Design and synthesis of new imidazo[1,2-a]pyridine and imidazo[1,2-a]pyrazine derivatives with antiproliferative activity against melanoma cells

Article abstract of DOI:10.1016/j.ejmech.2015.12.001

Melanoma is an aggressive form of skin cancer and it is generally associated with poor prognosis in patients with late-stage disease. Due to the increasing occurrence of melanoma, there is a need for the development of novel therapies. A new series of diarylamide and diarylurea derivatives containing imidazo[1,2-a]pyridine or imidazo[1,2-a]pyrazine scaffold was designed and synthesized to investigate their in vitro efficacy against the A375P human melanoma cell line. We found several compounds expressing submicromolar IC₅₀ values against the A375P cells, from which 15d, 17e, 18c, 18h, 18i demonstrated the highest potencies with IC₅₀ below 0.06 μM.

Full text of DOI:10.1016/j.ejmech.2015.12.001

European Journal of Medicinal Chemistry 108 (2016) 623e643
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Research paper
Design and synthesis of new imidazo[1,2-a]pyridine and imidazo
[1,2-a]pyrazine derivatives with antiproliferative activity against
melanoma cells
a
,
b
b
b
b
b
€
ꢀ
ꢀ
Rita Garamvolgyi , Judit Dobos , Anna Sipos , Sandor Boros , Eszter Illyes ,
b
b
b
b
b, c
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
€
ꢀ
Ferenc Baska , Laszlo Kekesi , Istvan Szabadkai , Csaba Szantai-Kis , Gyorgy Keri
,
a, b, *
}
ꢀ
ꢀ
Laszlo Orfi
a Department of Pharmaceutical Chemistry, Semmelweis University, Budapest, Hungary
b Vichem Chemie Research Ltd., Budapest, Hungary
c MTA-SE Pathobiochemistry Research Group, Department of Medical Chemistry, Semmelweis University, Budapest, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
Melanoma is an aggressive form of skin cancer and it is generally associated with poor prognosis in
patients with late-stage disease. Due to the increasing occurrence of melanoma, there is a need for the
development of novel therapies. A new series of diarylamide and diarylurea derivatives containing
imidazo[1,2-a]pyridine or imidazo[1,2-a]pyrazine scaffold was designed and synthesized to investigate
their in vitro efficacy against the A375P human melanoma cell line. We found several compounds
expressing submicromolar IC50 values against the A375P cells, from which 15d, 17e, 18c, 18h, 18i
Received 13 February 2015
Received in revised form
28 November 2015
Accepted 1 December 2015
Available online 12 December 2015
demonstrated the highest potencies with IC50 below 0.06 mM.
Keywords:
© 2015 Elsevier Masson SAS. All rights reserved.
Imidazo[1,2-a]pyridine
Imidazo[1,2-a]pyrazine
Diarylamide
Diarylurea
Antiproliferative activity
A375P
Melanoma
1. Introduction
have been increasing for decades and it was estimated that
approximately 76,100 new melanoma cases would be identified in
the United States in 2014 [3].
Melanoma is a highly aggressive form of skin cancer that arises
from the pigment-producing melanocytes of the epidermis. The
major risk factors that contribute to the formation of melanoma
include genetic predisposition, exposure to UV irradiation and past
history of skin cancer. The most important prognostic factors that
are incorporated into the TNM melanoma staging system (devel-
oped by the American Joint Committee on Cancer in 2009) are
tumour thickness, ulceration, mitotic rate, nodular involvement
and lactate dehydrogenase (LDH) levels [1]. While the 5-year sur-
vival rate is 98.3% for patients with localized melanoma, it
dramatically decreases for patients with the regional-stage (62.4%)
and distant-stage disease (16.0%) [2]. Melanoma incidence rates
Besides surgery there is a growing number of treatment options
that has been approved by the FDA or currently being evaluated in
clinical trials (immunotherapy, targeted therapies or combination
therapies) [4]. Discovery of the molecular mechanisms behind
melanoma have led to the development of novel targeted therapies.
The MAPK (Ras-Raf-MEK-ERK) pathway became an important
target, being the most commonly affected pathway in melanoma
[5]. The activating mutation of the oncogene BRAF leads to
constitutive activation of the MAPK pathway, thus promoting
proliferation and malignant transformation. Sorafenib (BAY 43-
9006, Fig. 1) was the first non-selective B-Raf inhibitor with in vitro
efficacy against melanoma that was used in clinical trials [6,7].
However, it has not gained approval as monotherapy for this indi-
cation due to its limited activity in patients with advanced mela-
noma [8]. The therapeutic benefit of targeting the MAPK pathway
* Corresponding author. Department of Pharmaceutical Chemistry, Semmelweis
}
University, Hogyes Endre Street 9, H-1092, Budapest, Hungary.
}
E-mail address: orfi.laszlo@pharma.semmelweis-univ.hu (L. Orfi).
http://dx.doi.org/10.1016/j.ejmech.2015.12.001
0223-5234/© 2015 Elsevier Masson SAS. All rights reserved.

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Fig. 1. Structures of Sorafenib and Vemurafenib.
became clinically validated by the FDA approval of Vemurafenib
(PLX4032, Fig. 1), a compound that potently inhibits the growth of
melanoma cells harbouring BRAF mutation at codon 600 [9,10].
Attempts have also been made to develop Melanocyte-Directed
Enzyme Prodrug Therapy (MDEPT), where cytotoxic agents can be
selectively released in the melanocytes by the tyrosinase enzyme
[11,12].
catalyzed Suzuki coupling reaction with 3-aminophenylboronic
acid led to the corresponding amino compound (5). This amino
group was further modified with benzoic acid derivatives or aryl
isocyanates leading to the planned analogues (6ae6p, 7ae7g).
The imidazo[1,2-a]pyrazine derivatives were prepared as shown
on Scheme 2. The imidazo[1,2-a]pyrazine scaffold was built up from
2-amino-3-chloropyrazine (8) and in situ generated bromoace-
taldehyde affording the formation of 8-chloroimidazo[1,2-a]pyr-
azine (9), which was brominated with N-bromosuccinimide to give
3-bromo-8-chloroimidazo[1,2-a]pyrazine (10) [32]. From this in-
termediate 3-bromoimidazo[1,2-a]pyrazin-8-amine (11) was pre-
pared by amination [33]. Analogous approach to the previously
described synthetic sequence was not suitable in this case (when
the acylation in position 8 precedes the Suzuki coupling in position
3), because under the conditions of the Suzuki reaction cleavage of
the amide bond could be observed. Therefore compound 11 was
rather modified by Suzuki coupling reaction with 3-
aminophenylboronic acid resulting 3-(3-aminophenyl)imidazo
[1,2-a]pyrazin-8-amine (12). The phenylamino group could be
selectively substituted with aromatic carboxylic acid derivatives or
aryl isocyanates to give the corresponding amide (13ae13v) or urea
analogues (16ae16l). Using higher temperature and excess of re-
agents allowed us to functionalize the amino group at position 8 on
the imidazo[1,2-a]pyrazine scaffold leading to the targeted ana-
logues (14ae14q, 15ae15p, 17ae17q, 18ae18i).
The increasing occurrence of melanoma together with the
emerging resistance against targeted drugs [13] emphasizes the
need for the development of novel therapies. A wide variety of
studies exploring diarylamide and diarylurea compounds con-
taining 1,3,4-triarylpyrazole [14e16], aminoquinoline [17,18], pyr-
rolo[2,3-d]pyrimidine [19], pyrrolo[3,2-b]pyridine [20], pyrimidin-
4-yl-1H-imidazole [21], 1,4-dihydropyrazolo[4,3-d]imidazole [22],
aminoquinazoline [23], amino-1H-pyrazole [24], 1H-pyrrolo[3,2-c]
pyridine [25,26], acet(benz)amidophenyl [27], indazole [28] scaf-
fold or different linkers [29] demonstrates that diarylamide and
diarylurea derivatives have promising antiproliferative activity
against melanoma cells. There is only a limited number of pub-
lished diarylamide and diarylurea analogues possessing 8-
aminoimidazo[1,2-a]pyridine or 8-aminoimidazo[1,2-a]pyrazine
moiety [30,31] and their melanoma inhibitory activity has not been
described yet. Based on these data we aimed to synthesize further
diarylamides and diarylureas containing imidazo[1,2-a]pyridine or
imidazo[1,2-a]pyrazine scaffold (Fig. 2) to evaluate their in vitro
efficacy against the A375P human melanoma cell line.
In this paper we report the synthesis and in vitro anti-
proliferative activity of the designed compounds, as well as the B-
Raf kinase inhibitory activity of the most potent analogues.
2.2. Biological activity
The BRAF V600E mutant A375P human melanoma cell line was
used to evaluate the biological activity of the synthesized com-
pounds. Sorafenib and Vemurafenib were chosen as references
2. Results and discussion
(IC50 values were 6.25 mM and 0.37 mM, respectively) based on their
clinical significance in melanoma. The antiproliferative activity of
the newly synthesized compounds is summarized in Tables 1e9.
IC50 values are average of at least two independent experiments.
As a starting point for our research a series of diarylamide
(6ae6p) and diarylurea analogues (7ae7g) were prepared pos-
sessing imidazo[1,2-a]pyridine scaffold and tested on A375P cells as
shown in Tables 1 and 2. Regarding the diarylamide derivatives it
can be seen, that most of the analogues have moderate or no effect
2.1. Chemistry
The synthesis of the imidazo[1,2-a]pyridine derivatives were
carried out as outlined in Scheme 1. The reaction of pyridine-2,3-
diamine (1) and 50% aq. chloroacetaldehyde resulted the forma-
tion of imidazo[1,2-a]pyridin-8-amine (2), from which the appro-
priate benzamide derivative (3) could be prepared using benzoic
acid in the presence of N-(3-dimethylaminopropyl)-N0-ethyl-
carbodiimide hydrochloride (EDCI) in pyridine. From this inter-
mediate bromination with N-bromosuccinimide and palladium-
on these cells, while 6i expressed an IC50 of 1.70 mM. Comparing the
activities of the corresponding amide and urea derivatives (6ce7b,
6he7d, 6ke7g) it was found that urea derivatives were generally
more potent towards the A375P cells, except in the case of 6ie7e
where the amide derivative showed superior potency.
To evaluate the role of the scaffold, we have synthesized imidazo
[1,2-a]pyrazine derivatives carrying the same substituents as their
corresponding imidazo[1,2-a]pyridine analogues. As shown in
Table 3, while the imidazo[1,2-a]pyridine derivative 6k did not
show any effect on the A375P cells, the additional nitrogen in the
imidazo[1,2-a]pyrazine scaffold significantly increased the anti-
proliferative activity (15a, IC50 ¼ 1.82
mM). In the case of the urea
derivatives (7ge18a) the nitrogen in position 7 of the scaffold
Fig. 2. General structure of the synthesized imidazo[1,2-a]pyridine and imidazo[1,2-a]
pyrazine derivatives.

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Scheme 1. Synthesis of the imidazo[1,2-a]pyridine derivatives. Reagents and conditions: (a) 50% aq. chloroacetaldehyde, EtOH, reflux, 3.5 h, 58%; (b) benzoic acid, EDCI, pyridine,
40 ꢀC, 4 h, 67%; (c) N-bromosuccinimide, CH2Cl2, rt, 30 min, 83%; (d) 3-aminophenylboronic acid, Pd(PPh3)4, Na2CO3, 1,4-dioxane, H2O, microwave, 140 ꢀC, 1.5 h, 64%; (e) benzoic acid
derivative, EDCI, pyridine, 70 ꢀC, 2 h, 52e84%; (f) aryl isocyanate, anhydrous pyridine, rt, 2 h, 56e90%.
Scheme 2. Synthesis of the imidazo[1,2-a]pyrazine derivatives. Reagents and conditions: (a) Bromoacetaldehyde diethyl acetal, 48% aq. HBr solution, reflux, 1.5 h, NaHCO3/IPA, then
8, reflux, 3 h, 73%; (b) N-bromosuccinimide, CH2Cl2, rt, 3 h, 93%; (c) 25% aq. NH4OH solution, IPA, microwave, 120 ꢀC, 3 h, 85%; (d) 3-aminophenylboronic acid, Pd(PPh3)4, Na2CO3,
1,4-dioxane, H2O, microwave, 140 ꢀC, 1.5 h, 75%; (e) benzoic acid derivative, EDCI, pyridine, 40 ꢀC, overnight, 35e70%; (f) benzoic acid derivative, EDCI, pyridine, 70 ꢀC, 6 h, 11e81%;
(g) aryl isocyanate, anhydrous pyridine, rt, 2 h, 20e69%; (h) benzoic acid derivative, EDCI, pyridine, 70 ꢀC, 6 h, 10e64%.
moderately enhanced the potency. Based on these results the imi-
dazo[1,2-a]pyrazine scaffold had been chosen to design further
analogues.
the substituents of the benzamide group significantly affect the
antiproliferative activity. When the benzamide moiety was
unsubstituted submicromolar IC50 value could be measured (13a
To investigate the effect of the terminal benzamide moiety a set
of diarylamide derivatives were prepared possessing imidazo[1,2-
a]pyrazine scaffold, on which the 8-amino group remained
unsubstituted (13ae13v). The results in Table 4 clearly show that
IC50 ¼ 0.85
mM). Additionally, introduction of 3,5-difluoro (13c),
2,3-dichloro (13d), 3-chloro-4-fluoro (13g), 4-bromo (13j), 4-
trifluoromethoxy (13q) or 3,5-dimethyl (13s) substituents affor-
ded the most active compounds in this set. Upon comparing the

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Table 1
Table 4
Antiproliferative activity of compounds 6ae6p against A375P melanoma cell line.
Antiproliferative activity of compounds 13ae13v against A375P melanoma cell line.
Compound no.
R
IC50 (mM)
Compound no.
R
IC50 (mM)
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
H
>30
7.94
>30
8.04
7.34
7.07
6.35
>30
1.70
>30
>30
>30
21.28
>30
>30
9.47
13a
13b
13c
13d
13e
13f
13g
13h
13i
H
0.85
7.26
0.46
0.64
1.21
2.94
0.34
4.09
2.27
0.75
2.08
7.04
8.32
2.13
1.41
13.75
0.43
2.73
0.82
10.06
3.84
1.54
3,5-diF
2,4-diF
3,5-diF
2,3-diCl
3-Cl-4-F
3,5-diCl-4-F
3-Cl-4-CH3
4-Br
3-CF3
4-CF3
4-F-3-CF3
4-Cl-3-CF3
3-OCF3
2,3-diCl
3,4-diCl
3,5-diCl
3-Cl-4-F
3,5-diCl-4-F
3-Cl-4-CH3
4-Br
3-CF3
4-CF3
3,5-bisCF3
4-F-3-CF3
4-Cl-3-CF3
3-OCF3
13j
13k
13l
4-OCF3
13m
13n
13o
13p
13q
13r
13s
13t
13u
13v
2,5-diCH3
3,5-diCH3
3,4-diOCH3
4-OCF3
2,5-diCH3
3,5-diCH3
2-CH3-3-OCH3
3,4-diOCH3
3,4,5-triOCH3
Table 2
Antiproliferative activity of compounds 7ae7g against A375P melanoma cell line.
activities of the 3,5-disubstituted analogues 13c, 13f, 13m, 13s the
following activity sequence can be observed: 3,5-difluoro > 3,5-
dimethyl > 3,5-dichloro > 3,5-bis(trifluoromethyl). It can be seen
by examining the dichloro compounds (13de13f) that moving the
2-chloro substituent to position 4 or 5 attenuates the activity. The
trifluoromethyl substituent is more favourable in position 3 than in
position 4 (13ke13l), whereas moving the trifluoromethoxy group
from position 3 to position 4 on the terminal phenyl ring signifi-
cantly increased the activity (13pe13q).
Compound no.
R
IC50 (mM)
7a
7b
7c
7d
7e
7f
3-Cl
7.36
15.88
4.46
4.29
3.01
2.08
2.32
2,3-diCl
3,4-diCl
3-CF3
4-CF3
3,5-bisCF3
4-Cl-3-CF3
From 13g, which was the most potent analogue in this series
(IC50 ¼ 0.34
mM), 8-benzoylamino derivatives were prepared
7g
(14ae14q). The results in Table 5 show that the insertion of the
substituted benzoyl group could not further enhance the biological
activity compared to the 8-amino compound 13g. However, almost
all the compounds in this set showed low micromolar or sub-
micromolar IC50 against A375P cells. Comparing the activity of
compounds 14ce14e shows that moving one of the chlorine sub-
stituents to position 2 on this phenyl ring leads to the loss of
activity.
Table 3
The effect of the scaffold on the antiproliferative activity against A375P melanoma
cell line in case of diarylamide (6k, 15a) and diarylurea (7g, 18a) derivatives.
Compound 13o (IC50 ¼ 1.41
mM), which carries the 4-chloro-3-
(trifluoromethyl)phenyl moiety known from Sorafenib, was also
functionalized with various aromatic carboxylic acids, affording
compounds 15ae15p (Table 6). In this case it was found, that the
addition of the benzoyl moiety can increase the activity, compared
to 13o (IC50 ¼ 1.41
mM), especially when it bears 3,4-dichloro (15c),
3,5-dichloro (15d), 3,5-bis(trifluoromethyl) (15k), 4-fluoro-3-
trifluoromethyl (15l) or 3,5-dimethyl (15p) substituents. From
these molecules 15d expressed the strongest antiproliferative ac-
Compound no.
X
L
IC50 (mM)
6k
15a
7g
C
N
C
eNHeCOe
eNHeCOe
eNHeCOeNHe
eNHeCOeNH-
>30
tivity with an IC50 of 0.04 mM. Based on the IC50 values of com-
1.82
2.32
1.41
pounds 15c, 15e and 15g a chloro substituent in position 4 is more
advantageous than a fluoro or a methyl group. Placing one of the
chlorine atoms in position 5 instead of position 4 (15ce15d)
enhanced the activity by one fold. By comparing the potency of the
18a
N

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Table 5
Table 7
Antiproliferative activity of compounds 14ae14q against A375P melanoma cell line.
Antiproliferative activity of compounds 16ae16l against A375P melanoma cell line.
Compound no.
R
IC50 (mM)
Compound no.
R
IC50 (mM)
16a
16b
16c
16d
16e
16f
16g
16h
16i
H
1.14
0.92
5.01
1.27
4.34
4.64
5.23
1.10
9.06
11.21
2.70
3.00
14a
14b
14c
14d
14e
14f
14g
14h
14i
14j
14k
14l
14m
14n
14o
14p
14q
H
1.16
0.45
23.28
0.90
1.15
0.89
1.29
0.98
0.49
1.08
0.56
1.16
1.14
1.08
1.50
0.44
1.64
2,4-diF
3-Cl
2,3-diCl
3-Cl-4-F
4-Br
3-CF3
4-CF3
3,5-bisCF3
4-Cl-3-CF3
4-CH3
4-OCH3
3,5-diF
2,3-diCl
3,4-diCl
3,5-diCl
3-Cl-4-F
3,5-diCl-4-F
3-Cl-4-CH3
4-Br
3-CF3
4-CF3
3,5-bisCF3
4-F-3-CF3
4-Cl-3-CF3
3-OCF3
16j
16k
16l
enhance the potency. The trifluoromethyl moiety is less preferable
in position 3 (16g, 16h), and the presence of an additional chlorine
atom in position 4 (16j) further reduces the activity.
4-OCF3
3,5-diCH3
From 16b (IC50 ¼ 0.92
mM), which was the most active com-
pound from the diarylurea series, 8-benzoylamino derivatives were
synthesized (17ae17q). The IC50 values of the compounds 17ae17q
are summarized in Table 8. The 3,5-dichloro compound (17e)
Table 6
Antiproliferative activity of compounds 15ae15p against A375P melanoma cell line.
proved to be the most active in this set with an IC50 of 0.06 mM.
Furthermore, compounds bearing 2,3-dichloro (17c), 3,5-dichloro-
4-fluoro (17g), 3-trifluoromethyl (17j), 3,5-bis(trifluoromethyl)
(17l), 4-fluoro-3-trifluoromethyl (17m), 4-chloro-3-trifluoromethyl
(17n) and 3,5-dimethyl (17q) substituents could also express
improved potency towards the A375P cells.
As previously, the 4-chloro-3-(trifluoromethyl)phenyl group
Compound no.
R
IC50 (mM)
containing compound (16j IC50 ¼ 11.21
mM) was also chosen to
prepare the corresponding 8-benzoylamino analogues (18ae18i,
15a
15b
15c
15d
15e
15f
15g
15h
15i
15j
15k
15l
15m
15n
15o
15p
H
1.82
1.62
0.66
0.04
2.86
3,5-diF
3,4-diCl
3,5-diCl
3-Cl-4-F
3,5-diCl-4-F
3-Cl-4-CH3
4-Br
3-CF3
4-CF3
3,5-bisCF3
4-F-3-CF3
4-Cl-3-CF3
3-OCF3
Table 8
Antiproliferative activity of compounds 17ae17q against A375P melanoma cell line.
>30
2.79
1.80
12.67
1.60
0.55
0.46
2.46
1.03
1.31
0.18
4-OCF3
3,5-diCH3
Compound no.
R
IC50 (mM)
17a
17b
17c
17d
17e
17f
17g
17h
17i
17j
17k
17l
17m
17n
17o
17p
17q
H
1.99
5.82
0.17
1.89
0.06
1.55
0.39
1.98
3.75
0.44
2.73
0.11
0.41
0.80
0.95
3.79
0.12
3,5-diF
2,3-diCl
3,4-diCl
3,5-diCl
3-Cl-4-F
3,5-diCl-4-F
3-Cl-4-CH3
4-Br
3-CF3
4-CF3
3,5-bisCF3
4-F-3-CF3
4-Cl-3-CF3
3-OCF3
3,5-disubstituted compounds (15b, 15d, 15k, 15p) it can be seen,
that the dichloro substitution is the most favourable (3,5-
dichloro > 3,5-dimethyl > 3,5-bis(trifluoromethyl) > 3,5-difluoro).
The antiproliferative activity of the diarylurea derivatives are
summarized in Tables 7e9. To explore the effect of the substituents
on the terminal phenyl ring compounds 16ae16l were synthesized,
containing the 8-aminoimidazo[1,2-a]pyrazine moiety (Table 7).
From these compounds 16b, bearing 2,4-difluoro substituents,
showed the strongest potency (IC50 ¼ 0.92
mM). By comparing the
activity of 16c, 16d, 16e it can be observed that the introduction of a
fluorine atom to position 4 on the phenyl ring did not affect the
activity, but an additional chloro substituent in position 2 could
4-OCF3
3,5-diCH3

