution was quickly
added to the surfactant solution and stirred for 20 h at 40 °C. The resulting clear suspension was
transferred to a Teflon-lined stainless steel autoclave and heated to 100 °C for 20 h. The
recovered white solid was filtered and washed three times by demineralized water and two times
with ethanol. The sample was dried overnight at 100 °C. The template P123 was removed by
calcination for 10 h at 550 °C with a heating ramp of 1 °C /min to achieve empty hexagonal
pores of Al-SBA-15. The template P123 had a uniform hexagonal framework of Al-SBA-15
(from TEOS and aluminum triisopropoxide) and finally was removed from the inside of
mesoporous channels to obtain empty channels.
2.4. Preparation of CPTMS@Al-SBA-15
In a 50 mL three-necked, round-bottomed flask, (3-chloropropyl) trimethoxysilane (1 mL,
5.5 mmol) was added dropwise to a suspension of Al-SBA-15 (1 g) in dry toluene (30 mL) under
N2 atmosphere. The mixture was refluxed for 24 h. After that, the obtained solid was filtered and
washed repeatedly with dichloromethane to remove unreacted starting material, and dried in a
vacuum at 120 °C for 8 h to obtain white powder of CPTMS@Al-SBA-15.
2.5. Preparation of NN'PhBIA @Al-SBA-15
In a 50 mL round-bottomed flask, 2-amino-N-{2-[(2-aminobenzoyl)amino]phenyl}benzamide
(0.7 g, 2 mmol) was added to the suspension of CPTMS@Al-SBA-15 (2 g) in absolute ethanol
(30 mL). The solution was refluxed for 24 h. Then, the solid was filtered and washed with ice-
cold EtOH and dried at room temperature by infrared radiation. NN'PhBIA@Al-SBA-15 was
obtained as a solid.
5

2.6. Preparation of CoCl2NN'PhBIA@Al-SBA-15
In a 50 mL round-bottomed flask, NN'PhBIA@Al-SBA-15 (0.2 g) was added to solution of
CoCl2 (0.1 mmol) in absolute ethanol (25 mL). This mixture was stirred at room temperature for
24 h, the solid was filtered and washed several times by absolute ethanol until the eluent became
colorless, and then dried at room temperature by infrared radiation. The obtained solid was
CoCl2NN'PhBIA@Al-SBA-15.
2.7. General procedure for the synthesis of 3-benzoxazol-2-yl-chromen-2-one derivatives
A mixture of ethyl 2-oxo-2H-chromene-3-carboxylate (1 mmol), 2-amino phenol (1.2 mmol) and
CoCl2NN'PhBIA@Al-SBA-15 (2 mg) in 5 ml EtOH was stirred at reflux for a desired time.
Progression of the reaction was monitored by TLC. After completion of the reaction the mixture
was cooled to room temperature. Then the catalyst was removed by centrifuging. Finally the
residue was recrystallized with appropriate solvent to yield the crude product.
3. Results and discussion
3.1. Synthesis and characterization of CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst
The NN'PhBIA ligand was prepared through condensation between 1,2-phenylene diamine and
isatoic anhydride with molar ratio 1:2 (scheme 2).
O
NH2
O
O
O
+
NH2
N
O
N
N
H
H
H
H2N
NH2
Scheme 2. Synthesis of N,N'-(1,2-phenylene)bis(2-aminobenzamide) ligand.
The general procedure used to synthesize CoCl2NN'PhBIA@Al-SBA-15 from Al-SBA-15 is
illustrated in scheme 3. Pluronic acid P123 was used as a template and dissolved in hydrochloric
acid to create a micellar surfactant (surfactant solution). The TEOS and aluminum
triisopropoxide solution was added to the surfactant solution to form hexagonal structure of silica
and aluminium around the micellar surfactant of P123. Then the template P123 was eliminated
by calcination to obtain empty hexagonal channels of Al-SBA-15. Afterward the surface of
6

