Synthesis of 1,4-dihydropyridine derivatives under solvent-free and grinding conditions

Article abstract of DOI:10.1080/00397911.2010.499488

An efficient and environmentally friendly synthesis of 6-amino-5-cyano-1,4- dihydropyridine derivatives was developed by the one-pot reaction of ethyl acetoacetate, [(2-aryl)methylene]malononitriles, and ammonium acetate at room temperature with grinding.

Full text of DOI:10.1080/00397911.2010.499488

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Synthesis of 1,4-Dihydropyridine
Derivatives Under Solvent-Free and
Grinding Conditions
Adeleh Moshtaghi Zonouz a & Davoud Moghani a
a Chemistry Department, Faculty of Science, Azarbaijan University
of Tarbiat Moallem, Tabriz, Iran
Available online: 20 May 2011
To cite this article: Adeleh Moshtaghi Zonouz & Davoud Moghani (2011): Synthesis of 1,4-
Dihydropyridine Derivatives Under Solvent-Free and Grinding Conditions, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry, 41:14, 2152-2160
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Synthetic Communications1, 41: 2152–2160, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.499488
SYNTHESIS OF 1,4-DIHYDROPYRIDINE DERIVATIVES
UNDER SOLVENT-FREE AND GRINDING CONDITIONS
Adeleh Moshtaghi Zonouz and Davoud Moghani
Chemistry Department, Faculty of Science, Azarbaijan University of Tarbiat
Moallem, Tabriz, Iran
GRAPHICAL ABSTRACT
Abstract An efficient and environmentally friendly synthesis of 6-amino-5-cyano-1,4-
dihydropyridine derivatives was developed by the one-pot reaction of ethyl acetoacetate,
[(2-aryl)methylene]malononitriles, and ammonium acetate at room temperature with
grinding. The key advantages are the short reaction times, good yields, simple workup,
and easy purification. The present method does not involve any hazardous solvent.
Keywords 1,4-Dihydropyridines; grinding; Hantzsch reaction; multicomponent reaction;
solvent-free
INTRODUCTION
1,4-Dihydropyridines (1,4-DHPs) are important class of compounds in the
field of drugs and pharmaceuticals.[1–3] Hantzsch 1,4-DHPs (dialkyl 1,4-dihydro-
2,6-dimethylpyridine-3,5-dicarboxylates) are widely used clinically as calcium chan-
nel blockers for the treatment of cardiovascular diseases, including hypertension and
angina pectoris. 1,4-DHPs possess a variety of biological activities,[4] such as vaso-
dilator, bronchodilator, antiatherosclerotic, antitumor, and antidiabetic activities.
Recent studies have revealed that 1,4-DHPs exhibit several medicinal applications,[5]
which include neuroprotectant and platelet anti-aggregatory activity, in addition to
cerebral anti-ischemic activity in the treatment of Alzheimer’s disease and as a chemo-
sensitizer in tumor therapy. Structure–activity relationships (SARs) show that the
combination of the substituents at the C3, C4, and C5 positions of Hantzsch esters
modulates the activity and tissue selectivity.[6,7] In general, the presence of an aryl
Received February 22, 2010.
Address correspondence to Adeleh Moshtaghi Zonouz, Chemistry Department, Faculty of Science,
Azarbaijan University of Tarbiat Moallem, Tabriz, Iran. E-mail: adelehmz@yahoo.com
2152

