Synthesis, Dissociation Constants, and Some Pharmacological Properties of Schiff Base Hydrazones and their Cyclization to 1,3-Thiazolidin-4-one Derivatives

Article abstract of DOI:10.1002/jhet.2257

This study presents the synthesis, dissociation constants, and pharmacological properties of Schiff base hydrazones. The derivatives were synthesized by the condensation reaction of carboxylic acid hydrazides containing 1,2,4-triazole system with various

Full text of DOI:10.1002/jhet.2257

Month 2014
Synthesis, Dissociation Constants, and Some Pharmacological Properties
of Schiff Base Hydrazones and their Cyclization to 1,3-Thiazolidin-4-one
Derivatives
a
b
b
b
c
c
*
Ł. Popiołek, A. Chodkowska, A. Tryka, K. Pawłowski, M. Kiełczykowska, J. Kocot,
M. Wujec,a and E. Jagiełło-Wójtowiczb
aDepartment of Organic Chemistry, Faculty of Pharmacy, Medical University of Lublin, 4A Chodzki Str., 20-093 Lublin, Poland
bDepartment of Toxicology, Faculty of Pharmacy, Medical University of Lublin, 8 Chodzki Str., 20-093 Lublin, Poland
cDepartment of Medical Chemistry, Faculty of Medicine, Medical University of Lublin, 4A Chodzki Str., 20-093 Lublin, Poland
*
E-mail: lukasz.popiolek@umlub.pl
Received February 20, 2014
DOI 10.1002/jhet.2257
Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com).
This study presents the synthesis, dissociation constants, and pharmacological properties of Schiff base
hydrazones. The derivatives were synthesized by the condensation reaction of carboxylic acid hydrazides
containing 1,2,4-triazole system with various aldehydes. The new derivatives of 1,3-thiazolidin-4-one were
prepared by the cyclization reaction of Schiff base hydrazones with the mercaptoacetic acid in the presence
of 1,4-dioxane. The structure of all obtained compounds was confirmed by means of 1H NMR and 13C NMR
spectra. The dissociation constants were determined using spectrophotometric method. The effects of four
synthesized Schiff base hydrazones 6, 7, 11, and 12 on the central nervous system of mice in behavioral tests
were examined.
J. Heterocyclic Chem., 00, 00 (2014).
INTRODUCTION
acetic acid in ethanol and gave good yield of products 5–16.
Through the modification of the Schiff bases hydrazones, we
were able to obtain new 1,3-thiazolidin-4-one derivatives. In
the second step of the reactions, 1,3-thiazolidin-4-one
derivatives 17–20 were obtained by cyclization reaction of
Schiff base hydrazones (5–8), in the presence of 1,4-
dioxane. The reaction was carried in room temperature.
All obtained compounds are air stable solids and soluble
in DMSO at ambient temperature. The purity of the synthe-
sized compounds was checked by elemental analyses and
TLC. The structures of prepared derivatives were deter-
A wide variety of heterocyclic systems have been
explored for developing pharmaceutically important mole-
cules. Among them, the derivatives of 1,2,4-triazole and
1,3-thiazolidine and their derivatives have played an im-
portant role in the medicinal chemistry, due to its facile
synthesis and wide applications.
These heterocycles have been found to possess a wide
spectrum of biological activities such as analgesic [1],
antifungal [2–4], antibacterial [5–7], antiviral [8–11], anti-
phlogistic [12–14], and antituberculous [15] action.
In the view of these fact, we hereby report the synthesis,
dissociation constants, and some pharmacological properties
of Schiff base hydrazone derivatives possessing the 1,2,4-
triazole moiety and their cyclization to 1,3-thiazolidin-4-ones.
1
mined on the basis of H NMR and 13C NMR spectra,
and all of the synthesized compounds have satisfactory
1
analyses for their proposed structures. H NMR spectra
results for all compounds together with hydrogen assign-
ments and 13C NMR spectra results are presented in the
Experimental Section.
1
In the H NMR spectra of compounds 5–16, the singlet
RESULTS AND DISCUSSION
peak due to the hydrazone proton (NH) appeared in the re-
gion of δ 8.11–11.98 ppm, which confirmed the successful
formation of the desired products, whereas the singlet sig-
nal for –S–CH2– protons was observed in the region of δ
3.43–4.55 ppm. All other aliphatic and aromatic protons
were observed at expected regions.
Chemistry.
The synthetic pathway leading to the
Schiff base hydrazone derivatives 5–16 and new 1,3-
thiazolidin-4-one derivatives 17–20 was carried out
according to the steps shown in Scheme 1. In the initial
step, the condensation reaction of [(4-phenyl-5-substituted-
4H-1,2,4-triazol-3-yl)sulfanyl]acethydrazides with various
aryl aldehydes was carried out in the presence of glacial
In the 13C NMR spectra of 5–16 derivatives, the carbon
of –S–CH2– group had a typical signal at about 30 ppm.
© 2014 HeteroCorporation

Ł. Popiołek, A. Chodkowska, A. Tryka, K. Pawłowski, M. Kiełczykowska,
J. Kocot, M. Wujec, and E. Jagiełło-Wójtowicz
Vol 000
Scheme 1. Synthetic route to new 1,3-thiazolidin-4-one derivatives.
