Ethylene diamine grafted nanoporous UiO-66 as an efficient basic catalyst in the multi-component synthesis of 2-aminithiophenes

Article abstract of DOI:10.1002/aoc.4307

This study demonstrates ED-UiO-66 as a novel and effective solid nanoporous basic catalyst prepared through the amine grafting onto the pores of UiO-66. The manufactured nanoparticles were identified by FT-IR, XRD, TGA, FESEM, TEM, CHN and BET and the characterization results certified formation of a single phase nanoporous substance with the medium grain size less than 90?nm. The synthesized material was employed as an efficient catalyst for the preparation of 2-aminotiophenes through the Gewald method. This thermochemically stable nanocatalyst was environmentally safe, reusable and economic. Therefore, this methodology can be simply extended for industrial goals.

Full text of DOI:10.1002/aoc.4307

Received: 9 November 2017
DOI: 10.1002/aoc.4307
Revised: 3 January 2018
Accepted: 5 January 2018
F U L L P A P E R
Ethylene diamine grafted nanoporous UiO‐66 as an efficient
basic catalyst in the multi‐component synthesis of 2‐
aminithiophenes
N. Erfaninia1 | R. Tayebee1
| M. Dusek2 | M.M. Amini3
1 Department of Chemistry, Hakim
Sabzevari University, Sabzevar 96179‐
76487, Iran
2 Institute of Physics of the Czech
Academy of Sciences, Na Slovance 2,
18221 Prague 8, Czech Republic
This study demonstrates ED‐UiO‐66 as a novel and effective solid nanoporous
basic catalyst prepared through the amine grafting onto the pores of UiO‐66.
The manufactured nanoparticles were identified by FT‐IR, XRD, TGA, FESEM,
TEM, CHN and BET and the characterization results certified formation of a
single phase nanoporous substance with the medium grain size less than
90 nm. The synthesized material was employed as an efficient catalyst for the
preparation of 2‐aminotiophenes through the Gewald method. This
thermochemically stable nanocatalyst was environmentally safe, reusable and
economic. Therefore, this methodology can be simply extended for industrial
goals.
3 Department of Chemistry, Shahid
Beheshti University, G.C, Tehran, Iran
Correspondence
R. Tayebee, Department of Chemistry,
Hakim Sabzevari University, Sabzevar,
96179‐76487, Iran.
Email: rtayebee@hsu.ac.ir
KEYWORDS
Funding information
ethylene diamine, metal‐organic framework, multi‐component, solid base catalyst, UiO‐66
Center for International Scientific Studies
& Collaboration (CISSC)
1 | INTRODUCTION
MOF, with high thermal, chemical and unique
mechanical stabilities along with high surface area
Green and sustainable synthetic chemistry has been
progressed by alteration of homogeneous catalysis
concepts in heterogeneous catalysis and introducing
novel different heterogeneous catalysts. In this respect,
promising novel organic‐inorganic hybrid nanoporous
solid materials called MOFs (metal‐organic frameworks)
are often considered as potential catalysts in research
and development activities.[1–12] MOFs have attracted
great attention over the past decade and have been
exploited as effective materials in separation technologies
and gas storage devices,[13–20] medicine,[21] chemical
sensing[22] and catalysis.[23] Furthermore, the post‐
modification strategy on the linkers in these materials
gives rise to the assembly of various compatible and
flexible MOFs.[24,25]
(1147 m2/g). The UiO‐66 framework has emerged as a
new crystalline microporous material with excellent
properties involving uniform micropores and open
porous framework structure with large achievable pore
volumes.[26–28]
In the category of heterogeneous solid base catalysis,
catalyst may function as a base toward reactants which
ordinarily behave as acids either by abstraction of a proton
from the reactants (Boensted base) or by donation of an
electron pair to the reagents (Lewis base) to form anionic
intermediates which undergo catalytic cycle.[29,30]
Recently, we examined the catalytic efficacy of ZnO,
ZnO/nanoclinoptilolite and ZnFe2O4 in the preparation
of substituted 2‐aminothiophenes.[31–34]
Herein, we study grafting of ethylene diamine (ED)
onto the active pores of UiO‐66 through direct anchoring;
thus, the remaining amine group of ED can act as a strong
base in the form of an immobilized solid base catalyst.