1,4-DIHYDROPYRIDINE DERIVATIVES
2153
group at C4 and esters, acyl, sulfonyl, or nitrile groups at C3 and C5 of the 1,4-
DHP ring has proved to be a fundamental requirement for the pharmacological
activity.[8–10] In spite of the widely developed chemistry of the 1,4-DHPs, little is
known about 1,4-DHPs bearing substituents other than hydrogen atoms or alkyl
groups at C2 and C6.[11,12] A survey of the current literature has shown that the syn-
thesis and pharmacology of 6-amino substituted 1,4-DHPs (I) have been described in
the literature.[13,14] Most of these compounds induced a remarkable neuroprotective
affect against toxicity caused by [kþ]-elicited [Ca2þ] overload, preventing calcium
overload and neuronal death.
All these facts prompted us to find a new ecofriendly method and to employ
grinding at room temperature for the multicomponent synthesis of the ethyl
6-amino-4-aryl-5-cyano-1,4-dihydro-2-methyl-3-pyridinecarboxylic acids 2a–g in a
solvent-free environment.
RESULTS AND DISCUSSION
The synthesis of a number of 6-amino-4-aryl-5-cyano-1,4-dihydropyridines (I)
has been reported.[13,14] The compounds of type I have been prepared by reacting
2-arylmethylene-3-oxo-butanoic acid ethyl esters (II) with 3,3-diaminoacrylonitrile
(III), obtained in situ from ethyl 2-cyanoacetimidate hydrochloride (IV), in the
presence of ammonium acetate in methanol under reflux (Scheme 1).
1,4-DHPs are generally synthesized by the classical Hantzsch reaction, which
involves the condensation of an aldehyde with an active methylene carbonyl com-
pound (e.g., ethyl acetoacetate) and ammonia (or a primary amine or ammonium
acetate) in refluxing ethanol or other lower alcohols. A number of improved methods
have been reported in the literature to modify this reaction.[15] To develop an
efficient and environmentally benign methodology for the synthesis of Hantzsch
esters, we initially examined the one-pot reaction of aromatic aldehydes (1 equiv.),
ethyl acetoacetate (1 equiv.), and ammonium acetate (1.5 equiv.) under solvent-free
Scheme 1. Synthesis of 1,4-DHPs of type 1.

2154
A. MOSHTAGHI ZONOUZ AND D. MOGHANI
conditions at room temperature on grinding. No reaction was performed. Then, for
the synthesis of 6-amino substituted 1,4-DHPs (I), we initiated our studies by reac-
tion of aromatic aldehydes (1 equiv.), ethyl acetoacetate (1 equiv.), malononitrile
(1 equiv.), and ammonium acetate (1.5 equiv.) in one pot under solvent-free con-
ditions at room temperature with grinding. However, after workup and purification,
the 1H NMR spectrum of the obtained product did not show any aromatic protons.
1H NMR data show only the reaction of ethyl acetoacetate and malononitrile. So we
used a one-pot, two-stage synthesis of this specific group of 1,4-DHPs via a Knove-
nagel condensation involving malononitrile and a subsequent Micheal addition=
cyclization. Treatment of aromatic aldehydes (1 equiv.) with malononitrile (1 equiv.)
in the presence of ammonium acetate (1.5 equiv.) under solvent-free conditions at
room temperature on grinding gave benzylidene malononitrile derivatives 1a–i via
the Knovenagel condensation without any purification. To the same reaction vessel,
we added ethyl acetoacetate (1 equiv.) and followed this by grinding (Scheme 2).
After workup and purification, the 6-amino-4-aryl-5-cyano-1,4-dihydropyridines
2a–f were obtained in good yields. The results with different aldehydes are depicted
in Table 1.
The reaction of ethyl acetoacetate with 3-methoxybenzylidene malononitrile
(1g) and 3-hydroxybenzylidene malononitrile (1h) in the presence of ammonium acet-
ate under solvent-free conditions at room temperature on grinding gave a complex
mixture of products. We also prepared m-chlorobenzylidene malononitrile (1i) by this
method. We did not continue the reaction with it, because it is very lachrymal.
To prove the mechanism=structures proposed as intermediates, identification
of the proposed intermediates should be made. For this purpose, we performed
Scheme 2. Synthesis of 6-amino-4-aryl-5-cyano-1,4-dihydropyridines.

1,4-DIHYDROPYRIDINE DERIVATIVES
2155
Table 1. Synthesis of 6-Amino-4-aryl-5-cyano-1,4-dihydropyridines 2a–g by grinding
Entry
1
Aldehyde
Product
Yield (%)
Mp (ꢀC)
2a
78
190–192
2
3
2b
2c
57
81
177.5–178.5 (lit.[14b] mp 123–125)
187–188 (lit.[14b] mp 218–220)
4
5
2d
2e
76
59
175–176 (lit.[14b] mp 240–242)
196–197 (lit.[14b] mp 209–211
6
7
2f
68
68
176–177
204–205
2g
the Knovenagel condensation of aromatic aldehydes and malononitrile in the
presence of ammonium acetate by grinding under solvent-free conditions at room
temperature. Reaction of aromatic aldehydes (1 equiv.) with malononitrile (1 equiv.)
in the presence of ammonium acetate (1.2 equiv.) under solvent-free conditions at
Table 2. Knoevenagel condensation of aromatic aldehydes and malononitrile by
grinding for preparation of benzylidene malononitrile derivatives 1
Entry
X
Yield (%)
1
2
3
4
5
6
7
H
4-Me
85
71
75
77
90
70
87
2-MeO
3-MeO
3-NO2
2-NO2
3-Cl

2156
A. MOSHTAGHI ZONOUZ AND D. MOGHANI
room temperature by grinding gave benzylidene malononitrile derivatives 1 after
recrystallization from ethanol 95% in good yields. The results with different
aldehydes are depicted in Table 2.
CONCLUSIONS
In conclusion, we have developed a simple and efficient method for the syn-
thesis of 6-amino substituted 1,4-DHPs at room temperature in solvent-free con-
ditions. The experimental simplicity, mildness of conversion, efficient yields, short
reaction times, low cost, simple workup, and easy purification make this procedure
attractive to synthesize a variety of these derivatives.
EXPERIMENTAL
Preparation of Ethyl 6-Amino-5-cyano-2-methyl-4-phenyl-1,4-
dihydropyridine-3-carboxylate (2a), a Typical Procedure
A mixture of benzaldehyde (10 mmol, 1 ml), malononitrile (10 mmol, 0.66 g),
and ammonium acetate (15 mmol, 1.15 g) was thoroughly mixed in a mortar by
grinding until the completion of reaction as indicated by thin-layer condensation
(TLC) (15 min). The mixture was solidified during the grinding. Then, ethyl acetoa-
cetate (10 mmol, 1.26 ml) was added to the same vessel. The mixture, which was
initially in a partial liquid state, solidified during the process of grinding (15 min).
The pure product (2a) was obtained by recrystallized from ethanol (2.21 g, 78%).
ꢀ
ꢀ
Mp 190–192 C; IR (KBr) n ¼ 3402 (s), 3328 (s), 3223 (m), 2966 (w), 2189 (s),
1693 (s), 1259 (s), 1060 (s) cmꢁ1
;
1H NMR (300 MHz, CDCl3): d ¼ 1.10 (t,
J ¼ 7.20 Hz, 3H, CH3 ester), 2.38 (s, 3H, CH3-2), 4.05 (m, 2H, CH2 ester), 4.45 [s,
1H, C(4)-H], 4.50 (br, s, 2H, NH2), 7.17–7.35 (m, 5H, Ar-H) ppm; 13C NMR
(75 MHz, CDCl3): d ¼ 13.86 (CH3 ester), 18.37 (CH3-2), 38.75 (C-4), 60.64 (CH2
ester), 62.58 (C-5), 108.00 (C-3), 118.80 (CN), 127.17 (C-40), 127.50 (C-30,50), 128.56
(C-20,6 0), 143.72 (C-10), 156.76, 157.39 (C-2, 6), 165.83 (CO) ppm.
Selected Data
Ethyl 6-amino-5-cyano-2-methyl-4-(2-nitrophenyl)-1,4-dihydropyridine-
ꢀ
ꢀ
3-carboxylate (2b). Mp 177.5–178.5 C; IR (KBr) n ¼ 3453 (s), 3294 (s), 3215 (s),
3185 (s), 2984 (w), 2208 (s), 1719 (s), 1684 (s), 1601 (s), 1530 (s), 1381 (s), 1225 (s),
1
1062 (s), 786 (s), 726 (s) cmꢁ1; H NMR (300MHz, CDCl3): d ¼ 0.99 (t, J ¼ 7.20Hz,
3H, CH3 ester), 2.41 (s, 3H, CH3-2), 3.96 (m, 2H, CH2 ester), 4.67 (br, s, NH2),
5.26 [s, 1H, C(4)-H], 7.32–7.40 (m, 2H, Ar-H40, H60), 7.58 (dt, J1 ¼ 7.50 Hz,
J2 ¼ 1.20 Hz, 1H, Ar-H50), 7.82 (dd, J1 ¼ 7.70 Hz, J2 ¼ 1.20 Hz, 1H, Ar-H30) ppm;
13C NMR (75 MHz, CDCl3): d ¼ 13.66 (CH3 ester), 18.45 (CH3-2), 32.97 (C-4),
60.95 (CH2 ester), 63.50 (C-5), 107.30 (C-3), 118.21 (CN), 124.06 (C-30), 127.91
(C-40), 130.61 (C-60), 133.23 (C-50), 139.08 (C-10), 149.09 (C-20), 158.05, 158.24
(C-2, 6), 165.04 (CO) ppm.
Ethyl 6-amino-5-cyano-2-methyl-4-(3-nitrophenyl)-1,4-dihydropyridine-
ꢀ
ꢀ
3-carboxylate (2c). Mp 187–188 C; IR (KBr) n ¼ 3402 (s), 3328 (s), 3221 (m),

