Isomeric acetoxy analogs of celecoxib and their evaluation as cyclooxygenase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2011.08.053

A group of celecoxib analogs having a SO₂NH₂ (9a-f), or SO₂Me (12a-f), COX-2 pharmacophore at the para-position of the N-1 phenyl ring in conjunction with a C-5 phenyl ring having a variety of substituents (4-, 3-, 2-OAc;

Full text of DOI:10.1016/j.bmcl.2011.08.053

Bioorganic & Medicinal Chemistry Letters 21 (2011) 6074–6080
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Isomeric acetoxy analogs of celecoxib and their evaluation
as cyclooxygenase inhibitors
M. Abdur Rahim a, P.N. Praveen Rao b, Atul Bhardwaj a, Jatinder Kaur a,
Zhangjian Huang a, Edward E. Knaus a,
⇑
a Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2N8
b School of Pharmacy, Health Science Campus, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 July 2011
Revised 8 August 2011
Accepted 11 August 2011
Available online 19 August 2011
A group of celecoxib analogs having a SO2NH2 (9a–f), or SO2Me (12a–f), COX-2 pharmacophore at the para-
position of the N-1 phenyl ring in conjunction with a C-5 phenyl ring having a variety of substituents (4-,
3-, 2-OAc; 4-Me,2-OAc, 4-Me,3-OAc, 4-F,2-OAc) was synthesized for evaluation as cyclooxygenase (COX)
inhibitors of the COX-1/COX-2 isozymes. Within this group of compounds, 1-(4-aminosulfonylphenyl)-
3-trifluoromethyl-5-(2-acetoxy-4-fluorophenyl)pyrazole (9f) emerged as the most potent (COX-1
IC50 = 0.7
exhibited good anti-inflammatory activity (ED50 = 42.3 mg/kg) which was lower than the reference drug
celecoxib (ED50 = 10.8 mg/kg), but greater than ibuprofen (ED50 = 67.4 mg/kg) and aspirin (ED50
128.7 mg/kg). Molecular modeling studies for 9f showed that the SO2NH2 group assumes a position within
the secondary pocket of the COX-2 active site wherein the SO2NH2 oxygen atom is hydrogen bonded to the
H90 residue (2.90 Å), the SO2NH2 nitrogen atom forms a hydrogen bond with L352 (NÁ Á ÁO = 2.80 Å), and the
acetyl group is positioned in the vicinity of the S530 residue where the acetyl oxygen atom undergoes
hydrogen bonding to L531 (2.99 Å).
lM; COX-2 IC50 = 0.015 lM) and selective (COX-2 selectivity index = 47) inhibitor agent that
Keywords:
Celecoxib
Acetoxy regioisomers
Cyclooxygenase-1 and -2 inhibition
Molecular modeling
Anti-inflammatory activity
=
Ó 2011 Elsevier Ltd. All rights reserved.
Acetylsalicyclic acid (aspirin, 1), a moderately active anti-
inflammatory (AI) and non-narcotic analgesic agent, is a unique
nonselective cyclooxygenase (COX) inhibitor based on its ability
to acetylate the Ser530 hydroxyl group in the primary COX binding
site of the COX-1 and COX-2 isozymes (see structures 1–4 in Figure
1). In this context, aspirin is a 10- to 100-fold more potent inhibitor
of the COX-1, compared to the COX-2, isozyme.1 Acetylation of the
weakly nucleophilic Ser530 OH group by aspirin is envisioned to
involve electrostatic binding of its COOH (anionic carboxylate site)
to the Arg120 (cationic guanidinium site) residue near the mouth
of the COX binding site, which orients the ortho-acetoxy moiety
in close proximity to the Ser530 OH, which is acetylated. The con-
stitutive COX-1 isozyme provides important physiological mainte-
nance actions such as gastroprotection and vascular homeostasis.2
In comparison, the COX-2 isozyme is induced by mitogenic and
proinflammatory stimuli3 resulting in peripheral inflammatory ac-
tions.4 Some of aspirin’s desirable clinical effects can be attributed
to acetylation of COX-2, while its antithrombotic and ulcerogenic
effects are attributed to acetylation of COX-1. The ability of aspirin
to inhibit blood platelet aggregation is currently considered to be a
clinically useful prophylactic effect that can reduce the incidence
of thrombus formation. These observations were exploited in the
design of the N-acetylsulfonamides 25 and 3,6 that are potent and
selective COX-2 inhibitors. In an earlier study, we reported a novel
class of isomeric acetoxy analogs of rofecoxib (4), which are potent
and selective COX-2 inhibitors.7 We now report the synthesis,
COX-1/COX-2 inhibitory and some AI activities, and molecular
modeling studies for a group of celecoxib analogs (9a–f, 12a–f)
possessing an acetoxy moiety, that may like aspirin, have the po-
tential to acetylate the COX-1 and/or COX-2 isozyme.
The 1-(4-aminosulfonylphenyl)-3-trifluoromethyl-5-(4-aryl)pyr-
azoles (9a–f) were synthesized using the synthetic methodologies
illustrated in Scheme 1. Thus, Claisen condensation of a substituted-
acetophenone 5a–f with ethyl trifluoroacetate in methyl tert-butyl
ether (MTBE) afforded the respective 1,3-dicarbonyl compound
6a–f as illustrated in Scheme 1. 1H NMR spectra indicate that 6a–f
in CDCl3 solution exist predominantly (>99%) as the enolic tauto-
mer—C(@O)–CH@C(CF3)OH. In this regard, the 1H NMR spectrum
for compound 6a showed a 1H singlet at d 6.52 (@CH) and a broad
1Hsinglet atd 15.5 (@CHOH). The high stability of the enolic tautomer
is attributed to a hydrogen bonding interaction between the enolic
hydroxyl group and a fluorine atom of the CF3 moiety.8 Condensation
of a 1,3-dione 6a–f with (4-aminosulfonylphenyl)hydrazine hydro-
chloride afforded the respective 1,5-diarylpyrazole 7a–f. O-Demeth-
ylation of the methoxyphenyl compounds 7a–e using NaSEt afforded
the corresponding hydroxyphenyl compound 8a–e, which on
⇑
Corresponding author. Tel.: +1 780 492 5993; fax: +1 780 492 1217.
E-mail address: eknaus@pharmacy.ualberta.ca (E.E. Knaus).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.08.053

M. Abdur Rahim et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6074–6080
6075
fluoromethyl-5-(acetoxyphenyl)pyrazole 9a–e. In contrast, the 2-
acetoxy-4-fluorophenyl compound9f wassynthesized by O-demeth-
ylation of 7f upon reaction with pyridine hydrochloride9 at
190–220 °C for 1 h to give the 2-hydroxy-4-fluorophenyl compound
8f that was subsequently acetylated to provide the target 2-acet-
oxy-4-fluorophenyl product 9f.
CO2H
CO2H
F
O
C
O
Me
SO2NHCOMe
F
Aspirin (1)
(2)
O
The 1-(4-methylsulfonylphenyl)-3-trifluoromethyl-5-(4-aryl)pyr-
azoles (12a–f) were synthesized using the synthetic methodologies
illustrated in Scheme 2. The Claisen condensation of 1,3-diones 6a–f
with (4-methylthiophenyl)hydrazineÁHCl in EtOH at reflux tempera-
ture yielded the respective pyrazole product 10a–f. Methyl sulfonyl
analogs of 10a–e, havingaSO2Me substituent in place of the SMe group
present in 10a–e, could not be O-demethylated using NaSEt since the
SO2Me moiety was preferentially replaced by a SEt substituent.
Fortunately, the methylthiophenyl compounds 10a–e were success-
fully O-demethylated using NaSEt to furnish the respective phenolic
product 11a–e. In contrast, the attempted O-demethylation of
1-(4-methylthiophenyl)-3-trifluoromethyl-5-(2-methoxy-4-fluo-
rophenyl)pyrazole 10f using NaSEt also resulted in concomitant dis-
placement of the F-atom by a SEt substituent. Further investigation
showed that the 2-methoxy-4-fluorophenyl compound 10f could be
selectively O-demethylated upon treatment with 48% HBr in the
presenceof the phase transfercatalyst hexadecyltributylphosphoni-
um bromide at reflux temperature for 5 h to furnish the required 2-
hydroxy-4-fluorophenyl compound 11f. Subsequent acetylation of
the phenols 11a–f using acetyl chloride in the presence of Et3N
yielded the respective acetates. Subsequent oxidation of the SMe
MeO2S
4
3
CH2CO2H
O
C
O
Me
2
F
SO2NHCOMe
(3)
O
(4)
Figure 1. Chemical structures of the non-selective COX-1/COX-2 inhibitor aspirin
(1), and the selective COX-2 inhibitors N-acetyl-2-carboxy-4-(2,4-difluoro-
phenyl)benzenesulfonamide (2),5 N-acetyl-3-carboxymethyl-6-fluorobenzensulf-
onamide (3)6 and the regioisomeric analogs of rofecoxib (4).7
R1
2
3
O
C
1
R
a
CF3
OH
4
Me
O
5a: R1 = 4-OMe
5b: R1 = 3-OMe
5c: R1 = 2-OMe
6a: R1 = 4-OMe
6b: R1 = 3-OMe
6c: R1 = 2-OMe
5d: R1 = 4-Me,2-OMe
5e: R1 = 4-Me,3-OMe
5f: R1 = 4-F,2-OMe
6d: R1 = 4-Me,2-OMe
6e: R1 = 4-Me,3-OMe
6f: R1 = 4-F,2-OMe
CF3
R1
3
2
b
4
N
CF3
CF3
CF3
OH
N
R1
a
N
N
N
O
c
N
R1
R1
6a: R1 = 4-OMe
6b: R1 = 3-OMe
6c: R1 = 2-OMe
SMe
10a: R1 = 4-OMe
6d: R1 = 4-Me,2-OMe
6e: R1 = 4-Me,3-OMe
6f: R1 = 4-F,2-OMe
10b: R1 = 3-OMe
SO2NH2
SO2NH2
10c: R1 = 2-OMe
8a: R1 = 4-OH
7a: R1 = 4-OMe
10d: R1 = 4-Me,2-OMe
10e: R1 = 4-Me,3-OMe
10f: R1 = 4-F,2-OMe
8b: R1 = 3-OH
7b: R1 = 3-OMe
8c: R1 = 2-OH
7c: R1 = 2-OMe
8d: R1 = 4-Me,2-OH
8e: R1 = 4-Me,3-OH
8f: R1 = 4-F,2-OH
7d: R1 = 4-Me,2-OMe
7e: R1 = 4-Me,3-OMe
7f, R1 = 4-F, 2-OMe
b
CF3
CF3
d
N
N
N
N
R1
CF3
c, d
R1
9a: R1 = 4-OAc
N
N
9b: R1 = 3-OAc
R1
9c: R1 = 2-OAc
SO2Me
9d: R1 = 4-Me,2-OAc
9e: R1 = 4-Me,3-OAc
9f: R1 = 4-F,2-OAc
SMe
11a: R1 = 4-OH
12a: R1 = 4-OAc
11b: R1 = 3-OH
12b: R1 = 3-OAc
12c: R1 = 2-OAc
SO2NH2
11c: R1 = 2-OH
Scheme 1. Reagents and conditions: (a) CF3COOEt, methyl tert-butyl ether (MTBE),
NaOMe (25% w/v in MeOH), reflux, 24 h; (b) (4-aminosulfonylphenyl)hydra-
zineÁHCl, EtOH, reflux, 24 h; (c) NaSEt, DMF, 120 °C, 3 h for O-demethylation of
7a–e, and pyridineÁHCl, 190–220 °C, 1 h for O-demethylation of 7f; (d) AcCl, Et2O,
0 °C?25 °C, 1 h.
11d: R1 = 4-Me,2-OH
11e: R1 = 4-Me,3-OH
11f: R1 = 4-F,2-OH
12d: R1 = 4-Me,2-OAc
12e: R1 = 4-Me,3-OAc
12f: R1 = 4-F,2-OAc
Scheme 2. Reagents and conditions: (a) (4-Methylthiophenyl)hydrazineÁHCl, EtOH,
reflux, 24 h; (b) NaSEt, DMF, 120 °C, 3 h for O-demethylation of 10a–e, and 48% HBr,
hexadecyltributylphosphonium bromide, 115 °C, reflux, 5 h for O-demethylation of
10f; (c) AcCl, Et3N, Et2O, 0 °C?25 °C, 1 h; (d) Oxone, MeOH, 25 °C, 16 h.
subsequent acetylation with acetyl chloride, employing a one-pot
procedure furnished the respective 1-(4-aminosulfonylphenyl)-3-tri

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M. Abdur Rahim et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6074–6080
Table 1
In vitro COX-1 and COX-2 inhibition, and COX-2 selectivity index (SI), data
CF3
R2
2
N
3
N
4
R1
R1
R2
IC50 (lM)
Anti-inflammatory activityc
a
Compound
COX-1
COX-2
COX-2 SIb
% Inhibition (dose mg/kg po)d or ED50 valuee (mg/kg po)
9a
9b
9c
8d
9d
8e
9e
9f
12a
12b
12c
12d
12e
12f
Celecoxib
Ibuprofen
Aspirin
SO2NH2
SO2NH2
SO2NH2
SO2NH2
SO2NH2
SO2NH2
SO2NH2
SO2NH2
SO2Me
SO2Me
SO2Me
SO2Me
SO2Me
SO2Me
SO2NH2
4-OAc
3-OAc
2-OAc
4-Me,2-OH
4-Me,2-OAc
4-Me,3-OH
4-Me,3-OAc
4-F,2-OAc
4-OAc
3-OAc
2-OAc
4-Me,2-OAc
4-Me,3-OAc
4F,2-OAc
4-Me
>100
>100
>100
36
>100
>100
>100
0.7
80.3
>100
NT
>100
NT
38.0
17.1
>100
3
2.1
1.7
7.3
0.015
4.1
22.3
NT
7.5
>2.6
5.8
—
Inactive (50 mg/kg po)d
NTf
NT
12
Inactive (10 mg/kg po)d
>47
>58
>13
46.6
19.6
>4.4
—
>13
—
>5.3
110
2.64
0.13
Inactive (50 mg/kg po)d
NT
Inactive (50 mg/kg po)d
42.3e
NT
NT
NT
NT
NT
Inactive (10 mg/kg po)d
>100
7.7
2.9
18.7
0.07
1.1
NT
10.8d
67.4d
128.7d
0.3
2.4
a
The in vitro test compound concentration required to produce 50% inhibition of ovine COX-1 or COX-2. The result (IC50, lM) is the mean of two determinations acquired
using the enzyme immuno assay kit (Catalog No. 560101, Cayman Chemicals Inc., Ann Arbor, MI, USA) and the deviation from the mean is <10% of the mean value.
b
In vitro COX-2 selectivity index (COX-1 IC50/COX-2 IC50).
Inhibitory activity in a carrageenan-induced rat paw edema assay.
The results are expressed as mean value (n = 4) at 3 h following administration of the test compound at the specified dose.
ED50 value.
c
d
e
f
NT = not tested.
substituent to a SO2Me substituent afforded the target pyrazoles
12a–f.
Many selective COX-2 inhibitors belong to a tricyclic class of
compounds which have two vicinal (adjacent) aryl substituents
attached to a five-membered central ring that acts as a scaffold
such as the furanone ring in rofecoxib or the pyrazole ring in cele-
coxib.10,11 para-Substituents on the adjacent aryl rings that provide
optimal COX-2 selectivity, potency and oral activity are usually a
Figure 2. Molecular modeling (docking) (a) compound 8e (carbon atoms in orange) in the binding site of COX-2 (pdb ID 6COX; Eintermolecular = À15.54 kcal/mol), and (b)
compound 8e (carbon atoms in orange) in the binding site of COX-1 (pdb ID 1EQG; Eintermolecular = À7.50 kcal/mol). Hydrogen atoms of amino acid residues have been removed
to improve clarity.

M. Abdur Rahim et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6074–6080
6077
COX-2 pharmacophore on one ring (–SO2Me, –SO2NH2) and a F, Me
or H substituent on the other aryl ring.12 An ortho-substituent on
an aryl ring, which may distort the active orientation of the two
aryl rings, such as 2-MeO-C6H4-, may lower or abolish COX-2
inhibitory activity.13 These structure–activity relationships (SARs)
show that the nature and position of substituents on the central
ring, and on the two vicinal aryl ring moieties attached to the cen-
tral ring, are important determinants of the overall drug volume
(size and shape), and their type of binding interactions to the
COX-2 active site, which in turn dictates COX-2/COX-1 selectivity.
