Nano-ferrous ferric oxide (nano-Fe3O4): Magnetite catalytic system for the one-pot four-component tandem imine/enamine formation-Knoevenagel-Michael-cyclocondensation reaction of dimedone, aldehydes, β-ketoesters and ammonium acetate under green media

Article abstract of DOI:10.1039/c4ra03980g

In this work, magnetite nano-Fe₃O₄ was applied as a green, efficient, heterogeneous and reusable catalytic system for the atomic economic preparation of hexahydroquinolines via the one-pot multi-component reaction of aryl aldehydes, dimedone (5,5-dimethylcyclohexane-1,3-dione), β-ketoesters and ammonium acetate at 50 °C under mild and solvent-free conditions. The catalyst was synthesized and characterized by several techniques including Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), vibrating sample magnetometry (VSM) and transmission electron microscopy (TEM). Also, optimization of the reaction conditions was investigated using the response surface method {Central Composite Design (CCD)}. the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra03980g

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Nano-ferrous ferric oxide (nano-Fe O ): magnetite
3
4
catalytic system for the one-pot four-component
tandem imine/enamine formation-Knoevenagel–
Michael-cyclocondensation reaction of dimedone,
aldehydes, b-ketoesters and ammonium acetate
under green media†
Cite this: RSC Adv., 2014, 4, 32142
a
b
a
Ardeshir Khazaei,* Ahmad Reza Moosavi-Zare,* Hadis Afshar-Hezarkhani
a
and Vahid Khakyzadeh
3 4
In this work, magnetite nano-Fe O was applied as a green, efficient, heterogeneous and reusable catalytic
system for the atomic economic preparation of hexahydroquinolines via the one-pot multi-component
reaction of aryl aldehydes, dimedone (5,5-dimethylcyclohexane-1,3-dione), b-ketoesters and ammonium
ꢀ
acetate at 50 C under mild and solvent-free conditions. The catalyst was synthesized and characterized
Received 30th April 2014
Accepted 8th July 2014
by several techniques including Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD),
vibrating sample magnetometry (VSM) and transmission electron microscopy (TEM). Also, optimization of
the reaction conditions was investigated using the response surface method {Central Composite Design
(CCD)}.
DOI: 10.1039/c4ra03980g
www.rsc.org/advances
Multi-component reactions (MCRs) are important in combina- to prevent loss of the catalyst. Recently, chemists have focused
torial chemistry due to their ability to prepare target on catalytic aspects of nano-Fe to improve methods of
3 4
O
10–15
compounds with more efficiency and atomic economy by the catalytic activity.
reaction of three or more compounds together in a single step. Improvement on the DHP ring, like the introduction of
Moreover, MCRs increase simplicity and synthetic efficiency of hetero atoms or variant substituents could not only result in
1
–5
the conventional organic transformations.
decreased photosensitivity of these materials, but also enrich
Transition-metal catalyzed organic transformations are the diversity of DHPs chemistry and could modify structure–
oen carried out to follow the principles of “Green Chemistry” activity relationship bearing novel aspects into the molecular
1
6,17
due to minimization of waste, cleaner auxiliaries, catalysts or interactions.
reagents and minimum use of energy. Nanocatalysts are tion on the DHP periphery could result in important inuence
It is also recognized that structural modica-
18,19
important as a bridge between heterogeneous and homoge- in their pharmacological activities.
neous catalysts. One of the interesting properties of nano- DHPs with an improved structural scaffold is hexahydroquino-
One of the categories of
6
materials is that they have a high specic surface area of the lines (HHQs) that could be obtained through Hantzsch
7
active part, leading to an increase in contact with the reactants.
synthesis utilizing aromatic aldehydes, dimedone, b-ketoesters
Moreover, a higher surface area gives the nanomaterials a more and ammonium acetate via a one-pot multi-component reac-
20,21
active surface; they are hard to be separated. Therefore, it is tion.
Quinoline derivatives with a 1,4-dihydropyridine scaf-
attractive to design a recoverable and well-dispersed catalyst. fold are promising structures because of their pharmacological
Magnetite nanoparticles (MNPs) as catalysts are very promising properties. This category of quinolines has diverse applications
because of their magnetic properties and large specic surface in medicinal chemistry, being used as antiasthmatic, antibac-
8,9
area. They can be collected very easily with a magnet for reuse terial antihypertensive, anti-inammatory, antimalarial, and
22–27
tyrosine kinase inhibiting materials.
Additionally, some
a
other protocols and catalysts have been developed for the
Faculty of Chemistry, Bu-Ali Sina University, Hamedan, 6517838683, Iran. E-mail:
28–39
Khzaei_1326@yahoo.com; Fax: +98 8118257407; Tel: +98 8118282807
b
synthesis of HHQs.
