Preparation of a superior liquid catalyst by hybridization of three solids of nanoZnO, urea, and choline chloride for Knoevenagel-based reactions

Article abstract of DOI:10.1007/s13738-017-1144-7

Abstract: The complex catalyst of [ZnClO.urea]^?[Ch.urea]⁺ has been prepared by dissolving of nanoZnO in choline chloride:2urea at 50 °C. The concentration of [ZnClO.urea]^? in the given liquid is 19,987 ppm and 10.5 times h

Full text of DOI:10.1007/s13738-017-1144-7

J IRAN CHEM SOC
DOI 10.1007/s13738-017-1144-7
ORIGINAL PAPER
Preparation of a superior liquid catalyst by hybridization
of three solids of nanoZnO, urea, and choline chloride
for Knoevenagel‑based reactions
Fatemeh Tamaddon1 · Davood Azadi1
Received: 6 December 2016 / Accepted: 25 May 2017
© Iranian Chemical Society 2017
Abstract The complex catalyst of [ZnClO.urea]−[Ch.
urea]+ has been prepared by dissolving of nanoZnO in
choline chloride:2urea at 50 °C. The concentration of
[ZnClO.urea]− in the given liquid is 19,987 ppm and 10.5
times higher than similar solution made from bulk ZnO.
This organic/inorganic hybrid catalyst represents a high
catalytic performance in Knoevenagel-based synthesis of
pyrans, chromenes, and electron-defcient alkenes. Due to
the high diffusion of ZnO nanoparticles in DESs, synergy
of nanoZnO with DESs, and much contact of this fuid cat-
alyst with starting materials, all Knoevenagel-based reac-
tions occur with higher yields at lower catalyst loading and
shorter times than individual ChCl:2urea, nanoZnO, or
even previously catalysts used for this purpose. High polar-
ity and reusability are other advantages of anionic complex
[ZnClO.urea]− and homogenized shape of nanoZnO.
Electronic supplementary material The online version of this
article (doi:10.1007/s13738-017-1144-7) contains supplementary
material, which is available to authorized users.
* Fatemeh Tamaddon
ftamaddon@yazd.ac.ir
1
Department of Chemistry, Yazd University, Yazd 89195-741,
Iran
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J IRAN CHEM SOC
Graphical Abstract
Keywords Deep eutectics · NanoZnO · [ZnClO.
shape and closest structure of fuids to homogeneous cat-
alysts, design and use of these dual incentive NMO-fuids
is highly desirable.
urea]−[Ch.urea]+ · Chromenes · Pyrans · Knoevenagel
Deep eutectic solvents (DESs) are more advantageous
alternatives for high cost and toxic ionic liquids (ILs) that
originally designed to reply to environmental challenges
[15–17]. DESs are very polar liquids made from two or more
low-priced solids that interact with each other by >200 °C
depression of melting points [18–22]. Owing to cheapness,
biodegradability, and non-toxicity of choline chloride (ChCl)
and urea, ChCl:2urea is among the most favorite DESs that
their ability to dissolving of zi−nc oxide as anionic complexes
of [ZnClO.urea]− and ZnCl3 confrmed by Abbott et al.
[18–22]. These anionic complexes have been specifed in sol-
ubilized ZnO in ChCl:2urea and ChCl:malonic acid by mass
spectroscopy, while concentration of [ZnClO.urea]− and
Introduction
In the past decade, design of hybrid catalysts with prof-
its of homogeneous and heterogeneous materials has
been the core of chemical researches [1–4]. Nanometal
oxides (NMO) are of these bridge catalysts that have
been extensively settled to promote organic transforma-
tions [5]. The available catalytic sites of NMOs depend
on their particle size, morphology, and aggregation type
[6]. NanoZnO is an amphoteric NMO catalyst that has
been used for acceleration of organic reactions [7–14].
Due to the maximum active sites of nanoZnO in fuid
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J IRAN CHEM SOC
−
ZnCl3 has been determined by inductively coupled plasma
Results and discussion
atomic emission spectroscopy (ICP-AES) [21, 22].
