Effect of solvent ratio and counter ions on the morphology of copper nanoparticles and their catalytic application in β-enaminone synthesis

Article abstract of DOI:10.1039/c6ra22017g

This work reports the synthesis of shape selective copper nanoparticles (NPs) using a microwave irradiation method, using diverse ratios of an ethylene glycol (EG)/water system. The solvent ratio of EG/water plays a pivotal role in the selective formation of CuO NPs. The alteration of the counter ion of the copper precursor leading to the selective synthesis of copper (CuO, Cu₂O, Cu(OH)₂) NPs has been observed. The synthesized copper NPs are well characterized using FEG-SEM, TEM, XRD, XPS, NH₃-TPD and BET surface area. The prepared CuO NPs show high activity towards the synthesis of β-enaminones and β-enamino esters from 1,3 diketones and amines.

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Effect of solvent ratio and counter ions on the morphology of
copper nanoparticles: Its catalytic application in β-enaminones
synthesis
Received 00th January 20xx,
Accepted 00th January 20xx
Aravind L. Gajengi,a T. Sasakib and Bhalchandra M. Bhanagea
DOI: 10.1039/x0xx00000x
This work reports the synthesis of shape selective copper nanoparticles (NPs) under microwave irradiation method using
diverse ratios of ethylene glycol (EG)/water system. The solvent ratio of EG/water plays a pivotal role for the selective
formation of CuO NPs. The alteration of counter ion of copper precursor lead to selective synthesis of copper (CuO, Cu2O,
Cu(OH)2 NPs has been observed. The synthesized copper NPs are well characterized by FEG-SEM, TEM, XRD, XPS, NH3-TPD
and BET surface area. The prepared CuO NPs shows high activity towards the synthesis of β-enaminones and β-enamino
esters from 1,3 diketones and amines.
www.rsc.org/
of reaction parameters such as heating power of microwave,
volume ratios of mixed solvent and counter ions.16,17 The
mixed solvent system of EG and water was used for the
Introduction
Nanomaterials and microstructures has gained the
valuable importance due to their distinctive structures and
diverse properties such as optical, electrical, magnetic,
thermal, catalytic and extensive applications.1 Consequently,
due wide variety structures and properties, copper
nanoparticles are considered to as interesting applications in
current research. Nowadays, copper NPs have found various
applications in the different fields such as catalysis,2 sensors,3
photocatalyst,4 fuel cells,5 lithium batteries,6 water-splitting
systems.7 There are different methods of synthesis of copper
NPs such as wet chemical method,8 biological method,2a
microwave methods,9 physical vapour deposition in ionic
liquids,10 solvothermal route,11 polyol method.12
morphology controlled synthesis of CuO superstructures.18.
There are some methods where they used the synthesis of
CuO by using mixed solvents of EG and water.3,18 Recently,
Zhou et al. synthesized Cu2O/CuO microparticles by using
EG/water as a mixed solvent in the autoclave by using copper
acetate as a precursor.3 In this protocol they used only one
volume ratio of EG/water i.e. 9:1 and observed the formation
of Cu2O/CuO microparticles.
The β-enaminones and β-enamino esters are important
starting materials for the synthesis organic compounds.19
These compounds used for synthesis of heterocycles,20
nitrogen containing compounds21, pharmaceutical drugs as an
anticonvulsant,22 natural alkaloids,23 antibacterial.24 There are
various methods have been developed for the synthesis of
enaminones such as condensation of carbonyl compounds
with amines by using various catalysts such as CoCl2,25
Yb(OTf)3,26 Cu NPs,27 Ag NPs,28 perchlorates,29 InBr3,30
tungstophosphoric acid31 and by ultrasonic method.32 These
reported methods having one or more disadvantages such as
uses of moisture sensitive metal triflates and difficulties in the
work up,26 use of harmful reagents,29 use of homogenous
catalyst.25 There is need to develop an efficient catalytic
method for the synthesis of β-enaminones which operates at
mild reaction conditions.
