Novel magnetic nanoparticles with ionic liquid tags as a reusable catalyst in the synthesis of polyhydroquinolines

Article abstract of DOI:10.1039/c6ra16459e

In this study, we have introduced {Fe₃O₄SiO₂(CH₂)₃Im}C(NO₂)₃ as a novel and heterogeneous reusable catalyst for the four component preparation of polyhydroquinoline derivatives under mild and eco-friendly reaction conditions. The structural confirmation of the novel heterogeneous reusable promoter was fully made using FT-IR, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS) elemental mapping analysis, high resolution transmission electron microscopy (HRTEM), thermogravimetry (TG), derivative thermal gravimetric (DTG), differential thermal (DTA) and vibrating sample magnetometer (VSM) analyses. The nanomagnetic heterogeneous catalyst was successfully applied for the synthesis of polyhydroquinoline derivatives via a four component condensation of a good range of aryl aldehydes, dimedone, ethyl acetoacetate or methyl acetoacetate as a β-ketoester, and ammonium acetate as a nitrogen source under solvent free conditions. Moreover, experimental evidence has demonstrated that {Fe₃O₄@SiO₂@(CH₂)₃Im}C(NO₂)₃ could act as a recoverable nanomagnetic and reusable catalyst without any considerable drop in the yield and the reaction time for at least eight times.

Full text of DOI:10.1039/c6ra16459e

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A novel magnetic nano particles with ionic liquids tags as a
reusable catalyst in the synthesis of polyhydroquinolines
Received 00th January 20xx,
Accepted 00th January 20xx
Meysam Yariea, Mohammad Ali Zolfigol*a, Yadollah Bayatb, Asiye Asgarib, Diego A. Alonso*c, and
Abbas Khoshnood*c
DOI: 10.1039/x0xx00000x
In this paper, we have introduced {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as a novel and heterogeneous reusable catalyst for the
four component preparation of the polyhydroquinoline derivatives under mild and eco-friendly reaction conditions. The
structural confirmation of the novel heterogeneous reusable promoter was fully made using appropriate technical skills
such as FT-IR, X-ray diffraction patterns (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive
spectroscopy (EDS) elemental mapping analysis, High Resolution transmission electron microscopy (HRTEM),
thermogravimetry (TG), derivative thermal gravimetric (DTG), differential thermal (DTA) and vibrating sample
magnetometer (VSM) analysis. The presented nano magnetic heterogeneous catalyst was successfully applied for the
synthesis of the polyhydroquinoline derivatives via a four component condensation of a good range arylaldehydes,
dimedone, ethyl acetoacetate or methyl acetoacetate as β-ketoester, and ammonium acetate as nitrogen source under
solvent free conditions. Also, the experimental evidence has demonstrated that the {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 could
act as a nano magnetically recoverable and reusable catalyst without any meaningful drop in the yield and the reaction
time at least for eight times.
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Keywords: Magnetic nano particles, {Fe3O4@SiO2@(CH2)3Im}C(NO2)3, heterogeneous reusable catalyst, trinitromethane,
nitroform, polyhydroquinoline, solvent free conditions
[4-10]. Although the widespread applications of ionic liquids,
investigations have disclosed that in some case the ionic liquids
Introduction
In recent times, development and expanding of the magnetic nano
particles (MNPs) as versatile supports be revealed as an influential
branch in the field of green chemistry due to the environmentally
benign nature of these compounds. For the reason of easy
separation of the magnetically based materials from the reaction
system, many attempts were focused for the surface modification
of them in order to construct varied heterogeneous magnetically
recoverable promoters for the organic functional transformation
[1]. Also, using nano magnetic heterogeneous catalytic systems for
promotion of the reaction, represent high catalytic performance as
in the case of the homogeneous catalysts and passed them from
the facile and efficient recovery point of view through applying a
simple external magnet and these merits led to a surprising spread
of their potential applicability's [2]. The chemistry of MNPs have
been extensively reviewed [1-3].
disadvantaged due to the toxic nature of them [11,12]. Therefore, it
is worthy that the ongoing studies impact on the enhancement of
the defects connected with conventional not safe ionic liquids and
replacing them with safer and more productive ones. Therefore, the
combination of the ionic liquids and magnetic nano particles
(MNPs) as versatile supports for the immobilization of the ionic
liquids offers several merits such as easy synthesis pathway, large
surface area, high thermal stability, facile separation from the
reaction mixture, and low toxicity and price [13].
The building up of the complex compounds with high atom and step
economy, improvement of the effectiveness and plainness in the
synthetic pathway, providing easy and straightforward approach to
library molecules and diversity-oriented synthesis (DOS) are the
principal interest of the one pot multicomponent reactions (MCRs)
and this beneficial technical protocol persuaded both academic and
industrial chemists to access molecular diversity by this way [14-
17].
On the other hand, the capabilities of the ionic liquids as reagents,
catalyst, reaction media and proper solvent for different goals in
the field of green chemistry are well documented in past few years
Recently, due to the varied pharmaceutical and biological
applications connected to the polyhydroquinolines structural motif,
a huge attention has been paid to the production of these versatile
organic compounds. Substituted 1,4-dihydropyridines are
renowned as calcium channel modulators and they can be applied
as a treatment for the therapy of the cardiovascular diseases [18].
a.Department of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University,
Hamedan, Iran. Fax: +988138257407, E-mail: zolfi@basu.ac.ir;
b.Faculty of Chemistry and chemical Engineering, Malek Ashtar University of
Technology, Tehran, Iran
cOrganic Chemistry Department and Organic Synthesis Institute, Alicante
University, Apdo. 99, 03080 Alicante, Spain. Phone: +34965909841, E-Mail:
diego.alonso@ua.es; abbas.khoshnood@ua.es
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Some biologically active species base on 1,4-dihydropyridines emission scanning electron microscopy (FESEM), elemental
moiety are illustrated in Fig. 1[19].
mapping, high resolution transmission electron microscopy
(HRTEM), thermogravimetry (TG), and vibrating sample
magnetometer (VSM) analysis.
Cl
Cl
Cl
CO2t-Bu
CO2Et
MeO2C
Me
MeO2C
Me
CO2Et
MeO2C
Me
CO2Et
NH2
O
N
Me
N
N
Me
H
H
H
Amiodipine
Felodipine
Lacidipine
NO2
O
N
N
O
O
NO2
i-PrO2C
Me
CO2Et MeO2C
Me Me
CO2Et
O
O
N
N
H
N
Me
Me
N
Me
H
H
Azelnidipine
Isradipine
Nifedipine
Fig. 1: Biologically active 1,4-dihydropyridines
Due to the above listed excellent therapeutic applications of the
1,4-dihydropyridine derivatives, synthetic chemists have explored
several protocols for the synthesis of them using different reaction
conditions and varied catalytic systems as follows: Yb(OTf)3 [20],
[pyridine-SO3H]Cl [21], [Dsim]HSO4 [22], Triton X-100 in water [23],
TiO2 NPs [24], SnO2 NPs [25], silica-bonded imidazolium-sulfonic
acid chloride [26], [2-MPyH]OTf [27], SBA-15/SO3H [28], Ni-
Scheme 1: Synthesis of polyhydroquinoline derivatives in the presence of
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3
H
N
MeO
MeO
MeO
Si
Cl
O
TEOS
N
Si
Cl
Fe3O4
SiO2
Fe3O4
O
O
Fe3O4
A
Toluene, Reflux, 12h
1. Toluene, Sonication, 2h
2. Toluene, Reflux, 12h
SiO2
B
nanoparticles [29], IL-HSO4@SBA-15 [30], Baker’s yeast [31], L-
C
proline [32], and [bmim]BF4 [33]. Although the reported methods
offer several merits and provide improvements for the synthesis of
the target molecules, many of these protocols need longer reaction
times, hard reaction conditions, using unsafe organic solvents, and
drastic workups. Therefore, surveying a newer environmentally
compatible catalytic system is still in great demand.
