Synthesis of some thiadiazolotriazinone derivatives as possible antimicrobial agents

Article abstract of DOI:10.1080/10426500601096435

A series of 7-substituted-3-t-butyl 4(H)-1,3,4-thiadiazolo(2,3-c)-1,2,4- triazine-4-one (3) have been synthesized by condensing 4-amino-6-t-butyl-3- mercapto-1,2,4-triazin-5(4H)-one (1) with substituted Arylfuroic acids (2) using POCl3 as a cyclizing agen

Full text of DOI:10.1080/10426500601096435

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Synthesis of Some
Thiadiazolotriazinone
Derivatives as Possible
Antimicrobial Agents
D. Jagadeesh Prasad a , M. S. Karthikeyan a , Prakash
B. Karegoudar b , Boja Poojary a , B. Shivarama Holla
a & N. Suchetha Kumari c
a Department of Postgraduate Studies and
Research in Chemistry , Mangalore University ,
Mangalagangotri, India
b Strides Research and Speciality Chemicals Private
Limited , Baikampady, Mangalore, India
c Department of Biochemistry, K. S. Hegde Medical
Academy , Mangalore, India
Published online: 19 Apr 2007.
To cite this article: D. Jagadeesh Prasad , M. S. Karthikeyan , Prakash B.
Karegoudar , Boja Poojary , B. Shivarama Holla & N. Suchetha Kumari (2007)
Synthesis of Some Thiadiazolotriazinone Derivatives as Possible Antimicrobial Agents,
Phosphorus, Sulfur, and Silicon and the Related Elements, 182:5, 1083-1091, DOI:
10.1080/10426500601096435
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Phosphorus, Sulfur, and Silicon, 182:1083–1091, 2007
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500601096435
Synthesis of Some Thiadiazolotriazinone Derivatives as
Possible Antimicrobial Agents
D. Jagadeesh Prasad
M. S. Karthikeyan
Department of Postgraduate Studies and Research in Chemistry,
Mangalore University, Mangalagangotri, India
Prakash. B. Karegoudar
Strides Research and Speciality Chemicals Private Limited,
Baikampady, Mangalore, India
Boja Poojary
B. Shivarama Holla
Department of Postgraduate Studies and Research in Chemistry,
Mangalore University, Mangalagangotri, India
N. Suchetha Kumari
Department of Biochemistry, K. S. Hegde Medical Academy, Mangalore,
India
A series of 7-substituted -3-t-butyl 4(H)-1,3,4-thiadiazolo(2,3-c)-1,2,4-triazine-4-
one (3) have been synthesized by condensing 4-amino-6-t-butyl-3-mercapto-1,2,4-
triazin-5(4H)-one (1) with substituted Arylfuroic acids (2) using POCl3 as a cy-
clizing agent. The newly synthesized compounds are characterized by elemental
analysis, IR, 1H NMR, and mass spectral studies. The compounds were screened
for their antibacterial and antifungal activities. Some of the compounds showed
promising antibacterial and antifungal activity.
Keywords Antimicrobial; Aryl furoic acids; phosphorus oxychloride; thiadiazolotriazi-
nones
Received July 12, 2006; accepted October 12, 2006.
The authors are thankful to IISc, Bangalore, CDRI, Lucknow, and Department of
Chemistry, Mangalore University for providing NMR/Mass/IR spectra of the compounds
reported. The authors are also thankful to the Government of India, Department of Sci-
ence and Technology, for providing CHNS Instrument Facility under DST-FIST fund in
the Department of Chemistry, Mangalore University, Mangalagangotri.
Address correspondence to D. Jagadeesh Prasad, Department of Chemistry, Manga-
lore University, Mangalagangotri, 574199 Karnataka State, India. E-mail: jprasad 2003@
yahoo.co.in
1083

1084
D. Jagadeesh Prasad et al.
INTRODUCTION
Triazinones and their condensation products find important applica-
tions in the field of medicine and agriculture.1 Many such compounds
exhibit antidiuretic and neuro-depressent activities.2 Mannich bases
derived from substituted triazinones find a significant place in the field
of pharmaceutical chemistry3 Some of the S-alkylated mercapto triazi-
nones exhibit herbicidal activities.4 Among such derivatives Sencor5
(4-amino-3-methylthio-6-t-butyl-1,2,4-triazin-5-(4H)-one) is being used
as a commercial herbicide for the control of weeds in potato crops. Hete-
rocyclic compounds containing substituted arylfuran moiety are found
to exhibit diverse biological activities such as antimalarial, and antivi-
ral, antifungal, antibacterial, and anticancer activities.6−12 A number
of thiadiazole derivatives possess antibacterial properties comparable
with those of sulfonamide drugs.13 Subsequently, thiadiazole deriva-
tives have found applications as anti-tumor agents and pesticides.14−17
literature survey revealed that only a few thiadiazolotriazinones con-
taining arylfuran moiety are reported. Prompted by the varied biolog-
ical activities of 1,2,4 triazinones and 1,3,4 thiadiazoles and in contin-
uation of our work on the synthesis of N- bridged heterocycles derived
from 1,3,4 triazinones, a series of 7-substituted -3-t-butyl 4(H)-1,3,4-
thiadiazolo(2,3-c)-1,2,4-triazine-4-one (3) have been synthesized and
screened for their antibacterial and antifungal activities.
Materials and Methods
For the present work different aryl furoic acids have been synthesized
according to the procedure described in the literature.18 (Here we made
use of of meerweins reaction19 where a copper ion would be the catalyst.)
Thus the Aryl furoic acids (1) obtained by this method were cyclized
with commercially obtained Sencor compound, i.e., 4-amino-6-t-butyl-
3-methylthio-1,2,4-triazine-5(H)–ones (2) in the presence of POCl3 at
80◦C. The products thiadiazolotriazinones were obtained in good yields
and were confirmed by elemental analysis and spectral studies.
The characterization data of thiadiazolotriazinones (3) are given in
Table I.
Results and discussion
The formation of 7-[5-(2,4,5-trichlorophenyl)-2-furyl]-3-t-butyl-4(H)-
1,3,4-thiadiazolo (2,3-c)-1,2,4-triazin-4-ones 3a and the formation
of 7-(2-trifluoromethyl-5-aryl-2-furyl)-3-t-butyl-4H-1,3,4-thiadiazolo
(2,3-c)-1,2,4-triazin- 4-ones 3c were confirmed by elemental analysis,

Thiadiazolotriazinone Derivatives
1085
TABLE I Characterization Data of the Preparation of
7-substituted-3-t-butyl- 4(H)-1,3,4-thiadiazolo (2, 3-c)-1,2,4-triazine-
4–ones (3)
Elemental Analysis
(%) Found (Calculated)
Compound
R
Mol. Formula
Yied (%) M.P (◦C)
C
H
N
3a
2,4,5-tri -Cl
C18H13N4SO2Cl3 95
237–240 50.80 3.86 23.70
(50.83) (3.83) (23.71)
3b
3c
3d
3e
3f
2-NO2-4 -Cl
2-CF3
C18H14N5SO4Cl
C19H15N4SO2F3
C18H15N5SO4
95
88
86
220–224 61.52 4.17 17.93
(61.52) (4.19) (17.93)
176–180 54.26 3.57 13.30
(54.28) (3.57) (13.30)
235–236 51.37 2.55 15.96
(51.36) (2.58) (15.97)
205–206 54.18 3.75 14.84
(54.18) (3.74) (14.86)
192–194 54.18 3.75 14.84
(54.18) (3.74) (14.86)
210–214 53.39 4.01 16.38
(52.19) (3.98) (16.22)
219–223 50.17 3.14 16.38
(50.03) (2.99) (16.28)
08–210 62.28 4.95 15.29
(62.01) (4.76) (15.07)
3-NO2
3,4-Cl2
2,5-Cl
C18H14N4SO2Cl2 92
18H14N4SO2Cl2 85
84
C19H14N4SO2ClF3 91
C
3g
3h
3i
4-MeO-2- Nitro C19H17SO5N5
2-Cl-5-CF3
4-Me
C
C
19H18 SO2N4
19H18 SO3N4
87
90
85
90
3j
4-Meo
218–223 59.67 4.70 14.64
(59.68) (4.71) (14.65)
202–205 55.47 4.36 17.03
(55.47) (4.37) 17.03
183–185 54.26 3.57 13.30
(54.28) (3.57) (13.30)
3k
3l
2-NO2-4- -Me C19H18 SO4N5
3-CF3 C19H15SO2N4F3
1
IR, H NMR, and mass spectral studies. IR spectrum of compound 3a
showed no absorption band due to −NH2 group; this confirmed the
involment of N-NH2 group in the cyclization. The carbonyl stretching
frequency was observed at 1699 cm−1. The absorption band due to C-N
stretching was observed at 1652 and 1573 cm−1. The absorption band
at 785 cm−1 and 628 cm−1 are due to the presence of chlorine atoms
on the benzene ring of the aryl furan moiety. The aromatic C-H proton
was observed at 3069 cm−1 and t-butyl C-H proton was observed at
2925 cm−1. The characteristic absorption band of the SH group of the
parent triazinone (2) was absent in the IR spectrum of the cyclized
product. Similarly, in compound 3c the carbonyl stretching frequency
appeared at 1697 cm−1. The aromatic C-H, C=N-, and C-F appeared at
1
3066, 1591, 1542, and at 810 cm−1, respectively. The H NMR spectra

1086
D. Jagadeesh Prasad et al.
of compound 3a showed a singlet at δ 1.44 integrating for nine protons,
which were due to t-butyl group. The furan C3-H signal appeared as a
closely spaced doublet at δ 7.58 (J = 4Hz), while the signal due to C4-H
of the furan ring appeared at δ 8.09(J = 4Hz). The aromatic protons of
the trichloro phenyl group were observed as two signets at δ 8.09 and
1
8.20. The H NMR spectra of compound 3c showed a singlet at δ 1.43
integrating for nine protons, which were assigned to t-butyl group. The
furan C3-H signal appeared as a closely spaced doublet at δ 7.25 (J =
3.7Hz), while the signal due to C4-H of the furan ring appeared at δ
7.80(J = 3.7Hz). The aromatic C3 and C6protons appeared as doublet
at δ 7.98, C4 proton appeared as a triplet at δ 7.86, and C5 proton
appeared as triplet at 7.75. The formation of 3a was also confirmed by
recording its mass spectrum. The molecular ion peak m/z appeared at
455, which is in accordance with its molecular formula. Similarly, in
3c the molecular ion peak m/z appeared at 420, thus confirming the
formation of the previously discussed compound.
Antibacterial activity
The newly synthesized compounds (3a–3l) were screened for their an-
tibacterial activities against Escherichia coli (ATTC-25922), Staphylo-
coccus aureus (ATTC-25922) Pseudomonas aeruginosa (ATTC-27853)
and Klebsiella pneumoniae bacterial stains by the disc diffusion
method.20,21 Discs measuring 6.25 mm in diameter were punched from
Whatman no. 1 filter paper. Batches of 100 discs were dispensed to each
screw-capped bottle and sterilized by dry heat at 140◦C for an hour. The
test compounds were prepared with different concentrations such as <
10µg/mL and > 10 µg/mL in N, Ndimethyl formamide. One milliliter
containing 100 times the amount of chemical in each disc was added
to each bottle, which contained 100 discs. The discs of each concen-
tration were placed in triplicate in nutrient agar medium separately
seeded with fresh bacteria. The incubation was carried out at 37◦C for
24 h. Nitrofurazone was used as standard drug at a concentration of 10
µg/mL. Solvent and growth controls and zones of inhibition were noted.
The results of such studies are given in Table II.
The antibacterial results indicated that among the tested com-
pounds, 3b, 3c, 3f, 3g, 3h, 3j, and 3l have shown excellent antibac-
terial activity against E. coli. Compounds 3b, 3g, 3h, 3j, and 3l have
shown excellent activity against S. aureus. Compounds 3b, 3g, 3h, 3j,
3k, and 3l have shown good activity against P. aeruginosa. Compounds
3b, 3c, 3g, 3h, 3j, and 3k have shown excellent antibacterial activity
against K. pneumoniae, and were comparable with the standard drug
active against K. Pneumonia. The antibacterial activity of rest of the

Thiadiazolotriazinone Derivatives
1087
TABLE II Antibacterial Activity Data of Compounds 3a–3l (MIC
Values in µg/mL)
Staphylococcus
aureus
Pseudomonas
aeruginosa
Klebsiella
Pneumoniae
Compound
Escherichia coli
3a
3b
3c
3d
12.5
6.25
6.25
—
—
6.25
—
—
6.25
—
12.5
6.25
6.25
—
—
—
3e
3f
3g
3h
12.5
6.25
6.25
6.25
—
12.5
—
6.25
6.25
—
12.5
12.5
6.25
6.25
—
—
12.5
6.25
6.25
—
3i
3j
3k
3l
6.25
12.5
6.25
6.25
6.5
6.25
6.25
6.25
12.5
6.25
—
6.25
12.5
12.5
6.25
12.5
Nitrofurazone
compounds were comparable with the standard drug. It is noteworthy
to mention that 3d and 3i were not active against any of the four bac-
terial stains used. It was concluded that compounds 3b, 3g, 3h, 3j, and
3l were found to be promising antibacterial agents.
Antifungal Activity
All newly synthesized compounds (3a–3l) were screened for their anti-
fungal activity against Candida Albicans (NICM No. 300), Aspergillus
Fumigatus (NICM No. 902), Aspergillus Flavus (NICM No. 524), and
Trichophyton mentagrophytes (recultured) in DMSO by serial plate di-
lution method.22,23 Sabourands agar media was prepared by dissolving
peptone (1 g), D-glucose (4 g), and agar (2 g) in distilled water (100 mL)
and adjusting the pH to 5.7. Normal saline was used to make suspension
of the spore of fungal strain for lawning. A loopful of particular fungal
stain was transferred to 3 mL saline to get a suspension of correspond-
ing species. Twenty ml of agar media was poured into each Petri dish.
Excess suspension was decanted, and the plates were dried by being
placed in an incubator at 37◦C for 1 h. Using an agar punch, wells were
made on the seeded agar plates, and, < 10µg/mL and >10 µg/mL of the
test compounds in N, N dimethyl formamide were added into each well
labeled. A control also was prepared for the plates in the same way using
solvent DMSO. The Petri dishes were prepared in triplicate and main-
tained at 37◦C for 3–4 days. Antifungal activity was determined by mea-
suring the diameter of the inhibition zone. Activity of each compound

1088
D. Jagadeesh Prasad et al.
TABLE III Antifungal Activity Data of Compounds 3a–3l, (MIC Valves
in µg/mL)
Candida
albicans
Aspergillus
fumigatus
Trichophyton
mentagrophytes
Aspergillus
flavus
Compound
3a
3b
3c
3d
—
12.5
6.25
6.25
—
12.5
6.25
6.25
—
12.5
6.5
6.5
6.25
6.25
—
—
3e
3f
12.5
—
12.5
—
6.25
—
12.5
—
3g
3h
3i
3j
3k
3l
6.25
12.5
—
6.25
6.25
6.25
6.25
6.25
12.5
6.25
6.25
—
6.25
6.25
—
6.25
—
6.25
6.25
—
6.5
6.5
—
12.5
12.5
12.5
12.5
12.5
Fluconazole (standard)
was compared with Fluconazole as standard. The minimum inhibitory
concentration (MIC) for Fluconazole in DMF was in the range 0.01–16
µg/mL against the tested species. Results of screening studies are given
in Table III. Screening studies revealed that compounds 3b, 3c, 3g, 3j,
3k, and 3l have shown excellent antifungal activity against C. albicans.
Compounds 3b, 3c, 3g, 3i, and 3j have shown excellent activity against
A. fumigatus. Compounds 3b, 3c, 3e, 3g, and 3j have shown very good
activity against T. mentagrophytes. Similarly compounds 3b, 3c, 3g, 3h,
and 3k have shown very good activity against A. flavus. The antifungal
activities of the rest of the compounds were comparable with the stan-
dard drug. It was concluded that compounds 3b, 3c, 3g, and 3j were
found to be promising antifungal agents.
All these results are based on preliminary tests; more studies are to
be conducted to get conclusive results.
EXPERIMENTAL SECTION
Melting points were taken in open capillary tubes and are uncor-
rected. The purity of the compounds was confirmed by thin layer chro-
matography using Merk (Darmstadt, Germany) of manufacturer at
first mention. silica gel 60 F254 coated alumina plates. IR spectra were
recorded on a SHIMADZU-FTIR infrared spectrometer in KBr (νmax
1
in cm−1). HNMR spectra were recorded in DMSO-d6 on a amx (400
MHz) Spectrometer using TMS as internal standard. FABMS spectra
were recorded on a JEOL SX 102/DA-6000 mass spectrometer using
argon/Xenon (6 kv, 10 mA) as the FAB gas. Elemental analysis was
recorded on Vario EL, elementar.

Thiadiazolotriazinone Derivatives
1089
Preparation of Substituted aryl furoic acid (1)
A mixture containing substituted aniline (100 mmol), hydrochloric acid
(15%, 60 mL), and water (90 mL), was heated until clear solution was
obtained; it was cooled to O◦, diazotized with aqueous sodium nitrite
(30%, 24 mL), and filtered. To the filtered solution, water (50 mL) and
furoic acid (9.6 g, 100 mmol) were added. Aqueous solution of cupric
chloride (2.5 g in 10 mL of water) was added dropwise and stirred for
4 h at r.t. and kept aside for 16 h. The resulting solid was filtered off,
suspended in water, and purified by steam distillation in the presence of
sodium carbonate to give the corresponding aryl furoic acid. These com-
pounds were then recrystallized from a mixture of dimethyl formamide
and ethanol.
Preparation of 7-[5-(Substituted-aryl)-2-furyl]-3-t-butyl-4(H)-
1,3,4-thiadiazolo (2,3-c)-1,2,4-triazine-4-ones (3)
A mixture of triazinone (1 mmol), substituted aryl furoic acid (1.2
mmol), and phosphorus oxy chloride (5 mL) were refluxed on a wa-
ter bath for about 6 h (Scheme 2). Excess phosphorus oxychloride was
removed under reduced pressure, and the reaction mixture was cooled
and poured onto crushed ice. The solid product was filtered washed
with sodium bicarbonate solution (2%), and followed by distilled wa-
ter. It was dried and recrystalized from a mixture of ethanol and diax-
ane. The characterization data of thiadiazolotriazinones (3) prepared
according to the method is given in Table I.
SCHEME 1 Synthesis of Aryl furoic acids (1).

1090
D. Jagadeesh Prasad et al.
SCHEME 2 Synthesis of 7-substituted-3-t-butyl-4(H)-1,3,4-thiadiazolo(2,3-c)-
1,2,4-triazine-4-one.
3b IR (KBr) ν/cm−1: 1697(C=O str), 1649, 1572(C=N str), 780 and
622 (C-Cl str), 3055(Ar-H str), 2893 (t-butyl C-H str), 1518 (NO2 assy
str) 1345 (NO2Sym str) 1HNMR (DMSO-d6)δ: 1.43 (s, 9H of t-butyl), 7.8
(d, 1H of furan ring), 7.4 (d, 1H of furan ring), 8.8 (d, 1H of phenyl ring),
8.7 (d, 1H of phenyl ring), 8.96 (d, 1H of phenyl ring), MS(m/z,%): 431
(M+.), 403 (M+, 18%), 433 (M+2), 222 (25%), 194 (22%).
3c IR (KBr) ν/cm−1: 1699 (C=O str), 1652 and 1591 (C=N str), 810
(C-F str), 2925(t-butyl C-H str), 3069 (Ar-H str). 1HNMR (DMSO-d6)δ:
1.43(s, 9H, t-butyl), 7.25(d, 1H, furan ring C3, j = 3.7Hz), 7.80 (d, 1H,
furanC4, J = 3.7Hz), 7.98 (d, C3and C4proton of phenyl ring), 7.82–7.86
(t, 1H, C4 of phenylring) 7.7–7.86 (t, 1H, C5of phenyl ring). MS (m/z,
%): 420 (M+.), 392 (M+, 40%), 211(20%), 183 (13), 222 (25%).
3e IR (KBr) ν/cm−1: 1699 (C=O str), 1658 (C=N str), 785 (C-Cl
str), 2890 (t-butyl C-H str), 3028 (Ar-H str). 1HNMR (DMSO-d6)δ: 1.44
(s, 9H, t-butyl), 7.24 (d, 1H of furan ring J = 3.6Hz), 6.91 (d, 1H of furan
ring J = 3.6Hz), 7.33–7.36 (m, 2H 3,4-dichloro phenyl), 7.43 (s, 1H of
phenyl ring ).
3f IR (KBr) ν/cm−1: 1699 (C=O str), 1662 (C=N str), 785 (C-Cl str),
1
2918 (t-butyl C-H str), 3033 (Ar-H str). HNMR (DMSO-d6)δ: 1.40(s,
9H, t-butyl), 7.7(d, 1H of furan ring J = 3Hz), 7.31 (d, 1H of furan ring
J = 3Hz), 7.63 (d, 1H of phenyl ring J = 3.8Mz), 7.38 (d, 1H of phenyl

Thiadiazolotriazinone Derivatives
1091
ring J = 3.8Mz), 7.48 (s, 1H of phenyl ring), MS (m/z,%): 420 (M+.),
422(M+2), 424(M+4), 392 (M+, 47%), 211(24%), 183 (15%).
3g IR (KBr) ν/cm−: 1695 (C=O str), 1648 (C=N str), 753 (C-Cl
str), 2836 (t-butyl C-H str), 3045 (Ar-H str). 1513 (NO2 assy str) 1340
1
(NO2Sym str), HNMR (DMSO-d6)δ: 1.43 (s, 9H, t-butyl), 7.17 (d, 1H
of furan ring J = 3Hz), 6.71(d, 1H of furan ring J = 3Hz), 8.3 (d, 1H
phenyl ring, J = 8.5 Hz), 7.9 (d, 1H Phenyl ring, J = 8.5Hz) 7.6 (d, 1H,
J = 7Hz, phenyl ring, meta coupling), 3.9 (s, 3H, OCH3) MS (m/z, %):
427(M+. ), 399 (M+, 52%), 218(30%), 190 (17%).
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