Synthesis and antioxidant properties of some new 3-(4-chlorophenyl)-5- (pyridin-4-yl)-4H-1,2,4-triazole derivatives

Article abstract of DOI:10.1515/znb-2008-0512

A series of new 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethyleneamino)- 4H-1,2,4-triazole derivatives 3 were prepared in good yields by treatment of 4-amino-3-(4-chlorophenyl)-5-(pyridine-4-yl)-4H-1,2,4-triazole (2) with selected aldehydes. Compounds 3 were reduced with NaBH₄ to afford the corresponding 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethylamino)-4H-1,2,4- triazole derivatives 4. Eighteen new compounds were synthesized and characterized by elemental analyses, IR, ¹H NMR and ¹³C NMR spectral data. The compounds were screened for their antioxidant and antiradical activities.

Full text of DOI:10.1515/znb-2008-0512

Synthesis and Antioxidant Properties of Some New 3-(4-Chlorophenyl)-5-
(pyridin-4-yl)-4H-1,2,4-triazole Derivatives
a
b
b
b
¨
Olcay Bekircan , Tevfik Ozen , Nurhan Gu¨mru¨kcu¨og˘lu , and Hakan Bektas¸
a Chemistry Department, Faculty of Arts and Science, Karadeniz Technical University,
61080-Trabzon, Turkey
b Chemistry Department, Faculty of Arts and Science, Giresun University, 28049-Giresun, Turkey
Reprint requests to Dr. Olcay Bekircan. E-mail: obekircan@gmail.com
Z. Naturforsch. 2008, 63b, 548 – 554; received November 27, 2007
A series of new 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethyleneamino)-4H-1,2,4-triazole
derivatives 3 were prepared in good yields by treatment of 4-amino-3-(4-chlorophenyl)-5-(pyrid-
ine-4-yl)-4H-1,2,4-triazole (2) with selected aldehydes. Compounds 3 were reduced with NaBH4 to
afford the corresponding 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethylamino)-4H-1,2,4-triazo-
le derivatives 4. Eighteen new compounds were synthesized and characterized by elemental analyses,
IR, 1H NMR and 13C NMR spectral data. The compounds were screened for their antioxidant and
antiradical activities.
Key words: 4H-1,2,4-Triazoles, 4-Amino-4H-1,2,4-triazoles, 4-Arylmethyleneamino-4H-1,2,4-
triazoles, 4-Arylmethylamino-4H-1,2,4-triazoles, Antioxidant Activity
Introduction
A large number of heterocyclic compounds con-
Results and Discussion
In the current study, ethyl p-chlorobenzoate 4-pyrid-
taining the 1,2,4-triazole ring are associated with di- inoylhydrazone (1) was synthesized from the reaction
verse pharmacological properties, such as anticonvul- of ethyl imido-p-chlorophenylbenzoate hydrochloride
sant, antifungal, antimicrobial, antihypertensive, anal- with isonicotinohydrazide. 4-Amino-3-(4-chloro-
gesic, antiviral, anti-inflammatory, antioxidant, antitu- phenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole (2) was
mor and anti-HIV activity [1 – 15]. Some compounds obtained from the reaction of compound 1 with hydr-
containing a 1,2,4-triazole ring are known as drugs. azine hydrate. Compound 2 was treated with some
For example, fluconazole is used as an antimicrobial aromatic aldehydes in acetic acid to give 3-(4-chloro-
drug in medicine [16], vorozole, letrozole and anas- phenyl)-5-(pyridin-4-yl)-4-(arylmethyleneamino)-4H-
trozole are non-steroidal drugs used for the treatment 1,2,4-triazoles (3). Subsequently, compounds 3 were
of cancer [17], and loreclezole is used as an anticon- converted to 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-
vulsant drug [18]. Furthermore, in recent years, some (arylmethylamino)-4H-1,2,4-triazoles(4) by treatment
Schiff base derivatives of 1,2,4-triazoles and their re- with NaBH4 in methanol (Scheme 1).
duced derivatives have also been found to possess phar-
It was reported that Schiff bases can be obtained
macological activities [19 – 26]. It is also observed that as their E and Z geometrical isomers at the C=N
incorporation of an aryloxymethyl and a halogen sub- double bond [27– 30]. According to literature data,
stituent into the heterocyclic ring systems augments the the signals of the azomethine protons of the E iso-
biological activities considerably [26]. These biologi- mers of triazole derivatives appear at higher field
cal data prompted us to synthesize new 1,2,4-triazole with respect to the corresponding signals of the Z
derivatives. The synthesized compounds were evalu- isomers [27 – 30]. On the basis of these findings, we
ated for antioxidant and free radical scavenging activ- assigned the E configuration to the isomers with the
ity. Furthermore, we observed that some compounds higher percentage in the mixtures. The percentage of
possess more potent antioxidant and antiradical scav- each isomer was calculated using the integral values
enging activities than butylated hydroxyanisole (BHA) of each singlet pair in Table 1. Moreover, in the
and butylated hydroxytoluene (BHT).