Pyrans [26–29] and chromenes are biologically active
multifunctional molecules that have been prepared by
Knoevenagel-based multi-component reactions (MCRs)
which pass through electron-defcient Michael-acceptor
intermediates [35–40]. Due to the importance of pyrans
and chromenes, their synthesis has been developed using
various acid/base catalysts and conditions, though devel-
opment of new hybrid organic/inorganic catalysts for more
effcient synthesis of these compounds is desirable. Herein,
for the frst time, we hybridized nanoZnO and eutectics to
give nanofuid catalysts containing high concentration of
[ZnClO.urea]− and ZnCl3 complexes and used very low
loading of the new hybrid catalyst of nanoZnO/ChCl:2urea
in advanced synthesis of electron-defcient alkenes [23–
25], pyrans [26–29] and chromenes [30–34] (Scheme 1).
Initially, for a more effcient preparation of anionic com-
plexes [ZnClO.urea]− and ZnCl3−, nanoZnO was prepared
by following a previous method [11], while the surface
area of the given nanoZnO was 33.6 m2/g and higher than
5 m2/g for ZnO in commercial grade. The characteristic
narrow peaks of the (100), (002), (101), (102), (110), (103),
(112), (201), and (004) at various 2θs from 30° to 80° in
the XRD pattern of the given nanoZnO are compatible with
standard JCPDS 36-1451 indexed for hexagonal wurtzite
ZnO [41]. The strong intensities of these peaks show high
crystallinity of the prepared nanoZnO (Fig. 1).
The FESEM image of nanoZnO also displays a mixture
of fake, disk, and rod surface morphologies with some
hexagonal wurtzite cross sections in nano-dimensions
(Fig. 2).
Scheme 1 Catalytic usage of nanoZnO/ChCl:2urea in Knoevenagel-based reactions
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J IRAN CHEM SOC
Then 0.08–1.44 g of nanoZnO was dissolved in 5 mL
of freshly made ChCl:2urea or ChCl:malonic acid DESs at
50 °C to give one-phase clear viscose solutions of [ZnClO.
urea]− or chlorometalate of ZnCl3− [20–22]. These solutions
were stable and did not change by even high-speed centrifu-
gation. To assign the above anionic complexes, which have
been documented earlier by Abbot et al. [21, 22] in the given
fuid, various spectroscopic techniques were employed. For
example, characterized peaks at various m/z = 174 (base
peak), 176, and 178 in mass spectrum of a sample prepared
from nanoZnO (1.44 g) and ChCl:2urea (5 mL) and typical
peaks at m/z = 1176, 174, 172, and 170 (base peak) in mass
spectrum of the given nanofuid from nanoZnO (1.44 g) and
ChCl:malonic acid (5 mL) were compatible with previous
reports on anionic complexes of [ZnClO.urea]− and ZnCl3
[21, 22]. Typically, the FT-IR spectrum of the fuid given
from 1.44 g nanoZnO and uDES (5 mL) shows all vibra-
tional modes of functional groups of nanoZnO, urea, and
choline chloride-based materials in Fig. 3. Thus, adsorption
band at ~500 cm−1 is respected to Zn–O stretching, the well-
defned bands at 3342– 3408 and 3205 cm−1 are due to over-
lapped stretchings NH2/OH in uDES, and the strong bands
at 1670 and 1620 cm−1 are assigned to C=O stretching and
N–H bending, respectively (Fig. 3d).
Fig. 1 XRD pattern of the prepared nanoZnO
Similarly, elemental analysis of this hybrid catalyst
showed 30.01% C, 7.80%H, and 19.05%N, which are very
close to calculated percent of elements for this fuid as
29.12%C, 7.60% H, 9.55% Cl, 18.87% N, 17.24% O, and
17.6% Zn. According to these results, the following struc-
ture is proposed for nanoZnO/ChCl:2urea as complex of
[ZnClO.(urea)]−[Ch.urea]+ (Scheme 2).
Fig. 2 The FESEM of the prepared nanoZnO
Fig. 3 FT-IR spectra of a ChCl
b urea c nanoZnO d nanoZnO/
uDES
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J IRAN CHEM SOC
Table 2 Comparative Performances of [ZnClO.urea]−[Ch.urea]+ in
Synthesis of 4a
Entry Conditions
Catalyst(mol%)/Solvent/Temp
Time (h) Yield (%)[Ref].
(°C)
1
2
3
nanoZnO (10)/EtOH:H2O/r.t.
