Ultrasound-Assisted Heterogeneous Oxidation of 1,4-Dihydropyridines

Full text of DOI:10.1080/00304948.2020.1760687

Organic Preparations and Procedures International
The New Journal for Organic Synthesis
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Ultrasound-Assisted Heterogeneous Oxidation of
1,4-Dihydropyridines
M. Abdoli-Senejani & K. Karami
To cite this article: M. Abdoli-Senejani & K. Karami (2020): Ultrasound-Assisted Heterogeneous
Oxidation of 1,4-Dihydropyridines, Organic Preparations and Procedures International, DOI:
10.1080/00304948.2020.1760687
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ORGANIC PREPARATIONS AND PROCEDURES INTERNATIONAL
https://doi.org/10.1080/00304948.2020.1760687
EXPERIMENTAL PAPER
Ultrasound-Assisted Heterogeneous Oxidation of
1,4-Dihydropyridines
M. Abdoli-Senejani and K. Karami
Department of Chemistry, Arak Branch, Islamic Azad University, Arak, Iran
ARTICLE HISTORY Received 5 July 2019; Accepted 25 November 2019
1,4-Dihydropyridines are of enormous interest to synthetic chemists, in part because of their
interesting biological applications. For example, they function as lead molecules for com-
pounds with a wide variety of cardiovascular activities.1 Oxidation of 1,4-dihydropyridine
derivatives has attracted much attention because these compounds are oxidized to the corre-
sponding pyridines by cytochrome p-450 in the liver.2,3
Some applications of manganese reagents for the oxidation of Hantzsch 1,4-dihydropyri-
dines have been studied. Researchers have reported oxidation of 3,5-diester 1,4-dihydropyri-
dines by manganese dioxide,4 manganese triacetate,5 potassium permanganate in the
presence of tungstate sulfuric acid,6 potassium permanganate in dichloromethane/water,7
and in acetic acid.8 Although some of the reported procedures have been successfully
implemented for this purpose, a number of them have disadvantages, which include lengthy
reaction times, low yields and cumbersome workup. There is thus a need for mild, green,
inexpensive, and convenient methods for the oxidation of 1,4-dihydropyridines. In the
course of our study of 1,4-dihydropyridines,9–12 we have investigated the heterogeneous oxi-
dation of 3,5-diacyl or 3,5-diester 1,4-dihydropyridines using KMnO4/CuSO4ꢀ5H2O under
ultrasound irradiation.
In heterogeneous reactions involving solids dispersed in liquids, the reactivity
depends upon the available reactive surface area. Ultrasound leads to fragmentation and
consequent particle size reduction.13 In previous investigations, it was reported that,
under heterogeneous reaction conditions, permanganate could be used for the oxidation
of some compounds.14–18 The ultrasound effect on the heterogeneous permanganate
oxidation of benzyl alcohols and alkyl benzenes was reported.19 Hence, in our present
study, we aimed to investigate oxidation of 1,4-dihydropyridines with potassium per-
manganate adsorbed on a solid support, such as CuSO4ꢀ5H2O, in a nonpolar organic
solvent, accelerated by ultrasonic irradiation.
Ten 1,4-dihydropyridines were synthesized to investigate their conversions to the cor-
responding pyridines with KMnO4 under ultrasonic irradiation (see Scheme 1).
For optimization of the reaction, we used diethyl 2,6-dimethyl-4-phenyl-1,4-dihydro-
pyridine-3,5-dicarboxylate (1b) as a representative compound. Several solid supports
were used for our heterogeneous oxidation reactions under ultrasonic irradiation
(Table 1).
CONTACT M. Abdoli-Senejani
mabdoli@iau-arak.ac.ir
Department of Chemistry, Arak Branch, Islamic Azad
University, Arak, Iran
ß 2020 Taylor & Francis Group, LLC

2
M. ABDOLI-SENEJANI AND K. KARAMI
O
O
O
R2
R2
O
H
R1
R1
R1
R1
.
KMnO4/CuSO4 5H2O
)
))
H3C
N
H
CH3
H3C
N
CH3
Scheme 1. Heterogeneous oxidative aromatization of 1,4-dihydropyridines.
