Synthesis of new 2,4-diaryl-6-methyl-5-nitropyrimidines as antibacterial and antioxidant agents

Article abstract of DOI:10.1002/jhet.1645

A new series of 2,4-diaryl-6-methyl-5-nitropyrimidines (5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i) were synthesized in good yields by Suzuki-Miyaura coupling of 2,4-dichloro-6-methyl-5-nitropyrimidine (3) with various aryl boronic esters (4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i) in the presence of 1,1′- bis(diphenylphosphino)ferrocene dichloropalladium(II) (Pd(dppf) ₂Cl₂). Further, antibacterial and antioxidant properties were screened for the title compounds 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i. Most of the compounds possessed significant activity against Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis and Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae. The antioxidant activity of the title compounds showed significant antioxidant activity when compared with vitamin C.

Full text of DOI:10.1002/jhet.1645

November 2013 Synthesis of New 2,4-Diaryl-6-methyl-5-nitropyrimidines as Antibacterial
and Antioxidant Agents
1395
b
a
a
*
Mallikarjun Reddy Sura, Vasu Govardhana Reddy Peddiahgari, Rajendra Prasad Reddy Bhoomireddy,
and Rama Krishna Vaddec
aDepartment of Chemistry, Yogi Vemana University, Kadapa, 516003, Andhra Pradesh, India
bDepartment of Chemistry, Rayalaseema University, Kurnool, 518002, Andhra Pradesh, India
cDepartment of Biotechnology & Bioinformatics, Yogi Vemana University, Kadapa, 516003, Andhra Pradesh, India
*
E-mail: vasu_chem9@rediffmail.com
Received December 6, 2011
DOI 10.1002/jhet.1645
Published online 4 October 2013 in Wiley Online Library (wileyonlinelibrary.com).
OH
OH
Cl
Ar
NO2
NO2
NO2
N
N
N
c
N
a
b
HO
N
HO
N
Cl
N
Ar
N
1
2
3
5a-i
A new series of 2,4-diaryl-6-methyl-5-nitropyrimidines (5a–i) were synthesized in good yields by
Suzuki–Miyaura coupling of 2,4-dichloro-6-methyl-5-nitropyrimidine (3) with various aryl boronic esters
(4a–i) in the presence of 1,10- bis(diphenylphosphino)ferrocene dichloropalladium(II) (Pd(dppf)2Cl2).
Further, antibacterial and antioxidant properties were screened for the title compounds 5a–i. Most of
the compounds possessed significant activity against Gram-positive bacteria Staphylococcus aureus and
Bacillus subtilis and Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae. The antioxidant
activity of the title compounds showed significant antioxidant activity when compared with vitamin C.
J. Heterocyclic Chem., 50, 1395 (2013).
INTRODUCTION
compounds derived by aryl substitution at the 2- and 4-
positionsof2,4-dichloro-6-methyl-5-nitropyrimidine(Scheme1)
and tested their antibacterial and antioxidant activities.
The development of novel synthetic methods leading to
pyrimidine derivatives has attracted much attention in
recent years because of their prevalence and wide utility
in organic synthesis. Furthermore, they play an important
role in several biological and pharmacological active sub-
stances such as antimicrobial and antitumor agents [1–4]
and agrochemical and veterinary products [5–7]. Some of
the pyrimidinone derivatives are also used as potent and
orally bioavailable HIV-1 integrase inhibitors [8] and
anti-inflammatory and analgesic agents [9].
The Suzuki cross-coupling reaction is a powerful
method for carbon–carbon bond formation that has
been applied in a variety of settings, ranging from natural-
product synthesis to materials chemistry, including large-
scale production [10]. Among the attractive features of
the Suzuki reaction are the wide availability, stability to
air and moisture, and low toxicity of boronic acids, as
well as the facile removal of the boron-containing side
products of the coupling process. Catalyst systems based
on palladium precatalysts to generate biaryls have also
proven to be highly effective [11,12]. Herein, we report
the synthesis of 2,4-diaryl pyrimidine derivatives by using
the catalytic system 1,10- bis(diphenylphosphino)ferrocene
dichloropalladium(II) (Scheme 1) for the Suzuki–Miyaura
reaction of aryl boronic esters and 2,4-dichloro-6-methyl-
5-nitropyrimidine.