O2
N
NO2
NO2
Toluene, Reflux, 12h
O2
N
NO2
NO2
O
O
Si
N
Si
N
Fe3O4
SiO2
Fe3O4
O
O
O
O
N
NH
SiO2
D
E
Scheme
2:
Synthetic
pathway
for
the
preparation
of
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as a heterogeneous core-shell catalyst
In this effort, in order to explore a newer protocol to overpower the
above mentioned difficulties in the way to the production of
polyhydroquinoline derivatives and to continue our constant
investigations on the knowledge-based maturation of the design,
construction and applications of ionic liquids [34], molten salts [35],
nano catalysts, magnetic nano particles (MNPs) [36], magnetic nano
particles with ionic liquid tags [37], and trinitromethane [38] for
organic functional group transformations, we wish to report the
design, synthesis and applicability of a novel nano magnetically
As depicted in Fig. 2, the FT-IR spectrum of the novel nano magnetic
heterogeneous core-shell catalyst in comparison with different step
by step synthetic pathway compounds from Fe3O4@SiO2 to
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 was investigated in the range of
400-4000 cm-1. The overall differences in the FT-IR spectrums can
be used as
a proof for the preparation of the novel nano
magnetically recoverable and reusable promoter catalyst. According
to the FT-IR spectrum, the two peaks discerned at 1394 and 1592
cm-1 can be attributed to the nitro functional groups in the
structure of the prepared catalyst. Furthermore, the overlapping of
the uncoated hydroxyl groups and N-H stretching mode in the
imidazolium ring has caused a broad peak in the region of about
2900-3700 cm-1.
recoverable
and
reusable
promoter
catalyst
namely
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 at the preparation of the
polyhydroquinolines through a four component condensation of
several arylaldehydes, dimedone, ethyl acetoacetate or methyl
acetoacetate as β-ketoester, and ammonium acetate as a nitrogen
source under mild and solvent free conditions (Schemes 1 and 2).
In a comparative manner, for the investigation of the purity and the
phase of the applied materials for the synthesis of the presented
catalyst, the X-ray diffraction patterns (XRD) of the different
stepwise prepared materials were explored and the attained data
were collected in Fig. 3. From the XRD patterns, it can be deduced
that the addition of each layer to the surface of the Fe3O4
Characterization of the novel catalyst
The structural verification of the novel nano magnetically
recoverable
and
reusable
promoter
namely
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 were made using appropriate
technical skills such as FT-IR, X-ray diffraction patterns (XRD), field
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nanoparticles lead to a change compare with the previous stage In another assay, for the investigation of the size and morphology of
which is an indication of the synthesis of the novel nano magnetic the novel catalyst, field emission scanning electron microscopy
core-shell catalyst. The X-ray diffraction pattern of the prepared (FESEM) images were obtained (Figures 4 a-c). As the recorded
catalyst confirmed that it has a crystalline nature with diffraction FESEM images show, the size of the catalyst particles is in the
lines at 2θ= 13.35o, 16.30o and 24.90o. In another study, according nanometer scale being between 19.6 and 53.7 nm.
to the Scherrer equation D= Kλ/(β cos θ), where λ is the X-ray
wavelength, K the Scherrer constant, β the peak width of half
(a)
maximum and
θ the Bragg diffraction angle, the XRD data
comprising 2θ value, peak width, size of particles and interplanar
distance, were extracted and embedded in Table 1.
255
1592 cm-1
1394 cm-1
Novel catalyst
2900-3700 cm-1
205
155
105
55
Fe3O4@SiO2@(CH2)3Im
Fe3O4@SiO2@(CH2)3Cl
Fe3O4@SiO2
(b)
3400
2900
2400
1900
1400
900
400
Fig. 2: FT-IR spectrum of the novel nano magnetic heterogeneous catalyst in
comparison with different stepwise synthetic pathway materials
(c)
1000
900
800
700
600
500
Novel catalyst E
400
300
200
100
0
D
Fig. 4. (a,b) Field emission scanning electron microscope (FESEM) images of
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as a new nano magnetic core-shell catalyst.
Inset (c) expansion of image b.
C
B
A
7
17
27
37
47
57
67
77
Moreover, in order to explore the elemental composition of the
catalyst {Fe3O4@SiO2@(CH2)3Im}C(NO2)3, an energy-dispersive
spectroscopy (EDS) elemental mapping analysis was conducted
(Figure 5a-5g). Examination of the SEM-EDS mapping images, which
are shown in Figures 5b-5g), proved the presence of Si, Fe, N, O,
and C elements in the catalyst. As shown in Figures 5b-5f, the
elements were well distributed in the catalyst surface.
2θ degree
Fig. 3. XRD pattern of the new catalyst and comparison with the different
stepwise synthesized intermediates.
Table 1: XRD extracted data related to novel presented nano magnetic
catalyst
Peak width [FWHM]
(degree)
Size
Inter planar
Entry
2θ
[nm]
distance [nm]
1
2
3
13.35
16.30
24.90
0.68
0.64
0.80
11.76
12.54
10.17
0.662439
0.543152
0.357164
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(a)
(b)
Si
(c)
(d)
Fe
N
Fig. 6. Energy dispersive X-ray (EDX) spectrum of the new heterogeneous
catalyst.
(e)
(f)
High Resolution transmission electron microscopy (HRTEM) images
of {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 were recorded and illustrated to
obtain in more detail structural information of the catalyst. As
depicted in Figures 8a and 8b, all the nanoparticles presented well-
defined uniform spherical shapes, highly dispersed by the ionic
liquid tags over Fe3O4NPs after sonication in ethanol. As shown in
the HRTEM image (Figures 8a-8c), amorphous silica coating layers
over the crystalline nanoparticles of Fe3O4NPs are clearly revealed
at low or high magnification of HRTEM. According to Fig. 8c, the
thickness of silica shell (@SiO2@(CH2)3Im}C(NO2)3) is around 2 to 3
nm with an interplanar crystalline spacing value of Fe3O4NPs around
0.50 nm Figure 7. Moreover, it is worthy to mention that the
obtained images from both FESEM and HRTEM analyses are in good
agreement with XRD extracted data.
