Synthesis of novel 3,4-diaryl-5-aminopyrazoles as potential kinase inhibitors

Article abstract of DOI:10.1016/j.tet.2011.04.077

Synthesis of a diverse series of novel 3,4-diaryl-5-aminopyrazoles as candidates in the development of new protein kinase inhibitors is reported for the first time. In the course of a wider study into bisindolylmaleimide (BIM) derivatives, we examined a novel 5-aminopyrazole heterocyclic moiety as a structural analogue of the highly potent VEGF-R2/3 inhibitor pyrrole-2-one (8). The versatile nature of this pharmacophore allows considerable scope for derivatisation and hence exploration of structure activity relationships. Consequently, a variety of structural modifications were used in order to diversify the aminopyrazole ring substituents. Bicyclic derivatives of the parent aminopyrazoles (11, 12) were also synthesised as a means of probing the kinase active site, leading to formation of complex planar pyrimidine moieties. This work provides the framework for new explorations into kinase inhibition and critical investigations into selectivity of inhibitory activity.

Full text of DOI:10.1016/j.tet.2011.04.077

Tetrahedron 67 (2011) 4601e4611
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of novel 3,4-diaryl-5-aminopyrazoles as potential kinase inhibitors
*
Larry T. Pierce, Michael M. Cahill, Florence O. McCarthy
Department of Chemistry and Analytical and Biological Chemistry Research Facility, University College Cork, Cork, Ireland
a r t i c l e i n f o
a b s t r a c t
Article history:
Synthesis of a diverse series of novel 3,4-diaryl-5-aminopyrazoles as candidates in the development of
new protein kinase inhibitors is reported for the first time. In the course of a wider study into bi-
sindolylmaleimide (BIM) derivatives, we examined a novel 5-aminopyrazole heterocyclic moiety as
a structural analogue of the highly potent VEGF-R2/3 inhibitor pyrrole-2-one (8). The versatile nature of
this pharmacophore allows considerable scope for derivatisation and hence exploration of structure
activity relationships. Consequently, a variety of structural modifications were used in order to diversify
the aminopyrazole ring substituents. Bicyclic derivatives of the parent aminopyrazoles (11, 12) were also
synthesised as a means of probing the kinase active site, leading to formation of complex planar py-
rimidine moieties. This work provides the framework for new explorations into kinase inhibition and
critical investigations into selectivity of inhibitory activity.
Received 21 December 2010
Received in revised form 8 April 2011
Accepted 21 April 2011
Available online 28 April 2011
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
increased conformational distortion and hence, unique enzyme-
ligand binding interactions.16 Bisindolylmaleimide 2 was found to
Protein kinases (PKs) constitute 1.7% of the total number
of human genes and are one of the largest and most functionally
disparate gene families in nature.1 These enzymes control the
synchronised function of downstream proteins by regulatory
phosphorylation, orchestrating the flow of information from extra-
cellular stimuli to intracellular signalling pathways.2,3 As a validated
target class for new mechanism-based therapeutic intervention,
small-molecule inhibitors of aberrant kinase activity in epigenetic
growth pathways constitute a central tenet of anti-cancer chemo-
therapy with low systemic toxicity.4 Inhibition of deregulated ki-
have an IC50 of 0.11 mM for PKC, implicated in unabated growth
responses reported in several malignancies in vivo.17 Replacement
of an indole ring with a benzofuran moiety in 3 has been reported
to afford selective and potent GSK-3
b
inhibition (Fig. 1).18
H
N
O
H
N
O
O
Cl
nases have also been indicated in treatment of diabetes (PKC-b),
N
N
rheumatoid arthritis (p38 MAPK), and Parkinson’s disease (MLK).4e8
A small number of ATP-competitive small-molecule kinase in-
hibitors, such as GleevecÒ, with a variety of selectivity profiles have
now reached full clinical fruition; crystallographic data suggests
a multitude of chemical scaffolds possess avid non-specific binding
affinity for key residues occupying the widely conserved ATP-
binding site, formed at the cleft between the N and C-terminal
lobes.9e11 Staurosporine 1 was identified as a pankinase inhibitor,
competing for the ATP-binding site and exhibiting low nanomolar
activity against PKC (IC50¼2.7 nM) and CDK1 (IC50¼4 nM).5,12e14
Structurally related to the unselective lead compound 1,
a number of 3,4-diarylmaleimides demonstrate relatively selective
anti-tumour activity derived from inhibition within the aberrant
kinome.15 The binding mode of bisindolylmaleimides is more
complex than compounds possessing a planar ring system, due to
O
H
N
N
H3C
H3CO
1
2
NHCH3
R
H
N
NH
O
O
N
O
F
I
N
N
N
O
O
4
3
R = H, SH, OH, NH2
Fig. 1. Structures of small-molecule kinase inhibitors comprising a panel of modified
* Corresponding author. E-mail address: f.mccarthy@ucc.ie (F.O. McCarthy).
diaryl substituted lactam derivatives.
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.04.077

