Nanosize Co3O4 as a novel, robust, efficient and recyclable catalyst for A3-coupling reaction of propargylamines

Article abstract of DOI:10.1016/j.catcom.2011.09.012

Nanosize Co₃O₄ was prepared via hydrothermal synthesis and characterized using TEM, XRD, EDAX, XPS and BET surface area analysis. Prepared nanosize Co₃O₄ was found to be highly efficient catalyst for the synthes

Full text of DOI:10.1016/j.catcom.2011.09.012

Catalysis Communications 16 (2011) 114–119
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Nanosize Co O as a novel, robust, efficient and recyclable catalyst for A -coupling
3
4
3
reaction of propargylamines
Kushal D. Bhatte, Dinesh N. Sawant, Krishna M. Deshmukh, Bhalchandra M. Bhanage ⁎
Department of Chemistry, Institute of Chemical Technology, N.M.Parekh Marg, Matunga, Mumbai-400019, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 July 2011
Received in revised form 5 September 2011
Accepted 12 September 2011
Available online 18 September 2011
3 4
Nanosize Co O was prepared via hydrothermal synthesis and characterized using TEM, XRD, EDAX, XPS and BET
3 4
surface area analysis. Prepared nanosize Co O was found to be highly efficient catalyst for the synthesis of
propargylamines via A -coupling reaction. The catalyst was recycled up to ten consecutive cycles without any
3
loss in its activity. The developed protocol offers efficient synthesis of diverse propargylamines eliminating the
use of co-catalyst and activator as reported in earlier literature.
©
2011 Elsevier B.V. All rights reserved.
Keywords:
Propargylamines
Nanosize Co
3 4
O
A
3
coupling reactions
Heterogeneous and recyclable catalyst
C–H activations
1
. Introduction
aldehyde and amine by C–H activation wherein water is formed as
theoretical by-products [19, 20]. Several homogenous catalysts like
The catalytic applications of metal and metal oxide nanoparticles in
3 3
Ag, Au salts, FeCl , InCl , Ir complexes, Cu salts, Cu/Ru bimetallic
various organic transformations have gained considerable attention in
past few decades [1–3]. The differences in the activities of metal and
metal oxide and their nanoparticles including catalysis are directly
related to the particle size on nanometer length scale. The metallic
cobalt and cobalt oxide can be considered as a one of the best example
to understand the catalytic activity based on the variable particle size
[
4–8]. In past few years several reports showed the catalytic activity of
nanosize Co in Fischer Tropsch synthesis and CO oxidation [8–12]
reactions. However, less attention has been paid for catalytic activities
of nanosize Co for various organic transformations. Hence, identifi-
cation of new catalytic properties of nanosize Co for new transfor-
mations is one of the unexplored areas.
3 4
O
3 4
O
3 4
O
Propargylamines have wider applications in organic synthesis as
they are important building blocks for the synthesis of heterocyclic
compounds such as pyrrolidones, oxoazoles and pyrroles [13–15]
etc. They also serve as an important intermediate for natural product
synthesis [16–18]. Recently, propargylamines synthesis is carried out
using an atom economic pathway from catalytic coupling of alkyne,
⁎
Corresponding author. Tel.: +91 22 3361 1111/2222; fax: +91 22 3361 1020.
E-mail addresses: bm.bhanage@gmail.com, bm.bhanage@ictmumbai.edu.in
(B.M. Bhanage).
3 4
Fig. 1. TEM image of nanosize Co O with SAED pattern inside.
1566-7367/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.catcom.2011.09.012