Noticeably, this issue does not necessarily involve the
The stability of MOFs is greatly dependent on the
nature of the available structure and chemical bonds
in the inorganic building unit. UiO‐66 (isoreticular
UiO‐67 and UiO‐68) is introduced as an important
Appl Organometal Chem. 2018;e4307.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4307

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ERFANINIA ET AL.
surface alteration of the mesoporous materials which does
not bear any unsaturated sites in general. Eventually, the
synthesized nanoporous ED‐UiO‐66 displayed potential
catalytic activity in the multi‐component fabrication of
2‐aminothiophenes through Gewald condensation
reaction (Scheme 1). Up to now, different basic catalysts
have been employed for this condensation reaction
involving malonodinitrile, sulfur powder, and different
ketones. To the best of our knowledge, this report is the
first on the very fast and efficient synthesis of these
pharmaceutically important compounds.
linear connection was retained. Thermogravimetric
analysis (TGA) was analyzed on a Bahr STA‐503 device
in air at a heating rate of 10 °C/min−1. The quantitative
analyses of elemental hydrogen, carbon, and nitrogen
were performed on a Thermo Finnigan Flash EA112.
2.2 | Synthesis of UiO‐66
Solvothermal procedure introduced by Cavka et al. was
applied for the synthesis of UiO‐66.[35] In a typical
synthesis, ZrCl4 (0.208 g, 0.893 mmol) was dissolved in
20 ml of DMF; afterwards, the mixture was stirred with
0.148 g of H2BDC (0.893 mmol) under a nitrogen
atmosphere at 28 °C. The obtained mixture was enclosed
in a solvothermal autoclave and warmed to 120 °C in an
oven for 24 h. Crystallization allowed for nucleation in a
static condition. After cooling to 25 °C, the acquired
powdered solid product was broken up and washed three
times with 5 ml of DMF to give a white solid precipitate.
The solid product was dispersed in chloroform at room
temperature, and the solvent was withdrawn. The white
powder crystals were dried under vacuum at 140 °C for
8 h.[36]
2 | EXPERIMENTAL
2.1 | Materials
All reagents and beginning compounds were provided by
Fluka and Merck and were utilized without extra
purification. All of the synthesized products were well
known and characterized by comparison of their chemical
and physical data to the literature.[34–36] Melting points
were obtained on a Bumstead electrothermal 9200
apparatus. General distribution and morphology of the
nanoparticles were observed by field emission scanning
electron microscopy (FESEM) on a Mira 3‐XMU FESEM
microscope and Transmission Electron Microscope
(TEM) on a philips CM30, V=150 kV microscope. X‐ray
diffraction patterns (XRD) were acquired in
Bragg‐rentano geometry on an Xpert MPDdiffractometer
with Cu Kα radiation at 30 mA and 40 kV, and a scanning
rate of 3° min‐1 in the 2θ domain. FT‐IR spectra were
recorded on an 8400 Shimadzu Fourier transform
spectrophotometer using KBr pellets. A freeze dryer,
Model FD‐10, Pishtaz Equipment Engineering Co, Iran,
was applied for drying of the prepared nanomaterials.
Porosimetry measurements were studied through N2
physisorption on a Belsorp mini instrument with data
analysis. Samples were degassed for 4 h at 120 °C before
analysis via nitrogen adsorption at ‐196 °C. BET surface
areas accounted over the range of P/P0= 0.990 where a
2.3 | Preparation of ED‐UiO‐66
In a general reaction, 0.5 g of UiO‐66 was dispersed in
anhydrous toluene (50 ml). To this suspension, 0.5 g of
ED was added and the mixture was refluxed for 24 h.
Finally, the obtained precipitate was accumulated and
dispersed in 20 ml ethanol and dried at room
temperature.
2.4 | Catalytic synthesis of 2‐
aminothiophene derivatives
For this purpose, 5 mmol of malonodinitrile, 5 mmol of
sulfur powder and 5 mmol of ketone were thoroughly
mixed. Then, 0.02 g of ED‐UiO‐66 nanoparticles were
SCHEME 1 Reaction scheme for the synthesis of 2‐aminothiophenes

ERFANINIA ET AL.
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included, and the mixture was warmed to 100 °C with
constant stirring for 5 min. Eventually, the reaction was
stopped, ED‐UiO‐66 was separated, and the final product
was dissolved in 10 ml of hot ethanol. Afterwards, the
reaction mixture was cooled to room temperature and
decanted into 50 ml ice‐water. The final precipitate was
removed, washed with cold water (5 °C) and dried at
25 °C for 12 h. Further purification was achieved by silica
gel column chromatographywith hexane: ethyl acetate
(10:1) as an eluent.
7.61 (m, 2H), 7.45 (m, 2H), 7.37 (m, 1H), 6.32 (s, 1H),
5.03 (brs, 2H); 13C NMR (100 MHz,CDCl3): 164.1, 139.8,
134.3, 128.8, 128.2, 127.3, 116.2, 105.9, 88.0.
2.5.6 | 2‐Amino‐4‐(4‐methylphenyl)thio-
phene‐3‐carbonitrile
IR (KBr): 3341, 3210, 2896, 2205, 1611, 1560, 1522, 1430,
1305, 1192, 824, 720, 476 cm−1 1H NMR (400 MHz,
;
CDCl3): 7.48 (d, J 8.0 Hz, 2H), 7.24 (d, J 8.4 Hz, 2H),
6.32 (s, 1H), 4.85 (brs, 2H), 2.38 (s, 3H); 13C NMR
(100 MHz, CDCl3): 163.6, 141.0, 138.1,131.4,129.4, 127.0,
116.0, 105.4, 88.4, 21.2.
2.5 | Spectral data for some selected
compounds[29–33]
2.5.1 | 2‐Amino‐4‐ethyl‐5‐
2.5.7 | 2‐Amino‐4‐(4‐nitrophenyl)thio-
phene‐3‐carbonitrile
methylthiophene‐3‐carbonitrile
IR (KBr): 3421, 3340, 3215, 3050, 2936, 2875, 2200, 1600,
IR (KBr): 3320, 3450, 2202, 2930, 3200, 1661, 1730, 1130,
1516,1390,1310,1241,1160, 845, 494 cm−1
;
1H NMR
1321,1520, 680 cm−1 1H NMR (400 MHz, DMSO‐d6):
;
(400 MHz, CDCl3): 4.0 (brs, 2H), 2.48 (q, J.7.6 Hz, 2H),
2.17 (s, 3H), 1.16 (t, J.7.6 Hz,3H); 13C NMR (100 MHz,
CDCl3): 160.0, 136.2, 116.6, 116.1, 89.1, 20.9, 14.2, 12.1.
8.28 (d, J.9.1 Hz, 2H), 7.81 (d, J 8.9 Hz), 7.40 (s, 2H),
6.83 (s, 1H) ppm; 13C NMR(100 MHz, DMSO‐d6): 166.3,
146.0, 140.1, 135.5, 127.3, 123.6,115.8, 108.0, 82.1.
2.5.2 | 2‐Amino‐5‐methylthiophene‐3‐
carbonitrile
3 | RESULTS AND DISCUSSION
IR (KBr): 3420, 3333, 3227, 2916, 2198, 1626, 1519, 1385,
3.1 | Structural characterization of the
functionalized nanoporous ED‐UiO‐66
1276,1105, 897, 812, 504 cm−1 1H NMR (400 MHz,
;
CDCl3): 6.34 (s, 1H),4.71 (brs, 2H), 2.27 (s, 3H); 13C
NMR (100 MHz, CDCl3): 161.4,124.3, 122.0, 115.8, 86.8.
The powder X‐ray diffraction analysis of UiO‐66
confirmed the successful synthesis of this MOF. The single
crystal structure of UiO‐66 demonstrated an inner
Zr6O4(OH)4 moiety that the triangular faces of the Zr6
octahedron are capped by μ3‐O and μ3‐OH groups.[37] All
the polyhedron edges are bridged via the carboxylates
[μ2‐(CO2)] coming from the dicarboxylic acids to form a
Zr6O4(OH)4(CO2)12 cluster. As a result, each Zr atom is
eight‐coordinated with square‐antiprismatic coordination
geometry with all ligands being bonded via oxygen atoms.
