Potent, orally available, selective COX-2 inhibitors based on 2-imidazoline core

Article abstract of DOI:10.1016/j.ejmech.2014.07.023

A novel series of compounds containing a polar, non-flat 2-imidazoline core was designed based on the SAR information available for aromatic azole cyclooxygenase-2 inhibitors. While the majority of the compounds prepared using an earlier developed imidazoline N-arylation methodology turned out to be inferior to the known COX-2 inhibitors, one lead compound displayed potency (300 nM) comparable to clinically used Celecoxib and was shown to be more selective. The series represents the first example of selective COX-2 inhibitors built around a distinctly polar core, contradicting an earlier accepted view that a lipophilic scaffold is required for high inhibitor potency. The lead compound demonstrated very good oral bioavailability in mice, slow metabolic degradation, modest distribution into the brain and a remarkable anti-inflammatory efficacy in carrageenan-induced mouse paw edema model. A foundation has therefore been laid for a chemically novel series of COX-2 inhibitors that has a potential for diverse therapeutic applications in inflammatory disease area.

Full text of DOI:10.1016/j.ejmech.2014.07.023

European Journal of Medicinal Chemistry 84 (2014) 160e172
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Potent, orally available, selective COX-2 inhibitors based
on 2-imidazoline core
Pakornwit Sarnpitak a, Prashant Mujumdar a, Christophe Morisseau b, Sung Hee Hwang b,
Bruce Hammock b, Vladimir Iurchenko c, Sergey Zozulya c, Antonis Gavalas d,
, f, *
Athina Geronikaki d, Yan Ivanenkov e, Mikhail Krasavin a
a Eskitis Institute for Drug Discovery, Griffith University, Nathan, Queensland 4111, Australia
b Department of Entomology, University of California, One Shields Avenue, Davis, CA 95616-8584, United States
c Enamine Ltd, 78 Chervonotkatska Street, Kyiv 02094, Ukraine
d School of Pharmacy, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece
e Moscow Institute of Physics & Technology (State University) Dolgoprudny, Moscow Region 141700, Russia
f Department of Chemistry, St. Petersburg State University, 26 Universitetskyi Prospekt, Peterhof 198504, Russia
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of compounds containing a polar, non-flat 2-imidazoline core was designed based on the
SAR information available for aromatic azole cyclooxygenase-2 inhibitors. While the majority of the
compounds prepared using an earlier developed imidazoline N-arylation methodology turned out to be
inferior to the known COX-2 inhibitors, one lead compound displayed potency (300 nM) comparable to
clinically used Celecoxib and was shown to be more selective. The series represents the first example of
selective COX-2 inhibitors built around a distinctly polar core, contradicting an earlier accepted view that
a lipophilic scaffold is required for high inhibitor potency. The lead compound demonstrated very good
oral bioavailability in mice, slow metabolic degradation, modest distribution into the brain and a
remarkable anti-inflammatory efficacy in carrageenan-induced mouse paw edema model. A foundation
has therefore been laid for a chemically novel series of COX-2 inhibitors that has a potential for diverse
therapeutic applications in inflammatory disease area.
Received 25 April 2014
Received in revised form
5 July 2014
Accepted 7 July 2014
Available online 8 July 2014
Keywords:
Coxibs
Non-aromatic
High-sp3
Anti-inflammatory
Amidines
© 2014 Elsevier Masson SAS. All rights reserved.
Bloodebrain barrier
Mouse paw edema
1. Introduction
aromatic groups, one of which contains a sulfonyl or a primary
sulfamide group (as well as some known bioisosteres thereof [6]) in
The last decade of 20th century was marked by the advent of a
new generation of non-steroidal anti-inflammatory drugs (NSAIDs)
with selective inhibition of cyclooxygenase-2 (COX-2) as the prin-
cipal mode of action [1]. Examples of drugs belonging to this class
(so-called coxibs) include Merck's Rofecoxib (Vioxx) [2] and Pfizer's
Celecoxib (Celebrex) [3] both of which were markedly successful
commercially at the start of this century [4]. In addition, there are
many other known coxibs at various stages of drug development
cycle, all of which are based on a common pharmacophore (derived
from the prototypical compound DuP697) [5], namely, an almost
predominantly five-membered cyclic core (with some examples of
six-membered counterparts) decorated with two adjacently placed
position 4, a substitution pattern required for selective COX-2 in-
hibition (Fig. 1) [7].
The development of this exciting area of anti-inflammatory
pharmacology was severely hampered by the emerging serious
cardiovascular liabilities associated with some of the approved
drugs e leading, most notably, to the voluntary withdrawal of Vioxx
(by Merck in 2004) and Bextra (by Pfizer in 2005) from the market.
Moreover, the entire field of selective COX-2 inhibitors has been
tarnished by the potential side-effect risks [8]; a view of COX-2
inhibition being innately linked to adverse effects on vasocon-
striction, platelet aggregation XZ and thrombosis appeared to be
convincingly supported by the thorough analysis of the perturba-
tions in prostaglandin synthesis introduced by coxib treatment [9].
However, this clinically validated area of chemotherapeutic
treatment and prevention may see a renaissance in the upcoming
years as potential use of COX-2 inhibitors in the areas other than the
traditional systemic treatment of inflammatory conditions (such as
* Corresponding author. Department of Chemistry, St. Petersburg State Univer-
sity, 26 Universitetskyi Prospekt, Peterhof 198504, Russia.
E-mail address: m.krasavin@hotmail.com (M. Krasavin).
http://dx.doi.org/10.1016/j.ejmech.2014.07.023
0223-5234/© 2014 Elsevier Masson SAS. All rights reserved.

P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
161
Fig. 1. Common pharmacophore and representative examples of selective COX-2
inhibitors.
Scheme 1. Synthesis of known imidazole-based selective COX-2 inhibitor 3.
rheumatoid arthritis) is supported by the scientific evidence. In
particular, selective inhibition of this enzyme in central nervous
system has been suggested as a novel therapeutic approach to such
conditions as Parkinson's disease [10] or ischemic brain injury [11].
More recently, selective COX-2 inhibitors have been also found
effective in treating inflammatory neurodegeneration and there-
fore implicated as potential treatments for major depressive dis-
orders and schizophrenia [12]. Additionally, COX-2 inhibition has
been shown to slow down neuroblastoma growth [13,14] and
retard the onset of Alzheimer's Disease [15].
As the majority of new therapeutic applications for COX-2 in-
hibitors are envisioned in central nervous system disease area,
development of structurally novel series of inhibitors, with the
emphasis on bloodebrain barrier permeability and elimination of
structural motifs that could be responsible for the unwanted side-
effects, is likely to be needed. The central core (scaffold) of the
known selective COX-2 inhibitors appears to contribute little to the
interaction with the amino acid residues of the enzyme's active site
and is mainly responsible for projecting the two pharmacophoric
aromatic rings in correct orientation for the efficient binding.
Moreover, a dogma was introduced stating that, due to the high
lipophilicity of the enzyme's active site, in order for a compound to
exert COX-2 inhibitory activity, its scaffold should too be relatively
lipophilic [16]. This notion is a likely reason for the vast majority of
known COX-2 inhibitors being designed with a flat aromatic het-
erocycle (most prominently, an azole) at their core. In fact, only a
small number of examples (Fig. 2) of non-flat COX-2 inhibitor
scaffolds can be found in the literature (including, interestingly,
Rofecoxib, its lactam analog Imrecoxib [17], Searle's 1,2-
diarylcyclopentene SC-57666 (1) [18], and non-selective pyrazo-
line-based COX-1/2 inhibitor 2 [19]). This seeming requirement for
the high degree of unsaturation can, in fact, be a limiting factor for
the development and subsequent clinical use of these compounds
as drugs. Indeed, according to the recent observation by a Wyeth
team [20], the average degree of saturation (or fraction of sp3-hy-
bridized carbons, Fsp3) increases for the clinical candidates and
approved drugs compared to early pre-clinical research com-
pounds. This general trend suggests potential advantages of front-
loading this requirement in compound's development life-cycle
and perhaps introducing it as early as the lead generation stage.
Earlier, we described [21] a concise synthesis of Searle's
imidazole-based selective COX-2 inhibitor 3 [22] employing Pd-
catalyzed N-arylation of 2-imidazolines (Scheme 1) [23]. In the
course of development of this synthetic strategy, a somewhat
sluggish aromatization of the intermediate 2-imidazolines 4 upon
treatment with Pd/C [24] was noted. This stability of 4 toward the
conversion into the known, flat, aromatic imidazoles gave us an
idea to consider 4 as a novel (and, surprisingly, hitherto unex-
plored) chemotype for the design of potential selective COX-2 in-
hibitors that would also be sufficiently stable toward potential
cytochrome-mediated aromatization [25] in vivo (in analogy with
other imidazoline-based drugs, such as moxonidine [26] that is a
clinically used antihypertensive drug). In addition to its novelty, the
2-imidazoline scaffold, if validated as the basis for COX-2 inhibitor
design, promised to offer certain advantages from the standpoint of
prospective drug development. Firstly, it is a non-flat, non-aromatic
core, which is an attractive feature according to Wyeth's ‘flatland’
dogma (vide supra). Further, 2-imidazoline is a markedly polar
motif and its suitability for COX-2 inhibitor design would contrast
the lipophilic scaffolds used earlier. Should the chemical nature of
the clinically used coxibs be responsible for the observed adverse
Fig. 2. Examples on coxibs based on a non-flat heterocyclic scaffold.

162
P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
Fig. 3. Analysis of the SAR for Searle's imidazolines and our design of the pilot 2-imidazoline-based library (6).
effects, 2-imidazoline-based inhibitors would occupy a drastically
different chemical space which may help avoid compounds' un-
wanted liabilities. Finally, the high basicity of 2-imidazolines
(somewhat attenuated by the electron-withdrawing group in the
para-position of the N1-aryl substituent [27]) may ensure not only
the high solubility of these compounds in the aqueous medium due
to protonation but also their permeability with respect to the
bloodebrain barrier or BBB (in analogy to Astra Zeneca's cyclic
amidine BACE-1 inhibitors reported recently [28]) and even po-
tential propensity to active transport across the BBB by the organic
cation transport system [29]. Herein, we report the results of our
studies toward novel selective COX-2 inhibitors based on 2-
imidazoline core.
available for Searle's (now Pfizer's) imidazole inhibitors similar to 3
[22,30], we chose to base our pilot library design on that
foundation.
Analysis of the COX inhibition data from Searle available in the
literature [22,30] revealed certain generalizations that could be
made regarding the structural features of imidazoles that are
favorable for selective COX-2 blockage. In particular, suitability of
both methylsulfonyl and (even more so) primary sulfonamide
substituents in position 4 of N1-Ph group was evident, so was the
favorable influence on the biological activity of halogen or methoxy
groups in the second peripheral aromatic group. Furthermore,
imidazole's inhibitory potency appeared particularly sensitive to
any substitutions in position 4, which led to the loss of activity,
while small substituents like methyl or trifluoromethyl enhanced
COX-2 inhibition. On the basis of these observations, we designed a
series of 2-imidazolines containing substituted phenyl groups in
positions 1 and 2 of the imidazoline core. The prospective set of
compounds was to include both 4-MeSO2- and 4-H2NSO2-
substituted compounds with 2-imidazoline core left unsubstituted
or containing 4-methyl substitutent (in case the SAR available for
imidazoles turns out to be not transferrable to imidazolines). The
choice of substitutions for the aromatic ring at position 2 of imi-
dazoline was also dictated by the favorable SAR disclosed by Searle
(Fig. 3). With such a design in mind, we set off to synthesize a pilot
2. Results
In order to establish whether the remarkably polar and basic 2-
imidazoline scaffold could indeed serve as a scaffold for selective
COX-2 inhibitor assembly, a relatively small pilot library was
envisioned. As 2-imidazolines were expected to be drastically
different in their physicochemical nature from other scaffolds
explored to-date in this area of medicinal chemistry, we could, in
principle, base our design on any available structureeactivity
relationship information. Considering the wealth of biological data
Scheme 2. Synthesis of 2-imidazolines compounds 4, 8e36 studied in this work.