K.D. Bhatte et al. / Catalysis Communications 16 (2011) 114–119
115
efficient, robust and recyclable catalyst for propargylamines synthe-
sis. To the best of our knowledge this is first report for the use of nano-
3 4
size Co O catalyst for any coupling reaction or multi-component
reaction.
2
. Experimental
The details regarding materials, catalyst preparation, catalyst
characterization and typical procedure for the A
are included in the supporting information.
3
coupling reactions
2.1. Chemicals and reagents
3 4
Fig. 2. Histogram of nanosize Co O obtained from DLS measurement.
All chemicals and reagents of A.R. grade were purchased from
Spectrochem Chemicals Ltd., Mumbai, India and used without further
purification.
3
. Results and discussion
The Co nanoparticles were prepared using the different proce-
3 4
O
dures mentioned in the experimental section and characterized using
various techniques like TEM, EDAX, BET, XRD, and DLS histogram
analysis. TEM image of cobalt oxide revealed that particles are in
nanosize and SAED pattern inside TEM image indicated crystalline
nature of particles (Fig. 1). The average particle size of cobalt oxide
was found to be 45 nm with histogram received by DLS measurement
(Fig. 2). The X-Ray diffraction pattern (Fig. 3) of cobalt oxide exhibited
prominent peak of (111), (220), (311), (222), (400), (422) correspond-
ing to spinel structure which is in agreement with JCPDS file no-421467.
EDAX spectrum of cobalt oxide samples showed peaks corresponding
to cobalt and oxygen only (Fig. 4a), which proves that catalyst is es-
3 4
Fig. 3. X -Ray diffraction pattern of nanosize Co O .
sentially pure. The BET surface area of catalyst was found to be
2
2
7.86 m /g. The complete XPS survey spectrum of synthesized nano-
materials is represented in Fig. 4b. In the survey spectra, the main
peaks are attributed to Co 2p and O 1 s and C 1 s region indicating ab-
sence of any other metallic or inorganic species. To conclude, by hy-
3
systems [18–29] and heterogeneous systems like LDH–AuCl [28],
zinc dust [29], Ni–zeolite [30], Ag–SBA [31] have been developed for
propargylamines synthesis. The scope of these reported methodol-
ogies are limited due to the use of an expensive, moisture sensitive re-
agents, toxicity, long reaction time and difficulties in catalyst
3 4
drothermal synthesis essentially pure Co O obtained are well in
nanoregion with average particle size 45 nm and average surface
2
area 27 m /g.
3 4
The application of prepared nanosize Co O for propargylamines
recyclability. Recently, Shreedhar et al. [32] utilized Fe
O
3 4
nanoparticles
synthesis via A -coupling reactions was explored (Scheme 1). The
3
as a heterogeneous catalyst for propargylamines synthesis, but a
high quantity of the catalyst i.e. 20 mol% was required. In present
work we have developed nanosize cobalt oxide (Co O ) as an
3 4
coupling of benzaldehyde, piperidine and phenyl acetylene was selected
as a model reaction and the influence of various reaction parameters like
solvent, catalyst loading, temperature were studied.
3 4 3 4
Fig. 4. a. EDAX spectrum of nanosize Co O . Fig. 4b. XPS spectra of nanosize Co O .

116
K.D. Bhatte et al. / Catalysis Communications 16 (2011) 114–119
Scheme 1. Synthesis of propargylamines using cobalt oxide nanoparticles.
To obtain the optimum reaction conditions for synthesis of pro-
pargylamines, the optimization of various reaction parameters like ef-
fect of temperature, catalyst loading, solvent and time was carried
cyclic amines. The napthaldehyde was found to react well for
present protocol providing excellent yield of desired product
(Table 4, entry 11). Thus, propargylamines synthesis was found
to be influenced with nature of alkynes.
An important criterion of heterogeneous catalyst is the reusability
of catalyst which makes the process more economically feasible. The
out. The final optimal reaction conditions are: nanosize Co
prepared by hydrothermal synthesis (10 mol%), solvent: toluene
3 mL), temp: 130 °C and time 15 h (Please refer Tables 1–3 for
detailed study). We also studied the influence of method of catalyst
preparation on model reaction. It was found that Co prepared
by hydrothermal synthesis showed better catalytic activity than
oxidation method due to larger particle size of Co prepared by
3 4
O catalyst
(
3 4
recyclability of nanosize Co O was studied using the series model reac-
3
O
4
tion and was found to exhibit remarkable activity up to ten recycle
without any significant decrease in yield of desired product (Table 5,
entry 1–10). The TEM images of the catalyst taken after 10th recycle
run showed small agglomeration which can be accountable for small
decrease in catalyst activity (Fig. 5).
3 4
O
oxidation method.(Please refer Table 1, entry 5,11 and supporting
information).
The generality and efficiency of developed protocol was investi-
gated using aldehydes with different functional groups, various
amines and alkynes to understand the scope and efficiency of the
nanosize cobalt oxide as a catalyst for different propargylamines syn-
thesis (Table 4). Various amines were tested for the propargylamines
synthesis, in which alicyclic amines like pyrrolidone, morpholine and
piperidine gave good yield of corresponding products (Table 4, en-
tries 1–10). It was observed that aldehydes with electron withdraw-
ing and donating groups offers good to moderate yield. Various
aldehydes with substituents at different positions were also studied.
It was observed that the substituent's at para and meta position
gave good yields (Table 1, entries 5–7). In case of ortho substituent
lower yield (Table 4, entry 8) was obtained. This can be attributed
to the steric hindrance by ortho substituent. Propargylamines synthe-
sis involving phenyl acetylene proceeded smoothly as compared to
aliphatic alkynes like 1-hexyne. Present protocol was not so com-
patible for aromatic amines like aniline (Table 4, entries 1–10).
This may be due to difference in nucleophilicity of aniline and
A plausible mechanism (Scheme 2) is proposed on the basis of
literature for the probable sequence of events involving activation
of the C–H bond of alkyne by Co
3 4
O . The cobalt–acetylide interme-
diate A generated due the reaction of acetylene and Co
3 4
O . Then A
Table 2
Effect of solvent a.
Entry
Solvent
Temperature, °C
% Yieldb
Effect of solvent
1
2
3
4
5
6
Water
Ethylene Glycol
Toluene
Solvent free
Acetonitrile
THF
100
130
130
130
100
100
Traces
——
90
——
Traces
30
a
Reaction conditions : benzaldehyde (1 mmol), piperidine (1.2 mmol), phenyl acetylene
(
1.5 mmol), nano Co
3
O
4
(20 mol%),solvent 3 mL, Time 24 h. All the reactions were
performed in sealed tube.
b
GC Yield.
Table 1
a
Effect of temperature and catalyst screening .
Table 3
Entry
Catalyst
Temperature (°C)
Yield (%)
a
Effect of catalyst loading and time .
Effect of Temperature
Yield (%)b
Entry
Catalyst Loading (mol%)
Time (h)
1
2
3
4
5
—————
110
110
RT
90
130
——
70
nano Co
nano Co
nano Co
nano Co
3
O
3
O
3
O
3
O
4
4
4
4
Effect of catalyst loadings
——
1
2
3
4
5
7.5
10
12.5
15
24
24
24
24
24
72
88
90
90
90
40
90
Effect of Catalyst Screening
20
6
7
8
9
1
1
nano ZnO
nano Nb
bulk Co
bulk CoCl
bulk Co(NO
130
130
130
130
130
130
85
——
43
30
45
79
2
O
5
Effect of time
3
O
4
6
7
8
9
10
10
10
10
9
75
82
88
88
2
12
15
24
0
1
3 2
)
c
3 4
nano Co O
a
a
Reaction conditions: benzaldehyde (1 mmol), piperidine (1.2 mmol),phenyl acetylene
Reaction conditions: benzaldehyde (1 mmol), piperidine (1.2 mmol), phenyl acetylene
(
1.5 mmol), catalyst (20 mol%), time 24 h,toluene 3 mL. All the reactions were performed
(1.5 mmol), nano Co
3 4
O ,toluene 3 mL. All the reactions were performed in sealed tube.
b
C
b
in sealed tube. GC Yield. nanosize cobalt oxide prepared by using oxidation method.
GC Yield.