13C NMR spectra of compounds 3a – h the N=CH
c
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O. Bekircan et al. · Some New 3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole Derivatives
549
Scheme 1. Synthetic pathway for the prepa-
ration of target compounds 2 – 4.
Table 1. Determination of the configuration of the Schiff
and standard compounds was determined by the thio-
barbituric acid method (TBA) in linoleic acid. The
TBA method was used to measure the amount of per-
oxide produced during the initial stages of oxidation.
The effects of some of the new compounds (50 µg
mL−1) on lipid peroxidation was found to range from
44.1 to 75.4 % (Table 2), higher than that of BHA
(63.7 %) and BHT (67.8 %). Compounds 3b, e – h and
4b, c, e – h showed the highest activities, with com-
pounds 4h, 4b and 3f bearing 2-hydroxy-5-methoxy,
4-chloro, and 2-hydroxy substituents, respectively, be-
ing the most active ones.
bases 3a – h by assignment of the azomethine hydrogen sig-
nals and their relative integrals in the 1H NMR spectra ([D6]-
DMSO, 200 MHz).
— δ (ppm) —
Compound
E-isomer
Z-isomer
Ratio E:Z
3a
3b
3c
3d
3e
3f
8.69
8.73
8.69
8.76
8.72
8.73
8.67
8.74
8.64
8.70
8.63
8.72
8.67
8.69
8.63
8.71
7.5 : 1
9 : 1
5 : 1
8.3 : 1
15 : 1
7.2 : 1
11.2 : 1
3.8 : 1
3g
3h
Antiradical activity
signals of the E, Z isomers appeared at 170.64/170.17,
170.64/170.58, 170.79/170.30, 170.17/169.62, 163.94/
163.17, 167.93/167.47, 165.57/165.45 and 164.34/
164.27 ppm, respectively.
Radical scavenging activities are an important prop-
erty because of the deleterious role of free radicals
in foods and biological systems. Excessive formation
of free radicals accelerates the oxidation of lipids in
foods and decreases food quality and consumer accep-
tance [32]. The chosen assay is considered valid and
easy for the evaluation of the free radical scavenging
activity of antioxidants, since the radical compound is
stable and does not have to be generated as for other
radical scavenging assays [33]. With this method it
was possible to determine the antiradical power of an
antioxidant by measuring the decrease of absorbance
of DPPH• at 517 nm. Compounds 4g, 2, 4h, 3g, 3f,
The reduction of 3 with NaBH4 occurred at the
imino group exclusively, without affecting the hetero
1
ring [23, 24, 31]. The characteristic H NMR signals
for the -NH–CH2- group of reduced compounds 4a –
e were observed as triplets at δ = 7.40 ppm (t, 1H,
NH) and doublets at δ = 3.75 ppm (d, 2H, CH2). The
-NH–CH2- carbon signals of compounds 4a – e were
recorded between δ = 47.14 and 53.75 ppm.
Antioxidant activity
The antioxidant activity of some new 3-(4-chloro- 4f, 3h, 3b, and 4e showed highest interactions with
phenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole derivatives the DPPH• radical, even better than BHA and BHT
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O. Bekircan et al. · Some New 3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole Derivatives
Table 2. The antioxidant and antiradical activities of
some new 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-tri-
azole derivatives.
δ = 1.35 (t, 3H, CH3), 4.33 (q, 2H, OCH2), 7.47 – 7.27 (m,
5H, Ar-H), 8.63 – 8.74 (m, 3H, Ar-H), 10.97 (s, 1H, NH). –
13C NMR ([D6]-DMSO): δ = 14.00 (CH3), 63.33 (OCH2),
121.10 (2C), 128.78 (2C), 129.45, 129.66, 135.21, 140.76
(2C), 150.03 (2C) (all Ar-C), 160.75 (C=N), 164.34 (C=O).
