SO3H-dendrimer functionalized magnetic nanoparticles (Fe3O4@D–NH–(CH2)4–SO3H): Synthesis, characterization and its application as a novel and heterogeneous catalyst for the one-pot synthesi

Article abstract of DOI:10.1016/j.poly.2019.01.055

In this study, novel SO₃H-dendrimer functionalized magnetic nanoparticles (Fe₃O₄@D–NH–(CH₂)₄–SO₃H) were prepared and characterized by using FT-IR, X-ray diffraction patterns, scanning elect

Full text of DOI:10.1016/j.poly.2019.01.055

Accepted Manuscript
SO3H-Dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH-
(CH2)4-SO3H): synthesis, characterization and its application as a novel and
heterogeneous catalyst for the one-pot synthesis of polyfunctionalized pyrans
and polyhydroquinolines
Behrooz Maleki, Oliver Reiser, Ehsan Esmaeilnezhad, Hyoung Jin Choi
PII:
S0277-5387(19)30077-4
https://doi.org/10.1016/j.poly.2019.01.055
POLY 13728
DOI:
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
21 December 2018
20 January 2019
22 January 2019
Please cite this article as: B. Maleki, O. Reiser, E. Esmaeilnezhad, H.J. Choi, SO3H-Dendrimer functionalized
magnetic nanoparticles (Fe3O4@D-NH-(CH2)4-SO3H): synthesis, characterization and its application as a novel and
heterogeneous catalyst for the one-pot synthesis of polyfunctionalized pyrans and polyhydroquinolines,
Polyhedron (2019), doi: https://doi.org/10.1016/j.poly.2019.01.055
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SO3H-Dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH-(CH2)4-SO3H):
synthesis, characterization and its application as a novel and heterogeneous catalyst for
the one-pot synthesis of polyfunctionalized pyrans and polyhydroquinolines
Behrooz Maleki,*a,b Oliver Reiserb, Ehsan Esmaeilnezhad,c Hyoung Jin Choid
aDepartment of Chemistry, Hakim Sabzevari University, Sabzevar, 96179-76487, Iran
E-mail:malekibehrooz@gmail.com; Tel:+985144013324
bInstitut fȕr Organische Chemie, Universitat Regensburg, Universitatsstr. 31, 93053
Regensburg, Germany
cDepartment of Petroleum Engineering, Hakim Sabzevari University, Sabzevar, Iran
dDepartment of Polymer Science and Engineering, Inha University, Incheon 22212, Korea
Abstract: In this research, the novel SO3H-dendrimer functionalized magnetic nanoparticles
(Fe3O4@D-NH-(CH2)4-SO3H) were prepared and characterized by using FT-IR, X-ray
diffraction patterns, scanning electron microscopy, transmission electron microscopy,
thermogravimetry analysis, and energy-dispersive X-ray spectroscopy. The synthesized
nanosized catalyst was successfully applied to the synthesis of highly substituted pyrans and
polyhydroquinolines via a straightforward one-pot multicomponent condensation reaction.
The key advantages are the short reaction time, high yields, simple workup, and purification
of products by non-chromatographic methods, by simple recrystallization from ethanol.
Keywords: SO3H-Dendrimer functionalized magnetic nanoparticles, Dendrimer, Pyrans,
Polyhydroquinolines.
1. Introduction
Dendrimers, a unique class of polymers, are highly branched macromolecules, in which their
size and shape can be precisely controlled. The well-defined structure, a monodisperse size
distribution, surface functionalization capability, and stability are properties of dendrimers
that make them attractive drug carrier candidates.[1] Dendrimers have been also utilized for
several applications[2] including homogeneous catalysis.[3] Interestingly, in many cases, the
soluble dendritic catalysts were found to be more efficient or selective than the traditional
analogues of metal complexes. In recent years, dendrimers immobilized on silica or polymers
have been investigated intensively and applied to several catalytic organic transformations.[4]
1

