Encapsulation of copper(I)-Schiff base complex in NaY nanoporosity: An efficient and reusable catalyst in the synthesis of propargylamines via A 3-coupling (aldehyde-amine-alkyne) reactions

Article abstract of DOI:10.1016/j.apcata.2013.03.008

Nanodimensional microreactor containing bis[2-(phenylthio)benzylidene]-1,2- ethylenediamine copper(I) complexes, [Cu(N₂S₂)]X-Y (X = CN, Cl, Br, I) was successfully prepared. This nano composite was used as a catalyst in one-pot multicomponent coupling reaction of aldehydes, amines and alkynes toward synthesis of propargylamines. The copper(I) complex with N ₂S₂ donor Schiff base ligand was readily trapped in the nanocavity of zeolite-Y through a template synthetic (TS) method. Two consecutive processes in the liquid phase were carried out: (i) preparation of a solution of [Cu(MeCN)₄]X coordinated with 2-(phenylthio)- benzaldehyde in the presence of zeolite-Y. This process caused the inclusion of [Cu(MeCN)₂(S₂O₂)]X complex into the nanopores of zeolite Y via pre-adsorption method; (ii) template synthesis of the [Cu(MeCN)₂(N₂S₂)]X-Y, through Schiff condensation between [Cu(MeCN)₂(S₂O₂)]X and 1,2-ethylenediamine moiety into the nanopores of NaY. The resulting catalysts were fully characterized by spectroscopic techniques such as AAS, FT-IR, BET isotherm, XRD, UV-Vis and TGA. The results confirmed encapsulation of Y-zeolite with copper(I) complex of N₂S₂ donor ligand. The catalytic activity of this nanocomposite material was investigated for preparation of propargylamines via three-component reaction of aldehydes, amines and alkynes. Also, the effective factors on this condensation reaction were discussed, such as reaction temperature, solvent, catalyst loading, leaching and reusability of the catalyst.

Full text of DOI:10.1016/j.apcata.2013.03.008

Accepted Manuscript
Title: Encapsulation of copper(I)-Schiff base complex in NaY
nanoporosity: An efficient and reusable catalyst in the
synthesis of propargylamines via A3-coupling
(aldehyde-amine-alkyne) reactions
Author: <ce:author id="aut0005"> Hossein Naeimi<ce:author
id="aut0010"> Mohsen Moradian
PII:
S0926-860X(13)00128-2
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2013.03.008
APCATA 14129
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
13-11-2012
13-2-2013
6-3-2013
Please cite this article as: H. Naeimi, M. Moradian, Encapsulation of copper(I)-
Schiff base complex in NaY nanoporosity: An efficient and reusable catalyst in
the synthesis of propargylamines via A3-coupling (aldehyde-amine-alkyne) reactions,
Applied Catalysis A, General (2013), http://dx.doi.org/10.1016/j.apcata.2013.03.008
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Encapsulation of copper(I)-Schiff base complex in NaY nanoporosity: An
efficient and reusable catalyst in the synthesis of propargylamines via A3-
coupling (aldehyde-amine-alkyne) reactions
Hossein Naeimi* Mohsen Moradian
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan, Kashan, 87317, I.R.Iran
Fax No: +98-361-5912397
E-mail address: naeimi@kashanu.ac.ir
Highlights
Development of New N2S2-donor salen-type ligand.
Preparation of New host/NaY–guest/Cu(I) N2S2-thiosalen complex material.
High activity of the hybrid material in the synthesis of propargylamines.
High stability and catalytic activity of the catalyst due to the rich electron-donating.
Reusability of the catalyst with negligible leaching of metal ion in the A3-coupling reaction.
Abstract
Nanodimensional microreactor containing bis[2-(phenylthio)benzylidene]-1,2-ethylenediamine
copper(I) complexes, [Cu(N2S2)]X-Y (X=CN, Cl, Br, I) have been successfully prepared. This nano
composite used as a catalyst in one-pot multicomponent coupling reaction of aldehydes, amines and
alkynes toward synthesis of propargylamines. The copper (I) complex with N2S2 donor Schiff base
ligand was readily trapped in the nanocavity of zeolite-Y through a template synthesis method (TS).