ChCl:2urea (excess)/80
[ZnClO.urea]−[Ch.urea]+ (5)/-
3.5
4
92 [26]
82 [27]
Scheme 2 Proposed structure for anionic complex [ZnClO.urea]−
formed in nanoZnO/ChCl:2urea
0.15
95 (This work)
/r.t.
and viscose solution was stable at room temperature and
remained liquid even by high-speed centrifugation.
To evaluate the catalytic activity of fuidic complexes of
[ZnClO.urea]− and ZnCl3−, typical three-component reac-
tion of benzaldehyde (1a), malononitrile (2), and acetyl
acetone (3a) for synthesis of pyran 4a was attempted with
these catalysts under various conditions (Table 1).
The maximum catalytic activity in terms of reaction time
and yield was for 5 mol% of [ZnClO.(urea)]−[Ch.urea]+ at
room temperature (Table 1, entry 11). The superiority of
this complex versus other catalysts is attributed to its high
polarity, stability, homogeny, and its chemical structure for
better diffusion to reaction mixture and activation of start-
ing materials.
Table 1 Optimization of Reaction Conditions
Entry Conditions
Catalyst (mol%)/Solvent/Temp. (°C)
Time (h) Yield (%)a
1
-/-/r.t.b
24
3
Trace
63
80
52
65
25
80
30
35
70
95
92
85
94
90
90
68
84
2
ZnO (10)/-/r.t.
3
ZnO/ChCl:2urea (10)/-/r.t.
3
4
ChCl (10)/-/r.t.
3
5
ChCl:2urea (10)/-/r.t.
3
However, Table 2 shows the catalytic performance of
[ZnClO.urea]−[ChCl.urea]+ versus recently reported proto-
cols for synthesis of 4a.
6
ChCl:malonic acid (10)/-/r.t.
3
7
nanoZnO (10)/-/r.t.
3
8
[ZnCl3]−[Ch.malonic acid]+ (10)/-/r.t.
[ZnCl3]−[Ch.malonic acid]+ (20)/-/r.t.
[ZnClO.urea]−[Ch.urea]+ (2.5)/-/r.t.
[ZnClO.urea]−[Ch.urea]+ (5)/-/r.t.
[ZnClO.urea]−[Ch.urea]+ (10)/-/r.t.
[ZnClO.urea]−[Ch.urea]+ (20)/-/r.t.
[ZnClO.urea]−[Ch.urea]+ (5)/-/40
[ZnClO.urea]−Ch.urea]+ (5)/-/60
[ZnClO.urea]−Ch.urea]+ (5)/-/80
[ZnClO.urea]−Ch.urea]+ (5)/H2O/r.t.
3
The recoverability and reusability of homogeneous cata-
lysts is an important challenge in catalysis issues and indus-
trial usage of catalyst. Due to the insolubility of DESs in
EtOAc, for reusability test of [ZnClO.(urea)]−[Ch.urea]+,
after the frst run of the model reaction in 50 mmol scale,
EtOAc was added, product 4a was extracted, the remained
catalyst was washed with EtOAc, dried under vacuum, and
reused with a poor loss of activity after the third reaction
run (Fig. 4).
The comparative FT-IR of the recycled and fresh cata-
lysts support no signifcant changes in vibrational bands
of recycled catalyst and confrms the preservation of the
structure of catalyst after extraction of product by EtOAc
(Fig. 5).
9
3
10
11
12
13
14
15
16
17
18
1
0.15
0.15
0.15
0.15
0.15
0.15
1
[ZnClO.urea]−[Ch.urea]+ (5)/
1
EtOH/r.t.
19
[ZnClO.urea]−[Ch.urea]+ (5)/
CH3CN/r.t.
2
4
50
42
[ZnClO.urea]−[Ch.urea]+ (5)/
Next the prepared complex of [ZnClO.urea]−[Ch.urea]+
was tested in the effcient synthesis of pyrans (Table 3).
According to the results, aldehydes bearing electron-
withdrawing groups react faster than substrates bear-
ing electron-donating groups, due to much positivity of
carbonyl group in these molecules. The order of reac-
tivity observed for activated methylene groups was due
to dimedone > acetyl acetone > and ethyl acetoacetate
which is in agreement with their acidity. Mechanistically,
we proposed the following roles for [ZnClO.urea]−[Ch.
urea]+ in each step of the synthesis of pyrans (Scheme 3).
CHCl3/r.t.
a
Isolated yield
b
Room temperature
The ICP-AES experiments showed that replacing
nanoZnO with ZnO leads to growth in solubility of this
metal oxide in ChCl:2urea, so the concentration of [ZnClO.
urea]− from 1894 ppm at 50 °C for bulk ZnO [22] reached
to 19,987 ppm for nanoZnO in this work. The given clear
1 3

J IRAN CHEM SOC
The versatility of this homogeny shape of nanoZnO
was also demonstrated in MCR synthesis of 2-amino-4H-
chromenes (Table 4).
The results in Table 4 show that reactions with alde-
hydes bearing electron-withdrawing and electron-donat-
ing groups occurred quickly to give the corresponding
products.
with malononitrile in the presence of this catalyst
(Table 5).
As results show, Knoevenagel products were isolated
in excellent yields from the reaction of various aldehydes
and malononitrile using a small amount of catalyst.
To set up the mechanism for the [ZnClO.(urea)]−[Ch.
urea]+-catalyzed synthesis of pyrans and chromenes, the
isolated 2-benzylidenemalononitrile 7a from the reac-
tion of benzaldehyde and malononitrile (Table 5, entry
1) reacted with either acetylacetone or 1-naphthol under
Similarly, synthesis of tri-substituted alkenes was
attempted by Knoevenagel condensation of aldehydes
95
92
91
100
80
60
40
20
0
1
2
3
Number of runs
Fig. 4 Reusability of [ZnClO.urea]−[Ch.urea]+ in nanoZnO/
Ch:2urea
Fig. 5 Comparative FT-IR spectra of the fresh and recycled catalyst
Table 3 Synthesis of Polysubstituted 4H-Pyrans using [ZnClO.urea]−[Ch.urea]+
Entry
Ar
3
Product
Time (min)
Yield (%)a
m.p. (°C)/(lit.)
1
C6H5
Acetyl acetone
Acetyl acetone
Acetyl acetone
Acetyl acetone
Acetyl acetone
Acetyl acetone
Ethyl acetoacetate
Ethyl acetoacetate
Ethyl acetoacetate
Ethyl acetoacetate
Dimedone
4a
4b
4c
4e
4d
4f
10
30
95
92
98
92
96
93
95
89
98
95
96
94
97
92
162–163 (164) [26]
169–170 (170) [26]
153–155 (154) [26]
156–158 (156) [26]
140 (140) [26]
2
4-O2NC6H4
4-ClC6H4
4-H3COC6H4
4-FC6H4
3
10
4
100
15
5
6
4-CH3C6H4
C6H5
90
136–137 (136) [26]
192–194 (192) [26]
180–181 (182) [26]
170–171 (170) [26]
136–139 (134–136) [27]
232–234 (233) [27]
181–183 (180–182) [27]
214–216 (214–217) [27]
200–202 (195–199) [27]
7
4g
4h
4i
120
60
8
4-O2NC6H4
4-ClC6H4
4-H3COC6H4
C6H5
9
90
10
11
12
13
14
4j
120
20
4k
4l
4-O2NC6H4
4-ClC6H4
4-H3COC6H4
Dimedone
40
Dimedone
4m
4n
20
Dimedone
80
a
Isolated yield
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J IRAN CHEM SOC
Scheme 3 Proposed mecha-
nism for [ZnClO.urea]−[Ch.
urea]+-catalyzed synthesis of
pyrans
similar conditions and the desired products 4a and 6a
were isolated quantitatively after 15 min. This supports
the presence of Michael-acceptor intermediate 7a in these
[ZnClO.(urea)]−[Ch.urea]+-catalyzed MCRs (Scheme 4).
In summary, all three types high-yielding organic reac-
tions occurred at the shortest possible time in the pres-
ence of [ZnClO.urea]−[Ch.urea]+ to give the oxygenated
heterocycles of pyrans and chromenes as well as sub-
stituted alkenes which are excellent Michael-acceptor
intermediates.
bond donor like urea (20 mmol, 1.2 g) or malonic acid
(10 mmol, 1.1 g) at 100 °C to give a clear liquid [22],
while nanoZnO was prepared by following a previ-
ous procedure [11]. To prepare the designed nanofuids,
nanoZnO (0.85 g) with mean particle size of 38–60 nm
was magnetically dispersed in 10 mL of prepared DESs
as fuid’s base for 5 h at 50 °C. Only for ChCl:2urea a
homogeny clear viscose solution was obtained and dis-
persion of nanoZnO in Ch:malonic acid resulted in the
suspensions with no agglomeration or sedimentation of
nanoparticles.