Compound
Antioxidant activity
Antiradical activity
1
2
3a
3b
3c
3d
3e
3f
3g
3h
4a
4b
4c
4d
4e
4f
56.84 1.43
73.22 1.37
61.88 0.98
70.39 0.66
47.05 3.19
44.06 1.02
73.64 1.13
74.04 1.52
71.44 0.54
70.87 0.50
64.13 0.47
74.71 0.91
71.73 1.30
54.57 3.54
72.11 0.92
73.62 0.28
73.43 0.96
75.42 0.55
63.71 0.79
67.77 0.61
68.30 0.85
93.38 1.04
80.60 0.30
89.70 0.71
79.77 0.57
57.84 1.89
85.28 6.50
91.84 0.40
92.54 0.70
90.83 0.30
79.47 1.05
65.69 5.20
80.94 0.30
70.47 2.30
89.30 0.25
91.24 0.65
94.71 0.45
92.64 0.71
87.29 0.85
88.63 0.72
Synthesis of compound 2
Compound 1 (0.005 mol) was added to a solution of hydr-
azine hydrate (0.01 mol) in 50 mL of 1-propanol and the
mixture was refluxed for 24 h. On cooling, a precipitate
was formed. This product was filtered and, after drying, was
washed with 20 mL of benzene. The remaining solid was
recrystallized from 1-propanol to afford pure compound 2.
Yield: 54 %, m. p. 261 – 262 ◦C. – IR (KBr): ν = 3311, 3184
(NH2), 1602 (C=N), 835, 731, 699 (arom. ring) cm−1. –
1H NMR ([D6]-DMSO): δ = 6.44 (s, 2H, NH2), 7.61 – 7.65
(d, 2H, Ar-H), 8.03 – 8.09 (m, 4H, Ar-H), 8.74 – 8.77 (m, 2H,
Ar-H). – 13C NMR ([D6]-DMSO): δ = 121.83 (2C), 125.46,
128.59 (2C), 129.96 (2C), 134.13, 134.67, 149.97 (2C) (all
Ar-C), 152.25 (triazole C3), 154.08 (triazole C5). – Anal. for
C13H10N5Cl (271.7): calcd. C 57.47, H 3.71, N 25.78; found
C 57.77, H 3.72, N 25.48.
4g
4h
BHA
BHT
(Table 2). The inhibition values for these compounds
were 89.6 – 94.7 % at 50 µg mL−1. Compounds 4g, 2,
4h and 3g had the strongest interactions with the stable
free radical DPPH•.
General method for the synthesis of compounds 3a – 3h
The corresponding aldehyde (0.005 mol) was added to
a solution of compound 2 (0.005 mol) in 20 mL of glacial
acetic acid, and the mixture was refluxed for 4 h. After cool-
ing, the mixture was poured into a beaker containing 100 mL
of ice-water. The precipitate formed was filtered. After dry-
ing in vacuo, the product was recrystallized from an appro-
priate solvent to give the desired compound.
Experimental Section
Melting points were determined on a Barnstead Elec-
trothermal melting point apparatus and are uncorrected.
1H NMR and 13C NMR spectra (δ, ppm) were recorded on a
Varian-Mercury 200 MHz spectrometer using tetramethylsil-
ane as an internal reference. IR spectra (ν, cm−1) were run on
a Perkin-Elmer 1600 FTIR spectrometer by using KBr pel-
lets. Elemental analyses were performed on an ECS 4010 el-
emental combustion system CHNS-O. The necessary chem-
icals were purchased from Merck and Fluka.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-fluorobenzyliden-
amino)-4H-1,2,4-triazole (3a)
Recrystallized from ethanol-water (1 : 1), yield 55 %,
m. p. 230 – 231 ◦C. – IR (KBr): ν = 1560, 1602 (C=N), 829,
770, 686 (arom. ring) cm−1. – 1H NMR ([D6]-DMSO): δ =
Ar-H [7.34 – 7.44 (m, 3H), 7.57 – 7.61 (m, 3H), 7.80 – 7.97
(m, 6H)], 8.69 and 8.64 (s, 1H, -N=CH, E and Z isomers). –
13C NMR ([D6]-DMSO): δ = 116.82, 121.72 (2C), 124.62,
127.66 (2C), 129.02 (2C), 129.96 (2C), 132.02 (2C), 133.41,
134.85, 148.30 (2C), 167.70 (all Ar-C), 149.87 (triazole
C-3), 150.31 (triazole C-5), 170.64 and 170.17 (N=CH, E
and Z isomers ). – Anal. for C20H13N5ClF (377.8): calcd.
C 63.58, H 3.47, N 18.54; found C 63.59, H 3.48, N 18.10.
Synthesis of compound 1
A solution of isonicotinic acid hydrazide (0.01 mol) in
25 mL of absolute ethanol was added to a solution of ethyl
imido-p-chlorobenzoate hydrochloride (0.01 mol) in 25 mL
of◦absolute ethanol. The mixture was stirred for 6 h at 0 –
5 C and subsequently for 2 h at r. t. The reaction mixture
was poured into a beaker containing 40 mL of cold water
and 10 g of ice. The precipitate formed was washed with
50 mL of ice-water and then dried. The product◦was recrys-
tallized from benzene-petroleum ether (40 – 60 C) ◦(1 : 2) to
give pure compound 1. Yield: 85 %, m. p. 80 – 81 C. – IR
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-chlorobenzyliden-
amino)-4H-1,2,4-triazole (3b)
Recrystallized from ethanol-water (1 : 1), yield 71 %,
(KBr): ν = 3203 (NH), 1671 (C=O), 1617 (C=N), 838, m. p. 233 – 234 ◦C. – IR (KBr): ν = 1559, 1603 (C=N), 850,
752, 706 (arom. ring) cm−1. – 1H NMR ([D6]-DMSO): 823, 773, 687 (arom. ring) cm−1. – 1H NMR ([D6]-DMSO):
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O. Bekircan et al. · Some New 3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole Derivatives
551
δ = Ar-H [7.56 – 7.64 (m, 6H), 7.81 – 7.88 (m, 6H)], 8.73 and 3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-hydroxybenzylid-
8.70 (s, 1H, -N=CH, E and Z isomers). – 13C NMR ([D6]- enamino)-4H-1,2,4-triazole (3f)
DMSO): δ = 121.74 (2C), 124.56, 129.02 (2C), 129.48 (2C),
Recrystallize◦d from ethanol-water (1 : 1), yield 63 %,
129.77, 129.97 (2C), 130.82 (2C), 133.36, 134.87, 138.45,
m. p. 215 – 216 C. – IR (KBr): ν = 3131 (OH), 1570, 1607
148.29 (2C) (all Ar-C), 149.84 (triazole C-3), 150.31 (tri-
azole C-5), 170.64 and 170.58 (N=CH, E and Z isomers). –
Anal. for C20H13N5Cl2 (394.3): calcd. C 60.93, H 3.32,
N 17.76; found C 60.71, H 3.32, N 17.85.
(C=N), 831, 764, 725 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = Ar-H [6.86 – 6.95 (m, 2H), 7.40 – 7.61 (m, 4H),
7.82 – 7.95 (m, 6H)], 8.73 and 8.69 (s, 1H, -N=CH-, E and
Z isomers), 10.43 (s, 1H, OH). – 13C NMR ([D6]-DMSO):
δ = 117.44, 118.24, 120.53 (2C), 122.67, 126.00, 128.26
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-bromobenzyliden-
amino)-4H-1,2,4-triazole (3c)
(2C), 129.73 (2C), 130.72, 134.50, 135.35, 136.08, 150.12
(2C), 159.60 (all Ar-C), 150.64 (triazole C-3), 151.09 (tri-
azole C-5), 167.93 and 167.47 (-N=CH-, E and Z isomers). –
Anal. for C20H14N5OCl (375.8): calcd. C 63.92, H 3.75,
N 18.63; found C 63.97, H 4.16, N 18.48.
Recrystallized from ethanol-water (1 : 1), yield 68 %,
m. p. 186 – 187 ◦C. – IR (KBr): ν = 1588, 1602 (C=N),
840, 822, 724, 689 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = Ar-H [7.56 – 7.85 (m, 12H)], 8.69 and 8.63 (s,
1H, -N=CH, E and Z isomers). – 13C NMR ([D6]-DMSO)
δ = 121.43 (2C), 123.58, 129.00 (2C), 129.87 (2C), 129.98,
130.92, 131.79 (2C), 132.44 (2C), 133.15, 134.90, 147.63
(2C) (all Ar-C), 150.24 (triazole C-3), 150.33 (triazole C-5),
170.79 and 170.30 (N=CH, E and Z isomers). – Anal. for
C20H13N5BrCl (438.7): calcd. C 54.76, H 2.99, N 15.96;
found C 54.66, H 3.10, N 15.56.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-hydroxy-5-bromo-
benzylidenamino)-4H-1,2,4-triazole (3g)
Recrystallize◦d from ethanol-water (1 : 1), yield 95 %,
m. p. 254 – 255 C. – IR (KBr): ν = 3043 (OH), 1597, 1602
(C=N), 828, 775, 728 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = Ar-H [6.84 – 6.88 (d, 2H), 7.58 – 7.62 (m, 4H),
7.80 – 7.96 (m, 5H)], 8.67 and 8.63 (s, 1H, -N=CH-, E and
Z isomers), 10.78 (s, 1H, OH). – 13C NMR ([D6]-DMSO):
δ = 110.85, 119.00 (2C), 119.31, 124.80, 125.09, 128.98,
129.00 (2C), 129.99 (2C), 130.09, 134.80, 137.50, 149.81
(2C), 157.29 (all Ar-C), 150.29 (triazole C-3 and triazole
C-5), 165.57 and 165.45 (-N=CH-, E and Z isomers). –
Anal. for C20H13N5OBrCl (454.7): calcd. C 52.83, H 2.88,
N 15.40; found C 53.09, H 2.99, N 14.93.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-trifluoromethyl-
benzylidenamino)-4H-1,2,4-triazole (3d)
Recrystallized from ethanol-water (1 : 1), yield 64 %,
m. p. 177 – 178 ◦C. – IR (KBr): ν = 1572, 1601 (C=N), 829,
750, 721 (arom. ring) cm−1. – 1H NMR ([D6]-DMSO): δ =
Ar-H [7.57 – 7.62 (m, 4H), 7.82 – 7.93 (m, 8H)], 8.76 and
8.72 (s, 1H, -N=CH, E and Z isomers). – 13C NMR ([D6]-
DMSO): δ = 121.84 (2C), 126.19, 129.00 (2C), 129.73 (2C),
129.86, 129.96 (2C), 130.06, 133.35, 134.76 (2C), 134.96,
149.34 (2C) (all Ar-C), 124.84 (CF3), 149.85 (triazole C-3),
150.35 (triazole C-5), 170.17 and 169.62 (-N=CH-, E and Z
isomers). – Anal. for C21H13N5ClF3 (427.8): calcd. C 58.96,
H 3.06, N 16.37; found C 58.97, H 3.19, N 16.64.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-hydroxy-5-meth-
oxybenzylidenamino)-4H-1,2,4-triazole (3h)
Recrystallized from ethanol-water (1 : 1), yield 56 %,
m. p. 215 – 216 ◦C. – IR (KBr): ν = 3235 (OH), 1573 –
1
1603 (C=N), 823, 750, 654 (arom. ring) cm−1. – H NMR
([D6]-DMSO): δ = 3.85 (s, 3H, OCH3), Ar-H [6.98 (d,
2H), 7.36 (d, 2H), 7.57 – 7.63 (m, 3H), 7.86 – 7.95 (m, 4H)],
8.74 and 8.71 (s, 1H, -N=CH-, E and Z isomers), 10.22 (s,
1H, OH). – 13C NMR ([D6]-DMSO): δ = 53.72 (OCH3),
121.65 (2C), 124.65, 125.26, 127.83, 128.64, 128.72 (2C),
129.70 (2C), 133.86, 134.70, 139.85, 149.97 (2C), 153.08,
153.70 (all Ar-C), 152.01 (triazole C-3 and triazole C-5),
164.34 and 164.27 (-N=CH-, E and Z isomers). – Anal. for
C21H16N5O2Cl (405.8): calcd. C 62.15, H 3.97, N 17.26;
found C 62.37, H 3.96, N 17.25.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-fluoro-4-chloro-
benzylidenamino)-4H-1,2,4-triazole (3e)
Recrystallized from ethanol-water (1 : 1), yield 73 %,
m. p. 187 – 188 ◦C. – IR (KBr): ν = 1562, 1607 (C=N),
828, 755, 722, 689 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = Ar-H [7.48 – 7.67 (m, 5H), 7.80 – 7.84 (m,
4H), 8.01 – 8.09 (m, 2H)], 8.72 and 8.67 (s, 1H, -N=CH-,
E and Z isomers). – 13C NMR ([D6]-DMSO): δ = 117.04,
118.00, 121.92 (2C), 124.64, 126.00, 128.98 (2C), 129.81,
General method for the synthesis of compound 4a –4h
The corresponding compound 3a – h (0.005 mol) was dis-
130.13 (2C), 133.45, 134.93, 139.36, 149.27 (2C), 158.79 solved in 50 mL of dried methanol, and NaBH4 (0.005 mol)
(all Ar-C), 149.77 (triazole C-3), 150.32 (triazole C-5), was added in small portions to this solution. The mixture was
163.94 and 163.17 (-N=CH-, E and Z isomers). – Anal. for refluxed for 20 ◦min and then allowed to cool. After evapora-
C20H12N5Cl2F (412.3): calcd. C 58.27, H 2.93, N 16.99; tion at 25 – 30 C under reduced pressure, the solid residue
found C 58.27, H 2.93, N 16.56.