P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
163
Table 1
set of 30 compounds for biological testing. It is noteworthy that we
COX inhibition data for compounds 4, 8e36 investigated in this work.
had found this library size to be optimal for identifying biological
activities for newly designed chemotypes, similarly to the NIH
Roadmap Molecular Libraries Program's guidelines for pilot-scale
libraries intended for biological screening [31].
The synthesis of the compounds in the methylsulfone series was
achieved in a similar fashion to our synthesis of 4. However, direct
arylation of the imidazoline core with unprotected 4-
bromophenylsulfonamide was not feasible and led to N-arylation
of the sulfonamide functionality instead (i.e. homocoupling).
Therefore, the primary sulfonamide function was protected with
2,4-dimethoxybenzyl (DMB) groups [32] prior to imidazoline N-
arylation. Efficient removal of DMB groups was achieved on treat-
ment with TFA [33]. Notably, in both cases, the arylation of methyl-
substituted imidazolines proceeded in highly regiospecific fashion,
at the less sterically hindered nitrogen atom (according to NOESY
data), in line with our earlier observations (Scheme 2) [21].
The 30 compounds thus prepared (4, 8e36) were tested for
inhibition of COX-2 and COX-1 using indomethacin and celecoxib as
reference standards. None of the compounds studied inhibited
Compound Ar
R
R0
Yield COX-1 %
COX-2
IC50, mM
(%)
inh at 100
m
M
Indomethacin
Celecoxib
73.5
21.7
ꢁ5.2
12.6
6.3
87 %a
98 %a
>10
>10
>10
7.1
4
4-ClC6H4
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me 52
83
Me 62
8
4-FC6H4
H
9
4-FC6H4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
4-ClC6H4
3-BrC6H4
3-BrC6H4
3-FC6H4
H
H
59
31
3.2
12.6
11.1
0.7
1.4
6.0
ꢁ1.6
ꢁ4.3
1.2
9.2
1.9
6.8
Me 24
>10
>10
8.1
>10
>10
>10
>10
>10
2.1
3.6
6.9
>10
3.4
>10
2.9
>10
7.2
2.5
>10
9.5
>10
6.2
6.7
0.3
1.8
H
H
H
H
H
H
H
H
H
H
25
47
77
53
52
58
49
41
24
73
3-ClC6H4
3-MeC6H4
3-F,4-MeOC6H3
4-F,3-MeOC6H3
COX-1 significantly at 100
mM. A half of the compounds investigated
3-Cl,4-MeOC6H3 Me
also showed no appreciable inhibition (IC50 > 10
mM) of COX-2. A
3,4-diFC6H3
3,4-diClC6H3
4-Cl,3-F3CC6H3
4-FC6H4
4-FC6H4
4-ClC6H4
4-ClC6H4
3-BrC6H4
3-BrC6H4
3-FC6H4
Me
Me
Me
NH2
NH2 Me 36
NH2 66
NH2 Me 51
NH2 36
NH2 Me 64
NH2
NH2
NH2
NH2
NH2
number of compounds displayed a full inhibition of the target
enzyme with potencies in the single-digit micromolar range. To our
outmost delight, however, one compound (35) displayed a sub-
micromolar inhibition of COX-2 (IC50 ¼ 300 nM), i.e. was found to
be nearly equipotent not only to Searle's imidazoles like 4 but also
similar in activity to the clinically used celecoxib e and remarkably
more selective than the latter (celecoxib's COX-2 IC50 ¼ 91 nM and
4.7
11.4
5.5
H
0.4
3.2
H
12.9
20.2
ꢁ1.4
ꢁ8.0
1.5
ꢁ5.5
ꢁ13.0
3.0
H
H
H
H
H
H
H
H
H
61
79
37
68
66
63
46
80
24
COX-1 IC50 ¼ 2.8
mM as measured in PGE2 production assay in
3-ClC6H4
human dermal fibroblasts and lymphoma cell, respectively [34]). In
general, the primary sulfonamide subset of COX-2 inhibitors was
more potent compared to the methylsulfonyl one (Table 1). How-
ever, the compounds containing methyl substituent in position 4 of
the imidazoline core were all inactive and less potent compared to
their non-methylated counterparts. This is in sharp contrast to the
SAR established for Searle's imidazoles and may possibly suggest a
different binding mode for the newly discovered series of COX-2
inhibitors.
3-MeC6H4
3-F,4-MeOC6H3
4-F,3-MeOC6H3
3-Cl,4-MeOC6H3 NH2
3,4-diFC6H3
NH2
NH2
NH2
6.6
8.7
2.7
3,4-diClC6H3
4-Cl,3-F3CC6H3
a
% inhibition at the highest concentration tested (10 mM).
We performed a docking study of the lead compound (35) using
the available X-ray crystallographic data for COX-2 with a known
inhibitor (4-[5-(4-bromophenyl)-3-(trifluoromethyl)-1H-pyrazol-
1-yl]benzenesulfonamide) [7]. The docking algorithm was vali-
dated by de-novo docking of the same compound into the active
site of the enzyme that led to a full superposition of the co-
crystallized and docked structures (Fig. 4). Docking of compound
35 (Fig. 5) revealed that the binding mode of this compound is
identical to that of the pyrazole (and, by analogy, of the imidazole)
inhibitors. This supports the similar trend in biological activity
observed for the methylsulfone compounds compared to primary
sulfonamides. In order to rationalize the complete loss of activity
for the methyl-substituted imidazolines, we scrutinized the vicinity
of the pocket formed by Arg120, Tyr355 and Ala516. It was
observed that, unlike the flat aromatic imidazoles [22,30], ring-
methylated imidazolines, that exist as a racemic mixture of two
enantiomers, can experience steric clashes with specific amino acid
residues of the protein backbone: more specifically, with Arg120 in
case of (R)-35 and with Leu379 and Val349 in case of (S)-35. Finally,
we were curious to see why 3,4-dichloro substitution of the phenyl
ring in 35 leads to the observed pronounced increase in potency
compared to both 4-chloro (23) and 3-chloro (29) counterparts
and Phe518. In our opinion, this convincingly explains the observed
additive effect of the two substituents.
Since the level of COX-2 inhibition by the lead compound (35)
was comparable to the clinically used compounds, we undertook
no further optimization at this point and proceeded to investigate
the pharmacokinetic profile of this compound. Pharmacokinetic
assessment of compound 35 in mice at 10 mg/kg p.o. confirmed
that for this compound, sufficiently high plasma levels
(Cmax ¼ 16.6 M corresponding to approximately 55 ꢀ its in vitro
m
IC50) can be achieved at that dosing [35]. Plasma volume of distri-
bution of 35 was 1220 mL/kg, which corresponds to approximately
1.7 volume of the total body water and suggests broad distribution
to extravascular liquids without significant tissue binding or deep
penetration.
Mindful of the recent results that justify the need for brain-
penetrating selective COX-2 inhibitors [10e15] we also performed
assessment of the pharmacokinetic profile of compound 35 in brain
tissue. The plasma and brain PK data are presented in Table 2.
Apparently, the distribution into the brain for 35 is relatively low
(only 4%). This is in accordance with the general wisdom with re-
gard to the range of calculated properties that make BBB crossing
more favorable [36]. Indeed, the molecular parameters critical for a
good distribution into the brain appear to be borderline with
respect to that range for compound 35 (Table 4) [37]. However, the
Cmax that was achieved on 10 mg/kg p.o. dosing corresponds to ~2ꢀ
(IC50 of 3.4 mM and 2.5 mM, respectively). The 3-Cl substituent was
found to be involved in dipoleedipole interaction with the OH
group of Tyr385 while 4-Cl substituent appears to completely fill
the shared van-der-Waals (VDW) cavity formed by Tyr385, Trp387

164
P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
Fig. 5. Docking of compound 35 in the crystal structure of COX-2: contributing in-
teractions with the key amino acid residues in 2D and 3D (a and b, respectively), su-
perposition of compounds 35, 29, methylated analog of 35 (not prepared) and the
reference pyrazole compound (orange) in COX-2 active site. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of
this article.)
Fig. 4. Available crystal structure of COX-2 with a pyrazole inhibitor (a), key amino acid
interactions (b), superposition (RMSD ¼ 0.1) of co-crystallized (orange) and docked
structures in COX-2 active site (c). (For interpretation of the references to colour in this
figure legend, the reader is referred to the web version of this article.)
in vitro IC50 for this compound. Therefore, this compound can be
viewed as a starting point for developing more advanced com-
pounds for studying the effects of COX-2 inhibition in CNS, possibly
at higher dosing. Low brain penetration, however, is traditionally
considered an advantageous pharmacokinetic aspect as far as
systemic anti-inflammatory applications are concerned [38].
Therefore, 35 can be considered as a new lead for COX-2 inhibitors
that are based on a non-flat, polar heterocyclic core and that may
serve as an effective substitute or follow-on to the existing sys-
temically acting anti-inflammatory agents.

