New quinoline derivatives: Synthesis and investigation of antibacterial and antituberculosis properties

Article abstract of DOI:10.1016/j.ejmech.2010.04.022

Four new series of quinoline derivatives were synthesized starting from 2-trifluoromethyl aniline through multi-step reactions. In the reaction sequence,substituted aniline was cyclized to 4-hydroxy quinoline 1,which was then transformed to 4-chloro-2,8-bis(trifluoromethyl)quinoline 2. The key scaffold 4-hydrazinyl-2,8-bis(trifluoromethyl)quinoline 3,obtained from the compound 2,was successfully converted to target quinoline derivatives,viz. hydrazones 4aet,ureas 5aee,thioureas 6aec and pyrazoles 7aed,in good yields. The newly synthesized title compounds were evaluated for their in vitro antibacterial activity against Escherichia coli,Staphylococcus aureus,Pseudomonas aeruginosa and Klebsiella pneumoniae (recultured) and antituberculosis activity against Mycobacterium tuberculosis H₃₇Rv and MDR-TB. Preliminary results indicated that most of the hydrazone derivatives demonstrated very good antibacterial and antituberculosis activities while other derivatives showed moderate activity.

Full text of DOI:10.1016/j.ejmech.2010.04.022

European Journal of Medicinal Chemistry 45 (2010) 3374e3383
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
New quinoline derivatives: Synthesis and investigation of antibacterial
and antituberculosis properties
,
c
c
a
Sumesh Eswaran a, Airody Vasudeva Adhikari b , Imran H. Chowdhury , Nishith K. Pal , K.D. Thomas
*
a Anthem Biosciences Pvt. Ltd, 49 Bommasandra Industrial Area, Bommasandra, Bangalore 560099, Karnataka, India
b Department of Chemistry, National Institute of Technology Karnataka, Surathkal, Srinivasnagar, Mangalore 575025, Karnataka, India
c Department of Bacteriology and Serology, Calcutta School of Tropical Medicine, Kolkata 700073, West Bengal, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new series of quinoline derivatives were synthesized starting from 2-trifluoromethyl aniline
through multi-step reactions. In the reaction sequence, substituted aniline was cyclized to 4-hydroxy
quinoline 1, which was then transformed to 4-chloro-2,8-bis(trifluoromethyl)quinoline 2. The key
scaffold 4-hydrazinyl-2,8-bis(trifluoromethyl)quinoline 3, obtained from the compound 2, was
successfully converted to target quinoline derivatives, viz. hydrazones 4aet, ureas 5aee, thioureas 6aec
and pyrazoles 7aed, in good yields. The newly synthesized title compounds were evaluated for their in
vitro antibacterial activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and
Klebsiella pneumoniae (recultured) and antituberculosis activity against Mycobacterium tuberculosis H37Rv
and MDR-TB. Preliminary results indicated that most of the hydrazone derivatives demonstrated very
good antibacterial and antituberculosis activities while other derivatives showed moderate activity.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Received 15 January 2010
Received in revised form
17 April 2010
Accepted 21 April 2010
Available online 28 April 2010
Keywords:
Quinoline
Mefloquine
Antibacterial
Antituberculosis activity
X-ray crystallography
1. Introduction
declared TB as a global health emergency and aimed at saving 14
million lives between 2006 and 2015 [4]. All the above facts reveal
Tuberculosis (TB) is an infectious disease caused by different
species of mycobacteria. Though it is a treatable epidemic disease,
the latest statistics reveals that around 2 million people throughout
the world die annually from tuberculosis and there are around 9
million new cases each year. In the statistics, developing countries
show major share [1]. As a result, it has become a major public
health and socioeconomic problem in most of the developing
countries. Amongst HIV-infected people with weakened immune
system, TB is a leading killer pandemic. Every year about 0.2 million
people living with HIV/AIDS die from TB [2]. Furthermore, in recent
times the appearance of multidrug-resistant TB (MDR-TB), a form of
TB that does not respond to the first-line TB drugs has become
a serious threat to TB control and its treatment. It is a shocking
revelation that MDR-TB is present in almost all countries as per the
current survey, made by the World Health Organization (WHO) and
its partners. A recent estimation by WHO has revealed that within
next 20 years approximately 30 million people will be infected with
the bacillus [3]. Keeping in view of the above statistics, WHO
that there is an urgent need for development of new drugs with
divergent and unique structure and with a mechanism of action
possibly different from that of existing drugs.
In the recent time, quinoline nucleus has gathered an immense
attention among chemists as well as biologists as it is one of the key
building elements for many naturally occurring compounds.
Among the important heterocyclic moieties of biological and
pharmacological interest, the quinoline ring is endowed with
various activities, such as antituberculosis [5], antimalarial [6], anti-
inflammatory [7], anticancer [8], antibiotic [9], antihypertensive
[10], tyrokinase PDGF-RTK inhibiting agents [11], and antiHIV
[12,13]. In spite of its wide range of pharmacological activities, very
few activity studies have been reported against tuberculosis in
comparison with other classes. Keeping this in view, we have
designed four new series of quinoline derivatives with possibly
a new mode of action. The design concepts have been drawn in
Fig. 1, which explains the structural similarity of our new target
compounds with renowned drug mefloquine.
Mefloquine, a well-known antimalarial drug is still being used
today in spite of its numerous side-effects [14]. Further, a number of
its analogues have been reported to possess very good antibacterial
as well as antituberculosis activities [15e18]. Moreover, it is
important to note that quinoline is a core pharmacophore in the
* Corresponding author. Tel.: þ91 (0)824 2474000x3203; fax: þ91 (0)824
2474033.
E-mail addresses: avadhikari123@yahoo.co.in, avchem@nitk.ac.in (A.V.
Adhikari).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.04.022

S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
3375
The key intermediate 4-hydrazinyl-2,8-bis(trifluoromethyl)
quinoline (3) was readily converted to different hydrazones 4aet by
reacting it with aliphatic and (hetero)aromatic aldehydes in pres-
ence of catalytic amount of acetic acid in alcoholic medium. Further,
the compound 3 on heating with substituted isocyanate in toluene
at 110 ꢀC gave the corresponding urea derivatives 5aee, while 3 on
condensing with substituted isothiocyanate at 110 ꢀC in the pres-
ence of toluene yielded the corresponding thiourea derivatives
6aec. The target compounds 7aed were conveniently prepared
from the compound 3 by the sequential addition of substituted
acetoacetate to it, followed by cyclization of the resulting inter-
mediate by treating with sodium ethoxide in ethanol at 80 ꢀC. The
crude compounds thus obtained were purified by column chro-
matography. The reaction sequences employed for the synthesis of
title compounds, viz. 4aet, 5aee, 6aec and 7aed have been
described in Scheme 2.
Fig. 1. Design concept for new quinoline derivatives.
The structures of all the newly synthesized compounds were
confirmed by 1H, 13C NMR and LCeMS studies. The cyclization of
2,8-bis(trifluoromethyl)quinolin-4-ol, (1) from 2-trifluoromethyl
aniline was evidenced by its 1H NMR spectrum and LCeMS. Its
recently developed anti tuberculosis drug, viz. TMC207, a diary-
lquinoline (DARQ), whose activity is mainly due to its interaction
with the proton pump of the ATP synthase of Mycobacterium
tuberculosis [19].
1H NMR spectrum showed a sharp singlet at
d
7.27 due to C3
proton of quinoline ring and the appearance of a broad singlet at
12.78, which disappeared on D2O exchange, attributed to eOH
On the basis of these observations and as a part of our general
program in the continued research for new antibacterials and
antitubercular agents [20e22], we have designed some new quin-
oline derivatives, wherein active pharmacophores, viz. hydrazones,
ureas, thioureas and pyrazoles have been attached at the 4th
position of the quinoline ring containing active trifluoromethyl
groups at 2nd and 8th positions, hoping that the newly designed
molecules would exhibit improved biological activity. Structures of
target molecules have been designed on the basis of combinatorial
synthesis, which is the current trend being practiced in most of the
drug discoveries. In this communication, we report the synthesis of
hitherto unknown title compounds 4aet, 5aee, 6aec and 7aed
starting from 2-trifluoromethy aniline (1) and evaluation of their in
vitro antibacterial property against four pathogenic strains, viz.
Escherichia coli (ATTC-25922), Staphylococcus aureus (ATTC-25923),
Pseudomonas aeruginosa (ATCC 27853) and Klebsiella pneumoniae
(recultured) and antituberculosis activity against M. tuberculosis
H37Rv (ATCC 27294).
d
proton, clearly indicating the smooth cyclization. In fact, the total
proton count for compound 1 perfectly matched with its struc-
ture. The LCeMS spectrum of 1 showed a molecular ion peak at
m/z 282 (M þ 1), which matches with its molecular formula
C11H5F6NO.
The formation of 4-chloro-2,8-bis(trifluoromethyl)quinoline (2)
from the compound 1 was confirmed by its 1H NMR spectral and
LCeMS data. In the 1H NMR spectrum, shifting of the singlet from
d
7.27 to 7.95 due to C3 proton and the disappearance of a broad
singlet at 12.78 confirmed the chlorination at the C4 position of
d
the quinoline ring. Further, the LCeMS spectrum of 2 showed
a molecular ion peak at m/z 300 (M þ 1), which matches with its
molecular formula C11H4ClF6N.
