Development of a scalable synthesis of a Bruton's tyrosine kinase inhibitor via C-N and C-C bond couplings as an end game strategy

Article abstract of DOI:10.1021/op4001077

A scalable and convergent synthesis of a BTK (Bruton's tyrosine kinase) inhibitor has been developed. Synthetic routes to key intermediates were explored for the scale-up campaign, especially the process for 6-dimethylaminodihydroisoquinolinone, which was prepared via a regioselective cyclization of an isocyanate, mediated by AlCl3. Improved routes to key building blocks were demonstrated by expedient multikilogram productions. The target compound was assembled through a Pd-catalyzed amidation reaction followed by a Suzuki-Miyaura cross-coupling reaction.

Full text of DOI:10.1021/op4001077

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Full Paper
Development of a Scalable Synthesis of a BTK Inhibitor
via C-N and C-C Bond Couplings as an Endgame Strategy
Jun-Bae Hong
Org. Process Res. Dev., Just Accepted Manuscript • DOI: 10.1021/op4001077 • Publication Date (Web): 27 Aug 2013
Downloaded from http://pubs.acs.org on September 25, 2013
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Development of a Scalable Synthesis of a BTK Inhibitor
via C-N and C-C Bond Couplings as an Endgame
Strategy
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Jun-Bae Hong, James P. Davidson, Qingwu Jin, Gary R. Lee, Michael Matchett, Erin O’Brien, Michael
Welch, Bill Bingenheimer and Keshab Sarma
Technical Sciences - Chemical Synthesis, Roche Palo Alto LLC, 3431 Hillview Ave. Palo Alto, CA
94304, USA
junbae.hong@gmail.com
RECEIVED DATE
ABSTRACT. A scalable and convergent synthesis of a BTK (Bruton’s Tyrosine Kinase) inhibitor has
been developed. Synthetic routes to key intermediates were explored for the scale-up campaign,
especially the process for 6-dimethylaminodihydroisoquinolinone, which was prepared via a
regioselective cyclization of an isocyanate, mediated by AlCl3. Improved routes to key building blocks
were demonstrated by expedient multi-kg productions. The target compound was assembled through
Pd-catalyzed amidation reaction followed by a Suzuki-Miyaura cross coupling reaction.
KEYWORDS. BTK inhibitor, Dihydroisoquinolinone, Selective cyclization, Friedel-Craft acylation,
Pyridone synthesis, Pd-catalyzed amidation, Suzuki-Miyaura cross coupling.
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Introduction
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Bruton’s Tyrosine Kinase (BTK) is a member of the Tec family of tyrosine kinases and an important
cell signaling enzyme.1 Activation of BTK triggers a cascade of signaling events that culminates in the
generation of calcium mobilization and fluxes, cytoskeletal rearrangements, and transcriptional
regulation involving nuclear factor-κB (NF-κB).2 Therefore, BTK has been known to be a critical
regulator of early B cell development, and mature B cell activation and survival,3 and it has been
clinically validated that B cells play a key role in the pathogenesis of autoimmune and inflammatory
diseases.4 Protein-based therapeutics that deplete B cells showed good efficacy against autoantibody-
driven inflammatory diseases such as rheumatoid arthritis.5 Therefore, inhibition of the protein kinase
that is crucial in B cell activation should be a novel approach as useful therapeutics for B cell mediated
diseases.3-5 As good evidence for a role of BTK in autoimmune and inflammation diseases has been
already provided by a BTK-deficient mouse model, our Medicinal Chemistry group identified
compound 1 shown below as a potent BTK inhibitor (Figure 1), which was selected for further
development for the potential treatment of rheumatoid arthritis.6
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O
N
OH
N
N
HN
O
N
N
1, Clinical Lead Compound
O
O
Figure 1. Drug candidate 1.
The target BTK inhibitor consists of four main key building blocks; selectivity group, linker, core
group and front group (Figure 2). Therefore, the synthetic strategy was to develop a process for each
component, then assemble them through Pd-catalyzed reactions and SNAr chemistry. The most
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challenging part was the synthesis of the dihydroisoquinolinone derivative, a selectivity group, which
was prepared originally by the Medicinal Chemistry group from the corresponding indanone through a
Schmidt-type ring expansion,7 a step deemed unsuitable for direct scale-up due to safety issues and poor
selectivity. In an effort to avoid an unsuitable step for scale up, intensive process research activities
were undertaken to identify a potential scalable synthetic route. Synthesis of the core group was rather
straight forward from a commercially available staring material, but in order to ensure a safe and benign
process, the work-up procedure was modified accordingly. In addition, the choice of the linker was very
important since it is the pivotal reaction center to construct the whole molecule and also to improve the
efficiency of the end game. The selection of 2-bromo-6-chlorobenzaldehyde as a linker provided high
selectivity as well as reactivity in the Buchwald C-N bond forming reaction,8 and the subsequent
Suzuki-Miyaura cross coupling9 was performed to afford the core structure of a BTK inhibitor. Each
process and also the crystallization of API will be discussed in detail in this paper.
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C-C bond formation via Suzuki-Miyaura coupling
N
OH
O
N
C-N bond formation via SNAr
N
HN
O
N
N
C-N bond formation via Pd(Cu)-catalysis
O
O
X
N
OP
N
O
N
X''
X'
HN
H2N
X
O
N
O
O
Front group
Core group
Linker
Selectivity group
Figure 2. Structural analysis of BTK inhibitor; 4 main subunits.
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Results and Discussion
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Synthesis of the selectivity group. The original Medicinal Chemistry route for the selectivity group 5
shown in Scheme 1 was not amenable to scale-up due to several issues. First of all, the use of hazardous
hydrazoic acid was a significant safety problem. Secondly, lack of selectivity in the Schmidt
rearrangement resulted in the generation of a 1:1 isomeric mixture (desired 3 and undesired 4), that
required chromatographic separation, which is not desirable on large scale. Lastly, 4-fluoroindanone (2)
was a relatively expensive starting material when considering the 27% overall yield of 5.
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F
F
N
Me2NH, EtOH
150 ºC, 7 h
NaN3
HN
HN
CH3SO3H
CH2Cl2
O
O
3
O
2
+
44% yield
5
F
45% yield
with chromatography
O
N
H
4
Scheme 1. Original Medicinal Chemistry synthesis of N,N-dimethylaminodihydroisoquinolinone.
Various alternative syntheses of 5 were pursued. Our first strategy involved the discrete synthesis of
the isoquinolinone according to the protocol established by Staab et al.,10 which utilized cyclization of
an acylamidine to build the isoquinolinone scaffold under basic conditions (Scheme 2). Easily
accessible dimethyltoluidine 6 was used as the starting material in this first generation approach.
Ammonium acetate-catalyzed bromination of 6 in acetonitrile was found to be quite selective and facile.
To avoid any significant over-bromination, the reaction was conducted with a slight undercharge of
NBS, which resulted in a 93% isolation yield of the desired product. High purity product 7 was
precipitated out of the reaction mixture simply by drowning with an adequate amount of water. The
halogen–metal exchange reaction of 7 with either n-BuLi or i-PrMgCl was problematic. However, the
corresponding Grignard species was prepared by treatment with Mg in the presence of a catalytic
amount of MeMgCl, which was then allowed to react with carbon dioxide by pressurizing the reactor
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with carbon dioxide gas at 1-2 psig and maintaining a pot temperature of -15 to 0 °C to yield 8. The
reaction mixture was filtered to remove any unreacted Mg and then treated with a citric acid solution,
which caused precipitation of the product in high yield (94%) and high purity (>99%). Benzoic acid 8
was successfully converted to the desired amide 9 via sequential treatment with 1 equiv. of CDI at
ambient temperature and conc. aqueous NH4OH in THF. The reaction of amide 9 with a slight excess of
DMF-DMA in THF at 60 °C provided the remarkably stable acylamidine 10, which was isolated by
crystallization from heptane after solvent replacement. Cyclization of 10 in the presence of KOtBu in
THF proved to be rather sluggish, but could be driven to >96% completion at 60 °C over 24 h.