Microwave-assisted synthesis has attracted much attention
because it has advantages of being fast, simple, easy operation
and more energy efficient.9a,13 The microwave synthesis
enhances the kinetics of reactions by one or two orders of
magnitude over conventional methods due to rapid initial
heating and generation of the localized high pressure zone at
reaction sites. The microwave process is more efficient than
the conventional processes for the preparation of various
metal oxide NPs due to shape selective synthesis of NPs.14,15 It
is well known that the morphology of NPs varies by variation
In this report, we synthesized and characterized the CuO
NPs under microwave irradiation by using different volume
ratios of EG/water as solvent. The effect of various copper
precursor leads to shape selective formation of Copper NPs
such as CuO, Cu2O, Cu(OH)2. This synthesized CuO NPs having
acidic in nature and shows excellent catalytic activity towards
the synthesis of β-enaminones and β-enamino esters from 1,3
di-ketones and amines at mild conditions.
a.Department of Chemistry, Institute of Chemical Technology, Matunga, Mumbai-
400 019, India.
b.Department of Complexity Science and Engineering, Graduate School of Frontier
Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8561,
Japan.
*corresponding author, Tel.: + 91- 22 33612603; Fax: +91 33611020.
E-mail address: bm.bhanage@gmail.com, bm.bhanage@ictmumbai.edu.in
† Footnotes relaꢀng to the ꢀtle and/or authors should appear here.
Electronic Supplementary Information (ESI) available: [XRD, 1HNMR, GC-MS data of
products]. See DOI: 10.1039/x0xx00000x
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gun-scanning electron microscopy (FEG-SEM) analysis was
done by Tescan MIRA 3 model with secondary electron (SE)
detector between 10.0 kV to 20.0 kV. For Transmission
electron microscopy (TEM), Philips, CM 200, was used as
operating voltage of 200 KV model CM 200). X-ray
photoelectron spectroscopy (XPS) was carried out using PHI
5000 Versa Probe Scanning ESCA Microprobe, The Brunauer–
Emmett–Teller (BET) surface area by was analyzed on ASAP
2010 (Micromeritics, USA) instrument. NH3-Temperature
programmed desorption (NH3-TPD) was recorded on Thermo
scientific TPDRO 1100.
Experimental
Chemicals and reagents
Copper acetate [Cu(CH3COO)2·H2O], Copper chloride
[CuCl2·2H2O], copper nitrate [Cu(NO3)2] and ethylene glycol
were procured from S.D. Fine Chemicals Pvt. Ltd. India and
they were used as received without further purification.
Preparation of CuO NPs
For the synthesis of CuO NPs, the mixture of 200 mg of
copper acetate is dissolved in different volume ratios of
EG/water in mL (i.e. 1:9, 3:7, 5:5, 7:3, 9:1) and transferred to
100 mL glass beaker and kept inside the microwave oven for 4
min at 600 W with on–off mode of microwave oven having
time interval of 30 s. After microwave heating, the colour of
the reaction mixture changes to blue to black precipitate
indicating formation of CuO NPs. The product was separated
by centrifugation at 7000 rpm for 10 min and washed with
distilled water and ethanol for several times. The obtained
product was dried in the oven and used for further
characterization. The CuO NPs prepared at different volume
ratios of EG/water i.e 1:9, 3:7, 5:5, 7:3, 9:1in mL are labelled as
CuO (a), CuO (b), CuO (c), CuO (d) and CuO (e) respectively.
General procedure for synthesis of β-enaminones and β-enamino
esters
The experiment was carried out in 25 mL reaction vial, in a
typical reaction procedure; the CuO NPs as a catalyst was
introduced into a reaction vial containing acetylacetone (1
mmol) and an amine (1 mmol). The reaction mixture was
stirred at 60 °C temperature for 9 h. The progress of the
reaction was monitored by TLC. After completion of the
reaction, the catalyst was recovered by filtration. The mixture
was concentrated under vacuum. The residue was purified by
chromatography to afford the desired compound. All products
are well known in the literature and were characterized using
GC-MS (Shimadzu QP 2010) and were also compared with
authentic samples.
