Synthesis, characterization and antimicrobial activity of some new 1-(fluorobenzoyl)-3-(fluorophenyl)thioureas

Article abstract of DOI:10.1016/j.jfluchem.2009.09.003

Synthesis of a variety of new 1-(isomeric fluorobenzoyl)-3-(isomeric fluorophenyl)thioureas (1a-t) was accomplished in two steps. The synthetic route involves the reaction of equimolar quantities of isomeric fluorobenzoyl chlorides with potassium thiocyanate in anhydrous acetone to afford the corresponding isothiocyantes in situ, followed by treatment with equimolar quantities of isomeric fluoroanilines. All of the synthesized compounds (1a-t) were screened for their in vitro antibacterial activity using Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aureginosa). The minimum inhibitory concentration (MIC) was also determined for the most active compounds. In vitro antifungal activity was also determined against the five fungal species (Rhizopus oryzae, Aspergillus tereus, Fusarium oxysporum, Aspergillus niger, Aspergillus fumigatus). In general, the antifungal activity of compounds was better than their antibacterial activity.

Full text of DOI:10.1016/j.jfluchem.2009.09.003

Journal of Fluorine Chemistry 130 (2009) 1028–1034
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis, characterization and antimicrobial activity of some new
1-(fluorobenzoyl)-3-(fluorophenyl)thioureas
a
b
b
Aamer Saeed a, , Uzma Shaheen , A. Hameed , S.Z. Haider Naqvi
*
a Department of Chemistry, Quaid-I-Azam University, Islamabad 45320, Pakistan
b Department of Microbiology, Quaid-I-Azam University, Islamabad 45320, Pakistan
A R T I C L E I N F O
A B S T R A C T
Article history:
Synthesis of a variety of new 1-(isomeric fluorobenzoyl)-3-(isomeric fluorophenyl)thioureas (1a–t) was
accomplished in two steps. The synthetic route involves the reaction of equimolar quantities of isomeric
fluorobenzoyl chlorides with potassium thiocyanate in anhydrous acetone to afford the corresponding
isothiocyantes in situ, followed by treatment with equimolar quantities of isomeric fluoroanilines. All of
the synthesized compounds (1a–t) were screened for their in vitro antibacterial activity using Gram-
positive bacteria (Staphylococcus aureus, Bacillus subtilis) and Gram-negative bacteria (Escherichia coli,
Pseudomonas aureginosa). The minimum inhibitory concentration (MIC) was also determined for the
most active compounds. In vitro antifungal activity was also determined against the five fungal species
(Rhizopus oryzae, Aspergillus tereus, Fusarium oxysporum, Aspergillus niger, Aspergillus fumigatus). In
general, the antifungal activity of compounds was better than their antibacterial activity.
ß 2009 Elsevier B.V. All rights reserved.
Received 13 July 2009
Received in revised form 24 August 2009
Accepted 1 September 2009
Available online 18 September 2009
Keywords:
Fluorine substituted thioureas
Antibacterial activity
Antifungal activity
In vitro studies
1. Introduction
novel class of potent influenza virus neuraminidase inhibitors [8].
Thiourea derivatives are effective against HIV [9–10] and possess
Due to unique properties of fluorinated compounds, the
substitution of hydrogen by fluorine has become a common
strategy in drug development. The fluorinated molecules resulting
from isosteric substitution of hydrogen by fluorine, generally also
fit in the biological recognition site. The inclusion of fluorine into
organic molecules may increase the lipophilicity and thus enhance
the rate of cell penetration and transport of a drug to an active site.
The higher polarizability due to the C–F bond may give new
possibilities for binding to the receptor. The fluorinated com-
pounds are more resistant to metabolic degradation due to the
high bond energies and heats of formation of the H–O and C–O
bonds relative to those of the F–O bond [1–3]. Fluorinated
chemicals are of growing importance with applications in
medicine, agrochemicals and organic electronics. Fluorine sub-
stitution at a certain position in a drug molecule can influence not
only pharmacokinetic properties such as absorption, tissue
distribution, secretion and the route and rate of biotransformation
but also its pharmacodynamics, toxicology and improves the
efficiency of medicine [4].
bactericidal action [11]. Thioureas containing both carbonyl and
thiocarbonyl groups are versatile ambidentate donor ligands for
transition metal ions [12]. N,N-dialkyl-N-aroyl thioureas are
efficient ligands for the separation of platinum group metals
[13]. 1,3-Dialkyl or diaryl thioureas exhibit significant antifungal
activity against plant pathogens Pyricularia oryzae and Drechslera
oryzae [14]. 1-Benzoyl-3-(4,6-disubstituted-pyrimidinyl)thioureas
have shown excellent herbicidal activity [15]. Acyl thioureas are
well known for their superior pesticidal, fungicidal, antiviral and
plant growth regulating activity [16]; others are reported to show
potent anti-inflammatory and analgesic activities [17]. Thioureas
have extensively been used in enantioselective synthesis, such as
nitro-Mannich reactions, Aza–Henry reaction and the Michael
addition [18–20]. Symmetrical and asymmetrical phenethyl
thioureas, 5-halo-substituted thiophene pyridyl thioureas and
heterocyclic thioureas are non-nucleoside inhibitors of HIV-1
reverse transcriptase [21].
Condensation of thiourea derivatives with carbonyl compounds
has been used in the synthesis of N-alkyl-1,3-thiazol-2-amines, 3-
alkyl-1,3-thiazolimines [22], 1-aroyl-3-aryl-4-substituted imida-
zole-2-thiones [23] and 2-(aroylimino)-3-aryl-4-methyl/phenyl-
1,3-thiazolines [24]. Cyclocondensation of unsymmetrical perfluor-
oalkyl substituted beta-diketones with urea, thiourea, and guani-
dine leads to various heterocycles [25]. Regioselective synthesis of
2H-[1,2,4]thiadiazolopyrimidine derivatives [26] and 2-(9H-fluo-
ren-9-ylmethoxycarbonylamino)-thiazole-4-carboxylic acidsvia N-
Fmoc thioureas has recently been described [27].
Fluorinated thioureas are convenient synthons for preparation
of versatile fluorine-containing heterocycles: [1,3]-benzothiazin-
4-ones [5,6], 1-aryl-2-ethylthio-quinazolin-4-one, thiazolidine
and 1H-1,2,4-triazoles [7]. Fluorinated thioureas constitute a
* Corresponding author.
E-mail address: aamersaeed@yahoo.com (A. Saeed).
0022-1139/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2009.09.003

A. Saeed et al. / Journal of Fluorine Chemistry 130 (2009) 1028–1034
1029
Scheme 1. Synthesis of some new 1-(fluorobenzoyl)-3-(fluorophenyl)thioureas.
Taking into consideration the aforementioned biological and
2. Results and discussion
synthetic significance of thioureas, synthesis of some new 1-
(isomeric fluorobenzoyl)-3-(isomeric fluorophenyl)thiourea deri-
vatives was undertaken as a continuation of our efforts towards
synthesis, characterization and crystal structure of new thiourea
derivatives as precursors towards novel heterocycles and for the
systematic study of their bioactivity and complexation behavior.
2.1. Synthesis
The synthetic sequence leading to the thioureas is outlined in
Scheme 1. Isomeric fluoro benzoic acids were converted into
corresponding acid chlorides by treatment with thionyl chloride
Table 1
Physicochemical elemental and mass spectral data of thioureas (1a–t).
Compound
R
R0
Yield
(%)
Rfa
Mp
Molecular formula
(MW)
EIMS [M]+
Analysis (calcd./found)
(8C)
C (%)
H (%)
N (%)
S (%)
1a
1b
2-F
2-F
2-Cl
63
84
0.52
0.34
164
186
C14H10N2OSFCl (308.76)
C17H17N2O4SF (364.39)
302.0
364.0
54.46/54.16
56.03/56.05
3.26/3.36
4.70/4.72
9.07/9.02
7.69/7.65
10.39/10.32
8.80/8.82
3,4,5-
Tri-OCH3
2-F
1c
1d
1e
1f
2-F
2-F
2-F
3-F
3-F
61
51
81
53
82
0.57
0.58
0.51
0.46
0.33
115
112
170
129
178
C14H10N2OSF2 (292.3)
292.0
292.0
292.0
302.0
364.0
57.53/57.46
57.53/57.42
57.53/57.59
54.46/54.22
56.03/56.13
3.45/3.43
3.45/3.41
3.45/3.42
3.26/3.21
4.70/4.80
9.58/9.61
9.58/9.52
9.58/9.62
9.07/9.03
7.69/7.62
10.97/10.98
10.97/11.08
10.97/11.01
10.39/10.41
8.80/8.78
3-F
C
C
C
14H10N2OSF2 (292.3)
14H10N2OSF2 (292.3)
14H10N2OSFCl (308.76)
4-F
2-Cl
1g
3,4,5-
Tri-OCH3
2-F
C17H17N2O4SF (364.39)