These new catalytic materials are sometimes highly efficient in terms of reactivity and
selectivity and are easily recyclable.
Heterogeneous catalysis is noteworthy for both academic and industrial synthesis due to
its advantages over homogeneous catalysis.[5-6] It is clear that green chemistry not only
requires the use of environmentally benign reagents and solvents but also it is very crucial to
recover and reuse the catalysts. One method to prove this target, is the immobilization of a
catalytic homogeneous tag on a nanomagnetic hybrid solid material, to convert it to a
heterogeneous catalyst with homogeneous action in chemical-based processes. In thes.e types
of solids, the reactive centers are highly mobile similar to homogeneous catalysts and at the
same time these species have the advantage of being recyclable in the same fashion as
heterogeneous catalysts. In view of this issue, several types of solid sulfonic acid have been
synthesized and applied as an alternative to traditional sulfonic acid resins and homogeneous
acids in catalyzing chemical transformations.[7] Application of solid acids in organic
transformation has an important role because of their wide range of advantages, such as,
simplicity in handling, decreased reactor and plant corrosion problems, easy separation from
products without the necessity of washing, and more environmentally safe disposal.
Among the four types of magnetic nanoparticles (MNPs), including metals, alloys, metal
oxides, and ferrites, iron oxides are by far the most widely used supports of magnetically
recoverable catalysts. This is due to their low cost, easy preparation, biocompatibility
properties [SPIONs (superparamagnetic iron oxide nanoparticles) are also much used for
biomedical applications], stability, and ease of their surfaces functionalizing with other metal
particle fragments (Au, Pd, Pt, Cu, Ni, Ir), inorganic and organometallic catalysts,
organocatalysts, and enzymes.[8]
Compounds bearing a pyran framework are significant intermediates in organic synthesis
and display several physiological properties and pharmacological activities, for example
antibacterial,[9] antitumor,[10] anti-inflammatory,[11] anti-HIV, analgesic and myorelaxant[12]
activities. In recent years, syntheses of these type of molecules have been studied, with
reagents such as, nano-structured diphosphate (Na2CaP2O7),[13] silica-coated magnetic
NiFe2O4 nanoparticle-supported Preyssler heteropolyacid (H14 [NaP5W30O110]),[14] silica-
coated magnetic NiFe2O4 nanoparticles-supported H3PW12O40,[15] nano α-Al2O3 supported
ammonium dihydrogen phosphate (NH4 H2PO4/Al2O3),[16] nano ZnO,[17] Fe3O4@D-NH2-
HPA,[18] sodium selenite,[19] and 1-butyl-3-methyl imidazolium hydroxide ([bmim]OH),[20]
and ammonium acetate.[21] Fe3O4@PEO-SO3H,[22] CuFe2O4/chitosan,[23] L-proline,[24]
diacetoxyiodobenzene, [25] nano MgO,[26] and SO3H–functionalized nano-MGO-D-NH2.[27]
2