was washed with cold water. After drying in vacuo, the solid
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552
O. Bekircan et al. · Some New 3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole Derivatives
product was recrystallized from an appropriate solvent to af- (d, 2H), 7.53 – 7.60 (m, 2H), 7.81 – 7.91 (m, 4H), 8.69 (d,
ford the desired compound.
2H)], 7.48 (t, 1H, NH). – 13C NMR ([D6]-DMSO): δ =
53.74 (CH2), 121.67 (2C), 125.56(2C), 128.67 (2C), 128.76
(2C), 129.62 (2C), 129.71, 133.87, 134.72, 134.97, 139.88,
149.99 (2C) (all Ar-C), 124.75 (CF3), 152.03 (triazole C-3),
153.10 (triazole C-5). – Anal. for C21H15N5ClF3 (429.8):
calcd. C 58.68, H 3.52, N 16.29; found C 59.05, H 3.53,
N 16.19.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-fluorobenzyl-
amino)-4H-1,2,4-triazole (4a)
Recrystallized from ethanol-water (1 : 1), yield 85 %,
m. p. 215 – 216 ◦C. – IR (KBr): ν = 3245 (NH), 1560 –
1603 (C=N), 830, 733 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = 3.75 (d, 2H, CH2), Ar-H [6.68 – 6.82 (m, 4H),
7.58 – 7.68 (m, 2H), 7.78 – 8.07 (m, 4H), 8.72 – 8.78 (m,
2H)], 7.42 (t, 1H, NH). – 13C NMR ([D6]-DMSO): δ =
53.75 (CH2), 114.91 (2C), 121.62 (2C), 125.37, 128.74 (2C),
129.55 (2C), 129.65 (2C), 130.75 (2C), 134.93, 149.96 (2C),
159.07 (all Ar-C), 152.02 (triazole C-3), 153.69 (triazole
C-5). – Anal. for C20H15N5ClF (379.8): calcd. C 63.25,
H 3.98, N 18.44; found C 63.29, H 3.99, N 18.72.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-fluoro-4-chloro-
benzylamino)-4H-1,2,4-triazole (4e)
Recrystallize◦d from ethanol-water (1 : 1), yield 66 %,
m. p. 234 – 235 C. – IR (KBr): ν = 3254 (NH), 1610, 1582
(C=N), 825, 820, 734 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = 3.78 (d, 2H, CH2), Ar-H [6.74 – 6.98 (m, 3H),
7.55 – 7.61 (m, 3H), 7.84 – 7.94 (m, 3H), 8.70 (d, 2H)], 7.47
(t, 1H, NH). – 13C NMR ([D6]-DMSO): δ = 47.27 (CH2),
115.14, 121.50 (2C), 125.09, 128.49, 128.60 (2C), 129.47,
129.58 (2C), 132.54, 133.67, 134.64, 134.91, 149.84 (2C),
162.87 (all Ar-C), 151.93 (triazole C-3), 153.66 (triazole
C-5). – Anal. for C20H14N5Cl2F (414.3): calcd. C 57.99,
H 3.41, N, 16.91; found C 57.99, H 3.42, N 16.48.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-chlorobenzyl-
amino)-4H-1,2,4-triazole (4b)
Recrystallize◦d from ethanol-water (1 : 1), yield 84 %,
m. p. 262 – 263 C. – IR (KBr): ν = 3270 (NH), 1601, 1565
(C=N), 836, 810, 824, 780 (arom. ring) cm−1. – H NMR
1
([D6]-DMSO): δ = 3.72 (d, 2H, CH2), Ar-H [6.72 – 6.76 (d,
2H), 7.065 (d, 2H), 7.56 – 7.62 (m, 2H), 7.83 – 7.93 (m, 4H),
8.70 (d, 2H)], 7.38 (t, 1H, NH). – 13C NMR ([D6]-DMSO):
δ = 53.40 (CH2), 121.65 (2C), 125.34, 127.88 (2C), 128.74
(2C), 129.59 (2C), 129.68 (2C), 130.62, 132.31, 134.00,
134.96, 149.97 (2C) (all Ar-C), 152.01 (triazole C-3), 153.69
(triazole C-5). – Anal. for C20H15N5Cl2 (396.3): calcd.