1h
1i
3-F
3-F
3-F
4-F
4-F
85
50
62
80
87
0.53
0.60
0.63
0.44
0.32
117
93
C14H10N2OSF2 (292.3)
292.0
292.0
292.0
302.0
364.0
57.53/57.49
57.53/57.46
57.53/57.47
54.46/54.40
56.03/56.09
3.45/3.41
3.45/3.35
3.45/3.40
3.26/3.21
4.70/4.72
9.58/9.53
9.58/9.47
9.58/9.62
9.07/9.03
7.69/7.71
10.97/10.95
10.97/10.91
10.97/10.93
10.39/10.36
8.80/8.79
3-F
C
C
C
14H10N2OSF2 (292.3)
14H10N2OSF2 (292.3)
14H10N2OSFCl (308.76)
1j
4-F
130
171
161
1k
1l
2-Cl
3,4,5-
Tri-OCH3
2-F
C17H17N2O4SF (364.39)
1m
1n
1o
1p
1q
4-F
56
84
60
83
92
0.51
0.61
0.62
0.49
0.32
110
131
138
154
160
C14H10N2OSF2 (292.3)
292.0
292.0
292.0
342.0
398.0
57.53/57.57
57.53/57.50
57.53/57.59
48.99/50.02
51.19/51.11
3.45/3.42
3.45/3.47
3.45/3.39
2.64/2.61
4.04/4.07
9.58/9.54
9.58/9.59
9.58/9.48
8.16/8.19
7.02/7.08
10.97/10.93
10.97/11.01
10.97/10.90
9.34/9.37
4-F
3-F
C
C
C
14H10N2OSF2 (292.3)
14H10N2OSF2 (292.3)
14H9N2OSFCl2 (343.2)
4-F
4-F
3-Cl-4-F
3-Cl-4-F
2-Cl
3,4,5-
Tri-OCH3
2-F
C17H16N2O4SFCl (398.84)
8.04/8.00
1r
1s
1t
3-Cl-4-F
3-Cl-4-F
3-Cl-4-F
59
69
89
0.51
0.64
0.63
111
158
114
C14H9N2OSF2Cl (326.75)
326.0
326.0
288.0
51.46/51.39
51.46/51.36
56.67/56.59
2.78/2.79
2.78/2.73
5.94/5.97
8.57/8.52
8.57/8.59
11.01/11.05
9.81/9.89
9.81/9.75
12.61/12.57
4-F
C
C
14H9N2OSF2Cl (326.75)
12H14N2OSFCl (288.77)
t-Butyl
a
Solvent system: hexane:ethyl acetate (8:2).
Recrystallization solvent: methanol.

Table 2
(IR, 1H, 13C NMR) spectral data of thioureas (1a–t).
Compound
IR (
y
, cmꢀ1
)
1H NMR (
d
, ppm, J (Hz))
13C NMR (
d, ppm)
1a
3355 (NH), 1679 (C5O),
12.48 (br s, 1H, NH), 9.34 (br s, 1H, NH), 8.44 (dt, J = 2.1, 7.5 Hz,
177.9 (C5S), 165.9 (C5O), 155.1 (d, 1J = 247 Hz), 133.5, 131.8, 131.2, 131.0,
130.8, 127.8 (d, 3J = 8.25 Hz), 127.6, 125.3, 124.1 (d, 4J = 3.75 Hz),
125.94 (d, 3J = 10.5 Hz), 115.97 (d, 2J = 19.5 Hz)
1538 (C5C), 1277 (C5S), 1129 (C–N)
1H, Ar–H), 7.83 (td, J = 0.9, 7.2 Hz, 1H, Ar–H), 7.55–7.18 (m, 7H, Ar–H)
1b
1c
3315 (NH), 1662 (C5O),
12.75 (br s, 1H, NH), 9.17 (br s, 1H, NH), 8.43 (dt, J = 2.1, 7.2 Hz,
1H, Ar–H), 7.31–7.17 (m, 3H, Ar–H), 7.12 (s, 2H, Ar–H), 3.96
(s, 3H, O–CH3), 3.95 (s, 6H, 2[O–CH3])
178.5 (C5S), 166.7 (C5O), 155.0 (d, 1J = 247 Hz), 153.5 (2C), 142.9, 127.8
(d, 3J = 8.25 Hz), 126.4, 125.9 (d, 3J =10.5 Hz), 125.3, 124.1 (d, 4J = 3.75 Hz),
115.6 (d, 2J =19.5 Hz), 104.9 (2C), 61.0 (OCH3), 56.5 (2C, 2[OCH3])
1584 (C5C), 1239 (C5S), 1131 (C–N)
3300 (N–H), 1669 (C5O),
12.57 (br s, 1H, NH), 9.70 (br d, J = 14.7 Hz, 1H, NH), 8.44 (dt, J = 2.1,
7.5 Hz, 1H, Ar–H), 8.11 (dt, J = 1.8, 7.8 Hz, 1H, Ar–H), 7.71–7.63 (m,
1H, Ar–H), 7.39 (dt, J = 1.2, 7.8 Hz, 1H, Ar–H), 7.30–7.23 (m, 4H, Ar–H)
177.5 (C5S), 166.2 (C5O), 160.5 (d, 1J = 250 Hz), 155.2 (d, 1J = 247 Hz),
135.9 (d, 3J =9.75 Hz), 132.2, 127.9 (d, 3J = 8.25 Hz), 125.9 (d, 3J = 10.5 Hz),
125.6 (d, 4J =3.75 Hz), 125.3, 124.1 (d, 4J = 3.75 Hz), 118.8 (d, 3J = 9.75 Hz),
116.7 (d, 2J =24 Hz), 115.7 (d, 2J =19.5 Hz)
1550 (C5C), 1281 (C5S), 1138 (C–N)
1d
3240 (N–H), 1677 (C5O),
12.63 (br s, 1H, NH), 9.28 (br s, 1H, NH), 8.39 (dt, J = 1.8, 7.5 Hz, 1H,
Ar–H), 7.71–7.17 (m, 7H, Ar–H)
178.7 (C5S), 166.3 (C5O), 162.9 (d, 1J = 251 Hz), 155.1 (d, 1J = 247 Hz),
140.1 (d, 3J = 8.75 Hz), 132.0 (d, 3J = 10.75 Hz), 127.8 (d, 3J = 8.25 Hz),
125.9 (d, 3J =10.5 Hz), 125.3, 124.1 (d, 4J = 3.75 Hz), 122.3 (d, 4J = 3 Hz),
116.2 (d, 2J =22 Hz), 115.6 (d, 2J =19.5 Hz), 114.3 (d, 2J = 26.25 Hz)
1557 (C5C), 1269 (C5S), 1152 (C–N)
1e
1f
3350 (N–H), 1653 (C5O),
12.43 (br s, 1H, NH), 9.65 (br s, 1H, NH), 8.45 (dt, J = 2.1, 7.5 Hz, 1H,
Ar–H), 8.07–7.05 (m, 7H, Ar–H)
177.5 (C5S), 166.8 (C5O), 164.9 (d, 1J = 250 Hz), 155.0 (d, 1J = 247 Hz,),
133.0 (2C, d, 3J = 8.25 Hz), 131.6, 127.8 (d, 3J = 8.25Hz), 125.9 (d, 3J = 10.5 Hz),
125.2, 124.1 (d, 4J = 3.75 Hz), 115.6 (d, 2J = 19.5 Hz), 114.8 (2C, d, 2J = 21.75 Hz)
1581 (C5C), 1282 (C5S), 1146 (C–N)
3200 (N–H), 1677 (C5O),
12.49 (br s, 1H, NH), 9.33 (br s, 1H, NH), 7.79–6.97 (m, 8H, Ar–H)
177.6 (C5S), 166.2 (C5O), 165.6 (d, 1J = 245 Hz), 138.9 (d, 3J = 10.5 Hz), 133.5,
131.9, 131.2, 131.0, 130.5, 130.6 (d, 3J = 9.75 Hz), 127.6, 119.4 (d, 4J = 3 Hz),
113.7 (d, 2J =21.75 Hz), 111.2 (d, 2J = 26.25 Hz)
1545 (C5C), 1281 (C5S), 1156 (C–N)
1g
1h
3290 (N–H), 1649 (C5O),
12.75 (br s, 1H, NH), 9.17 (br s, 1H, NH), 7.75 (dt, J = 2.1, 10.2 Hz, 1H,
Ar–H), 7.42–7.35 (m, 4H, Ar–H), 7.11 (s, 2H, Ar–H), 7.04–6.98 (m, 1H,
Ar–H), 3.95 (s, 6H, O–CH3), 3.95 (s, 3H, 2[O–CH3])
178.5 (C5S), 166.4 (C5O), 165.5 (d, 1J = 244 Hz, Ar-C), 153.6 (2C), 142.9,
139.6 (d, 3J =10.5 Hz), 130.6 (d, 3J = 9.75 Hz), 125.4, 119.4 (d, 4J = 3 Hz), 113.6
(d, 2J = 21 Hz), 111.2 (d, 2J = 26Hz), 104.9 (2C), 61.2 (OCH3), 56.6 (2C, 2[OCH3])
1634 (C5C), 1281 (C5S), 1142 (C–N)
3295 (N–H), 1667 (C5O),
12.67 (br s, 1H, NH), 9.68 (br d, J = 14.7Hz, 1H, NH), 8.11
(dt, J = 1.8, 7.8 Hz, 1H, Ar–H), 7.77 (td, J = 2.1, 10.2 Hz, 1H, Ar–H),
7.70–6.96 (6H, m, Ar–H)
177.9 (C5S), 164.2 (C5O), 162.0 (d, 1J = 247 Hz), 160.5 (d, 1J = 250 Hz),
139.6 (d, 3J =10.5 Hz), 135.9 (d, 3J =9.75 Hz), 132.2, 130.0 (d, 4J = 3 Hz),
125.5 (d, 4J =3.75 Hz), 119.4 (d, 4J = 3 Hz), 118.8 (d, 3J = 9.75 Hz),
116.8 (d, 2J =24 Hz), 113.6 (d, 2J =21 Hz), 111.2 (d, 2J = 25.5 Hz)
1574 (C5C), 1280 (C5S), 1138 (C–N)
1i
1j
3275 (N–H), 1667 (C5O),
12.62 (br s, 1H, NH), 9.20 (br s, 1H, NH), 7.51 (td, J =1.5, 10.2 Hz,
1H, Ar–H), 7.69–6.98 (m, 7H, Ar–H)
178.6 (C5S), 166.4 (C5O), 162.9 (d, 1J = 251 Hz), 162.6 (d, 1J = 245 Hz),
140.2 (d, 3J = 8.75 Hz), 139.7 (d, 3J =10.5 Hz), 132.0 (d, 3J = 10.75 Hz),
130.1 (d, 3J = 9.75 Hz), 112.3 (d, 4J =3 Hz), 119.4 (d, 4J = 3.75 Hz), 116.2
(d, 2J = 22 Hz), 114.6 (d, 2J = 26.5 Hz), 113.7 (d, 2J = 21.75 Hz), 111.2 (d, 2J = 25 Hz)
1574 (C5C), 1280 (C5S), 1138 (C–N)
3325 (N–H), 1664 (C5O),
12.39 (br s, 1H, NH), 9.69 (br s, 1H, NH), 8.08–8.00 (2H, m, Ar–H),
7.77 (td, J = 2.1, 10.2 Hz, 1H, Ar–H), 7.43–6.96 (m, 5H, Ar–H)
178.0 (C5S), 166.6 (C5O), 165.5 (d, 1J = 244.5 Hz), 164.9 (d, 1J = 250 Hz),
138.9 (d, 3J =10.5 Hz), 133.0 (2C, d, 3J = 8.25 Hz), 131.6, 130.6 (d, 3J = 9.75 Hz),
119.4 (d, 4J =3 Hz), 114.8 (2C, d, 2J = 21.25 Hz), 113.8 (d, 2J = 21.75 Hz),
114.8 (2C, d, 2J = 21.75 Hz)
1579 (C5C), 1276 (C5S), 1159 (C–N)
1k
1l
3155 (N–H), 1675 (C5O),
12.29 (br s, 1H, NH), 9.34 (br s, 1H, NH), 7.77 (dd, J = 1.2, 8.1 Hz, 1H,
Ar–H), 7.70–7.10 (m, 7H, Ar–H)
178.3 (C5S), 166.2 (C5O), 161.0 (d, 1J = 246 Hz), 133.5, 133.4, 132.0, 131.2,
131.0, 130.5, 127.6, 126.3 (2C, d, 3J = 8.25 Hz), 115.8 (2C, d, 2J = 22.5 Hz)
1543 (C5C), 1279 (C5S), 1166 (C–N)
3235 (N–H), 1608 (C5O),
12.7 (br s, 1H, NH), 9.16 (br s, 1H, NH), 7.68–7.13 (m, 4H, Ar–H),
7.11 (s, 2H, Ar–H), 3.95 (s, 6H, 2[O–CH3]), 3.85 (s, 3H, O–CH3)
178.5 (C5S), 166.4 (C5O), 161.0 (d, 1J = 246 Hz), 153.5 (2C), 142.9,
133.5 (d, 4J =3 Hz), 126.5, 126.3 (2C, d, 3J = 8.75 Hz), 115.7 (2C, d, 2J = 22.5 Hz),
104.9 (2C), 61.1 (OCH3), 56.5 (2C, 2[OCH3])
1574 (C5C), 1240 (C5S), 1133 (C–N)
1m
1n
3215 (N–H), 1660 (C5O),
12.5 (br s, 1H, NH), 9.78 (br d, J = 15 Hz, 1H, NH), 8.12 (dt, J = 1.8, 7.8 Hz,
1H, Ar–H), 7.63–7.71 (m, 3H, Ar–H), 7.38 (dt, J = 1.2, 7.8 Hz, 1H, Ar–H),
7.30–7.10 (m, 3H, Ar–H)
178.7 (C5S), 163.1 (d, J = 9.75 Hz, C5O), 161.0 (d, 1J = 246 Hz), 160.5 (d, 1J = 250 Hz),
135.9 (d, 3J =9.75 Hz), 133.6 (d, 4J = 3 Hz), 132.1, 126.3 (d, 3J = 8.25 Hz),
1539 (C5C), 1279 (C5S), 1144 (C–N)
125.5 (d, 4J =3 Hz), 118.9 (d, 3J = 9.75 Hz), 116.8 (d, 2J = 24 Hz), 115.8 (d, 2J = 22.5 Hz)
3210 (N–H), 1674 (C5O),
12.5 (br s, 1H, NH), 9.14 (br s, 1H, NH), 7.69–7.52 (m, 5H, Ar–H),
7.38 (ddt, J = 0.9, 2.4, 8.1 Hz, 1H, Ar–H), 7.18–7.09 (m, 2H, Ar–H)
178.8 (C5S), 164.4 (C5O), 162.9 (d, 1J = 251 Hz), 161.1 (d, 1J = 247 Hz),
140.1 (d, 3J = 8.75 Hz), 133.6 (d, 4J =3 Hz), 132.0 (d, 3J = 10.75 Hz),
126.3 (2C, d, 3J = 8.25 Hz), 122.3 (d, 4J = 3.75 Hz), 116.2 (d, 2J = 22 Hz),
115.8 (2C, d, 2J = 22.5 Hz), 114.3 (d, 2J = 26.25 Hz)
1523 (C5C), 1261 (C5S), 1156 (C–N)

A. Saeed et al. / Journal of Fluorine Chemistry 130 (2009) 1028–1034
1031
according to standard procedure. The latter were treated with an
equimolar quantity of potassium thiocyanate in acetone to afford
the corresponding isothiocyanate intermediates which were not
separated. Condensation of the isothiocyanates with isomeric
fluoroanilines furnished the 1-(substituted fluorobenzoyl)-3-
(substituted fluoroaryl)thiourea derivatives (1a–t) [28].
Typically, thioureas are characterized by IR absorptions at 3350,
3200 for free and associated NH, at 1600–1695 for carbonyl and at
1230–1285 cmꢀ1 for thiocarbonyl groups respectively. The char-
acteristic broad singlets at ca.
d 9.0 and 12.0 ppm for HN(1) and
HN(3) and peaks at ca. 167, 178 for carbonyl and thiocarbonyl were
also observed in the 1H and 13C NMR spectra respectively. The
physicochemical properties and the spectroscopic data of thiour-
eas 1a–t are given in Tables 1 and 2 respectively. Mass spectra of all
of the compounds showed the molecular ion peaks. The major
fragment corresponds to the N-McLafferty rearrangement and the
base peaks are derived from the aroyl cation.
2.2. Biological activities
2.2.1. Antibacterial activity
In vitro evaluation of antibacterial activity was carried out by
disk diffusion method (Kirby–Bauer method) against Staphylococ-
cus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas
aureginosa [29]. The tests were repeated three times and the
results are reported as means of at least three determinations and
the results are summarized in Table 3. The figures represent the
zone of inhibition in millimeters. As is evident from the table all
compounds 1a–t exhibited good to significant inhibitory activity
against the two strains, viz. B. subtilis and P. aureginosa, compared
to standard drug at the tested concentration. Some of them were
active against S. aureus but most of them are inactive against E. coli.
Good to significant activity against B. subtilis is observed for all of
the compounds. Four compounds which show excellent activity
are 1e (73%), 1f (78%), 1i (66%) and 1s (66%). Overall good results
are obtained for compounds 1f–j (R = 3-F) against B. subtilis.
Compounds 1b–d, 1g, 1m, 1o, and 1t have been found to exhibit
moderate activity against S. aureus. All compounds show weak to
Table 3
Antibacterial bioassay screening of thioureas (1a–t).
Compound
Antibacterial activitya
Gram-positive
Gram-negative
Staphylococcus
aureus
Bacillus
Escherichia coli
Pseudomonas
aureginosa
subtilis
1a
1b
1c
1d
1e
1f
–
–
07
08
09
09
13
14
10
07
12
06
06
06
09
07
08
07
10
07
12
08
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
01
–
–
–
–
05
05
06
05
14
06
–
–
06
–
–
1g
1h
1i
–
05
10
–
05
04
03
03
01
06
05
08
04
05
07
11
05
1j
1k
1l
–
–
1m
1n
1o
1p
1q
1r
1s
1t
07
07
–
–
07
07
–
06
Imipenem
21
18
16
18
Concentration used: 2 mg/1 ml; –: no activity.
a
Zone of inhibition (radius, mm).

1032
A. Saeed et al. / Journal of Fluorine Chemistry 130 (2009) 1028–1034
Fig. 1. Antibacterial bioassay screening of thioureas (1a–t).
Table 4
was used as the standard drug. It is an intravenous
b-lactam
Minimum inhibitory concentration (MIC) of selected compounds.
antibiotic (subgroup carbapenems) having an extremely broad
spectrum of activity. Imipenem is principally active against
Pseudomonas aeruginosa and the Enterococcus species but is not
active against S. aureus. Imipenem exhibits its antimicrobial action
through inhibiting cell wall synthesis of bacteria and is very stable
Compound
Minimum inhibitory concentration (MIC) (
m
g/ml)
S. aureus
B. subtilis
E. coli
P. aureginosa
1c
1d
1e
1g
1i
–
500
–
250
250
125
250
125
250
250
125
–
–
–
–
–
–
–
–
500
500
125
–
in the presence of b-lactamase produced by some bacteria. Since it
is rapidly degraded by the renal enzyme dehydropeptidase 1 when
administered alone, therefore it is always co-administered with
cilastatin to prevent this inactivation [30]. Compounds 1e (4-F on
aroyl 2-F on aryl ring; zone of inhibition 14 mm against B. subtilis)
and 1f (2-Cl on aroyl, 3-F on aryl, zone of inhibition 14 mm against
P. aureginosa) possess antibacterial action close to that of
Imipenem having zone of inhibition 18 mm for each of these
strains.
–
250
500
250
–
1000
500
500
125
1m
1q
1s
moderate activity against bacterial strain P. aureginosa with the
exception of compounds 1e (78%) and 1s (62%) that possess
noteworthy activity (Fig. 1). Imipenem (5R,6S)-6-[(1R)-1-hydroxy
ethyl]-3-({2-[(iminomethyl)amino] ethyl}thio)-7-oxo-1-azabicy-
clo[3.2.0]hept-2-ene-2-carboxylic acid (molecular mass 299.347)
The minimum inhibitory concentrations (MICs) of the com-
pounds were recorded as the lowest concentration of each of the
compounds in the petri plates with no turbidity (i.e. no growth) of
Table 5
Antifungal bioassay screening of thioureas (1a–t).
Compound
Antifungal activity
Rhizopus oryzae
Aspergillus tereus
Fusarium
sporum
oxy-
Aspergillus niger
Aspergillus fumiga-
tus
ZI
PI
16.7
ZI
PI
37.5
ZI
PI
ZI
PI
44.4
ZIa
PI
33.3
1a
1b
1c
1d
1e
1f
7.5
8.5
1.5
9.0
7.5
9.0
1.0
7.0
7.5
3.0
8.0
8.5
2.0
8.5
7.0
9.0
9.0
8.5
9.0
8.0
5.0
5.0
5.0
4.5
4.0
7.5
5.5
3.0
3.5
3.5
5.5
4.5
5.5
4.0
3.0
5.0
4.0
3.5
5.0
6.0
6.0
6.0
3.2
3.0
4.5
6.5
3.2
4.5
4.5
2.0
6.5
3.5
4.5
5.4
5.0
6.0
3.0
6.0
4.0
5.0
25.0
25.0
60.0
62.5
43.8
18.8
60.0
43.8
43.8
75.0
18.8
56.3
43.8
32.5
37.5
25.0
62.5
25.0
50.0
37.5
5.0
9.0
4.0
5.5
5.5
9.0
9.0
5.0
9.0
9.0
4.0
9.0
8.0
6.0
9.0
9.0
5.0
4.0
5.0
5.0
6.0
8.5
4.0
6.0
7.0
8.5
9.0
7.5
7.5
9.0
4.5
9.0
8.5
5.5
9.0
7.0
5.0
5.0
4.0
6.0
5.60
37.5
37.5
43.8
50.0
–
5.50
83.4
–
55.5
38.8
38.8
–
55.5
33.3
22.2
16.7
–
6.30
5.50
1g
1h
1i
88.9
22.3
16.7
66.7
11.2
31.3
62.5
56.3
56.3
31.3
43.8
31.3
50.0
62.5
37.5
50.0
56.3
37.5
25.0
–
–
44.4
–
16.6
16.6
–
1j
–
1k
1l
55.5
–
50.0
–
5.60
77.8
5.60
1m
1n
1o
1p
1q
1r
1s
1t
11.1
33.3
–
5.50
38.8
–
22.3
–
–
22.2
44.4
44.4
55.5
33.3
–
44.4
55.5
44.4
44.4
5.6
–
11.2
Control
9.0
0
–
8.0
0
–
8.0
0
–
9.0
0
–
9.0
0
–
Nystatin
100
100
100
100
100
ZI: zone of inhibition; PI : percent inhibition ¼ 100 ꢀ fungal growth in sampleðcmÞ=fungal growth in controlðcmÞ ꢁ 100; –: no activity.
a
Radius (cm).

A. Saeed et al. / Journal of Fluorine Chemistry 130 (2009) 1028–1034
1033
Fig. 2. Antifungal bioassay screening of thioureas (1a–t).
inoculated bacteria (Table 4). Compounds 1e having a fluorine
substituent at 4-position of aroyl ring and 2-position of aryl ring and
1s having fluorine at 4-position of both aroyl ring and aryl ring along
with a chloro substituent at 3-position of aryl ring show good
activity. In general fluorinated thioureas show better antifungal
activity than the antibacterial activity. The position of fluorine
substituent on aroyl and aryl rings has significant effect on the
antimicrobial activity.
antibacterial activity at very low concentration (125
mg/ml) against
B. subtilis and P. aureginosa. Moreover, compound 1i exhibited
significant activity against B. subtilis at low concentration.
4. Experimental
Melting points were recorded using a digital Gallenkamp
(SANYO) model MPD.BM 3.5 apparatus and are uncorrected. 1H
and 13C NMR spectra were determined in CDCl3 at 300 MHz and
75 MHz respectively using a Bruker spectrophotometer. IR spectra
were recorded on an IR Shimadzu 460 spectrophotometer as KBr
pellets. Mass Spectra (EI, 70 eV) on a GC–MS instrument Agilent
technologies and elemental analyses were conducted using a
LECO-183 CHNS analyzer. Bioactivities were carried out at the
Department of Microbiology, Quaid-i-Azam University, Islamabad,
Pakistan. Thin layer chromatography (TLC) was conducted on
0.25 mm silica gel plates (60 F254, Merck). Visualization was made
with ultraviolet light. Reagents were obtained commercially and
used as received.
2.2.2. Antifungal activity
Antifungal activity is also affected by the nature and position of
substituents on aroyl and aryl ring. Significant activity is observed
when fluorine is present at ortho position of aroyl ring and at meta
position of aryl ring whereas for absence of fluorine on aroyl ring
lowers the activity (Table 5). Fig. 2 graphically presents the percent
inhibition of isomeric 1-fluoroaroyl-3-fluoroaryl thioureas against
different fungal strains. In case of R. oryzae the compounds
showing significant to excellent activity are 1c (83.4%), 1g (88.9%),
1j (66.7%) and 1m (77.8%). In the case A. tereus, all of the
compounds possess low to good inhibition with reference to
control. Good to significant results are obtained for compounds
1h–j (R = 3-F; R0 = F). Some of the compounds possessing moderate
to good activity are 1h (62.5%), 1i (56.3%), 1j (56.3%), 1o (62.5%)
and 1r (56.3%). For fungal strain F. oxysporum good to significant
activity was observed. Thus compounds 1c (60%), 1d (62.5%), 1g
(60%), 1j (75%), 1l (56.3%) and 1q (62.5%) exhibited significant
inhibition. In the case A. niger some of the compounds are inactive
while the compounds 1c (55.5%), 1k (55.5%) and 1r (55.5%) showed
good inhibitions. Low activity is observed for compounds 1f–1e
against A. fumigates for R = 3-F whilst good results are observed for
R = 2-F and R = 3-Cl-4-F and significant results have been observed
for compounds 1c (55.5%), 1k (50%) and 1s (55.5%).
Nystatin (mol. mass 926.09) isolated from Streptomyces noursei
is a polyene antifungal drug effective against many molds and
fungi including Candida and Cryptococcus spp. It is considered a
relatively safe drug for treating oral or gastrointestinal fungal
infections. Nystatin like amphotericin B and natamycin, binds to
ergosterol, a major component of the fungal cell membrane. When
present in sufficient concentrations, it forms pores in the
membrane that lead to K+ leakage and death of the fungus [31].
Nystatin was used as negative control (as standard drug) with no
growth (100% inhibition) of all fungal strains at the same
concentration.
4.1. General procedure for the preparation of 1-(fluorobenzoyl)-3-
(fluorophenyl)thioureas (1a–t)
A freshly distilled solution of substituted fluorobenzoyl chloride
(10 mmol) in anhydrous acetone (50 ml) was added dropwise to a
suspension of potassium thiocyanate (10 mmol) in acetone (30 ml)
at room temperature. The reaction mixture was refluxed for
30 min. and cooled to room temperature. A solution of the
fluorinated aniline (10 mmol) in anhydrous acetone (20 ml) was
added dropwise and the reaction mixture was refluxed further for
2–3 h. On completion of reaction (t.l.c.) the mixture was poured
into cold water and the precipitated thioureas were filtered and
recrystallized from methanol.
The physicochemical elemental and mass spectral data of
compounds is given in Table 1 whereas IR and NMR data is
presented in Table 2.
4.2. Biological assay
4.2.1. Antibacterial activity
The antibacterial activity of all synthesized fluorinated 1-aroyl-
3-aryl thioureas has been investigated against four strains of
bacteria (E. coli ATCC 25922, P. aureginosa ATCC 10197, B. subtilis
DSM 3256, S. aureus ATCC 25923) by the Agar well diffusion assay.
Imipenem was used as a standard antibiotic, 2 mg of compounds
were dissolved in 1 ml of DMSO. In nutrient broth medium 24 h
3. Conclusions
A variety of new fluorinated thioureas (1a–t) were synthesized
characterized and screened for in vitro antibacterial and antifungal

1034
A. Saeed et al. / Journal of Fluorine Chemistry 130 (2009) 1028–1034
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% age of fungal inhibition ¼ 100
fungal growth in test sampleðcmÞ
ꢀ
fungal growth in controlðcmÞ
ꢁ 100
Nystatin was used as negative control (as standard drug) with no
growth (100% inhibition) of all fungal strains at the same
concentration.