K.D. Bhatte et al. / Catalysis Communications 16 (2011) 114–119
117
Table 4
Synthesis of different propargylamines .
a
No
1
Aldehyde
Amine
Acetylene
Product
Yield (%) b, c
87[33]
CHO
N
H
N
2
70[33]
CHO
CHO
N-H
N
3
90[33]
O
N
O
N
H
4
70[33]
H CO
CHO
N
H
3
N
H CO
3
5
85[33]
N
H
F
CHO
N
F
6
O N
65[33]
2
N
H
H
N
CHO
O N
2
7
70[33]
H CO
CHO
O
N
3
8
30[34]
CHO
N
H
N
(continued on next page)

118
K.D. Bhatte et al. / Catalysis Communications 16 (2011) 114–119
Table 4 (continued)
No
9
Aldehyde
Amine
Acetylene
Product
Yield (%) b, c
10[33]
C5H11
CHO
CHO
N
H
N
C5H
11
–
10
NH2
NH
11
90[33]
CHO
N
H
N
b
GC Yield.
a
3 4
Reaction conditions : aldehyde (1 mmol), amine (1.2 mmol), acetylene (1.5 mmol), nano Co O (10 mol%), toluene (3 mL), time (15 h). All the reactions were performed in
sealed tube.
reacts with iminium ion B (generated from aldehyde and amine ) to
provide corresponding amine as a product.
3 4
activity nanosize Co O first time ever for any multi-component
reactions (MCR) or coupling reactions.
Acknowledgments
4
. Conclusion
The authors are greatly thankful to University Grant Commission,
India for providing financial support under UGC-SAP Green Technolo-
gy Center, collaborative program of Institute of Chemical Technology
and University of Mumbai, India.
In conclusion we have developed an efficient, simple and eco-
nomical protocol for propargylamines synthesis via A
3
coupling
reaction using nanosize Co as a heterogeneous and robust cat-
3 4
O
alyst. Advantages offered by the developed methodology involve
easy work up of reaction, elimination of co-catalyst or activator
and divergent synthesis of propargylamines with good to moder-
ate yield under ambient reaction conditions. The catalyst was ef-
fectively recycled up to ten consecutive runs without significant
loss in the yield of desired product. We have explored catalytic
Appendix A. Supplementary data
Supplementary data to this article can be found online at doi:10.
1016/j.catcom.2011.09.012.
Table 5
Recyclability study of nano Co
3 4
O catalyst.
Recycle run (No)
Yield (%)
Fresh
85
85
85
82
80
80
80
78
78
77
78
1
2
3
4
5
6
7
8
9
10
aReaction condition : benzaldehyde (1 mmol), piperidine
1.2 mmol), phenyl acetylene (1.5 mmol), nano Co
0 mol%, toluene 3 mL, time 15 h.
(
3 4
O
1
b
GC Yield.
Fig. 5. TEM image of catalyst recycled after 10th cycle.

K.D. Bhatte et al. / Catalysis Communications 16 (2011) 114–119
119
Scheme 2. Mechanistic pathway of propargylamines using cobalt oxide nanoparticles.
[
16] A. Hu, G.T. Yee, W. Lin, Journal of the American Chemical Society 125 (2005)
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