P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
165
Table 2
Pharmacokinetic parameters of compound 35 determined in male C57Bl mice (10 mg/kg p.o.) in plasma and brain tissue.
Tmax (min)
Cmax (ng/mL)
AUC0/240 min (ng min/mL)
AUC0/∞ (ng min/mL)
T1/2 (min)
Vd (mL/kg)
CL (mL/min/kg)
Plasma
Brain
5
30
6138
267
704,258
29,471
762,758
31,489
65
58
1220
nd
13
nd
The pharmacokinetic profile of compound 35 suggests its fairly
slow systemic elimination (considering both the T1/2 and CL values).
In order to determine if potential cytochrome-mediated aromati-
zation [25] of in vivo of this lead compound could be a contributing
factor, we monitored the levels of a [Mꢁ2]þ metabolite (i. e. the
respective imidazole) in the same tissues. The PK profile of a pu-
tative imidazole metabolite is presented in Table 3. While the
‘dehydroimidazoline’ metabolite was indeed observable, it accu-
mulation does not appear to be predominant and the majority of 35
survives the first-pass metabolic events and remains intact for
exerting its COX-2 inhibitory effects, particularly in the first 2 h post
dosing (i. e. until Cmax for the imidazole metabolite is achieved).
While pharmacodynamic readouts and animal disease models
relevant to COX-2 inhibition in the central nervous system remain
to be established, assessment of systemic effects of COX-2 inhibi-
tion is a relatively routine undertaking [39]. In order to assess
systemic anti-inflammatory effects of compound 35 in vivo, the
carrageenan-induced mouse paw edema model was used. Intra-
peritoneal injection of 3.7 mg/kg of 35 in a vehicle led to a pro-
nounced, statistically significant volume reduction of the inflamed
mouse paw (56%), compared to the no-treatment control group
(Figs. 5 and 6). Indomethacin that was used as an efficacy standard
in this experiment provided 47% reduction at an equivalent dose.
induced mouse paw edema. In conclusion, we have validated 2-
imidazolines as a suitable, novel, polar, non-flat scaffold for the
design of orally available, efficacious anti-inflammatory COX-2 in-
hibitors. The lead compound demonstrated some (though clearly
not pronounced) potential for entering the CNS from the blood
stream. The series will be developed and evaluated further in the
context of novel therapeutic applications. In addition to that, po-
tential cardiotoxicity of our new lead will be evaluated in cellular
models, in comparison to the known cardiotoxic coxibs. The results
of these studies will be reported in due course.
4. Experimental section
4.1. Cyclooxygenase inhibition assay
Inhibition by test compounds 4, 8e36 of ovine COX-1 and hu-
man recombinant COX-2 (% inhibition at 100
mM and IC50 values
(mM), respectively) was assessed using a COX Fluorescent Inhibitor
Screening Assay Kit (catalog number 700100, Cayman Chemical,
Ann Arbor, MI) according to the manufacturer's instructions. Stock
solutions of test compounds were prepared in a minimum volume
of DMSO. Briefly, to a series of supplied reaction buffer solutions
(150
(10
substrate (10
test compound solutions ([I]final between 0.01 and 100
reactions were initiated by quickly adding 10 l of arachidonic acid
m
l, 100 mM TriseHCl, pH 8.0) with either COX-1 or COX-2
l) enzyme in the presence of Heme (10 l) and fluorometric
l) were added 10 l of various concentrations of the
M). The
m
m
m
m
3. Conclusions
m
m
While developing an alternative synthesis of
a known
solution and then incubated for 2 min at room temperature. Fluo-
rescence of resorufin that is produced by the reaction between
PGG2 and the fluorometric substrate, ADHP (10-acetyl-3,7-
dihydroxyphenoxazine) was read with an excitation wavelength
of 535 nm and an emission wavelength of 590 nm. The intensity of
this fluorescence is proportional to the amount of resorufin, which
is proportional to the amount of PGG2 present in the well during
the incubation. Percent inhibition was calculated by comparison
from the 100% initial activity sample value (no inhibitor). The
concentration of the test compound causing 50% inhibition of COX-
imidazole-based selective COX-2 inhibitor [21], we became inter-
ested in exploring the potential of 2-imidazoline scaffold (which, in
our approach, was an intermediate en route to imidazoles) for
design of novel inhibitors of this clinically validated enzyme target.
2-Imidazolines, in particular, appeared as a daring addition to the
existing COX-2 inhibitor space considering the widely accepted
dogma that a non-polar, lipophilic core is required for COX-2
inhibitory potency [16]. Very few non-flat, non-aromatic cores
have been studied so far in a similar context. Moreover, 2-
imidazolines were expected to invigorate the field due to their
basic character (and, hence, improved aqueous solubility) and a
potential to cross the bloodebrain barrier (similarly to Astra-
Zeneca’s amidine-based BACE-1 inhibitors [28]). A library of 30 2-
imidazoline compounds was designed, synthesized and tested for
COX inhibition. A lead compound (35) that displayed potency
comparable to and selectivity superior to the clinically used NSAIDs
was identified. It demonstrated a very good plasma pharmacoki-
netic profile in mice but only a modest distribution into the brain
(4%). We have shown the metabolic conversion of our lead com-
pound (presumably, to the corresponding imidazole) to be slow,
thereby alleviating concerns of a fast CYP-mediated aromatization
[25] of our inhibitors being a liability. The lead compound
demonstrated a remarkable efficacy in reducing carrageenan-
2 (IC50, mM) was calculated from the concentration-inhibition
response curve (triplicate determinations).
4.2. Pharmacokinetic experiments
Male C57Bl mice (~2 months old, body weight 18.1e23.6 g and
average body weight across all groups e 20.7 g) were used in this
study. The animals were randomly assigned to the treatment
groups before the pharmacokinetic study; all animals were fasted
overnight before dosing. Each of the treatment groups included 4
animals; there was also one plasma control group of 4 non-dosed
animals. Dosing was done by peroral gavage. Animals were sacri-
ficed by cervical dislocation and blood samples were withdrawn by
Table 3
Pharmacokinetic parameters of a putative aromatization metabolite corresponding to compound 35 in plasma and brain tissue.
Tmax (min)
Cmax (ng/mL)
AUC0/240 min (ng min/mL)
AUC0/∞ (ng min/mL)
T1/2 (min)
CL (mL/min/kg)
Plasma
Brain
120
120
735
33
145,573
5969
364,739
8533
279
112
27
nd

166
P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
Table 4
calibration curve, 500
were mixed with 20
and 20 l of the IS solution.
m
l aliquots of the supernatant of a blank brain
Molecular parameters of 35 vs. the favorable range for high bloodebrain barrier
permeability.
m
l of corresponding working standard solution
m
Parameter
The target range
Compound 35
PSA, Å2
HBD
<90
<3
84
2
4.3. Carrageenan-Induced Mouse Paw Edema Model [40]
clogP
Mol. weight
2e5
450
1.95
370
Edema was induced in the right hind paw of mice (AKR) by the
intradermal injection of 0.05 mL of 2% carrageenan in water. Both
sexes were used, but pregnant females were excluded. Each group
was composed of 6e10 animals. The animals, which have been bred
in our laboratory, were housed under standard conditions and
received a diet of commercial food pellets and water ad libitum
prior to experimentation, but they were fasted during the experi-
mental period. The tested compounds (0.01 mmol/kg body weight)
were suspended in water with a few drops of Tween-80 and ground
in a mortar before use and were given intraperitoneally simulta-
neously with the carrageenan injection. The mice were euthanized
3.5 h after the carrageenin injection. The difference between the
weight of the injected and uninjected paws was calculated for each
animal. It was compared with that in control animals (treated with
water) and expressed as a percent inhibition of the edema CPE%
values. Each experiment was performed in duplicate, and the
standard deviation was less than 10%.
intra-cardiac puncture. Blood samples were collected in EDTA tubes
at pre-dose and 5, 15, 30, 60, 120 and 240 min post-dose. Plasma
and whole brain samples were immediately prepared and stored
frozen at ꢁ80 ꢂC until further processing and bioanalysis.
Analyses of plasma and brain samples were conducted by high
performance liquid chromatography-mass spectrometry (HPLC-
MS) method. The LC system comprised a Shimadzu liquid chro-
matograph equipped with isocratic pumps (Shimadzu LC-10ADvp),
an autosampler (Shimadzu SIL-HTc), a switching valve (FCV-14AH)
and a degasser (Shimadzu DGU-14A). Mass spectrometric analysis
was performed using an API 3000 (triple-quadrupole) instrument
from AB Sciex (USA) with an electro-spray (ESI) interface. The data
acquisition and system control was performed using Analyst 1.5.2
software from AB Sciex. Accessory equipment used: Mixer Lab
Dancer (IKA, Germany); BMT-20-S tubes with stainless steel balls
and ULTRA-TURRAX Tube Drive (IKA, Germany); Eppendorf 5417R
centrifuge (USA), Sigma 4e15C centrifuge (USA), Barnstead
NANOpure Diamond ultrapure-water generating system.
4.4. Docking studies
3D Molecular docking study was performed in ICM Pro Software
[41] on the basis of X-Ray data obtained for COX-2/1-
phenylsulfonamide-3-trifluoromethyl-5-
Plasma samples (0.050 mL) were transferred to 1.3 mL tube,
mixed with 200
m
l of the IS solutions (400 ng/ml). After mixing by
parabromophenylpyrazole complex (PDB ID - 6COX) [7]. The model
was properly self- and cross-validated using analogues structures
(PDB ID e 3NTG, 6COX, 1CX2) and indomethacin (PDB ID e 6COX).
Other reference compounds have been docked successfully as well,
with high similarity to the available X-Ray data. Internal Coordinate
Mechanics (ICM) was used for modeling. A rigid ICM model of the
protein was constructed on the basis of PDB standard coordinates
using the ICM conversion procedure. The resulting 3D map was
calculated with a grid size of 0.5 Å, step of 0.5 Å, and size of 119,756.
The potential fit of compounds into the active site of COX-2 was
then assessed using the constructed model. For each molecule, at
least ten different conformations were generated in ICM-Pro. All
conformations from the output were within a particular range
around the minimum of the potential energy. For assessment we
used internal “score” functions calculated automatically in ICM-Pro.
Generally, a score of ꢁ30 or lower was considered good, depending
on the receptor (e.g., exposed pockets or pockets with metal ions
may give scores higher than ꢁ30). All scores generated were
thoroughly analyzed and of these values, we have selected the best
score for the conformation that is most closely related to the
template supramolecular interface was selected.
pipetting five times and centrifuging for 5 min at 6000 rpm, 3
m
l of
each supernatant was injected into LC-MS system. Weighted brain
samples (about 0.4 g) were placed into BMT-20-S tubes, five
stainless steel balls (5 mm diameter) and 5 mL of homogenization
solvent (67% methanol) were added to each tube. Following solvent
addition, samples were homogenized using an ULTRA-TURRAX
Tube Drive for 2 min at the speed set up to position 6. Thereafter,
0.75 mL of the homogenate was centrifuged for 5 min at 5 ꢂC and
14,000 rpm (20,817 rcf); 500
ml of the supernatants obtained were
mixed in microtubes with 20
ml of the IS solution (5000 ng/ml in
67% methanol) by pipetting up and down 5 times. To construct
4.5. Chemistry general procedures
All chemicals and solvents were used as received from the
suppliers. The crude reaction mixtures were concentrated under
reduced pressure by removing organic solvents on rotary evapo-
rator. Column chromatography was performed using silica gel 60
(particle size 0.040e0.063 mm, 230e400 mesh ASTM). Analytical
thin-layer chromatography (TLC) was performed with silica gel 60
F254 aluminum sheets. Proton and carbon-13 nuclear magnetic
resonance (1H NMR and 13C NMR) spectra were recorded on a
Varian Unity INOVA 500 MHz spectrometer. Chemical shifts for
nuclear magnetic resonance (NMR) spectra were reported in parts
Fig. 6. Carrageenan-induced mouse paw edema reductiona achieved by administration
of 35 (3.7 mg/kg i.p.).
per million (ppm,
d) using the residual solvent peak(s) as internal
standard. Splitting patterns are described as singlet (s), doublet (d),

