Ni(II)-Schiff base/SBA-15: a nanostructure and reusable catalyst for one-pot three-component green synthesis of 3,4-dihydropyrano[3,2-c]chromene derivatives

Article abstract of DOI:10.1007/s11164-019-03954-6

An efficient, rapid, and environmentally benign Ni(II)-Schiff base/SBA-15-catalyzed one-pot three-component cyclocondensation process was described via the reaction between malononitrile, 4-hydroxycoumarin, and various aldehydes in aqueous media for the s

Full text of DOI:10.1007/s11164-019-03954-6

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-019-03954-6
Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable
catalyst for one‑pot three‑component green synthesis
of 3,4‑dihydropyrano[3,2‑c]chromene derivatives
Nader Noroozi Pesyan1 · Ghasem Rezanejade Bardajee2 · Elmira Kashani1 ·
Marzieh Mohammadi1 · Hana Batmani1
Received: 10 April 2019 / Accepted: 14 August 2019
© Springer Nature B.V. 2019
Abstract
An efcient, rapid, and environmentally benign Ni(II)-Schif base/SBA-15-cata-
lyzed one-pot three-component cyclocondensation process was described via the
reaction between malononitrile, 4-hydroxycoumarin, and various aldehydes in
aqueous media for the synthesis of 3,4-dihydropyrano[3,2-c]chromene derivatives.
This nanocatalyst was characterized using FT-IR, SEM, TGA, TEM, BET, AFM,
and XRD techniques. It is possible to reuse the heterogeneous catalyst without any
marked change in its catalytic activity at least fve times. Other remarkable features
of this method include excellent yields in pure form, convenient operation, a much
milder procedure, short reaction time, simple workup and avoidance of hazardous
reagents/solvents.
Keywords Heterogeneous catalysis · Ni(II)-Schif base · SBA-15 · Green chemistry ·
3,4-Dihydropyrano[3,2-c]chromene
Introduction
Nowadays, there is an increasing importance for more accessible eco-friendly
approaches in the fne chemical synthesis, pharmaceutical industries, and small het-
erocyclic synthesis. This progressive development is known as ‘Green Chemistry’
or ‘Sustainable Technology’ which leads to avoiding extensive usages of hazardous
and toxic solvents and reagents. In addition, this development reduces harsh reaction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1116
4-019-03954-6) contains supplementary material, which is available to authorized users.
*
Nader Noroozi Pesyan
n.noroozi@urmia.ac.ir; nnp403@gmail.com
1
2
Department of Organic Chemistry, Faculty of Chemistry, Urmia University, Urmia 57159, Iran
Department Chemistry, Payame Noor University (PNU), P.O. Box 19395-3697, Tehran, Iran
Vol.:(0123456789)
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N. Noroozi Pesyan et al.
conditions as well as expensive and sophisticated catalysts [1–5]. To achieve these
desirable syntheses in modern synthetic organic chemistry, multicomponent reac-
tions (MCRs) have appeared as an efective tool. MCRs permit to carry out the reac-
tion of various new bonds in a one-pot reaction and exhibit signifcant benefts such
as convergence, facile automation, and operational simplicity. It should be noted
that using these operative methods considerably decreases the number of extrac-
tion, workup, purifcation processes, and waste generation [6–12]. In addition, the
use of water in these reactions has been an important and fertile area of research in
recent years [13–15]. Water is the cheapest, most abundant, and non-toxic chemical
in nature. Many organic reactions have been performed successfully in water as the
reaction medium, and several books and reviews have been devoted to such an appli-
cation [16].
Since chromene derivatives have a wide range of biological and pharmacologi-
cal properties such as blood anticoagulant [17, 18], diuretic, spasmolytic, antican-
cer, and anti-anaphylactin agents [19], they are of our interest to be developed.
Moreover, as cognitive enhancers, they can be utilized to treat many diseases such
as Alzheimer’s disease, Huntington’s disease, amyotrophic lateral sclerosis, Parkin-
son’s diseases, AIDS-associated dementia, Down’s syndrome, schizophrenia, and
myoclonus [20, 21]. Among the bioactive chromenes, pyrano[3,2-c] chromenes
have special importance due to their application in the synthesis of pharmacologi-
cal agents as valuable synthons [22–26]. Because of this, several methods were
developed for the synthesis of these compounds using many diferent catalysts such
as MgO [27], K2CO3 [28], tetrabutylammonium bromide (TBAB) [29], urea [30],
potassium hydrogen phthalate [31], H6P2W18O62·18H2O [32] (NH4)42[MoVI 72MoV
60O372(CH3COO)30(H2O)72] [33], DBU [34], KF-montmorillonite [35], heteropo-
lyacids [36, 37], ionic liquid [38–40], molten salt [41], nano-organo particles [42],
nanofber sepiolite [43], and magnetic nanocatalysts [44, 45]. However, extended
reaction times, use of toxic solvents, unsatisfactory yields and non-reusability of the
catalyst are disadvantages of these reported procedures. Hence, it can be concluded
that more efective methods are still needed for their preparation.
In the last decade, transition metal–ligand complexes have attracted great atten-
tion because of their potential use in various felds [46, 47]. These metal particles,
which are often in nanoscale, are immobilized on diferent supports to better activ-
ity [48–51]. Much recent attention has focused on the Schif base transition metal
complexes in the last two decades. They can potentially be utilized as catalysts in a
wide range of reactions [52], and because of their important role in homogeneous
or heterogeneous catalysis, many complexes have been given enough attention by
chemists all over the world. Frequently, inert porous solids such as alumina [53],
clays [54], polymers [55], zeolites [56], and silica [57] have been used for the immo-
bilization of homogeneous Schif base complexes to raise catalyst stability and allow
for catalyst recycling and product separation. One of the most prevailing supporting
materials, mesoporous silica materials, have been extensively utilized as versatile
solid supports to create several hybrid materials in catalysis, enzyme immobiliza-
tion, and drug delivery taking advantages of their high surface areas and large pores.
Among them, because of larger pore diameters (ranging from 3 to 30 nm with nar-
row size distributions), rod-like hexagonally ordered mesoporous SBA-15 material
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Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Scheme 1 The one-pot synthesis of 3,4-dihydropyrano[c]chromene derivatives
has been more frequently utilized as support comparing with MCM series (MCM-
48, MCM-41, and MCM-15) [58–61]. It should be mentioned that the larger and
thick walls pore for SBA-15 permits immobilization of larger biomolecules which
is not possible to be accommodated in small pores. In addition, the applicability of
SBA-15 materials can be extended by surface modifcation using organic functional
groups for anchoring metals and metal complexes through a Schif base [62, 63].
In continuation of our eforts to develop new, green chemistry methods as well
as our interest on the application of heterogeneous metal complexes of Schif bases
supported on SBA-15-catalyzed organic reactions [63, 64], we have studied the one-
pot multicomponent reaction (MCR) in order to synthesize substituted 3,4 dihy-
dropyrano[3,2 c]chromenes using Ni(II)-Schif base/SBA-15 as heterogeneous and
reusable catalyst and water as a greener solvent (Scheme 1).
Experimental
Characterization techniques
Melting points are uncorrected and measured by employing the capillary
tube method with a Buchi B540 melting point apparatus. The infrared spectra
(500–4000 cm−1) of samples were recorded on a Jasco 4200 FT-IR spectrophotom-
eter employing a KBr disk method. Proton nuclear magnetic resonance (300 MHz)
and carbon nuclear magnetic resonance (75 MHz) spectra were measured with
Bruker NMR-Spectrometer using CDCl3 or DMSO-d6 solution with tetramethyl-
silane (TMS) as an internal standard. [Coupling constants (J) were in hertz, and
chemical shift values were reported in parts per million (ppm) units.] Transmission
electron microscopy (TEM) micrographs were recorded in a Hitachi H-700 CTEM
in order to approve the size and the morphology of the samples. The SEM images
were performed with the TESCAN VEGA scanning electron microscope by set-
ting an acceleration voltage of 15 kV. The Ni content was measured by ICP-OES
(Model: VISTA-PRO, Varian, Australia). AFM was recorded with an Easyscan2
Flex AFM probe microscope in the air. The X-ray powder difraction (XRD) pat-
tern was collected by a Bruker D8 ADVANCE with Ni-fltered Cu Kα radiation at a
wavelength λ=1.5406 Å, the scan speed of 2° min−1, and a step of 0.05°. Thermo-
gravimetric analysis (TGA) curves were recorded using a TGA/DTA Shimadzu-50
instrument where the maximum heating rate was set to be 10 °C min−1. Nitrogen
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N. Noroozi Pesyan et al.
adsorption/desorption isotherms were measured at the liquid nitrogen temperature,
using a Quantachrome Autosorb-1 apparatus. Before measurements, the samples
were outgassed at 120 °C overnight to characterize material properties. Moreover,
the Brunauer–Emmett–Teller (BET) method was employed to calculate the surface
areas and pore-size distributions were evaluated from the desorption branches of the
nitrogen isotherms using the Barrett–Joyner–Halenda (BJH) model. The concentra-
tion of metal ions was obtained using a Shimadzu AA-6300 fame atomic absorp-
tion spectrometer. To this end, 0.1 g of the catalyst was digested by HNO3 and then
stirred for a week at room temperature. Next, the obtained mixture was fltered, and
the solid was washed several times with water to achieve a colorless fltrate solution.
Materials
In this research, all the utilized chemicals were obtained from commercial sources
in high purity and used without any purifcation. In addition, to identify the known
products, their spectral and physical data were compared with those reported in the
literature.
Preparation of the catalyst Ni (II)‑Schif base/SBA‑15
While Ni(II)-Schif base complex was prepared by following the procedure reported
in [65], the following procedure was employed to synthesize the mesoporous SBA-
15 support [66]. Briefy, salicylaldehyde (1 mmol, 0.12 g) was added to 5 mL
MeOH, to which 3-aminopropyl (trimethoxy)silane (1 mmol, 0.18 g) was added.
The obtained solution instantly became yellow because of the imine formation.
Then, nickel (II) acetate (0.5 mmol, 0.088 g) was added to the solution. At the next
step and for a further 3 h, the mixture was stirred in order to allow the new ligands
to complex the nickel. Activated SBA-15 (1.5 g) was suspended in 20 mL methanol
solution containing (0.38 g) Schif base complex. Then, the obtained mixture was
stirred for a day. At the next step, a rotary evaporator was used to remove the sol-
vent. Moreover, the obtained solid was dried at 80 °C overnight. The fnal product
was washed with deionized water and MeOH till the washings became colorless.
Finally, in an oven at 80 °C and for 8 h, the resulted solid product was dried.
Preparation of 3,4‑dihydropyrano[3,2‑c]chromene derivatives (7)
An aromatic aldehyde (1 mmol), 4-hydroxycoumarin (1 mmol), and malononitrile
(1 mmol) were added in a 25-mL round-bottomed fask containing Ni(II)-Schif
base/SBA-15 in water (5 mL). The resulting mixture was stirred and heated at 70 °C
for an appropriate time. The reaction mixture was allowed to cool at room tempera-
ture after completion of the reaction (as monitored by TLC). The reaction mixture
was diluted with acetone (for the dissolution of the crude product), and the acetone
solution was fltered to remove the catalyst. After evaporation of the solvent, the
crude product recrystallized from hot acetone. All compounds provided satisfactory
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Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
spectral data (1H NMR and 13C NMR), and spectral data for all heterocycles are
reported in Electronic Supplementary data section.
Spectral data
2‑Amino‑4‑(4‑nitrophenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7a) Yellow solid (M.p.: 253–255 °C); FT-IR (KBr, neat) νmax (cm−1)=3454, 3390,
3163, 2968, 2195, 1729, 1660, 1612, 1669, 1510, 1365, 1295, 1226, 1185, 820, 740,
384; 1H NMR (300 MHz, DMSO-d6, CDCl3) δ 8.10 (d, J=8.4 Hz, 2H, ar–H), 7.88
(m, 1H, ar–H), 7.59 (dd, J=7.8 Hz, J=7.8 Hz, 1H, ar–H), 7.48 (d, J=8.7 Hz, 2H,
ar–H), 7.38–7.28 (m, 2H, ar–H), 7.2 (s, 2H, NH2), 4.61 (s, 1H, benzylic–CH); 13C
NMR (75 MHz, DMSO-d6, CDCl3) δ 158.6 (C=O), 154.3 (=C–O–), 152.7 (=C–
NH2), 150.5 (Car–O–), 147.0 (Car), 133.1 (Car), 129.1 (Car), 124.7 (Car), 123.8 (Car),
123.1 (Car), 119.0 (CN), 116.7 (Car), 113.1 (Car), 103.2 (Car), 57.2 (=C–C=O), 40.3
(=C–CN), 37.3 (benzylic–C).
2‑Amino‑4‑(2‑nitrophenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7b) Yellow solid (M.p.: 255–256 °C); FT-IR (KBr, neat) νmax (cm−1)=3500, 3480,
3143, 2955, 1731, 2095, 1668, 1602, 1500, 1355, 1294, 1216, 1180, 815, 735, 382;
1H NMR (300 MHz, DMSO-d6, CDCl3) δ 7.89 (d, J=7.8 Hz, 1H, ar–H), 7.78 (d,
J=8.1 Hz, 1H, ar–H), 7.55 (dd, J=10.2 Hz, J=7.8 Hz, 2H, ar–H), 7.39–7.32 (m,
3H, ar–H), 7.25 (d, J=9.0 Hz, 2H, ar–H), 7.18 (s, 2H, NH2), 5.32 (s, 1H), benzylic–
CH; 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 160.0 (C=O), 159.0 (=C–O–), 154.0
(=C–NH2), 152.6 (Car–O–), 149.5 (Car), 137.7 (Car), 133.5 (Car), 133.1 (Car), 131.0
(Car), 128.3 (Car), 124.7 (Car), 124.1 (Car), 123.0 (Car), 118.8 (CN), 116.7 (Car),
113.0, 103.7 (=C–C=O), 56.9 (=C–CN), 31.7 (benzylic–C).
2‑Amino‑4‑(4‑chlorophenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7c) Yellow solid (M.p.: 270–271 °C); FT-IR (KBr, neat) νmax (cm−1)=3460,
3380, 3103, 2965, 1761, 2089, 1660, 1632, 1602, 1510, 1345, 1284, 1206, 1185,
1
805, 745, 402; H NMR (300 MHz, DMSO-d6, CDCl3) δ 7.89 (m, 1H, ar–H), 7.58
(dd, J=7.2 Hz, J=7.5 Hz, 1H, ar–H), 7.37–7.23 (m, 6H, ar–H), 7.12 (s, 2H, NH2),
5.44 (s, 1H, benzylic–CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 159.9, (C=O),
158.5 (=C–O–), 153.9 (=C–NH2), 152.6 (Car–O–), 142.0 (Car), 132.9 (Car), 132.5
(Car), 129.6 (Car), 128.6 (Car), 124.7 (Car), 123.0 (Car), 119.2 (CN), 116.7 (Car),
113.2 (Car), 104.0 (=C–C=O), 58.0 (=C–CN), 36.9 (benzylic–C).
2‑Amino‑4‑(3‑chlorophenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7d) Yellow solid (M.p.: 253–256 °C); FT-IR (KBr, neat) νmax (cm−1)=3460, 3380,
3103, 2965, 1761, 2089, 1660, 1632, 1602, 1510, 1345, 1284, 1206, 1185, 805, 745,
402; 1H NMR (300 MHz, DMSO-d6, CDCl3) δ 7.88 (d, J=7.8 Hz, 1H, ar–H), 7.56
(dd, J=7.8 Hz, J=7.8 Hz, 1H, ar–H), 7.15–7.34 (m, 6H, ar–H), 7.01 (s, 2H, NH2),
4.44 (s, 1H, benzylic–CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 162.3 (C=O),
160.0 (=C–O–), 158.5 (=C–NH2), 152.6 (Car–O–), 145.2 (Car), 133.9 (Car), 132.9
1 3

