Amine modified nanozeolites for the three component synthesis of chromenes

Article abstract of DOI:10.1007/s11164-019-03858-5

Abstract: New amine modified nanozeolites were prepared and characterized using FT-IR, TGA, DTG, SEM, and TEM. Then the synthesized nanozeolites were employed as novel, recyclable and safe catalysts for the one-pot, three-component condensation of 4-hydro

Full text of DOI:10.1007/s11164-019-03858-5

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-019-03858-5
Amine modifed nanozeolites for the three component
synthesis of chromenes
Fatemeh Babaei1 · Sakineh Asghari1,2 · Mahmoud Tajbakhsh1
Received: 13 February 2019 / Accepted: 15 May 2019
© Springer Nature B.V. 2019
Abstract
New amine modifed nanozeolites were prepared and characterized using FT-IR,
TGA, DTG, SEM, and TEM. Then the synthesized nanozeolites were employed
as novel, recyclable and safe catalysts for the one-pot, three-component condensa-
tion of 4-hydroxycoumarin with aldehydes and malononitrile to produce new and
known pyrano[2,3-c]chromenes as potent biologically active compounds. This novel
method has many advantages, such as high product yield and a simple work-up
procedure.
Graphical abstract
Keywords Amine modifed nanozeolites · One-pot reaction · Three-component ·
4-Hydroxycoumarin · Diethylenetriamine · Chromenes
Extended author information available on the last page of the article
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F. Babaei et al.
Scheme 1 Synthesis of 3,4-dihydropyrano[c] chromenes using amine functionalized nanozeolites
Introduction
Multicomponent reactions (MCRs) are special types of synthetically useful organic
reactions in which three or more various substrates react to give a fnal product
in a one-pot procedure [1, 2]. These reactions are a powerful tool in the organic
synthesis and pharmaceutical chemistry, due to their wide range of usage in the
preparation of various structural scafolds and discovery of new drugs [3–5]. The
3,4-Dihydropyrano[c] chromene and its derivatives are very useful compounds in
various felds of chemistry, biology and pharmacology. Some of these compounds
exist widely in natural products and exhibit many features such as anticancer, anti-
anaphylactin, anticoagulant, diuretic, and spasmolytic activities [6–9]. In addition,
they have been applied to cure neurodegenerative disorders, such as Alzheimer’s
disease, amyotrophic lateral sclerosis, Parkinson’s disease, Huntington’s disease and
Down’s syndrome for the treatment of schizophrenia and myoclonus [10].
These compounds have been prepared from reaction of aromatic aldehyde, malo-
nonitrile and 4-hydroxycoumarin in the presence of a variety of acidic catalysts
including diammonium hydrogen phosphate (DAHP) [11], H6P2W18O62·18H2O [12]
and various bases like pyridine [13], tetrabutylammonium bromide (TBAB) [14]
and (S)-proline [11]. However, many of these reported methods sufer from draw-
backs like harsh reaction conditions, low yields, time-consuming reaction, cumber-
some product isolation procedures and difculty in recovery and reusability of the
catalysts. Therefore, the progress of novel approaches for synthesizing these com-
pounds is a great goal for organic chemists and pharmacists.
The use of heterogeneous catalysts in organic synthesis is a fascinating method to
access green catalysts, because they are well-matched with high-interest in diferent
processes of environmentally friendly chemical transformations [15]. Recently, the
preparation of catalysts based on zeolites and associated compounds has attracted
high attention in synthetic chemistry and technology, due to some reasons such as
the lack of need for separation through distillation or extraction [16–18]. Nanozeo-
lites have unique properties including excellent thermal stability, easy availability,
nontoxicity, low cost and reusability [19–21]. Because of extremely small dimen-
sions and large surface-to-volume ratio of nanozeolites, which increase the rate
and the reaction selectivity, we report here the synthesis of new modifed nanoze-
olites with multifunctional amines, and use them in the three component reaction
of 4-hydroxycoumarin 1, aromatic aldehyde 2 and malononitrile for synthesizing
3,4-dihydropyrano[c] chromenes (Scheme 1).
1 3

Amine modifed nanozeolites for the three component synthesis…
Experimental
Methods and materials
The chemicals such as (3-chloropropyl trimethoxysilane) (CPTMS), diethylenetri-
amine (DET), triethylenetetramine (TET) and tetraethylenepentamine (TEP) were
purchased from Merk (Germany). All the solvents were obtained from Sigma-
Aldrich Chemical Co. (St Louis, MO, USA). NaY nanozeolite with Si/Al = 2.5
was purchased from Zeolyst company (USA). Fourier transform infrared (FT-
IR) spectra of the neat and functionalized nanozeolites were taken by means of
a Bruker Tensor 27 spectrometer (Bruker, Karlsruhe, Germany). Vibration bands
were reported as the wavenumber (cm−1) and the spectra were recorded using the
KBr method. Melting points were measured in open glass capillaries using an
Electrothermal IA9100 series digital melting point apparatus (Electrothermal,
Essex, UK). 1H and 13C NMR spectra were obtained in CDCl3 solution by means
of a Bruker Avance DRX-400 spectrometer (Bruker, Ettlingen, Germany) at a
temperature of 25 °C. Thermo gravimetric analysis (TGA) was carried out on a
Netzsch TG 209 F1 analyzer (Netzsch, Selb, Germany) from ambient temperature
to 600 °C at a heating rate of 10 °C per min under a nitrogen atmosphere. The
morphology and the chemical composition of the products were characterized
using high-resolution feld emission scanning electron microscopy on a MIRA
3-XMU (Tescan, Brno, Czech Republic) coupled with energy dispersive X-ray
analysis (FE-SEM/EDX). The specifc surface area, pore volume, and pore size
distribution were measured by the nitrogen adsorption–desorption method using
the Brunauer–Emmett–Teller (BET) model and t-plot. All data were recorded and
analyzed with BELsorp, Japan.
General procedure for the synthesis of amine modifed nanozeolites
with multifunctional amines (ZS‑DET, ZS‑TET, ZS‑TEP)
To a three-necked round-bottomed fask equipped with a magnetic stirrer, a nitro-
gen inlet and refux condenser, NaY nanozeolite (1 g) was added into 30 mL of
anhydrous toluene at 110 °C for 30 min. Then 1.82 mL (10 mmol) of (3-chlo-
ropropyl trimethoxysilane) (CPTMS) was poured into the mixture. The reaction
mixture was refuxed for 4 h. Then, the mixture was cooled and fltrated to sepa-
rate the solid residue. For removing of non-grafted CPTMS, the solid was placed
in a Soxhlet extractor and extracted by 150 mL of ethanol (99.5%) for 24 h. Then,
the obtained silane–functionalized zeolite (ZS) was poured into 30 mL of anhy-
drous dichloromethane at ambient temperature under an inert atmosphere of nitro-
gen. Then, 1.38 mL (10 mmol) of triethylamine and 10 mmol of the respective
amine (DET, TET or TEP) were poured into the mixture and stirred for 24 h. The
catalyst was isolated via fltration. To remove the non-grafted amine, the solid
was placed in a Soxhlet extractor and extracted by 150 mL of ethanol (99.5%) for
24 h. The obtained solid was dried in an oven overnight.
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F. Babaei et al.
General procedure to prepare pyrano[2,3‑c]coumarin derivatives 4a‑am
4-Hydroxycoumarin 1 (1 mmol), aromatic aldehydes 2 (1 mmol), malononitrile 3
(1.1 mmol) and ZS-DET (10 mg) were added to a 10 mL EtOH in a 25-mL Pyrex
fask and stirred for an appropriate time (Table 3). Progress of the reaction was
controlled by thin layer chromatography (TLC) using hexane/EtOAc (3:2). At the
end of the reaction, nano-zeolit catalyst (ZS-DET) was separated through fltra-
tion. The solvent of the residue solution was removed under vacuum, and then the
residue was recrystallized in EtOH to produce the compounds 4a–4m.
Spectral data
1
Compound 4a H NMR (DMSO, 400 MHz): δ 7.90 (dd, 1H, J = 8.0, 1.6 Hz),
7.72 (td, 1H, J = 8.0, 1.6 Hz), 7.50 (d, 2H, J = 8.4 Hz), 7.48–7.45 (m, 4H), 7.25
(d, 2H, J = 8.4 Hz), 4.47 (s, 1H). 13C NMR (DMSO, 100 MHz): δ 160.00, 158.40,
158.36, 154.02, 152.64, 143.22, 133.49, 131.82, 130.48, 125.16, 122.97, 120.69,
119.56, 117.06, 113.40, 103.88, 57.87.
1
Compound 4b H NMR (DMSO, 400 MHz): δ 7.90 (dd, 1H, J = 8.0, 1.6 Hz),
7.72 (td, 1H, J = 8.0, 1.6 Hz), 7.50 (t, 2H, J = 7.2 Hz), 7.45 (s, 2H), 7.37 (d, 2H,
J = 8.4 Hz), 7.31 (d, 2H, J = 8.4 Hz), 4.49 (s, 1H). 13C NMR (DMSO, 100 MHz):
δ 160.00, 158.42, 158.38, 154.02, 152.65, 142.79, 133.48, 132.15, 130.11,
128.90, 125.16, 122.98, 119.54, 117.05, 113.41, 103.95, 57.97, 36.89, 36.85.
1
Compound 4c H NMR (DMSO, 400 MHz): δ 7.91 (dd, 1H, J = 8.0, 1.6 Hz),
7.80 (d, 2H, J = 8.4 Hz), 7.73 (td, 1H, J = 8.0, 1.6 Hz), 7.51 (d, 2H, J = 8.4 Hz),
7.49–7.46 (m, 4H), 4.60 (s, 1H). 13C NMR (DMSO, 100 MHz): δ 160.04, 158.49,
154.40, 152.72, 149.25, 133.60, 132.97, 129.36, 125.19, 123.04, 119.40, 119.19,
117.09, 113.40, 110.41, 103.33, 57.35, 37.47.
1
Compound 4d H NMR (DMSO, 400 MHz): δ 7.91 (dd, 1H, J = 8.0, 1.6 Hz),
7.80 (d, 2H, J = 8.4 Hz), 7.73 (td, 1H, J = 8.0, 1.6 Hz), 7.51 (d, 2H, J = 8.4 Hz),
7.49–7.46 (m, 4H), 4.60 (s, 1H). 13C NMR (DMSO, 100 MHz): δ 160.04, 158.49,
154.40, 152.72, 149.25, 133.60, 132.97, 129.36, 125.19, 123.04, 119.40, 119.19,
117.09, 113.40, 110.41, 103.33, 57.35, 37.47.
1
Compound 4e H NMR (DMSO, 400 MHz): δ 7.92–7.89 (m, 2H), 7.72 (td,
1H, J = 8.0, 1.6 Hz), 7.66 (td, 1H, J = 8.0, 1.2 Hz), 7.56 (s, 2H), 7.54–7.53 (m,
1H), 7.52-7.51 (m, 1H), 7.50-7.47 (m, 1H), 7.45 (d, 1H, J = 8.4 Hz), 5.25 (s, 1H).
13C NMR (DMSO, 100 MHz): δ 160.18, 159.06, 159.02, 154.06, 152.64, 149.64,
137.80, 134.15, 133.59, 131.62, 128.93, 125.24, 124.43, 123.03, 119.14, 117.12,
113.30, 103.77, 56.53, 32.06, 32.01.
1
Compound 4f H NMR (DMSO, 400 MHz): δ 7.90 (dd, 1H, J = 8.0, 1.6 Hz),
7.73 (td, 1H, J = 8.0, 1.6 Hz), 7.58 (d, 1H, J = 2.0 Hz), 7.53–7.47 (m, 4H), 7.39 (d,
1H, J = 8.4 Hz), 7.35 (dd, 1H, J = 8.4, 2.0 Hz), 4.98 (s, 1H). 13C NMR (DMSO,
100 MHz): δ 159.89, 158.59, 154.62, 152.69, 139.88, 133.60, 132.85, 132.56,
129.32, 128.34, 125.22, 123.00, 119.15, 117.10, 113.28, 102.94, 56.46, 34.38.
1 3

Amine modifed nanozeolites for the three component synthesis…
1
Compound 4h H NMR (CDCL3, 400 MHz): 8.06 (d, 1H, J = 7.2 Hz), 7.83
(dd, 1H, J = 7.2, 1.6 Hz), 7.57 (td, 1H, J = 8.0, 1.6 Hz), 7.35-7.30 (m, 3H), 7.17
(d, 1H, J = 8.4 Hz), 4.91 (s, 1H), 4.09 (q, 2H, J = 7.2 Hz), 1.19 (t, 3H, J = 7.2 Hz).
13C NMR (CDCL3, 100 MHz): δ 168.55, 160.67, 157.95, 152.84, 152.60, 142.90,
132.32, 131.09, 129.89, 128.24, 128.15, 125.21, 124.36, 123.36, 122.26, 116.89,
113.35, 107.42, 79.72, 35.07, 14.19.
1
Compound 4i H NMR (CDCL3, 400 MHz): 8.06 (d, 1H, J=7.2 Hz), 7.83 (dd,
1H, J=7.2, 1.6 Hz), 7.57 (td, 1H, J=8.0, 1.6 Hz), 7.35–7.30 (m, 3H), 7.17 (d, 1H,
J=8.4 Hz), 4.91 (s, 1H), 4.09 (q, 2H, J=7.2 Hz), 1.19 (t, 3H, J=7.2 Hz). 13C NMR
(CDCL3, 100 MHz): δ 168.55, 160.67, 157.95, 152.84, 152.60, 142.90, 132.32,
131.09, 129.89, 128.24, 128.15, 125.21, 124.36, 123.36, 122.26, 116.89, 113.35,
107.42, 79.72, 35.07, 14.19.
1
Compound 4j H NMR (CDCL3, 400 MHz): δ 7.84 (dd, 1H, J=8.0 Hz), 7.58
(td, 1H, J=8.4, 1.6 Hz), 7.36–7.32 (m, 3H), 7.29 (d, 1H, J=2.4 Hz), 7.15 (dd,
1H, J=8.0, 2.4 Hz), 6.57 (s, 2H), 5.21 (s, 2H), 4.09 (q, 2H, J=7.2 Hz), 1.19 (t,
3H, J=7.2 Hz). 13C NMR (CDCL3, 100 MHz): δ 168.60, 160.37, 158.11, 153.78,
152.72, 139.11, 134.65, 133.55, 132.95, 132.46, 129.63, 126.58, 124.35, 122.34,
116.91, 113.08, 105.25, 78.13, 60.13, 34.26, 14.22.
1
Compound 4k H NMR (DMSO, 400 MHz): δ 7.98 (dd, 1H, J=8.0, 1.6 Hz),
7.93 (s, 2H), 7.71 (d, 2H, J=8.0 Hz), 7.69 (dd, 1H, J=8.0, 1.6 Hz), 7.49 (td, 1H,
J=8.0, 1.2 Hz), 7.44 (d, 3H, J=8.0 Hz), 4.74 (s, 1H), 3.98 (q, 2H, J=7.2 Hz), 1.08
(t, 3H, J=7.2 Hz). 13C NMR (DMSO, 100 MHz): δ 167.74, 160.33, 158.97, 153.98,
152.65, 150.99, 133.40, 132.42, 129.77, 125.15, 123.07, 119.31, 117.03, 113.48,
109.65, 106.02, 76.46, 59.62, 36.21, 14.61, 14.58.
1
Compound 4l H NMR (DMSO, 400 MHz): δ 8.12 (d, 2H, J=8.8 Hz), 7.99
(dd, 1H, J=8.0, 1.6 Hz), 7.96 (s, 2H), 7.71 (td, 1H, J=8.0, 1.6 Hz), 7.53 (d, 2H,
J=8.8 Hz), 7.50–7.48 (m, 1H), 7.45 (d, 1H, J=8.4 Hz), 4.81 (s, 1H), 3.98 (q,
2H, J=7.2 Hz), 1.10 (t, 3H, J=7.2 Hz). 13C NMR (DMSO, 100 MHz): δ 167.70,
160.31, 158.96, 158.90, 154.02, 153.04, 152.70, 146.54, 133.45, 130.02, 125.17,
123.68, 123.08, 117.07, 113.48, 105.92, 76.34, 59.65, 36.06, 14.60.
