Design and Synthesis of a Series of Novel Macrocycle Janus Kinase 2 Inhibitors

Article abstract of DOI:10.1002/cjoc.201900316

Macrocycle has attracted the attention of many researchers in the field of medicinal chemistry due to its unique advantages and good prospects, but the difficulties in drug design and synthesis of macrocycle limit its applications. In this study, a series of macrocyclic derivatives designed from anaplastic lymphoma kinase (ALK) inhibitor lorlatinib were synthesized as Janus kinase 2 (JAK2) selective inhibitors. Among them, 17f had the best inhibitory activity (IC₅₀ = 0.177 μmol·L^–1) and selectivity for JAK2 over JAK1 and JAK3, which indicated that design of the macrocyclic derivatives might be a feasible strategy for the discovery of novel selective JAK2 inhibitors.

Full text of DOI:10.1002/cjoc.201900316

Article
pubs.acs.org/OPRD
Cite This: Org. Process Res. Dev. 2019, 23, 1918−1925
Synthesis of Imatinib by C−N Coupling Reaction of Primary Amide
and Bromo-Substituted Pyrimidine Amine
Cuiling Wang,*,† Xiao Bai,† Rui Wang,† Xudong Zheng,† Xiumei Ma,† Huan Chen,† Yun Ai,†,‡
Yajun Bai,§ and Yifeng Liu∥
†College of Life Sciences, Northwest University, Xi’an 710069, China
‡Xi’an Institute for Food and Drug Control, Xi’an 710054, China
§Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry &
Materials Science, Northwest University, Xi’an 710127, China
∥Applied Chemical Institute, Northwest University, Xi’an 710069, China
S
* Supporting Information
ABSTRACT: A new method for imatinib synthesis is described by using the C−N coupling reaction of 4-(4-methylpiperazine-
1-methyl)benzamide with N-(5-bromo-2-tolyl)-4-(3-pyridyl)pyrimidin-2-amine to form imatinib. In this synthetic route, the
high efficiency and high selectivity of nano-ZnO as a catalyst is key to the mild hydrolysis of 4-(4-methylpiperazine-1-
methyl)benzonitrile into the corresponding amide. The total imatinib yield was 51.3%, and the purity was 99.9%. This simple
and effective synthetic pathway avoids gene-impurity production (as classified by the FDA Center for Drug Evaluation and
Research), and the synthesis is environmentally friendly with a short reaction time.
KEYWORDS: imatinib, nano-ZnO, C−N coupling reaction, bromopyrimidine, piperazine amide
Scheme 1. Zimmermann’s Method of Synthesis of Imatinib
INTRODUCTION
■
Imatinib mesylate is a synthetic tyrosine kinase inhibitor,
which is used widely in the clinical treatment of chronic
myeloid leukemia.1,2 Chronic myeloid leukemia is an acquired
myeloproliferative disorder that is characterized by cytogenetic
translocation, which forms a fusion kinase BCR-Abl.3,4
Imatinib(4-[(4-methyl-1-piperazinyl)methyl]-N-[4-methyl-3-
[[4-(3-pyridyl)-2-pyrimidinyl] amino]-phenyl]benzamide))
(1) is the first specific molecular targeting drug inhibitor of
BCR-Abl fusion protein and a first-line therapeutic drug for
this type of case.5,6 In recent years, its applications have
gradually expanded to the treatment of diffuse cutaneous
mastocytosis and benign prostatic hyperplasia.7
Because it is a well-established gold-standard drug in the
treatment of chronic myeloid leukemia, many methods have
been developed for the synthesis of imatinib.8−10 The synthetic
route was first proposed by Zimmermann (Ciba−Geigy).8 The
Zimmermann route (Method A in Scheme 1) is the most
mainstream synthetic route, and it mainly converts aniline (2)
to a guanido-containing compound (3), which is then reduced
to a pyrimidine amine (5) by a two-step hydrazine and enone
amine (4) treatment. Compound 5 reacts with an acyl chloride
(6) to form imatinib (1). In 2008, we proposed a synthetic
imatinib method (Method B in Scheme 2),10a which uses a
new starting material, 2-bromo-4-nitrotoluene (7), and the
copper-catalyzed C−N coupling reaction, followed by a
reduction of the nitro group to compound 5 by the N2H4·
H2O/FeCl3/C system, and finally the target compound (1) is
produced. This improved method for imatinib preparation is
less hazardous and more environmentally friendly and has
potential for industrial application.
