Microwave-assisted and conventional synthesis of novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton

Article abstract of DOI:10.1515/hc-2016-0019

Carbothioamides 4a,b, obtained from nalidixic acid, were converted to the corresponding 1,3-thiazolidine derivatives 5a,b by cyclocondensation with 2-bromo-1-(4-chlorophenyl)ethanone. Treatment of 4a,b with base afforded 1,2,4-triazoles 6a,b. The synthesis of 1,3-oxazolidine 7 was performed by the reaction of compound 4a with ethyl bromoacetate. Treatment of 4a with acid produced 1,3,4-thiadiazole 8. The reaction of compounds 6a and 6b with several heterocyclic amines in the presence of formaldehyde gave the corresponding Mannich bases 9-15 containing various pharmacophore groups. Conventional and microwave-assisted methods were used for the synthesis. The effect of an acid catalyst on Mannich reactions was investigated. The structures of the newly synthesized compounds were elucidated on the basis of ¹H NMR, ¹³C NMR, FTIR, EIMS techniques, and elemental analysis. All compounds were screened for their antimicrobial activity.

Full text of DOI:10.1515/hc-2016-0019

Heterocycl. Commun. 2016; 22(4): 229–237
Sule Ceylan*, Hacer Bayrak, Serap Basoglu Ozdemir, Yıldız Uygun, Arif Mermer,
NMesilicharnoDwemairbvaes a-nadsSesrdiasrtUelkedr and conventional synthesis
of novel antimicrobial 1,2,4-triazole derivatives
containing nalidixic acid skeleton
DOI 10.1515/hc-2016-0019
Received March 25, 2016; accepted June 15, 2016; previously
published online July 27, 2016
synthetic quinolone derivative introduced for the treat-
ment of urinary tract infections in 1963 [1]. It inhibits
DNA synthesis by promoting cleavage of bacterial DNA in
the DNA-enzyme complexes of DNA gyrase, resulting in
rapid bacterial death [2]. It is particularly effective against
Gram-negative bacteria [3, 4]. Since the introduction of
nalidixic acid for the treatment of bacterial infections,
a number of derivatives have been synthesized. Among
them, fluoroquinolones such as norfloxacin, pefloxa-
cin, enoxacin, ofloxacin, and ciprofloxacin play a major
role in the treatment of bacterial infections by displaying
excellent pharmacokinetic properties, high antimicrobial
activity, and low side effects [5–9]. Quinolones have been
reported to have wide-ranging biological activities includ-
ing antitubercular [10], fungicidal [11], antimalarial [12],
anticancer and anti-HIV [12], antiviral [13], and antibacte-
rial [14] properties.
Abstract: Carbothioamides 4a,b, obtained from nalidixic
acid, were converted to the corresponding 1,3-thiazoli-
dine derivatives 5a,b by cyclocondensation with 2-bromo-
1-(4-chlorophenyl)ethanone. Treatment of 4a,b with base
afforded 1,2,4-triazoles 6a,b. The synthesis of 1,3-oxazo-
lidine 7 was performed by the reaction of compound 4a
with ethyl bromoacetate. Treatment of 4a with acid pro-
duced 1,3,4-thiadiazole 8. The reaction of compounds 6a
and 6b with several heterocyclic amines in the presence of
formaldehyde gave the corresponding Mannich bases 9–15
containing various pharmacophore groups. Conventional
and microwave-assisted methods were used for the synthe-
sis. The effect of an acid catalyst on Mannich reactions was
investigated. The structures of the newly synthesized com-
pounds were elucidated on the basis of 1H NMR, 13C NMR,
FTIR, EIMS techniques, and elemental analysis. All com-
pounds were screened for their antimicrobial activity.
The considerable biological importance of triazoles
has stimulated a lot of interest in their derivatives [15].
A large number of 1,2,4-triazoles exhibit antibacterial,
antifungal, antitubercular, analgesic, antiinflammatory,
Keywords: 1,2,4-triazole; antimicrobial activity; Mannich anticancer, anticonvulsant, antiviral, insecticidal, antide-
base; nalidixic acid; norfloxacin.
pressant, and central nervous system-affecting activities.
1,2,4-Triazoles, by virtue of their ambident nucleophilic
centers, are good starting materials for the synthesis of
several interesting N- and S-bridged heterocycles. The tria-
zoles can be converted to thiazolotriazoles, triazolothiadi-
Introduction
Nalidixic
acid
[1-ethyl-7-methyl-4-oxo-1,4-dihydro- azoles, triazolooxazolidines, and various Mannich bases
1,8-naphthyridine-3-carboxylic acid, 1] was the first [16–20]. In addition, a 1,3,4-thiadiazole system constitutes
the active part of several biologically active compounds
[21–24]. A thiazolidinone ring is an attractive target for
*Corresponding author: Sule Ceylan, Department of Occupational
Health and Safety, Artvin Çoruh University, Faculty of Medical
combinatorial synthesis as its structure-activity relation-
ship belongs to an important class of N- and S-containing
heterocycles, which are widely used in drug design and
synthesis [25, 26]. Related oxazolidinones are also biologi-
cally active [27–30].
Sciences, 08000 Artvin, Turkey, e-mail: sulecanim@hotmail.com
Hacer Bayrak: Department of Chemistry and Chemical Processing
Technology, Karadeniz Technical University, Maçka Vocational
School, 61750 Trabzon, Turkey
Serap Basoglu Ozdemir, Yıldız Uygun, Arif Mermer and Neslihan
Demirbas: Department of Chemistry, Faculty of Science, Karadeniz
Technical University, 61080 Trabzon, Turkey
In this paper, we report the synthesis of new hybrid
compounds which are derivatives of the systems men-
tioned above and possess an interesting profile of anti-
microbial activity. The synthetic work was enhanced by
Serdar Ulker: Department of Biology, Faculty of Science, Recep
Tayyip Erdoğan University, 53100 Rize, Turkey
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ꢀꢀꢀꢁ
230ꢀ ꢀS. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton
using Mannich reaction [31], homogeneous catalysis [32], Synthesis of 3 required 20–22 h of heating under reflux
and eco-friendly microwave irradiation [33].
conditions and the yield was 75–78%. Under microwave
irradiation at 100°C for 15 min, the yield was 88–98%.
Compound 3 was converted to carbothioamides 4a,b
by treatment with benzylisothiocyanate and ethyliso-
thiocyanate, respectively (Scheme 1). Again, the use of
microwave irradiation was superior to the conventional
synthesis. Condensation of compounds 4a,b with 4-chlo-
rophenacyl bromide in ethanolic solution furnished the
Results and discussion
Chemistry
The main aim of this study was to synthesize antimicrobial corresponding thiazoles 5a,b (Scheme 2). Again, the
hybrid molecules containing different heterocyclic moie- microwave method was preferred. The remaining prepa-
ties. The synthetic strategies adopted to obtain the target rations shown in Schemes 2 and 3 also benefited from the
compounds are depicted in Schemes 1–3. The synthesis use of the microwave irradiation methodology. Triazoles
was achieved by using both microwave (eco-friendly) and 6a,b were obtained by intramolecular cyclization of com-
conventional methods. The structures of all products were pounds 4a,b. The aim was to introduce the 1,2,4-triazole
established on the basis of physicochemical, spectral, and nucleus to the nalidixic acid skeleton because it is known
elemental analysis data.
that more efficacious antibacterial compounds can be
The esterification of nalidixic acid (1) with ethanol designed by joining two biologically active components
in the presence of a catalytic amount of sulfuric acid fur- together into a single molecular framework [34–38]. The
nished ester 2. Then, compound 2 was converted to the synthesis of carbohydrazide 7 was performed by the reac-
acetohydrazide 3 by treatment with hydrazine hydrate. tion of compound 4a with ethyl bromoacetate in ethanolic
S
O
O
O
O
O
O
O
O
OEt
OH
NHNH2
NHNH
NHR
i
ii
iii
N
N
N
N
N
N
N
N
4a: R = Bn
4b: R = Et
Et
Et
Et
Et
1
3
2
Scheme 1ꢀReactions and conditions. i: H2SO4, EtOH, 22 h reflux or MW irradiation; ii: EtOH, H2NNH2, 6 h reflux or MW irradiation; iii: CH2Cl2,
PhCH2NCS or EtNCS, 24 h room temprature or MW irradiation.
