Conventional and microwave techniques for synthesis and antimicrobial studies of novel 1-[2-(2-chloro(3-quinolyl))-5-(4-nitrophenyl)-(1,3,4- oxadiazolin-3-yl)]-3-(aryl)prop-2-en-1-ones

Article abstract of DOI:10.1007/s00044-011-9670-9

In this article, we have described the conventional and microwave method for the synthesis of 1-[2-(2-chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4- oxadiazolin-3-yl)]-3-(aryl)prop-2-en-1-ones (4a-l). Through this method, we have achieved reduction in react

Full text of DOI:10.1007/s00044-011-9670-9

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:1480–1490
DOI 10.1007/s00044-011-9670-9
ORIGINAL RESEARCH
Conventional and microwave techniques for synthesis
and antimicrobial studies of novel 1-[2-(2-chloro(3-quinolyl))-5-
(4-nitrophenyl)-(1,3,4-oxadiazolin-3-yl)]-3-(aryl)prop-2-en-1-ones
•
N. C. Desai Amit M. Dodiya
Received: 17 March 2011 / Accepted: 10 May 2011 / Published online: 25 May 2011
Ó Springer Science+Business Media, LLC 2011
Abstract In this article, we have described the conven-
tional and microwave method for the synthesis of 1-[2-(2-
chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-3-yl)]-
3-(aryl)prop-2-en-1-ones (4a–l). Through this method, we
have achieved reduction in reaction time and better yield
than the previously described conventional method. The
application of microwave irradiation (MWI) is used for
carrying out chemical transformations which are pollution-
free and eco-friendly. The structure of the compounds
was characterized by spectral data. These compounds
(4a–l) were evaluated for their in vitro antimicrobial
screening on different strains of bacteria and fungi.
described for these compounds are normally ascribed, at
least, to two main mechanisms: one, which is associated
with protein, involves trapping of a protein enzyme–DNA
cleavable intermediate, whereas the other, a non-protein-
associated mechanism, is related to redox cycling of the
quinone moiety, which produces damaging free-radical
species (Murray, 2000).
In searching for agents with an improved pharmacoki-
netic properties, potency or spectrum and lower side
effects, a large number of quinoline derivatives and related
compounds have been prepared and several of these have
shown promise in clinical trials (Lown, 1998). Regarding
structural and chemical modifications of this system, one of
the most interesting modification has been the introduction
of heteroatoms (N, S) into different positions of the chro-
mophore through incorporation of one or more of five or
six-members heterocyclic ring to the basic quinoline sys-
tem (Krapcho et al., 1990, 1994, 1998). These bioisosteres
would clearly differ from their carbocyclic counterparts in
their interaction with DNA and enzymes, as well as in their
reduction potential.
Keywords Quinoline-oxadiazole-based chalcones ꢀ
2-Chloroquinoline-3-carbaldehyde ꢀ Microwave method
for quinoline–oxadiazole derivatives
Introduction
Quinoline containing drugs such as doxorubicin and
mitoxantrone have been established as one of the most
effective class of anticancer agents in clinical use today
with broad applications in the treatment of several
leukaemia and lymphomas as well as in combination
chemotherapy of solid tumours (Wakelin and Waring,
1990). However, toxic dose-related side effects such as
myelosuppression and cardiotoxicity, limited their clinical
applications (Cheng and Zee-Cheng, 1983; Murray, 2000).
The potent anticancer activity as well as toxic effects
The chemistry of 1,3,4-oxadiazoles have received con-
siderable attention from synthetic organic chemists due to
their diverse biological activities (Omar et al., 1996; Hui
et al., 2002; Mohan et al., 2004). Several research groups
have contributed for the development of methods for the
synthesis of 1,3,4-oxadiazoles (Chiba and Mitsuhiro, 1992;
Bacu et al., 2003; Bhat et al., 2004). However, these pro-
cedures are time consuming and proceed in low yields.
Therefore, a more convenient and eco-friendly method for
the synthesis of 1,3,4-oxadiazoles is highly desirable.
Chalcones are natural biocides (Geiger and Conn, 1945)
and are well known intermediates for synthesizing various
heterocycles. Chalcones and their derivatives are also
medicinally important. Many chalcone derivatives have
N. C. Desai (&) ꢀ A. M. Dodiya
Medicinal Chemistry Division, Department of Chemistry,
Bhavnagar University, Bhavnagar 364 002, India
e-mail: dnisheeth@rediffmail.com
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Med Chem Res (2012) 21:1480–1490
1481
been reported to possess antimalarial and antimicrobial
properties (Katritzky, 1984). Anticancer properties of some
simple chalcone derivatives have also been reported in
literature (Rezig et al., 2000; Ducki et al., 1996). However,
the synthesis of quinolinyl chalcones is scarcely reported in
literature. Sayed et al. (1976) and Ibrahim et al. (1996)
have synthesized a few quinoline–chalcone derivatives by
Claisen–Schmidt condensation reaction.
assisted by microwave irradiation in organic synthesis can
increase the purity of the resulting products, enhance the
chemical yield and shorten the reaction time. Solvent-free
reaction leads to a clean, eco-friendly and economic tech-
nology. Reactions on solid support without using solvent
usually with close vessel in Synthos-3000, Anton Paar
microwave reaction system is currently popular among the
synthetic chemists to create eco-friendly atmosphere (Loupy,
2002; Rana et al., 2009).
Dominquez et al. (2001) have reported the synthesis of
some quinoline–chalcones and claimed their antimalarial
activity. Moussaoui et al. (2002) have also described the
synthesis of quinolinyl chalcones and claimed their cyto-
toxicity in K 562 human leukaemia cell lines.
Looking at the medicinal importance of quinolines,
1,3,4-oxadiazoles and chalcones, we have designed and
synthesized a series of 1-[2-(2-chloro(3-quinolyl))-5-(4-
nitrophenyl)(1,3,4-oxadiazolin-3-yl)]-3-(aryl)prop-2-en-1-
ones (4a–l) (Scheme 1) by conventional and microwave
methods. The difference of reaction times and yields are
shown in Table 2. The structures of the compounds syn-
The formation of heterocyclic rings by cyclocondensa-
tion reactions is typically a process well-suited for micro-
wave technology. Many of these condensation reactions
require high temperature and conventional reaction con-
ditions very often involve heating the reactants in an oil,
metal or sand bath for many hours or even days. An
example is the formation of 4-hydroxy-1-H-quinoline-2-
ones from anilines and malonic esters. The corresponding
conventional, thermal protocol involves heating the two
components in equimolar amounts in an oil bath at
220–300°C for several hours (without solvent), whereas
similar high yields can be obtained by microwave heating
at 250°C for 10 min (Kappe, 2004). This prompted us to
adopt the MWI method for the synthesis of bio-active
heterocyclic molecules.
1
thesized were assigned on the basis of IR, H NMR, 13C
NMR and mass spectral data.
Reaction mechanism of the synthesized
compounds (4a–l)
In the first step, acetic anhydride is cleaved to give acetyl
carbocation and acetate carbanion, which will be used in the
reaction with aroylhydrazone intermediate. The lone pair
present over nitrogen atom will attack on the cationic carbon
of 2-chloroquinoline-3-carbaldehyde moiety, which will
undergo self condensation reaction to form aroylhydrazone
derivative. Due to the keto-imine tautomerization, the keto
The present study aims at preparing quinoline–oxadiaz-
ole–chalcone derivatives. The solvent-free organic reactions
Scheme 1 Synthesis of 1-[2-(2-
chloro(3-quinolyl))-5-(4-
N
NH
H
CONHNH2
C
O
nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(aryl)prop-2-en-1-ones
(4a–l)
O
+
Ethanol
HAc-
Cl
N
Cl
N
(2)
(1)
NO2
NO2
(CH3CO)2O
CH3
O
C
O
CH CH
N
C
N
N
N
Ethanol
KOH
R
O
O
OHC
NO2
Cl
N
R
NO2
R = Different substituents
Cl
N
(3)
(4a-l)
Sr. No.
R
Sr. No.
R
Sr. No.
R
4a
4b
4c
4d
=
-2-Cl
-3-Cl
-4-Cl
4i
4j
4k
4l
=
-4-OH
-4-CH
4e
=
-3-NO
2
=
=
=
4f
4g
=
=
-4-NO
-2-OH
=
=
=
2
3
-4-OCH
3
-2-NO
2
4h
=
-3-OH
-3,4,5-(OCH )
3
3
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Med Chem Res (2012) 21:1480–1490
O
C
Scheme 2 The mechanism of
the synthesized compounds 4a–l
H C
3
+
-
CH COO
3
CH CO
3
+
O
H C
3
C
O
H
H
N
H
C
CONHNH
2
O
C
NH
C
H
O
OH
Cl
+
N
N
Cl
-H O
2
1
NO
2
NO
2
N
N
C
N
N
C
CH
Cl
CH
Cl
O
O
+
-H
N
N
NO
2
2
NO
2
O
H
CH
2
COCH
N
3
C
N
N
N
CH
C
CH
Cl
C
O
O
N
Cl
N
NO
2
NO
3
2
-
(i) OH (ii)
O
C
H
R
H
O
O
CH CH
CH CH
OH
C
N
C
N
R
R
N
C
N
CH
CH
Cl
C
O
O
-H O
2
N
Cl
N
4a-l
NO
2
NO
2
R = Different substituents
group of aroylhydrazone derivative converts to hydroxyl
group. The negatively charged oxygen atom which is
formed due to deprotonation of the hydroxyl group will
attack on C=N bond to form oxadiazole ring. The nitrogen
anion will attack on acetyl carbocation to form acetyl
derivative of oxadiazole moiety. Here acetyl group under-
goes Claisen–Schmidt condensation reaction which is a well
known reaction. The reaction mechanism is described in
(Scheme 2) by taking the example of compound (4a–l).
same reactions were completed in 3–5 min, and also found
in good yield as compared to the conventional method. A
comparative study in terms of yield and reaction period is
shown in Table 2.
IR-data
The IR spectrum of the title compound 4h (molecular
formula C26H17ClN4O5, m.w. 500.09) has given vibration
at 3,048 cm-1 over the range which shows multiple weak
absorption peak corresponding to Qu-H and Ar-H stretch-
ing vibration absorption peaks. The strong absorption at
1,675 cm-1 is due to the C=O stretching vibration and the
moderate intensity absorption at 1,611 cm-1 corresponds
to a C=N stretching vibration and C=C linkage appeared
Results and discussion
All the reactions (steps-2, 3 and 4) were completed in
6–8 h by conventional method, while under MWI, the
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Med Chem Res (2012) 21:1480–1490
1483
stretching vibration at 1,595 cm-1. The absorption at
1,354 cm-1 is due to the symmetric stretching of –NO2
group while the absorption at 1,533 cm-1 is due to the
asymmetric stretching of –NO2 group. The high frequency
region of the IR spectra of these compounds contain –OH
stretching vibration band at 3,429 cm-1. While in oxadi-
azole nucleus C–O–C linkage appeared in the range of
1,207 cm-1. Methylene (CH=CH) linkage appeared stretch-
ing vibration in the range of 3,093 cm-1, while methylene
linkage appeared bending vibration in the range of
825 cm-1. The absorption peak at 758 cm-1 arises due to
the C–Cl group and absorption peak at 764 cm-1 indicates
that mono substituted benzene ring is present.
attached to a carbonyl group and then appeared at
d = 118.8 ppm. While alkene carbon at C-20 directly
conjugated to the phenyl ring, indicates downfield chemical
shift at d = 144.0 ppm. The carbons of the phenyl ring (C-
21, C-22, C-24, C-25, C-26) conjugated to the alkene
functionality have chemical shifts in the range d = 115.1
to 136.6 ppm. While C-23, which is attached to a hydroxyl
group appeared at d = 158.4 ppm, under the strong elec-
tron withdrawing influence exerted by the hydroxyl group.
While, the carbons which are present in oxadiazole nucleus
C-10 and C-11 both are on one side directly attached to
oxygen atom and on the other side C-10 is attached to
nitrogen with a single bond. Therefore, it gives a chemical
shift at d = 70.1 ppm, while on the other side C-11 is
attached to nitrogen atom by a double bond, so, it gives a
chemical shift at d = 155.0 ppm. The carbons of the
quinoline ring (C-2, C-3, C-4, C-5, C-6, C-7, C-8) appeared
upfield between d = 125.8 to 136.4 ppm compared to
those quinoline ring carbons at C-1 and C-9. The carbon
C-12 which is present in phenyl ring and which is attached
to oxadiazole nucleus carbon C-11, appeared at 135.9 ppm.
The equivalent carbons C-13 and C-17 appeared at
d = 130.1 ppm, while other equivalent carbons C-14 and
C-16 appeared at 124.0 ppm. While C-15 which is directly
attached to nitro group appeared at 150.2 ppm, respec-
tively. Carbon numbering is described in Fig. 1.
H-NMR-data
It can be seen from the chemical structure of compound 4h
that different pairs of carbons, e.g. C-13 and C-17, C-14 and
C-16 are attached to chemically equivalent protons, which
appeared at d = 8.09 and 8.34 ppm, respectively. The pro-
ton attached to C-7 position appeared as a multiplet at
7.78 ppm due to mutual coupling with C-6 and C-8, while
the proton attached to C-6 position also appeared as a mul-
tiplet at d = 7.80 ppm due to mutual coupling with C-5 and
C-7. The protons of the C-5 and C-8 appeared as a doublet at
8.06 and 7.83 ppm, respectively. Chemical shift in the aro-
matic region with a multiplet centered at d = 8.05 ppm
corresponds to C-3, while the C-10 (–CH group) present in
the oxadiazole nucleus appeared at d = 6.61 ppm. The
protons, which are present in alkene linkage, C-19 and C-20
gives doublet, C-19 appeared at d = 6.84 ppm, because of
vicinity of carbonyl group at C-18, while the proton of C-20
appeared at d = 7.55 ppm, because it is directly attached to
the phenyl ring. The proton of the –OH group, which is
attached to carbon C-23 appeared as a singlet at
d = 9.83 ppm, while four other protons of the phenyl ring
attached to carbons C-22, C-24, C-25 and C-26 appeared as a
multiplet at d = 6.61–7.04 ppm.
Antimicrobial activity
For the antibacterial activity, the newly synthesized com-
pounds were screened for their antibacterial activity against
Gram positive bacteria Staphylococcus aureus (MTCC-96)
and Streptococcus pyogenes (MTCC-442) and Gram neg-
ative Escherichia Coli (MTCC-443) and Pseudomonas
aeruginosa (MTCC-1688)]. Antibacterial activity was
carried out by serial broth dilution method (Ghalem and
Mohamed, 2009; Desai and Trivedi, 1993; Al-Bayati and
Al-Mola, 2008). The standard strains used for the antimi-
crobial activity was procured from Institute of Microbial
Technology, Chandigarh. The compounds (4a–l) were
screened for their antibacterial activity in triplicate against
Escherichia coli, Staphylococcus aureus, Pseudomonas
13C-NMR-data
The final compound 4h contains three moieties like quin-
oline, oxadiazole and chalcone. The chemical shifts of the
carbons of the final compound 4h carbons varies from
d = 167.0 to 70.1 ppm. The carbon nuclei under the
influence of a strong electronegative environment appeared
downfield, e.g. the C-18 carbonyl, which is directly linked
to the ring nitrogen has a chemical shift at d = 167.0 ppm,
whereas the C-1 linked to one chlorine and other nitrogen
atom, appeared at d = 150.8 ppm. The chemical shift of
the ring carbon at C-9 is affected by the presence of
directly attached ring nitrogen atom and appeared at
d = 143.5 ppm. While alkene carbon at C-19 is directly
26
25
19
CH
20
CH
24
21
O
C
22
18
23
N
OH
N
17
3
5
11
4
16
10
Cl
12
13
O
6
2
15
7
9
1
NO2
N
14
8
Fig. 1 Carbon numbering of the compound 4h
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Med Chem Res (2012) 21:1480–1490
Table 1 Antibacterial and antifungal data for the final synthesized compounds (4a–l)
S. no. Compd. –R
Minimum inhibitory concentration for bacteria lg/ml SD Minimum inhibitory concentration for fungi lg/
ml SD
Gram positive
Gram negative
E. coli
MTCC-443
P. aeruginosa S. aureus
MTCC-1688 MTCC-96
S. pyogenes C. albicans
MTCC-442 MTCC-227
A. niger
MTCC-282
A. clavatus
MTCC-1323
1
4a
4b
4c
4d
4e
4f
–2-Cl
500 2.34* 500 3.35*
100 3.65* 200 3.55*
500 3.6* 500 3.34* 250 4.36*
100 4.04* 100 3.43* 100 3.55*
500 3.50*
100 2.44*
500 3.11*
500 3.20*
2
–3-CI
3
–4-C1
200 3.30* 100 2.13* 1000 3.34* 500 4.13* 100 4.34*
200 3.02* 1000 3.23*
4
–2-NO2
–3-NO2
–4-NO2
–2-OH
–3-OH
–4-OH
–4-CH3
–4-OCH3
50 3.23* 50 4.57*
1000 3.56* 500 2.18*
100 4.45* 500 2.58*
500 3.32* 250 2.69*
25 3.56* 50 4.57*
250 3.12* 50 2.66*
200 4.35* 100 2.42*
100 4.24* 500 3.45*
500 3.23* 200 2.53* 500 2.48*
500 3.04* 100 4.55* 100 4.24*
500 3.5*
100 3.4*
100 3.36*
500 3.41*
100 3.31*
500 3.25*
100 3.35*
500 3.3*
5
6
100 2.56* 500 2.53* 500 4.25* 1000 3.5*
7
4g
4h
4i
500 4.13* 250 3.05* 1000 3.2*
200 3.08* 100 4.93* 500 3.4*
100 3.45* 500 4.73* 500 3.53*
500 2.02*
200 3.12*
100 3.55*
8
9
10
11
12
4j
200 3.36* 250 3.6*
250 3.75*
100 3.4* 1,000 3.40*
4k
4l
100 3.53* 100 4.02* 500 4.8* 1,000 3.2*
100 2.30*
100 4.15*
–
–3,4,5-(OCH3)3 200 4.36* 200 3.55*
500 3.36* 500 3.53* 100 3.43*
100 3.54*
–
Ampicillin
100 4.57* 100 4.12*
250 4.15* 100 3.55*
–
Griseofulvin
–
–
–
–
500 2.64*
100 3*
100 3.46*
SD standard deviation
* P B 0.0001
aeruginosa and Streptococcus pyogenes at different con-
centrations of 1000, 500, 200, 100, 50, 25, 12.5 lg/ml as
shown in Table 1. The drugs which were found to be active
in primary screening were similarly diluted to obtain 100,
50, 25, 12.5 lg/ml concentrations. 10 lg/ml suspensions
were further inoculated on appropriate media and growth
was noted after 24 and 48 h. The lowest concentration,
which showed no growth after spot subculture was con-
sidered as MIC for each drug. The highest dilution showing
at least 99% inhibition is taken as (MIC). The test mixture
should contain 108 cells/ml. The standard drug used in the
present study was ‘ampicillin’ for evaluating antibacterial
activity which showed (100, 100, 250 and 100 lg/ml) MIC
against E. coli, P. aeruginosa, S. aureus and S. pyogenes,
respectively.
108 spores/ml MIC. ‘Griseofulvin’ was used as a standard
drug for antifungal activity, which showed (500, 100
and 100 lg/ml) MIC against C. albicans, A. niger and
A. clavatus, respectively. The results of antimicrobial
evaluation of derivatives (4a–l) are collected in (Table 1).
Antibacterial activity
From screening results, it has been observed that final
compounds 4b, 4f and 4k possess good activity against
E. coli while compound 4d possess very good activity
against E. coli and compound 4h possess excellent activity
against E.coli. Final compounds 4c and 4j possess good
activity against P. aeruginosa and compounds 4d, 4h and
4i possess very good activity against P. aeruginosa. Final
compounds 4b, 4f, 4i and 4k possess very good activity
against S. aureus, while compounds 4c and 4j possess
excellent activity against S. aureus. Final compounds 4b,
4e, 4h and 4k were considered as good active against
S. pyogenes and compound 4f possess very good activity.
The remaining compounds of the series possess moderate
to poor antibacterial activity. The discussion and compar-
ison of antibacterial activity was given with respect to
ampicillin antibiotic.
While for the antifungal activity, same compounds were
tested for antifungal activity in triplicate against Candida
albicans, Aspergillus niger and Aspergillus clavatus at
various concentrations of 1000, 500, 200 and 100 lg/ml as
shown in Table 1. The results were recorded in the form of
primary and secondary screening. The synthesized com-
pounds were diluted at 1,000 lg/ml concentration, as a
stock solution. The synthesized compounds which were
found to be active in this primary screening were further
tested in a second set of dilution against all microorgan-
isms. The lowest concentration, which showed no growth
after spot subculture was considered as (MIC) for each
drug. The highest dilution showing at least 99% inhibition
is taken as MIC. The test mixture should contain
Antifungal activity
Antifungal screening data showed that final compounds 4d,
4f, 4h, 4i and 4k possess good activity against C. albicans,
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Med Chem Res (2012) 21:1480–1490
1485
while compound 4j possess very good activity against
C. albicans and compounds 4b, 4c, 4e and 4l possess
excellent activity. Compounds 4b, 4e, 4i, 4j and 4l possess
good activity against A. niger. Compounds 4d, 4f, 4h, 4k and
4l possess good activity against A. clavatus. The remaining
compounds of the entire series possess only moderate to
poor antifungal activity. The discussion and comparison of
antifungal activity was compared with griseofulvin.
while in microwave irradiation Silica gel (1 g) was added
to the mixture of aroylhydrazone (2) and acetic anhydride
(2 ml) and was irradiated in microwave oven at 400 W
intermittently at 30 s interval three to four times to yield
(3). In the final step, intermediate (3) was reacted with
substituted aldehydes in the presence of ethanolic-KOH
solution for 6 h to furnish the final product 1-[2-(2-
chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-3-
yl)]-3-(aryl)prop-2-en-1-ones (4a–l), while the same
product is obtained in microwave irradiation at 100 W
intermittently at 30 s intervals for the specified time. Thus,
the final product (4a–l) is obtained.
Statistical analysis
The standard deviation value is expressed in terms of SD.
On the basis of the calculated value by using ANOVA
method, it has been observed that the differences below
0.0001 level (P B 0.0001) were considered as statistically
significant.
General procedure for the synthesis of N-[(1E)-1-aza-2-
(2-chloro(3-quinolyl))vinyl]-(4-
nitrophenyl)carboxamide (2)
(A) Conventional method
Experimental
A mixture of 2-chloroquinoline-3-carbaldehyde (1) and
4-nitrophenyl hydrazide was mixed and dissolved in etha-
nol and a catalytic amount of glacial acetic acid was added
and the mixture was refluxed for 5–6 h by using reflux
condenser. After cooling, the crystals formed were filtered
off and recrystallized from absolute alcohol (99.5%) to
give product (2).
Materials and methods
All the required chemicals were purchased from E. Merck.
2-Chloroquinoline-3-carbaldehyde was synthesized by Nar-
ine et al. (Meth-Cohn and Narine, 1978) and modified (Kappe
et al., 1994; Bawa and Kumar, 2009). IR spectra were recor-
ded on Perkin Elmer FT-IR spectrophotometer. 1H-NMR and
13C-NMR spectra were recorded on Bruker DPX-40C
instrument at 400 MHz. Chemical shifts are reported in ppm
referenced to the residual solvent signal. Mass spectra were
recordedonJEOL SX-102. Elementalanalysiswasperformed
by Perkin-Elmer 2400-CHN analyzer. Melting points were
recorded on Gallenkemp apparatus and were uncorrected.
Aluminium coated TLC plates 60 F245 (E. Merck) were used
for monitoring of reaction and purity of compounds. In the
conventional method, compounds were synthesized by using
Random synthesizer. Bookie Rotavapour was used for dis-
tillation, while microwave irradiation was carried out in
Synthos-3000 Anton Paar, microwave Reaction System.
M.P. 128–130°C; Yield 71%; IR (KBr): t = 3034
(aromatic-H), 1676 (C=O), 1608 (C=N), 1593, 1563, 1432
(C=C and quinoline ring), 1340 (–NO2 symmetric stretch-
ing), 1522 (–NO2 asymmetric stretching), 761, 774 (C–Cl
1
bond, mono substituted benzene); H-NMR: d 7.51–8.90
(m, 9H, quinoline-H and Ar–H), 10.88 (s, 1H, O=C–N–H),
7.50 (s, 1H, N=C–H); 13C-NMR: d 124.0, 124.1, 126.4,
126.6, 127.0, 128.4, 132.5, 136.6, 137.2, 140.3, 142.9,
147.8, 151.3, 151.6, 162.9; MS: m/z 354.09 (M?). Anal.
calc. For C17H11ClN4O3: C-57.56; H-3.13; N-15.79.
Found: C, 57.61; H. 3.18; N, 15.85%.
(B) Microwave method
Chemical synthesis
A mixture of 2-chloroquinoline-3-carbaldehyde (0.01 mol),
4-nitrophenyl hydrazide (0.01 mol) and 1,4-dioxane (5
drops) was subjected to microwave irradiation at 200 W
intermittently at 30 s interval for the specified time (Table 2).
On completion of the reaction, it was monitored by TLC. The
reaction mixture was cooled and treated with chilled water.
The precipitate thus obtained was filtered, washed with water
and recrystallized from ethanol to afford 2.
The conventional method involves the reaction of
2-chloroquinoline-3-carbaldehyde (1) and 4-nitro-hydra-
zide in the presence of catalytic amount of glacial acetic
acid in ethanol to form aroylhydrazone (2), the same
reaction when performed under the microwave irradiation,
same starting material in 1,4-dioxane (5 drops) was sub-
jected to microwave irradiation at 200 W intermittently at
30 s intervals for the specified time to obtained aroylhyd-
razone (2) as a product. In the third step, aroylhydrazone
(2) was cyclized by refluxing with excessive amount of
acetic anhydride for 6 h which resulted in product (3),
The progress of the reaction and the purity of the
compound were routinely checked on TLC aluminium
sheet silica gel 60 F245 (E. Merck) using benzene-aceto-
nitrile (4:1 v/v) as an irrigator and was developed in iodine
chamber.
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Med Chem Res (2012) 21:1480–1490
Table 2 The compounds (4a–
l) synthesized by conventional
and microwave method
S. no. –R
Molecular formula M.P.
Conventional method Microwave method
Yield
Time (in h)
Yield Time (in min.)
4a
4b
4c
4d
4e
4f
–2Cl
C26H16Cl2N4O4
221–223 76
201–203 64
6
77
68
78
71
65
72
70
74
63
73
77
69
1.7
2.5
1.5
3.5
4.2
3
–3Cl
C
26H16Cl2N4O4
26H16Cl2N4O4
5
–4Cl
C
195–197 73
187–189 68
203–205 62
238–240 69
232–234 67
202–204 65
197–199 58
188–190 70
205–207 75
218–220 64
7.5
7
–2NO2
–3NO2
–4NO2
–2OH
–3OH
–4OH
–4CH3
–4OCH3
C26H16ClN5O6
C26H16ClN5O6
C26H16ClN5O6
6.5
5.5
6
4g
4h
4i
C26H17ClN4O5
C26H17ClN4O5
C26H17ClN4O5
2.5
3.5
2
7
6.8
6.5
8
4j
C27H19ClN4O4
C27H19ClN4O5
4
4k
4l
2.5
3
–3,4,5-(OCH3)3 C29H23ClN4O7
7.5
General procedure for the synthesis 3-acetyl-2-(2-
chloro(3-quinolyl))-5-(4-nitrophenyl)-1,3,4-
oxadiazoline (3)
Dilution of methanol solution with ice-cold water gave the
crude product, which was filtered, washed with water and
recrystallized from methanol to give product (3).
The progress of the reaction and the purity of the com-
pound were routinely checked on TLC aluminium sheet
silica gel 60 F245 (E.Merck) using benzene–acetonitrile (4:1
v/v) as an irrigator and was developed in iodine chamber.
(A) Conventional method
Acetic anhydride (0.02 mol) was added to aroylhydrazone
(2) (0.01 mol) and refluxed for 2 h. After cooling, the
reaction mixture was poured into ice-cold water. The pre-
cipitate was filtered off, washed with water, dried and re-
crystallized from DMF–ethanol to give product (3).
M.P. 185–187°C; Yield 67%; IR (KBr): t = 3034
(aromatic-H), 2958 (–CH3 stretching), 1675 (C=O), 1607
(C=N), 1590, 1563, 1431 (C=C and quinoline ring), 1341
(–NO2 symmetric stretching), 1523 (–NO2 asymmetric
stretching), 1454 (–CH3 bending), 1204 (C–O–C linkage),
762, 774 (C–Cl bond, mono substituted benzene); 1H-
NMR: d 7.47–8.34 (m, 9H, quinoline-H and Ar-H), 2.02 (s,
3H, –CO–CH3), 6.61 (s, 1H, N–CH-quinoline ring); 13C-
NMR: d 24.7, 69.8, 124.0,125.8, 126.4, 126.5, 130.1,
130.7, 131.4, 135.6, 135.9, 136.4, 143.5, 150.2, 150.8,
155.0, 168.5; MS: m/z 396.06 (M?). Anal. calc. For
C19H13ClN4O4: C, 57.51; H, 3.30; N, 14.12. Found: C,
57.57; H, 3.36; N, 14.15%.
General synthesis of 1-[2-(2-chloro(3-quinolyl))-5-(4-
nitrophenyl)(1,3,4-oxadiazolin-3-yl)]-3-(aryl)prop-2-
en-1-ones (4a–l)
(A) Conventional method
A mixture of (3) (0.01 mol) and different substituted alde-
hydes (0.01 mol) was stirred in ethanolic potassium hydrox-
ide for 2 h. The yellow crystals formed were filtered off,
washed with water and crystallized from ethanol (99.5%).
(B) Microwave method
A mixture of compound (3) (0.01 mol), different substi-
tuted aldehydes (0.01 mol), potassium hydroxide and eth-
anol (95%) (1 ml) was subjected to microwave irradiation
at 100 W intermittently at 30 s interval for the specified
time (Table 2). On completion of the reaction as monitored
by TLC, the reaction mixture was cooled. The precipitate
thus obtained was filtered and recrystallized from ethanol
(95%) to afford final compound (4h).
(B) Microwave method
Silica gel (1 g) was added to the mixture of aroylhydrazone
(0.01 mol) and acetic anhydride (2 ml) at room tempera-
ture. The reaction mixture was thoroughly mixed and the
absorbed material was dried in air and irradiated in
microwave oven at 400 W intermittently at 30 s interval
for the specified time (Table 2). The reaction mixture was
cooled and the product was extracted from methanol.
The progress of the reaction and the purity of the
compound were routinely checked on TLC aluminium
sheet silica gel 60 F245 (E. Merck) using benzene–aceto-
nitrile (4:1 v/v) as an irrigator and was developed in iodine
chamber.
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Med Chem Res (2012) 21:1480–1490
1487
Other compounds of the series were prepared by using
the same conventional and microwave method.
=C–H), 6.61 (s, 1H, N–CH-quinoline ring); 13C-NMR: d
70.1, 118.8, 124.0, 125.8, 126.4, 126.5, 127.8, 128.7,
130.7, 130.1, 131.4, 133.3, 133.5, 135.6, 135.9, 136.4,
143.5, 144.0, 150.2, 150.8, 155.0, 167.0; MS: m/z 533.37
(M?). Anal. calc. For C26H16Cl2N4O4, C, 60.13; H, 3.11;
N, 10.79%. Found: C, 60.14; H, 3.17; N, 10.85%.
Physical constants and characterization
of 1-[2-(2-Chloro(3-quinolyl))-5-(4-nitrophenyl)
(1,3,4-oxadiazolin-3-yl)]-3-(2-chlorophenyl)
prop-2-en-1-one (4a)
Physical constants and characterization
of 1-[2-(2-Chloro(3-quinolyl))-5-(4-nitrophenyl)
(1,3,4-oxadiazolin-3-yl)]-3-(2-nitrophenyl)
prop-2-en-1-one (4d)
IR (KBr): t = 3038 (aromatic-H), 3058 (CH=CH group),
1672 (C=O), 1609 (C=N), 1595, 1561, 1433 (C=C, ben-
zene and quinoline ring), 1342 (–NO2 symmetric stretch-
ing), 1543 (–NO2 asymmetric stretching), 1218 (C–O–C
linkage), 760, 771 (C–Cl bond, mono substituted benzene)
IR (KBr): t = 3063 (aromatic-H), 3058 (CH=CH group),
1687 (C=O), 1590 (C=N), 1585, 1545, 1427 (C=C, ben-
zene and quinoline ring), 1219 (C–O–C linkage), 1349
(–NO2 symmetric stretching), 1516 (–NO2 asymmetric
stretching), 758, 775 (C–Cl bond, mono substituted ben-
1
cm-1; H-NMR (DMSO-d6): d 7.06–8.34 (m, 13H, quin-
oline-H and Ar-H), 6.67 (d, 1H, O=C–C–H), 7.82 (d, 1H,
=C–H), 6.61 (s, 1H, N–CH-quinoline ring); 13C-NMR: d
24.7, 70.1, 118.8, 124.0, 125.8, 126.4, 126.5, 126.8, 127.8,
128.7, 129.4, 130.1, 130.7, 131.1, 131.4, 133.0, 135.6,
135.9, 136.4, 143.5, 150.0, 150.8, 155.0, 167.0; MS: m/z
519.34 (M?). Anal. calc. For C26H16Cl2N4O4, C, 60.13; H,
3.11; N, 10.79%. Found: C, 60.15; H, 3.17; N, 10.85%.
1
zene) cm-1; H-NMR (DMSO-d6): d 7.56–8.34 (m, 13H,
quinoline-H and Ar-H), 6.91 (d, 1H, O=C–C–H), 8.11 (d,
1H, =C–H), 6.61 (s, 1H, N–CH-quinoline ring); 13C-NMR:
d 70.1, 118.8, 123.8, 124.0, 125.8, 126.4, 126.5, 127.2,
127.3, 128.9, 130.1, 130.7, 131.4, 134.8, 135.6, 135.9,
136.4, 143.5, 144.0, 145.0, 150.2, 150.8, 155.0, 167.0; MS:
m/z 529.08 (M?). Anal. calc. For C26H16ClN5O6: C, 58.93;
H, 3.04; N, 13.22. Found: C, 58.97; H, 3.09; N, 13.28%.
Physical constants and characterization
of 1-[2-(2-Chloro(3-quinolyl))-5-(4-nitrophenyl)
(1,3,4-oxadiazolin-3-yl)]-3-(3-chlorophenyl)
prop-2-en-1-one (4b)
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(3-nitrophenyl)prop-2-en-1-one (4e)
IR (KBr): t = 3052 (aromatic-H), 3063 (CH=CH group),
1682 (C=O), 1614 (C=N), 1583, 1541, 1433 (C=C, ben-
zene and quinoline ring), 1346 (–NO2 symmetric stretch-
ing), 1522 (–NO2 asymmetric stretching), 1209 (C–O–C
linkage), 761, 775 (C–Cl bond, mono substituted benzene)
IR (KBr): t = 3057 (aromatic-H), 3081 (CH=CH group),
1678 (C=O), 1608 (C=N), 1589, 1558, 1430 (C=C, benzene
and quinoline ring), 1219 (C–O–C linkage), 1353 (–NO2
symmetric stretching), 1524 (–NO2 asymmetric stretching),
763, 774 (C–Cl bond, mono substituted benzene) cm-1; 1H-
NMR (DMSO-d6): d 7.57–8.34 (m, 13H, quinoline-H and
Ar-H), 7.09 (d, 1H, O=C–C–H), 7.66 (d, 1H, =C–H), 6.61
(s, 1H, N–CH-quinoline ring); 13C-NMR: d 24.7, 70.1,
118.8, 120.0, 123.1, 124.0, 125.8, 126.4, 126.5, 129.6,
130.1, 130.7, 131.4, 132.5, 135.6, 135.9, 136.1, 136.4,
143.5, 144.0, 147.8, 150.2, 150.8, 155.0, 167.0; MS: m/z
529.08 (M?). Anal. calcd. For C26H16ClN5O6: C, 58.93; H,
3.04; N, 13.22. Found: C, 58.98; H, 3.07; N, 13.28%.
1
cm-1; H-NMR (DMSO-d6): d 7.15–8.34 (m, 13H, quin-
oline-H and Ar–H), 6.84 (d, 1H, O=C–C–H), 7.55 (d, 1H,
=C–H), 6.61 (s, 1H, N–CH-quinoline ring); 13C-NMR: d
70.1, 118.8, 124.0, 125.8, 126.4, 126.5, 127.8, 128.7,
130.1, 130.7, 131.4, 133.3, 133.5, 135.6, 135.9, 136.4,
143.5, 144.0, 150.2, 150.8, 155.0, 167.0; MS: m/z 519.34
(M?). Anal. calc. For C26H16Cl2N4O4, C, 60.13; H, 3.11;
N, 10.79%. Found: C, 60.17; H, 3.16; N, 10.86%.
Physical constants and characterization
of 1-[2-(2-Chloro(3-quinolyl))-5-(4-nitrophenyl)
(1,3,4-oxadiazolin-3-yl)]-3-(4-chlorophenyl)
prop-2-en-1-one (4c)
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(4-nitrophenyl)prop-2-en-1-one (4f)
IR (KBr): t = 3039 (aromatic-H), 3064 (CH=CH group),
1684 (C=O), 1609 (C=N), 1607, 1571, 1443 (C=C, ben-
zene and quinoline ring), 1343 (–NO2 symmetric stretch-
ing), 1521 (–NO2 asymmetric stretching), 1205 (C–O–C
linkage), 757, 778 (C–Cl bond, mono substituted benzene)
IR (KBr): t = 3039 (aromatic-H), 3065 (CH=CH group),
1672 (C=O), 1616 (C=N), 1597, 1561, 1434 (C=C, ben-
zene and quinoline ring), 1216 (C–O–C linkage), 1342
(–NO2 symmetric stretching), 1523 (–NO2 asymmet-
ric stretching), 756, 768 (C–Cl bond, mono substituted
1
cm-1; H-NMR (DMSO-d6): d 7.15–8.34 (m, 13H, quin-
oline-H and Ar-H), 6.84 (d, 1H, O=C–C–H), 7.55 (d, 1H,
123

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Med Chem Res (2012) 21:1480–1490
benzene) cm-1
;
1H-NMR (DMSO-d6): d 7.57–8.34 (m,
1608, 1564, 1423 (C=C, benzene and quinoline ring),
1341 (–NO2 symmetric stretching), 1522 (–NO2
asymmetric stretching), 1219 (C–O–C linkage), 761, 769
13H, quinoline-H and Ar-H), 7.13 (d, 1H, O=C–C–H), 7.69
(d, 1H, =C–H), 6.61 (s, 1H, N–CH-quinoline ring);
13C-NMR: d 70.1, 118.8, 123.8, 124.0, 125.8, 126.4, 126.5,
127.3, 130.1, 130.7, 131.4, 135.6, 135.9, 136.4, 141.3,
143.5, 144.0, 147.1, 150.2, 150.8, 155.0, 167.0; MS: m/z
529.08 (M?). Anal. calc. For C26H16ClN5O6: C, 58.93; H,
3.04; N, 13.22. Found: C, 58.99; H, 3.08; N, 13.26%.
1
(C–Cl bond, mono substituted benzene) cm-1; H-NMR
(DMSO-d6): d 7.57–8.83 (m, 13H, quinoline-H and Ar-
H), 6.67 (d, 1H, O=C–C-H), 7.82 (d, 1H, =C–H), 6.61 (s,
1H, N–CH-quinoline ring), 9.82 (s, 1H, aromatic-OH
group); 13C-NMR: d 70.1, 115.8, 118.8, 124.0, 125.8,
126.4, 126.5, 127.8, 130.1, 130.7, 131.4, 135.6, 135.9,
136.4, 143.5, 144.0, 150.2, 150.8, 155.0, 157.7, 167.0;
MS: m/z 500.09 (M?). Anal. calc. For C26H17ClN4O5: C,
62.34; H, 3.42; N, 11.19. Found: C, 62.39; H, 3.47; N,
11.24%.
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(2-hydroxyphenyl)prop-2-en-1-one (4g)
IR (KBr): t = 3060 (aromatic-H), 3420 (aromatic-OH
group), 3087 (CH=CH group), 1681 (C=O), 1612 (C=N),
1608, 1565, 1405 (C=C, benzene and quinoline ring), 1212
(C–O–C linkage), 1353 (–NO2 symmetric stretching), 1468
(C–H bending), 1523 (–NO2 asymmetric stretching), 756,
768 (C–Cl bond, mono substituted benzene) cm-1; 1H-NMR
(DMSO-d6): d 6.68–8.34 (m, 13H, quinoline-H and Ar–H),
6.67 (d, 1H, O=C–C–H), 7.82 (d, 1H, =C–H), 6.61 (s, 1H,
N–CH-quinoline ring), 9.82 (s, 1H, aromatic-OH group);
13C-NMR: d 70.1, 115.5, 116.5, 118.8, 121.3, 124.0, 125.8,
126.4, 126.5, 127.8, 129.4, 130.1, 130.7, 131.4, 135.6, 135.9,
136.4, 143.5, 144.0, 150.2, 150.8, 155.0, 158.3, 167.0; MS:
m/z 500.09 (M?). Anal. calc. For C27H19ClN4O5: C, 62.34;
H, 3.42; N, 11.19. Found: C, 62.39; H, 3.47; N, 11.23%.
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(4-methylphenyl)prop-2-en-1-one (4j)
IR (KBr): t = 3032 (aromatic-H), 3072 (CH=CH group),
2892 (C–H stretching), 1681 (C=O), 1605 (C=N), 1579,
1554, 1432 (C=C, benzene and quinoline ring), 1440 (C–H
bending), 1345 (–NO2 symmetric stretching), 1535 (–NO2
asymmetric stretching), 1209 (C–O–C linkage), 761, 775
1
(C–Cl bond, mono substituted benzene) cm-1; H-NMR
(DMSO-d6): d 2.43 (s, 3H, –CH3 group), 7.57–8.34 (m,
13H, quinoline-H and Ar-H), 6.84 (d, 1H, O=C–C–H),
7.55 (d, 1H, =C–H), 6.61 (s, 1H, N–CH-quinoline ring);
13C-NMR: d 24.7, 70.1, 118.8, 124.0, 125.8, 126.3, 126.4,
126.5, 128.9, 130.1, 130.7, 131.4, 132.2, 135.6, 135.9,
136.4, 137.6, 143.5, 144.0, 150.2, 150.8, 155.0, 167.0;
MS: m/z 498.11 (M?). Anal. calc. For C27H19ClN4O5: C,
62.58; H, 3.92; N, 10.88. Found: C, 62.63; H, 3.98; N,
10.94%.
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(3-hydroxyphenyl)prop-2-en-1-one (4h)
IR (KBr): t = 3048 (aromatic-H), 3429 (aromatic-OH
group), 3093 (CH=CH group), 1675 (C=O), 1611 (C=N),
1593, 1561, 1425 (C=C, benzene and quinoline ring), 1354
(–NO2 symmetric stretching), 1533 (–NO2 asymmetric
stretching), 1207 (C–O–C linkage), 758, 764 (C–Cl bond,
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(4-methoxyphenyl)prop-2-en-1-one (4k)
1
mono substituted benzene) cm-1; H-NMR (DMSO-d6): d
7.57–8.34 (m, 13H, quinoline-H and Ar-H), 6.84 (d, 1H,
O=C–C–H), 7.55 (d, 1H, =C–H), 6.61 (s, 1H, N–CH-
quinoline ring), 9.82 (s, 1H, aromatic-OH group);
13C-NMR: d 70.1, 112.1, 115.1, 188.8, 119.0, 124.0, 125.8,
126.4, 126.5, 130.1, 130.7, 131.4, 135.6, 135.9, 136.4,
136.6, 143.5, 144.0, 150.2, 150.8, 155.0, 158.4, 167.0; MS:
m/z 500.09 (M?). Anal. calc. For C27H19ClN4O5: C, 62.34;
H, 3.42; N, 11.19. Found: C, 62.38; H, 3.46; N, 11.24%.
IR (KBr): t = 3041 (aromatic-H), 3068 (CH=CH group),
2833 (Ar-OCH3), 1673 (C=O), 1609 (C=N), 1611, 1562,
1436 (C=C, benzene and quinoline ring), 1342 (–NO2
symmetric stretching), 1520 (–NO2 asymmetric stretching),
1277 (Ar–O–Me, bending), 1209 (C–O–C linkage), 758,
780 (C–Cl bond, mono substituted benzene) cm-1 1H-
.
NMR (DMSO-d6): d 6.68–8.34 (m, 13H, quinoline-H and
Ar-H), 3.85 (s, 3H, –OCH3 group), 6.84 (d, 1H, O=C–C–
H), 7.55 (d, 1H, =C–H), 6.61 (s, 1H, N–CH-quinoline
ring); 13C-NMR: d 55.8, 70.1, 114.2, 118.8, 124.0, 125.8,
126.4, 126.5, 127.4, 127.5, 130.1, 130.7, 131.4, 135.6,
135.9, 136.4, 143.5, 144.0, 150.2, 150.8, 155.0, 159.8,
167.0; MS: m/z 514.10 (M?). Anal. calc. For
C27H19ClN4O5: C, 62.98; H, 3.92; N, 10.88. Found: C,
62.99; H, 3.98; N, 10.93%.
Physical constants and characterization of 1-[2-(2-
Chloro(3-quinolyl))-5-(4-nitrophenyl)(1,3,4-oxadiazolin-
3-yl)]-3-(4-hydroxyphenyl)prop-2-en-1-one (4i)
IR (KBr): t = 3064 (aromatic-H), 3429 (aromatic-OH
group), 3075 (CH=CH group), 1673 (C=O), 1602 (C=N),
123

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tion of 2,5-disubstituted-indazolo[4,3-gh]isoquinolin-6(2H)-ones
(9-aza-anthrapyrazoles). J Med Chem 41:5429–5444
Loupy A (ed) (2002) Microwaves in organic synthesis. Wiley-VCH
Verlag Gmbh & Co. KgaA, Weinhein
IR (KBr): t = 3070 (aromatic-H), 3064 (CH=CH group),
2841 (Ar-OCH3 stretching), 1671 (C=O), 1610 (C=N),
1608, 1570, 1442 (C=C, benzene and quinoline ring), 1343
(–NO2 symmetric stretching), 1522 (–NO2 asymmetric
stretching), 1284 (Ar-O–Me bending), 1359 (–NO2 sym-
metric stretching), 1466 (C–H bending), 1525 (–NO2
asymmetric stretching), 1209 (C–O–C linkage), 756, 774
1
(C–Cl bond, mono substituted benzene) cm-1; H-NMR
(DMSO-d6): d 6.78–8.34 (m, 10H, quinoline-H and Ar-H),
3.71-3.83 (s, 9H, –OCH3 group) 6.84 (d, 1H, O=C–C–H),
7.55 (d, 1H, =C–H), 6.61 (s, 1H, N–CH-quinoline ring);
13C-NMR: d 70.1, 56.1, 103.8, 118.8, 124.0, 125.8, 1226.4,
126.5, 129.5, 130.1, 130.7, 131.4, 135.6, 135.9, 136.4,
143.5, 144.0, 150.2, 150.7, 150.8, 155.0, 167.0; MS: m/z
574.13 (M?). Anal. calc. For C29H23ClN4O7: C, 60.58; H,
4.03; N, 9.74. Found: C, 60.64; H, 4.07; N, 9.80%.
Conclusion
We have synthesized a variety of quinoline–oxadiazole
containing chalcone derivatives under classical and
microwave conditions. In general, improvements in rate
and yield of reactions were observed in MWI. When
organic reactions were carried out under microwave as
compared to classical conditions, it may be observed that
activation occurs at different temperatures with these
techniques and, therefore strict comparisons will require a
balance between effectiveness and energy costs. In general,
compounds with electron withdrawing groups showed
good antibacterial and antifungal activities. These results
proved that novel quinoline, oxadiazole and chalcone based
heterocyclic compounds are found to be interesting lead
molecules for further synthetic and biological evaluation.
Acknowledgments The authors are thankful to Department of
Chemistry, Bhavnagar University, Bhavnagar for providing research
facilities. One of the authors AMD is thankful to University Grants
Commission, New Delhi for providing UGC-meritorious fellowship.
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