Herein, we have introduced the nano-ferrous ferric oxide
nano-Fe ) as a highly efficient, stable, reusable and hetero-
Department of Chemistry, University of Sayyed Jamaleddin Asadabadi, Asadabad,
6
+
†
1
541835583, Iran. E-mail: moosavizare@yahoo.com; Fax: +98 8123237451; Tel:
(
3 4
O
98 8123237450
geneous catalyst for the preparation of hexahydroquinolines, at
Electronic supplementary information (ESI) available. See DOI:
0.1039/c4ra03980g
ꢀ
5
0 C under solvent-free conditions (Scheme 1). Interestingly,
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model. Aer programming optimization (Table S3 and S4†), two
polynomial response surface models based on signicant levels
and actual values for time and yield were obtained (Fig. 1 and 2).
2
Time ¼ +7.33 ꢁ 1.02A ꢁ 4.73B + 2.74B
(1)
(2)
2
2
Yield ¼ +88.89 + 1.86A + 6.17B ꢁ 1.18A ꢁ 3.02B
Scheme 1 The one-pot four-component preparation of hexahy-
droquinolines catalyzed by nano-Fe O .
3 4
For nding of accurate optimum area, with using of obtained
equations and calculation of desirability functions, the results
showed that accurate optimal operational conditions was
the presented protocol has efficiently improved and solved
some drawbacks in the preparation of the title compounds.
ꢀ
(
A ¼ 50 C, B ¼ 5 mol%, C ¼ 2.5 mmol) (Fig. 3). It should be
First of all, the catalyst (nano-Fe
3
O
4
) was prepared according
mentioned that corresponding maximum prediction conver-
sion was 95.96% in introduced optimal point.
15,40
to the previous literature.
The synthesized catalyst was
identied by X-ray diffractometer (XRD), vibrating sample
magnetometer (VSM), Fourier transform infrared spectroscopy
In the next step, the accuracy of the theoretical results, were
examined by empirical research. For this purpose, as model
reaction, a mixture of dimedone (1 mmol), 4-nitrobenzaldehyde
(
FT-IR) and transmission electron microscopy (TEM). To
conrm that the magnetite was correctly produced, in the rst
3 4
step, the XRD pattern of it was studied. XRD pattern of Fe O
(
(
1 mmol), ethyl acetoacetate (1 mmol) and ammonium acetate
1.2 mmol), was stirred in the presence of different amounts of
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
nanoparticles reveal at 2q z 30.24 , 35.62 , 43.33 , 53.63 ,
5
nano-Fe
3
O
4
at range of 25 to 80 C under solvent-free condition.
ꢀ ꢀ
7.29 and 62.80 respectively, that was conrmed by the
The respective results are displayed in Table 1. As it can be seen
reported value (JCPDS 01-1111) (Fig. S1a†). The average crys-
tallite size D was calculated using the Debye–Sherrer equation
in Table 1, indicates that 0.0116 g (5 mol%) of Fe O4
3
(
D ¼ Kl/(b cos q), l the X-ray wavelength, where K is Scherrer
constant, b the peak width of half-maximum, and q is the Bragg
diffraction angle). The obtained average size of the catalyst by
this equation, was about 9 nm, which is basically in a good
accordance with the transmission electron micrographs of the
3 4
nano-Fe O (Fig. S1b†).
In the second step, magnetic property of the catalyst was also
recorded by a vibrating sample magnetometer (VSM) at 298 K.
The magnetization graph reveal which the magnetization
ꢁ1
saturated up to 60 emu g at an applied eld of 7000 Oe and
conrmed the super paramagnetic properties at room temper-
ature (Fig. S2†).
Finally, to further prove the preparation of the catalyst, an
FT-IR spectrum of Fe
Fig. S3,† the peak at 582 cm is related to the interactions of
Fe–O bonds in structure of nano-Fe
Aer the full characterization of nano-Fe O , we tested the
3 4
O was investigated. As it is shown in
ꢁ
1
3 4
O .
Fig. 1 Three dimensional response surfaces for the effect of factors
on the reaction time.
3
4
catalytic activity of it to promote the preparation of hexahy-
droquinolines. For this purpose, a mixture of dimedone,
4-nitrobenzaldehyde, ethyl acetoacetate and ammonium
acetate in the present of nano-Fe under solvent-free condi-
3 4
O
tion was chosen as model reaction, optimization of the reaction
condition was investigated using the response surface method
{
Central Composite Design (CCD)} with ve replicate at central
point for developing a second order model with 19 runs
Table S1†). Three variables that can effect on yield and time of
(
the reaction are temperature (A with levels of the variables 35 to
ꢀ
6
5 C), amount of catalyst (B with levels of the variables 2.8 to
.2 mol%) and amount of ammonium acetate (C with levels of
8
the variables 2.2 to 2.8 mmol). The levels of the variables and
the corresponding response values of the CCD are shown in
Table S2.† Yield and time of the reaction were used as the
dependent variables and were tted to a quadratic polynomial
Fig. 2 Three dimensional response surfaces for the effect of factors
on the reaction yield.