Cl
O
N
NH
O
O
S
S
N
R
N
R
N
N
H
N
N
N
N
Et
i
ii
5a, 5b
6a, 6b
S
Et
O
N
O
NHNH NHR
N
4a, 4b
iv
O
iii
N
Bn
NH
S
N
O
N
O
O
N
Bn
S
N
H
a: R = Bn
b: R = Et
N
N
N
N
7
8
Et
Et
Scheme 2ꢀReactions and conditions. i: EtOH, ClC6H4COCH2Br, CH3COONa, reflux for 54 h (5a) or EtOH, C2H5Br, CH3COONa, reflux for 45 h (5b)
or MW irradiation; ii: 2 N NaOH in EtOH/H2O, 16 h (6a) or 14 h (6b) reflux or MW irradiation; iii: BrCH2COOEt in EtOH, CH3COONa, 24 h reflux
or MW irradiation; iv: H2SO4, 3 h at room temperature or MW irradiation.
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S. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeletonꢂ
ꢂ231
N
S
O
N
N
NH
N
O
S
S
N
O
N
N
O
N
N
N
OAc
R
N
N
S
N
O
S
N
Et
COOH
10a-b
R
R
N
N
N
N
9a-b
11a-b
Et
Et
F
O
i
ii
iii
N
N
N
N
O
N
N
COOH
O
N
N
N
S
N
vi
iv
Et
S
N
6a, 6b
R
N
N
Bn
14
12a-b
N
N
Et
Et
vii
v
F
O
NH
N
N
O
N N
O
N
N
COOH
N
S
N
S
N
R
N
H
Bn
N
N
N
N
15
13a-b
a: R = Bn
b: R = Et
Et
Et
Scheme 3ꢀConditions: amine, CH2O in DMSO (see Experimental). The amines: i, morpholine; ii, thiomorpholine; iii, 7-aminocephalospo-
ranic acid; iv, norfloxacin; v, ciprofloxacin; vi, 1-phenylpiperazine; vii, tryptamine.
solution, while the cyclization of 4a in an acidic medium with the minimal inhibition concentration (MIC) values in
yielded a 1,3,4-thiadiazole 8.
the range of 0.49–500 μg/mL (Table 1). Compounds 4a,b
Mannich bases are physiologically reactive agents and 6a,b are exceptionally active against Escherichia coli
[39–41]. Mannich bases 9–15 were obtained by treatment (E. coli), Gram-negative bacteria. Mannich bases 9–15
of compounds 6a,b with formaldehyde and several bio- show good-to-moderate activity against some of the test
logically active amines (Scheme 3) [6, 8, 34, 42, 43]. Three microorganisms. Among these, compounds 11a,b with
different methods were used for the Mannich reactions. a β-lactam nucleus attached to nalidixic acid skeleton
These were a conventional method in the absence of a cat- display remarkable antimicrobial activities against two
alyst, a conventional method in the presence of a catalyst, Gram-positive bacteria. Compound 11a is active against
and microwave irradiation-assisted synthesis. The clas- Mycobacterium smegmatis (M. smegmatis), a nonpig-
sical heating in the absence of any catalyst furnished the mented rapidly growing mycobacterium with the MIC
desired products in low-yield after 24 h. The same products value ꢀ<ꢀ1 μg/mL, which is better than that for standard
were obtained in the yields of 53–97% at room temperature drug streptomycin. Compound 11b is active against Ente-
after 5 h in the presence of InCl3 or p-toluenesulfonic acid rococcus faecalis (E. faecalis), for which the MIC value of
as a Brønsted-Lowry acid catalyst. In the microwave irradi- 6 μg/mL is better than that for the reference drug ampicil-
ation-assisted method the temperature was held constant lin. Exceptional activity can be observed for some other
at 50oC, the reaction time was 5 min and the Mannich bases Mannich bases (Table 1).
were obtained in yields of 43–99%. Thus, microwave irra-
diation provided more efficient and green way to Mannich
products and a relatively higher yield.
Conclusions
Antimicrobial activity
Several biologically active hybrid compounds containing
a nalidixic acid moiety were obtained. The antimicrobial
All synthesized compounds were screened for their anti- screening showed that compounds containing norfloxa-
microbial activity. Compounds 2, 3, 4a,b, 5a,b, 6a,b, 7, cine, ciprofloxacine or 7-aminocephalosporanic acid
and 8 are active against some of the test microorganisms system display excellent antimicrobial activity. Several
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232ꢀ ꢀS. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton
Table 1ꢀAntimicrobial activity of the compounds.
Comp.
Minimal inhibition concentration (μg/mL)
Ec
Yp
Pa
Sa
Ef
Bc
Ms
Ca
Sc
2
3.9
1.9
0.49
0.49
7.8
7.8
0.98
0.98
7.8
7.8
7.8
3.9
15.6
3.9
125
15.6
ꢃ<ꢃ1
15.6
3.9
7.81
7.81
3.9
31.25
7.81
3.91
31.25
3.9
–
125
500
–
–
62.5
31.25
125
–
–
125
–
125
31.3
7.81
15.65
78
–
–
250
500
62.5
15.65
15.65
–
3
62.5
4a
62.5
62.5
–
15.65
4b
125
–
31.25
–
5a
–
5b
–
–
–
–
39
–
–
–
–
6a
125
62.5
–
–
31.25
31.25
39
ꢃ>ꢃ1000
39
250
–
–
6b
125
–
–
62.5
–
–
7
156
312.5
–
–
–
8
–
–
–
125
–
78
–
39
9a
31.25
62.5
3.9
–
–
9b
156
–
–
–
–
ꢃ>ꢃ1000
625
ꢃ>ꢃ1000
ꢃ>ꢃ1000
39
62.5
–
–
–
10a
10b
11a
11b
12a
12b
13a
13b
14
–
–
156
–
62.5
7.8
156
–
–
312.5
156
6
–
ꢃ<ꢃ1
–
–
–
–
312.5
–
31.25
3.9
156
9.7
9.7
9.7
9.7
–
–
–
78
–
9.7
9.7
–
19
1.9
1.9
ꢃ<ꢃ1
ꢃ<ꢃ1
–
–
156
–
ꢃ<ꢃ1
3.9
19
–
ꢃ<ꢃ1
ꢃ<ꢃ1
7.8
7.8
10
ꢃ<ꢃ1
9.7
–
9.7
–
156
–
ꢃ<ꢃ1
9.7
–
9.7
–
3.9
–
156
39
–
–
15
62.5
32
–
–
–
–
–
312.5
Amp
Strep
Flu
ꢃ>ꢃ128
35
10
15
4
ꢃ<ꢃ8
ꢃ<ꢃ8
Ec, E. coli ATCC 35218; Yp, Y. pseudotuberculosis ATCC 911; Pa, P. aeruginosa ATCC 10145; Sa, S. aureus ATCC 25923; Ef, E. faecalis ATCC
29212; Bc, B. cereus 709 Roma; Ms, M. smegmatis ATCC607; Ca, C. albicans ATCC 60193; Sc, S. cerevisiae RSKK 251; Amp, ampicillin; Strep,
streptomycin; Flu, fluconazole; (–), no activity at test concentrations.
for 22 h, then cooled to room temperature and concentrated under
compounds are more active against E. coli and M. smegma-
tis than the reference drug ampicillin and streptomycin.
reduced pressure. The resultant white residue of 2 was crystallized
from ethanol.