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Table 10
Table 9). The introduction of the benzoyl function remarkably
Enzimatic activity of the selected compounds (15d, 17e, 18c, 18h, 18i) on B-Raf(wt)
and B-Raf(V600E) kinases.
increased the antiproliferative activity, resulting compounds 18c,
18h and 18i with IC50 of 0.03 mM, 0.01 mM and 0.06 mM, respectively.
IC50 (mM)
Based on the cellular data we can conclude that the imidazo[1,2-
a]pyrazine scaffold is more favourable than the imidazo[1,2-a]
pyridine. By comparing the amide and urea linker no clear supe-
riority could be observed. The introduction of the substituted
benzoyl group to position 8 on the imidazo[1,2-a]pyrazine scaffold
is not essential for the antiproliferative activity, but it can greatly
modify the efficacy. The substituents of the terminal phenyl ring
and on the 8-benzoylamino group can significantly influence the
cellular potency.
A375P
B-Raf(wt)
B-Raf(V600E)
15d
17e
18c
18h
0.04
0.06
0.03
0.01
0.06
0.37
>12.5
>12.5
>12.5
>12.5
>12.5
1.14
>12.5
>12.5
>12.5
>12.5
5.01
18i
Vemurafenib
0.28
Being able to indentify compounds with potent antiproliferative
activity on melanoma cells, we aimed to investigate the mechanism
of their action. Since BRAF is the most commonly mutated gene in
melanoma and the A375P cell line harbours BRAF V600E mutation,
the kinase inhibitory activity of our most active compounds (15d,
17e, 18c, 18h, 18i) against B-Raf(wt) and B-Raf(V600E) was deter-
mined. According to the results summarized in Table 10, these
molecules do not show any inhibitory activity on either of the B-Raf
kinases that would explain their cellular efficacy. Thus, we aim to
carry out further experiments to identify the possible target(s) of
this compound family.
Table 11
Antiproliferative activity of selected compounds (15d, 17e, 18c, 18h) against A375P,
A549, H358, PC9, PC9ER, HCT116 and HKE3 cell lines.
IC50 (mM)
A375P
A549
H358
PC9
3.61
2.77
11.58
11.57
PC9ER
HCT116
HKE3
15d
17e
18c
18h
0.04
0.06
0.03
0.01
3.23
2.61
8.44
4.21
4.17
8.58
7.55
3.63
2.56
8.01
1.81
0.88
9.51
5.31
0.83
0.62
10.02
6.35
10.43
14.62
The most promising compounds were also tested on different
lung (A549, H358, PC9, PC9ER) and colon tumour cell lines (HCT116,
HKE3). The results in Table 11 suggest that these molecules do not
act as general cytotoxic agents since they can selectively inhibit the
proliferation of melanoma cells.
and the selectivity over lung and colon tumour cell lines these
compounds were selected for further studies.
4. Experimental section
3. Conclusions
4.1. General information
In summary, we designed and synthesized a novel series of
diarylamides and diarylureas having imidazo[1,2-a]pyridine or
imidazo[1,2-a]pyrazine scaffold and carried out detailed structure-
activity relationship studies. In some cases superior potencies could
be observed compared to both Sorafenib and Vemurafenib against
the A375P human melanoma cell line in cell proliferation experi-
ments. Compounds 15d, 17e, 18c, 18h and 18i were identified as the
The commercially available reagents and solvents were used
without further purification. The reactions were monitored by thin-
layer chromatography (TLC) using Kieselgel 60 F254 plates (Merck),
visualized by UV light. Geduran® Si60 silica gel (0.063e0.200 mm)
was used for column chromatography and Kieselgel 60 F254 glass
plates (1 mm, 20 ꢁ 20 cm, Merck) were used for preparative thin-
layer chromatography.
most potent analogues with IC50 of 0.04
mM, 0.06 mM, 0.03 mM,
Analytical HPLC-MS was performed on a Waters HPLC-MS sys-
tem using reverse phase. Method: Waters XBridge C18 column
0.01 M and 0.06 M, respectively. According to the biochemical
m
m
assay results these molecules do not exert the antiproliferative ef-
fect via the inhibition of B-Raf.
(5 cm ꢁ 4.6 mm, 3.5
mm); solvent A: Water/0.1% formic acid, solvent
B: acetonitrile; gradient: 0e95% solvent B (0.00 min 5% solvent B,
0.50 min 5% solvent B, 5.50 min 95% solvent B, 6.00 min 95% solvent
B, 6.50 min 5% solvent B, 7.00 min 5% solvent B); flow ¼ 2.0 ml/min.
Separation module was Waters Alliance 2795. Chromatograms
were recorded using a Waters 996 PDA detector. Mass spectra were
obtained using Waters SQD MS detector (ionization: ESIþ/ESI-,
source block temperature: 120 ꢀC, desolvation temperature: 300 ꢀC,
desolvation gas: 500 L/h, cone gas: 80 L/h, capillary: 3000 V, cone:
25 V, extractor: 3V, Rf lens: 0.2 V, scan: 120e1000 m/z in 1 s, inter-
scan delay: 0.1 s). The purity of the target compounds was found to
be over 95%.
Based on the high potency against the A375P melanoma cell line
Table 9
Antiproliferative activity of compounds 18ae18i against A375P melanoma cell line.
The NMR spectra were recorded on a Bruker Avance DRX 300
NMR spectrometer (controlled by TopSpin 1.3 software package) in
DMSO-d6 solution at 30 ꢀC. Besides the 1H NMR spectra usually zqs-
TOCSY and e when it was necessary e zqs-easy-ROESY, 13C, ed-
HSQC and HMBC experiments were carried out to confirm the
Compound no.
R
IC50 (mM)
18a
18b
18c
18d
18e
18f
18g
18h
18i
H
1.41
1.94
0.03
1.28
1.16
0.56
1.75
0.01
0.06
structure. The 1H NMR chemical shifts (
d) are given in parts per
3,5-diF
3,5-diCl
3-Cl-4-F
3-Cl-4-CH3
3-CF3
4-CF3
3,5-bisCF3
4-F-3-CF3
million (ppm) referenced to tetramethylsilane.
Melting points were determined on a Büchi Melting Point B-540
instrument.
For compound name generation ACD/ChemSketch software
(product version: 9.07) was used, which incorporates the IUPAC
recommendations.

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629
4.2. Synthetic procedures and analytical data
sodium sulphate, filtered and concentrated under reduced pres-
sure. The crude product was purified by column chromatography
(silica gel, eluent: chloroform) to give the title compound (1.80 g).
Yield: 64%. Mp 147e148 ꢀC.
4.2.1. Imidazo[1,2-a]pyridin-8-amine (2)
To the solution of pyridine-2,3-diamine (1) (5.00 g, 45.82 mmol)
in ethanol (100 ml) 50% aqueous chloroacetaldehyde (6.40 ml,
50.40 mmol) was added and the mixture was stirred at reflux
temperature for 3.5 h. The reaction mixture was poured onto
400 ml 10% aqueous sodium hydrogen carbonate solution, stirred
for 10 min and extracted with 250 ml chloroform (3ꢁ). The com-
bined organic layers were dried over sodium sulphate, filtered and
concentrated under reduced pressure. The crude product was pu-
rified by column cromatography (silica gel, eluent: chloroform:
methanol ¼ 98: 2) to give the title compound (3.56 g).
Yield: 58%. Mp 65e66 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.89 (br. s, 1H); 8.32 (dd,
J ¼ 6.9 and 0.7 Hz, 1H); 8.04 (dm, J ¼ 7.2 Hz, 2H); 7.98 (dd, J ¼ 7.5
and 0.7 Hz, 1H); 7.68 (s, 1H); 7.66 (tt, J ¼ 7.2 and 1.5 Hz, 1H); 7.59
(ddm, J ¼ 7.2 and 7.2 Hz, 2H); 7.20 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.01
(dd, J ¼ 7.5 and 6.9 Hz, 1H); 6.86 (dd, J ¼ 2.0 and 1.7 Hz, 1H); 6.78
(ddd, J ¼ 7.5, 1.7 and 1.0 Hz, 1H); 6.65 (ddd, J ¼ 8.1, 2.0 and 1.0 Hz,
1H); 5.30 (br. s, 2H).
LCMS (ESI) m/z 329.2 (M þ H)þ; 327.2 (MꢂH)ꢂ; calculated:
328.1; Rt: 2.23 min.
1H NMR (300 MHz, DMSO-d6)
d
ppm 7.78 (s, 1H); 7.77 (dm,
4.2.5. General procedure for the preparation of compounds 6a-6p
A mixture of compound 5 (100 mg, 0.31 mmol), pyridine (2 ml),
N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide hydrochloride
(64 mg, 0.34 mmol) and the benzoic acid derivative (0.32 mmol)
was stirred at 70 ꢀC for 2 h.
J ¼ 7.0 Hz, 1H); 7.40 (s, 1H); 6.60 (dd, J ¼ 7.2 and 7.0 Hz, 1H); 6.21 (d,
J ¼ 7.2 Hz, 1H); 5.55 (br. s, 2H).
LCMS (ESI) m/z 133.9 (M þ H)þ; calculated: 133.1; Rt: 0.44 min.
4.2.2. N-imidazo[1,2-a]pyridin-8-ylbenzamide (3)
Method A: The solvent was evaporated and the residue was
taken up in chloroform. The organic layer was washed with water
(2ꢁ), dried over sodium sulphate, filtered and concentrated under
reduced pressure. The crude product was triturated with diiso-
propyl ether, filtered and washed with acetonitrile to give the
desired products.
Method B: The solvent was evaporated. The residue was tritu-
rated with diisopropyl ether, filtered and washed with acetonitrile
to give the desired products.
A mixture of compound 2 (1.68 g, 12.62 mmol), pyridine (30 ml),
N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide hydrochloride
(2.90 g, 15.14 mmol) and benzoic acid (1.85 g, 15.14 mmol) was
stirred at 40 ꢀC for 4 h. The solvent was evaporated and the residue
was taken up in chloroform. The organic layer was washed with
water (2ꢁ), dried over sodium sulphate, filtered and concentrated
under reduced pressure. The crude product was triturated with
diisopropyl ether and filtered to give the title compound (2.02 g).
Yield: 67%. Mp 64e66 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 9.85 (br. s, 1H); 8.36 (dd,
4.2.5.1. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}
benzamide (6a). Method A was used for the isolation of the title
compound.
J ¼ 6.7 and 0.8 Hz, 1H); 8.02 (m, 2H); 8.02 (d, J ¼ 1.3 Hz, 1H); 7.92
(dd, J ¼ 7.4 and 0.8 Hz, 1H); 7.63 (m, 1H); 7.59 (m, 2H); 7.59 (d,
J ¼ 1.3 Hz, 1H); 6.93 (dd, J ¼ 7.4 and 6.7 Hz, 1H).
LCMS (ESI) m/z 238.1 (M þ H)þ; 235.9 (MꢂH)ꢂ; calculated:
237.1; Rt: 1.75 min.
Yield: 64%. Mp 175e176 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.43 (br. s, 1H); 9.93 (br. s,
1H); 8.43 (d, J ¼ 6.9 Hz, 1H); 8.12 (dd, J ¼ 1.5 and 1.5 Hz, 1H);
7.96e8.08 (ovl. m, 5H); 7.92 (dm, J ¼ 7.5 Hz, 1H); 7.82 (s, 1H);
7.50e7.72 (ovl. m, 7H); 7.43 (dm, J ¼ 7.5 Hz, 1H); 7.07 (dm, J ¼ 6.9
and 7.2 Hz, 1H).
4.2.3. N-(3-bromoimidazo[1,2-a]pyridin-8-yl)benzamide (4)
To the solution of compound 3 (0.47 g, 1.98 mmol) in dichloro-
methane (50 ml) N-bromosuccinimide (0.35 g, 1.98 mmol) was
added and the mixture was stirred at room temperature for 30 min.
The reaction mixture was diluted with dichloromethane, washed
with 10% aqueous sodium carbonate solution (2ꢁ), dried over so-
dium sulphate, filtered and concentrated under reduced pressure.
The crude product was triturated with diisopropyl ether and
filtered to give the title compound (0.52 g).
LCMS (ESI) m/z 433.3 (M þ H)þ; 431.2 (MꢂH)ꢂ; calculated:
432.2; Rt: 3.28 min.
4.2.5.2. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
3,5-difluorobenzamide (6b). Method A was used for the isolation of
the title compound.
Yield: 69%. Mp 209e211 ꢀC.
Yield: 83%. Mp 187e188 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.53 (br. s, 1H); 9.93 (br. s,
1H NMR (300 MHz, DMSO-d6)
d
ppm 9.97 (br. s, 1H); 8.17 (dd,
1H); 8.42 (d, J ¼ 7.0 Hz, 1H); 8.09 (dd, J ¼ 1.5 and 1.5 Hz, 1H); 8.05
(dm, J ~ 7.5 Hz, 2H); 8.00 (d, J ¼ 7.4 Hz,1H); 7.89 (dm, J ¼ 7.8 Hz,1H);
7.82 (s, 1H); 7.72 (m, 2H); 7.66 (tt, J ¼ 7.0 and 1.5 Hz, 1H); 7.61 (ddm,
J ¼ 7.5 and 7.0 Hz, 2H); 7.58 (dd, J ¼ 7.9 and 7.8 Hz, 1H); 7.55 (tt,
J ¼ 10.2 and 2.5 Hz, 1H); 7.47 (dm, J ¼ 7.9 Hz, 1H); 7.08 (dd, J ¼ 7.4
and 7.0 Hz, 1H).
J ¼ 6.9 and 0.6 Hz, 1H); 7.98e8.06 (ovl. m, 3H); 7.77 (s, 1H); 7.64 (m,
1H); 7.58 (m, 2H); 7.15 (dd, J ¼ 7.5 and 6.9 Hz, 1H).
LCMS (ESI) m/z 316.0 (M þ H)þ; 314.0 (MꢂH)ꢂ; calculated:
315.0; Rt: 3.50 min.
4.2.4. N-[3-(3-aminophenyl)imidazo[1,2-a]pyridin-8-yl]benzamide
(5)
LCMS (ESI) m/z 469.2 (M þ H)þ; 467.2 (MꢂH)ꢂ; calculated:
468.1; Rt: 3.68 min.
The solution of compound 4 (2.70 g, 8.54 mmol) in 1,4-dioxane
(100 ml) was stirred at room temperature under argon for 10 min.
Tetrakis(triphenylphosphine)palladium(0) (493 mg, 0.43 mmol)
was added to the mixture and it was stirred for another 30 min
under argon. After the addition of 3-aminophenylboronic acid
(1.75 g, 12.81 mmol) and sodium carbonate (3.62 g, 34.16 mmol) in
24 ml water, the mixture was stirred at 140 ꢀC for 1.5 h in a mi-
crowave reactor. Then the reaction mixture was filtered through
Celite, washed with ethyl acetate and concentrated under reduced
pressure. The residue was taken up in chloroform, washed with 10%
aqueous sodium hydrogen carbonate solution (2ꢁ), dried over
4.2.5.3. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
2,3-dichlorobenzamide (6c). Method A was used for the isolation of
the title compound.
Yield: 80%. Mp 202e203 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.77 (br. s, 1H); 9.93 (br. s,
1H); 8.38 (d, J ¼ 6.9 Hz, 1H); 7.97e8.09 (ovl. m, 4H); 7.75e7.85 (ovl.
m, 3H); 7.66 (tt, J ~ 7.5 and 7.5 Hz, 1H); 7.61 (ddm, J ~ 7.5 and 7.5 Hz,
2H); 7.59 (dm, J ~ 7.5 Hz, 1H); 7.57 (dd, J ¼ 7.6 and 7.5 Hz, 1H); 7.51
(dd, J ¼ 7.8 and 7.8 Hz, 1H); 7.46 (dm, J ¼ 7.6 Hz,1H); 7.06 (dd, J ¼ 7.4
and 6.9 Hz, 1H).