Table 1. Effect of solid support on the oxidation with potassium permanganate.
Entry
Solid support (g)
KMnO4 (g)
Time (min)
Yield (%)
1
2
3
4
5
6
7
8
CuSO4ꢀ5H2O (1.25)
CuSO4ꢀ5H2O (2.5)
CuSO4ꢀ5H2O (1.25)
Silica gel (2.5)
1.25
1.25
0
1.25
1.25
1.25
1.25
1.25
20
30
45
40
50
40
35
70
94
92
0
87
78
70
80
89
BaCl2ꢀ2H2O (1.25)
Al2O3 (1.25)
MgSO4ꢀ7H2O (1.25)
————
As shown in Table 1, copper (II) sulfate pentahydrate is a more suitable support for
this reaction. The oxidant was prepared by grinding equal amounts of potassium per-
manganate and copper sulfate pentahydrate.
The physical features of ultrasound irradiation enhance the kinetics and yield of per-
manganate oxidation.20 In order to compare the effects of ultrasound and mechanical
mixing, 1 mmol of 1b, 2.5.g oxidant, and 20 cc CH2Cl2 at room temperature was irradi-
ated under ultrasound irradiation or stirred without ultrasound (Table 2). The results
indicated that ultrasonic irradiation leads to a shorter reaction time. In addition, oxida-
tion of 1b yields 2b with retention of the substituent in position 4.
The results of oxidation of 1,4-dihydropyridines by KMnO4/CuSO4ꢀ5H2O in CH2Cl2
under ultrasonic irradiation are summarized in Table 3.
As can be seen in Table 3, oxidation of 1a-1j yielded 2a-2j with retention of the sub-
stituent in position 4. Compounds 1a and 1f, with no substituent in position 4 of the dihy-
dropyridine ring, converted to the corresponding pyridine in a shorter time than other 3,5-
diester and 3,5-diacetyl 1,4-dihydropyridines. However, oxidation of 3,5-diacetyl 1,4-dihy-
dropyridines was slower than 3,5-diester 1,4-dihydropyridines under the same conditions.
Furthermore, the efficiency of KMnO4/CuSO4ꢀ5H2O under ultrasonic irradiation has
been compared with other reagents used in the oxidative aromatization (Table 4). Most of
these methods are used only for oxidation of 3,5-diester 1,4-dihydropyridines. The results
of this study have now revealed that KMnO4/CuSO4ꢀ5H2O under ultrasonic irradiation is
an efficient, inexpensive, and safe reagent for the oxidation of 3,5-diacetyl and 3,5-diester
1,4-dihydropyridine derivatives with retention of the substituent in position 4.
Experimental section
All Hantzsch 1,4-dihydropyridines were synthesized according to the known proce-
dures.26–28 All products’ specifications were determined, and their physical and spectro-
scopic data were compared with those of authentic samples. Melting points were

ORGANIC PREPARATIONS AND PROCEDURES INTERNATIONAL
3
Table 2. The effect of ultrasound on the heterogeneous oxidation of 1,4-dihydropyridines with
KMnO4/CuSO4ꢀ5H2O.
Condition
stirring
)))
Time
yield (%)
72 h
90
20 min
94
Table 3. Heterogeneous oxidative aromatization of some 1,4-dihydropyridines using KMnO4/
CuSO4ꢀ5H2O under ultrasonic irradiation.
Comp.