However, additional problems have surfaced in recent years
with the increase in clinical cases of imatinib. The genotoxic
impurities in imatinib drugs have raised much attention. Two
impurities in imatinib mesylate, namely, N-(5-amino-2-
methylphenyl)-4-(3-pyridinyl)-2-pyridineamine (5) and 4-
chloromethyl-N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-yl-
amino)-phenyl]benzamide (10), have been reported by the
FDA’s Center for Drug Evaluation and Research. The
impurities in imatinib mesylate have the potential for direct
DNA damage and toxicity to genes, with genotoxic impurity
limits of below 20 (5) and 10 ppm (10), respectively. In
previous reports, these two substances were found mostly as
intermediates (Schemes 1 and 2). Purification to remove two
genotoxic impurities is difficult. The most effective way to
Received: May 15, 2019
Published: July 31, 2019
© 2019 American Chemical Society
1918
DOI: 10.1021/acs.oprd.9b00227
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reaction times. Thus the development of an effective method
for imatinib synthesis is required that avoids the production of
these genotoxic impurities. We designed a new synthetic
imatinib route (Scheme 4) by using the C−N coupling
reaction of N-(5-bromo-2-tolyl)-4-(3-pyridyl) pyrimidin-2-
amine (17) with 4-(4-methylpiperazine-1-methyl)benzamide
(18) to synthesize imatinib (1). This simple and effective
synthetic pathway avoids gene-impurity production (com-
pounds: 5 and 10), and the synthesis is environmentally
friendly with a short reaction time.
Scheme 2. Our Previous Imatinib Synthetic Route
RESULTS AND DISCUSSION
■
According to our designed synthetic route, six steps are
required to synthesize imatinib. The synthesis of N-(5-bromo-
2-tolyl)-4-(3-pyridyl)pyrimidin-2-amine (17) and 3-(dimethy-
lamino)-1-(3-pyridyl)-2-propen-1-one (4) has been reported
in the literature. The latter synthesis requires toluene or xylene
as a solvent during the reaction, and the equipment utilization
rate is low with a long reaction time. We obtained satisfactory
results by using the solvent-free synthesis of 3-(dimethylami-
no)-1-(3-pyridyl)-2-propen-1-one (4). To improve this
method, a Vigreux rectification column needs to be installed
on the reaction unit. During the reaction, byproduct methanol
that was produced by the reaction was fractionated
continuously, the enamine (4) yield exceeded 95% after 4−6
h. The solid-phase synthesis of 4-(4-methylpiperazine-1-
methyl)benzonitrile (20) and its hydrolysis to amide (18)
and the synthesis of imatinib (1) by the C−N coupling
reaction occurred as follows.
resolve this problem is to modify the synthetic route and to
avoid the production of these genotoxic impurities.
In fact, in 2003, Zimmermann’s inverse synthesis route was
designed by Loiseleur et al. (Methods C and D in Scheme 3).9
Method C consists of 3-nitro-4-methyl aniline (12) as the
starting material with the first acylation; then, the pyrimidine
ring was built. Method D uses 3-bromo-4-methylaniline (15)
as the starting material and the C−N coupling reaction to build
phenylaminopyrimidine, in combination with two precious
catalysts: tris(dibenzylideneacetone)dipalladium (Pd2(dba)3)
a n d o r g a n o p h o s p h o r u s l i g a n d
(
) - 2 , 2 ′ - b i s -
(diphenylphosphine)-1,1′-binaphthyl (rac-BINAP). Both
routes do not produce genotoxic impurities. However, these
methods have some shortcomings, such as the poor selectivity
of the acylation reaction, high synthesis costs, and long
Scheme 3. Loiseleur’s Methods for Imatinib Synthesis
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Scheme 4. Newly Designed Synthetic Methods and Pathways for Imatinib
Table 1. Results from the Solid-Phase Synthesis of 4-(4-Methylpiperazine-1-methyl)benzonitrile
no.
piperazine/mol
benzonitrile/mol
NaOH/mol
KOH/mol
H2O/mL
target products/g
yield/%
1
2
3
4
5
0.2
0.2
0.2
0.2
0.2
0.19
0.19
0.19
0.19
0.19
0.2
0.2
0.2
6
6
6
6
6
39.1
40.2
39.6
39.3
39.1
90.8
93.4
92.0
91.3
90.8
0.2
0.2
Solid-Phase Synthesis of 4-(4-Methylpiperazine-1-
methyl)benzonitrile (20). The conventional synthesis of 4-
(4-methylpiperazine-1-methyl)benzonitrile (20) was achieved
by a solvent method. Kompella et al.11 used chloroform as a
solvent to react N-methyl piperazine (11) with 4-bromomethyl
benzonitrile at room temperature for 4 h to obtain 4-(4-
methylpiperazine-1-methyl)benzonitrile (20). Cheng et al.12
provided chloroform as a solvent in the presence of sodium
carbonate for reaction at 25−30 °C for 12 h to yield 4-(4-
methylpiperazine-1-methyl)benzonitrile (20). Umezu et al.13
reported that N-methyl piperazine (11) was condensed with 4-
chloromethyl benzonitrile (19) in the presence of sodium
carbonate in xylene to form 4-(4-methylpiperazine-1-methyl)-
benzonitrile (20). These methods have many drawbacks: (a)
The use of a large amount of chloroform as a solvent is harmful
to the environment and the operator, and chloroform is a
solvent that is restricted in technical guidance for the research
of residual solvents of chemical drugs. The use of chloroform is
highly restricted. (If chloroform is used, then the solvent
residue must be controlled below 0.006%.) (b) 4-Bromo-
methyl benzonitrile is costly and severely toxic, and 4-
chloromethyl benzenitrile (19) should be used, which is
affordable and easily available. (c) Many byproducts result, and
the tertiary amine of N-methyl piperazine (11) reacts easily
with the chloromethyl group to form quaternary ammonium
hydroxide (23), which easily converts the nitrile group into
carboxylate (24) when alkali is added. (d) The reaction time is
long, and the synthesis efficiency is low.
We used solid-phase organic synthesis to obtain 4-(4-
methylpiperazine-1-methyl)benzonitrile (20) by the solid-
phase formation of N-methyl piperazine (11) and 4-
chloromethyl benzonitrile (19) in the absence of solvent
(Scheme 4c). The reaction formula is as follows (see part of
Scheme 4).
Certain amounts of 4-chloromethyl benzonitrile (19), N-
methyl piperazine (11), and 50% aqueous sodium hydroxide
solution were added to the solid grinding vessel, and after
grinding at room temperature for 30 min under cooling, the
reaction mixture was placed in the reactor for 0.5 h. 4-(4-
Methylpiperazine-1-methyl)benzonitrile (20) was obtained by
extraction, cooling, crystallization, and filtration with cyclo-
hexane at 70 °C, and its yield exceeded 95%. Under the control
of the reaction conditions, almost no side reactions occurred.
This method is environmentally friendly, saves time, and
produces high yields of target products. Table 1 shows results
from the solid-phase synthesis of 4-(4-methylpiperazine-1-
methyl)benzonitrile.
The excess of N-methyl piperazine (11) relative to 4-
chloromethyl benzonitrile (19) allows for the complete
1920
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Table 2. Results from the Synthesis of 4-(4-Methylpiperazine-1-methyl)benzamide by Nitrile Hydrolysis
no.
benzonitrile/mol
H2O/mol
nano-ZnO/mol
KOH/mol
NaOH/mol
benzamide/g
yield/%
1
2
3
4
5
6
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.01
0.01
0.01
0.02
0.02
0.02
0.02
43.5
42.8
44.0
30.5
40.5
39.1
93.1
91.6
94.2
65.3
86.7
83.7
0.01
0.01
0.02
0.02
reaction of 4-chloromethyl benzonitrile (19) to avoid
difficulties in the removal of unreacted 4-chloromethyl
benzonitrile (19). When the mole ratio of piperazine (11)/
benzonitrile (19)/NaOH or KOH is 0.2:0.19:0.2 regardless of
the base, the yields of 4-(4-methylpiperazine-1-methyl)-
benzonitrile (20) are higher (90.8, 93.4, 92.0, 91.3, and
90.8%) (Table 1). Because NaOH or KOH must be
moisturized by water for its complete participation in the
reaction, a minimal amount of water was used to moisturize
NaOH or KOH. In this experiment, when 0.2 mol NaOH or
KOH was added to the reaction system, 6 mL of water was
sufficient to moisturize it. Therefore, the ideal reaction
conditions are as follows: The mole ratio of piperazine (11)/
benzonitrile (19)/NaOH or KOH is 0.2:0.19:0.2 with a small
amount of water, ensuring a smooth reaction. The results also
indicate that sodium and potassium hydroxide are ideal raw
materials, but sodium hydroxide is cheaper and is more
suitable.
some methods use inexpensive Cu and Ni, they are
supplemented with a large amount of organic compounds,
such as acetaldehyde oxime, which makes the reaction system
more complicated and the product purification more difficult.
We used a combination of high-efficiency and highly
selective catalysts, nano-ZnO (15−25 nm, 99.5% metals
basis) and KOH, to mildly hydrolyze 4-(4-methylpiperazine-
1-methyl)benzonitrile (20) to 4-(4-methylpiperazine-1-
methyl)benzoylamide (18) (Scheme 4c). The reaction
conditions are mild and the selectivity is high, so excessive
nitrile hydrolysis is effectively controlled. The reaction formula
is as follows (consider part of Scheme 4).