However two consecutive process in the liquid phase were performed: (i) preparing a solution of
[Cu(MeCN)4]X and coordinated with 2-(phenylthio)-benzaldehyde in the presence of zeolite-Y. This
process caused the inclusion of [Cu(MeCN)2(S2O2)]X complex into the nanopores of Y via pre-
adsorption method. (ii) Template synthesis of the [Cu(MeCN)2(N2S2)]X-Y, through Schiff
condensation between [Cu(MeCN)2(S2O2)]X and 1,2-ethylenediamine moiety into the nanopores of
NaY. The resulting catalysts were fully characterized by spectroscopic techniques such as AAS, FT-
IR, BET isotherm, XRD, UV-Vis and TGA. The results was indicated the encapsulation of Y-zeolite
with copper(I) complex of N2S2 donor ligand. The catalytic activity of this nanocomposite material
1
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was investigated for preparation of propargylamines via three-component reaction of aldehydes,
amines and alkynes. Also, the effective factors on this condensation reaction such as; reaction
temperature, solvent, catalyst loading, leaching and reusability of the catalyst were discussed.
Keywords:
N2S2-Schiff base, Cu(I)-complex, heterogeneous, Y-zeolite, catalyst, propargylamine
1. Introduction
The C-C bond formation reactions such as preparation of propargylamines catalyzed by
transition-metal complexes are among the most important fundamental transformations in synthetic
chemistry [1]. The propargylamines are significant intermediates for synthesis of various nitrogen
compounds as pharmaceutical active ingredients [2] and natural products such as -lactams,
peptides, isosteres and therapeutic drug molecules [2, 3]. These compounds can be obtained by an
A3-coupling reaction between aldimines and activated C-H of alkynes[4] via copper source as
heterogeneous catalyst [5-10]. However, copper (I) halides[11] such as; CuCl[12], CuBr[13], and
CuI[6] or coordinated with organic donor ligands have been used as catalysts[14, 15].
Schiff base ligands are easily synthesized and coordinate with almost all metal ions to form
relative complexes. These complexes can catalyze various reactions depending on the type of metal
ion [16, 17]. However, some of the homogeneous transition metal complexes demonstrate
noteworthy catalytic properties (activities and selectivity). The homogeneous catalysts are unsuitable
for separating from the reaction medium and making their reuse difficult and infecting the reaction
products. Heterogenization of homogeneous transition metal catalysts via immobilization on solid
supports[18] can mitigate these problems. The host-guest zeolite structures suggest an ideal support
for the immobilization of metal complexes [19, 20]. Zeolite encapsulated metal complexes (ZEMC)
could provide an opportunity for easy recovering and recycling of the catalyst[21], facile product
purification and possibly, continuous or multiple processing of compounds[10, 22, 23].
Recent reports in this field have included the development of recoverable and reusable
catalysts through organic- inorganic hybrid materials. Li and Wang, have reported an efficient and
reusable heterogeneous copper (I) organic-inorganic hybrid material (SiO2-CHDA-CuI) as a catalyst
in this reaction[24]. Likhar et al., described an imine-functionalized copper complex immobilized on
2
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o
silica (SiO2-Py-CuI) in acetonitrile at 90 C[25], also Lei Wang and co-workers, prepared an N-
heterocyclic carben (NHC) silica supported complex with CuI for the synthesis of
propargylamines[26]. Immobilizing the copper metal as an efficient catalyst in the reaction via silica
supports[27], molecular sieves[28], magnetite[29], zeolites[30], Pybox complexes on polystyrene
resin[31] and Cu(I)–MOF[32] as heterogeneous catalysts were as well reported.
We developed a new N2S2-donor ligand of phenylthioether used as phenolic units of Schiff
base (N2O2 salen-type), and coordinated with copper(I) halides within nanopores of Y-zeolite. Due to
the electron-donating rich character of sulfur atoms, the thiosalen ligand increase the stability of the
complex and improve catalytic activity of copper(I) especially in the A3-coupling reaction of
aldimines and alkynes toward propargylamines. The reaction does not require any co-catalyst and
after completion of the reaction, the catalyst was recovered by filtration and reused several times
with only a slight decrease of activity under the same reaction conditions.
2. Experimental
2.1. Material and physical measurements
All the solvents were purchased from Merck Company (reagent grades) and were used as
received unless otherwise specified. The NaY zeolite with the Si:Al ratio of 2.53 in powder form was
purchased from Aldrich (Art No. 334448); IR spectra were recorded as KBr pellets on a Nicolet FT-
IR spectrophotometer. 1H and 13C-NMR spectra were recorded in CDCl3 on a Bruker DRX-400
spectrometer with tetramethylsilane as internal reference. XRD patterns were recorded by an
X'PertPro (Philips) instrument with 1.54 Ångström wavelengths of x-ray beam and Cu anode
material. Nitrogen adsorption measurements were performed at 77K using a Coulter Ofeisorb 100CX
instrument. Micropore volumes were determined by the t-method. The copper determination was
carried out by a Unicam 929 model flame A. A. spectrophotometer.
2.2. Synthesis of 2-phenylthiobenzaldehyde
Freshly prepared magnesium methoxide (0.90 g, 10 mmol) was placed in a 50-mL reaction
flask. N,N-Dimethylformamide (30 ml), 2-nitrobenzaldehyde (1.50 g, 10 mmol), and thiophenol
(1.10 g, 10 mmol) were added and stirred at 80 ºC for 4 hours. The progress of the reaction was
monitored by TLC, after completion of the reaction, water (50 ml) was added, and the aqueous
solution was extracted twice with ethyl acetate (2×10 ml). The combined organic layers were dried
over magnesium sulfate. The solvent was evaporated at a reduced pressure to produce the yellow oil,
followed the purification by column chromatography using n-hexane/ethyl acetate (8/2) as eluent to
3
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afford 2-phenylthiobenzaldehyde (1.85 g 87% yield). IR (thin film): 3060 (H-Ar), 2846, 2738
(HCO), 1686 (C=O), 1584, 1445 (C=C, Ar), 1392, 1299, 1195, 751, 694. 1H NMR (CDCl3): 10.38
(s, 1 H, HC=O), 7.88 (s, 1 H, Ar), 7.26-7.43 (m, 7 H, Ar), 7.10 (s, 1 H, Ar). 13C NMR (CDCl3):
126.3, 128.4, 129.7, 130.3, 131.9, 133.1, 133.2, 133.7, 134.1, 141.5, 191.4. MS: 215 ([M+1]+, 1.5),
215 (M+, 12), 185 (45), 109 (74), 105 (23), 76 (100). Anal. Calcd. for C13H10OS (214.28): C 72.8, H
4.7; Found: C 72.7, H 4.6[33].
2.3. Preparation of the catalyst [Cu(N2S2)]X@Y (X=Cl, Br, I, CN)
Two consecutive process was done toward preparation of guest [Cu(N2S2)]X /host (Y-zeolite)
nanocomposite material. First of all, 1.0 mmol of each one of the CuCl, CuBr, CuI and CuCN as
halides of copper(I), was added to 25 ml acetonitrile at 50 oC with continues stirring for about 2 h to
give relative clear solutions of [Cu(MeCN)4]X (X=Cl, Br, I, CN) complexes. These four solutions
were used during the preparation of target catalyst in the subsequent processes. To each one of these
solutions, Zeolite-Y 2 g (previously dried in a vacuum oven in 80 ºC for 10 h) was added, and the
mixture was stirred for 5 h at room temperature. A solution of 2-phenylthiobenzaldehyde (2.0 mmol,
0.430 g) in 10 ml methanol was added and with further stirring at 50 oC for 15 h, the
[Cu(MeCN)2(S2O2)]X@Y complexes (a) was prepared. The reaction mixture was filtered off and the
solid collected and placed immediately in a new reaction container. A solution of 1,2-
ethylenediamine (10 mmol, 0.6 g) in 10 ml absolute ethanol was added to the modified zeolite. The
suspensions were stirred for 20 h under reflux conditions. The solid was collected, washed with
ethanol (3×10 ml) and then CHCl3 (3×10 ml) till the filtrate was free from any organic moieties (by
TLC of filtrate) content. The modified zeolite (b), was dried at 60oC under vacuum overnight to
obtain the corresponding nanoscale microreactors host (Y zeolite) /guest [Cu(N2S2)]X (X= Cl, Br, I,
CN) materials as light orange powders (c). Before characterization, the obtained catalysts were
soxhlet extracted for 3 h in methanol to remove the remaining uncomplexed metal and species
adsorbed on the external surface of the zeolite.
4
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N
N
N
O
N
N
O
N
S
S
S
CuX
S
S
S
CuX
Cu
X
N
N
a
c
b
2.4. General procedure for the synthesis of propargylamines by the catalyst
All of the reactions were carried out at 70 oC in a 25 ml flask equipped with a magnetic stirring
bar and reflux condenser. In a typical procedure, to a mixture of the selected aldehyde (1.0 mmol),
the selected secondary amine (1.1 mmol) and the selected alkyne (1.2 mmol) in dichloroethane
(DCE) as solvent, 697 mg from desired catalyst (containing 3 mol % copper based on copper halide)
was added. The final mixture was stirred at 70 oC, after completion of the reaction (monitored by
TLC); the resulting mixture was then filtered through a pad of celite and solid catalyst washed with
CH2Cl2 (3×5 ml) and methanol (3×5 ml). The filtered was evaporated under reduced pressure to give
a crude product as viscous oil. The product was purified over silicagel by column chromatography
(10% EtOAc in hexane as eluent) to give the desired propargylamine.
3. Results and discussion
Zeolite-Y is an inert microporous crystalline aluminosilicate that forming nano-cavities and
nano-channels of strictly regular dimensions. The NaY consists of almost spherical 1.3 nm cavities
interconnected through apertures of 0.74 nm diameters[34]. The structure of the large size of the
encapsulated homogeneous catalysts and their rigidity make them difficult to escape out of the
zeolite cages. Since, the catalyst is usually comprised of several specific active sites, the atomically
uniform dispersion of metal catalysts is highly beneficial for significant improvement of catalytic
action[35].
3.1. Characterization of the catalyst
The Y-zeolite encapsulated with N2S2 thiosalen copper(I) complex were investigated by
infrared, UV-Vis, XRD pattern, thermal gravimetry, BET theory and atomic absorption
spectroscopy.
5
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FT-IR spectroscopy is very important technique and can provide valuable information of the
crystalinity and on the encapsulated metal complex inside the host zeolite. A comparison between
the IR spectra of catalyst with that of the initial NaY indicates the presence of the organometallic
complex inside the zeolite cavities (Fig. 1). The FT-IR spectra of NaY is dominated by some of the
major zeolite framework bands in the range of 720-790 cm-1 νs (Si-O), 1020 cm-1 (Si-OH), 1130 cm-1
νas (Si-O and Al-O) and 3550 cm-1 for isolated silanol (Si-OH)[36, 37]. These bands detected in all of
the encapsulated zeolite and support the fact that the encapsulation process does not modify the
zeolite structure.
The IR spectra of the free ligand showed the strong band at 1614 cm-1 is assigned to stretching
vibration of C=N group. This band shift to lower position by 6-9 cm-1 in complexes that suggests
coordination of copper through C=N functional groups (Fig. 1). The encapsulated complexes exhibit
very similar IR data concerning those of the corresponding free complexes and confirm the presence
of [Cu(N2S2)]X in the nanoporosity of Y-zeolite, and suggest that its structure is almost identical to
that of the free. The intensity of IR bands of [Cu(N2S2)]Cl@Y depends on their loading and normally
is weaker that, due to the low concentration of the complexes. For instance, in the Fig. 1, we show
the FT-IR spectra for [Cu(N2S2)]Cl complex (a), NaY (b), and [Cu(N2S2)]Cl@Y-zeolite (c).
Fig. 1. FT-IR spectra of [Cu(N2S2)]Cl complex (a), NaY (b) and [Cu(N2S2)]Cl@Y-zeolite (c)
6
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Powder X-ray diffraction patterns of zeolite-Y are normally measured in the range 10–70o. The
X-ray diffraction (XRD) patterns of modified NaY with organo-copper complex are similar to those
of untouched zeolite (Fig. 2). Upon encapsulation, a very slight change in the intensity and
broadening of the peaks was observed which can be shown a negligible loss that may occur in
crystallinity of the Y-zeolite [38, 39]. This pattern also confirms that the framework of the NaY does
not destroy, and the complexes were well distributed in the pores. We present the XRD pattern of Y-
zeolite (a) and [Cu(N2S2)]Cl@Y nanocomposite (b) in the Fig. 2.
Fig. 2. X-ray diffraction patterns of (a) zeolite-Y and (b) zeolite encapsulated CuCl-thiosalen
The electronic spectrum of thiosalen ligand shows two bands at 248 and 372 nm in CH2Cl2 as
solvent which arise due to π→π* and n→π* transitions. Since no d→d transitions are expected for
d10 complexes, the UV-vis bands of the [Cu(N2S2)]Cl complex at 454 nm are assigned to the metal-
ligand charge transfer (MLCT) or ligand centered π→π* transitions [40]. The comparison of UV-Vis
spectrums for ligand, complex and encapsulated nanoreactor (diffuse reflective spectrum) in Fig. 3
confirmed the incorporation of thiosalen-CuCl complex into the Y-zeolite supercages.
Fig. 3. Uv-vis and DRS absorption of neat thiosalen
7
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ligand (a), [Cu(N2S2)]Cl complex (b) and [Cu(N2S2)]Cl@Y (c)
Data on BET surface area and pore volume of the zeolite and modified zeolite are presented in
Table 1. An effective decrease in BET surface area was observed on modified Y-zeolite with the
reduction in the pore volume.
Table 1
Pore volume and surface area of the encapsulated zeolite getting from nitrogen
adsorption isotherm
Sample
Surface area (m2/g)a
Pore volume (cm3/g)b
NaY
545
384
379
364
373
0.32
0.21
0.19
0.20
0.22
[Cu(N2S2)]Cl-NaY
[Cu(N2S2)]Br-NaY
[Cu(N2S2)]I-NaY
[Cu(N2S2)]CN-NaY
a Monolayer equivalent area calculated as explained in reference[41]
b Calculated by t-method
Since zeolite framework structure is not affected by encapsulation (as shown by XRD pattern)
these reductions in the surface area and pores volume, provides direct evidence for the presence of
complexes in the cavities[42]. Fig. 4 shows the adsorption/desorption N2 isotherms (77 K) for the
parent zeolite and [Cu(N2S2)]Cl-NaY encapsulated complex. The BET isotherm of the encapsulated
complex is characterized by a slightly sloped or plateau form, and also by a low degree of hysteresis.
This is in agreement with the XRD analysis, which indicated no significant changes in the
crystallinity patterns of the zeolite structures.
Fig. 4. The nitrogen adsorption/desorption isotherms for the NaY and encapsulated complex
8
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The thermal stability of catalyst was studied by TGA and DTA. Y-zeolite shows an
endothermic two stage of weight loss in the 50-230 oC due to the (i) physically adsorbed water on
surface and (ii) chemisorbed intra zeolite water in the form of OH groups. The thermal gravimetric
curves of NaY and [Cu(N2S2)]Cl@NaY are shown in Fig. 5. The mass loss in the temperature range
between 30-160 oC is related to the expulsion of adsorbed water. The mass loss in the temperature
range between 290-580 oC can be due to the removal of Schiff base ligand. The copper halide was
ultimately oxidized into CuO and the final residue of decomposition was found to be zeolite and
CuO. However, these results confirm that the CuCl-thiosalen complex entrapped to the nanocavity of
zeolite pores.
Fig. 5. TGA pattern of NaY and [Cu(N2S2)]Cl@Y-zeolite
Analysis of the copper ions in the zeolite samples was carried out by the destroying of zeolite
lattice using atomic absorption technique. A known weight of the sample was treated with
concentrated hydrochloric acid followed by concentrated nitric acid. The solution was maintained at
boiling temperature for 3 hours on an oil bath. It was then cooled, diluted with water and filtered
using ash-less filter paper and was used for the estimation of copper. Consequently, the amounts of
copper were obtained about 0.041–0.045 mmol/g of encapsulated zeolite (Table 2).
Table 2
Amounts of the copper (I) loaded in the nanoporosity of Y
Entry
1
catalyst
[Cu(N2S2)]Cl-NaY
Cu (mmol/ga)
0.043
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2
3
4
[Cu(N2S2)]Br-NaY
[Cu(N2S2)]I-NaY
[Cu(N2S2)]CN-NaY
0.041
0.041
0.045
a Determined by atomic absorption spectroscopy
3.2. Activity of the catalyst
The catalytic Mannich reaction of benzaldehyde, morpholine and phenylacetylene was
performed in the presence of [Cu(N2S2)]X@Y as a heterogeneous and reusable catalyst (Table 3,
entries 4-7). As it can be seen in Table 3, all of the encapsulated Cu(I) solid catalysts shown good
results for this reaction. However, comparing activities of four species of the prepared catalyst’s
evidence that, the chloride as copper halide gave a higher conversion and was found to be the most
effective one (Table 3, entry 4).
Table 3
Search for optimal reaction conditionsa
O
O
O
N
Cat.
DCE
+
+
N
H
Time
(h)
20
20
17
12
12
12
12
15
20
90
20
10
10
Yield
(%)b
-
Entry
Catalyst (mol %)
Temp. (oC)
1
2
3
4
5
6
7
8
9
10
11
12
13
-
70
70
70
70
70
70
70
60
50
30
70
70
70
NaY
[Cu(N2S2)]Cl
-
60
90
84
73
65
82
74
67
19
90
90
[Cu(N2S2)]Cl-Y (3 mol %)
[Cu(N2S2)]I-Y (3 mol %)
[Cu(N2S2)]Br-Y (3 mol %)
[Cu(N2S2)]CN-Y (3 mol %)
[Cu(N2S2)]Cl-Y (3 mol %)
[Cu(N2S2)]Cl-Y (3 mol %)
[Cu(N2S2)]Cl-Y (3 mol %)
[Cu(N2S2)]Cl-Y (1 mol %)
[Cu(N2S2)]Cl-Y (5 mol %)
[Cu(N2S2)]Cl-Y (10 mol %)
a Benzaldehyde (1.00 mmol), Phenylacetylene (1.20 mmol), morpholine (1.10
mmol), encapsulated Cu(I) catalyst and DCE (5 ml) as solvent.
b Isolated yields based on benzaldehyde.
The occurring of reaction in the presence of NaY under the same reaction conditions was
shown any product even after the prolong reaction time. This was resulted that the host zeolite was
inert in this reaction (Table 3, entries 1, 2). Also, by using of the [Cu(N2S2)]Cl as catalyst in the
reaction was obtained the product in low yield. While, the used encapsulated complexes in this
reaction was shown the higher activity than ones because of the site isolation of the copper ion
(Table 3, compare entries 3 and 4).