R1
R2
yield (%)a
Time (min)
1a
1b
1c
1d
1e
1f
1g
1h
1i
OC2H5
OC2H5
OC2H5
OC2H5
OC2H5
CH3
CH3
CH3
CH3
CH3
H
C6H5
4-ClC6H4
3-NO2C6H4
4-OCH3C6H4
H
90
94
91
92
97
90
95
90
90
96
15
20
35
25
30
18
23
42
30
32
C6H5
4-ClC6H4
3-NO2C6H4
4-OCH3C6H4
1j
aIsolated yield.
determined on a Barnstead Electrothermal apparatus and were uncorrected; literature
values are provided in parentheses, and the literature reference is supplied. IR spectra
1
were recorded on Shimadzu IR-470 spectrometer, HNMR data were obtained using a
€
Bruker 300 MHz spectrometer in CDCl3. Ultraviolet (UV) spectra were measured on an
Agilent 8453 spectrometer. Elemental analyses were performed using a Perkin–Elmer
2400 Series II CHNS/O analyzer.
General procedure for preparation of oxidant
The oxidant was prepared by simply grinding equal weights of potassium permanganate
and copper sulfate pentahydrate with a mortar and pestle until homogeneous.
General procedure for oxidation of 1,4-dyhdropyridines using potassium
permanganate, supported on copper (II) sulfate pentahydrate, under ultrasonic
irradiation
The 1,4-dihydropyridine (1.0 mmol) in CH2Cl2 (20 cc) and the oxidant (2.5 g) were irra-
diated in a glass reactor fitted to an ultrasonic horn (20 kHz, 400W) at room tempera-
ture. The progress of the reaction was followed by TLC (silica gel, petroleum ether:ethyl
acetate 3:1) . In the next step when the reaction had completed, the reaction mixture
was filtered and the residue was washed with CH2Cl2. Then the residue was allowed to
dry and recrystallized using petroleum ether/ethyl acetate (4:1). The structures of the
products were confirmed by spectroscopy, elemental analysis and comparison with
authentic samples, which were prepared by methods in the literature.4,5,28–32
Diethyl-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (1a)
M.p.: 170-172 ꢁC (172-174 ꢁC)33; UV-Vis (Methanol, nm): k (log e)¼372 (3.84), 230
1
(4.18); FT- IR (KBr, cmꢂ1): 1696 (C ¼ O), 3346 (N-H); H NMR (300 MHz, CDCl3,

4
M. ABDOLI-SENEJANI AND K. KARAMI
Table 4. Oxidative aromatization of 1,4-dihydropyridines with KMnO4/CuSO4ꢀ5H2O under ultrasonic
irradiation.
Reagent
Conditions
Yield (%)
Timeref.
KMnO4/CuSO4ꢀ5H2O
)))/ CH2Cl2 / r.t.
CH2Cl2 / 20 ˚C
))) /CH2Cl2, H2O / r.t.
CH3CO2H / heat
CH2Cl2 / r.t.
CH3CO2H / r.t.
EtOAC / air./ r.t.
CH2Cl2 / r.t.
90-97
81-94
>80
15-42 minThis work
5-200 min4
150-300 s7
5 h8
MnO2
KMnO4 / Montrnorillonite
KMnO4
34-80
90-97
91-98
73-96
79-98
94-98
71-99
50-97
TSAa/KMnO4
7-40 min6
20-90 min5
2-6 h21
Mn (OAc)3
Na2SO4 / TBHPb
poly(4-vinylpyridinium nitrate) / silica sulfuric acid
I2
0.5-9 h22
))) / CH3CN
EtOAC, CH3Cl / reflux
CH3CN / H2O2
5-45 min23
40-120 min24
9-90 min25
CuBr2
SVAc–H2O2
aTungstate sulfuric acid.
btert-Butylhydroperoxide.
cSilica vanadic acid.
ppm): d ¼ 1.28 (t, J ¼ 6.5 Hz, 6H, CO2CH2CH3), 2.19 (s, 6H, 2 and 6-CH3), 3.26 (s, 2H,
4-H) , 4.16 (q, J ¼ 6.5 Hz, 4H, CO2CH2CH3), 5.45 (br. s, 1H, NH).
Anal. Calcd for C13H19NO4: C, 61.64; H, 7.56; N, 5.53. Found: C, 61.58; H, 7.61;
N, 5.50.
