Copper(I)-N2S2-salen type complex covalently anchored onto MCM-41 silica: An efficient and reusable catalyst for the A 3-coupling reaction toward propargylamines

Article abstract of DOI:10.1002/aoc.2976

The immobilization of copper complexes by covalent anchoring of the ligand on the surface of mesoporous MCM-41 has been described. Bis[2-(phenylthio) benzylidene]-1,2-ethylenediamine as a new N₂S₂ donor salen-type ligand was covalently anchored onto nanopores of MCM-41 coordinated with copper (I) halide. The organic-inorganic hybrid material was achieved readily using 3-mercaptopropyltrimethoxysilane as a reactive surface modifier. 2-Nitrobenzaldehyde was reacted smoothly with the thiol moieties in order to form functionalized nanoporous silica with carbaldehyde groups. The resulting supported organic moieties were converted to thiosalen ligand and coordinated with CuX (X = CN, Cl, Br, I). Characterization of the heterogeneous catalyst by X-ray diffraction, N₂ sorption, FT-IR, diffuse reflectance UV-visible and TGA techniques indicated successful grafting of the copper complex inside the nano-channels of MCM-41. The heterogenized catalyst was evaluated by the Mannich condensation reaction of aldehydes, amines and alkynes. In this reaction, the corresponding propargylamines were obtained as single products in good to excellent yields. Factors such as reaction temperature, solvent, catalyst loading, leaching and reusability of the catalyst also were discussed. The use of MCM-41 as support permits an easier separation and recycles with only a marginal decrease in reactivity. Copyright 2013 John Wiley & Sons, Ltd. A new N₂S₂-donor salen-type ligand, coordinated with copper covalently anchored onto nanopores of MCM-41 was prepared. The catalytic behavior of the organically modified MCM-41 as solid support was evaluated by the mannich condensation reaction of aldehydes, amines and alkynes with a view to synthesis of propargylamines. Copyright

Full text of DOI:10.1002/aoc.2976

Full Paper
Received: 7 October 2012
Revised: 15 January 2013
Accepted: 21 January 2013
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.2976
Copper(I)-N S -salen type complex covalently
2
2
anchored onto MCM-41 silica: an efficient and
3
reusable catalyst for the A -coupling reaction
toward propargylamines
Hossein Naeimi* and Mohsen Moradian
The immobilization of copper complexes by covalent anchoring of the ligand on the surface of mesoporous MCM-41 has been
described. Bis[2-(phenylthio)benzylidene]-1,2-ethylenediamine as a new N S donor salen-type ligand was covalently
2 2
anchored onto nanopores of MCM-41 coordinated with copper (I) halide. The organic–inorganic hybrid material was achieved
readily using 3-mercaptopropyltrimethoxysilane as a reactive surface modifier. 2-Nitrobenzaldehyde was reacted smoothly
with the thiol moieties in order to form functionalized nanoporous silica with carbaldehyde groups. The resulting supported
organic moieties were converted to thiosalen ligand and coordinated with CuX (X = CN, Cl, Br, I). Characterization of the
2
heterogeneous catalyst by X-ray diffraction, N sorption, FT-IR, diffuse reflectance UV-visible and TGA techniques indicated
successful grafting of the copper complex inside the nano-channels of MCM-41. The heterogenized catalyst was evaluated
by the Mannich condensation reaction of aldehydes, amines and alkynes. In this reaction, the corresponding propargylamines
were obtained as single products in good to excellent yields. Factors such as reaction temperature, solvent, catalyst loading,
leaching and reusability of the catalyst also were discussed. The use of MCM-41 as support permits an easier separation and
recycles with only a marginal decrease in reactivity. Copyright © 2013 John Wiley & Sons, Ltd.
3
Keywords: thiosalen; copper(I); heterogeneous; MCM-41; catalyst; A -coupling; propargylamine
[
24–26]
and CuI,
or coordinated with organic donor ligands have
Introduction
[
27]
been widely used as the most extensively utilized catalysts.
