CuPy2Cl2: A novel and efficient catalyst for synthesis of propargylamines under the conventional method and microwave irradiation

Article abstract of DOI:10.1080/00397910802109307

CuPy₂Cl₂ is an efficient catalyst for the preparation of propargylamines via three-component coupling reaction of aromatic aldehydes, amines, and aromatic alkynes stirred at 95°C without using any solvent to afford the corresponding products in good yields. The reaction mixture was irradiated at 450 W in a microwave oven to furnish the expected products in excellent yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802109307

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CuPy Cl : A Novel and Efficient
2
2
Catalyst for Synthesis of
Propargylamines Under the
Conventional Method and
Microwave Irradiation
a
a
J. Venu Madhav , B. Suresh Kuarm , P. Someshwar
a
a
b
,
B. Rajitha , Y. Thirupathi Reddy & Peter A.
b
Crooks
a
Department of Chemistry, National Institute of
Technology, Warangal, India
b
Department of Pharmaceutical Sciences, College
of Pharmacy, University of Kentucky, Lexington,
Kentucky, USA
Published online: 09 Sep 2008.
To cite this article: J. Venu Madhav , B. Suresh Kuarm , P. Someshwar , B. Rajitha ,
Y. Thirupathi Reddy & Peter A. Crooks (2008): CuPy Cl : A Novel and Efficient
2
2
Catalyst for Synthesis of Propargylamines Under the Conventional Method and
Microwave Irradiation, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 38:18, 3215-3223
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1
Synthetic Communications , 38: 3215–3223, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802109307
CuPy Cl : A Novel and Efficient Catalyst for
2
2
Synthesis of Propargylamines Under the
Conventional Method and Microwave Irradiation
1
1
1
J. Venu Madhav, B. Suresh Kuarm, P. Someshwar, B. Rajitha,
1
2
Y. Thirupathi Reddy, and Peter A. Crooks
Department of Chemistry, National Institute of Technology,
Warangal, India
2
1
2
Department of Pharmaceutical Sciences, College of Pharmacy,
University of Kentucky, Lexington, Kentucky, USA
2 2
Abstract: CuPy Cl is an efficient catalyst for the preparation of propargyla-
mines via three-component coupling reaction of aromatic aldehydes, amines,
ꢀ
and aromatic alkynes stirred at 95 C without using any solvent to afford the cor-
responding products in good yields. The reaction mixture was irradiated at 450 W
in a microwave oven to furnish the expected products in excellent yields.
Keywords: CuPy Cl , propargylamine, solvent free, three-component coupling
2
2
INTRODUCTION
One-pot multicomponent coupling reactions are very interesting and
attractive in organic synthesis because they introduce several elements
[1]
of diversity into a molecule in a single step. The best example is
3
three-component coupling of aldehydes, amines, and alkynes [A coup-
ling] via CH activation, which has received great attention in recent
[
2]
years. The resultant propargylamines are versatile synthetic inter-
mediates for organic synthesis to construct important natural products,
[
therapeutic drug molecules, and biologically active compounds such
3]
Received February 7, 2008.
Address correspondence to B. Rajitha, Department of Chemistry, National Insti-
tute of Technology, Warangal, AP, India. E-mail: rajitabhargavi@yahoo.com
3
215