O
C
(g)
~ 0.50 nm
Fig. 5. (a) SEM image, and SEM-EDS elemental mapping images of (b) Silicon
(red), (c) Iron (green), (d) Nitrogen (blue), (e) Oxygen (cyan), (f) Carbon
(purple) and (g) overlapping of Si, Fe, N, O,
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3
C elements in
The collected data from energy dispersive X-ray (EDX) analysis of
the new heterogeneous catalyst showed all predicted elements in
the structure of the catalyst, namely iron, silicon, oxygen, carbon,
and nitrogen as indicated in Figure 6. Besides, SEM-coupled EDX
data for the presented catalyst derive that it derive C (0.53), N (.27), Fig. 7. Average of crystalline distance layer of Fe3O4NPs in
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3
Fe (93.56), O (4.64) and Si (0.99).
4 | J. Name., 2012, 00, 1-3
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(a)
(c)
(b)
0.50 nm
Fig. 8. HRTEM images of the {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 (a,b), and magnified HRTEM images of one nano particle (c).
Fig. 9. Thermal gravimetric (TG), derivative thermal gravimetric (DTG), and
differential thermal (DTA) analyses of the novel core-shell catalyst.
In order to investigate the thermal stability of the novel nano
magnetic catalyst, thermal gravimetric (TG), derivative thermal
gravimetric (DTG), and differential thermal (DTA) analyses were
conducted (Figure 9). From the performed studies, it could be
inferred that the main weight loss upon heating from ambient
temperature to about 100 oC can be attributed to the evaporation
of the physically adsorbed water and other organic solvents used
during the catalyst preparation. Weight loss at around 210 oC is due
to thermal decomposition of the ionic tag of the catalyst. Finally,
decomposition of the catalyst occurred between 300-550 oC. Also,
the study of the DTA analysis diagram revealed that it is downward
and exothermic.
In another exploration and in order to study the magnetic
properties of the new catalyst, the vibrating sample magnetometer
(VSM) analysis of the catalyst was compared with nano magnetic
Fe3O4 (Figure 10). By investigation the obtained magnetization
curves data, it was disclosed that the saturation of the
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as catalyst reduced from 52.42 emu
g-1 for Fe3O4 nano particles to 37.48 emu g-1. This decrease can be
related to surface modification of the Fe3O4 nano particles during
the preparation of the catalyst.
60
10
8
3400
3350
3300
3250
3200
3150
3100
3050
3000
45
Fe3O4
30
6
Catalyst
4
15
0
DTA( uV)
DTG(ug/mg)
TG(ug)
2
-10000 -8000 -6000 -4000 -2000
0
2000 4000
6000 8000 10000
0
-15
-30
-45
-60
0
100
200
300
400
500
-2
-4
-6
-8
-10
Fig. 10. VSM magnetization curves of catalyst compare with Fe3O4 nano
particles
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After approving of the presented nano magnetic catalyst using the ethylacetoacetate, and ammonium acetate was picked up as test
aforementioned technical skills, the applicability of the described reaction. The resulting data for the optimization of temperatures,
catalyst was explored for the synthesis of polyhydroquinoline catalyst loadings, and solvents exhibited that the best results were
derivatives through a four component condensation of several acquired when the reaction was carried out under solvent-free
arylaldehydes, dimedone, ethyl acetoacetate or methyl conditions
in
the
presence
of
7
mg
of
acetoacetate as β-ketoester, and ammonium acetate as a nitrogen {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as catalyst at 80 oC (Table 2, Entry
source. For this goal, and in order to achieve the optimized reaction 4). The related obtained data for the optimization of the reaction
conditions, the condensation of 4-chlorobenzaldehyde, dimedone, conditions is included in Tale 2.
Table 2: Optimization of reaction conditions for the synthesis of polyhydroquinolines.a
Entry
Solvent
Load of catalyst (mg)
Temperature (oC)
Time (min)
Yield (%)b
1
2
3
4
5
6
7
8
9
-
10
10
10
7
100
80
15
16
25
18
22
60
80
70
80
93
92
85
92
87
54
55
35
60
-
-
60
-
80
-
-
4
80
-
80
EtOAc
n-Hexane
CH3CN
7
Reflux
Reflux
Reflux
7
7
10
11
EtOH
H2O
7
7
Reflux
Reflux
90
90
90
78
a Reaction conditions: 4-chlorobenzaldehyde (1 mmol, 0.144 g), dimedone (1 mmol, 0.140 g), ethyl acetoacetate (1 mmol, 0.130 g),
ammonium acetate (3 mmol, 0.231 g). b Isolate yield.
After appraisal of the appropriate reaction conditions, we
studied the scope and productivity of the presented process for
the synthesis of biologically active target molecules in the
presence of {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as a heterogeneous
recoverable catalyst. Thus, polyhydroquinoline derivatives were
prepared via a four component reaction of a wide range of
aromatic aldehydes bearing electron-withdrawing and electron-
releasing groups, ethyl acetoacetate or methyl acetoacetate,
dimedone, and ammonium acetate under solvent free
conditions. The obtained results are displayed in Table 3.
Table 3: Synthesis of the polyhydroquinolines in the presence of {Fe3O4@SiO2@(CH2)3Im}C(NO2)3.a
Product
X
Y
Time (min)
18
Yield (%)b
92
M. p (oC) found [Lit]ref
243-245 [242-244]36c
1a
4-Cl
OEt
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1b
1c
1d
1e
1f
H
2,4-Cl2
4-OMe
3-Br
OEt
OEt
19
16
18
18
20
17
16
18
22
14
15
17
18
17
19
22
18
17
17
91
93
90
91
94
90
92
90
88
92
95
93
89
90
90
91
91
92
90
224-226 [224-226] 36c
244-246 [242-244] 36c
255-257 [255-257]36c
206-208[229-231]26
207-209 [208-209]39
263-265 [263-265]36c
205-207 [204-206]36c
193-195 [193-195]36c
242-243 [241-242]36c
249-251 [248-250]41
195-196 [190-192]36c
231-234 [230-232]36c
257-258 [219-222]40
259-261 [257-259]26
261-263 [263-264]42
251-253 [250-252] 42
254-257 [256-259]26
297-298 [232-234]26
270-273 [283-285]23
OEt
OEt
2-Cl
OEt
1g
1h
1i
4-Me
3,4-(OMe)2
4-F
OEt
OEt
OEt
1j
4-NO2
2-OMe
3-OEt-4-OH
3-OH
OEt
1k
1l
OEt
OEt
1m
1n
1o
1p
1q
1r
OEt
4-Cl
OMe
OMe
OMe
OMe
OMe
OMe
OMe
H
4-Br
2,4-Cl
4-OMe
4-OH
1s
1t
4-Me
aReaction conditions: aromatic aldehyde (1 mmol,), dimedone (1 mmol, 0.140 g), ethyl acetoacetate or methyl acetoacetate (1 mmol),
ammonium acetate (3 mmol, 0.231g). b Isolated yields.