Preparation of Cu2O NPs
In the synthesis of Cu2O NPs, the mixture of 188 mg of
Cu(NO3)2 was dissolved in 3:7 and 7:3 volume ratios of
EG/water in mL and transferred to 100 mL glass beaker and
kept inside the microwave oven for 4 min at 600 W with on–
off mode of microwave oven having time interval of 30 s. After
microwave heating, the colour of the reaction mixture changes
blue to red precipitate indicating formation of Cu2O NPs. The
product was separated by centrifugation at 7000 rpm for 10
min and washed with distilled water and ethanol as several
times. The obtained product was dried in the oven and used
for further characterization.
Results and discussion
Effect of morphology of CuO NPs with different ratio of EG/water
Initially, by using the copper acetate as the metal precursor
we started investigation for the synthesis CuO NPs with
different of volume solvent ratio of the EG/water under the
microwave irradiation at 600W for 4 minutes. The variation of
volume ratio of EG/water leads to change in morphology (Fig.
1). By using the 1:9 of the EG/water ratio the aggregation of
sphere like CuO NPs was observed in SEM (Fig. 1a). When the
composition ratio of EG/water changes to 3:7, the spindle
shaped CuO NPs are observed (Fig. 1b). The disturbed spindle
shaped morphology was observed when 5:5 of EG/water was
used (Fig. 1c). Interestingly, flower like morphology observed
in SEM as well as TEM when 7:3 EG/water was used (Fig. 1d
and Fig. 1f). In case of 9:1 ratio of EG/water spherical CuO
micro particles is observed (Fig. 1e). From this it was
concluded that the volume ratio of EG/water controls the
shape and size of the CuO NPs.
Preparation of Cu(OH)2 NPs
In the synthesis of Cu(OH)2 NPs, the mixture of 170 mg of
copper chloride was dissolved in 3:7 and 7:3 volume ratios of
EG/water in mL and transferred to 100 mL glass beaker and
kept inside the microwave oven for 4 min at 600 W with on–
off mode of microwave oven having time interval of 30 s. After
microwave heating, the colour of the reaction mixture changes
to blue to green precipitate indicating formation of Cu(OH)2
NPs. The product was separated by centrifugation at 7000 rpm
for 10 min and washed with distilled water and ethanol several
times. The obtained product was dried in the oven and used
for further characterization.
After the successful synthesis of NPs we further
characterized these NPs by using the various techniques such
as XRD, XPS and NH3-TPD. The XRD pattern of CuO NPs which
synthesized at volume of 3:7 and 7:3 in mL of EG/water (Fig.2)
shows lattice planes of (-111) and (200) planes which
corresponding Braggs angles at 35.6° and 38.8°. Which
matches the characteristic peaks of pure monoclinic CuO
crystallites (JCPDS card 05-0661).33 The XRD of patterns of CuO
NPs which were synthesized at different volume of EG/water
ratios also matches to the standard (ESI-S1, Fig. 1).
Characterization methods of CuO, Cu2O, Cu(OH)2 NPs
The prepared CuO, Cu2O and Cu(OH)2 NPs were
characterized using various analytical techniques. X-ray diffract
meter (Shimadzu XRD-6100 using Cu Kα = 1.54 Å) with a
scanning rate 2° per min and 2 theta (θ) angle ranging from 20°
to 80° with current 30 mA and voltage 40 kV, Field emission
2 | J. Name., 2012, 00, 1-3
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For the determination of surface analysis of synthesised
NPs we further characterized by using the XPS analysis. The
presence of Cu and O elements were confirmed by XPS
analysis (Fig. 3a). The peak observed at a binding energy of
529.5 eV which corresponds to O1s and confirms O2− from of
CuO (Fig. 3b). The peaks observed at a binding energy of 933.6
eV, 952.9 eV corresponds to Cu2p3/2 and Cu2p1/2 (Fig. 3c) which
can be attributed to CuO and are well reported in the
literature.34 Along with the Cu2p3/2 and Cu2p1/2 peaks satellite
peaks also observed at ~940 eV and ~959.8 eV which are
characteristic of partially filled d-orbitals (3d9 in this case of
Cu2+).35
Fig. 3 XPS spectra of CuO NPs (d): (a) survey spectrum, (b) O1s region and (c) Cu2p
region.