Method 2ꢁA solution of compound 1 (1 mmol) and sulfuric acid
Experimental
(4 drops) in ethanol was microwave irradiated in a closed vessel
at 100°C for 15 min and then poured into ice water. The resultant
solid product 2 was collected by filtration and crystallized from
ethanol.
All chemicals were purchased from Fluka Chemie AG (Buchs,
Switzerland) and used without further purification. Melting points
were determined in open capillaries on a Büchi B-540 melting point
apparatus and are uncorrected. Reactions were monitored by thin layer
chromatography (TLC) on silica gel using 60 F254 aluminum sheets. The
mobile phase was ethyl acetate/diethyl ether (1:1) and detection was
under UV light. FT-IR spectra were recorded using a Perkin Elmer 1600
series FT-IR spectrometer. 1H NMR and 13C NMR spectra were registered
in DMSO-d6 on a Bruker Avene II 400 MHz NMR spectrometer (400 MHz
for 1H and 100 MHz for 13C). The elemental analysis was performed on
a Costech Elemental Combustion System CHNS-O elemental analyzer.
Yield 76% (method 1); yield 88% (method 2); mp 207–208°C; IR
1
(υmax, cm-1): 3072, 2980, 1720, 1683, 1616; H NMR: δ 1.3 (t, 3H J ꢀ=ꢀ 7.2
Hz), 1.4 (t, 3H, J ꢀ=ꢀ 6.9 Hz), 2.6 (s, 3H), 4.2 (q, 2H, J ꢀ=ꢀ 6.9 Hz,), 4.5 (q,
2H, J ꢀ=ꢀ 7.2 Hz), 7.4 (d, 1H, J ꢀ=ꢀ 8.1 Hz,), 8.4 (d, 1H, J ꢀ=ꢀ 8.1 Hz), 8.8 (s, 1H);
13C NMR: δ 14.3, 23.6, 27.9, 41.1, 44.5, 110.8, 118.2, 125.6, 136.2, 148.9,
154.6, 148.1, 162.2, 176.3. Anal. Calcd for C14H16N2O3: C, 64.60; H, 6.20;
N, 10.76. Found: C, 64.25; H, 5.93; N, 10.41.
1-Ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-
3-carbohydrazide (3)
Ethyl 1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyri-
dine-3-carboxylate (2)
Method 1ꢁA solution of compound 2 (2.60 g, 0.01 mol) and hydra-
zine hydrate (1.46 mL, 0.03 mol) in ethanol was heated under reflux
for 20 h, then cooled and kept in the refrigerator for 12 h. The result-
ant solid was collected by filtration and crystallized from ethanol.
Method 1ꢁA solution of nalidixic acid (1, 2.31 g, 0.01 mol) and con-
centrated sulfuric acid (4 drops) in ethanol was heated under reflux
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Method 2ꢁA solution of compound 2 (1 mmol) and hydrazine resultant solid was filtered, washed with water and crystallized from
hydrate (3 mmol) in ethanol was microwave-irradiated in a closed dimethyl sulfoxide/water (1:3).
vessel at 100°C for 15 min. After the completion of the reaction, as
monitored by TLC, the mixture was concentrated and the residue was Method 2ꢁA solution of 4-chlorophenacyl bromide (1 mmol),
crystallized from ethanol.
sodium acetate (5 mmol), compound 4a (1 mmol) or compound 4b
Yield 75% (method 1); yield 98% (method 2); mp 163–165°C; IR (1 mmol) in ethanol was microwave-irradiated in a closed vessel at
(υmax, cm-1): 3316, 3222, 3033, 2958, 1685, 1604; 1H NMR: δ 1.32 (s, 3H), 150°C for 15 min. After completion of the reaction, as monitored by
2.60 (s, 3H), 4.51 (s, 2H), 7.40 (s, 1H), 8.42 (s, 1H), 8.94 (s, 1H), 10.50 (s, TLC, the mixture was poured into ice water. The crude product was
2H), 12.50 (s, 1H); 13C NMR: δ 14.3, 24.8, 40.1, 111.6, 119.4, 122.5, 135.8, filtered and crystallized from dimethyl sulfoxide/water (1:3).
147.9, 153.6, 147.2, 163.1, 175.8. Anal. Calcd for C12H14N4O2: C, 58.53; H,
5.73; N, 22.75. Found: C, 58.40; H, 5.93; N, 22.48.
N′-[3-Benzyl-5-(4-chlorophenyl)-1,3-thiazol-2(3H)-ylidene]-
1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-
carbohydrazide (5a)ꢁYield 65% (method 1); yield 80% (method
2); mp 175–177°C; IR (υmax, cm-1): 3043, 3079, 2980, 1716, 1521, 1129;
1H NMR: δ 1.41 (brs, 3H), 2.67 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 4.24 (brs, 2H, 4.41 (q,
2H, J ꢀ=ꢀ 8.0 Hz), 5.03 (s, 1H), 7.05 (d, 1H, J ꢀ=ꢀ 8.0 Hz), 7.17–7.63 (m, 9H),
7.62 (d, 1H, J ꢀ=ꢀ 8.0 Hz), 7.98 (brs, 1H), 9.17 (s, 1H); 13C NMR: δ 14.7, 25.5,
43.6, 47.3, 110.0, 117.2, 123.1, 127.8, 128.3, 129.5, 130.2, 130.3, 135.4, 136.1,
136.3, 140.3, 147.6, 148.1, 160.0, 166.2, 149.8, 166.8, 168.8, 176.1, 178.6.
Anal. Calcd for C28H24ClN5O2S: C, 65.45; H, 4.56; N, 13.21. Found: C,
65.31; H, 4.78; N, 13.01.
General synthesis of compounds 4a,b
Method 1ꢁTo a solution of compound 3 (2.46 g, 0.01 mol) in dichlo-
romethane, benzyl isothiocyanate (for 4a, 2.46 g, 0.01 mol) or ethyl
isothiocyanate (for 4b, 1.75 g, 0.02 mol), was added and the mixture
was stirred at room temperature for 24 h and then concentrated
under reduced pressure. The residue was crystallized from ethanol
(4a) or from dimethyl sulfoxide/water (1:3) (4b).
N′-[5-(4-Chlorophenyl)-3-ethyl-1,3-thiazol-2(3H)-ylidene]-
1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-3-
carbohydrazide (5b)ꢁYield 70% (method 1); yield 87% (method 2);
Method 2ꢁA mixture of compound 3 (1 mmol) and the correspond-
ing isothiocyanate (1 mmol) in ethanol was irradiated in a closed ves-
sel with the pressure control at 100°C for 10 min. After cooling the
mixture was poured into ice water and the resultant solid was crystal-
lized from an appropriate solvent.