10
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When 3 mol % copper(I) as a heterogeneous catalyst loaded in the reaction mixture, the
reaction was generally completed (Table 3, entry 4). With attention to the results that show in this
Table, the time was inversely proportional to the temperature. We also loaded different amounts of
the selected catalyst in this reaction (Table 3, entries 11-13) in order to optimization. Thus, the
optimized reaction conditions for catalyst loading and temperatures of the reactions are 3 mol % of
catalyst based on copper and 70 oC respectively.
The solvents also play an important role in this three-component coupling Mannich type
reaction. In an effort to seek improved yields and a more effective solvent, various solvents were
screened in the reaction of benzaldehyde, morpholine and phenylacetylene under similar reaction
conditions (Table 4). With attention to the results in Table 5, DCE provided excellent yields and
proved to be the solvent of choice. Polar solvents such as DMSO, DMF and acetonitrile were found
to be suited for this reaction with comparable yields (Table 4, entries 7-9). Due to the leaching of
copper ion from the solid catalyst in these solvents (20-24 %), make these solvents unfavorable for
this reaction. The optimum mol ratio of aldehyde, amine and alkyne was found to be 1:1.1:1.2
respectively.
Table 4
Solvent study in the A3-coupling reaction toward propargylamine
synthesisa
Entry
solvent
DCE
Temp. (oC)
Time (h)
12
12
25
25
12
20
12
12
Yield (%)b
1
2
3
4
5
6
7
8
9
70
70
40
60
70
65
70
70
70
90
81
47
55
5
38
79
83
80
PhCH3
CH2Cl2
CHCl3
Cyc. Hex.
MeOH
DMSO
MeCN
DMF
12
a Benzaldehyde (1.00 mmol), Phenylacetylene (1.20 mmol),
morpholine (1.1 mmol), 697 mg. heterogeneous [Cu(N2S2)]Cl-Y as
catalyst that equal with 0.03 mmol copper.
b Isolated yields.
In order to investigate the scope and generality of the encapsulated zeolite as solid catalyst in
the A3-coupling reaction, several aldehydes with variety of functional groups were applied. The
obtained results are summarized in Table 5. Electron-poor aryl aldehydes afforded high yields (Table
5, entries 3, 8-10) in compare with an electron donating group in entries 4-6.
Table 5
Zeolite-Y encapsulated Cu(I) catalyzed three-component synthesis of
substituted propargylaminesa
11
Page 11 of 18

R1
O
N
R1CHO +
+
N
H
O
Yield
(%)b
Entry
1
aldehyde
Product
Time (h)
12
Ref.
O
90
87
[10, 30]
a
O
2
3
14
12
[24, 43]
[30]
b
c
H3C
O
91
85
O2N
O
4
14
[22]
[22]
d
OMe
O
5
6
7
17
19
15
78
87
84
e
f
N
O
[24, 30,
43]
MeO
O
[43]
g
O
8
9
13
20
83
86
[30]
[24]
h
i
F
O
Cl
Cl
O
10
11
17
87
[43]
j
NO2
16
16
82
80
[30]
[24]
k
l
3
O
O
12
5
a
Aldehyde (1.0 mmol), Phenylacetylene (1.20 mmol), morpholine (1.1 mmol),
heterogeneous Cu(I) catalyst (680 mg, contains 0.03 mmol of CuCl) in DCE
(5.0 ml) at 70 oC.
b
Isolated yields based on aldehyde
To examine the scope of this A3-coupling reaction to alkyne and secondary amine substrates,
various types of these moieties were tested in the presence of the solid catalyst in optimized
conditions (Table 6). The coupling reaction proceeded readily and smoothly to afford the
corresponding propargylamines in good to excellent yields. Among the various amines that studied,
morpholine and piperidine as aliphatic amines gave higher yields than that aromatic
12
Page 12 of 18

phenylmethylamine. However, the dibenzylamine afforded a poor yield of the desired products Table
6, entries 3, 8, 11).
Aromatic alkynes and n-pentyne as aliphatic alkyne also underwent the corresponding coupling
reaction smoothly and generated the products in excellent yields under the present reaction
conditions.
