Regioselective reaction: Synthesis and pharmacological study of Mannich bases containing ibuprofen moiety

Article abstract of DOI:10.1016/j.ejmech.2009.03.044

A series of 4-[(4-aryl)methylidene]amino-2-(substituted-4-ylmethyl)-5-{1-[4-(2-methylpropyl)phenyl]ethyl}-2,4-dihydro-3H-1,2,4-triazole-3-thione (6) were synthesized from an arylpropionic acid namely, ibuprofen by a three-component Mannich reaction. Amino

Full text of DOI:10.1016/j.ejmech.2009.03.044

European Journal of Medicinal Chemistry 44 (2009) 3697–3702
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Regioselective reaction: Synthesis and pharmacological study
of Mannich bases containing ibuprofen moiety
,
K.V. Sujith a, Jyothi N. Rao a, Prashanth Shetty b, Balakrishna Kalluraya a
*
a Department of Studies in Chemistry, Mangalore University, Mangalagangothri 574199, Karnataka, India
b Department of Pharmacology, NGSM Institute of pharmaceutical Science, Deralakatte 574160, Karnataka, 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 4-[(4-aryl)methylidene]amino-2-(substituted-4-ylmethyl)-5-{1-[4-(2-methylpropyl)phenyl]ethyl}-
2,4-dihydro-3H-1,2,4-triazole-3-thione (6) were synthesized from an arylpropionic acid namely, ibuprofen by
a three-component Mannich reaction. Aminomethylation of 4-[(4-aryl)methylidene]amino-5-{1-[4-(2-meth-
ylpropyl)phenyl] ethyl}-4H-1,2,4-triazole-3-thiol (5) with formaldehyde and a secondary amine furnished this
novel series of Mannich bases (6). Both Schiff bases (5) and Mannich bases (6) were well characterized on the
basis of IR, NMR, mass spectra1 data and elemental analysis. They were screened for their anti-inflammatory,
analgesic, antibacterial and antifungal activities. Some of the Mannich bases (6) carrying morpholino and N-
methylpiperazino residues were found to be promising anti-inflammatory and analgesic agents.
Ó 2009 Elsevier Masson SAS. All rights reserved.
Received 11 December 2008
Received in revised form
11 March 2009
Accepted 29 March 2009
Available online 14 April 2009
Keywords:
Ibuprofen
Schiff base
Mannich base
Anti-inflammatory agents
Analgesic agents
1. Introduction
these side effects has long been awaited. Selective COX-2 inhibitors
with better safety profile have been marketed as a new generation
Non-steroidal anti-inflammatory drugs (NSAIDs) such as
ibuprofen are widely used in the treatment of pain and inflam-
mation, including osteoarthritis and rheumatoid arthritis [1–3].
Prostaglandins (PGs) are well known to be the mediators of
inflammation, pain and swelling. They are produced by the action
of cyclooxygenase (COX) enzyme on arachidonic acid. Metabolites
of the COX pathway are widely accepted as mediators of the
inflammatory response. COX is known to be the principal target of
non-steroidal anti-inflammatory drugs (NSAIDs). NSAIDs, block the
formation of PGs and have analgesic, antipyretic and anti-inflam-
matory activities [4]. In the early 1990s, it was discovered that the
COX enzyme exists as two isoforms, one constitutive (COX-1) and
the other inducible (COX-2) [5]. COX-1 is constitutively expressed
and provides cytoprotection in the gastrointestinal (GI) tract while
COX-2 is inducible and mediates inflammation [6–8]. The tradi-
tional NSAIDs show greater selectivity for COX-1 than COX-2 [9].
In fact, prolonged use of NSAIDs like ibuprofen has been asso-
ciated with gastrointestinal complications ranging from stomach
irritation to life-threatening GI ulceration bleeding and nephro-
toxicity [10,11]. Therefore the development of new NSAIDs without
of NSAIDs [12]. Thus there remains a compelling need for effective
NSAIDs with an improved safety profile. Chronic use of NSAIDs,
including ibuprofen, may elicit appreciable GI toxicity [13]; there-
fore, synthetic approaches based upon NSAIDs chemical modifica-
tion have been undertaken with the aim of improving the NSAID
safety profile. The GI damage from NSAIDs is generally attributed to
two factors, local irritation by the carboxylic acid moiety, common
to most NSAIDs (topical effect) and decreased tissue prostaglandin
production, which undermines the physiological role of cytopro-
tective prostaglandins in maintaining the GI health and homeo-
stasis [14]. It has been reported that the derivatization of the
carboxyl function of representative NSAIDs, resulted in an
increased anti-inflammatory activity with reduced ulcerogenic
effect [15,16]. The search for novel analgesic and anti-inflammatory
agents devoid of side effects continues to be an active area of
research in medicinal chemistry. In fact 1,2,4-triazoles and their
derivatives have been reported to possess various biological activ-
ities such as anti-inflammatory activity [17] and analgesic proper-
ties [18]. Similarly Mannich bases also possess comprehensive
bioactivities like anticancer [19], analgesic [20], antibacterial and
antifungal activities [21].
Multi-component reactions (MCRs) constitute a major part in
the present day organic synthesis with advantages ranging from
lower reaction times, increased reaction rates to higher yields and
* Corresponding author. Tel.: þ91 824 2287262; fax: þ91 824 2287367.
E-mail addresses: bkalluraya@gmail.com, kallurayab@yahoo.com (B. Kalluraya).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.03.044

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K.V. Sujith et al. / European Journal of Medicinal Chemistry 44 (2009) 3697–3702
reproducibility [22]. Mannich reaction is
a
three-component
yield. Mannich reaction of these Schiff bases was further obtained
with formaldehyde and secondary amine in ethanol medium to give
the N-Mannich bases (6) rather than the S-Mannich bases (Scheme
2). The structures of newly synthesized compounds were confirmed
on the basis of spectral, elemental and crystal data. Characterization
data of these compounds are given in Tables 1 and 2.
condensation reaction involving active hydrogen containing
compound, formaldehyde and a secondary amine [23]. The ami-
noalkylation of aromatic substrates by Mannich reaction is of
considerable importance for the synthesis and modification of
biologically active compounds [24]. Similarly Schiff base derivatives
of 1,2,4-triazole have displayed good biological activity [25]. So we
herein synthesized some novel Schiff bases and Mannich bases
carrying both the triazole nucleus as well as ibuprofen moiety and
studied their biological properties.
3. Pharmacology
Some of the selected compounds were evaluated for analgesic
and anti-inflammatory activities. The test compounds were admin-
istered in the form of a suspension (1% carboxy methyl cellulose as
vehicle). Anti-inflammatory and analgesic activities of the test
compounds were measured with respect to the control and
compared with respect to the standard drug; diclofenac. All the
pharmacological data are expressed as mean ꢀ SEM; statistical
analysis was applied to determine the significance of the difference
between the control group and groups of animals treated with the
test compounds. Ibuprofen is used as a second reference for
comparison of anti-inflammatory activity. Similarly antibacterial and
antifungal activity studies were carried out for selected compounds.
2. Chemistry
The title compounds were synthesized in a one-pot multi-
component Mannich reaction involving ibuprofen triazole (4),
formaldehyde and secondary amine in ethanol medium. The reac-
tion proceeds via the formation of immonium salt which subse-
quently attacks the N-1 of triazole giving rise to regioselective
Mannich base. It is interesting to note that the reaction is highly
regioselective and furnishes only N-Mannich base and none of the
S-Mannich derivatives, though the intermediate Schiff base can
exist in the thiol–thione tautomeric equilibrium.
3.1. Anti-inflammatory activity
Ibuprofen triazole (4) was prepared according to the procedure
outlined in Scheme 1. Ibuprofen hydrazide (2) was obtained by the
hydrazinolysis of its corresponding ester. The required dithio-
carbazinate (3) was synthesized by reacting acid hydrazide with
carbon disulphide and potassium hydroxide in ethanol. This salt
underwent ring closure on reacting with hydrazine hydrate to give
the ibuprofen triazole [26]. Whereas ibuprofen triazole (4) was also
synthesized in a one-pot reaction, involving the fusion of ibuprofen
(1) and thiocarbohydrazide (TCH). This alternative one-pot
synthesis has matured into a highly useful technique because of
higher yield and shorter reaction time. In this one-pot synthesis
several disadvantages like long reaction procedure and tedious
work-up can be overcome. Due to these facts the one-pot procedure
for ibuprofen triazole dominates over conventional Reid and
Heindel method [27]. The triazole so synthesized was then
condensed with suitable aldehydes in the presence of few drops of
conc. Sulphuric acid as a catalyst to yield Schiff bases (5) in good
Anti-inflammatory activity was determined by the carrageenan-
induced paw edema method in Wistar albino rats by using pleth-
ysmography following the method of Winter et al. [28]. Diclofenac
at an oral dose of 20 mg/kg served as the standard drug for
comparison. The test compounds (20 mg/kg) were administered
orally 30 min prior to administration of carrageenan (0.1 mL of 1%
w/v) in the plantar region of the paw. The paw volumes were
measured at 30, 60, 90, 120, 150 and 180 min after carrageenan
administration. The results are presented in Table 3.
3.2. Analgesic activity
Analgesic activities were evaluated on Swiss albino mice by hot
plate method. In this method heat is used as a source of pain.
Animals are grouped into 5, each containing 6 animals (n ¼ 6).
CH3
CH3
O
H3C
COOH
H3C
i) EtOH, H2SO4
ii) N2H4.H2O
NH
NH2
CH3
CH3
(2)
(1)
CS2
KOH, EtOH
CH3
CH3
O
N
N
H3C
H3C
N2H4.H2O
NH
NH
S
SH
N
CH3
CH3
S K
NH2
(4)
(3)
Fusion
CH3
S
H3C
COOH
+
H2N NH
TCH
NH
NH2
CH3
(1)
Scheme 1.

K.V. Sujith et al. / European Journal of Medicinal Chemistry 44 (2009) 3697–3702
3699
CH3
CH3
N
N
H3C
N
N
H3C
EtOH
Ar CHO
+
SH
Ar
SH
H2SO4
N
N
N
CH3
CH3
NH2
(5)
(4)
R
CH3
CH3
H
N
N
H3C
N
N
H3C
R-H + HCHO / EtOH
S
S
N
N
N
CH3
Stirr.