Accordingly, we envisaged that (i) it may be possible to reduce the
COX-2 selectivity of celecoxib by incorporating an acetoxy substi-
tuent at the ortho-, meta- or para-position of the C-5 phenyl ring in
compounds 9a–f and 12a–f, and (ii) these acetoxy compounds
may have the ability to acetylate COX-1 in platelets like aspirin
to provide an anti-thrombotic effect.
sponding SO2Me analog (3-OAc, 9b > 12b; 4-Me,2-OAc, 9d > 12d;
4-F,2-OAc, 9f > 12f). The SO2Me compounds 12, like the SO2NH2
compounds 9, were weak or inactive inhibitors of the COX-1
isozyme.
AI activities were determined using a carrageenan-induced rat
foot paw edema model (see data in Table 1). Among the group of
compounds evaluated as AI agents (8d, 9a, 9d, 9e, 9f, 12e), 1-(4-
aminosulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxy-4-fluoro-
phenyl)pyrazole (9f) was the only compound that showed AI
activity. The 4-F,2-OAc compound 9f exhibited good anti-inflam-
matory activity (ED50 = 42.3 mg/kg) which was lower than the ref-
erence drug celecoxib (ED50 = 10.8 mg/kg), but greater than
ibuprofen (ED50 = 67.4 mg/kg) and aspirin (ED50 = 128.7 mg/kg).
Molecular modeling (docking) experiments were performed,
using X-ray crystal structure data for COX-1 and COX-2, to further
corroborate the biological assay results acquired for this new group
of celecoxib analogs and gain insight into their plausible mode of
interaction(s) within the COX-1 and COX-2 isozymes. The
In vitro COX-1/COX-2 enzyme inhibition studies (see data in
Table 1) for the three acetoxy (AcO) regioisomers 9a–c showed
the position of the AcO substituent was a determinant of COX-2
potency where the relative COX-2 inhibitory potency order was
4-Me,3-OH compound 8e (COX-2 IC50 = 1.7 lM) assumes a favor-
able orientation within the COX-2 binding site (Fig. 2a) where (i)
the SO2NH2 group is positioned near Y385, Y348 and F381 active
site residues, (ii) a SO2NH2 nitrogen atom shows hydrogen bonding
(NÁ Á ÁHO = 2.35 Å) with Y385, (iii) the pyrazole ring is positioned
near the entrance of the secondary pocket region of the COX-2 ac-
tive site in the vicinity of H90, G192, A516, V523 and I517, and (iv)
the CF3 group is inserted deep into the secondary pocket region
where it is in close proximity to the H90 and R513 residues. The
4-Me,2-OH regioisomer 8d (data not shown) assumes a similar ori-
entation and undergoes similar binding interactions within the
COX-2 active site.
3-AcO (IC50 = 17.1
IC50 >100 M) relative to the more potent parent drug celecoxib
(IC50 = 0.07 M). The approximately equipotent di-substituted
4-Me,2-OH (8d, IC50 = 3.0 M) and 4-Me,2-OAc (9d, IC50 = 2.1 M)
l
M) > 4-AcO (IC50 = 38.0
lM) ꢀ 2-AcO (inactive,
l
l
l
l
compounds were more potent COX-2 inhibitors than the mono-
substituted AcO compounds 9a–c. In contrast, the di-substituted
4-F,2-OAc compound 9f exhibited more potent COX-2 inhibition
(IC50 = 0.015 lM) than celecoxib. It is noteworthy that the 4-F,2-
OAc compound 9f is a more potent COX-2 inhibitor than the
4-Me,2-OAc analog 9d. Within the sulfonamide group of com-
pounds 8d and 9a–f, the 4-Me,2-OH (8d, IC50 = 36.0
4-F,2-OAc (9f, IC50 = 0.7 M) compounds are the only two com-
pounds, that like celecoxib (COX-1 IC50 = 7.7 M), also inhibited
the COX-1 isozyme. Consequently, the 4-F,2-OAc compound 9d,
which is a dual COX-2/COX-1 inhibitor, has a lower COX-2 selectiv-
ity index (46.6) than celecoxib (110). In comparison, the SO2NH2
group of compounds 9, with the exception of the 4-OAc compound
(12a > 9a), were more potent COX-2 inhibitors than the corre-
l
M) and
A docking study (Fig. 3a) for the 4-F,2-OAc compound 9f (COX-2
IC50 = 0.015 lM) indicates that the SO2NH2 group assumes a posi-
l
l
tion within the secondary pocket of the COX-2 active site wherein
the SO2NH2 oxygen atom is hydrogen bonded to the H90 residue
(2.90 Å) and the nitrogen atom forms a hydrogen bond with L352
(NÁ Á ÁO = 2.80 Å). Consistent with our design, the acetyl group pres-
ent in 9f is located in the vicinity of the S530 residue where acetyl
oxygen atom undergoes hydrogen bonding to L531 (2.99 Å). These
Figure 3. Molecular modeling (docking) (a) compound 9f (carbon atoms in orange) in the binding site of COX-2 (pdb ID 6COX; Eintermolecular = À16.36 kcal/mol), and (b)
compound 9f (carbon atoms in orange) and ibuprofen (green) in the binding site of COX-1 (pdb ID 1EQG; Eintermolecular = À13.50 kcal/mol). Hydrogen atoms of amino acid
residues have been removed to improve clarity.

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M. Abdur Rahim et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6074–6080
carbon resonances appear as negative peaks. Elemental analyses were
performed for C, H, and N (Micro Analytical Service Laboratory, Department
of Chemistry, University of Alberta). Silica gel column chromatography was
performed using Merck Silica Gel 60 ASTM (70–230 mesh). All other reagents
were purchased from the Aldrich Chemical (Milwaukee, WI). In cases where
the acetophenone (5) was not commercially available, it was prepared using a
conventional method.19 In vitro COX-1 and COX-2 inhibition assays were
performed using an enzyme immunoassay (EIA) kit purchased from Cayman
Chemical, Ann Arbor, MI. Male Sprague-Dawley rats, used in the anti-
inflammatory assay, were purchased from Animal Health Services, University
of Alberta. All experiments involving animals were carried out using protocols
approved by the Animal Welfare Committee, University of Alberta.
appreciable interactions of 9f with COX-2 active site residues in
consistent with the experimentally observed potent COX-2
inhibition.
Docking the inactive 4-Me,3-OH compound 8e (COX-1 IC50
=
>100 M) within the COX-1 binding site showed that 8e undergoes
l
only partial insertion into the COX-1 active site since the SO2NH2
moiety is not able to gain complete entry into the COX-1 active site
(Fig. 2b). In contrast, a docking study (Fig. 3b) employing the 4-F,2-
OAc compound 9f (COX-1 IC50 = 0.7 lM) showed that 9f undergoes
complete entry into the COX-1 active site, and that its SO2NH2
group is located in a similar position to the COOH group of ibupro-
fen when bound to the COX-1 enzyme (X-ray crystal structure).14
The interspatial distance between the carbonyl carbon atom of
the acetoxy moiety and the oxygen atom of the S530 hydroxyl
group that could potentially be acetylated is 3.63 Å. The COX-1,
but not COX-2, isozyme is present in platelets. In this regard, the
acetoxy group in 9f could potentially inhibit thrombus formation
by acetylation of platelet COX-1 thereby preventing platelet aggre-
gation. This favorable orientation of 9f within the active site of
COX-1 is consistent with the modest COX-1 inhibitory activity ob-
served. Other docking experiments showed that three acetoxy
General method for the preparation of 4,4,4-trifluoro-1-(aryl)butane-1,3-diones
(6a–f): A solution of NaOMe (25% w/v) in MeOH (6.0 ml) was added to a
solution of ethyl trifluoroacetate (2.5 mL, 21 mmol) in methyl tert-butyl ether
(MTBE, 10 mL) with stirring during
a period of 5 min. A solution of an
acetophenone (5a–f, 19 mmol) in MTBE (5.0 mL) was then added drop wise
during 5 min, the reaction mixture was heated at reflux for 24 h, and the
mixture was cooled to 25 °C prior to quenching with 10% HCl (20 mL).
Extraction with EtOAc (3 Â 20 mL), drying the combined EtOAc extracts
(Na2SO4), and removal of the solvent in vacuo furnished a red solid which
was purified by silica gel column chromatography (CH2Cl2/hexane, 9:1, v/v) to
afford the respective product 6a–6f. Representative physical, spectroscopic and
microanalytical data for 6a and 6f are listed below.
4,4,4-Trifluoro-1-(4-methoxyphenyl)butane-1,3-dione (6a): Yield, 42%; mp 57–
58 °C; IR (KBr): 2934 (enolic-OH), 1593 (C@O) cmÀ1 1H NMR (CDCl3): d 3.91 (s,
;
3H, OCH3), 6.52 (s, 1H, @CH), 6.99 (d, J = 8.9 Hz, 2H, phenyl H-2, H-6), 7.95 (d,
J = 8.9 Hz, 2H, phenyl H-3, H-5), 15.5 (broad s, 1H, enolic-OH). 13C NMR
(CDCl3): d 55.8 (OCH3), 91.5 (@CH, enolic), 114.6, 125.3, 130.0, 164.6 (phenyl
carbons), 117.4 (q, 1JC,F = 283.3 Hz, CF3), 175.6 (q, 2JC,F = 36.3 Hz, C-3), 186.1 (C-
3 CO). Anal. Calcd for C11H9F3O3: C, 53.67; H, 3.68. Found: C, 54.04; H, 3.64.
4,4,4-Trifluoro-1-(2-methoxy-4-fluorophenyl)butane-1,3-dione (6f): Yield, 65%;
regioisomers 9a–9c (COX-1 IC50’s >100 lM) do not show signifi-
cant binding interaction within the COX-1 active site.
In conclusion, a group of 3-trifluoromethyl-5-(4-aryl)pyrazoles
that possess a 1-(4-aminosulfonylphenyl) (9a–f), or 1-(4-meth-
ylsulfonylphenyl) (12a–f), substituent were synthesized15 for
evaluation as COX-1/COX-2 inhibitors16 and AI agents,17 and for
molecular modeling (docking) studies.18 Among this group of com-
pounds, a ‘lead-compound’ 1-(4-aminosulfonylphenyl)-3-trifluoro-
methyl-5-(2-acetoxy-4-fluorophenyl)pyrazole (9f) was identified
(i) that exhibited a good COX-2 selectivity index of 46.6 (COX-1
mp: 85–86 °C; IR (KBr): 3385 (enolic-OH), 1600 (CO) cmÀ1 1H NMR (CDCl3): d
;
3.96 (s, 3H, OCH3), 6.70–6.82 (m, 2H, phenyl hydrogens), 6.94 (s, 1H, @CH),
8.00–8.06 (m, 1H, phenyl hydrogen), 15.05–15.50 (broad resonance, 1H,
enolic-OH). Anal. Calcd for C11H8F3O4: C, 50.01; H, 3.05. Found: C, 49.75; H,
2.89.
General method for the preparation of 1-(4-aminosulfonylphenyl)-3-
trifluoromethyl-5-(4-aryl)pyrazoles (7a–f): (4-Aminosulfonylphenyl)hydrazine
hydrochloride20 (1.97 g, 8.8 mmol) was added to a stirred solution of a dione
6a–f (8 mmol) in EtOH (24 mL of 95% w/v), and the mixture was heated at
reflux with stirring for 24 h. After cooling to 25 °C, the solvent was removed in
vacuo, and the residue obtained was dissolved in water (25 mL). The organic
material was extracted with EtOAc (3 Â 25 mL), the combined EtOAc extracts
were washed with water (20 mL) and brine (20 mL), and the EtOAc fraction
was dried (Na2SO4). Filtration and removal of the solvent in vacuo furnished
the respective product 7a–f. Representative physical, spectroscopic and
microanalytical data for 7a and 7f are listed listed.
IC50 = 0.7 lM; COX-2 IC50 = 0.015 lM), and (ii) showed good AI
activity (ED50 = 42.3 mg/ko po).
Acknowledgment
We are grateful to the Canadian Institutes of Health Research
(MOP-14712) for financial support of this research.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(4-methoxyphenyl)pyrazole (7a):
Yield, 76%; mp 151–152 °C; IR (KBr): 3365, 3268 (NH), 1320, 1159 (SO2) cmÀ1
;
1H NMR (CDCl3): d 3.84 (s, 3H, OCH3), 4.98 (s, 2H, SO2NH2), 6.73 (s, 1H, pyrazole
H-4), 6.90 (d, J = 8.6 Hz, 2H, Ar-H), 7.16 (d, J = 8.9 Hz, 2H, Ar-H), 7.49 (d,
J = 8.9 Hz, 2H, Ar-H), 7.91 (d, J = 8.6 Hz, 2H, Ar-H). Anal. Calcd for
References and notes
C
17H14F3N3O3S: C, 51.38; H, 3.55; N, 10.57. Found: C, 51.50; H, 3.57; N, 10.42.
1. Meade, E. A.; Smith, W. L.; DeWitt, D. L. J. Biol. Chem. 1993, 268, 6610.
2. Smith, W. L.; DeWitt, D. L. Adv. Immunol. 1996, 62, 167.
3. Herschman, H. R. Biochem. Biophys. Acta 1996, 1299, 125.
4. Dubois, R. N.; Abramson, S. B.; Crofford, L.; Gupta, R. A.; Simon, L. S.; Van de
Putta, L. B. A.; Lipsky, P. E. FASEB J. 1998, 12, 1063.
5. Chen, Q.-H.; Praveen Rao, P. N.; Knaus, E. E. Bioorg. Med. Chem. 2005, 13, 2459.
6. Chen, Q.-H.; Praveen Rao, P. N.; Knaus, E. E. Bioorg. Med. Chem. 2005, 13, 4694.
7. Abdur Rahim, M.; Praveen Rao, P. N.; Knaus, E. E. Bioorg. Med. Chem. Lett. 2002,
12, 2753.
8. Park, J. D.; Brown, H. A.; Lacher, J. R. J. Am. Chem. Soc. 1953, 75, 4753.
9. Dikshit, D. K.; Singh, S.; Singh, M. M.; Kamboj, V. P. Ind. J. Chem. 1990, 29B, 954.
10. Khanna, I. K.; Weier, R. M.; Yu, Y.; Collins, P. W.; Miyashiro, J. M.; Koboldt, C. M.;
Veenhuizen, A. W.; Currie, J. L.; Seibert, K.; Isakson, P. C. J. Med. Chem. 1997, 40,
1619.
11. Penning, T. D.; Tally, J. J.; Bertenshaw, S. R.; Carter, J. S.; Collins, P. W.; Doctor,
S.; Graneto, M. J.; Lee, L. F.; Malecha, J. W.; Miyashiro, J. M.; Rogers, R. S.; Rogier,
D. J.; Yu, S. S.; Anderson, G. D.; Burton, E. G.; Cogburn, J. N.; Gregory, S. A.;
Koboldt, C. M.; Perkins, W. E.; Seibert, K.; Veenhuizen, A. W.; Zhang, Y. Y.;
Isakson, P. C. J. Med. Chem. 1997, 40, 1347.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(4-fluoro-2-
methoxyphenyl)pyrazole (7f): Yield, 68%; mp 165–166 °C; IR (KBr): 3355, 3250
(NH2), 1285, 1165 (SO2) cmÀ1 1H NMR (CDCl3): d 3.42 (s, 3H, OCH3), 4.90 (s,
;
2H, SO2NH2), 6.58 (dd, J = 10.7, 2.4 Hz, 1H, ArH), 6.72 (s, 1H, pyrazole H-4),
6.73–6.80 (m, 1H, ArH), 7.26–7.31 (m, 1H, ArH), 7.45 (d, J = 8.9 Hz, 2H, ArH),
7.89 (d, J = 8.9 Hz, 2H, ArH). Anal. Calcd for C17H13F4N3O3S: C, 49.16; H, 3.15; N,
10.12. Found: C, 48.91; H, 3.20; N, 10.21.
General methods for the preparation of 1-(4-aminosulfonylphenyl)-3-
trifluoromethyl-5-(4-aryl)pyrazoles (8a–f): NaSEt (1.51 g, 18 mmol) was added
to a solution of a methoxyphenyl compound 7a–e (5.4 mmol) in DMF (18 mL),
and the reaction mixture was heated at reflux temperature for 3 h. The reaction
mixture was cooled to 25 °C, and quenched by addition of 1 N HCl (20 mL).
Extraction with EtOAc (3 Â 25 mL), washing the combined EtOAc extracts with
water (50 mL), drying the EtOAc fraction (Na2SO4), and removal of the solvent
in vacuo gave the respective product 8a–e which was purified by silica gel
column chromatography using hexane/EtOAc (1:1, v/v) as eluant. O-
Demethylation of 7f was carried out by heating a mixture of 7f (1.25 g,
3.0 mmol) and excess pyridine hydrochloride (3.47 g, 30.0 mmol) at 190–
220 °C for 1 h. After cooling to 25 °C, the reaction mixture was quenched by
addition of water (50 ml) and the organic material was extracted with EtOAc
(3 Â 20 mL). The combined EtOAc extracts were washed with H2O (25 mL), the
organic fraction was dried (Na2SO4), and the solvent was removed in vacuo to
give 8f which was used without further purification to prepare the
acetoxyphenyl product 9f. Representative physical, spectroscopic and
microanalytical data for 8a, 8d and 8e are listed below.
12. Pinto, D. J.; Copeland, R. A.; Covington, M. B.; Pitts, W. J.; Batt, D. G.; Orwat, M.
J.; Lam, G. W.; Joshi, M.; Chan, Y.-C.; Wang, S.; Trzaskos, J. M.; Magolda, R. L.;
Kornhauser, D. M. Bioorg. Med. Chem. Lett. 1996, 6, 2907.
13. Khanna, I. K.; Weier, R. M.; Yu, Y.; Xu, X. D.; Koszyk, F. J.; Collins, P. W.; Koboldt,
C. M.; Veenhuizen, A. W.; Perkins, W. E.; Casler, J. J.; Masferrer, J. L.; Zhang, Y.
Y.; Gregory, S. A.; Seibert, K.; Isakson, P. C. J. Med. Chem. 1997, 40, 1634.
14. Selinsky, B. S.; Gupta, K.; Sharkey, C. T.; Loll, P. J. Biochemistry 2001, 40, 5172.
15. General: Melting points were determined using a Buchi capillary apparatus and
are uncorrected. Infrared (IR) spectra were recorded using a Nicolet 550 Series
II Magna FT-IR spectrometer. Nuclear magnetic resonance (1H NMR, 13C NMR)
spectra were recorded on a Bruker AM-300 spectrometer. 13C NMR spectra
were acquired using the J modulated spin echo technique where methyl and
methine carbons appear as positive peaks and methylene and quaternary
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(4-hydroxyphenyl)pyrazole (8a):
Yield, 54%; mp 206–208 °C; IR (KBr): 3362, 3257 (OH, NH), 1352, 1157 (SO2)
cmÀ1 1H NMR (DMSO-d6): d 6.77 (d, J = 8.5 Hz, 2H, Ar-H), 7.09–7.13 (m, 3H, Ar-
;
H and pyrazole H-4), 7.51–7.54 (m, 4H, Ar-H and SO2NH2), 7.87 (d, J = 8.5 H, 2H,
Ar-H), 9.90 (s, 1H, Ar-OH). Anal. Calcd for C16H12F3N3O3S: C, 50.13; H, 3.16; N,
10.96. Found: C, 50.15; H, 3.08; N, 10.72.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(2-hydroxy-4-

M. Abdur Rahim et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6074–6080
6079
methylphenyl)pyrazole (8d): Yield, 79%; mp 184–185 °C; IR (KBr): 3375, 3230
(OH, NH), 1355, 1155 (SO2) cmÀ1 1H NMR (DMSO-d6): d 2.23 (s, 3H, 4-CH3–
C6H3–), 6.63 (s, 1H, pyrazole H-4), 6.70 (d, 7.6 Hz, 1H, Ar-H), 6.97 (s, 1H, Ar-H)
7.14 (d, J = 7.6 Hz, 1H, Ar-H), 7.48–7.50 (m, 4H, Ar-H, SO2NH2), 7.81 (d,
J = 8.9 Hz, 2H, Ar-H), 9.80 (s, 1H, OH). Anal. Calcd for C17H14F3N3O3 S: C, 51.38;
H, 3.55; N, 10.57. Found: C, 50.98; H, 3.43; N, 10.38.
5-(4-aryl)pyrazoles (10a–f): (4-Methylthiophenyl)hydrazine hydrochloride21
(0.95 g, 5.0 mmol) was added to a stirred solution of a dione 6a–f (5.0 mmol) in
EtOH (15 mL of 95% w/v), and the reaction was allowed to proceed at reflux
with stirring for 24 h. After cooling to 25 °C, the reaction mixture was
concentrated in vacuo, and water (10 mL) was added to the residue. The
organic material was extracted with EtOAc (3 Â 20 mL), the combined EtOAc
extracts were washed with water (50 mL) and brine (25 mL), the organic
fraction was dried (Na2SO4), and the solvent was removed in vacuo. The
residue obtained was purified by silica gel column chromatography using
hexane/EtOAc (2:1, v/v) as eluant to furnish the respective product 10a–f.
Representative physical, spectroscopic and microanalytical data for 10a and
10f are listed below.
1-(4-Methylthiophenyl)-3-trifluoromethyl-5-(4-methoxyphenyl)pyrazole (10a):
Yield, 64%; 1H NMR (CDCl3): d 2.48 (s, 3H, SCH3), 3.81 (s, 3H, OCH3), 6.67 (s,
1H, pyrazole H-4), 6.85 (d, J = 8.5 Hz, 2H, Ar-H), 7.13–7.26 (m, 6H, Ar-H). Anal.
Calcd for C18H15F3N2OS: C, 59.33; H, 4.15; N, 7.69. Found: C, 59.21; H, 4.12; N,
7.63.
1-(4-Methylthiophenyl)-3-trifluoromethyl-5-(4-fluoro-2-methoxyphenyl)pyrazole
(10f): Yield, 81%; mp 85–86 °C; 1H NMR (CDCl3): d 2.46 (s, 3H, SCH3), 3.46 (s,
3H, OCH3), 6.56 (dd, J = 10.7 [o-F-coupling], 2.1 Hz, [m-F-coupling], 1H, Ar-H),
6.67–6.73 (m, 2H, pyrazole H-4 and Ar-H), 7.17–7.26 (m, 5H, Ar-H). Anal. Calcd
for C18H14F4N2OS: C, 56.54; H, 3.69; N, 7.33. Found: C, 56.32; H, 3.61; N, 7.12.
General methods for the preparation of 1-(4-methylthiophenyl)-3-trifluoromethyl-
5-(4-aryl)pyrazoles (11a–f): NaSEt (0.63 g, 7.5 mmol) was added to a solution of
a methoxyphenyl compound 10a–e (3 mmol) in DMF (9 mL) with stirring , and
the mixture was heated to 120 °C and then at reflux for 3 h. The reaction
mixture was cooled to 25 °C, and the reaction was quenched by addition of 1 N
HCl (10 mL). Extraction with EtOAc (3 Â 25 mL), washing the combined EtOAc
extracts with water (50 mL) and brine (25 mL), drying the EtOAc fraction
(Na2SO4), and removal of the solvent in vacuo gave a light yellow solid.
Purification by silica gel column chromatography using hexane/EtOAc (3:1, v/
v) as eluant afforded the respective product 11a–e. O-Demethylation of 10f
was carried out by mixing 10f (0.1 mmol) with 48% HBr (1.2 mL) and
hexadecyltributylphosphonium bromide (0.10 g, 0.2 mmol), heating the
mixture to 115 °C and then reaction at reflux temperature for 5 h. The
reaction mixture was cooled to 25 °C, the mixture was extracted with EtOAc
(3 Â 25 mL), the EtOAc extracts were washed with water (50 mL), the EtOAc
fraction was dried (Na2SO4), the solvent was removed in vacuo, and the residue
was purified by silica gel column chromatography using hexane/EtOAc (1:1, v/
v) as eluant to afford 11f. Representative physical, spectroscopic and
microanalytical data for 11a and 11f are listed below.
;
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(3-hydroxy-4-
methylphenyl)pyrazole (8e): Yield, 43%; mp 97–98 °C; IR (KBr): 3366, 3235 (OH,
NH), 1346, 1153 (SO2) cmÀ1 1H NMR (DMSO-d6): d 2.12 (s, 3H, 4-CH3–C6H3–),
;
6.63 (d, J = 7.6 Hz, 1H, Ar-H), 6.70 (s, 1H, pyrazole H-4), 7.08–7.11 (m, 2H, Ar-
H), 7.52–7.55 (m, 4H, SO2NH2, Ar-H), 7.88 (d, J = 8.2 Hz, 2H, Ar-H), 9.62 (s, 1H,
OH). Anal. Calcd for C17H14F3N3O3S: C, 51.38; H, 3.55; N, 10.57. Found: C, 51.17;
H, 3.47; N, 10.11.
General method for the preparation of 1-(4-aminosulfonylphenyl)-3-
trifluoromethyl-5-(4-aryl)pyrazoles (9a–f): Triethylamine (0.31 mL, 2.2 mmol),
and then acetyl chloride (0.16 mL, 2.2 mmol), was added slowly to a stirred
solution of a phenol (8a–f, 2 mmol) in ether (50 mL) at 0 °C with stirring. The
reaction was allowed to proceed for 1 h at 25 °C prior to quenching by addition
of water (10 mL). The mixture was extracted with EtOAc (3 Â 25 mL), the
combined EtOAc extracts were dried (Na2SO4), the solvent was removed in
vacuo, and the residue obtained was purified by silica gel column
chromatography using EtOAc/hexane (1:1, v/v) as eluant to furnish the
respective acetoxyphenyl product 9a–f. Physical, spectroscopic and
microanalytical data for the target products 9a–f are listed below.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(4-acetoxyphenyl)pyrazole (9a):
Yield, 80%; mp 146–147 °C; IR (KBr): 3370, 3265 (NH), 1772 (CO), 1350,
1172 (SO2) cmÀ1 1H NMR (CDCl3): d 2.31 (s, 3H, COCH3), 5.17 (s, 2H, SO2NH2),
;
6.77 (s, 1H, pyrazole H-4), 7.12 (d, J = 8.6 Hz, 2H, Ar-H), 7.25 (d, J = 8.5 Hz, 2H,
Ar-H), 7.46 (d, J = 8.6 Hz, 2H, Ar-H), 7.90 (d, J = 8.5 Hz, 2H, Ar-H); 13C NMR
1
(CDCl3): d 21.1 (COCH3), 106.7, pyrazole C-4, 120.9 (q, JC,F = 268.0 Hz, CF3),
122.1, 125.4 (Carom-H), 126.1 (Carom-C-5), 127.5, 130.0 (Carom-H), 141.7 (Carom
SO2NH2), 142.1 (Carom-N), 144.0 (q, JC,F = 38.5 Hz, pyrazole C-3), 144.1
(pyrazole C-5), 151.4 (Carom-OAc) 169.1 (C@O). Anal. Calcd for
-
2
C
18H14F3N3O4S: C, 50.82; H, 3.32; N, 9.88. Found: C, 50.73; H, 3.26; N, 9.51.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(3-acetoxyphenyl)pyrazole (9b):
Yield, 43%; mp 155–156 °C; IR (KBr): 3347, 3265 (NH), 1765 (CO), 1335,
1175 (SO2) cmÀ1 1H NMR (CDCl3): d 2.28 (s, 3H, COCH3), 4.96 (s, 2H, SO2NH2),
;
6.82 (s, 1H, pyrazole H-4), 6.95 (dd, J = 2.0, 2.0 Hz, [m-coupling], 1H, Ar-H),
7.12–7.17 (m, 2H, Ar-H), 7.42 (dd, J = 8.1, 8.1 Hz, 1H, Ar-H), 7.50 (d, J = 8.9 Hz,
2H, Ar-H), 7.95 (d, J = 8.9 Hz, 2H, Ar-H); 13C NMR (CDCl3): d 20.5 (COCH3), 106.1
1
(pyrazole C-4), 118.7 (q, JC,F = 269.2 Hz, CF3), 121.7, 122.2, 124.7, 125.6, and
126.8 (Carom-H), 129.3 (Carom-pyrazole C-5), 129.5 (Carom-H), 140.8 (Carom
-
1-(4-Methylthiophenyl)-3-trifluoromethyl-5-(4-hydroxyphenyl)pyrazole
(11a):
2
SO2NH2), 142.9 (Carom-N), 143.1 (q, JC,F J = 37.4 Hz, pyrazole C-3), 143.4
(pyrazole C-5), 150.3 (Carom-OAc), 168.4 (CO). Anal. Calcd for C18H14F3N3O4S: C,
50.82; H, 3.32; N, 9.88. Found: C, 50.80; H, 3.28; N, 9.96.
Yield, 47%; mp 157–158 °C; IR (KBr); 3242 (OH) cmÀ1 1H NMR (DMSO-d6): d
;
2.5 (s, 3H, SCH3), 6.75 (d, J = 8.9 Hz, 2H, Ar-H), 7.03 (s, 1H, pyrazole H-4), 7.10
(d, J = 8.5 Hz, 2H, Ar-H), 7.24–7.33 (m, 4H, Ar-H), 9.86 (s, 1H, OH). Anal. Calcd
for C17H13F3N2OS: C, 58.28; H, 3.74; N, 8.00. Found: C, 57.98; H, 3.64; N, 7.89.
1-(4-Methylthiophenyl)-3-trifluoromethyl-5-(4-fluoro-2-hydroxyphenyl)pyrazole
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxyphenyl)pyrazole (9c):
Yield, 72%; mp 76–77 °C; IR (KBr): 3330, 3250, (NH),1757 (CO), 1340, 1170
(SO2) cmÀ1
;
1H NMR (CDCl3): d 2.10 (s, 3H, COCH3), 5.00 (s, 2H, SO2NH2), 6.88
(11f): Yield, 70%; mp 120–121 °C; IR (KBr): 3250 (OH) cmÀ1 1H NMR (CDCl3): d
;
(s, 1H, pyrazole H-4), 7.10 (d, J = 7.8 Hz, 1H, Ar-H), 7.18–7.26 (m, 2H, Ar-H),
7.47 (dd, J = 8.5, 7.8 Hz, 1H, Ar-H), 7.54 (d, J = 8.5 Hz, 2H, Ar-H). 7.88 (d,
2.46 (s, 3H, SCH3). 5.65 (s, 1H, OH), 6.59–6.65 (m, 2H, Ar-H), 6.75 (s, 1H,
pyrazole H-4), 6.97–7.02 (m, 1H, Ar-H), 7.14–7.26 (m, 4H, Ar-H). Anal. Calcd for
C17H12F4N2OS: C, 55.43; H, 3.28; N, 7.61. Found: C, 55.32; H, 3.01; N, 7.52.
J = 8.5 Hz, 2H, Ar-H); 13C NMR (CDCl3): d 20.7 (COCH3), 107.3 (pyrazole C-4),
1
120.9 (q, JC,F = 269.2, CF3), 123.4, 124.8, 126.5, 127.5, 131.1, and 131.2 (Carom
-
General method for the preparation of 1-(4-methylsulfonylphenyl)-3-
trifluoromethyl-5-(acetoxyphenyl)pyrazoles (12a–f): Triethylamine (0.2 mL,
1.4 mmol), and then acetyl chloride (0.1 mL, 1.4 mmol), were added to a
stirred solution of a methylthiophenyl compound 11a–f (1.1 mmol) in ether
(5 mL) at 0 °C. The reaction was allowed to proceed for 1 h at 25 °C prior to
quenching by addition of water (25 mL). Extraction with EtOAc (3 Â 25 mL),
drying the combined EtOAc extracts (Na2SO4), and removal of the solvent in
vacuo gave a pale yellow oil which was dissolved in MeOH (10 mL). OxoneÒ
(1.72 g, 2.8 mmol) in water (8.4 mL) was added to this solution slowly over
10 min at 0 °C, and the reaction was allowed to proceed with stirring for 16 h at
25 °C. Removal of the solvent in vacuo gave a residue which was dissolved in
water (25 mL). Extraction with EtOAc (3 Â 25 mL), washing the combined
EtOAc extracts with water (25 mL), drying the EtOAc extracts (Na2SO4), and
removal of the solvent in vacuo afforded the a residue that was purified by
silica gel column chromatography using hexane/EtOAc (1:1, v/v) as eluant to
afford the respective target product 12a–f. Physical, spectroscopic, and
microanalytical data for 12a–f are listed below.
H), 140.1 (Carom-C-5), 141.4 (Carom-SO2NH2), 142.1 (pyrazole C-5), 143.9 (q,
2JC,F = 38.5 Hz, pyrazole C-3), 148.3 (Carom-OAc), 168.9 (CO). Anal. Calcd for
C
18H14F3N3O4S: C, 50.82; H, 3.32; N, 9.88. Found: C, 50.77; H, 3.28; N, 9.75.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxy-4-
methylphenyl)pyrazole (9d): Yield, 69%, mp 77–79 °C; IR (KBr): 3356, 3273
(NH), 1770 (CO), 1341, 1159 (SO2) cmÀ1 1H NMR (CDCl3): d 2.07 (s, 3H,
;
COCH3), 2.39 (s, 3H, 4-CH3–C6H3–), 4.92 (s, 2H, SO2NH2), 6.73 (s, 1H, pyrazole
H-4), 6.93–7.03 (m, 3H, Ar-H), 7.53 (d, J = 8.6 Hz, 2H, Ar-H), 7.88 (d, J = 8.6 Hz,
2H, Ar-H); 13C NMR (CDCl3): d 21.3 (4-CH3–C6H3–), 107.1 (pyrazole C-4), 119.2
1
(Carom-C-5), 120.9 (q, JC,F = 269.2 Hz, CF3), 123.8, 124.8, 127.4, and 130.7
(Carom-H), 140.2 (Carom-methyl), 141.3 (Carom-SO2NH2), 142.0 (Carom-N), 142.3
(pyrazole C-5), 143.9 (q, 2JC,F = 38.5 Hz, pyrazole C-3), 148.0 (Carom-OAc), 169.0
(CO). Anal. Calcd for C19H16F3N3O4S: C, 51.93; H, 3.67; N, 9.56. Found: C, 51.63;
H, 3.71; N, 9.25.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(3-acetoxy-4-
methylphenyl)pyrazole (9e): Yield, 74%; mp 163–164 °C; IR (KBr): 3347, 3278
(NH), 1753 (CO), 1340, 1169 (SO2NH2) cmÀ1
;
1H NMR (CDCl3): d 2.20 (s, 3H,
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(4-acetoxyphenyl)pyrazole
(12a): Yield, 73%; mp 68–70 °C; IR (KBr): 1762 (COCH3), 1316, 1159 (SO2)
COCH3), 2.28 (s, 3H, 4-CH3–C6H3–), 5.04 (s, 2H, SO2NH2), 6.77 (s, 1H, pyrazole
H-4), 6.83 (d, J = 1.5 Hz, 1H, Ar-H), 7.03 (dd, J = 1.5, 8.5 Hz, 1H, Ar-H), 7.25 (d,
J = 8.5 Hz, 1H, Ar-H), 7.47 (d, J = 8.5 Hz, 2H, Ar-H), 7.92 (d, J = 8.5 Hz, 2H, Ar-H);
13C NMR (CDCl3): 15.9 (4-CH3–C6H3–), 20.6 (COCH3), 106.2 (pyrazole C-4),
cmÀ1 1H NMR (CDCl3): d 2.33 (s, 3H, COCH3), 3.07 (s, 3H, SO2CH3), 6.78 (s, 1H,
;
pyrazole H-4), 7.14 (d, J = 8.6 Hz, 2H, Ar-H), 7.26 (d, J = 8.5 Hz, 2H, Ar-H), 7.55
(d, J = 8.5 Hz, 2H, Ar-H), 7.96 (d, J = 8.5 Hz, 2H, Ar-H); 13C NMR (CDCl3): d 21.1
1
1
122.4 (q, JC,F = 269.3 Hz, CF3), 122.3, 125.1, 126.1 (Carom-H), 127.1
(COCH3), 44.4 (SO2CH3), 106.8 (pyrazole C-4), 120.8 (q, JC,F = 269.2 Hz, CF3),
(Carom-methyl), 127.2, 131.5 (Carom-H), 131.8 (Carom-C-5), 141.5 (Carom
-
122.4, 125.6 (Carom-H), 126.0 (Carom-pyrazole C-5), 128.5, 129.9 (Carom-H), 140.0
(Carom-SO2Me), 143.1 (Carom-N), 143.7 (q, JC,F = 38.5 Hz, pyrazole C-3), 144.2
(pyrazole C-5), 151.5 (Carom-pyrazole C-5), 168.8 (CO). Anal. Calcd for
2
2
SO2NH2), 142.6 (Carom-N), 143.6 (q, JC,F = 37.4 Hz, pyrazole C-3), 143.8
(pyrazole C-5), 149.2 (Carom-OAc), 168.5 (CO). Anal. Calcd for C19H16F3N3O4S:
C, 51.93; H, 3.67; N, 9.56. Found: C, 52.04; H, 3.70; N, 9.42.
C19H15F3N2O4S: C, 53.77; H, 3.56; N, 6.60. Found: C, 53.34; H, 3.49; N, 6.34.
1-(4-Aminosulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxy-4-
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(3-acetoxyphenyl)pyrazole
fluorophenyl)pyrazole (9f): Yield, 67% starting from 7f); mp 86–87 °C; IR (KBr):
(12b): Yield, 54 %; mp 144–146 °C; IR (KBr): 1765 (COCH3), 1317, 1157 (SO2)
3355, 3257 (NH2), 1765 (CO), 1345, 1157 (SO2) cmÀ1
;
1H NMR (CDCl3): d 2.10
cmÀ1 1H NMR (CDCl3): d 2.26 (s, 3H, COCH3), 3.07 (s, 3H, SO2CH3), 6.81 (s, 1H,
;
(s, 3H, COCH3), 4.97 (s, 2H, SO2NH2), 6.77 (s, 1H, pyrazole H-4), 6.78–7.01 (m,
2H, Ar-H), 7.07–7.12 (m, 1H, Ar-H), 7.53 (d, J = 8.5 Hz, 2H, Ar-H), 7.91 (d,
J = 8.5 Hz, 2H, Ar-H). Anal. Calcd for C18H13F4N3O4S: C, 48.76; H, 2.96; N, 9.48.
Found: C, 48.74; H, 2.90; N, 9.07.
pyrazole H-4), 6.96–6.98 (m, 1H, Ar-H), 7.09–7.16 (m, 2H, Ar-H), 7.40 (dd,
J = 7.9, 7.9 Hz, 1H, Ar-H), 7.53 (d, J = 8.9 Hz, 2H, Ar-H), 7.95 (d, J = 8.9 Hz, 2H, Ar-
H); 13C NMR (CDCl3): d 21.0 (COCH3), 44.5 (SO2CH3), 106.9 (pyrazole C-4),
123.5 (q, 1JC,F = 290.4 Hz, CF3), 122.3, 122.8, 125.6, 126.1, 128.6 (Carom-H), 129.7
(Carom-pyrazole C-5), 130.2 (Carom-H), 140.1 (Carom-SO2Me), 143.0 (Carom-N),
General method for the preparation of 1-(4-methylthiophenyl)-3-trifluoromethyl-

6080
M. Abdur Rahim et al. / Bioorg. Med. Chem. Lett. 21 (2011) 6074–6080
2
3
144.0 (pyrazole C-5), 145.1 (q, 2JC,F = 37.3 Hz, pyrazole C-3), 150.9 (Carom-OAc),
168.7 (CO). Anal. Calcd for C19H15F3N2O4S: C, 53.77; H, 3.56; N, 6.60. Found: C,
53.57; H, 3.55; N, 6.54.
H), 114.0 (d, JC,F = 22.0 Hz, Carom-H), 118.5 (d, JC,F = 3.3 Hz, Carom- C-5), 120.7
(q, 1JC,F = 269.2 Hz, CF3), 124.9, 128.6 (Carom-H), 132.1 (d, 3JC,F = 8.8 Hz, Carom-H),
139.3 (Carom-SO2Me), 140.1 (Carom-N), 143.0 (pyrazole C-5), 144.2 (q,
3
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxyphenyl)pyrazole
(12c): Yield, 95%, mp 129–130 °C; IR (KBr): 1759 (COCH3), 1310, 1160 (SO2)
2JC,F = 39.6 Hz, pyrazole C-3), 149.4 (d, JC,F = 11.0 Hz, Carom-OAc), 163.5 (d,
1JC,F = 253.8 Hz, Carom-F), 168.1 (CO). Anal. Calcd for C19H14F4N2O4SÁ1/3H2O: C,
cmÀ1 1H NMR (CDCl3): d 2.13 (s, 3H, COCH3), 3.08 (s, 3H, SO2CH3), 6.82 (s, 1H,
;
50.85; H, 3.23; N, 6.33. Found: C, 51.08; H, 3.16; N, 6.11.
pyrazole H-4), 7.13 (d, J = 7.8 Hz, 1H, Ar-H), 7.21–7.30 (m, 2H, Ar-H), 7.52 (dd,
J = 7.8, 7.8 Hz, 1H, Ar-H), 7.64 (d, J = 8.6 Hz, 2H, Ar-H), 7.95 (d, J = 8.6 Hz, 2H, Ar-
H); 13C NMR (CDCl3): d 20.7 (COCH3), 44.4 (SO2CH3), 107.3 (pyrazole C-4),
16. Cyclooxygenase inhibition assays: The ability of the test compounds listed in
Table 1 to inhibit ovine COX-1 and COX-2 (IC50 value,
lM) was determined
using an enzyme immuno assay (EIA) kit (catalog no. 560101, Cayman
Chemical, Ann Arbor, MI, USA) according to our previously reported method
(Rao, P. N. P.; Amini, M.; Li, H.; Habeeb, A.; Knaus, E. E. J. Med. Chem. 2003, 46,
4872).
1
120.8 (q, JC,F = 268.0 Hz, CF3), 122.3 (Carom-pyrazole C-5), 123.3, 124.9, 126.5,
128.4, 131.0, 131.2 (Carom-H), 139.8 (Carom-SO2Me), 140.14 (Carom-N), 143.13
(pyrazole C-5), 144.1 (q, 2JC,F = 38.5 Hz, pyrazole C-3), 148.3 (Carom-OAc), 168.6
(CO). Anal. Calcd for C19H15F3N2O4S: C, 53.77; H, 3.56; N, 6.60. Found: C, 53.61;
H, 3.51; N, 6.50.
17. In vivo anti-inflammatory assay: The test compounds 8d, 9a, 9d, 9e, 9f, 12e and
the reference drug celecoxib were evaluated using the in vivo carrageenan-
induced rat foot paw edema model reported previously (Winter, C. A.; Risley, E.
A.; Nuss, G. W. Proc. Soc. Exp. Biol. Med. 1962, 111, 544).
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxy-4-
methylphenyl)pyrazole (12d): Yield, 50%; mp 69–71 °C; IR (KBr): 1759 (COCH3),
1305, 1150 (SO2) cmÀ1
;
1H NMR (CDCl3): d 2.09 (s, 3H, COCH3), 2.41 (s, 3H,
18. Molecular Modeling (Docking) procedure. Crystal coordinates from the X-ray
crystal structure of COX-1 (ovine, 1EQG, ibuprofen bound in the active site) and
COX-2 (murine, 6COX, SC558 bound in the active site) were taken from the
protein data bank. Compounds were constructed using the builder toolkit of
the software package ArgusLab 4.0.1 (Mark, A. ArgusLab, Version 4.0.1;
Thompson Planaria Software LLC: Seattle, WA; http://www.arguslab.com),
and energy minimized using the semi-empirical quantum mechanical method
PM3. The monomeric structure of the enzyme was chosen and the active site
was defined around the ligand. The molecule to be docked in the active site of
the enzyme was inserted in the work space carrying the structure of the
enzyme. The docking program implements an efficient grid based docking
algorithm which approximates an exhaustive search within the free volume of
the binding site cavity. The conformational space was surveyed by the
geometry optimization of the flexible ligand (rings are treated as rigid) in
combination with the incremental construction of the ligand torsions. Thus,
docking occurred between the flexible ligand parts of the compound and
enzyme. The ligand orientation was determined by a shape scoring function
based on Ascore and the final positions were ranked by lowest interaction
energy values. The Einteraction is the sum of the energies involved in H-bond
interactions, hydrophobic interactions and van der Waal’s interactions. H-Bond
and hydrophobic interactions between the compound and enzyme were
explored by distance measurements.
4-CH3–C6H3–), 3.05 (s, 3H, SO2CH3), 6.76 (s, 1H, pyrazole H-4), 6.94–7.05 (m,
3H, Ar-H), 7.62 (d, J = 8.8 Hz, 2H, Ar-H), 7.93 (d, J = 8.8 Hz, 2H, Ar-H); 13C NMR
(CDCl3): d 20.30 (4-CH3–C6H3–), 21.71 (COCH3), 44.5 (SO2CH3), 107.2 (pyrazole
1
C-4), 119.1 (Carom-pyrazole C-5), 122.2 (q, JC,F = 237.4 Hz, CF3), 123.8, 125.0,
127.3, 128.4, 130.7 (Carom-H), 139.8 Carom-methyl), 140.3 (Carom-SO2Me), 142.1
2
(Carom-N), 143.2 (pyrazole C-5), 143.9 (q, JC,F = 38.5 Hz, pyrazole C-3), 148.17
(Carom-OAc), 168.7 (CO). Anal. Calcd for C20H17F3N2O4SÁ1/2H2O: C, 53.69; H,
4.05; N, 6.26. Found: C, 53.89; H, 3.87; N, 6.05.
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(3-acetoxy-4-
methylphenyl)pyrazole (12e): Yield, 46%; mp 180–182 °C; IR (KBr): 1762
(COCH3), 1330, 1160 (SO2) cmÀ1 1H NMR (CDCl3): d 2.04 (s, 3H, COCH3),
;
2.22 (s, 3H, 4-CH3–C6H3–), 3.07 (s, 3H, SO2CH3), 6.78 (s, 1H, pyrazole H-4), 6.88
(s, 1H, Ar-H), 7.01 (d, J = 7.9 Hz, 1H, Ar-H), 7.20 (d, J = 7.9 Hz, 1H, Ar-H) 7.54 (d,
J = 8.6 Hz, 2H Ar-H), 7.96 (d, J = 8.6 Hz 2H, Ar-H); 13C NMR (CDCl3): d 16.0 (4-
CH3–C6H3–), 20.7 (COCH3), 44.4 (SO2CH3), 106.6 (pyrazole C-4), 119.1 (q,
1JC,F = 269.2 Hz, CF3), 122.6, 125.6, 126.1 (Carom), 127.2 (Carom-pyrazole C-5),
128.5, 131.8 (Carom-H), 132.1 (Carom-methyl), 140.0 (Carom-SO2Me), 143.0
2
(Carom -N), 144.1 (pyrazole C-5), 144.2 (q, JC,F = 39.6 Hz, pyrazole C-3), 149.4
(Carom-OAc), 168.4 (CO). Anal. Calcd for C20H17F3N2O4S: N, 6.39. Found: N, 6.11.
1-(4-Methylsulfonylphenyl)-3-trifluoromethyl-5-(2-acetoxy-4-
fluorophenyl)pyrazole (12f): Yield, 66%; mp 175–176 °C; IR (KBr): 1777
(COCH3), 1330, 1120 (SO2) cmÀ1
;
1H NMR (CDCl3): d 2.09 (s, 3H, COCH3),
19. Harrowven, D. C.; Lucas, M. C.; Howes, P. D. Tetrahedron 1999, 55, 1187.
20. Soliman, R. J. Med. Chem. 1979, 22, 321.
21. Hondgson, H. H.; Handley, W. F. J. Chem. Soc. 1928, 1882.
3.06 (s, 3H, SO2CH3), 6.77 (s, 1H, pyrazole H-4), 6.95–7.01 (m, 2H, Ar-H), 7.06–
7.12 (m, 1H, Ar-H), 7.60 (d, J = 8.9 Hz, 2H, Ar-H), 7.94 (d, J = 8.9 Hz, 2H, Ar-H);
13C NMR (CDCl3): d 20.7 (COCH3), 44.5 (SO2CH3), 111.6 (d, 2JC,F = 25.3 Hz, Carom
-