RESULTS AND DISCUSSION
The synthesis of 5a–i was carried out according to
Scheme 1. Briefly, 6-methylpyrimidine-2,4-diol (1) was
prepared by the reaction of ethylacetoacetate with urea in
the presence of NaOMe in methanol at reflux temperature
[13]. Nitration of 1 in the presence of H2SO4 and fuming
nitric acid obtained 6-methyl-5-nitropyrimidine (2) [1]. It
reacted with POCl3 in the presence of N,N0-dimethylaniline
and tetrabutylammoniumchloride to afford 2,4-dichloro-6-
methyl-5-nitropyrimidine (3) [2]. Finally, diarylation of
compound 3 with various aryl boronic esters (4a–i) in the
presence of 1,10-bis(diphenylphosphino)ferrocenedichloro-
palladium(II) and Na2CO3 in 1,4-dioxane/water by Suzuki–
Miyaura coupling [10,14] furnished the title compounds
as 2,4-diaryl-6-methyl-5-nitropyrimidines (5a–i). We deter-
1
mined the of synthesized derivatives by IR, H NMR, and
13C NMR, and their molecular masses were determined by
mass spectrometry (Table 1).
The IR spectra of 5a–i exhibited characteristic absorption
bands in the regions 1548–1559 and 1335–1375 cmꢀ1
for NO2 antisymmetric and symmetric stretching bands,
aromatic C═C stretching absorption bands showed at
1575–1592 cmꢀ1, and C–H antisymmetric and symmetric
stretching absorption bands of methyl group exhibited at
In view of the biological significance of pyrimidine
derivatives, we are interested in obtaining some new
2935–2956 and 2840–2877 cmꢀ1
.
© 2013 HeteroCorporation

1396
M. R. Sura, V. G. R. Peddiahgari, R. P. R. Bhumireddy, and V. R. Krishna
Vol 50
Scheme 1. Reaction conditions for analog synthesis: (a) HNO3, H2SO4; (b) Bu4NCI, PhN(Me)2, POCI3; (c) aryl boronic esters 4a–i, Pd(dppf)2CI2/
Na2CO3, 1,4-dioxane/H2O, 75–85%.
OH
OH
Cl
Ar
NO2
NO2
NO2
N
N
N
c
N
a
b
HO
N
HO
N
Cl
N
Ar
N
1
2
3
5a-i
Table 1
2,4-Diaryl-6-methyl-5-nitropyrimidines 5a–i.
Entry
Ar
Entry
Ar
5a
5f
5b
5g
5c
5h
5i
5d
5e
1
The H NMR spectra of 5a showed four doublets at d
8.56 (J = 8.0 Hz, 1H, Ar–H), 8.55 (J = 8.4 Hz, 1H, Ar–H)
and 7.81 (J = 7.6 Hz, 1H, Ar–H), 7.77 (J = 8.0 Hz, 1H,
Ar–H), a multiplet at d 7.57–7.49 (m, 6H, Ar–H) for aromatic
protons, and the protons in methyl group appeared as singlet
at d 2.69 (s, 3H, CH3). In compound 5d, the aromatic protons
resonated as doublet of doublets at d 7.61, 7.58 (J = 8.8,
8.7 Hz, 1H) and 7.47, 7.44 (J= 8.7, 8.7 Hz, 1H) and multiplets
at d 7.16–7.09 (2H), 7.02–6.98 (1H), 6.85–6.80 (1H).
The OCH protons appeared as multiplet in the region d
4.61–4.43 (2H, 2OCH), the methyl protons of pyrimidine ring
resonated as singlet at d 2.78 (3H, CH3), and the two methyl
groups of the isopropyl moiety attributed as doublets at d
1.35 (J=6.0 Hz, 6H, 2ꢁCH3) and 1.23 (J= 5.7 Hz, 6H,
2ꢁCH3). Similarly, the other compounds 5b, 5c, and 5e–i
were also characterized by the 1H NMR spectra, and their data
are given in the Experimental section.
The 13C NMR spectra of 5a showed 11 peaks in the
aromatic region at d 163.68, 160.01, 157.53, 143.52,
136.07, 134.16, 131.76, 131.18, 129.00, 128.66, and
128.10 and methyl carbon signal found at d 20.72. The
other compounds (5b–i) were also characterized by the
13C NMR spectra, and their data are given in the Experi-
mental section. Chemical ionization mass spectra of 5a–i
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

November 2013
Synthesis of New 2,4-Diaryl-6-methyl-5-nitropyrimidines
as Antibacterial and Antioxidant Agents
1397
gave molecular ion peaks at their respective expected
m/z values.
We monitored the compounds 5a–i for antibacterial
activity against both Gram-positive bacteria and Gram-
negative bacteria by the literature method [6,15]. Assays
of Gram-positive bacteria Staphylococcus aureus and
Bacillus subtilis and Gram-negative bacteria Escherichia
coli and Klebsiella pneumoniae by the disc diffusion
method in nutrient agar medium at two concentrations
(50, 100 mg/mL) in DMSO were carried out. The com-
pounds were diluted in DMSO for biological assays. The
samples were tested in triplicate, and average results
were recorded. The results were presented in Table 2 and
compared with ampicillin (50 mg/mL). The results revealed
that the compounds 5b, 5c, and 5d confer the highest
antibacterial activity against all tested bacterial strains
in both 50- and 100-mg concentrations. This is due to
fluorine and oxygen showing highly negative-inductive
effect, and NO2 is a highly electron-withdrawing moiety.
However, the other compounds 5a and 5e–i exhibited a
moderate activity.
Antioxidants help organisms deal with oxidative stress,
and its main characteristic is its ability to trap free radicals.
The free radical scavenging capacity of 5a–i compounds
were evaluated by 1,1-diphenyl-2-picrylhydrazyl radical
(DPPH) [16,17] and nitric oxide radical scavenging activity
[18,19] methods (Table 3). The results confirmed that the
compound 5e showed high DPPH scavenging activity with
32 mg/mL; it is due to the electron-donating phenoxyphenyl
group and –NO2 substituent’s role in 5e, which affect
the electron-donating capacitates appearing to be useful in
inducing antioxidant activity. The other compounds 5b and
5c also exhibit the high activity because fluorine exhibits
highly negative-inductive effect and –NO2 is a highly
electron-withdrawing moiety; therefore, electron density
around nitrogen heterocycle decreases and increases affinity
towards aromatic ring derived from free radicals and mobi-
lizes reactive oxygen species to be scavenged out of a
living organism. The compounds 5b–5e also showed the
highest NO scavenging activity compared with other com-
pounds. The title compounds 5a–i, containing nitrogen
heterocycle, are expected to be more active because of the
presence of hetero atoms containing non-bonded electron
pairs that serve as binding sites in the bio-matrix. The
compounds 5a, 5d, and 5f–i displayed appreciable antioxidant
activity because these compounds contain –NO2 group in the
parent pyrimidine moiety.
EXPERIMENTAL
All reactions were carried out under nitrogen atmosphere.
Glassware was dried in an oven prior to use. Reactions were
monitored by TLC with Merck silica gel 60 F254 plates or
with neutral aluminum oxide 60 F254 plates (Merck, India). Flash
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1398
M. R. Sura, V. G. R. Peddiahgari, R. P. R. Bhumireddy, and V. R. Krishna
Vol 50
Table 3
129.00, 128.66, 128.10, 20.72; MS (ESI, 0 V), m/z 292 (M + 1,
100%). Anal. Calcd for C17H13N3O2: C, 70.09; H, 4.50; N, 14.42.
Found: C, 70.17; H, 4.64; N, 14.28.
DPPH radical and nitric oxide radical scavenging activity of 5a–i
compounds.
2,4-Bis(3-fluorophenyl)-6-methyl-5-nitropyrimidine 5b. Amor-
phous solid (0.63 g, 2.5 mmol, 77%); mp 135–137 ꢂC; IR (KBr)
DPPH assay
NO scavenging activity
3112, 3016, 2952, 2840, 1586, 1556, 1335 cmꢀ1 1H NMR
;
Compound
IC50 (mg/mL)
IC50 (mg/mL)
(300 MHz, CDCl3): d 8.35 (d, J= 7.9 Hz, 1H, Ar–H), 8.25
(d, J= 9.9 Hz, 1H, Ar–H), 7.54–7.44 (m, 4H, Ar–H), 7.28 (s, 2H,
Ar–H), 2.65 (s, 3H, CH3); 13C NMR (75MHz, CDCl3): d
164.31, 162.56, 160.49, 156.15, 143.49, 138.11, 135.88, 130.93,
124.66, 123.76, 119.08, 115.87, 20.78; MS (ESI, 0 V), m/z 328
(M + 1, 100%). Anal. Calcd for C17H11F2N3O2: C, 62.39; H,
3.39; N, 12.84. Found: C, 62.30; H, 3.48; N, 12.69.
5a
5b
5c
5d
5e
5f
5g
5h
44
34
36
42
32
40
41
40
50
31
34
35
32
42
43
44
2,4-Bis(4-fluorophenyl)-6-methyl-5-nitropyrimidine 5c. Amor-
phous solid (0.65 g, 2.5 mmol, 80%); mp 142–144 ꢂC; IR (KBr)
5i
43
68.25
45
65.35
Ascorbic acid
(vitamin C)
3121, 3019, 2949, 2866, 1587, 1548, 1337 cmꢀ1 1H NMR
;
(300 MHz, CDCl3): d 8.29 (d, J= 8.4 Hz, 2H, Ar–H), 8.15
(d, J= 9.0 Hz, 2H, Ar–H), 7.46–7.49 (m, 4H, Ar–H), 2.68
(s, 3H, CH3); 13C NMR (75 MHz, CDCl3): d 164.10, 162.42,
159.87, 154.41, 142.89, 137.41, 135.32, 130.26, 123.96, 123.46,
118.88, 115.51, 20.45; MS (ESI, 0 V), m/z 328 (M + 1, 100%).
Anal. Calcd for C17H11F2N3O2: C, 62.39; H, 3.39; N, 12.84.
Found: C, 62.24; H, 3.50; N, 12.71.
column chromatography was performed on silica gel 60 (70–230
mesh ASTM) from Merck. All other chemicals such as Pd(dppf)
Cl2 and aryl boronic esters, in which its preparation is not de-
scribed in the succeeding texts, were brought from Aldrich,
Acros, Merck, or Combi-blocks. Melting points were determined
on a Buchi R-535 apparatus and are uncorrected. IR spectra were
recorded on a Perkin-Elmer FTIR 240-c spectrophotometer with
2,4-Bis(5-fluoro-2-isopropoxyphenyl)-6-methyl-5-nitropyrimidine
5d. Amorphous solid (0.86 g, 2.5 mmol, 78%); mp 118–120 ꢂC;
IR (KBr) 3122, 3018, 2934, 2870, 1575, 1553, 1360, 1120cmꢀ1
;
1H NMR (300 MHz, CDCl3): d 7.60 (dd, J = 8.7 Hz, 1H, Ar–H),
7.45 (dd, J = 8.7, 1H, Ar–H), 7.16–7.09 (m, 2H, Ar–H), 7.02–6.98
(m, 1H, Ar–H), 6.85–6.80 (m, 1H, Ar–H), 4.61–4.52 (m, 1H,
2OCH), 4.52–4.41 (m, 1H, 2OCH), 2.78 (s, 3H, CH3); 1.35
(d, J = 6.0 Hz, 6H, (CH3)2), 1.23 (d, J = 5.7 Hz, 6H, (CH3)2); 13C
NMR (75MHz, CDCl3): d 163.80, 160.65, 157.59, 156.05,
154.44, 152.56, 150.69, 142.89, 128.75, 125.98, 118.61, 117.63,
114.87, 71.56, 21.94, 20.81; MS (ESI, 0 V), m/z 444 (M+ 1,
100%). Anal. Calcd for C23H23F2N3O4: C, 62.30; H, 5.23; N,
9.48. Found: C, 62.21; H, 5.37; N, 9.56.
the use of KBr optics. H and 13C NMR spectra were recorded
1
on an AMX 400 MHz NMR or 300 MHz NMR spectrometer
from Bruker in CDCl3 unless otherwise stated. Mass spectra were
recorded on a Finnigan MAT 1020/Micro-Mass Q-T of micro
AMPS MAX 10/6A, Hz 60/50 system fitted with a built-in inlet
system. Standard strains of Gram-positive bacteria S. aureus and
B. subtilis and Gram-negative bacteria E. coli and K. pneumoniae
were obtained from IMTECH, Chandigarh, India.
The starting material 2,4-dichloro-6-methyl-5-nitropyrimidine
was synthesized by the procedure reported in the literature[1,2,13].
General procedure for the preparation of 2,4-diaryl-6-
methyl-5-nitropyrimidines.
2,4-Bis(4-phenoxyphenyl)-6-methyl-5-nitropyrimidine 5e. Amor-
phous solid (0.90 g, 2.5 mmol, 76%); mp 122–124 ꢂC; IR
(KBr) 3100, 3018, 2947, 2856, 1591, 1559, 1461, 1375,
1
1151 cmꢀ1; H NMR (400 MHz, CDCl3): d 8.51 (d, J= 9.6 Hz, 2H,
Preparation of 4-methyl-5-nitro-2,6-diphenylpyrimidine 5a. Phenyl
boronic ester (4,4,5,5-tetramethyl-2-phenyl-1,3,2-dioxaborolane)
4a (2.04 g, 0.01mol, 4 eq) and sodium carbonate (0.94 g,
0.01mol, 4 eq) were added to a stirred solution of 2,4-dichloro-
6-methyl-5-nitropyrimidine 3 (0.520g, 0.0025 mol, 1 eq) in 1,4-
dioxane (20mL) and water (5 mL). The reaction mixture was
degassed with nitrogen gas and stirred at room temperature for
30min. To this reaction mixture, Pd(dppf)2Cl2 (0.365g,
0.0005 mol, 0.2 eq, 20 mol%) was added and heated at 110ꢂC for
overnight. After cooling to room temperature, solvent was
removed under reduced pressure. Water was then added, and the
impure product was extracted into ethyl acetate. The combined
organic layers were dried over anhydrous Na2SO4, and the
solvent was removed under vacuum. The crude product was
Ar–H), 7.75 (d, J= 7.2 Hz, 2H, Ar–H), 7.41–7.37 (m, 4H, Ar–H),
7.21–7.16 (m, 2H, Ar–H), 7.10–7.05 (m, 8H, Ar–H), 2.65 (s, 3H,
CH3); 13C NMR (75MHz, CDCl3): d 162.14, 160.38, 159.83, 156.54,
155.32, 142.35, 130.85, 130.30, 128.19, 124.62, 119.83, 118.02, 20.67;
MS (ESI, 0 V), m/z 476 (M + 1, 100%). Anal. Calcd for C29H21N3O4:
C, 73.25; H, 4.45; N, 8.84. Found: C, 73.36; H, 4.54; N, 8.73.
4-Methyl-2,6-bis(3,5-dimethylphenyl)-5-nitropyrimidine
5f. Amorphous solid (0.70 g, 2.5 mmol, 80%); mp 134–136 ꢂC;
IR (KBr) 3132, 3021, 2943, 2863, 1589, 1554, 1427, 1372 cmꢀ1
;
1H NMR (400 MHz, CDCl3): d 8.12 (s, 2H, Ar–H), 7.78 (s, 2H,
Ar–H), 7.52 (s, 2H, Ar–H), 2.78 (s, 3H, CH3); 2.35 (s, 6H, 2
(CH3)), 2.31 (s, 6H, 2(CH3)); 13C NMR (100 MHz, CDCl3): d
163.87, 161.07, 158.30, 142.85, 136.41, 134.65, 131.56, 131.32,
129.48, 128.19, 128.40, 23.78, 20.45; MS (ESI, 0 V), m/z 348
(M+ 1, 100%). Anal. Calcd for C21H21N3O2: C, 72.60; H, 6.09;
N, 12.10. Found: C, 72.44; H, 6.27; N, 12.28.
purified by FCC (3% MeOH/CH2Cl2) to give
a pure
compound 5a as an amorphous solid (0.62 g, 2.5 mmol,
85%); mp 131–133 ꢂC; IR (KBr) 3123, 3021, 2943, 2857,
2,4-Bis(3-cyanophenyl)-6-methyl-5-nitropyrimidine 5g. Amor-
1584, 1550, 1362cmꢀ1 1H NMR (400 MHz, CDCl3): d 8.56
;
phous solid (0.64 g, 2.5 mmol, 75%); mp 140–142 ꢂC; IR (KBr)
3124, 3026, 2942, 2877, 2228, 1590, 1565, 1421, 1348 cmꢀ1
;
(d, J = 8.0 Hz, 1H, Ar–H), 8.55 (d, J = 8.4 Hz, 1H, Ar–H), 7.81
(d, J= 7.6 Hz, 1H, Ar–H), 7.77 (d, J= 8.0 Hz, 1H, Ar–H), 7.57–7.49
(m, 6H, Ar–H), 2.69 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3): d
163.68, 160.01, 157.53, 143.52, 136.07, 134.16, 131.76, 131.18,
1H NMR (400 MHz, CDCl3): d 8.02 (d, J= 8.2 Hz, 1H, Ar–H),
7.91 (d, J= 8.6 Hz, 1H, Ar–H), 7.50–7.41 (m, 4H, Ar–H), 7.35
(s, 2H, Ar–H), 2.63 (s, 3H, CH3); 13C NMR (100MHz, CDCl3):
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

November 2013
Synthesis of New 2,4-Diaryl-6-methyl-5-nitropyrimidines
as Antibacterial and Antioxidant Agents
1399
d 163.75, 161.32, 158.03, 143.65, 136.87, 133.91, 131.43, 131.21,
129.80, 128.41, 128.10, 115.32, 21.13; MS (ESI, 0 V), m/z 342
(M + 1, 100%). Anal. Calcd for C19H11N5O2: C, 66.86; H, 3.25;
N, 20.52. Found: C, 66.68; H, 3.38; N, 20.69.
slightly modified methods of Green et al. [18] and Marcocci
et al. [19]. Nitric oxide radicals were generated from sodium
nitroprusside. One milliliter of sodium nitroprusside (mM) and
1.5 mL of phosphate buffer saline (0.2 M, pH7.4) were added to
the different concentrations (20, 40, 60, 80, and 100mg) of the
compounds and incubated for 150min at 25ꢂC. After incubation,
1 mL of the reaction mixture was treated with 1 mL of
Griess reagent (1% sulfanilamide, 2% of H3PO4, and 0.1%
naphthylethylene diamine dihydrochloride). Absorbance was
measured at 546nm. The percent of inhibition of free radical
production was calculated with the use of the following equation,
using ascorbic acid (vitamin C) as a standard control.