Synthesis of 4-(4-Methylpiperazine-1-methyl)-
benzamide (18) by Nitrile (20) Hydrolysis. A method to
convert 4-(4-methylpiperazine-1-methyl)phenylnitrile (20)
into 4-(4-methylpiperazine-1-methyl)benzamide (18) has not
been reported in previous literature, but an increased number
of reports exist of similar nitriles being converted to amides.
Four main methods exist: (a) Acid and alkali hydrolysis:14 The
classical hydrolysis method uses a strong acid and a strong base
as a catalyst, which requires a higher reaction temperature and
is prone to excessive hydrolysis and the formation of
byproducts. The process yield is low, and the byproduct,
carboxylic acid, is not easily removed. (b) Oxidation method:
During oxidation, nitrile is converted to amide using hydrogen
peroxide as an oxidant. The synthetic pathway for hydrogen
peroxide to oxidize nitrile to yield amide was described by
McMaster’s group in 1916. However, the shortcoming of this
approach is that the oxidation reaction has a poor selectivity. In
recent years, scientists have tried to improve the reaction
results by adding some highly selective catalysts, such as
heteropolyacids.15 (c) Enzymatic catalysis:16,17 The nitrile is
hydrolyzed to the amide by nitrile hydratases. Nitrile
hydratases contain two different metal centers, cobalt and
iron. Therefore, the addition of Co2+ and Fe2+ in a bacterial
culture has a strong promoting effect on the enzyme activity.
This method has the advantage of a high reaction selectivity,
mild conditions, and environmental protection. However, it
also has the disadvantage of being more responsive and
sensitive to the environment. (d) Transition-metal catalytic
hydrolysis: This approach is a commonly used method for the
hydrolysis of nitriles to amides. The metal ions are mainly Pd,
Cu, In, Au, and Ru.18−20 Ma et al.21 reported that the aromatic,
fatty, and heterocyclic nitriles were smoothly hydrolyzed to the
corresponding amide in the presence of acetaldehyde oxime by
using NiCl2·6H2O as a catalyst. However, most methods use
precious metals, which increases the reaction cost. Although
During the reaction, by using isopropanol as the solvent and
nano-ZnO, KOH, or NaOH in a catalytic amount and with the
addition of a theoretical amount of water (based on the moles
of nitrile), 4-(4-methylpiperazine-1-methyl)benzonitrile (20)
can be hydrolyzed to 4-(4-methylpiperazine-1-methyl)-
benzamide (18) at the isopropanol reflux temperature. The
hydrolysis test results of 4-(4-methylpiperazine-1-methyl)-
benzonitrile (20) are given in Table 2.
The classical hydrolysis method of nitrile to amide uses a
strong acid or a strong base as a catalyst, which is prone to
excessive hydrolysis, and the formation of byproducts
carboxylic acid is not removed easily. A good yield was
obtained by catalyzing the hydrolysis of 4-(4-methylpiperazine-
1-methyl)benzonitrile (20) with a combination of nano-ZnO
and KOH (nano-ZnO (mol)/KOH (mol) 1:2). When the
mole ratio of benzonitrile (20)/water/nano-ZnO/KOH is
0.2:0.2:0.01:0.02, 4-(4-methylpiperazine-1-methyl)benzamide
(18) is produced in higher yield (93.1, 91.6, and 94.2%). In
contrast, compound (18) was generated in lower yield (65.3%)
in the absence of nano-ZnO in this reaction system. The
synergistic effect of nano-ZnO is very obvious, but the specific
reaction mechanism is still unclear. The catalyst with KOH in
the hydrolysis has a better yield (>90%) than the NaOH
catalysis (∼80% more), which may be related to the alkaline
strength.
Synthesis of Imatinib (1) Based on C−N Coupling
Reaction. The usual C−N coupling reaction is carried out
mostly by using an aromatic amine or other more basic amine
and a halogenated aromatic hydrocarbon. In recent years,
many reports have been produced on the C−N coupling
reaction of amides,22,23 but because the amide basicity is much
weaker than that of the aromatic amine or pyrimidine amine,
the yield of the target product that is obtained from the C−N
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Table 3. Results from C−N Coupling Reaction of Pyrimidinyl Amine (17) and Benzamide (18)
no.