There is a continuing well-known importance in the synthesis of polyhydroquinolines due
to the diverse biological properties associated with this system. Current studies reveal that
polyhydroquinolines exhibit several medicinal applications which include neuroprotectant,[28]
platelet antiaggregatory activity,[29] cerebral antischemic activity in treatment of alzheimer’s
diasease,[30] and chemo sensitizer acting in tumor therapy.[31] Polyhydroquinolines derivatives
are commonly synthesized by one-pot four-component reaction of aldehyde, cyclic 1,3-
dicarbonyl compounds, ethyl acetoacetate and ammonium acetate using numerous catalysts
such as poly(AMPS-co-AA),[32] SbCl3-SiO2,[33] 1,3-Di (bromo or chloro)-5,5-
dimethylhydantoin,[34] silica sulfuric acid,[35] K7[PW11CoO40],[36] sulfamic acid,[37]
tetraethylammonium 2-(carbamoyl)benzoate.[38] -Fe2O3/Cu@cellulose,[39] Fe3O4/SiO2-
OSO3H,[40] Fe3O4@PEO-SO3H,[41] Fe3O4@SiO2@PPh3@[CrO3Br],[42] SBA15@AMPD-Co,
[43]
2 [44]
cerium (IV) sulfate tetrahydrate,[45], and melamine
‐
Fe3O4@SiO2@PPh3@Cr2O7 ,
trisulfonic acid.[46]
In this work, we have reported the synthesis and characterization of SO3H-dendrimer
functionalized magnetic nanoparticles (Fe3O4@D-NH-(CH2)4-SO3H) as a novel and
heterogeneous catalyst for the one-pot synthesis of highly substituted pyrans and
polyhydroquinolines.
2. Experimental section
2.1. Preparation of dendrimer PAMAM
A solution of 1 g diethylenetriamine in 5 ml of dried methanol was added dropwise to a
solution of 10 g methyl acrylate in 25 ml of dried methanol. The resulting reaction's mixture
was stirred for 5 days at 25 °C under inert atmosphere. After evaporation of all volatiles in
oil-pump vacuum, the first generation with 5-OCH3 terminated groups (G0.5) was obtained.
To this, 20 mL of dried methanol and 40 mL of ethylenediamine (0.5 mol) was added in one
portion and kept for stirring under inert atmosphere for 5 days at 25 °C. The unreacted
ethylenediamine and excess of methanol were removed under liquid N2 in vacuum. The first
generation dendrimer bearing 5-NH2 end-grafted groups (G1) was obtained, which was
purified till all the traces of organic volatiles were completely removed. To grow the obtained
dendrimer to the next generation, 6.74 g (0.01 mol) of the first generation dendrimer and 30
mL (0.36 mol) of methyl acrylate was added in a single portion and again kept for stirring for
7 days at 25 °C. A thick yellowish liquid of the 10-arm-OCH3 terminated dendrimer (G1.5)
was obtained, which was again purified under liquid N2 in vacuum to remove excess of
3

methyl acrylate and methanol. To this thick yellow liquid, 60 mL ethylenediamine (in excess)
was added and kept for stirring for 10 days under inert atmosphere at 25 °C. The reaction
solution was then purified and thus, the desired second generation dendrimer with 10-NH2
terminal groups (G2) (Scheme 2) was obtained as pale yellow oily substance.
2.2. Preparation of nano- Fe3O4
Nano-Fe3O4 was prepared according to the reported procedure in the literature.[47] For this
reason, FeCl3.6H2O (2 mol) and FeCl2.4H2O (1 mol) were dissolved in 20 mL of deionized
water. Under vigorous magnetic stirring (600 rpm), gradually the pH was raising by addition
(dropwise for 2 minute) of 25% NH3 solution (5 ml) to around 10 and the mixed solution was
stirred at room temperature for 60 min. The resultant magnetite nanoparticles were collected
by an external magnetic field and washed several times with ethanol (10 ml) and deionized
water (10 ml). Then, the product was dried under vacuum at 50 °C for 6 h.
2.3. Preparation of dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH2)
The initially prepared Fe3O4 nanoparticles (2.5 g) were ultrasonically dispersed into 50 mL
deionized water at 20-50 °C for 20 min. Dendrimer PAMAM (7 mL) dissolved in 10 mL of
deionized water was added to this solution and again sonicated at 80 °C for 5 h. The resulting
Fe3O4@D-NH2 nanoparticles were isolated by an external magnetic field, washed with
deionized water (10 mL) and methanol (10 mL), and dried under vacuum at 50 °C for 6h.
2.4. Preparation of SO3H-dendrimer functionalized magnetic nanoparticles (Fe3O4@D-
NH-(CH2)4-SO3H)
2.5 g of Fe3O4@D-NH2 nanoparticles were ultrasonically dispersed into 50 mL toluene at 20-
50°C for 30 min. Then, 2.5 mL of 1,4-butane sultone was added dropwise to the mixture and
again sonicated at 80 °C for 5 h. The resulting Fe3O4@D-NH-(CH2)4-SO3H nanoparticles
were isolated by an external magnetic field, washed with deionized water (20 mL) and
methanol (20 mL), and dried under vacuum at 50 °C for 6h.
2.5. One-pot synthesis of tetrahydrobenzo[b]pyrans and 2-amino-3-cyano-4H-pyrans
Fe3O4@D-NH-(CH2)4-SO3H (0.05 g) was added to a mixture of the aldehydes 1 (1 mmol),
malononitrile 2 (0.08 g, 1.2 mmol), and 1,3-cyclohexandione 3 or ethyl acetoacetate 5 (1
mmol), and 5 ml of ethanol in a 20 ml round bottom flask fitted with a reflux condenser. The
resulting mixture was heated to reflux (an oil bath) for the appropriate time (see Table 2) with
stirring (spin bar). After the completion of the reaction (monitoring by TLC; hexane-ethyl
acetate, 4:1), the nanomagnetic catalyst was separated from the reaction mixture by use of an
external magnetic field. The resulting crude product was poured onto crushed ice, and the
4