3216
J. V. Madhav et al.
as conformationally restricted peptide isosters, oxotremorine analogs,
and b-lactams. Several methods for the synthesis of propargylamines
using various types of reagents have been developed, mainly transition-
3
metal catalysts able to carryout A coupling reactions, including the
[
Ag(I) salts, Au(I)=Au(III) salts, Au(III)–salen complexes, Cu(I)
4]
[5]
[6]
[
7]
[8]
salts, and Cu=Ru bimetallic system under homogeneous conditions.
The available methods have a number of drawbacks, such as long reac-
tion times and low yields. Moreover, most of the reactions need to be per-
formed under an inert atmosphere, and these reactions often proceed
slowly in water. Some of the catalysts are very expensive. But, all of these
systems suffer from the loss of the precious catalysts at the end of the
reaction. To overcome these limitations, we found a new catalyst for
the synthesis of propargylamines, CuPy Cl . The catalyst is stable in
2
2
air and water, soluble in water, immiscible in common organic solvents,
and reusable and has high thermal stability. In addition, its toxicity is
low, and it can effectively promote some of the organic reactions such
[9]
[10]
as the Pechmann condensation and Biginelli reaction in good yields.
On the other hand, microwave irradiation has been extensively used
for the rapid synthesis of a variety of heterocyclic compounds, because of
short reaction times and increase of yields with high purity. Microwave
[
11]
reactions are believed to meet the demands of green chemistry.
our earlier communications, we reported several organic transformations
In
[12]
in a domestic microwave oven.
RESULTS AND DISCUSSION
Herein, we report for the first time CuPy Cl as an efficient catalyst for
2
2
the three-component coupling of aldehyde, alkyne, and amine to generate
propargylamines, without using any other cocatalyst or additives. We
examined the reaction process for the three-component coupling reaction
of benzaldehyde, phenylacetylene, and morpholine in the presence of the
catalyst. In method A [microwave (MW) irradiation], the reaction
mixture was irradiated in a domestic microwave oven at 300 W over
3
0-s intervals in an open vessel for 5 min. The progress of the reaction
was checked by thin-layer chromatograohy (TLC). At 300 W only 50%
of the reaction was completed, whereas at 450 W, the reaction success-
fully completed within 2 min. In method B (conventional), when the reac-
ꢀ
tion was carried out at 55 to 60 C, no progress was observed; at 60 to
0 C, only a part of the reaction proceeded. At 95 C, a single product
ꢀ
ꢀ
8
was obtained. Comparatively, MW irradiation is more advantageous
than the conventional method, because it required a shorter reaction time
and generated good yields with high purity.

CuPy Cl
2
2
as Catalyst for Propargylamines
3217
We have carried out the reaction with varies amines such as diethyl
amine, morpholine, piperdine, and piperzine. Except for piperzine, other
amines displayed good activity and gave excellent yields. In this article,
we report simple and ordinary reaction conditions. Therefore, we believe
that our procedure is more suitable for the synthesis of propargylamines
than the literature methods.
EXPERIMENTAL
1
The progress of the reaction was monitored by TLC. H NMR spectra
was measured on a Varian Gemini 200-MHz spectrometer using TMS
as internal standard. The C, H, and N analysis of the compound was
done on a Carlo Erba model EA1108. Mass spectra were recorded on
a Jeol JMS D-300 spectrometer.
Method A (Microwave Irradiation)
A mixture of aldehyde (1 mmol), amine (1.5 mmol), alkyne (1.5 mmol),
and CuPy Cl (0.01 mmol) was placed in an open vessel in a microwave
2
2
oven and irradiated at 450 W for an appropriate time (Table 1). Com-
pletion of the reaction was confirmed by TLC. After completion of the
reaction, reaction contents were cooled to room temperature, water
(
2 ml) was added and then extracted with EtOAc, and the product was
dried over anhydrous MgSO . The solvent was evaporated under reduced
4
pressure and the crude product was purified by chromatography on sil-
ica-gel (100–200) using hexane–EtOAc (6:2) mixture as eluent to afford
the expected product as a light red oil. The pure product was confirmed
by spectroscopic data.
Method B (Conventional Method)
To a mixture of aldehyde (1 mmol), amine (1.5 mmol), and alkyne
(
1.5 mmol), CuPy Cl (0.01 mmol) was added. The reaction contents were
2 2
ꢀ
stirred at 95 C. The progress of the reaction was monitored by TLC.
After completion of the reaction, the reaction mixture was cooled to
room temperature, water (2 ml) was added and then extracted with
EtOAc, and the product was dried over anhydrous MgSO . The solvent
4
was evaporated under reduced pressure, and the crude product was pur-
ified by chromatography on silica-gel (100–200) using a hexane–EtOAc
(6:2) mixture as eluent to afford the expected product as a light red oil.
The pure products were confirmed by spectroscopic data.

3218
J. V. Madhav et al.
Table 1. CuPy Cl
2
and amine
2
–Catalyzed three-component coupling of aldehyde, alkyne,
Method A
Method B
Time
(min)
Yield
a
(%)
Time
(min)
Yield
a
(%)
1
2
Entry
R
Amine
R
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
Ph
4-ClC
4-MeC H
6 4
Morpholine
Morpholine
Morpholine
Morpholine
Morpholine
Morpholine
Piperidine
Piperidine
Piperidine
Piperidine
Piperidine
Piperzine
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
2
3
3
3
4
4.5
3
3
4
3
5
2
3
3
3
7
92
91
89
90
92
54
94
90
91
93
93
92
92
90
91
52
40
40
55
50
50
75
45
60
55
45
50
35
50
55
55
120
90
88
87
89
91
57
91
88
89
90
91
91
90
87
87
45
6
H
4
4-MeOC H
6
4
4-BrC
6
H
4
4-NO2C
Ph
6
H
4
6 4
4-MeC H
6 4
4-MeOC H
1
1
1
1
1
1
1
4-ClC H
6 4
4-BrC
6
H
4
Ph
Ph
4-ClC H
6
4-MeC
4-MeOC
Diethyl amine Ph
Diethyl amine Ph
Diethyl amine Ph
Diethyl amine Ph
4
6 4
H
6 4
H
a
Yields refer to isolated pure products and were characterized by comparison of
NMR and mass spectral data with those of authentic samples.
Spectral Data
4
-(1,3-Diphenylprop-2-ynyl)morpholine (entry1):
1
H NMR (CDCl ): d ¼ 7.45–7.60 (m, 5H), 7.25–7.39 (m, 5H), 4.75 (s,
3
þ
1
Calcd. for C H NO: C, 82.28; H, 6.90; N, 5.05. Found: C, 82.32; H,
H), 3.60–3.78 (m, 4H), 2.50–2.70 (t, 4H); EI-MS: m=z ¼ 277 (M ).
1
9
1
9
6
.94; N, 5.01.
Scheme 1. CuPy Cl –catalyzed synthesis of propargylamines.
2
2