pyrimidinyl amine/mol
benzamide/mol
H2O/mL
d-isoascorbate/mol
CuI/mol
K2CO3/mol
DMED/mol
imatinib yield/%
1
2
3
4
5
6
0.1
0.1
0.1
0.1
0.1
0.1
0.13
0.13
0.13
0.11
0.13
0.13
5
5
5
5
0.005
0.005
0.005
0.005
0.005
0.02
0.02
0.02
0.02
0.02
0.02
0.2
0.2
0.2
0.2
0.2
0.2
0.015
0.015
0.015
0.015
0.015
0.015
83.5
82.8
84.1
80.0
65.4
20.1
5
coupling reaction with the brominated aromatic hydrocarbon
is very low. Previous methods for synthesizing imatinib
(Scheme 2, Method B; Scheme 3, Method D) were C−N
coupling reactions with pyrimidine amines and brominated
aromatic hydrocarbons,10,24 which proceeded easily, and the
yields were high. In our synthetic imatinib route (Scheme 4),
4-(4-methylpiperazine-1-methyl)benzamide (18) and N-(5-
bromo-2-methylphenyl)-4-(3-pyridyl)pyrimidine-2-amine (17)
reacted according to conventional C−N coupling reaction
conditions, and the obtained imatinib yield was low. Therefore,
it is noteworthy that an increase in the yield of the C−N
coupling reaction of this amide has become a key issue.
After years of research, we finally resolved this problem. We
found that water can promote this C−N coupling reaction in a
nonpolar solvent. The use of the antioxidant d-ascorbate can
replace the protection of nitrogen or other inert gases. This
simplifies the process equipment and the difficulty of
operation. The results of the C−N coupling reaction tests as
conducted in accordance with this synthesis method are shown
in Table 3.
When the mole ratio of pyrimidinyl amine (17)/benzamide
( 1 8 ) / d - i s o a s c o r b a t e / C u I / K 2 C O 3 / D M E D i s
0.1:0.13:0.005:0.02:0.2:0.015, imatinib can be synthesized by
a C−N coupling reaction with water (5 mL) with a yield of
83.5, 82.8, and 84.1% (Table 3). We found that water has a
significant promoting effect on this C−N coupling reaction in a
nonpolar solvent (toluene, xylene). When the solvent was
DMF or DMSO, water failed to facilitate the reaction. Imatinib
was obtained in a yield of 65.4% in the absence of water in the
reaction system (Table 3). The protective effect of the
antioxidant d-sodium ascorbate on the reaction system is also
very obvious. Without the protective effect of antioxidant d-
sodium ascorbate, the yield of imatinib is only 20.1%. In
addition, it is necessary to add excessive 4-(4-methylpiper-
azine-1-methyl)benzamide (18) to the reaction system so that
N-(5-bromo-2-methylphenyl)-4-(3-pyridyl)pyrimidine-2-
amine (17) is reacted as completely as possible to facilitate the
subsequent imatinib purification. Because the properties of N-
(5-bromo-2-methylphenyl)-4-(3-pyridyl)pyrimidine-2-amine
(17) are close to those of imatinib, their separation is difficult.
Whereas 4-(4-methylpiperazine-1-methyl)benzamide (18) has
a certain solubility in hot water, imatinib is completely
insoluble in water and can be easily removed from the target
product. The elemental analysis of the synthesized imatinib, as
well as the IR, MS, and 1H NMR spectral analysis, was
consistent with the expected structural characterization data.
High-performance liquid chromatography (HPLC) was used
to analyze the content, and HPLC-MS was used to detect the
genetoxic impurities (compounds 5 and 10). The content of
imatinib that was obtained by our synthetic method was 99.9%,
and it did not detect genetic impurities in imatinib from our
new method (data provided in the Supporting Information).
Therefore, the new synthetic route of Scheme 4 was used to
couple N-(5-bromo-2-methylphenyl)-4-(3-pyridyl)pyrimidine-
2-amine (17) and 4-(4-methylpiperazine-L-methyl)benzamide
(18) with 2-methyl-5-bromoaniline (21) as a raw material
through the C−N coupling reaction of amide to produce
imatinib (total yield: 51.3%), which did not result in genotoxic
impurities restricted by the FDA.
CONCLUSIONS
■
A new synthetic imatinib route has been developed by the C−
N coupling reaction of 4-(4-methylpiperazine-1-methyl)-
benzamide (18) with N-(5-bromo-2-tolyl)-4-(3-pyridyl) pyr-
imidin-2-amine (17). The intermediate, 4-(4-methylpipera-
zine-1-methyl)benzonitrile (20), was obtained by the reaction
of N-methyl piperazine (11) with 4-chloromethyl benzonitrile
(19) under solvent-free conditions at room temperature with a
yield of 93.4%. By using a high-efficiency and selective nano-
ZnO catalyst, 4-(4-methylpiperazine-1-methyl)benzonitrile
(20) was mildly hydrolyzed into the corresponding amide
(18) with a yield of 94.2%. This synthetic route and process is
simple and environmentally friendly and has a short reaction
time and good selectivity, and the total yield of imatinib (1)
was 51.3% (2-methyl-5-bromoaniline (21) as raw material),
with a purity of 99.9%. More importantly, the final product
imatinib does not contain genotoxic impurities, as reported by
the FDA’s Center for Drug Evaluation and Research.