1
mp 192–193°C; IR (υmax, cm-1): 3068, 3068, 2971, 1702, 1519; H NMR:
δ 1.05 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.41 (t, 3H J ꢀ=ꢀ 4.0 Hz), 2.70 (brs, 3H), 3.67
(brs), 4.60 (q, 2H, J ꢀ=ꢀ 8.0 Hz), 5.03 (s, 1H), 7.48–7.58 (m, 6H), 7.58 (brs,
1H), 9.18 (s, 1H); 13C NMR: δ 13.3, 15.5, 25.5, 46.6, 47.3, 98.9, 109.1, 119.5,
120.0, 121.0, 123.1, 129.4, 129.5, 130.1, 131.0, 136.1, 148.8, 159.9, 150.1,
163.8, 166.0, 171.6, 178.6. Anal. Calcd for C23H22ClN5O2S: C, 59.03; H,
4.74; N, 14.97. Found: C, 59.33; H, 4.38; N, 14.69.
N-Benzyl-2-[(1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthy-
ridin-3-yl)carbonyl]hydrazinecarbothioamide (4a)ꢁYield 80%
(method 1); yield 98% (method 2); mp 197–200°C; IR (υmax, cm-1): 3137,
1
3062, 2974, 1649, 1541, 1187; H NMR: δ 1.40 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 2.71
(brs, 3H), 4.73 (d, 2H, J ꢀ=ꢀ 4.0 Hz), 4.94 (s, 2H), 7.29 (d, 1H, J ꢀ=ꢀ 8.0 Hz),
7.31–7.38 (m, 5H), 7.42 (d, 1H, J ꢀ=ꢀ 8.0 Hz), 8.58 (q, 1H, J ꢀ=ꢀ 8.0 Hz), 9.04
(s, 1H), 9.18 (s, 1H), 09.47 (s, 1H); 13C NMR: δ 15.5, 25.5, 46.6, 48.5, 119.1,
122.6, 123.4, 127.6, 127.7, 128.7, 129.3, 136.5, 148.6, 163.9, 165.1, 166.1,
General synthesis of compounds 6a,b
150.0, 175.9, 178.5, 183.1. Anal. Calcd for C20H21N5O2S: C, 60.74; H, 5.35; Method 1ꢁA solution of carbothioamide 4a (3.95 g, 0.01 mol, for 6a)
N, 17.71. Found: C, 60.40; H, 5.83; N, 17.48.
or 4b (3.33 g, 0.01 mol, for 6b) in ethanol/water (1:1) was heated under
reflux in the presence of 2 N NaOH for 16 h (for 6a) or 14 h (for 6b) with
N-Ethyl-2-[(1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyri- the progress of the reaction monitored by TLC. Then, the solution was
din-3-yl)carbonyl]hydrazinecarbothioamide (4b)ꢁYield 75% cooled to room temperature and acidified to pH 7 with 37% HCl. The
(method 1); yield 85% (method 2); mp 180–182°C; IR (υmax, cm-1): 3144, precipitate formed was filtered off, washed with water, and crystal-
3058, 2986, 1679, 1541, 1189; 1H NMR: δ 1.07 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.39 (t, lized from methanol (for 6a) or ethanol /water (1:3) (for 6b).
3H, J ꢀ=ꢀ 8.0 Hz), 2.69 (brs, 3H), 3.41 (brs, 2H), 4.57 (q, 2H, J ꢀ=ꢀ 8.0 Hz),
7.44–7.47 (m, 4H), 7.56 (d, 1H, J ꢀ=ꢀ 8.0 Hz), 7.92 (brs, 2H), 8.53 (q, 1H, J ꢀ=ꢀ Method 2ꢁA mixture of compound 4a or 4b (1 mmol) and 2N NaOH
8.0 Hz), 9.00 (s, 1H), 9.15 (s, 1H), 10.54 (s, 1H); 13C NMR: δ 14.8, 15.5, (2 mmol) in ethanol (10 mL) was microwave-irradiated in a closed
25.5, 46.4, 47.2, 121.8, 123.0, 136.3, 148.5, 163.9, 165.1, 149.9, 175.8, 178.5, vessel at 150°C for 4 min with the progress of the reaction monitored
182.1. Anal. Calcd for C15H19N5O2S: C, 54.04; H, 5.74; N, 21.01. Found: C, by TLC. Then the resulting solution was cooled to room temperature
54.40; H, 5.93; N, 21.10.
and acidified to pH 5 with 37% HCl. The precipitate formed was fil-
tered off, washed with water, and crystallized from an appropriate
solvent indicated above.
General synthesis of compounds 5a,b
3-(4-Benzyl-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)-
1-ethyl-7-methyl-1,8-naphthyridin-4(1H)-one (6a)ꢁYield 63%
Method 1ꢁ4-Chlorophenacyl bromide (2.33 g, 0.01 mol) and sodium (method 1); yield 86% (method 2); mp ꢀ>ꢀ270°C; IR (υmax, cm-1): 3061,
1
acetate (4.1 g, 0.05 mol) were added to the solution of compound 4a 2985, 2959, 1717, 1517, 1128; H NMR: δ 1.17 (s, 3H), 2.50 (s, 3H), 4.33
(3.95 g, 0.01 mol, for 5a) or compound 4b (3.33 g, 0.01 mol, for 5b) (brs, 2H), 5.25 (s, 2H), 7.13–7.33 (m, 7H), 8.34 (s, 1H), 9.16 (s, 1H); 13C
in ethanol and the mixture was heated under reflux for 54 h (for 5a) NMR: δ 15.4, 25.5, 45.6, 47.3, 109.2, 118.8, 121.6, 123.1, 127.2, 127.9, 128.8,
or 45 h (for 5b), as monitored by TLC. Then, the mixture was cooled 136.1, 136.9, 146.5, 148.8, 163.7, 150.0, 166.1, 174.7, 178.5. Anal. Calcd for
to room temperature and concentrated under reduced pressure. The C20H19N5OS: C, 63.64; H, 5.07; N, 18.55. Found: C, 63.28; H, 5.38; N, 18.89.
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234ꢀ ꢀS. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton
1-Ethyl-3-(4-ethyl-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)-7-
methyl-1,8-naphthyridin-4(1H)-one (6b)ꢁYield 67% (method 1);
yield 88% (method 2); mp 216-218°C; IR (υmax, cm-1): 3090, 2988, 2957,
1717 2, 1537, 1130; 1H NMR: δ 1.14 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.41 (t, 3H, J ꢀ=ꢀ 8.0
Hz), 2.66 (s, 3H), 3.93 (q, 2H, J ꢀ=ꢀ 8.0 Hz), 4.49 (q, 2H, J ꢀ=ꢀ 8.0 Hz), 7.44–
7.61 (m, 2H), 8.61 (d, 1H, J ꢀ=ꢀ 8.0 Hz), 9.19 (s, 1H); 13C NMR: δ 13.8, 15.5,
25.5, 45.9, 47.3, 108.8, 119.5, 121.9, 136.2, 149.1, 163.6, 148.5, 167.1, 174.9,
178.6. Anal. Calcd for C15H17N5OS: C, 57.12; H, 5.43; N, 22.21. Found: C,
57.28; H, 5.87; N, 22.60.