Table 6
Formation of propargylamine compounds through three-component coupling reactiona
R4 R3
N
O
R4
R3
Cat.
N
H
+
+ R2
CH
R2
R1
R1
Yield
(%)b
Entry
1
Aldehyde
Alkyne
sec. amine
Product
Ref.
[3, 10,
24]
O
88
m
Ph
CH
N
H
H
N
O
O
2
3
85
81
[22]
[10]
n
o
Ph
Ph
CH
CH
Ph
HN
Ph
O
O
O
4
5
6
84
87
86
[30]
[43]
[10]
p
q
r
N
H
O
N
H
O
N
H
H3C
H
N
O
O
O
7
8
9
83
83
89
[30]
[10]
s
t
H3C
H3C
Ph
HN
Ph
[3, 10]
u
N
H
O2N
13
Page 13 of 18

H
N
O
O
10
11
84
82
[30]
[22]
v
O2N
O2N
Ph
Ph
w
HN
a
Aldehyde (1.0 mmol), alkyne (1.20 mmol), secondary amine (1.1 mmol), heterogeneous Cu(I)
catalyst (680 mg, contains 0.03 mmol of CuBr) in DCE (5 ml) at 70 oC.
b
Based on isolated yields.
Zeolites with low ratios of Si/Al have a high number of compensating cations, which will
produce electrostatic fields in channels and cavities. Fields of this magnitude in the internal voids of
the pores, stabilize positive species such as metal ions in organometallic complexes as van der Waals
contacts as same as behavior of highly polar and non-nucleophilic solvents. These interactions can be
stabilize the encapsulated catalyst in the pores and enhance their catalytic activity in the reaction.
For catalyst leaching study, after occurring of the reaction in first step, the solid catalyst was
separated by filtration. The liquid phase was subjected as solvent to further reaction with the new
three moieties of starting substrates without any catalyst and under the same reaction conditions.
However, there was no further conversion of moieties to desired products when the catalyst was
removed from the reaction system. The reaction in the presence of filtrate cannot perform, and a
negligible product was occurred (<6%) after 30 h reaction time. This means that the active catalyst
did not leach from the zeolite. As analyzed on the final reaction solution using atomic absorption
spectroscopy, provided <1% leaching of the copper metal from the heterogenized catalyst. In accord
with the X-ray diffraction patterns of [Cu(N2S2)]Cl@Y before and after the using in reaction media,
the crystalinity of catalyst was preserved. The recyclability of the catalyst also was studied. After the
reaction, the solid modified zeolite was recovered by filtration of mixture under vacuum using
sintered glass funnel and thoroughly washed with CH2Cl2 (5 ml) and Et2O (5 ml) respectively. The
solid catalyst was dried on an oven 60oC and used for next reaction without any reactivation. In this
case a slow decrease in yields was observed (Fig. 4). However, the solid catalyst can be reused for at
least eight consecutive runs without major loss of activity.
14
Page 14 of 18

Fig. 4. Recyclability of the heterogeneous [Cu(N2S2)]Cl@Y
as recoverable catalyst for the A3-coupling reaction
4. Conclusion
The results show that the novel N2S2 donor ligand as organocopper (I) complex, [Cu(N2S2)Cl],
can be encapsulated readily in the nano-dimentional cavities of zeolite-Y by template synthesis
method (TS). This strategy appears to be remarkably efficient for the heterogenization of copper(I)
catalysts based on Schiff base ligands. The immobilized organometallic complex show high activity
in the synthesis of propargylamines via three-component coupling reaction. High conversions were
obtained using the CuCl as copper halide, also over several cycles in dichloroethane as solvent the
activity of catalyst was maintained. Furthermore, the catalyst could be readily recovered and reused,
whilst no leaching was observed after utilization of the catalyst.
Acknowledgment
The authors are grateful to University of Kashan for supporting this work by Grant No. 159148/14.
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