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L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
In this context, the potential of new flexible 3,4-diarylpyrrole
unique activity profiles via application of novel inhibitor classes
maintaining both active trimethoxyphenyl and indolyl substituents
in place, while replacing the variable pyrrolic head-group present
for compounds 7e9. An example of this would represent an
adaptable bidentate pyrrolic nucleus containing auxiliary polar
character in order to exploit putative new modes of inhibitor
binding within the ATP-binding kinase hinge region.
Recently, Bossi and co-workers revealed that PHA-E429 10 (ALK;
IC50¼91 nM) furnished an effective donoreacceptoredonor series
of hydrogen bonds between the 5-aminopyrazole moiety and ALK
hinge residues (Fig. 3).23 Thus, comparison of rational binding
congeners to yield synergistic kinase selectivity is a tantalising
phenomenon at the forefront of current anti-cancer research. This
report will thus investigate further structural insights into the key
‘heterocyclic paradigm’ of novel H-bonding anti-kinase inhibitor
design, complementing our previously disclosed innovation of a li-
brary of bisindolylpyrimidin-4-ones 4, currently being evaluated
for in vitro anti-cancer activity.19
Treatment of numerous diseases involving dysregulation of
vascular perfusion has also attracted pharmaceutical attention due
to the remarkable success of inhibitors of VEGFR2 to disrupt
pathologic tumour neovascularisation (solid tumour growth), age-
related macular degeneration, rheumatoid arthritis and psoriasis.20
An important contribution in this area was proffered by Peifer and
co-workers following anti-angiogenesis evaluation of a panel of
combretastatin A-4 analogues with a conserved stilbene moiety
represented by the lead compound 5. Rationalising that other cisoid
3,4-diaryl substituted compounds, such as 6 (containing a critical
enzyme-interacting maleimide warhead) would display significant
activity, preliminary compound screening confirmed 4-(3,4,5-tri-
methoxyphenyl)-3-(indol-3-yl)-1H-pyrrole-2,5-dione derivative 7
with an IC50 value of 2.5 nM for VEGFR2 (Fig. 2).15
modes for
a 3-aryl-4-(indol-3-yl)-pyrrol-2-one scaffold with
a closely analogous pyrazolic H-bonding orientation led us to
identification of 3-(3,4,5-trimethoxyphenyl)-4-(indol-3-yl)-1H-
pyrazole-5-amine derivatives containing a novel 5-aminopyrazole
bioisostere as a potential new PK inhibitor class (11, Fig. 3). We now
report synthesis of a library of novel derivatives based on the
postulated ability of the diaryl-5-aminopyrazole system to mimic
an active lactam conformation, as well as promote further H-
bonding interactions in the kinase pocket.
R2
R1
N
N
1
H
N
N
N
N
5
HN
2
N
3
NH
O
H
N
H
N
4
O
O
O
O
O
O
X
N
HO
O
O
HO
O
10
O
X = CH; R1, R2 = H
X = N; R1, R2 = H
11
12
N
H
O
O
O
O
O
5
6
Fig. 3. Structures of PHA-E429 10 containing H-bonding acylaminopyrazole and
substituted 4-(indol-3-yl)-3-(3,4,5-trimethoxyphenyl)-5-aminopyrazole core (11 and
12).
H
H
N
It has been noted in the literature that replacement of an indole
unit with a 7-azaindole moiety can alter inherent pharmacological
properties in these compounds, while also enhancing drug-complex
affinity by auxiliary formation of hydrogen bonds orientated within
the active site of target enzymes.24 In recent years, replacement of
indole with 7-azaindole subunits in indolocarbazole and BIM ana-
logues has consequentlyled to an awareness of selective cytotoxicity
profiles associated with these congeners in vitro.25,26 A complete
series of 7-azaindole analogues (12; Fig. 3) was developed during
this work, representing a key strategy for study of a 3-(7-azaindol-3-
yl)-4-aryl-fused heterocyclic kinase inhibitory template.
N
O
O
R1
O
O
N
H
N
H
O
O
O
O
9
R1 = C=O
7
8
R
1 = CH2
In addition, the synthesis of complex purine-like pyrazolopyr-
imidine derivatives 13 and 14, structurally related to 4,5-diaryl
substituted pyrazolo[3,4-c]pyridazine 15, a selective inhibitor of
Fig. 2. Novel diaryl-substituted N-heterocyclic anti-kinase molecular templates con-
serving binary H-bonding amide network.
CDK1/cyclin B (IC50¼6.1
m
M) (Fig. 4) has also been accomplished.27
Envisaging that this aromatic substitution pattern comprised
a key molecular scaffold, a simplified pyrrol-2-one analogue 8 was
subsequently uncovered to exhibit attractive VEGFR2 inhibitory
activity (IC50¼31 nM).21 Modelling of 8 within the ATP site of
VEGFR2 illustrated important proteineligand interactions between
the peptide backbone carbonyl of Glu915 and pyrrole NH, as well as
between the backbone NH of Cys917 and hydrogen bond acceptor
carbonyl group.22 Introduction of enzyme selectivity aligned with
strategic modification of this heterocyclic ring system was con-
firmed by the differential activity exhibited by regioisomeric pyr-
R1
R2
R1
H
N
N
N
N
N
N
O
N
H2N
O
N
O
15
R1 = CF3; R2 = CH
R1 = OH; R2 = N
13
14
rolone
9
(IC50¼11
mM), hypothesised to result from altered
orientation of the lactam in the kinase pocket (Fig. 2). Furthermore,
this analogue 9 displayed single digit micromolar activity against
other therapeutically-relevant kinases such as ARK5, Aurora A/B
and SAK.21 These data also illustrate an opportunity to develop
Fig. 4. Comparison of 4,5-diarylpyrazolo[3,4-c]pyridazine 15 with novel analogues
comprising a fused bicyclic pharmacophore (13, 14).

