A novel method for synthesis of 1,4-dihydropyridines using robust laterite catalyst under ultrasonic irradiation

Article abstract of DOI:10.14233/ajchem.2019.21607

An efficient method for the synthesis of 1,4-dihydropyridine derivatives from various aryl or heteroaryl aldehydes, β-ketoester and ammonium acetate in presence of laterite catalyst in ethanol under ultrasonication is reported. Catalyst study done with wet chemical analysis, FT-IR, XRD, SEM and EDS techniques. The catalyst can be recovered and reused without noticeable loss of activity even after five cycles.

Full text of DOI:10.14233/ajchem.2019.21607

Asian Journal of Chemistry; Vol. 31, No. 1 (2019), 128-134
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2019.21607
A Novel Method for Synthesis of 1,4-Dihydropyridines Using
Robust Laterite Catalyst under Ultrasonic Irradiation
1
2,*
S.S. CHINE and C.S. PATIL
1
2
Department of Engineering Sciences, SRES' Sanjivani College of Engineering, Kopargaon-423601, India
Department of Chemistry, Deogiri College, Aurangabad-431005, India
*
Corresponding author: E-mail: chabu251962@yahoo.co.in
Received: 24 July 2018; Accepted: 31 August 2018;
Published online: 30 November 2018;
AJC-19170
An efficient method for the synthesis of 1,4-dihydropyridine derivatives from various aryl or heteroaryl aldehydes, β-ketoester and ammonium
acetate in presence of laterite catalyst in ethanol under ultrasonication is reported. Catalyst study done with wet chemical analysis, FT-IR,
XRD, SEM and EDS techniques. The catalyst can be recovered and reused without noticeable loss of activity even after five cycles.
Keywords: Laterite, Wet chemical analysis, Ultrasonication, Heterogeneous catalysis.
nium phosphate [23], diphenyl ammonium triflate [24], nano
crystalline solid acid catalyst [25], melamine trisulfonic acid
INTRODUCTION
1
,4-Dihydropyridine (DHP) belongs to the class of nitrogen
[
26], visible light [27], eutectic solvent [28], perchloric acid
resting on magnetic Fe nano-particles [29], graphene oxide
nanoparticles [30], CsCl ·7H O [31], cerric ammonium nitrate
32], Fe (SO ·xH O [33], [Tb(mim)]Cl /AlCl [34], benzyl-
triphenylphosphonium chloride (BTPPC) [35], TiCl [1],
containing heterocycles and exhibits significant biological
activities. Out of five regioisomers only 1,2-dihydropyridine
and 1,4-dihydropyridine have gained significant attention because
of their utility in the synthesis of various natural products [1].
3
O
3
4
2
[
2
4
)
3
2
2
3
4
1
,4-Dihydropyridine derivatives have been used as potential
ultrasound irradiation [36], functionalize multi-walled carbon
nanotube (MWCNTs) [37], etc. The most part of accessible
methods of 1,4-dihydropyridines synthesis bear with draw-
backs such as less yield, inconsiderate reaction conditions,
expensive catalyst and long reaction time.
Hence, in context of green chemistry to develop novel
catalytic scheme in an environmentally compassionate fashion
is the real challenge to organic chemists. Therefore, we wish to
report the synthesis of 1,4-dihydropyridines catalyzed by laterite
clay under ultrasound irradiation. Laterite is abundantly available
drug in the form of nifedipine, amlopdipine, isradipine, feldo-
pine, nicardipine for the treatment of hypertension [2,3]. 1,4-
Dihydropyridines also act as antidepressive, hypnotic, antitu-
bercular [4] and anticancer agent [5,6].
1
,4-Dihydropyridines normally synthesized by Hantzsch
method. 1,4-Dihydropyridine-3,5-dicarboxylates are called
Hantzsch dihydropyridines or Hantzsch esters. It involves conden-
sation of aryl aldehydes, β-ketoester and ammonium acetate
or ammonia in presence of acetic acid or refluxing in alcohol
[
7,8]. This needs longer reaction time and gave low to reason-
in nature and contains significant amount of SiO
2
, Fe
O
2 3
and
able yield of product [2,9]. Literature reveals that till today
various attempts have been made to improve the Hantzsch
synthesis using alternative catalyst and greener protocols [10].
Al , etc. It showed application as an adsorbent in the removal
O
2 3
of heavy metal ions from waste water [38]. Recently, iron rich
laterite has been reported as heterogeneous catalyst in the photo
fenton process [39].
These methods involves use of microwave [11,12], Cu(OTf)
13], hydrotalcites [14], AlCl ·6H O [2], silica/sulphuric acid
15], Bi(NO ·5H O [16], Y(OTf) [17], nickel nanoparticles
18], silica gel–supported polyphosphoric acid (PPA-SiO ) [19],
]) [22], alumi-
2
[
[
[
3
2
EXPERIMENTAL
3
)
3
2
3
2
All the chemicals used without further purification and
were ofAR grade. Ultrasonication was done in sonicator with a
L-proline [20], ionic liquids [21], ([BPy][BF
4
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(