General synthesis of compounds 9–13 (a,b)
Method 1ꢁTo a solution of compound 6a or 6b (0,01 mol) in dime-
thyl sulfoxide (10 mL), morpholine (for 9a and 9b, 0.87 mL, 0.01 mol)
or thiomorpholine (for 10a and 10b, 0.94 mL, 0.01 mol) or 7-amino-
cephalosporanic acid (for 11a and 11b, 2.72 g, 0.01 mol) or norfloxacin
(for 12a and 12b, 3.19 g, 0.01 mol) or ciprofloxacin (for 13a and 13b,
3.31 g, 0.01 mol) was added in the presence of formaldehyde (37%,
3.72 mL, 0.05 mol) and the mixture was stirred at room temperature
for 22 h. The solution was poured into ice-cold water and the result-
ant solid was crystallized from ethanol/water (1:3) (for 9a,b, 10a,b),
from ethyl acetate (for 11a,b) and from dimethyl sulfoxide/water (1:3)
(for 12a,b, 13a,b).
N′-[3-Benzyl-5-thioxo-1,3-oxazolidin-2-ylidene]-
1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naphthyridine-
3-carbohydrazide (7)
Method 2ꢁTo a solution of compound 6a,b (1 mmol) in dimethyl
sulfoxide (10 mL), morpholine (for 9a and 9b, 1 mmol) or thiomor-
pholine (for 10a and 10b, 1 mmol) or 7-aminocephalosporanic acid
(for 11a and 11b, 1 mmol) or norfloxacin (for 12a and 12b, 1 mmol) or
ciprofloxacin (for 13a and 13b, 1 mmol) was added in the presence
of formaldehyde (5 mmol) and the mixture was stirred at room tem-
perature for 15 min. Then, a catalytic amount of a suitable catalyst
(InCl3 or p-TsOH) was added and the stirring was continued for an
additional 5 h. The mixture was poured into ice water and a resultant
solid was crystallized from an appropriate solvent indicated above.
Method 1ꢁEthyl bromoacetate (1.28 mL, 0.01 mol) and sodium ace-
tate (4.1 g, 0.05 mol) were added to the solution of compound 4a
(3.95 g, 0.01 mol) in ethanol and the mixture was heated under reflux
for 24 h. Then, the mixture was cooled to room temperature and con-
centrated under reduced pressure. The residue was filtered, washed
with water, and crystallized from dimethyl sulfoxide/water (1:3).
Method 2ꢁA mixture of compound 4a (1 mmol), ethyl bromoacetate
(1 mmol) and sodium acetate (5 mmol) in ethanol was irradiated in
a closed vessel at 150°C for 13 min with the progress of the reaction
monitored by TLC. After the completion of the reaction, the mixture
was poured into ice water and the resultant precipitate was filtered
and crystallized from dimethyl sulfoxide/water (1:3).
Yield 55% (method 1); yield 76% (method 2); mp 230–232°C; IR
(υmax, cm-1): 3031, 1698 2, 1495, 1127; 1H NMR: δ 1.42 (s, 3H), 4.23 (s, 2H),
4.63 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 4.79 (s, 2H), 7.26-742 (m, 7H), 8.59 (t, 1H, J ꢀ=ꢀ
8.0 Hz), 9.03 (s, 1H); 13C NMR: δ 15.5, 25.4, 40.4, 44.1, 45.9, 109.1, 118.8,
123.1, 127.0, 127.3, 127.6, 127.7, 128.0, 136.1, 136.3, 148.8, 160.1, 150.1,
165.1, 166.1, 172.2, 178.6. Anal. Calcd for C22H21N5O3S: C, 60.67; H, 4.86;
N, 16.08. Found: C, 60.32; H, 4.49 H; N, 16.28.
Method 3ꢁThe mixture, obtained as described above for method 2,
was irradiated at 50°C in a microwave oven for 5 min with the pro-
gress of the reaction monitored by TLC. After cooling the solution was
poured into ice water and the resultant precipitate was filtered off
and crystallized from an appropriate solvent indicated above.
3-[4-Benzyl-1-(morpholin-4-ylmethyl)-5-thioxo-4,5-dihydro-
1H-1,2,4-triazol-3-yl]-1-ethyl-7-methyl-1,8-naphthyridin-4(1H)-
one (9a)ꢁYield 73% (method 1); yield 75% (method 2, InCl3); yield
77% (method 2, p-TsOH); yield 90% (method 3); mp 106–108°C; IR
1
(υmax, cm-1): 1629, 1498, 1152, 1078; H NMR: δ 1.19 (t, 3H, J ꢀ=ꢀ 4.0 Hz),
2.56 (s, 4H), 2.73 (s, 3H), 3.36 (s, 4H), 4.37 (brs, 2H), 5.14 (s, 2H), 5.31
(s, 2H), 6.97 (brs, 2H), 7.15–7.30 (m, 5H), 7.46 (d, 2H J ꢀ=ꢀ 8.0 Hz), 8.52 (s,
1H); 13C NMR: δ 15.4, 25.3, 45.7, 48.6, 50.8, 66.6, 69.6, 108.6, 119.3, 121.8,
127.5, 127.8, 128.0, 128.8, 136.2, 136.3, 147.6, 148.8, 146.5, 163.7, 169.1,
174.7. Anal. Calcd for C25H28N6O2S: C, 63.00; H, 5.92; N, 17.63. Found: C,
63.28; H, 6.01; N, 17.32.
3-[5-(Benzylamino)-4,5-dihydro-1,3,4-thiadiazol-2-yl]-
1-ethyl-7-methyl-1,8-naphthyridin-4(1H)-one (8)
Method 1ꢁA solution of carbothioamide 4a (3.95 g, 0.01 mol) in con-
centrated sulfuric acid (11 mL, 0.20 mol) was stirred for 15 min at 0°C,
then allowed to reach room temperature and stirred for an additional
3 h. The solution was poured into ice-cold water and made alkaline
to pH 7 with ammonia. The precipitated product was filtered, washed
with water, and crystallized from ethanol/water (1:3).
1-Ethyl-3-[4-ethyl-1-(morpholin-4-ylmethyl)-5-thioxo-4,5-di-
hydro-1H-1,2,4-triazol-3-yl]-7-methyl-1,8-naphthyridin-4(1H)-
one (9b)ꢁYield 65% (methods 1 and 2); yield 66% (method 2,
p-TsOH); yield 85% (method 3); mp 209–210°C; IR (υmax, cm-1): 1710,
1519, 1162, 1081; 1H NMR: δ 1.17 (s, 3H), 1.40 (s, 3H), 2.68 (s, 3H), 3.35
(s, 4H), 3.57 (s, 4H), 3.95 (brs, 2H), 4.49 (s, 2H), 5.06 (s, 2H), 7.46 (d,
2H, J ꢀ=ꢀ 8.0 Hz), 8.46 (brs, 1H), 8.65 (s, 1H); 13C NMR: δ 13.6, 15.4, 25.4,
46.0, 50.8, 52.0, 66.5, 69.1, 108.2, 119.4, 121.6, 136.2, 147.2, 149.1, 146.8,
163.6, 168.1, 178.5. Anal. Calcd for C20H26N6O2S: C, 57.95; H, 6.32; N,
20.27. Found: C, 57.71; H, 6.01; N, 20.01.
Method 2ꢁA solution of compound 4a (1 mmol) in concentrated sul-
furic acid (1.5 mL) was irradiated in a closed vessel at 50°C for 4 min
with the progress of the reaction monitored by TLC. After completion
of the reaction, the mixture was poured into ice water and the result-
ant crude product was collected by filtration and crystallized from
ethanol/water (1:3).
