Synthesis, characterization, and antiviral activity of novel fluorinated isatin derivatives

Article abstract of DOI:10.1007/s00706-013-1034-3

New series of Schiff's bases, hydrazones, thiosemicarbazones, thiazoles, and thiocarbohydrazones of 5-fluoroisatin were synthesized by the reaction of 5-fluoroisatin with primary amines, hydrazine hydrate, and thiocarbohydrazides. Thiosemicarbazones were prepared by reacting hydrazone derivatives with isothiocyanates. Upon treatment of thiosemicarbazone derivatives with chloroacetone, the thiazole derivatives were obtained. Some of the prepared compounds exhibited antiviral activity. Springer-Verlag Wien 2013.

Full text of DOI:10.1007/s00706-013-1034-3

Monatsh Chem
DOI 10.1007/s00706-013-1034-3
ORIGINAL PAPER
Synthesis, characterization, and antiviral activity of novel
fluorinated isatin derivatives
•
Samir Y. Abbas Awatef A. Farag Yousry A. Ammar
•
•
•
Abeer A. Atrees Aly F. Mohamed Ahmed A. El-Henawy
•
Received: 29 September 2012 / Accepted: 9 June 2013
Ó Springer-Verlag Wien 2013
Abstract New series of Schiff’s bases, hydrazones, thio-
semicarbazones, thiazoles, and thiocarbohydrazones of
5-fluoroisatin were synthesized by the reaction of 5-fluo-
roisatin with primary amines, hydrazine hydrate, and
thiocarbohydrazides. Thiosemicarbazones were prepared by
reacting hydrazone derivatives with isothiocyanates. Upon
treatment of thiosemicarbazone derivatives with chloroace-
tone, the thiazole derivatives were obtained. Some of the
prepared compounds exhibited antiviral activity.
vaccinia [2], rhino virus [3], Moloney leukemia virus [4], and
SARS virus [5]. Previous works have also reported the
inhibitory activity of isatin-thiosemicarbazones and isatin
derivatives on HIV replication [6–8]. In addition, methisa-
zone (an isatin-thiosemicarbazone) plays an important role
as a prophylactic agent against several viral diseases [9].
There has been increasing interest in recent years concerning
the introduction of fluorine into organic compounds [10, 11].
Incorporation of one or several fluorine atoms into an organic
molecule can improve the pharmacokinetic and pharmaco-
dynamic properties such as absorption, tissue distribution,
secretion, the route and rate of biotransformation, toxicol-
ogy, bioavailability, metabolic stability, and lipophilicity
[12, 13]. Many of the compounds containing a fluorine atom
have a significant therapeutic impact. Fluorinated isatin
derivatives have become a focus in the development of new
biologically active compounds [14].
Keywords Schiff bases ꢀ Carbonyl compounds ꢀ
Thiosemicarbazones ꢀ Thiazoles
Introduction
The antiviral activities of isatin derivatives have been widely
reported, especially their action against pox virus [1],
In view of these observations and as a continuation of
our effort in developing broad-spectrum chemotherapeutics
[15–18], we report the preparation of some newer fluori-
nated iminoisatin derivatives in the hope of obtaining better
antiviral drugs without side effects.
S. Y. Abbas (&)
Organometallic and Organometalloid Chemistry Department,
National Research Centre, Cairo, Egypt
e-mail: samiryoussef@rocketmail.com
A. A. Farag ꢀ A. A. Atrees
Results and discussion
Chemistry Department, Faculty of Education, Taif University,
Taif, Saudi Arabia
Chemistry
A. A. Farag ꢀ Y. A. Ammar ꢀ A. A. El-Henawy
Chemistry Department, Faculty of Science, Al-Azhar University
(Girls), Cairo, Egypt
In the present investigation, the reactivity of 5-fluoroisatin
(1) towards some different types of nitrogen nucleophile was
studied with the objective of obtaining biologically active
compounds. Thus, reaction of 5-fluoroisatin with 3-amino-2-
thioxothiazolidin-4-one afforded the corresponding Schiff’s
base 2. Reaction of 1 with a fluorinated aromatic amine,
2-amino-N-[3-(trifluoromethyl)phenyl]benzamide, afforded
Y. A. Ammar
Chemistry Department, Faculty of Science,
King Khaled University, Abha, Saudi Arabia
A. F. Mohamed
Applied Research Sector, VACSERA, Cairo, Egypt
123

S. Y. Abbas et al.
the corresponding Schiff’s base 3. The spectral data of the
isolated products were in complete agreement with their
structures. The aromatic signals were observed in all cases as
multiplets for the 5-fluorisatin protons owing to F–H and
H–H couplings. The structures of 2 and 3 were assigned the
basis of analytical and spectral data. The IR spectrum of 2
displayed absorption bands at m = 3,238 (NH), 1,700, 1,668
(C=O, amidic C=O) cm-1. Its 1H NMR spectrum exhibited a
sharp singlet signal at d = 5.80 ppm assigned to CH2 pro-
tons, three signals at 6.87, 8.60, and 7.30 ppm owing to
indole protons, and a D2O-exchangeable singlet signal at
11.40 ppm due to NH proton.
Moreover the mass spectrum of compound 8c showed the
molecular ion peak at 332 (M?, 84.2 %) (Scheme 1).
In continuation with our work in this area, we decided to
prepare and evaluate the biological activity of some new
isatin thiocarbohydrazone derivatives. When the 5-fluoroi-
satin was reacted with thiocarbohydrazide, 5-fluoroisatin
thiocarbohydrazone (9) was obtained. The IR spectrum
showed absorption bands at 3,270, 3,160, and 3,106 cm-1
,
1
corresponding to NH2 and NH functions. The H NMR
spectrum revealed D2O-exchangeable signals at 2.51, 4.92,
10.40, and 12.54 ppm assignable to NH2 and NH protons.
Thiocarbohydrazone 9 was used as a starting material in the
synthesis of different types of isatin thiocarbohydrazone
derivatives. Thus, when compound 9 was condensed with
some selected aldehydes, the corresponding thiocarbohyd-
razones 10a–10e were obtained in good yield. The structure
of 10 was established on the basis of its spectral data beside
its independent synthesis via the reaction of N-thiocarbo-
hydrazones with 5-fluoroisatin which afforded products
identical in all respects with those obtained previously.
When 9 was condensed with 5-fluoroisatin, the corre-
sponding bis-isatin thiocarbohydrazone 11 was obtained in
quantitative yield. Finally, trifluoroacyl derivative 12 was
prepared by the reaction of thiocarbohydrazone derivative
9 with trifluoroacetic anhydride. The structure of 11 was
based of analytical and spectral data. Thus the mass
spectrum of this product showed the molecular ion peak at
m/z = 400 (M?, 12.6), with a base peak at 136. The IR
spectrum revealed absorption bands at 3,256, 3,212, and
Hydrazone derivative 4 was prepared according to a
literature procedure by treatment of 5-fluoroisatin (1) with
hydrazine hydrate in ethanol [19].
It was of interest to synthesize some new sulfonamide
derivatives. Thus, sulfonamide derivatives 5a–5c were
prepared by heating the hydrazone 4 with sulfonyl chloride
derivatives (namely methanesulfonyl chloride, benzene-
sulfonyl chloride, or 4-methylbenzenesulfonyl chloride) in
dioxane containing a catalytic amount of triethylamine.
Sulfonamide derivative 5c was prepared previously by the
reaction of 5-fluoroisatin with tolylsulfonylhydrazine and
reported in a patent [20]. The IR spectrum of 5a revealed
absorption bands at 3,178 and 3,106 cm-1 due to two NH
groups, and a band near 1,660 cm-1 that was attributed to
1
the carbonyl group. Its H NMR spectrum revealed singlet
signals at 2.83 ppm due to CH3 protons beside two singlet
signals in the region of 10.68 and 11.80 ppm due to two
NH groups. The mass spectroscopic measurements of 7c
showed m/z = 333 (M?, 5.8) which indicates structure 5.
Interaction of the hydrazone derivative 4 with trifluo-
roacetic anhydride afforded the corresponding hydrazone
derivative 6. The spectral data of the isolated product was
in complete agreement with its structure. The IR spectrum
of 6 revealed absorption bands at 3,255 and 3,107 cm-1
(NH) and 1,696 and 1,661 cm-1 (C=O).
1
3,187 cm-1 (NH) and 1,667 cm-1 (C=O). The H NMR
spectrum revealed signals at 7.10–7.64 ppm due to the
aromatic protons. The IR spectrum of compound 12
showed a broad absorption band around 3,340–3,210 cm-1
due to NH groups besides two carbonyl absorption bands at
1,697 and 1,670 cm-1. Its 1H NMR spectrum revealed four
D2O-exchangeable signals at 10.87, 11.45, 12.12, and
14.34 ppm due to four NH protons (Scheme 2).
In this study, the reactivity of hydrazone 4 towards iso-
thiocyanate derivatives was investigated. Thus, when
hydrazone 4 was left to react with different isothiocyanate
derivatives in ethanol, the corresponding thiosemicarbazone
derivatives 7a–7f were obtained. Thiosemicarbazone
derivatives 7a–7f were prepared previously by treatment of
5-fluoroisatin with different N-substituted thiosemicarba-
zide derivatives [21]. We have extended our synthetic
program to utilize structures 7a–7f as the key starting
materials for alkylation with chloroacetone in ethanol con-
taining fused sodium acetate to furnish the corresponding
thiazole derivatives 8a–8f. The IR spectrum of compound 8a
revealed absorption bands at 3,212 and 1,675 cm-1 char-
acteristic for NH and C=O groups, respectively. Its 1H NMR
spectrum revealed signals at 1.76 and 2.76 ppm due to two
methyl groups and at 5.85 ppm due to the CH proton.
Biological activity
Cytotoxicity and antiviral activities
The selected synthesized isatin derivatives 7a–7e, 10a–
10e, and 11 were evaluated for their inhibitory effect on the
replication of vesicular stomatitis virus (VSV) as well as
cytotoxicity evaluation in Vero clone CCL-81 cell lines.
Evaluation of the antiviral activity of isatin derivatives and
interferon as standard was determined according to Shinji’s
method [22] and the results are summarized in Table 1.
Certain aspects of the structure–activity relationships for
these compounds can be more clearly highlighted using the
general structures provided in Table 1. From the tabulated
data, it was found that six compounds showed activities
against the tested virus. In the Vero clone CCL-81 cell
123

Synthesis, characterization, and antiviral activity
Scheme 1
S
CF3
S
F
N N
F
N
O
F
O
O
a
b
O
O
N
N
H
O
N
N
H
H
H
3
2
1
O
S
S
H
F
N
O
N
Ar
F
N NH2
O
N
O
ArSO2Cl
F
RNCS
N
NHR
O
H
N
H
N
H
N
H
4
7a-7f
5a, Ar = CH3 5c, Ar = C6H4CH3-4
5b, Ar = C6H5
ClCH2COCH3
(CF3CO)2O
F
R
CH3
O
N
F
N N
O
N
N
H
CF3
S
N
N
H
O
H
8a-8f
6
7,8a, R = CH3
7,8b, R = C2H5
7,8d, R = n-C4H9
7,8e, R = C6H5
a: 3-amino-2-thioxothiazolidin-4-one
b: 2-amino-N-[3-(trifluoromethyl)phenyl]benzamide
7,8c, R = CH2CHCH2 7,8f, R = C6H11
Scheme 2
S
F
O
O
NH2NHCSNHN=CHAr
ArCHO
F
N
O
N
Ar
N
N
H
H
N
H
1
N
H
CS(NHNH2)2
10a, Ar = C6H5
10d, Ar = Furyl
10b, Ar = C6H4F-4 10e, Ar = Thienyl
10c, Ar = C6H4N(CH3)2
S
F
N
NH2
N
N
H
H
S
N
H
O
F
F
N
O
N
O
1
N
N
9
H
H
N
N
H
H
11
S
H
F
N
O
N
CF3
(CF3CO)2O
N
H
N
H
O
N
H
12
123

S. Y. Abbas et al.
Table 1 Cytotoxicity and antiviral activity for the selected compounds
S
S
F
N
F
N
O
N
R
N
NHR
N
N
H
H
H
N
H
O
N
H
7a-7f
10a-10e,11
Compound
R
IC50/lmol cm-3
Antiviral activity
Virus titer log10
Virus titer difference log
Effect
Control
7a
–
–
6.28
6.43
6.33
5.40
5.49
6.40
–
–
–CH3
12.8
25.3
24.8
24.9
5.7
0.15
0.05
0.88
0.76
0.20
Increased
Increased
Decreased
Decreased
Increased
7b
–CH2CH3
7c
–CH2CH=CH2
–(CH2)3CH3
7d
7e
10a
10b
10c
23.6
1.0
6.49
5.38
5.57
0.21
0.90
0.68
Increased
Decreased
Decreased
H
C
H
C
F
3.0
CH3
CH3
H
C
N
10d
10e
11
1.5
12.2
12.6
6.59
6.00
6.11
0.31
0.28
0.17
Increased
Decreased
Decreased
O
S
H
C
H
C
O
N
H
Interferon
4.40
1.88
Decreased
123

Synthesis, characterization, and antiviral activity
heated under reflux for 1 h and left to cool. The solid
product was filtered and recrystallized from ethanol to give
2 as brown crystals. Yield 85 %; m.p.: [300 °C; IR:
lines, compound 7c, which has an allyl moiety, was found
to be the most active among compounds 7 against repli-
cation of VSV with a log virus titer difference of 0.88;
when the allyl moiety of this compound was replaced by an
n-butyl moiety, as in the case of compound 7d, the log
virus titer difference decreased to 0.76. No positive activ-
ities were noticed in the other tested samples among the
series of tested structure. Compound 10b, which has a
4-fluorophenyl moiety, showed the highest activity among
compounds 10 against replication of VSV with a log virus
titer difference of 0.90; when this moiety was replaced by a
4-dimethylphenyl moiety, as in the case of compound 10c,
the activity decreased and showed a log virus titer differ-
ence of 0.68. Compounds 10e and 11 exhibited weak
activity, whereas the other tested compounds showed no
positive antiviral activity. In pharmacological terms, the
presence of the 4-fluorophenyl moiety on the skeleton of
structure 10 may be directly responsible for its antiviral
activity, whereas the presence of the allyl moiety in com-
pound 7c makes it a promising antiviral agent.
m = 3,238 (NH), 1,700, 1,668 (C=O) cm-1 1H NMR:
;
d = 5.80 (s, 2H, CH2), 6.94 (m, 1H, indole C7-H), 7.21 (m,
1H, indole C6-H), 7.44 (m, 1H, indole C4-H), 11.40 (s, 1H,
NH) ppm; 13C NMR: d = 33.7, 108.1, 112.5, 117.7, 121.8,
131.4, 138.9, 158.6, 163.1, 174.5, 177.3 ppm.
2-(5-Fluoro-2-oxoindolin-3-ylideneamino)-N-
[3-(trifluoromethyl)phenyl]benzamide
(3, C22H13F4N3O2)
A mixture of 5-fluoroisatin (1, 0.01 mol) and 2-amino-N-[3-
(trifluoromethyl)phenyl]benzamide (0.01 mol) in 30 cm3
ethanol was heated under reflux for 1 h. The solution was
concentrated, then left to cool. The solid product was filtered
and recrystallized from toluene to give 3 as pale yellow solid.
Yield 86 %; m.p.: 176–177 °C; IR: m = 3,235, 3,192 (2NH),
1,665 (C=O) cm-1 1H NMR: d = 7.13–7.76 (m, 11H,
;
Ar–H), 9.12, 11.32 (2s, 2H, 2NH) ppm.
N0-(5-Fluoro-2-oxoindolin-3-ylidene)-
arylsulfonohydrazides 5a–5c
A mixture of hydrazone derivative 4 (0.01 mol), the appro-
priate sulfonyl chloride (namely methanesulfonyl chloride,
benzenesulfonyl chloride, or 4-methylbenzenesulfonyl chlo-
ride) (0.01 mol), and 0.5 cm3 triethylamine in 30 cm3
dioxane was heated under reflux for 2 h. The reaction mixture
was poured into crushed ice. The resulting precipitate was
filtrated, dried, and crystallized from ethanol to afford 5a–5c.
Conclusion
A new series of 5-fluoroisatin derivatives was synthesized.
The antiviral screening of some selected compounds
showed good inhibitory activities as antiviral agents.
Among the tested compounds, N1-(5-fluoro-2-oxoindolin-
3-ylidene)-N4-(p-fluoro- (or p-dimethylamino)benzylidene)
thiocarbohydrazone and N-allyl (or n-butyl)-2-(5-fluoro-2-
oxoindolin-3-ylidene) hydrazine carbothioamide were the
most active members.
N0-(5-Fluoro-2-oxoindolin-3-ylidene)-
methanesulfonohydrazide (5a, C9H8FN3O3S)
Brown crystals; yield 76 %; m.p.: 248–250 °C; IR:
1
m = 3,178, 3,106 (2NH), 1,660 (C=O) cm-1; H NMR:
d = 2.83 (s, 3H, CH3), 6.84, 6.95, 7.14 (3 m, 3H of indolyl),
10.68, 11.80 (2s, 2H, 2NH) ppm; 13C NMR: d = 40.4 (CH3),
109.8 (C4-indolyl), 112.9 (C7-indolyl), 114.4 (C6-indolyl),
123.5 (C4a-indolyl), 136.6 (C7a-indolyl), 156.5 (C5-indolyl),
158.9 (C=N-indolyl), 162.9 (C=O-indolyl) ppm.
Experimental
All melting points were determined on an electrothermal
Gallenkamp apparatus. The IR spectra were measured on a
Mattson 5000 FTIR spectrophotometer as potassium bro-
mide discs. The 1H NMR and 13C NMR spectra were
recorded as solutions in DMSO-d6 on a Bruker WP spec-
trometer (300 MHz for 1H NMR and 75 MHz for 13C
NMR) with the chemical shifts downfield from TMS as an
internal standard. The mass spectra were recorded on
Finnegan MAT 212 instrument (the ionizing voltage was
70 eV) at the Faculty of Science, Cairo University. Ele-
mental analyses were carried out by the microanalytical
unit of the Faculty of Science, Cairo University.
N0-(5-Fluoro-2-oxoindolin-3-ylidene)-
benzenesulfonohydrazide (5b, C14H10FN3O3S)
Brown crystals; yield 76 %; m.p.: 287–288 °C; IR:
1
m = 3,178, 3,106 (2NH), 1,660 (C=O) cm-1; H NMR:
d = 7.40–7.96 (m, 8H, Ar–H), 9.56, 11.43 (2s, 2H, 2NH)
ppm; 13C NMR: d = 110.3, 112.3, 116.4, 118.6, 125.4
(2C), 127.5, 129.8 (2C), 136.7, 139.2, 154.4, 158.0,
161.0 ppm.
4-Methyl-N0-(5-fluoro-2-oxoindolin-3-ylidene)benzene-
sulfonohydrazide (5c, C15H12FN3O3S)
3-(5-Fluoro-2-oxoindolin-3-ylideneamino)-2-
Brown crystals; yield 75 %; m.p.: 198–199 °C; IR:
thioxothiazolidin-4-one (2, C11H6FN3O2S2)
A mixture of 5-fluoroisatin (1, 0.01 mol) and 3-amino-2-
thioxothiazolidin-4-one (0.01 mol) in 30 cm3 ethanol was
1
m = 3,178, 3,106 (2NH), 1,660 (C=O) cm-1; H NMR:
d = 2.36 (s, 3H, CH3), 7.40–7.98 (m, 7H, Ar–H), 10.96,
123

S. Y. Abbas et al.
11.80 (2s, 2H, 2NH) ppm; 13C NMR: d = 21.9 (CH3),
110.3, 112.3, 116.4, 118.6, 125.4 (2C), 127.5, 129.8 (2C),
136.7, 139.2, 154.4 (12 Ar–C), 158.0 (C=N of indolyl),
161.0 (C=O of indolyl) ppm; MS: m/z (%) = 333 (M?,
5.8), 299 (6.2), 271 (15.3), 257 (5.2), 179 (42.4), 151
(52.5), 136 (55.80), 108 (100).
N-Cyclohexyl-2-(5-fluoro-2-oxoindolin-3-ylidene)hydra-
zinecarbothioamide (7f)
Yellow crystals; yield 89 %; m.p.: 249–250 °C (Ref. [21]
249–250 °C).
Synthesis of thiazole derivatives 8a–8f
2,2,2-Trifluoro-N0-(5-fluoro-2-oxoindolin-3-ylidene)aceto-
hydrazide (6, C10H5F4N3O2)
A mixture of the thiosemicarbazide derivatives 7a–7f
(0.01 mol), chloroacetone (0.01 mol), and fused sodium
acetate (0.02 mol) in 40 cm3 ethanol was heated under
reflux for 5 h and left to cool. The obtained product was
collected by filtration and recrystallized from the appro-
priate solvent to give 8a–8f.
A mixture of the hydrazone 4 (0.01 mol) and 5 cm3
trifluoroacetic anhydride was stirred for 1 h at room
temperature. The solution was concentrated under vacuum.
The resultant precipitate was collected by filtration and
crystallized from ethanol to give compound 6 as orange
crystals. Yield 71 %; m.p.:[300 °C; IR: m = 3,255, 3,107
3-[(3,4-Dimethylthiazol-2(3H)-ylidene)hydrazono]-5-
fluoroindolin-2-one (8a, C13H11FN4OS)
(2NH), 1,696, 1,661 (C=O) cm-1 1H NMR: d = 6.82
;
(m, 1H of indolyl), 7.36 (m, 1H of indolyl), 7.66 (m, 1H of
indolyl), 11.46, 14.05 (2s, 2H, 2NH) ppm; 13C NMR:
d = 111.0 (C4-indolyl), 113.4 (C7-indolyl), 114.7 (C6-
indolyl), 123.5 (C4a-indolyl), 136.5 (C7a-indolyl), 157.2
(C5-indolyl), 158.9 (C=N-indolyl), 163.2 (C=O-indolyl)
ppm.
Orange crystals from ethanol; yield 63 %; m.p.:
297–298 °C; IR: m = 3,212 (NH), 2,986–2,876 (CH-aliph),
1,675 (C=O) cm-1 1H NMR: d = 1.76, 2.76 (2s, 6H,
;
2CH3), 5.85 (s, 1H, thiazole-H), 6.92 (m, 1H, indole), 7.32
(m, 1H, indole-H), 7.63 (m, 1H, indole-H), 10.41 (s, H,
NH) ppm; 13C NMR: d = 21.2, 31.3 (2 CH3), 95.3, 148.3,
162.2 (3C-thiazole), 117.4, 118.8, 122.5, 131.3, 135.3,
154.7 (6C-indole), 164.4 (C=N indole), 165.1 (indole C=O)
ppm.
Synthesis of thiosemicarbazone derivatives 7a–7f
A mixture of hydrazone 4 (0.01 mol) and the requisite
isothiocyanate (namely methyl-, ethyl-, allyl-, n-butyl-,
phenyl-, cyclohexylisothiocyanate) (0.01 mol) in 20 cm3
ethanol was heated under reflux for 1 h and left to cool.
The resultant precipitate was collected and crystallized to
give 7a–7f.
3-[(3-Ethyl-4-methylthiazol-2(3H)-ylidene)hydrazono]-5-
fluoroindolin-2-one (8b, C14H13FN4OS)
Brown crystals from ethanol; yield 65 %; m.p.: 276–277 °C;
IR: m = 3,218 (NH), 2,978–2,865 (CH-aliph), 1,668 (C=O)
1
cm-1; H NMR: d = 1.23 (t, 3H, ethyl-CH3), 1.78 (s, 3H,
CH3), 3.68 (q, 2H,ethyl-CH2), 5.87 (s, 1H, thiazole), 6.89 (m,
1H, indole-H), 7.20 (m, 1H, indole-H), 7.68 (m, 1H, indole-
H), 10.98 (s,1H, NH) ppm; 13C NMR: d = 14.2 (ethyl-CH3),
22.3 (C-CH3), 40.1 (ethyl-CH2), 93.1, 157.3, 161.2 (3C-thi-
azole), 116.3, 119.2, 121.8, 125.4, 131.4, 152.6 (6C-indolyl),
159.9 (C=N indole), 163.5 (C=O indole) ppm.
2-(5-Fluoro-2-oxoindolin-3-ylidene)-N-
methylhydrazinecarbothioamide (7a)
Yellow crystals; yield 87 %; m.p.: 271–273 °C (Ref. [21]
271–274 °C).
N-Ethyl-2-(5-fluoro-2-oxoindolin-3-ylidene)-
hydrazinecarbothioamide (7b)
3-[(3-Allyl-4-methylthiazol-2(3H)-ylidene)hydrazono]-5-
fluoroindolin-2-one (8c, C15H13FN4OS)
Greenish yellow; yield 92 %; m.p.: 243–245 °C (Ref. [21]
245–246 °C).
Brown crystals from ethanol; yield 61 %; m.p.:
278–279 °C; IR: m = 3,232 (NH), 2,967–2,864 (CH-aliph),
1,676 (C=O) cm-1; 1H NMR: d = 1.76 (s, 3H, CH3), 4.28 (t,
2H, allyl C1-H), 5.14 (d, 1H, allyl-H), 5.45 (d, 1H, allyl C3-
H), 5.67–5.85 (m, 1H, allyl C2-H), 6.21(s, 1H, thiazol-H),
6.93 (m, 1H, indole-H), 7.19 (m, 1H, indole-H), 7.51 (m, 1H,
indole-H), 11.20, (s, 1H, NH) ppm; 13C NMR: d = 21.2
(C-CH3), 78.7, 120.2, 120.2 (3C-propenyl), 93.4, 157.7,
161.5 (3C-thiazole), 116.3, 119.4, 121.8, 126.3, 131.4, 155.6
(6C-indolyl), 159.9 (C=N indole), 163.5 (C=O indole) ppm.
N-Allyl-2-(5-fluoro-2-oxoindolin-3-ylidene)hydra-
zinecarbothioamide (7c)
Yellow crystals; yield 74 %; m.p.: 219–220 °C (Ref. [21]
219–220 °C).
N-Butyl-2-(5-fluoro-2-oxoindolin-3-ylidene)-
hydrazinecarbothioamide (7d)
Greenish yellow crystals; yield 81 %; m.p.: 211–212 °C
(Ref. [21] 211–212 °C).
2-(5-Fluoro-2-oxoindolin-3-ylidene)-N-phenylhy-
drazinecarbothioamide (7e)
3-[(3-Butyl-4-methylthiazol-2(3H)-ylidene)hydrazono]-5-
fluoroindolin-2-one (8d, C16H17FN4OS)
Yellow crystals; yield 79 %; m.p.: 254–255 °C (Ref. [21]
218 °C).
Red crystals from methanol; yield 66 %; m.p.:
248–250 °C: IR: m = 3,232 (NH), 2,967–2,864 (CH-aliph),
123

Synthesis, characterization, and antiviral activity
1,676 (C=O) cm-1; 1H NMR: d = 1.02 (t, 3H, butyl-CH3),
1.35–1.37 (m, 2H, butyl C3-H), 1.67 (m, 2H, butyl C2-H),
1.75 (s, 3H, CH3), 3.69 (q, 2H, butyl C1-H), 6.12 (s, 1H,
thiazole-H), 6.67 (m, 1H, indole-H), 7.16 (m, 1H, indole-
H), 7.64 (m, 1H, indole-H), 10.54 (s, 1H, NH) ppm; 13C
NMR: d = 14.2 (butyl CH3), 20.3 (butyl C3), 31.3 (butyl
C2), 46.6 (butyl-C1), 23.2 (C-CH3), 98.5, 157.3, 164.3
(3C-thiazole), 112.4, 117.6, 121.8, 125.4, 131.3, 155.7
(6C-indole), 162.4 (C=N-indole), 163.4 (indole C=O) ppm;
MS: m/z (%) = 332 (M?, 84.2), 276 (12.3), 262 (6.8), 247
(36.5), 177 (29.3), 162 (28.4), 134 (35.2), 94 (29.4),
55(100).
aldehyde (namely benzaldehyde, 4-fluorobenzaldehyde,
4-(dimethylamino)benzaldehyde, furan-2-carbaldehyde, or
thiophene-2-carbaldehyde) (0.01 mol). The reaction mix-
ture was heated under reflux for 1 h and left to cool. The
solid product so formed was filtered and recrystallized to
give 10a–10e.
Method B: a solution of isatin 1 (0.01 mol) and the
requisite thiocarbohydrazone derivative (0.01 mol) in eth-
anol was heated under reflux for 1 h. The solid product was
filtered and recrystallized (m.p. and mixed m.p.).
N4-Benzylidene-N1-(5-fluoro-2-oxoindolin-3-ylidene)-
thiocarbohydrazone (10a, C16H12FN5OS)
5-Fluoro-3-[(4-methyl-3-phenylthiazol-2(3H)-ylidene)hy-
drazono]indolin-2-one (8e, C18H13FN4OS)
Orange crystals; yield 74 %; m.p.: 287–288 °C; IR:
m = 3,223, 3,160, 3,106 (NH), 1,665 (C=O) cm-1 1H
;
Red crystals from methanol; yield 62 %; m.p.:
265–267 °C; IR: m = 3,236 (NH), 2,964–2,862 (CH-aliph),
1,667 (C=O) cm-1; 1H NMR: d = 1.75 (s, 3H, CH3), 5.64
(s, 1H, CH-thiazole), 6.93–7.65 (m, 8H, Ar–H), 11.27 (s,
1H, NH) ppm; 13C NMR: d = 22.3, 108.1, 112.5, 117.3
(2C), 118.4, 121.8, 125.7, 126.3 (2C), 129.4, 131.5, 138.9,
157.3, 158.7, 161.2, 165.2, 166.1 ppm.
NMR: d = 6.96 (m, 1H, indole-H), 7.22 (m, 1H, indole-H),
7.35 (m, 1H, indole-H), 7.48 (m, 3H, Ar–H), 7.48 (m, 2H,
Ar–H), 8.34 (s, 1H, CH=N), 11.36, 12.44, 14.63 (3s, 3H,
3NH) ppm; 13C NMR: d = 116.3, 118.3, 124.8, 125.4,
126.6, 127.5, 128.5, 129.5, 130.4, 131.4, 132.5, 157.7 (6C
of indolyl ? 6C-Ph), 159.6 (CH=N), 161.0 (C=N of
indolyl), 162.8 (C=O of indolyl), 179.6 (C=S) ppm.
3-[(3-Cyclohexyl-4-methylthiazol-2(3H)-ylidene)-
N1-(5-Fluoro-2-oxoindolin-3-ylidene)-N4-
(4-fluorobenzylidene)thiocarbohydrazone
(10b, C16H11F2N5OS)
hydrazono]-5-fluoroindolin-2-one (8f, C18H19FN4OS)
Orange crystals from methanol; yield 64 %; m.p.:
287–289 °C; IR: m = 3,230 (NH), 2,960–2,868 (CH-aliph),
Orange crystals; yield 75 %; m.p.: 265–266 °C; IR:
1,675 (C=O), 1,611, 1,602 (2 C=N) cm-1 1H NMR:
;
m = 33,412–3,110 (3NH), 1,697 (C=O) cm-1; H NMR:
1
d = 1.15, 1.28–1.35, 1.42–1.51, 1.64, 1.77, 1.92 (m, 10H,
cycl), 1.78 (s, 3H, CH3), 4.18–4.21(m, 1H, cycl-C1-H),
5.89 (s, 1H, thiazole-H), 6.90 (m, 1H, indole-H), 7.32
(m,1H, indole-H), 7.76 (m, 1H, indole-H), 11.25 (s, 1H,
indole NH) ppm; 13C NMR: d = 25.3 (2C), 25.5, 31.9
(2C), 54.2 (6C-cycl), 117.7, 118.4, 121.8, 125.7, 131.5,
138.9, 158.7 (6C indole), 165.2 (C=N), 166.1 (indole C=O)
ppm.
d = 7.22–7.86 (m, 7H, Ar–H), 8.54 (s, 1H, CH=N), 11.28,
12.76, 14.62 (3s, 3H, 3NH) ppm; 13C NMR: d = 116.3,
118.3, 124.8, 125.4, 126.6, 127.5, 128.5, 129.5, 131.4,
132.5, 156.4, 157.7 (6C of indolyl ? 6C-Ph), 159.6
(CH=N), 161.4 (C=N of indolyl), 162.8 (C=O of indolyl),
179.6 (C=S) ppm.
N4-(4-Dimethylaminobenzylidene)-N1-(5-fluoro-2-
oxoindolin-3-ylidene)thiocarbohydrazone
(10c, C18H17FN6OS)
N1-(5-Fluoro-2-oxoindolin-3-ylidene)thiocarbohydrazone
(9, C9H8FN5OS)
Reddish brown crystals; yield 70 %; m.p.: 277–278 °C; IR:
m = 3,243, 3,198, 3,161 (NH), 1,660 (C=O) cm-1 1H
;
A mixture of isatin 1 (0.01 mol) and thiocarbohydrazide
(0.01 mol) in 20 cm3 ethanol was heated under reflux for
0.5 h. The solid product so formed was filtered and
recrystallized to give 9 as brown crystals. Yield 71 %;
m.p.: [300 °C; IR: m = 3,270, 3,160, 3,106 (NH, NH2),
NMR: d = 2.88 (s, 6H, 2CH3), 7.18–7.76 (m, 7H, Ar–H),
8.11 (s, 1H, CH=N), 11.38, 12.60, 14.44 (3s, 3H, 3NH)
ppm; 13C NMR: d = 45.4, 45.4 (2CH3), 116.6, 118.4,
124.7, 125.6, 126.9, 127.8, 128.4, 129.5, 131.8, 132.2,
145.8, 157.9 (6C of indolyl ? 6C-Ph), 159.6 (CH=N),
161.4 (C=N of indolyl), 162.8 (C=O of indolyl), 179.2
(C=S) ppm.
1
1,665 (C=O) cm-1; H NMR: d = 2.51 (s, 1H, NH), 4.92
(bs, 2H, NH2),7.34, 7.42, 7.96 (3 m, 3H of indolyl), 10.40,
12.54 (2s, 2H, 2NH) ppm; 13C NMR: d = 116.3, 118.3,
124.8, 127.5, 132.5, 157.7 (6C of indolyl), 161.0 (C=N of
indolyl), 162.4 (C=O of indolyl), 179.4 (C=S) ppm.
N1-(5-Fluoro-2-oxoindolin-3-ylidene)-N4-
(2-furylmethylene)thiocarbohydrazone
(10d, C14H10FN5O2S)
Synthesis of thiocarbohydrazones 10a–10e
Brown crystals; yield 75 %; m.p.: 235–236 °C; IR:
m = 3,240, 3,212, 3,173 (NH), 1,668 (C=O) cm-1 1H
;
Method A: a solution of isatinthiocarbohydrazone 9
(0.01 mol) in 30 cm3 dioxane was treated with the requisite
NMR: d = 6.87–7.56 (m, 6H, Ar–H), 8.11 (s, 1H, CH=N),
11.22, 12.61, 14.41 (3s, 3H, 3NH) ppm; 13C NMR:
123

S. Y. Abbas et al.
antibiotics (100 U of penicillin/cm3, 100 g of streptomy-
d = 111.3, 113.3, 116.6, 118.4, 125.6, 131.8, 144.2, 144.3,
145.8, 157.9 (6C of indolyl ? 4C-furyl), 159.7 (CH=N),
161.6 (C=N of indolyl), 163.1 (C=O of indolyl), 179.2
(C=S) ppm.
cin/cm3) at 37 °C and incubated in 5 % CO2 atmosphere.
Cytotoxicity assay
Organic compounds (50 lmol) were dissolved in 2 cm3
phosphate buffer saline, pH 7.2 0.2. Test materials were
filtered through 0.2-lm membranes using Millipore dis-
posable syringe filters. The cytotoxicity assay of the tested
organic compounds was performed according to the pre-
vious reports [23], whereby sterile filtrated organic test
materials were twofold serially diluted in MEM and added
to precultured Vero cells. A negative cell control was
included. Plates were incubated at 37 °C for 24 h. Cell
culture-treated plates were microscopically examined using
an inverted microscope for detection of cellular changes.
The test compounds treatment medium was discarded.
Plates were washed using PBS. Cell viability was evaluated
using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (MTT). The cytotoxicity of each compound was
expressed as the 50 % cytotoxic concentration (CC50),
which is the concentration required to reduce cell viability
to 50 % of the control.
N1-(5-Fluoro-2-oxoindolin-3-ylidene)-N4-
(2-thienylmethylene)thiocarbohydrazone
(10e, C14H10FN5O2S2)
Brown crystals; yield 74 %; m.p.: 282–284 °C; IR:
m = 3,248, 3,223, 3,190 (NH), 1,665 (C=O) cm-1 1H
;
NMR: d = 7.18–7.98 (m, 6H, Ar–H), 8.54 (s, 1H, CH=N),
11.67, 12.43, 14.00 (3s, 3H, 3NH) ppm; 13C NMR:
d = 116.6, 118.4, 123.3, 125.6, 126.1, 126.4, 127.6,
127.8, 134.2, 157.9 (10C of indolyl), 159.7 (CH=N),
161.6 (C=N of indolyl), 163.4 (C=O of indolyl), 179.4
(C=S) ppm.
N1,N4-Bis(5-fluoro-2-oxoindolin-3-ylidene)-
thiocarbohydrazone (11, C17H10F2N6O2S)
A mixture the thiocarbohydrazone 9 (0.01 mol) and
5-fluoroisatin (0.01 mol) in 20 cm3 dioxane was heated
under reflux for 2 h. The solid product so formed was
filtered and recrystallized from dioxane to give 11 as red
crystals. Yield 68 %; m.p.:[300 °C; IR: m = 3,256, 3,212,
1
3,187 (NH), 1,667 (C=O) cm-1; H NMR: d = 7.10–7.64
Antiviral activity
Antiviral activity of the synthetic compounds and interferon
against VSV isolate was determined according to the
method reported by Shinji [22], whereby nontoxic con-
centrations of test chemical compounds and rh-IFN (10 IU/
0.1 cm3) as a positive control were used for the treatment of
precultured Vero cells for 24 h at 0.1 cm3/well. One plate
was maintained and left untreated for viral control titration.
A virus infectivity titer was determined according to a
reported method [24]; VSV was tenfold serially diluted in
199 E-Hepes buffer (10-1–10-8). Each dilution was dis-
pensed as 100 mm3/well onto preculture Vero cells. Plates
were inoculated using 10 CCID50 of VSV isolate tested.
Plates were incubated at 37 °C. Seven days post infection
the 50 % end point (CCID50) was determined. Antiviral
activity was determined by subtracting the VSV mean titer
in the treated and non-treated cell titers. The difference
between both titers refers to the antiviral activity.
(m, 6H, indole-H), 10.76, 11.54, 12.23, 14.11 (4s, 4H,
4NH) ppm; 13C NMR: d = 116.6, 116.7, 118.4, 118.7,
122.4, 123.3, 125.4, 126.1, 134.1, 134.2, 156.5, 157.9 (12C
of indolyl), 161.6, 161.9 (2C=N of indolyl), 163.1, 163.4
(2C=O of indolyl), 178.1 (C=S) ppm; MS: m/z (%) = 400
(M?, 12.6), 373 (32.26), 221 (36.4), 179 (86.4), 164 (46.8),
136 (99.28), 108 (100), 94 (48.24), 81 (52.35).
2,2,2-Trifluoro-N0-(2-(5-fluoro-2-oxoindolin-3-ylidene)-
hydrazinecarbonothioyl)acetohydrazide
(12, C11H7F4N5O2S)
A solution of the thiocarbohydrazone 9 (0.01 mol) in
10 cm3 trifluoroacetic anhydride was stirred at room
temperature for 1 h. The solution was concentrated under
vacuum. The solid product so formed was filtered off,
washed with ethanol, dried well, and recrystallized to give
12 as red crystals. Yield 79 %; m.p.: [300 °C; IR:
1
m = 3,340–3,210 (br-NH), 1,697, 1,670 (C=O) cm-1; H
NMR: d = 7.18–7.56 (3 m, 3H, indole-H), 10.87, 11.45,
12.12, 14.34 (4s, 4H, 4NH) ppm; 13C NMR: d = 116.6,
118.4, 123.3, 125.6, 127.8, 134.2, 157.9 (6C of indo-
lyl ? CF3), 161.6 (C=N of indolyl), 163.4 (C=O of
indolyl), 169.7 (CO-CF3), 179.4 (C=S) ppm.
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