Crystalline 11 was isolated in 74% yield by quenching the crude reaction mixture with 20% citric acid,
separating the phases and replacing the organic phase solvent with ethanol. This synthetic sequence was
straightforward, and all reactions were successfully demonstrated on a multi-kg scale.
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NBS
NH4OAc
N
N
Mg, THF
CDI, THF
N
N
HO
H2N
CO2
94%
ACN
93%
NH4OH
93%
Br
O
O
6
7
8
9
N
Me2N
N
N
N
Pd/C, H2
DMF-DMA
t-BuOK
HN
HN
EtOH
70%
THF
97%
THF
74%
O
O
O
5
10
11
Scheme 2. The first generation process route.
The final hydrogenation turned out to be a little more challenging as it also generated small quantities
of the over-hydrogenated byproduct 12 (Figure 3).11 We also could not afford to carry unreacted 11 into
the next reaction since it would cause the Pd-catalyzed amidation to stall. The need of multiple
isolations was an additional factor to lead us to seek alternative, more efficient approaches to 5.
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1
2
N
3
4
HN
5
6
O
12
7
8
9
Figure 3. Structure of over-hydrogenated byproduct.
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An intramolecular Friedel–Crafts cyclization was viewed as a viable way to access the dihydroiso-
quinolinone scaffold. Acyl azide 15 was prepared from aldehyde 13, and then a Curtius rearrangement12
of 15 and subsequent cyclization of isocyanate 16 with AlCl3 in CH2Cl2 at ambient temperature
produced a mixture of 5 and 17 in only a 5:1 ratio (Scheme 3). Poor selectivity was also observed with a
bromo-isocyanate. An isocyanate containing a fluorine substituent was then considered as a potential
substrate for this cyclization, given that fluorodihydroisoquinolinone 3 undergoes aminolysis to give the
desired product 5 based on the Medicinal Chemistry route. This modification led to improve efficiency
in the synthesis of 5 (Scheme 4).
NaN3
ClCOOC2H5
i) Malonic acid
pyridine, piperdine
O
O
O
N
N
N
N3
HO
NEt3, Acetone
ii) H2, Pd/C, THF
14
13
15
AlCl3
CH3Ph
110 °C
N
N
O
HN
+
5
CH2Cl2
25 °C
O
N
16
17
Regioselectivity: 5 : 1
Scheme 3. Exploration of Friedel-Craft cyclization to dihydroisoquinolinone structure.
The precursor of the Friedel–Crafts cyclization, isocyanate 19, was prepared from commercially
available fluorophenethylamine 18. The formation of isocyanate 19 proceeded smoothly at or below 10
°C employing 0.35 equiv. of bis(trichloromethyl)carbonate and 1.05 equiv. of triethylamine.13 The
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precipitated triethylammonium chloride salts were largely removed by filtration, then a crude solution
of 19 (>95% purity by AN GC) could be carried directly into the next step. Alternatively, the DCM
solution of 19 could be washed with water and dried over sodium sulfate with minimal hydrolysis.
Isocyanate 19 was smoothly converted to 3 via addition of the crude DCM filtrate to a slurry of AlCl3 (3
equiv.), followed by stirring at ambient temperature for 12–16 h. After the addition of 4:1 citric
acid/water (3 equiv.), the crude product was obtained as a solution in DCM (typically 85–90% pure by
AN HPLC). High regioselectivity was achieved in this AlCl3-mediated Friedel–Crafts acylation such
that it gave the desired cyclized product 3 exclusively.14
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Fortunately, the crude DCM solution of 3 again could be carried directly into the amination step,
which had already been demonstrated by the Medicinal Chemistry group. However, the conversion of 3
to dihydroisoquinolinone 5 was conducted using a modification of the existing Medicinal Chemistry
protocol (3 + excess 33 wt% dimethylamine in EtOH at 150 °C in a sealed tube) in order to match the
capabilities of existing fixed equipment in our pilot plant. On a 20-g scale, the aminolysis reaction was
conducted at 130 °C in a stirred Hastelloy C autoclave using 4–5 equiv. of dimethylamine. At pressures
ranging from 120 to 160 psig, the reaction was complete within 16 h. However, the fact that one
equivalent of fluoride will be released during the aminolysis could lead to etching of the glass-lined
autoclave under the rather vigorous conditions employed. The etching test with glass coupons
confirmed this possibility as the glass surfaces of the samples were seriously degraded. This observation
of significant glass erosion prompted an investigation of alternate means to effect this transformation
that would be more compatible with existing equipment. The possibility of a direct SNAr-type
displacement using metal amides was initially explored. In a small scale reaction, a THF solution of 3
was added to a preformed suspension of 3 equiv. of LiNMe2 in THF/hexane at 0–10 °C and the
resulting mixture was allowed to warm to ambient temperature. Complete conversion of 3 to the lithium
salt of 5 was typically observed within 3 h. However, the extreme reactivity of LiNMe2 as a solid
precluded its use on larger scale, necessitating in-situ formation of the reagent from nBuLi and
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dimethylamine. Also, the presence of fluoride salts interfered with the crystallization of 5 from EtOH or
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3
EtOH/water mixtures.
4
5
6
7
HNMe2, EtOH
8
9
N
F
F
CO(OCCl3)2
NEt3, DCM
i) AlCl3, DCM
ii) Citric acidaq
TMSOEt
3
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NH2
NCO
HN
130-145 °C
O
18
19
5
64% from
18
Scheme 4. The second generation synthesis of 5; a highly selective telescoped process.
Another approach to render the aminolysis of 3 compatible with the glass-lined autoclave would be to
scavenge the fluoride ions generated from the reaction mixture as they form. To this end, several
experiments incorporating TMSOEt as a component of the reaction mixture were performed in Parr
Hastelloy pressure vessels containing samples of the DeDietrich glass liner. On a 10–50-g scale,
addition of 1.5–3.0 equiv. of the silane to the standard aminolysis mixture had no adverse effect on the
course of the substitution reaction other than a modest reduction in apparent reaction rate. However, the
glass liner samples were recovered essentially intact, even upon prolonged heating at 145 °C. Complete
conversion of 3 was observed within 24–36 h. In addition, the absence of fluoride salts in the crude
reaction mixture rendered isolation of the product via concentration much more efficient, providing 60–
75% first crop yields of high quality crystalline material (> 99% by AN HPLC). This added benefit
provided a compelling rationale for the choice of the protocol to be scaled up. Therefore, aminolysis of
the crude fluoroarene 3 produced in the pilot plant was conducted in the 35-L glass-lined autoclave
using 1.5 equiv. of TMSOEt and 4 equiv. of dimethylamine at 135–140 °C (maximum internal pressure
130 psig). Due to the limited reactor volume, the reaction was carried out in three portions, with each
cycle lasting 36–48 h. No significant corrosion of the reactor liner was detected. The combined
solutions were concentrated by distillation at ambient temperature to give 6.1 kg of 5 (64% yield) after
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filtration and drying. This whole 3 step process was performed in a telescope manner with only one
isolation step (Scheme 4).
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8
Preparation of the core group and front group. The core group, 3-amino-5-bromo-1-methyl-2H-
pyridone (22), was prepared from the corresponding bromonitropyridone 20 via methylation followed
by iron reduction (Scheme 5). A minor modification was made to the Medicinal Chemistry route, which
used methyl iodide as the methylating agent and Cs2CO3 as the base initially.
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H
K2CO3, Me2SO4
O
N
Fe, HOAc
87%
O
N
O
N
DMF
76%
O2N
Br
O2N
H2N
Br
Br
20
21
22
Scheme 5. Synthesis of the core group, 3-amino-5-bromo-1-methyl-2H-pyridone (22).
Methylation was carried out by treating 20 with dimethyl sulfate and K2CO3 in DMF (Scheme 5). As
an initial isolation procedure, the crude product crystallized upon the addition of water, and then it was
slurried in EtOAc/n-heptane (1/1) to remove 5–10% of the isomeric O-methylated product.15 This
simple operation afforded an orange colored solid in 98% purity as judged by AN HPLC. Interestingly,
the subsequent iron reduction showed only around 60% yield despite the lack of any significant
byproducts. Upon closer examination of 21, via elemental analysis, however it was found that the
isolated solid contained about 15 wt% of potassium. Moreover, examination of the UV spectrum
revealed completely reversible pH sensitivity, which indicated significant changes in the conjugation of
the π–system. In anticipation of scale up, it was standard practice to evaluate concentrated reaction
mixtures and isolated intermediates by DSC, which showed the isolated product decomposed
exothermically above 100 °C, and that led us to reevaluate the process.