Effect of counter ion for synthesis of CuO, Cu2O and Cu(OH)2
Further study of the effect of morphology was investigated
by changing the counter ions of Cu metals at the 3:7 and 7:3
ratios of EG/water under microwave irradiation. Surprisingly, it
was observed that the use of copper nitrate as a precursor
provide the formation of Cu2O NPs (Fig. 4a and 4b). While the
use of copper chloride as a precursor affords the formation of
disturbed spherical particles Cu(OH)2 particles when 3:7
EG/water was used (Fig. 4c) and fibre, flake like morphology
obtained when 7:3 EG/water was used (Fig. 4d).
Fig. 1 FEG-SEM images of CuO NPs synthesized at different volume ratio of EG/water in
mL (a) 1:9 (b) 3:7 (c) 5:5 (d) 7:3 (e) 9:1 (f) TEM image of 7:3 of EG/water synthesized at
600 W for 4 min.
Fig. 4 SEM images of Cu NPs by changing the metal precursor (a) and (b) Cu2O NPs from
Cu(NO3)2 (c) and(d) Cu(OH)2 microparticles synthesised from CuCl2.
Fig. 2 XRD pattern of CuO NPs (a) 3:7 and (b) 7:3 of EG/ water as solvent system
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In order to further optimise the reaction conditions, the
CuO NPs (d) was chosen for the synthesis of β-enaminones and
β-enamino esters due to its high activity. In a study of catalyst
loading, an increase in the catalyst from 1.5 to 2.5 mol%
increases the yield of 3aa (Table 1, entries 7-8). However, an
increase from 3.0 to 7.5 mol%, slightly decreases the yield of
product 3aa (Table 1, entries 8-10). Importantly, to check the
optimum time for reaction, for this reaction carried at 3h, 6h,
9h and 12 h and it was observed that the increase in time from
3h to 9h there was an increase in the yield of product 3aa and
further increase in the time to 12 h there was no effect on the
yield of the product 3aa (Table 1, entries 11-13). Next, in the
solvent study the use of solvent such as methanol, ethanol,
acetonitrile and toluene gave the lesser yield than the reaction
carried under neat condition (Table 1, entries 14-17). Finally,
temperature study was done at RT, 40°C, 50°C, 60°C and 70 °C
The increase in the temperature form RT to 60 °C there was an
increase in the yield of product 3aa and further increase in the
temperature there was slightly changed in the yield of product
3aa (Table 1, entries 18-22). So, the final optimum reaction
conditions were catalyst: 2.5 mol % and time: 9 h at 60 °C
under solvent free condition.
Fig. 5 Comparative NH3-TPD of synthesized CuO NPs.
The XRD patterns of Cu2O NPs and Cu(OH)2 also matches
with reported JCPDS data (ESI S1, Fig. 2 ).36,37 Hence, the ratio
of EG/water controls the morphology of the particles and
precursor for the selective formation of copper NPs. The NH3-
TPD of synthesized CuO NPs was recorded and it was observed
that the acidity of NPs varies with morphology (Fig. 5). The
amount of NH3 desorbed for CuO (a), CuO (b), CuO (c), CuO (d)
and CuO (e) are 1817, 2502, 2751, 9813 and 2106 μmol/g
respectively. The CuO NPs (d) having flower like morphology
showed the highest NH3 desorption (9813 μmol/g) hence,
expected to have highest acidity.
Table 1 Optimisation of reaction conditionsa
Ph
O
O
O
HN
CuO NPs cat.
Temp.
Ph NH2
+
2a
1a
3aa
BET-Specific surface area of the catalyst is an important
parameter for the high catalytic activity and the observed BET
specific surface area for CuO (a), CuO (b), CuO (c), CuO (d) and
CuO (e) are 98, 115, 118, 123 and 25 m²/g respectively.
Entry
Catalyst
Mol %
Solvent
Temp.
Time
Yield
[%]b
(°C)
(h)
Effect of catalyst screening
1
2
3
4
5
6
Methanol
Methanol
Methanol
Methanol
Methanol
Methanol
60
60
60
60
60
60
9
9
9
9
9
9
Trace
38
-
(a)
(b)
(c)
(d)
(e)
5
5
5
5
5
Catalytic application of βꢀenaminones and βꢀenamino esters
using CuO NPs
45
50
To investigate the catalytic application of the synthesized
NPs, the reaction of 1,3-dicarbonyl compound 1a and amines
2b carried out to synthesize β-enaminones 3aa. Initially, the
reaction was carried out without the catalyst and it was
observed that only trace amount of product 3aa was obtained
(Table 1, entry 1). Then, we screened various CuO NPs (Table
1, entries 2-6), among them CuO NPs (d) shows highest
catalytic activity and providing yield up to 58 % (Table 1, entry
5). The higher catalytic activity of the flower shaped CuO (d)
may be due higher acidity and BET specific surface area (123
m2/g) than other catalyst. The sphere like CuO (a) and micro
sized CuO (e) shows lesser acidity and BET specific surface area
due this giving a lesser yield of the product 3aa (Table 1,
entries 2 and 6). Also, spindle shaped CuO (b) gave less yield of
product 3aa due less acidity and BET surface area as compared
to CuO (d) (Table 1, entry 3). The disturbed spindle shaped
CuO (c) shows a higher acidity and BET specific surface area
than CuO (b) and showing higher yield of product 3aa than
that of catalyst CuO (b) (Table 1, entry 4). So acidity and
specific surface area are important for the catalytic activity of
CuO NPs
58
39
Effect of catalyst loading
7
Methanol
Methanol
Methanol
Methanol
60
60
60
60
9
9
9
9
50
64
60
57
(d)
(d)
(d)
(d)
1.5
2.5
3.0
7.5
8
9
10
Effect of time
11
12
13
Methanol
Methanol
Methanol
60
60
60
3
6
51
57
60
(d)
(d)
(d)
2.5
2.5
2.5
12
Effect of solvent
14
Ethanol
Acetonitrile
Toluene
-
60
60
60
60
9
9
9
9
68
33
39
83
(d)
2.5
2.5
2.5
2.5
15
(d)
16
(d)
17
(d)
Effect of temperature
18
19
20
-
-
-
RT
40
50
9
9
9
44
63
70
(d)
(d)
(d)
2.5
2.5
2.5
4 | J. Name., 2012, 00, 1-3
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21
-
-
60
70
9
9
83
84
Dicarbonyl
compound
(d)
2.5
2.5
Entry
1
Amine
Product
Yield [%]b
22
(d)
a
Reaction conditions: acetylacetone (1.0 mmol), aniline (1.0 mmol), CuO NPs
(mol% with respect to starting material), under N2 atmosphere, b GC Yield. The GC
yield was quantified with external standard using methyl 4-(phenylamino)pent-3-
en-2-one.
83
On the basis of the above optimized reaction conditions,
the scope of substrates for β-enaminones and β-enamino
esters synthesis was evaluated (Table 2). The condensation of
aniline 1a with acetylacetone 2a provided an excellent yield of
3aa (Table 2, entry 1). The effect of electron donating and
withdrawing groups on aniline was studied. It was found that
electron donating group –Me and withdrawing group –F
produced corresponding products 3ab-3ac in good yields
(Table 2, entries 2 and 3). Then studied the aliphatic primary
2
3
1a
1a
80
78
amine such as 2d, 2e and 2f gives the desired products 3ad-3af
(Table 2, entries 4-6). The heterocyclic secondary amines such
as 2g and 2h give the excellent yield of product 3ag-3ah (Table
2, entries 7-8). Next, reaction carried out by change of 1,3-
carbonyl compound such as ethylacetoacetate 1b and
methyacetoacetate 1c with various amines. The reactions of
1a
1a
4
5
93
97
1b with 2a
product 3ba-3bh (Table 2, entries 9-13). Finally, the reaction of
1c with 2a 2f and 2h gives the corresponding yield of product
, 2e, 2f, 2g and 2h give good to excellent yield of
,
3ca-3ch (Table 2, entries 14-16).
