Synthesis of some new 1,2,4-triazoles starting from isonicotinic acid hydrazide and evaluation of their antimicrobial activities

Article abstract of DOI:10.1016/j.ejmech.2009.05.022

5-Pyridin-4-yl-1,3,4-oxadiazole-2-thiol (2) was obtained from the reaction of isonicotinic acid hydrazide with carbon disulfide in basic media and converted into 4-amino-5-pyridin-4-yl-4H-1,2,4-triazole-3-thiol (5) by the treatment with hydrazine hydrate. The synthesis of 3 and 6 was performed from the reaction of 2 and 5 with ethyl bromide. The treatment of 5 with 4-fluorobenzaldehyde or indol-3-carbaldehyde resulted in the formation of 4-[(arylmethylene)amino]-5-pyridin-4-yl-4H-1,2,4-triazole-3-thiols (7a and 7b). The reactions of 2, 5 and 7a with some primary and secondary amines in the presence of formaldehyde afforded the corresponding Mannich bases, 4a, 4b, 9a-9c and 8. All newly synthesized compounds were screened for their antimicrobial activity. The antimicrobial activity study revealed that all the compounds screened showed good or moderate activity except compounds 2, 7a, 7b, 8 and 9b.

Full text of DOI:10.1016/j.ejmech.2009.05.022

European Journal of Medicinal Chemistry 44 (2009) 4362–4366
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis of some new 1,2,4-triazoles starting from isonicotinic acid hydrazide
and evaluation of their antimicrobial activities
Hacer Bayrak , Ahmet Demirbas , Neslihan Demirbas ,*, Seng u¨ l Alpay Karaoglu b
a
a
a
a
Karadeniz Technical University, Department of Chemistry, 61080 Trabzon, Turkey
Rize University, Department of Biology, 53100 Rize, Turkey
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 December 2008
Received in revised form
5-Pyridin-4-yl-1,3,4-oxadiazole-2-thiol (2) was obtained from the reaction of isonicotinic acid
hydrazide with carbon disulfide in basic media and converted into 4-amino-5-pyridin-4-yl-4H-1,2,4-
triazole-3-thiol (5) by the treatment with hydrazine hydrate. The synthesis of 3 and 6 was performed
from the reaction of 2 and 5 with ethyl bromide. The treatment of 5 with 4-fluorobenzaldehyde or
indol-3-carbaldehyde resulted in the formation of 4-[(arylmethylene)amino]-5-pyridin-4-yl-4H-1,2,4-
triazole-3-thiols (7a and 7b). The reactions of 2, 5 and 7a with some primary and secondary amines in
the presence of formaldehyde afforded the corresponding Mannich bases, 4a, 4b, 9a–9c and 8.
All newly synthesized compounds were screened for their antimicrobial activity. The antimicrobial
activity study revealed that all the compounds screened showed good or moderate activity except
compounds 2, 7a, 7b, 8 and 9b.
18 May 2009
Accepted 20 May 2009
Available online 28 May 2009
Keywords:
Isonicotinic acid hydrazide
1
,3,4-Oxadiazole
,2,4-Triazole
Antimicrobial activity
1
Ó 2009 Published by Elsevier Masson SAS.
1. Introduction
a Schiff base structures were synthesized in our laboratories as
antitumor agents [10–13].
During the past decades, the human population affected with
life-treating infectious diseases caused by multidrug-resistant
Gram-positive and Gram-negative pathogen bacteria increased an
alarming level around the world. Due to this reason, new classes of
antibacterial agents with novel mechanisms are crucial need to
combat with the multidrug-resistant infections. In the past years,
some azole derivatives were developed as new antimicrobial
agents, for instance, Linezolid and Eperezolid (Chart 1) are
currently used for the treatment of multidrug-resistant Gram-
positive infections [1–3]. There are a number of antimicrobial
compounds containing a 1,2,4-triazole ring in their structures such
as Fluconazole, Itraconazole, Voriconazole, Ravuconazole and Pos-
aconazole that are important antifungal drugs (Chart 1) [4].
Heterocycles containing a 1,2,4-triazole or 1,3,4-thiadiazole
moiety, and the compounds consisting of 1,2,4-triazole and 1,3,4-
thiadiazole condensed nucleus systems constitute a class of
compounds possessing a wide spectrum of biological activities such
as anti-inflammatory, antiviral and antimicrobial and antitumoral
properties [5–8]. Furthermore, Schiff bases derived from various
heterocycles were reported to possess some biological activities [9].
Among these, some 1,2,4-triazole derivatives containing also
Mannich bases of 1,2,4-triazoles containing N-methylpiperazine
moiety are known as antimicrobial agents. More recently, some
Mannich bases possessing antimicrobial activity were synthesized
by using 1,2,4-triazole-Schiff bases and methyl piperazine or mor-
pholine [14]. The drugs, Prazosin, Lidoflazine and Urapidil,
containing piperazine nucleus are used as cardiovascular agents
(Chart 2) [15–17]. Moreover, Norfloxacin, Ciprofloxacin and Oflox-
acin (Chart 2), that are effective drugs against respiratory, urinary,
gastrointestinal tracts, skin and soft tissue infections caused by
either Gram-positive or Gram-negative bacteria, contain a methyl
piperazine or piperazine ring in their structures [18,19], as well as
Itraconazol and Posaconazol (Chart 1).
Heterocycles including amino and mercapto groups together
can be considered as useful intermediates in organic synthesis.
Some triazolothiadiazoles or triazolothiadiazines were obtained in
our laboratories starting from 4-amino-5-mercapto-1,2,4-triazoles.
The amino and mercapto groups are ready-made nucleophilic
centers for the synthesis of condensed heterocyclic rings [20–22].
Moreover, these groups can react with electrophiles. For instance,
some alkylation and Mannich reactions that take place at S- or N-
atom were reported [23–25].
In view of these facts, the aim of this present study is to obtain
1,3,4-oxadiazole and 1,2,4-triazole derivatives incorporating also
Schiff Base and Mannich Base structures (Scheme 1) as antimicro-
bial agents.
*
Corresponding author. Tel.: þ90 462 3772600; fax: þ90 4623253196.
E-mail address: ndemirbas651@ktu.edu.tr (N. Demirbas).
0223-5234/$ – see front matter Ó 2009 Published by Elsevier Masson SAS.
doi:10.1016/j.ejmech.2009.05.022

H. Bayrak et al. / European Journal of Medicinal Chemistry 44 (2009) 4362–4366
4363
OH
O
O
N
N
O
O
O
N
CN
N
N
N
O
N
N
F
S
N
NHAc
NHAc
OH
F
F
F
Eperezolid
Linezolid
Ravuconazole
N
CH3
N
O
N
N
N
N
N
O
N
N
N
N
F
O
N
N
N
Cl
O
OH
F
Itraconazole
Fluconazole
Cl
F
OH
N
N
N
N
O
N
N
N
N
N
N
N
F
OH
N
O
N
F
O
F
Voriconazole
F
Posaconazole
Chart 1.
2
. Chemistry
3. Results and discussion
Compound 2 was obtained from the reaction of isonicotinic acid
hydrazide with CS in basic media in good yield. The treatment of 2
with hydrazine hydrate produced compound 5. Both compounds 2
and 5 are known [5,26]. Reaction of 5-pyridin-4-yl-1,3,4-oxadia-
zole-2-thiol and 4-amino-5-pyridin-4-yl-4H-1,2,4-triazole-3-thiol
The appearance of the signals approximately at 1.44 ppm (CH
3
)
2
and 3.19–4.12 ppm (CH ) integrating three and two protons,
2
1
respectively, in the H NMR spectra of compounds 3 and 6
confirmed the conversion of 2 and 5 into the corresponding S-
ethylated derivatives (3 and 6). Aromatic protons of compounds 3
and 6 were observed at 7.93 and 8.94 ppm as doublets. These
(
2 and 5) with ethyl bromide in basic media afforded compounds 3
and 6, respectively. The synthesis of 4-{[(4-fluorophenyl)- or
-{[1H-indol-3-ylmethylene]amino}-5-pyridin-4-yl-4H-1,2,4-tri-
13
groups were observed at 121.43–153.65 ppm in the C NMR
spectra. Compound 6 did not give molecular ion peak in the mass
spectrum. Compounds 4a, 4b, 9a–9c and 8 which are Mannich base
derivatives of compounds 2, 5 and 7a gave a singlet at 5.12 ppm and
4
azole-3-thiols (7a and 7b) was performed by the treatment of
compound 5 with the corresponding aromatic aldehydes. On the
other hand, the reactions of compounds 2, 5 and 7a with several
amines in the presence of formaldehyde solution afforded the
corresponding Mannich base derivatives (4a, 4b, 9a–9c and 8)
incorporating piperazine or morpholine ring.