The potassium content, low yield for the subsequent step, and the pH sensitive UV spectrum
observations led to the hypothesis that due to excess base in the methylation reaction, hydroxide was
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added to the electron-deficient pyridone to give 21a or, alternatively, a ring-opened product 21b, which
should be in equilibrium with 21 depending upon the pH (Scheme 6).16
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7
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9
K+ –
H
HN
Water, base
water, acid
O
O
N
N
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KO2C
O2N
OH
Br
Br
O2N
Br
O2N
21b
21
21a
Hypothetical structures
Scheme 6. pH dependent equilibrium of the intermediate 21.
Working with this hypothesis, the procedure was modified in order to isolate 21 safely. In the new
procedure, upon consumption of 20, the heterogeneous mixture was filtered to remove insoluble salts. A
small volume of toluene was then added, followed by concentrated sulfuric acid. Lastly, water was
added to precipitate 21 as large crystals. These modifications on work-up procedure allowed for the
direct isolation of pure 21, which had no thermal instability upon heating, and removed up to 10% of the
isomeric O-methylated byproduct completely.
The reduction of the nitro group was also optimized. Initially, 21a was subjected to reduction with
iron powder in acetic acid at 35 °C, leading to complete reaction within 30 min. However, with pure 21,
the iron reduction stalled. One hypothesis was that some base is required to push the reaction to
completion. Therefore, after the iron powder, as slurry in acetic acid, was activated by the addition of a
small amount of hydrochloric acid, a small amount of sodium hydroxide was added to generate sodium
acetate, which was reliably demonstrated to increase the rate of reaction and to prevent the reaction
from stalling near the end. Once the iron activation and NaOH addition was complete, the DCM
solution of 21 was added at the rate to maintain the reaction temperature in the range of 30-40 °C. The
most important modification was to move away from trying to remove the unwanted iron salts by
filtration at the end of the reaction. It was found that the iron salts contaminated 22, regardless of the
volume of solvent used to wash the filter cake. Fortunately, it was discovered that the iron salts could be
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effectively removed by adding 2 M aqueous citric acid to the dichloromethane suspension, which gave
an easily separable two-phase mixture. Subsequent wash with water and 2 M sodium citrate gave a tan
to brown clear solution of 22 in dichloromethane. The product was then isolated from this solution by
concentration and solvent replacement with heptane. Residual iron levels were generally <100 ppm, and
the material routinely passed elemental analysis. This two-step protocol was successfully demonstrated
at a 20-kg scale and resulted in a 76% yield for the methylation and an 87% yield for the reduction to
give 11.7 kg of 22. Safety was considered as this was an addition controlled process and a flame
arrester was incorporated into the reactor train that diluted any hydrogen gas generated with 50-100
volumes of nitrogen.
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The preparation of the front piece 24 and coupling with 22 was rather straightforward, starting from
acid chloride 23 (Scheme 7). After amide formation with 23 and morpholine in presence of
triethylamine, the solution of amide 24 was then combined with amine 22. The solvent was removed by
distillation with concurrent addition of toluene for azeotropic drying. Toluene was subsequently
replaced with NMP. The final NMP solution was chilled and added to a slurry of sodium hydride in
heptane to afford 25 (90% yield, >99% purity by AN HPLC).17 Scale up considerations were guided by
ARSST testing and the use of a flame arrester in the plant runs to handle the hydrogen generated from
NaH.
N
O
Cl
Cl
Br
HN
N
N
Morpholine-TEA
DCM
N
22, NaH
N
N
NMP, heptane
O
O
Cl
O
O
23
24
O
25
Scheme 7. Synthesis of the front piece 24 and coupling with 22.
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Synthesis of the linker and coupling with the selectivity group. The original Medicinal Chemistry
procedure to construct the right side of molecule utilized 2,6-dibromobenzyl acetate (28) as the linker,
which was prepared from 2,6-dibromotoluene (26) through a radical benzylic bromination and
subsequent substitution with potassium acetate (Scheme 8). Then, the C-N bond forming reaction with 5
was catalyzed by CuI.18
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
5, CuI
NBS
Br
OAc
Br
N
OAc
N
Bz2O2
K2CO3
KOAc
DMF
Br
Br
Br
Br
Br
Br
DMSO
150 oC
CCl4
O
26
27
28
62% yield from 26
29
40% yield
Scheme 8. First generation synthesis of the linker and the C-N bond forming reaction.
The Cu-catalyzed reaction was problematic since it proceeded in only poor yield even with a high
catalyst loading (40 mol%) and vigorous heating for several days. Therefore, we sought a more robust
palladium catalyzed C-N bond formation, and also explored alternative linkers. Keeping in mind that we
needed another metal catalyzed C-C bond formation process and an alcohol functional group at the end,
2,6-dibromobenzaldehyde (31a) was considered a better choice for the linker in terms of a facile
oxidative addition in the metal catalyzed reactions and a subsequent simple transformation of the
aldehyde group to an alcohol. Low-temperature lithiation of 1,3-dihalobenzene 30 produced an
aryllithium species that was allowed to react sequentially with DMF and aqueous acid to give 31. In the
initial attempt with 31a, Buchwald’s amidation was directly adopted for the coupling with the
selectivity piece, 5, to afford the desired product (Scheme 9).8, 19
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O
1
2
3
4
5
6
5, 2 mol% Pd(OAc)2
3 mol% XantPhos
N
O
o
Br
X
i) LDA, THF, -70 C
Br
X
N
X
ii) DMF
1.4 eq. Cs2CO3
dioxane, 100 oC
O
7
8
30a (X=Br);
30b (X=Cl)
31a (80%);
31b (87%)
32a (76%);
32b (84%)
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 9. Second generation linker and Pd-catalyzed C-N bond forming reaction.
However, excess of 31a was required to obtain reasonable selectivity in amidation. Even with 2 molar
equivalents of 31a, significant amount of double-amidation product was detected on HPLC (Table 1,
Entry 1). The reaction with 4-5 molar equivalents of 31a showed acceptable selectivity in Buchwald’s
amidation (Table 1, Entry 3 and 4). This initial study was implemented in multi-gram scale reaction to
demonstrate Pd-catalyzed C-N bond formation, and excess 31a was easily removed by a single
crystallization (Scheme 9).
Table 1. Pd-catalyzed C-N bond forming reaction of dibromobenzaldehyde (31a).a
Molar equivalent
HPLC yield of double- Isolation yield of
Entry
HPLC yield of 32a (%)
of 31a
amidation (%)
32a (%)b
1
2
3
2
3
4
5
78
83
88
90
16
12
7
Na
53
79
78
4
6
a
reaction conditions; 5 (1.0 mmol), Pd(OAc)2 (0.02 mmol), Xantphos (0.03 mmol), Cs2CO3 (1.4
b
mmol), and 1,4-dioxane (2 mL). 100 °C, 16 hr.
(EtOAc/Heptane).
isolation by column chromatography
However, further exploration for a more suitable linker found that 2-bromo-6-chlorobenzaldehyde
(31b) provided much better selectivity in the amidation step, where only around 2-3% of double-
amidation product was detected on HPLC and completely removed by crystallization at the end.20
XantPhos was found to be an effective ligand for the C-N bond formation reaction while X-Phos gave
only very poor reactivity. And dppf also showed comparable reactivity but gave a slower reaction rate.
Only a slight excess of 31b (1.2 equiv.) was needed to give full conversion, and Buchwald coupling of
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31b with 5 was successfully demonstrated with a 2% catalyst loading to produce multi-hundred grams
of 32b, which was crystallized from the reaction mixture by simple water drowning at 70 °C and
isolated in 84% yield and >97% HPLC purity (Scheme 9).