Characterization of ZnO‑nanofuids
Experimental
To characterize the ZnO-nanofuids, the prepared nanoZnO
was frstly specifed by surface area (BET), X-ray diffrac-
tion (XRD), feld emission scanning electron micrograph
(FESEM), and comparative FT-IR spectra of ChCl, urea,
nanoZnO and [ZnClO.(urea)]−[Ch.urea]+.
Preparation of ZnO‑nanofuids
The deep eutectics were typically prepared by stirring
a mixture of ChCl (10 mmol, 1.4 g) with a hydrogen
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J IRAN CHEM SOC
Table 4 The [ZnClO.urea]−[Ch.urea]+-Catalyzed Synthesis of
4H-Chromenes
5‑Acetyl‑2‑amino‑6‑me‑
thyl‑4‑(4‑nitrophenyl)‑4H‑pyran‑3‑carbonitrile
(Table 3, entry 2)
Yellow crystal; yield 92%; m.p. 169–170 °C, IR (KBr): νmax
3441, 3338, 3195, 2193, 1663, 1344, 1219 cm−1 1H
;
NMR (400 MHz, CDCl3): δ 2.14 (3H, s, CH3), 2.37 (3H,
s,CH3), 4.57 (1H, s, CH), 6.13 (2H, s, NH2), 7.38 (2H, d,
J = 18.7 Hz, ArH), 8.20 (2H, d, J = 18.7 Hz, ArH) ppm;
13C NMR (100 MHz, CDCl3): δ 19.8, 24.7, 29.6, 30.0,
115.2, 124.0, 124.4, 124.7, 127.2, 128.1, 129.1, 129.9,
161.5, 197.5 ppm.
Entry Ar
Product Time Yield (%)a m.p. (°C) (lit.)
(min)
1
2
3
4
5
6
7
8
C6H5
6a
6b
6c
6d
6e
30
40
5
91
99
97
98
93
97
97
90
210–211
(210–212) [30]
4-O2NC6H4
4-FC6H4
233–235
(235–236) [30]
5‑Acetyl‑2‑amino‑6‑me‑
thyl‑4‑(4‑fuorophenyl)‑4H‑pyran‑3‑carbonitrile
(Table 3, entry 5)
230–232
(229–231) [30]
4-ClC6H4
5
284–285
(284–286) [30]
Yellow crystal; yield 96%; m.p. 140 °C, IR (KBr):
2,4-Cl2C6H3
30
120
20
15
222–224
(223–225) [30]
νmax 3396, 3329, 3203, 2925, 2199, 1694, 1668, 1600,
1220 cm−1 1H NMR (400 MHz, DMSO-d6): δ 2.07
;
3-H3COC6H4 6f
4-H3COC6H4 6g
230–232
(232–233) [31]
(3H, s, CH3), 2.24 (3H, s, CH3), 4.51 (1H, s, CH), 6.89
(2H, s, NH2), 7.16 (2H, t, J = 110 Hz, ArH), 7.22 (2H,
dd, J1 = 110, J2 = 16, ArH) ppm; 13C NMR (100 MHz,
DMSO-d6): δ 18.9, 30.3, 38.5, 58.1, 115.4, 115.9, 120.2,
129.5, 141.3, 155.3, 158.7, 161.5, 198.8 ppm.
186–188
(188–190) [30]
4-H3CC6H4
6h
203–205
(202–204) [30]
a
Isolated yield
2‑Amino‑7,7‑dimethyl‑4‑(4‑nitrophenyl)‑5‑oxo‑4a,5,6,7,
8,8a‑hexahydro‑4H‑chromene‑3‑carbonitrile (Table 3,
entry 12)
General procedure for synthesis of 4H‑pyrans
and 2‑amino‑4H‑chromenes
White solid; yield 94%; m.p. 181–183 °C, IR (KBr): νmax
3397, 3322, 2191, 1683, 1654, 1522, 1347, 1215 cm−1;1H
NMR (400 MHz, DMSO-d6): δ 0.96 (3H, s, CH3) 1.04
(3H, s, CH3),2.12 (1H, d, J = 116 Hz, CH), 2.27 (1H, d,
J = 116 Hz, CH), 2.50 (2H, s, CH2), 4.37 (1H, s, CH),
7.18 (2H, s, NH2), 7.45 (2H, d, J = 18.3 Hz, ArH), 8.17
(2H, d, J = 18.3 Hz, ArH) ppm; 13C NMR (100 MHz,
CDCl3+DMSO-d6): δ 13.7, 20.5, 27.1, 28.4, 31.7, 35.5,
50.0, 58.3, 59.7, 112.2, 118.7, 123.2, 128.2, 146.3, 151.1,
158.3, 162.3, 195.4 ppm.
For synthesis of pyrans, a mixture of malononitrile (5 mmol),
aldehyde (5 mmol), active methylene dicarbonyl compound
(5 mmol), and ZnO-nanofuid [ZnClO.(urea)]−[Ch.urea]+
(5 mol%) was stirred at room temperature for the given
times. For synthesis of 2-amino-4H-chromenes, a mixture of
benzaldehyde (10 mmol), 1-naphthol (10 mmol), malononi-
trile (10 mmol), and ZnO-nanofuid (10 mol%) was stirred at
100 °C. After the completion of each reaction (TLC moni-
toring), EtOAc was added, the mixture was decanted, and
the product was isolated by evaporation of the solvent under
vacuum. The structures of the products were compatible with
those reported in the literature.
2‑Amino‑4‑(4‑chlorophenyl)‑4H‑benzo[h]
chromene‑3‑carbonitrile (Table 4, entry 4)
General procedure for the synthesis of arylidene malo‑
nonitriles
Pale yellow solid, yield 98%; m.p. 284–285 °C, IR (KBr):
νmax 3454, 3333, 2191, 1663, 1598, 1573, 1375, 1096,
1
801 cm−1; H NMR (400 MHz, DMSO-d6): δ 4.95 (1H, s,
A mixture of malononitrile (5 mmol), aldehyde (5 mmol)
and [ZnClO.(urea)]−[Ch.urea]+ (5 mol%) was stirred at
room temperature for the given times (Table 5). After com-
pletion of the reaction, the product was isolated as above.
The structures of all products were compatible with those
reported in the literature.
CH), 7.09 (1H, d, J = 18.5 Hz, ArH), 7.21 (2H, s, NH2),
7.28 (2H, d, J = 18 Hz, ArH), 7.38 (2H, d, J = 18 Hz,
ArH), 7.62 (3H, m, ArH), 7.89 (1H, d, J = 18 Hz, ArH),
8.25 (1H, d, J = 18.3 Hz, ArH) ppm; 13C NMR (100 MHz,
CDCl3+DMSO-d6): δ 40.9, 58.9, 116.7, 120.2, 120.9,
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J IRAN CHEM SOC
Table 5 [ZnClO.urea]−[Ch.urea]+-Catalyzed Synthesis of Tri-Substituted Alkenes
Entry
1
Ar
Product
7a
Time (min)
5
Yield (%)a
95
m.p. (°C)/(lit.)
C6H5
82–84
(82–83) [24]
2
4-O2NC6H4
4-FC6H4
7b
7c
7d
7e
7f
1
1
2
3
7
3
5
7
5
5
5
7
98
93
95
90
92
93
90
97
91
96
92
94
133–135
(135) [23]
3
126–128
(125–126) [24]
4
4-ClC6H4
162–163
(161–163) [24]
5
2,4-Cl2C6H3
4-CH3C6H4
3-H3COC6H4
4-H3COC6H4
4-(Me)2N C6H4
2,4-(MeO)2C6H3
4-HOC6H4
2-furyl
148–150
(149) [23]
6
132–134
(134–135) [24]
7
7g
7 h
7i
106–108
(107–108) [25]
8
115–116
(113–114) [24]
9
189–191
(190–191) [25]
10
11
12
7j
140–142
(141–142) [25]
7k
7l
188–189
(187–188) [24]
72–74
(71–72) [24]
13
4-pyridyl
7n
100–102
a
Isolated yield
123.2, 124.4, 125.9, 126.6, 126.8, 127.6, 128.8, 129.4,
132.8, 133.2, 143.3, 143.4, 159.7 ppm.