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LCMS (ESI) m/z 501.1 (M þ H)þ; 499.1 (MꢂH)ꢂ; calculated:
1H); 8.43 (dd, J ¼ 6.9 and 1.0 Hz, 1H); 8.32 (dd, J ~ 1.5 and 1.5 Hz,
500.1; Rt: 3.72 min.
1H); 8.31 (dm, J ~ 8.0 Hz, 1H); 8.11 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.05
(dm, J ~ 7.5 Hz, 2H); 8.03 (dd, J ~ 7.2 and 1.0 Hz, 1H); 8.00 (dm,
J ¼ 7.6 Hz, 1H); 7.90 (ddd, J ¼ 8.5, 1.5 and 1.0 Hz, 1H); 7.83 (s, 1H);
7.82 (dd, J ~ 8.0 and 7.5 Hz, 1H); 7.66 (tt, J ~ 7.2 and 2.0 Hz, 1H); 7.60
(ddm, J ~ 8.0 and 7.2 Hz, 2H); 7.59 (dd, J ¼ 8.0 and 7.6 Hz, 1H); 7.47
(ddd, J ¼ 7.6, 1.5 and 1.0 Hz, 1H); 7.08 (dd, J ¼ 7.2 and 6.9 Hz, 1H).
LCMS (ESI) m/z 501.2 (M þ H)þ; 499.2 (MꢂH)ꢂ; calculated:
500.1; Rt: 3.94 min.
4.2.5.4. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
3-chloro-4-fluorobenzamide (6d). Method A was used for the
isolation of the title compound.
Yield: 77%. Mp 176e177 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.51 (br. s, 1H); 9.93 (br. s,
1H); 8.42 (d, J ¼ 6.9 Hz, 1H); 8.24 (dd, J ¼ 7.2 and 2.1 Hz, 1H); 8.09
(dd, J ~ 1.5 and 1.5 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz, 2H); 8.03 (d,
J ¼ 7.3 Hz, 1H); 8.02 (ddd, J ~ 7.8, 5.5 and 2.1 Hz, 1H); 7.89 (dm,
J ¼ 8.1 Hz, 1H); 7.82 (s, 1H); 7.67 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.63 (dd,
J ¼ 9.3 and 7.8 Hz, 1H); 7.61 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.57 (dd,
J ¼ 8.1 and 7.8 Hz, 1H); 7.45 (dm, J ¼ 7.8 Hz, 1H); 7.07 (dd, J ¼ 7.3 and
6.9 Hz, 1H).
4.2.5.9. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
4-(trifluoromethyl)benzamide (6i). Method A was used for the
isolation of the title compound.
Yield: 84%. Mp 216e218 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.65 (br. s, 1H); 9.94 (br. s,
LCMS (ESI) m/z 485.2 (M þ H)þ; 483.1 (MꢂH)ꢂ; calculated:
484.1; Rt: 3.85 min.
1H); 8.43 (d, J ¼ 6.8 Hz, 1H); 8.19 (dm, J ¼ 8.1 Hz, 2H); 8.12 (dd,
J ¼ 1.5 and 1.5 Hz, 1H); 8.05 (dm, J~ 8.0 Hz, 2H); 8.03 (d, J ¼ 7.5 Hz,
1H); 7.94 (dm, J ¼ 8.1 Hz, 2H); 7.91 (dm, J ~ 8.0 Hz, 1H); 7.82 (s, 1H);
7.66 (tt, J ¼ 7.5 and 1.5 Hz, 1H); 7.60 (ddm, J ~ 8.0 and 7.5 Hz, 2H);
7.59 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.46 (dm, J ¼ 7.5 Hz, 1H); 7.08 (dd,
J ¼ 7.5 and 6.8 Hz, 1H).
4.2.5.5. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
3,5-dichloro-4-fluorobenzamide (6e). Method A was used for the
isolation of the title compound.
Yield: 68%. Mp 235e236 ꢀC.
LCMS (ESI) m/z 501.2 (M þ H)þ; 499.2 (MꢂH)ꢂ; calculated:
500.1; Rt: 3.91 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.58 (br. s, 1H); 9.94 (br. s,
1H); 8.41 (dd, J ¼ 7.0 and 1.0 Hz, 1H); 8.21 (d, J ¼ 6.3 Hz, 2H); 8.07
(dd, J ¼ 1.5 and 1.5 Hz,1H); 8.05 (dm, J ¼ 7.5 Hz, 2H); 8.03 (dd, J ¼ 7.0
and 1.0 Hz,1H); 7.88 (dm, J ¼ 8.1 Hz,1H); 7.82 (s, 1H); 7.66 (tt, J ¼ 7.2
and 1.5 Hz, 1H); 7.61 (ddm, J ¼ 7.5 and 7.2 Hz, 2H); 7.58 (dd, J ¼ 8.1
and 7.8 Hz, 1H); 7.47 (dm, J ¼ 7.8 Hz, 1H); 7.07 (t, J ¼ 7.4 and 7.0 Hz,
1H).
4.2.5.10. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]
phenyl}-4-fluoro-3-(trifluoromethyl)benzamide (6j). Method A was
used for the isolation of the title compound.
Yield: 67%. Mp 188e189 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.64 (br. s, 1H); 9.94 (br. s,
LCMS (ESI) m/z 519.1 (M þ H)þ; 517.1 (MꢂH)ꢂ; calculated: 518.1;
Rt: 4.31 min.
1H); 8.42 (d, J ¼ 6.8 Hz, 1H); 8.35e8.42 (ovl. m, 2H); 8.09 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ¼ 7.2 Hz, 1H);
7.88 (dm, J ¼ 8.1 Hz, 1H); 7.82 (s, 1H); 7.73 (dd, J ¼ 10.5 and 9.6 Hz,
1H); 7.66 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.61 (ddm, J ~ 7.5 and 7.5 Hz,
2H); 7.59 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.47 (dm, J ¼ 7.5 Hz, 1H); 7.07
(dd, J ¼ 7.2 and 6.8 Hz, 1H).
4.2.5.6. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
3-chloro-4-methylbenzamide (6f). Method A was used for the
isolation of the title compound.
Yield: 52%. Mp 177e178 ꢀC.
LCMS (ESI) m/z 519.2 (M þ H)þ; 517.2 (MꢂH)ꢂ; calculated: 518.1;
Rt: 4.03 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.45 (br. s, 1H); 9.94 (br. s,
1H); 8.42 (d, J ¼ 6.9 Hz,1H); 8.10 (dd, J ¼ 1.5 and 1.5 Hz, 1H); 8.06 (d,
J ¼ 1.0 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ¼ 7.4 Hz, 1H); 7.91
(dm, J ~ 7.5 Hz, 1H); 7.89 (dd, J ¼ 8.0 and 1.0 Hz, 1H); 7.82 (s, 1H);
7.66 (tt, J ~ 7.5 and 1.5 Hz,1H); 7.61 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.56
(dd, J ¼ 7.5 and 7.5 Hz, 1H); 7.55 (d, J ¼ 8.0 Hz, 1H); 7.44 (dm,
J ¼ 7.5 Hz, 1H); 7.07 (dd, J ¼ 7.4 and 6.9 Hz, 1H); 2.42 (s, 3H).
LCMS (ESI) m/z 481.2 (M þ H)þ; 479.2 (MꢂH)ꢂ; calculated:
480.1; Rt: 3.97 min.
4.2.5.11. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
4-chloro-3-(trifluoromethyl)benzamide (6k). Method A was used for
the isolation of the title compound.
Yield: 73%. Mp 231e232 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.69 (br. s, 1H); 9.94 (br. s,
1H); 8.43 (d, J ¼ 2.0 Hz, 1H); 8.42 (d, J ¼ 7.2 Hz, 1H); 8.30 (dd, J ¼ 8.5
and 2.0 Hz,1H); 8.09 (dd, J ¼ 1.5 and 1.5 Hz,1H); 8.05 (dm, J ~ 8.0 Hz,
2H); 8.03 (d, J ¼ 7.2 Hz, 1H); 7.96 (d, J ¼ 8.5 Hz, 1H); 7.88 (dm,
J ¼ 8.1 Hz, 1H); 7.82 (s, 1H); 7.66 (tt, J ¼ 7.2 and 1.5 Hz, 1H); 7.61
(ddm, J ¼ 8.0 and 7.2 Hz, 2H); 7.59 (dd, J ¼ 8.1 and 8.1 Hz, 1H); 7.47
(dm, J ¼ 8.1 Hz, 1H); 7.08 (d, J ¼ 7.2 and 7.2 Hz, 1H).
4.2.5.7. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
4-bromobenzamide (6g). Method B was used for the isolation of the
title compound.
Yield: 71%. Mp 216e217 ꢀC.
LCMS (ESI) m/z 535.1 (M þ H)þ; 533.1 (MꢂH)ꢂ; calculated:
534.1; Rt: 4.24 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.49 (br. s, 1H); 9.93 (br. s,
1H); 8.42 (d, J ¼ 6.8 Hz, 1H); 8.10 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.05
(dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ~ 7.5 Hz, 1H); 7.95 (dm, J ¼ 8.3 Hz, 2H);
7.89 (dm, J ¼ 8.0 Hz, 1H); 7.81 (s, 1H); 7.77 (dm, J ¼ 8.3 Hz, 2H); 7.66
(tt, J ~ 7.5 and 1.5 Hz,1H); 7.60 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.57 (dd,
J ¼ 8.0 and 7.6 Hz, 1H); 7.44 (d, J ¼ 7.6 Hz, 1H); 7.07 (dd, J ¼ 7.2 and
6.8 Hz, 1H).
4.2.5.12. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]
phenyl}-3-(trifluoromethoxy)benzamide (6l). Method A was used
for the isolation of the title compound.
Yield: 60%. Mp 180e182 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.55 (br. s, 1H); 9.93 (br. s,
LCMS (ESI) m/z 511.1 (M þ H)þ; 509.1 (MꢂH)ꢂ; calculated: 510.1;
Rt: 3.76 min.
1H); 8.42 (d, J ¼ 6.8 Hz, 1H); 8.11 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.06
(dm, J ~ 8.0 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ¼ 7.2 Hz, 1H);
7.95 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.89 (dm, J ¼ 8.2 Hz, 1H); 7.82 (s,
1H); 7.71 (dd, J ¼ 8.0 and 8.0 Hz,1H); 7.65 (tt, J ~ 7.5 and 1.5 Hz); 7.64
(dm, J ~ 8.0 Hz, 1H); 7.61 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.58 (dd,
J ¼ 8.2 and 7.5 Hz, 1H); 7.46 (dm, J ¼ 7.5 Hz, 1H); 7.07 (dd, J ¼ 7.2 and
6.8 Hz, 1H).
4.2.5.8. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]phenyl}-
3-(trifluoromethyl)benzamide (6h). Method A was used for the
isolation of the title compound.
Yield: 57%. Mp ~80 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.65 (br. s, 1H); 9.94 (br. s,
LCMS (ESI) m/z 517.2 (M þ H)þ; 515.2 (MꢂH)ꢂ; calculated: 516.1;

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Rt: 4.03 min.
(2ꢁ), dried over sodium sulphate, filtered and concentrated under
reduced pressure. The crude product was triturated with diiso-
propyl ether, filtered and washed with acetonitrile to give the
desired products.
Method B: The solvent was evaporated. The residue was tritu-
rated with diisopropyl ether, filtered and washed with acetonitrile
to give the desired products.
4.2.5.13. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]
phenyl}-4-(trifluoromethoxy)benzamide (6m). Method A was used
for the isolation of the title compound.
Yield: 66%. Mp 189e190 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.53 (br. s, 1H); 9.94 (br. s,
1H); 8.42 (d, J ¼ 6.8 Hz, 1H); 8.12 (dm, J ~ 9.0 Hz, 2H); 8.10 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ¼ 7.2 Hz, 1H);
7.89 (dm, J ¼ 8.1 Hz, 1H); 7.82 (s, 1H); 7.66 (tt, J ~ 7.5 and 1.5 Hz, 1H);
7.61 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.57 (dd, J ¼ 8.1 and 7.5 Hz, 1H);
7.56 (dm, J ~ 9.0 Hz, 2H); 7.45 (dm, J ¼ 7.5 Hz, 1H); 7.07 (dd, J ¼ 7.2
and 6.8 Hz, 1H).
4.2.6.1. N-[3-(3-{[(3-chlorophenyl)carbamoyl]amino}phenyl)imidazo
[1,2-a]pyridin-8-yl]benzamide (7a). Method B was used for the
isolation of the title compound.
Yield: 90%. Mp 209e211 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.93 (br. s, 1H); 8.96 (br. s,
LCMS (ESI) m/z 517.2 (M þ H)þ; 515.2 (MꢂH)ꢂ; calculated: 516.1;
Rt: 3.99 min.
1H); 8.95 (br. s, 1H); 8.39 (d, J ¼ 6.9 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz,
2H); 8.02 (d, J ¼ 7.2 Hz, 1H); 7.82 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.79 (s,
1H); 7.72 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.66 (tt, J ~ 7.5 and 1.5 Hz, 1H);
7.60 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.45e7.54 (ovl. m, 2H); 7.27e7.34
(ovl. m, 3H); 7.06 (dd, J ¼ 7.2 and 6.8 Hz, 1H); 7.03 (m, 1H).
LCMS (ESI) m/z 482.1 (M þ H)þ; 480.2 (MꢂH)ꢂ; calculated:
481.1; Rt: 3.71 min.
4.2.5.14. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]
phenyl}-2,5-dimethylbenzamide (6n). Method B was used for the
isolation of the title compound.
Yield: 79%. Mp 232e234 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.44 (br. s, 1H); 9.93 (br. s,
1H); 8.39 (d, J ¼ 6.8 Hz, 1H); 8.06 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.04
(dm, J ~ 7.5 Hz, 2H); 8.02 (dm, J ¼ 7.2 Hz, 1H); 7.87 (dm, J ¼ 8.1 Hz,
1H); 7.80 (s, 1H); 7.66 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.60 (ddm, J ~ 7.5
and 7.5 Hz, 2H); 7.54 (dd, J ¼ 8.1 and 7.5 Hz,1H); 7.41 (dm, J ¼ 7.5 Hz,
1H); 7.32 (br. s, 1H); 7.17e7.25 (ovl. m, 2H); 7.06 (dd, J ¼ 7.2 and
6.8 Hz, 1H); 2.36 (s, 3H); 2.34 (s, 3H).
4.2.6.2. N-[3-(3-{[(2,3-dichlorophenyl)carbamoyl]amino}phenyl)imi-
dazo[1,2-a]pyridin-8-yl]benzamide (7b). Method A was used for the
isolation of the title compound.
Yield: 83%. Mp 161e163 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.93 (br. s, 1H); 9.69 (br. s,
1H); 8.54 (br. s,1H); 8.40 (dd, J ¼ 6.9 and 1.0 Hz,1H); 8.17 (dd, J ¼ 7.5
and 2.1 Hz,1H); 8.04 (dm, J ~ 7.5 Hz, 2H); 8.02 (dd, J ¼ 7.2 and 1.0 Hz,
1H); 7.82 (dd, J ¼ 1.5 and 1.5 Hz,1H); 7.80 (s, 1H); 7.66 (tt, J ¼ 7.2 and
2.2 Hz, 1H); 7.60 (ddm, J ¼ 7.5 and 7.2 Hz, 2H); 7.47e7.56 (ovl. m,
2H); 7.27e7.39 (ovl. m, 3H); 7.05 (dd, J ¼ 7.2 and 6.9 Hz, 1H).
LCMS (ESI) m/z 516.1 (M þ H)þ; 514.1 (MꢂH)ꢂ; calculated: 515.1;
Rt: 4.02 min.
LCMS (ESI) m/z 461.3 (M þ H)þ; 459.3 (MꢂH)ꢂ; calculated:
460.2; Rt: 3.69 min.
4.2.5.15. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]
phenyl}-3,5-dimethylbenzamide (6o). Method A was used for the
isolation of the title compound.
Yield: 62%. Mp 207e208 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.34 (br. s, 1H); 9.93 (br. s,
4.2.6.3. N-[3-(3-{[(3,4-dichlorophenyl)carbamoyl]amino}phenyl)imi-
dazo[1,2-a]pyridin-8-yl]benzamide (7c). Method B was used for the
isolation of the title compound.
1H); 8.42 (d, J ¼ 6.8 Hz, 1H); 8.11 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.05
(dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ¼ 7.2 Hz,1H); 7.91 (dm, J ¼ 8.1 Hz,1H);
7.81 (s, 1H); 7.66 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.60 (ddm, J ~ 7.5 and
7.5 Hz, 2H); 7.60 (d, J ~ 1.5 Hz, 2H); 7.55 (dd, J ¼ 8.1 and 7.5 Hz, 1H);
7.42 (dm, J ¼ 7.5 Hz, 1H); 7.24 (t, J ~ 1.5 Hz, 1H); 7.07 (dd, J ¼ 7.2 and
6.8 Hz, 1H); 2.37 (s, 6H).
Yield: 82%. Mp 198e199 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.93 (br. s, 1H); 9.08 (br. s,
1H); 9.01 (br. s,1H); 8.38 (d, J ¼ 6.9 Hz,1H); 8.04 (dm, J ~ 7.5 Hz, 2H);
8.02 (d, J ¼ 7.2 Hz, 1H); 7.89 (d, J ¼ 2.4 Hz, 1H); 7.81 (dd, J ~ 1.5 and
1.5 Hz, 1H); 7.79 (s, 1H); 7.66 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.61 (ddm,
J ~ 7.5 and 7.5 Hz, 2H); 7.53 (d, J ¼ 8.7 Hz, 1H); 7.45e7.53 (ovl. m,
2H); 7.36 (dd, J ¼ 8.7 and 2.4 Hz, 1H); 7.32 (m, 1H); 7.05 (dd, J ¼ 7.2
and 6.9 Hz, 1H).
LCMS (ESI) m/z 461.3 (M þ H)þ; 459.3 (MꢂH)ꢂ; calculated:
460.2; Rt: 3.84 min.
4.2.5.16. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyridin-3-yl]
phenyl}-3,4-dimethoxybenzamide (6p). Method B was used for the
isolation of the title compound.
LCMS (ESI) m/z 516.1 (M þ H)þ; 514.2 (MꢂH)ꢂ; calculated: 515.1;
Rt: 4.04 min.
Yield: 77%. Mp 207e208 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.25 (br. s, 1H); 9.93 (br. s,
4.2.6.4. N-{3-[3-({[3-(trifluoromethyl)phenyl]carbamoyl}amino)
phenyl]imidazo[1,2-a]pyridin-8-yl}benzamide (7d). Method A was
used for the isolation of the title compound.
1H); 8.43 (d, J ¼ 6.8 Hz, 1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.05
(dm, J ~ 7.5 Hz, 2H); 8.03 (d, J ¼ 7.2 Hz,1H); 7.87 (dm, J ¼ 7.5 Hz,1H);
7.81 (s, 1H); 7.67 (dd, J ~ 8.0 and 2.0 Hz, 1H); 7.65 (tt, J ~ 7.5 and
1.5 Hz, 1H); 7.61 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.57 (d, J ~ 7.0 Hz, 1H);
7.56 (dd, J ~ 7.5 and 7.5 Hz, 1H); 7.42 (dm, J ¼ 7.5 Hz, 1H); 7.11 (d,
J ~ 8.0 Hz, 1H); 7.07 (dd, J ¼ 7.2 and 6.8 Hz, 1H); 3.86 (s, 3H); 3.85 (s,
3H).
Yield: 67%. Mp ~115 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.93 (br. s, 1H); 9.13 (br. s,
1H); 9.00 (br. s, 1H); 8.39 (d, J ¼ 6.8 Hz, 1H); 8.05 (dm, J ~ 7.5 Hz,
2H); 8.02 (d, J ¼ 7.2 Hz, 1H); 8.01 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.82
(dd, J ¼ 1.5 and 1.5 Hz, 1H); 7.79 (s, 1H); 7.56e7.71 (ovl. m, 4H);
7.45e7.56 (ovl. m, 3H); 7.32 (ovl. m, 2H); 7.05 (dd, J ¼ 7.2 and 6.8 Hz,
1H).
LCMS (ESI) m/z 493.3 (M þ H)þ; 491.3 (MꢂH)ꢂ; calculated:
492.2; Rt: 3.16 min.
LCMS (ESI) m/z 516.2 (M þ H)þ; 514.2 (MꢂH)ꢂ; calculated:
515.2; Rt: 3.87 min.
4.2.6. General procedure for the preparation of compounds 7a-7g
A mixture of compound 5 (100 mg, 0.31 mmol), anhydrous
pyridine (2 ml) and the aryl isocyanate (0.34 mmol) was stirred at
room temperature for 2 h.
Method A: The solvent was evaporated and the residue was
taken up in chloroform. The organic layer was washed with water
4.2.6.5. N-{3-[3-({[4-(trifluoromethyl)phenyl]carbamoyl}amino)
phenyl]imidazo[1,2-a]pyridin-8-yl}benzamide (7e). Method B was
used for the isolation of the title compound.
Yield: 87%. Mp 234e235 ꢀC.

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1H NMR (300 MHz, DMSO-d6)
d
ppm 9.93 (br. s, 1H); 9.19 (br. s,
triturated with diisopropyl ether and filtered to give the title
1H); 9.01 (br. s,1H); 8.39 (d, J ¼ 6.9 Hz,1H); 8.05 (dm, J ~ 7.5 Hz, 2H);
8.02 (d, J ¼ 7.3 Hz, 1H); 7.83 (dd, J ¼ 1.5 and 1.5 Hz, 1H); 7.79 (s, 1H);
7.56e7.73 (ovl. m, 7H); 7.46e7.56 (ovl. m, 2H); 7.32 (dm, J ¼ 6.3 Hz,
1H); 7.05 (dd, J ¼ 7.3 and 6.9 Hz, 1H).
compound (14.40 g).
Yield: 93%. Mp 191e193 ꢀC.
1H NMR (300 MHz, DMSO-d6)
(s, 1H); 7.87 (d, J ¼ 4.6 Hz, 1H).
d
ppm 8.48 (d, J ¼ 4.6 Hz,1H); 8.04
LCMS (ESI) m/z 516.2 (M þ H)þ; 514.2 (MꢂH)ꢂ; calculated:
515.2; Rt: 3.95 min.
LCMS (ESI) m/z 231.9 (M þ H)þ; calculated: 230.9; Rt: 2.29 min.
4.2.9. 3-bromoimidazo[1,2-a]pyrazin-8-amine (11)
4.2.6.6. N-{3-[3-({[3,5-bis(trifluoromethyl)phenyl]carbamoyl}amino)
phenyl]imidazo[1,2-a]pyridin-8-yl}benzamide (7f). Method A was
used for the isolation of the title compound.
To the solution of compound 10 (3.00 g, 12.85 mmol) in 2-
propanol (30 ml), 25% aqueous ammonium hydroxide solution
(90 ml) was added. The mixture was stirred at 120 ꢀC for 3 h in a
microwave reactor. The reaction mixture was diluted with 200 ml
water and stirred for 10 min. The precipitate was filtered and
washed with water (3ꢁ) to give the title compound (2.34 g).
Yield: 85%. Mp 243e244 ꢀC.
Yield: 77%. Mp 237e238 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.94 (br. s, 1H); 9.50 (br. s,
1H); 9.21 (br. s, 1H); 8.38 (d, J ¼ 6.8 Hz, 1H); 8.16 (m, 2H); 8.05 (dm,
J ¼ 7.8 Hz, 2H); 8.02 (d, J ¼ 7.2 Hz, 1H); 7.82 (dd, J ¼ 1.5 and 1.5 Hz,
1H); 8.70 (s, 1H); 7.66 (m, 1H); 7.65 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.61
(ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.57 (dm, J ~ 8.0 Hz, 1H); 7.51 (dd,
J ¼ 8.1 and 7.4 Hz,1H); 7.34 (dm, J ¼ 7.5 Hz, 1H); 7.05 (dd, J ¼ 7.2 and
6.8 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 7.66 (s, 1H); 7.56 (d,
J ¼ 4.5 Hz, 1H); 7.36 (d, J ¼ 4.5 Hz, 1H); 7.06 (br. s, 2H).
LCMS (ESI) m/z 212.9 (M þ H)þ; calculated: 212.0; Rt: 0.46 min.
LCMS (ESI) m/z 584.2 (M þ H)þ; 582.2 (MꢂH)ꢂ; calculated:
583.1; Rt: 4.43 min.
4.2.10. 3-(3-aminophenyl)imidazo[1,2-a]pyrazin-8-amine (12)
The solution of compound 11 (3.80 g,17.84 mmol) in 1,4-dioxane
(200 ml) was stirred at room temperature under argon for 10 min.
Tetrakis(triphenylphosphine)palladium(0) (1.03 g, 0.89 mmol) was
added to the mixture and it was stirred for another 30 min under
argon. After the addition of 3-aminophenylboronic acid (2.90 g,
21.40 mmol) and sodium carbonate (7.56 g, 71.35 mmol) in 48 ml
water, the mixture was stirred at 140 ꢀC for 1.5 h in a microwave
reactor. Then the reaction mixture was filtered through Celite and
washed with ethyl acetate. The filtrate was washed with 10%
aqueous sodium hydrogen carbonate solution (2ꢁ), brine, dried
over sodium sulphate, filtered and concentrated under reduced
pressure. The crude product was triturated with diisopropyl ether,
filtered and washed with acetonitrile to give the title compound
(3.01 g).
4.2.6.7. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyridin-8-yl}benzamide
Method A was used for the isolation of the title compound.
Yield: 56%. Mp 219e220 ꢀC.
(7g).
1H NMR (300 MHz, DMSO-d6)
d ppm 9.93 (br. s, 1H); 9.25 (br. s,
1H); 9.05 (br. s, 1H); 8.38 (dd, J ¼ 6.9 and 1.0 Hz, 1H); 8.10 (d,
J ¼ 2.1 Hz, 1H); 8.04 (dm, J ~ 7.5 Hz, 2H); 8.02 (dd, J ~ 7.5 and 1.0 Hz,
1H); 7.81 (dd, J ¼ 1.5 and 1.5 Hz, 1H); 7.79 (s, 1H); 7.57e7.71 (ovl. m,
5H); 7.46e7.57 (ovl. m, 2H); 7.32 (ddd, J ¼ 6.9, 1.5 and 1.0 Hz, 1H);
7.05 (dd, J ¼ 7.5 and 6.9 Hz, 1H).
LCMS (ESI) m/z 550.2 (M þ H)þ; 548.1 (MꢂH)ꢂ; calculated:
549.1; Rt: 4.14 min.
Yield: 75%. Mp 110e111 ꢀC.
4.2.7. 8-chloroimidazo[1,2-a]pyrazine (9)
1H NMR (300 MHz, DMSO-d6)
d
ppm 7.72 (d, J ¼ 4.8 Hz, 1H); 7.59
A
mixture of bromoacetaldehyde diethyl acetal (29 ml,
(s, 1H); 7.25 (d, J ¼ 4.8 Hz, 1H); 7.18 (t, J ¼ 7.9 and 7.2 Hz, 1H); 6.90
(br. s, 2H); 6.81 (dd, J ¼ 2.0 and 1.5 Hz,1H); 6.74 (ddd, J ¼ 7.2,1.5 and
1.0 Hz, 1H); 6.63 (ddd, J ¼ 7.9, 2.0 and 1.0 Hz, 1H); 5.29 (br. s, 2H).
LCMS (ESI) m/z 226.1 (M þ H)þ; calculated: 225.1; Rt: 0.45 min.
192.77 mmol) and 48% aqueous hydrogen bromide solution (7 ml)
was stirred at reflux temperature for 1.5 h. After cooling back to
room temperature it was poured onto a suspension of sodium
hydrogen carbonate (14.50 g, 172.62 mmol) and 2-propanol
(230 ml) and stirred until the gas evolution ceased. The formed
precipitate was filtered, then 2-amino-3-chloropyrazine (8) (7.51 g,
58 mmol) was added to the filtrate and stirred at reflux tempera-
ture for 3 h. The reaction mixture was allowed to cool down to
room temperature, the resulting solid was collected by filtration
and washed with 2-propanol. The solid was partitioned between
chloroform and 10% aqueous sodium hydrogen carbonate solution.
The layers were separated and the aqueous layer was extracted
with chloroform (2ꢁ). The combined organic layers were dried over
sodium sulphate, filtered and concentrated under reduced pres-
sure. The crude product was triturated with diisopropyl ether and
filtered to give the title compound (6.48 g).
4.2.11. General procedure for the preparation of compounds 13a-
13v
A mixture of compound 12 (100 mg, 0.44 mmol), pyridine
(2 ml), N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydro-
chloride (85 mg, 0.44 mmol) and the benzoic acid derivative
(0.44 mmol) was stirred at 40 ꢀC overnight.
Method A: The solvent was evaporated and the residue was
taken up in chloroform. The organic layer was washed with water
(2ꢁ), dried over sodium sulphate, filtered and concentrated under
reduced pressure. The crude product was triturated with diiso-
propyl ether, filtered and washed with acetonitrile to give the
desired products.
Yield: 73%.
Method B: The solvent was evaporated. The residue was tritu-
rated with diisopropyl ether, filtered and washed with acetonitrile
to give the desired products.
LCMS (ESI) m/z 153.9 (M þ H)þ; calculated: 153.0; Rt: 1.42 min.
4.2.8. 3-bromo-8-chloroimidazo[1,2-a]pyrazine (10)
To the solution of compound 9 (6.47 g, 42.13 mmol) in
dichloromethane (140 ml) N-bromosuccinimide (7.50 g,
42.13 mmol) was added and the mixture was stirred at room
temperature for 3 h. The reaction mixture was diluted with
dichloromethane and stirred with 10% aqueous sodium carbonate
solution for 1 h before the layers were separated. The organic layer
was washed with water (2ꢁ), dried over sodium sulphate, filtered
and concentrated under reduced pressure. The crude product was
4.2.11.1. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]benza-
mide (13a). Method A was used for the isolation of the title
compound.
Yield: 64%. Mp 246e248 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.42 (s, 1H); 8.09 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.99 (dm, J ~ 7.5 Hz, 2H); 7.90 (dm, J ¼ 8.2 Hz,
1H); 7.83 (d, J ¼ 4.8 Hz, 1H); 7.74 (s, 1H); 7.60 (tt, J ~ 7.5 and 1.5 Hz,
1H); 7.57 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.54 (dd, J ¼ 8.2 and 7.8 Hz,

