Synthesis of novel N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl]-piperazine-1-carboxamide or -carbothioamide derivatives and their antimicrobial activity

Article abstract of DOI:10.1007/s10593-015-1660-2

A series of novel N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl]-piperazine-1-carboxamide or -carbothioamide derivatives was synthesized by cyclization of 5-bromo-2-fluorobenzaldehyde and guanidine carbonate in the presence of dimethylacetamide follow

Full text of DOI:10.1007/s10593-015-1660-2

DOI 10.1007/s10593-015-1660-2
Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
Synthesis of novel N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl]-
piperazine-1-carboxamide or -carbothioamide derivatives
and their antimicrobial activity
D. Suresh Babu1, Doddaga Srinivasulu1*, Venkata S. Kotakadi1
1 Sri Venkateswara University,
Tirupati – 517502, Andhra Pradesh, India; e-mail: doddaga_s@yahoo.com
Published in Khimiya Geterotsiklicheskikh Soedinenii,
2015, 51(1), 60–66
Submitted August 31, 2014
Accepted after revision November 27, 2014
A series of novel N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl]-piperazine-1-carboxamide or -carbothioamide derivatives was synthe-
sized by cyclization of 5-bromo-2-fluorobenzaldehyde and guanidine carbonate in the presence of dimethylacetamide followed by treatment
with isoamylnitrite and diiodomethane in the presence of copper iodide to afford 6-bromo-2-iodoquinazoline. The latter was treated with
piperazine in the presence of triethylamine followed by (2-fluoropyridin-3-yl)boronic acid in the presence of Pd(PPh3)2Cl2 to afford
6-(2-fluoropyridin-3-yl)-2-(piperazin-1-yl)quinazoline which was further treated with various substituted arylisocyanates and arylisothio-
cyanates to obtain the title compounds. The chemical structures of the synthesized compounds were confirmed by means of LC-MS, 1H, 13
C
NMR, IR, and mass spectra and elemental analysis. All the synthesized compounds were evaluated for their in vitro antibacterial activity
against two Gram-positive and two Gram-negative bacterial species, as well as two different strains of antibiotic-resistant E. coli and for
antifungal activity against two fungal strains. Some of the compounds have shown potential antimicrobial activity.
Keywords: arylisocyanates, arylisothiocyanates, piperazine, quinazoline, Suzuki coupling, antimicrobial activity.
Quinazolines are heterocyclic compounds with an
important place in the field of medicinal chemistry. The
quinazoline ring system is present in the structure of
approximately 150 naturally occurring pharmacologically
active alkaloids, isolated from a number of families of the
plant and animal kingdom, as well as various microorga-
nisms.1 Quinazoline derivatives possess diverse biological
and therapeutic activities such as antibacterial,2–4 antifun-
gal,5 anti-inflammatory,6 anticancer,2,7 antituberculosis,8
antiplasmodial,9 antimicrobial,10 and antioxidant.4,11 Hence,
quinazoline is a lead moiety for designing potential bio-
active agents.
Piperazine and substituted piperazine are important
pharmacophores found in many marketed drugs and drugs
under clinical trials.12,13 Pyridine derivatives containing
another heterocyclic nucleus also have shown potent phar-
macological properties like antifungal14 and antimicrobial15
activity. Piperazine moiety, too, was explored for several
biological activities including antimicrobial.16,17 The pola-
rity of the nitrogen atoms of piperazine ring enhances
favorable interaction with biomacromolecules and thus
confers the biological activity.18,19 A combination of quin-
azoline, pyridine, and piperazine heterocyclic rings in one
molecule has recently shown to be highly biological active
towards several bacterial and fungal species, and these
moieties are thought to have a synergistic effect against
pathogens causing infectious diseases.20
A growing interest and an urgent need for the
discovery of new, selective, and promising inhibitors of
microbial growth with an improved safety and efficacy
profile was the stimulus to present an attractive approach
towards design and development of new active com-
pounds. Urea and thiourea are important functional
moieties commonly found in natural products, drug inter-
mediates, and their derivatives often display a wide range
of biological activities.21 In particular, urea and thiourea
derivatives have exhibited broad spectrum of biological
activities such as antimicrobial22 or antimalarial.23 Due to
the importance of urea and thiourea in pharmacological
applications, there is an incentive to develop more
0009-3122/15/5101-0060©2015 Springer Science+Business Media New York
60

Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
Scheme 1
efficient urea and thiourea derivatives as antibacterial and
antifungal agents.
THF to give 6-bromo-2-iodoquinazoline (4). Compound 4
was treated with piperazine in THF to give compound 5
which was used in the Suzuki coupling reaction24–26 with
(2-fluoropyridin-3-yl)boronic acid in toluene–ethanol–
water mixture, 1:1:1, to give compound 6 (Scheme 1).
Further, compound 6 was treated with various aromatic
isocyanates or isothiocyanates to give final products 7a–e
and 8a–e in good yields (Table 1).
Compounds 7a–e and 8a–e were characterized by using
LC-MS, 1H, 13C NMR, IR spectroscopy and elemental ana-
lysis. The IR spectra of all compounds contained absorp-
tion bands at 3278–3662, 1625–1672, 1429–1481, and
1313–1365 cm–1 corresponding to NH, C=O, C=N, and CN
Based on the many known applications of quinazoline
derivatives, as well as those of urea and thiourea
derivatives, we have designed and synthesized a novel
series of N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl]-
piperazine-1-carboxamide and -carbothioamide derivatives
with an objective to screen them for antibacterial and
antifungal activities. The synthetic scheme started from
5-bromo-2-fluorobenzaldehyde (1) and guanidine carbo-
nate (2) in dimethylacetamide (DMA) to form 6-bromo-
quinazolin-2-amine (3) (Scheme 1). Compound 3 was
treated with isoamyl nitrite, CuI, and diiodomethane in
Table 1. Yields and melting points of the synthesized compounds 7a–e and 8a–e
Com-
pound
Com-
pound
Ar
Yield, %
73
Mp, °C
262–264
Ar
Yield, %
74
Mp, °C
244–246
7a
8a
Cl
Cl
78
81
76
274–276
257–259
246–248
82
78
78
230–232
214–216
226–228
7b
7c
7d
8b
8c
8d
Cl
79
254–256
82
234–236
7e
8e
61

Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
Table 2. Antibacterial activity of compounds 7a–e and 8a–e expressed as DIZ, mm
Gram-positive bacteria
P.aeruginosa
Gram-negative bacteria
K.pneumoniae
Mutant E. coli
Com-
pound
B.megaterium
S. aureus
Donor E. coli
14
12
13
13
Nd*
9
13
15
14
12
Nd
5
13
12
12
10
Nd
8
Nd
14
10
12
Nd
9
Nd
13
15
18
Nd
19
15
30
16
10
22
13
12
14
14
Nd
14
15
16
14
19
23
7a
7b
7c
7d
7e
8a
14
17
16
16
24
25
19
9
10
19
10
Nd
22
14
14
13
8
8b
8c
8d
8
8e
24
20
Amoxiclav
* Nd – Not detected.
1
groups, respectively. H NMR signals at 8.76–9.60 cor-
respond to NH proton and those at 3.50–4.00 – to the
piperazine methylene group protons. 13C NMR signals of
the C=O, C=S, CH2N, and C–F group carbon atom were
observed around 158.6, 162.5, 43.4, and 160.8 ppm,
respectively.
The antibacterial activity was also evaluated in terms of
the minimum inhibitory concentration (MIC), which is the
lowest drug concentration that prevents visible
microorganism growth after overnight incubation.29 The
MIC values are important in diagnostic laboratory to
confirm resistance of microorganisms to antimicrobial
agents and also to monitor the activity of new antimicrobial
agents. MIC measurements were performed using a
modified agar well diffusion method.30
The obtained MIC values of the tested compounds are
presented in Table 3. The results revealed that compound 7b
showed good activity against Gram-positive and Gram-
negative bacteria due to the presence of 3-CF3 and 4-F sub-
stituents on the phenylurea benzene ring. Compound 8c
showed potent antibacterial activity against the tested
microorganisms due to the presence of 3-CF3 group on the
phenylthiourea ring. Compounds 7d and 8a showed good
activity against K. pneumoniae and B. megaterium due to
the presence of electron-withdrawing groups NO2 and Cl.
Compound 8b showed potent activity against P. aeruginosa
in DIZ measurements and also against both Gram-positive
All the synthesized compounds 7a–e and 8a–e were
evaluated for their antibacterial activity by using agar well
diffusion method.27,28 The synthesized compounds were
tested against two Gram-positive (Staphylococcus aureus
and Pseudomonas aeruginosa) and two Gram-negative
(Klebsiella pneumoniae and Bacillus megaterium) bacteria
strains. Additionally, two different strains of antibiotic-
resistant E. coli Gram-negative bacteria were also used in
the present study (streptomycin-resistant mutant E. coli
strain and rifampin-resistant donor E. coli strain), and
Amoxiclav was used as a standard drug. The antibacterial
activity was evaluated based on the diameter of inhibition
zone (DIZ), which is the area on an agar plate where the
growth of a control organism is prevented by a test compound.
The obtained DIZ values are presented in Table 2.
Table 3. Antibacterial activity of compounds 7a–e and 8a–e expressed as MIC, µg/ml
Gram-positive bacteria
Gram-negative bacteria
Com-
pound
S. aureus
75
Mutant E. coli
P. aeruginosa
25
Donor E. coli
K. pneumoniae
B. megaterium
5
Nd
Nd
25
7a
2.5
50
5
5
5
25
5
25
5
7b
7c
7d
7e
50
25
Nd
50
25
Nd
50
25
Nd
25
5
5
Nd*
Nd
Nd
50
2
100
2.5
50
50
50
25
5
5
5
5
8a
8b
5
5
5
–
5
50
50
–
5
50
Nd
–
25
25
50
–
2.5
5
5
25
5
8c
8d
50
–
8e
Amoxiclav
–
* Nd – Not detected.
62

Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
Table 4. Antifungal activity of compounds 7b,c, and 8a,b,c
spectrometer (100 MHz) in DMSO-d6. TMS was used as
internal standard. LC-MS spectra were recorded on an
Acquity Ultra Performance Liquid Chromatography instru-
ment coupled with an API 3000 mass spectrometer
operating in electrospray positive ionization mode.
Elemental analyses were done by using Thermo Scientific
Flash 2000 organic elemental analyzer. Melting points
were determined in open capillaries on Guna melting point
apparatus and are uncorrected. All chemicals were
purchased from Sigma Aldrich and Merck, and the solvents
were used without further purification. Deionized water
was used for all workup procedures, and doubly deionized
water was used for biological experiments. All reactions
were magnetically stirred and progress of the reactions was
monitored by TLC on Merck silica plates.
Com-
pound
Aspergillus niger
Penicillium spinulosum
DIZ, mm
DIZ, mm
8
5
10
7
7b
7c
6
5
8a
9
12
Nd
12
8b
8c
10
10
Fluconazole
* Nd – Not detected.
bacteria strains in MIC measurements due to the presence
of 2,4-dichlorophenylthiourea functionality. Compound 7c
showed good activity against K. pneumoniae and B.
megaterium in terms of MIC due to the presence of
3,4-dichloro group on the phenylurea ring. Compound 8c
exhibited good antibacterial activity against donor E. coli
antibiotic-resistant strain due to the presence of 3-CF3
phenylthiourea functionality, while compound 7b showed
good activity against both donor and mutant E. coli
antibiotic-resistant strains due to the presence of 3-CF3 and
4-F substituents on the phenylurea ring. The remaining
compounds showed moderate activity against both
antibiotic-resistant E. coli strains.
Based on the assessment of their antibacterial activity,
the compounds 7b,c, 8a–c were screened for antifungal
activity against two fungal strains (Aspergillus niger and
Penicillium spinulosum) using poison plate technique.31
The results, expressed as DIZ (Table 4), reveal that
compounds 7b and 8b possess good antifungal activity
against Aspergillus niger and Penicillium spinulosum due
to the presence of 3-CF3 and 4-F or 2-Cl and 4-Cl substi-
tuents, respectively, on the phenylurea benzene ring,
whereas compound 8c demonstrates excellent antifungal
activity against Aspergillus niger due to the presence of
3-CF3 group on the phenylthiourea benzene ring. The
obtained results of the antifungal activity in DIZ are
presented in Table 4.
In conclusion, we have synthesized a series of N-aryl-
4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl]piperazine-1-carb-
oxamide and N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazolin-
2-yl]piperazine-1-carbothioamide derivatives in good
yields and evaluated the in vitro antimicrobial activity of
these compounds. The compounds having 3-CF3 sub-
stituent, 3-CF3 and 4-F, or 2-Cl and 4-Cl substituents on the
phenylurea benzene ring have shown potent antimicrobial
activity against the tested microorganisms. Based on the
above results, some of the compounds may be regarded as
potential drug candidates for treatment of different
microbial infections caused by multidrug-resistant
organisms.
6-Bromoquinazolin-2-amine (3).32 Guanidine carbonate (2)
(4.47 g, 36.9 mmol) was added to a solution of 5-bromo-
2-fluorobenzaldehyde (1) (5.00 g, 24.6 mmol) in dimethyl-
acetamide (50 ml). The reaction mixture was heated at
150°C for 5 h. The progress of the reaction was monitored
by TLC using AcOEt–hexane, 1:1, as eluent. The reaction
mixture was cooled and quenched with ice water, and
stirred for 30 min. Then the obtained solid was filtered off,
and water was removed by azeotropic distillation with
PhMe to get 4.00 g (73%) of compound 3. Mp 270–272°C.
1H NMR spectrum (300 MHz), δ, ppm (J, Hz): 7.04 (2H, s,
NH2); 7.37 (1H, d, J = 9.0, H Ar); 7.78 (1H, dd, J = 9.0,
J = 2.4, H Ar); 8.05 (1H, d, J = 2.4, H Ar); 9.09 (1H, s,
H Ar). Mass spectrum, m/z: 225 [M+H]+.
6-Bromo-2-iodoquinazoline (4).33 6-Bromoquinazolin-
2-amine (3) (4.00 g, 17.9 mmol) was dissolved in THF
(40 ml), and purged with nitrogen gas followed by addition
of copper iodide (5.66 g, 17.8 mmol), isoamylnitrite (6.48 g,
55.3 mmol), and diiodomethane (23.91 g, 5 equiv,
89.3 mmol). The reaction mixture was heated at 80°C for 2 h.
The progress of the reaction was monitored by TLC using
AcOEt–hexane, 1:1, as eluent. The reaction mixture was
cooled and quenched with ice water, and extracted with
AcOEt (2 × 100 ml). The organic layer was washed with
water and brine and dried over sodium sulphate. The
solution was filtered and concentrated under reduced
pressure. The resultant crude residue was purified by
column chromatography using AcOEt–hexane, 1:1, as
1
eluent. Yield 2.60 g (43%). Mp 121–123°C. H NMR
spectrum (300 MHz), δ, ppm (J, Hz): 7.88 (1H, d, J = 9.0,
H Ar); 8.00 (1H, dd, J = 9.0, J = 2.1, H Ar); 8.08 (1H, d,
J = 2.1, H Ar); 9.03 (1H, s, H Ar). Mass spectrum, m/z: 335
[M+H]+.
6-Bromo-2-(piperazin-1-yl)quinazoline (5). Piperazine
(0.565 g, 6.56 mmol) and triethylamine (1.810 g,
17.9 mmol) were added to a solution of 6-bromo-2-iodo-
quinazoline (4) (2.00 g, 5.97 mmol) in THF (20 ml). The
reaction mixture was heated at 60°C for 2 h. The progress
of the reaction was monitored by TLC using 10% methanol
in chloroform as eluent. The reaction mixture was
quenched with water and extracted with 10% methanol in
chloroform. The organic layer was dried over sodium
sulphate, filtered, and concentrated under reduced pressure.
The resultant crude product was purified by column
Experimental
IR spectra were recorded on a JASCO FT-IR 5300
spectrometer in KBr pellets. 1H NMR spectra were
recorded on Bruker Avance 400 (400 MHz) and Varian
Mercury+ 300 (300 MHz) spectrometers in DMSO-d6. 13C
NMR spectra were recorded on a Bruker Avance 400
63

Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
chromatography using 5–10% methanol in chloroform.
Yield 1.200 g (69%). Mp 138–140°C. H NMR spectrum
119.1 (C-15); 120.0 (C-5',9'); 121.4 (C-7'), 122.7 (C-20);
1
125.4 (C-8); 127.2 (C-6',8'); 128.2 (C-5); 131.0 (C-6);
134.7 (C-7); 139.9 (C-4'); 141.2 (C-21); 146.4 (C-19); 151.1
(C-8a); 154.7 (C-2'); 158.8 (C-4); 160.8 (C-16); 162.5 (C-2).
Mass spectrum (EI, 70 eV), m/z: 509 [M(81Br)+H]+. Found, %:
C 56.63; H 3.78; N 16.29. C24H20BrFN6O. Calculated, %:
C 56.82; H 3.97; N 16.56.
(300 MHz), δ, ppm (J, Hz): 2.96–2.99 (4H, m, 11,13-CH2);
3.90–3.94 (4H, m, 10,14-CH2); 7.47 (1H, d, J = 9.0,
H Ar); 7.85 (1H, dd, J = 9.0, J = 2.4, H Ar); 8.13 (1H, d,
J = 2.1, H Ar); 9.22 (1H, s, H Ar). Mass spectrum (EI,
70 eV), m/z: 295 [M(81Br)+H]+. Found, %: C 49.02; H 4.32;
N 18.93. C12H13BrN4. Calculated, %: C 49.16; H 4.47;
N 19.11.
4-[6-(2-Fluoropyridin-3-yl)quinazolin-2-yl)-N-
[4-fluoro-3-(trifluoromethyl)phenyl]piperazine-1-carb-
oxamide (7b). Off-white solid. IR spectrum, ν, cm–1: 3431
(N–H), 2862 (C–H), 1672 (C=O), 1481 (C=N), 1327 (C–N),
1234 (C–F). 1H NMR spectrum (400 MHz), δ, ppm (J, Hz):
3.60–3.63 (4H, m, 10,14-CH2); 3.95–3.97 (4H, m,
11,13-CH2); 7.48–7.51 (1H, m, H Ar); 7.56 (1H, d, J = 8.8,
H Ar); 7.64 (1H, d, J = 8.8, H Ar); 7.83 (1H, dd, J = 8.8,
J = 2.4, H Ar); 7.97–8.00 (1H, m, H Ar); 8.07 (1H, d,
J = 2.4, H Ar); 8.14 (1H, s, H Ar); 8.19–8.25 (2H, m,
H Ar); 9.07 (1H, s, NH); 9.32 (1H, s, H Ar).13C NMR
spectrum (100 MHz), δ, ppm: 43.4 (C-10,11,13,14); 117.8
(C-8'); 119.1 (C-5′); 121.5 (C-6'); 121.9 (C-4a); 122.0 (C-15);
122.7 (C-20); 123.8 (C-6′'); 125.4 (C-8); 127.3 (C-9');
128.2 (C-4'); 131.5 (C-5); 132.5 (C-6); 140.1 (C-7); 141.2
(C-21); 146.4 (C-19); 151.1 (C-8a); 154.4 (C-7'); 158.4 (C-2');
158.8 (C-4); 160.7 (C-16); 162.5 (C-2). Mass spectrum, m/z:
515 [M+H]+. Found, %: C 58.15; H 3.69; N 16.11. Mass
spectrum, m/z: 515 [M+H]+. Found, %: C 58.15; H 3.69;
N 16.11. C25H19F5N6O. Calculated, %: C 58.37; H 3.72;
N 16.34.
6-(2-Fluoropyridin-3-yl)-2-(piperazin-1-yl)quin-
azoline (6). Sodium carbonate (0.90 g, 8.5 mmol) and
(2-fluoropyridin-3-yl)boronic acid (0.57 g, 4.1 mmol) were
added to a solution of 6-bromo-2-(piperazin-1-yl)quinazo-
line (5) (1.00 g, 3.41 mmol) in PhMe–EtOH–H2O, 1:1:1.
The reaction mixture was degassed with nitrogen, and
Pd(PPh3)2Cl2 (0.11 g, 0.05 mol %, 1.69 mmol) was added.
The reaction mixture was heated at 90°C under nitrogen
atmosphere for 1 h. The progress of the reaction was
monitored by TLC using CHCl3–MeOH, 9:1, as eluent.
The reaction mixture was quenched with water and
extracted with CHCl3–MeOH, 9:1 (3 × 100 ml). The
organic layer was dried over sodium sulphate, then filtered
and concentrated under reduced pressure. The crude
product was purified by column chromatography using 5–
10% methanol in chloroform. Yield 0.60 g (57%). Mp
158–160°C. 1H NMR spectrum (300 MHz), δ, ppm (J, Hz):
2.80–2.83 (4H, m, 10,14-CH2); 3.83–3.86 (4H, m, 11,13-
CH2); 7.46–7.51 (1H, m, H Ar); 7.58 (1H, d, J = 9.0, H
Ar); 7.96 (1H, d, J = 9.0, H Ar); 8.10 (1H, s, H Ar); 8.17–
8.24 (2H, m, H Ar); 9.26 (1H, s, H Ar). Mass spectrum, m/z:
310 [M+H]+. Found, %: C 65.91; H 4.99; N 22.37.
C17H16FN5. Calculated, %: C 66.01; H 5.21; N 22.64.
Synthesis of N-aryl-4-[6-(2-fluoropyridin-3-yl)quinazo-
lin-2-yl)]piperazine-1-carboxamides 7a–e and N-aryl-
4-[6-(2-fluoropyridin-3-yl)quinazolin-2-yl)]piperazine-
1-carbothioamides 8a–e (General Method). Compound 6
(0.10 g, 0.32 mmol) was dissolved in THF (20 ml), than
TEA (0.13 ml, 0.96 mmol) was added, followed by the
addition a substituted aryl isocyanate (0.48 mmol). The
reaction mixture was refluxed for 3 h under nitrogen
atmosphere. The progress of the reaction was monitored by
TLC using CHCl3–MeOH, 9:1, as eluent. The reaction
mixture was cooled, diluted with water, extracted with
CHCl3–MeOH, 9:1, and washed with brine. The organic
layer was dried over sodium sulphate, filtered, and
concentrated under reduced pressure. The obtained crude
residue was purified by column chromatography on silica
gel (60–120 mesh) using 2–5% methanol in chloroform as
the eluent.
N-(3,4-Dichlorophenyl)-4-[6-(2-fluoropyridin-3-yl)-
quinazolin-2-yl]piperazine-1-carboxamide (7c). Off-
white solid. IR spectrum, ν, cm–1: 3278 (N–H), 2858 (C–H),
1664 (C=O), 1475 (C=N), 1365 (C–N), 1234 (C–F).
1H NMR spectrum (400 MHz), δ, ppm (J, Hz): 3.59–3.61
(4H, m, 10,14-CH2); 3.94–3.96 (4H, m, 11,13-CH2); 7.48–
7.51 (3H, m, H Ar); 7.62 (1H, d, J = 8.8, H Ar); 7.86 (1H,
s, H Ar); 7.97 (1H, d, J = 9.2, H Ar); 8.14 (1H, s, H Ar);
8.19–8.25 (2H, m, H Ar); 8.91 (1H, s, NH); 9.32 (1H, s,
H Ar). 13C NMR spectrum (100 MHz), δ, ppm: 44.0 (C-10,
C-11,13,14); 119.7 (C-4a); 120.9 (C-15); 123.2 (C-9');
123.4 (C-20); 126.0 (C-8); 127.8 (C-5',7'); 128.7 (C-5);
130.6 (C-6); 131.0 (C-7,8'); 135.2 (C-6'), 141.3 (C-4');
141.7 (C-21); 146.8 (C-19); 146.9 (C-8a); 151.7 (C-4);
155.0 (C-16); 159.3 (C-2'); 163.0 (C-2). Mass spectrum, m/z:
497 [M+H]+ . Found, %: C 57.79; H 3.67; N 16.72.
C24H19Cl2FN6O. Calculated, %: C 57.96; H 3.85; N 16.90.
4-[6-(2-Fluoropyridin-3-yl)quinazolin-2-yl]-N-(4-nitro-
phenyl)piperazine-1-carboxamide (7d). Off-white solid.
IR spectrum, ν, cm–1: 3329 (N–H), 2858 (C–H), 1625
1
(C=O), 1481 (C=N), 1365 (C–N), 1219 (C–F). H NMR
N-(4-Bromophenyl)-4-[6-(2-fluoropyridin-3-yl)quin-
azolin-2-yl]piperazine-1-carboxamide (7a). Off-white
solid. IR spectrum, ν, cm–1: 3448 (N–H), 2922 (C–H), 1654
spectrum (400 MHz), δ, ppm (J, Hz): 3.60–3.95 (8H, m,
10,11,13,14-CH2); 7.39–7.49 (4H, m, H Ar); 7.62 (2H, d,
J = 8.8, H Ar); 7.98–8.04 (1H, m, H Ar); 8.00 (1H, s,
H Ar); 8.14–8.25 (2H, m, H Ar); 8.77 (1H, s, NH); 9.32
(1H, s, H Ar). 13C NMR spectrum (100 MHz), δ, ppm: 43.5
(C-10,11,13,14); 113.2 (C-4a); 119.1 (C-15); 120.0
(C-5',9'); 121.7 (C-20); 125.2 (C-8); 127.1 (C-6',8'); 128.4
(C-5); 131.1 (C-6); 133.6 (C-7); 139.7 (C-4'); 141.1 (C-7');
141.3 (C-21); 146.4 (C-19); 151.1 (C-8a); 154.4 (C-2');
158.6 (C-4); 161.7 (C-16); 181.1 (C-2). Mass spectrum, m/z:
1
(C=O), 1475 (C=N), 1313 (C–N), 1238 (C–F). H NMR
spectrum (400 MHz), δ, ppm (J, Hz): 3.58–3.61 (4H, m,
10,14-CH2); 3.93–3.96 (4H, m, 11,13-CH2); 7.41–7.51
(4H, m, H Ar); 7.64 (2H, d, J = 8.8, H Ar); 7.97–8.00 (1H,
m, H Ar); 8.14 (1H, s, H Ar); 8.19–8.25 (2H, m, H Ar);
8.76 (1H, s, NH); 9.31 (1H, s, H Ar). 13C NMR spectrum
(100 MHz), δ, ppm: 43.5 (C-2,3,19,20); 113.2 (C-4a);
64

Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
474 [M+H]+. Found, %: C 60.66; H 4.18; N 20.52.
H Ar); 9.33 (1H, s, NH); 9.48 (1H, s, H Ar). 13C NMR
spectrum (100 MHz), δ, ppm: 43.1 (C-11,13); 47.6
(C-10,14); 119.2 (C-4a); 120.4 (C-15); 121.9 (C-5'); 122.7
(C-20); 123.8 (C-6''); 125.5 (C-8); 126.7 (C-8'); 127.3
(C-9'); 128.2 (C-6'); 129.8 (C-7'); 134.7 (C-5); 141.2 (C-6);
141.4 (C-21); 142.6 (C-7); 146.3 (C-4'); 151.1 (C-19);
158.4 (C-8a); 158.7 (C-4); 160.7 (C-16); 162.5 (C-2');
181.2 (C-2). Mass spectrum, m/z: 513 [M+H]+. Found, %:
C 58.47; H 3.82; N 16.10; S 5.99. C25H20F4N6S. Calcu-
lated, %: C 58.59; H 3.93; N 16.40; S 6.26.
C24H20FN7O3. Calculated, %: C 60.88; H 4.26; N 20.71.
N-(3-Cyanophenyl)-4-[6-(2-fluoropyridin-3-yl)quin-
azolin-2-yl]piperazine-1-carboxamide (7e). Off-white
solid. IR spectrum, ν, cm–1: 3116 (N–H), 2922 (C–H), 1627
1
(C=O), 1477 (C=N), 1317 (C–N), 1224 (C–F). H NMR
spectrum (400 MHz), δ, ppm (J, Hz): 3.97–4.14 (8H, m,
10,11,13,14-CH2); 7.33–7.37 (4H, m, H Ar); 7.48–7.52 (1H,
m, H Ar); 7.65 (1H, d, J = 8.8, H Ar); 8.00 (1H, d, J = 8.8, H
Ar); 8.15 (1H, s, H Ar); 8.22–8.25 (2H, m, H Ar); 9.33 (1H,
13
s, NH); 9.44 (1H, s, H Ar). C NMR spectrum (100 MHz),
N-(3-Bromophenyl)-4-[6-(2-fluoropyridin-3-yl)quin-
azolin-2-yl]piperazine-1-carbothioamide (8d). Off-white
solid. IR spectrum, ν, cm–1: 3398 (N–H), 2862 (C–H), 1627
δ, ppm: 43.1 (C-11,13); 47.5 (C-10,14); 119.1 (C-6'); 121.9
(C-6''); 122.7 (C-15, 20); 125.4 (C-5'); 126.8 (C-8); 127.3
(C-9'); 127.8 (C-7'); 128.2 (C-5,6); 134.7 (C-7,8'); 139.9 (C-
4'); 141.1 (C-21); 146.3 (C-19); 151.1 (C-8a); 158.6 (C-2',4);
162.5 (C-16); 181.4 (C-2). Mass spectrum, m/z: 454 [M+H]+.
Found, %: C 65.98; H 4.39; N 21.36. C25H20FN7O.
Calculated, %: C 66.22; H 4.45; N 21.62.
1
(C=O), 1429 (C=N), 1332 (C–N), 1220 (C–F). H NMR
spectrum (400 MHz), δ, ppm (J, Hz): 3.99–4.04 (4H, m,
10,14-CH2); 4.05–4.11 (4H, m, 11,13-CH2); 7.11–7.51
(5H, m, H Ar); 7.65 (1H, d, J = 8.8, H Ar); 8.00 (1H, d,
J = 8.8, H Ar); 8.15 (1H, s, H Ar); 8.19–8.25 (2H, m, H Ar);
9.33 (1H, s, NH), 9.38 (1H, s, H Ar). 13C NMR spectrum
(100 MHz), δ, ppm: 43.1 (C-11,13); 47.4 (C-10,14); 114.6
(C-4a); 119.1 (C-15); 121.9 (C-20); 122.2 (C-7'); 122.7
(C-9'); 125.4 (C-6'); 127.6 (C-5'); 128.2 (C-8); 134.7 (C-8');
137.2 (C-5); 141.2 (C-6); 146.4 (C-7); 151.1 (C-21); 157.9
(C-4'); 158.4 (C-19); 158.7 (C-8a); 160.3 (C-4); 160.7
(C-16); 162.5 (C-2'); 181.6 (C-2). Mass spectrum, m/z: 525
[M(81Br)+H]+. Found, %: C 54.88; H 3.81; N 15.76;
S 5.89. C24H20BrFN6S. Calculated, %: C 55.07; H 3.85;
N 16.06; S 6.13.
N-(4-Chlorophenyl)-4-[6-(2-fluoropyridin-3-yl)quin-
azolin-2-yl]piperazine-1-carbothioamide (8a). Off-white
solid. IR spectrum, ν, cm–1: 3421 (N–H), 2862 (C–H), 1632
1
(C=O), 1473 (C=N), 1346 (C–N), 1223 (C–F). H NMR
spectrum (400 MHz), δ, ppm (J, Hz): 4.00–4.15 (8H, m,
10,11,13,14-CH2); 7.36 (1H, d, J = 8.4, H Ar); 7.41–7.45
(1H, m, H Ar); 7.52 (1H, s, H Ar); 7.65–7.68 (2H, m, H Ar);
8.00 (1H, d, J = 8.7, H Ar); 8.18 (1H, s, H Ar); 8.26–8.28
(2H, m, H Ar); 9.36 (1H, s, NH); 9.39 (1H, s, H Ar). 13C
NMR spectrum (100 MHz), δ, ppm: 43.2 (C-10,11,13,14);
118.4 (C-5'); 119.1 (C-9'); 121.7 (C-4a); 122.6 (C-15); 123.4
(C-20); 125.1 (C-8); 127.7 (C-6',8'); 128.0 (C-5); 130.1 (C-6,
21); 132.2 (C-7'); 134.1 (C-7); 140.5 (C-4'); 141.7 (C-19);
146.2 (C-8a); 151.0 (C-4); 158.6 (C-16); 162.7 (C-2'); 181.5
(C-2). Mass spectrum, m/z: 479 [M+H]+. Found, %: C 60.12;
H 4.19; N 17.32; S 6.41 C24H20ClFN6S. Calculated, %: C
60.18; H 4.21; N 17.55; S 6.69.
N-(2,4-Dichlorophenyl)-4-[6-(2-fluoropyridin-3-yl)-
quinazolin-2-yl]piperazine-1-carbothioamide (8b). Off-
white solid. IR spectrum, ν, cm–1: 3662 (N–H), 2895 (C–H),
1625 (C=O), 1436 (C=N), 1332 (C–N), 1224 (C–F).
1H NMR spectrum (400 MHz), δ, ppm (J, Hz): 3.99–4.07
(4H, m, 10,14-CH2); 4.08–4.13 (4H, m, 11,13-CH2); 7.42–
7.70 (5H, m, H Ar); 7.74 (1H, s, H Ar); 7.98 (1H, d, J = 1.6,
H Ar); 8.15 (1H, s, H Ar); 8.19–8.25 (1H, m, H Ar); 9.33 (1H,
s, NH); 9.60 (1H, s, H Ar). 13C NMR spectrum (100 MHz),
δ, ppm: 43.1 (C-11,13); 47.6 (C-10,14); 119.2 (C-4a); 120.0
(C-15); 121.9 (C-8'); 122.7 (C-20); 127.3 (C-8); 128.2 (C-9');
128.4 (C-6'); 128.6 (C-5); 129.0 (C-6); 129.4 (C-7'); 134.7
(C-7); 141.8 (C-5'); 146.3 (C-4'); 146.4 (C-21); 151.1 (C-19);
158.4 (C-8a); 158.7 (C-4); 160.8 (C-16); 162.5 (C-2'); 181.2
(C-2). Mass spectrum, m/z: 515 [M(37Cl)+H]+. Found, %:
C 55.89; H 3.71; N 16.02; S 5.94. C24H19Cl2FN6S. Calculated,
%: C 56.14; H 3.73; N 16.37; S 6.25.
N-(4-Fluorophenyl)-4-[6-(2-fluoropyridin-3-yl)quin-
azolin-2-yl]piperazine-1-carbothioamide (8e). Off-white
solid. IR spectrum, ν, cm-1: 3367 (N–H), 2860 (C–H), 1674
1
(C=O), 1429 (C=N), 1323 (C–N), 1234 (C–F). H NMR
spectrum (400 MHz), δ, ppm (J, Hz): 3.59–3.65 (4H, m,
10,14-CH2); 3.93–3.99 (4H, m, 11,13-CH2); 7.37–7.67
(4H, m, H Ar); 7.76–7.78 (1H, m, H Ar); 7.95–7.99 (2H,
m, H Ar); 8.13 (1H, s, H Ar); 8.19–8.25 (2H, m, H Ar);
8.97 (1H, s, NH); 9.31 (1H, s, H Ar). 13C NMR spectrum
(100 MHz), δ, ppm: 43.5 (C-10,11,13,14); 118.9 (C-6');
119.1 (C-8'); 121.9 (C-4a); 122.7 (C-15); 123.8 (C-20);
125.4 (C-8); 127.3 (C-9', 5'); 128.2 (C-5); 130.1 (C-6);
134.7 (C-7); 140.2 (C-4'); 141.2 (C-19); 146.4 (C-8a);
151.1 (C-4); 154.6 (C-7'); 158.8 (C-16); 160.7 (C-2'); 162.5
(C-2). Mass spectrum, m/z: 463 [M+H]+. Found, %: C 62.07;
H 4.28; N 17.87; S 6.57. C24H20F2N6S. Calculated, %:
C 62.32; H 4.36; N 18.17; S 6.93.
Antimicrobial activity. Each of the tested compounds
(200 μg) was dissolved in DMSO (1 ml). Centrifuged pellets
of bacteria from 24 h old culture containing approximately
104–106 colony forming units (CFU) per ml were spread on
the surface of nutrient agar plates. Nutrient agar medium was
prepared by suspending nutrient agar (28 g) in distilled water
(1 l), autoclaved, and cooled to 45°C. Then the agar it was
seeded with 15 ml of prepared inocula of the bacteria to
obtain concentration 106 CFU/ml. Petri dishes were prepa-
red by pouring 10 ml of seeded nutrient agar. Wells were
created in the medium with the help of a sterile metallic
borer, and a test solution was added into each of them. The
experimental plates were incubated for 24 h at 37°C, and the
diameter of the inhibition zone around each well was measured.
4-[6-(2-Fluoropyridin-3-yl)quinazolin-2-yl]-N-[3(tri-
fluoromethyl)phenyl]piperazine-1-carbothiomide (8c).
Off-white solid. IR spectrum, ν, cm–1: 3662 (N–H), 2843
(C–H), 1625 (C=O), 1431 (C=N), 1317 (C–N), 1222 (C–F).
1H NMR spectrum (400 MHz), δ, ppm (J, Hz): 4.00–4.11
(8H, m, 10,11,12,14-CH2); 7.23–7.65 (6H, m, H Ar); 7.97–
8.00 (1H, m, H Ar); 8.15 (1H, s, H Ar); 8.19–8.25 (2H, m,
65

Chemistry of Heterocyclic Compounds 2015, 51(1), 60–66
Antifungal activity. Test compounds 7b,c, 8a–c were
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