EXPERIMENTAL SECTION
■
General. Melting points were determined on a WRS-1B
digital melting-point apparatus (Shanghai YiCe Instrument
Equipment) in open capillary tubes and were uncorrected.
Elemental analyses were performed by an Elementar Vario EL
III instrument. IR spectra were recorded on a Bruker Equinox-
1
55 apparatus. H NMR spectra were recorded on a Varian
Inova 600 MHz instrument using DMSO-d6 as a solvent with
chemical shifts that were reported relative to tetramethylsilane.
The product purity was analyzed by using an Agilent 1100
HPLC with a DAD detector and a Zorbax SB-C18 column (250
mm × 4.6 mm, 5 μm), a column temperature of 30 °C, a
mobile phase of methanol (0.1% formic acid)-water (50:50), a
flow rate of 0.6 mL·min−1, a detection wavelength of 254 nm,
and an injection volume of 10 μL. Liquid chromatography
(LC-MS) was performed by using an Agilent 1200 HPLC
apparatus coupled to an Agilent 6520 quadrupole time-of-flight
mass spectrometer (EI). Flash-column chromatography was
performed with silica gel (100−200 mesh). An imatinib
standard sample was purchased from Sigma-Aldrich Life
Science and High Technology. ZnO (15−25 nM, 99.5%
metals basis, Aladdin Reagent). All other reagents were used as
purchased from commercial suppliers without further
purification. All materials were weighed in air.
General Procedure for the Synthesis of Compounds.
3-(Dimethylamino)-1-(3-pyridyl)-2-propen-1-one (4). Acetyl-
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pyridine (68.6 mL, 0.6 mol) and N,N-dimethylformamide
dimethylacetal (94.7 mL, 0.72 mol) were charged into a
reaction flask equipped with a mechanical stirrer and a Vigreux
column. The reaction mass was heated slowly with stirring, and
the Vigreux column top temperature was controlled at 65 °C.
After being maintained for 5 h, the temperature of the reaction
mass was gradually heated to 100 °C, and the methanol that
was formed in the reaction was distilled off. The reaction mass
was cooled to 80 °C, and a mixture of toluene (20 mL) and
hexane (10 mL) was added to the reaction mass and stirred for
10 min until the liquid reaction mass and solvents were well
mixed. The resultant reaction mass was poured into a beaker
and cooled to room temperature. The crystalline solid was
filtered off under vacuum and dried at 50−60 °C to yield 3-
(dimethylamino)-1-(3-pyridyl)-2-propen-1-one as an orange
crystal (101.5 g, yield: 96.0%). Melting point: 81.5−82.2 °C
(consistent with the literature).25
H), 343.0 (bromine isotope peak), 363.0 (M + Na). IR (KBr,
cm−1): 3204.3, 3156.2, 3039.6, 2947, 2892.1, 1581.9, 1533.5,
1454.7, 1421, 1403, 1384, 1337.3, 1294.7, 1024, 990.48,
858.96, 799.05, 710.47, 655, 612.47. 1H NMR (DMSO-d6, 600
MHz) δ 9.26 (s, 1H, NH), 9.03 (s, 1H), 8.69 (d, 1H), 8.54
(dd, 1H), 8.41 (d, 1H), 7.89 (dd, 1H), 7.54−753 (m, 1H),
7.48 (dd, 1H), 7.22 (d, 1H), 7.19 (d, 1H), 2.22 (s, 3H).
4-(4-Methylpiperazin-1-ylmethyl)-benzonitrile (20). N-
Methylpiperazine (22.2 mL, 0.2 mol) and a solution of
NaOH (8 g, 0.2 mol) in 6 mL of water were charged into a 90
mm diameter ceramic mortar. The reaction mass was ground
constantly in an ice bath until the liquid became semisolid. 4-
Chloromethylbenzonitrile (19) (28.8 g, 0.19 mol) was
gradually added over 30 min, and the temperature of the
reaction mass was maintained below room temperature.
Thereafter, the reaction mass remained stationary for 2 h
before being transferred to a beaker that was charged with 30
mL of cyclohexane. The reaction mixture was heated to 70 °C
for 10 min. The cyclohexane layer was poured out and cooled
to room temperature. The product was filtered to give 4-(4-
methylpiperazin-1-ylmethyl)-benzonitrile (20) as white gran-
ular crystals (39.1 g, yield: 90.8%). Melting point: 65−68 °C.