2‑Amino‑4‑(4‑methoxyphenyl)‑4H‑benzo[h]
chromene‑3‑carbonitrile (Table 4, entry 7)
Yellow solid; yield 97%; m.p. 186–188 °C, IR (KBr):
νmax 3442, 3300, 3181, 2202, 1653, 1371, 1094, 805,
1
736, 696 cm−1; H NMR (400 MHz, DMSO-d6): δ 3.76
(3H, s, CH3), 4.90 (1H, s, CH), 7.12 (1H, d, J = 18.5 Hz,
Scheme 4 Confrmation of intermediate 7a in the synthesis of pyrans
and chromenes
ArH), 7.14 (2H, s, NH2), 7.24 (2H, m, ArH), 7.32 (2H,
1 3

J IRAN CHEM SOC
11. F. Tamaddon, F. Aboee, A. Nasiri, Catal. Commun. 16, 194
(2011)
t, J = 17.5 Hz, ArH), 7.63 (3H, m, ArH), 7.89 (1H, d,
J = 18.1 Hz, ArH), 8.25 (1H, d, J = 18.3 Hz, ArH) ppm;
13C NMR (100 MHz, CDCl3 + DMSO-d6): δ 40.7, 55.1,
59.3, 114.0, 117.5, 120.4, 120.9, 123.2, 124.1, 126.1,
126.4, 126.5, 127.5, 129.0, 133.0, 137.2, 143.1, 158.5,
159.6 ppm.
12. P.P. Ghosh, A.R. Das, Tetrahedron Lett. 53, 3140 (2012)
13. M. Hosseini-Sarvari, J. Iran. Chem. Soc. 8, S119 (2011)
14. H. Sharma, N. Kaur, N. Singh, D. Jang, Synfacts 11, 1218 (2015)
15. M.A. Martins, C.P. Frizzo, D.N. Moreira, N. Zanatta, H.G.
Bonacorso, Chem. Rev. 108, 2015 (2008)
16. E.L. Smith, A.P. Abbott, K.S. Ryder, Chem. Rev. 114, 11060
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1,1‑Dicyano‑2‑(pyridine‑4‑yl)ethylene (Table 5, entry
13)
17. S. Khandelwal, Y.K. Tailor, M. Kumar, J. Mol. Liq. 215, 345
(2016)
18. A.P. Abbott, D. Boothby, G. Capper, D. Davies, R. Raymond, V.
Tambyrajah, Chem. Commun. 7, 70 (2003)
White needles; yield 94%; m.p. 100–102 °C, IR (KBr):
νmax 3023, 2933, 2233, 1610, 1590, 1548, 1416, 1403,
1236, 1219, 1067, 933, 947, 819, 771, 621 cm−1; 1H NMR
(400 MHz, CDCl3): δ 7.69 (2H, d, J = 15.3 Hz, ArH), 7.83
(1H, s, VinylH), 8.88 (2H, d, J = 15.3 Hz, ArH) ppm; 13C
NMR (100 MHz, CDCl3): δ 89.0, 111.7, 112.9, 123.0,
137.4, 151.9, 158.0 ppm.
19. A.P. Abbott, D. Boothby, G. Capper, D.L. Davies, R. Raymond,
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Conclusions
24. N.M. Abd El-Rahman, A.A. El-Kateb, M.F. Mady, Synth. Com-
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30 (2012)
26. P. Bhattacharyya, K. Pradhan, S. Paul, A.R. Das, Tetrahedron
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28. M.H. Elnagdi, M.S. Moustafa, S.M. Al-Mousawi, R.A.
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In conclusion, we have developed a profcient method for
preparation and application of [ZnClO.urea]− in a homog-
enized nanoZnO-fuid that have dual catalytic advanta-
geous of either DESs or nanoZnO. This polar and reusable
hybrid catalyst represents multiple roles in Knoevenagel-
based reactions for rapid synthesis of substituted pyrans,
chromenes, and electron-defcient alkenes.
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Acknowledgements We gratefully thank the supports from Yazd
University Research Council.
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