One of the excellent merits connected with nano magnetic
8
7
heterogeneous core-shell catalysts is the recycling possibility
6
5
and easy separation of them from the reaction mixture in a
4
3
catalyzed system after completion of the reaction. In order to
2
1
demonstrate the reusability of our catalyst, the reaction of
benzaldehyde, dimedone, ethyl acetoacetate, and ammonium
0
10
20
30
40
acetate was preferred as a model process. After performance of
50
60
70
80
90
each run, hot ethanol was added to the reaction mixture to
1
2
3
4
5
6
7
8
dissolve the crude product. Then, the nano magnetic catalyst
was separated from the reaction mixture by applying an external
magnet. The catalyst was reused for the next run after washing
it with ethanol and drying. As depicted in Figure 11, the catalytic
activity of {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 was conserved for
eight consecutive runs without any discernible reduction.
Yield (%)
91
91
90
90
89
89
88
87
Time (min)
19
19
19
19
20
20
21
22
Fig. 11. Reusability test of the {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as a novel
nano magnetic catalyst
Finally, as embedded in Table 4, the catalytic activity of
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 was compared with some
previously investigated recoverable catalysts. As depicted, it can
be deduced that the previously reported methods suffer from
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different drawbacks such as, elevated temperatures, use of
organic solvents and/or transition metal catalyst, activation by
sonication irradiation, longer reaction times, or harsh reaction
conditions.
(XRD), field emission scanning electron microscopy (FESEM),
high Resolution transmission electron microscopy (HRTEM),
thermogravimetry (TG), derivative thermal gravimetric (DTG),
differential thermal (DTA), and vibrating sample magnetometer
(VSM)
analyses.
The
catalytic
performance
of
Table 4: Catalytic activity of presented nano magnetic catalyst
compared with some other recoverable catalysts for the
synthesis of compound 1b
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 was successfully explored in the
four component preparation of polyhydroquinoline derivatives
under mild and eco-friendly reaction conditions. The
encouraging points of this study are the eco-friendly and mild
reaction conditions, easy separation and reusability of the
catalyst, short reaction times with high products yields, and also
easy work-up.
Entry Reaction conditions
Time
Yield Lit.
(min) (%)
1
[TBA]2[W6O19] (7 mol%), Solvent- 20
93
43
free, 110 oC
2
3
Trifluoroethanol (TFE), 70 oC
180
98
97
44
45
Fe3O4-SA-PPCA (10 mg), EtOH, 50 120
oC
4
5
6
7
8
9
Mn@PMO-IL (1 mol%), Solvent-
free, 80 oC
20
95
97
96
90
89
95
46
47
48
49
50
51
Co3O4-CNTs (0.03 g), EtOH, 50 oC, 15
Sonication
Nafion-H®, PEG 400-water
(60:40), 50 oC
90
20
6
(bzacen)MnCl (2.5 mol%), EtOH,
Reflux
Nano-Fe3O4 (5 mol%), Solvent-
free, 50 oC
Nanocat Fe-Ce (100 mg), EtOH,
20
r.t.
10
Hf(NPf2)4 (1 mol%), C10F18, 60 oC
180
19
95
91
52
-
This
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3
work (7 mg), Solvent-free, 80 oC
A
suggested mechanistic pathway for the synthesis of
polyhydroquinoline derivatives is portrayed in Figure 12, where
initially the in-situ generated NH3 form ammonium acetate
reacts with activated β-ketoster to yield the corresponding
intermediate 2. On the other hand, in the presence of the novel
nano magnetic catalyst, dimedone is converted to its enol form
Fig. 12. Suggested catalytic mechanism for the synthesis of target
molecules
which performs
a nucleophilic addition to the activated
Exprimental:
General
arylaldehyde, providing the corresponding knoevenagel adduct
3. Then, the reaction between these two intermediates
generates intermediate 4. Tautomerization of 4 leads to the
Solvents and reagents were purchased from Sigma- Aldrich, Alfa
Aesar, and Merck and were used without further purification.
Melting points were obtained with a Amstrad/electrothermal
apparatus. 1H NMR (400 MHz) and 1H NMR (300 MHz) spectra
were recorded on a Bruker Avance 400 and a Bruker Avance 300
NMR spectrometers, respectively, in proton coupled mode
formation of derivative
5 which suffers an intramolecular
nucleophilic attack of the amino group to the activated carbonyl
group providing intermediate 6. Finally, dehydration of this
intermediate forms the desired target molecules 1a-t.
using, unless otherwise stated, deuterated DMSO as solvent. 13
C
Conclusion
NMR (101 MHz) spectra were recorded on Bruker Avance 400
NMR spectrometer, in proton decoupled mode at 20 oC in
deuterated DMSO as solvent, unless otherwise stated; chemical
shifts are given in δ (parts per million) and the coupling
constants (J) in Hertz. 19F NMR (282 MHz) spectra were recorded
on a Bruker Avance 300 NMR spectrometer, in proton coupled
In this study, the design and synthesis of
heterogeneous reusable catalyst
a
novel and
namely
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 has been reported. The
structure of the presented catalyst was fully characterized using
proper techniques such as, FT-IR, X-ray diffraction patterns
8 | J. Name., 2012, 00, 1-3
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mode. Infrared spectra were recorded with an FT-IR 4100 LE
(JASCO, Pike Miracle ATR) spectrometer. HRTEM was carried out
on a high Resolution transmission electron microscope JEOL
JEM-2010. This microscope is equipped with an X-ray detector
OXFORD INCA Energy TEM 100 for microanalysis (EDS). The
acquisition of the images was performed using a GATAN ORIUS
SC600 digital camera mounted on-axis, integrated with the
program GATAN Digital Micrograph 1.80.70 for GMS 1.8.0. Field
emission scanning electron microscope (FESEM) images were
recorded on a Merlin VP Compact from Zeiss equipped with an
EDS microanalysis system Quantax 400 from Bruker. The
resolution was 0.8 nm at 15 kV and 1.6 nm at 1 kV. Field
emission equipment is able to work at very reduced voltages
(from 0.02 kV to 30 kV) allowing to observe beam sensitive
samples without damaging them and minimizing the charging
effects. Scanning electron microscope (SEM) studies were
added to compound C dispersed in toluene. The resulting
mixture was refluxed for 12 h. Finally, trinitromethane (6 mmol,
0.906 g) was added to compound D in toluene and the obtained
reaction mixture was stirred for 12 h in refluxing toluene to form
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 (E) as a reusable nano magnetic
core-shell catalyst with a ionic tag (Scheme 2).
General procedure for the synthesis of
polyhydroquinolines as target molecules (Scheme 1)
To a round bottom flask containing a mixture of aromatic
aldehyde (1 mmol), dimedone (1 mmol, 0.14 g), ethyl
acetoacetate or methyl acetoacetate as β-ketoster (1 mmol),
and ammonium acetate as a nitrogen source (3 mmol, 0.23 g), 7
mg of {Fe3O4@SiO2@(CH2)3Im}C(NO2)3 were added as MNPs@IL
catalyst. Then, the reaction mixture was stirred at 80 oC for
adequate times under solvent-free conditions as embedded in
Table 3. After accomplishment of the reactions, as monitored by
TLC (n-hexane/ethyl acetate), the reaction mixture was cooled
to ambient temperature. Afterwards, in order to separate and
recover the catalyst, hot ethanol was added to the mixture to
dissolve the desired products and un-reacted starting materials.