One square face of the square antiprism is organized by
oxygen atoms provided by the carboxylates, while the
second square face is formed by the oxygen atoms from
the μ3‐O and μ3‐OH groups.[37]
N2 adsorption‐desorption isotherms were conducted
to evaluate the porosity of the fabricated UiO‐66, and
ED‐UiO‐66 and the Langmuir surface areas were
consequently computed (Figure 1).[38,39] This observation
proved that the anchoring of ED did not destroy the
structural integrity of UiO‐66. ED‐UiO‐66 with a BET sur-
face area of 13.47 m2 g‐1 is much lower than that of the
fresh UiO‐66. This is in accordance with the pore volume
of 0.04 cm3 g‐1. The dramatic decrease in the surface area
and pore volume could be attributed to both reduced free
existing space and bonding of ED molecules in the cages
2.5.3 | 2‐Amino‐5‐ethylthiophene‐3‐
carbonitrile
IR (KBr): 3440, 3361, 3220, 2961, 2220, 1651, 1560, 1461,
1
1380,1081, 840 cm−1. H NMR (400 MHz, CDCl3): 6.34
(s, 1H), 4.74(brs, 2H), 2.60 (q, J.7.2 Hz, 2H), 1.21 (t,
J.7.2 Hz, 3H); 13C NMR(100 MHz, CDCl3): 161.0, 132.1,
120.2, 115.7, 86.7, 23.1, 15.2.
2.5.4 | 2‐Amino‐4,5,6,7‐tetrahydro‐1‐
benzothiophene‐3‐carbonitrile
IR (KBr): 3440, 3340, 3200, 2911, 2840, 2203, 1650, 1640,
1
1522, 1320, 1120, 681 cm−1; H NMR (250 MHz, CDCl3):
1.78 (t, 4H, 2CH2), 4.65 (s, 2H, NH2), 2.49 (m, 4H,
2CH2); 13C NMR (100 MHz,CDCl3): 22.10, 23.35, 23.72,
24.11, 88.45, 115.58, 120.50, 132.27,160.1.
2.5.5 | 2‐Amino‐4‐phenylthiophene‐3‐
carbonitrile
IR (KBr): 3420, 3321, 3200, 2221, 1630, 1572, 1430, 1302,
1
1190, 941, 768, 715 cm−1; H NMR (400 MHz, CDCl3):

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ERFANINIA ET AL.
However, in view that the partical size is not extremely
small, this could also be due to the statistical distribution
of ED without periodicity over the MOF backbone, which
would also lead to decreased crystallinity of ED‐UiO‐66
and lowering of the diffraction intensity.[41]
Structural integrity and stability of the prepared
UiO‐66 and ED‐UiO‐66 nanoparticles at high
temperatures were analyzed by TGA as shown in
Figure 3. The TGA analysis was associated with a broad
endothermic weight loss between 20‐300 °C which is
assigned to the loss of solvent. A second higher
temperature and strongly exothermic loss between 300‐
500 °C was ascribed to the decomposition of UiO‐66
backbone and formation of ZrO2. The curve UiO‐66
demonstrated a stable plateau in the domain of 300–
500 °C before the second step of augmented weight loss
occurred as a result of the thermal corruption of the solid
and formation of ZrO2. For ED‐UiO‐66, the second step
showed a larger weight loss than the one observed for
UiO‐66, because of the higher comparative weight of
the ligand. Moreover, the different thermal stability
measurements showed higher thermal stability for the
electron rich NH2‐tagged ED‐UiO‐66 compared to
UiO‐66 with intermediate steric hindrance which was
decomposed at much lower temperature ∼350 °C.[42]
Furthermore, the CHN analysis of ED‐UiO‐66 revealed
carbon, hydrogen, and nitrogen contents as C, 30.62%; H,
4.262%; and N, 8.472% and the amount of the loaded amine
was attained as 18.03%. The surface morphology of UiO‐66
nanomaterial was further investigated by FESEM
(Figure 4a), in which visualized irregular nano‐scale
spherical aggregates comprised of approximately 40 nm
nanoparticles possessing a narrow size distribution. The
morphology of the as‐synthesized ED‐UiO‐66 can be seen
FIGURE
functionalized ED‐UiO‐66
1
N2 adsorption‐desorption isotherms for the
of UiO‐66. These changes demonstrated that the post‐
functionalization steps induced substantial pore blockage.
Nanoparticles of ED‐UiO‐66 exhibited yellow color
compared to the white UiO‐66. The crystallinity of the
synthesized ED‐UiO‐66 was further explored by wide angle
XRD (Figure 2). The diffraction patterns obtained for the
as‐synthesized samples of UiO‐66 and ED‐UiO‐66 revealed
that both materials are crystalline. The observed 2θ values
for ED‐UiO‐66 (7.2°, 111 and 8.9°, 222) were consistent
with the as‐synthesized UiO‐66 source material and with
the standard diffraction card (JCPDS 15010‐64283).[40]
Results corroborated that the tagged ED‐UiO‐66
nanoparticles were topologically similar to UiO‐66. The
approximately unchanged XRD templates for ED‐UiO‐66
and UiO‐66 established that the ED grafting took place
without apparent loss of crystallinity. However, some
variations in the Bragg intensities were also detected. A
significant decrease in the comparative diffraction peak
intensities for ED‐UiO‐66 would be due to the trapping of
ED molecules into the UiO‐66 pores. It should be noted
that attempts to locate ED in UiO‐66 by XRD were
unsuccessfull. In one hand, this can be due to poor quality
of the powder diffraction peaks caused by small particles.
FIGURE 2 Wide angle XRD patterns of UiO‐66 and ED‐UiO‐66.
The upper and lower profiles are on the same intensity scale
FIGURE 3 TGA profiles for UiO‐66 and ED‐UiO‐66

ERFANINIA ET AL.
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TEM image of nanoporous ED‐UiO‐66 is shown in
Figure 5. Obviously, this study confirmed the nano‐scale
octahedron‐like aggregates for the framework comprised
of approximately 90 nm particles involving a narrow size
distribution.
Substantially,
functionalization
and
anchoring of ethylene diamine had no a critical impact
on the structure and morphology of UiO‐66.
Surface and structural properties of UiO‐66 and
ED‐UiO‐66 nanoparticles were explored by FT‐IR between
400‐4000 cm‐1 (Figure 6) to confirm the successful
FIGURE 6 FT‐IR spectra of UiO‐66 and functionalized ED‐UiO‐
66
FIGURE 4 The FESEM images of (a) UiO‐66 and (b) ED‐UiO ‐66
in Figure 4(b), in which ED‐UiO‐66 exhibited an
octahedron‐like appearance. The average edge length of
these ED‐UiO‐66 crystals was 100( 10) nm, revealing their
nanoscale sizes. Functionalization and anchoring of
ethylene diamine had no a critical impact on the structure
and morphology of UiO‐66.
FIGURE 7 Effect of ED‐UiO‐66 amount on the condensation of
malonodinitrile, cyclohexanone and elemental sulfur
FIGURE 5 TEM images of the
nanoporous ED‐UiO‐66

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ERFANINIA ET AL.
incorporation of ED onto the nanoparticles of UiO‐66.[43]
The FT‐IR spectrum of the tagged ED‐UiO‐66 is compared
with the spectrum of the parent UiO‐66. According to the
chemical structure of ED‐UiO‐66 and observation of the
aliphatic C–H stretching vibrations due to the alkyl group at
2940–2960 cm‐1 and N‐H stretching vibrations in 3400 cm‐1,
loading of ED onto the framework of UiO‐66 has been
confirmed unambiguously. Noteworthy, the detected
aliphatic C‐H stretching vibrations (2800–3000 cm‐1) are
shifted to higher wavenumbers. Moreover, the bands at
1080, 1370, and 900, 1500 cm‐1 are assigned to C‐N, C‐H,
and N‐H bending vibrations, respectively. The appearance
of an absorption band at 1590 cm−1 indicated the existence
of –COOH. The band at 1500 cm−1 is referred to both C=C
bond of aromatic phenyl rings and N‐H bending vibra-
tions.[44,45] The bands at 758, 665 and 575 cm −1 are ascribed
to ZrO2 as longitudinal and transverse modes. In the
spectrum of pristine UiO‐66, the pronounced doublet at
1600 and 1400 cm‐1 can be designated to the in‐ and out‐of‐
phases stretching modes of the carboxylate groups. In
comparison, after ED loading, the original bands at 1600
and 1400 cm‐1 are blue‐shifted to 1570 and 1370 cm‐1,
respectively.[45]
3.2 | Catalytic tests
3.2.1 | Studying impact of catalyst amount
on the condensation reaction
FIGURE 8 Effect of reaction temperature on the condensation of
malononitrile, cyclohexanone and sulfur powder in the presence of
0.02 g of ED‐UiO‐66. The reaction time of 5 min was chosen in all
cases
A model reaction was accomplished by applying 0‐0.05 g
of ED‐UiO‐66 for the preparation of 2‐aminothiophene
derivatives (Figure 7). The first reaction did not yield
any product corresponding to the condensation reaction
of malononitrile, cyclohexanone and elemental sulfur
after 4 h (entry 1), clearly demonstrating that a presence
of catalyst was essential for the condensation reaction.
It was found that 0.01 g of the catalyst prompted 77%
yield after 5 min, revealing the high catalytic activity of
ED‐UiO‐66. The reaction in the presence of 0.02 g
catalyst gave the corresponding chromene in 95% yield,
and with further increasing of the catalyst's amount the
yield remained the same. Thus, 0.02 g of the catalyst
was found to be the optimal quantity to push the reaction
forward.
TABLE 1 Comparing catalytic activity of ED‐UiO‐66 with UiO‐
66a
Entry Catalyst
Amount (g) Time (min) Yield (%)
1
2
3
‐
‐
240
240
5
6
6
UiO‐66
0.03
0.03
ED‐UiO‐66
95
aA mixture of malononitrile (5 mmol), cyclohexanone (5 mmol), sulfur pow-
der (5 mmol) and catalyst was stirred at 100 °C. Eventually, the catalyst was
separated and the desired product was filtered off and purified as described in
the experimental section.
TABLE 2 Comparison of the catalytic activity of nanoporous ED‐UiO ‐66 with some reported catalysts
Entry Catalyst Time (h) Temp. (
C) Yield (%) Condition/ solvent Cat. (g) E‐Factora (g) TONb Ref.
̊
1
2
3
4
5
6
7
ED‐UiO ‐66
5 min
4
100
100
100
100
60
95
76
65
70
91
74
91
free
0.02
0.05
0.04
0.02
0.05
0.04
0.2
0.15
6.30
4750
1520
1625
3500
1820
1850
455
This work
[32]
ZnO34%/NCP
Bulk ZnO
Nano ZnO
MgO/Al2O3
Bulk TiO2
KF/Al2O3
free
[33]
[32]
[46]
[33]
[47]
10
6
free
7.60
free
6.95
8
ethanol
free
17.04
6.52
10
3.5
100
78
ethanol
15.84
aE‐Factor is the actual amount of waste created in the process, defined as the weight of waste generated per weight of product and waste and is defined as every-
thing except for the desired product.[48,49]
bTurnover number (TON) was calculated as yield(%)/g of catalyst.

ERFANINIA ET AL.
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as negative charge density speared over oxygen and
nitrogen atoms, structural distortions, and approach of
the substrate molecule into UiO‐66 framework and
ethylenediamine would contribute to the catalytic effi-
ciency of the catalyst.
3.2.2 | Effect of reaction temperature on
the condensation reaction
To acquire the optimum reaction condition, the impact
of temperature was contemplated (Figure 8). As antici-
pated, the yield was growing with temperature until
100 °C, and remained the same above this temperature.
Thus, the reaction temperature 100 °C was kept for all
runs. Moreover, the catalytic activity of ED‐UiO‐66 was
compared with bare UiO‐66 to confirm that the
functionalization of the UiO‐66 framework is essential
to accomplish the best results (Table 1). Variables such
3.2.3 | Comparison of the present
approach with some reported protocols
The success of the nanoporous ED‐UiO‐66 catalyst was
compared with some reported catalysts for the
TABLE 3 Synthesis of different 2‐aminothiophene derivatives under the optimized reaction conditions
Entry
Carbonyl compound
Product
Yield (%)
Time (min)
M.P.
1
75
5
143‐145
2
3
95
85
5
5
146‐147
127‐130
a
4
5
6
7
21
240
240
24
104‐106
104‐106
120‐123
136–137
20a
40a
66
O
H
60
8
85
26
50
60
60
60
142–144
120–122
108‐110
9
10
aIn absolute ethanol (4 h reflux). Reaction conditions are described below Table 1. Yields refer to the separated pure products. The desired pure products were
characterized by comparison of their physical information with those of known compounds. Melting points are uncorrected.

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ERFANINIA ET AL.
preparation
of
2‐amino‐4,5,6,7‐tetrahydro‐1‐
hydrogen, and nitrogen contents as C, 5.767%; H,
0.502%; and N, 1.39%; which confirmed that the amount
of the loaded ED was decreased by ~3 %. Comparison of
this amount (3%) with the amount obtained for the fresh
catalyst (18%) unambiguously proved leaching of ED
during the condensation reaction and explains decreasing
of the catalyst efficiency and lengthening of the reaction
time for the consecutive runs.
benzothiophene‐3‐carbonitrile. Table 2 compares the cat-
alyst amount, temperature, reaction time, E‐factor, yield
and turnover number. Although some of the introduced
catalysts pushed the reaction at better reaction conditions,
nonetheless, they needed higher amounts of catalyst and
solvents. The present solvent‐less catalytic route conveys
distinct advantages in competition with the already
revealed pathways; straightforward work‐up, good yield,
at a very short time.
3.2.6 | Hot filtration test
3.2.4 | Development of different 2‐
aminothiophenes catalyzed by the
nanoporous ED‐UiO‐66
Considering the above findings and inspecting high
activity of ED in the Gewald reaction, we carried out
another study of the leaching of ED from UiO‐66. Here a
hot filtration test was arranged and 0.02 g of ED‐UiO‐66
was added to a mixture of malononitrile, cyclohexanone
and sulfur powder and the reaction was continued for
3 min. At this stage, the product yield was 58%. Then,
ethanol was added, the catalyst was separated off and with
the filtrate, the reaction continued for another 60 min at
100 °C. The resulting yield was only 67% (compared with
expected 95%), and this decrease is explained by leaching
of ED from ED‐UiO‐66. This finding is in accord with the
unsuccessful attempt to locate ED in UiO‐66 by XRD
which proved distribution of ED over the MOF framework
statistically.
Selective and efficient generation of a wide range of 2‐
aminothiophene derivatives with the assembled
nanocatalyst ED‐UiO‐66 was studied by carrying out the
condensation reaction under the optimized conditions
and by utilizing different aromatic carbonyl compounds
bearing electron withdrawing (donating) groups and
halogen‐substituted counterparts. All the applied ketones
and aldehydes successfully provided the favored products
with high selectivity and excellent yields in a short time
compared with all reported methods at once (Table 3).
3.2.5 | Stability and reusability of the ED‐
UiO‐66 nanoparticles
To study stability and reusability of ED‐UiO‐66 after
fulfillment of the primary run, ethanol was added to the
reaction mixture and the insoluble catalyst was recovered
by simple filtration. The separated nanocatalyst was
totally washed with ethanol; then, dried at 100̊C and
applied in another run. The nanocatalyst was reused for
subsequent four runs. Figure 9 shows good reusability of
ED‐UiO‐66 nanoparticles. Noteworthy, the CHN analysis
of the four times reused ED‐UiO‐66 showed carbon,
SCHEME
2
Proposed reaction pathway for the Gewald
FIGURE 9 Yield as a function of reusability of nano ED‐UiO‐66
condensation reaction

ERFANINIA ET AL.
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ACKNOWLEDGEMENTS
3.2.7 | Suggesting a plausible reaction
pathway
This work has been supported by the Center for Interna-
tional Scientific Studies & Collaboration (CISSC). Partial
financial/material support of Hakim Sabzevari University
and of the ASTRA lab established within the Operation
program Prague Competitiveness‐project CZ.2.16/3.1.00/
24510 is also greatly appreciated.
Until now, a number of reaction pathways have been
proposed for the synthesis of 2‐amino thiophenes under
different reaction conditions.[33,50] For the catalyst
ED‐UiO‐66 we propose mechanism displayed in
Scheme 2. The first step of the Gewald reaction is the
Knoevenagel condensation of the starting carbonyl
compound (ketone or aldehyde) with the activated nitrile
to produce an α,β‐unsaturated nitrile. Then, addition of
elemental sulfur to the unsaturated nitrile takes place to
produce a sulfur compound. According to the literature,
the ring closure step is the most crucial step in this
mechanism that is performed by an intra‐molecular
nucleophilic mercaptide attack to the triple bond of
the cyano compound to provide the final intermediate.
At the end, the final aromatization rearrangement
occurred to produce the desired 2‐aminotiophene.
Dual catalytic function is suggested for the nanocompos-
ite in the proposed pathway. In the first step, ED on the
surface of ED‐UiO‐66, would activate the carbonyl group
by coordination to the oxygen atom which increases
activity of the carbonyl group. In the next step, the Lewis
basic sites of the ED‐UiO‐66, would activate
malonodinitrile by deprotonation; then, the nucleophilic
attack to the activated carbonyl group pushes the
reaction forward.
ORCID
R. Tayebee http://orcid.org/0000-0003-1211-1472
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How to cite this article: Erfaninia N, Tayebee R,
Dusek M, Amini MM. Ethylene diamine grafted
nanoporous UiO‐66 as an efficient basic catalyst in
the multi‐component synthesis of 2‐
aminithiophenes. Appl Organometal Chem. 2018;
e4307. https://doi.org/10.1002/aoc.4307
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