CuPy Cl
2
2
as Catalyst for Propargylamines
3219
4
-(1-(4-Chlorophenyl)-3-phenylprop-2-ynyl)morpholine (entry 2):
1
H NMR (CDCl ): d ¼ 7.42–7.56 (m, 4H), 7.23–7.39 (m, 5H), 4.81 (s,
3
þ
1
Calcd. for C H ClNO: C, 73.19; H, 5.82; N, 4.49. Found: C, 73.22;
H), 3.65–3.81 (m, 4H), 2.55–2.74 (t, 4H); EI-MS: m=z ¼ 311 (M ).
1
9
18
H, 5.77; N, 4.47.
4
-(3-Phenyl-1-p-tolylprop-2-ynyl)morpholine (entry 3):
1
H NMR (CDCl ): d ¼ 7.47–7.61 (m, 4H), 7.28– 7.41( m, 5H), (s, 1H),
3
3
.63–3.75 (m, 4H), 2.53–2.69 (m, 4H), 2.31 (s, 3H); EI-MS: m=z ¼ 291
þ
(
M ). Calcd. for C H NO: C, 82.44; H, 7.26; N, 4.81. Found: C,
2
0
21
8
2.39; H, 7.28; N, 4.78.
4
-(1-(4-Bromophenyl)-3-phenylprop-2-ynyl)morpholine (entry 5):
1
H NMR (CDCl ): d ¼ 7.59–7.71 (m, 4H), 7.37–7.49 (m, 5H), 4.65
3
(
s, 1H), 3.59–3.75 (m, 4H), 2.52–2.69 (m, 4H); EI-MS: m=z ¼ 356
þ
(
M ). Calcd. for C H BrNO: C, 64.06; H, 5.09; N, 3.93. Found: C,
9
1
18
6
4.08; H, 5.03; N, 3.95.
1
4
-(1-(4-Nitrophenyl)-3-phenylprop-2-ynyl)morpholine (entry 6):
H
NMR (CDCl ): d ¼ 7.60–7.69 (m, 2H), 7.50–7.57 (m, 2H), 7.35–7.45
3
(
m, 5H), 4.68 (s, 1H), 3.65–3.81 (m, 4H), 2.57–2.75 (t, 4H); EI-MS:
þ
m=z ¼ 322 (M ). Calcd. for C H N O : C, 70.79; H, 5.63; N, 8.69.
1
9
18
2
3
Found: C, 70.82; H, 5.61; N, 8.62.
1
-(1,3-Diphenylprop-2-ynyl)piperidine (entry 7):
1
H NMR (CDCl ) d ¼ 7.62–7.68 (m, 2H), 7.49–7.57 (m, 2H),7.31–7.45
3
(
m, 6H), 4.80(s, 1H), 2.56 (t, 4H, J ¼ 5.4 Hz), 1.55–1.65 (m, 4H), 1.44–
þ
1
H, 7.69; N, 5.09. Found: C, 87.25; H, 7.72; N, 5.05.
.53 (m, 2H); EI-MS: m=z ¼ 275 (M ). Calcd. for C H N: C, 87.23;
2
0
21
1
-(3-Phenyl-1-p-tolylprop-2-ynyl)piperidine (entry 8):
1
H NMR (CDCl ) d ¼ 7.62–7.69 (m, 2H), 7.50–7.58 (m, 2H), 7.37–7.47
3
(
m, 5H), 4.95 (s, 1H), 2.55 (t, 4H, J ¼ 5.4 Hz), 2.10 (s, 3H), 1.57–1.75
þ
(
C H N: C, 87.15; H, 8.01; N, 4.84. Found: C, 87.12; H, 8.03; N, 4.81.
m, 4H), 1.41–1.52 (m, 2H); EI-MS: m=z ¼ 289 (M ). Calcd. for
2
1
23

3220
J. V. Madhav et al.
1
-(1-(4-Methoxyphenyl)-3-phenylprop-2-ynyl)piperidine (entry 9):
1
H NMR (CDCl ) d ¼ 7.68–7.72 (m, 2H), 7.54–7.57 (m, 2H) 7.41–7.49
3
(
(
m, 5H), 4.82 (s, 1H), 3.81 (s, 3H) 2.59 (t, 4H, J ¼ 5.4 Hz), 1.59–1.68
þ
m, 4H), 1.48–1.55 (m, 2H); EI-MS: m=z ¼ 305 (M ). Calcd. for
C H NO: C, 82.58; H, 7.59; N, 4.59. Found: C, 82.55; H, 7.61; N, 4.54.
2
1
23
1
-(1-(4-Bromophenyl)-3-phenylprop-2-ynyl)piperidine (entry 11):
1
H NMR (CDCl ) d ¼ 7.65–7.75 (m, 2H), 7.52–7.60 (m, 2H),7.32–7.47
3
(m, 5H), 4.85 (s, 1H), 2.61 (t, 4H, J ¼ 5.4 Hz), 1.60–1.69 (m, 4H),
þ
1
6
.51–1.58 (m, 2H); EI-MS: m=z ¼ 354 (M ). Calcd. for C H BrN: C,
2
0
20
7.80; H, 5.69; N, 3.95. Found: C, 67.83; H, 5.62; N, 3.91.
N,N-Diethyl-1,3-diphenylprop-2-yn-1-amine (entry 12):
1
H NMR (CDCl ) d ¼ 7.65–7.69 (m, 2H), 7.47–7.55 (m, 2H),7.21–7.38
3
(
m, 6H), 5.03 (s, 1H), 2.51–2.68 (m, 4H), 1.08 (t, 6H, J ¼ 7.1 Hz); EI-MS:
þ
m=z ¼ 263 (M ). Calcd. for C H N: C, 86.65; H, 8.04; N, 5.32. Found:
1
9
21
C, 86.61; H, 8.09; N, 5.28.
1
-(4-Chlorophenyl)-N,N-diethyl-3-phenylprop-2-yn-1-amine (entry 13):
1
H NMR (CDCl ) d ¼ 7.61–7.66 (m, 2H), 7.48–7.55 (m, 2H),7.30–7.44
3
(
m, 5H), 4.99 (s, 1H), 2.48–2.67 (m, 4H), 1.07 (t, 6H, J ¼ 7.1 Hz); EI-MS:
þ
m=z ¼ 297 (M ). Calcd. for C H ClN: C, 76.62; H, 6.77; N, 4.70.
1
9
20
Found: C, 76.65;H, 6.75; N, 4.73.
N,N-Diethyl-3-phenyl-1-p-tolylprop-2-yn-1-amine (entry 14):
1
H NMR (CDCl ) d ¼ 7.53–7.64 (m, 4H), 7.31–7.39 (m, 3H),7.14–7.21
3
(m, 2H), 5.04(s, 1H), 2.51–2.74 (m, 4H), 2.37 (s, 3H), 1.13( t, 6H,
þ
J ¼ 7.1 Hz); EI-MS: m=z ¼ 277 (M ). Calcd. for C H N: C, 86.59; H,
2
0
23
8
.36; N, 5.05. Found: C, 86.54;H, 8.39; N, 5.08.
N,N-Diethyl-1-(4-methoxyphenyl)-3-phenylprop-2-yn-1-amine(entry15):
1
H NMR (CDCl ) d ¼ 7.56–7.59 (m, 2H), 7.48–7.54 (m, 2H),7.29–7.38
3
(m, 3H), 6.86–6.89 (m, 2H), 4.98 (s, 1H), 3.81 (s, 3H), 2.50–2.66 (m,

CuPy Cl
2
2
as Catalyst for Propargylamines
3221
þ
4
C H NO: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.83;H, 7.92; N, 4.81.
H), 1.07 (t, 6H, J ¼ 7.1Hz); EI-MS: m=z ¼ 293 (M ). Calcd. for
2
0
23
1
-(1,3-Diphenylprop-2-ynyl)piperazine (entry 16):
1
H NMR (CDCl ) d ¼ 7.45–7.58 (m, 5H), 7.23–7.38 (m, 5H), 4.89 (s,
3
þ
1
Calcd. for C H N : C, 82.57; H, 7.29; N, 10.14. Found: C, 82.52; H,
H), 2.45–2.51 (m, 4H), 2.61–2.70 (m, 4H); EI-MS: m=z ¼ 276 (m ).
1
9
20
2
7
.31; N, 10.11.
CONCLUSIONS
In summary, we have successfully developed a facile economic and green
method for construction of propargylamines by employing a three-
component coupling of aldehyde, amine, and alkyne in the presence of
CuPy Cl under solvent-free conditions. The notable factors of this reac-
2
2
tion are (a) reasonably good yields, (b) fast reaction, and (c) easy recov-
ery of the catalyst, CuPy Cl . Thus, we believe that our procedure will
2
2
find important application in the synthesis of propargylamines through
a one-pot coupling reaction to cater to the needs of academia as well
as pharmaceutical industries.
ACKNOWLEDGMENTS
Financial assistance from University Grants Commission (Rajiv Gandhi
National Research Fellowship) Grant No. F.16–158=2006(SA-II), New
Delhi, is greatly acknowledged.
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