Al-SBA-15 was modified by the reaction with CPTMS and chloropropyl linkers are immobilized
on Al-SBA-15. The NN'PhBIA ligand was covalently attached to the CPTMS@Al-SBA-15 by
substitution of amino group instead of Cl on the Al-SBA-15 surface. Finally CoCl2 was added to
the prepared complex to yield CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst. The structure of the
nanocatalyst was confirmed by FT-IR, XRD, EDS, SEM, TEM and N2 adsorption-desorption
techniques.
Scheme 3. Overall schematic for the preparation of CoCl2NN'PhBIA@AL-SBA-15.
Figure 1 presents the Fourier-transform infrared (FT-IR) spectra of Al-SBA-15,
CPTMS@Al-SBA-15, NN'PhBIA ligand, NN'PhBIA@Al-SBA-15 and CoCl2 NN'PhBIA@Al-
SBA-15. The peaks at 600–1200 cm−1 can be ascribed to the vibration of Si–O groups in the
mesoporous silica framework. The absorption bands of Al-SBA-15 based materials at 1078, 802
7

and 460 cm−1 are attributed to the Si–O–Si anti-stretching vibration, the Si–O–Si stretching
vibration, and the bending vibrations of Si–O, respectively. The bare ligand characteristic peaks
at 3463, 3352 and 3268 cm−1 are related to the stretching vibration of –NH2 in amine and amide
groups. Also the characteristic band of C=O from aminobenzamide is at 1636 cm−1 and the
stretching vibrations of aromatic rings are at 1611 and 1577 cm−1. By immobilization of
NN'PhBIA over CPTMS@Al-SBA-15, two charactristic peaks for stretching vibration of –NH
amine and amide appeared at 3352 and 3271 cm−1 with weak peak intensity because of loading
on CPTMS@Al-SBA-15. After NN'PhBIA@Al-SBA-15 coordinated with Co, the absorption at
1636 cm−1 shifted to 1694 cm−1, indicating formation of a Co–ligand bond. The results above
demonstrate the anchoring of NN'PhBIA on the surface of Al-SBA-15 and coordination to
cobalt. Also the structure of these functional moieties can be retained in CoCl2NN'PhBIA@Al-
SBA-15.
The low-angle XRD patterns of Al-SBA-15 and CoCl2NN'PhBIA@Al-SBA-15 are
depicted in figure 2. The Bragg peaks in the 2θ range of 0.8–2 can be indexed as (1 0 0), (1 1 0)
and (2 0 0) reflections for the 2D-hexagonal structure of the SBA-15 material. As shown in the
XRD pattern of CoCl2NN'PhBIA@Al-SBA-15 the framework of mesoporous material is
preserved after functionalization and Co immobilization. The diffraction peaks of Co species
cannot be revealed, and there is no major change in the crystallinity of Al-SBA-15. These results
demonstrate that the Co species were immobilized into the pore channels of Al-SBA-15 in the
atom dispersion, and no crystal Co species existed in the sample. The intensity of distinct
diffraction peaks diminish in the XRD pattern of CoCl2NN'PhBIA@Al-SBA-15 due to partly
blocking the pores by functionalization which can decrease the mesoscopic ordering [37].
Figures 3a and 3b show SEM micrographs of Al-SBA-15 and CoCl2NN'PhBIA@Al-
SBA-15, respectively. The SEM image of Al-SBA-15 exhibits bagel-shaped particles with
relatively uniform sizes. After functionalization by NN'PhBIA and Co the surface morphology of
Al-SBA-15 is unchanged (figure 3b).
The TEM image of CoCl2NN'PhBIA@Al-SBA-15 shows the hexagonal arrangement of
pores channels regularly distributed (figure 4). The accumulation of cobalt in the pores is not
observed, which confirmed Co2+ ions are coordinated with N in NN'PhBIA @Al-SBA-15.
The elemental compositions of the CoCl2NN'PhBIA@Al-SBA-15 were obtained by
Energy Dispersive Spectroscopy (EDS) as shown in figure 5. Elemental analysis results
8