P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
167
triplet (t), quartet (q), multiplet (m), broad (br), doublets of doublet
(dd). High resolution mass spectra (HRMS) were acquired using a
Fourier Transform Ion Cyclotron Resonance spectrometer fitted
with an electrospray source and operating in positive ion mode.
4.5.5. 2-(3,4-Dichlorophenyl)-4,5-dihydro-1H-imidazole (7b)
Prepared according to General Procedure 1 commencing with
3,4-dichlorobenzaldehyde. White solid was obtained.
Yield 946 mg (44%). MP 125e127 ꢂC.
1H NMR (500 MHz, CDCl3)
d
8.09 (d, J ¼ 2.0 Hz, 1H), 7.86 (dd,
J ¼ 8.3, 2.0 Hz, 1H), 7.52 (d, J ¼ 8.3 Hz, 1H), 3.80 (s, 4H).
13C NMR (125 MHz, CDCl3)
162.6, 134.5, 131.6, 131.1, 129.4,
4.5.1. General procedure 1
d
Ethylenediamine (10.5 mmol) was added to a stirred solution of
aldehyde (10.0 mmol) in CH2Cl2 (50 mL) at 0 ꢂC, and the resulting
solution was stirred for 20 min. N-bromosuccinimide (10.5 mmol)
was then added in portions over 10 min. The reaction mixture was
warmed to room temperature and stirred for an additional 12 h,
during which time a precipitate formed. A solution of KOH (1 M,
50 mL, 50 mmol) was added causing the precipitate to disappear
and a clear biphasic solution was formed. The organic layer was
separated, dried over anhydrous MgSO4, filtered and concentrated
at reduced pressure to afford the crude product. The analytically
pure imidazolines 7 were obtained by a brief crystallization from
EtOAc/hexane. All imidazolines 7 used in subsequent Pd-catalyzed
N-arylation are known compounds except for 7aec.
128.6 (q, JC-F ¼ 31.8 Hz), 126.2 (q, JC-F ¼ 5.3 Hz), 122.5 (q, JC-
¼ 273.6 Hz), 50.4.
F
4.5.6. 2-[4-Chloro-3-(trifluoromethyl)phenyl]-4,5-dihydro-1H-
imidazole (7c)
Prepared according to General Procedure 1 commencing with 4-
chloro-3-(trifluoromethyl)benzaldehyde.
obtained.
White
solid
was
Yield 1.32 g (53%). MP 116e118 ꢂC.
1H NMR (500 MHz, DMSO-d6)
d
8.02 (d, J ¼ 2.0 Hz, 1H), 7.80 (dd,
J ¼ 8.4, 2.0 Hz, 1H), 7.70 (d, J ¼ 8.4 Hz, 1H), 7.10 (br s, 1H), 3.62 (s,
4H).
13C NMR (125 MHz, DMSO-d6)
d 161.5, 132.7, 131.02, 130.98,
4.5.2. General procedure 2
130.5, 128.7, 127.1, 49.6.
A thick-glass screw-capped pressure tube (50 mL) was charged
with a suspension of starting imidazoline (3.0 mmol), 1-bromo-4-
(methylsulfonyl)benzene or 4-bromo-N,N-bis(2,4-dimethoxy-
benzyl)benzenesulfonamide [21] (3.0 mmol), Cs2CO3 (3.0 mmol),
and toluene (15 mL). Pd(OAc)2 (0.12 mmol) and BINAP (0.24 mmol)
were weighed as solids into a 10 mL screw-capped vial and toluene
(8 mL) was added. The resulting suspension was heated at 110 ꢂC
until a clear purple solution was obtained. The latter was rapidly
transferred, while still hot, to the screw-capped pressure tube using
a Pasteur pipette. The reaction vessel was filled with argon, sealed,
and the reaction mixture was vigorously stirred at 110 ꢂC for 20 h.
The reaction mixture was cooled to ambient temperature and
filtered through a Celite pad. The latter was washed with copious
amounts of EtOAc, and the combined filtrate and washings were
evaporated to dryness. The crude material was briefly fractionated
on silica (CH2Cl2:MeOH, 95:5) and the fractions containing the N-
aryl 2-imidazolines were collected and evaporated to dryness. The
residue was either purified further by chromatography under the
same conditions (methylsulfone compounds 8e21) or taken for-
ward to the next step without further purification.
4.5.7. 2-(4-Chlorophenyl)-4-methyl-1-[4-(methylsulfonyl)phenyl]-
4,5-dihydro-1H-imidazole (4)
Prepared as according to General Procedure 2 starting from 2-
(4-chlorophenyl)-4-methyl-4,5-dihydro-1H-imidazole [42] and 1-
bromo-4-(methylsulfonyl)benzene a yellow oil was obtained.
Yield 544 mg (52%).
1H NMR (500 MHz, CDCl3)
d
7.69 (d, J ¼ 8.8 Hz, 2H), 7.43 (d,
J ¼ 8.5 Hz, 2H), 7.33 (d, J ¼ 8.5 Hz, 2H), 6.76 (d, J ¼ 8.8 Hz, 2H),
4.39e4.32 (m, 1H), 4.20 (t, J ¼ 9.2 Hz, 1H), 3.70 (dd, J ¼ 9.2, 7.9 Hz,
1H), 3.01 (s, 3H), 1.41 (d, J ¼ 6.6 Hz, 3H).
13C NMR (125 MHz, CDCl3)
d 158.5, 146.8, 136.7, 133.2, 129.9,
129.1, 128.9, 128.3, 120.2, 60.0, 59.9, 44.6, 21.8.
HRMS m/z calcd for C17H18ClN2O2S (MþH)þ 349.0772 found
349.0768.
4.5.8. 2-(4-Fluorophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (8)
Prepared as according to General Procedure 2 starting from 2-
(4-fluorophenyl)-4,5-dihydro-1H-imidazole [43] and 1-bromo-4-
(methylsulfonyl)benzene. A yellow oil was obtained.
Yield 792 mg (83%).
4.5.3. General procedure 3
A 0 ꢂC solution of DMB-protected sulphonamides obtained ac-
cording to General Procedure 2 in CH2Cl2 (10 mL) was treated with
dropwise addition of neat TFA (3 mL) at 0 ꢂC. The stirring continued
at the same temperature for 30e60 min. The excess TFA was
neutralized with sat. aq. NaHCO3, the organic layer was separated
and dried over anhydrous MgSO4. The solution was filtered and
concentrated in vacuo. The resulting crude product was purified by
column chromatography on silica using an appropriate gradient of
MeOH in CH2Cl2 as eluent to provide sulfonamide products 22e36.
1H NMR (500 MHz, CDCl3)
d
7.68 (d, J ¼ 8.8 Hz, 2H), 7.51e7.43
(m, 2H), 7.07e7.00 (m, 2H), 6.77 (d, J ¼ 8.8 Hz, 2H), 4.15e4.03 (m,
3H), 2.99 (s, 2H).
13C NMR (125 MHz, CDCl3)
d
163.8 (d, JC-F ¼ 251.4 Hz), 159.8,
146.8, 133.1, 130.5 (d, JC-F ¼ 8.6 Hz), 128.7, 128.2, 127.9, 126.8 (d, JC-
¼ 3.4 Hz), 126.7, 120.3, 117.9, 115.8 (d, JC-F ¼ 21.9 Hz), 53.1, 53.0,
F
44.5.
HRMS m/z calcd for C16H16FN2O2S (MþH)þ 319.0911 found
319.0977.
4.5.4. 2-(3-Fluoro-4-methoxyphenyl)-4,5-dihydro-1H-imidazole
(7a)
Prepared according to General procedure 1 commencing with 3-
fluoro-4-methoxybenzaldehyde. Yellow solid was obtained.
Yield 1.22 g (63%). MP 148e150 ꢂC.
4.5.9. 2-(4-Fluorophenyl)-4-methyl-1-(4-(methylsulfonyl)phenyl)-
4,5-dihydro-1H-imidazole (9)
Prepared as according to General Procedure 2 starting from 2-
(4-fluorophenyl)-4-methyl-4,5-dihydro-1H-imidazole [44] and 1-
bromo-4-(methylsulfonyl)benzene. A white solid was obtained.
Yield 619 mg (62%). MP ¼ 63e65 ꢂC.
1H NMR (500 MHz, DMSO-d6)
d
7.64e7.59 (m, 2H), 7.21 (t,
J ¼ 7.6 Hz, 1H), 3.88 (s, 3H), 3.58 (s, 4H).
13C NMR (125 MHz, DMSO-d6)
d
162.2 (d, JC-F ¼ 2.5 Hz), 150.8 (d,
1H NMR (500 MHz, CDCl3)
d
7.68 (d, J ¼ 8.8 Hz, 2H), 7.48 (dd,
JC-F ¼ 243.7 Hz), 148.6 (d, JC-F ¼ 10.7 Hz), 123.8 (d, JC-F ¼ 4.0 Hz),
123.4 (d, JC-F ¼ 6.7 Hz), 114.4 (d, JC-F ¼ 18.9 Hz), 113.2 (d, JC-
J ¼ 8.6, 5.5 Hz, 2H), 7.04 (dd, J ¼ 8.6, 5.5 Hz, 2H), 6.76 (d, J ¼ 8.8 Hz,
2H), 4.37e4.28 (m, 1H), 4.19 (t, J ¼ 9.2 Hz, 1H), 3.70 (dd, J ¼ 9.2,
7.9 Hz, 1H), 3.00 (s, 3H), 1.41 (d, J ¼ 6.6 Hz, 3H).
¼ 1.7 Hz), 56.0, 49.5.
F