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Table 2 Effect of various solvents on the reaction of dimedone (1
mmol), 4-nitrobenzaldehyde (1 mmol), ethyl acetoacetate (1 mmol)
and ammonium acetate (1.2 mmol), in the presence of nano-Fe O
3 4
(0.0116 g, 5 mol%)
a
ꢀ
b
Entry
Solvent
CHCl
EtOAc
EtOH
Temp. ( C)
Time (min)
Yield (%)
1
2
3
4
5
6
7
3
50
50
50
Reux
50
Reux
50
50
25
30
21
19
35
15
20
5
80
78
81
83
70
85
81
92
CH
2
Cl
2
2
H O
Acetone
THF
c
8
—
a
ꢀ
All reactions were carried out at 50 C except entries 4 and 6, which was
b
c
proceeded at reux condition. Isolated yield. The reaction was
Fig. 3 Effect of temperature and catalyst on the desirability function.
proceeded in the absence of solvent.
ꢀ
nanoparticles was suitable to catalyze the reaction at 50 C. In
3 4
In another investigation, recyclability of nano-Fe O was
this reaction condition, the desired hexahydroquinoline was
efficiently prepared in 92% yield within 5 min (Table 1, entry 2)
which is in a good accordance with the response surface
method.
studied. For this purpose, the reaction of dimedone (1 mmol), 4-
nitrobenzaldehyde (1 mmol), ethyl acetoacetate (1 mmol) and
ammonium acetate (1.2 mmol) was performed in the presence
ꢀ
of nano-Fe O (0.0116 g, 5 mol%) at 50 C. Aer completion of
3
4
To compare the efficiency of the solution versus solvent-free
the reaction, the reaction mixture was cooled to room temper-
ature; ethanol (95%) (20 mL) was added, stirred and reuxed for
conditions,
a mixture of dimedone (2 mmol), 4-nitro-
benzaldehyde (2 mmol), ethyl acetoacetate (2 mmol) and
3
min. The catalyst was collected by a magnet and separated
ammonium acetate (2.4 mmol), as model reaction, using nano-
from the solution of product and remaining starting materials.
The remained catalyst was washed with hot ethyl acetate
ꢀ
Fe
3
O
4
in some various solvents was heated in an oil-bath (50 C).
Low yields of the product was isolated, even aer elongated
reaction times. Using solvents, such as CH Cl , CHCl , EtOAc,
EtOH, H O, acetone and THF, the product was obtained in low
yields (Table 2).
(
10 mL) and dried to use for the next run. Catalytic activity of
2
2
3
nano-Fe was restored within the limits of the experimental
errors for 12 successive recycle runs (Fig. 4).
3 4
O
2
In a plausible mechanism (Scheme 2) which is supported by
To investigate the efficacy and the generality of the catalyst,
dimedone was reacted with various aromatic aldehydes (benz-
aldehyde as well as aryl aldehyde containing electron-
withdrawing groups, electron-donating groups and halogens),
b-ketoesters (ethyl and methyl acetoacetate) and ammonium
acetate under the optimized reaction conditions; the results are
summarized in Table 3. As it is clear from Table 3, all reactions
proceeded efficiently to give the desired hexahydroquinoline
derivatives in high yields and in short reaction times. Therefore,
nano-Fe O , was a highly efficient and general catalyst for the
29,31,33,38,39
the literature,
at rst dimedone is converted to its enol
as Lewis acid and reacted to activated
3 4
aldehyde (by nano-Fe O ) to give intermediate I. Also, the acti-
3 4
form using nano-Fe O
vated b-ketoester (by the catalyst) and ammonia (resulted from
ammonium acetate) affords enamine II. Then, the intermediate
I and enamine II react with each other to produce intermediate
III. III is converted to IV by tautomerization, and intermediate
IV gives V by intramolecular nucleophilic attack of the NH2
group to the activated carbonyl group and then removing one
3
4
molecule H
tomerization of V.
2
O. As a result, hexahydroquinonine forms by tau-
preparation of HHQs.