2,4-Bis(4-cyanophenyl)-6-methyl-5-nitropyrimidine 5h. Amor-
solid (0.66 g, 2.5 mmol, 78%); mp 134–136 ꢂC; IR (KBr) 3124,
3031, 2935, 2864, 2226, 1579, 1553, 1411, 1343 cmꢀ1 1H
;
NMR (400 MHz, CDCl3): d 8.13 (d, J= 8.0 Hz, 2H, Ar–H),
7.86 (d, J= 8.3 Hz, 2H, Ar–H), 7.54–7.36 (m, 4H, Ar–H), 2.67
(s, 3H, CH3); 13C NMR (100 MHz, CDCl3): d 162.96, 160.67,
158.32, 144.19, 138.09, 135.48, 131.39, 130.95, 129.22, 128.66,
127.78, 115.34, 20.98; MS (ESI, 0 V), m/z 342 (M + 1, 100%).
Anal. Calcd for C19H11N5O2: C, 66.86; H, 3.25; N, 20.52.
Found: C, 66.74; H, 3.30; N, 20.59.
% Nitric oxide scavenging
½Absorbanceof control ꢀ Absorbanceof test sampleꢃ
2,4-Bis(4-cyanobenzyl)-6-methyl-5-nitropyrimidine 5i. Amor-
¼
100
solid (0.77 g, 2.5 mmol, 83%); mp 154–156 ꢂC; IR (KBr) 3107,
Absorbanceof control
1
3020, 2956, 2869, 2216, 1592, 1545, 1432, 1360 cmꢀ1; H NMR
(300 MHz, CDCl3): d 8.57 (d, J= 8.4 Hz, 2H, Ar–H), 7.80
(d, J= 8.4 Hz, 2H, Ar–H), 7.51–7.48 (m, 4H, Ar–H), 3.80 (s, 4H,
2CH2), 2.70 (s, 3H, CH3); 13C NMR (75 MHz, CDCl3): d
163.14, 162.67, 157.48, 145.94, 136.58, 134.36, 131.69, 130.56,
129.36, 128.71, 128.45, 118.54, 26.43, 20.24 MS (ESI, 0 V),
m/z 370 (M+ 1, 100%). Anal. Calcd for C21H15N5O2: C, 68.28;
H, 4.09; N, 18.96. Found: C, 68.42; H, 3.93; N, 18.91.
Acknowledgment. The authors are grateful to the Department
of Science & Technology, New Delhi, for providing the
financial support.
Antibacterial activity. Impregnated discs of each chemical
compound (5a–i) were prepared in separate vials with the use of
Hi Media sterilized discs (Hi Media Labs, Mumbai, India). The
title compounds were dissolved in DMSO, and these solutions
were added drop by drop to the respective disc and air dried.
The final concentration of the compound in disc was set to 50
or 100 mg of dry matter. Ampicillin was used as a positive control.
We also maintained DMSO as control, and its inhibitory zone
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was set to zero.
We carried out bactericidal activity assays by disc diffusion
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Antioxidant activity
2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging
assay. The free radical scavenging activity of 5a–i and ascorbic
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and the data are presented in Table 3. One milliliter of
various concentrations of the title compounds (20, 40, 60, 80, and
100 mg/mL) in methanol was added to 4 mL of 0.004% DPPH in
methanol. After a 30-min incubation period at room temperature,
the absorbance was measured against blank at 517 nm. The
antioxidant activity of these compounds was expressed as inhibitory
concentration 50% (IC50). The percent of inhibition of free radical
production from DPPH was calculated with the use of the
following equation, using ascorbic acid (vitamin C) as a standard
control. The percent of inhibition of free radical production from
DPPH was calculated with the use of the following equation.
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%DPPHradicalscavenging
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½Absorbanceof control ꢀ Absorbanceof test sampleꢃ
¼
100
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Absorbanceof control
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Nitric oxide scavenging activity. Nitric oxide scavenging activity
was measured for the title compounds 5 a–i with the use of
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet