228 Dündar et al.
Asian J. Chem.
TABLE-2
IR AND 1H NMR SPECTRAL DATA OF THE COMPOUNDS 4, 5a-5m
IR νmax (cm-1)
3291, 3109,
1633, 1592, 1309 (2H, s, CH2)
1H NMR δ (DMSO-d6)
Comp.
4
13,64 (1H, s, NH), 7.69 (1H, m, H7), 7.33 (1H, m, H4), 7.28 (1H, m, H6), 7.22 (1H, m, H5), 5,66 (2H, s, NH2), 5.24
5a
5b
5c
5d
5e
5g
5h
5i
3058,1685,
1591, 1275
3042,1657,
1596, 1263
3050, 1666,
1591, 1263
3040, 1666,
1586, 1254
3070, 1651,
1592, 1267
3070, 1653,
1595, 1269
3060, 1673,
1601, 1255
3040, 1657,
1590, 1256
3040, 1702,
1589, 1275
3064, 1667,
1583, 1249
3052, 1668,
1591, 1249
14.04 (1H, s, NH), 9.99 (1H, s, =CH), 7.86 (2H, d, phenyl-H2,6), 7.68 (1H, d, H7), 7.62 (1H, t, phenyl-H4), 7.54
(2H, t, phenyl-H3,5), 7.38 (1H, d, H4), 7.34 (1H, t, H6), 7.21 (1H, t, H5), 5.39 (2H, s, CH2)
14.04 (1H, s, NH), 9.96 (1H, s, =CH), 7.90 (2H, m, phenyl-H2,6), 7.68 (1H, d, H7), 7.42-7.32 (mH, m, phenyl-
H3,5, H4, H6), 7.23 (1H, t, H5), 5.39 (2H, s, CH2)
13.70 (1H, s, NH), 9.99 (1H, s, =CH), 7.90 (2H, d, phenyl-H2, 6), 7.68 (1H, d, H7), 7.62 (2H, d, phenyl-H3,5),
7.37-7.34 (2H, m, H4, H6), 7.23 (1H, t, H5), 5.40 (2H, s, CH2)
14.06 (1H, s, NH), 10.04 (1H, s, =CH), 7.82 (2H, d, phenyl-H2,6), 7.75 (2H, d, phenyl-H3, 5), 7.68 (1H, d, H7),
7.39-7.32 (2H, m, H4, H6), 7.23 (1H, t, H5), 5.04 (2H, s, CH2)
14.11 (1H, s, NH), 10.26 (1H, s, =CH), 8.11 (2H, d, phenyl-H2, 6), 7.91 (2H, d, phenyl-H3, 5), 7.68 (1H, d, H7),
7.38 (1H, d, H4), 7.34 (1H, t, H6), 7.22 (1H, t, H5), 5.43 (2H, s, CH2)
14.01 (1H, s, NH), 9.89 (1H, s, =CH), 7.81 (2H, d, H7, H4), 7.68 (1H, d, H6), 7.55 (2H, d, phenyl-H3, 5), 7.37-7.35
(2H, m, phenyl-H2, 6), 7.21 (1H, t, H5), 5.37 (2H, s, CH2), 1.33 (9H, s, CH3)
13.65 (1H, s, NH), 9.68 (1H, s, =CH), 7.82 (2H, d, phenyl-H2, 6), 7.67 (1H, d, H7), 7.38-7.32 (2H, m, H4, H6), 7.23
(1H, t, H5), 7.09 (2H, d, phenyl-H3, 5), 5.37 (2H, s, CH2), 3.86 (3H, s, OCH3)
14.01 (1H, s, NH), 10.42 (1H, s, =CH), 7.96 (1H, t, phenyl-4, 7.59 (2H, d, H7, H4), 7.30-7.23 (4H, m, phenyl-H3, 5,
6, H6), 7.12 (1H, t, H5), 5.32 (2H, s, CH2)
5j
14.11 (1H, s, NH), 10.81 (1H, s, =CH), 8.13 (1H, d, H7), 7.70 (1H, d, H4), 7.68-7.62 (2H, m, H6, phenyl-H6), 7.52-
7.48 (1H, m, H5), 7.39 (1H, d, phenyl-H3), 7.35 (1H, t, phenyl-H5), 7.22 (1H, t, phenyl-H4), 5.43 (2H, s, CH2)
14.01 (1H, s, NH), 10.70 (1H, s, =CH), 8.05-8.03 (1H, m, phenyl-H3), 7.73-7.70 (1H, m, phenyl-H5), 7.60 (1H, d,
H7), 7.45-7.43 (2H, m, phenyl-H4, 6), 7.31 (1H, d, H4), 7.27 (1H, t, H6), 7.13 (1H, t, H5), 5.34 (2H, s, CH2)
14.39 (1H, s, NH), 10.31 (1H, s, =CH), 7.94 (1H, dd, H7), 7.67(1H, d, H4), 7.60 (1H, t, H6), 7.39-7.32 (2H, m,
phenyl-H4, 6), 7.23-7.18 (2H, m, phenyl-H3, 5), 7.07 (1H, t, H5), 5.37 (2H, s, CH2), 3.89 (3H, s, OCH3)
5k
5m
acetate (2) catalyzed by potassium carbonate on exposure to
microwave irradiation in the presence. Benzothiazol-2(3H)-
one (1), ethyl(benzothiazol-2(3H)-one-3-yl) acetate (2) and
(benzothiazol-2(3H)-one-3-yl)acetic acid (3) were accomp-
lished according to the previously reported procedures29. 3-
[(4-Amino-5-thioxo-1,2,4-triazol-3-yl)methyl]benzothiazol-
2(3H)-one (4) was easily prepared from the reaction between
(benzothiazol-2(3H)-one-3-yl) acetic acid and thiocarbo-
hydrazide in an oil-bath. 3-[(o/p-substitutedphenylmethy-
lidene] amino-5-thioxo-1,2,4-triazol-3-yl)methyl]-benzo-
thiazol-2(3H)-one (5) derivatives thus obtained was reacted
with o/p-substituebenzaldehyde derivatives in acetic acid under
microwave irradiation. Most preparations of Schiff bases were
reacted in the ethanol solvent, using an acid as the catalyst.
But in this experiment, 3-[(4-amino-5-thioxo-1,2,4-triazol-3-
yl)methyl] benzothiazol-2(3H)-one was only slightly dissolved
in ethanol. Here in, the acetic acid played a role not only as a
solvent but also as a catalyst34. The significant advantages of
these procedures are operational simplicity, short reaction time,
pure products and good yields.
was seen as singlet at about 14.11-13.95 ppm. The signal due
to benzothiazol-2(3H)-one-CH2- methylene protons, present
in all compounds, appeared at 5.37-5.43 ppm, as singlet. The
-N=CH proton of compounds 5a-m appeared at 9.74-10.26
ppm as singlet. All the other aromatic and aliphatic protons
were observed at the expected regions. Mass spectra (MS
(TOF-MS)) of compounds showed M+1 peaks, in agreement
with their molecular formula.
The synthesized compounds were tested for their in vitro
antibacterial activity against some gram positive bacteria; S.
aureus ATCC 29213, methicillin-resistant S. aureus (MRSA,
clinical isolate), E. faecalisATCC 29212, E. faecalis (resistant
to vancomycin, clinical isolate), some gram negative bacteria;
E. coliATCC 25922, E. coliATCC 35218, E. coli isolate, which
has an extended spectrum beta lactamase enzyme (ESβL), P.
aeruginosa ATCC 27853, P. aeruginosa (resistant to gentamycin,
clinical isolate) and yeast-like fungi; C. albicans ATCC 10231
and C. kruseiATCC 6258 by using broth microdilution method.
Ampicillin and gentamycin were used as standard antimicrobial
agents and amphotericin B and fluconazole were used as standard
antifungal agents (Table-3). The synthesized compounds were
also tested in vitro for antimycobacterial activity against M.
tuberculosis H37RV ATCC 27294, M. tuberculosis (clinical
isolate) by using microplate alamar blue assay method.
Ethambuthol was used as standard antimycobacterial agent.
The biological activity results of the compounds were shown
in Table-3. Minimum inhibitory concentrations were recorded
as the minimum concentration of compound, which inhibits
the growth of tested microorganisms.
The structure of the compounds was elucidated by IR, 1H
NMR, mass spectral data and elemental analysis (Tables 1
and 2).
In the IR spectra of all the compounds C=N and C=C
bands were observed at ca. 1601-1430 cm-1 region and benzo-
thiazol-2(3H)-ones have C=O stretching bands at 1702-653
cm-1 region. According to the IR spectroscopic data of the
compounds 5a-m which have 3-[(4-substitued phenylmethy-
lidene]amino-5-thioxo-1,2,4-triazol-3-yl)methyl]- benzothiazol-
2(3H)-one structure, the observation of C=S stretching bands
at 1275-1249 cm-1 and the absence of an absorption at about
2600-2550 cm-1 region cited for SH group, have proved that
these compounds were in the thionic form.
As shown in Table-3, the synthesized compounds exhibited
a broad spectrum of activity with minimum inhibitory concen-
tration values 64-256 µg/mL against both gram-positive and
gram-negative bacteria. Generally, synthesized compounds
were more active against gram-positive bacteria rather than
gram-negative bacteria. Among the gram-positive bacteria
1
In the H NMR spectra of compounds (5a-m) that are
taken in DMSO-d6 (Table-2), NH proton of the Schiff base