Benzenesulfonamide bearing imidazothiadiazole and thiazolotriazole scaffolds as potent tumor associated human carbonic anhydrase IX and XII inhibitors

Article abstract of DOI:10.1016/j.bmc.2016.12.047

Two series of 20 novel heterocyclic compounds, imidazothiadiazoles (3a-3j) and thiazolotriazoles (4a-4j) bearing benzenesulfonamide moiety were synthesized in order to investigate the inhibition potential of both scaffolds against four selected human carbonic anhydrase isoforms (hCA I, II, IX & XII). Against human isoform hCA I, compounds 3j, 4a-4c, and 4j showed better inhibition potential (K_i?

Full text of DOI:10.1016/j.bmc.2016.12.047

Accepted Manuscript
Benzenesulfonamide bearing imidazothiadiazole and thiazolotriazole scaffolds
as potent tumor associated human carbonic anhydrase IX and XII inhibitors
Rajiv Kumar, Silvia Bua, Sita Ram, Sonia Del Prete, Clemente Capasso, Claudiu
T. Supuran, Pawan K. Sharma
PII:
S0968-0896(16)31297-4
DOI:
http://dx.doi.org/10.1016/j.bmc.2016.12.047
BMC 13474
Reference:
Bioorganic & Medicinal Chemistry
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Revised Date:
Accepted Date:
26 November 2016
25 December 2016
27 December 2016
Please cite this article as: Kumar, R., Bua, S., Ram, S., Del Prete, S., Capasso, C., Supuran, C.T., Sharma, P.K.,
Benzenesulfonamide bearing imidazothiadiazole and thiazolotriazole scaffolds as potent tumor associated human
carbonic anhydrase IX and XII inhibitors, Bioorganic & Medicinal Chemistry (2016), doi: http://dx.doi.org/10.1016/
j.bmc.2016.12.047
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Benzenesulfonamide bearing imidazothiadiazole and
thiazolotriazole scaffolds as potent tumor associated human
carbonic anhydrase IX and XII inhibitors
Rajiv Kumara, Silvia Buab, Sita Rama, Sonia Del Preteb,c, Clemente Capassoc, Claudiu T.
Supuranb*, Pawan K. Sharmaa*
aDepartment of Chemistry, Kurukshetra University, Kurukshetra-136119, India.
bUniversità degli Studi di Firenze, Laboratorio di Chimica Bioinorganica, Rm 188, and
Neurofarba Department, Sezione di Scienze Farmaceutiche, Via U. Schiff 6, I-50019 Sesto
Fiorentino (Firenze), Italy.
cIstituto di Bioscienze e Biorisorse, CNR, Via PietroCastellino111- 80131, Napoli, Italy.
Abstract
Two series of 20 novel heterocyclic compounds, imidazothiadiazoles (3a-3j) and
thiazolotriazoles (4a-4j) bearing benzenesulfonamide moiety were synthesized in order to
investigate the inhibition potential of both scaffolds against four selected human carbonic
anhydrase isoforms (hCA I, II, IX & XII). Against human isoform hCA I, compounds 3j, 4a-4c,
and 4j showed better inhibition potential (Ki < 100 nM) than the standard drug acetazolamide
(AZA). Against hCA II, all the compounds showed moderate inhibition with the exception of 3a
which showed nearly two fold better profile compared to AZA. Against hCA IX, all the
compounds showed moderate inhibitory potential than AZA, whereas against hCA XII,
compounds 3a-3c showed better inhibitory potential compared to AZA.
Keywords: imidazothiadiazoles; thiazolotriazoles; benzenesulfonamide; carbonic anhydrase
isoforms I, II, IX, XII; acetazolamide.
______
*Corresponding authors: Tel.: +91 9416457355; Fax: +91 1744 238277; e-
mail:pksharma@kuk.ac.in (PKS); Tel/Fax: +39-055-4573005, e-mail: claudiu.supuran@unifi.it
(CTS).
1

1. Introduction
Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread metalloenzymes which catalyze the
reversible hydration-dehydration of carbon dioxide and bicarbonate ions in organisms all over
the phylogenetic tree, including higher vertebrates and humans.1,2 Out of seven unrelated CA
gene families known to date (α, β, γ, δ, ζ, η and ɵ-CAs),3,4 the α family is the only class present
in mammals and comprises sixteen different human carbonic anhydrase (hCA) isoforms: hCA I,
II, III, VII and XIII (cytosolic isoforms), hCA IV, IX, XII and XIV (membrane bound isoforms),
hCA VA and VB (mitochondrial isoforms) and hCA VI (secreted isoform in saliva and milk).5
CA isoenzymes play crucial role in essential cellular processes such as pH regulation, secretion
of electrolytes, tumorigenicity, respiration and biosynthetic reactions that require CO2 and
–
HCO3 as substrates (e.g., lipogenesis, glucogenesis and ureagenesis) and many other processes.6
Besides the large number of physiological functions, hCA I and hCA II are targets for diseases
such as glaucoma, epilepsy, altitude sickness, etc.7 For the treatment/imaging of tumors, hCA IX
and hCA XII are drug targets as they are overexpressed in many cancers and influence processes
that promote cell proliferation, invasion or metastasis.1-3
A large number of sulfonamide based carbonic anhydrase inhibitor (CAI) drugs like
acetazolamide (AZA), methazolamide (MZA), ethoxzolamide (EZA), dorzolamide (DZA) (Fig.
1) are in clinical use for more than 70 years as diuretics, antiglaucoma, anticonvulsant or
,8,9
antiinfective drugs.1
Fused heterocyclic systems with S and N as heteroatoms have gained much importance in
the field of medicinal chemistry because of their broad spectrum of biological activities.10-24 The
anti-tumor potential of the 2-amino-1,3,4-thiadiazole skeleton is known25 for long and further its
fused derivatives with imidazo[2,1-b] ring system has resulted in compounds exhbiting potential
anticancer10, antitubercular11, antibacterial12, antifungal13, anticonvulsant, anti-inflammatory14,
and antisecretory15 activities. Consequently, a large number of imidazo[2,1-b][1,3,4]thiadiazole
derivatives have been reported to possess antitumor property.16-18 Also thiazolotriazoles are
known to exhibit a broad spectrum of biological activities such as antimicrobial19, analgesic,
anti-inflammatory20-22 , antipyretic22, anticancer16, vasodilatory23 etc. Imidazothiadiazole
derivative 124 and thiazolotriazole derivative 215 (Figure 1) have recently been reported to posses
2

anticancer activity. Motivated by these findings and continuing our interest in the design of
various classes of heterocyclic based CAIs, 26 - 32 we envisioned to synthesize two series of
Imidazothiadiazole (3a-3j) and thiazolotriazole (4a-4j) scaffolds bearing benzenesulfonamide
moiety and evaluated them for CA inhibition potential against hCA I, II, IX and XII.
O
O
N N
S
N
S
N
N
SO2NH2
SO2NH2
NH
N
SO2NH2
S
O
AZA
MZA
EZA
NHEt
F
SO2NH2
NH
F
H
SO2NH2
N
Cl
N
N
S
S
N
S
O
O
Me
S
O
O
DZA
IND
1
H2NO2S
R
R
N
S
N
N
N
N
Cl
O
N
N
S
N
N
H2NO2S
S
3a-3j
4a-4j
2
Figure 1.
2. Results and discussion
2.1. Chemistry
The synthetic routes followed to synthesize the differently substituted aryl derivatives of 4-
(imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3a-3j) and 4-(thiazolo[3,2-
b][1,2,4]triazol-2-yl)benzenesulfonamide (4a-4j) are depicted in Scheme 1. 4-(5-Amino-1,3,4-
thiadiazol-2-yl)benzenesulfonamide (7) was the key intermediate for achieving the synthesis of
aryl derivatives of 4-(imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide 3a-3j, that was
prepared by oxidation of readily available p-toluenesulfonamide (5) with KMnO4 under aqueous
conditions followed by condensation of resulting 4-sulfamoylbenzoic acid (6) with
thiosemicarbazide in the presence of phosphoroxychloride. Finally, target compounds 3a-3j were
obtained by cyclization of 7 with differently substituted phenacyl bromides by refluxing in
ethanol under anhydrous conditions (Scheme 1). The structures of newly synthesized target
3

1
13
compounds were elucidated through rigorous analysis of their spectral data (IR, H NMR, C
NMR and HRMS). In 1H-NMR, compounds 3a-3j showed a characteristic singlet around δ 8.84-
9.10 for proton of the imidazothiazole ring while free SO2NH2 group resonated around δ 7.59-
7.60 as singlet integrating for two protons.
Me
COOH
N
N
R
(i)
(ii)
(iii)
N
N
NH2
S
N
S
SO2NH2
SO2NH2
H2NO2S
H2NO2S
3a-3j
5
6
7
Me
CONHNH2
NH
N
O
(i), (iv), (v)
H
N
S
(vi)
(vii)
NH2
N
N
H
H
S
H2NO2S
SO2NH2
SO2NH2
H2NO2S
5
8
9
10
(viii)
R
(ix)
R
N
N
N
N
S
O
N
S
H
N
H2NO2S
H2NO2S
4a-4j
11a-11j
3,4,11
a
b
c
d
e
f
g
h
i
J
R
4-H
4-CH3
4-OCH3 4-NO2 3-NO2
4-F
4-Cl 4-Br 3-Br 4-Ph
Scheme 1. Reagents and conditions: (i) KMnO4, H2O, reflux; (ii) NH2NHCSNH2, POCl3, 85o C (iii) ArCOCH2Br,
EtOH, reflux; (iv) MeOH, H+, reflux; (v) NH2NH2.H2O, MeOH, reflux; (vi) KSCN, H+; (vii) NaOH, reflux; (viii)
ArCOCH2Br, MeOH, KOH, reflux; (ix) Conc. H2SO4
4-(5-Thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)benzenesulfonamide (10) was the key precursor
for the synthesis of thiazolotriazoles 4a-4j and was prepared by cyclization of thiourea
4

derivative 9 under reflux conditions in alkaline medium. Thiourea 9 was in turn prepared by
reaction of 4-aminosulfonyl benzoic acid hydrazide (8) with potassium thiocyanate in acidic
conditions33. Acid hydrazide 8 was prepared following an earlier reported methodology.28 5-
Thioxotriazole 10 thus obtained was then reacted with differently substituted phenacyl bromides
under alkaline conditions to give 11a-11j which upon cyclization with concentrated sulfuric acid
1
gave the envisioned target thiazolotriazoles 4a-4j (Scheme 1). In H-NMR, compounds 11a-11j
exhibited a singlet for two protons of CH2 at around δ 4.90. Cyclization of 11 to compounds 4a-
4j was confirmed by disappearance of signal for CH2 protons in the 1H NMR and appearance of
a singlet around δ 7.94-8.57 for thiazolotriazole ring proton. Free SO2NH2 protons of 11a-11j
and 4a-4j resonated in the range of 7.44-7.46.
2.2. CA inhibition
All the newly synthesized aryl derivatives of 4-(imidazo[2,1-b][1,3,4]thiadiazol-2-
yl)benzenesulfonamide 3a-3j and aryl derivatives of 4-(thiazolo[3,2-b][1,2,4]triazol-2-
yl)benzenesulfonamide 4a-4j were evaluated against cytosolic isoenzymes hCA I, hCA II and
membrane bound isoenzymes hCA IX, hCA XII for their CA inhibition potential by using
34
stopped-flow CO2 hydrase assay method
and the results are presented in Table 1.
Acetazolamide (AZA) was the reference drug chosen for the assay.
(i)
All newly prepared compounds 3a-3j and 4a-4j were found to be moderate inhibitors of
the cytosolic isoform hCA I with inhibition constant (Ki) in the range of 17.9-9665 nM.
Comparison of the results of hCA I inhibition of test compounds with the reference drug
AZA reveals that compounds 3b, 3f, 3j, 4a-4c, 4e and 4j were found to be better
inhibitors of hCA I than AZA. Comparison of series 3a-3j and 4a-4j shows that most of
the compounds of series 4a-4j namely 4a-4c, 4e and 4j show hCA I inhibition potential
(Ki≤ 97.5 nM) much better than all the compounds of series 3a-3j (Table 1). Overall,
nearly all the compounds of the first series 3a-3i and many of second series were found to
be poor inhibitors of hCA I as compared to AZA which is off target for designing
antitumor drugs with reduced side effects.
(ii)
All the tested compounds except 3a showed low activity against ubiquitous,
housekeeping isoform hCA II as compared to AZA which is a valuable property while
designing the compounds inhibiting only hCA IX and XII over hCA I and II. General
5

comparison of inhibiting potency of series 3a-3j and 4a-4j showed that compounds of
series 4a-4j were better inhibitors of hCA II as compared to compounds of series 3a-3j.
Compounds 4a-4c, 4e and 4j showed inhibiting potential (Ki ≤ 22.3 nM) comparable to
AZA (25.3 nM) against hCA II (Table 1).
(iii)
(iv)
The inhibition potential of newly synthesized imidazothiadiazoles 3a-3j and
thiazolotriazoles 4a-4j against hCA IX was not satisfactory as all the twenty compounds
(3a-3j and 4a-4j) were less effective as hCA IX inhibitors with Ki value ≥ 85.1 nM as
compared to AZA (Table 1).
The tested compounds, in general, showed better inhibitory profile against hCA XII than
hCA IX and the compounds 3a, 3b and 3c were better inhibitors of hCA XII as compared
to AZA with Ki value ≤ 4.1 nM. In general, imidazolothiadiazoles 3a-3j were good
inhibitors of tumor associated hCA XII (Ki ≤ 84.8 nM) as compared to thiazolotriazoles
4a-4j with Ki values in range of 22.3-359 nM.
(v)
Selectivity for inhibition of tumor associated isoforms (hCA IX and XII) over cytosolic
isoforms (hCA I and II) is prerequisite for CA inhibitors to act as potential antitumor
drug with minimum side effect. Selectivity ratio for desired inhibition has also been
presented in Table 1. It is evident that the compounds did not show a consistent
behaviour in their inhibitory properties against all the four tested isoforms (hCA I, II, IX
and XII). However, in terms of SAR, in the broader sense some compounds (4d, 4f, 4g
and 4h) in which electron withdrawing groups are present at position-4 of aromatic ring
attached to 6-position of thiazolotriazole scaffold, have shown better selectivity for hCA
IX and XII over hCA I and II. Moreover the selectivity profile seems to be better for
compounds containing electron withdrawing groups at position-4 as compared to
position-3. As the CA inhibition activity of these compounds is moderate,
aforementioned compounds can be helpful in designing isoform selective inhibitors with
enhanced activity after conducting suitable structural variations. It is also observed that
compounds 3a-3c showed better inhibition for hCA XII over cytosolic isoforms hCA I
and hCA II (Table 1).
Table 1
6

Inhibitory potency data against isoforms hCA I, II, IX and XII along with selectivity ratio for inhibition of
isoforms hCA IX and XII over hCA I and II for compounds 3a-3j and 4a-4j.
Compounds
R
Ki (nM)a
hCA I
318
selectivity ratio
hCA II hCA IX hCA XII
I/IX
1.53
0.88
0.30
0.94
2.97
1.60
0.41
0.68
1.10
0.25
0.07
0.94
0.57
II/IX
0.04
0.87
0.29
1.21
1.59
0.41
0.20
0.74
0.27
2.57
0.07
0.23
0.10
I/XII
77.56
73.64
II/XII
1.78
3a
3b
3c
3d
3e
3f
4-H
7.3
240
208
275
2830
306
172
136
1210
918
251
143
262
85.1
147
189
203
237
1680
172
1090
4.1
3.3
4-CH3
4-OCH3
4-NO2
3-NO2
4-F
243
72.73
849
830
3.8
223.42 218.42
287
369
48.1
50.4
79.4
80.1
84.8
75.6
62.1
147
23.8
22.3
35.1
362
359
26.7
302
41.4
5.97
10.12
2.75
6.24
7.36
3.65
0.57
0.12
3.35
3.74
7.67
5.44
0.71
3.05
8.03
0.89
5.93
0.12
0.82
0.68
510
274
218
56.2
244
3g
3h
3i
4-Cl
500
4-Br
624
681
3-Br
276
67.6
368
3j
4-Ph
35.5
17.9
79.8
83.3
9330
64.3
662
4a
4b
4c
4d
4e
4f
4-H
18.1
19.5
15.1
3865
13.2
301
4-CH3
4-OCH3
4-NO2
3-NO2
4-F
49.37 20.45 265.81 110.11
0.32
2.79
0.56
0.07
1.27
0.31
0.18
1.84
0.04
0.84
4g
4h
4i
4-Cl
943
529
35.32
32.10
229.71
19.81
21.03
62.08
4-Br
9695
9510
6350
2570
56.37 36.92
8.72 2.36
3-Br
7

4j
4-Ph
-
97.5
250
22.3
12.1
133
297
5.7
0.73
9.88
0.17
0.48
0.33
0.08
2.12
AZA
25.3
43.86
AZA = acetazolamide (reference compound).
a
Mean from 3 different assays, by a stopped flow technique (errors were in the range of ±5-10% of the reported
values).
3. Conclusion
Two different series of benzenesulfonamide containing imidazothiadiazoles 3a-3j and
thiazolotrizoles 4a-4j have been designed, synthesized and evaluated as inhibitors of human
carbonic anhydrases hCA I and II (cytosolic isoforms) as well as hCA IX and XII (tumor
associated transmebrane isoforms). The activity profile reveals that all the newly synthesized
compounds are moderate inhibitors of hCA I, II, IX and XII. However some of the compounds
(3a-3c) performed better against tumor associated isoform hCA XII, exhibiting low nanomolar
Ki values (< 5 nM) while some compounds were found to be weaker inhibitors of cytosolic
isoforms hCA I and hCA II. Although selectivity ratio of most compounds against hCA IX and
XII over off targets hCA I and II was not promising, still compounds 4d and 4h showed good
selectivity ratio with moderate activity potential. Finally, the results of this study suggest that
designed heterocyclic benzenesulfonamide scaffolds need to be modified to expect getting
compounds inhibiting only tumor associated isoforms hCA IX and XII over hCA I and II.
4. Experimental protocols
4.1. General
All the commercially available chemicals were used without further purification. All the solvents
were dried and/or purified according to standard procedures prior to use. All the reactions were
monitored by thin layer chromatography (TLC) on TLC silica gel on F254 aluminium plates using
a mixture of chloroform and methanol as eluent while UV lamp was used to visualize the spots.
Melting points were determined in open capillaries in an electrical melting point apparatus and
are uncorrected. The IR spectra were recorded on a Thermo scientific Nicolet 67000 FT-IR
1
spectrophotometer instrument using the KBr pellet technique. H NMR spectra were recorded on
13
400 MHz and 300 MHz instruments, while C NMR spectra were registered at 100 MHz, using
8

deuterated dimethyl sulfoxide (DMSO-d6) as solvent, and tetramethylsilane (TMS) as internal
standard at room temperature. Chemical shifts are reported as δ values in parts per million (ppm)
downfield from TMS. High resolution mass spectra were obtained from a MicroMass ESI-TOF
MS spectrometer. In NMR data, ‘im’ and ‘thi’ are used for imidazothiadiazolic and
thiazolotrizolic cores respectively. Multiplicities are described as singlet (s), doublet (d), doublet
of doublet (dd), doublet of a doublet of a doublet (ddd), triplet (t), quartet (q), multiplet (m),
exchangeable proton (ex) for NMR assignments and strong (s), medium (m) for IR assignments.
The coupling constants are expressed in hertz (Hz).
4.2. Synthesis of 4-(5-amino-1,3,4-thiadiazol-2-yl)benzenesulfonamide (7)
A stirring mixture of 4-sulfamoylbenzoic acid (6) (30 mmol), N-aminothiourea (30 mmol) in
POCl3 (20 mL) was heated at 85oC for 1h. After cooling down to room temperature, water was
added. The reaction mixture was refluxed for 4h. After cooling, the mixture was basified to pH 8
by dropwise addition of 50% NaOH solution under stirring. The precipitate was filtered and
recrystallized from ethanol to yield 5.45g (71%) of the target compound 7 as dirty white solid;
mp: 218-220oC; IR (KBr) cm-1: 3456 & 3196 (m, N-H stretch), 3186 & 3124 (m, SO2NH2
stretch), 1311 & 1142 (s, SO2 stretch); H1 NMR (400 MHz, DMSO-d6) δ (ppm): 7.90 (d, 2H, J =
13
8.0 Hz, Ar), 7.84 (d, J = 8.0 Hz, 2H, Ar), 7.55 (s, 2H, SO2NH2), 7.43 (s, 2H, NH2); C NMR
(100 MHz, DMSO-d6) δ (ppm): 169.85, 155.44, 144.91, 134.34, 127.16, 127.02; MS m/z 257.05
(M+1), C8H8N4O2S2, calcd 257.01.
4.3. Synthesis of benzenesulfonamide bearing imidazothiadiazole compounds (3a-3j)
General procedure: A mixture of 4-(5-Amino-1,3,4-thiadiazol-2-yl)benzenesulfonamide (7) (2.00
mmol) and variously substituted phenacyl bromides (2.00 mmol) was refluxed in ethanol (25
mL) with few drops of DMF for 20-24 h. The excess of solvent was removed under reduced
pressure and the solid hydrobromide separated was filtered, washed with cold ethanol and dried.
Neutralization of hydrobromide salts with cold aqueous solution of sodium carbonate afforded
the corresponding free base compounds 3a-3j.
4.3.1. 4-(6-Phenylimidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3a)
1
Yield 80%; mp: 300oC; IR(KBr) (ν, cm-1): 3394, 3261, 3119 (m, N-H), 1297 1165 (SO2); H
NMR (300 MHz, DMSO-d6) δ (ppm): 8.80 (s, 1H, im), 8.70 (d, J = 8.4 Hz, 2H, Ar), 8.24 (d, J =
9

8.4 Hz, 2H, Ar), 7.92 (d, J = 7.5 Hz, 2H, Ar), 7.60 (s, 2H, SO2NH2), 7.44 (m, 2H, Ar) 7.31 (t, 7.5
Hz, 1H, Ar); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 159.77, 146.53, 145.82, 144.52, 133.53,
132.31, 128.62, 127.44, 127.24, 126.72, 124.68, 110.62; HRMS (ESI-MS) m/z 357.0489
(M+H)+, C16H12N4O2S2H+, calcd 357.0480.
4.3.2. 4-(6-p-Tolylimidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3b)
o
Yield 83%; mp: 296 C; IR(KBr) (ν, cm-1): 3370, 3261, 3134 (m, N-H), 1312, 1159 (SO2); 1H
NMR (300 MHz, DMSO-d6) δ (ppm): 8.74 (s, 1H, im), 8.17 (d, J = 8.4 Hz, 2H, Ar), 8.02 (d, J =
8.4 Hz, 2H, Ar), 7.80 (d, J = 7.8 Hz, 2H, Ar), 7.59 (s, 2H, SO2NH2), 7.35 (d, J = 7.8 Hz, 2H, Ar),
13
2.33 (s, 3H, CH3); C NMR (100 MHz, DMSO-d6) δ (ppm): 159.54, 146.47, 145.96, 144.35,
136.74, 132.34, 130.78, 129.18, 127.21, 126.71, 124.63, 110.10, 20.74; HRMS (ESI-MS) m/z
371.0634 (M+H)+, C17H14N4O2S2H+, calcd 371.0636.
4.3.3. 4-(6-(4-Methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3c)
o
Yield 81%; mp: 290-292 C; IR(KBr) (ν, cm-1): 3380, 3259, 3123 (m, N-H), 1336, 1176 (SO2);
1H NMR (300 MHz, DMSO-d6) δ (ppm): ): 8.65 (s, 1H, im), 8.14 (d, J = 8.36 Hz, 2H, Ar), 8.02
(d, J = 8.36 Hz, 2H, Ar), 7.83 (d, J =8.64 Hz, 2H, Ar), 7.59 (s, 2H, SO2NH2), 6.99 (d, J = 8.64
13
Hz, 2H, Ar), 3.79 (s, 3H, OCH3); C NMR (100 MHz, DMSO-d6) δ (ppm): 159.33, 158.83,
146.50, 145.98, 144.38, 132.44, 127.22, 126.77, 126.24, 126.10, 114.09, 109.47, 55.10; HRMS
(ESI-MS) m/z 387.0490 (M+H)+, C17H14N4O3S2H+, calcd 387.0585.
4.3.4. 4-(6-(4-Nitrophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3d)
o
Yield 86%; mp: 278-280 C; IR(KBr) (ν, cm-1): 3370, 3261, 3134 (m, N-H), 1503, 1339 (s,
NO2), 1318, 1165 (SO2);1H NMR (300 MHz, DMSO-d6) δ (ppm): 9.10 (s, 1H, im), 8.32 (d, J =
8.7 Hz, 2H, Ar), 8.20-8.16 (m, 4H, Ar), 8.03 (d, J = 8.4 Hz, 2H, Ar), 7.60 (s, 2H, SO2NH2); 13C
NMR (100 MHz, DMSO-d6) δ (ppm): 160.95, 146.75, 146.12, 145.62, 143.49, 140.04, 132.08,
127.43, 126.73, 125.30, 124.15, 113.35; HRMS (ESI-MS) m/z 402.0336 (M+H)+,
C16H11N5O4S2H+, calcd 402.033.
4.3.5. 4-(6-(3-Nitrophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3e)
10

o
Yield 81%; mp: 284-286 C; 3369, 3267, 3140 (m, N-H), 1519, 1398 (s, NO2), 1346, 1163
(SO2);1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.99 (d, 6.4 Hz, 1H, Ar), 8.66 (s, 1H, im), 8.29
(d, J = 6.8 Hz, 1H, Ar), 8.14-8.08 (m, 3H, Ar), 8.01 (d, J = 8.4 Hz, 2H, Ar), 7.68 (t, J = 8.0 Hz,
1H, Ar) 7.59 (s, 2H, SO2NH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 160.62, 148.32,
146.75, 145.13, 143.43, 135.31, 132.14, 130.75, 130.21, 127.36, 126.74, 121.83, 118.84, 112.20;
HRMS (ESI-MS) m/z 402.0333 (M+H)+, C16H11N5O4S2H+, calcd 402.033.
4.3.6. 4-(6-(4-Fluorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3f)
Yield 86%; mp: 282-284 oC; IR(KBr) (ν, cm-1): 3396, 3331, 3249 (m, N-H), 1336, 1156 (SO2);
1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.78 (s, 1H, im), 8.15 (d, J = 7.8 Hz, 2H, Ar), 8.00 (d, J
13
= 7.8 Hz, 2H, Ar), 7.95-7.91 (m, 2H, Ar), 7.58 (s, 2H, SO2NH2), 7.29-7.23 (m, 2H, Ar); C
NMR (100 MHz, DMSO-d6) δ (ppm): 161.62 (d, 1JCF = 242 Hz), 159.89, 146.61, 144.96, 144.63,
132.36, 130.14 (d, 4JCF = 3 Hz), 127.32, 126.73, 126.69 (d, 3JCF = 8 Hz), 115.58 (d, 2JCF = 22 Hz),
110.53; HRMS (ESI-MS) m/z 375.0391 (M+H)+, C16H11FN4O2S2H+, calcd 375.0385.
4.3.7. 4-(6-(4-Chlorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3g)
Yield 83%; mp: 288-290 oC; IR(KBr) (ν, cm-1): 3292, 3226, 3113 (m, N-H), 1327, 1161 (SO2);
1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.80 (s, 1H, im), 8.14 (d, J = 8.4 Hz, 2H, Ar), 8.01 (d, J
= 8.4 Hz, 2H, Ar), 7.90 (d, J = 8.4 Hz, 2H, Ar), 7.59 (s, 2H, SO2NH2), 7.46 (d, J = 8.4 Hz, 2H,
13
Ar); C NMR (100 MHz, DMSO-d6) δ (ppm): 160.04, 146.66, 144.76, 144.66, 132.49, 132.27,
131.84, 128.65, 127.30, 126.75, 126.36, 111.04; HRMS (ESI-MS) m/z 391.0093/393.0066
(M+H)+/(M+H+2)+, C16H11ClN4O2S2H+, calcd 391.0090/393.0090.
4.3.8. 4-(6-(4-Bromophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3h)
o
Yield 85%; mp: 308-310 C; IR(KBr) (ν, cm-1): 3340, 3261, 3134 (m, N-H), 1336, 1159 (SO2);
1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.83 (s, 1H, im), 8.14 (dd, J = 6.8 Hz, 2.0Hz, 2H, Ar),
8.01 (dd, J = 6.8 Hz, 2.0Hz, 2H, Ar), 7.84 (dd, J = 6.8 Hz, 2.0 Hz, 2H, Ar), 7.62-7.58 (m, 4H, Ar,
13
SO2NH2), C NMR (100 MHz, DMSO-d6) δ (ppm): 160.07, 146.66, 144.78, 144.69, 132.86,
132.27, 131.56, 127.30, 126.52, 126.68, 120.36, 111.08; HRMS (ESI-MS) m/z
434.9588/436.9565 (M+H)+/(M+H+2)+, C16H11BrN4O2S2H+, calcd 434.9585/436.9585.
4.3.9. 4-(6-(3-Bromophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3i)
11

o
Yield 81%; mp: 258-260 C; IR(KBr) (ν, cm-1): 3302, 3140, 3072 (m, N-H), 1346, 1168 (SO2);
1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.84 (s, 1H, im), 8.12 (d, J = 8.4 Hz, 2H, Ar), 8.07 (m,
1H, Ar), 8.01 (d, J = 8.4 Hz, 2H, Ar), 7.88 (d, J = 8.0 Hz, 1H, Ar), 7.60 (s, 2H, SO2NH2), 7.44
(dd, J = 8.0 Hz, 0.8 Hz, 1H, Ar), 7.35 (d, J = 8.0 Hz, 1H, Ar); 13C NMR (100 MHz, DMSO-d6) δ
(ppm): 160.19, 146.67, 144.79, 144.12, 135.94, 132.22, 130.53, 129.98, 127.29, 126.72, 123.55,
122.15, 111.47; HRMS
(ESI-MS)
m/z 434.9589/436.9565 (M+H)+/(M+H+2)+,
C16H11BrN4O2S2H+, calcd 434.9585/436.9585.
4.3.10. 4-(6-Biphenylimidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (3j)
o
Yield 80%; mp: 306-308 C; IR(KBr) (ν, cm-1): 3331, 3249, 3134 (m, N-H), 1297, 1165 (SO2);
1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.81 (s, 1H, im), 8.14 (d, J = 8.4 Hz, 2H, Ar), 8.04 (d, J
= 8.4Hz, 2H, Ar), 7.98 (d, J = 8.4 Hz, 2H, Ar), 7.73-7.69 (m, 4H, Ar), 7.60 (s, 2H, SO2NH2),
7.48-7.44 (m, 2H, Ar), 7.37-7.35 (m, 1H, Ar); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 156.81,
146.61, 145.55, 144.68, 139.62, 139.04, 132.72, 132.36, 128.88, 127.27, 126.85, 126.76, 126.40,
125.28, 110.78; HRMS (ESI-MS) m/z 434.9588 (M+H)+, C22H16N4O2S2H+, calcd 434.9585.
4.4 Sythesis of 2-(4-sulfamoylbenzoyl)hydrazinecarbothioamide (9)
It is prepared as per the procedure given by Y. M. Beasley et al.33
4.5. Synthesis of 4-(5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)benzenesulfonamide (10)
To a solution of 100 mL of 5% NaOH, 0.01 mol of 9 was added and refluxed for 3 h. The rection
mixture was cooled, poured onto crushed ice, and neutralized with conc. HCl. The resulting solid
o
1
was filtered, dried, and recrystallized from ethanol. Yield 84%; mp 278-280 C; H NMR (400
MHz, DMSO-d6) δ (ppm): 13.87 (s, 2H, NH), 8.12 (dd, J = 6.8 Hz, J = 2 Hz, 2H, Ar), 7.98 (dd,
J = 6.8 Hz, J = 2 Hz, 2H, Ar), 7.56 (s, 2H, SO2NH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm):
167.35, 149.16, 145.43, 128.31, 126.37, 126.24; MS m/z 257.04 (M+1), C8H8N4O2S2, calcd
257.01.
4.6. Synthesis of 4-(5-((2-aryl-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11a-11j).
12

General procedure: A mixture of 4-(5-mercapto-4H-1,2,4-triazol-3-yl)benzenesulfonamide (10)
(1.95 mmol) and differently substituted phenacyl bromides (1.95 mmol) was refluxed in
methanol in presence of KOH (2.92 mmol) for 4-5 h. After completion of reaction, mixture was
poured into ice cold water. Solid separated was filtered, dried, and recrystallized with ethanol.
4.6.1. 4-(5-((2-Phenyl-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide (11a)
o
Yield 80%; mp: 150-152 C; IR(KBr) (ν, cm-1): 3327, 3234, 3103 (m, N-H), 1697 (CO), 1334,
1165 (SO2); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.08-8.05 (m, 4H, Ar), 7.92 (d, J = 7.2 Hz,
2H, Ar), 7.69 (d, J = 6.6 Hz, 1H, Ar), 7.60 (d, J = 7.2 Hz, 2H, Ar), 7.45 (s, 2H, SO2NH2), 4.94
(s, 2H, CH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm):193.99, 144.40, 135.26, 133.78, 128.83,
128.63, 128.42, 128.28, 126.36, 126.29, 125.58, 39.38; MS m/z 375.11 (M+1), C16H14N4O3S2,
calcd 375.05.
4.6.2. 4-(5-((2-Tolyl-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide (11b)
o
Yield 78%; mp: 184-186 C; IR(KBr) (ν, cm-1): 3361, 3257, 3089 (m, N-H), 1691 (CO), 1321,
1153 (SO2); 1H NMR (400 MHz, DMSO-d6) δ (ppm): ): 8.02 (d, J = 8.8 Hz, 2H, Ar), 7.91 (d, J =
8.4 Hz, 2H, Ar), 7.86 (d, J = 8.0 Hz, 2H, Ar), 7.42 (s, 2H, SO2NH2), 7.34 (d, J = 8.0 Hz, 2H, Ar),
13
4.87 (s, 2H, CH2); 2.36 (s, 3H, CH3); C NMR (100 MHz, DMSO-d6) δ (ppm):193.16, 144.75,
144.16, 133.01, 129.31, 128.50, 126.59, 126.30, 126.23, 40.09, 21.18; MS m/z 389.12 (M+1),
C17H16N4O3S2, calcd 389.06.
4.6.3. 4-(5-((2-(4-Methoxyphenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-
yl)benzenesulfonamide (11c)
o
Yield 79%; mp: 214-216 C; IR(KBr) (ν, cm-1): 3354, 3235, 3087 (m, N-H), 1691 (CO), 1320,
1
1150 (SO2); H NMR (400 MHz, DMSO-d6) δ (ppm): ): 14.51 (s, br, 1H, NH), 8.08 (d, J = 8.4
Hz, 2H, Ar), 8.04 (d, J = 8.8 Hz, 2H, Ar), 7.92 (d, J = 8.4 Hz, 2H, Ar), 7.45 (s, 2H, SO2NH2),
13
7.09 (d, J = 8.8 Hz, 2H, Ar), 4.89 (s, 2H, CH2); 3.87 (s, 3H, OCH3); C NMR (100 MHz,
DMSO-d6) δ (ppm): 191.93, 159.42, 144.11, 133.08, 131.35, 130.20, 129.06, 126.42, 126.23,
112.08, 110.81, 56.54, 39.06; MS m/z 405.13 (M+1), C17H16N4O4S2, calcd 405.06.
4.6.4. 4-(5-((2-(4-Nitrophenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11d)
13

o
Yield 86%; mp: 170-172 C; IR(KBr) (ν, cm-1): 3362, 3239, 3084 (m, N-H), 1693 (CO), 1319,
1150 (SO2); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.39-8.30 (m, 4H, Ar), 8.04-7.92 (m, 4H,
Ar), 7.46 (s, 2H, SO2NH2), 4.98 (s, 2H, CH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 193.30,
144.36, 140.05, 130.32, 129.65, 126.36, 126.27, 123.75, 123.23; 38.00; MS m/z 420.08 (M+1),
C16H13N5O5S2, calcd 420.04.
4.6.5. 4-(5-((2-(3-Nitrophenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11e)
o
Yield 86%; mp: 114-116 C; IR(KBr) (ν, cm-1): 3342, 3264, 3088 (m, N-H), 1682 (CO), 1331,
1
1172 (SO2); H NMR (300 MHz, DMSO-d6) δ (ppm): 8.74 (s, 1H, Ar), 8.51-8.45 (m, 2H, Ar),
8.02 (d, J = 7.8 Hz, 2H, Ar), 7.89-7.84 (m, 3H, Ar), 7.43 (s, 2H, SO2NH2), 4.97 (s, 2H, CH2);
13C NMR (100 MHz, DMSO-d6) δ (ppm):192.88, 147.67, 144.07, 136.34, 134.28, 131.21,
130.47, 127.62, 126.35, 126.20, 122.52, 37.77; MS m/z 420.08 (M+1), C16H13N5O5S2, calcd
420.04.
4.6.6. 4-(5-((2-(4-Florophenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11f)
o
Yield 82%; mp: 176-178 C; IR(KBr) (ν, cm-1): 3358, 3248, 3083 (m, N-H), 1692 (CO), 1319,
1149 (SO2); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.17-8.12 (m, 2H, Ar), 8.05 (d, J = 8.1 Hz,
2H, Ar), 7.91 (d, J = 8.1 Hz, 2H, Ar), 7.46 (s, 2H, SO2NH2), 7.43-7.38 (m, 2H, Ar), 4.91 (s, 2H,
13
1
CH2); C NMR (100 MHz, DMSO-d6) δ (ppm): 192.74, 165.26 (d, JCF = 252 Hz), 157.22,
4
3
2
144.11, 131.80 (d, JCF = 3 Hz), 131.28 (d, JCF = 10 Hz), 126.40, 126.24, 115.76 (d, JCF = 22
Hz), 37.01 ; MS m/z 393.10 (M+1), C16H13FN4O3S2, calcd 393.04.
4.6.7. 4-(5-((2-(4-Chlorophenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11g)
o
Yield 85%; mp: 182-184 C; IR(KBr) (ν, cm-1): 3362, 3243, 3096 (m, N-H), 1694 (CO), 1319,
1150 (SO2); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.09-8.04 (m, 4H, Ar), 7.91 (d, J = 8.1 Hz,
13
2H, Ar), 7.65 (d, J = 8.1 Hz, 2H, Ar), 7.44 (s, 2H, SO2NH2), 4.91 (s, 2H, CH2); C NMR (100
MHz, DMSO-d6) δ (ppm): 193.63, 145.11, 139.34, 134.65, 130.82, 129.49, 126.96, 126.91,
39.88; MS m/z 409.18/411.05 (M+1)/(M+3), C16H13ClN4O3S2, calcd 409.01/411.05.
14

4.6.8. 4-(5-((2-(4-Bromophenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11h)
o
Yield 84%; mp: 192-194 C; IR(KBr) (ν, cm-1): 3362, 3248, 3083 (m, N-H), 1690 (CO), 1319,
1
1150 (SO2); H NMR (300 MHz, DMSO-d6) δ (ppm): 8.05 (d, J = 8.1 Hz, 2H, Ar), 7.99 (d, J =
8.1 Hz, 2H, Ar), 7.91 (d, J = 8.1 Hz, 2H, Ar), 7.80 (d, J = 8.1 Hz, 2H, Ar), 7.45 (s, 2H, SO2NH2),
13
4.91 (s, 2H, CH2); C NMR (100 MHz, DMSO-d6) δ (ppm): 193.99, 145.16, 135.05, 132.55,
132.18, 130.99, 128.64, 127.10, 127.03,40.14; MS m/z 453.02/455.02 (M+1)/(M+3),
C16H13BrN4O3S2, calcd 452.96/454.96.
4.6.9. 4-(5-((2-(3-Bromophenyl)-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide
(11i)
o
Yield 82%; mp: 176-178 C; IR(KBr) (ν, cm-1): 3354, 3252, 3088 (m, N-H), 1691 (CO), 1320,
1150 (SO2); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.22 (s, 1H, Ar), 8.05 (d, J = 8.1 Hz, 3H,
13
Ar), 7.91 (d, J = 8.1 Hz, 3H, Ar), 7.57-7.46 (m, 3H, SO2NH2, Ar), 4.91 (s, 2H, CH2); C NMR
(100 MHz, DMSO-d6) δ (ppm):193.57, 157.42, 155.67, 143.88, 137.14, 136.24, 131.43, 130.90,
130.69, 127.20, 126.40, 126.23, 122.07, 37.68; MS m/z 453.02/455.02 (M+1)/(M+3),
C16H13BrN4O3S2, calcd 452.96/454.96.
4.6.10. 4-(5-((2-Biphenyl-2-oxoethyl)thio)-4H-1,2,4-triazol-3-yl)benzenesulfonamide (11j)
o
Yield 79%; mp: 148-150 C; IR(KBr) (ν, cm-1): 3358, 3256, 3082 (m, N-H), 1691 (CO), 1331,
1
1152 (SO2); H NMR (300 MHz, DMSO-d6) δ (ppm): 8.14 (d, J = 8.4 Hz, 2H, Ar), 8.08 (d, J =
8.1 Hz, 2H, Ar), 7.93-7.87 (m, 4H, Ar), 7.80-7.40 (m, 2H, Ar), 7.59-7.48 (m, 3H, Ar), 7.45 (s,
13
2H, SO2NH2), 4.98 (s, 2H, CH2); C NMR (100 MHz, DMSO-d6) δ (ppm):193.71, 157.37,
157.74, 145.03, 143.76, 138.29, 133.71, 131.58, 128.95, 128.41, 126.65, 126.32, 126.16, 37.69;
MS m/z 451.15 (M+1), C22H18N4O3S2, calcd 451.08.
4.7. Synthesis of of benzenesulfonamide bearing thiazolotriazole compounds (4a-4j)
General procedure: The compounds 4a-4j were synthesized by stirring compounds 11a-11j (1.5
o
mmol) in 12 mL conc. H2SO4 at 0 C for 3 h and then another 3 h at room temperature. The
reaction mixture was poured into crushed ice and the precipitate obtained was filtered off,
washed with water, dried, and recrystallized from mixture of ethanol and THF.
15

4.7.1. 4-(6-Phenylthiazolo[3,2-b][1,2,4]triazol-2-yl)benzenesulfonamide (4a)
o
1
Yield 80%; mp: 284 C; IR(KBr) (ν, cm-1): 3296, 3215, 3116 (m, N-H), 1338, 1159 (SO2); H
NMR (300 MHz, DMSO-d6) δ (ppm): 8.31 (d, J = 8.0 Hz, 2H, Ar), 8.25 (d, J = 6.8 Hz, 2H, Ar),
13
8.02-7.96 (m, 3H, Ar, thi), 7.83-7.81 (m, 2H, Ar), 7.60-7.52 (m, 3H, SO2NH2, Ar); C NMR
(100 MHz, DMSO-d6) δ (ppm): 164.47, 157.90, 145.00, 133.76, 128.99 ,127.68, 126.75, 126.38,
126.14, 126.00, 111.74, 111.29; HRMS (ESI-MS) m/z 357.0485 (M+H)+, C16H12N4O2S2H+,
calcd 357.048.
4.7.2. 4-(6-p-Tolylthiazolo[3,2-b][1,2,4]triazol-2-yl)benzenesulfonamide (4b)
o
Yield 78%; mp: 270-272 C; IR(KBr) (ν, cm-1): 3292, 3178, 3082 (m, N-H), 1344, 1159 (SO2);
1H NMR (300 MHz, DMSO-d6) δ (ppm): 8.57 (s, 1H, thi), 8.31 (d, J = 7.2 Hz, 2H, Ar), 8.15 (d, J
= 7.8 Hz, 2H, Ar), 7.98 (d, J = 7.2 Hz, 2H, Ar), 7.88 (s, 2H, SO2NH2), 7.40 (d, J = 7.8 Hz, 2H,
Ar), 2.63 (s, 3H, CH3); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 164.24, 157.79, 146.74,
144.85, 137.53, 133.70, 126.55, 126.39, 126.29, 124.46, 124.23, 110.55, 19.98; HRMS (ESI-
MS) m/z 371.1903 (M+H)+, C17H14N4O2S2H+, calcd 371.1636.
4.7.3. 4-(6-(4-Methoxyphenyl)thiazolo[3,2-b][1,2,4]triazol-2-yl)benzenesulfonamide (4c)
o
1
Yield 71%; mp: 256 C; IR(KBr) (ν, cm-1): 3287, 3099 (m, N-H), 1336, 1159 (SO2); H NMR
(400 MHz, DMSO-d6) δ (ppm): 8.45-8.24 (m, 4H, Ar), 7.99-7.88 (m, 4H, Ar), 7.45 (s, 2H,
SO2NH2), 7.25 (s, 1H, thi), 3.90 (s, 3H, OCH3); 13C NMR (100 MHz, DMSO-d6) δ (ppm):
164.29, 157.80, 157.35, 144.91, 133.79, 131.35, 128.83, 126.80, 126.59, 118.64, 112.30, 109.23,
57.71; HRMS (ESI-MS) m/z 387.0581 (M+H)+, C17H14N4O3S2H+, calcd 387.0585.
4.7.4. 4-(6-(4-Nitrophenyl)thiazolo[3,2-b][1,2,4]triazol-2-yl)benzenesulfonamide (4d)
Yield 79%; mp: 290-292oC; IR(KBr) (ν, cm-1): 3278, 3107 (m, N-H), 1517, 1460 (NO2) 1342,
1
1195 (SO2); H NMR (400 MHz, DMSO-d6) δ (ppm): 8.52 (dd, J = 6.8 Hz, J = 2 Hz, 2H, Ar),
8.35 (dd, J = 7.2 Hz, J = 1.6 Hz, 2H, Ar), 8.29-8.26 (m, 3H, Ar, thi), 7.96 (d, J = 7.2 Hz, 2H, Ar),
7.48 (s, 2H, SO2NH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 164.54, 158.01, 147.39,
145.12, 133.56, 133.31, 129.63, 127.20, 126.75, 126.38, 124.11, 115.59; HRMS (ESI-MS) m/z
402.0334 (M+H)+, C16H11N5O4S2H+, calcd 402.0330.
16

4.7.5. 4-(6-(3-Nitrophenyl)thiazolo[3,2-b][1,2,4]triazol-2-yl)benzenesulfonamide (4e)
Yield 84%; mp: 278-280oC; IR(KBr) (ν, cm-1): 3305, 3116 (m, N-H), 1530, 1456 (s, NO2)1344,
1268 (SO2); 1H NMR (400 MHz, DMSO-d6) δ (ppm): 9.13 (t, J = 2.0 Hz, 1H, Ar), 8.67 (ddd, J =
8.0 Hz, J = 1.6 H, J = 0.8 Hz, 1H, Ar), 8.31 (ddd, J = 8.8 Hz, J = 2.4 Hz, J = 0.8 Hz, 1H, Ar),
8.26 (m, 3H, Ar, thi), 7.95 (d, J = 8.8 Hz, 2H, Ar), 7.85 (t, J = 8.4 Hz, 1H, Ar), 7.46 (s, 2H,
13
SO2NH2); C NMR (100 MHz, DMSO-d6) δ (ppm): 164.45, 157.88, 148.10, 145.08, 133.51,
132.29, 130.56, 129.32, 128.90, 126.60, 126.36, 123.99, 120.69, 114.3; HRMS (ESI-MS) m/z
402.0333 (M+H)+, C16H11N5O4S2H+, calcd 402.0330.
4.7.6. 4-(6-(4-Fluorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (4f)
1
Yield 80%; mp: 270-272oC; IR(KBr) (ν, cm-1): 3319, 3136 (m, N-H), 1328, 1168 (SO2); H
NMR (400 MHz, DMSO-d6) δ (ppm): 8.33-8.29 (m, 2H, Ar), 8.28 (d, J = 8.8 Hz, 2H, Ar), 7.94
13
(m, 3H, Ar, thi), 7.45 (s, 2H, SO2NH2), 7.41 (d, J = 8.8 Hz, 2H, Ar),; C NMR (100 MHz,
DMSO-d6) δ (ppm): 164.48, 162.68 (d, 1JCF = 246.4 Hz), 157.88, 145.04, 133.75, 130.69, 128.02
3
2
(d, JCF = 8.4 Hz), 126.72, 126.40, 124.25, 116.04 (d, JCF = 21.8 Hz), 111.18; HRMS (ESI-MS)
m/z 375.0387 (M+H)+, C16H11FN4O2S2H+, calcd 375.0385.
4.7.7. 4-(6-(4-Chlorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (4g)
Yield 85%; mp: 266-270oC; IR(KBr) (ν, cm-1): 3412, 3331, 3197 (m, N-H), 1219, 1195 (SO2);
1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.31-8.28 (m, 4H, Ar), 8.02 (s, 1H, thi), 7.99 (dd, J =
13
8.4 Hz, 2.0 Hz, 2H, Ar), 7.65 (dd, J = 9.2 Hz, 2.4 Hz, 2H, Ar),7.45 (s, 2H, SO2NH2); C NMR
(100 MHz, DMSO-d6) δ (ppm): 164.43, 157.84, 145.01, 134.24, 133.63, 130.44, 128.97, 127.97,
126.64, 126.37, 126.32, 111.92; HRMS (ESI-MS) m/z 391.0100/393.0070 (M+H)+/(M+H+2)+,
C16H11ClN4O2S2H+, calcd 391.0090/393.0090.
4.7.8. 4-(6-(4-Bromorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (4h)
o
Yield 81%; mp: 270-272 C; IR(KBr) (ν, cm-1): 3410, 3271, 3093 (m, N-H), 1230, 1143 (SO2);
1H NMR (400 MHz, DMSO-d6) δ (ppm): 8.29 (d, J = 8.8 Hz, 2H, Ar), 8.10 (dd, J = 8.4 Hz, 2.0
Hz, 2H, Ar), 8.01 (s, 1H, thi), 7.98 (d, J = 8.8 Hz, 2H, Ar), 7.77 (d, J = 8.4 Hz, 2H, Ar),7.48 (s,
2H, SO2NH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm): 164.43, 157.83, 145.00, 133.63,
17

131.88, 130.50, 128.15, 126.70, 126.64, 126.32, 122.94, 111.96; HRMS (ESI-MS) m/z
434.9593/436.9571 (M+H)+/(M+H+2)+, C16H11BrN4O2S2H+, calcd 434.9585/436.9585.
4.7.9. 4-(6-(3-Bromorophenyl)imidazo[2,1-b][1,3,4]thiadiazol-2-yl)benzenesulfonamide (4i)
o
1
Yield 83%; mp: 274-276 C; IR(KBr) (ν, cm-1): 3296, 3113 (m, N-H), 1336, 1159 (SO2); H
NMR (400 MHz, DMSO-d6) δ (ppm): 8.48 (s, 1H, Ar), 8.35 (d, J = 8.0 Hz, 1H, Ar), 8.31 (d, J =
8.4 Hz, 2H, Ar), 8.15 (s, 1H, thi), 7.99 (d, J = 8.4 Hz, 2H, Ar), 7.74 (d, J = 8.0 Hz, 1H, Ar),7.60-
13
7.56 (m, 1H, Ar), 7.50 (s, 2H, SO2NH2); C NMR (100 MHz, DMSO-d6) δ (ppm): 164.47,
157.86, 145.04, 133.65, 132.33, 131.04, 129.98, 129.66, 128.69, 126.68, 126.39, 125.20, 122.19,
122.83; HRMS (ESI-MS) m/z 434.9591/436.9568 (M+H)+/(M+H+2)+, C16H11BrN4O2S2H+,
calcd 434.9585/436.9585.
4.7.10. 4-(6-Biphenylthiazolo[3,2-b][1,2,4]triazol-2-yl)benzenesulfonamide (4j)
o
1
Yield 73%; mp: 230-232 C; IR(KBr) (ν, cm-1): 3423, 3102 (m, N-H), 1336, 1159 (SO2); H
NMR (400 MHz, DMSO-d6) δ (ppm): 8.34 (d, J = 8.4 Hz, 2H, Ar), 8.29 (d, J = 8.4 Hz, 2H, Ar),
8.02 (s, 1H, thi), 7.95 (d, J = 8.4 Hz, 2H, Ar), 7.87 (d, J = 8.4 Hz, 2H, Ar),7.73-7.68 (s, 5H, Ar),
7.45 (s, 2H, SO2NH2); 13C NMR (100 MHz, DMSO-d6) δ (ppm):169.72, 163.25, 157.76, 150.24,
145.87, 144.52, 139.03, 136.55, 132.49, 131.99, 131.72, 131.57, 131.49; HRMS (ESI-MS) m/z
432.9970 (M+H)+, C22H16N4O2S2H+, calcd 433.0093.
Acknowledgement
One of the authors (Rajiv Kumar) is grateful to University Grants Commission, New Delhi, India
for the award of Junior Research Fellowship and the other (SitaRam) to the Council of Scientific
and Industrial Research, New Delhi, India for the award of Senior Research Fellowship.
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21

Benzenesulfonamide incorporating imidazo-thiadiazole and thiazolo-
triazole scaffolds show effective carbonic anhydrase II and XII
inhibitory action
Rajiv Kumar, Silvia Bua, Sita Ram, Sonia Del Prete, Clemente Capasso, Claudiu T. Supuran,
Pawan K. Sharma
R
R
Me
N
N
N
N
N
S
S
N
SO2NH2
H2NO2S
H2NO2S
3a-3j
4a-4j
3j, 4a, 4b, 4e Ki (nM) < 80 against hCA I
3a, 4a, 4c Ki (nM) < 20 against hCA II
3a-3c Ki (nM) < 5 against hCA XII