Synthesis and characterization of 5-heteroarylsulfanyl-4-aryl- 1,2,3-selena/thiadiazoles

Article abstract of DOI:10.1007/s12039-011-0160-x

Synthesis and spectral characterization of 2-methyl-5-[(4-aryl-1,2,3- selenadiazol-5-yl)sulfanyl]-1,3,4-thiadiazoles, 5-[4-aryl-1,2,3-selenadiazol-5- yl]sulfanyl-1-phenyl-1H-1,2,3,4-tetraazoles, 4-aryl-5-[(5-methyl-1,3,4- thiadiazol-2-yl)sulfanyl]-1,2,3-t

Full text of DOI:10.1007/s12039-011-0160-x

c
J. Chem. Sci. Vol. 124, No. 2, March 2012, pp. 463–468. ꢀ Indian Academy of Sciences.
Synthesis and characterization of 5-heteroarylsulfanyl-4-aryl-
1,2,3-selena/thiadiazoles
RAMAIYAN MANIKANNAN, MASILAMANI SHANMUGARAJA,
SEETHARAMAN MANOJVEER and SHANMUGAM MUTHUSUBRAMANIAN∗
Department of Organic Chemistry, Madurai Kamaraj University, Madurai 625021, India
e-mail: muthumanian2001@yahoo.com
MS received 9 May 2011; revised 12 July 2011; accepted 22 July 2011
Abstract. Synthesis and spectral characterization of 2-methyl-5-[(4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl]-
1,3,4-thiadiazoles, 5-[4-aryl-1,2,3-selenadiazol-5-yl]sulfanyl-1-phenyl-1H-1,2,3,4-tetraazoles, 4-aryl-5-[(5-
methyl-1,3,4-thiadiazol-2-yl)sulfanyl]-1,2,3-thiadiazole and 5-[4-aryl-1,2,3-thiadiazol-5-yl]sulfanyl-1-phenyl-
1H-1,2,3,4-tetraazole have been reported.
Keywords. 1,2,3-Selenadiazoles; 1,2,3-thiadiazoles; 5-methyl-1,3,4-thiadiazole; 1-phenyl-1H-tetrazole;
diheteroaryl sulfide.
1. Introduction
cycloheptindoles,18 pyridines19 and 5,7-diphenyl(4-
alkyl)trihydropyran20 have also been investigated. 1,2,
3-Selenadiazoles bearing benzene-sulfonamides at 4-
position have been tested for their antibacterial activity
and most of them showed strong activity against Bacil-
lus cereus and moderate activity against Escherichia
choli.21,22 1,2,3-Selenadiazoles have been effectively
utilized in the synthesis of semiconductor nanoparticles
or nanopowder.23
1,3,4-Thiadiazole derivatives have potent pharmaco-
logical activities like antibacterial,1 antifungal,2 antin-
flammatory,3 herbicidal,4 inhibitory activity,5 analgesic
activity,6 antihistaminic and anticholinergic,7 plant-
growth regulating activity etc.8 Compounds with a
1,2,3-thiadiazole moiety have been found to exhibit
various pharmacological properties like antifungal,9
pesticidal10 and antibacterial activities. 4,5-Bis(p-
methoxyphenyl)-1,2,3-thiadiazole possesses platelet
aggregation inhibitory activity in humans11 and some
1,2,3-thiadiazole derivatives are useful for the therapeu-
tic and prophylactic treatment of viral, bacterial, fungal,
and parasitic infections in humans and animals.12
2. Experimental
2.1 Materials, methods and instruments
Pentamethylene tetrazole is used as a stimulant for
the central nervous system and to counteract the effects
of over dosage of barbiturates.13 Anti-inflammatory
activity is shown by both substituted and unsubstituted
tetrazoles.14 A range of cephalosporin derivatives con-
taining substituted tetrazole rings has been prepared
and found to display antibacterial activity. An active
antilipemic tetrazole molecule has progressed to clin-
ical tests.15 A large number of substituted chromone
derivatives with tetrazole groups located at C-2 and C-3
have been prepared as potential antiallergic agents.
Compounds containing 1,2,3-selenadiazole moieties
are well-known for their pharmacological proper-
ties like antifungal16 and antibacterial activities.17
Antibacterial activities of selenadiazoles fused with
Melting points were determined in open capillaries
and are uncorrected. NMR spectra were recorded on a
Bruker 300 MHz instrument in DMSO-d6/CDCl3 using
TMS as internal standard. Chemical shifts are given
in parts per million (δ-scale) and coupling constants
are given in Hertz. NMR spectra are provided in the
Supporting Information section. Microanalyses were
carried out on a Perkin-Elmer instrument. Column chro-
matography was carried out in silica gel (60–120 mesh)
using pet ether-ethyl acetate as eluent.
2.2 The precursors for the semicarbazones 4a–c
2.2a 1-Phenyl-2-[(1-phenyl-1H-1,2,3,4-tetraazol-5-
yl)sulfanyl]-1-ethanone: 94% yield, m.p. 112◦C, time
∗For correspondence
1
10 min. H NMR (300 MHz, CDCl3): δ 5.10 (s, 2H,
463

464
Ramaiyan Manikannan et al.
-CH2), 7.55–7.67 (m, 8H, -Ar-H), 8.05 (d, J = 7.5 Hz, 157.7, 164.4, 165.0. Anal. Calcd. for C12H13N5OS2: C
2H, -Ar-H); 13C NMR (75 MHz, CDCl3): δ 42.6, 46.89 H 4.26 N 22.78. Found: C 46.98 H 4.36 N 22.86.
123.7, 128.5, 128.9, 129.9, 130.3, 133.4, 134.3, 134.8,
153.5, 192.1. Anal. Calcd. for C15H12N4OS: C 60.79 H
4.08 N 18.91. Found: C 60.91 H 4.16 N 19.02.
2.3b 1-(4-Methylphenyl)-2-[(5-methyl-1,3,4-thiadiazol-
2-yl)sulfanyl]ethylidene-1-hydrazine carboxamide (2b):
1
90% yield, m.p. 125-126◦C, time 1.5 h. H NMR
2.2b 1-(4-Nitrophenyl)-2-[(1-phenyl-1H-1,2,3,4-
(300 MHz, CDCl3): δ 2.39 (s, 3H, -CH3), 2.74 (s,
tetraazol-5-yl)sulfanyl]-1-ethanone: 93% yield, m.p.
3H, -CH3), 4.56 (s, 2H, -CH2), 5.02–6.30 (bs, 2H,
173–174◦C, time 10 min. 1H NMR (300 MHz, DMSO-
-NH2), 7.22 (d, J = 8.1 Hz, 2H, -ArH), 7.57 (d, J =
d6): δ 5.19 (s, 2H, -CH2), 7.67–8.38 (m, 10H, -Ar-H);
8.1 Hz, 2H, -ArH), 10.13 (s, 1H, -NH); 13C NMR
13C NMR (75 MHz, DMSO-d6): δ 41.8, 124.0∗, 130.0,
(75 MHz, CDCl3): δ 15.7, 21.3, 27.1, 125.9, 129.4,
130.6, 133.5, 140.1, 150.2, 153.4, 192.4. Anal. Calcd.
133.0, 139.8, 143.0, 157.7, 164.4, 165.9. Anal. Calcd.
for C15H11N5O3S: C 52.78 H 3.25 N 20.52. Found: C
for C13H15N5OS2: C 48.58 H 4.70 N 21.79. Found: C
52.84 H 3.34 N 20.67.
48.64 H 4.83 N 21.92.
2.2c 1-(4-Chlorophenyl)-2-[(1-phenyl-1H-1,2,3,4-
2.3c 1-(4-Methoxyphenyl)-2-[(5-methyl-1,3,4-thia-
tetraazol-5-yl)sulfanyl]-1-ethanone: 94% yield, m.p.
1
178◦C, time 10 min. H NMR (300 MHz, CDCl3): δ
diazol-2-yl)sulfanyl]ethylidene-1-hydrazinecarboxamide
1
(2c): 91% yield, m.p. 120–121◦C, time 1.5 h. H
5.04 (s, 2H, -CH2), 7.50 (d, J = 8.4 Hz, 2H, -Ar-H),
7.56–7.63 (m, 5H, -Ar-H), 8.00 (d, J = 8.7 Hz, 2H,
-Ar-H); 13C NMR (75 MHz, CDCl3): δ 42.3, 123.8,
129.4, 129.9, 130.0, 130.3, 133.2, 133.4, 140.9, 153.3,
191.0. Anal. Calcd. for C15H11ClN4OS: C 54.46 H 3.35
N 16.94. Found: C 54.58 H 3.43 N 17.02, are new and
have been prepared by the methods adopted for the
other ketones.
NMR (300 MHz, CDCl3): δ 2.73 (s, 3H, -CH3), 3.85
(s, 3H, -OCH3), 4.55 (s, 2H, -CH2), 5.10–6.40 (bs, 2H,
NH2), 6.92 (d, J = 8.7 Hz, 2H, -ArH), 7.64 (d, J =
8.7 Hz, 2H, -ArH), 10.05 (s, 1H, -NH); 13C NMR
(75 MHz, CDCl3): δ 15.7, 27.2, 55.3, 114.0, 127.5,
128.3, 142.7, 157.7, 160.8, 164.4, 165.9. Anal. Calcd.
for C13H15N5O2S2: C 46.27 H 4.48 N 20.76. Found: C
46.38 H 4.54 N 20.87.
2.3 General procedure for the preparation
of semicarbazones 2a–f and 4a–c
2.3d 1-(4-Chlorophenyl)-2-[(5-methyl-1,3,4-thia-
diazol-2-yl)sulfanyl]ethylidene-1-hydrazinecarboxamide
To a warm ethanolic solution of 2-(5-methyl-1,3,4-thia-
diazolesulfanyl)-1-aryl-1-ethanone/1-aryl-2-[(1-phenyl-1H-
1,2,3,4-tetraazol-5-yl)sulfanyl]-1-ethanone (0.005 mol),
aqueous solution of semicarbazide hydrochloride
(0.035 mol) and sodium acetate (0.035 mol) was added
carefully avoiding turbidity formation. The reaction
mixture was refluxed for 1.5–2 h, poured onto crushed
ice and filtered. Semicarbazones 2 were crystallized
from ethanol and semicarbazones 4, obtained as vis-
cous liquid, have not been characterized due to their
poor solubility in NMR solvents and used as such for
next stage.
1
(2d): 94% yiled, m.p. 148–149◦C, time 1.5 h. H
NMR (300 MHz, CDCl3): δ 2.72 (s, 3H,-CH3), 4.57
(s, 2H, -CH2), 5.12–6.40 (bs, 2H, -NH2), 7.36 (d, J =
8.4 Hz, 2H, -ArH), 7.62 (d, J = 8.4 Hz, 2H, -ArH),
10.29 (s, 1H, -NH); 13C NMR (75 MHz, CDCl3): δ
15.7, 27.3, 127.3, 128.8, 134.4, 135.4, 141.7, 157.7,
165.0, 166.1. Anal. Calcd. for C12H12ClN5OS2: C 42.16
H 3.54 N 20.49. Found: C 42.24 H 3.62 N 20.56.
2.3e 2-[(5-Methyl-1,3,4-thiadiazol-2-yl)sulfanyl]-1-
(4-nitrophenyl)ethylidene]-1-hydrazine carboxamide
(2e): 97% yield, m.p. 110–111◦C, time 1.5 h. H
1
2.3a 2-[(5-Methyl-1,3,4-thiadiazol-2-yl)sulfanyl]-1-
NMR (300 MHz, CDCl3): δ 2.74 (s, 3H, -CH3), 4.62
(s, 2H, -CH2), 5.12–6.40 (bs, 2H, -NH2), 7.87 (d, J =
9.0 Hz, 2H, -Ar-H), 8.27 (d, J = 9.0 Hz, 2H, -Ar-H);
10.55 (s, 1H, -NH); 13C NMR (75 MHz, CDCl3): δ
15.8, 27.4, 123.9, 126.7, 129.8, 130.1, 142.1, 157.9,
159.7, 160.3. Anal. Calcd. for C12H12N6O3S2: C 40.90
H 3.43 N 23.85. Found: C 40.98 H 3.52 N 23.94.
phenylethylidene-1-hydrazine
carboxamide
(2a):
1
90% yield, m.p. 115–116◦C, time 1.5 h. H NMR
(300 MHz, CDCl3): δ 2.71 (s, 3H, -CH3), 4.57 (s,
2H, -CH2), 5.02–6.30 (bs, 2H, NH2), 7.26–7.68 (m,
5H, -ArH), 10.21 (s, 1H, -NH); 13C NMR (75 MHz,
CDCl3): δ 15.7, 27.3, 127.3, 128.6, 129.5, 135.8, 142.7,

5-Heteroarylthio-4-aryl-1,2,3-selena/thiadiazoles
465
2.3f 2-[(5-Methyl-1,3,4-thiadiazol-2-yl)sulfanyl]-1-(2- 130.6, 140.6, 158.3, 159.8, 160.3, 167.8. Anal. Calcd.
naphthyl)ethylidene]-1-hydrazine carboxamide (2f): for C12H10N4OS2Se: C 39.02 H 2.73 N 15.17. Found:
93% yield, m.p. 132–133◦C, time 2 h. 1H NMR C 39.11 H 2.82 N 15.25.
(300 MHz, CDCl3): δ 2.72 (s, 3H, -CH3), 4.69 (s, 2H,
-CH2), 5.12–6.40 (bs, 2H, -NH2), 7.52–8.08 (m, 6H, -
Ar-H), 10.26 (s, 2H, -ArH, -NH); 13C NMR (75 MHz,
CDCl3): δ 15.6, 27.1, 123.2, 125.7, 126.6, 127.8, 128.4,
128.7, 129.7, 132.3, 131.1, 133.6, 142.7, 164.3, 165.4,
166.0. Anal. Calcd. for C16H15N5OS2: C 53.76 H 4.23
N 19.59. Found: C 53.87 H 4.32 N 19.67.
2.4d 2-[4-(4-Chlorophenyl)-1,2,3-selenadiazol-5-
yl]sulfanyl-5-methyl-1,3,4-thiadiazole (3d): 69% yield,
1
m.p. 145–146◦C. H NMR (300 MHz, CDCl3): δ 2.86
(s, 3H, -CH3), 7.56 (d, J = 8.3 Hz, 2H, -Ar-H), 7.83
(d, J = 8.3 Hz, 2H, -Ar-H); 13C NMR (75 MHz,
CDCl3): δ 16.1, 129.2, 129.4, 131.2, 141.8, 158.6,
159.3, 163.0, 167.8. Anal. Calcd. for C11H7ClN4S2Se:
C 35.35 H 1.89 N 14.99. Found: C 35.46 H 1.96 N
15.09.
2.4 General procedure for the preparation
of 1,2,3-selenadiazole derivatives 3a–f and 5a–b
A solution of (0.001 mol) of the appropriate semicar-
bazones 2 or 4 was dissolved in dry THF by gentle 2.4e 2-Methyl-5-[4-(4-nitrophenyl)-1,2,3-selena-
warming and (0.005 mol) of powdered selenium diox- diazol-5-yl]sulfanyl-1,3,4-thiadiazole (3e): 79% yield,
1
ide was added by portion. The reaction mixture was m.p. 125–126◦C. H NMR (300 MHz, CDCl3): δ 2.86
heated to reflux on a water bath for an hour. The (s, 3H, -CH3), 8.12 (d, J = 8.9 Hz, 2H, -Ar-H), 8.43
selenium deposited on cooling was removed by filtra- (d, J = 8.9 Hz, 2H, -Ar-H); 13C NMR (75 MHz,
tion and the filtrate was poured into crushed ice and CDCl3): δ 16.0, 129.0, 129.2, 129.3, 131.7, 141.7,
extracted with chloroform. The product was obtained 158.3, 159.6, 167.9. Anal. Calcd. for C11H7N5O2S2Se:
upon purification by column chromatography using C 34.38 H 1.84 N 18.22. Found: C 34.46 H 1.91 N
silica gel (60–120 mesh).
18.33.
2.4a 2-Methyl-5-[(4-phenyl-1,2,3-selenadiazol-5-
2.4f 2-Methyl-5-[4-(2-naphthyl)-1,2,3-selenadiazol-
yl)sulfanyl]-1,3,4-thiadiazole (3a): 74% yield, m.p. 5-yl]sulfanyl-1,3,4-thiadiazole (3f): 76% yield, m.p.
1
1
130–131◦C. H NMR (300 MHz, CDCl3): δ 2.82 (s, 140–141◦C, time 1 h. H NMR (300 MHz, CDCl3): δ
3H, -CH3), 7.60 (m, 3H, -Ar-H), 7.84 (d, J = 7.5 Hz, 2.82 (s, 3H, -CH3), 7.52–8.31 (m, 9H, -Ar-H), 8.59
2H, -Ar-H); 13C NMR (75 MHz, CDCl3): δ 16.0, (s, 1H, -Ar-H); 13C NMR (75 MHz, CDCl3): δ 16.0,
129.1, 129.2, 129.3, 131.7, 142.1, 158.4, 159.2, 167.9. 126.5, 126.7, 127.1, 127.8, 128.4, 128.8, 129.2, 130.7,
Anal. Calcd. for C11H8N4S2Se: C 38.94 H 2.38 N 133.1, 133.4, 142.0, 158.3, 159.6, 167.9. Anal. Calcd.
16.51. Found: C 39.05 H 2.48 N 16.65.
for C15H10N4S2Se: C 46.27 H 2.59 N 14.39. Found: C
46.34 H 2.65 N 14.45.
2.4b 2-Methyl-5-[4-(4-methylphenyl)-1,2,3-selena-
diazol-5-yl]sulfanyl-1,3,4-thiadiazole (3b): 70% yield,
2.4g 5-[4-Phenyl-1,2,3-selenadiazol-5-yl]sulfanyl-1-
phenyl-1H-1,2,3,4-tetraazole (5a): 65% yield, m.p.
1
m.p. 131–132◦C. H NMR (300 MHz, CDCl3): δ 2.45
1
152–153◦C. H NMR (300 MHz, CDCl3): δ 7.32–7.70
(s, 3H, -CH3), 2.81 (s, 3H, -CH3), 7.36 (d, J = 8.0 Hz,
2H, -Ar-H), 7.72 (d, J = 8.0 Hz, 2H, -Ar-H); 13C
NMR (75 MHz, CDCl3): δ 16.0, 21.4, 128.8, 129.1,
129.6, 139.4, 141.2, 158.5, 159.7, 167.8. Anal. Calcd.
for C12H10N4S2Se: C 40.79 H 2.85 N 15.86. Found: C
40.86 H 2.92 N 15.92.
(m, 10H, -Ar-H); 13C NMR (75 MHz, CDCl3): δ 123.9,
129.0, 129.2, 129.5, 129.8, 130.2, 131.1, 132.7, 140.3,
150.2, 159.4. Anal. Calcd. for C15H10N6SSe: C 46.76
H 2.62 N 21.81. Found: C 46.87 H 2.78 N 21.94.
2.4h 5-[4-(4-Nitrophenyl)-1,2,3-selenadiazol-5-yl]
sulfanyl-1-phenyl-1H-1,2,3,4-tetraazole (5b): 57%
2.4c 2-[4-(4-Methoxyphenyl)-1,2,3-selenadiazol-5-
yl]sulfanyl-5-methyl-1,3,4-thiadiazole (3c): 72% yield,
1
yield, m.p. 155–156◦C, time 1 h. H NMR (300 MHz,
1
m.p. 135–136◦C. H NMR (300 MHz, CDCl3): δ 2.69
DMSO-d6): δ 7.52–7.56 (m, 5H, -Ar-H), 7.92 (d, J =
8.6 Hz, 2H, -Ar-H), 8.26 (d, J = 8.6 Hz, 2H, -Ar-H);
13C NMR (75 MHz, DMSO-d6): δ 124.7, 125.4, 130.7,
130.9, 131.8, 132.2, 135.3, 146.4, 148.1, 159.8, 170.3.
(s, 3H, -CH3), 3.77 (s, 3H, -OCH3), 6.96 (d, J =
8.9 Hz, 2H, -Ar-H), 7.66 (d, J = 8.9 Hz, 2H, -Ar-H);
13C NMR (75 MHz, CDCl3): δ 16.0, 55.4, 114.3, 124.1,

466
Ramaiyan Manikannan et al.
Anal. Calcd. for C15H9N7O2SSe: C 41.87 H 2.11 N 136.1, 149.8, 159.8. Anal. Calcd. for C15H9ClN6S2: C
22.79. Found: C 41.99 H 2.18 N 22.84.
48.32 H 2.43 N 22.54. Found: C 48.41 H 2.48 N 22.64.
2.5 General procedure for the preparation
of 1,2,3-thiadiazole derivatives, 3g and 5c
3. Results and discussion
Heterocyclic compounds like 1,2,3- and 1,3,4-
thiadiazoles, tetarazole and 1,2,3-selenadiazole may
assume more importance, if we link any two of
these heterocyclic nuclei by a sulfur atom. The work
described in this article deals with the synthesis of
such type of compounds. Selenadiazole nuclei24–27 can
be generated from semicarbozones with α-methylene
hydrogen by the reaction with selenium dioxide.
Accordingly, appropriate semicarbazones have been
synthesized to generate new selenadiazole ring. The
semicarbazones 2/4 planned for this synthetic sequence
can be obtained from the ketone 1.28,29 The ketone 1
in turn can be prepared from appropriately substituted
phenacyl bromide and 2-mercapto-5-methyl-1,3,4-
thiadiazole/1-phenyl-1H- tetrazole-5-thiol in presence
of triethylamine. The substituted phenacyl bromides
have been prepared by the reaction of the corresponding
acetophenone with bromine in dry ether.
The semicarbazones 2/4 with α-methylene hydro-
gens when treated with selenium dioxide undergoes
oxidative cyclization to give 1,2,3-selenadiazole. The
reaction is very much facile in acetic acid, tetrahy-
drofuran or ethanol. In the present case, we employed
tetrahydrofuran as the solvent of choice. The semicar-
bazone and selenium dioxide was taken in tetrahydro-
furan and heated on a water bath, the ratio of semi-
carbazone and selenium dioxide taken being 1:5. Upon
heating for one hour, the reaction goes for completion
Appropriate semicarbazone of 0.01 mol was added by
portion to 10 ml of thionyl chloride while cooling to
−5◦C with a freezing mixture. The reaction mixture was
allowed to stir for about 2 h. The excess of thionyl chlo-
ride was decomposed using aqueous solution of sodium
carbonate and extracted with chloroform. The product
was obtained on purification by column chromatogra-
phy using silica gel (60–120 mesh).
2.5a 4-(4-Chlorophenyl)-5-[(5-methyl-1,3,4-thiadiazol-
2-yl)sulfanyl]-1,2,3-thiadiazole (3g): 65% yield, vis-
1
cous oil, time 1 h. H NMR (300 MHz, CDCl3): δ
2.82 (s, 3H, -CH3), 7.54 (d, J = 8.4 Hz, 2H, -Ar-H),
7.89 (d, J = 8.4 Hz, 2H, -Ar-H); 13C NMR (75 MHz,
CDCl3): δ 15.9, 128.5, 129.3∗, 130.2, 136.0, 138.6,
159.5, 168.1 (∗One carbon merged with other). Anal.
Calcd. for C11H7ClN4S3: C 40.42 H 2.16 N 17.14.
Found: C 40.53 H 2.24 N 17.23.
2.5b 5-[4-(4-Chlorophenyl)-1,2,3-thiadiazol-5-yl]
sulfanyl-1-phenyl-1H-1,2,3,4-tetraazole (5c): 69%
1
yield, m.p. 92–93◦C, time 2 h. H NMR (300 MHz,
CDCl3): δ 7.44–7.63 (m, 7H, -Ar-H), 7.34 (d, J =
8.7 Hz, 2H, -Ar-H); 13C NMR (75 MHz, CDCl3): δ
124.0, 127.9, 129.3, 129.6, 130.2, 131.1, 132.6, 135.2,
CH3
H2N
N
O
SeO2,THF,reflux/
SOCl2,-5 oC
N
NH
S
N
X
N
N
S
S
S
R
CH3
N
N
R
3
2
3a : R=Phenyl;X=Se
2a : R=Phenyl
2b : R=4-Methylphenyl
2c : R=4-Methoxyphenyl
2d : R=4-Chlorophenyl
2e : R=4-Nitrophenyl
2f : R=2-Naphthyl
3b : R=4-Methylphenyl;X=Se
3c : R=4-Methoxyphenyl;X=Se
3d : R=4-Chlorophenyl;X=Se
3e : R=4-Nitrophenyl;X=Se
3f : R=2-Naphthyl;X=Se
3g : R=4-Chlorophenyl;X=S
Scheme 1. Synthesis of 1,2,3-selena/thiadiazoles derivatives, 3.

5-Heteroarylthio-4-aryl-1,2,3-selena/thiadiazoles
467
N
H2N
N
O
N
N
SeO2, THF, reflux/
N
NH
X
SOCl2, -5 oC
N
N
S
S
N
N
N
N
R
4
5
4a : R = H
4b : R = NO2
4c : R = Cl
R
5a : R = H; X = Se
5b : R = NO2; X = Se
5c : R = Cl; X = S
Scheme 2. Synthesis of 1,2,3-selena/thiadiazoles derivatives, 5.
giving good yield of resultant selenadiazole 3a–f and
5a–b. (schemes 1 and 2).
After successfully generating selenadiazole
rings attached to the 2-mercapto-5-methyl-1,3,4-
The structure of the synthesized selenadiazole has thiadiazole/1-phenyl-1H- tetrazole-5-thiol, we plan
1
1
been confirmed by H and 13C NMR spectra. The H to prepare representative thiadiazole ring connected
NMR spectrum of 3c has four signals, two doublets and to tetrazole/thiadiazole with sulfur atom, as semi-
two singlets at 7.66, 6.96, 3.77 and 2.69 ppm respec- carbazones can also be subjected to cyclisation with
tively. The former two signals account for two hydro- thionyl chloride to give thiadiazole. The semicar-
gens each, while the latter two signals account for three bazones 2d and 4c were then treated with excess
hydrogens each. In the 13C NMR spectrum, the sig- thionyl chloride at low temperature to give consider-
nal for the methyl carbon appears at 16.0 ppm, the sig- able yield of final products 3g and 5c. Compounds 3g
1
nal for methoxy carbon appears at 55.4 ppm and the and 5c have been identified as the thiadiazole by H
methine carbons of the anisyl ring appear at 114.3 and and 13C NMR spectra.
130.6 ppm. The quaternary carbons appear at 124.1,
140.6, 158.3, 159.8, 160.3 and 167.8 ppm. The HMBC
spectrum helps to assign the different quaternary car-
4. Conclusion
bons. The methyl hydrogens at 2.69 ppm has HMBC
The synthesis of compounds in which two five-
contour with carbon at 167.8 ppm confirming this car-
membered heterocyclic compounds — each of them
bon to be the 5th carbon of the thiadiazole ring. The
having at least three heteroatoms — are connected by a
methoxy hydrogens at 3.77 ppm gives HMBC contour
sulfur atom has been described.
with the carbon at 160.3 ppm helping to assign this car-
bon as the carbon ipso to methoxy. This carbon has
HMBC contour with the hydrogens at 7.66 ppm also.
Supplementary information
These hydrogen are the hydrogens meta to methoxy.
The NMR spectra of the synthesized compounds are
These hydrogens give HMBC contour with carbon
provided in the supporting information and can be
found at www.ias.ac.in/chemsci.
159.8 ppm and hence this carbon should be the car-
bon adjacent to nitrogen in the selenadiazole ring. The
carbon para to methoxy can be easily assigned from
the fact that the doublet at 6.96 ppm gives a contour
Acknowledgement
with the quaternary carbon at 124.1 ppm. The remain-
ing two quaternary carbons are to be assigned between
the carbons ipso to the sulfide ring.
The authors thank the Department of Science and Tech-
nology (DST), New Delhi for the support under IRPHA
for NMR facility.

468
Ramaiyan Manikannan et al.
15. Nash D T, Gross L, Haw W and Agre K 1968 Clin.
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