CH3
N
Ar
Ar
(6)
H
H
N
H
N
H
N
N
H5C6
NH
C6H5
and
RH =
N
N
N
O
CH3
C6H5
C2H5
Scheme 2.
Table 1
Characterization data of 4-arylideneamino-5-{1-[4-(2-methylpropyl)phenyl]ethyl}-1,2,4-triazole-3-thiol 5a–f.
Compounds
Ar
Yield (%)
M.P. (ꢁC)
Mol. formula
/(mol. weight)
Analysis (%)
Calcd.
Found
5a
5b
5c
5d
5e
5f
C6H5
44
70
54
85
73
78
140–142
156
165–167
142
160–164
180–182
C21H24N4S/(364)
C ¼ 69.23; H ¼ 6.59; N ¼ 15.38; S ¼ 8.79
C ¼ 63.23; H ¼ 5.77; N ¼ 14.05; S ¼ 8.03
C ¼ 58.19; H ¼ 5.08; N ¼ 12.93; S ¼ 7.39
C ¼ 69.84; H ¼ 6.87; N ¼ 14.81; S ¼ 8.46
C ¼ 56.88; H ¼ 5.19; N ¼ 12.65; S ¼ 7.22
C ¼ 61.61; H ¼ 5.62; N ¼ 17.11; S ¼ 7.82
C ¼ 69.11; H ¼ 6.57; N ¼ 15.42; S ¼ 8.76
C ¼ 63.15; H ¼ 5.79; N ¼ 14.02; S ¼ 8.06
C ¼ 58.11; H ¼ 5.06; N ¼ 12.89; S ¼ 7.36
C ¼ 69.78; H ¼ 6.85; N ¼ 14.77; S ¼ 8.43
C ¼ 56.81; H ¼ 5.17; N ¼ 12.60; S ¼ 7.19
C ¼ 61.51; H ¼ 5.60; N ¼ 17.09; S ¼ 7.79
4-ClC6H4
2,6-Cl2C6H3
4-CH3C6H4
4-BrC6H4
4-NO2C6H4
C21H24N4SCl/(398.5)
C21H22N4SCl2/(433)
C22H26N4S/(378)
C21H23N4SBr/(443)
C21H23N5SO2/(409)
Animals are individually placed on a hot plate maintained at
constant temperature (55 ꢀ1 ꢁC) and the reaction of animals, such
as licking of the paw or jump response is taken as the end point. The
reaction time of the animals on the hot plate at 30, 60, 90 min after
drug administration (10 mg/kg) is noted. From this percentage
increase in reaction time (as index of analgesia) at each time
interval is calculated. A dose level of 10 mg/kg diclofenac served as
the standard drug for comparison. The test compounds were
administered orally by gavage. The responses produced in the
animal were observed for 30 min intervals and percentage in
reaction1 time was calculated for analgesic activity using the
following equation. Results are presented in Table 4.
antimicrobial activities after sterilizing by autoclaving. These
standard solutions were added to the well, digged using a borer and
incubated at 37 ꢁC for 24–48 hours and observed. But none of the
compounds showed any significant antibacterial or antifungal
activity compared with the standard drugs.
4. Results and discussion
4.1. Pharmacological screening
The anti-inflammatory activity of the target compounds 5 and 6
was evaluated by applying the carrageenan-induced rat paw edema
bioassay in rats. Diclofenac was used as a reference substance in the
assay. For comparison purposes, ibuprofen was additionally used as
a second standard reference. All the tested compounds were found
more potent than ibuprofen. In comparison to diclofenac, all the
test compounds showed comparable anti-inflammatory activity
(Table 3). Mannich base (6b) displayed the highest anti-inflam-
matory activity among the set of compounds tested in the present
study. Test compounds that exhibited the most potent anti-
inflammatory activity namely 6b, 6f, 6k and 6l were further eval-
uated for their analgesic activity in mice. In general, the tested
compounds showed a better analgesic activity compared to diclo-
fenac as illustrated in Table 4.
Some of the synthesized compounds 5 and 6 were tested for
their anti-inflammatory activity at an equimolar oral dose relative
to 20 mg/kg diclofenac and ibuprofen. The compounds showed
anti-inflammatory activity ranging from 56% to 74% (Table 3),
whereas standard drugs diclofenac and ibuprofen showed 65% and
42% inhibition after 3 hours. The anti-inflammatory activity data
ꢀ
ꢁ
RTAT
RTBT
% increase in reaction time ¼
ꢂ 1 ꢃ 100
where RTAT ¼ Reaction time after treatment; RTBT ¼ Reaction time
before treatment.
3.3. Antibacterial and antifungal activities
Well diffusion method was employed for the determination of
antibacterial and antifungal activities. Staphylococcus aureus (Gram
þve) and Escherichia coli (Gram ꢂve) are the bacteria used for the
antibacterial assay. Similarly Aspergillus was used for the antifungal
assay. Compounds in solution form, i.e. of concentration 1000 mg/
mL (10 mg of compound dissolved in 10 mL DMF) was assayed for
1
Maximum tolerated reaction time is used for calculation.

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K.V. Sujith et al. / European Journal of Medicinal Chemistry 44 (2009) 3697–3702
Table 2
Characterization data of 4-arylideneamino-2-substituted aminomethyl-5-{1-[4-(2-methylpropyl)phenyl]ethyl}-3H-1,2,4-triazole-3-thione 6a–n.
Compounds Ar
R
Yield (%)/
M.P. (ꢁC)
Mol. formula/
(mol. weight)
Analysis (%)
Calcd.
Found
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
C6H5
4-ClC6H4
4-ClC6H4
Morpholine
Morpholine
1-Methylpiperazine 63/115
80/70
92/69–71
C26H33N5OS/(463)
C ¼ 67.38; H ¼ 7.12; N ¼ 15.11; S ¼ 6.91
C ¼ 67.24; H ¼ 7.10; N ¼ 15.06; S ¼ 6.89
90/100–102 C26H32N5SOCl/(497.5) C ¼ 62.71; H ¼ 6.43; N ¼ 14.07; S ¼ 6.43 C ¼ 62.62; H ¼ 6.45; N ¼ 14.10; S ¼ 6.45
C27H35N6SCl/(510.5)
C26H31N5SOCl2/(532)
C ¼ 63.46; H ¼ 6.85; N ¼ 16.45; S ¼ 6.26 C ¼ 63.31; H ¼ 6.88; N ¼ 16.40; S ¼ 6.24
C ¼ 58.64; H ¼ 5.82; N ¼ 13.15; S ¼ 6.01 C ¼ 58.49; H ¼ 5.80; N ¼ 13.12; S ¼ 5.99
C ¼ 63.26; H ¼ 5.93; N ¼ 13.83; S ¼ 5.27 C ¼ 63.18; H ¼ 5.95; N ¼ 13.78; S ¼ 5.25
C ¼ 67.92; H ¼ 7.33; N ¼ 14.67; S ¼ 6.70 C ¼ 67.81; H ¼ 7.36; N ¼ 14.63; S ¼ 6.68
2,6-Cl2C6H3 Morpholine
2,6-Cl2C6H3 1-Phenylpiperazine 81/104–107 C32H36N6SCl2/(607)
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-CH3C6H4
4-BrC6H4
Morpholine
1-Methylpiperazine 47/65
Diphenylamine 89/116
1-Phenylpiperazine 88/104
Diphenylamine
63/61–63
C27H35N5SO/(477)
C28H38N6S/(490)
C35H37N5S/(559)
C33H40N6S/(552)
C ¼ 68.57; H ¼ 7.75; N ¼ 17.14; S ¼ 6.53
C ¼ 68.42; H ¼ 7.78; N ¼ 17.08; S ¼ 6.55
C ¼ 75.13; H ¼ 6.61; N ¼ 12.52; S ¼ 5.72 C ¼ 75.02; H ¼ 6.59; N ¼ 12.48; S ¼ 5.74
C ¼ 71.73; H ¼ 7.24; N ¼ 15.21; S ¼ 5.79
C ¼ 65.38; H ¼ 5.44; N ¼ 11.21; S ¼ 5.12
C ¼ 71.61; H ¼ 7.21; N ¼ 15.18; S ¼ 5.81
C ¼ 65.23; H ¼ 5.42; N ¼ 11.18; S ¼ 5.10
68/108–109 C34H34N5SBr/(624)
87/114
4-NO2C6H4 Morpholine
4-NO2C6H4 1-Methylpiperazine 87/116–117
4-NO2C6H4 Diphenylamine
4-NO2C6H4 1-Ethylpiperazine
C26H32N6SO3/(508)
C27H35N7SO2/(521)
C34H34N6SO2/(590)
C28H37N7SO2/(535)
C ¼ 61.41; H ¼ 6.29; N ¼ 16.53; S ¼ 6.29 C ¼ 61.34; H ¼ 6.27; N ¼ 16.48; S ¼ 6.31
C ¼ 62.18; H ¼ 6.71; N ¼ 18.80; S ¼ 6.14
C ¼ 62.07; H ¼ 6.69; N ¼ 18.75; S ¼ 6.16
95/95–96
52/200–02
C ¼ 69.15; H ¼ 5.76; N ¼ 14.23; S ¼ 5.42 C ¼ 69.08; H ¼ 5.75; N ¼ 14.19; S ¼ 5.44
C ¼ 62.80; H ¼ 6.91; N ¼ 18.31; S ¼ 5.98 C ¼ 62.71; H ¼ 6.88; N ¼ 18.26; S ¼ 5.96
showed that the compounds having morpholine group (6b) and
methylpiperazine (6l) possess highest activity (74%). Among the
Schiff bases tested for anti-inflammatory activity, 5e showed 74%
activity and 5b showed 64% activity. On aminomethylation of 5b, by
morpholine, anti-inflammatory activity changes to 74%. Replace-
ment of morpholine by methylpiperazine resulted in a slight
increase of activity (74%, p > 0.05). Further among Mannich bases,
6k showed 73% activity. Similarly 6f showed good anti-inflamma-
tory activity (68%, p > 0.05). The compounds that showed anti-
inflammatory activity higher than 70% were further tested for their
analgesic activity at an equimolar oral dose relative to 10 mg/kg
diclofenac. Compounds 6b, 6f, 6k and 6l showed analgesic activity
ranging from 64.32% to 79.6%, whereas the standard drug diclofe-
nac showed 79.24% inhibition. It was noted that the compounds
showing highest anti-inflammatory activity also exhibited highest
analgesic activity. Among these compounds, 6k showed activity
(79.60%, p > 0.05) more than that of standard diclofenac, whereas
compounds 6b (76.49%, p > 0.01), 6f (64.32%, p > 0.05) and 6l
(70.75%, p > 0.01) showed good analgesic activity.
structures are more likely to confer selectivity due to its wider
active site. Thus it seems that the conversion of carboxylic group of
ibuprofen to triazole and its Schiff and Mannich derivatives might
have caused good inhibitory activity, resulting in significant anal-
gesic and anti-inflammatory activities. On the basis of the results
obtained, ibuprofen triazole, Schiff and Mannich bases appear to be
suitable moiety in the field of medicine.
It could be concluded that replacement of the carboxyl function
of ibuprofen by certain bulkier moieties generally improves their
pharmacological profile. It was interesting to note that all the non-
carboxylic test compounds were found to have anti-inflammatory
activity greater than that of ibuprofen. More interestingly, some of
the test compounds were more potent than diclofenac.
6. Experimental protocols
Melting points were determined in open capillary tubes and are
uncorrected. IR spectra were recorded by dispersing the
compounds in KBr pellets on a Shimadzu FT-IR 157 spectrometer.
1H NMR spectra were recorded on a 400 MHz Bruker Avance II 400
NMR spectrophotometer and all the chemical shift values were
For further comparison, a graph was plotted showing the anti-
inflammatory activities of 4, 5b, 6b with ibuprofen (Fig. 1). This
graph indicates that all the ibuprofen analogues including its tri-
azole, Schiff and Mannich bases showed excellent anti-inflamma-
tory activity than ibuprofen at every time interval. Among these,
Mannich derivative of ibuprofen showed the highest activity.
reported as
d
(ppm). 13C NMR spectra were recorded on a Bruker
Avance II 400 NMR spectrometer. Mass spectra were recorded on
a JEOL SX-102 (FAB) mass spectrometer.
5. Conclusion
6.1. General procedure for the synthesis of 4-amino-5-{1-[4-(2-
methylpropyl)phenyl]ethyl}-1,2,4-triazole-3-thiol 4
It has been speculated that ibuprofen acts non-selectively
probably because of its relatively small size. It appears that bulkier
An equimolar mixture of thiocarbohydrazide (TCH) and
ibuprofen (1) was mixed and heated gently on an oil bath until the
evolution of H2S ceases. The reaction mixture was then cooled to
room temperature and poured into ice cold water and stirred well.
It was then filtered, dried and recrystallized from ethanol.
Table 3
Anti-inflammatory activity data of ibuprofen derivatives.
Compounds (% Inhibition ꢀ SEM)a
0.5 hours 1 hours
1.5 hours 2 hours
2.5 hours 3 hours
Diclofenac 83 ꢀ 2.38b 59 ꢀ 1.01b 70 ꢀ 2.56c 87 ꢀ 4.18c 69 ꢀ 3.9b 65 ꢀ 0.89c
Table 4
Ibuprofen
20 ꢀ 4.31 18 ꢀ 2.67b 25 ꢀ 2.69b 36 ꢀ 3.74b 39 ꢀ 4.25c 42 ꢀ 2.35b
30 ꢀ 1.97b 32 ꢀ 3.64 46 ꢀ 1.88b 45 ꢀ 4.08 50 ꢀ 1.26 56 ꢀ 3.38b
62 ꢀ 5.02 49 ꢀ 2.11 52 ꢀ 4.14 57 ꢀ 4.41b 62 ꢀ 0.79 64 ꢀ 4.1b
Analgesic activity data of 6b, 6f, 6k & 6l.
4
Compounds Before treatment After treatment
% Increase in reaction time
5b
5e
6b
6f
6j
ꢀ SEM
ꢀ SEM (1.5 hours) ꢀ SEMa
0
16 ꢀ 1.79 65 ꢀ 1.74b 60 ꢀ 1.15 70 ꢀ 1.99b 72 ꢀ 2.19b
90 ꢀ 2.27b 42 ꢀ 1.39b 61 ꢀ 4.27b 61 ꢀ 4.29c 73 ꢀ 5.31 74 ꢀ 0.77c
Diclofenac
6b
6f
6k
6l
2.12 ꢀ 0.18
2.27 ꢀ 0.26
2.49 ꢀ 0.29
2.02 ꢀ 0.17
2.50 ꢀ 0.26
3.80 ꢀ 0.16
4.01 ꢀ 0.27
4.10 ꢀ 0.22
3.63 ꢀ 0.16
4.21 ꢀ 0.19
79.24b
76.49c
64.32b
79.60b
70.75c
0
23 ꢀ 4.08 64 ꢀ 4.16b 60 ꢀ 3.72 67 ꢀ 3.31c 68 ꢀ 3.79b
9 ꢀ 3.87 10 ꢀ 4.42 38 ꢀ 1.48 38 ꢀ 1.29 57 ꢀ 2.84b 57 ꢀ 4.28
6k
6l
12 ꢀ 1.09b 52 ꢀ 1.93 65 ꢀ 3.92b 54 ꢀ 3.28 71 ꢀ 2.07b 73 ꢀ 1.56
38 ꢀ 3.23 70 ꢀ 2.98b 82 ꢀ 2.59 68 ꢀ 3.08b 75 ꢀ 2.8
74 ꢀ 1.78c
a
a
Results are expressed as their mean values (n ¼ 6).
Results are expressed as their mean values (n ¼ 6).
b
c
b
c
P < 0.05.
P < 0.05.
P < 0.01; significant from the control.
P < 0.01; significant from the control.

K.V. Sujith et al. / European Journal of Medicinal Chemistry 44 (2009) 3697–3702
3701
2H, J ¼ 7.20 Hz, CH2), 3.94 (q, 1H, J ¼ 7.20 Hz, CHCH3), 7.04 (d,
2H, J ¼ 8.10 Hz, 30,50-H), 7.09 (d, 2H, J ¼ 8.10 Hz, 20,60-H), 7.65
(d, 2H, J ¼ 8.80 Hz, 200,600-H), 8.02 (d, 2H, J ¼ 8.80 Hz, 300,500-H),
10.09 (s, 1H, N]CH), 10.53 (s, 1H, SH/NH); FABMS (m/z, %): 400
(Mþ þ 2, 89), 399 (Mþ þ 1, 82), 398 (Mþ, 100), 261 (67), 161 (18).
Ibuprofen (1)
90
80
70
60
50
40
30
20
Ibuprofen Triazole (4)
Schiff base (5b)
Mannich Base (6b)
6.2.2. Compound 5e
IR (KBr)
g
/cmꢂ1: 3132 (N–H), 2927 (C–H), 1608 (C]N), 1284
(C]S); 1H NMR (CDCl3)
d
: 0.80 (d, 6H, J ¼ 6.61 Hz, (CH3)2), 1.61
(d, 3H, J ¼ 7.20 Hz, CH3), 1.728–1.806 (m, 1H, CH–(CH3)2), 2.37
(d, 2H, J ¼ 7.20 Hz, CH2), 4.03 (q, 1H, J ¼ 7.20 Hz, CHCH3), 7.06 (d,
2H, J ¼ 8.12 Hz, 30,50-H), 7.12 (d, 2H, J ¼ 8.10 Hz, 20,60-H), 7.76 (d,
2H, J ¼ 8.80 Hz, 200,600-H), 8.10 (d, 2H, J ¼ 8.80 Hz, 300,500-H), 10.11
(s, 1H, N]CH), 10.67 (s, 1H, SH/NH); FABMS (m/z, %): 444
(Mþ þ 2, 100), 442 (Mþ, 99), 261 (100), 161 (10).
6.2.3. Compound 5f
IR (KBr)
g
/cmꢂ1: 3133 (N–H), 2942 (C–H), 1600 (C]N), 1283
(C]S); 1H NMR (CDCl3)
d
: 0.81 (d, 6H, J ¼ 6.58 Hz, (CH3)2), 1.70
(d, 3H, J ¼ 7.20 Hz, CH3), 1.75–1.81 (m, 1H, CH–(CH3)2), 2.39 (d,
2H, J ¼ 7.12 Hz, CH2), 4.20 (q, 1H, J ¼ 7.20 Hz, CHCH3), 7.03 (d,
2H, J ¼ 8.10 Hz, 30,50-H), 7.11 (d, 2H, J ¼ 8.10 Hz, 20,60-H), 7.65
(d, 2H, J ¼ 8.82 Hz, 200,600-H), 8.12 (d, 2H, J ¼ 8.82 Hz, 300,500-H),
10.23 (s, 1H, N]CH), 10.89 (s, 1H, SH/NH); FABMS (m/z, %): 410
(Mþ þ 1, 100), 409 (Mþ, 18), 161 (27).
0.5
1.0
1.5 2.0
Time (hours)
2.5
3.0
Fig. 1. Anti-inflammatory activity of ibuprofen and its derivatives at 20 mg/kg (molar
equivalent to ibuprofen).
6.3. General procedure for the synthesis of 4-arylideneamino-2-
substituted aminomethyl-5-{1-[4-(2-methylpropyl)phenyl]ethyl}-
3H-1,2,4-triazole-3-thione 6
IR (KBr)
(C]S); 1H NMR (DMSO-d6)
g
/cmꢂ1: 3319 (N–H), 2866 (C–H), 1600 (C]N), 1292
d: 0.85 (d, 6H, J ¼ 6.57 Hz, (CH3)2), 1.53
(d, 3H, J ¼ 7.20 Hz, CH3), 1.72–1.85 (m, 1H, CH–(CH3)2), 2.40 (d, 2H,
J ¼ 7.18 Hz, CH2), 4.33 (q, 1H, J ¼ 7.20 Hz, CH–CH3), 5.40 (s, 2H, NH2),
7.10 (d, 2H, J ¼ 7.90 Hz, 30,50-H), 7.15 (d, 2H, J ¼ 7.90 Hz, 20,60-H),
13.56 (s, 1H, SH/NH); FABMS (m/z, %): 277 (Mþ þ 1, 89), 276 (Mþ,
23), 261 (67), 188 (35), 161 (100).
A mixture of Schiff bases (5) (10 mmol), formaldehyde (40%,
1.5 mL) and appropriate secondary-amines (10 mmol) in ethanol
medium was stirred at room temperature for 12 hours. The
precipitated solid was filtered under suction, washed with cold
ethanol and recrystallized from hot ethanol. The characterization
data of these compounds are given in Table 2. In the 13C NMR
assignment for compounds 6h, aryl carbons showed characteristic
signals at 117.85–146.59 ppm and 161.94 (C]S) and 6j, aryl carbons
showed characteristic signals at 117.84–140.51 ppm and
161.53 ppm (C]S) (Fig. 2)
6.2. General procedure for the synthesis of 4-arylideneamino-5-
{1-[4-(2-methylpropyl)phenyl]ethyl}-1,2,4-triazole-3-thiol 5
A
mixture of 4-amino-5-[1(4-iso-butylphenyl)ethyl]-3-mer-
capto-1,2,4-triazole (4) (10 mmol), substituted benzaldehydes
(10 mmol) and 2–3 drops of concentrated sulphuric acid in ethanol
medium was heated to reflux for 3 hours. The resulting solution
was cooled to room temperature and the precipitated solid was
filtered under suction, washed with cold ethanol and recrystallized
from hot ethanol. The characterization data of these compounds are
given in Table 1.
6.3.1. Compound 6f
IR (KBr)
NMR (CDCl3)
g
/cmꢂ1: 2967, 2863 (C–H), 1615 (C]N), 1261 (C]S); 1H
d
: 0.83 (d, 6H, J ¼ 6.60 Hz, (CH3)2), 1.70 (d, 3H,
J ¼ 7.28 Hz, CH3), 1.72–1.79 (m, 1H, CH–(CH3)2), 2.39 (d, 2H,
J ¼ 7.16 Hz, CH2), 2.41 (s, 3H, C6H4–CH3), 2.86 (t, 4H, CH2NCH2), 3.72
(t, 4H, CH2OCH2), 4.39 (q, 1H, J ¼ 7.28 Hz, CHCH3), 5.17 (s, 2H,
NCH2N), 7.02 (d, 2H, J ¼ 8.12 Hz, 300,500-H), 7.14 (d, 2H, J ¼ 8.08 Hz,
30,50-H), 7.24 (d, 2H, J ¼ 8.08 Hz, 20,60-H), 7.63 (d, 2H, J ¼ 8.12 Hz,
200,600-H), 9.88 (s, 1H, N]CH); FABMS (m/z, %): 478 (Mþ þ 1, 57), 477
(Mþ, 32), 161 (76), 100 (100).
6.2.1. Compound 5b
IR (KBr)
(C]S); 1H NMR (CDCl3)
(d, 3H, J ¼ 7.20 Hz, CH3), 1.78–1.852 (m, 1H, CH–(CH3)2), 2.39 (d,
g
/cmꢂ1: 3134 (N–H), 2949 (C–H), 1570 (C]N), 1280
d
: 0.83 (d, 6H, J ¼ 6.60 Hz, (CH3)2), 1.67
64.97
H3C
64.6
N
H3C
N
36.36
30.19
36.43
30.16
N
N
N
N
H3C
19.63
H3C
19.64
S
S
45
161.53
161.94
153.4N
N
153.3
44.97
N
N
CH
CH
161.52
CH
159.03
22.393
CH3
22.36
146.53
Br
19.32
CH3
6h
6j
Fig. 2. 13C NMR assignment of some carbon atoms of compounds 6h and 6j.

3702
K.V. Sujith et al. / European Journal of Medicinal Chemistry 44 (2009) 3697–3702
6.3.2. Compound 6h
20,60-H), 7.62 (d, 2H, J ¼ 8.82 Hz, 200,600-H), 7.86 (d, 2H, J ¼ 8.82 Hz,
IR (KBr)
g
/cmꢂ1: 2970, 2859 (C–H), 1611 (C]N), 1254 (C]S); 1H
300,500-H), 10.32 (s, 1H, N]CH); FABMS (m/z, %): 591(Mþ þ 1, 84),
NMR (CDCl3)
d
: 0.81 (d, 6H, J ¼ 6.42 Hz, (CH3)2), 1.61 (d, 3H,
590 (Mþ, 81), 182 (100), 161 (55).
J ¼ 7.24 Hz, CH3), 1.67–1.78 (m, 1H, CH–(CH3)2), 2.37 (d, 2H,
J ¼ 7.16 Hz, CH2), 2.39 (s, 3H, C6H4–CH3), 4.32 (q, 1H, J ¼ 7.24 Hz,
CHCH3), 6.09 (s, 2H, NCH2N), 6.93–7.64 (m, 14H, Ar–H), 6.95 (d, 2H,
J ¼ 8.12 Hz, 300,500-H), 7.61 (d, 2H, J ¼ 8.12 Hz, 200,600-H), 9.92 (s, 1H,
N]CH); FABMS (m/z, %): 560 (Mþ þ 1, 52), 559 (Mþ, 46), 182 (100),
161 (95), 118 (38).
Acknowledgement
The authors S.K.V and B.K are thankful to the KSCSTE,
Trivandrum for the financial assistance and the Head, SAIF, CDRI,
Lucknow for providing mass and 1H NMR spectral data.
6.3.3. Compound 6j
IR (KBr)
g
/cmꢂ1: 2960, 2854 (C–H), 1608 (C]N), 1263 (C]S);
References
1H NMR (CDCl3)
d
: 0.81 (d, 6H, J ¼ 6.58 Hz, (CH3)2), 1.61 (d, 3H,
J ¼ 7.20 Hz, CH3), 1.68–1.76 (m, 1H, CH–(CH3)2), 2.37 (d, 2H,
J ¼ 7.20 Hz, CH2), 4.31 (q, 1H, J ¼ 7.20 Hz, CHCH3), 6.08 (s, 2H,
NCH2N), 6.94–7.57 (m, 18H, Ar–H), 10.17 (s, 1H, N]CH); FABMS
(m/z, %): 623 (Mþ þ 2, 85), 624 (Mþ þ 1, 89), 623 (Mþ, 78), 441
(59), 440 (29), 182 (100), 161 (27).
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6.3.4. Compound 6k
IR (KBr)
NMR (CDCl3)
J ¼ 7.24 Hz, CH3), 1.73–1.79 (m, 1H, CH–(CH3)2), 2.40 (d, 2H,
J ¼ 7.12 Hz, CH2), 2.87 (t, 4H, CH2NCH2), 3.73 (t, 4H, CH2OCH2), 4.42
(q, 1H, J ¼ 7.24 Hz, CHCH3), 5.18 (s, 2H, NCH2N), 7.06 (d, 2H,
J ¼ 8.12 Hz, 30,50-H), 7.13 (d, 2H, J ¼ 8.12 Hz, 20,60-H), 7.86 (d, 2H,
J ¼ 8.84 Hz, 200,600-H), 8.28 (d, 2H, J ¼ 8.84 Hz, 300,500-H), 10.65 (s, 1H,
N]CH); FABMS (m/z, %): 509 (Mþ þ 1, 68), 508 (Mþ, 25), 161 (86),
100 (100).
g
/cmꢂ1: 2951, 2868 (C–H), 1610 (C]N), 1264 (C]S); 1H
d: 0.82 (d, 6H, J ¼ 6.60 Hz, (CH3)2), 1.72 (d, 3H,
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6.3.5. Compound 6l
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10 (2001) 239–240.
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IR (KBr)
NMR (CDCl3)
g
/cmꢂ1: 2953, 2858 (C–H), 1607 (C]N), 1273 (C]S); 1H
d: 0.81 (d, 6H, J ¼ 6.60 Hz, (CH3)2), 1.71 (d, 3H,
J ¼ 7.20 Hz, CH3), 1.72–1.79 (m, 1H, CH–(CH3)2), 2.29 (s, 3H, N–CH3),
2.39 (d, 2H, J ¼ 7.12 Hz, CH2), 2.46 (t, 4H, CH2NCH2), 2.95 (t, 4H,
CH2NCH2), 4.38 (q, 1H, J ¼ 7.20 Hz, CHCH3), 5.28 (s, 2H, NCH2N),
7.04 (d, 2H, J ¼ 8.12 Hz, 30,50-H), 7.12 (d, 2H, J ¼ 8.10 Hz, 20,60-H), 7.84
(d, 2H, J ¼ 8.84 Hz, 200,600-H), 8.27 (d, 2H, J ¼ 8.84 Hz, 300,500-H), 10.62
(s, 1H, N]CH); FABMS (m/z, %): 522(Mþ þ 1, 55), 521 (Mþ, 41), 161
(78), 113 (100).
6.3.6. Compound 6m
IR (KBr)
NMR (CDCl3)
g
/cmꢂ1: 2961, 2855 (C–H), 1601 (C]N), 1255 (C]S); 1H
d: 0.81 (d, 6H, J ¼ 6.58 Hz, (CH3)2), 1.62 (d, 3H,
J ¼ 7.20 Hz, CH3), 1.69–1.77 (m, 1H, CH–(CH3)2), 2.39 (d, 2H,
J ¼ 7.18 Hz, CH2), 4.32 (q, 1H, J ¼ 7.20 Hz, CHCH3), 5.98 (s, 2H,
NCH2N), 7.02 (d, 2H, J ¼ 8.08 Hz, 30,50-H), 7.12 (d, 2H, J ¼ 8.08 Hz,
[27] J.R. Reid, N.D. Heindel, J. Heterocycl. Chem. 13 (1976) 925–926.
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