168
P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
13C NMR (125 MHz, CDCl3)
d
163.9 (d, JC-F ¼ 251.4 Hz), 158.5,
4.5.14. 2-(3-Chlorophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (14)
146.9, 133.1, 130.7 (d, JC-F ¼ 8.6 Hz), 128.3, 126.8, 120.2, 115.8 (d, JC-
¼ 21.9 Hz), 59.9, 59.8, 44.6, 21.8.
Prepared as according to General Procedure 2 starting from 2-
(3-chlorophenyl)-4,5-dihydro-1H-imidazole [49] and 1-bromo-4-
(methylsulfonyl)benzene. A light orange solid was obtained.
Yield 471 mg (47%); MP ¼ 131e133 ꢂC.
F
HRMS m/z calcd for C17H18FN2O2S (M þ H)þ 333.1068 found
333.1063.
1H NMR (500 MHz, CDCl3)
d
7.71 (d, J ¼ 8.8 Hz, 2H), 7.56 (s, 1H),
4.5.10. 2-(4-Chlorophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (10)
7.44e7.40 (m, 1H), 7.32e7.26 (m, 2H), 6.80 (d, J ¼ 8.8 Hz, 2H),
4.18e4.07 (m, 4H), 3.02 (s, 3H).
Prepared as according to General Procedure 2 starting from 2-
(4-chlorophenyl)-4,5-dihydro-1H-imidazole [45] and 1-bromo-4-
(methylsulfonyl)benzene. A yellow oil was obtained.
Yield 593 mg (59%).
13C NMR (125 MHz, CDCl3)
d 159.6, 146.6, 134.7, 133.3, 132.6,
130.6, 129.8, 128.5, 128.3, 126.5, 120.2, 53.2, 53.0, 44.6.
HRMS m/z calcd for C16H16ClN2O2S (M þ H)þ 335.0616 found
335.0607.
1H NMR (500 MHz, CDCl3)
d
7.69 (d, J ¼ 8.7 Hz, 2H), 7.41 (d,
J ¼ 8.5 Hz, 2H), 7.33 (d, J ¼ 8.5 Hz, 2H), 6.78 (d, J ¼ 8.7 Hz, 2H),
4.17e4.01 (m, 4H), 3.00 (s, 3H).
4.5.15. 1-(4-(Methylsulfonyl)phenyl)-2-m-tolyl-4,5-dihydro-1H-
imidazole (15)
13C NMR (125 MHz, CDCl3)
d 159.8, 146.8, 136.6, 133.3, 129.8,
Prepared as according to General Procedure 2 starting from 2-
(m-tolyl)-4,5-dihydro-1H-imidazole [50] and 1-bromo-4-(methyl-
sulfonyl)benzene. A yellow solid was obtained.
Yield 725 mg (77%); MP ¼ 74e74 ꢂC.
129.2, 128.9, 128.3, 120.3, 53.2, 53.0, 44.5.
HRMS m/z calcd for C16H16ClN2O2S (MþH)þ 335.0916 found
335.0611.
1H NMR (500 MHz, CDCl3)
d
7.69 (d, J ¼ 8.8 Hz, 2H), 7.40 (s, 1H),
4.5.11. 2-(3-Bromophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (11)
7.28e7.15 (m, 3H), 6.81 (d, J ¼ 8.8 Hz, 2H), 4.17e4.06 (m, 4H), 3.01 (s,
3H), 2.35 (s, 3H).
Prepared as according to General Procedure 2 starting from 2-
(3-bromophenyl)-4,5-dihydro-1H-imidazole [46] and 1-bromo-4-
(methylsulfonyl)benzene. A light yellow solid was obtained.
Yield 352 mg, 31%; MP ¼ 66e68 ꢂC.
13C NMR (125 MHz, CDCl3)
d 161.0, 146.7, 138.6, 131.3, 128.9,
128.8, 128.4, 128.1, 128.1, 125.4, 120.1, 52.8, 52.7, 44.5, 21.2.
HRMS m/z calcd for C17H19N2O2S (M þ H)þ 315.1162 found
315.1154.
1H NMR (500 MHz, CDCl3)
d 7.75e7.68 (m, 3H), 7.61e7.54 (m,
1H), 7.35e7.30 (m, 1H), 7.21 (t, J ¼ 7.9 HZ, 1H), 6.79 (d, J ¼ 8.2 Hz,
4.5.16. 2-(3-Fluoro-4-methoxyphenyl)-1-(4-(methylsulfonyl)
phenyl)-4,5-dihydro-1H-imidazole (16)
Prepared as according to General Procedure 2 starting from 2-
(3-fluoro-4-methoxyphenyl)-4,5-dihydro-1H-imidazole (7a) and
1-bromo-4-(methylsulfonyl)benzene. A yellow oil was obtained.
Yield 556 mg (53%).
2H), 4.18e4.02 (m, 4H), 3.01 (s, 3H).
13C NMR (125 MHz, CDCl3)
d 159.5, 146.6, 133.6, 133.4, 132.8,
131.4, 130.1, 128.4, 127.0, 122.7, 120.3, 53.3, 53.0, 44.6.
HRMS m/z calcd for C16H16BrN2O2S (M þ H)þ 379.0110 found
379.0105.
1H NMR (500 MHz, CDCl3)
d
7.71 (d, J ¼ 8.9 Hz, 2H), 7.27e7.18 (m,
4.5.12. 2-(3-Bromophenyl)-4-methyl-1-(4-(methylsulfonyl)
phenyl)-4,5-dihydro-1H-imidazole (12)
2H), 6.94e6.90 (m, 1H), 6.82 (d, J ¼ 8.9 Hz, 2H), 4.15e4.03 (m, 4H),
3.92 (s, 3H), 3.02 (s, 3H).
13C NMR (125 MHz, CDCl3)
d
159.6, 151.8 (d, JC-F ¼ 247.6 Hz),
Prepared as according to General Procedure 2 starting from 2-
(3-bromophenyl)-4-methyl-4,5-dihydro-1H-imidazole [47] and 1-
bromo-4-(methylsulfonyl)benzene. A white solid was obtained.
Yield 283 mg (24%); MP ¼ 118e120 ꢂC.
149.6, 149.5, 147.1, 133.2, 128.2, 125.0 (d, JC-F ¼ 3.7 Hz), 123.3, 120.4,
116.3 (d, JC-F ¼ 19.9 Hz), 113.1, 113.0, 56.2, 43.1, 43.2, 44.6.
HRMS m/z calcd for C17H18FN2O3S (M þ H)þ 349.1017 found
349.1007.
1H NMR (500 MHz, CDCl3)
d
7.74 (s, 1H), 7.70 (d, J ¼ 8.6 Hz, 2H),
7.58e7.54 (m, 1H), 7.34e7.30 (m, 1H), 7.20 (t, J ¼ 7.8 Hz, 1H), 6.77 (d,
J ¼ 8.6 Hz, 2H), 4.42e4.33 (m, 1H), 4.20 (t, J ¼ 9.2 Hz, 1H), 3.70 (dd,
J ¼ 9.2, 8.0 Hz, 1H), 3.01 (s, 3H), 1.41 (d, J ¼ 6.6 Hz, 3H).
4.5.17. 2-(4-Fluoro-3-methoxyphenyl)-1-(4-(methylsulfonyl)
phenyl)-4,5-dihydro-1H-imidazole (17)
Prepared as according to General Procedure 2 starting from 2-
(4-fluoro-3-methoxyphenyl)-4,5-dihydro-1H-imidazole [44] and 1-
bromo-4-(methylsulfonyl)benzene. A light yellow oil was obtained.
Yield 543 mg (52%).
13C NMR (125 MHz, CDCl3)
d 158.1, 146.7, 133.6, 133.3, 132.8,
131.5, 130.1, 128.3, 127.1, 122.8, 120.1, 60.1, 59.8, 44.6, 21.8.
HRMS m/z calcd for C17H18BrN2O2S (M þ H)þ 393.0267 found
393.0261.
1H NMR (500 MHz, CDCl3)
d
7.68 (d, J ¼ 8.8 Hz, 2H), 7.23e7.17 (m,
4.5.13. 2-(3-Fluorophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (13)
1H), 7.03e6.96 (m, 1H), 6.92e6.86 (m, 1H), 6.79 (d, J ¼ 8.8 Hz, 2H),
4.14e4.03 (m, 4H), 3.82 (s, 3H), 2.99 (s, 3H).
Prepared as according to General Procedure 2 starting from 2-
(3-flurophenyl)-4,5-dihydro-1H-imidazole [48] and 1-bromo-4-
(methylsulfonyl)benzene. A light yellow solid was obtained.
Yield 239 mg (25%); MP ¼ 119e121 ꢂC.
13C NMR (125 MHz, CDCl3)
d
160.0, 153.6 (d, JC-F ¼ 251.3 Hz),
147.8 (d, JC-F ¼ 10.9 Hz), 146.9, 133.2, 128.2, 127.0 (d, JC-F ¼ 4.4 Hz),
121.4 (d, JC-F ¼ 7.2 Hz), 120.4, 116.1 (d, JC-F ¼ 19 Hz), 113.6 (d, JC-
¼ 2.1 Hz), 56.2, 53.1, 53.0, 44.5.
F
1H NMR (500 MHz, CDCl3)
d
7.69 (d, J ¼ 7.7 Hz, 2H), 7.36e7.29
HRMS m/z calcd for C17H18FN2O3S (M þ H)þ 349.1017 found
(m,1H), 7.25e7.19 (m, 2H), 7.16e7.10 (m,1H), 6.78 (d, J ¼ 7.7 Hz, 2H),
349.1008.
4.17e4.05 (m, 4H), 3.00 (s, 1H).
13C NMR (125 MHz, CDCl3)
d
162.5 (d, JC-F ¼ 247.6 Hz), 159.7,
4.5.18. 2-(3-Chloro-4-methoxyphenyl)-1-(4-(methylsulfonyl)
phenyl)-4,5-dihydro-1H-imidazole (18)
Prepared as according to General Procedure 2 starting from 2-
(3-chloro-4-methoxyphenyl)-4,5-dihydro-1H-imidazole [23] and 1-
bromo-4-(methylsulfonyl)benzene. A yellow oil was obtained.
Yield 633 mg (58%).
146.7, 133.3, 132.9 (d, JC-F ¼ 7.8 Hz), 130.4 (d, JC-F ¼ 8.2 Hz), 128.3,
124.2 (d, JC-F ¼ 3.2 Hz), 120.3, 117.6 (d, JC-F ¼ 21.2 Hz), 115.6 (d, JC-
¼ 23.2 Hz), 53.3, 53.0, 44.6.
F
HRMS m/z calcd for C16H16FN2O2S (M þ H)þ 319.0911 found
319.0903.

P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
169
1H NMR (500 MHz, CDCl3)
d
7.72 (d, J ¼ 8.8 Hz, 2H), 7.60 (d,
13C NMR (125 MHz, CDCl3)
d
163.9 (d, JC-F ¼ 251.4 Hz), 160.1,
J ¼ 2.1 Hz, 1H), 7.29 (dd, J ¼ 8.5, 2.1 Hz, 1H), 6.88 (d, J ¼ 8.5 Hz, 1H),
146.2, 134.9, 130.6 (d, JC-F ¼ 8.6 Hz), 127.4, 126.8 (d, JC-F ¼ 3.4 Hz),
120.5, 115.8 (d, JC-F ¼ 21.9 Hz), 53.13, 53.11.
HRMS m/z calcd for C15H15FN3O2S (M þ H)þ 320.0864 found
320.0860.
6.83 (d, J ¼ 8.8 Hz, 2H), 4.15e4.03 (m 4H), 3.93 (s, 3H), 3.02 (s, 3H).
13C NMR (125 MHz, CDCl3)
d 159.4, 147.1, 133.2, 130.4, 128.3,
128.2, 123.7, 122.8, 120.4, 111.6, 56.2, 53.1, 53.0, 44.6.
HRMS m/z calcd for C17H18ClN2O3S (M þ H)þ 365.0721 found
365.0712.
4.5.23. 4-(2-(4-Fluorophenyl)-4-methyl-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (23)
Prepared as according to General Procedures 2 and 3 starting
from 2-(4-fluorophenyl)-4-methyl-4,5-dihydro-1H-imidazole [44]
and 4-bromo-N,N-bis(2,4-dimethoxybenzyl)-benzenesulfonamide.
A yellow solid was obtained.
4.5.19. 2-(3,4-Difluorophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (19)
Prepared as according to General Procedure 2 starting from 2-
(3,4-difluorophenyl)-4,5-dihydro-1H-imidazole [48] and 1-bromo-
4-(methylsulfonyl)benzene. A light yellow solid was obtained.
Yield 494 mg (49%); MP ¼ 125e126 ꢂC.
Yield 360 mg (36%); MP ¼ 157e159 ꢂC.
1H NMR (500 MHz, CD3OD)
d 7.86e7.82 (m, 2H), 7.57e7.53 (m,
1H NMR (500 MHz, CDCl3)
d
7.72 (d, J ¼ 8.8 Hz, 2H), 7.40e7.33
2H), 7.26e7.19 (m, 4H), 4.63e4.53 (m 2H), 4.14e4.06 (m 1H),
1.56e1.51 (m, 3H), NH2 protons in exchange.
(m,1H), 7.24e7.18 (m,1H), 7.16e7.10 (m,1H), 6.80 (d, J ¼ 8.8 Hz, 2H),
13C NMR (125 MHz, CD3OD)
d
166.7 (d, JC-F ¼ 254.0 Hz), 164.2,
4.16e4.04 (m, 4H), 3.01 (s, 3H).
13C NMR (125 MHz, CDCl3)
d
159.0, 151.7 (dd, JC-F ¼ 253.7,
143.3, 142.8, 133.1 (d, JC-F ¼ 9.4 Hz), 128.6, 125.5, 117.5 (d, JC-
¼ 22.6 Hz), 61.3, 55.8, 20.9.
F
12.5 Hz), 150.2 (dd, JC-F ¼ 250.4, 12.9 Hz), 146.7, 133.6, 128.4, 127.7
(dd, JC-F ¼ 6.0, 3.9 Hz), 125.1 (dd, JC-F ¼ 6.8, 3.8 Hz), 120.5, 117.8 (dd,
JC-F ¼ 20.3, 18.3 Hz), 53.3, 53.2, 44.6.
HRMS m/z calcd for C16H17FN3O2S (M þ H)þ 334.1020 found
334.1016.
HRMS m/z calcd for C16H15F2N2O2S (M þ H)þ 337.0817 found
337.0808.
4.5.24. 4-(2-(4-Chlorophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (24)
Prepared as according to General Procedures 2 and 3 starting
from 2-(4-chlorophenyl)-4,5-dihydro-1H-imidazole [45] and 4-
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfonamide. A yel-
low solid was obtained.
4.5.20. 2-(3,4-Dichlorophenyl)-1-(4-(methylsulfonyl)phenyl)-4,5-
dihydro-1H-imidazole (20)
Prepared as according to General Procedure 2 starting from 2-
(3,4-dichlorophenyl)-4,5-dihydro-1H-imidazole (7b) and 1-bromo-
4-(methylsulfonyl)benzene. A light yellow solid was obtained.
Yield 453 mg (41%); MP ¼ 158e160 ꢂC.
Yield 663 mg (66%); MP ¼ 141e143 ꢂC.
1H NMR (500 MHz, CD3OD)
d
7.81 (d, J ¼ 8.8 Hz, 2H), 7.54e7.46
(m, 4H), 7.08 (d, J ¼ 8.8 Hz, 2H), 4.36 (t, J ¼ 9.9 Hz, 2H), 4.14 (t,
1H NMR (500 MHz, CDCl3)
d
7.72 (d, J ¼ 8.3 Hz, 2H), 7.68 (d,
J ¼ 9.9 Hz, 2H), NH2 protons in exchange.
J ¼ 1.7, 1H), 7.41 (d, J ¼ 8.4 Hz, 1H), 7.23 (dd, J ¼ 8.4, 1.7, 1H), 6.80 (d,
J ¼ 8.3 Hz, 2H), 4.16e4.05 (m, 4H), 3.01 (s, 3H).
13C NMR (125 MHz, CD3OD)
d 163.9, 145.0, 140.7, 1387, 131.5,
130.1, 128.4, 128.3, 123.7, 54.3, 51.1.
13C NMR (125 MHz, CDCl3)
d 158.8, 146.6, 134.9, 133.7, 133.1,
HRMS m/z calcd for C15H15ClN3O2S (M þ H)þ 336.0568 found
130.7, 130.6, 130.4, 128.4, 127.5, 120.5, 53.4, 53.2, 44.6.
HRMS m/z calcd for C16H15Cl2N2O2S (M þ H)þ 369.0226 found
369.0216.
336.0564.
4.5.25. 4-(2-(4-Chlorophenyl)-4-methyl-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (25)
4.5.21. 2-(4-Chloro-3-(trifluoromethyl)phenyl)-1-(4-
(methylsulfonyl)phenyl)-4,5-dihydro-1H-imidazole (21)
Prepared as according to General Procedure 2 starting from 2-
[4-chloro-3-(trifluoromethyl)phenyl]-4,5-dihydro-1H-imidazole
(7c) and 1-bromo-4-(methylsulfonyl)-benzene. A light yellow solid
was obtained.
Prepared as according to General Procedures 2 and 3 starting
from 2-(4-chlorophenyl)-4-methyl-4,5-dihydro-1H-imidazole [42]
and 4-bromo-N,N-bis(2,4-dimethoxybenzyl)-benzenesulfonamide.
A light brown solid was obtained.
Yield 534 mg (51%); MP ¼ 160e162 ꢂC.
1H NMR (500 MHz, CD3OD)
d
7.85 (d, J ¼ 8.7 Hz, 2H), 7.53e7.47
Yield 289 mg (24%); MP ¼ 153e155 ꢂC.
(m, 4H), 7.26 (d, J ¼ 8.7 Hz, 2H), 4.67e4.58 (m, 2H), 4.17e4.09 (m,
1H), 1.58e1.50 (m, 3H), NH2 protons in exchange.
1H NMR (500 MHz, CDCl3)
d
7.94 (s, 1H), 7.74 (d, J ¼ 8.6 Hz, 2H),
13C NMR (125 MHz, CD3OD)
d 164.3, 143.5, 142.5, 140.5, 132.0,
7.52e7.45 (m, 2H), 6.81 (d, J ¼ 8.6 Hz, 2H), 4.18e4.06 (m. 4H), 3.01
(s, 3H).
130.6, 128.6, 125.7, 124.5, 61.3, 55.6, 20.8.
HRMS m/z calcd for C16H17ClN3O2S (M þ H)þ 350.0724 found
350.0719.
13C NMR (125 MHz, CDCl3)
d 158.8, 146.6, 134.6, 134.1, 132.5,
131.7, 129.6, 129.0 (q, JC-F ¼ 31.8 Hz), 128.5, 127.9 (q, JC-F ¼ 5.3 Hz),
122.3 (q, JC-F ¼ 273.6 Hz), 120.8, 53.4, 53.3, 44.6.
HRMS m/z calcd for C17H15ClF3N2O2S (M þ H)þ 403.0489 found
403.0478.
4.5.26. 4-(2-(3-Bromophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (26)
Prepared as according to General Procedures 2 and 3 starting
from 2-(3-bromophenyl)-4,5-dihydro-1H-imidazole [46] and 4-
4.5.22. 4-(2-(4-Fluorophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (22)
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfonamide.
white solid was obtained.
A
Prepared as according to General Procedures 2 and 3 starting
from 2-(4-fluorophenyl)-4,5-dihydro-1H-imidazole [43] and 4-
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfonamide. A light
yellow solid was obtained.
Yield 409 mg (36%); MP ¼ 194e194 ꢂC.
1H NMR (500 MHz, CD3OD)
d
7.73 (d, J ¼ 8.8 Hz, 2H), 7.68e7.64
(m, 2H), 7.40e7.36 (m, 1H), 7.31 (t, J ¼ 7.8 Hz,1H), 6.98 (d, J ¼ 8.8 Hz,
2H), 4.20 (td, J ¼ 9.3, 1.2 Hz, 2H), 4.05 (td, J ¼ 9.3, 1.2 Hz, 2H), NH2
protons in exchange.
Yield 700 mg (73%); MP ¼ 94e96 ꢂC.
1H NMR (500 MHz, CDCl3)
d
7.69 (d, J ¼ 8.8 Hz, 2H), 7.50e7.45
(m, 2H), 7.07e7.02 (m, 2H), 6.75 (d, J ¼ 8.8 Hz, 2H), 4.91 (br s, 2H),
13C NMR (125 MHz, CD3OD)
d
162.6, 146.2, 139.4, 134.8, 134.0,
4.15e4.03 (m, 4H).
132.3, 131.5, 128.5, 128.1, 123.5, 122.6, 54.1, 53.3.

170
P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
HRMS m/z calcd for C15H15BrN3O2S (M þ H)þ 380.0063 found
HRMS m/z calcd for C16H18N3O2S (M þ H)þ 316.1114 found
380.0057.
316.1107.
4.5.31. 4-(2-(3-Fluoro-4-methoxyphenyl)-4,5-dihydroimidazol-1-
yl)benzenesulfonamide (31)
4.5.27. 4-(2-(3-Bromophenyl)-4-methyl-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (27)
Prepared as according to General Procedures 2 and 3 starting
Prepared as according to General Procedures 2 and 3 starting
from 2-(3-bromophenyl)-4-methyl-4,5-dihydro-1H-imidazole [47]
and 4-bromo-N,N-bis(2,4-dimethoxybenzyl)-benzenesulfonamide.
A white solid was obtained.
from
2-(3-Fluoro-4-methoxyphenyl)-4,5-dihydro-1H-imidazole
(7a) and 4-bromo-N,N-bis(2,4-dimethoxy-benzyl)benzenesulfona-
mide. A yellow solid was obtained.
Yield 712 mg (68%); MP ¼ 195e197 ꢂC.
Yield 755 mg (64%); MP ¼ 180 ꢂC (decomp.)
1H NMR (500 MHz, CD3OD)
d 7.78e7.76 (m, 2H), 7.25 (t,
1H NMR (500 MHz, CD3OD)
d
7.91 (d, J ¼ 8.7 Hz, 2H), 7.86e7.83
J ¼ 7.3 Hz, 2H), 7.14 (t, J ¼ 7.6 Hz, 1H), 7.00e6.98 (m, 2H), 4.22 (t,
J ¼ 9.6 Hz, 2H), 4.06 (t, J ¼ 9.6 Hz, 2H), 3.95 (s, 3H), NH2 protons in
exchange.
(m, 1H), 7.81e7.78 (m, 1H), 7.48e7.37 (m, 4H), 4.75e4.68 (m, 2H),
4.32e4.24 (m, 1H), 1.63e1.60 (m, 3H), NH2 protons in exchange.
13C NMR (125 MHz, CD3OD)
d 164.7, 145.1, 141.0, 138.0, 133.2,
13C NMR (125 MHz, CD3OD)
d
163.6, 153.9 (d, JC-F ¼ 245.3 Hz),
132.2, 129.3, 128.8, 126.7, 125.9, 124.0, 51.5, 54.0, 20.4.
HRMS m/z calcd for C16H17BrN3O2S (M þ H)þ 394.0219 found
394.0214.
152.0 (d, JC-F ¼ 10.6 Hz), 147.5, 140.1, 128.9, 127.4 (d, JC-F ¼ 3.5 Hz),
124.8 (d, JC-F ¼ 7.0 Hz), 123.7, 118.1 (d, JC-F ¼ 20.0 Hz), 115.3, 57.6,
55.1, 53.8.
HRMS m/z calcd for C16H17FN3O3S (M þ H)þ 350.0969 found
350.0960.
4.5.28. 4-(2-(3-Fluorophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (28)
Prepared as according to General Procedures 2 and 3 starting
from 2-(3-fluorophenyl)-4,5-dihydro-1H-imidazole [48] and 4-
4.5.32. 4-(2-(4-Fluoro-3-methoxyphenyl)-4,5-dihydroimidazol-1-
yl)benzenesulfonamide (32)
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfonamide.
white solid was obtained.
A
Prepared as according to General Procedures 2 and 3 starting
from
2-(4-Fluoro-3-methoxyphenyl)-4,5-dihydro-1H-imidazole
Yield 584 mg (61%); MP ¼ 225e227 ꢂC.
[44] and 4-bromo-N,N-bis(2,4-dimethoxy-benzyl)benzenesulfona-
mide. A white solid was obtained.
1H NMR (500 MHz, CD3OD)
d 7.77e7.75 (m, 2H), 7.48e7.44 (m,
1H), 7.29 (t, J ¼ 7.4 Hz, 2H), 7.25 (d, J ¼ 8.0 Hz, 1H), 6.97e6.96 (m,
2H), 4.24 (t, J ¼ 9.6 Hz, 2H), 4.09 (t, J ¼ 9.6 Hz, 2H), NH2 protons in
exchange.
Yield 691 mg (66%); MP ¼ 248e249 ꢂC.
1H NMR (500 MHz, CD3OD)
d
7.79e7.76(m, 2H), 7.24 (dd, J ¼ 8.1,
1.8 Hz, 1H), 7.14 (dd, J ¼ 13.7, 8.3 Hz, 1H), 7.01e7.04 (m, 1H), 7.00 (d,
J ¼ 8.8 Hz, 2H), 4.25 (t, J ¼ 9.4 Hz, 2H), 4.09 (t, J ¼ 10.3 Hz, 2H), 3.83
(s, 3H), NH2 protons in exchange.
13C NMR (125 MHz, CD3OD)
d
164.7 (d, JC-F ¼ 244.6 Hz), 163.6,
147.1, 140.2, 134.9 (d, JC-F ¼ 7.8 Hz), 132.6 (d, JC-F ¼ 8.1 Hz), 128.9,
126.5 (d, JC-F ¼ 3.2 Hz), 123.5, 117.4 (d, JC-F ¼ 23.1 Hz), 119.4 (d, JC-
13C NMR (125 MHz, CD3OD)
d
164.1, 155.8 (d, JC-F ¼ 249.1 Hz),
¼ 21.1 Hz), 54.9, 54.2.
F
150.0 (d, JC-F ¼ 11.3 Hz), 147.3, 140.1, 130.7, 128.8, 123.7, 123.6, 118.0
(d, JC-F ¼ 19.0 Hz), 116.2 (d, JC-F ¼ 1.8 Hz), 57.6, 54.9, 53.8.
HRMS m/z calcd for C16H17FN3O3S (MþH)þ 350.09693 found
350.0960.
HRMS m/z calcd for C15H15FN3O2S (M þ H)þ 320.0864 found
320.0854.
4.5.29. 4-(2-(3-Chlorophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (29)
Prepared as according to General Procedures 2 and 3 starting
from 2-(3-chlorophenyl)-4,5-dihydro-1H-imidazole [49] and 4-
4.5.33. 4-(2-(3-Chloro-4-methoxyphenyl)-4,5-dihydroimidazol-1-
yl)benzenesulfonamide (33)
Prepared as according to General Procedures 2 and 3 starting
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfonamide.
white solid was obtained.
A
from
2-(3-chloro-4-methoxyphenyl)-4,5-dihydro-1H-imidazole
[23] and 4-bromo-N,N-bis(2,4-dimethoxy-benzyl)benzenesulfona-
mide. A white solid was obtained.
Yield 794 mg (79%); MP ¼ 188e190 ꢂC.
1H NMR (500 MHz, CD3OD)
d 7.78e7.76 (m, 2H), 7.54e7.56 (m,
Yield 712 mg (63%); MP ¼ 255e257 ꢂC.
1H NMR (500 MHz, CD3OD)
d
7.78 (d, J ¼ 8.6 Hz, 2H), 7.55 (s, 1H),
2H), 7.44e7.38 (m, 2H), 6.98e6.96 (m, 2H), 4.25 (t, J ¼ 9.4 Hz, 2H),
4.10 (t, J ¼ 9.7 Hz, 2H), NH2 protons in exchange.
7.38 (d, J ¼ 8.6 Hz,1H), 7.11 (d, J ¼ 8.4 Hz,1H), 6.99 (d, J ¼ 8.6 Hz, 2H),
4.23 (t, J ¼ 9.6 Hz, 2H), 4.06 (t, J ¼ 9.2 Hz, 2H), 3.97 (s, 3H), NH2
protons in exchange.
13C NMR (125 MHz, CD3OD)
d 163.5, 147.1, 140.2, 136.5, 134.7,
132.6, 132.2, 130.5, 129.0, 128.9, 123.5, 55.0, 54.2.
HRMS m/z calcd for C15H15ClN3O2S (M þ H)þ 336.0568 found
336.0560.
13C NMR (125 MHz, CD3OD)
d 163.5, 159.3, 147.5, 140.1, 132.3,
130.8, 129.0, 125.4, 124.6, 123.6, 114.0, 57.7, 55.1, 53.8.
HRMS m/z calcd for C16H17ClN3O3S (MþH)þ 366.0674 found
366.0664.
4.5.30. 4-(2-m-Tolyl-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (30)
Prepared as according to General Procedures 2 and 3 starting
from 2-(m-tolyl)-4,5-dihydro-1H-imidazole [50] and 4-bromo-N,N-
bis(2,4-dimethoxybenzyl)benzenesulfonamide. A cream solid was
obtained.
4.5.34. 4-(2-(3,4-Difluorophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (34)
Prepared as according to General Procedures 2 and 3 starting
from 2-(3,4-difluorophenyl)-4,5-dihydro-1H-imidazole [48] and 4-
Yield 350 mg (37%); MP ¼ 244e246 ꢂC.
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfon-amide.
white solid was obtained.
A
1H NMR (500 MHz, CD3OD)
d
7.73 (d, J ¼ 8.8 Hz, 2H), 7.37e7.26
(m, 3H), 7.22e7.18 (m, 1H), 6.99 (d, J ¼ 8.8 Hz, 2H), 4.28 (t,
J ¼ 10.3 Hz, 2H), 4.07 (t, J ¼ 10.3 Hz, 2H), 2.33 (s, 3H), NH2 protons in
exchange.
Yield 465 mg (46%); MP ¼ 177e179 ꢂC.
1H NMR (500 MHz, CD3OD)
(dd, J ¼ 10.6, 8.9 Hz, 1H), 7.38e7.30 (m, 2H), 6.98 (d, J ¼ 8.0 Hz, 2H),
4.24 (t, J ¼ 9.8 Hz, 2H), 4.09 (t, J ¼ 9.7 Hz, 2H), NH2 protons in
exchange.
d
7.78 (d, J ¼ 7.9 Hz, 2H), 7.46e7.44
13C NMR (125 MHz, CD3OD)
d
164.7, 145.5, 140.1, 140.0, 133.1,
130.3, 130.2, 129.8, 128.1, 126.9, 123.1, 54.1, 51.4, 21.3.

P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
171
13C NMR (125 MHz, CD3OD)
d
162.9, 153.8 (dd, JC-F ¼ 251.8,
benzenesulfonamide (SC-58635, celecoxib), J. Med. Chem. 40 (1997)
1347e1365.
[4] Analysts Rx Product Desk Reference, Merrill Lynch, London, 2001.
[5] G. Dannhardt, W. Kiefer, Cyclooxygenase inhibitors e current status and
future prospects, Eur. J. Med. Chem. 36 (2001) 109e126.
[6] A. Zarghi, P.N. Praveen Rao, E.E. Knaus, Sulfonamido, azidosulfonyl and N-
acetylsulfonamido analogues of rofecoxib: 4-[4-(N-acetylsulfonamido)
phenyl]-3-(4-methanesulfonylphenyl)-2(5H)furanone is a potent and selec-
tive cyclooxygenase-2 inhibitor, Bioorg. Med. Chem. Lett. 14 (2004)
1957e1960.
[7] R.G. Kurumbail, A.M. Stevens, J.K. Gierse, J.J. McDonald, R.A. Stegeman,
Y.P. Jina, D. Gildehaus, J.M. Miyashiro, T.D. Penning, K. Seibert, P.C. Isakson,
W.C. Stallings, Structural basis for selective inhibition of cyclooxygenase-2 by
anti-inflammatory agents, Nature 384 (1996) 644e648.
[8] S.E. Nissen, Cox-2 inhibitors and cardiovascular disease: considerable heat,
but not much light, Eur. Heart J. 33 (2012) 2631e2633.
[9] B.F. McAdam, F. Catella-Lawson, I.A. Mardini, J.A. Lawson, G.A. FitzGerald,
Systemic biosynthesis of prostacyclin by cyclooxygenase (COX)-2: the human
pharmacology of a selective inhibitor of COX-2, Proc. Natl. Acad. Sci. USA 96
(1999) 272e277.
[10] A.L. Bartels, K.L. Leenders, Cyclooxygenase and neuroinflammation in Par-
kinson’s disease neurodegeneration, Curr. Neuropharmacol. 8 (2010) 62e68.
[11] E. Candelario-Jalil, B.L. Fiebich, Cyclooxygenase inhibition in ischemic brain
injury, Curr. Pharm. Des. 14 (2008) 1401e1418.
12.5 Hz), 152.2 (dd, JC-F ¼ 248.6, 12.8 Hz), 147.1, 140.3, 129.8 (dd, JC-
¼ 6.3, 4.2 Hz), 129.0, 127.7 (dd, JC-F ¼ 6.7, 3.7 Hz), 123.7, 119.9 (d, JC-
F
¼ 19.0 Hz), 119.7 (d, JC-F ¼ 18.0 Hz), 55.1, 54.2.
F
HRMS m/z calcd for C15H14F2N3O2S (MþH)þ 338.0769 found
338.0760.
4.5.35. 4-(2-(3,4-Dichlorophenyl)-4,5-dihydroimidazol-1-yl)
benzenesulfonamide (35)
Prepared as according to General Procedures 2 and 3 starting
from 2-(3,4-dichlorophenyl)-4,5-dihydro-1H-imidazole (7b) and 4-
bromo-N,N-bis(2,4-dimethoxybenzyl)benzenesulfon-amide.
white solid was obtained.
A
Yield 886 mg (80%); MP ¼ 232e234 ꢂC.
1H NMR (500 MHz, CD3OD)
d 7.79e7.78 (m, 2H), 7.70 (s, 1H),
7.59e7.58 (m, 1H), 7.36e7.38 (m, 1H), 6.99e6.98 (m, 2H), 4.29e4.19
(m, 2H), 4.15e4.03 (m, 2H), NH2 protons in exchange.
13C NMR (125 MHz, CD3OD)
d 155.8, 147.0, 140.5, 136.7, 134.7,
133.0, 132.8, 132.6, 130.3, 129.1, 123.7, 55.2, 54.3.
HRMS m/z calcd for C15H14Cl2N3O2S (MþH)þ 370.0178 found
370.0169.
[12] N. Müller, COX-2 inhibitors as antidepressants and antipsychotics: clinical
evidence, Curr. Opin. Investig. Drugs 11 (2010) 31e42.
[13] J.I. Johnsen, M. Lindskog, F. Ponthan, I. Pettersen, L. Elfman, A. Orrego,
€
B. Sveinbjornsson, P. Kogner, Cyclooxygenase-2 is expressed in neuroblas-
toma, and nonsteroidal anti-inflammatory drugs induce apoptosis and inhibit
tumor growth in vivo, Cancer Res. 64 (2004) 7210e7215.
[14] L. Lau, L.M. Hansford, L.S. Cheng, M. Hang, S. Baruchel, D.R. Kaplan, M.S. Irwin,
Cyclooxygenase inhibitors modulate the p53/HDM2 pathway and enhance
chemotherapy-induced apoptosis in neuroblastoma, Oncogene 26 (2007)
1920e1931.
4.5.36. 4-(2-(4-Chloro-3-(trifluoromethyl)phenyl)-4,5-
dihydroimidazol-1-yl)benzenesulfonamide (36)
Prepared as according to General Procedures 2 and 3 starting
from
2-[4-chloro-3-(trifluoromethyl)phenyl]-4,5-dihydro-1H-
[15] J.J. Hoozemans, M.K. O'Banion, The role of COX-1 and COX-2 in Alzheimer's
disease pathology and the therapeutic potentials of non-steroidal anti-in-
flammatory drugs, Curr. Drug. Targets CNS Neurol. Disord. 4 (2005) 307e315.
[16] C. Michaux, C. Charlier, Structural approach for COX-2 inhibition, Mini Rev.
Med. Chem. 4 (2004) 603e615.
[17] X.H. Chen, J.Y. Bai, F. Shen, A.P. Bai, Z.R. Guo, G.F. Cheng, Imrecoxib: a novel
and selective cyclooxygenase 2 inhibitor with anti-inflammatory effect, Acta
Pharmacol. Sin. 25 (2004) 927e931.
[18] D.B. Reitz, J.J. Li, M.B. Norton, E.J. Reinhard, J.T. Collins, G.D. Anderson,
S.A. Gregory, C.M. Koboldt, W.E. Perkins, K. Seibert, P.C. Isakson, Selective
cyclooxygenase inhibitors: novel 1,2-Diarylcyclopentenes are potent and
orally active COX-2 inhibitors, J. Med. Chem. 37 (1994) 3878e3881.
[19] I.G. Rathish, K. Javed, S. Ahmad, S. Bano, M.S. Alam, K.K. Pillai, S. Singh,
V. Bagchi, Synthesis and antiinflammatory activity of some new 1,3,5-
trisubstituted pyrazolines bearing benzene sulphonamide, Bioorg. Med.
Chem. Lett. 19 (2009) 255e258.
imidazole (7c) and 4-bromo-N,N-bis(2,4-dimethoxybenzyl)benze-
nesulfon-amide. A white solid was obtained.
Yield 786 mg (65%); MP ¼ 215e217 ꢂC.
1H NMR (500 MHz, CD3OD)
d
7.98 (s, 1H), 7.79 (d, J ¼ 8.6 Hz, 2H),
7.66e7.58 (m, 2H), 7.00 (d, J ¼ 8.6 Hz, 2H), 4.27 (t, J ¼ 9.7 Hz, 2H),
4.12 (t, J ¼ 9.6 Hz, 2H), NH2 protons in exchange.
13C NMR (125 MHz, CD3OD)
d 162.7, 147.0, 140.7, 136.2 (unre-
solved q, JC-F ¼ 1.9 Hz), 135.5, 133.9, 132.1, 130.5 (q, JC-F ¼ 31.8 Hz),
130.0 (q, JC-F ¼ 5.1 Hz), 129.1, 124.7 (q, JC-F ¼ 271.1 Hz), 123.9, 55.2,
54.4.
HRMS m/z calcd for C16H14ClF3N3O2S (M þ H)þ 404.0442 found
404.0431.
[20] F. Lovering, J. Bikker, C. Humblet, Escape from flatland: increasing saturation
as an approach to improving clinical success, J. Med. Chem. 52 (2009)
6752e6756.
Acknowledgment
[21] M. Krasavin, Pd-catalyzed N-arylation of 2-imidazolines provides convenient
access to selective cyclooxygenase-2 inhibitors, Lett. Org. Chem. 10 (2013)
235e239.
[22] I.K. Khanna, R.M. Weier, Y. Yu, X. Xu, F.J. Koszyk, P.W. Collins, C.M. Koboldt,
A.W. Veenhuizen, W.E. Perkins, J.J. Casler, J.L. Masferrer, Y.Y. Zhang,
S.A. Gregory, K. Seibert, P. Isakson, 1,2-Diarylimidazoles as potent,
cyclooxygenase-2 selective, and orally active antiinflammatory agents, J. Med.
Chem. (1997) 1634e1647.
M. K. acknowledges support from Griffith University. Dr. Hoan
Vu of Eskitis Institute is thanked for high-resolution mass spec-
trometry measurements.
Appendix A. Supplementary data
[23] M. Krasavin, Novel diversely substituted 1-heteroaryl-2-imidazolines for
fragment-based drug discovery, Tetrahedron Lett. 53 (2012) 2876e2880.
[24] (a) Y. Amemiya, D.D. Miller, F.L. Hsu, Synthesis of novel 5H-1,2,4-triazolo[5',1':
2,3][1,3]thiazino[5,6-c]quinoline-5-ones, Synth. Commun. 20 (1990)
2483e2489;
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.ejmech.2014.07.023.
References
(b) M. Abdollahi-Alibeik, I. Mohammadpoor-Baltork, M.A. Zolfigol, Alumina
supported potassium permanganate: an efficient reagent for chemoselective
dehydrogenation of 2-imidazolines under mild conditions, Bioorg. Med.
Chem. Lett. 14 (2004) 6079e6082.
[1] R.J. Flower, The development of COX-2 inhibitors, Nat. Rev. Drug. Discov. 1
(2003) 179e191.
[25] H. Sun, W.J. Ehlhardt, P. Kulanthaivel, D.L. Lanza, C.A. Reilly, G.S. Yost, Dehy-
drogenation of Indoline by cytochrome P450 enzymes: a novel “Aromatase”
Process, J. Pharmacol. Exp. Ther. 322 (2007) 843e851.
[2] P. Prasit, Z. Wang, C. Brideau, C.-C. Chan, S. Charleson, W. Cromlish,
D. Ethier, J.F. Evans, A.W. Ford-Huchinson, J.Y. Gauthier, R. Gordon, J. Guay,
M. Gresser, S. Kargman, B. Kennedy, Y. Leblanc, S. Leger, J. Mancini,
G.P. O’Neil, M. Ouellet, M.D. Percival, H. Perrier, D. Reindeau, I. Rodger,
P. Tagari, M. Therian, P. Vickers, E. Wong, L.-J. Xu, R.N. Young, R. Zamboni,
S. Boyce, N. Rupniak, M. Forrest, D. Visco, D. Patrick, The discovery of
rofecoxib, [MK 966, Vioxx, 4-(4'-methylsulfonylphenyl)-3-phenyl-2(5H)-
furanone], an orally active cyclooxygenase-2-inhibitor, Bioorg. Med. Chem.
Lett. 9 (1999) 1773e1778.
[3] T.D. Penning, J.J. Talley, S.R. Bertenshaw, J.S. Carter, P.W. Collins, S. Docter,
M.J. Graneto, L.F. Lee, J.W. Malecha, J.M. Miyashiro, R.S. Rogers, D.J. Rogier,
S.S. Yu, G.D. Anderson, J.N. Cogburn, S.A. Gregory, C.M. Koboldt, W.F. Perkins,
K. Seibert, A.W. Veenhuizen, Y.Y. Zhang, P.C. Isakson, Synthesis and biological
evaluation of the 1,5-diarylpyrazole class of cyclooxygenase-2 inhibitors:
identification of 4-[5-(4-methylphenyl)-3- (trifluoromethyl)-1H-pyrazol-1-yl]
[26] C. Fenton, G.M. Keating, K.A. Lyseng-Williamson, Moxonidine: a review of its
use in essential hypertension, Drugs 66 (2006) 477e496.
ꢀ
[27] B. Fernandez, I. Perillo, S. Lamdan, 1,2-Diaryl-2-imidazolines.
A structur-
eebasicity relationship: application of the Hammett equation, J. Chem. Soc.
Perkin Trans. 2 (1973) 1371e1374.
€
[28] T. Ginman, J. Viklund, J. Malmstrom, J. Blid, R. Emond, R. Forsblom,
A. Johansson, A. Kers, F. Lake, F. Sehgelmeble, K.J. Sterky, M. Bergh,
€
A. Lindgren, P. Johansson, F. Jeppsson, J. Falting, Y. Gravenfors, F. Rahm, Core
Refinement toward permeable b-secretase (BACE-1) inhibitors with low hERG
activity, J. Med. Chem. 56 (2013) 4181e4205.
[29] A. Tsuji, Small molecular drug transfer across the blood-brain barrier via
carrier-mediated transport systems, NeuroRx 2 (2005) 54e62.