Similarly, the presence of the ═CH group was also con-
firmed by a signal at about 150 ppm and for C═O group
at 166 ppm. All other aliphatic and aromatic carbons were
observed at expected regions.
acetohydrazide (CH3 or Br) exerts the greatest influence
on the NH group ability to dissociate. The presence of elec-
tronegative bromine causes the decrease in pK value when
compared with the respective compound possessing
methyl group that does not have electron acceptor proper-
ties. The other parts of the structure display less effect. It
confirms the structure of the studied compounds as the
examined acid–base equilibrium concerns dissociation of
H atom bound to hydrazide part. The spectra of the studied
compounds show that in this case, the greatest influence is
exerted by the group attached to N-5 in 1,2,4-triazole ring.
The presence of aromatic ring in this position (phenyl—
compounds 11, 15, or 3-pyridyl—compounds 12 and 16)
causes the increase in absorbance both in the case of
neutral molecules and monoanion forms compared with
compounds that contain methyl or H atom. It is consistent
with the fact that these aromatic groups, as distinct from
phenyl groups at N-4, form the conjugated systems with
double bonds of 1,2,4-triazole ring. All the data regarding
dissociations constants are presented in Table 1 and
Graphs 1–4.
1H NMR spectra of compounds 17–20 showed singlet pro-
ton signal typical for the NH group in the δ 9.06–11.16 ppm
range, and singlet peak due to the proton of CH group which
appeared in the region of δ 8.45–8.89 ppm, confirmed the
successful formation of the desired products. In the 13C
NMR spectra of 17–20 derivatives the carbons of two C═O
groups had a typical signal at about 164 and 172 ppm and
for CH group at about 61 ppm. Both analytical and spectral
data of the synthesized compounds were in full agreement
with the proposed structures.
The results of the spectral data indicate that the cyclization
reaction leads to the formation of complex heterocylic com-
pounds, which contain 1,2,4-triazole and 1,3-thiazolidin-4-
one derivatives. The plausible mechanism of the formation of
new 1,3-thiazolidin-4-one derivatives is presented in Scheme 2.
DISSOCIATION CONSTANTS
The dissociation constants were established by spectro-
photometric method for compounds 9–16. The comparison
of the obtained pK values shows that the substituent
occurring in the phenyl ring bound to N atom of the
PHARMACOLOGY
The preliminary behavioral study showed that com-
pounds 6, 7, 11, and 12 exert depressive action on CNS
Scheme 2. The plausible mechanism of the formation of new 1,3-thiazolidin-4-one derivatives (17–20).
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Synthesis, Dissociation Constants, and some Pharmacological Properties of Schiff
Base Hydrazones and their Cyclization to 1,3-Thiazolidin-4-one Derivatives
Month 2014
Table 1
Concentrations of the working solutions, wavelengths λ, and pK values of compounds 9–16.
pK
Number of the
compound
Concentration of the working solutions (mol/L) cuvette width
λ (nm)
x SD
9
2.50 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
2.50 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
2.36 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
2.50 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
2.15 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
2.40 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
5.00 × 10ꢀ6 10% (v/v) water solution of CH3OH l = 5 cm
2.50 × 10ꢀ5 10% (v/v) water solution of CH3OH l = 1 cm
325
327
324
326
327
328
324
328
11,10 0,07
11,32 0,08
11,29 0,06
11,36 0,06
10,96 0,06
11,07 0,06
11,08 0,09
10,93 0,07
10
11
12
13
14
15
16
Neutral molecules of the compounds 9 - 12
Monoanions of the compounds 13 - 16
0.75
0.6
0.75
0.6
0.45
0.3
0.45
A
A
0.3
0.15
0
0.15
0
Graph 1. Neutral molecules of compounds 9–12.
Graph 4. Monoanions of compounds 13–16.
of mice with compound 6 having the weakest effect as it
was noticeable only in the 100 mg/kg i.p. None of the com-
pounds in a dose of 100 mg/kg i.p. had a neurotoxic effect
because they did not affect the motor coordination of mice
in the chimney test. Compounds 7, 11, and 12 in doses of
50 and 100mg/kg significantly decreased the body tempera-
ture of normothermic mice (Table 2). In the dose 25mg/kg,
the effect was not observed. Compounds 7, 11, and 12 given
in the same dose did not influence body temperature but
significantly prolonged the thiopental sleeping time in
mice. Compound 6 in doses of 50 and 100 mg/kg prolonged
the sleep induced by thiopental but did not influence the
body temperature of normothermic mice (Table 3). The
decrease of body temperature of monothermic mice by com-
pounds 7, 11, and 12 may confirm the influence of these
compounds on serotonergic system, which plays an impor-
tant role in central regulation of body temperature [16].
Among the four investigated derivatives, only com-
pound 7 in a wide dose range (12.5–100 mg/kg i.p.)
showed potent antinociceptive properties (Table 4).
These doses produced a decrease in the number of mice
exhibiting pain reactivity in the ‘writing syndrome’ test.
No dose–effect relation was observed.
Neutral molecules of the compounds 13 - 16
0.75
0.6
0.45
0.3
0.15
0
A
Graph 2. Neutral molecules of compounds 13–16.
Monoanions of the compounds 9 - 12
0.75
0.6
0.45
0.3
0.15
0
A
On the other hand, compounds 6 and 12 at doses of
100 mg/kg offered a protection against tonic seizures and
mortality in mice. Compounds 7 and 11 did not exhibit
Graph 3. Monoanions of compounds 9–12.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Ł. Popiołek, A. Chodkowska, A. Tryka, K. Pawłowski, M. Kiełczykowska,
J. Kocot, M. Wujec, and E. Jagiełło-Wójtowicz
Vol 000
Table 2
The effects of compounds 7, 11, and 12 on body temperature of normothermic mice.