Diethyl-2,6-dimethyl 4-phenyl–1,4-dihydropyridine-3,5-dicarboxylate (1b)
M.p.: 161-164 ꢁC (160-162 ꢁC)33; UV-Vis (Methanol, nm): k (log e)¼355 (3.93), 238 (4.33);
1
FT- IR (KBr, cmꢂ1): 1690 (C¼O), 3343 (N-H); H NMR (300MHz, CDCl3, ppm): d
¼ 1.23 (t, J ¼ 6Hz, 6H, CO2CH2CH3), 2.31 (s, 6H, 2 and 6-CH3), 4.09 (q, J ¼ 6Hz, 4H,
CO2CH2CH3), 5.00 (s, 1H, 4-H), 6.05 (brd s, 1H, NH), 7.24 (m, 5H, C6H5).
Anal. Calcd for C19H23NO4: C, 69.28; H, 7.04; N, 4.25. Found: C, 69.28; H, 7.03; N, 4.24.
Diethyl-4-(4-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (1c)
M.p.: 145-147 ꢁC (150 ꢁC)34; UV-Vis (Methanol, nm): k (log e)¼355 (3.90), 238 (4.36);
FT- IR (KBr, cmꢂ1): 1696(C¼O), 3359 (N-H); 1H NMR (300 MHz, CDCl3, ppm):
d ¼ 1.21 (t, J ¼ 7. 2 Hz, 6H, CO2CH2CH3), 2.31 (s, 6H, 2 and 6-CH3), 4.11 (q, J ¼ 7.
2 Hz, 4H, CO2CH2CH3), 4.96 (s, 1H, 4-H), 5.80 (brd s, 1H, NH), 7.19 (m, 4H, C6H4Cl).
Anal. Calcd for C19H22ClNO4: C, 62.72; H, 6.09; N, 3.85. Found: C, 62.68; H, 6.10;
N, 3.88.
Diethyl-2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate (1d)
M.p.: 163-165 ꢁC (163 ꢁC)34ꢁC; UV-Vis (Methanol, nm): k (log e)¼354 (3.81), 236 (4.43);
1
FT- IR (KBr, cmꢂ1):1706 (C¼O), 3345 (N-H); H NMR (300 MHz, CDCl3, ppm): d ¼ 1.25
(t, J ¼ 7. 0 Hz, 6H, CO2CH2CH3), 2.34 (s, 6H, 2 and 6-CH3), 4.11 (q, J ¼ 7. 0 Hz, 4H,
CO2CH2CH3), 5.01 (s, 1H, 4-H) , 5.85 (brd s, 1H, NH), 7.20 (m, 4H, C6H4NO2).
Anal. Calcd for C19H22N2O6: C, 60.95; H, 5.92; N, 7.48. Found: C, 60.98; H, 5.93;
N, 7.44.

ORGANIC PREPARATIONS AND PROCEDURES INTERNATIONAL
5
Diethyl-4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-
dicarboxylate (1e)
M.p.: 160-162 ꢁC (160 ꢁC)34ꢁC; UV-Vis (Methanol, nm): k (log e)¼354 (3.92), 222
(4.34); FT- IR (KBr, cmꢂ1): 1690(C¼O), 3343 (N-H); 1H NMR (300 MHz, CDCl3,
ppm): d ¼ 1.15(t, J ¼ 7. 1 Hz; 6H, CO2CH2CH3), 2.24 (s, 6H, 2 and 6-CH3), 3.68 (s, 3H,
4’-OCH3), 4.01 (q, J ¼ 7. 1, 4H, CO2CH2CH3), 4.85 (s, 1H, 4-H), 5.64 (brd s, 1H, NH),
7.12 (d.d, J ¼ 6.3. 0 and 4.1 Hz, 4H, C6H4OCH3).
Anal. Calcd for C20H25NO5: C, 66.84; H, 7.01; N, 3.90. Found: C, 66.85; H, 7.03; N, 3.87.
3,5-Diacetyl-2,6- dimethyl-1,4-dihydropyridine (1f)
M.p.: 213-214 ꢁC (213-215 ꢁC)33ꢁC; UV-Vis (Methanol, nm): k (log e)¼407 (3.88), 251 (4.05);
1
FT- IR (KBr, cmꢂ1): 1671 (C¼O), 3392 (N-H); H NMR (300 MHz, CDCl3, ppm): d ¼ 2.20
(s, 6H, 2 and 6-CH3), 2.24 (s, 6H, 3-and 5-COCH3), 5.30(s, 1H, NH), 4.37 (s, 2H, 4-H).
