Synthesis and antifungal activity of novel 5-substituted 4-(1,3,4-thiadiazol-2-yl)benzene-1,3-diols

Article abstract of DOI:10.1002/hc.20645

5-Substituted (amine, alkyl, aryl, heterocyclic) 4-(1,3,4-thiadiazol-2-yl) benzene-1,3- diols were synthesized, and their antifungal properties were examined. The compounds were obtained by the one-pot reaction of sulfinylbis((2,4-dihydroxyphenyl)methanethione) with hydrazides or thiosemicarbazides. Their structures were identified from elemental, IR, ¹H NMR, and MS spectra analyses. The activities of the derivatives against five phytopathogenic fungi in vitro were measured. Moderate fungicidal effect of the compounds under consideration was found.

Full text of DOI:10.1002/hc.20645

Heteroatom Chemistry
Volume 21, Number 7, 2010
Synthesis and Antifungal Activity of Novel
5-Substituted 4-(1,3,4-Thiadiazol-2-yl)
benzene-1,3-Diols
Joanna Matysiak, Alicja Skrzypek, and Andrzej Niewiadomy
Department of Chemistry, University of Life Sciences, Lublin, Poland
Received 7 July 2010; revised 4 September 2010
tivities against Rhizoctonia solani (R. solani), Botrytis
ABSTRACT: 5-Substituted (amine, alkyl, aryl,
cinerea (B. cinerea), and Dothiorella gregaria (D. gre-
heterocyclic)
4-(1,3,4-thiadiazol-2-yl)benzene-1,3-
garia) [11]. Especially various sulfone- and sulfoxide-
1,3,4-thiadiazoles have been synthesized and evalu-
ated for antifungal activities against several kinds
of fungi [13–17]. For the other 1,3,4-thiadiazole
derivatives, fungicidal activity under the in vivo
conditions was confirmed [18–21]. The 3D-QSAR
model of compounds gave good correlation between
the activity and the steric-electrostatic properties
[19].
The incorporation of dihydroxyphenyl moiety in
organic compounds, not limited to 1,3,4-thiadiazole
has attracted considerable attention due to its nat-
urally derived characterization and wide prevalence
in pesticides and medicinal compounds. In our pre-
vious work, many heterocyclic compounds contain-
ing 2,4-dihydroxyphenyl moiety were reported with
good fungicidal, antibacterial, and antitumor activ-
ities [22–24]. This substituent seems to be crucial
in the biological effects. It allows to reach a proper
degree of hydrophobic–hydrophilic balance of the
molecule that enables penetration of cell membranes
by compounds. The presence of hydroxyl groups
gives opportunity for the interactions with a poten-
tial molecular target by donor or acceptor hydrogen
bonds [25,26]. Extending our research in the area of
fungicidal compounds, we designed a series of new
1,3,4-thiadiazoles with 2,4-dihydroxyphenyl func-
tionality present in the heterocyclic ring. Herein,
we wish to report the synthesis and biological
studies in this area of some novel 1,3,4-thiadiazole
derivatives.
diols were synthesized, and their antifungal
properties were examined. The compounds were
obtained by the one-pot reaction of sulfinylbis((2,4-
dihydroxyphenyl)methanethione) with hydrazides
or thiosemicarbazides. Their structures were identi-
fied from elemental, IR, 1H NMR, and MS spectra
analyses. The activities of the derivatives against
five phytopathogenic fungi in vitro were measured.
Moderate fungicidal effect of the compounds under
ꢀ
C
consideration was found.
2010 Wiley Periodicals,
Inc. Heteroatom Chem 21:533–540, 2010; View this article
online at wileyonlinelibrary.com. DOI 10.1002/hc.20645
INTRODUCTION
Differently substituted 1,3,4-thiadiazoles are known
for their interesting antifungal bioactivities and have
attracted considerable attention to pesticide and
medicinal formulation. A large number of reports
on their synthesis and biological activities have ap-
peared during the past years [1–8]. Among them,
1,3,4-thiadiazoles with antifungal activity against
phytopathogenic fungi are an interesting group of
compounds [9–12]. For example reported 1,3,4-
thiadiazol-2-ylureas exhibit excellent fungicidal ac-
Correspondence to: Joanna Matysiak; e-mail: joanna.matysiak@
up.lublin.pl.
c
ꢀ
2010 Wiley Periodicals, Inc.
533

534 Matysiak, Skrzypek, and Niewiadomy
H
N
NH
R
S
N
S
R
HO
N
NH
1–5
H2N
OH
HO
OH
O
S
O
OH
S
S
OH
H2N
N
H
R
STB
R
S
HO
6–12
N
N
OH
FIGURE 1 Synthesis scheme of 5-substituted 4-(1,3,4-thiadiazol-2-yl)benzene-1,3-diols.
RESULTS AND DISCUSSION
Chemistry
In IR spectrum, there is a strong band in the re-
gion about 1630 cm−1 corresponding to the vibra-
tion of C N moiety and a weak one at 1050–1010 of
N C S C N, characteristic of the 1,3,4-thiadiazole
ring.
The mass spectra (EI-MS) of compounds gave
molecular ion peaks, however, with different inten-
sities. The major fragmentation pathway in most
derivatives involved the cleavage of the S C2 and
N–N bonds of 1,3,4-thiadiazole ring with formation
of (HO)2C6H3CN+ (m/z 135) and m/z [M – 135]+ ions
[29]. The cleavage of C2–N3 and S C5 bonds directed
toward (HO)2C6H3CS+ (m/z 153) fragmentation is
also observed.
The 1,3,4-thiadiazole derivatives exemplified in this
paper were prepared according to the route de-
scribed in Figure 1 [27,28]. Treatment of sulfinyl-bis
((2,4-dihydroxyphenyl)methanethione) (STB) with
appropriate 4-substituted-3-thiosemicarbazides in
methanol afforded N-substituted 4-(5-amino-1,3,4-
thiadiazol-2-yl)benzene-1,3-diols (1–5). Other ana-
logues, without the amine group (6–12), were
prepared from STB and hydrazides. STB as
the starting reagent was synthesized from 2,4-
dihydroxybenzenecarbodithioic acid and SOCl2 in
diethyl ether [27]. In the reaction of STB with nu-
cleophiles, first the linear product of thioacyl deriva-
tive is formed, which transforms into the thiol
form. Elimination of H2S or H2O molecule finally
gives the 1,3,4-thiadiazole ring. So, electrophilic sub-
strate STB also acts as an endogenous cyclizing
reagent. Purity of compounds was monitored by the
reversed-phase (RP-18) HPLC chromatography with
methanol-water as a mobile phase (Table 1).
The structures of compounds and their physical
and analytical data are presented in Table 1. The
spectroscopic data of new derivatives are in agree-
ment with the proposed structures and parameters
characterizing other analogs [24,27]. In the 1H NMR
spectrum in the range of low fields as a rule, two sig-
nals are registered corresponding to protons of the
OH group in the resorcinol moiety. The band about
9.5–9.9 ppm corresponds to the substituted amine
group of compounds 1–4. The resonance signals of
C5-H and C2-H protons of resorcinol moiety appear
as doublets in the range about 7.8–7.5 ppm with the
coupling constant J = 8.7 Hz and in the range 6.5–
6.4 with J = 2.3 Hz, respectively. However, C6-H is
registered in the doublet-doublets form at about 6.4–
6.3 ppm of coupling constants J = 8.5 and 2.3 Hz.
Biology
The results of in vitro screening against five strains
of phytopathogenic fungi Alternaria alternata, Botry-
tis cinerea, Rhizoctonia solani, Fusarium culmorum,
and Phytophthora cactorum are given in Table 2. The
panel substituents of 1,3,4-thiadiazole ring include
alkyls, aryls (differently modified) and heterocyclic
rings. Activity of compounds is expressed as relative
inhibition of growth (%) on the four degree scale
with two different concentrations (200 and 20 μg
mL−1). Commonly applied fungicides studied under
the same condition were used as the reference sys-
tems (Table 2).
The results presented in Table 2 show that an-
tifungal properties of compounds under considera-
tion are varied. In the laboratory studies at the con-
centration of 200 μg mL−1, compound 7 reveals a
significant fungistatic action (at the level 91–100%)
against four fungi. Compounds 2, 3, and 12 inhibit
development of three or two pathogens but at a
slightly lower level (50–90%). For the other com-
pounds, weak or no growth-inhibitory activity was
observed in vitro (Table 2). All compounds show a
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Antifungal Activity of Novel 5-Substituted 4-(1,3,4-Thiadiazol-2-yl)benzene-1,3-Diols 535
N
onud)
Clacd./F
(
H
Aanlyis
Eemntal
C
(PHLC)
k
lgo
t.
W
aM/ol.
u
m
r
F
Mlo.
C)
(
Mp
()%
edl
i
Y
-R
bisuent
S
.
No
Heteroatom Chemistry DOI 10.1002/hc

536 Matysiak, Skrzypek, and Niewiadomy
lower level of activity than the standard. With the
compounds at 20 μg mL−1 concentration, only com-
pound 7 inhibits growth of four pathogens at the
level 20–50%. F. culmorum seems to be the most re-
fractory but R. solani the most sensitive fungus in re-
lation to the evaluated 1,3,4-thiadiazole derivatives.
The structure–activity analysis shows that from
amino-1,3,4-thiadiazole group (1–5) the compound
with CF3-substituent acts more intense than with
CH3- substituent and 4-biphenyl derivative (3) than
naphthalen-1-yl derivative (4). The compound with
the tertiary amine group (5) exhibits the weakest
antifungal properties. Among the compounds with
other group (6–12), the most beneficial is the pres-
ence of the 4-hydroxy-3-methoxyphenyl substituent
(7). The antifungal effect intensifies also additional
heterocyclin ring in the form of benzo[d]imidazole
(12) but decreases the second 1,3,4-thiadiazole ring
(9) or thiophen-2-yl (10) moiety.
tained solute (t0) was determined by the injection of
a small amount of acetone dissolved in water. Log k
values for 70% of methanol (v/v) in the mobile phase
are presented.
Preparation of Title Compounds
4-(5-(p-Tolylamino)-1,3,4-thiadiazol-2-yl)benzene-
1,3-diol
(1). A
mixture
of
4-(p-tolyl)-3-
Co.
thiosemicarbazide (Alfa Aesar GmbH
&
KG, Karlsruhe, Germany) (0.01 mol) and STB
(0.075 mol) in methanol (50 mL) was refluxed
for 3 h. The hot reaction mixture was filtered,
and the filtrate was concentrated until to dry. The
removed product was crystallized from methanol
(2 × 50 mL).
1H NMR (400 MHz, DMSO-d6, δ): 10.85 (s, 1H,
C3-OH), 10.14 (s, 1H, C1-OH), 9.87 (s, 1H, NH), 7.74
(d, J = 8.6 Hz, 1H, C5-H), 7.51 (d, J = 8.5 Hz, 2H,
CꢁAR-H), 7.15 (d, J = 8.2 Hz, 2H, CAꢁ R-H), 6.42 (d,
J = 2.3 Hz, 1H, C2-H), 6.39 (dd, J = 8.5 and J = 2.3
Hz, 1H, C6-H); IR (ATR, cm−1): 3316, 3139 (OH,
NH), 3033 (CAR-H), 2917 (C-H), 2852 (C-H), 1620
(C N), 1599, 1515, 1460 (C C), 1454, 1426, 1321,
1250, 1226, 1181 (C-O), 1113, 1020, 988, 969, 872,
840, 815, 791, 760, 701, 678 (C-S-C); EI-MS (m/z, %):
299 (M+, 100), 298 (11), 296 (4), 164 (18), 163 (7),
153 (4), 150 (3), 135 (3), 131 (4), 121 (2), 106 (4), 95
(2), 94 (6), 77 (3), 69 (2), 66 (4), 65 (5).
In conclusion,
a series of novel 4-(1,3,4-
thiadiazol-2-yl)benzene-1,3-diol derivatives was
synthesized and evaluated for their fungicidal
activity. The compounds under consideration show
moderate fungicidal effect contrary to various
heterocyclic derivatives with 2,4-dihydroxyphenyl
moiety described previously [22,23].
EXPERIMENTAL
Analytical Studies
4-(5-(3-(Trifluoromethyl)phenylamino)-1,3,4-thi-
adiazol-2-yl)benzene-1,3-diol (2). A mixture of
4-[3-(trifluoromethyl)phenyl]-3-thiosemicarbazide
(Alfa Aesar Chemie GmbH, Steinheim, Germany)
(0.01 mol) and STB (0.075 mol) in methanol (50
mL) was refluxed for 3 h. The hot reaction mixture
was filtered, and the filtrate was left at room tem-
perature (24 h). The formed solid was filtered off
and crystallized from methanol (2 × 25 mL).
The melting point (mp) was determined using a
Buchi B-540 (Switzerland) melting point apparatus.
The elemental analysis was performed to determine
C, H, and N contents (Perkin-Elmer 2400). The anal-
yses were within 0.4% of the theoretical values.
The IR spectra were recorded with a Perkin-Elmer
FT-IR 1725X spectrophotometer (in potassium bro-
mide) or Varian 670-IR, FT-IR spectrometer (ATR).
The spectra were made in the range of 600–
4000 cm−1. 1H NMR spectra were recorded in DMSO-
d6 or CDCl3 using a Varian Mercury 400 or a Bruker
DRX 500 instrument. Chemical shifts (δ, ppm) were
given in relation to tetramethylsilane (TMS). The
spectra MS (EI, 70 eV) were recorded using the ap-
paratus AMD-604.
The purity of the compounds was examined by
a liquid chromatograph Knauer with a dual pump,
a 20-μL simple injection valve and a UV–visible de-
tector (330) nm. The Hypersil Gold C18 (1.9 μm,
100 × 2.1 mm) column was used as the stationary
phase. The mobile phase included different contents
of methanol and acetate buffer (pH 4, 20 nM) as the
aqueous phase. The flow rate was 0.5 mL min−1 at
room temperature. The retention time of an unre-
1H NMR (400 MHz, DMSO-d6, δ): 11.12 (s, 1H,
C3-OH), 8.28–8.27 (s, 1H, CꢁAR-H), 7.88–7.86 (d, J =
8.8 Hz, 1H, C5-H), 7.85–7.82 (d, J = 8.2 Hz, 1H, CAꢁ R
-
H), 7.60–7.56 (t, J = 8.1 Hz, 1H, CꢁAR-H), 7.33–7.31
(d, J = 8.2 Hz, 1H, CꢁAR-H), 6.55–6.54 (d, J = 2.4 Hz,
1H, C2-H), 6.45–6.42 (dd, J = 8.6 and J = 2.4 Hz, 1H,
C6-H); IR (KBr, cm−1): 3498 (OH, NH), 3048 (CAR
-
H), 1613 (C N, C C), 1579, 1498 (C C), 1550, 1457,
1387, 1334 (CF3), 1298, 1232, 1169 (C-O), 1128, 1073
(N C S C N), 982, 909, 842, 796, 762, 742, 695,
673 (C-S-C), 658, 603; EI-MS (m/z, %): 353 (M+, 100),
352 (6), 334 (4), 324 (2), 219 (4), 218 (29), 204 (2),
198 (7), 191 (2), 186 (3), 167 (2), 153 (5), 150 (4), 145
(4), 136 (5), 135 (3), 95 (2), 94 (6), 69 (2), 66 (3).
4-(5-(Biphenyl-4-ylamino)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol (3). A mixture of 4-(biphenyl-4-yl)-
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Antifungal Activity of Novel 5-Substituted 4-(1,3,4-Thiadiazol-2-yl)benzene-1,3-Diols 537
TABLE 2 Growth-Inhibitory Activity of 5-Substituted 4-(1,3,4-Thiadiazol-2-yl)benzene-1,3-diols According to the 4-Point Scalea
–1
at the Concentrations of Compound 200 (20b) μg mL
Mycelia Growth Inhibition
F. culmorum
No.
A. alternata
B. cinerea
P. cactorum
R. solani
1
2
1
2
1
2
0
0
1
2
1
2
3
4
2
0
2
0
0
0
1
1
1
1
5
6
7
8
1
1
0
1
0
0
0
1
1
0
2/1b
0
3/1b
0
3/0b
0
3/1b
2
3/1b
2
9
10
0
1
0
0
0
0
0
1
1
1
11
12
0
2
0
1
0
0
1
2
2
2
c
c
Prochloraz
Carbendazim
Procymidon
3/3
3/3
3/3
–
–
c
c
c
–
–
–
–
3/3
3/3
c
c
c
2/2
3/3
–
–
aThe results are given in the four-degree scale determining the percentage of mycelium growth inhibition compared with the control: 0: <20%
a lack of action, 1: 20–50% weak action, 2: 50–90% medium action, 3: >90% good action.
–1
bActivity at the concentrations of compound 20 μg mL
Test was not performed.
.
c
1H NMR (400 MHz, DMSO-d6, δ): 10.88 (s, 1H,
C3-OH), 10.17 (s, 1H, C1-OH), 9.92 (s, 1H, NH),
8.31–8.29 (m, 1H, CꢁAR-H), 8.21–8.19 (d, J = 7.3 Hz,
1H, CꢁAR-H), 7.97–7.93 (m, 1H, CAꢁ R-H), 7.81–7.78 (d,
1H, J = 8.4 Hz, C5-H), 7.69–7.67 (d, J = 8.2 Hz, 1H,
CꢁAR-H), 7.61–7.51 (m, 3H, CAꢁ R-H), 6.45–6.43 (d, 1H,
J = 2.4 Hz, C2-H), 6.42–6.39 (dd, J = 8.6 and J =
2.4 Hz, 1H, C6-H); IR (KBr, cm−1): 3427, 3172 (OH,
NH), 3058 (CAR-H), 1635 (C N), 1600, 1511, 1486
(C C), 1465, 1431, 1401, 1341, 1296, 1220, 1187 (C-
O), 1126, 1101, 1084 (N C S C N), 1047, 1022,
989, 971, 885, 835, 788, 736, 711, 678 (C-S-C), 640;
EI-MS (m/z, %): 335 (M+, 100), 334 (60), 201 (4), 200
(22), 199 (17), 185 (3), 173 (5), 172 (4), 168 (13), 167
(5), 153 (4), 150 (3), 141 (6), 140 (6), 135 (5), 128 (4),
127 (6), 126 (2), 121 (2), 115 (11), 94 (7), 77 (2), 66
(4), 63 (2), 51 (2), 39 (3).
3-thiosemicarbazide (Aldrich Chemie GmbH, Stein-
heim, Germany) (0.01 mol) and STB (0.075 mol) in
methanol (70 mL) was refluxed for 3 h. The formed
solid was filtered off and crystallized from methanol
(2 × 25 mL).
1H NMR (400 MHz, DMSO-d6, δ): 11.85 (s, 1H,
C3-OH), 10.20 (s, 1H, C1-OH), 9.47 (s, 1H, NH), 8.08–
8.06 (d, 1H, C5-H), 7.49–7.29 (m, 7H, CꢁAR-H), 7.36–
7.31 (m, 2H, CꢁAR-H), 6.39–6.38 (d, 1H, C2-H), 6.37–
6.36 (d, 1H, C6-H); IR (ATR, cm−1): 3372, 3243 (OH,
NH), 2952 (CAR-H), 1641 (C N), 1617, 1592, 1565,
1488 (C C), 1433, 1350, 1323, 1277, 1235, 1171 (C-
O), 1125, 1048, 1012, 986, 951, 872, 854, 811, 758,
738, 700, 677 (C-S-C); EI-MS (m/z, %): 361 (M+, 4),
345 (3), 329 (4), 302 (3), 228 (3), 256 (4), 225 (4), 211
(11), 210 (100), 170 (4), 169 (26), 168 (17), 167 (10),
153 (14), 150 (17), 149 (2), 137 (4), 135 (4), 121 (8),
108 (3), 97 (5), 95 (4), 94 (21), 93 (4), 84 (4), 81 (6),
80 (4), 79 (4), 77 (4), 75 (8), 69 (8), 67 (3), 66 (18), 65
(8), 63 (4), 53 (5), 52 (7), 51 (8), 45 (5), 44 (5), 40 (6),
39 (13).
4-(5-(Dimethylamino)-1,3,4-thiadiazol-2-yl)benzene-
1,3-diol (5). A mixture of 4,4-dimethyl-3-thiosem-
icarbazide (Aldrich) (0.01 mol) and STB (0.075
mol) in methanol (50 mL) was refluxed for 3 h.
The hot reaction mixture was filtered. The re-
moved product was crystallized from methanol (2 ×
30 mL).
4-(5-(Naphthalen-1-ylamino)-1,3,4-thiadiazol-2-
yl)benzene-1,3-diol (4). A mixture of 4-(2-naphthyl)-
3-thiosemicarbazide (Aldrich) (0.01 mol) and STB
(0.075 mol) in methanol (50 mL) was refluxed
for 3 h. The hot reaction mixture was filtered,
and the filtrate was concentrated until to dry. The
removed product was crystallized from methanol
(2 × 50 mL).
1H NMR (500 MHz, DMSO-d6, δ): 11.09 (s, 1H,
C3-OH), 9.00 (s, 1H, C1-OH), 6.69 (d, J = 8.6 Hz,
1H, C5-H), 6.46 (d, J = 2.3 Hz, 1H, C2-H), 6.39 (dd,
J = 8.6 and J = 2.3 Hz, 1H, C6-H), 3.17 (s, 6H, CH3);
IR (KBr, cm−1): 3197 (OH), 2945 (CH), 2818 (CH),
Heteroatom Chemistry DOI 10.1002/hc

538 Matysiak, Skrzypek, and Niewiadomy
1635 (C N), 1598, 1572 (C C), 1510, 1491, 1466
(C C), 1419, 1321, 1286, 1221, 1181 (C-O), 1096,
1066 (N C S C N), 986, 969, 924, 863, 844, 814,
748, 691 (C-S-C), 640, 616; EI-MS (m/z, %): 237 (M+,
100), 222 (5), 208 (18), 153 (19), 136 (7), 135 (22),
108 (6), 107 (5), 106 (2), 103 (3), 102 (26), 97 (8), 88
(28), 87 (13), 80 (4), 79 (3), 73 (4), 71 (4), 69 (9), 65
(4), 63 (4), 57 (5), 56 (5), 53 (5), 52 (8), 51 (7), 44 (14),
43 (17), 42 (17), 39 (8), 38 (5), 36 (14).
(19), 158 (4), 153 (15), 152 (9), 151 (53), 150 (10), 149
(17), 138 (13), 137 (34), 136 (13), 135 (15), 134 (11),
124 (5), 123 (10), 122 (5), 119 (6), 1108 (10), 107 (9),
106 (10), 97 (3), 81 (6), 80 (8), 79 (5), 77 (5), 69 (8),
65 (7), 64 (4), 63 (7), 55 (4).
4-(5-(3,4-Dimethoxybenzyl)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol
(8). A
mixture
of
3,4-
dimethoxyphenyl acetic acid hydrazide (Alfa
Aesar) (0.01 mol) and STB (0.075 mol) in methanol
(50 mL) was refluxed for 3 h. The hot reaction mix-
ture was filtered, and the filtrate was concentrated
until to dry. The removed product was crystallized
from methanol (2 × 30 mL).
4-(5-Heptyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol
(6). A mixture of octanoic hydrazide (Aldrich)
(0.01 mol) and STB (0.0075 mol) in methanol
(50 mL) was refluxed for 3 h. The hot reaction
mixture was filtered, and the filtrate was left at room
temperature (48 h). The formed solid was filtered
off and crystallized from methanol (2 × 30 mL).
1H NMR (500 MHz, CDCl3, δ): 10.91 (s, 1H, C3-
OH), 9.96 (s, 1H, C1-OH), 7.93–7.91 (d, J = 8.7 Hz,
1H, C5-H), 6.46–6.47 (d, J = 2.3 Hz, 1H, C2-H), 6.43–
6.41 (dd, J = 8.7 and 2.3 Hz, 1H, C6-H), 3.06–3.03
(t, J = 7.5 Hz, 2H, CH2), 1.76–1.70 (t, J = 7.5 Hz,
2H, CH2), 1.36–1.23 (m, 8H, CH2), 0.87–0.84 (t, 3H,
CH3); IR (KBr, cm−1): 3401 (OH), 3045 (CAR-H), 2953
(CH3), 2923, 2953 (CH2), 1604 (C N), 1520, 1470
(C C), 1420, 1394, 1322, 1284, 1245, 1210, 1180 (C-
O), 1151, 1119, 1080, 1034 (N C S C N), 987, 971,
912, 866, 809, 726, 668 (C-S-C), 643, 620; EI-MS (m/z,
%): 292 (M+, 25), 264 (3), 263 (19), 245 (11), 235 (7),
223 (4), 222 (14), 221 (57), 210 (5), 209 (12), 208
(100), 168 (2), 167 (4), 153 (18), 147 (40), 136 (13),
135 (9), 115 (3), 108 (3), 107 (3), 106 (2), 97 (3), 80
(3), 69 (3), 55 (6), 54 (3), 53 (3), 52 (6), 51 (3), 45 (3),
43 (7), 41 (16), 39 (8).
1H NMR (400 MHz, DMSO-d6, δ): 10.91 (s, 1H,
C3-OH), 10.01 (s, 1H, C1-OH), 7.95 (d, J = 8.6 Hz,
1H, C5-H), 6.97 (d, J = 2.0 Hz, 1H, Cꢁ2-H), 6.92 (d,
J = 8.3 Hz, 1H, Cꢁ5-H), 6.87 (dd, J = 8.3 and 2.0 Hz,
1H, Cꢁ6-H), 6.45 (d, J = 2.4 Hz, 1H, C2-H), 6.41 (dd,
J = 8.6 and J = 2.4 Hz, 1H, C6-H), 4.35 (s, 2H, CH2),
3.74 (s, 6H, CH3); IR (ATR, cm−1): 3315, 3175 (OH),
3075 (CAR-H), 2961 (CH), 2890 (CH), 1641 (C N),
1601, 1566, 1552 (C C), 1512, 1468, 1445, 1433,
1388, 1367, 1342, 1311, 1244, 1222, 1206 (C-O), 1163,
1129, 1088, 1037, 1022, 956, 916, 883, 858, 810, 800,
752, 699 (C-S-C); EI-MS (m/z, %): 345 (M+, 20), 344
(M+, 100), 343 (8), 329 (13), 315 (3), 301 (4), 210 (4),
209 (31), 194 (15), 182 (6), 177 (2), 167 (2), 153 (3),
151 (9), 136 (2), 135 (6), 108 (3), 107 (6), 106 (3), 91
(2), 77 (2), 65 (3).
4-(5-(4-(5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazol-
2-yl)phenyl)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol
(9). A mixture of terephthalic dihydrazide (Alfa
Aesar) (0.01 mol) and STB (0.0075 mol) in methanol
(50 mL) was refluxed for 3 h. The hot reaction
mixture was filtered, and the filtrate was left at room
temperature (24 h). The formed solid was filtered
off and crystallized from methanol (25 mL).
4-(5-(4-Hydroxy-3-methoxyphenyl)-1,3,4-thiadiazol-
2-yl)benzene-1,3-diol (7). A mixture of 4-hydroxy-3-
methoxybenzohydrazide (Alfa Aesar) (0.01 mol) and
STB (0.0075 mol) in methanol (50 mL) was refluxed
for 3 h. The hot reaction mixture was filtered, and
water (50 mL) was added to the filtrate. The formed
solid was filtered off and crystallized from methanol
(30 mL).
1H NMR (400 MHz, DMSO-d6, δ): 11.23 (s, 1H,
OH), 11.04 (s, 1H, OH), 10.14 (s, 1H, OH), 10.00 (s,
1H, OH), 8.17 (m, 2H, CAr-H), 8.12 (m, 4H, CAr-H),
6.53 (m, 2H, CAr-H), 6.47 (m, 2H, CAr-H). IR (KBr,
cm−1): 3349 (OH), 1630 (C N), 1598, 1510, 1461
(C C), 1413, 1258, 1165 (C-O), 1112, 1025, 872, 850,
710, 679 (C-S-C); EI-MS (m/z, %): 462 (M+, 2), 353
(2), 256 (5), 207 (7), 167 (5), 160 (3), 149 (8), 135 (4),
128 (4), 120 (4), 115 (3), 110 (6), 94 (7), 84 (4), 70 (4),
58 (22), 44 (100), 40 (66).
1H NMR (500 MHz, DMSO-d6, δ): 11.03 (s, 1H,
C3-OH), 10.04 (s, 1H, C1-OH), 9.70 (s, 1H, Cꢁ4-OH),
8.02 (d, J = 8.8 Hz, 1H, C5-H), 7.53 (d, J = 2.3 Hz,
1H, Cꢁ1-H), 7.40 (dd, J = 8.3 and J = 1.9 Hz, 1H, Cꢁ6-
H), 6.92 (d, J = 8.3 Hz, 1H, Cꢁ5-H), 6.51 (d, J = 2.5
Hz, 1H, C2-H), 6.44 (dd, J = 8.8 and J = 2.5 Hz, 1H,
C6-H), 3.88 (s, 3H, CH3); IR (KBr, cm−1): 3295 (OH),
1606 (C N, C C), 1505 (C C), 1326, 1269 (C-O-C),
1219, 1170 (C-O), 1121, 1027 (N C S C N), 979,
860, 648 (C-S-C); EI-MS (m/z, %): 316 (M+, 100), 315
(12), 302 (5), 301 (7), 300 (33), 287 (5), 271 (3), 243
(4), 213 (3), 181 (8), 169 (3), 168 (11), 167 (51), 166
4-(5-(Thiophen-2-yl)-1,3,4-thiadiazol-2-yl)benzene-
1,3-diol (10). A mixture of thiophene-2-carboxylic
hydrazide (Alfa Aesar) (0.01 mol) and STB
(0.0075 mol) in methanol (50 mL) was refluxed for
3 h. The hot reaction mixture was filtered, and the
Heteroatom Chemistry DOI 10.1002/hc

Synthesis and Antifungal Activity of Novel 5-Substituted 4-(1,3,4-Thiadiazol-2-yl)benzene-1,3-Diols 539
filtrate was concentrated until to dry. The formed
3397, 3147 (OH, NH), 3061 (CAr-H), 2968 (C-H),
2905 (C-H), 1611 (C N), 1514, 1476 (C C), 1420,
1348, 1319, 1272, 1226, 1187 (C-O), 1152, 1124, 1099
(N C S C N), 1036, 1009, 987, 931, 861, 811, 764,
745, 673 (C S C); MS (TS neg. Q1): 355 [M – H]−.
solid was crystallized from methanol (2 × 30 mL).
1H NMR (500 MHz, DMSO-d6, δ): 11.14 (s, 1H,
C3-OH), 10.08 (s, 1H, C1-OH), 8.07–8.05 (d, J = 8.7
Hz, 1H, C5-H), 7.79–7.78 (dd, J = 5.1 and J = 1.1 Hz,
1H, Ctph(5)-H), 7.76–7.75 (dd, J = 3.7 and J = 1.03
Hz, 1H, Ctph(3)-H), 7.24–7.22 (m, 1H, Ctph(4)-H), 6.53–
6.52 (d, J = 2.3 Hz, 1H, C2-H), 6.48–6.46 (dd, J = 8.7
and J = 2.3 Hz. 1H, C6-H); IR (KBr, cm−1): 3107
(OH), 1631 (C N), 1598, 1538, 1453 (C C), 1416,
1329, 1257, 1234, 1175 (C-O), 1139, 1097, 1060
(N C S C N), 986, 970, 918, 850, 795, 777, 745,
727, 710, 651 (C S C), 624. EI-MS (m/z, %): 276
(M+, 100), 247 (3), 168 (4), 167 (43), 153 (12), 143
(3), 142 (3), 141 (31), 138 (3), 135 (12), 127 (21), 124
(3), 119 (6), 114 (3), 112 (3), 111 (3), 110 (4), 109 (8),
108 (3), 107 (6), 106 (3), 97 (7), 96 (7), 95 (3), 83 (5),
82 (3), 80 (5), 71 (5), 70 (4), 69 (13), 65 (3), 63 (3), 58
(4), 53 (3), 52 (8), 51 (6), 45 (10), 39 (13).
Antifungal Activity Assays
The test in vitro estimating inhibition of mycelium in
the agar culture medium caused by the compound
under investigation was performed. Five strains of
phytopathogenic fungi: A. alternata, B. cinerea, R.
solani, F. culmorum, and P. cactorum were used. The
solutions (suspensions) were prepared at the concen-
tration making it possible to obtain 200 and 20 μg
mL−1 of the studied substance after dilution with the
potato dextrose agar. There were used Petri dishes
into which the agar culture medium, and the studied
substance were poured. When, the culture set, the in-
fectious material of the tested fungus in the form of
agar disk overgrown with mycelium was placed in
three sites of its surface. After 3–5 days (tempera-
ture 22 1) depending on the mycelium culture the
linear growth of the mycelium was measured. The
compound action was determined from the percent-
age of mycelium growth inhibition compared with
the control using the equation:
4-(5-((1H-Indol-2-yl)methyl)-1,3,4-thiadiazol-2-yl)
benzene-1,3-diol (11). A mixture of indole-3-acetic
acid hydrazide (Aldrich) (0.01 mol) and STB (0.075
mol) in methanol (60 mL) was refluxed for 3 h.
The hot reaction mixture was filtered. The removed
product was crystallized from methanol (2 × 40
mL).
1H NMR (400 MHz, DMSO-d6, δ): 11.04 (s, 1H,
C3-OH, 10.84 (s, 1H, C1-OH), 9.97 (s, 1H, NH), 7.92–
7.90 (d, J = 8.5 Hz, 1H, C5-H), 7.48–7.46 (m, J = 2.3
Hz, 1H, CꢁAr-H), 7.38–7.36 (m, 2H, CAꢁ r-H), 7.11–7.07
(m, 1H, CꢁAr-H), 6.99–6.95 (m, 1H, CAꢁ r-H), 6.41–6.40
(d, J = 2.1 Hz, 1H, C2-H), 6.39–6.36 (dd, J = 8.6 and
J = 2.39 Hz, 1H, C6-H), 4.52 (s, 1H, CH2); IR (KBr,
cm−1): 3426 (OH), 3111 (CAR-H), 2923 (C-H), 1633
(C N), 1529, 1460 (C C), 1337, 1305, 1262, 1229,
1159, 1133, 1091 (N C S C N), 986, 964, 926, 843,
747, 673 (C-S-C); EI-MS (m/z, %): 323 (M+, 100), 322
(8), 294 (3), 188 (7), 162 (2), 161 (14), 160 (3), 156
(3), 155 (9), 153 (2), 130 (26), 129 (3), 103 (3), 77 (3).
(C − T)
J =
100%
C
where J is percentage of colony growth inhibition,
C is a zone of fungus colony growth in the control
combination (mm), and T is a zone of the fungus
colony growth in the combination with the com-
pound (mm).
As standards, the following fungicides tested un-
der the same experimental conditions were used:
carbendazim (Sarfun 500SC, Organica, Chemical
Comp. S. A., Nowa Sarzyna, Poland); prochloraz
(Mirage 450EC, Makhteshim Agan Industries Ltd.,
Airport City, Israel); procymidone (Sumilex 500SC,
Sumitomo Chemical Comp. Ltd., Osaka, Japan). The
results are given in the four-degree scale determining
a percentage of mycelium growth inhibition com-
pared with the control [30] (Table 2). Biological stud-
ies were made in the Institute of Industry Organic
Chemistry in Warsaw with the SPR/BFF/01/b proce-
dures (certificate GLP-OECD -1997).
4-(5-((1H-Benzo[d]imidazol-2-ylthio)methyl)-1,
3, 4- thiadiazol-2-yl)benzene-1,3-diol (12). A mixture
of 2-(1H-benzo[d]imidazol-2-ylthio) acetohydrazide
(Alfa Aesar) (0.01 mol) and STB (0.0075 mol) in
methanol (50 mL) was refluxed for 3 h. The hot
reaction mixture was filtered, and water (50 mL) was
added to the filtrate The formed solid was filtered
off and crystallized from methanol (2 × 30 mL).
1H NMR (500 MHz, DMSO-d6, δ): 10.97 (s,
1H, C3-OH), 10.02 (s, 1H, C1-OH), 9.96–7.43 (d,
J = 8.7 Hz, 1H, C5-H), 7.52–7.48 (m, 2H, Cꢁ4,7-H),
7.18–7.15 (m, 2H, C5ꢁ ,6-H), 6.46 (d, J = 2.3 Hz, 1H,
C2-H), 6.41–6.39 (dd, J = 8.7 and J = 2.3 Hz, 1H,
C6-H), 5.02 (s, 2H, CH2); IR (KBr, cm−1): 3615,
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