solid product which separated was isolated by filtration and recrystallized from ethanol (5 ml)
to afford tetrahydrobenzo[b]pyrans (4a-o), and 2-amino-3-cyano-4H-pyrans (6a-e).
2.6. One-pot synthesis of polyhydroquinolines
A mixture of aldehydes (1b, 1mmol), 1,3-cyclohexandione (2, 1 mmol), ethyl acetoacetate (3,
1 mmol), ammonium acetate (4 mmol) and Fe3O4@D-NH-(CH2)4-SO3H (0.05 g), was heated
on an oil bath at 120 °C for the appropriate time (see Table 2) with stirring (spin bar).
Completion of the reaction was indicated by TLC (hexane:ethyl acetate, 2:1), after
completion, appropriate amount of EtOH (96%) was added and the mixture stirred for 2 min.
The catalyst was then separated by use of an external magnetic field. The filtrate was poured
onto crushed ice and the solid product, which separated was filtered and recrystallized from
ethanol to afford pure polyhydroquinolines (7a-c).
3. Results and discussion
In continuation of our previous researches on the design and application of heterogeneous
and reusable solid catalysts in organic synthesis and multi-component reactions,[48] here we
report an efficient, eco-friendly, safe, green, and practical method for the synthesis of
polyfunctionalized pyrans (tetrahydrobenzo[b]pyrans, 2-amino-3-cyano-4H-pyrans) and
polyhydroquinolines using SO3H-dendrimer functionalized magnetic nanoparticles
(Fe3O4@D-NH-(CH2)4-SO3H) as a catalyst (Scheme 1).
Scheme 1
In this work, the novel SO3H-dendrimer functionalized magnetic nanoparticles
(Fe3O4@D-NH-(CH2)4-SO3H) have been designed for the first time. We used this
heterogeneous catalyst as a highly efficient and novel catalyst for the one-pot synthesis of
polyfunctionalized pyrans and polyhydroquinolines. The synthesis of the second-generation
dendrimer used in the present work was reported in previous works.[49] Michael addition
method was used as a starting point from a multifunctional core (diethylenetriamine) with
branching monomers. The procedure is based on the consecutive condensation of
ethylenediamine with methyl acrylate to give the corresponding dendrimer (Scheme 2).
Scheme 2
5