The catalyst was insoluble in hot ethanol and easily separated
from the reaction mixture by utilizing an external magnet.
Finally, the target products were recrystallized from ethanol
with high to excellent yields as inserted in Table 3.
performed on
a Hitachi S3000N, equipped with an X-ray
detector Bruker XFlash 3001 for microanalysis (EDS) and
mapping. The scanning microscope is able to work in variable
pressure mode for observation of nonconductive specimens
without coating with any conductive material. Low-resolution
mass spectra (EI) were obtained at 70 eV with an Agilent 5973
Network spectrometer, with fragment ions m/z reported with
relative intensities (%) in parentheses. HRMS analyses were
carried out on Agilent 7200 (Q-TOF) spectrometers. Magnetic
measurements were performed using vibration sample
magnetometry VSM, (MDK Co. Kashan, Iran) analysis. TG-DTA
analyses were carried out on a METTLER TOLEDO equipment,
model TGA/SDTA851 and /SF/1100 TG-DTA. X-ray diffraction
(XRD) analysis was performed using a Bruker D8-Advance
apparatus with mirror Goebel (non-planar samples) equipped
with a high temperature Chamber (up to 900°C), a generator of
x-ray KRISTALLOFLEX K 760-80F (power: 3000W, voltage: 20-
60KV and current: 5-80mA), and a tube of RX with copper
anode. Preparative thin-layer chromatography was carried on
laboratory made TLC glass plates with silica gel 60 PF254
(Merck). Column chromatography was performed using silica gel
60 of 40–60 microns (hexane/EtOAc as eluent).
Spectral data
Ethyl
4-(4-chlorophenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1a)36c
melting point: 243-245 oC; FT-IR (KBr): υ(cm-1) = 3277, 3207,
3078, 2967, 1706, 1648, 1605, 1489, 1382, 1214; 1H NMR (400
MHz) δ 9.08 (br. s, 1H), 7.22 (s, 2H), 7.14 (s, 2H), 4.82 (s, 1H),
3.95 (m, 2H), 2.45 (d, J = 17.0, 1H), 2.35-2.25 (m with s at 2.27,
4H), 2.15 (d, J = 15.5, 1H), 1.96 (d, J = 15.5, 1H), 1.10 (br. s, 3H),
0.99 (s, 3H), 0.81 (s, 3H); 13C NMR (101 MHz) δ 194.7, 167.1,
150.0, 147.0, 145.8, 130.6, 129.7, 128.1, 110.1, 103.5, 59.5, 50.6,
36.0, 32.5, 29.5, 26.8, 18.7, 14.5; MS (EI) m/z (%): 375 (M++2, 5),
373 (M+, 14), 262.1 (100), 234 (20); TOF-HRMS (EI): m/z (M)+
calcd for C21H24ClNO3 373.1445; found 373.1428.
Ethyl
2,7,7-trimethyl-5-oxo-4-phenyl-1,4,5,6,7,8-
hexahydroquinoline-3-carboxylate: (1b) 36c
Synthetic Procedures
melting point: 224-226 oC; FT-IR (KBr): υ(cm-1) = 3289, 3216,
3081, 2962, 1701, 1614, 1485, 1382, 1212 ; 1H NMR (400 MHz) δ
9.03 (br. s, 1H), 7.15 (s, 4H), 7.05 (s, 1H), 4.85 (s, 1H), 3.96 (m,
2H), 2.41 (d, J = 17.0, 1H), 2.35-2.20 (m with s at 2.27, 4H), 2.15
(d, J = 16.0, 1H), 1.96 (d, J = 16.0, 1H), 1.11 (s, 3H), 1.00 (s, 3H),
0.83 (s, 3H); 13C NMR (101 MHz) δ 194.7, 167.3, 149.9, 148.1,
145.4, 128.1, 127.9, 126.1, 110.4, 104.1, 59.5, 50.7, 36.3, 32.6,
29.6, 26.9, 18.7, 14.6; MS (EI) m/z (%): 339 (M+, 13), 262 (100),
234 (20); TOF-HRMS (EI): m/z (M)+ calcd for C21H25NO3 339.1834;
found 339.1863.
General procedure for the preparation of novel silica-
coated magnetic nanoparticles with tags of ionic liquid
(Scheme 2)
At first, the Fe3O4 nanoparticles were synthesized according to a
previously reported method [53]. Then, the surface of the Fe3O4
nano particles was modified with a layer of SiO2 by treating with
tetraethyl orthosilicate (TEOS) to form compound B. In the next
step, silanization of the Fe3O4@SiO2 (B) by reaction with 3-
chloropropyltrimethoxysilane in refluxing toluene afforded
compound C. Subsequently, 6 mmol (0.408 g) of imidazole was
Ethyl
4-(2,4-dichlorophenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1c) 36c
melting point: 244-246 oC; FT-IR (KBr): υ(cm-1) = 3283, 3208,
1
3078, 2958, 1706, 1648, 1610, 1495; H NMR (400 MHz) δ 9.11
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Journal Name
(s, 1H), 7.33 (s, 1H), 7.27 (s, 2H), 5.14 (s, 1H), 3.93 (m, 2H), 2.41
(d, J = 17.1, 1H), 2.30-2.20 (m with s at 2.24, 4H), 2.13 (d, J =
16.1, 1H), 1.91 (d, J = 16.0, 1H), 1.07 (t, J = 6.8, 3H), 0.99 (s, 3H),
0.83 (s, 3H); 13C NMR (101 MHz) δ 194.3, 167.0, 150.3, 145.9,
144.7, 133.3, 133.2, 131.2, 128.6, 127.3, 109.7, 103.2, 59.5, 50.6,
35.2, 32.4, 29.5, 26.8, 18.7, 14.5; MS (EI) m/z (%): 411 (M++4, 1),
409 (M++2, 5), 407 (M+, 9), 372 (14), 262 (100), 234 (19); TOF-
HRMS (EI): m/z (M)+ calcd for C21H23Cl2NO3 407.1055; found
407.1062.
melting point: 205-207 oC; FT-IR (KBr): υ(cm-1) = 3280, 3213,
3081, 2941, 1696, 1605, 1514; 1H NMR (300 MHz, EtOH-d6) δ
6.80 (d, J = 1.2 Hz, 1H), 6.72-6.53 (m, 2H), 4.83 (s, 1H), 3.94 (q, J
= 7.1, 2H), 3.66 (s, 3H), 3.63 (s, 3H), 2.35 (d, J = 17.0 Hz, 1H),
2.29-2.19 (m with s at 2.26, 4H), 2.13 (d, J = 16.4 Hz, 1H), 1.98 (d,
J = 16.4 Hz, 1H), 1.09 (t, J = 7.1 Hz, 3H), 0.97 (s, 3H), 0.82 (s, 3H);
13C NMR (101 MHz) δ 194.7, 167.3, 149.7, 148.3, 147.3, 144.9,
140.8, 119.6, 112.0, 111.8, 110.4, 104.2, 59.4, 55.7, 55.6, 50.6,
35.5, 32.5, 29.6, 26.8, 18.6, 14.6; MS (EI) m/z (%): 399 (M+, 33),
370 (10), 262 (100), 234 (21); TOF-HRMS (EI): m/z (M)+ calcd for
C23H29NO5 399.2046; found 399.2056.