1
5.80 ppm in the H NMR spectra integrating two protons. Also these
2
individual –CH groups were observed at 66.43 ppm and 67.76 ppm
13
in the C NMR spectra. In the mass spectrum of compound 8,
a stable molecular ion peak was not observed whereas a peak due
F
CH3
O
H
N
CH3
O
CH O
N
N
3
N
N C
.
HCl
N
O
N
N
NH
N CH3
N
O
CH O
N
3
CH3
CH3
O
NH2
Prazosin
F
Urapidil
O
Lidoflazine
O
O
F
F
COOH
COOH
F
COOH
N
N
N
N
N
N
N
CH CH
N
O
2
3
N
H
CH3
H C
H
3
Norfloxacin
Ciprofloxacin
Ofloxacin
Chart 2.

4364
H. Bayrak et al. / European Journal of Medicinal Chemistry 44 (2009) 4362–4366
N
N
O
NHNH2
ii
C
N
N
S
O
SH
N
N
O
3
i
N
N
2
R
N
N
4a:R=
b:R=
N
N
CH3
1
S
iv
iii
O
4
NHCH CH2
N
O
2
4
a,b
N
N
N N
N NH
S
SH
7
a:R=
F
N
N
S
ii
v
N
N
N
N
NH2
NH2
N
7b:R=
CH
7a,b
R
6
5
N
H
iii
iii
N
N
N
N
R
S
CH2
N
N
S
N
N
N
N
N
NH2
CH
9
a-c
9
a:R =
b:R =
c:R =
i: CS /KOH, ii: NaOEt/ C H Br, iii: HCHO,amine, iv: H NNH , v: arom.aldehyde.
N
N
CH3
F
9
NHCH CH2
N
O
2
8
9
N
O
2
2
5
2
2
Scheme 1. Synthetic pathway for the preparation of compounds 2–9.
to M þ Na was present. On the other hand 9a displayed a stable
molecular ion peak. When compound 5 was converted into the
(70 eV) Instrument. Combustion analysis was performed on
Costech Elemental Combustion System CHNS-O elemental
a
corresponding Schiff bases (7a and 7b), additional one proton at
analyzer. All the chemicals were obtained from Fluka Chemie AG
Buchs (Switzerland). Compound 1 is available as commercial.
1
8
.18 and 8.23 ppm was observed in the H NMR spectra as a singlet.
þ
7
a and 7b gave stable M þ 1 or M ion peaks in the mass spectra,
respectively. All the newly synthesized compounds gave elemental
analysis data consistent to assigned structures.
4.1.1. General method for the synthesis of compounds 3 and 6
To a solution of compound 2 (for 3) or 5 (for 6) (10 mmol) in
absolute ethanol equivalent amount of sodium was added and the
mixture was stirred at room temperature for 30 min. Then, ethyl
bromide (10 mmol) was added and refluxed for 4 hours. After
evaporating the solvent in reduce pressure a solid appeared. This
was recrystallized from ethanol to obtain target compound.
Among the tested compounds, the S-ethylated compounds (3
and 6), displayed good antimicrobial activity against the test
microorganisms except Candida tropicalis (Ct.) and Candida albicans
(
Ca.). The corresponding Mannich bases (4a, 4b) of 2 showed
moderate activity towards the test microorganisms. Among the
corresponding Mannich bases (9a–9c) 9a was active against all test
microorganisms except C. tropicalis (Ct.) and C. albicans (Ca.); 9c
was active only against Escherichia coli (Ec.) and Yersinia pseudo-
tuberculosis (Yp.), while 9b displayed no activity. The Schiff bases
4.1.1.1. 4-[5-(Ethylthio)-1,3,4-oxadiazol-2-yl]pyridine (3). Yield 77.8%,
ꢀ
ꢁ1
m.p. 75–78 C. IR (KBr, cm ): 1606 and 1539 (2C]N); Anal. Calcd (%)
for C OS: C, 52.16; H, 4.38; N, 20.28. Found: C, 52.14; H, 4.33;
N, 20.32; H NMR (DMSO-d
CH ), 7.81–7.98 (2H, m, arH), 8.81 (2H, br s, arH); C NMR (DMSO-d
ppm): 14.55 (CH ), 27.67 (CH ), arC: [121.43 (pyridine C-2 and
9 9 3
H N
1
(7a and 7b) and the Mannich base (8) of compound 7a showed no
6 3
, d ppm): 1.44 (3H, t, CH ), 3.36 (2H, q,
13
activity against the test microorganisms.