Time (min)
60
Initial body
temperature
(°C)
Dose
mg/kg ip
15
Compound
30
45
90
120
180
Control
7
-
25
50
100
-
25
50
100
25
50
100
37.0 0.1
37.3 0.4
37.1 0.1
37.2 0.2
36.7 0.2
36.5 0.1
36.7 0.04
36.8 0.1
36.6 0.2
36.8 0.1
37.0 0.1
37.0 0.2
37.2 0.3
34.9 0.1*
35.1 0.2*
36.3 0.1
36.5 0.1
35.1 0.6*
35.6 0.3*
36.6 0.3
34.5 0.1*
34.8 0.2*
36.8 0.2
37.0 0.2
35.1 0.1*
35.0 0.1*
36.2 0.1
36.8 0.2
34.8 0.5*
35.5 0.3*
36.6 0.3
34.8 0.2*
35.0 0.3*
37.0 0.2
36.9 0.2
35.1 0.3*
35.4 0.2*
36.1 0.2
36.6 0.3
34.6 0.4*
35.5 0.3*
36.3 0.1
34.8 0.1*
35.2 0.2*
37.1 0.2
36.9 0.3
35.1 0.3*
35.7 0.2*
36.6 0.1
36.8 0.2
35.3 0.4*
35.9 0.3
36.8 0.1
35.3 0.1*
35.1 0.1*
37.0 0.1
37.0 0.2
35.6 0.2*
35.5 0.3*
36.2 0.2
36.6 0.3
35.3 0.3
36.3 0.2
36.3 0.4
36.0 0.1
35.0 0.2*
36.9 0.1
37.1 0.3
36.2 0.2
35.6 0.3*
36.2 0.2
36.5 0.3
36.0 0.3
36.8 0.2
36.6 0.3
36.3 0.2
36.2 0.2
37.2 0.1
36.9 0.2
36.8 0.2
36.8 0.2
36.4 0.2
36.1 0.3
36.3 0.3
37.0 0.3
36.8 0.3
36.7 0.2
37.0 0.3
Control
11
12
*p ≤ 0.05 versus the control group. Results are expressed as a mean temperature SEM.
Table 3
Table 5
The effects of the investigated compounds (6, 7, 11, 12) on thiopental-
The influence of the compounds 6 and 12 an pentetrazole-induced con-
induced sleep.
vulsions in mice.
Sleeping time (min)
Treatment
Treatment
mg/kg ip
Tonic
seizures (%)
Compound
Lethality (%)
Compound
mg/kg ip
%
Mean SEM
Control
6
-
50
100
50
87.5
100
37.5*
62.5
25*
62.5
75
25*
50
Control
6
-
25.0
50.0
100.0
12.5
25.0
-
12.5
25.0
12.5
25.0
18.9 1.6
16.9 3.4
34.1 11.3*
100.0 8.5
89.4 17.9
180.4 59.8*
12
100
12.5*
81.9 17.2** 433.3 91.0**
7
20.3 4.7
30.1 3.9*
24.6 2.5
19.6 4.7
44.0 7.2**
32.6 8.1
86.2 7.6**
107.4 24.9
159.3 20.6*
100 10.2
*p < 0.05 versus the control group.
Control
11
79.7 19.1
In conclusion, we have shown that the antinociceptive
activity of compound 7 is interesting and should be
examined in more detail.
178.9 29.3**
132.5 32.9
350.4 30.8**
12
*p < 0.05.
**p < 0.001 versus the control group.
EXPERIMENTAL
Chemistry. General.
All reagents were purchased from
Table 4
Sigma-Aldrich (Munich, Germany) and Merck Co. (Darmstadt,
Germany) and used without further purification. Melting points
were determined in Fisher–Johns blocks (Fisher Scientific,
Schwerte, Germany) and presented without any corrections. The
IR spectra (ν, cmꢀ1) were recorded in KBr tablets using a
Specord IR-75 spectrophotometer (Carl Zeiss, Jena, Germany).
The 1H NMR spectra were recorded on a Bruker Avance 300
apparatus (Bruker BioSpin GmbH, Rheinstetten/Karlsruhe,
Germany) in DMSO-d6 with TMS as internal standard. The 13C
NMR spectra were recorded on a Bruker Avance 300 apparatus.
Chemical shifts are given in ppm (δ scale). The purity of
obtained compounds was checked by TLC on aluminium oxide
60 F254 plates (Merck Co. Whitehouse Station, New Jersey,
USA), in a CHCl3/C2H5OH (10:1, v/v) solvent system. The
spots were detected by exposure to a UV lamp at 254 nm.
Elemental analyses of the obtained compounds were performed
for C, H, N on AMZ 851 CHX analyser (PG, Gdańsk, Poland).
The maximum percentage differences between calculated and
found values for each element were within the error and
amounted to 0.4%.
Antinociceptive activity of compound 7 in the ‘writhing syndrome’ test in
mice.
Treatment
mg/kg ip
Mean writhing
number X SEM
Inhibition*
(%)
Compound
Control
7
-
6.25
12.5
25
50
100
28.3 5.6
24.3 3.7
17.9 4.8*
12.9 0.7**
14.1 3.5**
9.1 2.4**
0.0
14.2
36.7*
54.5**
50.2**
67.8**
*% of inhibition obtained by comparison with the control group
*p < 0.05.