1
2
3
4
5
6
7
8
9
The final assembly: Suzuki-Miyaura cross coupling. As the end game, a Suzuki-Miyaura cross
coupling completed the build of the main skeleton of compound 1.9, 21 The original coupling reaction
was carried out with 29 and the corresponding boronate ester 33, which was prepared from 25 using
standard Miyaura borylation conditions. Final hydrolysis then afforded the target compound in 54%
yield over 2 steps (Scheme 10). Even though the yield of the Miyaura borylation was increased to 80%
through reaction optimization, the overall yield of the final sequence was too low.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
N
O
N
OH
N
i) , Pd(dba) XPhos
29
2,
N
O
K3PO4, n-BuOH
Bis(pinacolato)diborane
Pd(dba)2, XPhos
HN
B
HN
H2O, 100 ºC
O
O
N
N
25
N
N
ii) LiOH
THF, MeOH, H2O
KOAc, 1,4-dioxane
71% yield
54% yield
O
O
O
O
33
1
Scheme 10. The original Med. Chem. protocol for the end game.
As an efficient amidation with bromo-chlorobenzaldehyde 31b had been developed, the final coupling
reaction between aryl chloride 32b and boronate ester 33 was carefully examined. Whether the reaction
was run under dry or partially aqueous condition, de-boronation of starting material 33 was a constant
problem when 1,4-dioxane was used as the main solvent. Also, a significant volume of 1,4-dioxane was
needed to obtain a reasonable conversion, otherwise the coupling reaction stalled. Unlike dioxane,
reactions using X-Phos or XantPhos as the ligand in anhydrous DMF gave reliable and clean reaction
profiles with little or no de-boronation of 33. Because XantPhos was used in the Buchwald amidation, it
was selected as the preferred ligand over X-Phos in the hope that the Buchwald amidation might
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eventually be telescoped to the Suzuki–Miyaura coupling. Therefore, the Suzuki-Miyaura cross
coupling was carried out with 2 mol% Pd(OAc)2, 3 mol% XantPhos and 2 equiv. K2CO3 in DMF at 90–
100 °C for 12 h and, upon completion of reaction, the mixture was cooled, diluted with water and
extracted with dichloromethane. The organic extract was diluted with heptane to cause selective
precipitation of the homo-coupled byproduct of 33, which was then removed by filtration. Thereafter
the filtrate was diluted with acetone to induce a slow crystallization of 34. Removal of DCM by
distillation led to formation of a slurry of 34 in acetone, which was then cooled and filtered to afford the
desired product 34 in >98% HPLC purity and 84% isolated yield (Scheme 11).
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
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42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
N
O
2 mol% Pd(OAc)2
3 mol% XantPhos
HN
B
N
O
O
+
N
N
N
Cl
2 equiv. K2CO3, DMF
90-100 oC
O
O
84% yield
32b
O
33
O
N
N
O
N
HN
NaBH4
O
N
N
1
DCM, MeOH
89% yield
34
O
O
Scheme 11. Suzuki-Miyaura coupling reaction with Ar-Cl 32b and subsequent reduction to the API.
Finally, aldehyde reduction was achieved with NaBH4 as the reducing agent. Since the solubility of
crystallized aldehyde 34 was quite low in most organic solvents, except DCM, DMF, DMA, or DMSO,
dichloromethane containing a small amount of methanol was selected as the reaction solvent, and
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pellets of NaBH4 were used in order to achieve better control of the reaction as the pellets dissolve
slowly in the DCM/MeOH mixture. After the reduction was complete, 20% aqueous NaHSO3 solution
was added to precipitate the palladium, which was removed by filtration through a short pad of Solka-
floc.22 The desired product 1 was crystallized from IPA or IPA/MIBK in 87% isolated yield on a half-kg
scale. This end-game turned out to be quite efficient as compared to the original Medicinal Chemistry
route. However, during the reduction step, one unexpected impurity was observed and subsequently
identified to be the fused cyclic compound 36, and the origin of which was traced back to the Suzuki-
Miyaura coupling reaction (Figure 4).23
1
2
3
4
5
6
7
8
9
10
11
12
13
14
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18
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31
32
33
34
35
36
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41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
N
O
N
O
N
OH
N
N
N
HN
HN
O
O
N
N
N
N
35
36
O
O
O
O
Figure 4. Impurities identified in Suzuki-Miyaura coupling reaction.
Around 3-5% of the byproduct 35 was generated in the coupling step in a multi-hundred gram scale
reaction, which was then converted to the corresponding alcohol 36 in the subsequent NaBH4 reduction.
Fortunately, in this case it was possible to purge this impurity during the crystallization, but when the
coupling reaction was allowed to proceed for another 15 h, the amount of 35 formed increased to 20%
by HPLC analysis. Therefore, it was necessary to investigate methods to suppress this side reaction or
an alternative end-game approach based on the fact that the reaction time is prone to increase upon
further scale up. In a preliminary study, N-protection of 33 with a BOC group blocked the undesired
cyclization during the Suzuki-Miyaura coupling reaction, but it caused hydrolysis of the morpholine
amide during the BOC deprotection. On the other hand, this undesired cyclization could be prevented if
the aldehyde functional group was not present, as it seems to be labile in this coupling condition.
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Therefore, the reaction order was changed such that the aldehyde group in 32b was reduced first to give
the corresponding benzyl alcohol 37, which was then coupled with the boronate ester 33 to give the
final product (Scheme 12).
1
2
3
4
5
6
7
8
9
O
N
OH
N
33
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
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30
31
32
33
34
35
36
37
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45
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47
48
49
50
51
52
53
54
55
56
57
58
59
60
N
3 mol% Pd(dba)2
6 mol% PCy3
HN
OH
N
NaBH4
O
32b
N
N
Cl
N
DCM, IPA
94% yield
2 equiv. K2CO3
MeTHF/H2O
83% yield
O
1
O
37
O
Scheme 12. Completion of synthesis of BTK inhibitor 1.
As one of coupling partners had been modified to incorporate a more electron-rich aromatic ring, a
more basic phosphine ligand was needed to achieve a facile oxidative addition. After a quick screen of
phosphine ligands, tricyclohexylphosphine and Pd(dba)2 proved to be an quite efficient catalytic system
for this coupling reaction.24 In addition, running the coupling in MeTHF gave a comparable reactivity
and a much cleaner reaction profile as compared to DMF.25 After the reaction was complete, the crude
product was isolated by water drowning, followed by treatment with aqueous NaHSO3 solution and
activated carbon to remove palladium. Finally, the target API was crystallized from IPA as an IPA
solvate in 83% yield and 99% HPLC purity. No byproduct 36 was observed in this final sequence, and
all other usual impurities including des-boro and des-chloro compounds were effectively purged during
the crystallization.
Initially, it was quite difficult to obtain compound 1 as crystalline material. Even after intensive
studies to identify a suitable crystalline form for development, only amorphous material had been
isolated. Subsequently, ultra-sonication was suggested as a potential solution to produce crystalline
material of 1.26 Ultra-sonication in EtOH for 15 min successfully gave a crystalline EtOH solvate
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(Figure 5). Seed crystals generated in this manner then led to the development of a more conventional
crystallization method for the API.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
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42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(a)
(b)
Figure 5. Micro-spectrographs of (a) the amorphous form and (b) the crystalline EtOH solvate.
It turned out that compound 1 had a tendency to form various solvates such that a crystalline IPA
solvate was also obtained via the ultra-sonication technique. This IPA solvate was subjected to tumbling
experiments in diverse solvents and, since the IPA solvate was thermodynamically unstable, it
generated new crystalline forms in various solvents. In particular, stirring a suspension of the IPA
solvate in MIBK for 6 d gave crystalline non-solvated material, which was determined to be the most
stable form (Form A) with a high onset temperature at 265 °C in DSC. Even though ultrasound induced
crystallization in MIBK alone did not yield crystalline material, Form A was reproducibly obtained
from ultra-sonication in a MIBK/IPA (8/2) mixture. With this initial seed material in hand, a
conventional crystallization method was subsequently developed. However, the solubility of Form A
was extremely poor in water as well as in bio-relevant media and, moreover, the bioavailability of Form
A was too low (dog PK study, F = 2.5%, 20 mg/kg). On the other hand, the crystalline IPA solvate
(Form B) showed good kinetic solubility in bio-relevant media and acceptable bioavailability in dog (F
= 49%, 20 mg/kg). Therefore, the IPA solvate was selected for the toxicology studies even though it
contained 9 wt% of IPA.
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Cl
H
N
1
2
3
4
O
N
O2N
Br
5
6
7
8
i) Me2SO4
O
Cl
ii) Fe, AcOH
morpholine
61%
F
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
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30
31
32
33
34
35
36
37
38
O
N
NH2
NaH
90%
H2N
Br
i) CO(OCCl3)2
ii) AlCl3
O
N
iii) Me2NH
Cl
Br
HN
N
Br
64%
i) LDA
N
ii) DMF
HN
87%
O
N
O
O
CHO
Pd(OAc)2
XantPhos
Cl
Br
Pd(dba)2, XPhos
diborane
84%
80%
NaBH4
94%
O
N
O
B
Pd(dba)2
PCy3
HN
O H
N
O
N
N
Cl
N
83%
O
O
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
O
N
O H
N
N
HN
O
N
N
O
1
O
Scheme 13. The final process for a BTK inhibitor 1.
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The final process to synthesize a BTK inhibitor 1 was depicted in Scheme 13. We were able to avoid
the use of hazardous hydrazoic acid and eliminate column chromatographic separation by developing
scalable novel synthesis of key intermediate. And Pd-catalyzed amidation under Buchwald’s conditions
significantly improved a C-N bond forming step in terms of yield and selectivity with a suitable linker.
The end game was refined to minimize impurities in the final API, and crystallization method of API
was developed to obtain the desired solid state form. Most of steps were successfully demonstrated with
multi-kg scale in the pilot plant campaign. Further fine optimization of reaction conditions and full
safety assessment of couples of exothermic steps would be necessary in the next stage of process
development.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Conclusion. A modified, scalable, convergent synthesis of BTK inhibitor 1 was developed in order to
supply the required API for non-clinical safety studies. An efficient and robust, telescoped process for
the preparation of 5 was developed that proceeded via a regioselective AlCl3-mediated cyclization.
Improvements were made in the synthesis of 25, and a new linker group showed quite good reactivity in
the Pd-catalyzed amidation, as well as the Suzuki-Miyaura cross coupling reaction. As a result of all
these process improvements, the target compound was synthesized in 42% overall yield from 3-
fluorophenethylamine.
Experimental Section.
General. All HPLC analyses were carried out using a Waters 2690 liquid chromatography system
equipped with a Zorbax SB-C8: 3.0 x 100 mm column Component A 0.1% TFA in water; Component B
0.1% TFA in acetonitrile, Gradient 10% to 90% B from 0 to 3 minutes: Hold 90% B for 5 minutes,
Flow Rate, 1.2 mL/min. All GC analysis were carried out using an Agilent 6890 system equipped with a
DB-5MS column, 15m x 0.25 mm, 0.25 µm. packing (serial # US5326631A), He @ 7 PSI, 60 °C (2
min.) 15 °C/min to 300 °C, hold 2 min. FID, 300 °C. LC/MS analyses were carried out using an Agilent
1100MSD system equipped with an electrospray ionization source, nitrogen drying gas = 13 l/min@350
°C, nebulizer @ 60 psi, capillary voltage = 4 kV, fragmentor = 70V.
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6-Dimethylamino-3,4-dihydro-2H-isoquinolin-1-one (5) A reactor was charged with triphosgene
(5.2 kg, 17.5 mol) and dichloromethane (28 L), and the solution was cooled to 0 °C. A dichloromethane
(14 L) solution of 3-fluorophenethylamine (18, 7.0 kg, 50 mol) and triethylamine (5.3 kg, 52.5 mol) was
added at <10 °C. During the addition, precipitation of triethylammonium chloride occurred. Upon
reaction completion (conv. >99%), the salts were removed by filtration to provide a crude solution of 19
(>95% purity by GC) in DCM, which was then added to a slurry of AlCl3 (20 kg, 150 mol) in
dichloromethane (28 L), followed by stirring at ambient temperature for 12–16 h. After addition of 4:1
citric acid:water (36 kg) and phase separation, the crude 3 was obtained as a solution in DCM (90%
pure by HPLC). DCM was then removed by distillation at 40 °C under the slightly reduced pressure
while EtOH (30 L) was being added. The resulting EtOH solution was subjected to aminolysis with 33
wt% aqueous dimethylamine (27 kg, 200 mol) in the presence of TMSOEt (8.9 kg, 75 mol) at 135–140
°C. The reaction was carried out in three portions, with each cycle lasting 36–48 h. Upon completion of
the aminolysis (conv. >99%), the combined solutions were concentrated by distillation at ambient
temperature until onset of crystallization. After further concentration, ramped cooling, filtration and
drying, 6.1 kg of 5 (64% yield) was isolated as a white solid. 1H NMR (300 MHz, DMSO-d6) 7.63 (d, J
= 8.6 Hz, 1 H), 7.46 (s, 1 H), 6.60 (dd, J = 2.6, 8.7 Hz, 1 H), 6.50 (d, J = 2.5 Hz, 1 H), 3.31 (td, J = 2.8,
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13
6.4 Hz, 2 H), 2.95 (s, 6 H), 2.79 (t, J = 6.4 Hz, 2 H); C NMR (75.5 MHz, DMSO-d6) 165.4, 152.3,
140.5, 128.5, 116.8, 109.8, 109.3, 33.9, 28.5; ESI-HRMS calc’d for C11H15ON2 (M + H)+ 191.11789,
found 191.11770.
5-Bromo-1-methyl-3-nitro-1H-pyridin-2-one (21) A reactor was charged with 5-bromo-3-nitro-1H-
pyridin-2-one (20, 20 kg, 91.3 mol), K2CO3 (18.9 kg, 137 mol) and DMF (80 L), and the resulting slurry
was cooled down to –5 °C. Dimethyl sulfate (13.8 kg, 109.6 mol) was added slowly over 1.5 h at <15
°C. Upon completion of the addition, the mixture was warmed to ca. 25 °C, stirred for 12 h and filtered
to remove inorganic salts. The filtrate was diluted with toluene (21 L) and acidified with sulfuric acid (5
kg), then water (100 L) was slowly added to crystallize the product. Finally, filtration, followed by
washing with water (20 L) and toluene (20 L) afforded the desired product 21 (16.3 kg, 69.9 mol, 76%
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1
yield) as a yellow solid. H NMR (300 MHz, DMSO-d6) 8.58 (dd, J = 2.8, 7.8 Hz, 2 H), 3.57 (s, 3 H);
13C NMR (75.5 MHz, DMSO-d6) 152.9, 147.0, 140.4, 137.9, 92.9, 38.0; ESI-HRMS calc’d for
C6H6O3N2Br (M + H)+ 232.95563, found 232.95560.
1
2
3
4
5
6
7
8
9
3-Amino-5-bromo-1-methyl-1H-pyridin-2-one (22) Iron powder (325 mesh, 11.2 kg, 200 mol) and
acetic acid (36 kg, 600 mol) were added to a reactor, and to the resulting slurry was added conc. HCl
(400 mL) and 50% aqueous NaOH (5 kg) to activate the iron. (CAUTION: Hydrogen will be evolved.)
A solution of 21 (15.5 kg, 66.5 mol) in dichloromethane (150 L) was then added in a controlled fashion
while maintaining a temperature of 35 °C. Upon completion of the reaction (2 h at 35 °C), 2M aqueous
citric acid (120 kg) was added to dissolve the majority of the resulting iron salts. The organic layer was
separated and washed with water (50 L). The water layer was back-extracted once with a small volume
of dichloromethane (40 L). The combined organic layers were then treated with a solution of 2M
aqueous citric acid (112 kg) and 50% aqueous NaOH (50 kg), the pH of the mixture was adjusted to 8-
10, and the organic layer was separated and filtered. The filtrate was concentrated under vacuum and
once crystallization had initiated, heptane (160 L) was added. The resulting slurry was cooled to 0 °C,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
then filtered and dried to afford 22 (11.7 kg, 57.8 mol, 87% yield) as a brown solid. H NMR (300
13
MHz, DMSO-d6) 7.15 (d, J = 2.6 Hz, 1 H), 6.46 (d, J = 2.5 Hz, 1 H), 5.46 (b, 2 H), 3.41 (s, 3 H); C
NMR (75.5 MHz, DMSO-d6) 156.0, 139.3, 123.9, 111.3, 98.1, 36.6; ESI-HRMS calc’d for C6H8ON2Br
(M + H)+ 202.98145, found 202.98140.