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633
1H); 7.39 (dm, J ¼ 7.8 Hz,1H); 7.31 (d, J ¼ 4.8 Hz,1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 330.2 (M þ H)þ; 328.2 (MꢂH)ꢂ; calculated:
329.1; Rt: 2.39 and 2.49 min.
4.2.11.7. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-
chloro-4-fluorobenzamide (13g). Method A was used for the isola-
tion of the title compound.
Yield: 65%. Mp 224e225 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.51 (br. s, 1H); 8.23 (dd,
4.2.11.2. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-2,4-
difluorobenzamide (13b). Method B was used for the isolation of the
title compound.
J ¼ 7.0 and 2.0 Hz, 1H); 8.05 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.02 (ddd,
J ¼ 8.0, 4.8 and 2.0 Hz, 1H); 7.87 (dm, J ¼ 8.1 Hz, 1H); 7.82 (d,
J ¼ 4.5 Hz, 1H); 7.74 (s, 1H); 7.62 (dd, J ¼ 8.0 and 8.0 Hz, 1H); 7.55
(dd, J ¼ 8.1 and 7.8 Hz,1H); 7.41 (d, J ¼ 7.8 Hz,1H); 7.32 (d, J ¼ 4.5 Hz,
1H); 6.98 (br. s, 2H).
Yield: 51%. Mp 216e218 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.59 (br. s, 1H); 8.01 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.81 (ddd, J ~ 8.5, 5.5 and 4.5, Hz, 1H); 7.80
(dm, J ~ 8.0 Hz, 1H); 7.79 (d, J ¼ 4.6 Hz, 1H); 7.73 (s, 1H); 7.54 (dd,
J ~ 8.0 and 7.5 Hz, 1H); 7.44 (ddd, J ~ 10.5, 10.5 and 2.5 Hz, 1H); 7.41
(dm, J ~ 7.5 Hz,1H); 7.30 (d, J ¼ 4.6 Hz,1H); 7.25 (ddd, J ~ 8.5, 8.5 and
2.5 Hz, 1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 382.2 (M þ H)þ; 380.2 (MꢂH)ꢂ; calculated:
381.1; Rt: 2.95 min.
4.2.11.8. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,5-
dichloro-4-fluorobenzamide (13h). Method B was used for the
isolation of the title compound.
LCMS (ESI) m/z 366.2 (M þ H)þ; 364.2 (MꢂH)ꢂ; calculated:
365.1; Rt: 2.64 min.
Yield: 66%. Mp 253e255 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.58 (br. s, 1H); 8.21 (d,
4.2.11.3. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,5-
difluorobenzamide (13c). Method A was used for the isolation of the
title compound.
J ¼ 6.6 Hz, 2H); 8.04 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.86 (dm, J ¼ 8.1 Hz,
1H); 7.82 (d, J ¼ 4.8 Hz, 1H); 7.75 (s, 1H); 7.56 (dd, J ¼ 8.1 and 7.8 Hz,
1H); 7.43 (dm, J ¼ 7.8 Hz,1H); 7.32 (d, J ¼ 4.8 Hz,1H); 7.04 (br. s, 2H).
LCMS (ESI) m/z 416.2 (M þ H)þ; 414.2 (MꢂH)ꢂ; calculated:
415.0; Rt: 3.26 min.
Yield: 38%. Mp 220e221 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.52 (br. s, 1H); 8.06 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.87 (dm, J ¼ 8.1 Hz, 1H); 7.82 (d, J ¼ 4.6 Hz,
1H); 7.74 (s, 1H); 7.73e7.67 (dm, J ~ 8.0 Hz, 2H); 5.56 (dd, J ¼ 8.1 and
7.5 Hz,1H); 7.54 (tt, J ¼ 9.0 and 2.5 Hz,1H); 7.43 (dm, J ¼ 7.5 Hz,1H);
7.32 (d, J ¼ 4.6 Hz, 1H); 6.97 (br. s, 2H).
4.2.11.9. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-
chloro-4-methylbenzamide (13i). Method A was used for the isola-
tion of the title compound.
LCMS (ESI) m/z 366.2 (M þ H)þ; 364.2 (MꢂH)ꢂ; calculated:
365.1; Rt: 2.79 min.
Yield: 60%. Mp 236e238 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.43 (br. s, 1H); 8.03e8.09
(ovl. m, 2H); 7.85e7.92 (ovl. m, 2H); 7.82 (d, J ¼ 4.7 Hz, 1H); 7.74 (s,
1H); 7.50e7.58 (ovl. m, 2H); 7.40 (dm, J ¼ 7.8 Hz, 1H); 7.32 (d,
J ¼ 4.7 Hz, 1H); 6.97 (br. s, 2H); 2.42 (s, 3H).
4.2.11.4. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-2,3-
dichlorobenzamide (13d). Method B was used for the isolation of
the title compound.
LCMS (ESI) m/z 378.2 (M þ H)þ; 376.2 (MꢂH)ꢂ; calculated:
377.1; Rt: 3.04 min.
Yield: 35%. Mp 208e209 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.77 (br. s, 1H); 7.99 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.77e7.82 (ovl. m, 2H); 7.77 (d, J ¼ 4.8 Hz,
1H); 7.73 (s, 1H); 7.61 (dd, J ¼ 7.6 and 1.5 Hz, 1H); 7.55 (dd, J ¼ 8.0
and 7.8 Hz,1H); 7.51 (dd, J ¼ 7.7 and 7.6 Hz,1H); 7.42 (dm, J ¼ 7.8 Hz,
1H); 7.30 (d, J ¼ 4.8 Hz, 1H); 6.97 (br. s, 2H).
4.2.11.10. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-4-
bromobenzamide (13j). Method B was used for the isolation of the
title compound.
Yield: 69%. Mp 264e267 ꢀC.
LCMS (ESI) m/z 398.2 (M þ H)þ; 396.2 (MꢂH)ꢂ; calculated:
397.1; Rt: 2.85 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.48 (br. s, 1H); 8.07 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.95 (dm, J ¼ 8.4 Hz, 2H); 7.88 (dm, J ¼ 8.1 Hz,
1H); 7.82 (d, J ¼ 4.2 Hz, 1H); 7.77 (dm, J ¼ 8.4 Hz, 2H); 7.74 (s, 1H);
7.54 (dd, J ¼ 8.1 and 7.7 Hz, 1H); 7.40 (dm, J ¼ 7.7 Hz, 1H); 7.31 (d,
J ¼ 4.2 Hz, 1H); 6.98 (br. s, 2H).
4.2.11.5. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,4-
dichlorobenzamide (13e). Method A was used for the isolation of
the title compound.
LCMS (ESI) m/z 408.1 (M þ H)þ; 406.2 (MꢂH)ꢂ; calculated:
407.0; Rt: 2.92 min.
Yield: 70%. Mp 249e251 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.55 (br. s, 1H); 8.25 (d,
J ¼ 1.8 Hz, 1H); 8.06 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.97 (dd, J ¼ 8.4 and
1.8 Hz, 1H); 7.87 (dm, J ~ 8.0 Hz, 1H); 7.84 (d, J ¼ 8.4 Hz, 1H); 7.82 (d,
J ¼ 4.8 Hz, 1H); 7.74 (s, 1H); 7.55 (dd, J ¼ 8.0 and 7.7 Hz, 1H); 7.42
(dm, J ¼ 7.7 Hz, 1H); 7.32 (d, J ¼ 4.8 Hz, 1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 398.1 (M þ H)þ; 396.2 (MꢂH)ꢂ; calculated:
397.1; Rt: 3.13 min.
4.2.11.11. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(tri-
fluoromethyl)benzamide (13k). Method A was used for the isolation
of the title compound.
Yield: 47%. Mp 198e199 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.63 (br. s, 1H); 8.32 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 8.30 (dm, J ~ 7.5 Hz, 1H); 8.08 (dd, J ~ 1.5 and
1.5 Hz, 1H); 7.99 (dm, J ¼ 7.5 Hz, 1H); 7.88 (dm, J ¼ 8.1 Hz, 1H); 7.83
(d, J ¼ 4.8 Hz, 1H); 7.81 (dd, J ~ 7.5 and 7.5 Hz, 1H); 7.75 (s, 1H); 7.57
(dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.42 (dm, J ¼ 7.5 Hz, 1H); 7.32 (d,
J ¼ 4.8 Hz, 1H); 6.97 (br. s, 2H).
4.2.11.6. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,5-
dichlorobenzamide (13f). Method A was used for the isolation of the
title compound.
Yield: 51%. Mp 256e257 ꢀC.
LCMS (ESI) m/z 398.3 (M þ H)þ; 396.3 (MꢂH)ꢂ; calculated:
397.1; Rt: 3.03 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.57 (br. s, 1H); 8.05 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 8.01 (d, J ¼ 1.5 Hz, 2H); 7.88 (t, J ¼ 1.5 Hz,1H);
7.86 (dm, J ~ 8.0 Hz, 1H); 7.82 (d, J ¼ 4.7 Hz, 1H); 7.74 (s, 1H); 7.56
(dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.42 (d, J ¼ 7.5 Hz, 1H); 7.32 (d,
J ¼ 4.7 Hz, 1H); 6.97 (br. s, 2H).
4.2.11.12. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-4-(tri-
fluoromethyl)benzamide (13l). Method B was used for the isolation
of the title compound.
LCMS (ESI) m/z 398.2 (M þ H)þ; 396.2 (MꢂH)ꢂ; calculated:
397.1; Rt: 3.19 min.
Yield: 56%. Mp 272e273 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.63 (br. s, 1H); 8.18 (dm,

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J ¼ 8.1 Hz, 2H); 8.08 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.94 (dm, J ¼ 8.1 Hz,
2H); 7.89 (dm, J ¼ 8.1 Hz, 1H); 7.83 (d, J ¼ 4.8 Hz, 1H); 7.75 (s, 1H);
7.56 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.42 (dm, J ¼ 7.5 Hz, 1H); 7.32 (d,
J ¼ 4.8 Hz, 1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 414.2 (M þ H)þ; 412.3 (MꢂH)ꢂ; calculated:
413.1; Rt: 3.10 min.
4.2.11.18. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-2,5-
dimethylbenzamide (13r). Method B was used for the isolation of
the title compound.
LCMS (ESI) m/z 398.2 (M þ H)þ; 396.3 (MꢂH)ꢂ; calculated:
397.1; Rt: 3.03 min.
Yield: 57%. Mp 243e245 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.42 (br. s, 1H); 8.03 (dd,
4.2.11.13. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,5-
bis(trifluoromethyl)benzamide (13m). Method A was used for the
isolation of the title compound.
J ~ 1.5 and 1.5 Hz, 1H); 7.85 (dm, J ¼ 8.1 Hz, 1H); 7.79 (d, J ¼ 4.8 Hz,
1H); 7.72 (s, 1H); 7.52 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.37 (dm,
J ¼ 7.5 Hz, 1H); 7.31 (d, J ~ 1.5 Hz, 1H); 7.30 (d, J ¼ 4.8 Hz, 1H);
7.17e7.25 (ovl. m, 2H); 6.96 (br. s, 2H); 2.35 (s, 3H); 2.33 (s, 3H).
LCMS (ESI) m/z 358.3 (M þ H)þ; 356.3 (MꢂH)ꢂ; calculated:
357.2; Rt: 2.84 min.
Yield: 60%. Mp 258e260 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.82 (s, 1H); 8.64 (d,
J ~ 1.0 Hz, 2H); 8.39 (t, J ~ 1.0 Hz,1H); 8.08 (dd, J ~ 1.5 and 1.5 Hz,1H);
7.86 (dm, J ¼ 8.5 Hz, 1H); 7.83 (d, J ¼ 4.5 Hz, 1H); 7.75 (s, 1H); 7.59
(dd, J ¼ 8.5 and 7.7 Hz, 1H); 7.45 (d, J ¼ 7.7 Hz, 1H); 7.32 (d,
J ¼ 4.5 Hz, 1H); 6.98 (s, 2H).
4.2.11.19. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,5-
dimethylbenzamide (13s). Method A was used for the isolation of
the title compound.
LCMS (ESI) m/z 466.3 (M þ H)þ; 464.3 (MꢂH)ꢂ; calculated:
465.1; Rt: 3.46 min.
Yield: 63%. Mp 237e238 ꢀC.
4.2.11.14. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-4-
fluoro-3-(trifluoromethyl)benzamide (13n). Method A was used for
the isolation of the title compound.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.33 (br. s, 1H); 8.07 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.89 (dm, J ¼ 8.1 Hz, 1H); 7.83 (d, J ¼ 4.8 Hz,
1H); 7.74 (s, 1H); 7.59 (d, J ~ 1.5 Hz, 2H); 7.53 (dd, J ¼ 8.1 and 7.8 Hz,
1H); 7.38 (dm, J ¼ 7.8 Hz, 1H); 7.32 (d, J ¼ 4.8 Hz, 1H); 7.24 (t,
J ~ 1.5 Hz, 1H); 6.97 (br. s, 2H); 2.37 (s, 6H).
Yield: 53%. Mp 233e235 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.63 (br. s, 1H); 8.34e8.42
(ovl. m, 2H); 8.06 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.85 (dm, J ¼ 8.5 Hz,
1H); 7.82 (d, J ¼ 4.8 Hz,1H); 7.74 (s, 1H); 7.73 (dd, J ~ 10.0 and 9.5 Hz,
1H); 7.57 (dd, J ¼ 8.5 and 7.7 Hz, 1H); 7.43 (dm, J ¼ 7.7 Hz, 1H); 7.32
(d, J ¼ 4.8 Hz, 1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 358.3 (M þ H)þ; 356.3 (MꢂH)ꢂ; calculated:
357.2; Rt: 2.95 min.
4.2.11.20. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-
methoxy-2-methylbenzamide (13t). Method B was used for the
isolation of the title compound.
LCMS (ESI) m/z 416.2 (M þ H)þ; 414.3 (MꢂH)ꢂ; calculated:
415.1; Rt: 3.12 min.
Yield: 55%. Mp 219e221 ꢀ
C
4.2.11.15. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-4-
chloro-3-(trifluoromethyl)benzamide (13o). Method A was used for
the isolation of the title compound.
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.45 (br. s, 1H); 8.03 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.83 (dm, J ¼ 8.0 Hz, 1H); 7.79 (d, J ¼ 4.7 Hz,
1H); 7.72 (s, 1H); 7.52 (dd, J ¼ 8.0 and 7.7 Hz, 1H); 7.37 (dm,
J ¼ 7.7 Hz, 1H); 7.30 (dd, J ¼ 8.4 and 7.8 Hz, 1H); 7.29 (d, J ¼ 4.7 Hz,
1H); 7.09 (dm, J ¼ 8.4 Hz, 1H); 7.06 (dm, J ¼ 7.8 Hz, 1H); 6.96 (br. s,
2H); 3.84 (s, 3H); 2.21 (s, 3H).
Yield: 52%. Mp 201e202 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.68 (br. s, 1H); 8.41 (d,
J ¼ 1.6 Hz, 1H); 8.30 (dd J ¼ 8.5 and 1.6 Hz, 1H); 8.06 (dd, J ~ 1.5 and
1.5 Hz, 1H); 7.95 (d, J ¼ 8.5 Hz,1H); 7.86 (dm, J ¼ 8.3 Hz, 1H); 7.82 (d,
J ¼ 4.7 Hz, 1H); 7.74 (s, 1H); 7.57 (dd, J ¼ 8.3 and 7.8 Hz, 1H); 7.43
(dm, J ¼ 7.8 Hz, 1H); 7.32 (d, J ¼ 4.7 Hz, 1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 432.2 (M þ H)þ; 430.2 (MꢂH)ꢂ; calculated:
431.1; Rt: 3.25 min.
LCMS (ESI) m/z 374.3 (M þ H)þ; 372.3 (MꢂH)ꢂ; calculated:
373.2; Rt: 2.69 min.
4.2.11.21. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,4-
dimethoxybenzamide (13u). Method A was used for the isolation of
the title compound.
4.2.11.16. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(tri-
fluoromethoxy)benzamide (13p). Method A was used for the isola-
tion of the title compound.
Yield: 44%. Mp 199e201 ꢀC
1H NMR (300 MHz, DMSO-d6)
d ppm 10.24 (br. s, 1H); 8.08 (dd,
Yield: 61%. Mp 193e195 ꢀC.
J ~ 1.5 and 1.5 Hz, 1H); 7.85 (dm, J ~ 8.0 Hz, 1H); 7.83 (d, J ¼ 4.8 Hz,
1H); 7.74 (s, 1H); 7.66 (dd, J ¼ 8.4 and 1.8 Hz, 1H); 7.56 (d, J ¼ 1.8 Hz,
1H); 7.53 (dd, J ¼ 8.0 and 7.8 Hz, 1H); 7.38 (dm, J ¼ 7.8 Hz, 1H); 7.32
(d, J ¼ 4.8 Hz, 1H); 7.11 (d, J ¼ 8.4 Hz, 1H); 6.97 (br. s, 2H); 3.86 (s,
3H); 3.85 (s, 3H).
1H NMR (300 MHz, DMSO-d6)
d ppm 10.55 (br. s, 1H); 8.07 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 8.05 (dm, J ~ 8.0 Hz, 1H); 7.94 (dd, J ~ 1.5 and
1.5 Hz, 1H); 7.87 (dm, J ¼ 8.1 Hz, 1H); 7.83 (d, J ¼ 4.8 Hz, 1H); 7.74 (s,
1H); 7.70 (dd, J ¼ 8.0 and 7.8 Hz, 1H); 7.63 (dm, J ¼ 7.8 Hz, 1H); 7.56
(dd, J ¼ 8.1 and 7.8 Hz, 1H); 7.42 (dm, J ¼ 7.8 Hz, 1H); 7.32 (d,
J ¼ 4.8 Hz, 1H); 6.97 (br. s, 2H).
LCMS (ESI) m/z 390.3 (M þ H)þ; 388.3 (MꢂH)ꢂ; calculated:
389.1; Rt: 2.35 and 2.45 min.
LCMS (ESI) m/z 414.3 (M þ H)þ; 412.3 (MꢂH)ꢂ; calculated:
413.1; Rt: 3.10 min.
4.2.11.22. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3,4,5-
trimethoxybenzamide (13v). Method A was used for the isolation of
the title compound.
4.2.11.17. N-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-4-(tri-
fluoromethoxy)benzamide (13q). Method B was used for the isola-
tion of the title compound.
Yield: 61%. Mp 213e214 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.29 (br. s, 1H); 8.07 (dd,
Yield: 65%. Mp 234e236 ꢀC.
J ~ 1.5 and 1.5 Hz, 1H); 7.83 (d, J ¼ 4.8 Hz, 1H); 7.82 (dm, J ~ 8.0 Hz,
1H); 7.74 (s, 1H); 7.55 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.40 (dm,
J ¼ 7.5 Hz, 1H); 7.32 (dm, J ~ 7.5 Hz, 1H); 7.31 (s, 2H); 6.97 (br. s, 2H);
3.88 (s, 6H); 3.74 (s, 3H).
1H NMR (300 MHz, DMSO-d6)
d ppm 10.53 (br. s, 1H); 8.12 (dm,
J ¼ 8.7 Hz, 2H); 8.07 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.88 (dm, J ¼ 8.4 Hz,
1H); 7.82 (d, J ¼ 4.6 Hz, 1H); 7.74 (s, 1H); 7.56 (dm, J ¼ 8.7 Hz, 2H);
7.55 (dd, J ¼ 8.4 and 7.7 Hz, 1H); 7.41 (d, J ¼ 7.7 Hz, 1H); 7.32 (d,
J ¼ 4.6 Hz, 1H); 6.98 (br. s, 2H).
LCMS (ESI) m/z 420.3 (M þ H)þ; 418.3 (MꢂH)ꢂ; calculated:
419.2; Rt: 2.58 min.