C 60.62, H 3.82, N 17.67; found C 60.44, H 3.85, N 17.75.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-hydroxybenzyl-
amino)-4H-1,2,4-triazole (4f)
Recrystallized from ethanol-water (1 : 1), yield 80 %,
m. p. 293 – 294 ◦C. – IR (KBr): ν = 3265 (NH), 3070 (OH),
1607, 1557 (C=N), 825, 756, 733 (arom. ring) cm−1. –
1H NMR( [D6]-DMSO): δ = 3.75 (d, 2H, CH2), Ar-H [6.50 –
6.70 (m, 3H), 7.14 (bs, 1H), 7.59 – 7.62 (m, 3H), 8.00 – 8.06
(m, 4H), 8.70 (bs, 1H)], 7.00 (t, 1H, NH), 9.47 (s, 1H,
OH). – 13C NMR ([D6]-DMSO) δ = 49.14 (CH2), 114.67,
118.44, 121.09 (2C), 125.49, 128.48, 128.58 (2C), 128.96,
129.66 (2C), 130.56, 134.01, 134.74, 149.82 (2C), 155.71
(all Ar-C), 152.91 (triazole C-3), 153.62 (triazole C-5). –
Anal. for C20H16N5OCl (377.8): calcd. C 63.58, H 4.27,
N 18.54; found C 63.67, H 4.30, N 18.32.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-bromobenzyl-
amino)-4H-1,2,4-triazole (4c)
Recrystallize◦d from ethanol-water (1 : 1), yield 60 %,
m. p. 241 – 242 C. – IR (KBr): ν = 3248 (NH), 1602, 1547
(C=N), 834, 825, 732 (arom. ring) cm−1. – 1H NMR ([D6]-
DMSO): δ = 3.72 (d, 2H, CH2), Ar-H [6.72 (d, 2H), 7.21 (d,
2H), 7.43( d, 2H), 7.62 – 7.90 (m, 4H), 8.73 (bs, 2H)], 7.40
(bs, 1H, NH). – 13C NMR ([D6]-DMSO): δ = 53.52 (CH2),
120.96, 121.73 (2C), 125.37, 128.80 (2C), 129.74 (2C),
130.86 (2C), 131.01(2C), 134.44, 134.75, 135.03, 149.98
(2C) (all Ar-C), 150.12 (triazole C-3 and triazole C-5). –
Anal. for C20H15N5BrCl (440.7): calcd. C 54.51, H 3.43,
N 15.89; found C 54.68, H 3.53, N 16.19.
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-hydroxy-5-bromo-
benzylamino)-4H-1,2,4-triazole (4g)
Recrystallized from ethanol-water (1 : 1), yield 83 %,
m. p. 287 – 288 ◦C. – IR (KBr): ν = 3260 (NH), 3080 (OH),
1603, 1537 (C=N), 826, 820, 735 (arom. ring) cm−1. –
1H NMR ([D6]-DMSO): δ = 3.73 (d, 2H, CH2), Ar-H [6.48
(m, 1H), 6.80 (bs, 1H), 7.05 (m, 1H), 7.26 (bs, 1H), 7.57
(m, 3H), 7.93 (d, 4H)], 7.15 (t, 1H, NH), 9.69 (s, 1H,
OH). – 13C NMR ([D6]-DMSO): δ = 48.17 (CH2), 109.38,
116.61, 123.96 (2C), 125.37, 128.55 (2C), 129.57, 129.68
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(4-trifluoromethyl-
benzylamino)-4H-1,2,4-triazole (4d)
Recrystallize◦d from ethanol-water (1 : 1), yield 85 %, (2C), 131.17, 132.96, 134.56, 134.79, 149.81 (2C), 155.01
m. p. 216 – 217 C. – IR (KBr): ν = 3256 (NH), 1603, 1550 (all Ar-C), 151.96 (triazole C-3), 153.08 (triazole C-5). –
(C=N), 825, 770, 733 (arom. ring) cm−1. – 1H NMR ([D6]- Anal. for C20H15N5OBrCl (456.7): calcd. C 52.60, H 3.31,
DMSO): δ = 3.82 (d, 2H, CH2), Ar-H [6.94 (d, 2H), 7.33 N 15.33; found C 52.49, H 3.47, N 15.02.
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O. Bekircan et al. · Some New 3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-triazole Derivatives
553
3-(4-Chlorophenyl)-5-(pyridin-4-yl)-4-(2-hydroxy-5-meth-
oxybenzylamino)-4H-1,2,4-triazole (4h)
Analysis of all samples was done in triplicate and averaged.
The inhibition of lipid peroxidation in percent was calculated
by the following the equation:
Recrystallized from ethanol-water (1 : 1), yield 78 %,
m. p. 283 – 284 ◦C. – IR (KBr): ν = 3258 (NH), 3082 (OH),
1604, 1540 (C=N), 826, 803, 734 (arom. ring) cm−1. –
1H NMR ([D6]-DMSO): δ = 3.45 (s, 3H, OCH3), 3.73 (d,
2H, CH2 ), Ar-H [6.22 (bs, 1H), 6.50 (d, 2H), 7.54 – 7.60
(m, 3H), 7.97 – 8.00 (m, 4H), 8.65 (bs, 1H)], 7.16 (t, 1H,
NH), 8.92 (s, 1H, OH). – 13C NMR ([D6]-DMSO): δ =
48.87 (CH2), 54.85 (OCH3), 114.37, 115.23, 121.52 (2C),
125.50, 128.45, 128.53 (2C), 129.58, 129.68 (2C), 134.44,
134.69, 149.35, 149.81 (2C), 153.72 (all Ar-C), 151.89 (tri-
azole C-3), 153.01 (triazole C-5). – Anal. for C21H18N5O2Cl
(407.9): calcd. C 61.84, H 4.45, N 17.17; found C 61.49,
H 4.72, N 17.53.
Inhibition of lipid peroxidation (in %) = 100 × (A0 −
A1)/A0, where A0 is the absorbance of control and A1 is the
absorbance of compounds or standards.
Assay of antiradical activity
Some new 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4H-1,2,4-
triazole derivatives and standard compounds were tested for
their ability to bleach the stable radical DPPH• (1-diphenyl-
2-picryl-hydrazyl) as described by Blois at 50 µg mL−1 [37].
1 mL of DPPH• solution [0.1 mmol L−1, in 95 % ethanol
(v/v)] was incubated with different concentrations of ex-
tract. Thirty minutes later, the absorbance was measured at
517 nm. Lower absorbance of the reaction mixture indicated
the higher free radical scavenging activity. The DPPH• con-
centration (mM) in the reaction medium was calculated from
Assay of antioxidant activity
The compound, 50 µg mL−1, and a standard sample
(BHA, BHT) in 2.5 mL of potassium phosphate buffer
(0.04 M, pH = 7.0) were added to a linoleic acid emul-
sion in potassium phosphate buffer (2.5 mL, 0.04 mM, pH =
7.0) [34]. As a reference 5 mL of a control fluid consist-
ing of linoleic acid emulsion (2.5 mL) and potassium phos-
phate buffer (2.5 mL, 4 mM, pH = 7.0) were used. The re-
action mixture was incubated in a glass flask at 37 ◦C in the
dark. The solution without compounds or standard was used
as a blank sample. The lipid peroxide formation was then
monitored [35]. To 1 mL solution, 20 % trichloroacetic acid
(2 mL) and thiobarbituric acid (2 mL) were added. This mix-
ture was then placed in a boiling water bath for 25 min. After
cooling, it was centrifuged at 3000 rpm for 20 min. The ab-
sorbance of the supranatant was measured at 532 nm [36].
a calibration curve, determined by linear regression (R2
0.9998): Absorbance = 6.5781×[DPPH•]+0.058.
=
The activity to scavenge the DPPH• radical was calcu-
lated using the equation:
DPPH• scavenging effect (in %) = 100 × (A0 − A1)/A0,
where A0 is the absorbance of control and A1 is the ab-
sorbance of compounds or standards. The DPPH• solution
without sample solution was used as a control. Triplicate
samples were run for each set and averaged.
Acknowledgement
The authors are thankful to Prof. Dr. N. Yaylı, Department
of Chemistry, Faculty of Arts and Science, Karadeniz Tech-
nical University, Trabzon, Turkey, for elemental analyses.
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