Synthesis and antitubercular activity of novel pyrazole-quinazolinone hybrid analogs

Article abstract of DOI:10.1007/s00044-012-0351-0

A series of 2-(substituted-phenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H- pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-ones have been synthesized. The structures of the synthesized compounds were assigned on the basis of IR, ¹H NMR, ¹³C NMR, and mass spectral data, while their abilities to inhibit growth of Mycobacterium tuberculosis in vitro have been determined. The results show that compounds 5a, 5c, 5d, 5g, and 5k exhibited excellent antitubercular activity with percentage inhibition of 96, 90, 94, 93, and 92, respectively at a minimum inhibitory concentration (MIC) of <6.25 μg/mL, whereas compounds 5b, 5e, 5f, 5h, 5i, 5j, and 5l exhibited moderate- to- good antitubercular activity with percentage inhibition of 68, 70, 67, 64, 59, 73, and 67, respectively, at a MIC of >6.25 μg/mL. From the secondary screening, the actual MIC of compounds 5a, 5c, 5d, 5g, and 5k are <3.125.

Full text of DOI:10.1007/s00044-012-0351-0

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:3364–3371
DOI 10.1007/s00044-012-0351-0
ORIGINAL RESEARCH
Synthesis and antitubercular activity of novel
pyrazole–quinazolinone hybrid analogs
•
Unnat Pandit Amit Dodiya
Received: 17 September 2012 / Accepted: 8 November 2012 / Published online: 21 November 2012
Ó Springer Science+Business Media New York 2012
Abstract A series of 2-(substituted-phenyl)-3-(((3-(pyri-
din-4-yl)-1-(p-tolyl)-1H-pyrazol-4-yl)methylene)amino)
-quinazolin-4(3H)-ones have been synthesized. The struc-
tures of the synthesized compounds were assigned on the
become an important problem due to the emergence of
monodrug and multidrug-resistant strains of M. tubercu-
losis (Rattan et al., 1998; Singh et al., 2006). Therefore,
there is a need for developing new drugs of new structural
classes and with a novel mechanism of action other than
isoniazid (INH), rifampicin (RIF), and pyrazinamide
(PZA). In this regard, since the last decade, the search for
new antitubercular substances has been ranked among the
priority areas of chemotherapeutic research.
1
basis of IR, H NMR, 13C NMR, and mass spectral data,
while their abilities to inhibit growth of Mycobacterium
tuberculosis in vitro have been determined. The results
show that compounds 5a, 5c, 5d, 5g, and 5k exhibited
excellent antitubercular activity with percentage inhibition
of 96, 90, 94, 93, and 92, respectively at a minimum
inhibitory concentration (MIC) of \6.25 lg/mL, whereas
compounds 5b, 5e, 5f, 5h, 5i, 5j, and 5l exhibited moder-
ate- to- good antitubercular activity with percentage inhi-
bition of 68, 70, 67, 64, 59, 73, and 67, respectively, at a
MIC of [6.25 lg/mL. From the secondary screening, the
actual MIC of compounds 5a, 5c, 5d, 5g, and 5k are
\3.125.
Quinazoline derivatives represent one of the most active
classes of compounds possessing a wide spectrum of bio-
logical activity (Apfel et al., 2001). They are widely used
in pharmaceuticals and agrochemicals (Tobe et al., 2003);
for example, fluquinconazole fungicide for the control of
agriculture diseases (Guang-Fang et al., 2007). Several
reports have been published on the biological activities of
quinazoline derivatives, including their bactericidal, herbal,
and antitumor activity (Raffa et al., 1999; Chenard et al.,
2001). Thus, their synthesis has been of great interest in the
elaboration of biologically active heterocyclic compounds.
Recently, it was reported that some iodoquinazolines
exhibited moderate antibacterial activity (Alafeefy, 2008).
Prompted by these findings, this article reports the design
and synthesis of an extension series of 3-substituted
2-phenylquinazolin-4(3H)-one derivatives and tested their
antibacterial activities.
Keywords Quinazolinone derivatives ꢀ
Antitubercular activity ꢀ Pyrazole derivatives
Introduction
Tuberculosis is one of the serious health problems with a
wide variety of manifestations caused by Mycobacterium
tuberculosis, and as per the recent report, it has been
estimated that approximately onethird of the world’s pop-
ulation is infected with this microorganism. The treatment
of mycobacterial infections, especially the tuberculosis, has
H3
C
N
O
C6H4-p-CH3
O
O
N
U. Pandit (&) ꢀ A. Dodiya
S
NH2
N
CH3
Research & Development Division, Cadila Pharmaceuticals
Limited, Ahmedabad, India
e-mail: unnat.pandit@cadilapharma.co.in
N
F3C
Methaqualone
Celecoxib
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Med Chem Res (2013) 22:3364–3371
3365
Pyrazole derivatives are known to possess wide spec-
trum of pharmacological properties such as antibacterial
(Aggarwal et al., 2006), antifungal (Deohate et al., 2004),
antidiabetic (Kees et al., 1996), herbicidal (Meazza et al.,
2004), antitumor (Park et al., 2005) antianxiety (Wustrow
et al., 1998), and as active pharmacophore in celecoxib (as
COX-2 inhibitor) (Habeeb et al., 2001) and sildenafil cit-
rate (Martel et al., 1997) (as cGMP-specific phosphodies-
terase-type 5 inhibitor), etc. Pyrazoles play an essential role
in biological active compounds and therefore represent an
interesting template for medicinal chemistry.
and Ar–H - stretching vibrations. The absorption peak at
2,916 cm-1 is due to the stretching vibration of active
methylene group and the absorption peak at 2,860 cm-1 is
due to the stretching vibration of –CH3 group. The strong
absorption at 1,695 cm-1 is due to the [C=O stretching
vibration. The moderate intensity absorption at 1,601 and
1,590 cm-1 corresponds to a [C=N– stretching vibration.
The 1,533, 1,449 cm-1 absorptions are due to the skeleton
vibration of the aryl and heterocyclic rings. The vibrations
at 1,460 and 1,452 cm-1 are due to the bending vibration
of methyl and active methylene groups, respectively. The
absorption peak at 845 cm-1 is due to the chlorine atom,
the proton of which is present in pyrazole nucleus appeared
as a singlet at d = 8.43 ppm. The proton of the methyl
group appeared as a singlet at d = 2.43 ppm . The proton
attached at the nearest position of nitrogen atom in pyridine
ring appeared as a doublet at d = 8.75 ppm. The proton of
the =CH group appeared as a single at d = 8.20 ppm. The
chemical shifts of the final compound carbons vary from
d = 166.7 to 21.3 ppm. The carbon nuclei under the
influence of a strong electronegative environment appeared
downfield. The carbons of the pyrazole ring appeared
between d = 114.0 and 133.3 ppm. The carbon attached
with electronegative chloro atom appeared at d =
132.1 ppm. The carbon of the methylene group appear at
d = 143.3 ppm. The carbon of the carbonyl group which is
present in quinazolinone ring appeared as d = 166.7 ppm.
Moreover, the mass spectrum of (5a) showed a molecular
ion peak at m/z = 516.98 (M?), corresponding to a
molecular formula C30H21ClN6O.
Celecoxib contains pyrazole nucleus and is a sulfa
nonsteroidal anti-inflammatory drug (NSAID) and selec-
tive COX-2 inhibitor used in the treatment of osteoarthritis,
rheumatoid arthritis, acute pain, painful menstruation, and
menstrual symptoms, and to reduce numbers of colon and
rectum polyps in patients with familial adenomatous pol-
yposis. While Methaqualone contains quinazolinone
nucleus and is a sedative–hypnotic drug that produces
effect similar to barbiturates, a general central nervous
system depressant. The sedative–hypnotic activity was first
noted by Indian researchers in the 1950s, and in 1962,
methaqualone itself was patented in the U.S. by Wallace
and Tiernan.
Looking to the medicinal importance of 4(3H)-qui-
nazolinone and pyrazole, we report in this article the
synthesis of new class of heterocyclic molecules in which
all of these moieties are present and try to develop
potential bioactive molecules. The structures of the
compounds synthesized were assigned on the basis of
1
elemental analysis, IR, H NMR, 13C NMR , and Mass
spectral data. These compounds were evaluated for their
antitubercular activity.
Structure activity relationship
The structure–activity relationships (SARs) of compounds
(5a–l) were determined on the basis of results presented in
Table 1. SAR studies revealed that the presence of pyrazole
and quinazolinone was essential for a broad range of anti-
tubercular activity. From activity data, it is clear that final
compounds containing ortho-directing substitutions of
chloro, methyl, and methoxy in basic skeleton led to increase
in antitubercular activity. Compound 5a containing
2-Cl group showed excellent inhibition of 96 at MIC =
\6.25 lg/mL; compound 5d containing 2-CH3 group
showed excellent inhibition of 94 at MIC = \6.25 lg/mL
and compound 5g containing 2-OCH3 group showed excel-
lent inhibition of 93 at MIC = \6.25 lg/mL as compared
with the standard isoniazide having excellent inhibition of 99
at MIC = \6.25 lg/mL. The compound 5c containing 4-Cl
group showed excellent inhibition of 93 at MIC = \6.25
and compound 5k containing 3-NO2 group showed excellent
inhibition of 92 at MIC = \6.25 lg/mL. In general, com-
pounds containing electron- releasing groups, such as –CH3
and –OCH3 groups at ortho position and electro negative
Results and discussion
Synthesis
The synthetic pathway to obtain the intermediate and target
compounds in this study is depicted in Scheme 1. p-Methyl
phenyl hydrazine (starting compound-1) reacted with
1-(Pyridin-4-yl)ethanone by using methanol as solvent at
RT for 10 h to produce intermediate compound-2, which
on further treatment with DMF and POCl3 with constant
stirring at 100 °C produced intermediate-(3) compound.
Compound-(3) is reacted with different (4a–l) by ZnCl2 as
a catalyst and 1,4-dioxan as a solvent to produce final
compounds (5a–l) having good- to- excellent yields. The
final compound 5a was characterized using IR and
1H-NMR, 13C-NMR, and Mass spectra. IR spectra showed
that absorption bands at 3,065, 3,052 cm-1 ranges showed
multiple weak absorption peaks corresponding to Qu–H-
123

3366
Med Chem Res (2013) 22:3364–3371
CH3
NH
R1
CHO
R1
COCH3
NHNH2
O
N
H2N
N
100oC
N
RT,10h
+
+
N
CH3OH
DMF/POCl3
N
(1b)
R-C6H4
N
CH3
(4a-l)
(1a)
ZnCl2
(2)
(3)
CH3
CH3
1,4-dioxan
R1
N
H3C
N
O
CH
N
N
R = Different substituents
1 = Pyridine
R-C6H4
N
R
(5a-l)
Scheme 1 Synthetic route of the title compounds (5a–l)
Table 1 In vitro antitubercular screening data (5a–l)
H37Rv at lower concentrations to determine the actual
minimum inhibitory concentration (MIC).The actual MIC of
compounds 5a, 5c, 5d, 5g, and 5k are\3.125.
Sr. Compound
no. no.
R
Primary screening
Secondary
screening
MIC
Inhibition Actual
(lg/mL) (%)
MIC (lg/
mL)
Experimental part
1
2
3
4
5
6
7
8
9
5a
5b
5c
5d
5e
5f
2-Chlorophenyl
3-Chlorophenyl
4-Chlorophenyl
2-Methylphenyl
3-Methylphenyl
4-Methylphenyl
2-Methoxyphenyl
3-Methoxyphenyl
4-Methoxyphenyl
2-Nitrophenyl
\6.25
[6.25
\6.25
\6.25
[6.25
[6.25
\6.25
[6.25
[6.25
[6.25
\6.25
[6.25
\6.25
96
68
90
94
70
67
93
64
59
73
92
67
99
\3.125
–
Materials and methods
\3.125
\3.125
All reactions except those in aqueous media were carried
out by standard techniques for the exclusion of moisture.
Melting points were determined on an electrothermal
melting point apparatus and were reported uncorrected.
TLC on silica gel plates (Merck, 60, F254) was used
for purity checking and reaction monitoring. Column
chromatography on silica gel (Merck, 70–230 and
230–400 mesh ASTH for flash chromatography) was
applied when necessary to isolate and purify the reaction
products. Elemental analysis (% C, H, N) was carried out
by a Perkin-Elmer 2400 CHN analyzer. IR spectra of all
compounds were recorded on a Perkin-Elmer FT-IR
spectrophotometer in KBr. 1H NMR spectra were recorded
on Varian Gemini 300 MHz and 13C NMR spectra on
Varian Mercury-400, 100 MHz in DMSO-d6 as a solvent
and tetramethylsilane (TMS) as an internal standard. Mass
spectra were scanned on a Shimadzu LCMS 2010 spec-
trometer. Anhydrous reactions were carried out in an oven-
dried glassware in nitrogen atmosphere.
–
–
5g
5h
5i
\3.125
–
–
10 5j
–
11 5k
12 5l
3-Nitrophenyl
\3.125
–
4-Nitrophenyl
Isoniazide
0.125
group –Cl at ortho and para positions led to increase in
activity, while electro negative group at meta position led to
increased activity. owing to bulky group, ring strain
increased and made compound less stable and active. In
general, compounds come out as compounds exhibiting
more noteworthy antitubercular activity. Compounds dem-
onstrating at least 90 % inhibition in the primary screen
(MIC \ 6.25 ug/mL) are re-tested against M. tuberculosis
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Med Chem Res (2013) 22:3364–3371
3367
13C NMR (DMSO) d (ppm): 21.5, 114.0, 119.3, 121.5,
129.3, 129.7, 133.2, 135.6, 136.3, 140.2, 149.8, 185.3. MS :
m/z 263.29 (M?). Anal. calcd for C16H13N3O: C 72.99, H
4.98, N 15.96. Found C 73.08, H 4.92, N 16.03.
Methods of preparation and physical data
of synthesized compounds (2 to 5a–l)
4-(1-(2-(p-Tolyl)hydrazono)ethyl)pyridine (2)
To a solution of compound-(I) (0.01 mol) in methanol
(50 mL) was added the same amount of 1-(pyridin-4-yl)
ethanone (0.01 mol) with stirring and refluxed for 10 h;
after the completion of reaction, it was cooled and distilled
the excess solvent was distilled and it was poured into iced-
cold water. The resulting light brown color product was
obtained. The completion of the reaction was checked by
TLC [n-hexane/ethyl acetate (V/V = 1:3)]. The crude
product was recrystallized from 95 % ethanol to give the
intermediate compound-(II).
3-Amino-2-(substituted-phenyl)quinazolin-4(3H)-one
(4a–l)
The compounds (4a–l) were synthesized by method
described in literature (Siddappa et al., 2008).
General procedure for the synthesis of 2-(substituted-
phenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-pyrazol-4-
yl)methylene)amino)-quinazolin-4(3H)-ones (5a–l)
Yield: 89 %; m.p.: 170–172 °C; IR (KBr) mmax/cm-1
:
A solution of compound-3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazole-4-carbaldehyde (3) (0.01 mol) in 1,4-dioxan
(30 mL) was mixed with 3-amino-2-(substituted-phenyl)
quinazolin-4(3H)-one (4a–l). The reaction mixture was
stirred vigorously at 90 °C temperature for 1 h and then
add catalytic amount of fused ZnCl2 as a catalyst in it.
Then the mixture was refluxed for 4–5 h after the com-
pletion of reaction,it was cooled, excess solvent was dis-
tilled and then poured it into iced-cold water. The resulting
light brown color product was obtained. The completion of
the reaction was checked by TLC [n-hexane/ethyl acetate
(V/V = 1:3)]. The crude product was recrystallized from
95 % ethanol to give the final compounds-(5a–l).
3412 (–NH stretching), 3060, 3053 (C–H, aromatic), 2860,
2854 (–CH3 stretching), 1605, 1592 (C=N), 1537, 1444
1
(C=C), 1458, 1452 (–CH3 bending); H NMR (DMSO) d
(ppm): 2.34 (s, 3H, –CH3 group), 2.95 (s, 3H, C–CH3
group), 6.51–6.98 (m, 4H, Ar–H), 7.1 (s, 1H, –NH), 7.74
(d, 2H, J = 7.5 Hz, –N = CH–CH), 8.66 (d, 2H, N=CH–);
13C NMR (DMSO) d (ppm): 17.0, 21.3, 116.2, 124.1,
129.8, 131.2, 138.4, 149.4, 168.8. MS : m/z 225.29 (M?).
Anal. calcd for C14H15N3: C 74.64, H 6.71, N 18.64. Found
C 74.72, H 6.80, N 18.72.
3-(Pyridin-4-yl)-1-(p-tolyl)-1H-pyrazole-4-carbaldehyde
(3)
Dry N,N0-dimethylformamide (10.16 mol, 0.742 g) was
cooled to 0 °C in an inert atmosphere round- bottom flask,
and POCl3 (50.84 mol, 7.77 g) was added slowly under
stirring over 15–20 min, and stirring was continued for
another 15 min at the same temperature. To this mixture,
intermediate compound (2) (4-(1-(2-(p-tolyl)hydrazon-
o)ethyl)pyridine) (3.38 mol, 1 g) was added as solid
directly. The resulting reaction mixture was refluxed for
2 h at 100 °C in an oil-bath. After completion of the
reaction by TLC, the reaction mixture was poured onto
the crushed ice, neutralized with saturated NaHCO3; the
product obtained was filtered, washed with water and dried.
Purification of the crude product by column chromatogra-
phy on silica gel eluting with ethyl acetate/chloroform (3:7)
gave rise to pyrazole aldehyde (3) as a white solid.
2-(2-Chlorophenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5a)
Yield: 68 %; m.p.: 198–200 °C; IR (KBr) mmax/cm-1
:
3065, 3052 (C–H, aromatic), 2916 (=CH stretching), 2860
(–CH3 stretching), 1695 (C=O), 1601, 1590 (C=N), 1533,
1449 (C=C), 1460 (=CH bending), 1452 (–CH3 bending),
1
845 (C–Cl stretching); H NMR (300 MHz, DMSO-d6, d,
ppm): 2.34 (s, 3H, CH3), 8.20 (s, 1H, N=CH), 8.43 (s, 1H,
=CH–N), 7.99–8.75 (m, 4H, Pyridine-H), 7.40-8.03 (m,
12H, Ar–H); 13C NMR (100 MHz, DMSO-d6, d, ppm):
21.3, 114.0, 119.2, 119.4, 121.3, 121.9, 126.5, 121.8,
123.0, 126.6, 126.9, 127.3, 129.2, 129.6, 130.1, 131.5,
132.1, 132.3, 133.3, 133.5, 135.9, 136.7, 140.3, 143.3,
148.7, 149.6, 149.9, 153.6, 166.7. LCMS (m/z): 516.5
(M?); Anal. Calcd. For C30H21ClN6O: C-69.70, H-4.09,
N-16.26; Found: C-69.77, H-4.15, N-16.32 %.
Yield: 80 %; m.p.: 186–188 °C; IR (KBr) mmax/cm-1
:
3078, 3062 (C–H, aromatic), 2941 (–CH stretching, –CHO
group), 1680 (C=O stretching), 1609, 1588 (C=N stretch-
ing), 1562, 1440 (C=C, benzene ring), 1459 (–CH bendin–
CH3 group) 696 (mono substituted benzene ring). 1H NMR
(DMSO) d (ppm): 2.34 (s, 3H, –CH3 group), 7.42–7.50 (m,
4H, Ar–H), 7.99 (d, 2H, J = 7.7 Hz, –N=CH–CH), 8.43 (s,
1H, pyra-H), 8.75 (d, 2H, N=CH–). 9.73 (s, 1H, –CH=O),
2-(3-Chlorophenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5b)
Yield: 72 %; m.p.: 194–196 °C; IR (KBr) mmax/cm-1
3063, 3056 (C–H, aromatic), 2912 (=CH stretching), 2866
:
123

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Med Chem Res (2013) 22:3364–3371
3-(((3-(Pyridin-4-yl)-1-(p-tolyl)-1H-pyrazol-4-yl)
methylene)amino)-2-(m-tolyl)quinazolin-4(3H)-one (5e)
(–CH3 stretching), 1691 (C=O), 1576, 1593 (C=N), 1535,
1446 (C=C), 1463 (=CH bending), 1450 (–CH3 bending),
1
849 (C–Cl stretching); H NMR (300 MHz, DMSO-d6, d,
Yield: 67 %; m.p.: 221–222 °C; IR (KBr) mmax/cm-1
:
ppm): 2.36 (s, 3H, CH3), 8.23 (s, 1H, N=CH), 8.47 (s, 1H,
=CH–N), 7.97–8.73 (m, 4H, Pyridine-H), 7.46–8.06 (m,
12H, Ar–H); 13C NMR (100 MHz, DMSO-d6, d, ppm):
21.1, 114.2, 119.3, 119.5, 121.3, 121.6, 126.1, 126.6,
121.7, 126.8, 127.3, 129.3, 129.6, 130.0, 130.3, 130.6,
133.5, 133.6, 134.4, 135.8, 136.7, 140.3, 143.3, 148.6,
149.7, 149.9, 153.6, 166.9.LCMS (m/z): 516.5 (M?); Anal.
Calcd. For C30H21ClN6O: C-69.70, H-4.09, N-16.26;
Found: C-69.78, H-4.16, N-16.34 %.
3064, 3052 (C–H, aromatic), 2919 (=CH stretching), 2864,
2873 (–CH3 stretching), 1694 (C=O), 1573, 1592 (C=N),
1533 (C=C), 1452, 1458 (–CH3 bending), 856 (C–Cl
1
stretching); H NMR (300 MHz, DMSO-d6, d, ppm): 2.35
(s, 3H, p-CH3), 2.41 (s, 3H, m-CH3), 8.22 (s, 1H, N=CH),
8.45 (s, 1H, =CH–N), 7.96–8.79 (m, 4H, Pyridine-H), 7.41-
8.03 (m, 12H, Ar–H); 13C NMR (100 MHz, DMSO-d6, d,
ppm): 18.9, 21.3, 114.5, 119.3, 119.7, 121.4, 121.7, 126.5,
121.8, 125.2, 126.3, 126.6, 127.3, 128.5, 128.7, 129.2,
129.6, 130.4, 133.3, 133.5, 135.9, 136.7, 138.5, 140.0,
143.2, 148.7, 149.7, 149.9, 153.5, 166.7.; LCMS (m/z):
496.56 (M?); Anal. Calcd. For C31H24N6O: C-74.98,
H-4.87, N-16.92; Found: C-74.93, H-4.96, N-16.97 %.
2-(4-Chlorophenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5c)
Yield: 68 %; m.p.: 202–203 °C; IR (KBr) mmax/cm-1
:
3069, 3058 (C–H, aromatic), 2920 (=CH stretching), 2858
(–CH3 stretching), 1698 (C=O), 1572, 1596 (C=N), 1531,
1443 (C=C), 1460 (=CH bending), 1448 (–CH3 bending),
3-(((3-(Pyridin-4-yl)-1-(p-tolyl)-1H-pyrazol-4-yl)
methylene)amino)-2-(p-tolyl)quinazolin-4(3H)-one (5f)
1
Yield: 74 %; m.p.: 216–217 °C; IR (KBr) mmax/cm-1
:
843 (C–Cl stretching); H NMR (300 MHz, DMSO-d6, d,
ppm): 2.37 (s, 3H, CH3), 8.26 (s, 1H, N=CH), 8.47 (s, 1H,
=CH–N), 7.94–8.71 (m, 4H, Pyridine-H), 7.37–8.03 (m,
12H, Ar–H); 13C NMR (100 MHz, DMSO-d6, d, ppm):
21.5, 114.1, 119.4, 119.6, 121.6, 121.9, 126.6, 121.8,
126.6, 127.3, 128.9, 129.1, 129.4, 129.6, 133.3, 133.5,
135.6, 135.9, 136.7, 140.4, 143.4, 148.7, 149.4, 149.8,
153.6, 165.1, 166.6; LCMS (m/z): 516.5 (M?); Anal.
Calcd. For C30H21ClN6O: C-69.70, H-4.09, N-16.26;
Found: C-69.76, H-4.17, N-16.34 %.
3062, 3054 (C–H, aromatic), 2915 (=CH stretching), 2855,
2869 (–CH3 stretching), 1696 (C=O), 1570, 1591 (C=N),
1532, 1449 (C=C), 1458, 1449 (–CH3 bending), 847 (C–Cl
stretching); 1H NMR (300 MHz, DMSO-d6, d, ppm): 2.34,
2.39 (s, 6H, p-CH3), 8.24 (s, 1H, N=CH), 8.41 (s, 1H,
=CH–N), 7.95–8.72 (m, 4H, Pyridine-H), 7.36-8.09 (m,
12H, Ar–H); 13C NMR (100 MHz, DMSO-d6, d, ppm):
21.1, 21.5, 114.2, 119.1, 119.5, 121.3, 121.7, 126.5, 121.9,
126.6, 127.3, 129.2, 129.4, 129.6, 130.3, 133.3, 133.5,
135.7, 136.8, 139.8, 140.6, 143.3, 148.4, 149.2, 149.7,
153.2, 166.4; LCMS (m/z): 496.56 (M?); Anal. Calcd. For
C31H24N6O: C-74.98, H-4.87, N-16.92; Found: C-74.90,
H-4.95, N-16.99 %.
3-(((3-(Pyridin-4-yl)-1-(p-tolyl)-1H-pyrazol-4-yl)
methylene)amino)-2-(o-tolyl)quinazolin-4(3H)-one (5d)
Yield: 68 %; m.p.: 198–200 °C; IR (KBr) mmax/cm-1
:
2-(2-Methoxyphenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5g)
3064, 3053 (C–H, aromatic), 2910 (=CH stretching), 2860,
2868 (–CH3 stretching), 1689 (C=O), 1578, 1593 (C=N),
1536, 1440 (C=C), 1464 (=CH bending),1458, 1450 (–CH3
bending), 851 (C–Cl stretching); 1H NMR (300 MHz,
DMSO-d6, d, ppm): 2.34 (s, 3H, p-CH3), 2.48 (s, 3H, o-
CH3), 8.20 (s, 1H, N=CH), 8.43 (s, 1H, =CH–N), 7.99–8.75
(m, 4H, Pyridine-H), 7.40–8.03 (m, 12H, Ar–H); 13C NMR
(100 MHz, DMSO-d6, d, ppm): 18.9, 21.7, 114.4, 119.6,
121.6, 121.9, 126.7, 121.8, 125.8, 126.6, 127.3, 127.7,
129.2, 129.8, 130.0, 130.2, 131.5, 133.3, 133.5, 135.9,
136.7, 138.1, 140.3, 143.5, 148.7, 149.3, 149.7, 153.6,
166.3; LCMS (m/z): 496.56 (M?); Anal. Calcd. For
C31H24N6O: C-74.98, H-4.87, N-16.92; Found: C-74.92,
H-4.94, N-16.98 %.
Yield: 70 %; m.p.: 243–245 °C; IR (KBr) mmax/cm-1
:
3071, 3064 (C–H, aromatic), 2923 (=CH stretching), 2882
(–OCH3 stretching), 2861 (–CH3 stretching), 1692 (C=O),
1579, 1592 (C=N), 1530 (C=C), 1463, 1449 (–OCH3
bending), 1460 (=CH bending), 1454 (–CH3 bending), 854
(C–Cl stretching); 1H NMR (300 MHz, DMSO-d6, d,
ppm): 3.83 (s, 3H, –OCH3), 2.34 (s, 3H, CH3), 8.20 (s, 1H,
N=CH), 8.47 (s, 1H, =CH–N), 7.99–8.77 (m, 4H, Pyridine-
H), 7.26–8.05 (m, 12H, Ar–H); 13C NMR (100 MHz,
DMSO-d6, d, ppm): 21.4, 55.8, 106.2, 111.4, 114.3, 119.2,
119.4, 121.0, 121.2, 121.8, 125.1, 126.5, 121.5, 126.6,
127.4, 129.2, 129.6, 131.1, 133.7, 133.5, 135.9, 136.7,
123

Med Chem Res (2013) 22:3364–3371
3369
140.3, 143.3, 148.6, 149.5, 149.7, 153.2, 157.4, 166.9;
LCMS (m/z): 512.5 (M?); Anal. Calcd. For C31H24N6O2:
C-72.64, H-4.72, N-16.40; Found: C-72.72, H-4.79,
N-16.49 %.
symmetric stretching), 847 (C–Cl stretching); 1H NMR
(300 MHz, DMSO-d6, d, ppm): 2.39 (s, 3H, CH3), 8.23 (s,
1H, N=CH), 8.48 (s, 1H, =CH–N), 7.97–8.79 (m, 4H,
Pyridine-H), 7.59–8.09 (m, 12H, Ar–H); 13C NMR
(100 MHz, DMSO-d6, d, ppm): 21.2, 114.7, 119.1, 119.5,
120.3, 121.0, 121.5, 124.1, 126.5, 121.8, 126.6, 127.3,
129.2, 129.6, 131.0, 131.9, 133.3, 133.5, 134.9, 135.9,
136.7, 140.3, 143.3, 147.0, 148.7, 149.4, 149.6, 153.7,
166.3; LCMS (m/z): 527.53 (M?); Anal. Calcd. For
C30H21N7O3: C-68.30, H-4.01, N-18.59; Found: C-68.37,
H-4.08, N-18.66 %.
2-(3-Methoxyphenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5h)
Yield: 73 %; m.p.: 247–249 °C; IR (KBr) mmax/cm-1
:
3077, 3059 (C–H, aromatic), 2926 (=CH stretching), 2885
(–OCH3 stretching), 2863 (–CH3 stretching), 1694 (C=O),
1573, 1596 (C=N), 1535 (C=C), 1464 (–OCH3 bending),
1458 (=CH bending), 1452 (–CH3 bending), 855 (C–Cl
2-(3-Nitrophenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5k)
1
stretching); H NMR (300 MHz, DMSO-d6, d, ppm): 3.85
(s, 3H, –OCH3), 2.32 (s, 3H, CH3), 8.25 (s, 1H, N=CH),
8.43 (s, 1H, =CH–N), 7.95–8.75 (m, 4H, Pyridine-H),
7.05–8.1 (m, 12H, Ar–H); 13C NMR (100 MHz, DMSO-d6,
d, ppm): 21.2, 55.2, 110.2, 114.3, 115.7, 119.0, 119.2,
120.5, 121.2, 121.9, 126.5, 121.8, 126.6, 127.3, 129.2,
129.5, 129.7, 129.9, 133.3, 133.5, 135.9, 136.7, 140.3,
143.3, 148.5, 149.3, 149.7, 153.0, 160.8, 166.6.; LCMS (m/
z): 512.5 (M?); Anal. Calcd. For C31H24N6O2: C-72.64,
H-4.72, N-16.40; Found: C-72.71, H-4.80, N-16.48 %.
Yield: 67 %; m.p.: 141–143 °C; IR (KBr) mmax/cm-1
:
3067, 3058 (C–H, aromatic), 2932 (=CH stretching), 2869
(–CH3 stretching), 1696 (C=O), 1574, 1598 (C=N), 1555
(–NO2 gp, asymmetric stretching), 1533, 1444 (C=C), 1461
(=CH bending), 1457 (–CH3 bending), 1324 (–NO2 gp,
symmetric stretching), 844 (C–Cl stretching); 1H NMR
(300 MHz, DMSO-d6, d, ppm): 2.37 (s, 3H, CH3), 8.26 (s,
1H, N=CH), 8.46 (s, 1H, =CH–N), 7.94–8.82 (m, 4H,
Pyridine-H), 7.42–8.12 (m, 12H, Ar–H); 13C NMR
(100 MHz, DMSO-d6, d, ppm): 21.1, 114.3, 119.2, 119.5,
119.7, 121.4, 121.9, 125.4, 126.5, 121.6, 126.6, 127.3,
129.0, 129.3, 129.5, 129.9, 133.3, 133.5, 134.3, 135.7,
136.4, 140.3, 143.3, 148.0, 148.4, 149.3, 149.6, 153.9,
166.4; LCMS (m/z): 527.53 (M?); Anal. Calcd. For
C30H21N7O3: C-68.30, H-4.01, N-18.59; Found: C-68.38,
H-4.09, N-18.68 %.
2-(4-Methoxyphenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5i)
Yield: 68 %; m.p.: 237–239 °C; IR (KBr) mmax/cm-1
:
3074, 3063 (C–H, aromatic), 2929 (=CH stretching), 2877
(–OCH3 stretching), 2866 (–CH3 stretching), 1697 (C=O),
1574, 1597 (C=N), 1534, 1442 (C=C), 1466 (–OCH3
bending), 1460 (=CH bending), 1457 (–CH3 bending), 858
(C–Cl stretching); 1H NMR (300 MHz, DMSO-d6, d,
ppm): 3.87 (s, 3H, –OCH3), 2.33 (s, 3H, CH3), 8.22 (s, 1H,
N=CH), 8.47 (s, 1H, =CH–N), 7.92–8.79 (m, 4H, Pyridine-
H), 7.20–8.12 (m, 12H, Ar–H); 13C NMR (100 MHz,
DMSO-d6, d, ppm): 21.4, 55.8, 114.2, 114.5, 119.2, 119.4,
121.2, 121.7, 126.6, 121.6, 126.5, 127.3, 129.2, 129.5,
131.1, 133.3, 133.5, 135.7, 136.6, 140.1, 143.3, 148.7,
149.4, 149.7, 153.4, 159.4, 166.7; LCMS (m/z): 512.5
(M?); Anal. Calcd. For C31H24N6O2: C-72.64, H-4.72,
N-16.40; Found: C-72.73, H-4.81, N-16.47 %.
2-(4-Nitrophenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5l)
Yield: 69 %; m.p.: 156–157 °C; IR (KBr) mmax/cm-1
:
3061, 3053 (C–H, aromatic), 2932 (=CH stretching), 2864
(–CH3 stretching), 1698 (C=O), 1576, 1598 (C=N), 1558
(–NO2 gp, asymmetric stretching), 1539, 1445 (C=C), 1460
(=CH bending), 1452 (–CH3 bending), 1326 (–NO2 gp,
symmetric stretching), 853 (C–Cl stretching); 1H NMR
(300 MHz, DMSO-d6, d, ppm): 2.32 (s, 3H, CH3), 8.27 (s,
1H, N=CH), 8.44 (s, 1H, =CH–N), 7.93–8.75 (m, 4H,
Pyridine-H), 7.63–8.13 (m, 12H, Ar–H); 13C NMR
(100 MHz, DMSO-d6, d, ppm): 21.7, 55.9, 114.1, 114.4,
119.0, 119.4, 121.3, 121.7, 126.5, 121.6, 126.6, 127.1,
129.2, 129.4, 131.1, 133.3, 133.4, 135.6, 136.7, 140.0,
143.3, 148.8, 149.2, 149.6, 153.5, 159.4, 162.0, 166.2.;
LCMS (m/z): 527.53 (M?); Anal. Calcd. For C30H21N7O3:
C-68.30, H-4.01, N-18.59; Found: C-68.39, H-4.07,
N-18.67 %.
2-(2-Nitrophenyl)-3-(((3-(pyridin-4-yl)-1-(p-tolyl)-1H-
pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one (5j)
Yield: 63 %; m.p.: 134–136 °C; IR (KBr) mmax/cm-1
:
3068, 3054 (C–H, aromatic), 2924 (=CH stretching), 2867
(–CH3 stretching), 1690 (C=O), 1577, 1593 (C=N), 1550
(–NO2 gp, asymmetric stretching), 1536, 1440 (C=C), 1465
(=CH bending), 1453 (–CH3 bending), 1328 (–NO2 gp,
123

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Med Chem Res (2013) 22:3364–3371
Acknowledgment The authors are thankful to Cadila Pharmaceu-
ticals Limited, Dholka, Ahmedabad for providing research and library
facilities.
Biological activity
In vitro evaluation of the antitubercular activity was carried
out at the Tuberculosis Acquisition Antimicrobial Coordi-
nating Facility (TAACF) screening program, Alabama,
USA. Minimum inhibitory concentration (MIC) was
determined against M. tuberculosis H37Rv using the
radiometric BACTEC (Collins and Franzblau, 1997) and
broth dilution (Suling et al., 2000) assay methods. The
result of antitubercular activity is presented in Table 1. The
activity is considerably affected by substitutions at the
phenyl ring of the pyrazole–quinazolinone nucleus. For the
antitubercular activity, isoniazide is taken as a standard,
which showed a percentage inhibition of 99 at an MIC
range of below 6.25 lg/mL. It has been observed that
compounds 5a, 5d, and 5g having chloro, methyl, and
methoxy group at second position, showed excellent anti-
tubercular activity with percentage inhibition of 96, 94, and
93, respectively at an MIC range below 6.25 lg/mL,
whereas compound 5c having chloro group at para posi-
tion, and compound 5k having nitro group at meta position
showed excellent antitubercular activity with percentage
inhibitions of 90 and 92, respectively, at the same MIC
range. The presence of same substituent at any other
position of phenyl ring remarkably reduced the antituber-
cular activity. Compounds demonstrating at least 90 %
inhibition in the primary screen (MIC \ 6.25 ug/mL) are
re-tested against M. tuberculosis H37Rv at lower concen-
trations to determine the actual minimum inhibitory con-
centration (MIC). The actual MIC of compounds 5a, 5c,
5d, 5g, and 5k are \3.125.
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In summary, we have developed a new, efficient and
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1H-pyrazol-4-yl)methylene)amino)-quinazolin-4(3H)-one
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