Yield 74% (method 1); yield 83% (method 2); mp 193–195°C; IR
(υmax, cm-1): 3197, 1715, 1518, 1080; H NMR: δ 1.41 (s, 3H), 2.67 (t, 3H, 3-[4-Benzyl-1-(thiomorpholin-4-ylmethyl)-5-thioxo-4,5-dihy-
J ꢀ=ꢀ 8.0 Hz), 3.45 (brs, 2H), 4.63 (brs, 2H), 7.16–7.56 (m, 7H), 8.55 (brs, dro-1H-1,2,4-triazol-3-yl]-1-ethyl-7-methyl-1,8-naphthyridin-
1H), 9.16 (s, 1H); 13C NMR: δ 15.5, 25.5, 46.6, 47.9, 109.1, 119.9, 123.1, 127.3, 4(1H)-one (10a)ꢁYield 40% (method 1); yield 53% (method 2, InCl3
127.7, 128.6, 129.3, 136.0, 142.6, 148.9, 163.0, 165.1, 149.9, 166.0, 172.8, or p-TsOH); yield 47% (method 3); mp 100–102°C; IR (υmax, cm-1):
1
1
178.5. Anal. Calcd for C20H19N5O2: C, 66.47; H, 5.30; N, 19.38. Found: C, 3069, 2957, 1627, 1496, 1131; H NMR: δ 1.41 (t, 3H J ꢀ=ꢀ 8.0 Hz), 2.61 (s,
66.32; H, 4.89; N, 16.08.
4H), 2.71 (s, 3H), 3.36 (s, 4H), 4.29 (q, 2H, J ꢀ=ꢀ 8.0 Hz), 4.64 (brs, 2H),
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ꢁꢀꢀꢀ
S. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeletonꢂ
ꢂ235
5.27 (s, 2H), 6.45 (brs, 1H), 7.00–7.95 (m, 7H), 8.51 (s, 1H); 13C NMR: δ
15.3, 25.3, 40.7, 45.7, 48.3, 52.3, 70.0, 108.7, 111.3, 117.8, 121.8, 127.2, 127.5,
127.7, 128.8, 132.9, 136.2, 136.2, 147.6, 146.5, 148.8, 163.7, 174.7. Anal.
Calcd for C25H28N6OS2: C, 60.95; H, 5.73; N, 17.06. Found: C, 60.62; H,
5.91; N, 17.38.
166.6, 169.1, 174.7, 176.5, 178.5. Anal. Calcd for C37H37FN8O4S: C, 62.70;
H, 5.26; N, 15.81. Found: C, 62.31; H, 5.06; N, 16.03.
1-Ethyl-6-(4-{[4-ethyl-3-(1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-
naphthyridin-3-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]
methyl}piperazin-1-yl)-5-fluoro-4-oxo-1,4-dihydroquinoline-3-car-
boxylic acid (12b)ꢁYield 85% (method 1); yield 98% (method 2,
InCl3); yield 92% (method 2, p-TsOH); yield 96% (method 3); mp 220–
222°C; IR (υmax, cm-1): 3372, 1710, 1517, 1130; 1H NMR: δ 1.17 (s, 3H), 1.39
(t, 3H J ꢀ=ꢀ 8.0 Hz), 1.97 (s, 3H), 2.66 (brs, 3H), 2.95 (s, 4H), 3.36 (brs,
4H), 3.96 (s, 2H), 4.48 (brs, 2H), 4.56 (brs, 2H), 5.18 (s, 2H), 7.13 (s, 1H),
7.42 (brs, 1H), 7.54 (brs, 1H), 7.80 (brs, 1H), 8.88 (s, 1H), 9.03 (s, 1H),
15.27 (s, 1H); 13C NMR: δ 13.6, 14.8, 15.4, 25.5, 43.3, 45.8, 48.0, 49.5, 49.9,
50.2, 106.2, 109.8, 110.8, 119.4 and 119.5 (d, C, J ꢀ=ꢀ 15.0 Hz), 121.6 and
122.9 (d, CH, J ꢀ=ꢀ 136.0 Hz), 135.9 and 136.1 (d, CH, J ꢀ=ꢀ 17.0 Hz), 137.5,
145.8, 149.1 and 149.9 (d, C, J ꢀ=ꢀ 84.0 Hz), 154.1 and 156.1 (d, C, J ꢀ=ꢀ 200.0
Hz), 163.6 and 165.1 (d, C, J ꢀ=ꢀ 153.0 Hz), 107.5, 108.2, 149.2, 149.9, 166.5,
168.1, 174.9, 176.5, 178.4. Anal. Calcd for C32H35FN8O4S: C, 59.43; H, 5.45;
N, 17.33. Found: C, 59.31; H, 5.15; N, 17.03.
1-Ethyl-3-[4-ethyl-1-(thiomorpholin-4-ylmethyl)-5-thioxo-4,5-
dihydro-1H-1,2,4 -triazol-3-yl]-7-methyl-1,8-naphthyridin-4(1H)-
one (10b)ꢁYield 35% (method 1); yield 55% (method 2, InCl3); yield
56% (method 2, p-TsOH); yield 43% (method 3); mp 192–193°C; IR
1
(υmax, cm-1): 3087, 2980, 1710, 1518, 1128; H NMR: δ 1.17 (s, 3H), 1.40
(s, 3H), 2.67 (s, 3H), 2.99 (s, 4H), 3.34 (s, 4H), 3.95 (s, 2H), 4.49 (s, 2H),
5.08 (s, 2H), 7.45 (d, 2H, J ꢀ=ꢀ 8.0 Hz), 8.48 (brs, 1H), 8.63 (s, 1H); 13C
NMR: δ 13.6, 15.5, 25.3, 46.0, 50.6, 52.8, 66.6, 70.4, 108.2, 119.4, 121.6,
136.2, 147.2, 149.1, 146.8, 163.6, 167.9, 178.5. Anal. Calcd for C20H26N6OS2:
C, 55.79; H, 6.09; N, 19.52. Found: C, 55.61; H, 6.33; N, 19.28.
3-[(Acetoxy)methyl]-7-({[4-benzyl-3-(1-ethyl-7-methyl-4-oxo-1,4-
dihydro-1,8-naphthyridin-3-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-
triazol-1-yl]methyl}amino)-8-oxo-5-thia-1-azabicyclo[4.2.0]
oct-2-ene-2-carboxylic acid (11a)ꢁYield 55% (method 1); yield 64%
(method 2, InCl3); yield 60% (method 2, p-TsOH); yield 74% (method
3); mp 148–150°C; IR (υmax, cm-1): 3305, 3057, 1771, 1715 4, 1556, 1130; 1H
NMR: δ 1.41 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.91 (s, 3H), 2.73 (brs, 3H), 3.43 (q, 2H, J ꢀ=ꢀ
4.0 Hz), 3.96 (s, 1H), 4.34 (brs, 2H), 5.02 (d, 2H, J ꢀ=ꢀ 8.0 Hz), 5.29 (brs, 2H),
5.45 (s, 2H), 5.54 (s, 1H), 7.04-7.95 (m, 7H), 8.58 (s, 1H), 9.17 (s, 1H), 14.04
(s, 1H); 13C NMR: δ 14.7, 22.01, 26.3, 27.0, 45.7, 47.3, 59.2, 63.2, 68.1, 71.3,
108.9, 109.1, 119.4, 123.0, 125.0, 127.3, 127.9, 128.8, 136.0, 136.2, 146.4, 148.8,
148.8, 120.5, 150.0, 163.5, 163.7, 167.3, 168.1, 174.7, 178.5. Anal. Calcd for
C31H31N7O6S2: C, 62.26; H, 4.72; N, 14.82. Found: C, 62.01; H, 4.45; N, 14.51.
6-(4-{[4-Benzyl-3-(1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naph-
thyridin-3-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]
methyl}piperazin-1-yl)-1-cyclopropyl-5-fluoro-4-oxo-1,4-dihydroqui-
noline-3-carboxylic acid (13a)ꢁYield 82% (method 1); yield 90%
(method 2, InCl3); yield 97% (method 2, p-TsOH); yield 97% (method
3); mp ꢀ>ꢀ270°C; IR (υmax, cm-1): 3300, 1716 3, 1481, 1130; 1H NMR: δ 1.18
(s, 2H), 1.32 (s, 2H), 1.41 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 2.69 (brs, 3H), 2.99 (s, 4H),
3.38 (brs, 4H), 3.83 (brs, 2H), 4.33 (d, 4H, J ꢀ=ꢀ 8.0 Hz), 4.66 (brs, 1H),
5.25 (s, 2H), 6.98 (s, 1H), 7.13–7.84 (m, 7H), 7.95 (s, 1H), 8.61 (s, 1H),
9.01 (s, 1H), 15.15 (s, 1H); 13C NMR: δ 8.0 (2CH2), 15.3, 25.5, 36.3, 44.3
(N-2CH2), 47.3 (N-2CH2), 48.4, 49.9, 50.2, 106.9, 118.8, 119.0 and 120.3
(d, C, J ꢀ=ꢀ 129.0 Hz), 122.7, 123.9, 127.2, 127.6, 127.9 and 127.9 (d, CH, J ꢀ=ꢀ
7.0 Hz), 128.7 and 128.8 (d, CH, J ꢀ=ꢀ 6.0 Hz), 136.0, 136.1 (2C), 138.5 and
139.5 (d, C, J ꢀ=ꢀ 100.0 Hz), 144.5, 146.1 and 147.7 (d, C, J ꢀ=ꢀ 162.0 Hz),
148.6, 162.8 and 163.7 (d, C, J ꢀ=ꢀ 88.0 Hz)], 107.2, 118.6, 148.3, 148.8,
166.4, 169.1, 174.7, 176.7, 178.5. Anal. Calcd for C37H37FN8O4S: C, 63.32;
H, 5.17; N, 15.55. Found: C, 63.28; H, 5.06; N, 15.21.
3-[(Acetoxy)methyl]-7-({[4-ethyl-3-(1-ethyl-7-methyl-4-oxo-1,4-
dihydro-1,8-naphthyridin-3-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-
triazol-1-yl]methyl}amino)-8-oxo-5-thia-1-azabicyclo[4.2.0]
oct-2-ene-2-carboxylic acid (11b)ꢁYield 58% (method 1); yield 69%
(method 2, InCl3); yield 70% (method 2, p-TsOH); yield 81% (method
3); mp 140–142°C; IR (υmax, cm-1): 3280, 3047, 1768, 1710 4, 1562, 1130; 1H
NMR: δ 1.15 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.41 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.91 (s, 3H), 2.71
(brs, 3H), 3.32 (brs, 2H), 3.92 (s, 1H), 4.47 (brs, 2H), 4.63 (brs, 2H), 5.01
(d, 2H, J ꢀ=ꢀ 8.0 Hz), 5.53 (s, 1H), 7.44 (d, 1H, J ꢀ=ꢀ 8.0 Hz), 7.59 (d, 1H, J ꢀ=ꢀ 8.0
Hz), 8.60 (s, 1H), 9.16 (s, 1H), 13.82 (s, 1H); 13C NMR: δ 13.8, 15.4, 21.5, 25.5,
27.1, 45.9, 47.3, 58.2, 64.3, 69.1), 72.0, 108.8, 109.8, 118.8, 123.1, 136.2, 148.5,
149.1, 119.4, 150.0, 163.5, 165.1, 166.0, 167.1, 174.9, 178.6. Anal. Calcd for
C26H29N7O6S2: C, 52.07; H, 4.87; N, 16.35. Found: C, 52.31; H, 4.45; N, 16.51.
1-Cyclopropyl-6-(4-{[4-ethyl-3-(1-ethyl-7-methyl-4-oxo-1,4-dihydro-
1,8-naphthyridin-3-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]
methyl}piperazin-1-yl)-5-fluoro-4-oxo-1,4-dihydroquinoline-3-car-
boxylic acid (13b)ꢁYield 79% (method 1); yield 85% (method 2, InCl3);
yield 88% (method 2, p-TsOH);. yield 95% (method 3); mp 228–230°C;
IR (υmax, cm-1): 3456, 1710 3, 1558, 1159; 1H NMR: δ 1.18 (s, 2H), 1.32 (s, 2H),
1.40 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 1.96 (s, 3H), 2.69 (brs, 3H), 2.97 (s, 4H), 3.33 (brs,
4H), 3.82 (brs, 2H), 4.49 (d, 4H, J ꢀ=ꢀ 8.0 Hz), 4.64 (brs, 1H), 5.25 (s, 2H),
7.44–7.79 (m, 4H), 8.61 (s, 1H), 9.05 (s, 1H), 15.08 (s, 1H); 13C NMR: δ 8.0,
15.3, 25.4, 27.7, 36.4, 43.8, 45.9, 47.2, 48.8, 49.7, 51.2, 105.9, 109.8, 119.0 and
119.6 (d, C, J ꢀ=ꢀ 50.0 Hz), 121.7, 123.9, 125.9 and 125.9 (d, CH, J ꢀ=ꢀ 7.0 Hz),
128.1 and 128.8 (d, CH, J ꢀ=ꢀ 76.0 Hz), 135.0, 139.5 and 141.5 (d, C, J ꢀ=ꢀ 200.0
Hz), 146.1 and 148.6 (d, C, J ꢀ=ꢀ 253.0 Hz), 161.9 and 162.6 (d, C, J ꢀ=ꢀ 72.0
Hz), 107.7, 108.6, 143.6, 149.1, 166.2, 169.1, 173.9, 175.8, 178.3. Anal. Calcd for
C33H35FN8O4S: C, 60.17; H, 5.36; N, 17.01. Found: C, 60.31; H, 5.15; N, 17.37.