Vol. 31, No. 1 (2019)
Novel Method for Synthesis of 1,4-Dihydropyridines Using Robust Laterite Catalyst 129
frequency of 25 KHz. Synthesized products were characterized
RESULTS AND DISCUSSION
1
13
by IR, H NMR and C NMR spectroscopy data and melting
points. Perkin Elmer spectrometer with ATR technology was
Catalyst has been characterized using XRD, FTIR, SEM
and EDS techniques.
1
13
used to record IR spectra. H NMR and C NMR spectra were
recorded on 500 MHz Bruker FT NMR spectrometer using
X-ray diffraction pattern analysis: This study was done
in order to determine various minerals and inorganic phases
present in laterite. X-ray diffraction study was carried out on
Philips, Holland X-ray diffractometer. Fig. 1 represents XRD
peaks of laterite sample. By correlating the results with JCPDS,
CDCl solvent. Melting points were determined by an open
3
capillary method and were uncorrected.
Catalyst preparation: In order to prepare catalyst the
collected natural laterite sample was milled. It was then sieved
through various mesh sizes to remove coarser particles and to
get the particles with the average diameter 50 µm. The catalyst
was then rinsed with distilled water. It was then dried and
calcined at 300 °C for 3 h. The screened catalyst was stored in
polythene for further application. Chemical composition of
collected laterite was calculated by wet chemical analysis
method reported in Table-1.
laterite consists of SiO
diffraction peaks in this pattern at 2θ values 19, 20.76, 25.04,
9.46, 35.16, 49, 53.81, 66.67 are associated with SiO and
matches with literature values [39-41]. The diffraction peaks
at 2θ 31°, 33°, 62.69°, 64.23°, 66° representsAl and matches
with(JCPDS100425) [38,42,43]. The peaks at 2θ 24.25°, 32°,
3.02°, 67° are due to presence of hematite phase (Fe ) [38].
2
,Al
2 3
O ,Fe
2
O , FeO(OH) and FeO. The
3
2
2
2
O
3
3
O
2 3
The diffraction peaks at 2θ 21°, 26° and at 2θ 36°, 42°, 61°
are related to FeO(OH) and FeO, respectively [38].
TABLE-1
LATERITE COMPOSITION BY WET CHEMICAL ANALYSIS
Constituent
SiO2
Laterite (%)
47.17
7
00
600
00
400
Al O
39.20
11.95
0.33
2
3
Fe
Mg
5
Synthesis of 1,4-dihydropyridines: In a 50 mL round
bottom flask aromatic/heteroaromatic aldehyde (1 mmol),
ethyl acetoacetate (2 mmol), ammonium acetate (1.5 mmol),
in ethanol (5 mL), catalyst (20 wt % with respect to aldehyde)
was added and the solution was sonicated for appropriate time.
Advancement of reaction was observed by TLC. After comp-
letion of reaction the mixture was poured into cold water. Solid
product was obtained by filtration and then purified by recry-
stallization (Scheme-I). The catalyst was recovered during
recrystallization and reused without appreciable loss of activity
up to six cycles. The elemental analysis of the synthesized
compounds are shown in Table-2.
300
200
100
0
0
10
20
30
40
2
50
(°)
60
70
80
90
θ
Fig. 1. XRD pattern of catalyst-laterite
Infrared spectroscopy (FT-IR): FT-IR study of catalyst
was done to confirm presence of silica, iron and aluminum.
R
-1
The distinct band at 3694.7 and 3621 cm indicate existence
CHO
-1
of isolated OH group of Si, Al. The band at 461.93 cm
O
O
Laterite
EtOH
indicates O-Si-O bending mode whereas band at 1029.51,
+2
EtO
CH3
+
NH OAc
4
-1
EtOOC
H3C
COOEt
CH3
911.47 and 793.85 cm signify occurrence of Si-O-Fe, Al-
OH, Fe-OH vibrations. The bands at 538.87, 469.43 and 450.09
R
-1
cm are due to Fe-O bond stretching.
N
H
SEM and EDS: Scanning electron microscopy (SEM)
and energy dispersive spectroscopy were performed in a JEOL
Scheme-I: Synthesis of 1,4-DHPs using laterite catalyst
TABLE-2
ELEMENTAL ANALYSIS OF SYNTHESIZED COMPOUNDS
Elemental analysis (%): Calcd. (Found)
Entry
m.f.
C
H
N
X
1
2
3
4
5
6
7
8
9
C H NO Cl
62.89 (62.90)
67.04 (67.08)
66.28 (66.30)
61.13 (61.11)
69.51 (69.49)
55.03 (55.07)
65.55 (65.58)
66.60 (66.62)
71.90 (71.93)
5.79 (5.81)
6.70 (6.72)
6.39 (6.41)
5.63 (5.64)
6.71 (6.71)
5.16 (5.16)
5.46 (5.47)
5.35 (5.38)
6.19 (6.21)
3.86 (3.88)
3.91 (3.93)
4.07 (4.08)
7.51 (7.50)
4.27 (4.26)
3.44 (3.45)
8.82 (8.83)
8.32 (8.34)
8.68 (8.70)
9.79 (9.81)
19
21
4
C H NO
5
–
–
–
–
20
24
C H NO
5
19
25
C H N O
6
19
21
2
C H NO
4
19
22
C H NO Br
19.64 (19.66)
6.72 (6.74)
7.04 (7.06)
–
19
21
4
C H N O S
26
26
3
4
C H N O Cl
28
27
3
4
C H N O
4
29
30
3

