Synthesis, antibacterial, and analgesic activity of novel 4-hydroxy-3-(phenylthio)-2H-chromen-2-ones and 4-Hydroxy-3-[imidazol/tetrazolo- 2-yl)thio]-2H-chromen-2-ones

Article abstract of DOI:10.1080/10426507.2010.530630

A mild and efficient synthesis of new 4-hydroxy-3-(phenylthio)-2H-chromen- 2-ones 4a-k and 4-hydroxy-3-[imidazol/tetrazolo-2-yl)thio]-2H-chromen-2-ones 6a-d is described. The compounds 4a-c were further subjected to oxidation by m-CPBA to obtain 3-(phenylsulfonyl)-4-hydroxy-2H-chromen-2-ones 5a-c. The structures of the resulted new compounds were established by IR, ¹H NMR, mass, and elemental analysis. All the synthesized compounds were subjected to antibacterial activity against the Gram positive bacteria Staphylococcus aureus, Bacillus subtilis, and Streptococcus haemolytius and the Gram negative bacteria Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia. The analgesic activity was carried out using Swiss albino male mice by abdominal concentration method. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor &Francis Group, LLC.

Full text of DOI:10.1080/10426507.2010.530630

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Synthesis, Antibacterial, and Analgesic
Activity of Novel 4-Hydroxy-3-
(phenylthio)-2H-chromen-2-ones and
4-Hydroxy-3-[imidazol/tetrazolo-2-
yl)thio]-2H-chromen-2-ones
G. Rajesha a , Kittappa M. Mahadevan b , N. D. Satyanarayan b & H.
S. Bhojya Naik a
a Department of Post Graduate Studies and Research in Industrial
Chemistry, School of Chemical Sciences, Kuvempu University,
Shankaraghatta, Karnataka, India
b Department of Post Graduate Studies in Pharmaceutical Chemistry,
P. G. Centre, Kadur, Karnataka, India
Available online: 11 Aug 2011
To cite this article: G. Rajesha, Kittappa M. Mahadevan, N. D. Satyanarayan & H. S. Bhojya Naik
(2011): Synthesis, Antibacterial, and Analgesic Activity of Novel 4-Hydroxy-3- (phenylthio)-2H-
chromen-2-ones and 4-Hydroxy-3-[imidazol/tetrazolo-2-yl)thio]-2H-chromen-2-ones, Phosphorus,
Sulfur, and Silicon and the Related Elements, 186:8, 1733-1743
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Phosphorus, Sulfur, and Silicon, 186:1733–1743, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.530630
SYNTHESIS, ANTIBACTERIAL, AND ANALGESIC
ACTIVITY OF NOVEL 4-HYDROXY-3-
(PHENYLTHIO)-2H-CHROMEN-2-ONES AND
4-HYDROXY-3-[IMIDAZOL/TETRAZOLO-2-yl)THIO]-2H-
CHROMEN-2-ONES
G. Rajesha,1 Kittappa M. Mahadevan,2 N. D. Satyanarayan,2
and H. S. Bhojya Naik1
1Department of Post Graduate Studies and Research in Industrial Chemistry,
School of Chemical Sciences, Kuvempu University, Shankaraghatta,
Karnataka, India
2Department of Post Graduate Studies in Pharmaceutical Chemistry, P. G. Centre,
Kadur, Karnataka, India
GRAPHICAL ABSTRACT
OH
O
OH
OH
POCl3
O
O
+
AlCl3 reflux / 36hr
O
2
1
OH
OH
OH
O
OH
Br
O
NBS / CH3CN
S
ArSH/DMF
4a-k
6 hr, RT
O
K2CO3/reflux
O
O
O
R
3
Het-SH
Cs2CO3 / ethanol/reflux
Where R= 3-Cl, 3-Br, 3-F, -H, 4-Cl, 3-OCH3
2-Br, 2-F, 2-CF3, 3-CF3, 4-CF3
m-CPBA
DCM, RT
O
OH
OH
O
S
S
Het
O
O
O
O
R
5a-c
Where R = 3 - Cl, 3 - Br, 3 - F,
6a-d
Abstract A mild and efficient synthesis of new 4-hydroxy-3-(phenylthio)-2H-chromen-2-
ones 4a–k and 4-hydroxy-3-[imidazol/tetrazolo-2-yl)thio]-2H-chromen-2-ones 6a–d is de-
scribed. The compounds 4a–c were further subjected to oxidation by m-CPBA to obtain
3-(phenylsulfonyl)-4-hydroxy-2H-chromen-2-ones 5a–c. The structures of the resulted new
compounds were established by IR, 1H NMR, mass, and elemental analysis. All the synthe-
sized compounds were subjected to antibacterial activity against the Gram positive bacteria
Received 26 August 2010; accepted 6 October 2010.
The author is thankful to the Department of Chemistry, Kuvempu University, Shankaraghatta, India, for
providing laboratory facilities and Department of Biochemistry, Kuvempu University, Karnataka, India, for
biological testing. The authors are also indebted to Indian Institute of Science, Bangalore, India, for providing
spectral data.
Address correspondence to Kittappa M. Mahadevan, Department of Post Graduate Studies in Pharmaceutical
Chemistry, P G Centre, Kadur- 577 548, Karnataka, India. E-mail: mahadevan.kmm@gmail.com
1733

1734
G. RAJESHA ET AL.
Staphylococcus aureus, Bacillus subtilis, and Streptococcus haemolytius and the Gram neg-
ative bacteria Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella
pneumonia. The analgesic activity was carried out using Swiss albino male mice by abdominal
concentration method.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Keywords Analgesic activity; antibacterial activity; phenyl coumarinyl thioethers
INTRODUCTION
Coumarin and its derivatives represent one of the most active classes of compounds
possessing a wide spectrum of biological activity.1–9 Many of these compounds have
proved to be active as antitumor,1,2 antibacterial,3,4 antifungal,5–7 anticoagulant,8 and anti-
inflammatory9 agents. In addition, these compounds are also used as additives to food and
cosmetics,10 and have dispersed fluorescent and laser properties.11 Various 3-substituted
coumarins exhibit antimicrobial activity.12,13
The phenyl coumarinyl ethers constitute a group of naturally occurring oxygen hete-
rocyclic compounds, isolated principally in the Thymeliaceae family but also in the Legu-
minceae and Rutaceae families and various other plants.14–16 The various 3-substituted
4-hydroxy-coumarins are active nonpeptide HIV-PR inhibitors,17,18 which opens up a new
therapeutic possibility. In connection with the preparation of bioactive coumarins, the
structure-activity relationships of various 3-substituted-4-hydroxy coumarins have also
been reported.19 In addition, some coumarins are of interest because of their toxicity,20
carcinogenity,21 and photodynamic effects.22 Coumarins also act as intermediates for the
synthesis of furocoumarins, chromenes, coumarones, and 2-acylresorcinols.23 Some of the
naturally occurring coumarin ethers analogs are coumarin glycoside24 and daphnoretin.15
Thus, the influence of coumaryl ethers prompted us to synthesize various thio-
coumaryl ethers by condensing various thiophenols and heterocyclic thiols with 3-bromo-
4-hydroxy coumarin by developing a simple protocol, which is in continuation of our work
on biological testing of natural products as well as various synthetic compounds.25–31
Hence, a series of new 4-hydroxy-3-(phenylthio)-2H-chromen-2-ones 4a–k and 4-
hydroxy-3-[imidazol/tetrazolo-2-yl)thio]-2H-chromen-2-ones 6a–d was prepared in good
yields by the condensation of 3-bromo-4-hydroxy-coumarin 2 with various thiophenols
in the presence of K2CO3/DMF and Cs2CO3/EtOH. The compounds 4a–c were further
subjected to oxidation promoted by m-CPBA to obtain 3-(phenyl sulfonyl)-4-hydroxy-2H-
chromen-2-ones 5a–c. The structures of the resulted new compounds were established by
IR, 1H NMR, mass, and elemental analysis. All the synthesized compounds were subjected
to the evaluation of their antibacterial activity against the Gram positive bacteria Staphylo-
coccus aureus, Bacillus subtilis, and Streptococcus haemolytius and Gram negative bacteria
Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumonia.
RESULTS AND DISCUSSION
The generation of the required substrate 3-bromo-4-hydroxy-coumarin 3 is readily
achieved in 70–85% yield by the reaction of 4-hydroxycoumarin with NBS in acetonitrile
at 25–27◦C. The 1H NMR of compound 3 exhibited a double doublet at 7.37–7.43 δ that
corresponds to two protons, another triplet at 7.66–7.69 δ for one proton and a doublet at

NOVEL 4-HYDROXY-3-(PHENYLTHIO)-2H-CHROMEN-2-ONES
1735
7.96–7.98 δ integrated for one proton confirms the structure of compound 3. Further LC-MS
analysis of compound 3 gave a molecular ion peak at 242 (M +1) to ascertain the structure
of compound 3. Thus, coumarin 3 was first utilized to couple with various thiophenols in
the presence of base K2CO3 in DMF as solvent to obtain the corresponding 4-hydroxy-
3-(phenylthio)-2H-chromen-2-ones 4a–k in good yield (Table 1, Scheme 1) in which the
4-hydroxy group is necessary as much for its bonding to the HIV-PR for its inhibitory
potency.32 Besides their antithrombotic activity and analgesic activity, the 3-substituted
4-hydroxycoumarins also present interesting free-radical scavenging properties.33 Hence
the above biological information regarding 4-hydroxycoumarin derivatives prompted us to
screen for their antibacterial and analgesic activities.
OH
O
OH
OH
OH
POCl3
O
O
+
AlCl3 reflux / 36hr
O
2
1
OH
OH
O
OH
Br
O
NBS / CH3CN
S
ArSH/DMF
4a-k
6 hr, RT
O
K2CO3/reflux
O
O
O
R
3
Het-SH
Cs2CO3 / ethanol/reflux
Where R= 3-Cl, 3-Br, 3-F, -H, 4-Cl, 3-OCH3
2-Br, 2-F, 2-CF3, 3-CF3, 4-CF3
m-CPBA
DCM, RT
O
OH
OH
O
S
S
Het
O
O
O
O
R
5a-c
Where R = 3 - Cl, 3 - Br, 3 - F,
6a-d
Scheme 1
Further thiadiazole, triazole, tetrazole,34 and other heterocyclic derivatives of 3-
substituted coumarins35,36 are well known for their biological activities such as antimi-
crobial,37 anti-inflammatory,38 and anticancer.39 In view of the biological importance of
the above-mentioned heterocyclic compounds, we thought it worthwhile to develop a
new method for the rapid synthesis of such heterocyclic rings connected to coumarin
through a sulfur bridge. Thus 2-mercaptoimidazole, 1-N-methyl-2-mercaptoimidazole, 5-
mercapto-tetrazole, 1-N-methyl-5-mercapto-tetrazole are commercially available and were
used for the reaction without further purification (Scheme 1). So the various 4-hydroxy-3-
[imidazol/tetrazolo-2-yl)thio]-2H-chromen-2-ones 6a–d were prepared in good yields by
the condensation of 3-bromo-4-hydroxy-coumarin 2 with various 2-mercaptoimidazole, 1-
N-methyl-2-mercaptoimidazole, 5-mercapto-tetrazole, 1-N-methyl-5-mercapto-tetrazole,
in the presence of base Cs2CO3 in EtOH as solvent at reflux temperature. In this case,
the base such as K2CO3 did not give the expected 4-hydroxy-3-[imidazol/tetrazolo-2-
yl)thio]-2H-chromen-2-ones 6a–d in good yield, hence Cs2CO3 was used instead.

1736
G. RAJESHA ET AL.
Table 1 Reaction time, yield, and melting points of newly synthesized compounds 4a–k
Product
Structurea
Yield (%)b
79
Mp ◦C
Time (h)
5
4a
159–160
4b
4c
86
58
220–222
166–167
5
5
4d
4e
53
73
200–202
197–198
5
5
4f
60
83
176–177
210–213
5
5
4g
4h
4i
86
82
85
71
220–222
227–228
217–218
136–137
5
5
5
5
4j
4k
aReaction was carried out at reflux temperature in DMF.
bIsolated yields.

NOVEL 4-HYDROXY-3-(PHENYLTHIO)-2H-CHROMEN-2-ONES
1737
Table 2 Reaction time, yield, and melting points of newly synthesized compounds 5a–c
Product
Structurea
Yield (%)b
82
Mp (◦C)
170–172
Time (h)
7
5a
5b
5c
75
80
202–204
130–133
8
7
aReaction was carried out at room temperature in DCM.
bIsolated yields.
To make variations in the structure, the compounds 4a–c were oxidized with m-
chloroperbenzoic acid in dichloromethane at 25–27◦C to afford the corresponding 3-(phenyl
sulfonyl)-4-hydroxy-2H-chromen-2-one 5a-c in the yield of 60–75% (Table 2, Scheme 1).
In a typical experiment, 2-mercaptoimidazole was condensed with 3-bromo-4-
hydroxycoumarin in the presence of Cs2CO3 in ethanol to obtain the corresponding
4-hydroxy-3-[(1H-imidazol-2-yl)thio]-2H-chromen-2-ones, 4-hydroxy-3-[(1-methyl-1H-
imidazol-2-yl)thio]-2H-chromen-2-ones 6a and 6b and 4-hydroxy-3-[(1H-tetrazol-5-
yl)thio]-2H-chromen-2-ones,4-hydroxy-3-[(1-methyl-1H-tetrazol-5-yl)thio]-2H chromen-
2-ones 6c and 6d, respectively (Table 3).
Table 3 Reaction time, yield, and melting points of newly synthesized compounds 6a–d
Product
Structurea
Yield (%)b
75–80
Mp (◦C)
199–202
Time (h)
12
6a
6b
6c
6d
70–75
70–75
65–70
210–211
242–246
257–258
12
12
12
aReaction was carried out at reflux temperature in Ethanol.
bIsolated yields.

1738
G. RAJESHA ET AL.
The structures of all the products were determined by detailed study of the spectro-
scopic data. All the synthesized compounds were characterized on the basis of spectral data
and are evaluated for their antimicrobial activity. The structures of compounds 4a–k, 5a–c,
and 6a–d were established by 1H NMR and mass spectral data. 1H NMR of compound 4a
revealed the presence of multiplets at 7.14–7.98 δ for eight protons of the aromatic group,
and a molecular ion peak exhibited at MS 305 (M+1) confirms the formation of compound
4a. The conversion of compound 4a to 5a up on oxidation of 4a with m-CPBA in DCM
as solvent at room temperature directly confirmed LC-MS analysis. Thus the compound
5a exhibited molecular ion peaks at MS 335 (M–1). The structure of compound 6a was
confirmed by its 1H NMR spectra. It exhibited multiplets at 7.84–7.14 δ for four protons,
which confirmed its aromatic protons, and a broad singlet at 10.5 δ for one proton revealed
the presence of a NH group (D2O exchangeable). Finally, in its mass spectra, it exhibited a
molecular ion peak at MS 261 (M–1), which confirms its structure.
Antibacterial Activity
The activity was carried out using the cup plate agar diffusion method.40 All the
synthesized compounds (Table S1, available online in the Supplementary Materials) were
tested for their antibacterial activity against various bacterial strains belonging to Gram pos-
itive (Staphylococcus aureus, Bacillus subtilis, and Streptococcus haemolytius) and Gram
negative (Salmonella typhi, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella
pneumonia). The zone of inhibition was measured in millimeters. Streptomycin was used
as the standard drug for comparison. The compounds were tested at 40 µg/mL concentra-
tion, and DMSO was used as a vehicle. The results show that the synthesized compounds
were found to be active against the tested bacteria. The maximum activity was found in
6a, 6b, 6c, 6d, and 5b against all the bacteria, whereas 4a–e, 5a, and 5c shows moderate
activity.
Analgesic Activity41
Male Swiss albino mice were produced from Virus Diagnostic Laboratory, Shiva-
mogga, Karnataka, India. Analgesic activity was calculated as the percentage maximum
possible effect (% MPE), and the results are recorded in Table S2.
Analgesic properties of test compounds were compared with the activity of standard
drug aspirin having percentage of protection value 62.1. The compounds 4a, 4b and 5b,
5c exhibited almost equipotent percentage protection as compared with standard aspirin
and other compounds, and 5b, 5c and 6a, 6d showed a more significant percentage of
protection.
CONCLUSION
In conclusion, we have developed a simple methodology to prepare novel biologi-
cally important aryl/hetero aryl coumarinyl thioethers that resembles the structure of nat-
urally occurring phenyl coumarinyl ethers. The antibacterial and analgesic activity results
showed that the compounds coupled with nitrogen heterocycles are more active compared
to sulfonyl- and thionyl-coupled compounds. Further testing must be carried out to check
the minimum inhibitory concentration (MIC) values of the active compounds.

NOVEL 4-HYDROXY-3-(PHENYLTHIO)-2H-CHROMEN-2-ONES
1739
EXPERIMENTAL
The melting points are uncorrected. Column chromatography was performed on silica
gel (60–120 mesh, Merck). Commercial reagents and solvents were of analytical grade or
1
were purified by standard procedures prior to use. H NMR was recorded on a Bruker
Advance 400 MHz DPX spectrometer and referenced to TMS as internal standard. Mass
spectra were run by electron impact at 70 eV in a VG Auto spectrometer. Selected NMR
and mass spectra are shown in Figures S1–S6 (Supplemental Materials)
Synthesis of 3-Bromo-4-hydroxy-coumarin 3
4-Hydroxycoumarin (100 mg, 1 eq, 0.61 mmol) was dissolved in acetonitrile (10
mL), and powdered N-bromosuccinimide (1.1 eq, 0.67 mmol) was added at 25–27◦C under
constant stirring. The reaction mixture was poured into water. The precipitate thus obtained
was filtered, dried, and purified by column chromatography using chloroform:methanol
(9:1 v/v).
General Procedure for the Synthesis of 4-Hydroxy-3-
(phenylthio)coumarins 4a–k
In a dry, round-bottom flask, a mixture of 3-bromo-4-hydroxy-coumarin (100 mg, 1
eq, 0.41 mmol), potassium carbonate (3 eq, 1.24 mmol), and thiophenol (3 eq, 1.39 mmol)
was heated at 85◦C for 5 h in DMF (10 mL) as solvent. The progress of the reaction
was monitored by TLC, chloroform:methanol system (9:1 v/v). The reaction mixture was
filtered, poured into water, and neutralized with 1.5 N HCl solution. The solid thus separated
was filtered and washed with diethyl ether to remove excess thiophenols. Finally, the crude
product was purified by column chromatography by using chloroform:methanol (9:1 v/v).
General Procedure for the Synthesis of 3-[(-Chlorophenyl)sulfonyl]-
4-hydroxy-2H-chromen-ones 5a–c
3-[(3-Chlorophenyl)thio]-4-hydroxy-2H-chromen-2-one 4a (100 mg, 0.328 mmol)
was dissolved in dichloromethane (10 mL). To this, meta-chloroperbenzoic acid (2.5 eq,
0.82 mmol) was added. The reaction mixture was stirred at 25–27◦C for about 8 h and was
poured into 10% potassium carbonate solution to remove benzoic acid. Finally, the crude
product was extracted with ethyl acetate, washed with brine solution, dried by anhydrous
sodium sulfate, and purified by column chromatography using chloroform:methanol (9:1
v/v).
General Procedure for Synthesis of 4-Hydroxy-3-(imidazol/
tetrazolo-2-yl)thio]-2h-chromen-2-ones 6a–d
In a dry, round-bottom flask, a mixture of 3 (100 mg, 1 eq, 0.41 mmol), cesium
carbonate (Cs2CO3) (3 eq, 1.23 mmol), and mercapto compound (2 eq, 0.82 mmol) was
heated at 70◦C for 12 h in ethanol (10 mL) as solvent. The progress of the reaction was mon-
itored by TLC, chloroform:methanol (9:1 v/v) system. The reaction mixture was filtered,
poured into water, and neutralized with 1.5 N HCl solution. The solid obtained was filtered,
and was washed with diethyl ether to remove the excess mercapto compound. Finally, the
crude product was purified by column chromatography using chloroform:methanol (9:1
v/v).

1740
G. RAJESHA ET AL.
Spectral Details
3-[(3-Chlorophenyl)thio]-4-hydroxy-2H-chro men-2-one (4a). Mp: 159–
160◦C; IR (cm−1): 3422, 1719. NMR (DMSO-d6): 7.98 (d, J = 8.0 Hz, 1H), 7.74 (t, J =
7.2 Hz, 1H), 7.44 (m, J = 8.0 Hz, 2H), 7.32 (t, J = 7.6 Hz, 1H), 7.22 (d, J = 7.2 Hz, 2H),
7.16 (d, J = 8.0Hz, 1H), m/z: 305 (M+1). Anal. Calcd. For C15H9 ClO3S = C, 59.12; H,
2.98. Found: C, 59.05; H, 2.8.
3-[(3-Bromophenyl)thio]-4-hydroxy-2H-chromen-2-one (4b). Mp: 220–
222◦C; IR (cm−1): 3418, 1719. NMR (DMSO-d6): 7.97 (d, J = 7.6 Hz, 1H), 7.73 (t, J =
7.6 Hz, 1H), 7.67 (d, J = 8 Hz, 1H), 7.43 (m, J = 8 Hz, 2H), 7.24 (t, J = 7.6 Hz, 1H), 7.08
(t, J = 7.60 Hz, 1H), 6.91 (d, J = 8.4 Hz, 1H), m/z: 347(M-1). Anal. Calcd. For C15H9
BrO3S = C, 59.12; H, 2.98. Found: C, 58.95; H, 2.82.
3-[(3-Fluorophenyl)thio]-4-hydroxy-2H-chromen-2-one (4c). Mp: 166–
167◦C; IR (cm−1): 3396, 1719. NMR (DMSO-d6): 7.97 (d, J = 1.2 Hz, 1H), 7.72 (d, J =
0.8 Hz, 1H), 7.43 (t, J = 6.0 Hz, 2H), 7.29 (d, J = 8.4 Hz, 1H), 7.21 (d, J = 5.6 Hz, 2H),
7.16 (d, J = 7.60 Hz, 1H, m/z: 287 (M-1). Anal. Calcd. For C15H9 FO3S = C, 62.4; H,
3.15. Found: C, 61.7; H, 2.94.
4-Hydroxy-3-(phenylthio)-2H-chromen-2-one (4d). Mp: 200–202◦C; IR
(cm−1): 3392, 1719. NMR (DMSO d6): 7.97 (d, J = 6.8 Hz, 1H), 7.72 (t, J = 7.2 Hz, 1H),
7.44 (m, J = 5.2 Hz, 2H), 7.30 (t, J = 7.6 Hz, 2H), 7.19 (t, J = 7.6 Hz, 3H), m/z: 270
(M-1). Anal. Calcd. For C15H10O3S = C, 66.65; H, 3.73. Found: C, 66.52; H, 3.61.
3-[(4-Chlorophenyl)thio]-4-hydroxy-2H-chromen-2-one (4e). Mp: 197–
198◦C; IR (cm−1): 3390, 1719. NMR (DMSO-d6): 7.97 (d, J = 1.2 Hz, 1H), 7.73 (t, J =
7.2 Hz, 1H), 7.43 (t, J = 5.6 Hz, 2H), 7.33 (d, J = 7.2 Hz, 2H), 7.22 (d, J = 8.8Hz, 2H),
m/z: 303 (M-1). Anal. Calcd. For C15H9ClO3S = C, 59.12; H, 2.98 Found: C, 58.89; H,
2.73.
4-Hydroxy-3-[(3-methoxyphenyl)thio]-2H-chromen-2-one (4f). Mp: 176–
177◦C; IR (cm−1): 3389, 1719. NMR (DMSO-d6): 7.97 (d, J = 8 Hz, 2H), 7.73 (t, J = 7.2
Hz, 3H), 7.44 (m, J = 5.6 Hz, 2H), 7.21 (t, J = 8.4 Hz, 1H), 6.74 (t, J = 7.2 Hz, 3H), 3.75
(s,3H), m/z: 299 (M-1). Anal. Calcd. For C16H12O4S = C, 63.99; H, 4.03 Found: C, 63.88;
H, 3.9.
3-[(2-Bromophenyl)thio]-4-hydroxy-2H-chromen-2-one (4g). Mp: 210–
213◦C; IR (cm−1): 3388. NMR (DMSO-d6): 7.98 (d, J = 8 Hz, 1H), 7.73 (d, J = 8.4 Hz,
1H), 7.62 (d, J = 8 Hz, 1H), 7.45 (m, J = 8.4 Hz, 2 H), 7.23 (t, J = 7.20 Hz, 1H), 7.09
(d, J = 7.6 Hz, 1H), 6.92 (m, J = 0.8 Hz,1H), m/z: 347(M-1). Anal. Calcd. For C15H9
BrO3S = C, 51.59; H, 2.6 Found: C, 51.52; H, 2.41.
3-[(2-Fluorophenyl)thio]-4-hydroxy-2H-chromen-2-one (4h). Mp: 220–
222◦C; IR (cm−1): 3394, 1721. NMR (DMSO-d6): 8.05 (d, J = 1.6 Hz, 1H), 7.74 (d, J =
8.1 Hz, 1H), 7.46 (m, J = 7.6, 2H), 7.22 (s, 1H), 7.15 (m, J = .4 Hz, 3H), m/z: 287 (M-1).
Anal. Calcd. For C15H9 FO3S = C, 62.49; H, 3.15 Found: C, 62.38; H, 3.02.
4-Hydroxy-3-([2-(trifluoromethyl) phenyl]thio)-2H-chromen-2-one (4i).
Mp: 227–228◦C; IR (cm−1): 3417, 1719. NMR (DMSO-d6): 7.94 (d, J = 7.9 Hz, 1H),7.72
(t, J = 8 Hz, 1H),7.58 (d, J = 7.6 Hz, 1H), 7.42 (m, J = 8 Hz, 2H), 7.23 (m, J = 8 Hz, 1H),
7.07 (m, J = 4 Hz, 1H), 6.90 (d, J = 8 Hz, 1H), m/z: 337(M-1). Anal. Calcd. For C16H9
F3O3S = C, 56.80; H, 2.68 Found: C, 56.68; H, 2.55.
4-Hydroxy-3-[(3-(trifluoromethyl)phenyl)thio]-2H-chromen-2-one
(4j).
Mp: 217–218◦C; IR (cm−1): 3420, 1723. NMR (DMSO-d6): 7.97 (d, J = 6.8 Hz, 1H), 7.73

NOVEL 4-HYDROXY-3-(PHENYLTHIO)-2H-CHROMEN-2-ONES
1741
(t, J = 7.2 Hz, 1H), 7.5 (t, J = 4.0 Hz, 3H), 7.39 (m, J = 7.6 Hz) m/z 337 (M-1). Anal.
Calcd. For C16H9 F3O3S = C, 56.80; H, 2.68 Found: C, 56.61; H, 2.53.
4-Hydroxy-3-[(4-(trifluoromethyl)phenyl)thio]-2H-chromen-2-one (4k).
Mp: 136–137◦C; IR (cm−1) 3398, 1727. NMR (DMSO-d6): 7.99 (d, J = 8.0 Hz, 1H), 7.74
(m, J = 1.2 Hz, 1H), 7.61 (d, J = 8.4 Hz, 2H), 7.44 (t, J = 8.4 Hz, 2H), 7.369(t, J = 8.0
Hz, 2H), m/z 337 (M-1). Anal. Calcd. For C16H9 F3O3S = C, 56.80; H, 2.68 Found: C,
56.62; H, 2.51.
3-[(3-Chlorophenyl)sulfonyl]-4-hydroxy-2H-chromen-2-one (5a). Mp: 170–
172◦C; IR (cm−1): 3432, 1738, 1338–1288. NMR (DMSO-d6): 7.98 (d, J = 8.0 Hz, 1H),
7.74 (t, J = 7.2 Hz, 1H), 7.44 (m, J = 8.0 Hz, 2H), 7.32 (t, J = 7.6 Hz, 1H), 7.22 (d, J =
7.2 Hz, 2H), 7.16 (d, J = 8.0 Hz, 1H), m/z 335 (M-1). Anal. Calcd. For C15 H9 ClO5S).
Anal. Calcd. For C16H9 F3O3S = C, 53.5; H, 2.69 Found: C, 52.8; H, 2.55.
3-[(3-Bromophenyl)sulfonyl]-4-hydroxy-2H-chromen-2-one (5b). Mp: 202–
204◦C; IR (cm−1): 3438, 1731, 1341–1294. NMR (DMSO-d6): 7.97 (d, J = 7.6 Hz, 1H),
7.73 (t, J = 7.6 Hz, 1H), 7.67 (d, J = 8 Hz, 1H), 7.43 (m, J = 8 Hz, 2H), 7.24 (t, J = 7.6
Hz, 1H), 7.08 (t, J = 7.60 Hz, 1H), 6.91 (d, J = 8.4 Hz,1H), m/z 379 (M-1). Anal. Calcd.
For C15H9 BrO5S = C, 47.26; H, 2.38 Found: C, 47.11; H, 2.17.
3-[(3-Fluorophenyl)sulfonyl]-4-hydroxy-2H-chromen-2-one (5c). Mp: 130–
133◦C; IR (cm−1): 3428, 1727, 1329–1310. NMR (DMSO-d6): 7.97 (d, J = 1.2 Hz, 1H),
7.72 (d, J = 0.8 Hz, 1H), 7.43 (t, J = 6.0 Hz, 2H), 7.29 (d, J = 8.4 Hz, 1H), 7.21 (d, J =
5.6 Hz, 2H), 7.16 (d, J = 7.60 Hz, 1H, m/z 319 (M-1). Anal. Calcd. For C15H9 FO5S = C,
56.25; H, 2.83 Found: C, 56.08; H, 2.72.
4-Hydroxy-3-(1H-imidazol-2-ylthio)-2H-chromen-2-one (6a). Mp: 75–
80◦C; 1H NMR (DMSO d6): 7.84 (d, J = 1.6 Hz, 1H), 7.42 (t, J = 6.4 Hz, 1H), 7.14 (m,
J = 1.2 Hz, 2H), 10.5 (b, s, 1H, NH, D2 O exchangable), 6.76 (d, 2H, = CH), m/z: 261
(M-1) (100%), 211(25%), 157 (48%), 133 (70%). Anal. Calcd. For C12H8 N2O3S = C,
55.38; H, 3.10; N, 10.76 Found: C, 55.29; H, 2.87; N, 10.54.
4-Hydroxy-3-[(1-methyl-1H-imidazol-2-yl)thio]-2H-chromen-2-one (6b).
Mp: 70–75◦C; 1H NMR (DMSO d6): 7.77 (d, J = 1.2 Hz, 1H), 7.39 (t, J = 1.6 Hz, 1H),
7.10 (m, J = 7.6 Hz, 2H), 3.64 (s, 3H), 6.69 (d, 2H, = CH), m/z: 275 (M-1). Anal. Calcd.
For C13H10N2O3S = C, 56.92; H, 3.67; N, 10.21 Found: C, 56.83; H, 3.52; N, 10.02.
4-Hydroxy-3-(1H-tetrazol-5-ylthio)-2H-chromen-2-one (6c). Mp: 70–75◦C;
1H NMR (DMSO d6): 7.78 (d, J = 2 Hz, 1H), 7.45 (t, J = 1. 6 Hz, 1H), 7.15 (m, J = 7.2 Hz,
2H), m/z: 263 (M-1). Anal. Calcd. For C10H6N4O3S = C, 45.8; H, 2.31; N, 21.36 Found:
C, 45.78; H, 2.16; N, 21.19.
4-Hydroxy-3-[(1-methyl-1H-tetrazol-5-yl)thio]-2H-chromen-2-one (6d).
Mp: 65–70◦C; 1H NMR (DMSO d6): 7.78 (d, J = 2 Hz, 1H), 7.45 (t, J = 1. 6 Hz, 1H), 7.15
(m, J = 7.2 Hz, 2H), 3.9 (s,3H, -CH3), m/z: 277 (M-1). Anal. Calcd. For C11H8N4O3S =
C, 47.82; H, 2.92; N, 20.28 Found: C, 47.68; H, 2.75; N, 20.07.
BIOLOGICAL ACTIVITY
Antibacterial Activity
The present investigation deals with the antibacterial activity of synthesized com-
pounds which were studied comparatively with that of the antibiotic streptomycin, using
cup-plate method against Streptococcus haemolyticus, Staphylococcus aureus, Salmonella

1742
G. RAJESHA ET AL.
typhi, Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis, and Klebsiella pneu-
monia.
Analgesic Activity: Materials and Methods
Colony bred albino mice (Swiss strain) of either sex weighing 22–35 g were used
to evaluate analgesic activity.41 Analgesic activity was determined as described by the
method based on acetic acid–induced writhing in mice. The percentage of protection of the
compounds was compared with the activity of acetyl salicylic acid as standard drug, and
was calculated by using the following formula:
% of inhibition = [1 − Nt/Nc] × 100
where, Nt = mean number of writhing in test animals and Vc = mean number of writhing
in control. The results of analgesic activities are described in Table S2.
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