demonstrated the presence of carbon, nitrogen, oxygen, aluminium, silicon, cobalt and chlorine
with the amount 32.05, 7.71, 33.91, 0.29, 13.29, 5.44 and 7.31 (wt %), respectively.
Brunauer–Emmett–Teller (BET) specific surface area of nanocatalyst was measured
using N2 adsorption-desorption analysis at a relative pressure (P/P0). Figure 6 indicates the
nitrogen adsorption-desorption and pore-size distribution curves of Al-SBA-15 and
CoCl2NN'PhBIA@Al-SBA-15. The adsorption-desorption isotherms reveal a type IV isotherm
with an H1 hysteresis loop (starting from P/P0 = 0.6) which are in agreement with a typical
mesostructure. The y-axis in the N2 adsorption/desorption isotherms represents the adsorbed
volume of N2 gas allowed for estimation of the total micropore volumes. Compared with the
BET surface area of Al-SBA-15 (815 m2/g), the surface area of CoCl2NN'PhBIA@Al-SBA-15
declined to 581 m2/g due to incorporation of Ph-groups, NH2 and Co species into the pore
channels after functionalization of Al-SBA-15. The inset demonstrates the narrow pore size
distribution centered on 5.52 and 3.17 nm for Al SBA-15 and CoCl2NN'PhBIA@Al-SBA-15
samples, respectively. These results confirm that the surface of Al-SBA-15 has been successfully
modified by NN'PhBIA and cobalt species resulting in decrease in its pore size. Although the
surface area of CoCl2NN'PhBIA@Al-SBA-15 decreased in comparison with Al SBA-15 it still
has high surface area for catalytic activity. The catalytic activity of CoCl2NN'PhBIA@Al-
SBA-15 increased by the presence of NN'PhBIA ligand and cobalt species on the surface of Al-
SBA-15 which accelerate the synthesis of 3-benzoxazol-2-yl-chromen-2-one derivatives. Thus
CoCl2NN'PhBIA@Al-SBA-15 is a more selective catalyst than Al-SBA-15 while it still has
appropriate surface area for catalytic performance.
3.2. Synthesis of 3-benzoxazol-2-yl-chromen-2-one derivatives by CoCl2NN'PhBIA@Al-
SBA-15 nanocatalyst
The synthetic pathway for preparation of 3-benzoxazol-2-yl-chromen-2-one is depicted in
scheme 4. Ethyl coumarin-3-carboxylates were prepared through Knoevenagel condensation
between 2-hydroxy benzaldehydes and 1,3-dicarbonyl compounds catalyzed by MgFe2O4
nanoparticles under ultrasonic irradiation [36]. Derivatives of 3-benzoxazol-2-yl-chromen-2-one
were prepared from different coumarin-3-carboxylates and 2-aminophenols in the presence of
CoCl2NN'PhBIA@Al-SBA-15 as catalyst in EtOH at reflux.
9

The influence of solvent, type and amount of catalyst were examined to achieve the best
condition for preparation of 3-(benzoxazol-2-yl)-2H-chromen-2-one (5a) and the results are
recorded in table 1. EtOH is the best solvent for synthesis of 3-benzoxazol-2-yl-chromen-2-one
(table 1, entry 6). The efficacy of different catalysts including MgO, CuI, CoCl2, Al-SBA-15 and
CoCl2NN'PhBIA@Al-SBA-15 are presented in entries 7-12 of this table. The reaction
progressed efficiently by CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst. The best yield at the
shortest time for this synthesis was achieved by 2 mg of CoCl2NN'PhBIA@AL-SBA-15
nanocatalyst (table 1, entry 13).
Times and yields for different products are given in table 2.
O
3a: R1=H
CHO
OH
O
O
MgFe2O4
nanoparticle
3b: R1=6-Br
3c :R1=7-OCH3
3d: R1=6-OCH3
3e: R1=7-NEt2
3f: R1=6-Cl
OEt
+
EtO
OEt
Ultrasound
R1
R1
O
O
2
1
3a-f
NH2
OH
R2
4
CoCl2NN'PhBIA@AL-SBA-15
EtOH/reflux
5a: R1= R2 = H
R2
5b: R1=H, R2= 5-Br
5c: R1=H, R2= 5-CH3
5d: R1=H, R2= 5-Cl
5e: R1=6-Br, R2= H
5f: R1=6-Br, R2= 5-CH3
5g: R1=6-Br, R2= 5-Cl
5h: R1=7-OCH3, R2= H
5i: R1=6-OCH3, R2= H
5j: R1=7-NEt2, R2= H
5k: R1=6-Cl, R2= H
N
O
R1
O
O
5a-k
Scheme 4. Synthesis of 3-benzoxazol-2-yl-chromen-2-one derivatives.
10