Anal. Calcd for C11H15NO2: C, 68.37; H, 7.82; N, 7.25. Found: C, 68.39; H, 7.83; N, 7.24.
Diacetyl-2,6-dimethyl-4-phenyl-1,4-dihydropyridine (1g)
M.p.: 184-186 ꢁC (185-186 ꢁC)28; UV-Vis (Methanol, nm): k (log e) ¼ 382 (3.89), 255
1
(4.16); FT- IR (KBr, cmꢂ1): 1670 (C¼O), 3321 (N-H); H NMR (300 MHz, CDCl3,
ppm): d ¼ 2.19 (s, 6H, 2 and 6-CH3), 2.23 (s, 6H, 3-and 5-COCH3), 5.03 (s, 1H, 4-H),
6.52 (s, 1H, NH), 7.15 (m, 5H, C6H5).
Anal. Calcd for C17H19NO2: C, 75.81; H, 7.11; N, 5.20. Found: C, 75.83; H, 7.09; N, 5.21.
Diacetyl-4-(4-chlorophenyl)-2,6-dimethyl-1,4-dihydropyridine (1h)
M.p.: 140-142 ꢁC (140-141 ꢁC)28; UV-Vis (Methanol, nm): k (log e) ¼ 378 (3.29), 254
(3.67); FT- IR (KBr, cmꢂ1): 1652(C¼O), 3262 (N-H); 1H NMR (300 MHz, CDCl3,
ppm): d ¼ 2.13 (s, 6H, 2-and 6-CH3), 2.26 (s, 6H, 3-and 5-COCH3), 5.13 (s, 1H, 4-H),
6.52 (s, 1H, NH), 7.18 (s, 4H, C6H4Cl).
Anal. Calcd for C17H18ClNO2: C, 67.21; H, 5.97; N, 4.61. Found: C, 67.21; H, 5.98, N, 4.60.
Diacetyl-2,6-dimethyl-4-(3-nitrophenyl)–1,4-dihydropyridine (1i)
M.p.: 211-213 ꢁC (210-211 ꢁC)28; UV-Vis (Methanol, nm): k (log e)¼378 (3.33), 253
1
(3.88); FT- IR (KBr, cmꢂ1): 1628 (C¼O), 3297 (N-H); H NMR (300 MHz, CDCl3,
ppm): d ¼ 2.20 (s, 6H, 2-and 6-CH3), 2.30 (s, 6H, 3-and 5-COCH3), 5.22 (s, 1H, 4-H),
6.15 (s, 1H, NH), 7.95 (m, 5H, C6H4NO2).
Anal. Calcd for C17H18N2O4: C, 64.96; H, 5.77; N, 8.91. Found: C, 65.00; H, 5.75; N, 8.90.
Diacetyl-4-(4-methoxyphenyl)-2,6-dimethyl-1,4-dihydropyridine (1j)
M.p.: 174-175 ꢁC (175-176 ꢁC)28; UV-Vis (Methanol, nm): k (log e)¼353 (3.76), 223
1
(4.28); FT- IR (KBr, cmꢂ1): 1668 (C¼O), 3343 (N-H); H NMR (300 MHz, CDCl3,

6
M. ABDOLI-SENEJANI AND K. KARAMI
ppm): d ¼ 2.18 (s, 6H, 2-and 6-CH3), 2.23 (s, 6H, 3-and 5-COCH3), 4.96 (s, 1H, 4-H),
6.13 (s, 1H, NH), 7.08ppm (dd, 4H, C6H4CH3).
Anal. Calcd for C18H21NO3: C, 72.22; H, 7.07; N, 4.68. Found: C, 72.20; H, 7.08; N, 4.67.
Diethyl-2,6-dimethylpyridine-3,5-dicarboxylate (2a)
M.p.: 67-69 ꢁC (69-71 ꢁC)33; UV-Vis (Methanol, nm): k (log e) ¼ 273 (3.52); FT-IR
1
(KBr, cmꢂ1): 1717 (C¼O); H NMR (300 MHz, CDCl3, ppm): d ¼ 1.40 (t, J ¼ 7.0 Hz,
6H, CO2CH2CH3), 2.84 (s, 6H, 2 and 6-CH3), 4.38 (q, J ¼ 7.0 Hz, 4H, CO2CH2CH3),
8.67 (s, 1H, 4-H) .
Anal. Calcd for C13H17NO4: C, 62.14; H, 6.82; N, 5.57. Found: C, 62.11; H, 6.82;
N, 5.59.
Diethyl-2,6-dimethyl-4-phenylpyridine-3,5-dicarboxylate (2b)
M.p.: 64-65 ꢁC (63-65 ꢁC)33; UV-Vis (Methanol, nm): k (log e) ¼ 236 (3.75); FT-IR
1
(KBr, cmꢂ1): 1726 (C¼O); H NMR (300 MHz, CDCl3, ppm): d ¼ 0.86 (t, J ¼ 6.5 Hz,
6H, CO2CH2CH3), 2.58 (s, 6H, 2 and 6-CH3), 3.97 (q, J ¼ 6.5 Hz, 4H, CO2CH2CH3),
7.28 (m, 5H, C6H5).
Anal. Calcd for C19H21NO4: C, 69.71; H, 6.47; N, 4.28. Found: C, 69.75; H, 6.48;
N, 4.28.
Diethyl-4-(4-chlorophenyl)-2,6-dimethylpyridine-3,5-dicarboxylate (2c)
M.p.: 65-67 ꢁC (63-65 ꢁC)35; UV-Vis (Methanol, nm): k (log e) ¼ 212 (4.47); FT-IR
1
(KBr, cmꢂ1): 1716 (C¼O); H NMR (300 MHz, CDCl3, ppm): d ¼ 0.96 (t, J ¼ 7.1 Hz,
6H, CO2CH2CH3), 2.61 (s, 6H, 2 and 6-CH3), 4.03 (q, J ¼ 7.1 Hz, 4H, CO2CH2CH3),
7.25 (m, 4H, C6H4Cl).
Anal. Calcd for C19H20ClNO4: C, 63.07; H, 5.57; N, 3.87. Found: C, 63.04; H, 5.59;
N, 3.90.
Diethyl-2,6-dimethyl-4-(3-nitrophenyl) pyridine-3,5-dicarboxylate (2d)
M.p.: 62-64 ꢁC (62-64 ꢁC)36; UV-Vis (Methanol, nm): k (log e) ¼ 257 (4.75); FT-IR
1
(KBr, cmꢂ1): 1722 (C¼O); H NMR (300 MHz, CDCl3, ppm): d ¼ 1.01 (t, J ¼ 7.0 Hz,
6H, CO2CH2CH3), 2.68 (s, 6H, 2 and 6-CH3), 4.06 (q, J ¼ 7.0 Hz, 4H, CO2CH2CH3),
7.25 (m, 4H, C6H4NO2)) .
Anal. Calcd for C19H20N2O6: C, 61.28; H, 5.41; N, 7.52. Found: C, 61.24; H, 5.43;
N, 7.52.
Diethyl-4-(4-methoxyphenyl)-2,6-dimethylpyridine-3,5-dicarboxylate (2e)
M.p.: 53-56 ꢁC (49-52 ꢁC)36; UV-Vis (Methanol, nm): k (log e) ¼ 243 (4.96); FT-IR
1
(KBr, cmꢂ1): 1697 (C¼O); H NMR (300 MHz, CDCl3, ppm): d ¼ 0.99 (t, J ¼ 7.1 Hz,

ORGANIC PREPARATIONS AND PROCEDURES INTERNATIONAL
7
6H, CO2CH2CH3), 2.63 (s, 6H, 2 and 6-CH3), 3.95 (s, 3H, 40-OCH3),4.05 (q, J ¼ 7.1 Hz,
4H, CO2CH2CH3), 7.30 (m, 4H, C6H4OCH3)) .
Anal. Calcd for C20H23NO5: C, 67.21; H, 6.49; N, 3.92. Found: C, 67.22; H, 6.48;
N, 3.95.
3,5-Diacetyl-2,6-dimethylpyridine (2f)
M.p.: 66-67 ꢁC (65-67 ꢁC)33; UV-Vis (Methanol, nm): k (log e) ¼ 246 (4.14); FT-IR
1
(KBr, cmꢂ1): 1681 (C¼O); H NMR (300 MHz, CDCl3, ppm): d ¼ 2.62 (s, 6H, 2-and 6-
CH3), 2.77 (s, 6H, 3-and 5-COCH3), 4.30 (s, 1H, 4-H)).
Anal. Calcd for C11H13NO2: C, 69.09; H, 6.85; N, 7.32. Found: C, 69.07; H, 6.85;
N, 7.34.
Diacetyl-2,6-dimethyl-4-phenylpyridine (2g)
M.p.: 186-188 ꢁC (185-186 ꢁC)28; UV-Vis (Methanol, nm): k (log e) ¼ 258 (4.28); FT-IR
1
(KBr, cmꢂ1): 1699 (C¼O); H NMR (300 MHz, CDCl3, ppm) d ¼ 2.19 (s, 6H, 2-and 6-
CH3), 2.44 (s, 6H, 3-and 5-COCH3), 7.36 (m, 5H, C6H5)) .
Anal. Calcd for C17H17NO2: C, 76.38; H, 6.41; N, 5.24. Found: C, 76.37; H, 6.41;
N, 5.24.
3,5-Diacetyl-4-(4-chlorophenyl)-2,6-dimethylpyridine (2h)
M.p.: 172-174 ꢁC (174-175 ꢁC)28; UV-Vis (Methanol, nm): k (log e) ¼ 275 (4.39); FT-IR
1
(KBr, cmꢂ1): 1704 (C¼O); H NMR (300 MHz, CDCl3, ppm) d ¼ 1.86 (s, 6H, 2-and 6-
CH3), 2.43 (s, 6H, 3-and 5-COCH3), 7.22 (m, 4H, C6H4Cl)) ;
Anal. Calcd for C17H16ClNO2: C, 67.66; H, 5.34; N, 4.64. Found: C, 67.62; H, 5.37;
N, 4.65.
3,5-Diacetyl-2,6-dimethyl-4-(3-nitrophenyl)pyridine (2i)
M.p.: 124-126 ꢁC (126-127 ꢁC)28; UV-Vis (Methanol, nm): k (log e) ¼ 257 (4.73); FT-IR
1
(KBr, cmꢂ1): 1696 (C¼O); H NMR (300 MHz, CDCl3, ppm) d ¼ 2.18 (s, 6H, 2-and 6-
CH3), 2.58 (s, 6H, 3-and 5-COCH3), 7.65 (m, 4H, C3H4NO2).
Anal. Calcd for C17H16N2O4: C, 65.38; H, 5.16; N, 8.97. Found: C, 65.40; H, 5.17;
N, 8.97.
3,5-Diacetyl-4-(4-methoxyphenyl)-2,6-dimethylpyridine (2j)
M.p.: 165-166 ꢁC (164-165 ꢁC)28; UV-Vis (Methanol, nm): k (log e) ¼ 239 (4.42); FT-IR
1
(KBr, cmꢂ1): 1696 (C¼O); H NMR (300 MHz, CDCl3, ppm) d ¼ 1.88 (s, 6H, 2-and 6-
CH3), 2.48 (s, 6H, 3-and 5- COCH3), 3.83(s, 3H, 4-OCH3), 7.04 (m, 4H, C6H4OCH3).
Anal. Calcd for C18H19NO3: C, 72.71; H, 6.44; N, 4.71. Found: C, 72.68; H, 6.45;
N, 4.76.

8
M. ABDOLI-SENEJANI AND K. KARAMI
Acknowledgment
We are thankful to the Islamic Azad University, Arak Branch, for its financial support.
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