130 Chine et al.
Asian J. Chem.
6
360A scanning electron microscope working at 20 kV, with
TABLE-3
OPTIMIZATION OF CATALYST AMOUNT
an energy dispersive X-ray spectrometer.
a
The SEM photographs of the laterite particles are shown
in Fig. 2. The prepared particles were highly agglomerated
with homogeneous distribution. Formation of agglomerated
particles may arise due to calcinations. The surface appears
like a “platelet” type of morphology, as shown in Fig. 2. The
particles were of irregular shapes and different sizes.
All these characterization data clearly demonstrate
morphology and composition of catalyst [38,44].
Entry
1
2
3
Catalyst (wt %)
Time (min)
Yield (%)
Trace
69
–
55
40
30
30
10
20
30
92
85
4
a
Isolated yields
observed (Table-3, entry 4). From these observations 20 wt %
of catalyst can be considered as optimized amount in EtOH as
solvent.
Effect of solvent: We examined solvent effect on yield
of product and time of reaction using several solvents. Initially
reaction was performed without solvent and yields only 25 %
of product. Later on the same reaction was performed in
presence of water, ethanol and then in toluene. It was found
that comparatively ethanol is an efficient solvent which yields
92 % product in short reaction time (Table-4).
Optimization of reaction conditions: Optimization of
reaction conditions with respect to catalyst and solvent amount
was investigated on selected model reaction of 4-chloro benzal-
dehyde (1 mmol), ethyl acetoacetate (2 mmol) and NH
1.5 mmol). All reactions for optimization were performed
under ultrasonication.
4
OAc
(
Optimization of catalyst amount: In the beginning
reaction was performed without catalyst in presence of ethanol
and only trace amount of product was obtained after 55 min
(
Table-3, entry1). The same reaction was done with 10 wt %
Synthesis of 1,4-dihydropyridines using laterite under
ultrasonication:After the optimization of reaction conditions,
we investigated the synthesis of 1,4-dihydropyridines using aryl/
heteroaryl aldehyde (1 mmol), ethyl acetoacetate (2 mmol)
and ammonium acetate (1.5 mmol) with 20 wt % catalyst in
EtOH solvent under ultrasonic irradiation. From the results
of catalyst, 69 % of product obtained after 40 min (Table-3,
entry 2). As the catalyst amount increased from 10 to 20 wt %
the time of reaction was reduced from 40 to 30 min and yield
of product increased from 69 to 92 %. Further increase in the
catalyst amount to 30 wt % no increase in yield of product
0
2
4
6
8
10
keV
Fig. 2. SEM and EDS images of catalyst laterite