1,4-DIHYDROPYRIDINE DERIVATIVES
2157
1
2987 (w), 2190 (s), 1672 (s), 1531 (s), 1344 (s), 1063 (s) cmꢁ1; H NMR (400 MHz,
CDCl3): d ¼ 1.12 (t, J ¼ 7.20 Hz, 3H, CH3 ester), 2.41 (s, 3H, CH3-2), 4.05 (m, 2H,
CH2 ester), 4.58 (s, 1H, C(4)-H), 4.69 (br, s, NH2), 7.49 (t, J ¼ 8.00Hz, 1H, Ar-H50),
7.58 (td, J1 ¼ 8.00 Hz, J2 ¼ 0.80 Hz, Ar-H60), 8.06 (t, J ¼ 1.60 Hz, 1H, Ar-H20),
8.11 (md, J ¼ 8.00 Hz, 1H, Ar-H40) ppm; 1H NMR (400 MHz, DMSO-d6):
d ¼ 1.01 (t, J ¼ 7.20 Hz, 3H, CH3 ester), 2.07 (s, 2H, NH2), 2.34 (s, 3H, CH3-2),
3.36 (s, 1H, NH), 3.95 (m, 2H, CH2 ester), 4.52 [s, 1H, C(4)-H], 7.60–7.70 (m, 2H,
Ar-H50, H60), 7.98 (s, 1H, Ar-H20), 8.10 (dt, J1 ¼ 7.50 Hz, J2 ¼ 1.92 Hz, 1H, Ar-H40)
ppm; 13C NMR (100MHz, CDCl3): d ¼ 12.90 (CH3 ester), 17.64 (CH3-2), 37.75
(C-4), 59.95 (CH2 ester), 63.50 (C-5), 105.93 (C-3), 117.33 (CN), 121.39 (C-40),
121.55 (C-20), 128.51 (C-50), 133.01 (C-60), 145.10 (C-10), 147.47 (C-30), 159.77,
156.95 (C-2, 6), 164.26 (CO) ppm.
Ethyl 6-amino-5-cyano-2-methyl-4-(4-nitrophenyl)-1,4-dihydropyridine-
ꢀ
ꢀ
3-carboxylate (2d). Mp 175–176 C; IR (KBr) n ¼ 3404 (s), 3333 (s), 3204 (s), 2983
(w), 2200 (s), 1690 (s), 1650 (s), 1518 (s), 1345 (s), 1270 (s), 1060 (s) cmꢁ1; 1H NMR
(300 MHz, CDCl3): d ¼ 1.11 (t, J ¼ 7.20 Hz, 3H, CH3 ester), 2.42 (s, 3H, CH3-2), 4.05
(q, J ¼ 7.20 Hz, 2H, CH2 ester), 4.57 [s, 1H, C(4)-H], 4.67 (br, s, NH2), 7.39 (d,
J ¼ 7.70 Hz, 2H, Ar-H2,60), 8.18 (d, J ¼ 7.70 Hz, 1H, Ar-H30,50) ppm; 13C NMR
(75 MHz, CDCl3): d ¼ 13.92 (CH3 ester), 18.61 (CH3-2), 38.82 (C-4), 60.86 (C-5),
60.97 (CH2 ester), 106.79 (C-3), 118.28 (CN), 123.99 (C-20,60), 128.42 (C-30,50),
147.09 (C-10), 151.09 (C-40), 157.73, 158.05 (C-2, 6), 165.26 (CO) ppm.
Ethyl 6-amino-5-cyano-2-methyl-4-(2-methoxyphenyl)-1,4-dihydropyri-