6-(4-{[4-Benzyl-3-(1-ethyl-7-methyl-4-oxo-1,4-dihydro-1,8-naph-
thyridin-3-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]
methyl}piperazin-1-yl)-1-ethyl-5-fluoro-4-oxo-1,4-dihydroquinoline-
3-carboxylic acid (12a)ꢁYield 82% (method 1); yield 92% (method
2, InCl3); yield 91% (method 2, p-TsOH); yield 98% (method 3); mp
1
200–202°C; IR (υmax, cm-1): 3451, 1720, 1562, 1130; H NMR: δ 1.39 (t,
3H, J ꢀ=ꢀ 8.0 Hz), 1.96 (s, 3H), 2.64 (brs, 3H), 2.98 (s, 4H), 3.39 (brs, 4H),
4.34 (brs, 2H), 4.60 (brs, 2H), 5.25 (d, 4H, J ꢀ=ꢀ 8.0 Hz), 6.53 (s, 1H),
7.15–7.57 (m, 7H), 7.83 (brs, 1H), 8.47 (s, 1H), 8.92 (s, 1H), 14.89 (s, 1H);
13C NMR: δ 14.8 (CH3), 15.3 (CH3), 25.5 (CH3), 44.8 (N-2CH2), 46.4 (CH2),
47.2 (N-2CH2), 49.5, 49.9, 50.2, 106.0, 110.4, 112.3, 118.7, 119.6 and 119.7
(d, CH, J ꢀ=ꢀ 7.0 Hz), 121.8, 123.0, 126.1, 127.2 and 127.6 (d, CH, J ꢀ=ꢀ 47.0
Hz), 128.6 and 128.8 (d, CH, J ꢀ=ꢀ 17.0 Hz), 135.0 (CH), 135.9 and 136.2
(d, C, J ꢀ=ꢀ 26.0 Hz), 142.3 (C), 145.9 (CH), 146.5 and 147.7 (d, C, J ꢀ=ꢀ 122.0
Hz), 151.9 and 153.6 (d, C, J ꢀ=ꢀ 161.0 Hz), 165.1, 107.5, 108.4, 149.1, 149.9,
General synthesis of compounds 14 and 15
Method 1ꢁTo a solution of compound 6a (0.01 mol) in dimethyl sulf-
oxide, 1-phenylpiperazine (for 14, 1.52 mL, 0.01 mol) or tryptamine
(for 15, 1.60 g, 0.01 mol) was added in the presence of formaldehyde
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ꢀꢀꢀꢁ
236ꢀ ꢀS. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeleton
(37%, 3.72 mL, 0.05 mol) and the mixture was stirred at room tem-
perature for 24 h, then poured into ice-cold water. The resultant pre-
cipitate was crystallized from ethanol/water (1:3).
at 35°C. Brain heart infusion broth (BHI) (Difco, Detriot, MI, USA) was
used for M. smegmatis; incubation was for 48–72 h at 35°C [44]. Ampi-
cillin, streptomycin, and fluconazole were used as standard antibac-
terial and antifungal drugs. Dimethyl sulfoxide with a dilution of 1:10
was used as a solvent control.
Method 2ꢁTo a solution of compound 6a (1 mmol) in dimethyl sulfox-
ide, 1-phenylpiperazine (for 14, 1 mmol) or tryptamine (for 15, 1 mmol)
was added in the presence of formaldehyde (5 mmol) and the mixture
was stirred at room temperature for 15 min. Then, a catalytic amount
of a catalyst (InCl3 or p-TsOH) was added and the stirring was contin-
ued for an additional 5 h. The mixture was poured into ice water and
the resultant precipitate was crystallized from ethanol/water (1:3).
Acknowledgments: The financial support was provided by
Scientific and Technological Research Council of Turkey
(TUBITAK, Project no: 113Z181).
Method 3ꢁA solution, prepared as described above, was irradiated
at 50oC in the microwave oven for 5 min, then cooled to room temper-
ature and poured into ice water. The resultant precipitate was filtered
off and crystallized from ethanol/water (1:3).
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dihydro-1H-1,2,4-triazol-3-yl}-1-ethyl-7-methyl-1,8-naphthyridin-
4(1H)-one (14)ꢁYield 74% (method 1); yield 78% (method 2, InCl3);
yield 80% (method 2, p-TsOH); yield 93% (method 3); mp 106–108°C;
IR (υmax, cm-1): 1726, 1495, 1155; 1H NMR: δ 1.37 (t, 3H, J ꢀ=ꢀ 8.0 Hz), 2.59
(s, 3H), 2.92 (s, 4H), 3.13 (brs, 4H), 4.35 (brs, 2H), 5.23 (s, 2H), 5.32 (s,
2H), 6.77 (brs, 1H), 6.95 (d, 3H, J ꢀ=ꢀ 8.0 Hz), 7.15–7.29 (m, 7H), 7.45 (brs,
1H), 7.95 (s, 1H); 13C NMR: δ 15.4, 25.3, 47.3, 48.3, 48.8, 50.4, 69.4, 108.6,
116.1, 119.3, 119.4, 121.8, 127.4, 127.5, 127.8, 127.9, 128.6, 128.7, 128.8, 129.3,
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C31H33N7OS: C, 67.49; H, 6.03; N, 17.77. Found: C, 67.28; H, 6.06; N, 17.98.
3-[4-Benzyl-1-({[2-(1H-indol-3-yl)ethyl]amino}methyl)-5-thioxo-
4,5-dihydro-1H-1,2,4-triazol-3-yl]-1-ethyl-7-methyl-1,8-naphthy-
ridin-4(1H)-one (15)ꢁYield 71% (method 1); yield 80% (method 2,
InCl3), yield 82% (method 2, p-TsOH); yield 99% (method 3); mp 163–
165°C; IR (υmax, cm-1): 3029 2, 1710, 1503, 1155; 1H NMR: δ 1.20 (t, 3H, J ꢀ=ꢀ
8.0 Hz), 2.66 (s, 3H), 4.36 (t, 2H, J ꢀ=ꢀ 8.0 Hz), 4.64 (t, 2H, J ꢀ=ꢀ 8.0 Hz),
5.12 (s, 2H), 5.30 (s, 2H), 5.54 (s, 2H), 6.99 (brs, 3H), 7.14–7.31 (m, 7H),
7.48 (d, 2H, J ꢀ=ꢀ 8.0 Hz), 8.54 (s, 1H), 9.01 (s, 1H), 9.21 (s, 1H), 14.93 (s,
1H); 13C NMR: δ 15.3, 25.3, 25.5, 45.6, 47.3, 48.2, 71.3, 108.7, 119.3, 121.8,
123.1, 127.6 (2CH), 128.0 (2CH), 128.8 (2CH), 136.1, 136.2 (2CH), 146.4
(2CH), 147.9, 148.8, 152.2, 163.7, 150.1, 164.9, 167.9, 174.7. Anal. Calcd for
C31H31N7OS: C, 67.73; H, 5.68; N, 17.84. Found: C, 67.49; H, 6.05; N, 17.97.
Antimicrobial activity
The following test microorganisms were obtained from the Hifzissi-
hha Institute of Refik Saydam (Ankara, Turkey): E. coli ATCC35218,
Yersinia pseudotuberculosis (Y. pseudotuberculosis) ATCC911,
Pseudomonas aeruginosa (P. aeruginosa) ATCC43288, E. faecalis
ATCC29212, Staphylococcus aureus (S. aureus) ATCC25923, Bacil-
lus cereus (B. cereus) 709 Roma, M. smegmatis ATCC607, Candida
albicans (C. albicans) ATCC60193, and Saccharomyces cerevisiae (S.
cerevisia) RSKK 251. All synthesized compounds were weighed and
dissolved in hexane to prepare a stock solution of 20.0 μg/mL. The
antimicrobial effects of the substances were tested quantitatively
by using double microdilution; the MIC values (μg/mL) were deter-
mined. The antibacterial and antifungal assays were performed in
Mueller-Hinton broth (MH) (Difco, Detroit, MI, USA) at pH 7.3 and
buffered yeast nitrogen base (Difco, Detroit, MI, USA) at pH 7.0,
respectively. The microdilution test plates were incubated for 18–24 h
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S. Ceylan et al.: Novel antimicrobial 1,2,4-triazole derivatives containing nalidixic acid skeletonꢂ
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