The structure of compound 3 was elucidated by their NMR
spectral and LCeMS analyses. The 1H NMR spectrum of 3 showed
broad singlets at
d 4.72 and 9.34 corresponding to eNH2 and eNH
protons, respectively. Further, the total proton count for compound
3 perfectly matched with its structure. The LCeMS of it showed
a molecular ion peak at m/z 296 (M þ 1), which corresponds to its
molecular formula C11H7F6N3.
2. Chemistry
The reaction sequence employed for synthesis of the key scaf-
fold, 4-hydrazinyl-2,8-bis(trifluoromethyl)quinoline (3) is shown in
Scheme 1. The starting material 2-(trifluoromethyl) aniline was
conveniently cyclized to 2,8-bis(trifluoromethyl)quinolin-4-ol (1),
by heating it with ethyl 4,4,4-trifluoroacetoactate in presence of
polyphosphoric acid (PPA) at 150 ꢀC. The compound 1 on refluxing
with freshly distilled phosphorus oxychloride yielded the corre-
sponding 4-chloro derivative 2, which on condensation with
hydrazine hydrate in alcoholic medium smoothly underwent
nucleophilic substitution reaction to give 4-hydrazinyl-2,8-bis(tri-
fluoromethyl)quinoline (3) in good yield.
The formation of the title compounds, 4aet, 5aee, 6aec and
7aed from the hydrazine derivative, 3 were evidenced by 1H, 13
C
NMR spectral, LCeMS and elemental analysis data, explained in
experimental part. In addition, the molecular structure of the
compound 4l was established by single crystal X-ray diffraction
studies. The ORTEP view of the molecular structure shows the
spatial atomic positions of compound 4l, as shown in Fig. 2.
The structure of 1-(2,8-bis(trifluoromethyl)quinolin-4-yl)-4-(4-
fluorophenyl)semicarbazide (5a) was determined by 1H, 13C NMR
NH2
OH
Cl
HN
a
b
c
NH2
N
CF3
N
CF3
N
CF3
CF3
CF3
CF3
CF3
3
1
2
Scheme 1. Synthesis of 4-hydrazinyl-2,8-bis(trifluoromethyl)quinoline Reagents and conditions: (a) PPA, ethyl 4,4,4-trifluoroacetoactate, 150 ꢀC, 2 h; (b) POCl3, 80 ꢀC, 4 h; (c)
Hydrazine hydrate, EtOH, 90 ꢀC, 4 h.

3376
S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
2
R
R
N
N
O
NH2
HN
N
N
HN
a
b
c
N
CF3
CF3
N
3
CF3
CF3
4 a-t
R = alkyl, aryl, heteroaryl
CF3
7 a-d
CF3
2
R = alkyl, aryl
d
H
N
X
1
R
NH
HN
X = O, S
N
CF3
CF3
5 a-e
6 a-c
1
R = alkyl, aryl
Scheme 2. Reagents and conditions: (a) substituted aldehyde, EtOH, RT, 30 min; (b) substituted isocyanate, toluene, 110 ꢀC, 30 min; (c) substituted isothiocyanate, toluene, 110 ꢀC,
30 min; (d) substituted acetoacetate, EtOH, RT, 30 min, NaOEt, 80 ꢀC, 30 min.
and LCeMS data. In the 1H NMR spectrum, appearance of sharp
signals at
(4H)-one (7a) was evidenced by its 1H NMR spectrum. In its spec-
trum, the disappearance of broad singlet from 4.72 and 9.34
corresponding to eNH2 and eNH protons, respectively, and the
appearance of twosinglets at 2.32 and 3.59 corresponding to eCH3,
and eCH2 of pyrazole ring, respectively, confirmed the cyclization.
Further, the total proton count for compound 7a perfectly matched
with its structure, which further established the cyclization. The
LCeMS of it showed a molecular ion peak at m/z 362 (M þ 1), which
matches with its molecular formula C15H9F6N3O. The characteriza-
tion data of newly synthesized compounds are summarized in
experimental section.
d
8.80, 9.13 and 10.00 corresponding to ꢁNH (attached to
d
aromatic ring), ꢁNH (attached to ꢁNH) and eCONH, respectively
indicated the smooth condensation between 4-fluorobenzaldehyde
and hydrazine derivative 3. In addition, its mass spectrum showed
molecular ion peak at m/z 433 (M þ 1), which corresponds to its
molecular formula C18H11F7N4O.
d
The structures of compounds 6aec were elucidated by their 1H
NMR and LCeMS analyses. The 1H NMR spectrum of 6a, the
appearance of broad signals at d 9.96, 10.38, and 10.41 revealed the
presence of eCSNH, and two ꢁNH protons, respectively. Finally
the structure was confirmed by its LCeMS, which showed its
molecular ion peak at m/z 449 (M þ 1). This is in accordance with its
molecular formula C18H11F7N4S.
3. Pharmacology
The cyclization of quinoline hydrazine 3 to the corresponding
1-(2,8-bis(trifluoromethyl)quinolin-4-yl)-3-methyl-1H-pyrazol-5
3.1. Antibacterial studies
The newly synthesized compounds were screened for their in
vitro antibacterial activity against E. coli (ATTC 25922), S. aureus
(ATTC 25923), P. aeruginosa (ATCC 27853) and K. pneumoniae
(recultured) bacterial stains by serial plate dilution method [23,24]
using ciprofloxacin as standard. The MICs (mM) and zone of inhibi-
tion(mm)weredeterminedfor4aet, 5aee, 6aecand7aed andtheir
results are summarized along with that of ciprofloxacin in Table 1.
3.2. Antituberculosis studies
The encouraging results from the antibacterial studies impelled
us to go for the preliminary screening of the title compounds for
their in vitro antituberculosis activity. The compounds were eval-
uated against M. tuberculosis H37Rv and MDR-TB using broth
microdilution method with Resazurin as indicator [25,26] and the
observed MICs are presented in Table 2. Isoniazid (INH) and
Rifampicin (RIF) were used as standard drugs.
Fig. 2. ORTEP diagram showing the X-ray crystal structure of 4l.

S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
3377
Table 1
Table 2
Antibacterial activity of the title compounds 4aet, 5aee, 6aec and 7aed.
In vitro antituberculosis evaluation of the synthesized compounds 4aet, 5aee, 6aec
and 7aed.
Compounds
MIC in
m
g/mL and zone of inhibition in mm
E. coli P. aeruginosa
Compounds
MIC (
m
M)
% Inhibition
S. aureus
K. pneumoniae
(ATCC 25923) (ATCC 25922) (ATCC 27853) (recultured)
MTB
MDR-TBa
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
4t
5a
5b
5c
5d
5e
6a
6b
6c
7a
7b
7c
7d
12.5 (13)
6.25 (22)
12.5 (14)
6.25 (23)
50 (<10)
6.25 (22)
6.25 (24)
6.25 (21)
12.5 (12)
50 (<10)
6.25 (24)
6.25 (22)
12.5 (14)
6.25 (22)
6.25 (18)
6.25 (22)
6.25 (24)
12.5 (10)
6.25 (24)
6.25 (22)
12.5 (10)
50 (<10)
6.25 (21)
6.25 (23)
12.5 (10)
50 (<10)
12.5 (11)
50 (<10)
6.25 (24)
6.25 (22)
6.25 (18)
6.25 (20)
6.25 (26)
6.25 (22)
6.25 (21)
12.5 (13)
6.25 (25)
50 (<10)
6.25 (24)
6.25 (25)
6.25 (24)
6.25 (24)
50 (<10)
6.25 (25)
6.25 (24)
6.25 (21)
6.25 (20)
6.25 (22)
6.25 (20)
6.25 (27)
6.25 (20)
6.25 (26)
6.25 (23)
12.5 (10)
50 (<10)
6.25 (24)
6.25 (20)
12.5 (10)
50 (<10)
12.5 (10)
50 (<10)
6.25 (22)
6.25 (21)
12.5 (10)
12.5 (10)
6.25 (28)
12.5 (12)
6.25 (26)
12.5 (15)
6.25 (24)
50 (<10)
6.25 (25)
6.25 (23)
6.25 (26)
12.5 (14)
50 (<10)
6.25 (23)
6.25 (28)
12.5 (15)
6.25 (24)
6.25 (24)
6.25 (24)
6.25 (24)
12.5 (14)
6.25 (25)
6.25 (25)
12.5 (14)
50 (<10)
6.25 (22)
6.25 (24)
12.5 (14)
50 (<10)
12.5 (12)
50 (<10)
6.25 (25)
6.25 (24)
12.5 (12)
12.5 (12)
6.25 (31)
12.5 (13)
6.25 (18)
12.5 (12)
6.25 (22)
50 (<10)
6.25 (20)
6.25 (19)
6.25 (20)
12.5 (12)
50 (<10)
6.25 (18)
6.25 (18)
12.5 (12)
6.25 (21)
6.25 (20)
6.25 (21)
6.25 (19)
12.5 (11)
6.25 (22)
6.25 (20)
50 (<10)
50 (<10)
6.25 (18)
6.25 (22)
50 (<10)
50 (<10)
50 (<10)
50 (<10)
6.25 (20)
6.25 (22)
12.5 (10)
12.5 (10)
3.12 (24)
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
4t
5a
5b
5c
5d
5e
6a
6b
6c
7a
7b
7c
7d
>50b
12.5
12.5
>50b
25
e
<90
<90
95
e
12.5
6.25
>50b
>50
6.25
12.5
6.25
>50b
6.25
6.25
12.5
25
6.25
>50b
12.5
<90
95
<90
95
e
6.25
12.5
6.25
>50b
3.12
6.25
25
12.5
12.5
12.5
6.25
>50b
3.12
25
12.5
25
99
95
e
<90
<90
<90
95
e
12.5
25
12.5
>50b
6.25
>50b
12.5
>50b
12.5
6.25
>50b
>50b
25
99
e
<90
e
12.5
6.25
<90
95
e
25
>50b
25
e
e
>50b
>50b
6.25
6.25
12.5
12.5
12.5
25
e
3.12
6.25
12.5
6.25
1.5
99
95
<90
95
95
99
Ciprofloxacin
(Standard)
Isoniazid (INH)
Rifampicin (RIF)
0.5
a
Note: the MIC values were evaluated at concentration range, 3.125e50
m
g/mL. The
Mycobacterial tuberculosis resistant to three drugs viz., isoniazid (INH),
figures in the table show the MIC values in
inhibition in mm.
mg/mL and the corresponding zone of
Rifampicin (RFP) and ethambutol (EB).
b
Compound inactive up to MIC 50 mM.
4. Results and discussion
On the other hand antituberculosis screening data revealed that
all the tested compounds in series 4aet, 5aee and 7aed showed
good to moderate inhibitory activity, whereas all the compounds in
series 6aec were inactive against both MTB and MDR-TB.
Compounds 4k, 4s, and 7a were found to be very potent inhibitor,
being able to inhibit 99% growth of M. tuberculosis at a concentra-
The preliminary antibacterial screening revealed that most of
the tested compounds in series 4aet, 5aee and 7aed showed
moderate to very good inhibitory activity against all the strains,
where as 6a-c compounds were inactive. It was noteworthy to see
that among the hydrazone series, the compounds 4b, 4d, 4feh, 4k,
4l, 4neq, 4s, 4t showed very good activity against all the patho-
tion of 3.12
showed moderate to good activity with 95% growth inhibition of
mycobacterium at 6.25 g/mL.
mg/mL, while compounds 4d, 4g, 4i, 4l, 4q, 5b, 7b and 7d
genic bacterial strains with MIC 6.25 mg/mL, comparable to stan-
dards used. In the urea series, compounds 5c and 5d displayed good
activity, while all the three compounds in thiourea series did not
exhibit any activity. The compounds 7a and 7b which belong to
pyrazole series also exhibited very good activity same as it was with
hydrazone series. The good antibacterial activity of 4aet is attrib-
uted to the presence of active hetero-aryl groups in their structures.
In the urea derivatives 5c and 5d, the presence of electron donating
group, viz. eOCH3 and eCH3 attached to the aryl ring enhanced the
activity considerably. While the decreased activity in series 6aec
may be due to the reduced H-bonding ability of >C]S group.
Among pyrazole derivatives 7aed, it was observed that the pres-
ence of electron donating alkyl group attached to the pyrazole ring
brought about enhanced activity while presence of electron with-
drawing phenyl and pyridine rings (7c and 7d) resulted in reduced
activity. It is interesting to note that compounds 4a, 4i, 4m and 4r
showed very good activity against gram negative strains and poor
activity against other strains, whereas compounds 7c and 7d
showed very good activity against gram positive strains and
showed poor activity against other strains.
m
In addition, the compounds were screened against MDR-TB
(M. tuberculosis resistant to three drugs, viz. isoniazid (INH),
rifampicin (RFP) and ethambutol (EB)). Among the thirty two
compounds screened, most of them showed good activity against
MDR-TB strain with MIC ranging from 6.25 to 25 mg/mL and were
found to be more active than isoniazid (INH), rifampicin (RFP). It is
interesting to note that 9 compounds, viz. 4d, 4g, 4i, 4k, 4l, 4s, 5d,
7a and 7b were found to be more potent than INH (MIC: 12.5
with MIC 6.25 g/mL, while 9 compounds, viz. 4c, 4h, 4m, 4o, 4q,
5a, 5c, 7c and 6d were found to be twofold potent than RFP (MIC:
25 g/mL) with MIC 12.5 g/mL. Further, compounds 4b, 4n, 4p and
6b were shown to be as potent as RFP (MIC: 25 g/mL) with MIC
25 g/mL. The good anti-TB activity is attributed to the presence of
mg/mL)
m
m
m
m
m
pharmacologically active hetero-aryl groups, viz. pyrazole, imid-
azole, indole, etc, attached to the quinoline ring. It is surprising and
encouraging to see that compound 7a showed very good anti
tuberculosis activity against both the TB strains. It may be attrib-
uted to the presence of electron donating eCH3 group, which is

3378
S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
Table 3
scope for further derivatization with active pharmacophores in
order to establish the SAR.
Crystal data and measurement detail for compound 4l.
Crystal data
Empirical formula
Formula weight
Crystal system
Crystal dimension
Space group
C16H10ClF6N5
421.05
Triclinic
4.1. X-Ray Crystallographic Analysis of 4l
The X-ray crystallographic analysis of 4l was determined on
0.30 mm ꢂ 0.25 mm ꢂ 0.15 mm
a
colorless plate crystal, with approximate dimensions of
p111
ꢀ
a (A)
8.6445(6)
10.0487(8)
11.7731(9)
917.40(12)
84.131(6), 65.530(7), 80.495(6)
4
1.592
444
0.30 mm ꢂ 0.25 mm ꢂ 0.15 mm, grown from the slow evaporation
of a dilute ethanol solution at room temperature. The crystal
structure solution was solved by full matrix least-squares method
using SHELXL97. All the atoms were located in different Fourier
maps and refined isotropically, using a riding model and all the
projections were generated using ORTEP. The details of the crystal
data and refinement are shown in Table 3. Also the single crystal
images for compound 4l are given in Fig. 3.
ꢀ
b (A)
ꢀ
c (A)
Volume (A )
3
ꢀ
Angle
a
,
b,
g
Z
Crystal density, g/cm3
F000
m
(mmꢁ1
)
0.285
0.285
Absorption coefficient
Cut-off used in R-factor calculations
Fo2 > 2
0.0705
0.1910
293(2)
s
(Fo2)
R (Fo)
5. Conclusion
Rw (Fo2)
Temperature (T)
The present research study reports the successful synthesis,
antibacterial and antituberculosis studies of a four new series of
quinoline derivatives carrying biologically active entities viz.,
hydrazones, ureas, thioureas and pyrazoles. Their screening results
revealed that all the compounds showed moderate to very good
activities against pathogenic strains. On the basis of structur-
eebiological activity relationship it can be concluded that
a combination of hetero-aryl group at position-4 of quinoline core
showed an increased antibacterial and antituberculosis activity and
hence they are ideally suited for further modifications to obtain
more efficacious antibacterial and antituberculosis compounds.
Radiation wavelength
Radiation type
Radiation source
Radiation monochromator
hmin
hmax
kmin
kmax
0.71073
MoK
Fine-focus sealed tube
a
Graphite
ꢁ10
10
ꢁ11
11
lmin
lmax
ꢁ13
13
Reflns (Fo)
Structure refinement
4212
SHELXL97
responsible for stabilizing the pyrazole ring, thereby making the
quinoline ring more active species.
6. Experimental section
The study reveals that presence of CeNeN linkage with quin-
oline at its position-4 is the desired structural feature for enhanced
antituberculosis activity and hence the compound 7a has a good
6.1. General
All reagents were purchased from Aldrich. Solvents used were
extra dried. Final purifications were carried out using Quad biotage
Fig. 3. Single crystal images of compound 4l.

S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
3379
Flash purifier (A Dyax Corp. Company). TLC experiments were per-
formed on alumina-backed silica gel 40 F254 plates (Merck, Darm-
stadt, Germany). The plates were illuminated under UV (254 nm)
and molybidinic acid. Melting points were determined using Buchi
B-540 and are uncorrected. Elemental analyses were carried out on
an automatic Flash EA 1112 Series, CHNSOAnalyzer (Thermo). X-Ray
diffraction studies where carried on an Xcalibur E Oxford Diffraction
system (Varian, California, USA). All 1H and 13C NMR spectra were
recorded on a Bruker AM-300 (300.12 MHz), Bruker BioSpin Corp.,
Germany. Molecular weights of unknown compounds were char-
acterized by LCeMS 6200 series Agilent Technology. Chemical shifts
separated was filtered, dried and recrystallized from diethyl ether.
Some of the final compounds were purified by biotage column
chromatography using pet ether/ethyl acetate as the eluent.
6.5.1. 2-[(E)-{2-[2,8-Bis(trifluoromethyl)quinolin-4-yl]
hydrazinylidene}methyl]-5-fluorophenol (4a)
Compound 4a was obtained as yellow solid. M.P 246e249 ꢀC.
Yield 85%. 1H NMR (300 MHz, DMSO-d6)
d; 6.91e6.95 (m, eCH, 1H),
7.09e7.16 (m, eCH, 1H), 7.65e7.82 (m, eCH, 3H), 8.25 (d, eCH, 1H,
J ¼ 7.2 Hz), 8.72 (d, eCH, 1H, J ¼ 8.4 Hz), 8.80 (s, eN]CHe, 1H),
10.22 (s, eOH, 1H), 11.75 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
are reported in ppm (d) with reference to internal standard TMS. The
d; 97.1, 111.3, 111.6, 117.8,117.9, 118.1, 118.4, 120.1, 121.8, 121.9, 122.5,
signals are designated as follows: s, singlet; d, doublet;dd, doubletof
doublets; t, triplet; m, multiplet; brs, broad singlet, brt, broad triplet.
The newly synthesized compounds 4 aeh, 4 jet, 5 aee, 6aec
were recrystallized from absolute ethanol where as compounds 4i,
7aed were purified by column chromatography.
123.8, 125.7, 126.1, 126.6, 127.0, 127.3, 129.7, 142.0, 144.4, 148.0,
148.4, 149.6, 153.2, 154.6, 157.7. LCeMS (ESI) m/z 418 (M þ 1). Anal.
Calcd for C18H10F7N3O; Calc: C, 51.81; H, 2.42; N, 10.07; found: C,
51.90; H, 2.47; N, 10.12.
6.5.2. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-(3-(1,1,2,2-
tetrafluoroethoxy) benzylidene)hydrazine (4b)
6.2. Preparation of 2,8-bis(trifluoromethyl)quinolin-4-ol (1)
Compound 4b was obtained as off white solid. M.P 194e196 ꢀC.
To an equimolar solution of 2-trifluoromethyl aniline (25 g,
155.3 mmol) and ethyl 4,4,4-trifluoroacetoacetate (28.6 g,
155.3 mmol) was added polyphosphoric acid (125 g, 5 w/w). The
reaction mixture was stirred at 150 ꢀC for 2 h. Reaction completion
was monitored by TLC. The reaction mixture was poured into ice
water (500 mL) slowly with vigorous stirring. The precipitated solid
was filtered and dried in vacuum oven for 4 h to get the crude
product as white solid. The crude product was taken as such for the
next step without further purification.
Yield 79%. 1H NMR (300 MHz, DMSO-d6)
d; 6.69e7.04 (m, eCH, 1H),
7.38 (d, eCH, 1H, J ¼ 8.4 Hz), 7.60 (t, eCH, 1H, J ¼ 7.8 Hz), 7.72e7.74
(m, eCH, 2H), 7.79e7.85 (m, eCH, 2H), 8.25 (d, eCH, 1H, J ¼ 6.9 Hz),
8.50 (s, eN]CHe, 1H), 8.72 (d, eCH, 1H, J ¼ 8.1 Hz), 11.89 (s, eNH,
1H). 13 C NMR (75 MHz, DMSO-d6)
d; 97.3, 104.4, 104.9, 105.5, 107.7,
108.2, 108.8, 110.0, 111.0, 111.5, 116.5, 116.9, 117.3, 118.0, 119.7, 120.1,
120.5, 122.5, 123.1, 123.7, 125.7, 125.9, 126.3, 126.1, 126.7, 127.1, 127.3,
129.8, 131.2, 136.8, 144.4, 147.9, 148.4, 148.8, 149.0, 149.7. LCeMS
(ESI) m/z 500 (M þ 1). Anal. Calcd for C20H11F10N3O; Calc: C, 48.11;
H, 2.22; N, 8.42; found: C, 48.14; H, 2.28; N, 8.50.
Compound 1 was obtained as white solid. Yield 77%. 1H NMR
(300 MHz, DMSO-d6)
d; 7.27 (s, eCH, 1H), 7.78 (t, eCH, 1H,
J ¼ 7.8 Hz), 8.28 (d, eCH,1H, J ¼ 7.2 Hz), 8.52 (d, eCH,1H, J ¼ 8.4 Hz),
6.5.3. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-(3-hydroxy-
4-methoxybenzylidene)hydrazine (4c)
12.78 (brs, eOH, 1H, disappeared on D2O exchange).
Compound 4c was obtained as pale yellow solid. M.P.
6.3. Preparation of 4-chloro-2,8-bis(trifluoromethyl)quinoline (2)
203e206 ꢀC. Yield 78%. 1H NMR (300 MHz, DMSO-d6)
d; 3.82 (s,
eOCH3, 3H), 6.99(d, eCH,1H, J ¼ 8.4 Hz), 7.16 (d, eCH,1H, J ¼ 8.1 Hz),
7.37 (s, eCH, 1H), 7.67 (s, eCH, 1H), 7.79 (t, eCH, 1H, J ¼ 7.8 Hz), 8.25
(d, eCH, 1H, J ¼ 7.2 Hz), 8.36 (s, eN]CHe, 1H), 8.69 (d, eCH, 1H,
J ¼ 8.7 Hz), 9.37 (s, eOH, 1H), 11.60 (s, eNH, 1H). 13C NMR (75 MHz,
A mixture of 1 (25 g, 88.9 mmol) and freshly distilled POCl3
(125 mL) was heated at 80 ꢀC for 4 h. The reaction was monitored
by TLC. After completion of the reaction, excess of POCl3 was
distilled off. The residue thus obtained was stirred with ice water
for 15 min. After this, the solid phase was filtered and dried.
Compound 2 was obtained as pale yellow solid. Yield 82%. 1H
DMSO-d6) d; 56.2, 97.2, 115.8, 116.2, 119.1, 119.8, 122.8, 125.6, 126.1,
126.4,129.2,129.8,144.1,145.8,151.8,152.3,153.6,156.4. LCeMS (ESI)
m/z 430 (M þ 1). Anal. Calcd for C19H13F6N3O2; Calc: C, 53.16; H, 3.05;
N, 9.79; found: C, 53.12; H, 3.09; N, 9.84.
NMR (300 MHz, DMSO-d6)
eCH, 1H), 8.27 (d, eCH, 1H, J ¼ 7.2 Hz), 8.56 (d, eCH, 1H, J ¼ 8.4 Hz).
d
; 7.86 (t, eCH, 1H, J ¼ 7.8 Hz), 7.95 (s,
6.5.4. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-(2-fluoro-4-
methoxybenzylidene)hydrazine (4d)
6.4. Preparation of 4-hydrazinyl-2,8-bis(trifluoromethyl)-
quinoline (3)
Compound 4d was obtained as pale yellow solid. M.P
198e199 ꢀC. Yield 82%. 1H NMR (300 MHz, DMSO-d6)
d; 3.82 (s,
Compound 2 (10 g, 33.4 mmol) and hydrazine hydrate 60%
(50 mL) in 50 mL of ethanol was heated under reflux for 4 h.
Completion of the reaction was monitored by TLC. The reaction
mixture was concentrated and allowed to cool. The solid product
obtained was filtered, washed with water and dried.
eOCH3, 3H), 6.88e6.95 (m, eCH, 2H), 7.69 (s, eCH,1H), 7.78 (t, eCH,
1H, J ¼ 7.8 Hz), 7.98 (t, eCH, 1H, J ¼ 8.4 Hz), 8.23 (d, eCH, 1H,
J ¼ 7.2 Hz), 8.61 (s, eN]CHe, 1H), 8.68 (d, eCH, 1H, J ¼ 8.7 Hz),
11.69 (s, eNH, 1H). 13 C NMR (75 MHz, DMSO-d6)
d; 56.1, 95.7, 102.5,
110.3, 110.7, 119.0, 119.8, 125.6, 126.1, 126.4, 129.2, 129.4, 131.8, 143.0,
144.7, 151.8, 156.4, 160.5, 164.8. LCeMS (ESI) m/z 432 (M þ 1). Anal.
Calcd for C19H12F7N3O; Calc: C, 52.91; H, 2.80; N, 9.74; found: C,
52.96; H, 2.88; N, 9.79.
Compound 3 was obtained as off white solid. Yield 80%. 1H NMR
(300 MHz, DMSO-d6) d; 4.76 (brs, eNH2, 2H), 7.35 (s, eCH, 1H), 7.62
(t, eCH, 1H, J ¼ 7.8 Hz), 8.13 (d, eCH, 1H, J ¼ 7.5 Hz), 8.54 (d, eCH,
1H, J ¼ 8.4 Hz), 9.34 (s, eNH, 1H). LCeMS (ESI) m/z 296 (M þ 1).
6.5.5. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-((thiophen-
2-yl)methylene)hydrazine (4e)
6.5. General procedure for the synthesis of title compounds (4aet)
Compound 4e was obtained as pale yellow solid. M.P.
To a suspension of compound 3 (1 mmol) in dry ethanol, was
added substituted aldehyde (1 mmol) and catalytic amount of acetic
acid. The reaction mixture was stirred at room temperature for
30 min. Reaction completion was monitored by TLC. The reaction
mixture was concentrated under reduced pressure. The solid
184e186 ꢀC. Yield 86%. 1H NMR (300 MHz, DMSO-d6)
d; 7.16e7.18
(m, eCH, 1H), 7.53e7.57 (m, eCH, 2H), 7.70 (d, eCH, 1H, J ¼ 5.1 Hz),
7.79 (t, eCH, 1H, J ¼ 8.1 Hz), 8.24 (d, eCH, 1H, J ¼ 7.2 Hz), 8.66e8.69
(m, eN]CHe, eCH, 2H), 11.74 (s, eNH, 1H). 13C NMR (75 MHz,
DMSO-d6) d; 96.8, 117.9, 120.1, 122.5, 123.8, 125.5, 126.1, 126.7, 127.1,

3380
S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
127.2, 127.4, 128.4, 129.1, 129.7, 131.0, 139.3, 141.1, 144.4, 147.4, 147.9,
148.3, 149.4. LCeMS (ESI) m/z 390 (M þ 1). Anal. Calcd for
C16H9F6N3S; Calc: C, 49.36; H, 2.33; N, 10.79; S, 8.24; found: C,
49.39; H, 2.37; N, 10.72; S, 8.28.
6.5.11. (E)-2-((1H-imidazol-4-yl)methylene)-1-(2,8-bis
(trifluoromethyl)quinolin-4-yl)hydrazine (4k)
Compound 4k was obtained as yellow solid. M.P. 252e254 ꢀC.
Yield 65%. 1H NMR (300 MHz, DMSO-d6)
d; 7.42e7.84 (m, eCH, 4H),
8.23 (d, eCH, 1H, J ¼ 7.2 Hz), 8.42 (s, eN]CHe, 1H), 8.69 (d, eCH,
1H, J ¼ 8.4 Hz), 11.51 (s, eNH, 1H),12.92 (brs, eNH of imidazole, 1H).
LCeMS (ESI) m/z 374 (M þ 1). Anal. Calcd for C15H9F6N5; Calc: C,
48.27; H, 2.43; N, 18.76; found: C, 48.32; H, 2.49; N, 18.88.
6.5.6. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((pyridin-3-yl)methylene)hydrazine (4f)
Compound 4f was obtained as white solid. M.P. 256e258 ꢀC.
Yield 72%. 1H NMR (300 MHz, DMSO-d6)
d; 7.50e7.54 (m, eCH, 1H),
7.80e7.85 (m, eCH, 2H), 8.25e8.31 (m, eCH, 2H), 8.53 (s, eN]CHe,
1H), 8.62 (d, eCH, 1H, J ¼ 4.8 Hz), 8.76 (d, eCH, 1H, J ¼ 8.7 Hz), 8.97
6.5.12. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((4-chloro-1-methyl-1H-pyrazol-3-yl)methylene)hydrazine (4l)
(s, eCHe, 1H), 11.90 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d;
Compound 4l was obtained as white solid. M.P. 231e234 ꢀC.
Yield 70%. 1H NMR (300 MHz, DMSO-d6)
d; 3.89 (s, eNCH3, 3H), 7.71
97.4, 117.9, 120.1, 122.4, 123.8, 124.4, 125.7, 126.7, 127.1, 127.2, 129.8,
130.5, 133.7, 143.1, 144.3, 147.9, 148.4, 149.1, 149.6, 150.9. LCeMS
(ESI) m/z 385 (M þ 1). Anal. Calcd for C17H10F6N4; Calc: C, 53.13; H,
2.62; N, 14.58; found: C, 53.17; H, 2.52; N, 14.51.
(s, eCH, 1H), 7.80 (t, eCH, 1H, J ¼ 7.8 Hz), 8.10 (s, eCH, 1H), 8.26 (d,
eCH, 1H, J ¼ 7.2 Hz), 8.44 (s, eN]CHe, 1H), 8.69 (d, eCH, 1H,
J ¼ 8.4 Hz), 11.76 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 41.6,
97.3, 107.5, 117.9, 120.1, 122.5, 123.8, 125.8, 126.1, 126.7, 127.1, 127.3,
130.0, 131.8, 138.3, 142.2, 144.4, 147.9, 148.4, 149.8. LCeMS (ESI) m/z
422 (M þ 1). Anal. Calcd for C16H10ClF6N5; Calc: C, 45.57; H, 2.39; N,
16.61; found: C, 45.62; H, 2.32; N, 16.68.
6.5.7. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
(cyclohexylmethylene)hydrazine (4g)
Compound 4g was obtained as white solid. M.P. 204e206 ꢀC.
Yield 67%. 1H NMR (300 MHz, DMSO-d6)
d; 1.24e1.32 (m, cyclo-
hexyl eCH2, 5H), 1.63e1.88 (m, cyclohexyl eCH2, 5H), 2.38 (m,
cyclohexyl eCH, 1H), 7.51 (s, eCH, 1H), 7.72e7.77 (m, eCH, eN]
CHe, 2H), 8.22 (d, eCH, 1H, J ¼ 7.2 Hz), 8.62 (s, eCH, 1H, J ¼ 8.4 Hz),
6.5.13. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((2,3-dihydrobenzofuran-5-yl)methylene)hydrazine (4m)
Compound 4m was obtained as yellow solid. M.P. 220e221 ꢀC.
11.28 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 25.4, 25.9, 30.1,
Yield 73%. 1H NMR (300 MHz, DMSO-d6)
d; 3.25 (t, eCH2, 2H,
96.4, 117.6, 120.2, 122.5, 123.8, 125.4, 126.1, 126.6, 127.0, 127.3, 129.7,
129.8, 144.4, 147.9, 148.3, 150.2, 154.6. LCeMS (ESI) m/z 390 (M þ 1).
Anal. Calcd for C18H17F6N3; Calc: C, 55.53; H, 4.40; N, 10.79; found:
C, 55.61; H, 4.46; N, 10.88.
J ¼ 8.4 Hz), 4.60 (t, eOCH2, 2H, J ¼ 8.7 Hz), 6.87(d,eCH,1H, J ¼ 8.4 Hz),
7.54 (d, eCH,1H, J ¼ 7.8 Hz), 7.68 (s, eCH,1H), 7.75e7.79 (m, eCH, 2H),
8.23 (d, eCH, 1H, J ¼ 7.2 Hz), 8.42 (s, eN]CHe, 1H), 8.71 (d, eCH, 1H,
J ¼ 8.4 Hz), 11.57 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 29.1,
72.0, 96.7, 109.7, 117.9, 120.2, 123.8, 123.8, 125.5, 126.1, 126.6, 127.7,
127.1, 127.3, 128.8, 129.0, 129.7, 129.8, 144.4, 146.7, 147.9, 148.4, 149.8,
162.1. LCeMS (ESI) m/z 426 (M þ 1). Anal. Calcd for C20H13F6N3O; Calc:
C, 56.58; H, 3.01; N, 9.88; found: C, 56.66; H, 3.08; N, 9.99.
6.5.8. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
(3-(trifluoromethoxy)benzylidene)hydrazine (4h)
Compound 4h was obtained as white solid. M.P. 217e219 ꢀC.
Yield 77%. 1H NMR (300 MHz, DMSO-d6)
d; 7.43 (d, eCH, 1H,
J ¼ 8.4 Hz), 7.60 (t, eCH,1H, J ¼ 7.8 Hz), 7.74e7.86 (m, eCH, 4H), 8.24
6.5.14. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((1-methyl-1H-pyrrol-2-yl)methylene)hydrazine (4n)
Compound 4n was obtained as green solid. M.P 169e171 ꢀC.
(d, eCH, 1H, J ¼ 7.2 Hz), 8.47 (s, eN]CHe, 1H), 8.71 (d, eCH, 1H,
J ¼ 8.4 Hz), 11.85 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 97.3,
117.9, 118.8, 119.1, 120.1, 122.3, 122.4, 123.7, 125.6, 126.1, 126.3, 126.7,
127.1, 127.2, 129.8, 131.2, 137.0, 144.1, 144.3, 147.9, 148.3, 149.2, 149.6.
LCeMS (ESI) m/z 468 (M þ 1). Anal. Calcd for C19H10F9N3O; Calc: C,
48.84; H, 2.16; N, 8.99; found: C, 48.89; H, 2.18; N, 9.08.
Yield 70%. 1H NMR (300 MHz, DMSO-d6)
d; 3.94 (s, eNCH3, 3H), 6.14
(m, pyrrole eCH, 1H), 6.61 (m, pyrrole eCH, 1H), 7.04 (m, pyrrole
eNCH, 1H), 7.51 (s, eCH, 1H), 7.71 (t, eCH, 1H, J ¼ 7.8 Hz), 8.22 (d,
eCH, 1H, J ¼ 6.9 Hz), 8.43 (s, eN]CHe, 1H), 8.69 (d, eCH, 1H,
J ¼ 8.4 Hz), 11.47 (s, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 33.4,
6.5.9. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
octylidenehydrazine (4i)
96.2, 108.6, 110.2, 119.1, 120.0, 122.7, 125.6, 126.2, 126.4, 129.2, 129.5,
131.9, 139.3, 151.8, 152.3, 156.6. LCeMS (ESI) m/z 387 (M þ 1). Anal.
Calcd for C17H12F6N4; Calc: C, 52.86; H, 3.13; N, 14.50; found: C,
52.89; H, 3.20; N, 14.56.
Compound 4i was obtained as brown liquid. Yield 56%. 1H NMR
(300 MHz, DMSO-d6) d; 0.91 (m, eCH3, 3H), 1.23e1.52 (m, eCH2,
6H), 1.59e1.61 (m, eCH2, 4H), 1.69e1.73 (m, eCH2, 2H), 2.40e2.49
(m, eCH2, 2H), 7.46 (m, eN]CHe,1H), 7.55e7.62 (m, eCH,1H), 7.72
(s, eCH, 1H), 7.93e7.97 (m, eCH, 1H), 8.01 (d, eCH, 1H, J ¼ 7.2 Hz),
6.5.15. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-((benzo[c]
[1,2,5]oxadiazol-5-yl)methylene)hydrazine (4o)
8.28 (brs, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 14.2, 22.8, 26.3,
Compound 4o was obtained as yellow solid. M.P 263e264 ꢀC.
26.4, 29.1, 29.4, 40.1, 95.9, 119.1, 119.8, 125.6, 126.1, 126.5, 129.2,
129.4, 144.6, 148.2, 150.5, 154.1. LCeMS (ESI) m/z 406 (M þ 1). Anal.
Calcd for C19H21F6N3; Calc: C, 56.29; H, 5.22; N, 10.37; found: C,
56.22; H, 5.26; N, 10.42.
Yield 85%. 1H NMR (300 MHz, DMSO-d6)
d; 7.79e7.84 (m, eCH, 2H),
8.11 (d, eCH, 1H, J ¼ 9.3 Hz), 8.24e8.33 (m, eCH, 3H), 8.59 (s, eN]
CHe, 1H), 8.74 (d, eCH, 1H, J ¼ 8.7 Hz), 12.07 (s, eNH, 1H). 13C NMR
(75 MHz, DMSO-d6) d; 97.3, 111.8, 117.9, 119.7, 120.2, 122.3, 123.6,
6.5.10. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((4-bromofuran-3-yl)methylene)hydrazine (4j)
125.1, 125.4, 126.1, 126.6, 127.0, 127.3, 129.6, 129.8, 130.9, 134.6,
144.3, 145.6, 145.8, 147.9, 148.4, 149.6. LCeMS (ESI) m/z 426 (M þ 1).
Anal. Calcd for C18H9F6N5O; Calc: C, 50.83; H, 2.13; N, 16.47; found:
C, 50.88; H, 2.19; N, 16.55.
Compound 4j was obtained as off white solid. M.P 186e188 ꢀC.
Yield 88%. 1H NMR (300 MHz, DMSO-d6)
d; 7.76e7.84 (m, eCH, 2H),
8.11 (s, eCH, 1H), 8.26 (d, eCH, 1H, J ¼ 6.9 Hz), 8.39e8.41 (m, eN]
CHe, eCH, 2H), 8.71 (d, eCH, 1H, J ¼ 8.7 Hz), 11.77 (s, eNH, 1H). 13C
6.5.16. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-((1-methyl-
1H-benzo[d][1,2,3]triazol-5-yl)methylene)hydrazine (4p)
NMR (75 MHz, DMSO-d6) d; 97.3, 98.5, 117.8, 120.1, 121.1, 122.5,
Compound 4p was obtained as pale yellow solid. M.P. >300 ꢀC.
123.5, 126.1, 126.7, 127.1, 127.3, 129.8, 129.9, 137.1, 144.1, 144.4, 145.8,
148.0, 148.4, 149.8. LCeMS (ESI) m/z 452 (M þ 2). Anal. Calcd for
C16H8BrF6N3O; Calc: C, 42.50; H, 1.78; N, 9.29; found: C, 42.55; H,
1.73; N, 9.36.
Yield 82%. 1H NMR (300 MHz, DMSO-d6)
d; 4.33 (s, eNCH3, 3H),
7.74e7.79 (m, eCH, 2H), 7.91 (d, eCH, 1H, J ¼ 8.7 Hz), 8.16 (d, eCH,
1H, J ¼ 9 Hz), 8.22 (d, eCH, 1H, J ¼ 7.2 Hz), 8.35 (s, eCH, 1H), 8.62 (s,

S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
3381
eN]CHe, 1H), 8.71 (d, eCH, 1H, J ¼ 8.7 Hz), 11.77 (s, eNH, 1H). 13
C
6.6.1. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-(4-fluorophenyl)
semicarbazide (5a)
Compound 5a was obtained as white solid. M.P. 234e236 ꢀC.
Yield 88%. 1H NMR (300 MHz, DMSO-d6)
; 7.08e7.13 (m, eCH, 3H),
NMR (75 MHz, DMSO-d6)
d
; 34.7, 97.2, 111.2, 117.2, 119.1, 120.2,
122.5, 123.8, 125.0, 125.6, 126.1, 126.6, 127.0, 127.3, 129.7, 129.8,
130.9, 134.6, 144.3, 145.8, 145.9, 147.9, 148.4, 149.7. LCeMS (ESI) m/z
439 (M þ 1). Anal. Calcd for C19H12F6N6; Calc: C, 52.06; H, 2.76; N,
19.17; found: C, 52.12; H, 2.80; N, 19.23.
d
7.47e7.52 (m, eCH, 2H), 7.79 (t, eCH, 1H, J ¼ 8.1 Hz), 8.26 (d, eCH,
1H, J ¼ 7.5 Hz), 8.65 (d, eCH, 1H, J ¼ 8.4 Hz), 8.80 (s, eNH, 1H), 9.13
(s, eNH, 1H), 10.00 (s, eCONH, 1H). 13C NMR (75 MHz, DMSO-d6)
d;
6.5.17. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((7-methyl-1H-indol-3-yl)methylene)hydrazine (4q)
95.6, 115.4, 115.7, 118.5, 120.1, 121.4, 122.5, 123.8, 125.7, 126.1, 126.6,
127.0,127.4,127.7,128.6,129.3,129.8,129.9,136.1,144.1,148.0,148.4,
154.6, 156.0, 156.5, 159.6. LCeMS (ESI) m/z 433 (M þ 1). Anal. Calcd
for C18H11F7N4O; Calc: C, 50.01; H, 2.56; N,12.96; found: C, 50.05; H,
2.63; N, 12.88.
Compound 4q was obtained as yellow solid. M.P. 283e284 ꢀC.
Yield 73%. 1H NMR (300 MHz, DMSO-d6)
d; 2.51 (s, eCH3, 3H), 7.06
(d, eCH, 1H, J ¼ 7.2 Hz), 7.15 (t, eCH, 1H, J ¼ 7.8 Hz), 7.68 (s, eCH,
1H), 7.76 (t, eCH,1H, J ¼ 8.1 Hz), 7.96 (m, eCH,1H), 8.08 (d, eCH,1H,
J ¼ 7.8 Hz), 8.22 (d, eCH, 1H, J ¼ 7.2 Hz), 8.71e8.76 (m, eCH, eN]
CHe, 2H), 11.50 (s, eNH, 1H), 11.70 (brs, indole eNH, 1H). 13C NMR
6.6.2. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-(3-cyanophenyl)
semicarbazide (5b)
(75 MHz, DMSO-d6)
d
; 17.2, 96.1, 112.3, 117.9, 119.2, 120.3, 121.4,
Compound 5b was obtained as white solid. M.P. 242e245 ꢀC.
121.8, 123.8, 124.0, 124.3, 125.1, 126.6, 127.0, 127.4, 129.6, 131.1, 137.1,
144.2, 144.6, 148.0, 148.4, 149.7. LCeMS (ESI) m/z 437 (M þ 1). Anal.
Calcd for C21H14F6N4; Calc: C, 57.80; H, 3.23; N, 12.84; found: C,
57.85; H, 3.30; N, 12.93.
Yield 82%. 1H NMR (300 MHz, DMSO-d6)
d; 7.09 (s, eCH, 1H),
7.42e7.51 (m, eCH, 2H), 7.80 (m, eCH, 1H), 7.98 (s, eCH, 1H), 8.27
(d, eCH, 1H, J ¼ 7.2 Hz), 8.65 (d, eCH, 1H, J ¼ 8.7 Hz), 9.03 (s, eNH,
1H), 9.42 (brs, eNH, 1H), 10.05 (s, eCONH, 1H). 13C NMR (75 MHz,
DMSO-d6) d; 95.7, 112.1, 118.5, 119.2, 120.1, 122.1, 123.6, 124.0, 125.7,
6.5.18. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((5-(acetoxymethyl)furan-2-yl)methylene)hydrazine (4r)
Compound 4r was obtained as white solid. M.P 220e221 ꢀC.
126.1, 126.7, 127.1, 128.6, 129.3, 130.4, 130.6, 137.7, 140.8, 144.1, 148.1,
154.5, 155.8. LCeMS (ESI) m/z 440 (M þ 1). Anal. Calcd for
C19H11F6N5O; Calc: C, 51.95; H, 2.52; N, 15.94; found: C, 52.03; H,
2.59; N, 15.98.
Yield 70%. 1H NMR (300 MHz, DMSO-d6)
d; 2.08 (s, eCH3, 3H), 5.14
(s, eCH2, 2H), 6.70 (d, eCH, 1H, J ¼ 3 Hz), 7.03 (d, eCH, 1H,
J ¼ 3.3 Hz), 7.62 (s, eCH, 1H), 7.80 (t, eCH, 1H, J ¼ 7.8 Hz), 8.26 (d,
eCH, 1H, J ¼ 7.2 Hz), 8.34 (s, eN]CHe, 1H), 8.69 (d, eCH, 1H,
6.6.3. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-(2-
methoxyphenyl)semicarbazide (5c)
J ¼ 8.4 Hz), 11.73 (s, eCH, 1H). 13C NMR (75 MHz, DMSO-d6)
d
; 21.0,
Compound 5c was obtained as white solid. M.P 225e227 ꢀC.
58.0, 97.0, 113.5, 115.1, 118.0, 125.8, 127.3, 129.9, 130.0, 135.8, 144.4,
147.9, 148.3, 149.6, 150.0, 152.0, 170.4 (eC]O). LCeMS (ESI) m/z 446
(M þ 1). Anal. Calcd for C19H13F6N3O3; Calc: C, 51.25; H, 2.94; N,
9.44; found: C, 51.33; H, 2.99; N, 9.53.
Yield 84%. 1H NMR (300 MHz, DMSO-d6)
d; 3.84 (s, OCH3, 3H),
6.85e6.91 (m, eCH, 1H), 6.96e7.04 (m, eCH, 2H), 7.09 (s, eCH, 1H),
7.79 (m, eCH, 1H, J ¼ 8.1), 7.97 (d, eCH, 1H, J ¼ 7.5 Hz), 8.26 (d, eCH,
1H, J ¼ 7.2 Hz), 8.39 (s, eNH, 1H), 8.64 (d, eCH, 1H, J ¼ 8.4 Hz), 9.07
(s, eNH, 1H), 10.00 (brs, eCONH, 1H). 13C NMR (75 MHz, DMSO-d6)
6.5.19. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((4-methyl-1H-imidazol-5-yl)methylene)hydrazine (4s)
Compound 4s was obtained as yellow solid. M.P. 266e268 ꢀC.
d; 56.2, 95.7, 111.3, 118.3, 119.5, 120.1, 121.0, 122.5, 123.1, 123.7, 125.9,
126.1, 126.7, 127.1, 127.3, 128.4, 129.9, 144.1, 148.1, 148.5, 148.8, 154.7,
155.4. LCeMS (ESI) m/z 445 (M þ 1). Anal. Calcd for C19H14F6N4O2;
Calc: C, 51.36; H, 3.18; N, 12.61; found: C, 51.44; H, 3.11; N, 12.67.
Yield 65%. 1H NMR (300 MHz, DMSO-d6)
d; 2.43 (s, eCH3, 3H),
7.70e7.77 (m, eCH, 3H), 8.21 (d, eCH, 1H, J ¼ 7.2 Hz), 8.46 (s, eN]
CHe, 1H), 8.66 (d, eCH, 1H, J ¼ 8.4 Hz), 11.46 (s, eNH, 1H), 12.34
(brs, imidazole eNH, 2H). LCeMS (ESI) m/z 388 (M þ 1). Anal. Calcd
for C16H11F6N5; Calc: C, 49.62; H, 2.86; N, 18.08; found: C, 49.69; H,
2.93; N, 18.14.
6.6.4. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-
(3,5-dimethylphenyl)semicarbazide (5d)
Compound 5d was obtained as white solid. M.P 252e255 ꢀC.
Yield 89%. 1H NMR (300 MHz, DMSO-d6)
d; 2.20 (s, e(CH3)2, 6H),
6.62 (s, eCH, 1H), 7.07e7.12 (m, eCH, 3H), 7.78 (m, eCH, 1H), 8.26
(d, eCH, 1H, J ¼ 7.2 Hz), 8.65 (d, eCH, 1H, J ¼ 8.4 Hz), 8.72 (s, eNH,
1H), 8.91 (s, eNH, 1H), 9.98 (brs, eCONH, 1H). 13C NMR (75 MHz,
6.5.20. (E)-1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-2-
((5-methoxy-1H-indol-3-yl)methylene)hydrazine (4t)
Compound 4t was obtained as yellow solid. M.P. 238e240 ꢀC.
DMSO-d6) d; 21.5, 95.6, 117.3, 118.5, 120.1, 122.5, 123.8, 124.3, 125.6,
Yield 72%. 1H NMR (300 MHz, DMSO-d6)
d; 3.89 (s, eOCH3, 3H), 6.89
126.1,126.6,127.0,127.7,129.8,129.9, 137.9,139.6,144.1,148.0,148.4,
154.7, 155.8. LCeMS (ESI) m/z 443 (M þ 1). Anal. Calcd for
C20H16F6N4O; Calc: C, 54.30; H, 3.65; N, 12.67; found: C, 54.38; H,
3.69; N, 12.73.
(m, eCH,1H), 7.40 (d, eCH,1H, J ¼ 8.7 Hz), 7.72e7.91 (m, eCH, eN]
CHe, 4H), 8.22 (d, eCH,1H, J ¼ 7.5 Hz), 8.70e8.74 (m, eCH, 2H),11.53
(s, eNH, 1H), 11.59 (brs, indole eNH, 1H). 13C NMR (75 MHz, DMSO-
d6) d; 55.9, 95.6, 101.3, 109.6, 111.3, 117.6, 119.0, 119.8, 123.2, 125.6,
126.1, 126.3, 127.1, 127.8,129.2, 129.3, 130.9, 143.1, 146.5, 148.7, 149.9,
156.6. LCeMS (ESI) m/z 452 (M þ 1). Anal. Calcd for C21H14F6N4O;
Calc: C, 55.76; H, 3.12; N, 12.39;foundC, 55.82; H, 3.19; N, 12.32.
6.6.5. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-
pentylsemicarbazide (5e)
Compound 5e was obtained as white solid. M.P 181e182 ꢀC.
Yield 62%. 1H NMR (300 MHz, DMSO-d6)
d; 0.82 (t, eCH3, 3H,
6.6. General procedure for the synthesis of title compounds
(5aee, 6aec)
J ¼ 6.9 Hz), 1.21e1.25 (m, e(CH2)2, 4H), 1.35e1.39 (m, eCH2, 2H),
3.01e3.03 (m, eNCH2, 2H), 6.86 (m, eCH, 1H), 6.97 (s, eCH, 1H),
7.74 (t, eCH, 1H, J ¼ 7.8 Hz), 8.23 (d, eCH, 1H, J ¼ 6.9 Hz), 8.37 (s,
eNH, 1H), 8.62 (d, eCH, 1H, J ¼ 8.4 Hz), 9.84 (brs, eCONH, 1H). 13C
To a suspension of 3 (2 mmol) in dry toluene (4 mL) equimolar
quantity of substituted iso(thio)cyanate (2 mmol) was added
slowly and the reaction mixture was heated at 110 ꢀC for 30 min.
The completion of the reaction was monitored by TLC. The solid
obtained on cooling was filtered and washed with n-hexane
(50 mL).
NMR (75 MHz, DMSO-d6) d; 14.2, 22.3, 28.8, 29.9, 40.4, 95.4, 118.5,
120.3, 122.2, 123.8, 126.2, 126.3, 125.4, 127.8, 129.7, 129.9, 144.1,
148.4, 154.7, 158.2. LCeMS (ESI) m/z 409 (M þ 1). Anal. Calcd for
C17H18F6N4O; Calc: C, 50.00; H, 4.44; N, 13.72; found: C, 50.12; H,
4.52; N, 13.79.

3382
S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
6.6.6. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-(2-fluorophenyl)
thiosemicarbazide (6a)
CDCl3) d; 32.4, 37.1, 41.8, 101.2, 112.8, 115.2, 119.0, 119.6, 121.4, 125.3,
126.1, 126.4, 129.2, 129.3, 129.6, 146.1, 148.7, 148.7, 152.6, 155.6,
156.4, 172.6. LCeMS (ESI) m/z 496 (M þ 1). Anal. Calcd for
C23H15F6N3O3; Calc: C, 55.77; H, 3.05; N, 8.48; found: C, 55.82; H,
3.09; N, 8.52.
Compound 6a was obtained as white solid. M.P 199e201 ꢀC.
Yield 54%. 1H NMR (300 MHz, DMSO-d6)
d; 7.00 (s, eCH, 1H),
7.15e7.31 (m, eCH, 4H), 7.79 (m, eCH, 1H), 8.27 (d, eCH, 1H,
J ¼ 7.2 Hz), 8.62 (d, eCH,1H, J ¼ 8.1 Hz), 9.96 (brs, eCSNH,1H),10.38
(brs, eNH,1H),10.41 (brs, eNH,1H). 13C NMR (75 MHz, DMSO-d6)
d;
6.7.3. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-3-phenyl-1H-
pyrazol-5(4H)-one (7c)
96.0, 116.1, 116.4, 118.8, 120.1, 122.5, 123.7, 124.5, 125.7, 126.1, 126.6,
127.0, 127.3, 128.2, 129.1, 129.9, 130.9, 144.0, 148.0, 148.5, 153.3,
156.3, 183.1. LCeMS (ESI) m/z 449 (M þ 1). Anal. Calcd for
C18H11F7N4S; Calc: C, 48.22; H, 2.47; N, 12.50; S, 7.15; found: C, 48.2
9; H, 2.59; N, 12.58; S, 7.21.
Compound 7c was obtained as off white solid. M.P 196e198 ꢀC.
Yield 63%. 1H NMR (300 MHz, CDCl3)
d; 4.02 (s, eCH2, 2H),
7.48e7.57 (m, eCH, 3H), 7.71e7.82 (m, eCH, 3H), 8.09 (s, eCH, 1H),
8.24 (d, eCH, 1H, J ¼ 7.2 Hz), 8.47 (d, eCH, 1H, J ¼ 8.7 Hz). LCeMS
(ESI) m/z 424 (M þ 1). Anal. Calcd for C20H11F6N3O; Calc: C, 56.75; H,
2.62; N, 9.93; found: C, 56.79; H, 2.68; N, 9.97.
6.6.7. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-(2-methoxyethyl)
thiosemicarbazide (6b)
Compound 6b was obtained as white solid. M.P 226e227 ꢀC.
6.7.4. 1-(2,8-Bis(trifluo romethyl)quinolin-4-yl)-3-(pyridin-4-yl)-
1H-pyrazol-5(4H)-one (7d)
Yield 45%. 1H NMR (300 MHz, DMSO-d6)
d; 3.18 (s, eOCH3, 3H), 3.43
(t, eCH2, 2H, J ¼ 5.4 Hz), 3.59 (t, eCH2, 2H, J ¼ 5.4 Hz), 6.84 (s, eCH,
1H), 7.78 (t, eCH, 1H, J ¼ 7.8 Hz), 8.26 (d, eCH, 1H, J ¼ 7.2 Hz), 8.54
(brs, eCSNH, 1H), 8.57 (d, eCH, 1H, J ¼ 8.4 Hz), 9.87(brs, eNH, 1H),
Compound 7d was obtained as pale yellow solid. M.P
268e271 ꢀC. Yield 40%. 1H NMR (300 MHz, CDCl3)
d; 6.36 (s, eCH,
1H), 7.87 (m, eCH, 2H), 8.02 (t, eCH, 1H, J ¼ 7.8 Hz), 8.38 (s, eCH,
10.14 (brs, eNH, 1H). 13C NMR (75 MHz, DMSO-d6)
d; 43.7, 58.3,
1H), 8.46 (d, eCH, 1H, J ¼ 7.2 Hz), 8.66e8.58 (m, eCH, 3H), 12.75
70.4, 95.8, 118.7, 120.0, 122.5, 123.7, 125.6, 126.1, 126.6, 127.0, 128.1,
129.8, 144.0, 148.0, 148.4, 153.5, 182.2. LCeMS (ESI) m/z 413 (M þ 1).
Anal. Calcd for C15H14F6N4OS; Calc: C, 43.69; H, 3.42; N, 13.59; S,
7.78; found: C, 43.75; H, 3.48; N, 13.52; S, 7.83.
(brs, eOH, 1H). 13C NMR (75 MHz, CDCl3)
d; 86.1, 101.2, 114.8, 119.2,
120.3, 123.1, 124.7, 125.2, 126.6, 129.0, 130.7, 131.0, 133.3, 140.7,
144.8, 150.3, 150.6, 156.7. LCeMS (ESI) m/z 425 (M þ 1). Anal. Calcd
for C19H10F6N4O; Calc: C, 53.78; H, 2.38; N,13.20; found: C, 53.87; H,
2.46; N, 13.27.
6.6.8. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-4-
(3eCHlorophenyl)semicarbazide (6c)
6.8. Antibacterial testing by serial plate dilution method
Compound 6c was obtained as yellow solid. M.P 158e161 ꢀC.
Yield 36%. 1H NMR (300 MHz, DMSO-d6)
d
; 7.17e7.21 (m, eCH, 2H),
Serial dilutions of the drug in MullereHinton broth were taken in
tubes and their pH was adjusted to 5.0 using phosphate buffer. A
standardized suspension of the test bacterium was inoculated and
incubated for 16e18 h at 37 ꢀC. The minimum inhibitory concentra-
tion(MIC)wasnotedbyseeingthelowestconcentrationof thedrugat
which there was no visible growth. A number of antimicrobial discs
are placed on the agar for the sole purpose of producing zones of
inhibition in the bacterial lawn. Twenty milliliters of agar media was
poured into each Petri dish. Excess of suspension was decanted and
plates were dried by placing in an incubator at 37 ꢀC for 1 h. Using an
agar punch, wells were made on these seeded agar plates and
minimum inhibitory concentrations of the test compounds in dime-
thylsulfoxide (DMSO) were added into each labeled well. A control
was also prepared for the plates in the same way using solvent DMSO.
The Petri dishes were prepared in triplicate and maintained at 37 ꢀC
for 3e4 days. Antibacterial activity was determined by measuring the
diameter of inhibition zone. Activity of each compound was
compared with ciprofloxacin as standard [27,28].
7.30 (s, eCH, 1H), 7.36 (d, eCH, 1H, J ¼ 7.5), 7.59e7.68 (m, eCH, 1H),
8.09e8.15 (m, eCH, 1H), 8.33 (d, eCH, 1H, J ¼ 7.2 Hz), 8.68 (d, eCH,
1H, J ¼ 8.1 Hz), 9.89 (brs, eCSNH, 1H), 10.38 (brs, eNH, 1H), 10.40
(brs, eNH, 1H). LCeMS (ESI) m/z 465 (M þ 1). Anal. Calcd for
C18H11ClF6N4S; Calc: C, 46.51; H, 2.39; 12.05; S, 6.90; found: C,
46.57; H, 2.46; 12.09; S, 6.97.
6.7. General procedure for the synthesis of title compounds (7aed)
To a suspension of 3 (2 mmol) in ethanol (10 mL) was added
substituted acetoacetate (2 mmol). The reaction mixture was stir-
red for 30 min, to it was added sodium ethoxide (2 mmol) slowly
and the reaction mixture was heated at 80 ꢀC for 30 min. The
completion of the reaction was monitored by TLC. Reaction mixture
was concentrated and the brown residue obtained was purified by
column chromatography using pet ether/ethyl acetate (2:1) as the
eluent.
6.7.1. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-3-methyl-1H-
pyrazol-5(4H)-one (7a)
6.9. Antituberculosis testing by broth microdilution assay method
Compound 7a was obtained as off white solid. M.P 124e126 ꢀC.
The anti-TB activity of the compounds was tested by resazurin
micro plate assay (REMA) as per Martin et al., with slight modifi-
cation. Resazurin, a redox dye, is blue in its oxidized state. In the
presence of viable cells it is reduced into resorufin, which is pink in
color. M. tuberculosis H37Rv was grown in Middlebrook 7H9 broth
(Difco BBL, Sparks, MD, USA) supplemented with 10% OADC (Becton
Dickinson, Sparks, MD, USA) and 0.5% glycerol. The optical density
of the bacterial culture was adjusted to McFarland 1.0 unit and
Yield 58%. 1H NMR (300 MHz, CDCl3)
d; 2.32 (s, eCH3, 3H), 3.59 (s,
eCH2, 2H), 7.71 (m, eCH2, 2H), 8.00 (s, eCH, 1H), 8.21 (d, eCH, 1H,
J ¼ 6.9 Hz), 8.36 (d, eCH,1H, J ¼ 8.7 Hz). 13C NMR (75 MHz, CDCl3)
d;
17.2, 42.0, 110.0, 112.0, 119.1, 121.6, 122.7, 123.4, 125.2, 126.6, 128.7,
129.1, 129.2, 129.4, 143.2, 145.3, 148.3, 148.8, 158.5, 171.5. LCeMS
(ESI) m/z 362 (M þ 1). Anal. Calcd for C15H9F6N3O; Calc: C, 49.87; H,
2.51; N, 11.63; found: C, 49.81; H, 2.57; N, 11.69.
50 mL from this suspension was used as the inoculum. Stock solu-
6.7.2. 1-(2,8-Bis(trifluoromethyl)quinolin-4-yl)-3-(2-(benzo[d][1,3]
dioxol-6-yl)ethyl)-1H-pyrazol-5(4H)-one (7b)
tions of the test compounds were prepared in dimethyl formamide
(DMF) and were added to fresh medium in the wells of a 96-well
Compound 7b was obtained as brown liquid. Yield 47%. 1H NMR
micro plate to which 50
assay volume 200 L. The final concentrations of the test molecules
were 1.56, 3.12, 6.25, 12.5, 25 and 50 M. Growth control wells
contained medium and M. tuberculosis alone. Rifampicin (0.5 M)
ml inoculum was added making the total
(300 MHz, CDCl3)
d
; 2.88e3.01 (m, e(CH2)2, 4H), 3.49 (s, eCH2, 2H),
m
5.98 (s, eCH2, 2H), 6.69e6.81 (m, eCH, 3H), 7.71 (t, eCH, 1H,
m
J ¼ 8.1 Hz), 7.96 (s, eCH, 1H), 8.23 (m, eCH, 2H). 13 C NMR (75 MHz,
m

S. Eswaran et al. / European Journal of Medicinal Chemistry 45 (2010) 3374e3383
3383
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and isoniazid (1.5 mM) served as positive control for inhibition of
growth. Negative control wells contained the highest volume of
DMF used in test wells without any compound. After incubation at
37 ꢀC for 7 days, 15
ml of 0.01% resazurin (Sigma, St. Louis. MO, USA)
solution in sterile water was added to the first growth control wells
and incubated for 24 h. Once the first set of growth controls turned
pink, the dye solution was added to the second set of growth
controls and the test wells, and incubated for 24 h at 37 ꢀC. Blue
color in the wells containing the test compounds would indicate
inhibition of growth and pink would indicate lack of inhibition of
growth of M. tuberculosis.
Acknowledgments
Authors are thankful to Dr. Ganesh Sambhasivam, CEO, Anthem
biosciences, Bangalore, India, for his invaluable support and allo-
cation of resources for this work. They are thankful to Dr. Suchetha
Shetty, Department of Biochemistry, Justice K.S. Hegde Medical
Academy, Deralakatte, India, for carrying out antibacterial
screening. They are also grateful to Dr. Guru Row, Solid State and
Structural Chemistry Unit (SSCU), II.Sc, Bangalore, India, for
carrying out single crystal X-Ray diffraction studies.
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