Anal. calcd for C13H17N3: C, 72.52; H, 7.96; N, 19.52. Found:
C, 72.14; H, 7.48; N, 19.01. IR (KBr, cm−1): 3042.6, 2941.8,
2798.5, 2788.9, 2223.8, 1606.6, 1504.5, 1455.7, 1369.1, 1351.4,
5-Bromo-2-methylphenylguanidine (22). 5-Bromo-2-
methylaniline (21) (37.4 g, 0.2 mol) and methanol (60 mL)
were placed in a reactor flask with a mechanical stirrer and a
dropping funnel. Nitric acid (65%, 10.8 mL, 0.24 mol) was
added dropwise to the reaction mass over 20 min, and the
reaction temperature was increased to 60 °C. After stirring for
30 min, a 50% aqueous cyanamide solution (11.7 mL, 0.3 mol)
was added dropwise over 40 min. The reaction mixture was
heated to the reflux temperature and stirred for 1.5 h; then,
65% nitric acid (7.2 mL 0.16 mol) was added over 20 min.
While the reaction mixture was stirred for a further 30 min,
50% aqueous cyanamide solution (7.8 mL, 0.2 mol) was added
dropwise over 40 min. The reaction mixture was kept at the
reflux temperature for 3 h. After the completion of the
reaction, the reaction mass was cooled to room temperature.
The solid product was filtered, washed with toluene (20 mL),
and dried to yield 5-bromo-2-methylphenylguanidine nitrate as
light-brown granular crystals (46.5 g, yield: 79.9%). Melting
point: 183−184 °C. 5-Bromo-2-methylphenylguanidine nitrate
and distilled water (150 mL) were added to a beaker at room
temperature with the addition of 130 mL of 5% NaOH
aqueous solution. The reaction mass was stirred for 1 h and
filtered to yield a crude product of 5-bromo-2-methylphenyl-
guanidine. The crude product was recrystallized from toluene
to give 5-bromo-2-methylphenylguanidine as white powder
crystals (34.1 g, yield: 74.8%). Melting point: 76−79 °C. Anal.
calcd for C8H10BrN3: C, 42.13; H, 4.42; N, 18.42. Found: C,
42.51; H, 4.18; N, 18.09. IR (KBr, cm−1): 3452.4, 3376.8,
3139.1, 2963.8, 2758, 1699.3, 1671.9, 1631.5, 1580.2, 1479.7,
1
1318, 1283.7, 1162.7, 1141.7, 1010.7, 925.3, 855.4, 809.9. H
NMR (DMSO-d6, 600 MHz) δ 7.81 (d, 2H), 7.54 (d, 2H,),
3.57 (s, 2H, CH2), 2.39 (bs, 8H), 2.18 (s, 3H, CH3).
4-(4-Methylpiperazin-1-ylmethyl)benzamide (18). A reac-
tion flask was charged with 4-(4-methylpiperazin-1-ylmethyl)-
benzonitrile (20) (43.1 g, 0.2 mol), isopropyl alcohol (100
mL), water (3.6 mL, 0.2 mol), nano-ZnO (0.81 g, 0.01 mol),
and KOH (1.1 g, 0.02 mol). The reaction mixture was heated
to reflux for 6−8 h. After a portion of isopropyl alcohol had
been distilled off, the mother liquor was filtered by hot
filtration to remove the catalyst residue. The reaction mass was
poured into a beaker and brought to room temperature for 8 h.
The precipitated solid was isolated by filtration and placed into
a beaker charged with 100 mL of distilled water. The mixture
was heated to 90 °C for 10 min. Hot filtration was carried out,
and the mother liquor was brought to room temperature. The
solid product was filtered, washed with water, and dried to
yield 4-(4-methylpiperazin-1-ylmethyl)benzamide (18) as
white granular crystals (43.5 g, yield: 93.1%). Melting point:
156−159 °C. Anal. calcd for C13H19N3O: C, 66.92; H, 8.21; N,
18.01. Found: C, 66.31; H, 7.96; N, 17.92. MS: 234.16 (M +
H). IR (KBr, cm−1): 3385.5, 3177, 2937.7, 279.23, 1650.8,
1619.8, 1570, 1457, 1419.5, 1400.7, 1349.7, 1012.9, 852.94,
1
1392.8, 882.08, 797.81. H NMR (DMSO-d6, 600 MHz) δ
7.04 (d, 1H), 6.96 (d, 1H), 6.88 (s, 1H), 5.42 (bs, 4H), 2.02
(s, 3H).
1
818.16, 803.3. HNMR (DMSO-d6, 600 MHz) δ 7.89 (s, 1H,
N-(5-Bromo-2-methylphenyl)-4-(3-pyridyl)pyrimidine-2-
amine (17). A reaction flask was charged with 5-bromo-2-
methylphenylguanidine (22) (45.6 g, 0.2 mol), 3-(dimethyla-
mino)-1-(3-pyridyl)-2-propen-1-one (4) (38.8 g, 0.22 mol),
and ethylene glycol monomethyl ether (EGME) (120 mL).