Vol. 31, No. 1 (2019)
Novel Method for Synthesis of 1,4-Dihydropyridines Using Robust Laterite Catalyst 131
TABLE-4
Diethyl 1,4-dihydro-2,6-dimethyl-4-(1-phenyl-3-thio-
EFFECT OF SOLVENT ON PRODUCT
phene-2-yl)pyridine-3,5-dicarboxylate (entry 7): m.p.: 212
a
YIELD AND REACTION TIME
-1
°
9
(
(
(
C; FTIR (cm ): 3319, 1692,1635, 1488, 1299, 1211, 1096,
b
Entry
Solvent
–
Water
Ethanol
Toluene
Time (min)
Yield (%)
1
61, 827, 757,694; H NMR (500 MHz, CDCl
bs,6H, -CH ), 2.21 (s, 6H, -CH ), 2.38 (s, 3H, Ar-CH
bs, 2H, -CH -), 4.01 (bs, 2H, -CH -), 5.28 (s, 1H, -CH-), 5.6
s, 1H, -NH), 7.20-7.21 (m, 5H, Ar-H), 7.65-7.71 (m, 5H, Ar-
3
, δ ppm): 1.06
1
2
3
4
90
45
30
55
25
80
92
65
3
3
3
), 3.76
2
2
13
a
b
H); C NMR (100 MHz, CDCl ): 167.62, 151.21, 143.35,
3
Model reaction in the presence of 20 wt % catalyst; Isolated yields.
1
1
1
40.13, 137.01, 131.92, 129.20, 128.80, 128.65, 128.55,
27.04, 125.89, 118.78, 104.44, 59.70, 29.65, 21.30, 19.47,
4.28.
depicted in Table-5, products were obtained in good to excellent
yields. It is also observed that the conversions including
aldehydes with electron donating group complete in short
reaction time than aldehydes with electron donating group.
Diethyl 4-(3-(4-chlorophenyl)-1-phenyl-1H-pyrazol-4-
yl)-1,4-dihydro-2,6-dimethyl pyridine-3,5-dicarboxylate
TABLE-5
SYNTHESIS OF 1,4-DIHYDROPYRIDINES USING LATERITE UNDER ULTRASONICATION
a
Entry
Aldehyde
Product
Time (min)
Yield (%)
m.p. (°C)
Cl
CHO
1
30
92
145
EtOOC
H3C
COOEt
CH3
Cl
N
H
OMe
CHO
OMe
2
3
4
40
40
35
85
82
92
154
229
130
EtOOC
COOEt
CH3
H C
N
H
3
OH
CHO
OH
EtOOC
COOEt
CH3
H C
N
H
NO2
3
CHO
NO2
EtOOC
COOEt
CH3
H C
N
H
3

132 Chine et al.
Asian J. Chem.
CHO
5
35
87
155
EtOOC
COOEt
CH3
H C
3
N
H
Br
CHO
Br
6
30
88
150
EtOOC
COOEt
CH3
H C
N
H
3
N
N
N
N
7
35
30
35
89
90
87
212
S
S
EtOOC
COOEt
CH3
H
O
H C
3
N
H
Cl
N
N
N
8
N
166
Cl
H
COOEt
EtOOC
O
H C
N
H
CH3
3
H C
3
N
N
N
9
N
180
H C
H
3
COOEt
EtOOC
O
H C
N
CH3
3
H
Reaction condition: Aryl/hetero aryl aldehyde (1.0 mmol), EAA (2.0 mmol), ammonium acetate (1.5 mmol) and catalyst (20 wt %) in ethanol (5
a
mL, Isolated yields.

Vol. 31, No. 1 (2019)
Novel Method for Synthesis of 1,4-Dihydropyridines Using Robust Laterite Catalyst 133
-
1
(
1
entry 8): m.p.: 166 °C; FTIR (cm ): 3312, 3092, 1696, 1632,
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laterite catalyst under ultrasonic irradiation at room tempe-
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it could be recycled for at least six cycles without appreciable
loss of reactivity. The significant features of this protocol
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2
ACKNOWLEDGEMENTS
The authors are grateful toThe Principal S.R.E.S’, Sanjivani
College of Engineering, Kopargaon and Principal Deogiri College,
Aurangabad, India for providing necessary research amenities
and constant encouragement.
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