Ethyl
4-(4-methoxyphenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1d) 36c
melting point: 255-257 oC; FT-IR (KBr): υ(cm-1) = 3277, 3202,
Ethyl
4-(4-fluorophenyl)-2,7,7-trimethyl-5-oxo-
1
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1i) 36c
3078, 2957, 1701, 1649, 1606, 1496; H NMR (400 MHz) δ 8.99
melting point: 193-195 oC; FT-IR (KBr): υ(cm-1) = 3291, 3219,
3078, 2959, 1702, 1607, 1487, 1382, 1212, 853, 531; 1H NMR
(400 MHz) δ 9.06 (s, 1H), 7.14 (m, 2H), 6.99 (m, 2H), 4.83 (s, 1H),
3.96 (m, 2H), 2.40 (d, J = 17.1, 1H), 2.34 – 2.20 (m with s at 2.28,
4H), 2.15 (d, J = 15.8, 1H), 1.96 (d, J = 15.9, 1H), 1.10 (s, 3H), 0.99
(s, 3H), 0.82 (s, 3H); 13C NMR (101 MHz) δ 194.7, 167.2, 160.8 (d,
J = 241.2), 149.9, 145.6, 144.3, 129.6 (d, J = 8.0), 114.8 (d, J =
21.0), 110.4, 103.9, 59.5, 50.6, 35.7, 32.6, 29.5, 26.9, 18.7, 14.6;
MS (EI) m/z (%): 357 (M+, 21), 262 (100), 234 (22); 19F NMR (282
MHz, DMSO) δ -115.39; TOF-HRMS (EI): m/z (M)+ calcd for
C21H24FNO3 357.1740; found 357.1746.
(s, 1H), 7.04 (d, J = 8.2, 2H), 6.73 (d, J = 8.2, 2H), 4.78 (s, 1H),
3.96 (q, J = 6.9, 2H), 3.66 (s, 3H), 2.40 (d, J = 17.0, 1H), 2.35-2.20
(m with s at 2.26, 4H), 2.15 (d, J = 16.0, 1H), 1.96 (d, J = 16.0,
1H), 1.13 (t, J = 6.9, 3H), 1.00 (s, 3H), 0.84 (s, 3H); 13C NMR (101
MHz) δ 194.7, 167.4, 157.7, 149.6, 145.0, 140.5, 128.8, 113.5,
110.6, 104.4, 59.4, 55.3, 50.7, 35.4, 32.5, 29.6, 26.9, 18.7, 14.6;
MS (EI) m/z (%): 369 (M+, 33), 340 (13), 296 (11), 262 (100), 234
(21); TOF-HRMS (EI): m/z (M)+ calcd for C22H27NO4 369.1940;
found 369.1950.
Ethyl
4-(3-bromophenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1e)26
melting point: 206-208 oC; FT-IR (KBr): υ(cm-1) = 3273, 3073,
2958, 1702, 1604, 1489, 1380, 1211, 1071, 769; 1H NMR (400
MHz) δ 9.12 (s, 1H), 7.32 – 7.22 (m, 2H), 7.20 – 7.08 (m, 2H),
4.82 (s, 1H), 4.05-3.90 (m, 2H), 2.42 (d, J = 17.2, 1H), 2.38-2.25
(m with s at 2.29, 4H), 2.17 (d, J = 16.2, 1H), 1.99 (d, J = 15.8,
1H), 1.12 (t, J = 6.8, 3H), 1.00 (s, 3H), 0.85 (s, 3H); 13C NMR (101
MHz) δ 194.7, 167.0, 150.7, 150.3, 146.0, 130.8, 130.5, 129.0,
127.0, 121.5, 109.9, 103.4, 59.6, 50.6, 36.5, 32.6, 29.5, 26.8,
18.8, 14.5; MS (EI) m/z (%): 419 (M++ 2, 6), 417 (M+, 6), 262
(100), 234 (23); TOF-HRMS (EI): m/z (M)+ calcd for C21H24BrNO3
417.0940; found 417.0933.
Ethyl 2,7,7-trimethyl-4-(4-nitrophenyl)-5-oxo-1,4,5,6,7,8-
hexahydroquinoline-3-carboxylate: (1j) 36c
melting point: 242-243 oC; FT-IR (KBr): υ(cm-1) = 3274, 3189,
3076, 2966, 1703, 1649, 1609, 1493, 1349, 1215; 1H NMR (400
MHz) δ 9.22 (s, 1H), 8.09 (d, J = 8.5, 2H), 7.41 (d, J = 8.5, 2H),
4.96 (s, 1H), 3.96 (q, J = 6.9, 2H), 2.43 (d, J = 17.1, 1H), 2.35-2.25
(m with s at 2.31, 4H), 2.18 (d, J = 16.2, 1H), 1.97 (d, J = 16.2,
1H), 1.10 (t, J = 7.0, 3H), 1.00 (s, 3H), 0.81 (s, 3H); 13C NMR (101
MHz) δ 194.7, 166.8, 155.4, 150.5, 146.6, 146.1, 129.2, 123.6,
109.5, 102.8, 59.7, 50.5, 37.1, 32.6, 29.4, 26.9, 18.8, 14.5; MS
(EI) m/z (%): 384 (M+, 15), 262 (100), 234 (22); TOF-HRMS (EI):
m/z (M)+ calcd for C21H24N2O5 384.1685; found 384.1692.
Ethyl
4-(2-chlorophenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1f)39
melting point: 207-209 oC; FT-IR (KBr): υ(cm-1) = 3277, 3210,
3073, 2957, 1701, 1649, 1606, 1496, 1380; 1H NMR (400 MHz) δ
9.07 (s, 1H), 7.28 (d, J = 6.8, 1H), 7.24-7.12 (m, 2H), 7.06 (t, J =
7.0, 1H), 5.18 (s, 1H), 3.98-3.87 (m, 2H), 2.41 (d, J = 17.0, 1H),
2.32-2.20 (m with s at 2.24, 4H), 2.13 (d, J = 16.1, 1H), 1.91 (d, J =
16.1, 1H), 1.07 (t, J = 7.1, 3H), 1.00 (s, 3H), 0.84 (s, 3H); 13C NMR
(101 MHz) δ 194.3, 167.2, 150.1, 145.6, 145.4, 132.4, 131.9,
129.4, 127.7, 127.1, 110.0, 103.7, 59.4, 50.7, 35.4, 32.4, 29.6,
26.8, 18.6, 14.5; MS (EI) m/z (%): 375 (M++2, 7), 373 (M+, 22),
338 (39), 262 (100), 234 (48); TOF-HRMS (EI): m/z (M)+ calcd for
C21H24ClNO3 373.1445; found 373.1457.