ꢀ
ꢀ
dine-3-carboxylate (2e). Mp 196–197 C; IR (KBr) n ¼ 3403 (s), 3326 (s), 3220
(m), 2967 (w), 2933 (w), 2187 (s), 1693 (s), 1606 (m), 1256 (s), 1063 (s), 713 (s)
1
cmꢁ1; H NMR (300 MHz, CDCl3): d ¼ 1.06 (t, J ¼ 7.20 Hz, 3H, CH3 ester), 2.38
(s, 3H, CH3-2), 3.84 (s, 3H, OCH3), 4.00 (m, 2H, CH2 ester), 4.41 (br, s, 2H,
NH2), 4.88 [s, 1H, C(4)-H], 6.82–6.92 (m, 2H, Ar-H50, 30), 7.06 (dd, J1 ¼ 7.50 Hz,
J2 ¼ 1.50 Hz, 1H, Ar-H60), 7.19 (dt, J1 ¼ 7.50 Hz, J2 ¼ 1.50 Hz, 1H, Ar-H40) ppm;
13C NMR (75 MHz, CDCl3): d ¼ 13.77 (CH3 ester), 18.31 (CH3-2), 32.61 (C-4),
55.58 (OCH3), 60.42 (CH2 ester), 61.81 (C-5), 107.06 (C-3), 111.05 (C-30), 119.10
(CN), 120.65 (C-50), 128.24 (C-40), 128.68 (C-60), 131.79 (C-10), 157.07 (C-2),
157.45 (C-20), 157.94 (C-6), 166.08 (CO) ppm.
Ethyl 6-amino-5-cyano-2-methyl-4-(3-methylphenyl)-1,4-dihydropyri-
ꢀ
ꢀ
dine-3-carboxylate (2f). Mp 176–177 C; IR (KBr) n ¼ 3401 (s), 3330 (m), 3222
(m), 2981 (w), 2192 (s), 1697 (s), 1675 (s), 1647 (m), 1604 (m), 1372 (m), 1266 (s),
1
1058 (s), 721 (m) cmꢁ1; H NMR (300 MHz, CDCl3): d ¼ 1.11 (t, J ¼ 6.90 Hz, 3H,
CH3 ester), 2.33 (s, 3H, CH3-2), 2.38 (s, 3H, CH3), 4.05 (m, 2H, CH2 ester), 4.41
[s, 1H, C(4)-H], 4.45 (br, s, NH2), 6.92–7.25 (m, 4H, Ar-H) ppm; 13C NMR
(75 MHz, CDCl3): d ¼ 13.86 (CH3 ester), 18.37 (CH3-2), 21.45 (CH3), 38.68 (C-4),
60.61 (CH2 ester), 62.52 (C-5), 108.08 (C-3), 118.91 (CN), 124.62 (C-40), 127.96,
128.20, 128.40 (C-20,50,60), 138.07 (C-30), 143.64 (C-10), 156.61, 157.45 (C-2,6),
165.91 (CO) ppm.
Ethyl 6-amino-5-cyano-ꢀ2-methyl-4-(2-furyl)-1,4-dihydropyridine-3-
ꢀ
carboxylate (2g). Mp 204–205 C; IR (KBr) n ¼ 3393 (m), 3370 (m), 3202 (m),
1
2963 (m), 2193 (s), 1693 (s), 1685 (s), 1261 (s), 1065 (s), 802 (s) cmꢁ1; H NMR