The development of new mesoporous organic–inorganic hybrid
Recent reports in this field have included the development
materials, as an example of heterogeneous catalysts, has played
of recoverable and reusable catalysts through organic–
[
1,2]
[28–30]
a key role in eco-friendly industrial processes.
Producing side
inorganic hybrid materials.
Immobilizing the copper metal
[
31–33]
waste materials, difficulty in separating expensive catalysts and
contamination of the catalyst in the product are the major
drawbacks of homogeneous systems. Immobilization of metal
organic complexes on solid supports is highly desirable due to
the facilitation of both isolation and recycling of the catalyst by
simple filtration. Moreover, these catalysts exhibit a significant
improvement in activity, selectivity and stability, which are attrib-
as an efficient catalyst in the reaction via silica supports,
[
34]
[35]
[36]
molecular sieves, magnetite, zeolites or Pybox complexes
[
37]
[38]
on polystyrene resin
and Cu(I)–MOF
as heterogeneous
catalysts have also been reported.
This work describes our efforts in anchoring an copper(I)
complex of thiosalen ligand as bis[2-(phenylthio)benzylidene]-
cyclohexane-1,2-diamine (CuTS) into nano-channels of MCM-41
silica. The modified MCM-41 as a solid catalyst was used success-
fully in the C-H activation of alkynes on the Mannich-type reac-
tion in the synthesis of propargylamines. The reaction does not
require any co-catalyst and deactivation of the catalyst does
not occur. For further consideration, we studied the minimum
amounts of catalyst loading for the reaction. The stability and
reusability of the catalyst after each trial were also investigated.
Owing to the rich electron-donating nature of sulfur atoms, the
thiosalen ligand increases stability of the copper(I) complex,
[
3–5]
uted to contributions of isolated sites on the solid surface.
Efficient anchoring of a ligand to the ordered mesoporous
silica MCM-41 via a covalent bond has become an often
[
6]
employed method of catalyst heterogenization. Immobilization
inside the pores makes the catalysts more thermally stable, with a
[
7]
high surface area, and prevents them from dimerization.
Transition metal complex-catalyzed C-C bond formation reac-
tions have received increasing attention during recent decades.
The synthesis of propargylamines by
a three-component
Mannich-type reaction represents a highly attractive and powerful
[
8–10]
method in organic synthesis.
These compounds are key
intermediates for synthesis of different types of nitrogen com-
pounds and a structural potential of many pharmaceutically active
* Correspondence to: Hossein Naeimi, Department of Organic Chemistry,
Faculty of Chemistry, University of Kashan, Kashan 87317, Islamic Republic
of Iran. E-mail: naeimi@kashanu.ac.ir
[11,12]
[11,13–15]
compounds
and natural products.
Propargylamines
3
can be prepared by an A -coupling reaction between aldimines
[
16–19]
and activated C-H of alkynes by a catalyst
such as copper(I)
Department of Organic Chemistry, Faculty of Chemistry, University of Kashan,
Kashan 87317, Islamic Republic of Iran
[20]
[21]
[22]
[23]
complex,
various copper halides
such as CuCl,
CuBr
Appl. Organometal. Chem. 2013, 27, 300–306
Copyright © 2013 John Wiley & Sons, Ltd.

MCM-41-copper(I) complex as catalyst for synthesis of propargylamines
ꢁ
improves catalytic activity and, using toluene as non-polar
solvent, causes negligible leaching of copper from the catalyst.
mass to 27 C, the solids were filtered, successively washed with
acetone, dichloromethane, toluene and n-hexane and dried under
vacuum. Due to the poisoning of the nano-channels of MCM-41 by
irreversible pore blocking moieties, thorough washing of the
heterogeneous catalyst is essential. The obtained material will be
referred to as MCM-RSBz.