Ethyl
4-(2-methoxyphenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1k)41
melting point: 249-251 oC; FT-IR (KBr): υ(cm-1) = 3284, 3078,
2964, 1689, 1623, 1611, 1488, 1361, 1215, 751; 1H NMR (300
MHz, EtOH-d6) δ 7.15 (d, J = 7.0, 1H), 6.93 (t, J = 7.4, 1H), 6.79-
6.56 (m, 2H), 5.06 (s, 1H), 3.87 (q, J = 7.0, 2H), 3.65 (s, 3H), 2.32
(d, J = 17.0, 1H), 2.26-2.15 (m with s at 2.18, 4H), 2.14-1.97 (m,
1H), 1.91 (d, J = 16.4, 1H), 1.10-0.90 (m, 6H), 0.80 (s, 3H); 13C
NMR (101 MHz) δ 193.8, 167.3, 157.1, 149.9, 144.1, 134.9,
130.5, 126.9, 119.4, 111.0, 108.6, 102.9, 58.7, 55.1, 50.4, 32.8,
32.0, 29.3, 26.2, 18.0, 14.1; MS (EI) m/z (%): 369 (M+, 61), 340
(37), 262 (100), 234 (31); TOF-HRMS (EI): m/z (M)+ calcd for
C22H27NO4 369.1940; found 369.1946.
Ethyl
2,7,7-trimethyl-5-oxo-4-(p-tolyl)-1,4,5,6,7,8-
hexahydroquinoline-3-carboxylate: (1g) 36c
Ethyl
4-(3-ethoxy-4-hydroxyphenyl)-2,7,7-trimethyl-5-
melting point: 263-265 oC; FT-IR (KBr): υ(cm-1) = 3276, 3208,
3078, 2958, 1702, 1648, 1606, 1493, 1282; 1H NMR (400 MHz) δ
8.99 (s, 1H), 7.15-6.90 (m, 4H), 4.79 (s, 1H), 3.95 (m, 2H), 2.39 (d,
J = 17.1, 1H), 2.36-2.10 (m with 2s at 2.25 and 2.18, 8H), 1.95 (d,
J = 16.0, 1H), 1.12 (s, 3H), 0.99 (s, 3H), 0.83 (s, 3H); 13C NMR (101
MHz) δ 194.7, 167.3, 149.8, 145.2 (2c), 135.0, 128.7, 127.8,
110.5, 104.2, 59.4, 50.7, 35.8, 32.6, 29.6, 26.9, 21.0, 18.7, 14.6;
MS (EI) m/z (%): 353 (M+, 18), 262 (100), 234 (18); TOF-HRMS
(EI): m/z (M)+ calcd for C22H27NO3 353.1991; found 353.2005.
oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1l)36c
melting point: 195-196 oC; FT-IR (KBr): υ(cm-1) = 3443, 3282,
3200, 3079, 2959, 1657, 1616, 1493, 1381; 1H NMR (300 MHz,
EtOH-d6) δ 6.74 (s, 1H), 6.52 (s, 2H), 4.79 (s, 1H), 4.02-3.81 (m,
4H), 2.33 (d, J = 17.0, 1H), 2.28-2.18 (m with s at 2.25, 4H), 2.12
(d, J = 16.5, 1H), 1.98 (d, J = 16.4, 1H), 1.27 (t, J = 7.0, 3H), 1.08
(t, J = 7.1, 3H), 0.96 (s, 3H), 0.81 (s, 3H); 13C NMR (101 MHz) δ
194.8, 167.4, 149.6, 146.2, 145.3, 144.8, 139.4, 120.1, 115.4,
113.9, 110.6, 104.5, 64.2, 59.4, 50.7, 35.4, 32.5, 29.6, 26.8, 18.7,
15.2, 14.6; MS (EI) m/z (%): 399 (M+, 30), 370 (11), 262 (100),
Ethyl
4-(3,4-dimethoxyphenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1h) 36c
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234 (19); TOF-HRMS (EI): m/z (M)+ calcd for C23H29NO5 399.2046;
found 399. 2048.
(%): 397 (M++4, 1), 395 (M++2, 5), 393 (M+, 7), 358 (15), 248
(100); TOF-HRMS (EI): m/z (M)+ calcd for C20H21Cl2NO3 393.0898;
found 393.0910.
Ethyl
4-(3-hydroxyphenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1m) 36c
melting point: 231-234 oC; FT-IR (KBr): υ(cm-1) = 3463, 3291,
2961, 1669, 1620, 1487, 1381, 1277, 1216; 1H NMR (400 MHz) δ
9.05 (s, 1H), 9.00 (s, 1H), 6.94 (t, J = 7.7, 1H), 6.59-6.56 (m, 2H),
6.45 (d, J = 7.3, 1H), 4.78 (s, 1H), 3.98 (q, J = 7.0, 2H), 2.40 (d, J =
17.0, 1H), 2.32-2.25 (m with s at 2.27, 4H), 2.16 (d, J = 16.1, 1H),
1.99 (d, J = 16.1, 1H), 1.14 (t, J = 7.1, 3H), 1.00 (s, 3H), 0.87 (s,
3H); 13C NMR (101 MHz) δ 194.7, 167.4, 157.3, 149.9, 149.4,
145.1, 128.9, 118.6, 115.0, 113.1, 110.4, 104.1, 59.5, 50.8, 36.1,
32.5, 29.6, 27.0, 18.7, 14.6; MS (EI) m/z (%): 355 (M+, 13), 262
(100), 234 (20); TOF-HRMS (EI): m/z (M)+ calcd for C21H25NO4
355.1784; found 355.1792.
Methyl
4-(4-methoxyphenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1r)26
melting point: 254-257 oC; FT-IR (KBr): υ(cm-1) = 3188, 3067,
2961, 1705, 1649, 1605, 1498; 11H NMR (300 MHz, EtOH-d6) δ
7.03 (d, J = 8.1, 2H), 6.58 (d, J = 8.1, 2H), 4.82 (s, 1H), 3.59 (s,
3H), 3.46 (s, 3H), 2.33 (d, J = 17.0, 1H), 2.28-2.16 (m with s at
2.25, 4H), 2.12 (d, J = 16.5, 1H), 1.97 (d, J = 16.5, 1H), 0.96 (s,
3H), 0.80 (s, 3H); 13C NMR (101 MHz) δ 194.7, 167.8, 157.7,
149.6, 145.4, 140.3, 128.6, 113.6, 110.7, 104.0, 55.3, 51.1, 50.7,
35.2, 32.6, 29.6, 26.9, 18.7; MS (EI) m/z (%): 355.2 (M+, 26),
248.1 (100); TOF-HRMS (EI): m/z (M)+ calcd for C21H25NO4
355.1784; found 355.1788.
