The design, synthesis and antimicrobial activity of new biquinoline derivatives

Article abstract of DOI:10.2298/JSC110630197S

A simple and efficient method has been developed for the synthesis of some novel biquinoline derivatives bearing a thiazole moiety through a onepot three-component condensation of 2-chloro-3-formylquinolines, ethyl cyanoacetate and a β-enaminone using a catalytic amount of piperidine in refluxing ethanol. These molecules were evaluated in vitro for their antibacterial and antifungal activity. Most of the compounds exhibited moderate antibacterial and antifungal activity against all the tested strains.

Full text of DOI:10.2298/JSC110630197S

J. Serb. Chem. Soc. 76 (0) 1–16 (2011)
UDC
JSCS–5155
Original scientific paper
Design, synthesis and antimicrobial activity of
new biquinoline derivatives
NIRAV K. SHAH, NIMESH M. SHAH, MANISH P. PATEL and RANJAN G. PATEL*
Department of chemistry, Sardar Patel University, Vallabh Vidyanagar-388120,
Gujarat, India
(Received 30 June, revised 19 October 2011)
Abstract: A simple and efficient method has been developed for the synthesis
of some novel biquinoline derivatives bearing a thiazole moiety through a one-
pot three-component condensation of 2-chlro-3-formylquinolines, ethyl
cyanoacetate and β-enaminone using catalytic amount of piperidine in
refluxing ethanol. These molecules were evaluated in vitro for their
antibacterial and antifungal activity. Most of the compounds exhibited
moderate antibacterial and antifungal activity against all the tested strains.
Keywords: quinoline; thiazole; antibacterial; antifungal.
INTRODUCTION
Quinoline nucleus is one of the most important and widely exploited
heterocyclic ring for the development of bioactive molecules. Recent literature is
enriched with progressive findings about the synthesis and pharmacological
actions of quinoline and its derivatives. A number of quinoline derivatives are
known to possess antimicrobial, antimycobacterial, antidepressant, antimalarial,
anticonvulsant, antiviral, anticancer, hypotensive and anti-inflammatory
activities.1
Compounds containing thiazole rings have remarkable medicinal value due
to their potential chemotherapeutic,2 fungicidal,3 antiviral4 and pesticidal5
properties. In addition, 2-aminothiazole derivatives are reported to exhibit
significant biological activities such as anti-tuberculosis6, anti-inflammatory,7
enzyme inhibition 8 and antitumor activities.9
After the extensive literature search, it was observed that quinoline and
thiazole are the important pharmacophore, but till date enough efforts have not
been made to combine these two moieties as a single molecular scaffold. So, our
aim was to synthesize and make a biological screening of a series of new
compounds incorporating these moieties.
*Corresponding author. E-mail: patelranjanben@yahoo.com
doi: 10.2298/JSC110630197S
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SHAH et al.
RESULTS AND DISCUSSION
Chemistry
Following our interest on synthesizing biologically potent antimicrobials10
we report herein a new series of biquinoline synthesized by one pot three
component cyclocondensation reaction of 2-chloro-3-formylquinolines 2(a-d),
ethyl
cyanoacetate
and
3-(4-arylthiazol-2-ylamino)cyclohex-2-enone
(enaminone) 3(a-c). The synthetic route depicted in Scheme 2 outlines the
chemistry part of the present work. The key intermediates 2-chloro-3-formyl
quinolines 2(a-d) were prepared according to literature method11 (Scheme 1).
Solid phase reaction of 4-substituted acetophenone, thiourea and iodine for 4 h at
120°C afford to give 2-amino-4-arylthiazole12 (Scheme 1). The required β-
enaminones 3(a-c) were prepared by the reaction β-diketone with 2-amino-4-
arylthiazole by refluxing in methanol in presence of catalytic amount of acetic
acid.
To choose the most appropriate medium to synthesize compounds 4(a-l),
several reaction conditions were investigated. Looking for the optimal reaction
solvent, the reaction was examined in ethylene glycol, DMF, HOAc, THF, and
ethanol as solvent under reflux, respectively. The reaction in ethanol resulted in
higher yields and shorter reaction time than others, so ethanol was chosen as the
appropriate solvent. Moreover, to further improve the reaction yields, different
bases like NaOH, K2CO3, DMAP, Et3N, and piperidine were examined in
ethanol. Piperidine afforded the target product 4a in an 87 % yield. Therefore it
was chosen as the most suitable base for all further reactions.
The reaction occurs via an in situ initial formation of the heterylidenenitrile,
containing the electron-poor C=C double bond, from the Knoevenagel
condensation between 2-chloro-3-formyl quinolines and ethyl cyanoacetate by
loss of water molecules. Finally, Michael addition of or to the initially formed
unsaturated nitrile, i.e. nucleophilic attack of enaminone to the cyano olefins
affords cyclized quinoline derivatives 4(a-l).
The structures of the compounds were confirmed on the basis of elemental
analysis and spectral data. As an example, the IR spectra of compound 4d
(R1=Cl, R2=H) shows band at 3445 cm-1 for asym. N-H stretching, 3345 cm-1 for
sym. N-H stretching and 1660 & 1640 cm-1 for C=O stretching of carbonyl
group. 1H-NMR spectra of 4d showed a triplet signal at δ 1.01 for methyl group,
a multiplet signal at δ 1.71-2.25 for three methylene group, a quartet signal at
3.92 for OCH2 group, one singlet at δ 5.30 and δ 8.45 for methine group and
amine group respectively and a multiplet due to the aromatic protons around at δ
7.37-8.24. The 13C-NMR spectrum of 4d was in good agreement with the
structure assigned. The peak at δ 14.74 attributed to one methyl group, peak at
21.19, 27.46 and 36.58 attributed to three methylene carbons, δ 35.82 is
attributed to methine carbon. The peak at 77.93 is assigned to carbon attached

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW BIQUINOLINE DERIVATIVES
3
with carboxylate and the peaks at δ 114.17-156.98 are attributed to aromatic
carbon. The peak at δ 168.99 and 195.77 are assigned to carbonyl carbon. Mass
spectra of the compounds 4d and 4j showed an M++1 peaks in agreement with
their exact mass or molecular weight.
Biological evaluation
Antimicrobial activity. Reviewing of the antibacterial activities (Table 1) of
biquinolines indicate that among all the compounds 4a (R1 = H, R2 = H), 4c (R1 =
OCH3, R2 = H), 4d (R1 = Cl, R2 = H), 4e (R1 = H, R2 = Cl), 4h (R1 = Cl, R2 = Cl),
4k (R1 = OCH3, R2 = OH) and 4l (R1 = Cl, R2 = OH) exhibited good antibacterial
activity against the bacterial strain Escherichia coli. Similarly compounds 4a (R1
= H, R2 = H), 4c (R1 = OCH3, R2 = H), 4d (R1 = Cl, R2 = H), 4g (R1 = OCH3, R2
= Cl), 4h (R1 = Cl, R2 = Cl), 4k (R1 = OCH3, R2 = OH) and 4l (R1 = Cl, R2 = OH)
against Gram-positive bacterial species Bacillus subtilis and compounds 4a (R1 =
H, R2 = H), 4c (R1 = OCH3, R2 = H), 4d (R1 = Cl, R2 = H), 4f (R1 = OCH3, R2 =
Cl), 4h (R1 = Cl, R2 = Cl), 4k (R1 = OCH3, R2 = OH) and 4l (R1 = CH3, R2 = Cl)
against Gram-positive bacterial species Staphylococcus aureus showed good
activity. Remaining compounds showed moderate activity against tested bacterial
strain.
The antifungal evaluation of the synthesized compounds revealed that
compounds 4c (R1 = OCH3, R2 = H), 4g (R1 = OCH3, R2 = Cl) and 4k (R1 =
OCH3, R2 = OH) displayed excellent fungal activity towards Fuserium
oxysporum. Against Aspergillus niger compounds 4c (R1 = OCH3, R2 = H), 4g
(R1 = OCH3, R2 = Cl) 4h (R1 = Cl, R2 = Cl), 4k (R1 = OCH3, R2 = OH) and 4l (R1
= Cl, R2 = OH)and compounds 4c (R1 = OCH3, R2 = H), 4d (R1 = Cl, R2 = H), 4g
(R1 = OCH3, R2 = Cl), 4h (R1 = Cl, R2 = Cl) and 4k (R1 = OCH3, R2 = OH)
towards Rhizopus oryzae showed good activity. Remaining compounds showed
mild to moderate antifungal activity.
A close examination of the structures of the active compounds in Table 1
revealed that, their antimicrobial activity is strongly bound to the nature of the
substituent at the quinoline-C6, together with the substituent linked to the
arylthiazole part of the structure. In general, it could be clearly recognized that
compound 4c without a substituent in the arylthiazole ring (R2 = H) and
quinoline containing a methoxy substituent (R1 = OCH3) show greater activity
compared to the other compounds studied. Moreover, compound 4k quinoline
containing a methoxy substituent (R1 = OCH3) and with a hydroxyl substituent in
the arylthiazole ring (R2 = OH) have good antimicrobial profile while compound
4g quinoline also containing a methoxy substituent (R1 = OCH3) and with a
chloro substituent in the arylthiazole ring (R2 = Cl) exhibited moderate to good
antimicrobial activity. On the other hand, introduction of methyl group at
position-6 of the quinoline (compounds 4b, 4j and 4f) resulted in a noticeable

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SHAH et al.
decrease in the antimicrobial potential of these compounds. Compounds 4a (R1 =
H, R2 = H), 4h (R1 = Cl, R2 = Cl) and 4l (R1 = Cl, R2 = OH) showed a good
antibacterial activity together with a moderate antifungal profile. It is worthy to
mention that the biological activity of the target compounds depends not only on
the bicyclic heteroaromatic pharmacophore but also on the nature of the
substituents and may also upon their spatial relationships. Here, thiazole moiety
is introduced along with biquinoline ring for activity reinforcement. However,
based on the observation, it is immature to arrive at any conclusion on structure
activity aspect of these molecules and further evaluation is needed.
EXPERIMENTAL
Chemistry
Solvents used were of analytical grade. All melting points were taken in open capillaries
and are uncorrected. Thin-layer chromatography (TLC, on aluminium plates precoated with
silica gel, 60F254, 0.25 mm thickness) (Merck, Darmstadt, Germany) was used for
monitoring the progress of all reactions, purity and homogeneity of the synthesized
compounds; eluent-hexane:ethyl acetate 6:4. UV radiation and/or iodine were used as the
visualizing agents. Elemental analysis (% C, H, N) was carried out by a Perkin-Elmer 2400
series-II elemental analyzer (Perkin-Elmer, USA) and all compounds were within ±0.4% of
calculation. The IR spectra were recorded in KBr pellet on a Perkin-Elmer Spectrum GX FT-
IR Spectrophotometer (Perkin-Elmer, USA), and only the characteristic peaks were reported
1
in cm-1. H-NMR and 13C-NMR spectra were recorded in DMSO- d6 on a Bruker Avance
400F (MHz) spectrometer (Bruker Scientific Corporation Ltd., Switzerland) using solvent
peak as internal standard at 400 MHz and 100 MHz respectively. Chemical shifts were
reported in parts per million (ppm). Mass spectra were scanned on a Shimadzu LCMS 2010
spectrometer (Shimadzu, Tokyo, Japan).
General procedure for the synthesis of 2-amino-4-arylthiazole
2-amino-4-arylthiazole was synthesized, according to literature procedure12 by the solid
phase reaction of thiourea, 4-substituted acetophenone and iodine (Scheme 1)
General procedure for the synthesis of 3-(4-arylthiazole-2-ylamino)cyclohex-enone 3(a-c)
1,3-Dicarbonyl compound (30 mmol), 2-amino-4-arylthiazole (30 mmol), methanol (15
mL) and 2 drops of acetic acid were charged in 100 mL round bottom flask equipped with
refluxing condenser. The reaction mixture was slowly heated and refluxed for 1 h. On
completion of reaction, monitored by TLC using 30% EtOAc in toluene as eluent, the reaction
mixture was cooled to room temperature and the solid separated was filtered and washed with
methanol to obtain the pure compounds.
General procedure for the synthesis of Ethyl 2-amino-4-(2-chloro-6-(un)substituted(3-
quinolyl))-5-oxo-1-(4-arylthiazol-2-yl)-1,4,5,6,7,8-hexahydroquinolne-3-carboxylate 4(a-l)
A mixture of 2-chloro-3-formylquinolines (1 mmol), ethyl cyanoacetate (1 mmol), and
appropriate β-enaminone (1 mmol) in ethanol (10 ml) containing catalytic amount of
piperidine was slowly heated and refluxed for 3-4 h. On completion of reaction, monitored by
TLC (ethyl acetate:toluene::3:7), the reaction mixture was cooled to room temperature and the
solid separated was filtered and washed with mixture of chloroform and methanol (1:1) to

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW BIQUINOLINE DERIVATIVES
5
obtain the pure compounds. Analytical and spectroscopic characterization data of the
synthesized compounds are given below:
Ethyl
2-amino-4-(2-chloro(3-quinolyl))-5-oxo-1-(4-phenylthiazol-2-yl)-1,4,5,6,7,8-
hexahydroquinoline-3-carboxylate (4a). Yield: 87 %; m.p. 245-247 °C; Anal. Calcd. for
C30H25ClN4O3S: C, 64.68; H, 4.52; N, 10.06 %. Found: C, 64.82; H, 4.48; N, 09.90 %. IR
(KBr, ν, cm-1): 3425 & 3280 (asym. & sym. str. of -NH2), 1678 (C=O str.), 1640 (C=O str.).
1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.11 (3H, t, J = 7.16 Hz, CH3), 1.71-2.20 (6H, m,
3×CH2), 3.90 (2H, q, J = 7.16 Hz, OCH2), 5.36 (1H, s, CH), 7.31-8.28 (11H, m, Ar-H), 8.42
(2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.45 (CH3), 21.30, 26.82 (2C, CH2),
35.40 (C4), 36.12 (CH2-CO), 57.32 (OCH2), 78.25 (C-COOEt), 113.31, 117.78, 119.89,
126.65, 126.96, 128.54, 129.12, 129.41, 131.23, 131.30, 133.30, 140.28, 144.93, 150.41,
150.60, 152.53, 152.73, 152.82, 156.91 (19C, Ar-C), 168.75 (COOEt), 195.88 (C=O).
Ethyl
2-amino-4-(2-chloro-6-methyl(3-quinolyl))-5-oxo-1-(4-phenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4b). Yield: 89 %; m.p. 169-171 °C; Anal.
Calcd. for C31H27ClN4O3S: C, 65.20; H, 4.77; N, 09.81 %. Found: C, 65.28; H, 4.72; N, 09.93
%. IR (KBr, ν, cm-1): 3437 & 3333 (asym. & sym. str. of -NH2), 1672 (C=O str.), 1620 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.09 (3H, t, J = 7.4 Hz, CH3), 2.23 (3H, s,
CH3), 1.71-2.20 (6H, m, 3×CH2), 3.93 (2H, q, J = 7.2 Hz, OCH2), 5.31 (1H, s, CH), 7.29-8.25
(10H, m, Ar-H), 8.38 (2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.23 (CH3),
20.14 (CH3), 21.41, 26.02 (2C, CH2), 35.10 (C4), 36.32 (CH2-CO), 57.10 (OCH2), 78.74 (C-
COOEt), 113.14, 117.14, 119.41, 126.41, 126.47, 128.25, 129.45, 129.74, 131.13, 131.15,
133.25, 140.47, 144.78, 150.41, 150.45, 152.13, 152.71, 152.92, 156.45 (19C, Ar-C), 168.79
(COOEt), 195.45 (C=O).
Ethyl
2-amino-4-(2-chloro-6-methoxy(3-quinolyl))-5-oxo-1-(4-phenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4c). Yield: 83 %; m.p. 221-223 °C; Anal.
Calcd. for C31H27ClN4O3S: C, 63.42; H, 4.64; N, 09.54 %. Found: C, 63.58; H, 4.72; N, 09.73
%. IR (KBr, ν, cm-1): 3446 & 3240 (asym. & sym. str. of -NH2), 1668 (C=O str.), 1635 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.01 (3H, t, J = 7.4 Hz, CH3), 1.71-2.25 (6H,
m, 3×CH2), 3.89 (3H, s, OCH3), 3.90 (2H, q, J = 7.1 Hz, OCH2), 5.35 (1H, s, CH), 7.29-8.22
(10H, m, Ar-H), 8.32 (2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.64 (CH3),
21.23, 27.12 (2C, CH2), 35.14 (C4), 36.00 (CH2-CO), 57.23 (OCH3), 59.10 (OCH2), 77.74 (C-
COOEt), 105.27, 114.41, 119.32, 126.40, 126.84, 128.23, 129.18, 129.78, 131.41, 131.97,
133.41, 140.40, 144.68, 150.74, 150.92, 152.44, 152.64, 152.90, 156.01 (19C, Ar-C), 168.14
(COOEt), 195.38 (C=O).
Ethyl
2-amino-4-(2-chloro-6-chloro(3-quinolyl))-5-oxo-1-(4-phenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4d). Yield: 76 %; m.p. 232-234 °C; Anal.
Calcd. for C30H24Cl2N4O3S: C, 60.92; H, 4.09; N, 09.47 %. Found: C, 60.86; H, 4.05; N, 09.60
%. IR (KBr, ν, cm-1): 3445 & 3345 (asym. & sym. str. of -NH2), 1660 (C=O str.), 1640 (C=O
1
str.). H NMR (400 MHz, DMSO-d6, δ, ppm): 1.01 (3H, t, J = 7.12 Hz, CH3), 1.71-2.25 (6H,
m, 3×CH2), 3.92 (2H, q, J = 7.12 Hz, OCH2), 5.30 (1H, s, CH), 7.37-8.24 (10H, m, Ar-H),
8.45 (2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.74 (CH3), 21.19, 27.46 (2C,
CH2), 35.82 (C4), 36.58 (CH2-CO), 59.24 (OCH2), 77.93 (C-COOEt), 114.17, 117.70, 119.34,
126.61, 126.85, 128.22, 129.37, 129.87, 131.05, 131.81, 133.95, 140.70, 144.35, 150.66,
150.93, 152.55, 152.76, 152.87, 156.98 (19C, Ar-C), 168.99 (COOEt), 195.87 (C=O). MS:
M++1 591.1.
Ethyl
2-amino-4-(2-chloro(3-quinolyl))-5-oxo-1-(4-chlorophenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4e). Yield: 87 %; m.p. 195-197 °C; Anal.

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SHAH et al.
Calcd. for C30H24Cl2N4O3S: C, 60.92; H, 4.09; N, 09.47 %. Found: C, 60.96; H, 4.00; N, 09.65
%. IR (KBr, ν, cm-1): 3441 & 3260 (asym. & sym. str. of -NH2), 1668 (C=O str.), 1645 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.10 (3H, t, J = 7.16 Hz, CH3), 1.70-2.21 (6H,
m, 3×CH2), 3.94 (2H, q, J = 7.12 Hz, OCH2), 5.40 (1H, s, CH), , 7.30-8.22 (10H, m, Ar-H),
8.40 (2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.98 (CH3), 21.78, 26.54 (2C,
CH2), 35.45 (C4), 36.12 (CH2-CO), 57.98 (OCH2), 78.32 (C-COOEt), 113.87, 117.36, 119.74,
126.45, 126.65, 128.54, 129.56, 129.74, 131.36, 131.70, 133.12, 140.56, 144.56, 150.23,
150.45, 152.03, 152.65, 152.85, 156.19 (19C, Ar-C), 168.23 (COOEt), 195.98 (C=O).
Ethyl 2-amino-4-(2-chloro-6-methyl(3-quinolyl))-5-oxo-1-(4-chlorophenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4f). Yield: 81 %; m.p. 208-210 °C; Anal.
Calcd. for C31H26Cl2N4O3S: C, 61.49; H, 4.33; N, 09.25 %. Found: C, 61.41; H, 4.23; N, 09.35
%. IR (KBr, ν, cm-1): 3442 & 3280 (asym. & sym. str. of -NH2), 1678 (C=O str.), 1660 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.07 (3H, t, J = 7.2 Hz, CH3), 1.72-2.45 (6H, m,
3×CH2), 2.47 (3H, s, CH3), 3.87 (2H, q, J = 7.2 Hz, OCH2), 5.25 (1H, s, CH), 7.25-8.31 (9H,
m, Ar-H), 8.48 (2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.12 (CH3), 20.23
(CH3), 21.39, 27.28 (2C, CH2), 35.17 (C4), 36.36 (CH2-CO), 59.65 (OCH2), 78.54 (C-
COOEt), 113.07, 114.78, 116.89, 122.54, 125.41, 126.65, 128.10, 128.32, 129.21, 140.14,
141.74, 141.90, 147.12, 149.23, 152.00, 152.36, 156.03, 158.36, 158.96 (19C, Ar-C), 169.19
(COOEt), 195.37 (C=O).
Ethyl 2-amino-4-(2-chloro-6-methoxy(3-quinolyl))-5-oxo-1-(4-chlorophenylthiazol-2-
yl)-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4g). Yield: 79 %; m.p. 225-227 °C; Anal.
Calcd. for C31H26Cl2N4O4S: C, 59.91; H, 4.22; N, 09.01. Found: C, 59.82; H, 4.42; N, 09.23
%. IR (KBr, ν, cm-1): 3445 & 3285 (asym. & sym. str. of -NH2), 1670 (C=O str.), 1650 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.01 (3H, t, J = 7.2 Hz, CH3), 1.75-2.41 (6H, m,
3×CH2), 3.85 (2H, q, J = 7.1 Hz, OCH2), 3.95 (3H, s, OCH3), 5.32 (1H, s, CH), 7.29-8.24 (9H,
m, Ar-H), 8.46 (2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.78 (CH3), 21.89,
27.96 (2C, CH2), 35.65 (C4), 36.54 (CH2-CO), 56.41 (OCH3), 59.12 (OCH2), 78.23 (C-
COOEt), 105.32, 114.21, 116.14, 116.45, 122.55, 125.65, 128.85, 128.96, 129.74, 140.17,
141.20, 141.39, 147.23, 149.11, 152.75, 152.85, 156.63, 158.74, 158.32 (19C, Ar-C), 169.32
(COOEt), 195.97 (C=O).
Ethyl 2-amino-4-(2-chloro-6-chloro(3-quinolyl))-5-oxo-1-(4-chlorophenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4h). Yield: 75 %; m.p. 198-200 °C; Anal.
Calcd. for C30H23Cl3N4O4S: C, 57.56; H, 3.70; N, 08.95. Found: C, 57.72; H, 3.85; N, 08.77
%. IR (KBr, ν, cm-1): 3439 & 3281 (asym. & sym. str. of -NH2), 1670 (C=O str.), 1635 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.03 (3H, t, J = 7.4 Hz, CH3), 1.72-2.41 (6H, m,
3×CH2), 3.87 (2H, q, J = 7.16 Hz, OCH2), 5.20 (1H, s, CH), 7.25-8.28 (9H, m, Ar-H), 8.40
(2H, s, NH2). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.98 (CH3), 21.23, 27.45 (2C, CH2),
35.32 (C4), 36.89 (CH2-CO), 59.97 (OCH2), 78.56 (C-COOEt), 112.71, 114.82, 116.10,
116.98, 122.38, 125.30, 128.56, 128.91, 129.13, 140.17, 141.88, 141.99, 147.06, 149.12,
152.58, 152.30, 156.85, 158.06, 158.12 (19C, Ar-C), 169.87 (COOEt), 195.74 (C=O).
Ethyl
2-amino-4-(2-chloro(3-quinolyl))-5-oxo-1-(4-hydroxyphenylthiazol-2-yl)-
1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4i). Yield: 73 %; m.p. 198-200 °C; Anal.
Calcd. for C30H25ClN4O4S: C, 62.88; H, 4.40; N, 09.78. Found: C, 63.07; H, 4.56; N, 09.67 %.
IR (KBr, ν, cm-1): 3439 & 3295 (asym. & sym. str. of -NH2), 1675 (C=O str.), 1640 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.05 (3H, t, J = 7.12 Hz, CH3), 1.68-2.44 (6H,
m, 3×CH2), 3.90 (2H, q, J = 7.12 Hz, OCH2), 5.21 (1H, s, CH), 7.20-8.26 (10H, m, Ar-H),
8.29 (2H, s, NH2), 9.65 (1H, s, OH). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.11 (CH3),

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW BIQUINOLINE DERIVATIVES
7
20.92, 27.14 (2C, CH2), 35.47 (C4), 36.85 (CH2-CO), 59.52 (OCH2), 78.36 (C-COOEt),
113.36, 114.69, 116.78, 116.92, 122.12, 125.98, 128.32, 128.87, 129.40, 140.71, 141.43,
141.61, 147.91, 149.73, 152.82, 152.49, 156.93, 158.71, 158.25 (19C, Ar-C), 169.61
(COOEt), 195.40 (C=O).
Ethyl 2-amino-4-(2-chloro-6-methyl(3-quinolyl))-5-oxo-1-(4-hydroxyphenylthiazol-2-
yl)-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4j). Yield: 64 %; m.p. 236-238 °C; Anal.
Calcd. for C31H27ClN4O4S: C, 63.42; H, 4.64; N, 09.54 %. Found: C, 63.22; H, 4.48; N, 09.74
%. IR (KBr, ν, cm-1): 3442 & 3280 (asym. & sym. str. of -NH2), 1678 (C=O str.), 1630 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.03 (3H, t, J = 7.2 Hz, CH3), 1.70-2.41 (6H, m,
3×CH2), 2.45 (3H, s, CH3), 3.89 (2H, q, J = 7.16 Hz, OCH2), 5.24 (1H, s, CH), 7.25 -8.23 (9H,
m, Ar-H), 8.30 (2H, s, NH2), 9.62 (1H, s, OH). 13C NMR (100 MHz, DMSO-d6, δ, ppm):
14.23 (CH3), 20.98 (Ar-CH3), 21.12, 27.78 (2C, CH2), 35.45 (C4), 36.98 (CH2-CO), 59.56
(OCH2), 78.89 (C-COOEt), 112.54, 114.32, 116.36, 116.52, 122.00, 125.35, 128.34, 128.47,
129.10, 140.87, 141.71, 141.99, 147.40, 149.59, 152.81, 152.99, 156.63, 158.25, 158.86 (19C,
Ar-C), 169.10 (COOEt), 195.32 (C=O). MS: M++1 586.6.
Ethyl 2-amino-4-(2-chloro-6-methoxy(3-quinolyl))-5-oxo-1-(4-hydroxyphenylthiazol-2-
yl)-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4k). Yield: 81 %; m.p. 244-246 °C; Anal.
Calcd. for C31H27ClN4O5S: C, 61.74; H, 4.51; N, 09.29. Found: C, 61.88; H, 4.70; N, 09.07 %.
IR (KBr, ν, cm-1): 3445 & 3260 (asym. & sym. str. of -NH2), 1680 (C=O str.), 1660 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.05 (3H, t, J = 7.4 Hz, CH3), 1.70-2.41 (6H, m,
3×CH2), 3.91 (2H, q, J = 7.2 Hz, OCH2), 3.91 (3H, s, OCH3), 5.28 (1H, s, CH), 6.87-8.17 (9H,
m, Ar-H), 8.27 (2H, s, NH2), 9.72 (1H, s, OH). 13C NMR (100 MHz, DMSO-d6, δ, ppm):
14.72 (CH3), 21.26, 27.47 (2C, CH2), 35.63 (C4), 36.60 (CH2-CO), 56.08 (Ar-OCH3), 59.13
(OCH2), 78.35 (C-COOEt), 105.79, 114.48, 116.04, 116.25, 122.99, 125.28, 128.09, 128.59,
129.14, 140.27, 141.20, 141.90, 147.47, 149.01, 152.69, 152.91, 156.73, 158.10, 158.38 (19C,
Ar-C), 169.06 (COOEt), 195.81 (C=O).
Ethyl
2-amino-4-(2-chloro-6-chloro(3-quinolyl))-5-oxo-1-(4-hydroxyphenylthiazol-2-
yl)-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate (4l). Yield: 79 %; m.p. 256-258 °C; Anal.
Calcd. for C30H24Cl2N4O4S: C, 59.31; H, 3.98; N, 09.22. Found: C, 59.50; H, 4.05; N, 09.47
%. IR (KBr, ν, cm-1): 3440 & 3275 (asym. & sym. str. of -NH2), 1675 (C=O str.), 1640 (C=O
str.). 1H NMR (400 MHz, DMSO-d6, δ, ppm): 1.02 (3H, t, J = 7.12 Hz, CH3), 1.70-2.41 (6H,
m, 3×CH2), 3.91 (2H, q, J = 7.12 Hz, OCH2), 5.25 (1H, s, CH), 7.25-8.20 (9H, m, Ar-H), 8.26
(2H, s, NH2), 9.70 (1H, s, OH). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 14.12 (CH3), 21.23,
27.36 (2C, CH2), 35.32 (C4), 36.21 (CH2-CO), 59.45 (OCH2), 78.56 (C-COOEt), 105.65,
114.23, 116.10, 116.98, 122.34, 125.30, 128.23, 128.87, 129.13, 140.17, 141.78, 141.99,
147.56, 149.32, 152.23, 152.30, 156.30, 158.96, 158.32 (19C, Ar-C), 169.87 (COOEt), 195.96
(C=O).
Antimicrobial activity
The in vitro antimicrobial activity was carried out against 24 hr old cultures of three
bacteria and three fungi by disc diffusion method [13-14]. Compounds 4(a-l) have been tested
for their antibacterial activity against Escherichia coli as Gram-negative bacteria and Bacillus
subtilis and Bacillus cereus as Gram-positive bacteria and antifungal activity against
Aspergillus niger, Fuserium oxysporum, and Rhizopus. Nutrient agar and potato dextrose
were used to culture the bacteria and fungus respectively. The compounds were tested at 1000
ppm in DMF solution. Ciprofloxacin, Ampicillin and Griseofulvin were used as standards for
comparison of antibacterial and antifungal activities respectively. Inhibition was recorded by

8
SHAH et al.
measuring the diameter of the inhibition zone at the end of 24 hr for bacteria at 35°C and 48hr
for fungus at 28°C. The results are summarized in Table 1.
CONCLUSIONS
In conclusion, we have developed a simple and efficient method for the
synthesis of biquinoline derivatives. The straightforward approach, simplicity
and one-step method make it an interesting approach for the synthesis of said
compounds. Most of the compounds showed better antibacterial activity, further
optimization and development is needed in designing more potent antibacterial
and antifungal agents for therapeutic use.
Acknowledgements. The authors are thankful to Head, Department of Chemistry, Sardar
1
Patel University for providing H-NMR and 13C-NMR spectroscopy and research facilities.
We are also thankful to Oxygen Healthcare Research Pvt. Ltd., Ahmedabad, for providing
mass spectroscopy facilities, Vaibhav Laboratories, Ahmedabad, Gujarat, India for the FT-IR,
SICART, Vallabh Vidyanagar, for elemental analysis.
И З В О Д
ДИЗАЈН, СИНТЕЗА И АНТИМИКРОБНА АКТИВНОСТ НОВИХ
БИХИНОЛИНСКИХ ДЕРИВАТА
NIRAV K. SHAH, NIMESH M. SHAH, MANISH P. PATEL и RANJAN G. PATEL
Department of chemistry, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat, India
Развијен је једноставан и ефикасан поступак за синтезу нових бихинолинских деривата
који садрже тиазолински структурни фрагмент. Поступак се састоји из тро-компонентне
кондензације 2-хлор-3-формилхинолина, етил-цианоацетата
и β-енаминона у једном
реакционом кораку, катализован пиперидином у кључалом етанолу. Испитана је ин витро
антибактеријска и антифунгална инхибиторна активност добијених једињења. Већина
испитаних једињења показује умерену активност према испитиваним сојевима.
(Примљено 30. јуна, ревидирано 19. октобра 2011)
REFERENCES
1. a) C. Vittorio, B. Guyen, Y. Opoku-Boahen, J. Mann, S.M. Gowan, M. Lloyd, A. R.
Martin, N. Stephen, Bioorg. Med. Chem. Lett. 10 (2000) 2063; b) P. Senthilkumar, M.
Dinakaran, Y. Chandraseakaran, P. Yogeeswari, D. Sriram, Arch. Pharm. 342 (2009)
100; c) M. A. Khalil, O. A. El-Sayed, H. A. El-Shamy, Arch. Pharm. 326 (1993) 489; d)
M. Flipo, I. Florent, P. Grellier, C. Sergheraert, R. Deprez-Poulain, Bioorg. Med. Chem.
Lett. 13 (2003) 2659; e) L. -P. Guan, Q. -H. Jin, S. -F. Wang, F. -N. Li, Z. -S. Quan, Arch.
Pharm. 341 (2008) 774; f) X. -Y. Sun, C. -X. Wei, K. -Y. Chai, H. -R. Piao, Z. -S. Quan,
Arch. Pharm. 341 (2008) 288; g) S. Bawa, S. Kumar, Indian J. Chem. 48B (2009) 142; h)
J. M. McCall, R. E. Brink, B. V. Kamdar, L. L. Ska Letzky, S. C. Perricone, R. C. Piper,
P. J. Delehonty, J. Med. Chem. 29 (1986) 133; i) K. K. Luciana, C. H. Pavam, D.
Veronese, F. Coelho, J. E. De Carvalho, Wanda P. Almeida, Eur. J. Med. Chem. 41
(2006) 738; j) M. G. Carlos, V. K. Vladimir, A. S. Maximiliano, L. A. Sandra, A. Z.
Susana, Bioorg. Med. Chem. 16 (2008) 7908; k) A. B. Adnan, O. A. El-Sayed, Y. Hassan,
M. S. Yunus, N. A. Mohammed, J. Enz. Inhib. Med. Chem. 19 (2004) 33; l) G. Sathi, V.

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW BIQUINOLINE DERIVATIVES
9
R. Gujrati, M. Sharma, C. Nath, K. P. Bhargava, K. Shanker, Arch. Pharm. 316 (1983)
767
2. H. Liebig, H. Pfetzing, A. Grafe, Arzneim.- Forsch. 24 (1974) 887
3. R. B. Pathak, B. Jahan, S. C. Bahel, Bokin Bobai 9 (1981) 477
4. F. C. Spector, L. Liang, H. Giordano, M. Sivaraja, M. G. Peterson, J. Virol. 72 (1998)
6979
5. Z. Fan, Z. Shi, X. Liu, Z. Fan, Y. Ai, Faming Zhuanli Shenqing Gongkai Shuomingshu
(2006), pp. 17. Chinese patent:.CNXXEV CN 1810808 A 20060802.
6. K. M. Sytnik, I. Ye. Bylov, S. N. Kovalenko, Zhurnal Organichnoi ta Farmatsevtichnoi
Khimii 1 (2003) 71
7. B. Holla, K. Malini, B. Rao, B. Sarojini, N. Kumari, Eur. J. Med. Chem. 38 (2003) 313
8. J. Das, J. Furch, C. Liu, R. Moquin, J. Lin, S. Spergel, K. McIntyre, D. Shuster, K.
O'Day, B. Penhallow, Bioorg. Med. Chem. Lett. 16 (2006) 3706
9. H. I. El-Subbagh, H. Abadi. Ashraf, Lehmann. Jochen , Archiv der Pharmazie 332 (1999)
137
10. a) N. M. Shah. M. P. Patel, R. G. Patel, J. Het. Chem. (2011) DOI 10.1002/jhet.918; b) D.
C. Mungra, M. P. Patel, D. P. Rajani, R. G. Patel, Eur. J. Med. Chem. 46 (2011) 4192; c)
N. K. Shah, M. P. Patel, R. G. Patel, Phosphorus Sulfur Silicon Relate. Elem. 184 (2009)
2704; d) N. K. Shah, M. P. Patel, R. G. Patel, Indian J. Chem. Sect. B 48 (2009) 1170; e)
J. A. Makawana, M. P. Patel, R. G. Patel, Med. Chem. Res. (2011) DOI 10.1007/s00044-
010-9568-6; f) C. B. Sangani, M. P. Patel, R. G. Patel, Cent. Eur. J. Chem. 9 (2011) 635
(g) N. K. Ladani, M .P. Patel, R .G. Patel, Arkivoc vii (2009) 292
11. O. Meth-Cohn, N. A. Bramha, Tetrahedron Lett. 23 (1978) 2045
12. R. M. Dodson, L. C. King, J. Am. Chem. Soc. 67 (1945) 2242
13. C. H. Collins, P. M. Lyne, Microbial Methods, University Park Press: Baltimore, 1970
14. T. D. Thangadurai, K. Natarajan, Indian J. Chem. 40A (2001) 573

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SHAH et al.
Table I. Antimicrobial activity of the compounds 4(a-l)
Antibacterial activity
Antifungal activity
Zone of inhibition in mm
Zone of inhibition in mm
Compd.
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
E. coli
23
17
25
24
20
18
19
25
19
18
24
21
B. substilis S. aureus F. oxysporum A. niger R. oryzae
25
19
24
23
17
19
20
22
18
17
22
23
30
34
NT
22
18
23
25
18
20
18
24
15
16
23
25
30
33
NT
16
15
20
14
17
16
21
19
17
15
21
19
NT
NT
26
15
19
22
16
16
18
24
20
17
14
25
20
NT
NT
28
18
16
25
21
18
17
22
21
14
18
24
17
NT
NT
30
4l
Ampicillin
Ciprofloxacin 35
Griseofulvin NT
28
NT = not tested.
Control (DMF) (-) – No activity

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW BIQUINOLINE DERIVATIVES
11
Scheme 2

12
SHAH et al.
Captions for Scheme:
Scheme 1: Synthetic pathway for the intermediates 2(a-d) and 3(a-c)
Scheme 2: Synthetic pathway for the compounds 4(a-l)

SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF NEW BIQUINOLINE DERIVATIVES
13
Supplementary material
Physical data for compounds 2(a-d)
M.P.
(oC)
Mol.Wt.
(gm)
Mol.
Formula
Yield
(%)
Compound R1
2a
2b
2c
2d
H
145
191.61
205.64
221.64
226.06
C10H6ClNO 71
C11H8ClNO 73
C11H8ClNO2 68
C10H5Cl2NO 42
Me
OMe
Cl
125-26
148-49
165-66
EXPERIMENTAL
Chemistry
Analytical and spectroscopic characterization data of 3-(4-arylthiazole-2-
ylamino)cyclohex-enone 3(a-c) are given below:
3-(4-Phenylthiazol-2-ylamino)cyclohex-2-enone (3a). Yield: 74 %; m.p. 188-189 °C;
Anal. Calcd. for C15H14N2OS: C, 66.64; H, 5.22; N, 10.36 %. Found: C, 66.87; H, 4.98; N,
1
10.51 %. IR (KBr, ν, cm-1): 3395 (NH str.), 1665 (C=O str.). H NMR (400 MHz, DMSO-d6,
δ, ppm): 1.89-2.27 (6H, m, 3×CH2), 5.23 (1H, s, CH), 6.72-7.85 (6H, m, Ar-H), 10.48 (1H, s,
NH). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 20.19, 26.98 (CH2), 37.02 (CH2-CO), 106.41,
106.89, 112.47, 128.06, 132.79, 147.78, 153.56, 159.05, 161.67 (Ar-C), 197.28 (C=O).
3-(4-(4-chlorophenyl)thiazol-2-ylamino)cyclohex-2-enone (3b). Yield: 70 %; m.p. 199-
201 °C; Anal. Calcd. for C15H13ClN2OS: C, 59.11; H, 4.30; N, 09.19 %. Found: C, 58.95; H,
1
4.44; N, 09.27 %. IR (KBr, ν, cm-1): 3430 (NH str.), 1655 (C=O str.). H NMR (400 MHz,
DMSO-d6, δ, ppm): 1.87-2.26 (6H, m, 3×CH2), 5.27 (1H, s, CH), 6.87-7.94 (5H, m, Ar-H),
10.55 (1H, s, NH). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 20.37, 27.60 (CH2), 36.79 (CH2-
CO), 105.35, 106.78, 127.93, 129.25, 131.82, 148.63, 154.41, 159.30, 162.11 (Ar-C), 197.49
(C=O).
3-(4-(4-hydroxyphenyl)thiazol-2-ylamino)cyclohex-2-enone (3c). Yield: 75 %; m.p. 210-
212 °C; Anal. Calcd. for C15H14N2O2S: C, 62.92; H, 4.93; N, 09.78 %. Found: C, 63.07; H,
1
4.75; N, 09.66 %. IR (KBr, ν, cm-1): 3415 (NH str.), 1680 (C=O str.). H NMR (400 MHz,
DMSO-d6, δ, ppm): 1.83-2.29 (6H, m, 3×CH2), 5.25 (1H, s, CH), 6.81-7.71 (5H, m, Ar-H),
9.62 (1H, s, OH), 10.34 (1H, s, NH). 13C NMR (100 MHz, DMSO-d6, δ, ppm): 20.27, 27.33
(CH2), 37.00 (CH2-CO), 105.21, 106.62, 118.21, 127.10, 129.53, 148.87, 157.65, 159.48,
162.02 (Ar-C), 197.66 (C=O).
Antimicrobial activity
Sample preparation for the study of antibacterial activity. A 1000 ppm solution of newly
synthesized compounds has prepared in DMF.
Culture media for the study of antibacterial activity. The media: Nutrient broth (Hi-
Media, Mumbai, India) having following composition is used for the preparation of inoculums
for antibacterial study.

14
SHAH et al.
Ingredient
Peptic digest of animal tissue
Yeast extract
Gms/liter
5.00
1.50
Beef extract
1.50
Sodium chloride
5.00
Weighed quantities of all the components were dissolved in freshly prepared hot distilled
water.
Sterilization. The sterilization of culture media, culture tubes, and other materials was
done by autoclaving them at 15 lbs/sq.inch pressure for 15 min. The petri-dishes were
sterilized by keeping them overnight in an electrically heated air oven at 140 oC.
Preparation of Nutrient Plates:
20 ml of this sterilized media was poured in each sterilized petri dish and allowed to
solidify.
Preparation of Inoculum. The inoculum of organisms were prepared by transferring a
loopful of corresponding organism from the stock culture into the sterile broth and incubated
at 37 oC for 24 hrs under shaking conditions. The organisms were sub cultured on the nutrient
agar slants. The inoculum was prepared by dispensing colonies in sterile distilled water to
prepare a suspension.
Antibacterial susceptibility testing. A test tube containing sterile melted soft agar
o
(approximately 15 ml) was cooled to 45 C and inoculated with 0.2 ml suspension of the test
culture, mixed thoroughly and poured in the petri dish containing sterile N-agar medium and
allowed to solidify for five minutes. The cup-borer was sterilized by dipping into absolute
alcohol and flaming it and then allowed to cool down. With the sterile cup-borer, cups were
bored in the agar and marked. The cups were filled with 0.1 ml of respectively test sample
solution and the test sample was allowed to diffuse for 10 to 15 min. in refrigerator. The plate
o
was incubated at 37 C for 24 hr and on the next day the zone of inhibition of surrounding
each cup was observed and measured in mm.
Sample preparation for the study of antifungal activity. A 1000 ppm solution of newly
synthesized compounds has prepared in DMF.
Culture media for the study of antifungal activity. The media: Potato-dextrose agar (Hi-
Media, Mumbai, India) having following composition is used for the preparation of inoculum
for antibacterial study.
Ingredient
Potatoes infusion from
Dextrose
Gms/liter
200.00
20.0
Agar
15.0
Weighed quantities of all the components were dissolved in freshly prepared hot distilled
water.
All experimental conditions for antifungal activity are same as that of the antibacterial
activity only difference is culture media and the plate was incubated at 28 oC for 48 hr and the
zone of inhibition of surrounding each cup was observed and measured in mm.

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