After detail substrate study, moved towards study
recyclability of heterogeneous catalytic system. The
recyclability of CuO NPs catalyst was studied for synthesis of β-
enaminone 3aa under optimised reaction condition. After the
completion of the reaction, the catalyst was separated through
simple filtration technique. The catalyst washed with distilled
water and ethanol, dried under vacuum and then reused for
successive runs. Importantly, the catalyst was found to be
effective up to three consecutive runs without any significant
much loss in its catalytic activity (Fig.6). After recycle study
catalyst analysed by TEM (Fig. 7a) it was observed that there is
a slightly change in the morphology of the catalyst. In the XRD
pattern, it was observed that there is no much change in its
pattern (Fig. 7b). The comparison of the present catalytic
system takes less duration than some of the reported protocol
as shown in Table 3. Proposed mechanism for formation of β-
enaminones and β-enamino esters has been shown in scheme
1. In this carbonyl groups of 1,3-dicarbonyl compound interact
1a
1a
6
7
98
90
8
1a
95
with CuO NPs to form the intermediate
interacts with amine to give the intermediate
elimination of water gives the product
A
which further
and which on
9
2a
2e
78
75
B
β
-enaminone.
Table 2 Synthesis of β-enaminones and β-enamino esters catalysed by CuO NPsa
1b
10
11
1b
2f
90
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Table 3 Comparison of duration of reaction of present protocol with other reported
catalyst for synthesis of β- enaminones and β- enamino esters.
1b
2g
12
68
No
1
Catalyst
Yb(OTf)3
Time (h)
12 h
10 h
10 h
24 h
18 h
9 h
Reference
26
2
Pd(PPh3)4
38a
3
Ag/CNT
38b
4
Montmorillonite K-10
Co2(CO)8
38c
5
38d
13
1b
2h
80
70
6
CuO NPs
This work
R
O
HN
O
O
CuO NPs
2a
2f
+
14
15
H2O
O
O
O
OH
R
H
N
1c
B
A
98
70
1c
2h
H2N
R
16
Scheme 1 Reaction mechanism for the synthesis of β-enaminones catalysed by CuO
NPs.
a
Reaction conditions: 1,3-dicarbonyl compound (1.0 mmol), amine (1.0 mmol),
b
CuO NPs (2.5 mol%), solvent free, 60 °C, 9 h under N2 atmosphere, Isolated
Yield.
Conclusions
In summary, we have prepared shape selective and catalytic
active CuO NPs by different volume ratios of EG/water under
microwave irradiation method. The change of morphology of
CuO NPs with changes in the volume ratio of EG/water of Cu
NPs was observed. Interestingly, by changing the counter ion
of copper the change in Cu NPs were observed such as
Cu(OAc)2 provides CuO, Cu(NO3)2 provides Cu2O and CuCl2
provides the Cu(OH)2. Additionally, the synthesized CuO
shows high catalytic activation for the synthesis of β-
enaminones and β-enamino esters. The developed
methodology proceeds under solvent free, utilizes mild
reaction conditions and recyclable up three cycles.
Fig. 6 Recyclability in the synthesis of β-enaminones from 1,-3 dicarbonyl compounds
and amine catalysed by CuO NPs. Reaction conditions: 1, 3-dicarbonyl compound
(1mmol), amine (1mmol), 60 °C, 9 h, bGC Yield. The GC yield was quantified with
external standard using methyl 4-(phenylamino)pent-3-en-2-one.