**p < 0.001 versus the control group.
any anticonvulsive activity (Table 5). In the remaining
pharmacological tests, none of the compounds produced
a statistically significant effect.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Synthesis, Dissociation Constants, and some Pharmacological Properties of Schiff
Base Hydrazones and their Cyclization to 1,3-Thiazolidin-4-one Derivatives
Month 2014
Preparation of acethydrazide derivatives 5–16.
The
2-[(5-methyl-4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(4-
methylphenyl)methylidene] acethydrazide (10). Physicochemical
and spectroscopic data are consistent with the reference [17]. CAS
derivatives were obtained according to reference [17]. To a
suspension of hydrazide (1–4) (10 mmol) in ethanol (20 mL), an
equimolar of various aldehydes (10 mmol) was added. The
suspension was heated until clear solution was obtained. Then few
drops of glacial acetic acid were added as a catalyst. The solution
was refluxed for 4 h. After the completion of the reaction, the
solution was cooled at room temperature. The obtained precipitate
was filtered off and crystallized from ethanol.
2-[(4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(2-hydroxyphenyl)
methylidene]acethydrazide (5). Physicochemical and spectroscopic
data are consistent with reference [17]. Yield: 66%, mp 124–126°C;
1H nmr (DMSO-d6): δ 4.15 (s, 2H, CH2), 4.54 (s, 1H, OH),
6.90–7.73 (m, 9H, Ar–H), 8.40 (s, 1H, CH), 8.46 (s, 1H, CH),
8.94 (s, 1H, NH); 13C nmr: δ 30.1 (–S–CH2–), 117.4, 120.4,
121.2, 125.6, 128.5, 128.70, 129.2, 129.7, 137.5 11Car), 147.5
(C-3 triazole), 150.2 (═CH), 154.5 (C-5 triazole), 158.3 (Car),
166.5 (C═O); Anal. Calcd. for C17H15N5O2S (353.4): C, 57.78;
H, 4.28; N, 19.82. Found: C, 57.82; H, 4.22; N, 19.85%.
1
registry number: 62373-03-9. Yield: 73%, mp 186–188°C; H nmr
(DMSO-d6): δ 2.24 (s, 3H, CH3), 2.38 (s, 3H, CH3), 4.04 (s, 2H,
CH2), 7.21–8.19 (m, 9H, Ar–H), 8.71 (s, 1H, CH), 11.60 (s, 1H,
NH); 13C nmr: δ 12.5 (–CH3), 21.1 (–CH3), 30.1 (–S–CH2–),
127.3, 128.4, 129.1, 129.9, 130.2, 131.9, 136.2, 138.5 (12Car),
148.6 (═CH), 156.1 (C-5 triazole), 158.4 (C-3 triazole), 166.1
(C═O); Anal. Calcd. for C19H19N5OS (365,45): C, 62.44; H, 5.24;
N, 19.16. Found: C, 62.49; H, 5.22; N, 19.11%.
2-[(4,5-diphenyl-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(4-
methylphenyl) methylidene]acethydrazide (11). Physicochemical
and spectroscopic data are consistent with reference [17]. CAS
1
registry number: 93300-42-6. Yield: 84%, mp 214–216°C; H nmr
(DMSO-d6): δ 2.39 (s, 3H, CH3), 4.14 (s, 2H, CH2), 7.30–7.67
(m, 14H, Ar–H), 8.04 (s, 1H, CH), 8.22 (s, 1H, NH); 13C nmr: δ
21.1 (–CH3), 30.0 (–S–CH2), 125.6, 127.3, 128.6, 128.8, 129.1,
129.5, 130.1, 130.6, 131.9, 137.4, 138.5 (18Car), 148.5 (═CH),
159.5 (C-3 triazole), 166.1 (C═O), 167.4 (C-5 triazole); Anal.
Calcd. for C24H21N5OS (427.52): C, 67.43; H, 4.95; N, 16.38.
Found: C, 67.48; H, 4.98; N, 16.42%.
2-[(5-methyl-4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(2-
hydroxyphenyl)methylidene] acethydrazide (6). Physicochemical
and spectroscopic data are consistent with reference [17]. CAS
1
registry number: 62372-96-7. Yield: 68%, mp 200–202°C. H nmr
2-[(4-phenyl-5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(4-
(DMSO-d6): δ 2.26 (s, 3H, CH3), 4.04 (s, 2H, CH2), 4.41 (s, 1H,
OH), 6.89–7.76 (m, 9H, Ar–H), 8.52 (s, 1H, ═CH), 9.65 (s, 1H,
NH); 13C nmr: δ 12.5 (–CH3), 30.6 (–S–CH2–), 117.4, 120.4,
128.3, 128.5, 129.9, 130.2, 136.2 (11Car), 156.0 (C-5 triazole),
158.3 (Car), 158.4 (C-3 triazole), 166.1 (C═O); Anal. Calcd. for
C18H17N5O2S (367.42): C, 58.84; H, 4.66; N, 19.06. Found: C,
58.89; H, 4.70; N, 19.04%.
methylphenyl) methylidene]acethydrazide (12).