2
6
,
d
3
2
4
. Experimental
C-6), 140.44 (C), 153.65 (pyridine C-3 and C-5)], 165.14 (oxadiazole,
C-2), 166.32 (oxadiazole,C-5).
4.1. Chemistry
4
.1.1.2. 3-(Ethylthio)-5-pyridin-4-yl-4H-1,2,4-triazol-4-amine (6).
ꢀ
ꢁ1
Melting points were determined on a B u¨ chi B-540 melting point
Yield 74.3%, m.p. 125–127 C. IR (KBr, cm ): 3072 and 2987 (NH
1606 and 1581 (2C]N); Anal. Calcd (%) for C S: C, 48.85; H,
5.01; N, 31.65. Found: C, 48.89; H, 5.03; N, 31.69; H NMR (DMSO-
ppm): 1.43 (3H, t, CH ), 3.19–4.12 (2H, m, CH ), 7.93–8.02 (2H,
m, arH), 8.94 (2H, br s, arH), 11.66 (2H, s, NH
ppm): 13.66 (CH ), 27.43 (CH ), arC: [121.47 (pyridine C-2 and C-
2
),
1
13
apparatus and are uncorrected. H NMR and C NMR spectra were
recorded on a Varian-Mercury 200 MHz spectrometer. The IR
spectra were measured as potassium bromide pellets using a Per-
kin–Elmer 1600 series FTIR spectrometer. Mass spectra were
obtained for compounds 6, 8, 9a, 7a and 7b at a Quattro LC–MS
9 11 5
H N
1
d
6
,
d
3
2
13
2
6
); C NMR (DMSO-d ,
d
3
2

H. Bayrak et al. / European Journal of Medicinal Chemistry 44 (2009) 4362–4366
4365
6
2
), 139.87 (C), 153.45 (pyridine C-3 and C-5)], 165.03 (oxadiazole, C-
), 166.21 (oxadiazole,C-5); MS: m/z (%) 121 (47), 123 (22), 130 (22).
4.1.3.1. 4-Amino-2-[(4-methylpiperazin-1-yl)methyl]-5-pyridin-4-yl-
2,4-dihydro-3H-1,2,4-triazole-3-thione (9a). Yield 71%, m.p. 231–
ꢀ
ꢁ1
2
(
33 C. IR (KBr, cm ): 3276 and 3167 (NH
2C]N),1314 (C]S); Anal. Calcd (%) for C13
N, 32.10. Found: C, 51.16; H, 6.30; N, 32.14; H NMR (DMSO-d
ppm): 2.41 (3H, s, CH ), 2.82 (4H, t, 2CH ), 3.02 (4H, t, 2CH ), 5.80
), 7.62–8.23 (2H, m, arH), 8.41–7.00 (2H, m, arH), 13.84
2
), 1609 and 1572
H N S: C, 51.13; H, 6.27;
19 7
4.1.2. General method for the synthesis of compounds 4a, 4b,
1
6
,
8
and 9a–9c
d
3
2
2
To a solution of corresponding compound 2, 5 or 7a (10 mmol)
(
(
(
(
(
2H, s, CH
2
in dimethyl formamide, methyl piperazine (for 4a and 9a)
13
2 6 3
2H, br s, NH ); C NMR (DMSO-d , d ppm): 42.88 (CH ), 51.95
piperazine C-2 and C-6), 54.46 (piperazine C-3 and C-5), 67.76
CH ), arC: [120.10 (pyridine C-2 and C-6), 139.90 (C), 151.02
pyridine C-3 and C-5)], 148.99 (triazole C-3), 176.65 (triazole C-5);
MS: m/z (%) 119 (69), 184 (47), 305 (69), 305 (84), 305 (M , 97), 306
(
(
10 mmol), 2-(4-morpholinoethylamine) (for 4b and 9b)
10 mmol) or morpholine (for 9c) was added in the presence of
formaldehyde (40%, 1.5 mL) and the mixture was stirred at room
temperature for 2 hours. Then, water was added and kept over-
night in cold. The solid separated was collected by filtration and
recrystallized from dimethyl sulfoxide to yield the target
compounds.
2
þ
(25), 337 (11), 343 (11).
4.1.3.2. 4-Amino-2-{[(2-morpholin-4-ylethyl)amino]methyl}-5-pyr-
idin-4-yl-2,4-dihydro-3H-1,2,4-triazole-3-thione (9b). Yield 76%,
4
.1.2.1. 3-[(4-Methylpiperazin-1-yl)methyl]-5-pyridin-4-yl-1,3,4-
ꢀ
ꢁ1
ꢀ
m.p. 238–241 C. IR (KBr, cm ): 3273 and 3163 (NH
1570 (2C]N), 1314 (C]S); Anal. Calcd (%) for C14
H, 6.31; N, 29.23. Found: C, 50.09; H, 6.32; N, 29.18; H NMR
DMSO-d ppm): 2.29–2.32 (4H, m, 2CH ), 2.37–2.42 (4H, m,
CH ), 3.38–3.44 (4H, m, 2CH ), 5.53 (2H, s, CH ), 7.78–7.80 (2H, dd,
arH), 8.12 (2H, br s, NH ), 8.02–8.50 (2H, dd, arH), 11.07 (1H, s, NH);
ppm): 46.51 (CH ), 51.60 (CH ), 53.67 (mor-
pholine C-2 and C-6), 61.54 (CH ), 66.47 (morpholine C-3 and C-5),
2
), 1607 and
oxadiazole-2(3H)-thione (4a). Yield 88%, m.p. 240–241 C. IR (KBr,
cm ): 1315 (C]S); Anal. Calcd (%) for C13H N OS: C, 53.59; H,
17 5
ꢁ1
H N OS: C, 50.13;
21 7
1
1
5
d
.88; N, 24.04. Found; C, 53.64; H, 5.92; N, 24.00; H NMR (DMSO-
ppm): 2.19 (3H, s, CH ), 2.38–2.43 (4H, m, 2CH ), 2.78–2.85
), 5.12 (2H, s, CH ), 7.81–7.83 (2H, d, arH), 7.87–7.89
2H, d, arH); C NMR (DMSO-d ppm): 42.87 (CH ), 51. 94
piperazine C-2 and C-6), 54.44 (piperazine C-3 and C-5), 67.73
CH ), arC: [119.28 (pyridine C-2 and C-6), 141.09 (C), 150.96
pyridine C-3 and C-5)], 162.60 (oxadiazole C-3), 175.47 (oxadiazole
(
6
,
d
2
6
,
d
3
2
2
2
2
2
(
(
(
(
(
4H, m, 2CH
2
2
13
2
6
,
d
3
13
C NMR (DMSO-d
6
,
d
2
2
2
2
arC: [119.78 (pyridine C-2 and C-6), 135.67 (C), 151.12 (pyridine C-3
and C-5)], 147.85 (triazole C-3), 175.66 (triazole C-5).
C-5).
4
.1.3.3. 4-Amino-2-(morpholin-4-ylmethyl)-5-pyridin-4-yl-2,4-dihy-
4
.1.2.2. 3-{[(2-Morpholin-4-ylethyl)amino]methyl}-5-pyridin-4-yl-
ꢀ
dro-3H-1,2,4-triazole-3-thione (9c). Yield 65%, m.p. 234–236 C. IR
ꢀ
1,3,4-oxadiazole-2(3H)-thione (4b). Yield 86%, m.p.169–171 C. IR
ꢁ1
(KBr, cm ): 3274 and 3163 (NH
2
), 1607 and 1571 (2C]N), 1314
OS: C, 49.30; H, 5.52; N, 28.75.
ꢁ1
(
KBr, cm ): 1314 (C]S); Anal. Calcd (%) for C14
H, 5.96; N, 21.79. Found: C, 52.29; H, 5.99; N, 21.82; H NMR
DMSO-d ppm): 2.31 (2H, t, CH ), 2.42 (4H, t, CH ), 2.70 (2H, t,
CH ), 3.35–3.39 (4H, m, 2CH ), 5.43 (2H, s, CH ), 7.80–7.82 (2H, d,
arH), 7.86–7.88 (2H, d, arH), 10.56 (1H, br s, NH); C NMR (DMSO-
19 5 2
H N O S: C, 52.32;
(C]S); Anal. Calcd (%) for C12
H
16
N
6
1
1
Found: C, 49.27; H, 5.56; N, 28.79; H NMR (DMSO-d
.55–2.62 (4H, m, 2CH ), 3.34–3.41 (4H, m, 2CH ), 5.69 (2H, s, CH
.54–7.58 (2H, d, arH), 7.78–7.83 (2H, d, arH), 8.15 (2H, br s, NH
6
,
d
ppm):
),
);
ppm): 59.32 (morpholine C-2 and C-6), 60.44
morpholine C-3 and C-5), 67.51 (CH ), arC: [121.45(pyridine C-2
(
6
,
d
2
2
2
2
2
2
2
2
2
7
2
13
13
6
C NMR (DMSO-d , d
d
6
6
,
d
ppm): 46.51 (CH
2
), 51.58 (CH
2
), 53.67 (morpholine C-2 and C-
), arC: [119.16
(
2
), 61.60 (morpholine C-3 and C-5), 66.43 (CH
2
and C-6),139.83 (C),153.38 (pyridine C-3 and C-5)],148.07 (triazole,
C-3), 175.10 (triazole,C-5).
(
1
pyridine C-2 and C-6), 140.98 (C), 150.93 (pyridine C-3 and C-5)],
61.54 (oxadiazole C-3), 172.02 (oxadiazole C-5).
4
.1.4. General method for the synthesis of compounds 7a and 7b
A solution of the corresponding compound 5 (10 mmol) in
4
.1.2.3. 4-{[(4-Fluorophenyl)methylene]amino}-5-pyridin-4-yl-2-[(4-
methylpiperazin-1-yl)methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione
absolute ethanol was refluxed with appropriate aldehyde
10 mmol) for 3 hours. After cooling the mixture to room temper-
ꢀ
ꢁ1
(
8). Yield 73%, m.p. 133–135 C. IR (KBr, cm ): 1315 (C]S); Anal.
Calcd (%) for C20 SF: C, 58.38; H, 5.39; N, 23.83. Found; C,
8.42; H, 5.33; N, 23.88; H NMR (DMSO-d
(
22 7
H N
ature, a white solid appeared. This crude product was recrystallized
from dimethylsulfoxide/water (1:2) or ethanol to afford the desired
product.
1
5
6
,
d
ppm): 2.19 (3H, s,
), 2.62–2.71 (4H, m, 2CH ), 5.40 (2H, s,
), 7.22–7.34 (2H, m, arH), 7.45–7.48 (2H, m, arH), 8.42–8.44 (2H,
CH
CH
3
), 2.42–2.53 (4H, m, 2CH
2
2
2
13
dd, arH), 8.72–8.73 (2H, dd, arH), 11.02 (1H, s, SH); C NMR (DMSO-
ppm): 42.78 (CH ), 51. 96 (piperazine C-2 and C-6), 54.45
piperazine C-3 and C-5), 66.67 (CH ), arC: [115.03 (pyridine C-2
and C-6), 123.89 (phenyl C-2 and C-6), 131.34 (C), 132.44 (phenyl C-
and C-5), 132.77 (C), 150.11 (pyridine C-3 and C-5), 165.78 (C)],
35.45 (CH), 151.41 (triazole C3), 157.47 (triazole C5); MS: m/z (%)
4.1.4.1. 4-{[(4-Fluorophenyl)methylene]amino}-5-pyridin-4-yl-4H-
d
6
,
d
3
ꢀ
1,2,4-triazole-3-thione (7a). Yield 87%, m.p. 245–247 C. IR (KBr,
(
2
ꢁ1
cm ): 1317 (C]S), 3156 (NH); Anal. Calcd (%) for C14
6.18; H, 3.37; N, 23.40. Found: C, 56.22; H, 3.33; N, 23.43; H NMR
DMSO-d ppm): 7.41–7.43 (2H, m, arH), 7.45–7.57 (2H, m, arH),
.18 (1H, s, CH), 8.45–8.48 (2H, dd, arH), 8.51–8.54 (2H, dd, arH),
10 5
H N SF: C,
1
5
(
8
3
1
6
, d
1
5
24 (46),139 (48),149 (11),162 (25),179 (34), 301 (11), 423 (M þ Na,
13
1
1.07 (1H, s, SH); C NMR (DMSO-d
C-2 and C-6), 122.85 (phenyl C-2 and C-6), 130.89 (C), 131.42 (C),
33.32 (phenyl C-3 and C-5), 151.43 (pyridine C-3 and C-5), 165.77
6
, d ppm): arC: [115.09 (pyridine
0), 424 (14).
1
4
.1.3. General method for the synthesis of compounds 9a–9c
To the solution of corresponding compound 5 (10 mmol) in
(C)], 148.54 (triazole C-3), 153.71 (triazole C-5), 155.17 (CH); MS:
m/z (%) 109 (46), 120 (38), 124 (34), 139 (29), 149 (34), 161 (31), 162
(22), 164 (14), 180 (16), 199 (15), 301 (M þ 2, 24).
dimethyl formamide, formaldehyde (37%, 1.55 mL) and amine
10 mmol) were added and the mixture was stirred at room
(
temperature for 2.5 hours. Then, excess amount of pure water was
added to this solution and the mixture was kept overnight in cold.
The resulting solid separated was collected by filtration, washed
with water, recrystallized from dimethylsulfoxide/water (1:2) to
yield the title compounds.
4.1.4.2. 4-{[1H-Indol-3-ylmethylene]amino}-5-pyridin-4-yl-4H-
ꢀ
1,2,4-triazole-3-thione (7b). Yield 89%, m.p. 279.281 C. IR (KBr,
ꢁ
1
cm ): 1317 (C]S), 3167 (NH); Anal. Calcd (%) for C16
H
12
1
N
6
S: C,
59.96; H, 3.78; N, 26.23. Found: C, 59.99; H, 3.74; N, 26.17; H NMR
6
(DMSO-d , d ppm): 7.14–7.16 (1H, dd, arH), 7.41–7.43 (1H, m, arH),

4366
H. Bayrak et al. / European Journal of Medicinal Chemistry 44 (2009) 4362–4366
Table 1
Screening for antimicrobial activity of compounds (mm).
colony forming unit (cfu) per mL. They were ‘‘flood-inoculated’’
onto the surface of MH Agar and Sabouraud Dextrose Agar (SDA)
(Difco, Detroit, MI) and then dried. For C. albicans and C. tropicalis,
SDA was used. Five-millimeter diameter wells were cut from the
Compound no
Microorganisms and inhibition zone (mm)
Ec.
Yp.
Pa.
Ef.
Sa.
Bc.
Ct.
Ca.
a
agar using a sterile cork-borer, and 50 mL of the extract substances
2
3
–
–
–
–
10
25
17
14
34
25
–
–
–
28
–
–
–
30
7
–
–
–
8
8
–
–
–
–
25
7
–
–
–
a
were delivered into the wells. The plates were incubated for
30
23
13
34
30
–
–
–
30
–
20
–
22
15
13
30
24
–
–
–
24
–
13
–
25
28
13
42
25
–
–
–
35
–
–
25
17
15
24
25
–
–
–
25
–
–
18
17
14
20
20
7
–
–
22
–
–
ꢀ
4
4
5
6
7
7
8
9
9
9
aa
18 hours at 35 C. Antimicrobial activity was evaluated by
a
b
measuring the zone of inhibition against the test organism.
Ampicillin (10 mg) and Fluconazole (5 mg) were standard drugs.
Dimethylsulphoxide and ethanol were used as solvent control. The
antimicrobial activity results are summarized in Table 1.
a
a
8
8
ab
b
b
–
–
–
–
–
11
–
b
ab
b
c
Ethanol
DMSO
Amp.
Flu.
Acknowledgement
b
b
–
11
–
This work was supported by the Scientific and Technological
Research Council of Turkey (TUBITAK, Project no: 107T333).
–
–
18
–
–
10
–
–
35
–
–
15
–
10
–
18
25
25
References
Ec: Escherichia coli ATCC 25922, Yp: Yersinia pseudotuberculosis ATCC 911, Pa:
Pseudomonas aeruginosa ATCC 27853, Ef: Enterococcus faecalis ATCC 29212, Sa:
Staphylococcus aureus ATCC 25923, Bc: Bacillus cereus 702 Roma, Ct: Candida tro-
picalis ATCC 13803, Ca: Candida albicans ATCC 60193. Amp.: Ampicillin, Flu.: Flu-
conazole, (–): no activity.
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,
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(
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[
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(
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þ
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[
[
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4
.2. Antimicrobial activity
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[
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[
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[
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1
6
(
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