Characterisation data of products
4-(phenylamino)pent-3-en-2-one (Table 2, entry 1)39
1H NMR (400 MHz, CDCl3) δ 12.45 (s, 1H), 7.31 (m, 2H), 7.17
(m, 1H), 7.10 (d, J = 7.6 Hz, 2H), 5.17 (s, 1H), 2.09 (s, 3H), 1.98
(s, 3H). GC-MS (EI, 70 eV): m/z (%) = 176 (6) [M+], 175 (45), 160
(100), 132 (56), 118 (38), 77 (35), 51 (19), 44 (39).
4-(cyclohexylamino)pent-3-en-2-one (Table 2, entry 5)39
1H NMR (400 MHz, CDCl3) δ 10.95 (s, 1H), 4.88 (s, 1H), 3.35 (s,
1H), 1.96 (s, 3H), 1.91 (s, 3H), 1.83 (s, 2H), 1.74 (s, 2H), 1.55 (d,
J = 9.6 Hz, 1H), 1.36 – 1.21 (m, 5H). GC-MS (EI, 70 eV): m/z (%)
= 182 (16) [M+], 181 (76), 166 (30), 138 (61), 100 (78), 84 (83),
58 (100), 43 (49).
Fig. 7 (a) TEM and (b) XRD analysis of CuO NPs after recycle.
6 | J. Name., 2012, 00, 1-3
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4-(benzylamino)pent-3-en-2-one (Table 2, entry 6)40
19 E. Rafiee, M. Joshaghani, S. Eavani and S. Rashidzadeh, Green
Chem., 2008, 10, 982-989.
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2011, 76, 1538-1545.
21 C. Alan, A. C. Spivey, R. Srikaran, C. M. Diaper, J. David and D.
1H NMR (400 MHz, CDCl3) δ 11.14 (s, 1H), 7.32 (d, J = 7.1 Hz, 2H),
7.25 (t, J = 7.5 Hz, 3H), 5.03 (s, 1H), 4.44 (d, J = 6.3 Hz, 2H), 2.02 (s,
3H), 1.90 (s, 3H). GC-MS (EI, 70 eV): m/z (%) = 190 (9) [M+], 189
(48), 174 (33), 146 (26), 105 (12), 91 (100), 65 (19), 42 (17).
Turner, Org. Biomol. Chem., 2003, 1, 1638-1640.
22 I. O. Edafiogho, K. V. Ananthalakshmi and S. B. Kombian,
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24 T. Mahmud, R. Rehman, A. Gulzar, A. Khalid, J. Anwar, U.
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25 Z. H. Zhang and J. Y. Hu, J. Braz. Chem. Soc., 2006, 17, 1447-
1451.
Ethyl 3-(cyclohexylamino)but-2-enoate (Table 2, entry 10)32
1H NMR (400 MHz, CDCl3) δ 8.61 (s, 1H), 4.37 (s, 1H), 4.06 (q, J
= 7.1 Hz, 2H), 3.29 (d, J = 5.3 Hz, 1H), 1.91 (s, 3H), 1.75 – 1.53
(m, 3H), 1.31 – 1.19 (m, 10H). GC-MS (EI, 70 eV): m/z (%) = 212
(11) [M+], 211 (31), 182 (7), 166 (25), 130 (100), 122 (35), 84
(96), 55 (31), 41 (39).
26 F. Epifano, S. Genovese and M. Curinib, Tetrahedron Lett.,
2007,48, 2717-2720.
Acknowledgements
Author Aravind L. Gajengi thankful to the University Grand
Commission‒Basic Research Programme (UGC-BSR) for
providing fellowship.
27 M. Kidwai, S. Bhardwaj, N. K. Mishra, V. Bansal, A. Kumar and
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Effect of solvent ratio and counter ions on the morphology of copper
nanoparticles: Its catalytic application in βꢀenaminones synthesis
Aravind L. Gajengi,a Takehiko Sasaki,b Bhalchandra M. Bhanagea,*
a Department of Chemistry, Institute of Chemical Technology, Matunga,
Mumbai- 400 019, India.
b Department of Complexity Science and Engineering, Graduate School of
Frontier Sciences, The University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa,
Chiba 277-8561, Japan.
Graphical Abstract