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SOTOUDEHNIA ET AL.
reactions.[33–36] In an extension of our research, herein, we
wish to report the preparation and characterization of an
efficient recyclable kind of ZnO‐supported CuO/Al2O3
nanocatalyst (Cu/ZnO/Al2O3 nanocatalyst) as well as its
catalytic activity on the synthesis of propargylamines
under solvent‐free conditions (Scheme 1).
and crystallinity of the catalyst. The Scherrer equation
was used to determine the average crystallite size of the
sample. The BET surface area was tested by N2 adsorp-
tion–desorption method. The investigation was carried
out using an automated gas adsorption analyzer (Tristar
3020, Micromeritics). The sample was purged with nitro-
gen gas for 3 h at 300ºC by a VacPrep 061 degas system
(Micrometrics).
2 | EXPERIMENTAL
2.1 | General
2.4 | General procedure
Chemicals were purchased from Merck and Fluka.
The nanocatalyst was prepared by the co‐precipitation
method, and characterized by scanning electron micros-
copy (SEM), energy‐dispersive X‐ray spectroscopy (EDS),
X‐ray powder diffraction (XRD) and Brunauer–Emmett–
Teller (BET) surface area study. All obtained products
were characterized by comparison of their physical and
spectroscopic properties with those reported in the litera-
ture. NMR spectra were recorded on a Bruker Advance
400 MHz. Yields refer to isolated pure products.
In a round‐bottom flask, a heterogeneous mixture of alde-
hydes (1 mmol), amine (1 mmol) and phenylacetylene
(1.2 mmol) Cu/ZnO/Al2O3 nanocatalyst (0.05 g) was
stirred at 80°C for the appropriate times (mentioned in
Table 3) under solvent‐free conditions. The improvement
of the reaction was monitored by thin‐layer chromatogra-
phy (TLC). After reaction completion, the reaction mix-
ture was allowed to cool at room temperature. Then hot
chloroform was added and the catalyst was separated.
The solvent was evaporated under reduced pressure and
the residue was purified by silica gel column chromatog-
raphy to obtain the pure corresponding propargylamines.
The spectral and analytical data for the new prepared
compound are as follows:
2.2 | Catalyst preparation
The catalyst was prepared through a co‐precipitation pro-
cess, by adding Na2CO3 solution (0.5 M) drop‐wise into a
mixture of Cu (NO3)2·3H2O (0.03 M), Zn (NO3)3·6H2O
(0.03 M) and aluminum nitrate (0.03 M) solutions under
strong stirring. The obtained suspension was aged at
pH 8.5 for 15 min at 50°C, then filtered and washed with
warm deionized water. The precipitates were dried for 12
h at 100°C, followed by calcination at 300°C for 3 h to
obtain the CuO/ZnO/Al2O3 nanocatalyst.
1
Table 3, entry 9: Oil; H NMR (CDCl3, 400 MHz), δ
(ppm): 1.34–1.54 (m, 6H), 2.47 (br, 4H), 4.68 (s, 1H),
4.96 (s, 2H), 6.87 (d, 2H), 7.21–7.43 (m, 10H), 7.45 (d,
2H). 13C NMR (CDCl3, 100 MHz), δ (ppm): 24.48, 26.13,
50.58, 61.78, 70.05, 86.28, 87.76, 114.36, 127.57, 128.01,
128.11, 128.33, 128.64, 129.81, 131.85, 137.09, 158.31.
Elem. Anal. Found: C, 85.09%; H, 7.19% N, 3.73% (calcd
for C27H27NO: C, 85.00%; H, 7.13%; N, 3.67%).
2.3 | Catalyst characterization
3 | RESULTS AND DISCUSSION
3.1 | Catalyst characterization results
The morphology of the nanocatalyst was studied using
SEM by a JEOL JSM‐6500F device, equipped with
an EDS analytical system to study the existence of
different components of the catalyst. The XRD study
was performed using an X‐ray diffractometer, Cu‐Kα
monochromatized radiation source and a nickel filter
(Panalytical X'Pert‐Pro), in order to explore the structure
Figure 1 represents the SEM images of the Cu/ZnO/Al2O3
nanocatalyst with different magnifications. An aggrega-
tion of the Al2O3 and CuO nanoparticles was observed
on the surface of ZnO support. The sizes of these
nanoaggregates with different shapes are less than 20
nm. As a quantitative proof, the EDS (Figure 1d) analysis
has been performed, and presented the content of ZnO
support greater than 75% by weight.
The XRD pattern of the CuO/ZnO/Al2O3 nanocatalyst
was shown in Figure 2. The peaks centered at about 2θ =
31.9, 2θ = 34.76, 2θ = 56.84, 2θ = 69.18 corresponded to
the 100, 002, 110 and 200 crystalline planes of ZnO sup-
port, respectively.[37] The peaks observed at 2θ = 36.58,
2θ = 47.86 and 2θ = 63.32 may be related to 111, 202
and 113 planes of CuO, respectively.[38] It is valuable to
SCHEME 1 Synthesis of propargylamines catalyzed by Cu/ZnO/
Al2O3 nanocatalyst