3.3. Proposed mechanism
A plausible mechanism for the synthesis of 3-benzoxazol-2-yl-chromen-2-ones catalyzed by
CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst is illustrated in scheme 5. Co from the nanocatalyst
is a Lewis acid and coordinates to the carbonyl groups of carboxylate (from ethyl coumarin-3-
carboxylate). Transesterification is performed between the carboxylate group and OH (from 2-
aminophenol) and II is created. The reaction is followed by the formation of imine and
cyclization, through nucleophilic attack of the N (from amino group) to the C of the carbonyl
group and then dehydration, finally yielding 3-benzoxazol-2-yl-chromen-2-one. This occurred on
the high surface area of CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst with very effective catalytic
activity owing to the attachment of the organic-inorganic hybrid on the surface of Al-SBA-15.
Indeed the coordination of Co to the carbonyl groups hastens the conjugation and directs the
addition of the nucleophile to the corresponding substrate.
3.4. Recoverability of CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst
The CoCl2NN'PhBIA@Al-SBA-15 is reusable without important loss of catalytic performance.
After completion of the reaction, the nanocatalyst is recycled via filtration and washed with
ethanol to remove residual product. The nanocatalyst was reused for a new reaction of ethyl
coumarin-3-carboxylate and 2-aminophenol under similar reaction conditions up to eight cycles.
Slight loss of catalytic activity was observed and the product was produced in high yield
(figure 7).
The treatment of organic-inorganic hybrid CoCl2NN'PhBIA@Al-SBA-15 was studied by
TEM image before use and after reuse eight times (figure 8). Remarkably, the structure and
nanometer-size of the catalyst remained unchanged before and after the reaction. The results of
these images confirm the high stability of CoCl2NN'PhBIA@Al-SBA-15.
11

O
O
Cl
NH
Co
NH
O
O
Co
NH
NH
Cl
Cl
NH
Co
NH
Co
NH
NH
Cl
O
O
O
O
O
Al-SBA-15
OEt
O
O
OEt
Al-SBA-15
O
O
O
I
H
O
H2N
O
O
Cl
NH
Co
NH
H
N
Co
HO
NH
NH
Cl
H2N
O
O
O
O
O
O
O
Al-SBA-15
O
O
III
II
-H2O
N
O
O
O
5a
Scheme 5. Possible mechanism for the synthesis of 5a over CoCl2NN'PhBIA@Al-SBA-15
nanocatalyst.
4. Conclusion
In this research 3-benzoxazol-2-yl-chromen-2-one was synthesized by a convenient, efficient,
facile and green method using CoCl2NN'PhBIA@Al-SBA-15 as a highly effective catalyst. Easy
12

recoverability and reusability for the nanocatalyst, being environmentally benign and providing
excellent yields of 3-benzoxazol-2-yl-chromen-2-one at short reaction times, are some important
advantages of this procedure.
Acknowledgements
The authors are grateful to University of Kashan for supporting this work.
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14

[38]
Figure 1. FT-IR spectra of Al-SBA-15, CPTMS@Al-SBA-15, NN'PhBIA ligand,
NN'PhBIA@Al-SBA-15 and CoCl2NN'PhBIA@AL-SBA-15.
15

Figure 2. XRD pattern of Al-SBA-15 and CoCl2NN'PhBIA@Al-SBA-15.
(a)
(b)
Figure 3. SEM images of (a) Al-SBA-15 and (b) CoCl2NN'PhBIA@Al-SBA-15.
16

Figure 4. TEM image of CoCl2NN'PhBIA@Al-SBA-15.
Figure 5. EDS of CoCl2NN'PhBIA@Al-SBA-15.
17

0.45
0.3
0.15
0
Al-SBA-15
CoCl2NN'PhBIA@Al-SBA-15
(a)
(b)
800
400
0
Al-SBA-15
CoCl2NN'PhBIA@Al-SBA-15
0
0.5
1
1
10
100
Relative Pressure (P/P0)
Pore Diameter (nm)
Figure 6. (a) N2 adsorption-desorption isotherms of Al-SBA-15 and CoCl2NN'PhBIA@Al-
SBA-15, (b) Pore-size distribution curves of Al-SBA-15 and CoCl2NN'PhBIA@Al-SBA-15.
92
91
91
100
90
80
70
60
50
40
30
20
10
0
90
88
85
83
81
run1 run2 run3 run4 run5 run6 run7 run8
Figure 7. Recovery of CoCl2NN'PhBIA@Al-SBA-15 nanocatalyst for the synthesis of 5a.
18

(a)
(b)
Figure 8. TEM image of CoCl2NN'PhBIA@Al-SBA-15 (a) before use (b) after reuse of eight
times.
Table 1. Optimization of the reaction condition for the synthesis of 5aa.
Entry
Solvent
Catalyst
Time (min)
Yieldb (%)
No solvent (160 °C)
DMF (100°C)
CH3CN (reflux)
1,4-dioxane (reflux)
MeOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
EtOH (reflux)
PPA
180
80
80
80
75
60
240
85
85
80
80
60
60
60
45
55
1.
2.
CoCl2NN'PhBIA@Al-SBA-15 (6 mg)
CoCl2NN'PhBIA@Al-SBA-15 (6 mg)
CoCl2NN'PhBIA@Al-SBA-15 (6 mg)
CoCl2NN'PhBIA@Al-SBA-15 (6 mg)
CoCl2NN'PhBIA@Al-SBA-15 (6 mg)
No Catalyst
61
3.
63
4.
70
5.
90
6.
trace
38
7.
MgO (10 mol%)
8.
CuI (10 mol%)
43
9.
CoCl2 (10 mol%)
61
10.
11.
12.
13.
14.
Al-SBA-15 (5 mg)
59
CoCl2NN'PhBIA@Al-SBA-15 (4 mg)
CoCl2NN'PhBIA@Al-SBA-15 (2 mg)
CoCl2NN'PhBIA@Al-SBA-15 (1 mg)
91
92
89
a Reactions conditions: ethyl 2-oxo-2H-chromene-3-carboxylate (1 mmol), 2-amino phenol (1.2 mmol)
b Isolated yield
19

Table 2. Preparation of 3-benzoxazol-2-yl-chromen-2-ones catalyzed by CoCl2NN'PhBIA@Al-
SBA-15 nanocatalysta.
Entry
Name
5a
Productb
Time (min)
60
Yield (%)c
Mp(oC)
N
92
185-187
1
O
O
O
N
Br
5b
5c
65
60
86
90
252-254
159-161
2
3
O
O
O
CH3
N
O
O
O
Cl
N
5d
60
88
240-242
4
O
O
O
N
Br
O
5e
5f
60
60
91
90
230-232
247-250
5
6
O
O
CH3
N
Br
O
O
O
Cl
N
5g
5h
65
70
87
85
270-274
187-189
7
8
Br
O
O
O
N
O
H3CO
O
O
20

N
H3CO
O
5i
65
86
191-193
9
O
O
N
O
5j
65
65
88
87
178-180
203-204
10
11
Et2N
O
O
N
Cl
O
5k
O
O
a Reactions conditions: ethyl 2-oxo-2H-chromene-3-carboxylates (1 mmol), 2-amino phenols
(1.2 mmol) and CoCl2NN'PhBIA@Al-SBA-15 = 2 mg, EtOH (reflux).
b All products were characterized from their spectroscopic IR, 1H NMR.
c Isolated yield.
21