5-Bromo-1-methyl-3-[5-(morpholine-4-carbonyl)-pyridin-2-ylamino]-1H-pyridin-2-one (25) A
reactor was charged with 6-chloro-nicotinoyl chloride (23, 9.8 kg, 55.7 mol) and DCM (75 L)
consecutively. After cooling to 5-10 °C, TEA (11.6 kg, 114.7 mol) was added, followed by the addition
of morpholine (5.5 kg, 63.1 mol) while keeping the temperature below 30 °C. Upon completion (conv.
>99% within 1 h), water (48 L) was added to quench the reaction. After extraction, the organic layer
was transferred to another reactor containing solid 22 (10.0 kg, 49.3 mol). The solution was
concentrated by distillation at atmospheric pressure while adding toluene (230 L) until the pot volume
reached approximately 90 liters to remove residual water. After completion of the distillation, the
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solution was cooled to 20 °C, then NMP (82 L) was added and the resulting mixture was re-
concentrated under vacuum to a volume of approximately 90 liters. Once the distillation was complete,
the concentrated mixture was cooled to 5-10 °C. NaH (60 % dispersion in mineral oil, 3 x 2 kg) was
charged to a second, dry reactor. Then, heptane (17 L) was added, and the jacket was cooled to 5 °C.
The solution containing 22 and 24 was transferred to the resulting slurry of NaH in heptane.
(CAUTION: hydrogen will be evolved here and at the quench point). The temperature increased to
62 °C. The reaction mixture was cooled, then stirred overnight at 15-20 °C. Upon completion of the
reaction (conv. >99%), a solution of water (3.3 L) and NMP (40 L) was slowly added to the reaction
mixture. After all the remaining NaH was quenched, additional water (186 L) was added slowly. After
ca. 27 L of water had been added, crystallization occurred. Once the addition of water was complete, the
resulting slurry was stirred for 1.5 h and then filtered. The filter cake was washed with water (240 L)
and dried under vacuum at 70 °C to give 25 (17.4 kg, 44.2 mol, 90% yield) as an off-white solid. 1H
NMR (300 MHz, DMSO-d6) 9.07 (s, 1 H), 8.71 (d, J = 2.6 Hz, 1 H), 8.35 (d, J = 2.5 Hz, 1 H), 7.69 (dd,
J = 2.3, 8.7 Hz, 1 H), 7.59 (d, J = 2.5 Hz, 1 H), 7.40 (dd, J = 0.6, 8.7 Hz, 1 H), 3.62 (b, 4 H), 3.53 (s, 3
1
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4
5
6
7
8
9
10
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H), 3.52 (b, 4 H); C NMR (75.5 MHz, DMSO-d6) 167.3, 156.1, 155.5, 146.3, 136.7, 131.2, 128.5,
122.7, 119.7, 112.5, 97.3, 66.1, 37.2; ESI-HRMS calc’d for C16H18O3N4Br (M + H)+ 393.05568, found
393.05550.
2-Chloro-6-(6-dimethylamino-1-oxo-3,4-dihydro-1H-isoquinolin-2-yl)-benzaldehyde (32b)
A
reactor was charged with 5 (258 g, 1.36 mol), 2-bromo-6-chloro-benzaldehyde (31b, 358 g, 1.63 mol),
Pd(OAc)2 (6.1 g, 27.2 mmol), XantPhos (23.6 g, 40.8 mmol), and Cs2CO3 (620 g, 1.90 mol). After the
reactor was degassed under vacuum and purged with nitrogen 3 times, 1,4-dioxane (3.6 L) and the
reaction mixture was heated to reflux for 5.5 h. Once the reaction was complete (conv. >99%), the
solution was cooled to 70 °C, and water (2 L) was added slowly while the temperature was maintained
at 70 °C to effect crystallization. The resulting slurry was cooled to ambient temperature, filtered,
washed with 1:1 water:1,4-dioxane, and dried under vacuum to afford the desired product 32b (375 g,
1.14 mol, 84% yield) as a light yellow solid. 1H NMR (300 MHz, DMSO-d6) 10.02 (s, 1 H), 7.68 (m, 2
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H), 7.49 (m, 2 H), 6.66 (dd, J = 2.7, 8.8 Hz, 1 H), 6.58 (d, J = 2.6 Hz, 1 H), 3.95 (b, 2 H), 3.08 (t, J = 6.3
Hz, 2 H), 3.01 (s, 6 H); 13C NMR (75.5 MHz, DMSO-d6) 188.7, 164.1, 152.8, 144.4, 140.7, 133.9,
132.1, 130.2, 129.5, 128.2, 125.0, 115.6, 110.0, 109.0, 49.2, 28.3; ESI-HRMS calc’d for C18H18O2N2Cl
(M + H)+ 329.10513, found 329.10500.
1
2
3
4
5
6
7
8
9
1-Methyl-3-[5-(morpholine-4-carbonyl)-pyridin-2-ylamino]-5-(4,4,5,5-tetramethyl-[1,3,2]-dioxa-
borolan-2-yl)-1H-pyridin-2-one (33) Bromopyridone 25 (600 g, 1.53 mol), potassium acetate (granule,
898 g, 9.15 mol), palladium acetate (3.4 g, 15.3 mmol), X-Phos (14.5 g, 30.5 mmol), and
bis(pinacolato)diboron (542 g, 2.14 mol) were charged to a suitable vessel, and the atmosphere
exchanged with nitrogen. In a separate vessel, 1,4-dioxane (8 L) was degassed by heating to reflux,
cooled to near ambient temperature, and then added to the reaction mixture by vacuum transfer. The
resulting mixture was heated to 95–100 °C. Once the reaction was complete (conv. >99%), the mixture
was filtered hot to remove excess salts. The filtrate was then concentrated by distillation to about half
the original volume, and then diluted with heptane (3 L) at 90 °C to induce crystallization. The resulting
slurry was cooled to ambient temperature and filtered. Washing with a minimal volume of 50% heptane
in 1,4-dioxane, and drying in a vacuum oven afforded the desired product 33 (537 g, 1.22 mol, 80%
10
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16
17
18
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23
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25
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60
1
yield) as an off-white solid. H NMR (300 MHz, DMSO-d6) 8.80 (s, 1 H), 8.57 (d, J = 1.8 Hz, 1 H),
8.30 (d, J = 2.2 Hz, 1 H), 7.63 (dd, J = 2.4, 8.7 Hz, 1 H), 7.61 (d, J = 2.0 Hz, 1 H), 7.30 (d, J = 8.3 Hz, 1
13
H), 3.62 (b, 4 H), 3.58 (s, 3 H), 3.54 (b, 4 H), 1.29 (s, 12 H); C NMR (75.5 MHz, DMSO-d6) 167.4,
158.0, 156.0, 146.5, 137.8, 136.6, 133.5, 129.7, 122.0, 121.1, 111.9, 83.6, 66.3, 66.1, 37.2, 24.6; ESI-
HRMS calc’d for C22H30O5N4B (M + H)+ 441.23038, found 441.23000.
2-(3-Chloro-2-(hydroxymethyl)phenyl)-6-(dimethylamino)-3,4-dihydroisoquinolin-1(2H)-one
(37) The benzaldehyde derivative 32b (100 g, 0.30 mol) was dissolved in DCM (500 ml) in a reactor,
then IPA (300 ml) was added. The solution was cooled to 5 °C, then NaBH4 (4.6 g, 1.22 mol) was added
portion wise over 1 h. Upon completion of the reduction as indicated by HPLC (conv. >99%), the
reaction was quenched with 10% aqueous ammonium chloride solution (300 ml). After the DCM was
removed by distillation, the desired product was precipitated from IPA/H2O. The resulting slurry was
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stirred at 80 °C for 2-3 h, then slowly cooled to ambient temperature. Filtration, washing with a minimal
volume of 1:1 IPA:H2O, and drying under vacuum at 80 °C afforded 37 (94.7 g, 0.29 mol, 94% yield) as
an off-white solid. 1H NMR (300 MHz, DMSO-d6) 7.71 (d, J = 8.6 Hz, 1 H), 7.45 (dd, J = 1.6, 7.9 Hz, 1
H), 7.40 (t, J = 7.8 Hz, 1 H), 7.30 (dd, J = 1.5, 7.5 Hz, 1 H), 6.67 (dd, J = 2.5, 8.9 Hz, 1 H), 6.59 (d, J =
2.3 Hz, 1 H), 4.86 (dd, J = 4.3, 6.6 Hz, 1 H), 4.51 (dd, J = 4.1, 11.2 Hz, 1 H), 4.41 (dd, J = 6.5, 11.3 Hz,
1 H), 3.92 (td, J = 4.6, 11.2 Hz, 1 H), 3.71 (dt, J = 5.6, 11.7 Hz, 1 H), 3.23-3.12 (m, 1 H), 3.01 (s, 6 H),
1
2
3
4
5
6
7
8
9
10
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47
48
49
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51
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60
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3.00-2.93 (m, 1 H); C NMR (75.5 MHz, DMSO-d6) 164.4, 152.7, 144.8, 140.6, 136.4, 134.5, 129.7,
129.3, 128.3, 126.6, 116.1, 109.9, 109.1, 57.3, 49.8, 28.3; ESI-HRMS calc’d for C18H19O2N2ClNa (M +
Na)+ 353.10273, found 353.10240.
6-(dimethylamino)-2-(2-(hydroxymethyl)-3-(1-methyl-5-(5-(morpholine-4-carbonyl)pyridin-2-
ylamino)-6-oxo-1,6-dihydropyridin-3-yl)phenyl)-3,4-dihydroisoquinolin-1(2H)-one (1) To a reactor
was added 37 (65 g, 0.196 mol), 33 (112 g, 0.255 mol), Pd(dba)2 (3.4 g, 5.9 mmol),
tricyclohexylphosphine (3.3 g, 11.8 mmol), and potassium carbonate (54.3 g, 0.393 mol). The reaction
vessel was degassed under vacuum and backfilled with nitrogen, and then MeTHF/H2O (650 mL, 9/1)
was added. The resulting reaction mixture was then heated to reflux overnight. Upon completion (conv.
>99%), the reaction was quenched by adding water (330 mL) at 60-70 °C, then the resulting slurry was
slowly cooled to room temperature. The crude product was collected by filtration, and washed with
water. The filter cake was then dissolved in DCM (1 L), and 20% aqueous solution of NaHSO3 (350
mL) was added. The resulting mixture was heated to 60 °C with vigorous stirring for 4 h. After cooling
to ambient temperature, the mixture was diluted with 350 mL of water, and the organic layer was
separated. Activated carbon (20 g) was added and the resulting DCM mixture was heated to 40 °C for 4
h. After cooling to room temperature, the mixture was filtered through a short pad of Celite® and the
collected solids were washed with a small amount of DCM. The solvent was removed by distillation at
atmosphere pressure while gradually adding IPA. When most of the DCM had been removed, seed
crystals of the IPA solvate (Form B) were added at 60 and then 80 °C. DCM was completely removed
by chasing with IPA, and the resulting IPA slurry (ca. 1 L) was aged at 80 °C for 2-3 h, then slowly
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cooled to ambient temperature, and filtered. Washing with a small amount of IPA and drying under
vacuum at 80 °C overnight afforded the desired BTK inhibitor 1 (99 g, 163 mmol, 83% yield) as an off-
white crystalline solid. 1H NMR (300 MHz, DMSO-d6) 8.94 (s, 1 H), 8.74 (d, J = 2.2 Hz, 1 H), 8.26 (d,
J = 2.3 Hz, 1 H), 7.72 (d, J = 8.8 Hz, 1 H), 7.66 (dd, J = 2.4, 8.7 Hz, 1 H), 7.49-7.44 (m, 2 H), 7.38-7.30
(m, 3 H), 6.67 (dd, J = 2.5, 8.8 Hz, 1 H), 6.59 (d, J = 2.6 Hz, 1 H), 4.83 (t, J = 4.6 Hz, 1 H), 4.35 (d, J =
4.3 Hz, 2 H), 4.34 (1H, IPA), 3.94 (td, J = 4.4, 11.2 Hz, 1 H), 3.82-3.73 (m, 1 H), 3.82-3.73 (m, 1 H,
IPA), 3.61 (s, 3 H), 3.58 (br, 4 H), 3.50 (br, 4 H), 3.26-3.16 (m, 1 H), 3.01 (s, 6 H), 2.99-2.94 (m, 1 H),
1
2
3
4
5
6
7
8
9
10
11
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13
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17
18
19
20
21
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32
33
34
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36
37
38
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45
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48
49
50
51
52
53
54
55
56
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58
59
60
13
1.04 (d, J = 6.1 Hz, 6 H, IPA); C NMR (75.5 MHz, DMSO-d6) 167.4, 164.6, 156.6, 155.9, 152.6,
146.6, 144.2, 140.6, 139.9, 136.6, 136.1, 129.5, 129.2, 129.0, 128.7, 128.6, 126.9, 122.0, 120.4, 118.2,
116.4, 111.9, 109.9, 109.1, 66.1, 62.0, 57.4, 50.0, 37.5, 28.4, 25.5; ESI-HRMS calc’d for C34H37O5N6
(M + H)+ 609.28199, found 609.28250.
ACKNOWLEDGMENT. We thank Drs. Yan Lou and Timothy Owen for their helpful discussions
about chemistry and also Dr. Naina Patel for her valuable contribution to this work.
1
13
SUPPORTING INFORMATION. H and C NMR spectra for compound 5, 21, 22, 24, 25, 32b, 33,
36, 37 and 1. This material is available free of charge via the internet at http://pubs.acs.org.
REFERENCES.
1. Vetrie, D.; Vorechovsky, I.; Sideras, P.; Holland, J.; Davies, A.; Flinter, F.; Hammarstrom, L.;
Kinnon, C.; Levinsky, R.; Bobrow, M.; Smith, C. I. E.; Bentley, D. R. Nature 1993, 361, 226-233.
2. (a) Smith, C. I.; Baskin, B.; Humire-Greiff, P.; Zhou, J. N.; Olsson, P. G.; Maniar, H. S.;
Kjellen, P.; Lambris, J. D.; Christensson, B.; Hammarstrom, L.; Bentley, D.; Vetrie, D.; Islam, K. B.;
Vorechovsky, I.; Sideras, P. J. Immunol. 1994, 152, 557-565. (b) Conley, M. E.; Dobbs, A. K.; Farmer,
D. M.; Kilic, S.; Paris, K.; Grigoriadou, S.; Coustan-Smith, E.; Howard, V.; Campana, D. Annu. Rev.
Immunol. 2009, 27, 199-227.
26
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3. (a) Khan, W. F.; Alt, F. W.; Gerstein, R. M.; Malynn, B. A.; Larsson, I.; Rathbun, G.; Davidson,
L.; Müller, S.; Kantor, A. B.; Herzenberg, L. A.; Rosen, F. S.; Sideras, P. Immunity 1995, 3, 283-299.
(b) Ellmeier, W.; Jung, S.; Sunshine, M. J.; Hatam, F.; Xu, Y.; Baltimore, D.; Mano, H.; Littman, D. R.