Methyl
4-(4-chlorophenyl)-2,7,7-trimethyl-5-oxo-
Methyl
4-(4-hydroxyphenyl)-2,7,7-trimethyl-5-oxo-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1n)40
melting point: 257-258 oC; FT-IR (KBr): υ(cm-1) = 3288, 3198,
3076, 1682, 1606, 1492, 1226; 1H NMR (400 MHz) δ 9.12 (s, 1H),
7.23 (br. d, J = 6.6, 2H), 7.13 (br. d, J = 6.4, 2H), 4.83 (s, 1H), 3.51
(s, 3H), 2.40 (d, J = 17.0, 1H), 2.35-2.20 (m with s at 2.28, 4H),
2.16 (d, J = 16.0, 1H), 1.96 (d, J = 15.7, 1H), 0.99 (s, 3H), 0.81 (s,
3H); 13C NMR (101 MHz) δ 194.7, 167.6, 150.0, 146.8, 146.1,
130.7, 129.6, 128.2, 110.1, 103.2, 51.1, 50.6, 35.8, 32.6, 29.5,
26.8, 18.8; MS (EI) m/z (%): 361 (M++2, 4), 359 (M+, 11), 248
(100); TOF-HRMS (EI): m/z (M)+ calcd for C20H22ClNO3 359.1288;
found 359.1275.
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1s)26
melting point: 297-298 oC; FT-IR (KBr): υ(cm-1) = 3400, 3276,
3199, 2960, 1687, 1611, 1487, 1380, 1222, 1168, 768; 1H NMR
(300 MHz, EtOH-d6) δ 6.93 (d, J = 8.1 Hz, 2H), 6.49 (d, J = 8.1 Hz,
2H), 4.79 (s, 1H), 3.47 (s, 3H), 2.33 (d, J = 17.0 Hz, 1H), 2.22 (m
with s at 2.25, 4H), 2.11 (d, J = 16.5 Hz, 1H), 1.97 (d, J = 16.5 Hz,
1H), 0.96 (s, 3H), 0.80 (s, 3H); 13C NMR (101 MHz) δ 194.3, 167.5,
155.2, 149.1, 144.7, 138.2, 128.1, 114.5, 110.4, 103.7, 50.6, 50.3,
34.5, 32.1, 29.1, 26.4, 18.2; MS (EI) m/z (%): 341 (M+, 23), 248
(100); TOF-HRMS (EI): m/z (M)+ calcd for C20H23NO4 341.1627;
found 341.1628.
Methyl
2,7,7-trimethyl-5-oxo-4-phenyl-1,4,5,6,7,8-
Methyl
2,7,7-trimethyl-5-oxo-4-(p-tolyl)-1,4,5,6,7,8-
hexahydroquinoline-3-carboxylate: (1o)26
hexahydroquinoline-3-carboxylate: (1t)23
melting point: 259-261 oC; FT-IR (KBr): υ(cm-1) = 3278, 3202,
3079, 2986, 1709, 1607, 1789, 1309; 1H NMR (300 MHz, EtOH-
d6) δ 7.13 (d, J = 7.3, 2H), 7.02 (t, J = 7.4, 2H), 6.92 (t, J = 7.1, 1H),
4.89 (s, 1H), 3.53 (s, 3H), 2.34 (d, J = 17.0, 1H), 2.28-2.18 (m with
s at 2.26, 4H) , 2.12 (d, J = 16.5, 1H), 1.97 (d, J = 16.5, 1H), 0.96
(s, 3H), 0.79 (s, 3H); 13C NMR (101 MHz) δ 194.7, 167.7, 149.9,
147.9, 145.7, 128.2, 127.7, 126.1, 110.4, 103.6, 51.1, 50.7, 36.0,
32.6, 29.6, 26.8, 18.7; MS (EI) m/z (%): 325 (M+, 11), 248 (100);
TOF-HRMS (EI): m/z (M)+ calcd for C20H23NO3 325.1678; found
325.1673.
melting point: 270-273 oC; FT-IR (KBr): υ(cm-1) = 3191, 3072,
2958, 1686, 1644, 1503, 1491, 1227; 1H NMR (300 MHz, EtOH-
d6) δ 7.01 (d, J = 7.8, 2H), 6.83 (d, J = 7.6, 2H), 4.84 (s, 1H), 3.47
(s, 3H), 2.33 (d, J = 16.7, 1H), 2.27-2.19 (m with s at 2.25, 4H),
2.15-1.90 (m with s at 2.11, 5H), 0.96 (s, 3H), 0.80 (s, 3H); 13C
NMR (101 MHz) δ 194.7, 167.8, 149.7, 145.5, 145.0, 135.0,
128.8, 127.6, 110.5, 103.8, 51.0, 50.7, 35.6, 32.5, 29.6, 26.9,
21.0, 18.7; MS (EI) m/z (%): 339 (M+, 15), 248 (100); TOF-HRMS
(EI): m/z (M)+ calcd for C21H25NO3 339.1834; found 339.1834.
Methyl
4-(4-bromophenyl)-2,7,7-trimethyl-5-oxo-
Acknowledgements
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate: (1p)42
melting point: 261-263 oC; FT-IR (KBr): υ(cm-1) = 3291, 3202,
3078, 2958, 1683, 1606, 1492, 1382, 1332, 1227; 1H NMR (300
MHz, EtOH-d6) δ 7.17 (d, J = 8.3, 2H), 7.05 (d, J = 8.3, 2H), 4.85 (s,
1H), 3.47 (s, 3H), 2.34 (d, J = 17.0, 1H), 2.30-2.19 (m with s at
2.27, 4H), 2.12 (d, J = 16.4, 1H), 1.98 (d, J = 16.6, 1H), 0.96 (s,
3H), 0.79 (s, 3H); 13C NMR (101 MHz) δ 194.7, 167.5, 150.1,
147.2, 146.1, 131.1, 130.0, 119.2, 110.0, 103.1, 51.2, 50.6, 35.6,
32.6, 29.5, 26.9, 18.8; MS (EI) m/z (%): 405 (M++2, 7), 403 (M+,
7), 248 (100); TOF-HRMS (EI): m/z (M)+ calcd for C20H22BrNO3
403.0783; found 403.0674.
We thank Bu-Ali Sina University, Iran National Science
Foundation (INSF) (Allameh Tabataba'i's Award, Grant Number
BN093), University of Alicante (VIGROB-173), and the Spanish
Ministerio de Economía y Competitividad (CTQ2015-66624-P)
for financial support to our research groups.
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DOI: 10.1039/C6RA16459E
A novel magnetic nano particles with ionic liquids tags as a reusable catalyst
in the synthesis of polyhydroquinolines
Meysam Yariea, Mohammad Ali Zolfigol*a, Yadollah Bayatb, Asiye Asgarib, Diego A. Alonso*c and
Abbas Khoshnood*c
{Fe3O4@SiO2@(CH2)3Im}C(NO2)3 as a novel nanostructured heterogeneous reusable catalyst
was used for the four component preparation of the polyhydroquinoline derivatives under mild
and eco-friendly reaction conditions.
aDepartment of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan, Iran. E-mail:
zolfi@basu.ac.ir; mzolfigol@yahoo.com; Fax: +98 8138380709; Tel: +98 8138282807.
b Faculty of Chemistry and chemical Engineering, Malek Ashtar University of Technology, Tehran, Iran.
cOrganic Chemistry Department and Organic Synthesis Institute, Alicante University, Apdo. 99, 03080 Alicante,
Spain. Phone: +34965909841, E-Mail: diego.alonso@ua.es; abbas.khoshnood@ua.es