N. Noroozi Pesyan et al.
(Car), 130.1 (Car), 127.8 (Car), 127.4 (Car), 126.4 (Car), 124.6 (Car), 123.0 (Car), 119.2
(CN), 116.6 (Car), 113.1 (Car), 103.8 (=C–C=O), 58.0 (=C–CN), 37.1 (benzylic–C).
2‑Amino‑4‑(2,4‑dichlorophenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7e) Yellow solid (M.p.: 253–254 °C); FT-IR (KBr, neat) νmax (cm−1)=3405, 3375,
1
2963, 1756, 2060, 1658, 1630, 1611, 1507, 1333, 1200, 1180, 805, 740; H NMR
(300 MHz, DMSO-d6, CDCl3) δ 7.89 (d, J=7.8 Hz, 1H, ar–H), 7.59 (dd, J=7.8 Hz,
J=7.8 Hz, 1H, ar–H), 7.19–7.37 (m, 5H, ar–H), 7.10 (s, 2H, NH2), 4.94 (s, 1H, ben-
zylic–CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 159.7 (C=O), 158.5 (=C–O–),
154.6 (=C–NH2), 152.6 (Car–O–), 139.1 (Car), 133.9 (Car), 133.1 (Car), 133.0 (Car),
131.8 (Car), 129.3 (Car), 127.7 (Car), 124.7 (Car), 123.0 (Car), 118.9 (CN), 116.7
(Car), 113.0 (Car), 102.8 (=C–C=O), 56.8 (=C–CN), 34.5 (benzylic–C).
2‑Amino‑4‑(2‑chlorophenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7f) Yellow solid (M.p.: 271–272 °C); FT-IR (KBr, neat) νmax (cm−1)=3450, 3374,
3079, 2960, 1756, 2010, 1659, 1632, 1550, 1330, 1275, 1105, 804, 720, 401;1H
NMR (300 MHz, DMSO-d6, CDCl3) δ 7.90 (d, J=7.8 Hz, 1H, ar–H), 7.59 (dd,
J=7.8 Hz, J=8.55 Hz, 1H, ar–H), 7.37–7.00 (m, 8H, ar–H, NH2), 4.97 (s, 1H, ben-
zylic–CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 158.5 (C=O), 154.5 (=C–O–),
152.6 (=C–NH2), 133.2 (Car–O–), 133.1 (Car), 133.0 (Car), 132.9 (Car), 130.6 (Car),
129.8 (Car), 128.7 (Car), 127.5 (Car), 124.7 (Car), 123.0 (Car), 119.0 (CN), 116.7
(Car), 113.1 (Car), 103.2 (=C–C=O), 50.2 (=C–CN), 34.8 (benzylic–C).
2‑Amino‑5‑oxo‑4‑(3,4,5‑trimethoxyphenyl)‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carboni-
trile (7g) Yellow solid (M.p.: 237–239 °C); FT-IR (KBr, neat) νmax (cm−1)=3455,
3375, 3203, 2935, 1755, 2089, 1630, 1612, 1602, 1503, 1306, 1284, 1205, 1174,
1
815, 740, 412; H NMR (300 MHz, DMSO-d6, CDCl3) δ 7.89 (d, J=7.8 Hz, 1H,
ar–H), 7.59 (dd, J=7.8, J=8.4 Hz, 1H, ar–H), 7.34 (dd, J=10.8 Hz, J=8.4 Hz, 2H,
ar–H), 7.13 (s, 2H, NH2), 6.47 (s, 2H, ar–H), 4.40 (s, 1H, benzylic–CH), 3.72 (s,
6H, 2OCH3), 3.65 (s, 3H, OCH3); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 162.3
(C=O), 160.0 (=C–O–), 158.6 (=C–NH2), 153.8 (Car–O–), 153.1 (Car), 152.5 (Car),
138.9 (Car), 137.1 (Car), 132.9 (Car), 124.7 (Car), 123.0 (Car), 119.4 (CN), 116.7
(Car), 113.3 (Car), 105.2 (Car), 104.2 (=C–C=O), 60.3 (p-OCH3), 58.3 (=C–CN),
56.1 (m-OCH3), 37.6 (benzylic–C).
2‑Amino‑4‑(3‑methoxyphenyl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3
carbonitrile
(7h) Yellow solid (M.p.: 248–250 °C); FT-IR (KBr, neat) νmax (cm−1)=3410,
3365, 3185, 2968, 1768, 2019, 1620, 1602, 1600, 1513, 1316, 1200, 1170, 805,
735, 402; 1H NMR (300 MHz, DMSO-d6, CDCl3) δ 7.87 (d, J=6.9 Hz, 1H, ar–H),
7.56 (dd, J=7.2 Hz, J=7.2 Hz, 1H, ar–H), 7.25–7.34 (m, 2H, ar–H), 7.03–7.17 (m,
3H, ar–H), 6.79–6.69 (m, 3H, ar–H, NH2), 4.40 (s, 1H, benzylic–CH), 3.69 (s, 3H,
OCH3); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 160.3 (C=O), 159.6 (=C–O–),
158.5 (=C–NH2), 153.8 (Car–O–), 152.5 (Car), 144.8 (Car), 132.8 (Car), 129.7 (Car),
124.6 (Car), 122.9 (Car), 120.0 (Car), 119.4 (CN), 116.6 (Car), 114.1 (Car), 113.3 (Car),
112.1 (Car), 104.3 (=C–C=O), 58.5 (=C–CN), 55.1 (OCH3), 37.2 (benzylic–C).
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Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
2‑Amino‑4‑phenyl‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7i) Yellow
solid (M.p.: 271–273 °C); FT-IR (KBr, neat) νmax (cm−1)=3460, 3315, 3120, 2960,
1
2020, 1615, 1600, 1501, 1305, 1201, 1168, 800; H NMR (300 MHz, DMSO-d6,
CDCl3) δ 7.86 (m, 1H, ar–H), 7.54 (m, 1H, ar–H), 7.10–7.31 (m, 7H, ar–H), 6.85
(s, 2H, NH2), 4.44 (s, 1H, benzylic–CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ
160.0 (C=O), 158.4 (=C–O–), 153.8 (=C–NH2), 152.5 (Car–O–), 143.1 (Car), 132.7
(Car), 128.6 (Car), 127.8 (Car), 127.3 (Car), 124.5 (Car), 122.9 (Car), 119.3 (CN),
116.6 (Car), 113.3 (Car), 104.5 (=C–C=O), 58.9 (=C–CN), 37.3 (benzylic–C).
2‑Amino‑5‑oxo‑4‑(thiophen‑2‑yl)‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7j) Yellow solid (M.p.: 259–260 °C); FT-IR (KBr, neat) νmax (cm−1)=3470, 3390,
1
2960, 1765, 2022, 1660, 1620, 1600, 1510, 1306, 1210, 1165, 810, 710; H NMR
(300 MHz, DMSO-d6, CDCl3) δ 7.86 (d, J=7.8 Hz, 1H, ar–H), 7.57 (dd, J=7.8 Hz,
J=7.8 Hz, 1H, ar–H), 7.32 (m, 2H, ar–H, NH2), 7.16 (m, 3H, ar–H), 6.98 (m, 1H,
ar–H), 6.86 (m, 1H, ar–H), 4.79 (s, 1H, benzylic–CH); 13C NMR (75 MHz, DMSO-
d6, CDCl3) δ 159.9 (C=O), 158.9 (=C–O–), 153.5 (=C–NH2), 152.5 (Car–O–), 147.5
(Car), 132.9 (Car), 127.0 (Car), 125.3 (Car), 124.9 (Car), 124.7 (Car), 123.0 (Car), 119.3
(CN), 116.7 (Car), 113.3 (Car), 104.4 (=C–C=O), 58.4 (=C–CN), 32.3 (benzylic–C).
2‑Amino‑4‑(naphthalen‑1‑yl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7k) Yellow solid (M.p.: 253–254 °C); FT-IR (KBr, neat) νmax (cm−1)=3455, 3330,
3210, 2965, 1756, 2001, 1618, 1601, 1598, 1503, 1306, 1210, 1160, 805, 735;
1H NMR (300 MHz, DMSO-d6, CDCl3) δ 8.36 (d, J=7.8 Hz, 1H, ar–H), 7.93 (d,
J=7.5 Hz, 1H, ar–H), 7.80 (d, J=7.5 Hz, 1H, ar–H), 7.68 (d, J=7.8 Hz, 1H, ar–H),
7.21–7.57 (m, 7H, ar–H, NH2), 6.81 (d, J=7.5 Hz, 2H, ar–H), 5.38 (s, 1H, ben-
zylic–CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 160.0 (C=O), 158.3 (=C–O–),
154.3 (=C–NH2), 152.5 (Car–O–), 146.9 (Car), 140.4 (Car), 133.6 (Car), 133.2 (Car),
132.7 (Car), 131.3 (Car), 128.7 (Car), 126.3 (Car), 125.9 (Car), 125.7 (Car), 124.6 (Car),
123.4 (Car), 122.9 (Car), 119.4 (CN), 116.6 (Car), 113.2 (Car), 105.0 (=C–C=O),
59.5 (=C–CN), 33.2 (benzylic–C).
2‑Amino‑4‑(naphthalen‑2‑yl)‑5‑oxo‑4H,5H‑pyrano[3,2‑c]chromene‑3‑carbonitrile
(7l) Yellow solid (M.p.: 263–265 °C); FT-IR (KBr, neat) νmax (cm−1)=3450, 3295,
1
2985, 1765, 2010, 1618, 1610, 1560, 1510, 1315, 1208, 1140, 815, 745; H NMR
(300 MHz, DMSO-d6, CDCl3) δ 7.94–7.97 (m, 2H, ar–H), 7.69–7.74 (m, 3H, ar–H),
7.56–7.58 (m, 2H, ar–H), 7.29–7.39 (m, 6H, ar–H, NH2), 6.55 (s, 1H, benzylic–
CH); 13C NMR (75 MHz, DMSO-d6, CDCl3) δ 166.1 (C=O), 164.6 (=C–O–), 152.5
(=C–NH2), 135.6 (Car–O–), 133.3 (Car), 132.6 (Car), 132.1 (Car), 128.3 (Car), 128.1
(Car), 127.8 (Car), 127.5 (Car), 126.2 (Car), 125.7 (Car), 124.9 (Car), 124.4 (Car), 124.2
(Car), 117.0 (CN), 116.7 (Car), 104.7 (=C–C=O), 59.5 (=C–CN), 36.4 (benzylic–C).
1 3

N. Noroozi Pesyan et al.
Scheme 2 Preparation of Ni(II)-Schif base/SBA-15
Results and discussion
In this research, Ni(II)-Schif base/SBA-15 was prepared according to the proce-
dure shown in Scheme 2 [60, 61], and its application as a catalyst in the synthesis
of 2-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitrile deriv-
atives is studied. Nanocatalyst structure was characterized using scanning elec-
tron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, X-ray
difraction (XRD), transmission electron microscopy (TEM), thermogravimetric
analysis (TGA), atomic-force microscopy (AFM), and N2 adsorption/desorption
(BET) techniques.
FT‑IR analysis of Ni(II)‑Schif base/SBA‑15
Fourier-transform infrared (FT-IR) analysis on SBA-15 and Ni(II)-Schif base/
SBA-15 was performed for the frst characterization of the nature of surface
bonding. As shown in Fig. 1, an absorption band at 3435 cm−1 is observed, which
is assigned to hydroxyl stretching vibrations. Another band that represents the
vibration of Si–O–Si bond was also revealed at 1082 cm−1. A sharp absorption
band was assigned to C=N stretching vibration at 1625 cm−1 and C–H stretch-
ing vibration appearing at 2992 cm−1. The appearance of the above bands clearly
indicates that the Ni(II)-Schif base group was anchored to the surface of SBA-15
by the silanol groups.
1 3

Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Fig. 1 FT-IR spectra of SBA-15 and Ni(II)-Schif base/SBA-15
Fig. 2 XRD patterns of SBA-15 and Ni(II)-Schif base/SBA-15
XRD analysis of Ni(II)‑Schif base/SBA‑15
The XRD patterns for SBA-15 and Ni(II)-Schif base/SBA-15 are depicted in Fig. 2.
As it can be seen from this fgure, three difraction peaks in the 2θ region of 0.9–2.0
are observed (indexed as (100), (110), and (200) refections, associated with the
order hexagonal unit cell of the typical SBA-15 materials). In addition, Ni(II)-Schif
1 3

N. Noroozi Pesyan et al.
Fig. 3 a Nitrogen adsorption/desorption isotherms of SBA-15 and Ni(II)-Schif base/SBA-15 and b cor-
responding pore-size distribution profle of SBA-15 and Ni(II)-Schif base/SBA-15
Table 1 Textural properties of
Materials
SBA-15
C (M)a
SbBET
VcBJH
the SBA-15 and Ni(II)-Schif
base/SBA-15
–
0.14
540
460
1.01
0.84
Ni(II)-Schif base/
SBA-15
aInitial concentration of nickel species (mmol g−1
bSpecifc surface area (m2 g−1
cPore volume (cm3 g−1
)
)
)
base/SBA-15 has also three difraction peaks between 0.9 and 2.0. Nevertheless,
their intensities are lower in comparison with SBA-15 which shows an unchanged
mesoporous structure of Ni(II)-Schif base/SBA-15 but a decrease in the long-range
order signifcantly. The peak positions of Ni(II)-Schif base/SBA-15 also shift to
a higher angle which is indicative of smaller pore size due to a contrast matching
between the silicate framework and bulky organometallic groups (located inside the
channels of SBA-15 materials; see Fig. 2) [67, 68].
N2 adsorption–desorption isotherms and corresponding pore‑size distributions
of SBA‑15 and Ni(II)‑Schif base/SBA‑15
The nitrogen adsorption/desorption isotherms for pure SBA-15 and Ni(II)-Schif
base/SBA-15 catalyst are presented in Fig. 3a, b. The isotherm for SBA-15 is a
type-IV adsorption–desorption isotherm, which is characteristic of this mesoporous
material. The hysteresis loop is regular type H1 according to the IUPAC classif-
cation [69]. The adsorption/desorption isotherm of Ni(II)-Schif base/SBA-15
catalyst is also type IV. Table 1 displays the specifc area and the pore size where
Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods
were used to calculate them. In addition, the structure data of all these mesoporous
materials (BET surface area, pore size, total pore volume, and so on) are listed in
1 3

Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Fig. 4 Thermogravimetric
analysis results of: a SBA-15
and b Ni(II)-Schif base/SBA-15
this table. It is known that due to a high BET surface area (746 m2/g), pore size
(5.64 nm), and a large pore volume (0.97 cm3/g), SBA-15 can have potential applica-
tion as a host in materials. In comparison with those of pure SBA-15, SBA-15 after
functionalization with Ni(II)-Schif base through covalent bond to form Ni(II)-Schif
base/SBA-15 displays a smaller specifc area and a bit smaller pore size and pore
volume (decreases from 795 to 514 m2/g, 79 to 44 Å and 1.289 to 0.568 cm3 g−1,
respectively). The presence of organic ligand on the pore surface might be the main
reason for this issue.
Thermogravimetry analysis (TGA) of SBA‑15 and Ni(II)‑Schif base/SBA‑15,
inductively coupled plasma optical emission spectrometry (ICP‑OES)
Nanocatalyst thermal properties were studied by thermal gravimetric analysis
(TGA). Figure 4 displays the TGA plot of SBA-15 and Ni(II)-Schif base/SBA-15.
As shown in Fig. 4b, Ni(II)-Schif base/SBA-15 illustrates the two main steps of
weight loss in TGA curve. The frst step (endothermic), at temperatures to ~100 °C
(loss 8%), is related to the desorption of water molecules from the catalyst substrate.
(Pure siliceous SBA-15 also shows a signifcant decrease in the weight percentage
under 100 °C.) The second weight loss (exothermic) (47.5%) ranging from 200 and
700 °C is assigned to the decomposition of the ligand, and organic functional groups
from the surface of SBA-15 and CO, CO2 and NOx gases perhaps are released [70,
71].
Also, to extend the scope of catalyst characterization the exact amount of
Ni loaded on SBA-15 was investigated by ICP–OES analysis. It was found to be
0.39 mmol g−1.
AFM, TEM and SEM analyses
The TEM micrograph of Ni(II)-Schif base/SBA-15 nanocatalyst provides direct vis-
ualization of the well-ordered 2D p6 mm hexagonal structure of mesoporous chan-
nels along the directions parallel and perpendicular to the direction of the pore axis
(Fig. 5a). These results confrm that the characteristic pore dimensions and channel
1 3

N. Noroozi Pesyan et al.
Fig. 5 a TEM images of Ni(II)-Schif base/SBA-15, b SEM images of Ni(II)-Schif base/SBA-15, and c
SEM images of SBA-15
structures of the support material were unafected by the incorporation of the metal
complex to the SBA-15 matrix and show that TEM results are in agreement with the
XRD patterns. Figure 5b, c depicts the SEM images for SBA-15 and Ni(II)-Schif
base/SBA-15, respectively. Both SBA-15 and Ni(II)-Schif base/SBA-15 presented
similar fbrous structures, which showed that Ni(II) Schif base ligand groups graft
appeared to have no signifcant changes in the surface morphology occurred during
surface modifcation, and physical structure of the parent SBA-15 was saved. Fig-
ure 6 demonstrates the 2D and 3D AFM images of SBA-15 and Ni(II)-Schif base/
SBA-15 for the further investigation of surface properties, and particularly particle
dispersion. From the AFM images, the cone-shape is obvious for catalyst particles.
They are properly arranged and are well strewn from each other. These observations
supplement surface information obtained from the SEM images.
Application of immobilized Ni(II) Schif base complex supported on SBA‑15
as a heterogeneous catalyst
To study the efect of catalyst, the properly characterized Ni(II)-Schif base/SBA-
15 was then used as a catalyst in the one-pot synthesis of a class of 2-amino-
4H-chromene-3-carbonitrile derivatives. The model reaction was done simply by
mixing 4-hydroxycoumarin (1), 4-nitrobenzaldehyde (2a), and malononitrile (3)
1 3

Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Fig. 6 2D (a) and 3D (b) AFM images SBA-15; 2D (c) and 3D (d) AFM images of Ni(II)-Schif base/
SBA-15
Table 2 Screening of the
Entry Solvent Cat. (g) Temp. (°C) Time (min) Yield (%)a
reaction conditions for the
reaction of 4-nitrobenzaldehyde,
1
2
3
4
5
6
7
8
9
Free
H2O
Free
Free
Free
H2O
H2O
H2O
H2O
0
0
100
100
Rt
60
60
60
60
45
10
60
10
30
Trace
Trace
45
malononitrile, and
4-hydroxycoumarin for the
synthesis of 7a
0.05
0.10
0.05
0.05
0.005
0.10
0.05
Rt
45
70
70
70
70
70
Rt
98(97)b,c
83
90
80
Bold values indicate the best and greenly condition
All reactions were running under the following conditions:
4-nitrobenzaldehyde (1 mmol, 1 equiv), malononitrile (1.0 mmol,
1 equiv), 4-hydroxycoumarin (1.0 mmol, 1 equiv), and catalyst
(0–0.10 g) were heated for an appropriate time in the desired solvent
(2 mL) or solvent-free conditions
a% (based on GC yields)
bOptimum conditions
cIsolated yield in parentheses
to optimize reaction conditions for the synthesis of 2-amino-4-(4-nitrophenyl)-5-
oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile (7a) (Table 2). Various reaction
1 3

N. Noroozi Pesyan et al.
parameters such as the catalyst amount, solvent, and temperature were studied in
order to determine the efciency of the model reaction (Table 2). It is worth noting
that the model reaction was examined under solvent-free conditions at room tem-
perature, 70 °C and 100 °C. As shown in Table 2, entry 5, the yield was reasonable
at 70 °C. The reaction also failed to produce a product in the absence of the catalyst
(Table 2, entries 1, 2). In closing, it can be concluded that Ni(II)-Schif base/SBA-15
is an impressive catalyst for this condensation, the optimal amount of this catalyst
was 0.05 g in the water at 70 °C, and the corresponding product was obtained in
98% (Table 2, entry 6).
After optimizing the conditions and to indicate the applicability of the proposed
method, we decided to synthesize several 2-amino-4H-chromene derivatives from
three-component condensation reactions of diverse aromatic aldehyde, 4-hydroxy-
coumarin, and malononitrile at 70 °C in the presence of a catalytic amount of Ni(II)-
Schif base/SBA-15 (0.05 g) as a heterogeneous nanocatalyst and water as a green
solvent. Results are summarized in Table 3. All aromatic aldehydes bearing elec-
tron-withdrawing and electron-releasing substituents on their aromatic ring provided
the related products in good-to-excellent yields in shorter reaction time (10–15 min).
In Scheme 3, we have proposed a plausible mechanism for the synthesis of
2-amino-3-cyano-pyrano[3,2-c]chromen-5(4H)-one derivatives using Ni(II)-Schif
base/SBA-15 as a nanocatalyst. Firstly, Knoevenagel condensation of aromatic alde-
hyde (2) and malononitrile (3) in the presence of catalyst and water produced 2-ben-
zylidenemalononitrile (4) as an intermediate. In the fnal step, Michael addition of
intermediate (4) with 4-hydroxycoumarin (1) followed by cyclization and tautomeri-
zation then aforded the observed product (7).
To specify the advantages of the proposed method, a comparison of the catalytic
activity of Ni(II)-Schif base/SBA-15 with other diferent catalysts reported in the
literature to the synthesis of the model reaction (7a) is summarized in Table 4. As
shown, the newly built catalyst ofers several advantages over most of the litera-
ture methods such as clean reaction, short reaction time, simple workup procedure,
higher reusability, and higher yields. Therefore, the Ni(II)-Schif base/SBA-15 nano-
catalyst was found to be an efcient catalyst for this three-component condensation
of 2-amino-4-aryl-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile derivatives.
Catalyst reusability
Finally, recyclability and reusability of the catalyst were studied using the model
reaction when the conditions were optimized. Once the reaction was fnished, the
catalyst was easily and rapidly recovered from the reaction mixture by centrifuga-
tion and washed with acetone and water several times. Then, the catalyst was dried
and reused directly for fve runs without an appreciable loss of catalytic activity of
Ni(II)-Schif base/SBA-15. The partial loss of activity may be due to slight leaching
of nickel from the catalyst (Fig. 7).
Also, we carried out a hot fltration test for the condensation reaction of
4-nitrobenzaldehyde, malononitrile, and 4-hydroxycoumarin under optimized
reaction condition to examine the leaching of Ni in the reaction mixture. The
1 3

Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Table 3 Synthesis of 2-amino-4-phenyl-5-oxo-4H,5H-pyrano-[3,2-c]chromene-3-carbonitrile derivatives
(via condensation of aldehydes, 4-hydroxycoumarin, and malononitrile using Ni(II)-Schif base/SBA-15
as recoverable nanocatalyst in water)
Entry
Product
Yield
(%)[a]
M.P.
(ºC)
M.P.lit. (ºC)
1
97
254–255
251–253 [72]
7a
2
3
4
90
94
93
255 – 256
270–271
253– 256
257– 259 [51]
265–267 [72]
246– 248 [73]
7b
7c
7d
1 3

N. Noroozi Pesyan et al.
Table 3 (continued)
Entry
Product
Yield
(%)[a]
M.P.
(ºC)
M.P.lit. (ºC)
5
94
283– 284
281– 283 [74]
7e
6
92
273–274
267–269 [51]
7f
7
95
237–239
234–236 [51]
7g
8
93
248–250
241–243 [72]
7h
1 3

Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Table 3 (continued)
Entry
Product
Yield
(%)[a]
M.P.
(ºC)
M.P.lit. (ºC)
9
95
271–273
259–260
283–284
269–271 [75]
7i
10
94
255–256 [72]
7j
11
92
285–287 [72]
7k
12
90
263–265
241–243 [76]
7l
All reactions were running under the following conditions: Appropriate benzaldehyde derivatives
(1 mmol, 1 equiv), malononitrile (1.0 mmol, 1 equiv), 4-hydroxycoumarin (1.0 mmol, 1 equiv), and cata-
lyst (0.05 g of Ni(II)-Schif base/SBA-15 in water (2 mL) were heated with continuous stirring at 70 °C
for 10–15 min
aYield refers to that of pure isolated products
1 3

N. Noroozi Pesyan et al.
Scheme 3 A plausible mechanism for the Ni(II)-Schif base/SBA-15-catalyzed three-component cou-
pling reaction for the synthesis of pyran derivatives
Table 4 Comparison of Ni (II)-Schif base/SBA-15 with other catalysts reported in the literature for the
synthesis of 2-amino-4H-Chromenes (compound 7a)
Entry Catalyst
Amount; conditions
Time (min) Yield (%) Refs.
1
2
3
4
5
6
7
8
PPI
DBU
TMGT
Sepiolite
{Mo132
β-CD
15 mol%; H2O/refux
10 mol%; H2O/refux
0.025 g; 100 °C
10
5
25
95
91
81
90
95
87
95
98
[31]
[34]
[38]
[43]
[33]
[15]
[47]
This work
0.4 g; EtOH:H2O (1: 4)/refux 30
}
0.07 g; EtOH:H2O(1:1.2)/rt
10 mol%; H2O/60–65 °C
0.01 g; solvent-free/100 °C
10
120
16
Ni@Imine-Li+-MMT
Ni (II)-Schif base/SBA-15 0.05 g; H2O/70 °C
10
reaction was stopped, and the catalyst was fltered in half the time of the reac-
tion. At this step, the yield of the desired product was 55%. After that, the reac-
tion was continued under the same reaction condition. No increase in the prod-
uct yield was observed. This result clearly confrms the heterogeneous nature
of the Ni(II)-Schif base/SBA-15, and no leaching of Ni from the catalyst to the
reaction mixture occurred during the course of the catalytic reaction. The nature
of the recovered catalyst was investigated using SEM (Fig. 8). This result from
morphological changes for the recovered catalyst indicates that the catalyst can
be recycled fve times without any signifcant change in its structure or mesopo-
rosity of silicate parent.
1 3

Ni(II)‑Schif base/SBA‑15: a nanostructure and reusable…
Fig. 7 Investigation on the reusability of the catalyst for the preparation of 2-amino-4-(4-nitrophenyl)-5-
oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile (7a)
Fig. 8 SEM image of recovered Ni(II)-Schif base/SBA-15
Conclusions
In summary, the Ni(II)-Schif base/SBA-15 nanocatalyst was prepared by the
grafting of nickel Schif base complex on the surface of SBA-15, and then was
confrmed by FT-IR, TEM, TGA, XRD, AFM, and SEM analyses. This synthe-
sized heterogeneous nanocatalyst was used as an eco-friendly, green, mild, and
efcient catalyst for the synthesis of 2-amino-4-aryl-5-oxo-4H,5H-pyrano[3,2-c]
chromene-3-carbonitriles via a one-pot three-component reaction of an aromatic
aldehyde, malononitrile, and 4-hydroxycoumarin. Clean and simple procedure,
ease of separation, simple workup procedure, excellent yield, short reaction time,
1 3

N. Noroozi Pesyan et al.
avoidance of using dangerous organic solvents, and recyclability of the catalyst
are the key advantages of this protocol.
Acknowledgements The fnancial support of this work was gratefully acknowledged by the Research
Council of Urmia and Payame Noor Universities.
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