The reaction mixture was heated to reflux (∼120 °C) for 8 h,
and the reaction mass was cooled to room temperature. The
crude product was filtered under reduced pressure, and the
precipitate was washed with 20 mL of water on a filter funnel.
The product was recrystallized from toluene to yield 55.6 g
(81.5%) of N-(5-bromo-2-methylphenyl)-4-(pyridin-3-yl)-pyr-
imidin-2-ylamine (17) as a light-yellow powder. Melting point:
152−156 °C. Anal. calcd for C16H13BrN4: C, 56.32; H, 3.84;
N, 16.42. Found: C, 56.23; H, 3.86; N, 16.51. MS: 341.0 (M +
NH2α), 7.78 (d, 2H), 7.31 (d, 2H), 7.27 (s, 1H, NH2β), 3.45
(s, 2H, CH2), 2.31 (bs, 8H), 2.11 (s, 3H, CH3).
N-(4-Methyl-3-(4-(pyridin-3-yl)pyrimidin-2-ylamino)-
phenyl)-4-((4-methylpiperazin-1-yl)methyl)benzamide (1).
N-(5-Bromo-2-methylphenyl)-4-(pyridin-3-yl)-pyrimidin-2-yl-
amine (17) (34.1 g, 0.1 mol), 4-(4-methylpiperazin-1-
ylmethyl)benzamide (18) (30.3 g, 0.13 mol), cuprous iodide
(CuI) (3.81 g, 0.02 mol), potassium carbonate (K2CO3) (27.6
g, 0.2 mol), N,N′-dimethylethylenediamine (DMEDA) (1.32
g, 0.015 mol), sodium d-isoascorbate (0.99 g, 0.005 mol), 5
mL of distilled water, and 300 mL of toluene were charged into
a reaction flask. The reaction mixture was stirred in air for 24 h,
and the temperature was heated to the reflux temperature. The
reaction mass was returned to room temperature and
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Organic Process Research & Development
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ESMO clinical practice guidelines for diagnosis, treatment and
followup. Ann. Oncol. 2012, 23 (7), 72−77.
maintained for 2 h. The solid product was filtered, washed with
boiling water (100 mL) and toluene (50 mL), and dried at 60
°C. The crude product was purified by recrystallization from
ethylene glycol monomethyl ether to yield N-(4-methyl-3-(4-
(pyridin-3-yl)pyrimidin-2-ylamino)phenyl)-4-((4-methylpiper-
azin-1-yl)methyl)benzamide (1) as a light-yellow powder (41.2
g, yield: 83.5%; HPLC purity: 99.9%; genotoxic impurity (5)
and (10): not detected; o-toluidine: not detected). Melting
point: 206−209 °C. Anal. calcd for C29H31N7O: C, 70.56; H,
6.33; N, 19.86. Found: C, 70.18; H, 6.45; N, 19.32. MS: 494.3
(M + H). IR (KBr, cm−1): 3440.8, 3280.7, 3049.8, 2927.8,
2795.4, 1648, 1577.5, 1534.3, 1451.5, 1418.6, 1372.6, 1351.9,
1289.9, 1261.7, 1204.3, 1163, 1009.7, 923.6, 885.72, 856.53,
808.59, 747.49, 701.43, 646.2. 1H NMR (DMSO-d6, 600
MHz) δ 10.15 (s, 1H, NH), 9.26 (s, 1H), 8.96 (s, 1H), 8.67
(d, 1H), 8.50 (d, 1H), 8.46 (d, 1H), 8.07 (s, 1H), 7.89 (d,
2H), 7.51−7.41 (m, 5H), 7.19 (d, 1H), 3.51 (s, 2H), 2.37 (bs,
8H), 2.21 (s, 3H), 2.13 (s, 3H).
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.oprd.9b00227.
■
S
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1H NMR and IR spectra, MS data for each intermediate,
and analysis of the content of the standard sample from
Sigma-Aldrich and our synthetic imatinib by HPLC and
LC-MS (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail: wangcl@nwu.edu.cn.
ORCID
Cuiling Wang: 0000-0001-7806-1928
Notes
The authors declare no competing financial interest.
■
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ACKNOWLEDGMENTS
■
We are grateful for support from the Natural Science
Foundation of Shaanxi Province (nos. 2014JM4095,
2018JM7059), the Xi’an City Science and Technology project
(no. 2017085CG/RC048 (XBDX001)), the Shaanxi Province
Education Department Key Laboratory project (no. 16JS110),
the Shaanxi Province Key R&D project (no. 2018 SF-077), the
NSFC Enhanced Base Construction projects (no. J1210063),
and the Teaching Reform project of the Northwest University
(no. JX17088).
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