Physicochemical
and spectroscopic data are consistent with reference [17]. CAS
registry number: 903408-50-4. Yield: 65%, mp 184–186°C; 1H
nmr (DMSO-d6): δ 2.31 (s, 3H, CH3), 4.10 (s, 2H, CH2),
7.22–8.57 (m, 13H, Ar–H), 8.15 (s, 1H, CH), 9.93 (s, 1H, NH);
13C nmr: δ 21.0 (–CH3), 30.1 (–S–CH2–), 126.1, 127.4, 128.4,
128.7, 129.2, 130.1, 131.9, 132.2, 134.6, 137.4, 138.5, 146.3,
146.9 (17Car), 148.8 (═CH), 159.6 (C-3 triazole), 162.3 (C-5
triazole), 166.0 (C═O); Anal. Calcd. for C23H20N6OS (428.50):
C, 64.47; H, 4.70; N, 19.61. Found: C, 64.50; H, 4.72; N, 19.63%.
N-[(4-bromophenyl)methylidene]-2-[(4-phenyl-4H-1,2,4-triazol-
2-[(4,5-diphenyl-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(2-
hydroxyphenyl) methylidene]acethydrazide (7). Physicochemical
and spectroscopic data are consistent with reference [17]. CAS
1
registry number: 62372-96-7. Yield: 85%, mp 212–214°C; H nmr
(DMSO-d6): δ 4.15 (s, 2H, CH2), 4.54 (s, 1H, OH), 6.90–7.74 (m,
14H, Ar–H), 8.37 (s, 1H, CH), 8.48 (s, 1H, NH); 13C nmr: δ 30.2
(–S–CH2), 117.6, 120.7, 121.3, 125.8, 128.5, 128.6, 128.8, 130.1,
137.4 (17Car), 150.7 (═CH), 158.5 (Car) 159.5 (C-3 triazole), 166.5
(C═O), 167.4 (C-5 triazole); Anal. Calcd. for C23H19N5O2S
(429.49): C, 64.32; H, 4.46; N, 16.31. Found: C, 64.35; H,
4.48; N, 16.35%.
2-{[4-phenyl-5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl]sulfanyl}-N-[(2-
hydroxyphenyl)methylidene]acethydrazide (8). Physicochemical
and spectroscopic data are consistent with reference [17]. CAS
registry number: 903116-56-3. Yield: 90%, mp 210–212°C; 1H
nmr (DMSO-d6): δ 3.43 (s, 2H, CH2), 4.11 (s, 1H, OH), 6.82–8.56
(m, 13H, Ar-H), 8.41 (s, 1H, ═CH), 10.23 (s, 1H, NH); 13C nmr: δ
30.1 (–S–CH2), 117.3, 120.4, 121.2, 126.3, 128.5, 128.6, 128.8,
129.8, 130.2, 132.3, 134.7, 137.9, 146.4, 146.9 (16Car), 150.9
(═CH), 158.4 (Car), 159.5 (C-3 triazole), 162.4 (C-5 triazole),
166.2 (C═O); Anal. Calcd. for C22H18N6O2S (430.48): C, 61.38;
H, 4.21; N, 19.52. Found: C, 61.43; H, 4.28; N, 19.58%.
3-yl)sulfanyl]acethydrazide (13).
Physicochemical and
spectroscopic data are consistent with reference [17]. Yield:
1
75%, mp 140–142°C; H nmr (DMSO-d6): δ 4.07 (s, 2H, CH2),
7.50–8.03 (m, 9H, Ar–H), 8.21 (s, 1H, CH), 8.85 (s, 1H, CH),
11.71 (s, 1H, NH); 13C nmr: δ 30.1 (–S–CH2–), 123.9, 125.6,
128.8, 129.1, 129.3, 132.4, 132.5, 137.5 (12Car), 147.5 (C-3
triazole), 148.7 (═CH), 154.6 (C-5 triazole), 166.1 (C═O); Anal.
Calcd. for C17H14BrN5OS (416.29): C, 49.05; H, 3.39; N, 16.82.
Found: C, 49.01; H, 3.40; N, 16.85%.
N-[(4-bromophenyl)methylidene]-2-[(5-methyl-4-phenyl-4H-
1,2,4-triazol-3-yl)sulfanyl]acethydrazide (14). Physicochemical
and spectroscopic data are consistent with reference [17]. Yield:
1
65%, mp 126–128°C; H nmr (DMSO-d6): δ 2.26 (s, 3H, CH3),
4.03 (s, 2H, CH2), 7.49–8.22 (m, 9H, Ar–H), 8.75 (s, 1H, CH),
10.04 (s, 1H, NH); 13C nmr: δ 12.4 (–CH3), 30.0 (–S–CH2–),
123.9, 128.3, 129.3, 129.9, 130.2, 132.3, 132.5, 136.2 (12Car),
148.7 (═CH), 156.1 (C-5 triazole), 158,4 (C-3 triazole), 166.0
(C═O); Anal. Calcd. for C18H16BrN5OS (430.32): C, 50.24; H,
3.75; N, 16.27. Found: C, 50.29; H, 3.70; N, 16.31%.
2-[(4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]-N-[(4-methylphenyl)
methylidene]acethydrazide (9).
Physicochemical and
N-[(4-bromophenyl)methylidene]-2-[(4,5-diphenyl-4H-1,2,4-
spectroscopic data are consistent with reference [17]. Yield: 63%,
mp 130–132°C; H nmr (DMSO-d6): δ 2.39 (s, 3H, CH3); 4.13
triazol-3-yl)sulfanyl]acethydrazide (15).
Physicochemical and
1
spectroscopic data are consistent with reference [17]. CAS registry
number: 306756-39-8. Yield: 87%, mp 202–204°C; 1H nmr
(DMSO-d6): δ 4.08 (s, 2H, CH2), 7.31–7.97 (m, 14H, Ar–H),
8.16 (s, 1H, CH), 9.00 (s, 1H, NH); 13C nmr: δ 30.0 (–S–CH2–),
124.0, 125.6, 128.4, 128.6, 128.8, 129.3, 129.5, 130.1, 130.6,
132.4, 132.5, 137.4 (18Car), 148.7 (═CH), 159.5 (C-3 triazole),
166.1 (C═O), 167.5 (C-5 triazole); Anal. Calcd. for
(s, 2H, CH2); 7.22–8.20 (m, 9H, Ar–H), 8.20 (s, 1H, CH), 8.93
(s, 1H, NH), 8.98 (s, 1H, CH); 13C nmr: δ 1.2 (–CH3), 30.2
(–S–CH2), 125.6, 127.3, 127.8, 129.1, 131.9, 137.5, 138.5
(12Car), 147.5 (C-3 triazole), 148.6 (═CH), 154.4 (C-5 triazole),
166.0 (C═O); Anal. Calcd. for C18H17N5OS (351.42): C, 61,52;
H, 4.88; N, 19.93. Found: C, 61.55; H, 4.89; N, 19.90%.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Ł. Popiołek, A. Chodkowska, A. Tryka, K. Pawłowski, M. Kiełczykowska,
J. Kocot, M. Wujec, and E. Jagiełło-Wójtowicz
Vol 000
C23H18BrN5OS (492.39): C, 56.10; H, 3.68; N, 14.22. Found: C,
56.13; H, 3.72; N, 14.26%.
(C-5 triazole), 162.33 (C-3- triazole), 164.57 (C═O), 171.32
(C═O); Anal. Calcd. C24H20N6O3S2 for (504.58): C, 57.13; H,
4.00; N, 16.66. Found: C, 57.21; H, 4.08; N, 16.72%.
N-[(4-bromophenyl)methylidene]-2-{[4-phenyl-5-(pyridin-3-yl)-
4H-1,2,4-triazol-3-yl]sulfanyl}acethydrazide (16). Physicochemical
and spectroscopic data are consistent with reference [17]. CAS
registry number 903407-49-8. Yield: 76%, mp 228–230°C; 1H
nmr (DMSO-d6): δ 4.10 (s, 2H, CH2), 7.36–8.57 (m, 13H, Ar–H),
7.98 (s, 1H, ═CH), 10.16 (s, 1H, NH); 13C nmr: δ 30.2 (–S–
CH2–), 124.0, 126.2, 128.3, 128.7, 129.3, 130.0, 132.1, 132.5,
134.6, 137.4, 146.5, 146.8 (17Car), 148.6 (═CH), 159.4 (C-3
triazole), 162.3 (C-5 triazole), 166.1 (C═O); Anal. Calcd. for
C22H17BrN6OS (493.38): C, 53.56; H, 3.47; N, 17.03. Found: C,
53.62; H, 3.41; N, 17.09%.
Preparation of 1,3-thiazolidin-4-one derivatives 17–20. To
a solution of acethydrazide derivatives 5–8 (10 mmol) in 15 mL of
1,4-dioxane, mercaptoacetic acid (0.92 g, 10 mmol) was added
dropwise. The mixture was stirred under reflux for 6 h at room
temperature. Then the solvent was removed under reduced
pressure, after 15 mL of 10% water solution of sodium bicarbonate
was added. The precipitate was filtered off and purified by
recrystallization from ethanol.
DISSOCIATION CONSTANTS
The dissociation constants of the studied compounds
9–16 were determined using spectrophotometric method
in 10% (v/v) water solutions of methanol because of
poor solubility in water [18]. Using the stock solutions
in methanol, the working solutions of pH values ranged
from 5.5 to 14 were prepared and absorbance was mea-
sured in the 220–390 nm range (230–390 nm for strongly
alkaline ones). On the basis of the obtained spectra,
wavelength λ was chosen for each compound in such
way that the difference between absorbance of neutral
molecule and that of monoanion was the greatest.
The pK values for the equilibrium HA → H+ + Aꢀ were
calculated using the following formula:
N-[2-(2-hydroxyphenyl)-4-oxo-1,3-thiazolidin-3-yl]-2-[(4-phenyl-
4H-1,2,4-triazol-3-yl)sulfanyl]acetamide (17). Yield: 79%, mp
166–168°C. 1H nmr (DMSO-d6): δ 3.40 (s, 2H, CH2), 3.58
(s, 2H, CH2), 4.06 (s, 1H, OH), 7.52–7.73 (m, 9H, Ar–H), 8.89
(s, 1H, CH), 11.16 (s, 1H, NH); 13C nmr: δ 29.83 (CH2), 33.26
(CH2), 61.80 (CH), 117.11, 120.37, 122.44, 125.63, 128.37,
128.94, 129.16, 137.48 (11 Car), 147.51 (C-3 triazole), 149.70
(Car), 154.45 (C-5 triazole), 164.47 (C═O) 172.33 (C═O); Anal.
Calcd. for C19H17N5O3S2 (427.50): C, 53.38; H, 4.01; N, 16.38.
Found: C, 53.45; H, 4.06; N, 16.34%.
AA ꢀ A
pK ¼ pH þ
A ꢀ AHA
where AHA is the absorbance of the neutral molecule for
the chosen λ value, AA is the absorbance of the monoanion
form for the chosen λ value, and A is the absorbance
measured for the working solutions of different pH for
the chosen λ value.
An example of the calculation of the pK for compound
12 is presented in the Supplementary Material.
N-[2-(2-hydroxyphenyl)-4-oxo-1,3-thiazolidin-3-yl]-2-[(5-methyl-
4-phenyl-4H-1,2,4-triazol-3-yl)sulfanyl]acetamide (18).
Yield:
1
83%, mp 202–204°C; H nmr (DMSO-d6): δ 2.24 (s, 2H, CH2),
2.26 (s, 3H, CH3), 4.05 (s, 2H, CH2), 4.43 (s, 1H, OH), 6.89–7.06
(m, 2H, Ar–H), 7.27–7.72 (m, 7H, Ar–H), 8.45 (s, 1H, CH), 9.06
(s, 1H, NH); 13C nmr: δ 12.43 (CH3), 29.83 (CH2), 33.26 (CH2),
61.34 (CH), 117.71, 120.37, 123.54, 128.30, 128.37, 128,74,
129.95, 130.24, 136.20, 149.70 (12 Car), 156.02 (C-5 triazole),
158.40 (C-3 triazole), 164.55 (C═O), 172.43 (C═O); Anal.
Calcd. for C20H19N5O3S2 (441.53): C, 54.41; H, 4.34; N, 15.86%,
Found: C, 54.49; H, 4.38; N, 15.92%.
PHARMACOLOGICAL STUDIES
Materials and methods. The experiments were carried
out on male Albino–Swiss mice weighing 24–27 g, kept
at room temperature of 21 1°C under natural day–night
cycle. The animals were housed in colony cages with free
access to tap water and food (standard laboratory pellets;
Agropol, Motycz, Poland). The studies were performed
between 8 AM and 3 PM. The animal tests and experiments
were approved by the Ethical Board of the Medical
University of Lublin.
The investigated compounds 6, 7, 11, and 12 were
administered intraperitoneally (i.p.) as the suspension in
1% Tween 80 in the constant volume of 0.1 mL per 10 g
body weight of mice. Control animals were given appropri-
ate amounts of the solvent. The compounds were injected
in doses starting from 100 mg/kg i.p. and decreasing grad-
ually until there was no further pharmacological activity.
Each experimental group consisted of eight animals. Pre-
liminary screening of the CNS activity was performed in
the following tests: the effect of tested compound on motor
impairment was assessed in the chimney test [19,20]. The
rectal body temperature in mice was measured by an Ellab
thermometer. Explorative activity was determined using
N-[2-(2-hydroxyphenyl)-4-oxo-1,3-thiazolidin-3-yl]-2-[(4,5-
diphenyl-4H-1,2,4-triazol-3-yl)sulfanyl]acetamide (19).
Yield:
1
88%, mp 198–200°C. H nmr (DMSO-d6): δ 3.41–3.44 (m, 2H,
CH2), 3.80 (s, 2H, CH2), 6.85–7.13 (m, 5H, Ar–H), 7.37–7.44 (m,
3H, Ar–H), 7.55–7.64 (m, 5H, Ar–H), 7.97–7.99 (m, 1H, Ar–H),
9.62 (s, 1H, OH), 10.01 (s, 1H, NH); 13C nmr: δ 28.93 (CH2),
32.45 (CH2); 62.15 (CH), 117. 85, 120. 11, 122.44, 125.87,
128.67, 128.76, 129.56, 130.11, 130.78, 136.89, 149.07 (18 Car),
159.48 (C-5 triazole), 163.12 (C═O), 167.41 (C-3 triazole),
173.15 (C═O); Anal. Calcd. for C25H21N5O3S2 (503.59): C,
59.62; H, 4.20; N, 13.91. Found: C, 59.70; H, 4.28; N, 13.78%.
N-[2-(2-hydroxyphenyl)-4-oxo-1,3-thiazolidin-3-yl]-2-[(4-
phenyl-5-(pyridin-3-yl)-4H-1,2,4-triazol-3-yl)sulfanyl]acetamide
(20). Yield: 79%, mp 178–180°C. 1H nmr (DMSO-d6): δ 3.42–
3.45 (m, 2H, CH2), 3.93 (s, 2H, CH2), 6.76–7.16 (m, 5H, Ar–H),
7.58–7.62 (m, 4H, Ar–H), 8.03–8.05 (m, 2H, Ar–H), 8.20–8.21
(m, 1H, Ar–H), 8.65–8.70 (m, 1H, Ar–H), 9.93 (s, 1H, NH).
10.49 (s, 1H, OH); 13C nmr: δ 29.03 (CH2), 33.98 (CH2),
116.89, 120.44, 122.56, 126.15, 128.48, 128.88, 128.93, 130.11,
132.33, 134.67, 137.56, 146.44, 146.98, 148.97 (17 Car), 158.99
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Synthesis, Dissociation Constants, and some Pharmacological Properties of Schiff
Base Hydrazones and their Cyclization to 1,3-Thiazolidin-4-one Derivatives
Month 2014
[4] Ram, V. J.; Nath, M.; Shukla, P. K. Bioorg Med Chem Lett
1997, 16, 2137.
[5] Byrak, H.; Demirbas, A.; Demirbas, N.; Karaoglu, S. A. Eur J
Med Chem 2009, 44, 4362.
[6] Padmavathi, V.; Sudhakar, G. R.; Padmaja, A.; Kondaiah, P.;
Ali-Shazia. Eur J Med Chem 2009, 44, 2106.
the whole board test [21]. Anxiolytic activity was measured
by the ‘four plate’ test in mice [22]. The passive avoidance
task, which is considered to be a measure of long-term mem-
ory in animals, followed the procedure of Venault et al.[23].
Antidepressant activity was estimated by the forced swim-
ming test. Thiopental (75 mg/kg i.p.)-induced sleep time in
mice was also measured. Analgesic properties were measured
by the ‘writhing syndrome’ test [24]. Antiepileptic effects
were tested by reduction of pentetrazole (100 mg/kg s.c.)-
induced seizures. Antiserotoninergic effects were determined
by the Corne test [25].
[7] Liesen, A. P.; de Aquino, T. M.; Carvalho, C. S.; Lima, V. T.;
de Araújo, J. M.; de Lima, J. G.; de Faria, A. R.; de Melo, E. J.; Alves, A. J.,
Alves, E. W.; Alves A. Q.; Góes, A. J. Eur J Med Chem 2010, 45, 3685.
[8] Al-Soud, Y. A.; Al-Dweri, M. N.; Al-Masoudi, N. A. Farmaco
2004, 59, 775.
[9] Rao, A.; Carbone, A.; Chimirri, A.; De Clercq, E.; Monforte,
A. M.; Monforte, P.; Pannecouque, C.; Zappalà, M. Farmaco 2003, 58, 115.
[10] Barreca, M. L.; Chimirri, A.; De Clercq, E.; De Luca, L.;
Monforte, A. M.; Monforte, P.; Rao, A.; Zappalà, M. Farmaco 2003, 58, 259.
[11] Rawal, R. K.; Tripathi, R.; Katti, S. B.; Pannecouque, C.; De
Clercq, E. Med Chem 2007, 3, 355.
[12] El Shehry, M. F.; Abu-Hashem, A. A.; El-Telbani, E. M. Eur J
Med Chem 2010, 45, 1906.
[13] Salgm-Cökşen, U.; Gökhan-Kelekçi, N.; Göktaş, Ö.; Köysal, Y.;
Kılıç, E.; İşık, Ş.; Aktay, G.; Özalp, M. Bioorg Med Chem 2007,
15, 5738.
STATISTICS
Student’s t-test (for analyzing the data from Tables 2 to 4)
or Fisher’s two-tailed exact probability test (for analyzing
the data from Table 5) was used to evaluate the significance
of differences between mean values of the control and
tested groups. Differences were considered significant
when p < 0.05.
[14] Palaska, E.; Şahin, G.; Kelicen, P.; Durlu, N. T.; Altinok, G.
Farmaco 2002, 57, 101.
[15] Shiradkar, M. R.; Murahari, K. K.; Gangadasu, H. R.; Suresh, T.;
Kalyan, C. A.; Panchal, D.; Kaur, R.; Burange, P.; Ghogare, J.;
Mokale, V.; Raut, M. Bioorg Med Chem 2007, 15, 3997.
[16] Cox, B.; Lomax, P. Annu Rev Pharmacol Toxicol 1997,
17, 341.
[17] Popiołek, Ł.; Kosikowska, U.; Wujec, M.; Malm, A. Phospho-
rus Sulfur 2013. DOI: 10.1080/10426507.2013.789878
[18] Albert, A.; Serjeant, E. P. Ionisation Constants of Acids and
Bases; Methuen & Co Ltd.: London, 1962.
[19] Aron, C.; Simon, P.; Larousse, C.; Boissier, J. R. Neurophar-
macology 1971, 10, 459.
[20] Boissier, J. R.; Tardy, J.; Diverres, J. C. Med Exper 1960,
3, 81.
Acknowledgment. The project was partially supported by the
Research Grant for Young Scientists (MNmb25).
CONFLICT OF INTEREST
The authors declare no conflict of interest.
[21] Boissier, J. R.; Simon, P. Physiol Behav 1967, 2, 447.
[22] Venault, P.; Chapouthier, G.; de Carvalho, L. P.; Simiand, J.;
Morre, M.; Dodd, R. H.; Rossier, J. Nature 1986, 321, 864.
[23] Porsolt, R. D.; Bertin, A.; Jalfre, M. Arch Int Pharmacodyn
Ther 1977, 229, 327.
REFERENCES AND NOTES
[1] Turan-Zitouni, G.; Kaplanciki, Z. A.; Erol, K.; Kilic, F. S. Farmaco
1999, 54, 218.
[2] Omar, K.; Geronikaki, A.; Zoumpoulakis, P.; Camoutsis, C.;
Sokovic, M.; Ciric, A.; Glamoclija, J. Bioorg Med Chem 2010, 18, 426.
[3] Colin, X.; Sauleau, A.; Coulon, J. Bioorg Med Chem Lett
2003, 13, 2601.
[24] Witkin, L. B.; Heubner, C. F.; Galdi, F.; O’Keefe, E.;
Spitaletta, P.; Plumer, A. J. J Pharmacol Exp Ther 1961, 133, 400.
[25] Corne, S. J.; Pickering, R. W.; Warner, B. T. Br J Pharmacol
Chemother 1963, 20, 106.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet