Antioxidant and antibacterial studies of arylazopyrazoles and arylhydrazonopyrazolones containing coumarin moiety

Article abstract of DOI:10.1016/j.ejmech.2009.07.004

A series of novel 1-(4-methylcoumarinyl-7-oxyacetyl)-3,5-dimethyl-4(arylazo)pyrazoles and 1-(4-methylcoumarinyl-7-oxyacetyl)-3-methyl-4-(substituted phenyl) hydrazono-2-pyrazolin-5-ones were synthesised and evaluated for antibacterial and antioxidant acti

Full text of DOI:10.1016/j.ejmech.2009.07.004

European Journal of Medicinal Chemistry 44 (2009) 4690–4694
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Antioxidant and antibacterial studies of arylazopyrazoles and
arylhydrazonopyrazolones containing coumarin moiety
*
P. Manojkumar , T.K. Ravi, S. Gopalakrishnan
Department of Pharmaceutical Chemistry, College of Pharmacy, Sri Ramakrishna Institute of Paramedical Sciences, 395 Sarojini Naidu Road, Coimbatore 641044, Tamilnadu, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A
series of novel 1-(4-methylcoumarinyl-7-oxyacetyl)-3,5-dimethyl-4(arylazo)pyrazoles and 1-(4-
Received 4 November 2008
Received in revised form
2 July 2009
Accepted 9 July 2009
Available online 16 July 2009
methylcoumarinyl-7-oxyacetyl)-3-methyl-4-(substituted phenyl) hydrazono-2-pyrazolin-5-ones were
synthesised and evaluated for antibacterial and antioxidant activities. Compounds 3b, 3g, 5b, 5d and 5g
showed good antibacterial activity and compound 5e was found to be the most active antioxidant in the
series, and thus represent a new class of promising lead compounds.
Ó 2009 Elsevier Masson SAS. All rights reserved.
Keywords:
Antioxidant
Antibacterial
Pyrazole
1. Introduction
hydrazono and azo group has been reported to enhance the bio-
logical activity of heterocyclic compounds [9].
The active interest in coumarin compounds can be attributed to
their potent gram-positive antibacterial activity and especially the
sensitivity of methicillin-resistant strains of Staphylococcus to
coumarin antibiotics [1]. The coumarin nucleus incorporates the
styryl carbonyl moiety into a rigid framework, the presence of
which in coumarin is expected to affect the scavenging of reactive
substances derived from oxygen and influence the process
involving free radical mediated injury [2].
Keeping in view the biological importance of arylhy-
drazonogroup, arylazogroup, pyrazolones, pyrazoles and coumarin
nucleus, design of arylazopyrazoles and arylhydrazonopyrazolones
containing coumarin moiety was carried out. This was followed by
the synthesis of target compounds and their in vitro antibacterial
and antioxidant screening. The results of antibacterial and antiox-
idant activities are discussed in this paper.
Pyrazoles gained much attention as antimicrobial agents after
the discovery of natural pyrazole C-glycoside pyrazofurin which
showed broad spectrum antimicrobial activity [3]. Oxidised LDLs
play a prominent role in the preliminary stages of atherosclerosis
[4]. Literature review reveals the importance of pyrazoles as anti-
oxidants by inhibiting the oxidation of LDL [5].
Pyrazolin-5-one derivative, 3-methyl-1-phenyl-2-pyrazolin-5-
one has been reported to be a promising candidate for the treat-
ment of neonatal hypoxic-ischemic encephalopathy [6] and
paraquat poisoning [7] due to its free radical scavenging activity.
Pyrazolones are associated with broad spectrum of biological
activities including antimicrobial activity [8]. Incorporation of
2. Chemistry
4-Methylcoumarinyl-7-oxyaceticacid hydrazide (1) was
prepared from 4-methyl-7-hydroxy coumarin according to the
literature method [10]. 1,3-Diketo-1,3-dimethyl-2-(arylazo)pro-
pane 2a–g was prepared from substituted phenyl diazonium salts
and acetylacetone by Japp–Klingermann reaction [11]. Ethyl-2-
(substituted phenyl)hydrazono-3-oxobutyrate 4a–g was prepared
from substituted phenyl diazonium salts and ethylacetoacetate by
Japp–Klingermann reaction [9,12]. 4-Methylcoumarinyl-7-oxy-
aceticacid hydrazide (1) when treated with 2a–g and 4a–g in glacial
acetic acid produced 1-(4-methylcoumarinyl-7-oxyacetyl)-3,
5-dimethyl-4 (arylazo)pyrazoles 3a–g and 1-(4-methylcoumarinyl-
7-oxyacetyl)-3-methyl-4-(substituted phenyl) hydrazono-2-pyr-
azolin-5-ones 5a–g respectively .The reaction sequences are
outlined in Scheme 1.
* Corresponding author. Tel.: þ91 9443932988.
E-mail address: kmano1975@rediffmail.com (P. Manojkumar).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.07.004

P. Manojkumar et al. / European Journal of Medicinal Chemistry 44 (2009) 4690–4694
4691
Scheme 1.
3. Pharmacology
3.2. Scavenging effect on 1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical [2,15]
3.1. Antibacterial studies
1.5 ml methanolic solution of the synthesized compounds
(0.2 mM) was added to 1.5 ml (0.2 mM) solution of DPPH radical in
methanol (final concentration of DPPH and synthesized
compounds was 0.1 mM). The mixture was shaken vigorously and
allowed to stand for 30 min. After this, the absorbance at 517 nm
was determined and the percentage of scavenging activity was
calculated using the formula shown below. Ascorbic acid was used
as the reference compound. All tests and analyses were undertaken
on three replicates and the results were averaged. The results are
given in Table 1.
The newly synthesised compounds 3a–g and 5a–g were
screened for their antibacterial activity against Staphylococcus
aureus (NCIM 5021) and Bacillus subtilis (NCIM 2010) by disc
diffusion method [13,14]. A standard inoculum (1–2 ꢀ107 c.f.u./ml
0.5 McFarland standards) was introduced on to the surface of sterile
agar plates, and a sterile cotton swab was used for even distribution
of the inoculum. The discs measuring 6.25 mm in diameter were
prepared from Whatman no.1 filter paper and sterilized by dry heat
at 140 ꢁC for 1 h. The sterile discs previously soaked in a known
concentration of the test compounds were placed in nutrient agar
medium. Solvent and growth controls were kept. The plates were
inverted and incubated for 24 h at 37 ꢁC. Ciprofloxacin was used as
a standard drug. Inhibition zones were measured and compared
with the controls. The bacterial zones of inhibition values are given
in Table 1.
Scavengingactivityð%Þ [ f½ðAb DAsÞ LAmꢂ=Abg3 100%
Ab: absorbance of 0.1 mM methanolic solution of DPPH at 517 nm,
As: absorbance of 0.1 mM methanolic solution of test compound at
517 nm, Am: absorbance of methanolic mixture of the drug and
DPPH at 517 nm.
Among the compounds from the pyrazole series: 3b showed
moderate antioxidant activity. Among the compounds from the
pyrazolin-5-one series, 5a, 5d and 5e exhibited moderate antioxi-
dant activity. The activity exhibited by the compound 5e was the
highest.
The results of antibacterial screening showed compounds 3b, 5b
and 5g to be moderatively active against S. aureus at 250 mcg/disc
concentration. Compounds 3g and 5b were found to be moder-
atively active and 3b, 5d and 5g to be significantly active against B.
subtilis at 250 mcg/disc concentration. Rest of the compounds did
not show antibacterial activity.
3.2.1. Structure–activity relationship
3.1.1. Structure–activity relationship
The effect of various substituents on the phenyl ring of pyrazoles
(3a–g) in producing antioxidant activity in the descending order
were found to be: p-Br (3b) > m-NO2 (3e) > p-NO2 (3c), p-Cl (3d),
p-COOH (3f) > o-COOH (3g) > o,p-(CH3)2 (3a). Structure activity
relationship studies shows that among pyrazoles having ring
deactivating substituents, the highest antioxidant activity was
obtained with substituent having highest lipophilicity, lowest
electron withdrawing power and highest polarisability (i.e., bromo
compound 3b). Among pyrazolones (5a–g), substituents exerting
antioxidant activity in descending order of potency were found to
Substitution of bromo group at the para position of phenyl ring
imparted moderate gram-positive antibacterial activity to the
resulting pyrazole (3b) and pyrazolone (5b) against S. aureus; with
increased lipophilicity of the substituent (i.e., dimethyl compounds
3a and 5a) this activity was lost. The presence of o-carboxy
substituent favoured antibacterial activity for resulting pyrazolone
(compound 5g) against B. subtilis; an increase in the lipophilicity
and polarisability of substituent (i.e., bromo compound 5b) resulted
in drastic decrease in this activity. On the other hand, replacement
of p-bromosubstituent (compound 3b) by o-carboxy substituent
(compound 3g) displayed a opposite effect on antibacterial activity
of resulting pyrazoles against B. subtilis. The importance of
stereochemistry of substituents in determining the antibacterial
activity against B. subtilis was evident from the activity exhibited by
o-carboxyphenyl derivatives (compounds 3g and 5g) where as the
p-carboxyphenyl derivatives (compounds 3f and 5f) were devoid of
this activity.
be:
m-NO2
(5e) > o,p-(CH3)2
(5a) > p-Cl
(5d) > p-NO2
(5c) > o-COOH (5g). Among o-substituted phenyl derivatives and
o,p-disubstituted phenyl derivatives of pyrazolones, highest anti-
oxidant activity was observed with substituent possessing highest
lipophilicity (i.e., dimethyl compound 5a). Considering the effect of
orientation of nitro group in the phenyl ring of pyrazoles and pyr-
azolones on antioxidant activity, it was observed that compounds

4692
P. Manojkumar et al. / European Journal of Medicinal Chemistry 44 (2009) 4690–4694
Table 1
d
2.49–2.51. A singlet at
azolone ring where as singlet at
uted to OCH2 protons and C4 proton of coumarin respectively. A
multiplet at 7.00–7.74 indicated the presence of aromatic protons
and singlet at 10.32 indicated the presence of NH proton.
d
3.36 represented methyl protons of pyr-
Zone of inhibition (mm) and scavenging activity (%) of compounds (3a–g and 5a–g).a
d
4.78 and 6.25 could be attrib-
d
Comp.
Staphylococcus aureus
Bacillus subtilis
Scavenging activity (%)
d
3a
3b
3c
3d
3e
3f
3g
5a
5b
5c
5d
5e
5f
–
–
24
55
32
32
38
32
28
57
–
31
53
69
–
12.7 ꢄ 0.6
27.0 ꢄ 1.7
d
–
–
–
–
–
–
–
–
–
–
Formation of pyrazolin-5-one was confirmed from mass spec-
trum of compound 5a which showed molecular ion peak at m/z
445.3 (M-1)þ in conformity with the molecular formula
C24H22N4O5. The other fragment ions obtained were m/z 287.2
(40%), 219.2 (84%) and 175.4 (100%).
16.7 ꢄ 1.5
–
13.7 ꢄ 0.6
14.0 ꢄ 1.0
Further confirmation for pyrazolin-5-one formation was
–
–
reached from 13C NMR spectrum which showed signals at
d
18.12
38.62–40.29 for methyl carbons attached to
pyrazolin-5-one and aromatic ring, 66.19 for OCH2 carbon,
101.62 for coumarin C8, 111.46–126.49 for aromatic carbons, C3,
C5 to C7, C9 and C10 of coumarin and pyrazolone C4, 153.36 for
pyrazolone C3, 154.46 for coumarin C4, 160.03 for coumarin C2,
160.55 for pyrazolone C5 and 166.14 for >N–C]O. The charac-
11.3 ꢄ 1.5
24.3 ꢄ 1.5
for CH3 of coumarin,
d
–
–
–
–
d
5g
Stdb
Stdc
12.3 ꢄ 0.6
30.0 ꢄ 1.7
–
26.7 ꢄ 1.5
33.7 ꢄ 1.2
–
20
–
96
d
d
d
d
d
a
Data are means of three different experiments.
Ciprofloxacin is used as standard.
Ascorbic acid is used as standard;-Indicated compounds are inactive.
d
d
b
c
terisation data of pyrazoles and pyrazolin-5-ones (3 and 5) are
given in Table 2.
having nitro group in meta orientation (3e and 5e) gave better
activity than o-isomer (3c and 5c). Among carboxy derivatives of
pyrazoles, p-isomer (3f) gave better antioxidant activity in
comparison with o-isomer (3g), were as with pyrazolones this
effect was reversed.
5. Conclusion
The present work comprises the synthesis of seven coumarinyl
pyrazoles incorporated with arylazo substituent at C4 of pyrazoles
and seven coumarinyl pyrazolin-5-ones incorporated with arylhy-
drazono substituent at C5 of pyrazolone. Among the pyrazoles,
compound with 4-bromosubstituent in the phenyl ring exhibited
highest antibacterial activity. From pyrazolin-5-ones, compound
with 4-bromo substituent in the phenyl ring exhibited highest
antibacterial activity against S. aureus, where as compound with 2-
carboxy substituent in the phenyl ring showed highest antibacterial
activity against B. subtilis. Compound with 4-bromophenylsub-
stituent in the phenyl ring exhibited highest antioxidant activity
from pyrazole series and pyrazolin-5-one bearing 3-nitro-
substituent in the phenyl ring exhibited enhanced antioxidant
activity from the respective series.
4. Results and discussion
The IR spectrum of compound 3a showed absorption band at
2927 cmꢃ1 due to aliphatic CH stretch. The absorption band for
pyrazolyl C]N was observed at 1610 cmꢃ1. The other prominent
absorption bands in IR spectrum were observed at 1693 (C]O),
1510 (N]N) and 1287 (C–O–C) cmꢃ1
The 1H NMR spectrum of 3a showed a singlet at
sponding to CH3 protons of coumarin. The CH3 protons of 2,4-
dimethylphenyl moiety resonated between 2.50 and 2.51. The
protons of two methyl groups of pyrazole showed 1H NMR signal at
3.33 and 3.58. The OCH2 protons resonated as a singlet at 4.78.
A singlet at 6.30 integrating for one proton was attributable to the
C3 proton of coumarin moiety. Aromatic protons resonated as
multiplet at 6.98–7.74.
.
d
2.42 corre-
d
6. Experiment protocols
d
d
d
d
6.1. Chemistry
d
Melting points were determined by open capillary method and
are uncorrected. The IR spectra (in KBr pellets) were recorded on
a Jasco FT/IR-410 spectrophotometer. 13C NMR and 1H NMR spectra
were recorded on a Bruker 300 MHz NMR spectrometer. Mass
spectra were recorded on LC-MS/MS (API-4000), MDS SCIEX.
Micro analytical data were obtained from Quest Research and
Training Institute, Bangalore 560050, India. The purity of
compounds was checked by thin layer chromatography on silica gel
plate using mixture of toluene and methanol.
Further evidence for the formation of pyrazole (3a) was
obtained by recording its mass spectrum. The mass spectrum of the
compound (3a) showed molecular ion peak at m/z 444 (Mþ), in
conformity with the molecular formula C25H24N4O4 .The other
fragmentation peaks observed were at m/z 217 (10%), 189.1 (12%),
137.1 (55%) and 123.2 (100%). The formation of pyrazoles was
further supported by recording the 13C NMR spectrum of
compound 3a which showed signal at
d
18.12 for coumarinyl CH3,
d
38.59–40.25 for methyl carbons attached to pyrazole moiety and
Compounds 1 [10], 2a–g [11] and 4a–g [9,12] were prepared
according to the literature method.
aromatic ring,
d
66.16 for OCH2 carbon,
d
101.62–110.56 corre-
113.68 for
153.28 for pyrazole C3,
160.54 for coumarin C2 and 166.16 for
sponding to aromatic carbons, C3, C5 to C10 of coumarin,
pyrazole C4, 126.49 for pyrazole C5,
154.45 for coumarin C4,
>NC]O.
d
d
d
d
d
6.2. Synthesis of 1-(4-methylcoumarinyl-7-oxyacetyl)-3,5-
dimethyl-4-(arylazo)pyrazoles (3a–g)
The IꢃR1spectrum of compound 5a showed absorption bands at
3172 cm
(NH stretch), 3052 cmꢃ1 (aromatic CH stretch),
2971 cmꢃ1 (aliphatic CH stretch), 1722 cmꢃ1 (C]O stretch),
1510 cmꢃ1 (NH–N]C) and 1243 cmꢃ1 (C–O–C).
A mixture of 1,3-diketo-1,3-dimethyl-2-(arylazo)propane (2a–g)
(0.001 mol) and 4-methylcoumarinyl-7-oxyacetic acid hydrazide 1
(0.248 g, 0.001 mol) in glacial acetic acid (10 ml) was refluxed for
10 h. The resultant solution was cooled and allowed to stand over-
night. The resultant solid thrown out was collected by filtration,
purified by repeated washings with acetic acid and recrystallised
from acetic acid. The purity of all the compounds was established by
The type of protons and number of protons in compound 5a
were ascertained with the help of 1H NMR spectrum which showed
a singlet at
d 2.41 corresponding to CH3 protons of coumarin.
The CH3 protons of 2,4-dimethylphenyl moiety resonated at

P. Manojkumar et al. / European Journal of Medicinal Chemistry 44 (2009) 4690–4694
4693
Table 2
Characterisation data of compounds (3a–g and 5a–g).
Comp.
R
Mol. formula
M.p [ꢁC]
Yield [%]
Analysis. (%) found (calc.)
C
H
N
3a
3b
3c
3d
3e
3f
3g
5a
5b
5c
5d
5e
5f
2,4-(CH3)2
4-Br
4-NO2
4-Cl
3-NO2
4-COOH
2-COOH
2,4-(CH3)2
4-Br
4-NO2
4-Cl
3-NO2
4-COOH
2-COOH
C25H24N4O4
C23H19BrN4O4
C23H19N5O6
C23H19ClN4O4
C23H19N5O6
C24H20N4O6
C24H20N4O6
C24H22N4O5
208–210
258–260
218–220
266–268
268–270
242–244
216–218
254–256
195–197
190–192
248–250
250–253
185–188
175–177
54
66
65
70
62
64
62
48
62
58
65
55
64
45
67.45(67.55)
55.82(55.77)
59.92(59.87)
61.32(61.27)
59.92(59.87)
62.37(62.60)
62.37(62.60)
64.23(64.57)
52.94(53.13)
56.99(57.02)
57.96(58.35)
56.96(57.02)
59.64(59.74)
59.68(59.74)
5.48(5.44)
3.85(3.87)
4.18(4.15)
4.22(4.25)
4.13(4.15)
4.32(4.38)
4.47(4.38)
4.88(4.97)
3.39(3.45)
3.68(3.70)
3.76(3.78)
3.83(3.70)
3.83(3.92)
3.95(3.92)
12.59(12.60)
11.26(11.31)
15.13(15.18)
12.38(12.43)
15.29(15.18)
12.08(12.17)
11.99(12.17)
12.34(12.55)
11.18(11.27)
15.25(15.11)
7.94(7.83)
C22H17BrN4O5
C22H17N5O7
C22H17ClN4O5
C22H17N5O7
C23H18N4O7
C23H18N4O7
15.02(15.11)
12.26(12.12)
12.01(12.12)
5g
single spot on the TLC plates. The solvent system used was tolue-
ne:methanol (3:7).
OCH2), 6.25 (s, 1H, CH), 6.90–8.43 (m, 7H, Ar-H); mass (%): MHþ
462.2 (22), 257.6 (75), 175.4 (36), 137.0 (62), 121.2 (100).
Compound 3a: IR (KBr,
n
cmꢃ1): 2927 (CH), 1693 (C]O), 1610
Compound 3f: IR (KBr,
n
cmꢃ1): 3422 (OH), 2817 (CH), 1681
(C]N), 1287 (C–O–C); 1H NMR (DMSO-d6)
d
ppm: 2.42 (s, 3H,
(C]O), 1594 (C]N), 1206 (C–O–C); 1H NMR (DMSO-d6)
d ppm: 2.12
0
coumarin CH3), 2.50 (s, 3H, aromatic C2 –CH3), 2.51 (s, 3H, aromatic
0
(s, 3H, coumarin CH3), 2.25 (s, 3H, pyrazole C3–CH3), 3.14 (s, 3H,
pyrazole C5–CH3), 4.51 (s, 2H, OCH2), 6.01 (s, 1H, CH), 7.41–7.85 (m,
7H, Ar-H), 13.45 (COOH); mass (%): MHþ 461.3 (16), 256.3 (72),
219.4 (100), 136.8 (15), 123.2 (20).
C4 –CH3), 3.33 (s, 3H, pyrazole C3–CH3), 3.58 (s, 3H, pyrazole C5–
CH3), 4.78 (s, 2H, OCH2), 6.30 (s, 1H, CH), 6.98–7.74 (m, 6H, Ar-H);
ppm: 18.12 (coumarin CH3), 38.59 (CH3 of
pyrazole C5), 39.42 (CH3 of pyrazole C3), 39.70 (CH3 of aromatic C2 ),
13C NMR (DMSO-d6)
d
Compound 3g: IR (KBr,
n
cmꢃ1): 3446 (OH), 2922 (CH), 1650
ppm: 2.27
0
40.25 (CH3 of aromatic C4 ), 66.16 (OCH2), 101.62 (coumarin C8),
(C]O),1587 (C]N),1247 (C–O–C); 1H NMR (DMSO-d6)
d
0
102.25 (coumarin C6), 102.87 (coumarin C3), 104.12 (coumarin C10),
(s, 3H, coumarin CH3), 2.51 (s, 3H, pyrazole C3–CH3), 3.37 (s, 3H,
pyrazole C5–CH3), 4.78 (s, 2H, OCH2), 6.25 (s, 1H, CH), 6.97–8.04 (m,
7H, Ar-H), 10.32 (COOH); mass (%): MHþ 461.3 (18), 256.3 (65),
219.2 (100), 136.8 (22), 121.8 (26).
0
0
105.37 (aromatic C1 ), 106.11 (aromatic C5 ), 107.25 (coumarin C5),
0
0
0
107.87 (aromatic C6 ), 108.49 (aromatic C3 ), 109.12 (aromatic C2 ),
0
109.81 (aromatic C4 ), 110.10 (coumarin C9), 110.56 (coumarin C7),
113.68 (pyrazole C4), 126.49 (pyrazole C5), 153.28 (pyrazole C3),
154.45 (coumarin C4), 160.54 (coumarin C2), 166.16 (pNC]O); mass
(%): Mþ 444.0 (13), 217.0 (10), 189.1 (12), 137.1 (55), 123.2 (100).
6.3. Synthesis of 1-(4-methylcoumarinyl-7-oxyacetyl)-3-methyl-4-
(substituted phenyl) hydrazono-2-pyrazolin-5-one (5a–g)
Compound 3b: IR (KBr,
n
cmꢃ1): 2921 (CH), 1720 (C]O), 1621
ppm: 2.40 (s, 3H,
(C]N), 1282 (C–O–C); 1H NMR (DMSO-d6)
d
Ethyl-2-(substituted phenyl) hydrazono-3-oxobutyrate (4a–g)
coumarin CH3), 2.50 (s, 3H, pyrazole C3–CH3), 3.30 (s, 3H, pyrazole
C5–CH3), 4.78 (s, 2H, OCH2), 6.25 (s, 1H, CH), 6.86–7.74 (m, 7H, Ar-
(0.02 mol) was dissolved in glacial acetic acid (20 ml) acid and
4-methylcoumarinyl-7-oxyacetic acid hydrazide
1
(0.496 g,
H); 13C NMR (DMSO-d6)
d
ppm: 18.12 (coumarin CH3), 38.62 (CH3
0.002 mol) in glacial acetic acid (20 ml) was added and the mixture
was refluxed for 4 h, cooled and then allowed to stand overnight.
The resultant solid was dried and then recrystallised from ethanol
.The purity of all the compounds was established by single spot on
the TLC plates. The solvent system used was methanol:toluene
(7:3).
at C5 of pyrazole), 40.29 (CH3 at C3 of pyrazole), 66.19 (OCH2),
101.62 (coumarin C8), 102.25 (coumarinC6), 102.87 (coumarin C3),
0
0
104.12 (coumarin C10), 105.37 (aromatic C4 ), 106.62 (aromatic C1 ),
0
0
107.24 (coumarin C5), 107.87 (aromatic C2 ,C6 ), 109.12 (aromatic
0
0
C3 ,C5 ), 111.47 (coumarin C9), 112.55 (coumarin C7), 113.67 (pyr-
azole C4), 126.49 (pyrazole C5), 153.37 (pyrazole C3), 154.46
(coumarin C4), 160.55 (coumarin C2), 166.15 (pNC]O); mass (%):
(MH þ 2)þ 497.6 (15), MHþ 495.9 (17), 291.1 (86), 189.0 (42), 137.5
(62), 121.2 (100).
Compound 5a: IR (KBr,
n
cmꢃ1): 3172 (NH), 3053 (Ar.CH),
2971 (Aliph.CH), 1722 (C]O), 1510 (NH–N]C), 1243 (C–O–C); 1H
NMR (DMSO-d6)
d
ppm: 2.41 (s, 3H, coumarin CH3), 2.49 (s, 3H,
0
0
aromatic C2 –CH3), 2.51 (s, 3H, aromatic C4 –CH3), 3.36 (s, 3H,
pyrazolone CH3), 4.78 (s, 2H, OCH2), 6.25 (s, 1H, CH), 7.00–7.74
Compound 3c: IR (KBr,
n
cmꢃ1): 2925 (CH), 1672 (C]O), 1596
ppm: 2.24 (s, 3H,
(C]N), 1262 (C–O–C); 1H NMR (DMSO-d6)
d
(m, 6H, Ar-H), 10.32 (s, 1H, NH); 13C NMR (DMSO-d6)
d
ppm:
coumarin CH3), 2.48 (s, 3H, pyrazole C3–CH3), 3.44 (s, 3H, pyrazole
C5–CH3), 4.87 (s, 2H, OCH2), 6.22 (s, 1H, CH), 6.93–8.36 (m, 7H, Ar-
H); mass (%): MHþ 462.4 (20), 257.2 (90), 175.4 (34), 137.0 (58),
121.4 (100).
18.12 (coumarin CH3), 38.90 (pyrazolone CH3), 39.73 (CH3 of
0
0
aromatic C2 ), 40.29 (CH3 of aromatic C4 ), 66.19 (OCH2), 101.62
(coumarin C8), 111.46 (coumarin C6), 112.58 (coumarin C3),
0
112.94 (coumarin C10), 113.52 (aromatic C6 ), 113.59 (aromatic
Compound 3d: IR (KBr,
n
cmꢃ1): 2810 (CH), 1681 (C]O), 1604
ppm:
0 0
C5 ), 113.66 (coumarin C5), 114.45 (aromatic C4 ), 114.48 (pyrazole
(C]N), 1286 (C–O–C), 1078 (Ar–Cl); 1H NMR (DMSO-d6)
d
C4), 115.92 (aromatic C2 ), 116.14 (aromatic C3 ), 116.97 (aromatic
0
0
0
2.41 (s, 3H, coumarin CH3), 2.51 (s, 3H, pyrazole C3–CH3), 3.37 (s,
3H, pyrazole C5–CH3), 4.67 (s, 2H, OCH2), 6.25 (s, 1H, CH), 7.01–7.79
(m, 7H, Ar-H); mass (%): (MH þ 2)þ 453.1 (7), MHþ 450.9 (22), 246.2
(80), 189.3 (16), 123.2 (100).
C1 ), 117.36 (coumarin C9), 126.49 (coumarin C7), 153.36 (pyr-
azolone C3), 154.46 (coumarin C4), 160.03 (coumarin C2), 160.55
(pyrazolone C5) 166.14 (pNC]O); mass (%): (M-1)þ 445.3 (15),
287.2 (40), 219.2 (84) and 175.4 (100).
Compound 3e: IR (KBr,
O–C); 1H NMR (DMSO-d6)
(s, 3H, pyrazole C3–CH3), 3.37 (s, 3H, pyrazole C5–CH3), 4.78 (s, 2H,
n
cmꢃ1): 2945 (CH), 1598 (C]N), 1287 (C–
ppm: 2.36 (s, 3H, coumarin CH3), 2.51
Compound 5b: IR (KBr,
2971 (Aliph.CH), 1718 (C]O), 1517 (NH–N]C), 1260 (C–O–C);
1H NMR (DMSO-d6)
ppm: 2.41 (s, 3H, coumarin CH3), 2.51
n
cmꢃ1): 3164 (NH), 3058 (Ar.CH),
d
d

4694
P. Manojkumar et al. / European Journal of Medicinal Chemistry 44 (2009) 4690–4694
(s, 3H, pyrazolone CH3), 4.78 (s, 2H, OCH2), 6.25 (s, 1H, CH), 7.00–
7.73 (m, 7H, Ar-H), 10.32 (s, 1H, NH); 13C NMR (DMSO-d6)
ppm:
18.12 (coumarin CH3), 38.90 (pyrazolone CH3), 66.19 (OCH2), 101.62
(Coumarin C8), 111.47 (coumarin C6), 112.55 (coumarin C3), 112.74
6.25 (s, 1H, CH), 6.9–7.96 (m, 7H, Ar-H), 10.32 (s, 1H, NH), 11.44 (s,
1H, COOH); mass (%): MHþ 463.4 (20), 218.6 (63), 174.9 (100), 136.4
(34), 122.9 (16).
d
0
0
0
(aromatic C4 ), 112.92 (coumarin C10), 113.32 (aromatic C2 ,C6 ),
113.66 (coumarin C5), 114.46 (pyrazolone C4), 115.36 (aromatic
Acknowledgement
0
0
0
C3 ,C5 ), 115.96 (aromatic C1 ), 117.32 (coumarin C9), 126.48
(coumarin C7), 153.36 (pyrazolone C3), 154.46 (coumarin C4), 160.03
(coumarin C2), 160.54 (pyrazolone C5) 166.15 (pNC]O); mass (%):
(MH þ 2)þ 499.8 (13), MHþ 497.6 (12), 482.2 (40), 465.4 (100), 123.1
(55).
The authors are thankful to Sevaratna Dr. R. Venkatesalu Naidu,
Managing Trustee, SNR sons charitable trust for providing facilities
to carry out this research work.
References
Compound 5c: IR (KBr,
n
cmꢃ1): 3096 (Ar. CH), 2923 (Aliph. CH),
ppm: 2.44 (s,
1459 (NH–N]C), 1283 (C–O–C); 1H NMR (DMSO-d6)
3H, coumarin CH3), 2.50 (s, 3H, pyrazolone CH3), 4.78 (s, 2H, OCH2),
6.25 (s, 1H, CH), 6.96–8.30 (m, 8H, Aromatic and NH protons); mass
(%): MHþ 464.12 (18), 219.4 (78), 175.5 (100), 137.2 (36), 123.4 (45).
Compound 5e: IR (KBr,
(Aliph. CH), 1722 (C]O), 1508 (NH–N]C), 1263 (C–O–C), 1348
(Symmetric NO2 stretch); 1H NMR (DMSO-d6)
ppm: 2.41 (s, 3H,
coumarin CH3), 2.49 (s, 3H, pyrazolone CH3), 4.88 (s, 2H, OCH2),
6.25 (s, 1H, CH), 6.99–7.74 (m, 7H, Aromatic-H), 10.32 (s, 1H, NH);
mass (%): MHþ 464.4 (24), 219.2 (64), 175.7 (100), 137.4 (42), 122.8
(34).
d
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(2003) 51–54.
[8] B. Kalluraya, B. Lingappa, N.S. Rai, Indian J. Heterocycl. Chem. 17 (2007) 67–70.
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n
cmꢃ1): 3178 (NH), 3055 (Ar.CH), 2968
d
Compound 5f: IR (KBr,
n
cmꢃ1): 3310 (OH), 3230 (Ar.CH), 2968
ppm:
(Aliph. CH), 1725 (C]O), 1253 (C–O–C); 1H NMR (DMSO-d6)
d
2.41 (s, 3H, coumarin CH3), 2.50 (s, 3H, pyrazolone CH3), 4.78 (s, 2H,
OCH2), 6.25 (s, 1H, CH), 7.0–7.98 (m, 7H, Ar-H), 10.32 (s, 1H, NH),
11.66 (s, 1H, COOH); mass (%): MHþ 463.2 (16), 219.4 (72), 175.2
(100), 136.2 (42), 123.8 (10).
Compound 5g: IR (KBr,
(NH–N]C), 1263 (C–O–C); 1H NMR (DMSO-d6)
coumarin CH3), 2.50 (s, 3H, pyrazolone CH3), 4.78 (s, 2H, OCH2),
n
cmꢃ1): 3422 (OH), 1719 (C]O), 1595
ppm: 2.41 (s, 3H,
d
[15] M.-H. Shih, F.-Y. Ke, Bioorg. Med. Chem. 12 (2004) 4633–4643.