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4.2.12. General procedure for the preparation of compounds 14a-
14q
A mixture of compound 13g (100 mg, 0.26 mmol), pyridine
(2 ml), N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydro-
chloride (126 mg, 0.66 mmol) and the benzoic acid derivative
(0.66 mmol) was stirred at 70 ꢀC overnight.
Method A: The solvent was evaporated and the residue was
taken up in chloroform. The organic layer was washed with water
(2ꢁ), dried over sodium sulphate, filtered and concentrated under
reduced pressure. The crude product was triturated with diiso-
propyl ether, filtered and washed with acetonitrile to give the
desired products.
Method B: The solvent was evaporated. The residue was tritu-
rated with diisopropyl ether, filtered and washed with acetonitrile
to give the desired products.
1H); 8.11 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.04 (dd, J ~ 8.4 and 1.5 Hz, 1H);
8.03 (ddd, J ¼ 8.8, 4.7 and 2.1 Hz, 1H); 8.00 (s, 1H); 7.92 (dm,
J ¼ 8.1 Hz, 1H); 7.85 (d, J ¼ 8.4 Hz, 1H); 7.82 (br, 1H); 7.62 (dd, J ¼ 9.2
and 8.8 Hz,1H); 7.60 (dd, J ¼ 8.1 and 7.5 Hz,1H); 7.50 (dm, J ¼ 7.5 Hz,
1H).
LCMS (ESI) m/z 554.3 (M þ H)þ; 552.3 (MꢂH)ꢂ; calculated:
553.0; Rt: 4.53 min.
4.2.12.5. 3-chloro-N-(3-{8-[(3,5-dichlorobenzoyl)amino]imidazo[1,2-
a]pyrazin-3-yl}phenyl)-4-fluorobenzamide (14e). Method
used for the isolation of the title compound.
Yield: 81%. Mp 230e232 ꢀC.
A was
1H NMR (300 MHz, DMSO-d6)
d ppm 11.28 (br, 1H); 10.55 (br. s,
1H); 8.52 (br, 1H); 8.24 (dd, J ¼ 7.2 and 2.1 Hz, 1H); 8.12 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.08 (d, J ~ 1.5 Hz, 2H); 8.04 (ddd, J ¼ 8.8, 4.7 and
2.1 Hz, 1H); 8.01 (s, 1H); 7.92 (dm, J ~ 8.0 Hz, 1H); 7.92 (t, J ~ 1.5 Hz,
1H); 7.83 (br, 1H); 7.63 (dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.61 (dd, J ¼ 8.0
and 7.5 Hz, 1H); 7.50 (d, J ¼ 7.5 Hz, 1H).
4.2.12.1. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyrazin-3-yl]
phenyl}-3-chloro-4-fluorobenzamide (14a). Method A was used for
the isolation of the product and it was further purified by prepar-
ative TLC (eluent: chloroform: methanol ¼ 9: 1) to give the title
compound.
LCMS (ESI) m/z 554.3 (M þ H)þ; 552.3 (MꢂH)ꢂ; calculated:
553.0; Rt: 4.63 min.
Yield: 34%. Mp 234e236 ꢀC.
4.2.12.6. 3-chloro-N-(3-{8-[(3-chloro-4-fluorobenzoyl)amino]imi-
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.92 (br, 1H); 10.56 (br. s,
dazo[1,2-a]pyrazin-3-yl}phenyl)-4-fluorobenzamide
(14f).
1H); 8.51 (br, 1H); 8.24 (dd, J ¼ 6.9 and 2.0 Hz, 1H); 8.12 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.07 (dm, J ~ 7.5 Hz, 2H); 8.04 (ddd, J ¼ 8.8, 4.6 and
2.0 Hz, 1H); 7.99 (s, 1H); 7.92 (dm, J ¼ 7.8 Hz, 1H); 7.82 (br. d, J
~4.5 Hz, 1H); 7.65 (tt, J ¼ 7.5 and 1.5 Hz, 1H); 7.63 (dd, J ¼ 9.0 and
8.8 Hz, 1H); 7.60 (dd, J ¼ 7.8 and 7.7 Hz, 1H); 7.58 (ddm, J ~ 7.5 and
7.5 Hz, 2H); 7.51 (dm, J ¼ 7.7 Hz, 1H).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
Yield: 27%. Mp ~120 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.25 (br, 1H); 10.55 (br. s,
1H); 8.48 (br, 1H); 8.30 (dd, J ¼ 7.1 and 2.0 Hz, 1H); 8.24 (dd, J ¼ 7.2
and 2.1 Hz,1H); 8.11 (dd, J ~ 1.5 and 1.5 Hz,1H); 8.09 (ddd, J ~ 8.5, 4.5
and 2.0 Hz, 1H); 8.03 (ddd, J ¼ 8.7, 4.7 ans 2.1 Hz, 1H); 7.99 (s, 1H);
7.92 (dm, J ¼ 8.0 Hz, 1H); 7.79 (br, 1H); 7.63 (dd, J ¼ 9.2 and 8.8 Hz,
1H); 7.62 (dd, J ~ 8.5 and 8.0 Hz, 1H); 7.60 (dd, J ¼ 8.0 and 7.5 Hz,
1H); 7.50 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 486.3 (M þ H)þ; 484.3 (MꢂH)ꢂ; calculated:
485.1; Rt: 3.96 min.
4.2.12.2. 3-chloro-N-(3-{8-[(3,5-difluorobenzoyl)amino]imidazo[1,2-
a]pyrazin-3-yl}phenyl)-4-fluorobenzamide (14b). Method
used for the isolation of the title compound.
Yield: 58%. Mp 224e226 ꢀC.
A was
LCMS (ESI) m/z 538.3 (M þ H)þ; 536.3 (MꢂH)ꢂ; calculated:
537.1; Rt: 4.32 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.20 (br, 1H); 10.55 (br. s,
1H); 8.55 (br, 1H); 8.24 (dd, J ¼ 7.2 and 2.1 Hz, 1H); 8.12 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.6 and 2.1 Hz, 1H); 8.01 (s, 1H);
7.92 (dm, J ¼ 8.0 Hz, 1H); 7.85 (br, 1H); 7.77 (dm, J ~ 6.5 Hz, 2H); 7.62
(dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.61 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.58 (tt,
J ~ 9.0 and 1.5 Hz, 1H); 7.51 (dm, J ¼ 7.5 Hz, 1H).
4.2.12.7. 3,5-Dichloro-N-(3-{3-[(3-chloro-4-fluorobenzoyl)amino]
phenyl}imidazo[1,2-a]pyrazin-8-yl)-4-fluorobenzamide
Method A was used for the isolation of the title compound.
Yield: 37%. Mp 263e264 ꢀC.
(14g).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.28 (br, 1H); 10.55 (br. s,
LCMS (ESI) m/z 522.4 (M þ H)þ; 520.4 (MꢂH)ꢂ; calculated:
521.1; Rt: 4.21 min.
1H); 8.50 (br, 1H); 8.26 (d, J ¼ 6.3 Hz, 2H); 8.24 (dd, J ¼ 7.2 and
2.1 Hz, 1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.7
and 2.1 Hz, 1H); 8.00 (s, 1H); 7.92 (dm, J ¼ 8.4 Hz, 1H); 7.79 (br, 1H);
7.63 (dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.60 (dd, J ¼ 8.0 and 7.5 Hz, 1H);
7.50 (dm, J ¼ 7.5 Hz, 1H).
4.2.12.3. 2,3-Dichloro-N-(3-{3-[(3-chloro-4-fluorobenzoyl)amino]
phenyl}imidazo[1,2-a]pyrazin-8-yl)benzamide (14c). Method A was
used for the isolation of the title compound.
LCMS (ESI) m/z 572.2 (M þ H)þ; 570.3 (MꢂH)ꢂ; calculated:
571.0; Rt: 4.68 min.
Yield: 59%. Mp 161e163 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.35 (br. s,1H); 10.55 (br. s,
1H); 8.44 (d, J ¼ 4.8 Hz, 1H); 8.24 (dd, J ¼ 7.1 and 2.1 Hz, 1H); 8.10
(dd, J ~ 1.5 and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.8 and 2.1 Hz, 1H);
8.01 (s, 1H); 7.91 (dm, J ¼ 8.2 Hz, 1H); 7.76 (dd, J ¼ 7.9 and 1.5 Hz,
1H); 7.71 (d, J ¼ 4.8 Hz, 1H); 7.62 (dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.60
(dd, J ¼ 8.2 and 7.5 Hz, 1H); 7.56 (dd, J ~ 7.0 and 1.5 Hz, 1H); 7.49
(dm, J ~ 7.5 Hz, 1H); 7.48 (dd, J ¼ 7.9 and 7.0 Hz, 1H).
4.2.12.8. 3-chloro-N-(3-{8-[(3-chloro-4-methylbenzoyl)amino]imi-
dazo[1,2-a]pyrazin-3-yl}phenyl)-4-fluorobenzamide
(14h).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
Yield: 22%. Mp 221e222 ꢀC.
LCMS (ESI) m/z 554.2 (M þ H)þ; 552.2 (MꢂH)ꢂ; calculated:
553.0; Rt: 4.37 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.06 (br, 1H); 10.55 (br. s,
1H); 8.49 (br, 1H); 8.25 (dd, J ¼ 7.2 and 2.1 Hz, 1H); 8.12 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.11 (d, J ~ 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.7 and
2.1 Hz, 1H); 7.99 (s, 1H); 7.95 (dd, J ~ 8.0 and 1.5 Hz, 1H); 7.92 (dm,
J ~ 8.0 Hz, 1H); 7.81 (br, 1H); 7.63 (dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.60
(dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.56 (d, J ¼ 8.0 Hz, 1H); 7.50 (dm,
J ¼ 7.5 Hz, 1H); 2.44 (s, 3H).
4.2.12.4. 3,4-Dichloro-N-(3-{3-[(3-chloro-4-fluorobenzoyl)amino]
phenyl}imidazo[1,2-a]pyrazin-8-yl)benzamide (14d). Method A was
used for the isolation of the title compound.
Yield: 77%. Mp 194e196 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.22 (br, 1H); 10.55 (br. s,
LCMS (ESI) m/z 534.3 (M þ H)þ; 532.3 (MꢂH)ꢂ; calculated:
533.1; Rt: 4.45 min.
1H); 8.51 (br, 1H); 8.31 (d, J ~ 1.5 Hz, 1H); 8.24 (dd, J ¼ 7.1 and 2.1 Hz,

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4.2.12.9. N-(3-{8-[(4-bromobenzoyl)amino]imidazo[1,2-a]pyrazin-3-
yl}phenyl)-3-chloro-4-fluorobenzamide (14i). Method A was used
for the isolation of the product and it was further purified by pre-
parative TLC (eluent: chloroform: methanol ¼ 9: 1) to give the title
compound.
2.1 Hz, 1H); 8.12 (s, 1H); 8.03 (ddd, J ¼ 8.8, 4.6 and 2.1 Hz, 1H); 8.00
(s, 1H); 7.92 (dm, J ¼ 8.1 Hz, 1H); 7.85 (br, 1H); 7.73 (dd, J ¼ 10.0 and
9.4 Hz, 1H); 7.63 (dd, J ¼ 9.0 and 8.8 Hz, 1H); 7.60 (dd, J ¼ 8.1 and
7.8 Hz, 1H); 7.51 (dm, J ¼ 7.8 Hz, 1H).
LCMS (ESI) m/z 572.3 (M þ H)þ; 570.3 (MꢂH)ꢂ; calculated:
571.1; Rt: 4.46 min.
Yield: 26%. Mp 220e221 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.09 (br, 1H); 10.55 (br. s,
1H); 8.49 (br, 1H); 8.24 (dd, J ¼ 7.2 and 2.1 Hz, 1H); 8.11 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.6 and 2.1 Hz, 1H); 8.01 (dm,
J ~ 8.0 Hz, 2H); 7.99 (s, 1H); 7.92 (dm, J ¼ 8.1 Hz, 1H); 7.79 (br, 1H);
7.78 (dm, J ~ 8.0 Hz, 2H); 7.63 (dd, J ¼ 9.0 and 8.8 Hz, 1H); 7.60 (dd,
J ¼ 8.1 and 7.8 Hz, 1H); 7.50 (dm, J ¼ 7.8 Hz, 1H).
4.2.12.14. 3-chloro-N-[3-(8-{[4-chloro-3-(trifluoromethyl)benzoyl]
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]-4-fluorobenzamide (14n).
Method B was used for the isolation of the title compound.
Yield: 81%. Mp 236e238 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.40 (br, 1H); 10.55 (br. s,
LCMS (ESI) m/z 564.3 (M þ H)þ; 562.2 (MꢂH)ꢂ; calculated:
563.0; Rt: 4.31 min.
1H); 8.54 (br, 1H); 8.51 (br, 1H); 8.34 (br, 1H); 8.24 (dd, J ¼ 7.2 and
2.1 Hz, 1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.7
and 2.1 Hz, 1H); 8.01 (s, 1H); 7.95 (dd, J ~ 8.5 and 1.5 Hz, 1H); 7.92
(dm, J ~ 8.0 Hz, 1H); 7.85 (br, 1H); 7.62 (dd, J ¼ 9.3 and 8.8 Hz, 1H);
7.61 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.50 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 588.3 (M þ H)þ; 586.3 (MꢂH)ꢂ; calculated:
587.1; Rt: 4.63 min.
4.2.12.10. 3-chloro-4-Fluoro-N-[3-(8-{[3-(trifluoromethyl)benzoyl]
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide
(14j).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
Yield: 28%. Mp 134e136 ꢀC.
4.2.12.15. 3-chloro-4-Fluoro-N-[3-(8-{[3-(trifluoromethoxy)benzoyl]
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.37 (br, 1H); 10.55 (br. s,
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide
Method A was used for the isolation of the title compound.
Yield: 55%. Mp 159e160 ꢀC.
(14o).
1H); 8.50 (br, 1H); 8.42 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.37 (dm,
J ¼ 7.5 Hz, 1H); 8.24 (dd, J ¼ 7.2 and 2.4 Hz, 1H); 8.12 (dd, J ~ 1.5 and
1.5 Hz, 1H); 8.04 (ddd, J ¼ 8.8, 4.6 and 2.4 Hz, 1H); 8.02 (dm,
J ~ 8.0 Hz,1H); 8.00 (s,1H); 7.92 (dm, J ¼ 8.4 Hz,1H); 7.83 (dd, J ¼ 8.0
and 7.5 Hz, 1H); 7.80 (br, 1H); 7.63 (dd, J ¼ 9.0 and 8.8 Hz, 1H); 7.61
(dd, J ¼ 8.4 and 7.8 Hz, 1H); 7.51 (d, J ¼ 7.8 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.20 (br, 1H); 10.56 (br. s,
1H); 8.53 (br,1H); 8.24 (dd, J ¼ 7.2 and 2.1 Hz,1H); 8.13 (br,1H); 8.12
(dd, J ~ 1.5 and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.7 and 2.1 Hz, 1H);
8.00 (s, 1H); 7.92 (dm, J ¼ 8.4 Hz, 1H); 7.83 (br, 1H); 7.73 (dd, J ¼ 8.1
and 7.6 Hz, 1H); 7.68 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.67 (dm, J ~ 8.1 Hz,
1H); 7.63 (dd, J ¼ 9.3 and 8.8 Hz, 1H); 7.61 (dd, J ¼ 8.4 and 7.8 Hz,
1H); 7.51 (dm, J ¼ 7.8 Hz, 1H).
LCMS (ESI) m/z 554.3 (M þ H)þ; 552.4 (MꢂH)ꢂ; calculated:
553.1; Rt: 4.39 min.
4.2.12.11. 3-chloro-4-Fluoro-N-[3-(8-{[4-(trifluoromethyl)benzoyl]
LCMS (ESI) m/z 570.4 (M þ H)þ; 568.4 (MꢂH)ꢂ; calculated:
569.1; Rt: 4.47 min.
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide
(14k).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
4.2.12.16. 3-chloro-4-Fluoro-N-[3-(8-{[4-(trifluoromethoxy)benzoyl]
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide
Method A was used for the isolation of the title compound.
Yield: 45%. Mp 182e183 ꢀC.
(14p).
Yield: 39%. Mp 184e186 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.32 (br, 1H); 10.55 (br. s,
1H); 8.49 (br, 1H); 8.26 (dm, J ~ 8.0 Hz, 2H); 8.25 (dd, J ~ 7.0 and
2.0 Hz, 1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.6
and 2.0 Hz, 1H); 8.00 (s, 1H); 7.95 (dm, J ~ 8.0 Hz, 2H); 7.92 (dm,
J ~ 8.0 Hz, 1H); 7.81 (br. d, J ~4.5 Hz, 1H); 7.63 (dd, J ¼ 9.0 and 8.8 Hz,
1H); 7.61 (dd, J ¼ 8.0 and 7.8 Hz, 1H); 7.51 (dm, J ¼ 7.8 Hz, 1H).
LCMS (ESI) m/z 554.3 (M þ H)þ; 552.3 (MꢂH)ꢂ; calculated:
553.1; Rt: 4.39 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.09 (br, 1H); 10.55 (br. s,
1H); 8.52 (br, 1H); 8.24 (dd, J ¼ 7.1 and 2.1 Hz, 1H); 8.19 (dm,
J ¼ 8.0 Hz, 2H); 8.12 (dd, J ~ 1.5 and 1.5 Hz,1H); 8.03 (ddd, J ¼ 8.8, 4.6
and 2.1 Hz, 1H); 7.99 (s, 1H); 7.92 (dm, J ¼ 8.0 Hz, 1H); 7.83 (br, 1H);
7.63 (dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.61 (dd, J ¼ 8.0 and 7.5 Hz, 1H);
7.56 (dm, J ¼ 8.0 Hz, 2H); 7.50 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 570.3 (M þ H)þ; 568.3 (MꢂH)ꢂ; calculated:
569.1; Rt: 4.45 min.
4.2.12.12. N-[3-(8-{[3,5-bis(trifluoromethyl)benzoyl]amino}imidazo
[1,2-a]pyrazin-3-yl)phenyl]-3-chloro-4-fluorobenzamide
Method A was used for the isolation of the title compound.
Yield: 27%. Mp 193e195 ꢀC.
(14l).
4.2.12.17. 3-chloro-N-(3-{8-[(3,5-dimethylbenzoyl)amino]imidazo
[1,2-a]pyrazin-3-yl}phenyl)-4-fluorobenzamide (14q). Method
A
was used for the isolation of the product and it was further purified
by preparative TLC (eluent: chloroform: methanol ¼ 9: 1) to give
the title compound.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.79 (br, 1H); 10.55 (br. s,
1H); 8.71 (d, J ~ 1.0 Hz, 2H); 8.47 (br, 1H); 8.42 (t, J ~ 1.0 Hz, 1H); 8.24
(dd, J ¼ 6.8 and 2.2 Hz, 1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.04
(ddd, J ¼ 8.8, 4.6 and 2.2 Hz, 1H); 8.02 (s, 1H); 7.92 (dm, J ¼ 8.0 Hz,
1H); 7.79 (br, 1H); 7.62 (dd, J ¼ 9.0 and 8.8 Hz, 1H); 7.61 (dd, J ¼ 8.0
and 7.8 Hz, 1H); 7.51 (dm, J ¼ 7.8 Hz, 1H).
Yield: 24%. Mp 245e247 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.74 (br, 1H); 10.55 (br. s,
1H); 8.49 (br, 1H); 8.24 (dd, J ¼ 7.2 and 2.1 Hz, 1H); 8.11 (dd, J ~ 1.5
and 1.5 Hz, 1H); 8.03 (ddd, J ¼ 8.8, 4.7 and 2.1 Hz, 1H); 7.99 (s, 1H);
7.92 (d, J ¼ 8.2 Hz,1H); 7.81 (d, J ~ 4.5 Hz,1H); 7.68 (d, J ~ 1.5 Hz, 2H);
7.63 (dd, J ¼ 9.2 and 8.8 Hz, 1H); 7.60 (dd, J ¼ 8.2 and 7.6 Hz, 1H);
7.50 (dm, J ¼ 7.6 Hz, 1H); 7.28 (t, J ~ 1.5 Hz, 1H); 2.38 (s, 6H).
LCMS (ESI) m/z 514.3 (M þ H)þ; 512.4 (MꢂH)ꢂ; calculated:
513.1; Rt: 4.37 min.
LCMS (ESI) m/z 622.3 (M þ H)þ; 620.3 (MꢂH)ꢂ; calculated:
621.1; Rt: 4.83 min.
4.2.12.13. 3-chloro-4-Fluoro-N-[3-(8-{[4-fluoro-3-(trifluoromethyl)
benzoyl]amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide (14m).
Method A was used for the isolation of the title compound.
Yield: 13%. Mp 237e238 ꢀC.
4.2.13. General procedure for the preparation of compounds 15a-
15p
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.34 (br, 1H); 10.55 (br. s,
1H); 8.54 (br, 1H); 8.47 (br, 1H); 8.44 (br, 1H); 8.24 (dd, J ¼ 7.5 and
A mixture of compound 13o (100 mg, 0.23 mmol), pyridine