Experimental
Material and Physical Measurements
All the solvents were purchased from Merck Co. (reagent grades)
and were used as received unless otherwise specified. MCM-41
mesoporous silica material was purchased from Sigma Aldrich Co.
as 643645-ALDRICH identity code and in powder form (4.5–4.8 nm
Synthesis of Anchored Thiosalen and Copper Complexes
The heterogeneous catalyst was obtained through the synthetic
sequence as follows (Scheme 1). The MCM-RSBz was suspended
in 50 ml methanol and ethylenediamine (10 mmol, 0.6 ml) in a
suitable flask and refluxed for 12 h. After cooling the reaction
mixture, the solid MCM-TS was collected by filtration, washed
with methanol (3 ꢂ 10 ml) and dried under vacuum. Complexa-
tion of the MCM-TS was carried out in the presence of each of
3
ꢀ1
unit cell size, 0.98 cm g pore volume, 2.5–2.7 nm pore size and
2
ꢀ1
~
1000 m g specific surface area). Infrared spectra were recorded
1
13
as KBr pellets on a Nicolet FT-IR spectrophotometer. H and C NMR
spectra were recorded in CDCl on a Bruker DRX-400 spectrometer.
3
X-ray diffraction (XRD) patterns were recorded by an X’PertPro
[
40]
(Philips) instrument with 1.54 Å wavelength X-ray beam and Cu an-
the [Cu(MeCN) ]X (X = Cl, Br, I, CN) solutions
as copper source
4
ꢁ
ode material. Nitrogen adsorption measurements were performed
at 77K using a Coulter Ofeisorb 100CX instrument. A Unicam 929
model flame atomic absorption spectrophotometer was used
for copper determination. The atomic absorption spectrometer
equipped with a copper hollow cathode lamp (lamp current
in acetonitrile at 75 C and 15 h reaction time. The functionalized
mesoporous MCM-41 was filtered and dried under vacuum, and
the MCM-TSCuX catalyst was obtained.
General Procedure for the Synthesis of Propargylamines by
the Solid Catalyst
7
.5 mA, wavelength 324.8 nm, spectral bandwidth 1.3 nm). A
combination of hydrofluoric acid (5 ml) and nitric acid (5 ml)
was used for total decomposition of the silica support (0.100 g)
containing organic materials. Standard solutions of CuSO .8H O
The organic–inorganic hybrid material as catalyst was used for
3
4
2
the preparation of propargylamines via A -coupling reaction of
ꢀ
1
were prepared by dilution of 1.0 mg ml stock solution in a
aldehydes, amines and alkynes. In a typical procedure, to a
mixture of aldehyde (1.0 mmol), secondary amine (1.1 mmol)
and alkyne (1.2 mmol) in toluene (10 ml) as solvent was added
MCM-TSCuX as catalyst containing 3 mol% copper based on
ꢀ
1
3
solution of 0.2 mol l HNO .
Synthesis of Organo-functionalized MCM-41
ꢁ
copper halide. The mixture was stirred at 80 C. After completion
Surface modification of MCM-41 silica with 3-mercaptopropyltri-
methoxysilane (3-MPTMS) was carried out as follows. A 3.0 g
of the reaction (monitored by thin-layer chromatography), the
resulting mixture was filtered on a sintered glass funnel and the
sample of MCM-41 was placed in a round-bottom flask, dried at
solid catalyst washed with CH Cl2 (3 ꢂ 5 ml) and methanol
ꢁ
2
1
10 C in an oven overnight in order to remove physically
(
3 ꢂ 5 ml). The filtrated was evaporated under reduced pressure
adsorbed water and cooled to room temperature. To the mixture
of dried MCM-41 in 50 ml dry toluene, 2.0 g 3-MPTMS (10 mmol)
as silane modifier was added and stirred under reflux conditions
for 15 h. After completion of the reaction, the flask was cooled
and the pure thio-functionalized MCM-41 material (MCM-RSH)
was filtered on a sintered glass funnel, washed with toluene
to give the crude product as a viscous oil. The product was
purified by column chromatography (10% EtOAc in hexane as
eluent) to give the desired propargylamine. It should be noted
that, in order to achieve reusability of the catalyst, thorough
washing of the recovered heterogeneous catalyst is essential by
using CHCl
3
(3 ꢂ 5 ml), absolute ethanol (3 ꢂ 5 ml) and finally
(3 ꢂ 10 ml) and dried under vacuum.
THF (3 ꢂ 5 ml). This is on account of the poisoning of the
mesoporous catalyst by irreversible pore blocking and reduction
of yields in subsequent trials. Most of the compounds thus
Synthesis of functionalized MCM-41 with carbaldehyde moiety
[
33]
[33]
[31]
[8]
[33]
A suspension of MCM-RSH (3.0 g), 2-nitrobenzaldehyde (10 mmol,
formed are known: propargylamines a,
b,
d,
g, h,
[
26,41] [8]
[33] [33]
[20,27]
[42,43]
[31] [28]
[44]
1
.50 g) and magnesium methoxide (20 mmol, 1.73 g) in 40 ml
i,
j, k,
l,
m,
n,
o,
p
and q
have
ꢁ
[39]
DMF was refluxed at 80 C for 15 h. After cooling the resulting
been previously reported. The unknown products, e, c and f
Scheme 1. Preparation of the modified MCM-41 silica.
Appl. Organometal. Chem. 2013, 27, 300–306
Copyright © 2013 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

H. Naeimi and M. Moradian
(Fig. 5) were completely characterized by spectroscopic data as
followed;
N,N-Dimethyl-4-(1-morpholino-3-phenylprop-2-yn-1-yl)aniline (e)
Red oil; IR (thin film): 2955, 2892, 2854, 2815, 1965, 1611, 1521, 115,
1
7
57, 692, 556. H NMR (CDCl
3 2 2
, 400 MHz): 2.65 (m, 4 H, H C-17, H C-
2
1), 2.97 (s, 6 H, Me
2
N-22), 3.73 (m, 4 H, H C-18, H C-20), 4.70 (s, 1 H,
2
2
HC-7), 6.72 (d, J= 8.4 Hz, 2 H, HC-1, HC-3), 7.32 (m, 3H, HC-12, HC-14,
HC-16), 7.45 (m, 2H, HC-13, HC-15), 7.50 (m, 2H, HC-4, HC-6).
13
C NMR (CDCl , 100 MHz): 44.11 (C-23, 24), 49.25 (C-7), 61.48
3
(
C-17, 21), 68.03 (C-18, 20), 85.15 (C-10), 88.54 (C-9), 113.85 (C-1,
3
1
2
), 120.41 (C-11), 123.74 (C-13, 15), 128.19 (C-14), 130.04 (C-5),
31.21 (C-12, 16), 134.30 (C-4, 6), 152.71 (C-2). MS: 320 ([M + 1] ,
.7), 215 (M+, 11), 276 (38), 234 (22), 219 (38), 101 (10), 86
+
(
100), 76 (100). Anal. calcd for C H N O (320.43): C 78.71, H
21 24 2
7
.55, N 8.74; found: C 78.84, H 7.32, N 8.70.
4-(1-(4-Nitrophenyl)-3-phenylprop-2-yn-1-yl)morpholine (c)
Orange oil; IR (thin film): 3067, 2958, 2854, 2216, 1690, 1600,
1
1
522, 1450, 1347, 1275, 1113, 1006, 864, 819, 757, 695, 539. H
NMR (CDCl , 400 MHz): 2.63–2.66 (m, 4 H, H C-16, H C-12), 3.76
m, 4 H, H C-13, H C-15), 4.89 (s, 1 H, HC-7), 7.38 (s, 3 H, HC-21,
HC-17, HC-19), 7.53 (m, 2H, HC-20, HC-18), 7.88 (m, 2H, HC-4,
3
2
2
(
2
2
13
HC-6), 8.24 (m, 2H, HC-1, HC-3). C NMR (CDCl
9.90 (C-7), 61.45 (C-12, 16), 67.04 (C-13, 15), 83.16 (C-10), 89.78
C-9), 122.31 (C-20, 18), 123.48 (C-17, 19, 21), 128.45 (C-5),
28.72 (C-4, 6), 129.33 (C-11), 131.85 (C-1, 3), 145.45 (C-2). Anal.
calcd for C H N O (322): C 70.79, H 5.63, N 8.69; found:
3
, 100 MHz):
4
(
1
1
9 18 2 3
Figure 1. FT-IR spectra of thiosalen ligand (a), [Cu(TS)]I complex (b),
MCM-41 (c), MCM-TS (d) and MCM-TSCuI (e).
C 70.48, H 5.81, N 8.58.
4-(1-(3-Methoxyphenyl)-3-phenylprop-2-yn-1-yl)morpholine (f)
Orange oil; IR (thin film): 3057, 2995, 2851, 2750, 1965, 1599,
functionalization process does not modify the MCM-41 structure.
The IR spectra of the free ligand showed a strong band at 1614
1
7
H
486, 1449, 1314, 1256, 1314, 1256, 1150, 1115, 1044, 1001, 867,
1
ꢀ1
58, 692, 564. H NMR (CDCl
C-21), 3.77 (m, 4 H, H C-18, H
s, 1 H, HC-7), 6.87 (d, 8.3 Hz, 1 H, HC-2), 7.25–7.36 (m, 6 H, HC-1,
3
, 400 MHz): 2.66 (m, 4 H, H
2
C-17,
cm which was assigned to stretching vibration of the C¼N group.
ꢀ
1
C-20), 3.85 (s, 3 H, H C-22), 4.79
3
This band shifts to a lower position by 6–9 cm in complexes that
suggests coordination of copper through C¼N functional groups.
For instance, in Fig. 1 we show the FT-IR spectra for thiosalen ligand
(a), [Cu(TS)]I complex (b), MCM-41 (c), MCM-TS (d) and MCM-TSCuI (e).
The XRD pattern of MCM-41 typically demonstrates reflections
2
2
2
(
13
HC-4, HC-6, HC-12, HC-14, HC-16), 7.53 (m, 2H, HC-13, HC-15).
C
NMR (CDCl
7.20 (C-18, 20), 85.15 (C-10), 88.54 (C-9), 113.10 (C-2), 114.39
C-4), 120.99 (C-6), 123.03 (C-12, 16), 128.36 (C-14), 128.42 (C-5),
29.28 (C-13), 131.88 (C-15), 132.17 (C-11) , 139.57 (C-1), 159.71
C-3). Anal. calcd for C20 (307): C 78.15, H 6.89, N 4.56;
found: C 78.26, H 6.70, N 4.57.
3
, 100 MHz): 49.99 (C-7), 55.24 (C-22), 62.01 (C-17, 21),
6
(
1
ꢁ
ꢁ
between 2θ = 2 and 5 ; since the materials are not crystalline at
the atomic level, no reflections at higher angles are observed. The
XRD pattern of modified mesoporous material with organo-
copper complex is similar to that of untouched MCM-41 (Fig. 2),
showing that the mesoporosity of the mesoporous material
is retained.
(
H21NO
2
Results and Discussion
The electronic spectra of thiosalen ligand were recorded in
CH Cl as solvent. The bands observed at 248 and 372 nm arise
2 2
Analysis of Catalysts
due to p ! p* and n ! p* transitions. Since no d ! d transitions
10
The heterogeneous modified MCM-41 with N
2
S
2
thiosalen copper
are expected for d complexes, the UV-visible bands of the
thiosalen copper complex at 454 nm are assigned to metal-to-
ligand charge transfer (MLCT) or ligand-centered p ! p*
(I) complex was investigated by powder XRD, single-point N
2
adsorption–desorption method (BET), FT-IR, diffuse-reflectance
UV-visible spectroscopy and TGA techniques. The results indicated
successful anchoring of thiosalen complex to the internal surface of
MCM-41 nanopores.
A comparison of the IR spectra of the catalyst with that of the
initial mesoporous MCM-41 demonstrates the presence of
organometallic complex anchored to the surface of nanopores
[
45,46]
transitions.
Comparison of UV-visible spectra for ligand,
complex and functionalized mesoporous silica (diffuse reflective
spectrum) confirms the presence of the anchored thiosalen
complex (Table 1 and Fig. 3).
The single-point nitrogen sorption study for the functiona-
lized MCM-41 silica shows that the specific surface area and pore
volume are decreased. These results reasonably indicate that
functionalization of Cu complex occurs inside the nano-channels
of mesoporous MCM-41. The results on BET surface area
and pore volume of MCM-41 and MCM-TSCuI are presented
in Table 2.
(
Fig. 1). The FT-IR spectrum of MCM-41 is dominated by some
of the major mesoporous framework bands within the range
ꢀ
ꢀ
1
ꢀ1
ꢀ1
7
20–790 cm ns (Si-O), 1020 cm (Si-OH), 1130 cm nas (Si-O)
1
and 3550 cm for isolated silanol (Si-OH) groups. These bands were
detected in the functionalized material and supports that the
wileyonlinelibrary.com/journal/aoc
Copyright © 2013 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2013, 27, 300–306

MCM-41-copper(I) complex as catalyst for synthesis of propargylamines
Figure 2. X-ray diffraction patterns of (a) MCM-41 and (b) MCM-TSCuI.
Figure 4. TGA and DTA of MCM-41 and MCM-TSCuI.
Table 1. UV-visible and Diffraction Reflective Spectroscopy (DRS)
absorption information of neat thiosalen ligand, [Cu(TS)]I complex and
MCM-TSCuI
In order to analyze the copper in the solid modified silica, a
known weight of each of the samples was destroyed in concen-
trated hydrochloric acid. The mixture was maintained at boiling
temperature for 3 h 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 in the encapsulated catalysts. The
results of spectrophotometric determination of metal showed
the amounts of copper that loaded in the surface of catalyst to
Sample
Conditions
Bands
N
2
S
2
-thiosalen
CH
CH
Solid
2
Cl
2
248, 372
264, 454
277, 436
[Cu(TS)]I
3
CN
MCM-TSCuI
ꢀ
1
be 0.084–0.098 mmol g (Table 3). Figure 5
Catalytic Studies
The four heterogeneous and recoverable catalysts (MCM-TSCuX,
3
X = Cl, Br, I, CN) were initially tested for A -coupling Mannich-type
reaction of benzaldehyde, morpholine and phenylacetylene
(Table 4, entries 3–6). The trials were carried out at various
temperatures and catalyst loadings with toluene as solvent.
According to Table 4, all catalysts exhibited moderate to high
yields of propargylamine as unique product. However,
comparison of these four species of solid catalysts confirms that
MCM-TSCuI had a higher conversion of reaction than the other
corresponding halides (Table 4, entry 6) and it was found to be
the most effective one. In the presence of MCM-41, this reaction
exhibited no products even after prolonged the reaction time
under the same reaction conditions (Table 4, entry 2). However,
no reaction occurred in the absence of any copper source as
catalyst (Table 4, entry 1). Higher activity of functionalized
mesoporous complexes was shown due to the site isolation of
the copper halide in MCM-TSCuI as catalyst.
2 2 2 2
Figure 3. UV-visible spectra of N S -thiosalen ligand (a), [Cu(N S )]I (b)
and MCM-TSCuI (c).
Table 2. Specific surface area the MCM-41 and MCM-TSCuX getting
from the single-point BET method
2
ꢀ1
3
ꢀ1
Sample
Surface area (m g
)
Pore volume (cm g
)
MCM-41
1000
330
450
494
608
0.98
0.51
0.59
0.62
0.66
It is useful to mention here that, with 3 mol% catalyst based on
copper(I) as the solid catalyst loaded in the reaction mixture, the
reaction was generally completed in a reasonable number of
hours (Table 4, entry 6). We also loaded different amounts of
MCM-TSCuI
MCM-TSCuBr
MCM-TSCuCl
MCM-TSCuCN
Table 3. Determination of copper in the solid catalysts
Thermal stability of the modified ordered mesoporous silica
ꢀ1 a
Entry
Catalyst
Cu(I) (mmol g )
was studied by TGA. MCM-41 shows an endothermic weight loss
ꢁ
in the range 50–140 C due to water physically adsorbed to the
1
2
3
4
MCM-TSCuI
0.084
0.098
0.089
0.085
surface. The results of TGA for initial and modified silica are
MCM-TSCuBr
MCM-TSCuCl
MCM-TSCuCN
shown in Fig. 4. It is obvious that the TGA test shows continued
ꢁ
weight loss of the solid support, which extends up to 590 C
Fig. 4). However, these results confirm that the copper complex
was grafted into the nano-channels of MCM-41 silica.
(
a
Determined by atomic absorption spectroscopy.
Appl. Organometal. Chem. 2013, 27, 300–306
Copyright © 2013 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

H. Naeimi and M. Moradian
Figure 5. Structures of the new products.
a
3
Table 4. Search for optimal reaction conditions
Table 5. Solvent studya in the A -coupling reaction toward
propargylamine synthesis
O
N
ꢁ
b
O
Entry
Solvent
Temperature ( C)
Time (h)
Yield (%)
O
Cat.
1
2
3
4
5
6
7
8
9
PhCH
DCE
3
80
70
40
60
70
65
80
80
80
4
5
92
72
55
62
18
25
77
75
81
+
+
N
H
CH
CHCl
2
Cl
2
20
20
10
20
8
3
Cyc. hex.
MeOH
DMSO
MeCN
DMF
ꢁ
Entry
Catalyst (mol %)
Temp. ( C)
Time (h)
Yield
b
(
%)
–
8
1
2
3
4
5
6
7
8
9
–
110
110
80
80
80
80
70
50
40
80
80
80
80
20
20
4
8
MCM-41
–
a
MCM-TSCuCN (3 mol %)
MCM-TSCuCl (3 mol %)
MCM-TSCuBr (3 mol %)
MCM-TSCuI (3 mol %)
MCM-TSCuI (3 mol %)
MCM-TSCuI (3 mol %)
MCM-TSCuI (3 mol %)
MCM-TSCuI (1 mol %)
MCM-TSCuI (5 mol %)
MCM-TSCuI (10 mol %)
Nonporous Silica-TSCuI
72
74
85
92
78
72
58
35
91
92
45
Reaction conditions: benzaldehyde (1.00 mmol), phenylacetylene
1.20 mmol), morpholine (1.1 mmol), 360 mg heterogeneous MCM-
(
4
TSCuI as catalyst that is equal to 0.03 mmol copper.
4
b
Isolated yields based on benzaldehyde.
4
11
16
60
25
3
reaction was attempted. The results are summarized in Table 6.
It can be seen from these results that aromatic aldehydes with
an electron-withdrawing group afforded high yields compared
with an electron-donating group (Table 6, entries 3–6, 10). The
coupling reaction proceeded readily and smoothly to provide
the corresponding propargylamines in good to excellent yields
by using various alkynes and amines, including aromatic and
aliphatic substrates. Among the various amines studied,
morpholine and piperidine as aliphatic amines gave higher
yields than that aromatic phenylmethylamine. However, the
dibenzylamine afforded a poor yield of the desired products.
Aromatic alkynes and n-pentyne as aliphatic alkyne also under-
went the corresponding coupling reaction smoothly and
generated the products in excellent yields under the present
reaction conditions.
1
1
1
1
0
1
2
3
3
25
a
Reaction conditions: benzaldehyde (1.00 mmol), phenylacetylene
1.20 mmol), morpholine (1.10 mmol), MCM-TSCuX as catalyst and
(
PhCH
b
3
(5 ml) as solvent.
Based on isolated yields.
the selected catalyst in this reaction (Table 4, entries 10–12) in
order to achieve optimization. Thus the optimized reaction
conditions for catalyst loading and temperatures of the reaction
ꢁ
were 3 mol% catalyst based on copper and 70 C, respectively.
It is well known that terminal alkynes can produce Glaser-
type oxidative coupling products in the presence of copper
3
Solvents play an important role in this A -coupling Mannich-
[
47]
type reaction toward propargylamines. Various solvents were
screened in this reaction in order to look for improved yields
and more effective solvent (Table 4). With attention to the results
shown in Table 5, toluene provided excellent yields and proved
to be the solvent of choice. However, polar solvents such as
DMSO, DMF and acetonitrile were found to be suitable for this
reaction, with comparable yields (Table 5, entries 7–9), while
leaching out of the copper ions from the pores of solid catalyst
during the reaction makes these solvents unfavorable. The
perfect mole ratio of aldehyde, amine and alkyne was found to
be 1:1.1:1.2, respectively.
salts and oxygen of air.