1
Compound 4m H NMR (DMSO, 400 MHz): δ 8.12 (d, 2H, J=8.8 Hz), 7.99
(dd, 1H, J=8.0, 1.6 Hz), 7.96 (s, 2H), 7.71 (td, 1H, J=8.0, 1.6 Hz), 7.53 (d, 2H,
J=8.8 Hz), 7.50–7.48 (m, 1H), 7.45 (d, 1H, J=8.4 Hz), 4.81 (s, 1H), 3.98 (q,
2H, J=7.2 Hz), 1.10 (t, 3H, J=7.2 Hz). 13C NMR (DMSO, 100 MHz): δ 167.70,
160.31, 158.96, 158.90, 154.02, 153.04, 152.70, 146.54, 133.45, 130.02, 125.17,
123.68, 123.08, 117.07, 113.48, 105.92, 76.34, 59.65, 36.06, 14.60.
Results and discussion
Initially NaY nanozolite (Z) has been reacted with CPTMS leading silane–function-
alized zeolite (ZS). Then, it was reacted with DET as a tridentate amine to aford
ZS-DET as a basic nanocatalyst. Similarly, TET (as a tetradentate amine) and TEP
(as a pentadentate amine) instead of DET have been reacted with ZS, which led to
ZS-TET and ZS-TEP catalysts as presented in Scheme 2. FT-IR spectroscopy, TGA,
SEM and TEM were used to characterize the obtained catalysts.
1 3

F. Babaei et al.
Scheme 2 Preparation of amine functionalized nanozeolites (ZS-DET, ZS-TET and ZS-TEP)
Z
ZS
ZS-DET
ZS-TET
ZS-TEP
1640
3459
1014
2956
1637
3462
3476
1026
1024
2937
1471
1650
2954
2974
1468
1658
3477
1031
1479
1641
3476
1022
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm-1)
Fig. 1 IR spectra of Z, ZS, ZS-DET, ZS-TET and ZS-TEP
1 3

Amine modifed nanozeolites for the three component synthesis…
FT-IR spectra of Z, ZS, ZS-DET, ZS-TET and ZS-TEP are presented in Fig. 1.
The IR spectrum of Z shows signifcant bands at 3473, 1640, and 1029 cm−1,
which are associated with O–H stretching vibrations corresponding to the
hydrogen-bonded silanol groups, H–O–H bend and Si–O-Si asymmetric stretch-
ing vibrations, respectively [22]. The IR spectrum of ZS exhibits an addi-
tional absorption peak at 2800–2950 cm−1 relating to the C-H stretching of the
CH2CH2CH2–Cl group, confrming that CPTMS has been attached to the sur-
face of Z. The IR spectrum of ZS-DET exhibits signifcant bands at 1640 and
1470 cm−1, which can be related to NH2 bending vibration for the primary amine
group (RNH2); a broad peak at 3473 cm−1 for N–H stretching vibration for the
secondary amine group (R2NH) [22–26]. The IR spectra of ZS-TET and ZS-TEP
are as the same as that of ZS-DET. These outcomes prove that the ZS surface has
been functionalized by TET and TEP, respectively.
Figures 2 and 3 show the TGA and DTA of the pure Z and modifed ZSs with the
diverse types of amines, respectively. The samples were heated from 30 °C to 600 °C
by a speed of 10 °C per minute. The TGA profle of Z shows a weight loss occurred
near 100 °C and a sharp weight loss appeared at 150 °C, which could be ascribed to
the desorption of moisture or the surface absorbed water. The heating of pure Z from
160 to 600 °C, did not show any signifcant weight loss indicating the high ther-
mal stability of zeolite. The ZS-DET, ZS-TET and ZS-TEP had two weight losses.
The frst weight loss region <110 °C) is because of the evaporation of the adsorbed
water. The second region (for ZS-DET, ZS-TET and ZS-TEP 200–400 °C) can be
mostly ascribed to the removal of aliphatic amine groups. Further, as it is clear the
order of thermal stability based on char yield is: ZS-DET>ZS-TET>ZS-TEP.
Fig. 2 TGA curves of pure Z, ZS and amine-modifed ZSs
1 3

F. Babaei et al.
Fig. 3 DTA curves of pure Z, ZS and amine-modifed ZSs
Table 1 CHN analysis of ZS
Entry
Catalyst
C (wt%)
N (wt%)
and ZS-DET
1
2
ZS
ZS-DET
4.17
8.24
–
2.74
The amount of amine in the structure of ZS-DET was estimated to be about
1.84 mmol/g. In addition, the CHN analysis of ZS and ZS-DET is exhibited in
Table 1. Increasing percent of carbon and nitrogen in ZS-DET clearly confrm
the successful grafting of an amine group on the surface of ZS. According to the
found N% from the CHN analysis, the amount of amine grafted onto ZS is nearly
1.30 mmol/g which is closed to the results obtained from TGA.
The morphology of the nanocatalysts surface was investigated by SEM as repre-
sented in Fig. 4. The uniform and faky structure together with the existence of some
particulates at the ZS-DET surface indicate that DET has been grafted to ZS. Parti-
cle size of Z, ZS and ZS-DET was provided by SEM with a mean size ranging from
16 to 23 nm as indicated in the related fgure.
The TEM images of Z, ZS and ZS-DET are shown in Fig. 5 which show aggre-
gated particles and do not give any information about the sample particle size.
The BET model of Z, ZS and ZS-DET is depicted in Fig. 6a, b. According to
IUPAC classifcation, adsorption isotherms for Z and ZS are type I (Fig. 6a, b) while
for ZS-DET it is type III (Fig. 6c). This data suggests that the structure of ZS-DET
1 3

Amine modifed nanozeolites for the three component synthesis…
Fig. 4 SEM images of Z, ZS and ZS-DET
Fig. 5 TEM image of of Z, ZS and ZS-DET
has been changed from microporous to macroporous. The useful data was extracted
from BET and t-plot curves of nanozeolites (Z, ZS and ZS-DET). As it can be seen
from Table 2, total specifc surface area (SBET) reduced by functionalization of
nanozeolite Z by silanated agent (ZS) followed by amination with DET (ZS-DET).
This could be due to grafting of functional groups on the surface of Z and flling
the pores thus reducing the surface area. This trend is also observed for total spe-
cifc surface area (a1), External specifc surface area (a2) and micropore area (a1-
a2) which wasextracted from t-plot curves (Table 2). The result of the t-plot is not
reported for the ZS-DET because of its macroporous structure.
Following our previous investigations on the improvement of green synthetic
procedures for the preparation of heterocyclic compounds; herein, we report a
1 3

F. Babaei et al.
Fig. 6 BET plot and t-plot of Z (a), ZS (b) and ZS-DET (c)
Table 2 The pore structure properties of nanocatalysts that were calculated from BET model and t-plots
Catalyst
BET
t-plot
Total specifc surface
Total specifc surface External specifc sur-
Micropore area
area (SBET, m2 g−1
)
area (a1, m2 g−1
)
face area (a2, m2 g−1
)
(a1−a2, m2 g−1
)
Z
ZS
ZS-DET
934.0
452.7
6.50
1249.5
572.8
–
2.94
1.93
–
1246.55
570.91
–
new green condition for synthesizing some pyrano[2,3-c]coumarins 4 from the
condensation reaction of 4-hydroxycoumarin 1, aromatic aldehydes 2 and malo-
nonitrile 3 in the presence of a catalytic amount of the synthesized modifed
nanozeolites (Scheme 3).
To achieve green reaction conditions, we examined a three-component reaction
of malononitril, 4-bromo benzaldehyde and 4-hydroxycoumarin as a model reac-
tion in the presence of a base nanonocatalyst (ZS-DET) in various solvents. As is
observed in Table 3, EtOH is the optimal solvent in this reaction (entry 3).
1 3

Amine modifed nanozeolites for the three component synthesis…
Scheme 3 Synthesis of pyrano[2,3-c]chromenes using ZS-DET
Table 3 Optimized condition of
Entry
Catalyst
Solvent
Time (min)
Yield %a
the reaction: 4-hydroxycoumarin
(2 mmol), 4-bromo-
1
2
3
4
5
ZS-DET
ZS-DET
ZS-DET
ZS-DET
ZS-DET
MeOH
THF
EtOH
EtOH:H2O
H2O
60
60
40
60
60
65
trace
90
trace
trace
benzaldehyde (2 mmol), and
malononitrile (2 mmol), 10 mg
catalyst in 10 mL solvent at
ambient temperature
aIsolated yields
Table 4 Optimized
Entry
ZS-DET (mg)
Time (min)
Yield %a
conditions for reactions of
4-hydroxycoumarin (2 mmol),
4-bromo-benzaldehyde
(2 mmol), and malononitrile
(2 mmol) in the existence of
various amounts of ZS-DET
as catalyst in EtOH at diferent
times
1
2
3
4
5
10
25
50
60
40
40
40
40
75
90
91
89
88
5
100
aIsolated yields
The reaction was performed using diverse amounts of ZS-DET as catalyst (5, 10,
25, 50 and 100 mg). The achieved outcomes in Table 4 show that ZS-TET is 10 mg
at the optimized condition (Table 4, entry 2). Also, a higher amount of catalyst did
not improve the results.
This reaction was studied in the presence of the prepared heterogeneous catalysts
(Z, ZS, ZS-DET, ZS-TET and ZS-TEP). The obtained results in Table 5 well indi-
cate that this reaction proceeds successfully in the presence of amine functional-
ized nanozeolites (ZS-DET, ZS-TET and ZS-TEP) while trace product obtained in
the presence of Z or ZS (entries 3, 4 and 5 compared to entries 1 and 2). Among
heterogeneous catalysts, ZS-DET was aforded to the product in the highest yield.
1 3

F. Babaei et al.
Table 5 Study of the reaction of
4-hydroxycoumarin (2 mmol),
4-bromo-benzaldehyde
Entry
Catalyst
Amount of catalyst
Yield %a
1
2
3
4
5
6
7
8
Z
ZS
10 mg
10 mg
10 mg
10 mg
10 mg
1 eq
Trace
Trace
90
82
76
98
95
90
(2 mmol), and malononitrile
(2 mmol) in the various catalysts
ZS-DET
ZS-TET
ZS-TEP
DET
DET
TET
0.1 eq
1 eq
9
10
TET
TEP
0.1 eq
1 eq
85
87
11
TEP
0.1 eq
82
aIsolated yields
Also, the reaction was tested with various equivalents of the homogenous catalysts
(DET, TET and TEP) and then compared to the related heterogeneous catalysts. The
outcomes show that when DET is used in the reaction, the highest yield is obtained
(entries 6 and 7 compared to entries 8–11 in Table 5). Interestingly, the same trend
is found for the desired heterogeneous catalysts (for example, entry 3 compared to
entries 4 and 5 in Table 5). Considering the advantages of heterogeneous catalysts,
such as easy separation and reusability, ZS-DET was selected as the optimal hetero-
geneous catalysts for this reaction.
Table 6 is provided to demonstrate the merit of this technique for synthesizing
pyrano[2,3-c]coumarins in comparison with some previously reported ones [11,
27–32]. According to Table 6, DMAP was employed as a basic catalyst under
refuxing EtOH. Although this method afords excellent yields, it sufers from the
long time needed (entry 1). In the case of (S)-proline, the product is obtained in
low yield with a long time (entry 2). Using some catalysts, such as diammonium
Table 6 Comparison of the literature outcomes for the preparation of 4b with the results using this
method
Entry
Catalyst/amount
Conditions
Time (min)
Yield (%) [Ref]
1
2
3
4
5
6
7
8
9
DMAP/20 mol%
(S)-Proline/10 mol%
DAHP/10 mol%
EtOH/refux
H2O:EtOH/refux
H2O:EtOH/r.t
H2O:EtOH/refux
H2O:EtOH/r.t
EtOH/r.t
EtOH/refux
H2O:EtOH/refux
EtOH/r.t
300
240
180
260
150
240
240
75
94 [27]
78 [11]
85 [11]
86 [28]
82 [29]
92 [30]
90 [31]
89 [32]
92a
Fe3O4/SiO2-Met
Na2WO4 .2H2O/5 mol%
Silica gel/300 wt%
KF–Al2O3/0.125 g
H6P2W18O62·18H2O, 1 mol%
ZS-DET
40
aThis work
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Amine modifed nanozeolites for the three component synthesis…
hydrogen phosphate (DAHP) (entry 3), Fe3O4/SiO2 -Met (entry 4), sodium tung-
state (entry 5), Silica gel (entry 6), KF–Al2O3 (entry 7) and heteropoly acid
(entry 8) results in a time-consuming reaction. We believe that these reactions
can be efciently carried out under our suggested conditions with respect to reac-
tion times and product yield.
After optimization of the reaction conditions, to extend the scope of this reac-
tion, a variety of aromatic aldehydes 2 were reacted with 1 and 3 (Table 7). Char-
acterization of all the products was performed by comparing their spectra and
physical data with those reported in the literature.
A mechanistic rationale is suggested for formation of pyranochromenes 4,
presented in Scheme 4. It appears that the reaction occurs in three phases. It is
reasonable to assume that, the initial event involves the formation of the aryl-
methylene 5 via a Knoevenagel condensation of the aldehyde and malononitrile
catalyzed by nano-ZS-DET. In the next steps, a Michael-type added to the aryl-
methylene and following heterocyclization stimulated by nano ZS-DET provides
the relevant products 4.
The key disadvantage of many developed approaches for these reactions is
destruction of the catalysts in the workup process and so it cannot be retained or
recycled. In these procedures, as shown in Fig. 7, the nano ZS-DET showed recy-
clability up to four cycles, for which there are insignifcant losses in the catalytic
performance. However, the SEM image of recycled ZS-DET, after recycling four
times, was provided (Fig. 8) and compared with fresh catalyst (Fig. 4). Compari-
son of these two images showed no signifcant diference.
Table 7 Synthesis of 3,4-dihydropyrano[c]chromene derivatives
Product
Ar
X
Time (min)
Yield (%)a
Mp (°C)
Lit.Mp °C[Ref]
4a
4b
4c
4d
4e
4f
4g
4h
4i
4-Br–C6H4
4-Cl–C6H4
CN
CN
CN
CN
CN
CN
CN
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
CO2Et
40
30
30
45
60
10
60
30
30
30
40
40
60
90
92
94
90
88
98
84
80
84
90
86
82
75
253–254
260–261
291–293
257–259
256–257
255–256
166–169
141–143
195–196
199–201
207–209
241–242
207–209
256–258 [11]
262–264 [29]
289–290 [33]
258–260 [13]
252–255 [34]
257–259 [11]
168–170 [34]
142–144 [27]
192–194 [35]
200–201 [36]
–
4-CN–C6H4
4-NO2–C6H4
2-NO2–C6H4
2,4-diCl–C6H3
3-OH–C6H4
4-Br–C6H4
4-Cl–C6H4
4j
4k
4l
2,4-diCl–C6H3
4-CN–C6H4
4-NO2–C6H4
2-NO2–C6H4
241–244 [27]
–
4m
aIsolated yields
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F. Babaei et al.
Scheme 4 The suggested mechanism for synthesizing pyranocoumarins 4 catalyzed by nano ZS-DET
90
70
50
30
1
2
3
4
5
Cycle
Fig. 7 Reusability of the catalysts in the model reaction (in 40 min)
Conclusions
In this study, initially, the silanated nanozeolite (ZS) was synthesized from
the reaction of nanozeolite (Z) and CPTMS. Then, new modifed nanozeolites
(ZS-DET, ZS-TET and ZS-TEP) were synthesized from the reaction of ZS with
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Amine modifed nanozeolites for the three component synthesis…
Fig. 8 SEM image of ZS-DET catalyst after recycling four times
multifunctional amines (DET, TET and TEP). FT-IR, TGA, DTG, SEM, and
TEM were used to characterize the samples. Then, they were utilized in the reac-
tions of aromatic aldehydes, malononitrile and 4-hydroxycoumarin as basic het-
erogeneous catalysts. Among the prepared catalysts, ZS-DET was a more efec-
tive catalyst to form pyrano[2,3-c]chromens than ZS-TET and ZS-TEP. Simple
procedure, excellent efciencies in short reaction times, inexpensive workup, ease
of handling, cleaner reaction, and usage of reusable nanocatalyst are the attractive
properties of this protocol.
Acknowledgements The authors are thankful to University of Mazandaran for fnancial support in this
project.
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F. Babaei et al.
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Amine modifed nanozeolites for the three component synthesis…
Afliations
Fatemeh Babaei1 · Sakineh Asghari1,2 · Mahmoud Tajbakhsh1
* Sakineh Asghari
s.asghari@umz.ac.ir
1
Department of Organic Chemistry, Faculty of Chemistry, University of Mazandaran,
Babolsar 47416-95447, Iran
2
Nano and Biotechnology Research Group, University of Mazandaran, Babolsar 47416-95447,
Iran
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