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(2 ml), N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydro-
J ~ 7.5 Hz, 1H).
chloride (111 mg, 0.58 mmol) and the benzoic acid derivative
LCMS (ESI) m/z 604.2 (M þ H)þ; 602.3 (MꢂH)ꢂ; calculated:
(0.58 mmol) was stirred at 70 ꢀC for 6 h.
603.0; Rt: 4.95 min.
Method A: The solvent was evaporated and the residue was
taken up in chloroform. The organic layer was washed with water
(2ꢁ), dried over sodium sulphate, filtered and concentrated under
reduced pressure. The crude product was triturated with diiso-
propyl ether, filtered and washed with acetonitrile to give the
desired products.
Method B: The solvent was evaporated. The residue was tritu-
rated with diisopropyl ether, filtered and washed with acetonitrile
to give the desired products.
4.2.13.5. 3-chloro-N-[3-(3-{[4-chloro-3-(trifluoromethyl)benzoyl]
amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]-4-fluorobenzamide (15e).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
Yield: 18%. Mp ~150 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.15 (br, 1H); 10.70 (br. s,
1H); 8.48 (br, 1H); 8.42 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.5 and
1.8 Hz, 1H); 8.29 (dd, J ~ 6.5 and 1.5 Hz, 1H); 8.13 (dd, J ~ 1.5 and
1.5 Hz, 1H); 8.10 (br, 1H); 8.00 (s, 1H); 7.95 (d, J ¼ 8.5 Hz, 1H); 7.91
(dm, J ¼ 8.0 Hz, 1H); 7.80 (br. 1H); 7.62 (dd, J ~ 8.0 and 7.5 Hz, 1H);
7.61 (dd, J ~ 9.0 and 8.5 Hz, 1H); 7.52 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 588.2 (M þ H)þ; 586.3 (MꢂH)ꢂ; calculated:
587.1; Rt: 4.62 min.
4.2.13.1. N-{3-[8-(benzoylamino)imidazo[1,2-a]pyrazin-3-yl]
phenyl}-4-chloro-3-(trifluoromethyl)benzamide (15a). Method
A
was used for the isolation of the product and it was further purified
by preparative TLC (eluent: chloroform: methanol ¼ 9: 1) to give
the title compound.
Yield: 34%. Mp 274e275 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.89 (br, 1H); 10.73 (br. s,
4.2.13.6. 3,5-Dichloro-N-[3-(3-{[4-chloro-3-(trifluoromethyl)ben-
zoyl]amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]-4-fluorobenzamide
(15f). Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
1H); 8.51 (br, 1H); 8.43 (d, J ¼ 1.5 Hz, 1H); 8.31 (dd, J ¼ 8.4 and
1.5 Hz,1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz,1H); 8.07 (dm, J ¼ 7.5 Hz, 2H);
7.99 (s, 1H); 7.96 (d, J ¼ 8.4 Hz, 1H); 7.91 (dm, J ¼ 8.1 Hz, 1H); 7.83
(br, 1H); 7.65 (tt, J ~ 7.5 and 1.5 Hz, 1H); 7.62 (dd, J ¼ 8.1 and 7.5 Hz,
1H); 7.58 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.53 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 536.3 (M þ H)þ; 534.3 (MꢂH)ꢂ; calculated:
535.1; Rt: 4.28 min.
Yield: 18%. Mp ~150 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.30 (br, 1H); 10.73 (br. s,
1H); 8.45 (br, 1H); 8.42 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.3 and
1.8 Hz, 1H); 8.27 (d, J ¼ 6.6 Hz, 2H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H);
8.01 (s,1H); 7.96 (d, J ¼ 8.3 Hz,1H); 7.91 (dm, J ~ 8.0 Hz,1H); 7.78 (br,
1H); 7.62 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.53 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 622.2 (M þ H)þ; 620.2 (MꢂH)ꢂ; calculated:
621.0; Rt: 4.96 min.
4.2.13.2. 4-chloro-N-(3-{8-[(3,5-difluorobenzoyl)amino]imidazo[1,2-
a]pyrazin-3-yl}phenyl)-3-(trifluoromethyl)benzamide
Method A was used for the isolation of the title compound.
Yield: 64%. Mp 221e223 ꢀC.
(15b).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.20 (br, 1H); 10.73 (br. s,
1H); 8.53 (br, 1H); 8.43 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.5 and
1.8 Hz, 1H); 8.13 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.01 (s, 1H); 7.96 (d,
J ¼ 8.5 Hz, 1H); 7.91 (d, J ¼ 8.1 Hz, 1H); 7.83 (br, 1H); 7.77 (dm,
J ¼ 8.4 Hz, 2H); 7.62 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.58 (tm, J ~ 8.2 Hz,
1H); 7.52 (dm, J ¼ 7.5 Hz, 1H).
4.2.13.7. 3-chloro-N-[3-(3-{[4-chloro-3-(trifluoromethyl)benzoyl]
amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]-4-methylbenzamide
(15g). Method A was used for the isolation of the product and it
was further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
LCMS (ESI) m/z 572.2 (M þ H)þ; 570.2 (MꢂH)ꢂ; calculated:
571.1; Rt: 4.52 min.
Yield: 32%. Mp ~140 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.02 (br, 1H); 10.72 (br. s,
1H); 8.53 (br, 1H); 8.42 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.4 and
1.8 Hz, 1H); 8.09e8.15 (ovl. m, 2H); 8.00 (s, 1H); 7.96 (d, J ¼ 8.4 Hz,
1H); 7.94 (br, 1H); 7.91 (dm, J ¼ 8.0 Hz, 1H); 7.84 (br, 1H); 7.62 (dd,
J ¼ 8.0 and 7.5 Hz, 1H); 7.56 (dm, J ~ 7.5 Hz, 1H); 7.52 (dm, J ~ 7.5 Hz,
1H); 2.44 (s, 3H).
4.2.13.3. 3,4-Dichloro-N-[3-(3-{[4-chloro-3-(trifluoromethyl)ben-
zoyl]amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]benzamide
(15c).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
LCMS (ESI) m/z 584.2 (M þ H)þ; 582.3 (MꢂH)ꢂ; calculated:
583.1; Rt: 4.74 min.
Yield: 11%. Mp ~140 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.30 (br, 1H); 10.73 (s, 1H);
8.48 (br, 1H); 8.43 (d, J ~ 1.5 Hz, 1H); 8.31 (d, J ~ 1.5 Hz, 1H); 8.30 (dd,
J ~ 8.5 and 1.5 Hz, 1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.04 (dd,
J ~ 8.5 and 1.5 Hz, 1H); 8.00 (s, 1H); 7.96 (d, J ¼ 8.5 Hz, 1H); 7.91 (dm,
J ¼ 8.0 Hz, 1H); 7.85 (d, J ¼ 8.5 Hz, 1H); 7.80 (br, 1H); 7.62 (dd, J ¼ 8.0
and 7.5 Hz, 1H); 7.52 (dm, J ¼ 7.5 Hz, 1H).
4.2.13.8. N-(3-{8-[(4-bromobenzoyl)amino]imidazo[1,2-a]pyrazin-3-
yl}phenyl)-4-chloro-3-(trifluoromethyl)benzamide
(15h).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
LCMS (ESI) m/z 604.2 (M þ H)þ; 602.2 (MꢂH)ꢂ; calculated:
603.0; Rt: 4.83 min.
Yield: 39%. Mp 227e228 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.05 (br, 1H); 10.73 (br. s,
1H); 8.49 (br, 1H); 8.42 (d, J ¼ 1.9 Hz, 1H); 8.30 (dd, J ¼ 8.4 and
1.9 Hz, 1H); 8.12 (dd, J ¼ 1.5 and 1.5 Hz, 1H); 8.01 (dm, J ¼ 8.5 Hz,
2H); 7.99 (s, 1H); 7.96 (d, J ¼ 8.4 Hz, 1H); 7.91 (dm, J ¼ 8.1 Hz, 1H);
7.80 (br, 1H); 7.78 (dm, J ¼ 8.5 Hz, 2H); 7.62 (dd, J ¼ 8.1 and 7.8 Hz,
1H); 7.52 (dm, J ¼ 7.8 Hz, 1H).
4.2.13.4. 4-chloro-N-(3-{8-[(3,5-dichlorobenzoyl)amino]imidazo[1,2-
a]pyrazin-3-yl}phenyl)-3-(trifluoromethyl)benzamide
Method A was used for the isolation of the title compound.
Yield: 59%. Mp 244e246 ꢀC.
(15d).
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.25 (br, 1H); 10.73 (br. s,
LCMS (ESI) m/z 614.2 (M þ H)þ; 612.2 (MꢂH)ꢂ; calculated:
613.0; Rt: 4.60 min.
1H); 8.54 (br, 1H); 8.42 (d, J ~ 1.5 Hz,1H); 8.30 (dd, J ~ 8.5 and 1.5 Hz,
1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.07 (d, J ~ 1.5 Hz, 2H); 8.01 (s,
1H); 7.96 (d, J ~ 8.5 Hz, 1H); 7.92 (t, J ~ 1.5 Hz, 1H); 7.91 (dm,
J ~ 8.0 Hz, 1H); 7.84 (br, 1H); 7.62 (dd, J ~ 8.0 and 7.5 Hz, 1H); 7.52 (d,
4.2.13.9. 4-chloro-3-(trifluoromethyl)-N-[3-(8-{[3-(trifluoromethyl)
benzoyl]amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide (15i).

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638
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
LCMS (ESI) m/z 638.1 (M þ H)þ; 636.1 (MꢂH)ꢂ; calculated:
637.1; Rt: 4.90 min.
Yield: 36%. Mp ~130 ꢀC decomp.
4.2.13.14. 4-chloro-N-[3-(8-{[3-(trifluoromethoxy)benzoyl]amino}
imidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(trifluoromethyl)benzamide
(15n). Method A was used for the isolation of the title compound.
Yield: 15%. Mp ~130 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.31 (br, 1H); 10.73 (br. s,
1H); 8.51 (br, 1H); 8.43 (d, J ~ 2.0 Hz, 1H); 8.42 (dd, J ~ 1.5 and 1.5 Hz,
1H); 8.36 (dm, J ¼ 7.5 Hz, 1H); 8.31 (dd, J ¼ 8.5 and 2.0 Hz, 1H); 8.13
(dd, J ~ 1.5 and 1.5 Hz,1H); 8.03 (dm, J ~ 7.5 Hz,1H); 8.01 (s,1H); 7.96
(d, J ¼ 8.5 Hz, 1H); 7.92 (dm, J ¼ 8.1 Hz, 1H); 7.83 (br, 1H); 7.82 (dd,
J ¼ 7.5 and 7.5 Hz, 1H); 7.62 (dd, J ¼ 8.1 and 7.8 Hz, 1H); 7.53 (d,
J ¼ 7.8 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.21 (br, 1H); 10.74 (br. s,
1H); 8.54 (br, 1H); 8.43 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.5 and
1.8 Hz, 1H); 8.08e8.16 (ovl. m, 2H); 8.02 (ovl. m, 1H); 8.01 (s, 1H);
7.96 (d, J ¼ 8.5 Hz, 1H); 7.92 (dm, J ¼ 8.1 Hz, 1H); 7.84 (br, 1H); 7.72
(dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.67 (dm, J ~ 8.0 Hz, 1H); 7.62 (dd, J ¼ 8.1
and 7.5 Hz, 1H); 7.53 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 604.3 (M þ H)þ; 602.3 (MꢂH)ꢂ; calculated:
603.1; Rt: 4.67 min.
LCMS (ESI) m/z 620.3 (M þ H)þ; 618.4 (MꢂH)ꢂ; calculated:
619.1; Rt: 4.74 min.
4.2.13.10. 4-chloro-3-(trifluoromethyl)-N-[3-(8-{[4-(trifluoromethyl)
benzoyl]amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]benzamide (15j).
Method A was used for the isolation of the title compound.
Yield: 57%. Mp 183e185 ꢀC.
4.2.13.15. 4-chloro-N-[3-(8-{[4-(trifluoromethoxy)benzoyl]amino}
imidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(trifluoromethyl)benzamide
(15o). Method A was used for the isolation of the product and it
was further purified by preparative TLC (eluent: chloroform:
methanol ¼ 95: 5) to give the title compound.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.23 (br, 1H); 10.73 (br. s,
1H); 8.53 (br, 1H); 8.42 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.3 and
1.8 Hz, 1H); 8.25 (br. dm, J ~8.5 Hz, 2H); 8.13 (dd, J ~ 1.5 and 1.5 Hz,
1H); 8.01 (s, 1H); 7.96 (d, J ¼ 8.3 Hz, 1H); 7.95 (dm, J ¼ 8.5 Hz, 2H);
7.92 (dm, J ~ 8.0 Hz, 1H); 7.84 (br, 1H); 7.62 (dd, J ¼ 8.0 and 7.5 Hz,
1H); 7.53 (dm, J ¼ 7.5 Hz, 1H).
Yield: 39%. Mp ~130 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.09 (br, 1H); 10.73 (br. s,
LCMS (ESI) m/z 604.3 (M þ H)þ; 602.3 (MꢂH)ꢂ; calculated:
603.1; Rt: 4.67 min.
1H); 8.52 (br, 1H); 8.42 (d, J ¼ 1.8 Hz, 1H); 8.30 (dd, J ¼ 8.4 and
1.8 Hz,1H); 8.19 (dm, J ¼ 7.8 Hz, 2H); 8.13 (dd, J ~ 1.5 and 1.5 Hz,1H);
8.00 (s, 1H); 7.96 (d, J ¼ 8.4 Hz, 1H); 7.91 (dm, J ¼ 8.0 Hz, 1H); 7.83
(br, 1H); 7.62 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.56 (dm, J ¼ 7.8 Hz, 2H);
7.53 (dm, J ¼ 7.5 Hz, 1H).
4.2.13.11. N-[3-(8-{[3,5-bis(trifluoromethyl)benzoyl]amino}imidazo
[1,2-a]pyrazin-3-yl)phenyl]-4-chloro-3-(trifluoromethyl)benzamide
(15k). Method A was used for the isolation of the title compound.
Yield: 25%. Mp 223e224 ꢀC.
LCMS (ESI) m/z 620.3 (M þ H)þ; 618.3 (MꢂH)ꢂ; calculated:
619.1; Rt: 4.72 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.70 (br, 1H); 10.73 (br. s,
1H); 8.71 (d, J ~ 1.5 Hz, 2H); 8.48 (br,1H); 8.43 (t, J ~ 1.5 Hz,1H); 8.42
(d, J ~ 2.0 Hz, 2H); 8.30 (dd, J ¼ 8.4 and 2.0 Hz, 1H); 8.13 (dd, J ~ 1.5
and 1.5, 1H); 8.02 (s, 1H); 7.96 (d, J ¼ 8.4 Hz, 1H); 7.91 (dm,
J ¼ 8.1 Hz, 1H); 7.80 (br, 1H); 7.62 (dd, J ¼ 8.1 and 7.5 Hz, 1H); 7.53
(dm, J ¼ 7.5 Hz, 1H).
4.2.13.16. 4-chloro-N-(3-{8-[(3,5-dimethylbenzoyl)amino]imidazo
[1,2-a]pyrazin-3-yl}phenyl)-3-(trifluoromethyl)benzamide
(15p).
Method A was used for the isolation of the product and it was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
LCMS (ESI) m/z 672.3 (M þ H)þ; 670.3 (MꢂH)ꢂ; calculated:
671.1; Rt: 5.07 min.
Yield: 22%. Mp 235e236 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.72 (br. s, 2H); 8.51 (d,
J ~ 4.5 Hz, 1H); 8.43 (d, J ~ 1.5 Hz, 1H); 8.30 (dd, J ¼ 8.4 and 1.5 Hz,
1H); 8.12 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.99 (s, 1H); 7.96 (d, J ¼ 8.4 Hz,
1H); 7.91 (dm, J ¼ 8.7 Hz, 1H); 7.83 (d, J ~ 4.5 Hz, 1H); 7.68 (d,
J ~ 1.5 Hz, 2H); 7.62 (dd, J ¼ 8.7 and 7.2 Hz, 1H); 7.52 (dm, J ¼ 7.2 Hz,
1H); 7.28 (t, J ~ 1.5 Hz, 1H); 2.38 (s, 6H).
4.2.13.12. 4-chloro-N-[3-(8-{[4-fluoro-3-(trifluoromethyl)benzoyl]
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(trifluoromethyl)benza-
mide (15l). Method A was used for the isolation of the title
compound.
Yield: 36%. Mp 211e212 ꢀC.
LCMS (ESI) m/z 564.3 (M þ H)þ; 562.4 (MꢂH)ꢂ; calculated:
563.1; Rt: 4.68 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.35 (br, 1H); 10.73 (br. s,
1H); 8.53 (br, 1H); 8.44e8.52 (ovl. m, 2H); 8.42 (d, J ¼ 2.0 Hz, 1H);
8.30 (dd, J ¼ 8.2 and 2.0 Hz,1H); 8.13 (dd, J ~ 1.5 and 1.5 Hz,1H); 8.01
(s, 1H); 7.96 (d, J ¼ 8.2 Hz, 1H); 7.91 (dm, J ¼ 8.2 Hz, 1H); 7.84 (br,
1H); 7.73 (dd, J ¼ 9.4 and 9.0 Hz, 1H); 7.62 (dd, J ¼ 8.2 and 7.5 Hz,
1H); 7.53 (dm, J ¼ 7.5 Hz, 1H).
4.2.14. General procedure for the preparation of compounds 16a-
16l
A mixture of compound 12 (100 mg, 0.44 mmol), anhydrous
pyridine (2 ml) and the aryl isocyanate (0.44 mmol) was stirred at
room temperature for 2 h. The solvent was evaporated. The residue
was triturated with ethanol, filtered and washed with acetonitrile
and diisopropyl ether to give the desired products.
LCMS (ESI) m/z 622.2 (M þ H)þ; 620.2 (MꢂH)ꢂ; calculated:
621.1; Rt: 4.73 min.
4.2.13.13. 4-chloro-N-[3-(8-{[4-chloro-3-(trifluoromethyl)benzoyl]
amino}imidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(trifluoromethyl)benza-
mide (15m). Method B was used for the isolation of the title
compound.
4.2.14.1. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-
phenylurea (16a). Yield: 66%. Mp 164e166 ꢀC.
Yield: 61%. Mp 219e221 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 8.85 (br. s, 1H); 8.73 (br. s,
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.40 (br, 1H); 10.74 (s, 1H);
1H); 7.79 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.78 (d, J ~ 4.5 Hz, 1H); 7.71 (s,
1H); 7.42e7.51 (ovl. m, 4H); 7.30 (d, J ~ 4.5 Hz, 1H); 7.27 (ddm, J ~ 7.5
and 7.5 Hz, 2H); 7.25 (dm, J ~ 7.5 Hz, 1H); 6.98 (tt, J ¼ 7.2 and 1.5 Hz,
1H); 6.95 (br. s, 2H).
8.55 (br,1H); 8.50 (br,1H); 8.43 (d, J ¼ 1.8 Hz,1H); 8.34 (br,1H); 8.30
(dd, J ¼ 8.3 and 1.8 Hz, 1H); 8.13 (dd, J ~ 1.5 and 1.5 Hz, 1H); 8.01 (s,
1H); 7.96 (d, J ¼ 8.3 Hz, 1H); 7.95 (d, J ~ 8.5 Hz, 1H); 7.92 (dm,
J ~ 8.0 Hz, 1H); 7.85 (br, 1H); 7.62 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.53
(dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 345.3 (M þ H)þ; 343.3 (MꢂH)ꢂ; calculated:
344.1; Rt: 2.57 min.

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4.2.14.2. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(2,4-
difluorophenyl)urea (16b). Yield: 36%. Mp 152e153 ꢀC.
1H NMR (300 MHz, DMSO-d6)
ppm 9.21 (br. s, 1H); 8.56 (br. s,
(br. s, 2H).
LCMS (ESI) m/z 413.3 (M þ H)þ; 411.4 (MꢂH)ꢂ; calculated: 412.1;
d
Rt: 3.14 min.
1H); 8.07 (ddd, J ¼ 9.2, 9.1 and 6.2 Hz, 1H); 7.79 (dd, J ~ 1.5 and
1.5 Hz, 1H); 7.77 (d, J ¼ 4.8 Hz, 1H); 7.71 (s, 1H); 7.43e7.50 (ovl. m,
2H); 7.31 (ddd, J ~ 11.5, 9.2 and 2.9 Hz, 1H); 7.29 (d, J ¼ 4.8 Hz, 1H);
7.26 (m, 1H); 7.05 (dddd, J ~ 9.1, 8.5, 2.9 and 1.5 Hz, 1H); 6.96 (br. s,
2H).
4.2.14.9. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-[3,5-
bis(trifluoromethyl)phenyl]urea (16i). It was further purified by
preparative TLC (eluent: chloroform: methanol ¼ 9: 1) to give the
title compound.
LCMS (ESI) m/z 381.3 (M þ H)þ; 379.3 (MꢂH)ꢂ; calculated:
380.1; Rt: 2.73 min.
Yield: 36%. Mp ~150 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.48 (br. s, 1H); 9.18 (br, s,
1H); 8.15 (d, J ~ 1.0 Hz, 2H); 7.78 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.77 (d,
J ~ 4.5 Hz, 1H); 7.71 (s, 1H); 7.65 (t, J ~ 1.0 Hz, 1H); 7.55 (dm,
J ¼ 8.0 Hz, 1H); 7.49 (dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.30 (dm, J ~ 7.5 Hz,
1H); 7.29 (d, J ~ 4.5 Hz, 1H); 6.95 (br. s, 2H).
4.2.14.3. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(3-
chlorophenyl)urea (16c). Yield: 20%. Mp 200e202 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 8.97 (br. s, 1H); 8.95 (br. s,
1H); 7.79 (dd, J ~ 1.5 and 1.5 Hz,1H); 7.78 (d, J ~ 4.5 Hz,1H); 7.72 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.71 (s, 1H); 7.43e7.51 (ovl. m, 2H); 7.24e7.33
(ovl. m, 4H); 7.03 (m, 1H); 6.96 (br. s, 2H).
LCMS (ESI) m/z 481.3 (M þ H)þ; 479.3 (MꢂH)ꢂ; calculated:
480.1; Rt: 3.52 min.
LCMS (ESI) m/z 379.2 (M þ H)þ; 377.3 (MꢂH)ꢂ; calculated:
378.1; Rt: 2.94 min.
4.2.14.10. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-[4-
chloro-3-(trifluoromethyl)phenyl]urea
(16j). Yield:
53%.
Mp
188e189 ꢀC.
4.2.14.4. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(2,3-
1H NMR (300 MHz, DMSO-d6)
d ppm 9.24 (br. s, 1H); 9.03 (br. s,
dichlorophenyl)urea (16d). Yield: 66%. Mp 161e163 ꢀC.
1H); 8.10 (d, J ¼ 2.4 Hz, 1H); 7.78 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.77 (d,
J ¼ 4.5 Hz, 1H); 7.71 (s, 1H); 7.68 (dd, J ¼ 8.6 and 2.4 Hz, 1H); 7.62 (d,
J ¼ 8.6 Hz, 1H); 7.51 (dm, J ¼ 8.2 Hz, 1H); 7.48 (dd, J ¼ 8.2 and 7.2 Hz,
1H); 7.29 (d, J ¼ 4.5 Hz,1H); 7.28 (dm, J ¼ 7.2 Hz,1H); 6.96 (br. s, 2H).
LCMS (ESI) m/z 447.2 (M þ H)þ; 445.3 (MꢂH)ꢂ; calculated:
446.1; Rt: 3.33 min.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.67 (br. s, 1H); 8.53 (br. s,
1H); 8.16 (dd, J ¼ 7.5 and 1.8 Hz, 1H); 7.76e7.82 (ovl. m, 2H); 7.72 (s,
1H); 7.45e7.53 (ovl. m, 2H); 7.26e7.36 (ovl. m, 4H); 6.96 (br. s, 2H).
LCMS (ESI) m/z 413.3 (M þ H)þ; 411.3 (MꢂH)ꢂ; calculated: 412.1;
Rt: 3.14 min.
4.2.14.5. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(3-
4.2.14.11. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(4-
chloro-4-fluorophenyl)urea (16e). Yield: 64%. Mp 224e226 ꢀC.
methylphenyl)urea (16k). Yield: 48%. Mp 204e205 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 8.95 (br. s, 2H); 7.74e7.84
1H NMR (300 MHz, DMSO-d6)
d ppm 8.80 (br. s, 1H); 8.62 (br. s,
(ovl. m, 3H); 7.70 (s, 1H); 7.42e7.53 (ovl. m, 2H); 7.23e7.41 (ovl. m,
4H); 6.95 (br. s, 2H).
1H); 7.78 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.77 (d, J ¼ 4.8 Hz, 1H); 7.70 (s,
1H); 7.41e7.49 (ovl. m, 2H); 7.35 (dm, J ¼ 8.2 Hz, 2H); 7.29 (d,
J ¼ 4.8 Hz, 1H); 7.24 (m, 1H); 7.09 (dm, J ¼ 8.2 Hz, 2H); 6.95 (br. s,
2H); 2.24 (s, 3H).
LCMS (ESI) m/z 397.3 (M þ H)þ; 395.4 (MꢂH)ꢂ; calculated:
396.1; Rt: 2.98 min.
LCMS (ESI) m/z 359.3 (M þ H)þ; 357.3 (MꢂH)ꢂ; calculated:
358.2; Rt: 2.78 min.
4.2.14.6. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(4-
bromophenyl)urea (16f). Yield: 42%. Mp 234e235 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d
ppm 8.91 (br. s, 2H); 7.78 (dd,
4.2.14.12. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-(4-
J ~ 1.5 and 1.5 Hz,1H); 7.76 (d, J ¼ 4.8 Hz, 1H); 7.70 (s, 1H); 7.44e7.49
(ovl. m, 2H); 7.42e7.47 (ovl. m, 4H); 7.29 (d, J ¼ 4.8 Hz, 1H); 7.26 (m,
1H); 6.95 (br. s, 2H).
methoxyphenyl)urea (16l). Yield: 69%. Mp 191e193 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 8.78 (br. s, 1H); 8.54 (br. s,
1H); 7.78 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.77 (d, J ¼ 4.8 Hz, 1H); 7.70 (s,
1H); 7.41e7.52 (ovl. m, 2H); 7.36 (dm, J ¼ 9.0 Hz, 2H); 7.29 (d,
J ¼ 4.8 Hz, 1H); 7.22 (m, 1H); 6.96 (br. s, 2H); 6.87 (dm, J ¼ 9.0 Hz,
2H); 3.72 (s, 3H).
LCMS (ESI) m/z 423.3 (M þ H)þ; 421.3 (MꢂH)ꢂ; calculated:
422.0; Rt: 2.99 min.
4.2.14.7. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-[3-(tri-
LCMS (ESI) m/z 375.3 (M þ H)þ; 373.3 (MꢂH)ꢂ; calculated:
374.1; Rt: 2.52 min.
fluoromethyl)phenyl]urea (16g). Yield: 39%. Mp 204e206 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.12 (br. s, 1H); 8.98 (br. s,
1H); 8.00 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.78 (dd, J ~ 1.5 and 1.5 Hz,1H);
7.77 (d, J ¼ 4.8 Hz, 1H); 7.71 (s, 1H); 7.61 (dm, J ¼ 8.0 Hz, 1H); 7.53
(dd, J ~ 8.0 and 7.5 Hz, 1H); 7.51 (dm, J ~ 7.5 Hz, 1H); 7.48 (dd, J ~ 7.5
and 7.5 Hz,1H); 7.32 (dm, J ~ 7.5 Hz,1H); 7.29 (d, J ¼ 4.8 Hz,1H); 7.27
(dm, J ~ 7.5 Hz, 1H); 6.95 (br. s, 2H).
4.2.15. General procedure for the preparation of compounds
17ae17q
A mixture of compound 16b (100 mg, 0.26 mmol), pyridine
(2 ml), N-(3-dimethylaminopropyl)-N0-ethylcarbodiimide hydro-
chloride (126 mg, 0.66 mmol) and the benzoic acid derivative
(0.66 mmol) was stirred at 70 ꢀC for 6 h. The solvent was evapo-
rated and the residue was taken up in chloroform. The organic layer
was washed with water (2ꢁ), dried over sodium sulphate, filtered
and concentrated under reduced pressure. The crude product was
triturated with diisopropyl ether, filtered and washed with aceto-
nitrile to give the desired products.
LCMS (ESI) m/z 413.3 (M þ H)þ; 411.4 (MꢂH)ꢂ; calculated: 412.1;
Rt: 3.09 min.
4.2.14.8. 1-[3-(8-aminoimidazo[1,2-a]pyrazin-3-yl)phenyl]-3-[4-(tri-
fluoromethyl)phenyl]urea (16h). It was further purified by prepar-
ative TLC (eluent: chloroform: methanol ¼ 9: 1) to give the title
compound.
Yield: 38%. Mp 217e219 ꢀC.
4.2.15.1. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]benzamide (17a). Yield: 46%. Mp
204e206 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 9.18 (br. s, 1H); 8.99 (br. s,
1H); 7.80 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.79 (d, J ~ 4.5 Hz, 1H); 7.71 (s,
1H); 7.68 (dm, J ¼ 9.0 Hz, 2H); 7.64 (dm, J ¼ 9.0 Hz, 2H); 7.44e7.54
(ovl. m, 2H); 7.30 (d, J ~ 4.5 Hz, 1H); 7.28 (dm, J ~ 7.5 Hz, 1H); 6.95
1H NMR (300 MHz, DMSO-d6)
d
ppm 10.88 (br. s, 1H); 9.25 (s,
1H); 8.59 (br. s, 1H); 8.49 (d, J ¼ 4.5 Hz, 1H); 8.07 (ddd, J ¼ 9.3, 9.0

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and 6.3 Hz, 1H); 8.06 (dm, J ~ 7.5 Hz, 2H); 7.96 (s, 1H); 7.84 (dd,
J ~ 1.5 and 1.5 Hz, 1H); 7.81 (d, J ¼ 4.5 Hz, 1H); 7.64 (tt, J ~ 7.5 and
1.5 Hz, 1H); 7.58 (ddm, J ~ 7.5 and 7.5 Hz, 2H); 7.48e7.56 (ovl. m,
2H); 7.36 (dm, J ~ 7.5 Hz, 1H); 7.32 (ddd, J ¼ 11.5, 9.0 and 2.5 Hz,1H);
7.06 (dddd, J ¼ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
(dd, J ¼ 9.0 and 8.5 Hz, 1H); 7.47e7.56 (ovl. m, 2H); 7.35 (dm,
J ~ 7.5 Hz, 1H); 7.31 (ddd, J ~ 11.5, 9.0 and 2.5 Hz, 1H); 7.06 (dddd,
J ~ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
LCMS (ESI) m/z 537.3 (M þ H)þ; 535.3 (MꢂH)ꢂ; calculated:
536.1; Rt: 4.11 min.
LCMS (ESI) m/z 485.3 (M þ H)þ; 483.3 (MꢂH)ꢂ; calculated:
484.1; Rt: 3.70 min.
4.2.15.7. 3,5-Dichloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]
amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]-4-fluorobenzamide (17g).
Yield: 24%. Mp 197e199 ꢀC.
4.2.15.2. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-3,5-difluorobenzamide
(17b). Yield:
1H NMR (300 MHz, DMSO-d6)
d ppm 11.35 (br, 1H); 9.37 (br. s,
10%. Mp 229e231 ꢀC.
1H); 8.70 (br. s, 1H); 8.43 (br, 1H); 8.27 (d, J ¼ 6.6 Hz, 2H); 8.05 (ddd,
J ¼ 9.3, 9.0 and 6.3 Hz, 1H); 7.98 (s, 1H); 7.86 (dd, J ~ 1.5 and 1.5 Hz,
1H); 7.75 (br, 1H); 7.48e7.56 (ovl. m, 2H); 7.35 (dm, J ~ 7.5 Hz, 1H);
7.31 (ddd, J ¼ 11.5, 9.0 and 2.5 Hz, 1H); 7.06 (dddd, J ~ 9.0, 8.5, 2.5
and 1.5 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.17 (br, 1H); 9.26 (s, 1H);
8.60 (br. s, 1H); 8.48 (br, 1H); 8.06 (ddd, J ¼ 9.3, 9.0 and 6.3 Hz, 1H);
7.98 (s, 1H); 7.85 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.79 (br, 1H); 7.77 (dm,
J ~ 7.0 Hz, 2H); 7.58 (tt, J ~ 9.0 and 1.5 Hz, 1H); 7.48e7.58 (ovl. m,
2H); 7.35 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ¼ 11.5, 9.0 and 2.5 Hz, 1H);
7.06 (dddd, J ¼ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
LCMS (ESI) m/z 571.3 (M þ H)þ; 569.3 (MꢂH)ꢂ; calculated:
570.1; Rt: 4.49 min.
LCMS (ESI) m/z 521.3 (M þ H)þ; 519.3 (MꢂH)ꢂ; calculated:
520.1; Rt: 3.99 min.
4.2.15.8. 3-chloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}
phenyl)imidazo[1,2-a]pyrazin-8-yl]-4-methylbenzamide
(17h).
4.2.15.3. 2,3-Dichloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]
Yield: 44%. Mp 204e205 ꢀC.
amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]benzamide
(17c).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.02 (br, 1H); 9.26 (s, 1H);
Yield: 31%. Mp 187e189 ꢀC.
8.60 (br. s, 1H); 8.50 (br, 1H); 8.11 (d, J ~ 1.5 Hz, 1H); 8.07 (ddd,
J ¼ 9.3, 9.0 and 6.3 Hz, 1H); 7.97 (s, 1H); 7.94 (dd, J ~ 8.8 and 1.5 Hz,
1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.81 (br, 1H); 7.56 (d, J ¼ 8.8 Hz,
1H); 7.47e7.57 (ovl. m, 2H); 7.36 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd,
J ¼ 11.5, 9.0 and 2.5 Hz, 1H); 7.06 (dddd, J ¼ 9.0, 8.5, 2.5 and 1.5 Hz,
1H); 2.44 (s, 3H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.33 (br. s, 1H); 9.24 (s,
1H); 8.58 (br. s, 1H); 8.40 (d, J ¼ 4.8 Hz, 1H); 8.07 (ddd, J ¼ 9.3, 9.0
and 6.3 Hz, 1H); 7.98 (s, 1H); 7.82 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.76
(dd, J ¼ 7.8 and 1.0 Hz, 1H); 7.68 (d, J ¼ 4.8 Hz, 1H); 7.56 (dd, J ~ 7.5
and 1.0 Hz, 1H); 7.48e7.56 (ovl. m, 2H); 7.47 (dd, J ¼ 7.8 and 7.5 Hz,
1H); 7.34 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ~ 11.5, 9.0 and 2.5 Hz, 1H);
7.06 (dddd, J ~ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
LCMS (ESI) m/z 533.3 (M þ H)þ; 531.4 (MꢂH)ꢂ; calculated:
532.1; Rt: 4.23 min.
LCMS (ESI) m/z 553.3 (M þ H)þ; 551.2 (MꢂH)ꢂ; calculated:
552.1; Rt: 4.15 min.
4.2.15.9. 4-bromo-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}
phenyl)imidazo[1,2-a]pyrazin-8-yl]benzamide (17i). Yield: 45%. Mp
227e229 ꢀC.
4.2.15.4. 3,4-Dichloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]
amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]benzamide
(17d).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.03 (br, 1H); 9.26 (br. s,
Yield: 55%. Mp 190e193 ꢀC.
1H); 8.60 (br. s, 1H); 8.49 (br, 1H); 8.07 (ddd, J ¼ 9.3, 9.0 and 6.2 Hz,
1H); 8.00 (dm, J ¼ 8.2 Hz, 2H); 7.96 (s, 1H); 7.84 (dd, J ~ 1.5 and
1.5 Hz, 1H); 7.80 (br, 1H); 7.78 (dm, J ¼ 8.2 Hz, 2H); 7.45e7.59 (ovl.
m, 2H); 7.35 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ¼ 11.5, 8.7 and 2.5 Hz,
1H); 7.05 (dddd, J ¼ 9.0, 8.7, 2.5 and 1.5 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.22 (br, 1H); 9.28 (s, 1H);
8.62 (br. s, 1H); 8.47 (br, 1H); 8.31 (d, J ~ 1.5 Hz, 1H); 8.07 (ddd,
J ¼ 9.3, 9.0 and 6.3 Hz, 1H); 8.04 (dd, J ~ 8.0 and 1.5 Hz, 1H); 7.97 (s,
1H); 7.85 (d, J ¼ 8.0 Hz, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz,1H); 7.79 (br,
1H); 7.48e7.58 (ovl. m, 2H); 7.35 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd,
J ¼ 11.5, 9.0 and 2.6 Hz, 1H); 7.06 (dddd, J ¼ 9.0, 8.5, 2.6 and 1.5 Hz,
1H).
LCMS (ESI) m/z 563.2 (M þ H)þ; 561.2 (MꢂH)ꢂ; calculated:
562.1; Rt: 4.08 min.
LCMS (ESI) m/z 553.3 (M þ H)þ; 551.3 (MꢂH)ꢂ; calculated:
552.1; Rt: 4.32 min.
4.2.15.10. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-3-(trifluoromethyl)benzamide
(17j).
Yield: 48%. Mp 189e191 ꢀC.
4.2.15.5. 3,5-Dichloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]
1H NMR (300 MHz, DMSO-d6)
d ppm 11.30 (br, 1H); 9.25 (br. s,
amino}phenyl)imidazo[1,2-a]pyrazin-8-yl]benzamide
(17e).
1H); 8.59 (br. s, 1H); 8.50 (br, 1H); 8.41 (dd, J ~ 1.5 and 1.5 Hz, 1H);
8.36 (dm, J ¼ 7.0 Hz, 1H); 8.07 (ddd, J ¼ 9.3, 9.0 and 6.2 Hz, 1H); 8.03
(dm, J ~ 7.5 Hz,1H); 7.98 (s, 1H); 7.85 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.82
(dd, J ¼ 7.5 and 7.0 Hz,1H); 7.81 (br,1H); 7.48e7.51 (ovl. m, 2H); 7.36
(dm, J ~ 7.5 Hz, 1H); 7.32 (ddd, J ¼ 11.5, 8.7 and 2.5 Hz, 1H); 7.06
(dddd, J ¼ 9.0, 8.7, 2.5 and 1.5 Hz, 1H).
Yield: 59%. Mp 220e221 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.27 (br, 1H); 9.26 (s, 1H);
8.60 (br. s, 1H); 8.48 (br, 1H); 8.08 (d, J ~ 1.50 Hz, 2H); 8.07 (ddd,
J ~ 9.3, 9.0 and 6.3 Hz, 1H); 7.98 (s, 1H); 7.92 (t, J ~ 1.5 Hz, 1H); 7.84
(dd, J ~ 1.5 and 1.5 Hz,1H); 7.80 (br, 1H); 7.48e7.56 (ovl. m, 2H); 7.56
(dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ¼ 11.5, 9.0 and 2.5 Hz, 1H); 7.06
(dddd, J ¼ 9.0, 8.5, 2.5 and 1.5, 1H).
LCMS (ESI) m/z 553.3 (M þ H)þ; 551.3 (MꢂH)ꢂ; calculated:
552.1; Rt: 4.17 min.
LCMS (ESI) m/z 553.3 (M þ H)þ; 551.3 (MꢂH)ꢂ; calculated:
552.1; Rt: 4.43 min.
4.2.15.11. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-4-(trifluoromethyl)benzamide
(17k).
4.2.15.6. 3-chloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}
Yield: 54%. Mp 222e223 ꢀC.
phenyl)imidazo[1,2-a]pyrazin-8-yl]-4-fluorobenzamide
(17f).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.22 (s, 1H); 9.26 (s, 1H);
Yield: 64%. Mp 167e169 ꢀC.
8.60 (br. s, 1H); 8.51 (br, 1H); 8.23 (dm, J ~ 8.5 Hz, 2H); 8.07 (ddd,
J ¼ 9.3, 9.0 and 6.2 Hz, 1H); 7.98 (s, 1H); 7.95 (dm, J ~ 8.5 Hz, 2H);
7.85 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.82 (br, 1H); 7.47e7.57 (ovl. m, 2H);
7.36 (dm, J ~ 7.5 Hz, 1H); 7.32 (ddd, J ¼ 11.6, 9.0 and 2.7 Hz, 1H); 7.06
(dddd, J ¼ 9.0, 8.7, 2.7 and 1.4 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.14 (br, 1H); 9.26 (s, 1H);
8.59 (s, 1H); 8.51 (br, 1H); 8.29 (dd, J ¼ 5.8 and 1.5 Hz, 1H); 8.09
(ddd, J ~ 8.5, 6.5 and 1.5 Hz, 1H); 8.06 (ddd, J ~ 9.3, 9.0 and 6.3 Hz,
1H); 7.97 (s, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.80 (br, 1H); 7.62

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LCMS (ESI) m/z 553.3 (M þ H)þ; 551.3 (MꢂH)ꢂ; calculated:
4.2.15.17. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-3,5-dimethylbenzamide (17q). It was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
552.1; Rt: 4.18 min.
4.2.15.12. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-3,5-bis(trifluoromethyl)benzamide (17l).
Yield: 43%. Mp 180e182 ꢀC.
Yield: 19%. Mp 206e208 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.71 (br, 1H); 9.25 (s, 1H);
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.60 (br, 1H); 9.25 (br. s,
8.59 (br. s, 1H); 8.47 (br, 1H); 8.07 (ddd, J ¼ 9.3, 9.0 and 6.3 Hz, 1H);
7.96 (s, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.79 (br, 1H); 7.68 (br. d,
J ~1.5 Hz, 2H); 7.48e7.56 (ovl. m, 2H); 7.36 (dm, J ~ 7.5 Hz, 1H); 7.31
(ddd, J ~ 11.5, 9.0 and 2.5 Hz, 1H); 7.28 (t, J ~ 1.5 Hz, 1H); 7.06 (dddd,
J ~ 9.0, 8.5 2.5 and 1.5 Hz, 1H); 2.38 (s, 6H).
1H); 8.71 (d, J ~ 1.5 Hz, 2H); 8.59 (br. s, 1H); 8.46 (br, 1H); 8.42 (t,
J ~ 1.5 Hz, 1H); 8.07 (ddd, J ¼ 9.3, 9.0 and 6.3 Hz, 1H); 7.99 (s, 1H);
7.85 (dd, J ~ 1.5 and 1.5 Hz,1H); 7.79 (br, 1H); 7.48e7.58 (ovl. m, 2H);
7.36 (dm, J ~ 7.5 Hz, 1H); 7.32 (ddd, J ¼ 11.6, 9.0 and 2.6 Hz, 1H); 7.05
(dddd, J ¼ 9.0, 8.6, 2.4 and 1.5 Hz, 1H).
LCMS (ESI) m/z 513.3 (M þ H)þ; 511.3 (MꢂH)ꢂ; calculated: 512.2;
Rt: 4.14 min.
LCMS (ESI) m/z 621.3 (M þ H)þ; 619.3 (MꢂH)ꢂ; calculated:
620.1; Rt: 4.63 min.
4.2.16. General procedure for the preparation of compounds
18ae18i
4.2.15.13. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-4-fluoro-3-(trifluoromethyl)benzamide
(17m). It was further purified by preparative TLC (eluent: chloro-
form: methanol ¼ 9: 1) to give the title compound.
Yield: 17%. Mp ~140 ꢀC decomp.
A mixture of compound 16j (90 mg, 0.20 mmol), pyridine (2 ml),
N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride
(96 mg, 0.50 mmol) and the benzoic acid derivative (0.50 mmol)
was stirred at 70 ꢀC for 6 h. The solvent was evaporated and the
residue was taken up in chloroform. The organic layer was washed
with water (2ꢁ), dried over sodium sulphate, filtered and concen-
trated under reduced pressure. The crude product was triturated
with diisopropyl ether, filtered and washed with acetonitrile to give
the desired products.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.35 (br, 1H); 9.24 (s, 1H);
8.57 (br. s, 1H); 8.39e8.51 (ovl. m, 3H); 8.07 (ddd, J ¼ 9.3, 9.0 and
6.3 Hz, 1H); 7.97 (s, 1H); 7.85 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.77 (br,
1H); 7.72 (dd, J ¼ 9.8 and 9.2 Hz, 1H); 7.48e7.57 (ovl. m, 2H); 7.35
(dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ¼ 11.6, 9.0 and 2.5 Hz, 1H); 7.05
(dddd, J ¼ 9.0, 8.6, 2.5 and 1.5 Hz, 1H).
LCMS (ESI) m/z 571.3 (M þ H)þ; 569.3 (MꢂH)ꢂ; calculated:
570.1; Rt: 4.26 min.
4.2.16.1. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}benzamide (18a). It was
further purified by preparative TLC (eluent: chloroform:
methanol ¼ 9: 1) to give the title compound.
4.2.15.14. 4-chloro-N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}
phenyl)imidazo[1,2-a]pyrazin-8-yl]-3-(trifluoromethyl)benzamide
(17n). Yield: 38%. Mp 212e213 ꢀC.
Yield: 31%. Mp ~150 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 10.89 (br. s, 1H); 9.31 (br. s,
1H NMR (300 MHz, DMSO-d6)
d
ppm 11.48 (br, 1H); 9.25 (s, 1H);
1H); 9.10 (br. s, 1H); 8.49 (d, J ¼ 4.5 Hz, 1H); 8.11 (d, J ¼ 2.4 Hz, 1H);
8.06 (dm, J ¼ 7.1 Hz, 2H); 7.96 (s, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz,
1H); 7.82 (d, J ¼ 4.5 Hz,1H); 7.69 (dd, J ¼ 9.0 and 2.4 Hz,1H); 7.66 (tt,
J ~ 7.5 and 1.5 Hz, 1H); 7.62 (d, J ¼ 9.0 Hz, 1H); 7.59 (dm, J ~ 7.5 Hz,
1H); 7.57 (ddm, J ¼ 7.5 and 7.0 Hz, 2H); 7.53 (dd, J ~ 7.5 and 7.5 Hz,
1H); 7.37 (dm, J ¼ 7.5 Hz, 1H).
8.59 (br. s, 1H); 8.51 (d, J ~ 1.5 Hz, 1H); 8.44 (br, 1H); 8.35 (dd, J ~ 8.5
and 1.5 Hz, 1H); 8.07 (ddd, J ¼ 9.3, 9.0 and 6.3 Hz, 1H); 7.98 (s, 1H);
7.95 (d, J ¼ 8.5 Hz, 1H); 7.85 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.76 (br, 1H);
7.47e7.60 (ovl. m, 2H); 7.35 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ¼ 11.6,
9.0 and 2.5 Hz, 1H); 7.06 (dddd, J ~ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
LCMS (ESI) m/z 587.3 (M þ H)þ; 585.3 (MꢂH)ꢂ; calculated:
586.1; Rt: 4.42 min.
LCMS (ESI) m/z 551.3 (M þ H)þ; 549.3 (MꢂH)ꢂ; calculated:
550.1; Rt: 4.28 min.
4.2.15.15. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-3-(trifluoromethoxy)benzamide (17o).
Yield: 45%. Mp 211e212 ꢀC.
4.2.16.2. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-3,5-difluorobenzamide
(18b). It was further purified by preparative TLC (eluent: chloro-
form: methanol ¼ 9: 1) to give the title compound.
Yield: 26%. Mp 217e219 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.19 (br, 1H); 9.26 (s, 1H);
8.60 (s, 1H); 8.51 (br, 1H); 8.11 (dm, J ~ 7.5 Hz, 1H); 8.07 (ddd, J ¼ 9.3,
9.0 and 6.3 Hz, 1H); 8.00 (dd, J ~ 2.0 and 2.0 Hz, 1H); 7.97 (s, 1H);
7.85 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.82 (br, 1H); 7.73 (dd, J ¼ 8.3 and
7.6 Hz, 1H); 7.67 (dm, J ¼ 8.3 Hz, 1H); 7.48e7.56 (ovl. m, 2H); 7.36
(dm, J ~ 7.5 Hz, 1H); 7.32 (ddd, J ¼ 11.5, 9.0 and 2.5 Hz, 1H); 7.06
(dddd, J ~ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.19 (br, 1H); 9.28 (br. s,
1H); 9.08 (br. s, 1H); 8.49 (br, 1H); 8.10 (d, J ¼ 1.8 Hz, 1H); 7.98 (s,
1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.77 (dm, J ~ 7.0 Hz, 2H); 7.68
(dd, J ¼ 9.1 and 1.8 Hz, 1H); 7.62 (d, J ¼ 9.1 Hz, 1H); 7.59 (dm,
J ¼ 8.0 Hz, 1H); 7.58 (tm, J ~ 8.0 Hz, 1H); 7.51 (dd, J ¼ 8.0 and 7.2 Hz,
1H); 7.37 (dm, J ¼ 7.2 Hz, 1H).
LCMS (ESI) m/z 569.3 (M þ H)þ; 567.3 (MꢂH)ꢂ; calculated:
568.1; Rt: 4.24 min.
LCMS (ESI) m/z 587.3 (M þ H)þ; 585.3 (MꢂH)ꢂ; calculated:
586.1; Rt: 4.50 min.
4.2.15.16. N-[3-(3-{[(2,4-difluorophenyl)carbamoyl]amino}phenyl)
imidazo[1,2-a]pyrazin-8-yl]-4-(trifluoromethoxy)benzamide (17p).
Yield: 40%. Mp 207e209 ꢀC.
4.2.16.3. 3,5-Dichloro-N-{3-[3-({[4-chloro-3-(trifluoromethyl)
phenyl]carbamoyl}amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}benza-
mide (18c). It was further purified by preparative TLC (eluent:
chloroform: methanol ¼ 9: 1) to give the title compound.
Yield: 13%. Mp ~170 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.08 (br, 1H); 9.26 (s, 1H);
8.60 (br. s, 1H); 8.50 (br, 1H); 8.19 (dm, J ¼ 7.2 Hz, 2H); 8.07 (ddd,
J ¼ 9.3, 9.0 and 6.3 Hz, 1H); 7.97 (s, 1H); 7.85 (dd, J ~ 1.5 and 1.5 Hz,
1H); 7.81 (br, 1H); 7.56 (dm, J ¼ 7.2 Hz, 2H); 7.48e7.56 (ovl. m, 2H);
7.35 (dm, J ~ 7.5 Hz, 1H); 7.31 (ddd, J ~ 11.5, 9.0 and 2.5 Hz, 1H); 7.06
(dddd, J ~ 9.0, 8.5, 2.5 and 1.5 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.25 (br, 1H); 9.29 (br. s,
1H); 9.09 (br. s, 1H); 8.47 (br, 1H); 8.08 (d, J ~ 1.5 Hz, 2H); 8.10 (d,
J ¼ 1.8 Hz, 1H); 7.98 (s, 1H); 7.92 (t, J ~ 1.5 Hz, 1H); 7.84 (dd, J ~ 1.5
and 1.5 Hz,1H); 7.80 (br. s,1H); 7.68 (dd, J ¼ 8.8 and 1.8 Hz,1H); 7.63
(d, J ¼ 8.8 Hz, 1H); 7.58 (dm, J ~ 8.0 Hz, 1H); 7.53 (dd, J ~ 8.0 and
LCMS (ESI) m/z 569.4 (M þ H)þ; 567.4 (MꢂH)ꢂ; calculated:
568.1; Rt: 4.24 min.

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642
7.5 Hz, 1H); 7.37 (dm, J ~ 7.5 Hz, 1H).
1H); 9.21 (br. s, 1H); 8.71 (d, J ~ 1.5 Hz, 2H); 8.46 (br, 1H); 8.42 (t,
J ~ 1.5 Hz, 1H); 8.12 (d, J ¼ 1.7 Hz, 1H); 8.00 (s, 1H); 7.86 (dd, J ~ 1.5
and 1.5 Hz, 1H); 7.78 (br, 1H); 7.69 (dd, J ¼ 8.7 and 1.7 Hz, 1H); 7.62
(d, J ¼ 8.7 Hz, 1H); 7.59 (dm, J ~ 8.0 Hz, 1H); 7.53 (dd, J ¼ 8.0 and
7.5 Hz, 1H); 7.37 (dm, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 619.2 (M þ H)þ; 617.3 (MꢂH)ꢂ; calculated:
618.0; Rt: 4.91 min.
4.2.16.4. 3-chloro-N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]
carbamoyl}amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-4-
fluorobenzamide (18d). It was further purified by preparative TLC
(eluent: chloroform: methanol ¼ 9: 1) to give the title compound.
Yield: 20%. Mp ~150 ꢀC decomp.
LCMS (ESI) m/z 687.4 (M þ H)þ; 685.5 (MꢂH)ꢂ; calculated:
686.1; Rt: 5.06 min.
4.2.16.9. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-4-fluoro-3-(tri-
fluoromethyl)benzamide (18i). Yield: 42%. Mp 176e178 ꢀC.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.10 (br, 1H); 9.28 (br. s,
1H); 9.08 (br. s, 1H); 8.49 (br, 1H); 8.28 (m, 1H); 8.10 (d, J ¼ 2.0 Hz,
1H); 8.07 (br, 1H); 7.96 (s, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.82
(br, 1H); 7.69 (dd, J ¼ 8.8 and 2.0 Hz, 1H); 7.62 (d, J ¼ 8.8 Hz, 1H);
7.60 (br, 1H); 7.59 (dm, J ¼ 8.0 Hz, 1H); 7.52 (dd, J ¼ 8.0 and 7.5 Hz,
1H); 7.37 (dm, J ¼ 7.5 Hz, 1H).
1H NMR (300 MHz, DMSO-d6)
d ppm 11.33 (br, 1H); 9.28 (br. s,
1H); 9.08 (br. s, 1H); 8.55e8.37 (ovl. m, 3H); 8.11 (d, J ~ 1.5 Hz, 1H);
7.97 (s, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.80 (br. 1H); 7.73 (dd,
J ~ 9.5 and 8.5 Hz, 1H); 7.68 (dd, J ~ 8.5 and 1.5 Hz, 1H); 7.63 (d,
J ~ 8.5 Hz, 1H); 7.58 (dm, J ~ 8.0 Hz, 1H); 7.53 (dd, J ~ 8.0 and 7.5 Hz,
1H); 7.37 (dm, J ~ 7.5 Hz, 1H).
LCMS (ESI) m/z 603.3 (M þ H)þ; 601.3 (MꢂH)ꢂ; calculated:
602.1; Rt: 4.60 min.
LCMS (ESI) m/z 637.3 (M þ H)þ; 635.4 (MꢂH)ꢂ; calculated:
636.1; Rt: 4.71 min.
4.2.16.5. 3-chloro-N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]
carbamoyl}amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-4-
methylbenzamide (18e). It was further purified by preparative TLC
(eluent: chloroform: methanol ¼ 9: 1) to give the title compound.
Yield: 29%. Mp 219e221 ꢀC.
4.3. Biological evaluation
4.3.1. Determination of the antiproliferative activity against A375P,
A549, H358, PC9, PC9-ER, HCT116 and HKE3 cells
1H NMR (300 MHz, DMSO-d6)
d ppm 11.02 (br, 1H); 9.29 (br. s,
1H); 9.09 (br. s, 1H); 8.48 (br, 1H); 8.11 (br, 1H); 8.10 (d, J ¼ 2.0 Hz,
1H); 7.96 (s,1H); 7.94 (dm, J ~ 8.0 Hz,1H); 7.83 (dd, J ~ 1.5 and 1.5 Hz,
1H); 7.80 (br, 1H); 7.68 (dd, J ¼ 8.8 and 2.0 Hz, 1H); 7.62 (d,
J ¼ 8.8 Hz, 1H); 7.59 (dm, J ~ 8.0 Hz, 1H); 7.56 (d, J ¼ 8.1 Hz, 1H); 7.53
(dd, J ¼ 8.0 and 7.5 Hz, 1H); 7.37 (dm, J ¼ 7.5 Hz, 1H); 2.44 (s, 3H).
LCMS (ESI) m/z 599.4 (M þ H)þ; 597.3 (MꢂH)ꢂ; calculated:
598.1; Rt: 4.71 min.
A375P cells were made available for us by Prof. Axel Ullrich (Max
Planck Institute of Biochemistry, Martinsried, Germany). A549,
H358 and HCT116 cell lines were purchased from ATCC (American
Type Culture Collection, Manassas, VA). The PC9 and PC9-ER cell
lines were kindly provided by the Cancer Research UK London
Research Institute, Signal Transduction Laboratory. PC9-ER cells
were made erlotinib-insensitive by prolonged incubation with
erlotinib. HKE3 cell line was a kind gift from Cancer Research UK
Beatson Institute, Glasgow, United Kingdom. A375P and HKE3 cells
were maintained in DMEM (high glucose; Gibco, Life Technologies,
Carlsbad, CA), while A549, H358, HCT116, PC9 and PC9-ER cells in
RPMI-1640 medium, in the presence of 10% fetal bovine serum (FBS,
Gibco) and antibiotic-antimycotic solution (Gibco, Life Technolo-
gies) in a humidified atmosphere with 5% CO2 at 37 ꢀC. 1000 cells
were plated in each well on 384 well plates (Perkin Elmer, Boston,
MA). Following adherence cells were incubated for 72 h with the
test compounds using 10 different concentrations (3-fold serial
4.2.16.6. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-3-(trifluoromethyl)benza-
mide (18f). It was further purified by preparative TLC (eluent:
chloroform: methanol ¼ 9: 1) to give the title compound.
Yield: 46%. Mp ~140 ꢀC decomp.
1H NMR (300 MHz, DMSO-d6)
d ppm 11.30 (br, 1H); 9.29 (br. s,
1H); 9.09 (br. s, 1H); 8.48 (br, 1H); 8.42 (dd, J ~ 1.5 and 1.5 Hz, 1H);
8.36 (dm, J ~ 8.0 Hz,1H); 8.11 (d, J ¼ 2.2 Hz,1H); 8.03 (dm, J ¼ 8.0 Hz,
1H); 7.98 (s, 1H); 7.84 (dd, J ~ 1.5 and 1.5 Hz, 1H); 7.83 (dd, J ¼ 8.0
and 8.0 Hz, 1H); 7.80 (br, 1H); 7.68 (dd, J ¼ 9.0 and 2.2 Hz, 1H); 7.62
(d, J ¼ 9.0 Hz, 1H); 7.58 (dm, J ¼ 8.0 Hz, 1H); 7.53 (dd, J ¼ 8.0 and
7.5 Hz, 1H); 7.37 (dm, J ¼ 7.5 Hz, 1H).
dilution, 30 mM - 0.0015 mM). The antiproliferative activity of the
compounds was determined by CellTiter-Glo® Luminescent Cell
Viability Assay (Promega, Madison, WI) according to the manu-
facturer's instructions. The luminescent signal was measured by
Analyst® GT Multimode Reader (Molecular Devices, Sunnyvale, CA).
XLfit (IDBS) software was used to generate the doseeeffect curves
for IC50 determination.
LCMS (ESI) m/z 619.3 (M þ H)þ; 617.3 (MꢂH)ꢂ; calculated: 618.1;
Rt: 4.64 min.
4.2.16.7. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-4-(trifluoromethyl)benza-
mide (18g). It was further purified by preparative TLC (eluent:
chloroform: methanol ¼ 9: 1) to give the title compound.
Yield: 42%. Mp ~140 ꢀC decomp.
4.3.2. Determination of the inhibitory activity against B-Raf(wt)
and B-Raf(V600E) kinases
The kinase assays were performed by Transcreener® ADP2 FP
technology in low protein binding 384-well plates (Corning 3676).
The proteins were purchased from ProQinase (Freiburg, Germany),
the ADP2 Antibody and ADP Alexa633 Tracer from BellBrook Labs
(Madison, WI), while the rest of the reagents from SigmaeAldrich
(St. Louis, MO). The test compounds were diluted in DMSO and
were used in 12 different concentrations (3-fold serial dilution,
1H NMR (300 MHz, DMSO-d6)
d ppm 11.24 (br, 1H); 9.30 (br. s,
1H); 9.10 (br. s, 1H); 8.47 (br, 1H); 8.26 (dm, J ¼ 8.5 Hz, 2H); 8.11 (d,
J ¼ 2.1 Hz, 1H); 7.98 (s, 1H); 7.95 (dm, J ¼ 8.5 Hz, 2H); 7.84 (dd, J ~ 1.5
and 1.5 Hz, 1H); 7.79 (br, 1H); 7.68 (dd, J ¼ 8.9 and 2.1 Hz, 1H); 7.62
(d, J ¼ 8.9 Hz, 1H); 7.58 (dm, J ~ 8.0 Hz, 1H); 7.53 (dd, J ¼ 8.0 and
7.5 Hz, 1H); 7.37 (d, J ¼ 7.5 Hz, 1H).
LCMS (ESI) m/z 619.4 (M þ H)þ; 617.5 (MꢂH)ꢂ; calculated: 618.1;
Rt: 4.65 min.
12.5
mM - 0.00007
mM). In the case of B-Raf(wt) assay each reaction
consisted of 35 nM B-Raf enzyme, MEK1 K97M 0.01
m
g/ml, 2.1 mM
ATP (¼ Km ATP), 50 mM HEPES pH 7.5 kinase buffer, 1 mM DTT,
10 mM MgCl2 and 0.01% Brij 35. In the case of B-Raf(V600E) assay
each reaction consisted of 30 nM B-Raf(V600E) enzyme, MEK1
4.2.16.8. N-{3-[3-({[4-chloro-3-(trifluoromethyl)phenyl]carbamoyl}
amino)phenyl]imidazo[1,2-a]pyrazin-8-yl}-3,5-bis(trifluoromethyl)
benzamide (18h). Yield: 44%. Mp ~140 ꢀC decomp.
K97M 0.02
mg/ml, 3.6
mM ATP (¼ Km ATP), 50 mM HEPES pH 7.5 ki-
1H NMR (300 MHz, DMSO-d6)
d ppm 11.65 (br, 1H); 9.41 (br. s,
nase buffer, 1 mM DTT, 10 mM MgCl2 and 0.01% Brij 35. The enzyme

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643
(2012) 873e886.
(6
temperature. After the addition of 2
containing solution, the kinase reaction was incubated for 1 h at
room temperature. It was stopped by adding 8 l ADP Detection
Mixture (20 mM HEPES pH 7.5, 40 mM EDTA, 10 mM MgCl2, 0.02%
Brij 35, 16
g/ml ADP2 Antibody and 3 nM ADP Alexa633 Tracer).
m
l) was preincubated with the test compound for 90 min at room
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After an additional hour, fluorescence polarization (Ex: 630-35 nm,
Em: 680-30 nm, Dich: 650 nm) was measured using an Analyst® GT
Multimode Reader. IC50 curves were fitted and IC50 values were
calculated with XLfit (IDBS) curve fitting software.
Acknowledgements
The research leading to these results received funding from the
European Union Seventh Framework Programme (FP7/2007e2013)
PRIMES project under grant agreement number FP7-HEALTH-2010-
278568 and Lungtarget project under grant agreement number
HEALTH-F2-2010-259770.
Appendix A. Supplementary data
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.ejmech.2015.12.
001. These data include MOL files and InChiKeys of the most
important compounds described in this article.
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