Table 1 Effect of the catalyst amount and temperature on the reaction between dimedone, 4-nitrobenzaldehyde, ethyl acetoacetate and
ammonium acetate
ꢀ
a
Entry
Catalyst
Catalyst amount (g)
Temp. ( C)
Time (min)
Yield (%)
1
2
3
4
6
7
Nano-Fe
Nano-Fe
Nano-Fe
Nano-Fe
Nano-Fe
Nano-Fe
3
3
3
3
3
3
O
O
O
O
O
O
4
4
4
4
4
4
0.0116
0.0116
0.0116
0.0116
0.0068
0.0162
25
50
60
80
50
50
17
5
5
5
13
7
85
92
92
92
79
91
a
Isolated yield.
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Table 3 The solvent-free synthesis of HHQs from dimedone, aryl Table 3 (Contd.)
aldehydes, b-ketoesters and ammonium acetate catalyzed by nano-
ꢀ
Fe O
3 4
at 50 C
a
ꢀ
Entry Product
Time (min) Yield (%) M.p. C (lit.)
a
ꢀ
Entry Product
Time (min) Yield (%) M.p. C (lit.)
1
3
4
14
11
92
91
227–229 (229–231) [39]
205–207
1
6
5
89
92
204–205 (203–205) [20]
245–247 (242–244) [24]
1
2
3
4
5
6
1
1
1
5
6
7
6
5
5
89
90
85
256–259 (257–259) [38]
231–233 (235–236) [39]
233–235 (228) [41]
7
7
6
8
91
89
91
86
256–258 (257–259) [23]
262–263 (260–261) [23]
238–240 (232–234) [23]
250–252 (255–257) [20]
18
8
89
238–240 (246) [41]
1
2
9
0
4
9
92
87
208–209 (207) [41]
248–249 (245) [41]
7
8
8
6
90
91
229–230 (235–237) [20]
248–250 (245–246) [22]
2
1
6
90
205–206
9
8
5
87
91
255–256 (256–257) [39] 22
7
8
85
85
266–268 (—) [42]
232–233
23
1
0
244–245 (243–245) [38]
2
4
6
92
214–216 (220) [43]
1
1
1
2
6
90
91
220–221 (211–213) [38]
256–258 (260–262) [39]
a
Isolated yield.
10
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Conclusions
In summary, we have introduced nano-Fe
3
O
4
as a reusable,
stable, general and heterogeneous catalyst for the one-pot
multi-component reaction between dimedone, aryl aldehydes,
b-ketoesters and ammonium acetate leading to hexahy-
droquinolines. Also, optimization of the reaction condition was
investigated using the response surface method {Central
Composite Design (CCD)} which was in a good accordance with
empirical research. The promising points for the presented
method are efficiency, generality, high yields of the products,
short reaction times, simplicity, cleaner reaction prole, low
44
cost, ease preparation and reusability of the catalyst.
Fig. 4 The condensation of dimedone with 4-nitrobenzaldehyde,
ethyl acetoacetate and ammonium acetate in the presence of recycled
Acknowledgements
3 4
nano-Fe O .
The authors gratefully acknowledge partial support of this work
by the Research Affairs Office of Bu-Ali Sina University (Grant
number 32-1716 entitled development of chemical methods,
reagents and molecules), University of Sayyed Jamaleddin Asa-
dabadi and Center of Excellence in Development of Chemical
Method (CEDCM), Hamedan, I. R. Iran.
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2
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as catalyst.
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1
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44 Materials: all chemicals were purchased from Merck or
Fluka Chemical Companies. The known products were
identied by comparison of their melting points and
spectral data with those reported in the literature. Progress
of the reactions was monitored by TLC using silica gel SIL
2
2
2
1
13
G/UV 254 plates. The H NMR (400 or 300 MHz) and
C
NMR (100 or 75 MHz) were run on a BrukerAvance DPX-
250 FT-NMR spectrometer (d in ppm). Melting points were
recorded on a B u¨ chi B-545 apparatus in open capillary
tubes. General procedure for the preparation of
hexahydroquinolines: to a mixture of dimedone (0.28 g, 2
mmol), aryl aldehyde (2 mmol), b-ketoester (2 mmol) and
ammonium acetate (0.185 g, 2.4 mmol) in a test tube, was
added nano-Fe O (0.0232 g, 5 mol%), and the resulting
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2
3
3
3
4
mixture was rstly stirred magnetically, and aer
solidication of the reaction mixture with a small rod, at
2
ꢀ
3
3
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50 C. Aer completion of the reaction, as monitored by
TLC, the reaction mixture was cooled to room
temperature. Then, ethanol (95%) (20 mL) was added,
stirred and reuxed for 3 min. The catalyst was collected
by a magnet and separated from the solution of product
and remaining starting materials. The crude product was
puried by recrystallization from ethanol (95%). In this
work, the catalyst was recovered and reused for 12 times
without any signicant changes in the yield and the
reaction time.
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