2158
A. MOSHTAGHI ZONOUZ AND D. MOGHANI
(300 MHz, CDCl3): d ¼ 1.23 (t, J ¼ 7.20 Hz, 3H, CH3 ester), 2.37 (s, 3H, CH3-2), 4.16
(m, 2H, CH2 ester), 4.53 (br, s, 2H, NH2), 4.64 [s, 1H, C(4)-H], 6.102 (d, J ¼ 3.30 Hz,
1H, Ar-H50), 6.28 (m, 1H, Ar-H40), 7.31 (s, 1H, Ar-H30) ppm; 13C NMR (75 MHz,
CDCl3): d ¼ 14.00 (CH3 ester), 18.43 (CH3-2), 32.37 (C-4), 59.53 (C-5), 60.78 (CH2
ester), 105.71 (C-3), 105.93 (C-50), 110.33 (C-40), 118.62 (CN), 141.93 (C-30),
155.13 (C-10), 157.78, 158.54 (C-2,6), 165.63 (CO) ppm.
General Procedure for the Knovenagel Reaction
A mixture of aromatic aldehyde (10 mmol), malononitrile (10 mmol, 0.66 g),
and ammonium acetate (15 mmol, 1.15 g), was thoroughly mixed in a mortar by
grinding until the completion of reaction as indicated by TLC (15 min). The mixture
solidified during the grinding. The pure product was obtained by recrystallized from
ethanol 95%. The identity of these compounds was easily established by comparison
1
of their H NMR spectra with those of authentic samples.[16]
Selected Data
[16]
2-Benzylidenemalononitrile. Mp 84 ꢀC (lit. 84–85 C); IR (KBr) n ¼3032
ꢀ
ꢀ
1
(w), 2223 (s), 1654 (s), 1591 (s), 1450 (s), 755 (s), 678 (s) cmꢁ1; H NMR (400 MHz,
CDCl3): d ¼ 7.55 (t, J ¼ 7.20 Hz, 2H, Ar-H30,50), 7.65 (t, J ¼ 7.20 Hz, 1H, Ar-H40),
7.89 (s, 1H, ¼CH), 7.92 (d, J ¼ 7.20 Hz, 2H, Ar-H20,60) ppm.
2-(4-Methylbenzylidene)malononitrile. Mp 135 ꢀC (lit.[16] 140 ꢀC); IR
ꢁ1
ꢀ
(KBr) n ¼ 3035 (m), 2222 (s), 1605 (m), 1588 (s), 1221 (m), 1192 (m), 814 (s) cm
;
1H NMR (300 MHz, CDCl3): d ¼ 2.47 (s, 3H, CH3), 7.35 (d, J ¼ 7.25 Hz, 2H,
Ar-H30,50), 7.34 (s, 1H, ¼CH), 7.82 (d, J ¼ 7.25 Hz, 2H, Ar-H20,60) ppm.
2-(2-Methoxybenzylidene)malononitrile. Mp 86 ꢀC (lit.[16] 86 ꢀC); IR (KBr)
ꢁ1
ꢀ
n ¼ 3046 (m), 2944 (w), 2842 (w), 2224 (s), 1579 (s), 1252 (s), 1021 (s), 755 (s) cm
;
1H NMR (300 MHz, CDCl3): d ¼ 3.94 (s, 3H, OCH3), 7.00 (d, J ¼ 8.70 Hz, 1H,
Ar-H30), 7.08 (t, J ¼ 7.80 Hz, 1H, Ar-H50), 7.18 (dt, J1 ¼ 7.80 Hz, J2 ¼ 1.50 Hz, 1H,
Ar-H40), 8.19 (dd, J1 ¼ 8.1 Hz, J2 ¼ 1.50 Hz, 1H, Ar-H60), 8.31 (s, 1H, ¼CH) ppm.
2-(3-Methoxybenzylidene)malononitrile. Mp 107–109 ꢀC (lit.[16] 130 ꢀC);
IR (KBr) n ¼ 3038 (w), 2229 (m), 1571 (s), 1279 (s), 1040 (m) cmꢁ1; H NMR
1
ꢀ
(300 MHz, CDCl3): d ¼ 3.88 (s, 3H, OCH3), 7.18 (dt, J1 ¼ 7.20 Hz, J2 ¼ 2.10 Hz,
1H, Ar-H60), 7.40–7.53 (m, 3H, Ar-H20,40,50), 7.76 (s, 1H, ¼CH) ppm.
2-(3-Nitrobenzylidene)malononitrile. Mp 140 ꢀC (lit.[16] 140 ꢀC); IR (KBr)
n ¼ 3084 (w), 3046 (w), 2225 (m), 1596 (s), 1527 (s), 1355 (s), 1152 (m) cmꢁ1; H
1
ꢀ
NMR (300 MHz, CDCl3): d ¼ 7.80 (t, J ¼ 7.10 Hz, 1H, Ar-H50), 7.90 (s, 1H,
¼CH), 8.34 (d, J ¼ 7.10 Hz, 1H, Ar-H60), 8.48 (m, 1H, Ar-H40), 8.67 (t, J ¼ 2.1 Hz,
1H, Ar-H20) ppm.
ACKNOWLEDGMENT
We thank the Research Office of Azarbaijan University of Tarbiat Moallem
for financial support.

1,4-DIHYDROPYRIDINE DERIVATIVES
2159
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