Synthesis and antimicrobial activity of some heterocyclic 2,6-bis(substituted)-1,3,4-thiadiazolo-, oxadiazolo-, and oxathiazolidino- pyridine derivatives from 2,6-pyridine dicarboxylic acid dihydrazide

Article abstract of DOI:10.1002/jhet.690

In this work, we report on the synthesis and preliminary biological activity screening of several heterocyclic derivatives 2-15 based on N2′,N6′-diphenylthiosemi-carbazide pyridine-2,6-dicarbohydrazide 2, which has been obtained from the corresponding dihydrazide 1. The biological screening showed that many of these compounds have good antimicrobial activities. The structure of the new compounds has been established on the bases of chemical and spectroscopic evidences.

Full text of DOI:10.1002/jhet.690

September 2011
Synthesis and Antimicrobial Activity of Some Heterocyclic
2,6-Bis(substituted)-1,3,4-thiadiazolo-, Oxadiazolo-, and
Oxathiazolidino-Pyridine Derivatives from 2,6-Pyridine
Dicarboxylic Acid Dihydrazide
1103
Said A. S. Ghozlan,a Mohammed A. Al-Omar,b Abd El-Galil E. Amr,b*
Korany A. Ali,c and Ahmed A. Abd El-Wahabc
aDepartment of Chemistry, Faculty of Science, Cairo University, Cairo, Egypt
bDepartment of Pharmaceutical Chemistry, College Pharmacy, King Saud University,
Riyadh 11451, Saudi Arabia
cDepartment of Applied Organic Chemistry, National Research Centre, Dokki, Cairo, Egypt
*E-mail: aamr1963@yahoo.com
Received May 1, 2010
DOI 10.1002/jhet.690
Published online 27 May 2011 in Wiley Online Library (wileyonlinelibrary.com).
In this work, we report on the synthesis and preliminary biological activity screening of several heter-
ocyclic derivatives 2–15 based on N20,N60-diphenylthiosemi-carbazide pyridine-2,6-dicarbohydrazide 2,
which has been obtained from the corresponding dihydrazide 1. The biological screening showed that
many of these compounds have good antimicrobial activities. The structure of the new compounds has
been established on the bases of chemical and spectroscopic evidences.
J. Heterocyclic Chem., 48, 1103 (2011).
INTRODUCTION
tory [26] activities. In particular, 2,6-peptidopyridines
exhibited a general ionophoric potency [27] and were
used for inventing novel thiocyanate-selective membrane
sensors [28]. In view of these observations and in con-
tinuation of our previous work in heterocyclic pyridine
chemistry, we have herein synthesized of some new
derivatives containing pyridine moiety.
The considerable pharmacological importance of pyri-
dine derivatives has attracted a great deal of attention.
On the other hand, attachment of other heterocyclic
moieties, which are known to possess pharmacological
activity, to pyridine ring may enhance their biological
activity. In our previous work, we have reported that
certain of heterocyclic compounds exhibited antitumor
[1], antiparkinsonian [2–4], anti-microbial [5,6], and
anti-inflammatory [7–10] activities. Another an interesting
group of compounds were found to exhibit pharmacologi-
cal properties such as analgesic [11,12] and antiarihyth-
mic [13] activities. On the other hand, some synthetic
thiazoles exhibit a wide range of biological activities,
such as antitumor, antibiotic, antibacterial, antifungal, and
antiinflammatory activities [14–17]. Recent studies have
shown some new thiazole cand idates as antimicrobial
and anticancer agents [18–21]. In addition, we have
reported a newly substituted heterocyclic compounds as
antitumor [22–24], antimicrobial [25], and anti-inflamma-
RESULTS AND DISCUSSION
In this work, we report on the synthesis and prelimi-
nary biological activity screening of several heterocyclic
derivatives based on compound 2, which has been
obtained from the corresponding hydrazide 1 according
to the published procedure in the previous work [29].
Treatment of compound 2 with chloroacetic acid in abso-
lute ethanol afforded the corresponding derivative 3. On
the other hand, when 2 treated with phenacyl bromide in
the presence of catalytic amount of triethylamine gave
unexpected product 4 and the expected compound 5 not
C
V
2011 HeteroCorporation

1104
S. A. S. Ghozlan, M. A. Al-Omar, A. E. E. Amr, K. A. Ali, and A. A. A. El-Wahab
Vol 48
Scheme 1
formed (Scheme 1). Structure of 4 was identified by ana-
lytical and spectral data. EI-MS spectrum of 4 showed
the molecular ion peak at m/z 531 (43%) corresponding
to the molecular formula C29H21N7O2S instead of
C37H27N7O2S2 (665). As well as, a fragment ion peak at
160 (18%) was supported to the substituted oxadiazole
ring. Further confirmation for the unsymmetrical structure
The dihydrazide 1 was reacted with carbon disulfide
in ethanolic potassium hydroxide with stirring at room
temperature to afford the corresponding potassium salt
6, which was cyclized by refluxing with alcoholic potas-
sium hydroxide for 3 h, via elimination of two molecule
of potassium hydrogen sulfide to compound 7. The same
product 7 has been obtained by carrying the reaction
under reflux with carbon disulphide in alcoholic potas-
sium hydroxide in one step. Treatment of the potassium
salt 6 with hydrazine hydrate under reflux afforded the
corresponding compound 8, which was also obtained by
treating compound 7 with hydrazine hydrate. In addition,
treatment of the potassium salt 6 with sulfuric acid under
reflux afforded thiadiazole derivative 9 (Scheme 2).
1
4 was explained by H-NMR. It displayed an ABM spin
coupling system, each one proton, for the pyridine ring
protons at d 7.90 and 7.95 ppm (dd) and 8.30 (t). Addi-
tionally, only one CH proton was appeared at 6.21 along
with two singlet signals were assigned at d 8.90 and
10.35 ppm characteristic for two unequivalent NH pro-
tons. Accordingly, for the above spectral data, the struc-
ture 4 has been established.
The compound 1 was treated with acid chloride deriv-
atives, namely, benzoyl or 4-chlorobenzoyl chlorides
under stirring in dry pyridine to give the corresponding
The reasonable suggested mechanism that explains
formation of compound 4 was illustrated in Figure 1.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2011 Synthesis and Antimicrobial Activity of Some Heterocyclic 2,6-Bis(substituted)-
1,3,4-thiadiazolo-, Oxadiazolo-, and Oxathiazolidino-Pyridine Derivatives
1105
Figure 1. The suggested mechanism that explains formation of compound 4.
EXPERIMENTAL
compounds 10a,b. Also, 1 was condensed with aromatic
aldehydes, namely, 4-chloro- or 4-methoxy-benzaldhyde
in ethanol to give the corresponding Schiff bases 11a,b.
The carbohydrazide derivatives 10a,b were heated with
sulfuric acid at 120ꢀC to afford the corresponding oxa-
diazolyl derivative 12a,b. Also, compounds 10a,b were
treated with phosphorus pentasulphide in dry benzene to
afford the corresponding thiadizolylpyridine derivatives
13a,b. The reaction of the hydrazone derivative 11a
with mercaptoacetic acid in dry benzene, it afforded
oxothiazolidin-pyridine-dicarboxamide 14. Treatment of
11a with acetic anhydride under reflux afforded oxadia-
zolylpyridine derivative 15 (Scheme 3).
Antimicrobial activity. The newly synthesized com-
pounds were tested for their preliminary antimicrobial
activity against different microorganisms representing
Gram-positive bacteria (Bacillus subtilis, Bacillus aureus,
and Staphylococcus aureus), Gram-negative bacteria
(Escherichia coli), yeast (Candida albican), and fungi
(Aspergillus niger). The most active compounds were: 4,
6, 8, 10b, 11a, 12b, and 13b (all organisms), 3, 9, and
12a (B. aureus), 5, 10a, 14, and 15 (Staph. aureus), 7
and 11b (E. coli), 10b and 15 (C. albicans), and 9, 14,
and 15 (A. niger). The results are summarized in Table 1.
Melting points were determined on open glass capillaries
using a Electrothermal IA 9000 digital melting point apparatus
and corrected. Elemental analyses were performed on Elemen-
tar, Vario EL, Microanalytical Unit, National Research Center,
Cairo Egypt and were found within 60.4% of the theoretical
values. Infrared spectra were recorded on Carlzeise Spectro-
photometer model ‘‘UR 10’’ spectrophotometer using the KBr
disk technique. H-NMR and 13C-NMR spectra were recorded
1
on Varian Gemini 270 MHz spectrometer (DMSO-d6) and the
chemical shifts are given in d (ppm) downfield from tetrame-
thylsilane (TMS) as an internal standard. The mass spectra
were measured using a Finnigan SSQ 7000 mass spectrometer.
Follow-up of the reactions and checking the purity of the com-
pounds was made by TLC on silica gel-aluminum sheets
(Type 60 F254, Merck, Darmstadt, Germany).
N20,N60-Bis(4-oxo-3-phenylthiazolidin-2-ylidene)pyridine-
2,6-dicarbohydrazide (3). A mixture of 2 (0.46g, 1 mmol)
and chloroacetic acid (0.19 g, 2 mmol) in 20 mL absolute
ethanol was refluxed for 20 h. The solvent was concentrated
under reduced pressure and the residue was poured onto water,
the separated solid was filtered off, washed with water, dried,
and crystallized from dioxane to give the title compound 3 in
70% yield as red crystals, mp 306–308ꢀC; IR (KBr): m ¼
3332–3240 (NH), 1710 (C¼¼O), 1685 (C¼¼O), 1660 (C¼¼C)
cmꢁ1
;
1H-NMR (270 MHz, DMSO-d6): d ¼ 3.60 (s, 4H,
2CH2), 7.25–7.75 (m, 10H, ArAH), 8.14 (d, 2H, J ¼ 8.0 Hz,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1106
S. A. S. Ghozlan, M. A. Al-Omar, A. E. E. Amr, K. A. Ali, and A. A. A. El-Wahab
Vol 48
Scheme 2
pyrid-H), 8.51 (t, 1H, J ¼ 8.0 Hz, pyrid-H), 12.50 (bs, 2H,
2NH, exchangeable with D2O); 13C-NMR (67.5 MHz, DMSO-
d6): d ¼ 29.82 (2CH2), 121.05, 124.01, 128.32, 134.84 (12C,
2Ph), 124.32, 138.56, 148.60 (5C, pyrid-C), 147.76 (2C¼¼N),
156.74 (2C¼¼O, amides), 172.45 (2C¼¼O, thiazole); ms: m/z
545 (62), 399 (24), 320 (12), 192 (100), 60 (78); Anal. Calcd.
for C25H19N7O4S2: C, 55.04; H, 3.51; N, 17.97; S, 11.75.
Found: C, 54.95; H, 3.45; N, 17.93; S, 11.70.
126.48, 138.24, 150.88, 155.72 (5C, pyrid-C), 115.56, 116.05,
117.92, 118.16, 125.86, 127.36, 128.15, 128.96, 129.18, 133.68,
140.26, 142.90 (18C, 3Ph), 105.78, 147.05, 153.90 (3C, thiazole
ring), 150.70, 151.36 (2C, oxadiazole ring), 156.84 (C¼¼O, am-
ide); ms: m/z 531 (15), 440 (42), 288 (22), 220 (100), 160 (18),
135 (65); Anal. Calcd. for C29H21N7O2S: C, 65.52; H, 3.98; N,
18.44; S, 6.03. Found: C, 65.44; H, 3.92; N, 18.38; S, 5.95.
Potassium salt of thiosemicarbazid derivative (6). To a
stirred solution of 1 (1.95 g, 10 mmol) in absolute ethanol 10
mL containing potassium hydroxide (1.68 g, 30 mmol), carbon
disulfide (2.28 g, 30 mmol) was added. The reaction mixture
was stirred at room temperature for 8 h. After cooling, the
product was precipitated with dry ether, filtered off, washed
with ether to give the corresponding potassium salt 6 in pure
form (86% yield) as white powder; IR (KBr): m ¼ 3350–3280
(NH), 1688 (C¼¼O), 1259 (C¼¼S) cmꢁ1; Anal. Calcd. for
C9H7K2N5O2S4: C, 25.52; H, 1.67; N, 16.53; S, 30.28. Found
C, 25.46; H, 1.62; N, 16.48; S, 30.24.
6-(5-(Phenylamino)-1,3,4-oxadiazol-2-yl)-N0-(3,4-diphenylth-
iazol-2(3H)-ylidene) pyridine-2-carbohydrazide (4). To a mix-
ture of 2 (1.40 g, 3 mmol) and phenacyl bromide (0.60 g,
3 mmol) in 50 mL absolute ethanol, a catalytic amount of
TEA was added. The reaction mixture was heated under reflux
for 3 h, the obtained precipitate was filtered off, and crystal-
lized from ethanol to give the title compound 4 in 60% yield
as yellow crystals; mp 298–300ꢀC; IR (KBr): m ¼ 3334–3220
(NH), 1680 (C¼¼O), 1665 (C¼¼N), 1660 (C¼¼C) cmꢁ1
;
1H-NMR (270 MHz, DMSO-d6): d ¼ 6.21 (s, 1H, thiazole-H),
7.30–7.80 (m, 15H, ArAH), 7.90 (dd, 2H, J ¼ 8.0, 2.5 Hz,
pyrid-H), 7.95 (t, 2H, J ¼ 8.0 Hz, pyrid-H), 8.30 (dd, 1H, J ¼
8.0, 2.5 Hz, pyrid-H), 8.90, 10.35 (2s, 2H, 2NH, exchangeable
with D2O); 13C-NMR (67.5 MHz, DMSO-d6): d ¼ 118.38,
2,6-Bis(4,5-dihydro-5-thioxo-1H-1,2,4-oxadiazole-
3-yl)pyridine (7)
Method A. To a mixture of 1 (1.95 g, 10 mmol) and potas-
sium hydroxide (1.68 g, 30 mmol) in absolute ethanol 100 mL,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2011 Synthesis and Antimicrobial Activity of Some Heterocyclic 2,6-Bis(substituted)-
1,3,4-thiadiazolo-, Oxadiazolo-, and Oxathiazolidino-Pyridine Derivatives
1107
Scheme 3
carbon disulfide (2.28 g, 30 mmol) was added. The reaction mix-
ture was refluxed for 5 h. then diluted with water and acidified
with hydrochloric acid pH ꢂ 3–4. The precipitated solid was fil-
tered off, washed with water, dried, and crystallized from ethanol
to give compound 7 in 70% yield as yellow crystals.
refluxed for 4 h. The reaction mixture was diluted with water
and acidified with hydrochloric acid pH ꢂ 3–4. The formed
solid was collected by filtration, washed with water, dried, and
crystallized from ethanol to give the title compound 7 in 90%
yield as yellow crystals; mp 211–213ꢀC; IR (KBr): m ¼ 3393
Method B. A mixture of 6 (4.23 g, 10 mmol) and potassium
hydroxide (1.68 g, 30 mmol) in absolute ethanol 100 mL was
(NH), 1665 (C¼¼N), 1660 (C¼¼C) cmꢁ1
;
1H-NMR (270 MHz,
DMSO-d6): d ¼ 7.85–8.25 (m, 3H, pyrid-H), 10.85 (bs, 2H,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1108
S. A. S. Ghozlan, M. A. Al-Omar, A. E. E. Amr, K. A. Ali, and A. A. A. El-Wahab
Vol 48
Table 1
Antimicrobial activities of newly synthesized compounds 2–15.
Inhibition zones (cm)
Gram-positive bacteria
Gram-negative bacteria
Yeast
Fungi
Comp. No.
B. subtilis
B. aureus
S. aureus
E. coli
C. albicans
A. niger
2
3
4
5
6
7
8
9
10a
10b
11a
11b
12a
12b
13b
14
15
1.65
1.65
1.98
1.62
1.85
1.55
1.84
1.66
1.70
1.88
1.95
1.54
1.56
1.85
1.96
1.66
1.71
2.0
1.78
1.92
1.86
1.60
1.96
1.61
1.86
1.95
1.64
1.94
1.96
1.64
1.98
1.88
1.94
1.72
1.66
2.10
1.77
1.62
1.94
1.96
1.88
1.56
1.94
1.46
1.98
1.95
1.88
1.52
1.66
1.90
1.92
1.95
1.94
2.0
0.50
0.48
0.86
–
–
–
1.50
1.45
1.95
1.65
1.99
1.75
1.85
2.05
1.46
1.89
1.96
1.48
1.54
1.95
1.92
2.0
0.65
–
0.88
0.91
0.87
0.57
0.54
0.84
0.87
0.90
0.74
0.86
0.90
0.67
1.56
0.95
0.64
–
0.55
–
–
0.75
0.55
–
–
0.60
0.52
–
0.86
–
2.04
2.10
R
ChloramphinicolV
1
2NH, exchangeable with D2O); 13C-NMR (67.5 MHz, DMSO-
d6): d ¼ 125.48, 135.76, 146.90 (5C, pyrid-C), 149.36, 156.42
(4C, oxadiazole ring); ms: m/z 279 (8), 171 (32), 122 (14), 64
(100); Anal. Calcd. for C9H5N5O2S2: C, 38.70; H, 1.80; N,
25.07; S, 22.96. Found C, 38.64; H, 1.75; N, 24.98; S, 22.90.
2,6-Bis(4-amino-4,5-dihydro-5-thioxo-1H-1,2,4-triazole-
3-yl)pyridine (8)
cmꢁ1; H-NMR (270 MHz, DMSO-d6): d ¼ 7.97 (d, 2H, J ¼
8.0 Hz, pyrid-H), 8.01 (t, 1H, J ¼ 8.0 Hz, pyrid-H), 12.10
(s, 2H, 2NH, exchangeable with D2O); 13C-NMR (67.5 MHz,
DMSO-d6): d ¼ 125.24, 135.48 145.75 (5C, pyrid-C), 148.85,
179.66 (4C, thiadiazole ring); ms: m/z 311 (45), 204 (100),
144 (32), 103 (16), 75 (85); Anal. Calcd. for C9H5N5S4: C,
34.71; H, 1.62; N, 22.49; S, 41.18. Found: C, 34.65; H, 1.58;
N, 22.43; S, 41.09.
Method A. A solution of 6 (4.23 g, 10 mmol) in hydrazine
hydrate (5 mL, 70%) was refluxed for 3 h. After cooling, the white
solid formed was filtered off, dried, and crystallized from DMF/
EtOH to afford compound 8 in 75% yield as brown crystals.
Method B. A solution of 7 (2.80 g, 10 mmol) in absolute
ethanol 20 mL and hydrazine hydrate (5 mL, 70%) was
refluxed for 3 h. The reaction mixture was diluted with water
and acidified with diluted hydrochloric acid pH ꢂ 6. The pre-
cipitated solid was filtered off, dried, and crystallized from
DMF/EtOH to give compound 8 in 60% yield as brown crys-
tals; mp 240–242ꢀC; IR (KBr): m ¼ 3399–3224 (NH2, NH),
N20,N60-Diaroylpyridine-2,6-dicarbohydrazides (10a) and
(10b). A mixture of 1 (1.95 g, 10 mmol) and benzoyl chloride
or 4-chlorobenzoyl chloride (4 mmol) in dry pyridine 15 mL
was stirred for 24 h at room temperature. The reaction mixture
was poured onto crushed ice, the separated solid was filtered
off, washed with water, dried, and crystallized from ethanol to
give the title compounds 10a in 98% yield as colorless powder
and 10b in 93% yield as yellow solid.
N20,N60-Dibenzoylpyridine-2,6-dicarbohydrazide (10a). mp
268–270ꢀC; IR (KBr): m ¼ 3344–3243 (NH), 1690 (C¼¼O),
1664 (C¼¼N), 1658 (C¼¼C), 1258 (C¼¼S) cmꢁ1; H-NMR (270
1680 (C¼¼O), 1660 (C¼¼C) cmꢁ1
;
1H-NMR (270 MHz,
1
MHz, DMSO-d6): d ¼ 6.30 (bs, 2H, 2NH2 exchangeable with
D2O), 7.70 (d, 2H, J ¼ 8.0 Hz, pyrid-H), 8.10 (t, 1H, J ¼ 8.0
Hz, pyrid-H), 8.60 (bs, 2H, 2NH, exchangeable with D2O);
13C-NMR (67.5 MHz, DMSO-d6): d ¼ 121.68, 135.56, 153.86
(5C, pyrid-C), 154.15, 178.10 (4C, triazole ring); ms: m/z 307
(9), 274 (18), 213 (12), 146 (100), 56 (76); Anal. Calcd. for
C9H9N9S2: C, 35.17; H, 2.95; N, 41.01; S, 20.86. Found: C,
35.08; H, 2.88; N, 40.97; S, 20.80.
DMSO-d6): d ¼ 7.15–7.70 (m, 10H, ArAH), 8.10 (d, 2H, J ¼
8.0 Hz, pyrid-H), 8.40 (t, 1H, J ¼ 8.0 Hz, pyrid-H), 10.10,
10.90 (2s, 4H, 4NH, exchangeable with D2O); 13C-NMR (67.5
MHz, DMSO-d6): d ¼ 124.52, 138.48, 148.86 (5C, pyrid-C),
126.72, 127.98, 131.78, 133.86 (12C, 2Ph), 160.68, 163.92
(4C, 4C¼¼O, amides); ms: m/z 403 (100), 281 (44), 223 (22),
105 (43), 77 (68); Anal. Calcd. for C21H17N5O4: C, 62.53; H,
4.25; N, 17.36. Found: C, 62.46; H, 4.20; N, 17.30.
2,6-Bis(4,5-dihydro-5-thioxo-1H-1,2,4-thiadiazole-3-yl)-
pyridine (9). To a stirred ice-cold concentrated sulfuric acid
10 mL, compound 6 (4.23, 10 mmol) was added. The reaction
mixture was left over night and then gradually added to crush
ice. The separated precipitate was filtered off, washed with
water, dried, and crystallized from ethanol to give compound 9
in 78% yield as colorless powder; mp 196–198ꢀC; IR (KBr): m
¼ 3345–3302 (NH), 1662 (C¼¼N), 1660 (C¼¼C), 1242 (C¼¼S)
N20,N60-Bis(4-chlorobenzoyl)pyridine-2,6-dicarbohydrazide
(10b). mp 293–295ꢀC; IR (KBr): m ¼ 3359–3289 (NH), 1700
(C¼¼O), 1670 (C¼¼O), 1660 (C¼¼C) cmꢁ1
;
1H-NMR (270
MHz, DMSO-d6): d ¼ 7.50, 7.80 (2d, J ¼ 8.4 Hz, 8H,
ArAH), 7.95 (d, 2H, J ¼ 8.0 Hz, pyrid-H), 8.30 (t, 1H, J ¼
8.0 Hz, pyrid-H), 10.80, 11.30 (2s, 4H, 4NH, exchangeable
with D2O); 13C-NMR (67.5 MHz, DMSO-d6): d ¼ 124.55,
138.36, 148.88 (5C, pyrid-C), 128.05, 128.86, 131.78, 137.24
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

September 2011 Synthesis and Antimicrobial Activity of Some Heterocyclic 2,6-Bis(substituted)-
1,3,4-thiadiazolo-, Oxadiazolo-, and Oxathiazolidino-Pyridine Derivatives
1109
(12C, 2Ph), 160.55, 164.02 (4C, 4C¼¼O, amides); ms: m/z 471
(16), 473 (5%), 331 (100), 308 (18), 139 (7), 75 (48); Anal.
Calcd. for C21H15Cl2N5O4: C, 53.41; H, 3.20; Cl, 15.01; N,
14.83. Found: C, 53.36; H, 3.14; Cl, 14.88; N, 14.76.
128.55, 129.15, 133.56 (12C, 2Ph), 163.82, 165.45 (4C, oxadia-
zoles); ms: m/z 436 (10), 438 (3), 279 (75), 139 (100), 77 (86);
Anal. Calcd. for C21H11Cl2N5O2: C, 57.82; H, 2.54; Cl, 16.25;
N, 16.05. Found: C, 57.75; H, 2.50; Cl, 16.18; N, 15.96.
2,6-Bis-(5-aryl-1,3,4-thiadizol-2-y1)pyridines (13a) and
(13b). A mixture of 10a,b (8 mmol) and phosphorus pentasul-
fide (1.89 g, 16 mmol) in dry benzene 50 mL was refluxed for
7 h. The reaction mixture was filtered off while hot and then
the filtrate was concentrated under reduced pressure. The sepa-
rated yellow solid was filtered off, dried and crystallized from
dioxane to give compounds 13a in 60% yield as red powder
and 13b in 75% yield as yellow crystals.
N20,N60-Bis(4-substituted-benzylidene)pyridine-2,6-dicarbo-
hydrazide (11a) and (11b). A mixture of 1 (1.95 g, 10 mmol)
and 4-chloro- or 4-methoxy-benzaldhyde (20 mmol) in abso-
lute ethanol 50 mL was refluxed for 7 h. After cooling, the
solid precipitate was filtered off, washed with ethanol, dried,
and crystallized from ethanol to give compounds 11a in 95%
yield as yellow solid and 11b in 90% yield as red solid.
N20,N60-Bis(4-chlorobenzylidene)pyridine-2,6-dicarbohydra-
zide (11a). mp 209–211ꢀC; IR (KBr): m ¼ 3385 (NH), 1695
2,6-Bis-(5-phenyl-[1,3,4-thiadizol-2-yl)pyridine
(13a). mp
(C¼¼O), 1658 (C¼¼N), 1655 (C¼¼N) cmꢁ1
;
1H-NMR (270
304–306ꢀC; IR (KBr): m ¼ 1663 (C¼¼N), 1658 (C¼¼N) cmꢁ1
;
MHz, DMSO-d6): d ¼ 7.35 (s, 2H, 2CH¼¼N), 7.44, 7.82 (2d,
8H, J ¼ 8.5 Hz, ArAH), 7.96 (d, 2H, J ¼ 8.1 Hz, pyrid-H),
8.25 (t, 1H, J ¼ 8.1 Hz, pyrid-H), 11.18 (bs, 2H, 2NH,
exchangeable with D2O); 13C-NMR (67.5 MHz, DMSO-d6): (
¼ 124.62, 138.44, 148.94 (5C, pyrid-C), 128.15, 129.10,
131.68, 137.04 (12C, 2Ph), 142.66 (2C, 2C¼¼N), 157.12 (2C,
2C¼¼O, amides); ms: m/z 440 (15), 442 (5), 321 (42), 218
(100), 190 (32), 77 (56); Anal. Calcd. for C21H15Cl2N5O2: C,
57.29; H, 3.43; Cl, 16.10; N, 15.91. Found: C, 57.18; H, 3.34;
Cl, 16.00; N, 15.84.
1H-NMR (270 MHz, DMSO-d6): d ¼ 7.60–7.80 (m, 10H,
ArAH), 8.14 (d, 2H, J ¼ 8.1 Hz, pyrid-H), 8.51 (t, 1H, J ¼
8.1 Hz, pyrid-H); 13C-NMR (67.5 MHz, DMSO-d6): d ¼
121.48, 138.06, 156.88 (5C, pyrid-C), 126.08, 127.14, 128.56,
133.16 (12C, 2Ph), 172.18, 174.05 (4C, thiadiazoles); ms: m/z
397 (Mþ ꢁ2, 14), 383 (100), 326 (54); Anal. Calcd. for
C21H13N5S2: C, 63.14; H, 3.28; N, 17.53; S, 16.05. Found: C,
63.04; H, 3.18; N, 17.46; S, 15.94.
2,6-Bis[5-(4-chorophenyl)-1,3,4-thiadiazol-2-yl]pyridine
(13b). mp 310–312ꢀC; IR (KBr): m ¼ 1665 (C¼¼N), 1660
1
N20,N60-Bis(4-methoxybenzylidene)pyridine-2,6-dicarbohy-
drazide (11b). mp 203–205ꢀC; IR (KBr): m ¼ 3370 (NH),
(C¼¼N) cmꢁ1; H-NMR (270 MHz, DMSO-d6): d ¼ 7.72, 7.84
(2d, 8H, J ¼ 8.4 Hz, ArAH), 8.16 (d, 2H, J ¼ 8.0 Hz, pyrid-
H), 8.48 (t, 1H, J ¼ 8.0 Hz, pyrid-H); 13C-NMR (67.5 MHz,
DMSO-d6): d ¼ 121.50, 138.12, 156.92 (5C, pyrid-C), 128.38,
129.10, 130.86, 133.46 (12C, 2Ph), 172.24, 174.35 (4C, thia-
diazoles); ms: m/z 467 (Mþ ꢁ1, 100), 469 (30), 411 (65), 356
(78), 279 (32); Anal. Calcd. for C21H11Cl2N5S2: C, 53.85; H,
2.37; Cl, 15.14; N, 14.95; S, 13.69. Found: C, 53.80; H, 2.30;
Cl, 15.10; N, 14.90; S, 13.62.
1
1693 (C¼¼O), 1664 (C¼¼N), 1659 (C¼¼N) cmꢁ1; H-NMR (270
MHz, DMSO-d6): d ¼ 3.30 (s, 6H, 2OCH3), 7.18 (s, 2H,
2CH¼¼N), 7.55, 7.65 (2d, 8H, J ¼ 8.4 Hz, ArAH), 7.80 (d,
2H, J ¼ 8.0 Hz, pyrid-H), 8.30 (t, 1H, J ¼ 8.0 Hz, pyrid-H),
12.30 (bs, 2H, 2NH, exchangeable with D2O); 13C-NMR (67.5
MHz, DMSO-d6): d ¼ 55.55 (2C, OCH3), 124.58, 138.50,
149.04 (5C, pyrid-C), 114.20, 125.74, 129.38, 163.18 (12C,
2Ph), 142.72 (2C, 2C¼¼N), 157.18 (2C, 2C¼¼O, amides); ms:
m/z 431 (100), 400 (75), 254 (24), 77 (38); Anal. Calcd. for
C23H21N5O4: C, 64.03; H, 4.91; N, 16.23. Found: C, 63.88; H,
4.85; N, 16.16.
N20,N60-Bis(2-(4-chlorophenyl)-4-oxothiazolidin-3-yl)pyri-
dine-2,6-dicarboxamide (14). To a suspension of 11a (0.44 g,
1 mmol) in dry benzene 50 mL, mercaptoacetic acid (0.84 g, 2
mmol) in dry benzene 5 mL was added with stirring. The reac-
tion mixture was refluxed for 18 h. Then solvent was evapo-
rated under reduced pressure. The residue was triturated with
boiling water and left overnight; the formed solid was filtered
off, washed with water, dried, and crystallized from ethanol/
dioxane to afford the brown powder of compound 14 in 75%
yield; mp 224–226ꢀC; IR (KBr): m ¼ 3363 (NH), 1720
2,6-Bis-(5-aryl-1,3,4-oxadiazol-2-yl)pyridines (12a) and
(12b). An appropriate amount of 10a,b (1 mmol) was dis-
solved in concentrated sulfuric acid 5 mL and heated at 120ꢀC
for 3 h. The reaction mixture was cooled, poured onto crushed
ice, and left for 1 h. The formed solid was filtered off, dried,
and crystallized from dioxane to give the title compounds 12a
in 90% yield as yellow powder and 12b in 86% yield as
brown powder.
(C¼¼O), 1680 (C¼¼O) cmꢁ1
;
1H-NMR (270 MHz, DMSO-d6):
d ¼ 3.23, 3.34 (2d, 4H, J ¼ 2.5 Hz, AB 2CH2), 5.95 (s, 2H,
2CH), 7.35, 7.65 (2d, 8H, J ¼ 8.5 Hz, ArAH), 8.10–8.30 (m,
3H, pyrid-H), 11.20 (bs, 2H, 2NH, exchangeable with D2O);
13C-NMR (67.5 MHz, DMSO-d6): d ¼ 124.50, 138.38, 149.70
(5C, pyrid-C), 128.62, 129.85, 132.05, 136.90 (12C, 2Ph),
35.10, 56.98, 168.36 (6C, thiazoles), 160.92 (2C, 2C¼¼O,
amides); ms: m/z 588 (34), 590 (11), 334 (85), 212 (100), 176
(54), 105 (62); Anal. Calcd. for C25H19Cl2N5O4S2: C, 51.02;
H, 3.25; Cl, 12.05; N, 11.90; S, 10.90. Found: C, 50.95; H,
3.20; Cl, 11.98; N, 11.83; S, 10.85.
2,6-Bis-(5-phenyl-1,3,4-oxadiazol-2-yl)pyridine (12a). mp
274–276ꢀC; IR (KBr): m ¼ 1665 (C¼¼N), 1662 (C¼¼N) cmꢁ1
;
1H-NMR (270 MHz, DMSO-d6): d ¼ 7.36–7.72 (m, 10H,
ArAH), 8.18 (d, 2H, J ¼ 7.9 Hz, pyrid-H), 8.68 (t, 1H, J ¼
7.9 Hz, pyrid-H); 13C-NMR (67.5 MHz, DMSO-d6): d ¼
120.66, 137.98, 157.01 (5C, pyrid-C), 125.80, 126.85, 128.24,
129.04 (12C, 2Ph), 163.78, 165.32 (4C, oxadiazoles); ms: m/z
367 (12), 186 (28), 139 (100), 111 (15); Anal. Calcd. for
C21H13N5O2: C, 68.66; H, 3.57; N, 19.06. Found: C, 68.58; H,
3.50; N, 18.96.
2,6-Bis(4-acetyl-5-(4-chlorophenyl)-4,5-dihydro-1,3,4-oxa-
diazol-2-yl)pyridine (15). A solution of 11a (0.44 g, 1 mmol)
in acetic anhydride 15 mL was refluxed for 6–10 h. The sol-
vent was removed under reduced pressure to dryness and the
residue was solidified with ether. The obtained solid was fil-
tered off, washed with ether, dried, and crystallized from diox-
ane to give yellow crystals of compound 15 in 76% yield; mp
2,6-Bis-[5-(4-chlorophenyl)-1,3,4-oxadiazol-2-y1]pyridine
(12b). mp 284–386ꢀC; IR (KBr): m ¼ 1668 (C¼¼N), 1660
1
(C¼¼N) cmꢁ1; H-NMR (270 MHz, DMSO-d6): d ¼ 7.40, 7.75
(2d, 8H, J ¼ 8.5 Hz, ArAH), 8.21 (d, 2H, J ¼ 8.0 Hz, pyrid-
H), 8.75 (t, 1H, J ¼ 8.0 Hz, pyrid-H); 13C-NMR (67.5 MHz,
DMSO-d6): d ¼ 121.58, 138.18, 156.96 (5C, pyrid-C), 123.98,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

1110
S. A. S. Ghozlan, M. A. Al-Omar, A. E. E. Amr, K. A. Ali, and A. A. A. El-Wahab
Vol 48
250–252ꢀC; IR (KBr): m ¼ 1715 (C¼¼O), 1660 (C¼¼N), 1600
[4] Abd El-Latif, N. A.; Amr, A. E.; Ibrahiem, A. A. Monatsh
Chem 2007, 138, 559.
(C¼¼C) cmꢁ1
;
1H-NMR (270 MHz, DMSO-d6): d ¼ 2.55 (s,
[5] Amr, A. E. Indian J Heterocycl Chem 2000, 10, 49.
[6] Amr, A. E.; Abo-Ghalia, M. H.; Abdalla, M. M. Z Natur-
forsch 2006, 61b, 1335.
6H, 2CH3), 5.10 (s, 2H, 2CH), 7.60, 7.80 (2d, 8H, J ¼ 8.5 Hz,
ArAH), 7.95 (d, 2H, pyrid-H), 8.30 (t, 1H, pyrid-H); 13C-
NMR (67.5 MHz, DMSO-d6): d ¼ 23.08 (2C, 2CH3), 125.68,
135.86, 146.78 (5C, pyrid-C), 127.92, 128.15, 132.00, 137.88
(12C, 2Ph), 74.05, 155.18 (4C, oxadiazoles), 168.16 (2C,
2C¼¼O, COCH3); ms: m/z 523 (Mþ ꢁ1, 22), 525 (7), 439 (43),
359 (100), 258 (37); Anal. Calcd. for C25H19Cl2N5O4: C,
57.26; H, 3.65; Cl, 13.52; N, 13.36. Found: C, 57.20; H, 3.60;
Cl, 13.46; N, 13.30.
[7] Ouf, N. H.; Amr, A. E. Monatsh Chem 2008, 139, 579.
[8] Amr, A. E.; Sabry, N. M.; Abdulla, M. M. Monatsh Chem
2007, 138, 699.
[9] Amr, A. E.; Abo-Ghalia, M. H.; Abdulla, M. M. Arch
Pharm Chem Life Sci 2007, 340, 304.
[10] Abo-Ghalia, M. H.; Amr, A. E.; Abdulla, M. M. Z Natur-
forsch 2003, 58b, 903.
Antimicrobial assay. The newly synthesized compounds
were tested for their preliminary antimicrobial activity against
different microorganisms representing Gram-positive bacteria
(Bacillus subtilis, Bacillus aureus, and Staphylococcus aureus),
Gram-negative bacteria (Escherichia coli), yeast (Candida
albican), and fungi (Aspergillus niger).
Agar diffusion medium. Nine compounds were screened in
vitro for their antimicrobial activity against, by agar diffusion
method [30]. A suspension of the organisms were added to
sterile nutrient agar media at 45ꢀC and the mixture was trans-
ferred to sterile Petri dishes and allowed to solidify. Holes of
10 mm in diameter were made using a cork borer. Amounts of
0.1 mL of the synthesized compounds were poured inside the
holes. A hole filled with DMSO was also used as control. The
plates were left for 1 h at room temperature as a period of pre-
incubation diffusion to minimize the effects to variation in
time between the applications of the different solutions. The
plates were then incubated at 37ꢀC for 24 h and observed for
antibacterial activity. The diameters of zone of inhibition were
[11] Ouf, N. H.; Amr, A. E.; Fayed, A. A. Monatsh Chem 2008,
139, 281.
[12] Amr, A. E. Z Naturforsch 2005, 60b, 990.
[13] Shalaby, A. F. A.; Abdulla, M. M.; Amr, A. E. Monatsh
Chem 2007, 138, 1019.
[14] Kumar, Y.; Green, R.; Boryska, K. Z.; Wise, D. D.;
Wotring, L. L.; Townsend, L. B. J Med Chem 1993, 36, 3843.
[15] Michael, L. G.; Tachel, M. L.; Susan, L. M.; John, H. B.;
Milton, L. B. Bioorg Med Chem 2004, 12, 1029.
[16] Robert, A. F. Clin Microbiol Rev 1983, 1, 187.
[17] Jung, K. Y.; Kim, S. K.; Gao, Z. G.; Ariel, S. G.; Neli, M.;
Denneth, A. J.; Kim, Y. C. Bioorg Med Chem 2004, 12, 613.
[18] Bonde, C. G.; Gaikwad, N. J Bioorg Med Chem 2004,
12, 2151.
[19] Kucukguzel, G.; Kocatepe, A.; DeClercq, E.; Sahin, F.;
Gulluce, M. Eur J Med Chem 2006, 41, 353.
[20] Vicini, P.; Geroniki, A.; Anastasia, K.; Incerti, M.; Zani, F.
Bioorg Med Chem 2006, 14, 3859.
[21] Zhou, X.; Shao, L.; Jin, Z.; Liu, J. B.; Dai, H.; Fang, J. X.
Heteroatom Chem 2007, 18, 55.
measured and compared with that of the standard, the values
R
were tabulated. ChloramphinicolV (50 lg/mL) was used as
standard for antibiotic drug. The observed zone of inhibition is
presented in Table 1.
[22] Abou-Ghalia, M. H.; Amr, A. E. Amino Acids 2004, 26, 283.
[23] Hammam, A. G.; Fahmy, A. F. M.; Amr, A. E.; Mohamed,
A.M. Indian J Chem 2003, 42B, 1985.
[24] Hammam, A. G.; Sharaf, M. A.; Abdel Hafez, N. A. Indian
J Chem 2001, 40B, 213.
Acknowledgments. The kind help of Dr. El-Sayed E. Mostafa,
Department of Microbial Chemistry, National Research Center,
Cairo, Egypt, for carrying out the antimicrobial screening is
highly appreciated.
[25] Attia, A.; Abdel-Salam, O. I.; Amr, A. E.; Stibor, I.; Bude-
sinsky, M. Egypt J Chem 2000, 43, 187.
[26] Amr, A. E.; Abdulla, M. M. Indian J Heterocycl Chem
2002, 12, 129.
[27] Hassan, S. S. M.; Abou-Ghalia, M. H.; Amr, A. E.;
Mohamed, A. H. K. Talanta 2003, 60, 81.
REFERENCES AND NOTES
[28] Hassan, S. S. M.; Abou-Ghalia, M. H.; Amr, A. E.;
Mohamed, A. H. K. Anal Chem Acta 2003, 482, 9.
[29] Said, A. S. G.; Salwa, F. M.; Amr, A. E.; Mostafa, E. E.
M.; Abd El-Wahab, A. A. World J Chem 2009, 4, 83.
[30] Cruickshank, R.; Duguid, J. P.; Marion, B. P.; Swain, R. H.
A.Medicinal Microbiology, 12th ed.; Churchill Livingstone:London,
1975; Vol. II, pp 196–202.
[1] Amr, A. E.; Mohamed, A. M.; Mohamed, S. F.; Abdel-
Hafez, N. A.; Hammam, A. G. Bioorg Med Chem 2006, 14, 5481.
[2] Amr, A. E.; Hegab, M. I.; Ibrahiem, A. A.; Abdulla, M. M.
Monatsh Chem 2003, 134, 1395.
[3] Amr, A. E.; Sayed, H. H.; Abdulla, M. M. Arch Pharm
Chem Life Sci 2005, 338, 433.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet