Synthesis and antiviral activity of 5-(4-chlorophenyl)-1,3,4- thiadiazole sulfonamides

Article abstract of DOI:10.3390/molecules15129046

Starting from 4-chlorobenzoic acid, 10 new 5-(4-chlorophenyl)-N- substituted-N- 1,3,4-thiadiazole-2-sulfonamide derivatives were synthesized in six-steps. Esterification of 4-chlorobenzoic acid with methanol and subsequent hydrazination, salt formation and cyclization afforded 5-(4-chlorophen-yl)-1,3, 4-thiadiazole-2-thiol (5). Conversion of this intermediate into sulfonyl chloride 6, followed by nucleophilic attack of the amines gave the title sulfonamides 7a-7j whose structures were confirmed by NMR, IR and elemental analysis. The bioassay tests showed that compounds 7b and 7i possessed certain antitobacco mosaic virus activity.

Full text of DOI:10.3390/molecules15129046

Molecules 2010, 15, 9046-9056; doi:10.3390/molecules15129046
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis and Antiviral Activity of 5-(4-Chlorophenyl)-1,3,4-
Thiadiazole Sulfonamides
Zhuo Chen, Weiming Xu, Keming Liu, Song Yang *, Huitao Fan, Pinaki S. Bhadury, De-Yu Hu *
and Yuping Zhang
State Key Laboratory Breeding Base of Green Pesticide and Agricultural Bioengineering, Key
Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou
University, Guiyang 550025, China; E-Mails: gychecnzhuo@yahoo.com.cn (Z.C.);
xuweiming2009@163.com (W.X.); lkmingsd@126.com (K.L.); fanhuitao0818@163.com (H.F.);
bhadury@gzu.edu.cn (P.S.B.); zhangyupinggz@163.com (Y.Z.)
* Authors to whom correspondence should be addressed; E-Mails: gdjhzx@gmail.com (S.Y.);
fcc.dyhu@gzu.edu.cn (D.-Y.H.); Tel.: +86 (851) 829 2170; Fax: +86 (851) 362 2211.
Received: 23 August 2010; in revised form: 10 November 2010 / Accepted: 30 November 2010 /
Published: 9 December 2010
Abstract: Starting from 4-chlorobenzoic acid, 10 new 5-(4-chlorophenyl)-N-substituted-N-
1,3,4-thiadiazole-2-sulfonamide derivatives were synthesized in six-steps. Esterification of
4-chlorobenzoic acid with methanol and subsequent hydrazination, salt formation and
cyclization afforded 5-(4-chlorophen-yl)-1,3,4-thiadiazole-2-thiol (5). Conversion of this
intermediate into sulfonyl chloride 6, followed by nucleophilic attack of the amines gave
the title sulfonamides 7a-7j whose structures were confirmed by NMR, IR and elemental
analysis. The bioassay tests showed that compounds 7b and 7i possessed certain anti-
tobacco mosaic virus activity.
Keywords: sulfonamide derivatives; 1,3,4-thiadiazole moiety; synthesis; antiviral activity
1. Introduction
Sulfonamide drugs which have brought about an antibiotic revolution in medicine are associated
with a wide range of biological activities [1-3]. Sulfonamide derivatives have also been reported to
possess antifungal [4-6] and herbicidal [7] properties for potential agricultural applications.

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On the other hand, certain 1,3,4-thiadiazoles prepared by different groups have often displayed
other interesting bioactivities, e.g. anticonvulsant [8], antifungal and antibacterial properties [9-11].
Some representative examples of these derivatives possessing potent activity are shown in Figure 1.
Figure 1. Representative structures of some potent 1,3,4-thiadiazoles.
R=H, Z=SH
2
R=Ac, Z=SO
In our previous work, we synthesized a series of 2-alkylthio-5-(3,4,5-trimethoxyphenyl)-1,3,4-
thiadiazole derivatives to inhibit the growth of tumor cells [12]. We also obtained some chiral
thioureas and α-aminophosphonates, cyanoacrylates and certain heterocyclic compounds with the aim
of protecting tobacco plants affected with tobacco mosaic virus (TMV), but barring a few exceptional
cases, these compounds did not reveal the expected anti-TMV activity [13]. Since the incorporation of
sulfonamides into 1,3,4-thiadiazole rings can produce compounds that can act as carbonic anhydrase
inhibitors [3], herein we have combined the two pharmacophoric units into one structure to generate
new compounds with potential plant anti-viral activities. Thus, in the present investigation, 10 novel
sulfonamide derivatives containing 1,3,4-thiadiazole rings were synthesized and screened for their
1
anti-TMV activities. The structures of the synthesized products were confirmed by IR, H-NMR and
13C-NMR spectral data and elemental analysis. The bioactivity study results revealed that some of the
prepared compounds indeed possessed a certain degree of antiviral activity against TMV. Among
them, compounds 7b and 7i exhibited approximately 50% TMV inhibition, in the same range as that
displayed by the commercial antifungal ningnanmycin.
2. Results and Discussion
2.1. Chemistry
The synthetic routes to the intermediate 5 and title compounds 7a-7j are shown in Schemes 1 and 2
respectively. As shown in Scheme 1, the starting material 4-chlorobenzoic acid (1) was easily
converted into methyl benzoate 2 in 80% yield by methanol in the presence of concentrated sulfuric
acid. The methyl ester was then treated with hydrazine hydrate in ethanol to afford a 90% yield of
compound 3, which on treatment with KOH and CS2 in ethanol at ambient temperature gave the
corresponding potassium salt 4 in 94% yield. Finally, cyclization of 4 in acidic medium at 0 °C for 6 h
produced the thiol intermediate 5. The preparation of the next key intermediate, the sulfonyl chloride 6,
from thiol 5 by treatment with chlorine was then optimized in different solvents, e.g. acetic acid/water,
methylene chloride/water and 1,2-dichloroethane/water. The poor solubility of the starting material
thiol and the product sulfonyl chloride in acetic acid/water and ready dissolution of both the

Molecules 2010, 15
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components in methylene chloride/water rendered these solvents ineffective to monitor the progress of
the sulfonylation reaction.
Scheme 1. Synthetic route to intermediate 5.
Scheme 2. Synthetic route to title compounds 7a-7j.
O
ClCH2CH2Cl, H2O, HCl, Cl2
S
S
SH
Cl
S Cl
O
Cl
N
N
N
-2~0℃
N
6
5
R1
O
O
O
NHR1R2
S
S
S N
Cl
S Cl
O
Cl
R2
CH3CN, Et3N, r.t.
N
N
N
N
7a~7j
6
O
P
R1
OPr-i
OPr-i
R1=H, R2=
7f:
N
7a:
7b:
=
N
R2
F
R1=H, R2=
Me
R1=H, R2=
7g:
7h:
Cl
O
S
O
OEt
O
P OEt
F
R1=H, R2=
N N
S
7c:
, R2=
R1=
Cl
Me
Cl
7d: R1=H, R2=
7i:
7j:
R1=H, R2=
R1
O
7e:
=
P OPr-n
OPr-n
N
N
N Me
R1=H, R2=
R2
On the other hand, the poor solubility of the thiol and complete miscibility of sulfonyl chloride in
1,2-dichloroethane/water were crucial to follow the reaction to its completion. Thus, under optimal
conditions, a suspension of the thiol in 1,2-dichloroethane/water was bubbled with chlorine gas under
constant stirring at low temperature (Scheme 2). When the color of the reaction system turned
yellowish green, the gas flow was discontinued, the organic phase was separated, dried on anhydrous
magnesium sulfate and the solvent removed to afford the desired product. The title compounds 7a-7j
were then prepared by the reaction of nucleophilic amines with the intermediate 6, as shown in
Scheme 2. The role of various solvents, reaction temperatures and acid scavengers was studied for

Molecules 2010, 15
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optimization of the reaction conditions using compound 7b as the model. It is evident from the data
presented in Table 1 that out of the three solvents acetonitrile, dichloromethane and acetone selected
for the study, the first one (entry 1) afforded the best result in terms of chemical yield. Having
established acetonitrile as the ideal solvent for the reaction, the effect of two different organic bases,
e.g. triethylamine and pyridine was investigated. While triethylamine showed significant improvement
compared to the control, pyridine displayed much inferior results. With regard to the reaction
temperature (Table 2) for the model reaction with p-toluidine serving as the reacting amine, the highest
yield of the product 7b was recorded at room temperature (entry 2) compared to the one conducted at a
lower or higher temperature (entries 1 and 3). The reaction appears to be relatively sluggish at 10 °C
and might produce some side products at 40 °C or higher under the influence of the basic catalyst.
Therefore, under optimal conditions, the sulfonyl chloride 6 was reacted with the different amines
in acetonitrile at room temperature in the presence of triethylamine which was used as an acid
scavenger for the liberated HCl.
Table 1. The effect of solvent on the yield of compound 7b.
Entry
Solvent
Acetonitrile
Dichloromethane
Acetone
Time (h)
t (°C)
25
25
Yield (%)
32.8
1
2
3
5
5
5
17.5
trace
25
The structures of the title compounds 7a-7j were unequivocally characterized by spectral data and
elemental analyses. The existence of characteristic IR absorption in the 1,600–1,550 cm−1 region was
indicative of a C=N group and the two strong absorption bands around 1,160~1,190 cm−1 and
1
1,340~1,380 cm−1 respectively confirmed the presence of a sulfonyl functionality. In the H-NMR
spectra of the title compounds, the D2O exchangeable sulfonamide proton appeared at 10–11 ppm,
whereas the two different types of aromatic protons of the 4-chlorophenyl ring showed up as two
distinct doublets at 7.5–8.3 ppm with coupling constants of 7.5 and 8.6Hz, respectively.
Table 2. The effect of temperature on the yield of compound 7b.
Solvent
(V)
Acid acceptor
(V)
t
Time
(h)
Yield
(%)
Entry
(°C)
Acetonitrile Triethylamine
(15 mL) (0.15 mL)
Acetonitrile Triethylamine
(15 mL) (0.15 mL)
Acetonitrile Triethylamine
(15 mL) (0.15 mL)
1
2
3
10
r. t.
40
5
5
5
19.2
48.0
41.0
2.2. Antiviral activity bioassay
The newly synthesized derivatives were evaluated for their antiviral activity against tobacco mosaic
virus by the half leaf method. The bioassay results as obtained at 500 μg/mL using ningnanmycin as
the control are shown in Table 3. It is clear that the title compounds 7a-7j showed a certain degree of

Molecules 2010, 15
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antiviral activity against tobacco mosaic virus. The structural modification caused by changing the
substituents (R1 and R2) in the sulfonamide moiety has a wide impact on anti-viral activity of the
prepared compounds. Thus, amongst the compounds 7c, 7f and 7j bearing an α-aminophosphate
moiety, the one derived from diisopropyl phosphite and containing a 2-fluorophenyl group at the
α-carbon of the phosphonate (7f) exhibited better TMV inhibition. Nevertheless, these compounds
were found to be less potent than their counterparts 7b and 7i where the phosphonate moiety was
replaced by a 4-methylphenyl or 3-chlorophenyl group, respectively. The importance of these suitably
substituted aryl substituents (for 7b and 7i) was evident when their inhibitory activity was compared
with that of 7d with an unsubstituted phenyl ring, which showed much lower activity. Interestingly,
the title compound 7a bearing a heterocyclic ring substituent in the sulfonamide part displayed
reasonably good activity.
Table 3. The inhibitory activity of compounds 7a~7j to TMV.
Compd
Concentration (mg/mL )
Inhibition rate（%）
7a
7b
7c
7d
7e
7f
7g
7h
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
38.42
42.00
31.55
34.70
25.00
39.60
31.60
36.80
42.49
33.92
54.51
7i
7j
Ningnanmycin
3. Experimental
3.1. General
Melting points were determined on an X-4 melting point instrument. The 1H- and 13C NMR spectra
were recorded on a JOEL ECX-500 NMR spectrometer (operating at 500 and 125 MHz MHz
frequency, respectively). Chemical shifts were reported in ppm from internal tetramethylsilane used as
standard and are given in δ-units. The solvents used for the NMR spectra were DMSO-d6 or CDCl3.
Infrared spectra were taken on an IR Prestige-21 Fourier Transform infrared spectrophotometer in
potassium bromide pellets. Elemental analyses were performed on an Elementar Vario-III. All
reactions were monitored by thin layer chromatography, carried out on 0.3 mm silica gel F-254
(Merck) plates using UV light ZF-2 (253.7 and 365.0 nm) for detection. Commercial chemicals and
solvents were of reagent or analytical grade and used without further purification.
3.2. Preparation of methyl 4-chlorobenzoate (2)
A three-necked 250 mL flask fitted with a thermometer, dropping funnel and magnetic stirring bar
was charged with 4-chlorobenzoic acid (40 g, 0.26 mol) and anhydrous methanol (100 mL). To this

Molecules 2010, 15
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solution concentrated sulfuric acid (16 mL) was added dropwise through a dropping funnel. The
solution was heated to reflux for 6 h, cooled to room temperature and poured into an equal volume of
water. The organic phase was washed with saturated aqueous sodium bicarbonate solution (10 mL) to
a pH of 7–8. The crude product was dried over magnesium sulfate and the yellow oil was used for the
next step without further purification, yield 80%; 1H-NMR (CDCl3): δ 7.95 (d, 2H, ArH, J = 8.6 Hz),
7.39 (d, 2H, ArH, J = 8.6 Hz), 3.89 (s, 3H, CH3); 13C-NMR (CDCl3): δ 166.3, 139.4, 131.0, 128.8,52.3;
IR: ν 3035 (CH-Ar), 3021 (CH-Ar), 2953 (CH3), 1726 (C=O), 1597, 1435, 1400, 1286, 1278, 1116,
1091, 900, 761 cm−1; Anal. Calcd. for C8H7ClO2: C 56.32%, H 4.14%. Found: C 56.17%, H 4.29%.
3.3. Preparation of 4-chlorobenzohydrazide (3)
A three-necked 250 mL flask fitted with a thermometer, dropping funnel and magnetic stirring bar
was charged with 2 (37.6 g, 0.22 mol), anhydrous ethanol (80 mL) and hydrazine hydrate (40 mL,
80%). The solution was heated at reflux temperature for 8 h. The reaction mixture was cooled to 20 °C
when a white solid precipitated. The crude product was recrystallized from anhydrous ethanol to yield
30.9 g of 3 as white crystals, yield 80%, m.p. 165–167 °C; 1H-NMR (CDCl3): δ 8.85 (s, 1H, NH), 7.70
13
(d, 2H, ArH, J = 5.2 Hz), 7.42 (d, 2H, ArH, J = 5.2 Hz), 4.10 (s, 2H, NH2); C-NMR (DMSO-d6): δ
165.3 (C=O), 136.4 (C=C), 132.5, 129.4, 129.0; IR: ν 3307 (NH asymmetric stretching), 3223 (NH
asymmetric stretching), 3207 (NH), 3010 (CH-Ar), 1710 (CONH), 1640, 1560, 1346, 1095, 991, 883;
Anal. Calcd. for C7H7ClN2O: C 49.28%, H 4.14%, N 16.42%. Found: C 49.36% H 4.10%, N 16.27%.
3.4. Potassium N, p-chlorobenzoylhydrazinodithio formate (4)
A three-necked 250 mL flask fitted with a thermometer, dropping funnel and a magnetic stir bar
was charged with KOH (6.1 g, 0.11 mol), anhydrous ethanol (120 mL) and 3 (14.6 g, 0.09 mol). The
mixture was stirred to obtain a homogeneous solution and then CS2 (6.9 g) was slowly added through a
dropping funnel. The reaction system was stirred at room temperature for an additional 6 h, filtered,
and the resulting solid was used for the next step without further purification. White crystals, yield
94%, m.p. > 260 °C.
3.5. 5-(4--Chlorophenyl)-1,3,4-thiadiazole-2-thiol (5)
A three-necked 250 mL flask fitted with a thermometer and dropping funnel and magnetic stirring
bar was first charged with sulfuric acid (80 mL, 98%) and then cooled on an ice bath with vigorous
stirring. When the temperature reached below −2 °C, 4 (22.9 g, 0.08 mol) was slowly added into it.
After completion of the addition, the reaction mixture was kept below 0 °C and stirred for another 5 h.
The mixture was poured into ice water (200 mL) whenupon a large amount of white solid precipitated
which was separated by suction filtration. The solid was washed with water to a pH value of 6, the
cake was dissolved in 10% aqueous NaOH and the insoluble part was removed through filtration. The
filtrate was acidified by HCl (36%) to a pH of 2. The resulting white solid was filtered, washed with
water and recrystallized from EtOH to yield 14.6g of 5 as white crystals, yield 81%, m.p. 198–200 °C;
1H-NMR (DMSO-d6): δ 7.78 (d, 2H, ArH, J = 8.6 Hz), 7.61 (d, 2H, ArH, J = 8.6 Hz); 13C-NMR
(DMSO-d6): δ 188.2 (C-SH), 159.4 (C=N), 136.7(C=C), 130.0, 128.8, 127.9; IR: ν 3062 (CHAr), 1487,

Molecules 2010, 15
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1458, 1402, 1286, 1251 (N-N=C), 1124, 1087, 1066, 827; Anal. Calcd. for C8H5ClN2S2: C 42.01%, H
2.20%, N 12.25%. Found: C 42.03%, H 2.24%, N 12.56%.
3.6. 5-(4-Chlorophenyl)-1,3,4-thiadiazole-2-sulfonyl chloride (6)
A three-necked 50 mL flask fitted with a thermometer and magnetic stirring bar was successively
charged with H2O (8 mL), 1,2-dichloroethane (15 mL) and 5 (0.5 g, 2.2 mmol). The mixture was
stirred on an ice bath and then hydrochloric acid (2 mL) was added into it. When the temperature
reached −2 °C, the heterogeneous solution was slowly bubbled with chlorine gas. As soon as the color
of the mixture turned yellowish green, the flow of gas was discontinued. The completion of the
reaction was confirmed by TLC on silica gel (developing solvent: petroleum ether/ethyl acetate = 2:1,
v/v) and then the reaction mixture was transferred to a separating funnel and the organic phase was
separated, and the water solution was extracted with dichloromathane. The organic phase was dried
over MgSO4 and the solvent was removed by rotary evaporation. The crude product 6 was purified by
column chromatography on silica gel using a mixture of petroleum ether and ethyl acetate proportions
1
(2:1, V/V) as the eluent to afford yellow crystals, yield 42%, m.p. 112–114 °C; H-NMR (CDCl3): δ
8.08 (d, 2H, ArH, J = 8.6 Hz), 7.67 (d, 2H, ArH, J = 8.6 Hz); 13C-NMR (CDCl3): δ 165.8 (C=N), 152.8,
138.9 (C=C), 129.7, 128.1, 121.4; IR: ν 3082 (CH-Ar), 1595, 1490, 1436, 1402, 1220, 1089, 1037,
1012, 972, 900, 835 cm−1.
3.7. 1-(5-(4-Chlorophenyl)-1,3,4-thiadiazol-2-ylsulfonyl)piperidine (7a)
To a stirred solution of piperidine (1.0 mmol) in acetonitrile (5 mL), were added 6 (0.3 g, 1.0 mmol)
and triethylamine (0.15 mL) at room temperature. The stirring was continued for another 6 hours. The
solid was filtered under suction and dried. The pure compound was obtained by recrystallization from
1
ethanol, white crystals, yield 26.5%, m.p. 198–200 °C; H-NMR (DMSO-d6): δ 8.11 (d, 2H, ArH,
J = 8.6 Hz), 7.68 (d, 2H, ArH, J = 8.6 Hz), 3.27 (t, 4H, 2CH2, J = 5.1 Hz), 1.58–1.63 (m, 4H, 2CH2),
1.46–1.50 (m, 2H, CH2); 13C-NMR (DMSO-d6): δ 171.6 (C=N), 165.4, 137.8 (C=C), 130.6, 130.3,
127.8, 47.4, 25.2, 23.1; IR: 3088 (CH-Ar), 2954 (CH2), 2945, 2929, 2858, 1591, 1425, 1367, 1352,
1317, 1178, 1085, 941, 835, 715 cm−1; Anal. Calcd. for C13H14ClN3O2S2: C 45.41%, H 4.10%, N
12.22%. Found: C 45.46%, H 3.18, N 12.72%.
5-(4-Chlorophenyl)-N-p-tolyl-1,3,4-thiadiazole-2-sulfonamide (7b). To a stirred solution of p-toluidine
(1.0 mmol) in acetonitrile (5 mL), were added 6 (0.3 g, 1.0 mmol) and triethylamine (0.15 mL) at room
temperature. The stirring was continued for another 6 hours. The solid was filtered under suction and
dried. The pure compound was obtained by recrystallization from ethanol, white crystals, yield 37.8%,
m.p. 223–225 °C; 1H-NMR (DMSO-d6): δ 7.90 (d, 2H, ArH, J = 5.1 Hz), 7.66 (d, 2H, ArH, J = 8.6 Hz),
13
7.51 (d, 2H, ArH, J = 8.7 Hz), 7.16 (d, 2H, ArH, J = 8.7 Hz), 2.68 (s, 3H, CH3); C- NMR (DMSO-
d6): δ 160.7, 157.4, 131.4, 130.4, 129.8, 128.8, 127.8, 123.3, 120.9, 117.7, 20.9; IR: ν 3261 (NH), 3049
(CH-Ar), 2918 (CH3), 2858, 1614, 1602, 1573, 1485, 1402, 1093, 1051, 1012, 831, 819 cm−1; Anal.
Calcd. for C15H12ClN3O2S2: C 49.24%, H 3.31%, N 11.49%. Found: C 49.58%, H 3.51%, N 11.43%.
The compounds 7c-7j were obtained by following a similar method of preparation.

Molecules 2010, 15
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Diethyl(2-(4-chlorophenyl)-1,3,4-thiadiazole-5-sulfonamido)(2-fluorophenyl)methylphosphonate (7c).
1
yield 11.2%, m.p. 203–205 °C; H-NMR (DMSO-d6): δ 10.40 (s, 1H, SO2NH), 7.93 (d, 2H, ArH,
J = 8.6 Hz ), 7.64 (d, 2H, ArH, J = 7.5 Hz), 7.22 (dd, 1H, ArH, J = 8.6, 6.8 Hz ), 7.07 (t, 1H, ArH,
J = 14.7, 8.5 Hz), 7.02 (t, 1H, ArH, J = 15.0 Hz), 5.18 (d, 1H, CH, J = 24.0 Hz), 4.02–4.10 (m, 2H,
CH2), 3.86–3.94 (m, 1H, CH2), 3.75–3.83(m, 1H, CH2), 1.22 (t, 3H, CH3, J = 6.8 Hz), 1.03 (t, 3H,
13
CH3, J = 14.5 Hz); C-NMR (DMSO-d 6): δ 171.4, 167.9, 137.7, 130.7, 130.4, 130.2, 130.1, 127.6,
124.8, 115.6, 115.4, 63.8, 63.6, 48.3, 16.7, 16.4; IR: ν 3421 (NH), 3070 (CH-Ar), 2991 (CH3), 2893,
1494, 1458, 1357, 1284, 1248, 1165, 1112, 1093, 1074, 1053, 1031, 979, 837 cm-1; Anal. Calcd. for
C19H20ClFN3O5PS2 : C 43.89%, H 3.88%, N 8.08. Found: C 43.72%, H 3.35%, N 8.18%.
5-(4-Chlorophenyl)-N-phenyl-1,3,4-thiadiazole-2-sulfonamide (7d). White crystals, yield 30%; m.p.
1
201–203 °C; H-NMR (DMSO-d6): δ 10.43 (s, 1H, NH), 8.05 (d, 2H, ArH, J = 8.6 Hz), 7.67 (d, 2H,
ArH, J = 7.5 Hz), 7.34 (t, 2H, ArH, J = 18.3 Hz), 7.23 (d, 2H, ArH, J = 7.45 Hz), 7.18 (t, 1H, ArH,
13
J = 14.3 Hz); C-NMR (DMSO-d 6): δ 171.8, 167.3, 137.8, 136.4, 130.6, 130.2, 130.0, 127.6, 126.2,
122.2; IR: ν 3105 (NH), 3070 (CH-Ar), 2943, 2887, 2833, 1595, 1496, 1479, 1429, 1388, 1361, 1303,
1168, 1093, 1080, 1028, 1014, 937, 833 cm−1; Anal. Calcd. for C14H10ClN3O2S2: C 47.79%, H 2.86%,
N 11.94%. Found: C 47.98%, H 2.15%, N 12.03%.
1-(5-(4-Chlorophenyl)-1,3,4-thiadiazol-2-ylsulfonyl)-4-methylpiperazine (7e). White powder, yield
1
38.4%, m.p. 172–173 °C; H-NMR (DMSO-d6): δ 8.12 (d, 2H, ArH, J = 8.6 Hz), 7.68 (d, 2H, ArH,
13
J = 8.6 Hz), 3.30 (t, 4H, 2CH2, J = 4.6 Hz), 2.42 (t, 4H, 2CH2, J = 4.6 Hz), 2.19 (s, 3H, CH3); C-
NMR (DMSO-d 6): δ 171.7, 165.1,137.8, 130.6, 130.2, 127.8, 53.9, 46.5, 45.7; IR: ν 3109 (CH-Ar),
2956 (CH3), 2937, 2873, 2848, 1593, 1494, 1452, 1427, 1384, 1359, 1330, 1290, 1178, 1172, 1151,
1143, 1130, 1097, 1089, 1060, 979, 952, 831cm-1; Anal. Calcd. for C13H15ClN4O2S2: C 43.51%, H
4.21%, N 15.61. Found: C 43.54%, H 3.85%, N 15.95%.
Diisopropyl(2-(4-chlorophenyl)-1,3,4-thiadiazole-5-sulfonamido)(2-fluorophenyl) methylphosphonate
(7f). White powder, yield 21%, m.p. 210–212 °C; 1H-NMR (DMSO-d6): δ 10.29 (s, 1H, NH), 7.90 (d,
2H, ArH, J = 8.6 Hz), 7.65 (d, 2H, ArH, J = 8.6 Hz), 7.47 (t, 1H, ArH, J = 7.45 Hz), 7.18 (q, 1H, ArH,
J = 7.4 Hz), 7.08 (t, 1H, ArH, J = 8.6 Hz), 7.01 (t, 1H, ArH, J = 8.6 Hz), 5.07 (d, 1H, CH, J = 24.05
Hz), 4.62–4.68 (m, 1H, CH), 4.31–4.37 (m, 1H, CH), 1.26 (t, 6H, 2CH3, J = 6.3 Hz), 1.17 (d, 3H, CH3,
J = 6.3 Hz), 0.85 (d, 3H, CH3, J = 6.3 Hz); 13C-NMR (DMSO-d6): δ 175.9, 171.3, 167.9, 158.8, 137.6,
130.3, 130.2, 127.6, 124.7, 115.4, 115.4, 115.4, 115.2, 72.4, 48.7, 47.4, 24.3, 24.2, 23.8, 23.2; IR: ν
3062 (NH), 3049 (CH-Ar), 2981 (CH ), 2877, 1595, 1494, 1456, 1421, 1379, 1359, 1244, 1230, 1168,
1093, 1004, 921, 842, 821cm−1; Anal. Calcd. for C21H24ClFN3O5PS2: C 46.03%, H 4.41%, N 7.67%.
Found: C 45.64, H 3.83%, N 8.08%.
N,5-bis(4-Chlorophenyl)-1,3,4-thiadiazole-2-sulfonamide (7g). White powder, yield 30%, m.p.
1
245–247 °C; H-NMR (DMSO-d6): δ 8.07 (d, 2H, ArH, J = 8.6 Hz), 7.65 (d, 2H, ArH, J = 8.6 Hz),
13
7.41 (d, 2H, ArH, J = 8.6 Hz), 7.26 (d, 2H, ArH, J = 8.6 Hz); C-NMR (DMSO-d6): δ 171.9, 167.1,
130.6, 130.3, 130.2, 129.9, 127.6, 123.8; IR: ν 3093 (NH), 3045 (CH-Ar), 2912, 2872, 2819, 1489,
1431, 1404, 1363, 1182, 1172, 1093, 1012, 939, 840, 825 cm−1; Anal. Calcd. for C14H9Cl2N3O2S2: C
43.53%, H 2.35%, N 10.88%. Found: C 43.48%, H 2.65%, N 10.84%.

Molecules 2010, 15
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1-(5-(4-Chlorophenyl)-1,3,4-thiadiazol-2-ylsulfonyl)-4-methylpiperazine (7h). White powder, yield
1
21%, m.p. > 260 °C; H-NMR (DMSO-d6): δ 8.18 (d, 4H, ArH, J = 8.6 Hz), 7.73 (d, 4H, ArH,
J = 8.6 Hz), 7.56–7.50 (m, 2H, ArH), 7.34–7.40 (m, 2H, ArH), 2.24 (s, 3H, 2CH3); 13C-NMR (DMSO-
d6): δ 174.2, (C=N), 165.2, 138.5, 132.6, 131.8, 130.9, 130.6, 130.4, 130.2, 130.0, 127.3, 18.3; IR: ν
3089 (CH-Ar), 3053, 2880 (CH3), 1593, 1489, 1423, 1409, 1392, 1373, 1091, 981,952, 906, 860, 837
cm−1; Anal. Calcd. for C23H15Cl2N5O4S4: C 44.23%, H 2.42%, N 11.21%. Found: C 44.40%, H 2.28%,
N 11.54%.
N-(3-Chlorophenyl)-5-(4-chlorophenyl)-1,3,4-thiadiazole-2-sulfonamide (7i). White powder, yield
1
37%, m.p. 258–260 °C; H-NMR (DMSO-d6): δ 11.75 (s, 1H, NH), 8.07 (d, 2H, ArH, J = 8.6 Hz),
7.66 (d, 2H, ArH, J = 8.6 Hz), 7.39 (t, 1H, ArH, J = 8.0 Hz), 7.31–7.30 (m, 1H, ArH), 7.26–7.21 (m,
2H, ArH); 13C-NMR (DMSO-d6): δ 172.0, 167.1, 137.9, 134.0, 131.7, 130.7, 130.2, 127.6, 125.8,
121.1, 120.0; IR: ν 3053 (NH), 3014 (CH-Ar), 2804, 1589, 1475, 1431, 1392, 1357, 1168, 1093, 985,
833 cm−1; Anal. Calcd. for C14H9Cl2N3O2S2: C 43.53%, H 2.35%, N 10.88%. Found: C 43.59%, H
2.25%, N 10.78%.
Di-n-propyl(2-(4-chlorophenyl)-1,3,4-thiadiazole-5sulfonamido)-(phenyl)methylphosphonate
(7j).
1
White solid, yield 34.1%, m.p. 203–205 °C; H-NMR (DMSO-d6) δ: 10.23 (s, 1H, NH), 7.92 (d,
J = 8.6 Hz, 2H, ArH), 7.66 (d, J = 8.6 Hz, 2H, ArH), 7.34 (d, J = 7.4 Hz, 2H, ArH), 7.18 (t, 2H, ArH,
J = 8.0 Hz), 7.13 (t, J = 7.4 Hz, 6.8 Hz, 1H, ArH), 4.97 (d, J = 29.1 Hz, 1H, CH), 3.88–3.98 (m, 2H,
CH2), 3.75–3.81 (m, 1H, CH), 3.59–3.65 (m, 1H, CH), 1.53–1.60 (m, 2H, CH2), 1.36–1.43 (m, 2H,
13
CH2), 0.84 (t, 3H, CH3, J = 7.4 Hz), 0.72 (t, 3H, CH3, J = 7.4 Hz); C-NMR (DMSO-d6): δ 171.3,
168.4, 137.6, 134.3, 130.3, 130.2, 128.9, 128.4, 128.3, 127.7, 68.8, 55.8, 54.6, 23.8, 23.6, 10.4.10.3;
IR: ν 3064 (NH), 3015 (CH-Ar), 2966 (CH3), 2935, 2877, 1458, 1352, 1228, 1166, 1091, 1062, 1029,
1000, 923, 829, 694 cm-1; Anal. Calcd. for C21H25ClN3O5PS2: C 47.59%, H 4.75%, N 7.93%. Found: C
47.78%, H 4.30%, N 8.02%.
3.8. Antiviral biological assay
Purification of TMV. Using Gooding’s method [14], upper leaves of Nicotiana tabacum L
inoculated with TMV were selected and ground in phosphate buffer, then filtered through a double
layer pledget. The filtrate was centrifuged at 10,000 g, treated twice with PEG and centrifuged again.
The whole experiment was carried out at 4 °C. Absorbance values were estimated at 260 nm using an
ultraviolet spectrophotometer.
Virus concn = (A260 × dilution ratio)/E0.1%,260nm
1cm
Curative effect of compounds against TMV in vivo. Growing leaves of Nicotiana tabacum. L of the
same ages were selected. TMV (concentration of 6 × 10−3 mg/mL) was dipped and inoculated on the
whole leaves, then the leaves were washed with water and dried. The compound solution was smeared
on the left side and the solvent was smeared on the right side for control. The local lesion numbers
were then counted and recorded 3-4 d after inoculation [15]. For each compound, three repetitions
were measured. The inhibition rate of the compound was then calculated according to the following
formula (‘av’ means average):

Molecules 2010, 15
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av local lesion numbers of control (not treated with compound) − av local lesion numbers smeared with drugs
Inhibition rate (%)=
×100%
av local lesion numbers of control (not treated with compound)
4. Conclusions
In the present study, we have described a mild, efficient and convenient method for the synthesis of
5-(4-chlorophenyl)-N-substituted-1,3,4-thiadiazole-2-sulfonamide derivatives from easily accessible p-
chlorobenzoic acid. The incorporation of two different pharamacophores in a single structure led to the
development of novel derivatives with moderate activity. Although, slightly less effective than the
control agent ningnanmycin, compounds 7b and 7i showed promising anti-viral activity against TMV.
Due to lack of structural diversity of the investigated compounds, a definite SAR could not be
established and further research needs to be performed to identify lead structures with better activity.
Acknowledgements
The authors wish to thank the National Key Project for Basic Research (2010CB126105) and the
National Natural Science Foundation of China (20872021) for the financial support.
References and Notes
1. Ali, A.; Reddy, G.S.K.K.; Cao, H.; Anjum, S.G.; Nalam, M.N. L.; Schiffer, C.A.; Rana, T.M.
Discovery of HIV-1 protease inhibitors with picomolar affinities incorporating N-aryl
oxazolidinone-5-carboxamides as novel p2 ligands. J. Med. Chem. 2006, 49, 7342-7356.
2. McCarroll, A.J.; Bradshaw, T.D.; Westwell, A.D.; Matthews, C.S.; Stevens, M.F.G. Quinols as
novel therapeutic agents. 7. Synthesis of antitumor 4-[1-(arylsulfonyl-H-indol-2-yl)]-4-hydroxy-
cyclohexa-2,5-dien-1-ones by Sonogashira reactions. J. Med. Chem. 2007, 50,
1707-1710.
3. Wilkinson, B.L.; Bomaghi, L.F.; Houston, T.A.; Innocenti, A.; Vullo, D.; Supuran, C.T.; Poulsen,
S.-A. Carbonic anhydrase inhibitors: Inhibition of isozymes I, II and IX with triazle-linked O-
glycosides of benzene sulfonamides. J. Med. Chem. 2007, 50, 1651-1657.
4. Liane S.-U.; Maykel P.G.; Isidro G.C.; Rosario H.-G. Quantitative structure–activity relationship
studies for the prediction of antifungal activity of N-arylbenzenesulfonamides against Botrytis
cinerea. J. Mol. Graph. Mod. 2007, 25, 680-690.
5. Zhu, W.J.; Wu, P.; Liang, X.M.; Dong, Y.-H.; Zhang, J.-J.; Yuan, H.-Z.; Qi, S.-H.; Meng, X.-Q.;
Wu, J.-P.; Chen, F.-H.; Wang, D.-Q. Design, synthesis, and fungicidal activity of macrolactones
and macrolactams with a sulfonamide side chain. J. Agric. Food Chem. 2008, 56, 6547-6553.
6. Ezabadi, I.R.; Canoutsis, C.; Zoumpoulakis, P.; Geronikaki, A.; Sokovic, M.; Glamocilija, J.;
Ciric A. Sulfonamide-1,2,4-triazole derivatives as antifungal and antibacterial agents: Synthesis,
biological evaluation, lipophilicity, and conformational studies. Bioorg. Med. Chem. 2008, 16,
1150-1161.
7. Gonzalez, M.A.; Gorman, D.B.; Hamilton, C.T.; Roth, G.A. Process development for the
sulfonamide herbicide pyroxsulm. Org. Process. Res. Dev. 2008, 12, 301-303.

Molecules 2010, 15
9056
8. Sharna, R.; Misra, G.P.; Sainy, J.; Chaturvedi, S.C. Synthesis and biological evaluation of 2-
amino-5-sulfanyl-1,3,4-thiadiazole derivatives as antidepressant, anxiolytics and anticonvulsant
agents. Med. Chem. Res. 2010, doi 10.1007/s00044- 010-9308-3.
9. Abdel-Wahab, B.F.; Abdel-Aziz, H.A.; Ahmed, E.M. Synthesis and antimicrobial elevation of
some 1,3-thiazole, 1,3,4-thiadiazole, 1,2,4-triazole, and 1,2,4-triazolo [3,4-b][1,3,4]-thiadiazine
derivatives including a 5-(benzofuran-2-yl)-1-phenyl-pyrazole moity. Monatsh. Chem. 2009, 140,
601-605.
10. Aly, A.A.; El-Sayed, R. Synthesis and biological activity of new 1,3,4-thiadiazole derivatives.
Chem. Pap. 2006, 60, 56-60.
11. Jatav, V.; Kashaw, S.; Mishra, P. Synthesis, antibacterial and antifugal activity of some novel 3-
[5-(4-substituted phenyl)]1,3,4-thiadiazole-2-yl]-2-styryl quinazoline-4(3H)-ones. Med. Chem.
Res. 2008, 17, 169-181.
12. Song, B.-A.; Chen, C.-J.; Yang, S.; Jin, L.-H.; Xue, W.; Zhang, S.-M.; Zou, Z.-H.; Hu, D.-Y.; Liu,
G. Synthesis, structure and antitumor activity of 2-alkylthio-5-(3,4,5-trimethoxyphenyl)-1,3,4-
thiadiazole compounds. Acta Chim. Sinica 2005, 63, 1720-1726.
13. Song, B.A.; Yang, S.; Jin, L.H.; Bhadury, P.S. Environment Friendly Anti Plant Viral Agents, 1st
ed.; Chemical industry press: Beijing, China, Springer press: Heidelberg, Germany, 2010.
14. Gooding, G.V., Jr.; Hebert, T.T. A simple technique for purification of tabacco mosaic virus in
large quantities. Phytopathology 1967, 57, 1285-1290.
15. Song, B.A.; Zhang, H.P.; Wang, H.; Yang, S.; Jin, L.H.; Hu, D.Y.; Pang, L.L.; Xue, W. Synthesis
and antiviral activity of novel chiral cyanoacrylate derivatives. J. Agric. Food Chem. 2005, 53,
7886-7891.
Sample Availability: Samples of the compounds are available from the authors.
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(http://creativecommons.org/licenses/by/3.0/).