J. Exp. Med. 2000, 192, 1611-1624.
1
2
3
4
5
6
7
8
9
4. (a) Pan, Z,; Scheerens, H.; Li, S.-J.; Schultz, B. E.; Sprengeler, P. A.; Burrill, L. C.; Mendonca,
R. V.; Sweeney, M. D.; Scott, K. C. K.; Grothaus, P. G.; Jeffery, D. A.; Spoerke, J. M.; Honigberg, L.
A.; Young, P. R.; Dalrymple, S. A.; Palmer, J. T. Chem. Med Chem. 2007, 2, 58-61. (b) Jansson, L.;
Holmdahl, R. Clin. Exp. Immunol. 1993, 94, 459-465.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
5. Rastetter, W.; Molina, A.; White, C. A. Annu. Rev. Med. 2004, 55, 477-503.
6. (a) Dewdney, N. J.; Kennedy-Smith, J.; Kondru, R. K.; Loc, B. E.; Lou, Y.; McIntosh, J.; Owens,
T. D.; Soth, M.; Sweeney, Z. K.; Taygerly, J. P. G. (Roche Palo Alto LLC, USA). Preparation of
pyridinones and pyridazinones as Bruton’s tyrosine kinase (Btk) inhibitors. U.S. Pat. Appl.
2009/0306041, 2009. (b) Berthel, S.; Firooznia, F.; Fishlock, D.; Hong, J.-B.; Lou, Y.; Lucas, M.;
Owens, T. D.; Sarma, K.; Sweeney, Z. K.; Taygerly, J. P. G. (Roche Palo Alto LLC, USA). Inhibitors of
Bruton’s Tyrosine Kinase. U.S. Pat. Appl. 2010/0222325, 2010. (c) Dewdney, N. J.; Lou, Y.; Sjogren,
E. B.; Soth, M.; Sweeney, Z. K. (F. Hoffmann-La Roche AG, Switz.). Phenylpyrazinones derivatives as
kinase inhibitors and their preparation, pharmaceutical compositions and use in the treatment of
inflammation and autoimmune diseases. PCT Int. Appl. 2010/000633, 2010. (d) Lou, Y.; Owens, T. D.;
Kuglstatter, A.; Kondru, R. K.; Goldstein, D. M. J. Med. Chem. 2012, 55, 4539-4550.
7. Tangallapally, R. P.; Lee, R. E. B.; Lenaerts, A. J. M.; Lee, R. E. Bioorg. Med. Chem. Lett.
2006, 16, 2584-2589.
8. (a) Yin, J.; Buchwald, S. L. Org. Lett. 2000, 2, 1101-1104. For Pd-catalyzed C-N bond
formation with aryl halides and amines, see; (b) Harris, M. C.; Geis, O.; Buchwald, S. L. J. Org. Chem.
1999, 64, 6019-6022. (c) Guari, Y.; van Es, D. S.; Reek, J. N. H.; Kamer, P. C. J.; van Leeuwen, P. W.
N. M. Tetrahedron Lett. 1999, 40, 3789-3790.
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9. (a) Martin, R.; Buchwald, S. L. Acc. Chem. Res. 2008, 41, 1461-1473. (b) Wolfe, J. P.; Singer,
R. A.; Yang, B. H.; Buchwald, S. L. J. Am. Chem. Soc. 1999, 121, 9550-9561. (c) Billingsley, K.;
Buchwald, S. L. J. Am. Chem. Soc. 2007, 129, 3358-3366. (d) Achmatowicz, M.; Thiel, O. R.; Wheeler,
P.; Bernard, C.; Huang, J.; Larsen, R. D.; Faul, M. M. J. Org. Chem. 2009, 74, 795-809.
10. Staab, A. J.; Sin, N. (Bristol-Myers Squibb Company). Process for the preparation of substituted
heterocycles. U.S. Pat. Appl. 2007/0161670, 2007.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
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18
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20
21
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24
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30
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41
42
43
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45
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47
48
49
50
51
52
53
54
55
56
57
58
59
60
11. Cheng, C.-Y.; Tsai, H.-B.; Lin, M.-S. J. Heterocyclic Chem. 1995, 32, 73-77.
12. Brookings, D.; Davenport, R. J.; Davis, J.; Galvin, F. C. A.; Lloyd, S.; Mack, S. R.; Owens, R.;
Sabin, V.; Wynn, J. Bioorg. Med. Chem. Lett. 2007, 17, 562-565.
13. (a) Eckert, H.; Forster, B. Angew. Chem., Int. Ed. Engl. 1987, 26, 894-895. (b) Nowick, J. S.;
Powell, N. A.; Nguyen, T. M.; Noronha, G. J. Org. Chem. 1992, 57, 7364-7366.
14. (a) Hanessian, S.; Demont, E.; van Otterlo, W. A. L. Tetrahedron Lett. 2000, 41, 4999-5003. (b)
Wang, X.-J.; Tan, J.; Grozinger, K. Tetrahedron Lett. 1998, 39, 6609-6612.
15. Ahmad, Y.; Hey, D. H. J. Chem. Chem. 1954, 4516-4523.
16. Bradlow, H. L.; Vanderwerf, C. A. J. Org. Chem. 1951, 16, 73-83.
17. Considering the unfavorable characteristics of sodium hydride, alternative reagents were
evaluated also. The reagents that were tested included K2CO3, NaHMDS, KOtBu, iPrMgCl, DIEA,
tetramethylguanidine, DBU, TEA, and MsOH. But, sodium hydride was found to be superior to all in
terms of cleanness of the reaction.
18. (a) Klapars, A.; Huang, X.; Buchwald, S. L. J. Am. Chem. Soc. 2002, 124, 7421-7428. (b)
Clement, J.-B.; Hayes, J. F.; Sheldrake, H. M.; Sheldrake, P. W.; Wells, A. S. Synlett 2001, 1423-1427.
(c) Jones, C. P.; Anderson, K. W. Buchwald, S. L. J. Org. Chem. 2007, 72, 7968-7973.
19. (a) Manley, P. J.; Bilodeau, M. T. Org. Lett. 2004, 6, 2433-2435. (b) Fors, B. P.; Krattiger, P.;
Strieter, E.; Buchwald, S. L. Org. Lett. 2008, 10, 3505-3508. (c) Ligthart, G. B. W. L.; Ohkawa, H.;
Sijbesma, R. P.; Meijer, E. W. J. Org. Chem. 2006, 71, 375-378.
20. Ji, J.; Li, T.; Bunnelle, W. H. Org. Lett. 2003, 5, 4611-4614.
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21. (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457-2483. (b) Doucet, H. Eur. J. Org. Chem.
2008, 2013-2030. (c) Billingsley, K. L.; Barder, T. E.; Buchwald, S. L. Angew. Chem., Int. Ed. Engl.
2007, 46, 5359-5363. (d) Payack, J. F.; Vazquez, E.; Matty, L.; Kress, M. H.; McNamara, J. J. Org.
Chem. 2005, 70, 175-178.
1
2
3
4
5
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8
9
22. (a) Garrett, C. E.; Prasad, K. Adv. Synth. Catal. 2004, 346, 889-900. (b) Konigsberger, K.; Chen,
G.-P.; Wu, R. R.; Girgis, M. J.; Prasad, K.; Repic, O.; Blacklock, T. J. Org. Process Res. Dev. 2003, 7,
733-742.
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23. Fox, J. M.; Huang, X.; Chieffi, A. Buchwald, S. L. J. Am. Chem. Soc. 2000, 122, 1360-1370.
24. (a) Kudo, N.; Perseghini, M.; Fu, G. C. Angew. Chem., Int. Ed. Engl. 2006, 45, 1282-1284. (b)
Littke, A. F.; Fu, G. C. Angew. Chem., Int. Ed. Engl. 1998, 37, 3387-3388; Cy3P, XPhos, SPhos,
DavePhos, JohnPhos and tBu3P were evaluated for Suzuki-Miyaura coupling under the same reaction
conditions.
25. See the supporting information for the optimization of reaction conditions.
26. (a) Kaerger, J. S.; Price, R. Pharm. Res. 2004, 21, 372-381. (b) Amara, N.; Ratsimba, B.;
Wilhelm, A. M.; Delmas, H. Ultrason. Sonochem. 2001, 8, 265-270. (c) Hem. S. L. Ultrasonics 1967, 5,
202-207.
SYNOPSIS TOC.
H
N
CHO
O
Cl
Br
O
N
OH
N
N
O N
2
Br
H N
O
Cl
F
N
N H
2
O
N
O
O
Cl
- Total 5 + (3 + 2) + 1 = 11 steps with 8 isolations
- Longest linear sequence: 6 steps
- Overall 42% yield from fluorophenethylamine
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