172
P. Sarnpitak et al. / European Journal of Medicinal Chemistry 84 (2014) 160e172
[30] I.K. Khanna, Y. Yu, R.M. Huff, R.M. Weier, X. Xu, F.J. Koszyk, P.W. Collins,
J.N. Cogburn, P.C. Isakson, C.M. Koboldt, J.L. Masferrer, W.E. Perkins,
K. Seibert, A.W. Veenhuizen, J. Yuan, D.-C. Yang, Y.Y. Zhang, Selective
cyclooxygenase-2 inhibitors: heteroaryl modified 1,2-diarylimidazoles are
potent, orally active antiinflammatory agents, J. Med. Chem. 43 (2000)
3168e3185.
[36] S.A. Hitchcock, Blood-brain barrier permeability considerations for CNS-
targeted compound library design, Curr. Opin. Chem. Biol. 12 (2008) 318e323.
[37] Calculation of the Molecular Parameters for Compound 35 was Performed
using ACD/Labs 6.00 Software.
[38] K. Brune, A. Neubert, Pharmacokinetic and pharmacodynamic aspects of the
ideal COX-2 inhibitor: a pharmacologist's perspective, Clin. Exp. Rheumatol.
19 (Suppl. 25) (2001) S51eS57.
[31] https://mli.nih.gov/mli/.
[32] (a) B. Hill, Y. Liu, S.D. Taylor, Synthesis of a-fluorosulfonamides by electro-
philic fluorination, Org. Lett. 6 (2004) 4285e4288;
[39] C. Patrono, P. Patrignani, L.A. Garcia Rodriguez, Cyclooxygenase-selective in-
hibition of prostanoid formation: transducing biochemical selectivity into
clinical read-outs, J. Clin. Invest. 108 (2001) 7e13.
[40] A.A. Geronikaki, A.A. Lagunin, D.I. Hadjipavlou-Litina, P.T. Eleftheriou,
D.A. Filimonov, V.V. Poroikov, I. Alam, A.K. Saxena, Computer-aided discovery
of anti-inflammatory thiazolidinones with dual cyclooxygenase/lipoxygenase
inhibition, J. Med. Chem. 51 (2008) 1601e1609.
(b) B. Hill, V. Ahmed, D. Bates, S.D. Taylor, Enantioselective synthesis of pro-
tected L-4-[sulfonamido(difluoromethyl)] phenylalanine and L-4-[sulfonami-
do(methyl)]phenyl-alanine and an examination of Hexa- and tripeptide
platforms for evaluating pTyr mimics for PTP1B inhibition, J. Org. Chem. 71
(2006) 8190e8197;
(c) L. Navidpour, W. Lu, S.D. Taylor, Synthesis of alpha-fluorosulfonate and
alpha-fluorosulfonamide analogues of a sulfated carbohydrate, Org. Lett. 8
(2006) 5617e5620;
[41] MolSoft official Web-site: https://www.molsoft.com.
[42] M. Nasr-Esfahani, M. Montazerozohori, S. Mehrizi, J. Heterocycl. Chem. 48
(2011) 249e254.
(d) L. Chen, G. Gao, L. Bonnac, D.J. Wilson, E.M. Bennett, H.N. Jayaram,
K.W. Pankiewicz, Methylenebis(sulfonamide) linked nicotinamide adenine
dinucleotide analogue as an inosine monophosphate dehydrogenase inhibi-
tor, Bioorg. Med. Chem. Lett. 17 (2007) 3152e3155.
[43] S. Roy, M.P. Davydova, R. Pal, K. Gilmore, G.A. Tolstikov, S.F. Vasilevsky,
I.V. Alabugin, J. Org. Chem. 76 (2011) 7482e7490.
[44] P. Mujumdar, T. Grkovic, M. Krasavin, A simple two-step access to diversely
substituted imidazo[4,5-b]pyridines and benzimidazoles from readily avail-
able 2-imidazolines, Tetrahedron Lett. 54 (2013) 3336e3340.
[45] S. An, B. Yin, P. Liu, X. Li, C. Li, J. Li, Z. Shi, Synthesis 45 (2013) 2525e2532.
[46] M. Ishihara, H. Togo, Synthesis (2007) 1939e1942.
[33] M. Lopez, N. Drillaud, L.F. Bornaghi, S.-A. Poulsen, Synthesis of S-glycosyl
primary sulfonamides, J. Org. Chem. 74 (2009) 2811e2816.
[34] T. Yoshino, A. Kimoto, S. Kobayashi, M. Noguchi, M. Fukunaga, A. Hayashi,
K. Miyata, M. Sasamata, Pharmacological profile of celecoxib,
cyclooxygenase-2 inhibitor, Arzneim. Forsch. 55 (2005) 394e402.
a
specific
[47] M. Ishihara, H. Togo, Tetrahedron 63 (2006) 1474e1480.
[48] L.J. Crane, M. Anastassiadou, J.-L. Stigliani, G. Baziard-Mouysset, M. Payard,
Tetrahedron 60 (2004) 5325e5330.
[49] G.-Y. Bai, K. Xu, G.-F. Chen, Y.-H. Yang, T.-Y. Li, Synthesis (2011) 1599e1603.
[50] M. Anastassiadou, G. Baziard-Mouysset, M. Payard, Synthesis (2000)
1814e1816.
[35] Obtaining Pharmacokinetic Data on Intravenous (IV) Dosing was Hampered
by a Low Solubility of Compound 35 in the Dosing Vehicle Used (DMSO/NP40/
saline 5/5/90 v/v). Therefore, the Absolute Bioavailability (F, %) was Not
Determined for this Compound. However, the PK data on p.o. Dosing Reliably
Confirmed its Good Bioavailability and a Sufficient Systemic Exposure.