Then, nano magnetic Fe3O4 was prepared using a co-precipitation technique.[33] In order
to prepare the dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH2), the
synthesized dendrimer was mixed with nano magnetic Fe3O4 to give the corresponding
Fe3O4@D-NH2 (Scheme 3). Finally, the reaction of Fe3O4@D-NH2 with 1,4-butane sultone
produced SO3H-dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH-(CH2)4-
SO3H) (Scheme 4).
Scheme 3
Scheme 4
In order to confirm the SO3H-dendrimer functionalized magnetic nanoparticles
(Fe3O4@D-NH-(CH2)4-SO3H), we employed different characterization techniques such as X-
ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-
dispersive X-ray spectroscopy (EDS), Scanning electron spectroscopy (SEM), elemental
analytical and thermal gravimetric analysis (TGA).
Fig. 1 shows the XRD patterns of Fe3O4@D-NH-(CH2)4-SO3H) with peaks of their
crystalline structure at 30.18o, 35.41 o, 43.18 o, 57.12 o, 62.74 o 2θ which is very close to the
standard patterns of the crystalline magnetite and the diffraction peaks could be well indexed
with the inverse spinel cubic Fe3O4 structure by the ICDD (Reference code: 00-019-0629) as
well as present that the functionalizing process does not affect the crystal structure of the
Fe3O4 particles and there is no other phase, such as Fe2O3 or FeO.
Figure 1
Anchoring of dendrimer PAMAM on the surface of magnetic nanoparticles was
examined by FT-IR spectroscopy (Fig. 2). FT-IR spectral analysis of Fe3O4@D-NH2 (Fig.
2b) shows a broad band at 3425 cm-1 due to N-H stretching. Absorptions at 2923 cm-1 is due
to the alkyl chain stretching. There is also a strong vibration at 1634 cm-1. The presence of
vibration bands of the dendrimer along with a noticeable change in the intensities of the
peaks at different wave numbers indicates effective stabilization of the Fe3O4 nanoparticles.
A strong absorption band at 580 cm-1 is due to the Fe-O stretching vibration of the
nanoparticles and the weak absorption at 3425 cm-1 can be assigned to the O-H stretching
indicating a small amount of water in the sample.
6

The existence of sulfonic acid group (SO3H) in the samples was further confirmed by the
presence of an intense and broad absorption band from 2400 to 3400 cm−1 which corresponds
to S–OH stretching vibration, and the appearance of two important peaks at 1037 and 1169
cm−1 corresponding to the symmetric and asymmetric stretching vibrations of S═O,
respectively (Figure 2c) Thus, the FT‐IR spectra confirm the successful of ring opening of
1,4-butanesultone by NH2 groups of Fe3O4@D-NH2. We have characterized the recycled
nanocatalyst by FT-IR spectroscopy which showed suitable retention of its structure and
morphology and there was no considerable deformation or leaching after five times reusing.
Figure 2
TGA study of the Fe3O4@D-NH-(CH2)4-SO3H) and Fe3O4 was performed from room
temperature to 700 °C in the N2 atmosphere at heating rate of 10 °C/min. For Fe3O4 a
continuous weight loss was observed from the first to final temperature and TGA curve for
Fe3O4@D-NH-(CH2)4-SO3H) indicates organic degradation of the catalyst at 200°C and the
complete decomposition continues up to 700°C. The thermal decomposition of Fe3O4@D-
NH-(CH2)4-SO3H) shifts towards higher temperatures in comparison with Fe3O4 which shows
adsorption of polymer chain on the surface of magnetite, in the other words high level of
dendrimer PAMAM had been immobilized on the Fe3O4 (Fig. 3).
Figure 3
The SEM image of the synthesized Fe3O4@D-NH-(CH2)4-SO3H nanoparticle is shown in
Figure 4, which indicates well-dispersed spherical particles.
Figure 4
Further characterization of Fe3O4@D-NH-(CH2)4-SO3H was performed by transmission
electron microscopy (TEM) image. The TEM image of Fe3O4@D-NH-(CH2)4-SO3H showed
well-defined spherical Fe3O4 nanoparticles dispersed in a dendrimer matrix (Figure 5). Also,
the TEM image was used to confirm the core/shell morphology in the nanostructure including
Fe3O4 as dark core and dendrimer light shell.
7

Figure 5
The EDX results for Fe3O4@D-NH-(CH2)4-SO3H, shown in Figure 6, clearly showed the
presence of Fe, C, N, O and S in Fe3O4@D-NH-(CH2)4-SO3H.
Figure 6
To verify the immobilization of modified Fe3O4, CHNS elemental analysis of the catalyst
(Fe3O4@D-NH-(CH2)4-SO3H) was conducted. The result confirms (C, 8.32%; H, 1.64%, N,
2.30%; S, 2.46%) that a large amount of organic groups was loaded onto the Fe3O4.
After complete characterization of SO3H-dendrimer functionalized magnetic
nanoparticles (Fe3O4@D-NH-(CH2)4-SO3H), we investigated the application of this catalyst
for synthesis of polyfunctionalized pyrans (tetrahydrobenzo[b]pyrans, 2-amino-3-cyano-4H-
pyrans) and polyhydroquinolines. For initiating optimization of the reaction conditions, we
carried out one-pot three-component condensation of malononitrile, benzaldehyde and 1,3-
cyclohexanedione in the presence of Fe3O4@D-NH-(CH2)4-SO3H. The results are listed in
Table 1. It was observed that 0.05 g of catalyst was enough to catalyze the reaction to produce
high yields of 2–amino–3–cyano–4-(phenyl)-5–oxo-4H-5,6,7,8-tetrahydrobenzo[b]pyran
(4a). As can be seen in Table 1, the results showed that the efficiency and the yield of the
reaction in EtOH was higher than those obtained in other solvents, such as H2O, MeOH, and
CH3CN, or under solvent-free conditions. Increasing the amounts of the catalyst did not
improve the yield of the reaction (entry 7). As indicated in Table 1, to compare the efficiency
of this new nanocatalyst, we carried out a model reaction in the presence of various catalysts.
Fe3O4, Fe3O4@SiOD-NH2 and D-NH2 (entries 8, 9, 10) needed longer reaction times than
Fe3O4@D-NH-(CH2)4-SO3H under reflux in EtOH. To illustrate the need of Fe3O4@D-NH-
(CH2)4-SO3H for these reactions, an experiment was conducted in the absence of Fe3O4@D-
NH-(CH2)4-SO3H (entry 11). The yield in this case was trace after 20 min. Obviously,
Fe3O4@D-NH-(CH2)4-SO3H is an important component of the reaction.
Table 1
After optimization, a variety of other aldehydes and 1,3-dicarbonyl compounds (1,3-
cyclohexanedione and ethyl acetoacetate) were shown to undergo the reaction smoothly,
giving the desired tetrahydrobenzo[b]pyrans and 2-amino-3-cyano-4H-pyrans in good to high
8

yields. The results are summarized in Table 2. All products were fully characterized by
1
spectroscopic methods (IR, H and 13C NMR, Mass and elemental analysis) and compared
with authentic spectra (see supporting information).
In another assay, the applicability of the Fe3O4@D-NH-(CH2)4-SO3H catalyst was
explored for the synthetic reaction of 2-amino-3-cyano-4H-pyran and polyhydroquinoline
derivatives. Initially, to find the optimal reaction conditions for the synthesis, the reaction of
benzaldehyde, malononitrile and ethyl acetoacetate was chosen as a model reaction. The
resulting data demonstrate that the best conditions occur when the reaction was performed
under reflux conditions in the presence of 0.5 g of Fe3O4@D-NH-(CH2)4-SO3H catalyst.
Afterwards, the versatility and the generality of the optimized reaction conditions were
checked for the synthesis of various 2-amino-3-cyano-4H-pyrans and polyhydroquinolines
(Table 2).
Table 2
With due attention to the importance of recovery of the used catalyst in green synthetic
processes, we considered the recyclying capability of Fe3O4@D-NH-(CH2)4-SO3H through
synthesis reactions leading highly substituted pyrans and polyhydroquinolines production.
When the reaction was complete, the catalyst was recovered nearly quantitatively from the
reaction flask by an external magnet and was subsequently reused in several runs. The
obtained Results displayed in Table 3 approve that the magnetically separable Fe3O4@D-NH-
(CH2)4-SO3H could be reused and recycled for five runs without any remarkable loss of its
initial catalytic activity.
Table 3
A proposed mechanism for this reaction is shown in Scheme 5. In first step, Knoevenagal
condensation between aldehydes and malononitrile produced 2-benzylidenemalononitrile.
Second, Michael addition of 2-benzylidenemalononitrile with 1,3-cyclohexanedione or ethyl
acetoacetate accour, and finally followed cyclization and tauotomerization afforded the
corresponding products (tetrahydrobenzo[b]pyrans, 2-amino-3-cyano-4H-pyrans). Also, in a
similar mechanism, the corresponding polyhydroquinolines can be produced. In this process,
Fe3O4@D-NH-(CH2)4-SO3H with H+ could play a remarkable role in increasing of reaction
rate.
9

Scheme 5
In order to show the efficiency of our procedure, a comparison was done between the
present work and others earlier reports for the one-pot synthesis of polyfunctionalized pyrans
and polyhydroquinolines. The results summarized in Table 4 clearly demonstrate the
superiority of the present work in catalyst amount, time of reaction, high yields of the
products and the reusability of the nanocatalyst.
Table 4
4. Conclusion
In conclusion, we have developed an easy, convenient, inexpensive and friendly
environmental synthetic approach for the preparation of polyfunctionalized pyrans
(tetrahydrobenzo[b]pyrans, 2-amino-3-cyano-4H-pyrans) and polyhydroquinolines catalyzed
by Fe3O4@D-NH-(CH2)4-SO3H. The method is associated with several advantages such as
high yields, operational simplicity, non-toxic catalyst and solvents, utilization of a
heterogeneous catalyst, short reaction time and minimum pollution of the environment, which
makes it a useful and attractive process for the preparation of these compounds.
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13

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Figure and scheme legends
Scheme 1 One-pot synthesis of polyfunctionalized pyrans and polyhydroquinolines
Scheme 2 Preparation of dendrimer PAMAM
Scheme 3 Preparation of dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH2)
Scheme 4 Preparation of SO3H-dendrimer functionalized magnetic nanoparticles (Fe3O4@D-
NH-(CH2)4-SO3H)
Scheme 5 Proposed mechanism for multicomponent synthesis of polyfunctionalized pyrans
(tetrahydrobenzo[b]pyrans, 2-amino-3-cyano-4H-pyrans) and polyhydroquinolines
Figure 1 X-Ray diffraction pattern for the Fe3O4@D-NH-(CH2)4-SO3H)
Figure 2 FT-IR spectra for (a) Fe3O4 (b) Fe3O4@D-NH2 (c) Fe3O4@D-NH-(CH2)4-SO3H)
Figure 3 TGA of nano Fe3O4@D-NH-(CH2)4-SO3H vs Fe3O4
Figure 4 SEM image of Fe3O4@D-NH-(CH2)4-SO3H nanoparticles.
Figure 5 TEM image of Fe3O4@D-NH-(CH2)4-SO3H
Figure 6 EDX image of nano Fe3O4@D-NH-(CH2)4-SO3H
14

O
Ar
O
O
R
R
CN
O
2
R
NH2
CH2(CN)2
R
3
4a-l
EtOH/reflux
O
O
Ar
O
O
OC2H5
Me
CN
5
EtO
Fe3O4@Dendrimer-NH-(CH2)4-SO3H
ArCHO
NH2
CH2(CN)2
3
EtOH/reflux
Me
6a-e
1
O
O
Ar
OC2H5
O
O
Me
5
NH4OAc
OEt
Me
O
N
H
7a-c
O
Solvent-free/1200C
Scheme 1 One-pot synthesis of polyfunctionalized pyrans and polyhydroquinolines
15

Scheme 2 Preparation of dendrimer PAMAM
16

Scheme 3 Preparation of dendrimer functionalized magnetic nanoparticles (Fe3O4@D-NH2)
17

Scheme 4 Preparation of SO3H-dendrimer functionalized magnetic nanoparticles (Fe3O4@D-
NH-(CH2)4-SO3H)
18

Scheme 5 Proposed mechanism for multicomponent synthesis of polyfunctionalized pyrans
(tetrahydrobenzo[b]pyrans, 2-amino-3-cyano-4H-pyrans) and polyhydroquinolines
19

Figure 1 X-Ray diffraction pattern for the Fe3O4@D-NH-(CH2)4-SO3H)
20

Figure 2 FT-IR spectra for (a) Fe3O4; (b) Fe3O4@D-NH2; (c) Fe3O4@D-NH-(CH2)4-SO3H)
and (d) recycled Fe3O4@D-NH-(CH2)4-SO3H)
21

Figure 3 TGA of nano Fe3O4@D-NH-(CH2)4-SO3H vs Fe3O4
22

Figure 4 SEM image of Fe3O4@D-NH-(CH2)4-SO3H nanoparticles.
23

20 nm
Figure 5 TEM image of Fe3O4@D-NH-(CH2)4-SO3H
24

Figure 6 EDX image of nano Fe3O4@D-NH-(CH2)4-SO3H
25

Table 1. Optimization of Reaction Conditions for 4a
Time Yielda
Entry
Catalyst (g)
Conditions
(min)
20
(%)
84
1
Fe3O4@D-NH-(CH2)4-SO3H (0.05 g) EtOH/reflux
Fe3O4@D-NH-(CH2)4-SO3H (0.05 g) H2O/reflux
Fe3O4@D-NH-(CH2)4-SO3H (0.05g) MeOH/reflux
Fe3O4@D-NH-(CH2)4-SO3H (0.05 g) CH3CN/reflux
2
20
74
80
62
63
80
85
42
32
36
3
20
4
20
5
Fe3O4@D-NH-(CH2)4-SO3H (0.05 g) Solvent-free/800C 20
6
Fe3O4@D-NH-(CH2)4-SO3H (0.03 g) EtOH/reflux
Fe3O4@D-NH-(CH2)4-SO3H (0.07 g) EtOH/reflux
20
20
60
60
60
7
8
Fe3O4@D-NH2 (0.05 g)
Fe3O4 (0.05 g)
D-NH2 (0.05 g)
--b
EtOH/reflux
EtOH/reflux
EtOH/reflux
9
10
11
EtOH/reflux
20
trace
aIsolated yield. bThis reaction was carried out in the absence of any catalyst.
26

Table 2. One-pot synthesis of polyfunctionalized pyrans (tetrahydrobenzo[b]pyrans, 2-
amino-3-cyano-4H-pyrans) and polyhydroquinolines
Entry
Products
Time Yielda Mp (0C)
(min) (%)
Found
Reported
20
20
84
90
232-233 229-23114
O
4a
CN
NH2
O
234-236 -----
Br
4b
O
O
CN
NH2
O
30
40
82
80
222-224 -----
Br
CN
4c
NH2
O
256-257 257-25917
OH
4d
O
CN
NH2
O
27

40
20
82
92
219-221 -----
OH
O
4e
4f
CN
NH2
O
232-233 232-23314
NO2
O
O
CN
NH2
O
O
30
40
82
80
199-201 196-19820
NO2
CN
4g
4h
NH2
196-198 -----
O
O
CN
NH2
O
S
20
15
83
85
209-211 210-21217
CN
4i
4j
NH2
Br
O
228-230 225-22714
O
CN
NH2
O
28

NO2
CN
10
30
90
92
83
86
209-211 210-21216
234-236 236-23819
188-190 189-19114
O
O
4k
4l
NH2
OH
O
O
CN
NH2
O
6a
CN
EtO
NH2
O
Me
O
60
90
179-181 182-18414
Br
6b
CN
EtO
EtO
NH2
O
Me
O
90
60
84
90
180-182 183-18421oz
Br
CN
6c
NH2
O
Me
173-175 174-17614
NO2
6d
O
CN
EtO
NH2
O
Me
29