Whereas copper salts are used in
this reaction, Glaser-type coupling could compete with the
main reaction process and decrease yields of the propargyla-
mines. Thus, to avoid this side product, it is necessary to work
under an inert atmosphere and to use degassed solvents.
However, because we did not observe any Glaser-type
products using MCM-TSCuI as the catalyst, this reaction was
performed in air atmosphere. Due to coordination of the
copper metal in the N S thiosalen donor ligand, the oxidation
2
2
state of the metal strongly stabilizes, and copper is inactive for
the Glaser-type coupling.
Investigation of the scope and generality of secondary amines,
aldehydes and terminal alkynes applicable in the A -coupling
Furthermore, recyclability of the catalyst was studied because
of the potential benefits in commercial applications. After the
3
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Copyright © 2013 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2013, 27, 300–306

MCM-41-copper(I) complex as catalyst for synthesis of propargylamines
a
Table 6. Formation of propargylamine compounds through three-component coupling reaction
R4 R3
N
O
R4
R3
R2
N
H
Cat.
+
CH
+
R2
R1
R1
1
2
3
4
b
Entry
1
R
R
R
,
R
Product
Time (h)
4
Yield
92
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
a
2
3
4
5
6
7
8
9
p-CH
3
b
c
5
4
91
93
88
83
85
89
87
91
91
88
85
81
p-NO
2
p-OCH
p-N(CH
m-OCH
3
d
e
f
5
3
)
2
7
3
7
p-CH(Me
2
)
g
h
i
6
o-Cl
8
p-Cl
10
6
10
11
12
13
m-NO
2
j
H
k
l
5
m-CH
3
8
3
4
H
H
H
R = ꢀCH
3
R = ꢀPh
m
10
14
15
16
17
18
n-C
6
H
13
n
o
p
q
r
5
5
6
9
9
84
87
86
83
83
p-CH
3
C
6
H
4
p-OCH
3
Ph
Ph
p-CH
3
3
3
4
p-CH
n-C
4
H
9
R , R = ꢀCH
2
Ph
a
Aldehyde (1.0 mmol), alkyne (1.20 mmol), secondary amine (1.1 mmol), MCM-TSCuI as modified solid catalyst (350 mg, contains 0.03 mmol of Cu) in
ꢁ
PhCH
b
3
(5 ml) at 80 C.
Isolated yields based on aldehyde.
end of reaction, MCM-TSCuI solid catalyst was separated by
filtration of the reaction mixture and was used in the coupling
reaction of benzaldehyde, morpholine and phenylacetylene
seven times. The corresponding results are depicted in Scheme 2.
As can be seen, the solid catalyst can catalyze the reaction in at
least seven consecutive runs without loss of activity. Also, the
reaction in the non-polar solvent reduces leaching of the copper
ions and increases recycling ability.
Conclusion
In this research, complexes of the functionalized MCM-41 with Cu
(I)-thiosalen were prepared and characterized to verify the
structural and chemical properties by different chemical and
2 2
physical analysis methods. It was shown that the novel N S
donor salen-type ligand can be readily grafted into the nano-
pores of MCM-41 silica. The ligand was strongly coordinated with
copper(I) halides due to the soft donor atoms in their structure.
The prepared MCM-TSCuI silica was applied as the most effective
3
heterogeneous catalyst in the A -coupling reaction toward
synthesis of propargylamines. The products were obtained in
high to excellent yields and appropriate times, and the catalyst
could be easily recovered and reused several times. Furthermore,
over several cycles with toluene as solvent, catalyst activity was
maintained without any significant loss of its activity.
Acknowledgment
The authors are grateful to the University of Kashan for supporting
this work (Grant No. 159148/14).
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