R. Chutia, B. Chetia / Tetrahedron Letters 58 (2017) 3864–3867
3865
Experimental
Results and discussion
Biogenic synthesis of CuFe2O4 MNP’s
The biogenic CuFe2O4 MNP’S were characterized by powder
XRD-diffraction method as shown in Fig. 1. The sharp diffraction
peaks shows clearly the presence of highly pure crystalline
CuFe2O4 nanoparticles. The diffraction peaks appeared at
The leaves of Lantana camara were collected from Dibrugarh
University campus, Dibrugarh Assam. They were washed thor-
oughly with distilled water. The plant leaf broth solution was pre-
pared by taking 5 g of finely cut leaves and heating in a 250 mL
Erlenmeyer flask with 150 mL of sterile distilled water and then
boiling the mixture for 10 min before decanting it. To the decant
of Lantana camara, 50 mg of FeCl3 and 50 mg of Copper acetate
were added and stirred at room temperature for 1 h. To the stirring
solution 5 mL of 0.1 M NaOH was added. The resulting solution
was centrifuged and washed with ethanol. It was then subjected
to annealing at 300 °C for 2 h, which led to the formation of bio-
genic CuFe2O4 MNP’s.
2H = 24.174°, 33.196°, 34.28°, 35.65°, 38.714°, 40.876°, 44.374°,
49.482° corresponds to planes (1 0 0), (1 1 1), (1 1 1), (1 1 1),
(2 0 0), (2 1 0),(2 1 1) and (2 2 0) respectively.
The SEM images show the structure and morphology of the syn-
thesized nanoparticles (Fig. 2a). These images gives the structure of
the nanoparticles to be pure spherical and also their monodisper-
sity were observed from the SEM images. From the Energy
Dispersive X-ray (EDX) spectrum (Fig. 2b) the purity of the
nanoparticles was seen which clearly depicted the presence of
copper, iron and oxygen element.
The TEM and HR-TEM images (Fig. 3) determined size and mor-
phology of CuFe2O4 nanocrystals. The Selected Area Electron
diffraction (SAED) pattern Fig. 3(b) shows CuFe2O4 MNP’s which
contain the concentric diffraction of rings due to the (1 0 0),
(1 1 1) and (2 1 0) reflection of spherical Cu. From the HR-TEM
image (Fig. 3c) the fringes separation was found to be 1.61 A°
which is in good agreement with (1 0 0) plane and the other fringe
of 2.31 A° was found to be in agreement with (1 1 1) plane of
CuFe2O4 MNP’s. The average diameters of the NPs were found to
be 13.07 nm from the size distribution (Fig. 4).
General Procedure for the formation of ynones at room temperature
.
O
O
2mol% CuFe2O4 MNP's
+
R'
R
Cl
R
TEA, rt, 4 h
The magnetic measurements were carried out by using VSM at
room temperature. The VSM magnetization curves of biogenic
CuFe2O4 showed no remanence; and coercivity is negligible, indi-
cating the superparamagnetism of these nanomaterials (Fig. 5).
The saturation magnetization value of 12.92 emu gÀ1, from the
magnetic hysteresis curve of CuFe2O4 nanoparticles revealed that
it is suitable for magnetic separation. The sensitivity of the pre-
pared catalyst is strong enough to provide an easy and effective
way to separate the catalyst from the reaction system.
In the present study we first explored the influence of different
organic and inorganic bases on benzoyl chloride with phenyl acet-
ylene (Table 1). Owing to the weak nucleophilic nature of the alky-
nes, the use of an efficient base for enhancing the nucleophilicity
power of alkynes is efficient. The use of TEA as a base, proved to
be the most efficient for coupling of benzoyl chloride with phenyl
acetylene (Table 1, entry 4). K2CO3 and Cs2CO3 afforded moderate
yields of ynones (Table 1, entries 3, 4). Pyridine provided satisfac-
tory results but needed longer times for the completion of the reac-
tion. (Table 1, entry 5). The use of TEA however was preferred
because of its cheapness and also abundance.
R'
Scheme 1. Coupling of acid chlorides with terminal alkynes using CuFe2O4 MNP’s.
35000
111
30000
111
25000
20000
15000
100
111
220
210
200
10000
5000
211
20
30
40
50
Angle(2 theta)
Fig. 1. Powder XRD pattern of the synthesized CuFe2O4 MNP’s.
After identification of the proper base the role of different sol-
vents was tested on the model substrate of benzoyl chloride with
phenyl acetylene (Table 2). Toluene and dichloromethane were
noted to be good solvents for this coupling reaction but required
longer reaction time. For the diprotic solvents such as THF, DMF
and acetonitrile, the results were inferior. We were surprised to
find that the reaction was performed in highest yield without the
use of any solvent. All further reactions were consequently carried
out under neat anhydrous conditions and the results are recorded
in Table 2.
(a)
(b)
By using the optimised conditions the versatility, generality and
the applicability was explored for coupling 18 different
structurally diverse acid chlorides with different alkynes (Table 3).
With different aromatic acid chlorides and aromatic alkynes
bearing electron-withdrawing or electron-donating functionalities
the reaction were efficiently achieved using this method
(Scheme 1).
Aliphatic acid chlorides with aliphatic or aromatic alkynes were
also coupled efficiently, but needed longer reaction time (Table 3).
Fig. 2. (a) SEM images of the pure spherical CuFe2O4 MNP’s, (b) EDX image of the
nanospherical CuFe2O4 MNP’S.
Chutia, Rituparna