L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
4603
In this report, we describe the synthesis for the first time of
these diaryl-5-aminopyrazoles, branched mono-N-substituted
derivatives and bicyclic congeners.
1H-pyrazol-5-amine analogues (11; R1/R2sH) was successfully
synthesised by suitable methodology, engineering a panel of novel
compounds displaying unique hydrogen bonding networks.
Initial N1-acetylation was accomplished following treatment
with acetic anhydride at reflux overnight. On work-up, N1-acety-
lated aminopyrazole 23 was purified by chromatography, and iso-
lated as an off-white crystalline solid in a yield of 40%. Application
of these conditions in the presence of trifluoroacetic anhydride
provided the trifluoroacetamide analogue 24 (40%) (Scheme 2).
Construction of more complex derivatives bearing substituent H-
bonding functionalities capable of exploiting side-chain interactions
within the kinase hinge region also led to development of thioamide
congener 25, formed by heating in the presence of methyl iso-
thiocyanate overnight, in an overall yield of 34% (Scheme 2).
Bioactive molecules bearing methylsulfonamide character also
occupy an important role in current pharmaceutical research. Thus,
reaction of aminopyrazole 11 with methanesulfonyl chloride in
pyridine, at 90 ꢀC, afforded compound 26 in a yield of 35%.
Synthesis of a novel N1-guanylated compound 29 further ex-
panded our scope to investigate congeners with attractive struc-
tural and electronic properties in this series. Base-promoted
diimide coupling of 11 with (N,N0-di-tert-butoxycarbonyl)thiourea,
27, initially gave access to the Boc-protected compound 28, prior to
acidic liberation of trifluoroacetate salt 29 in an overall yield of 35%
(Scheme 2).32
2. Results and discussion
Previous reports describing the synthesis of 3-aryl-4-(indol-3-
yl)pyrrole derivatives involve efficient application of Faul’s Perkin-
type methodology involving one-pot condensation between ethyl
indole-3-glyoxylate and 3,4,5-trimethoxyphenylacetamide to af-
ford
4-(3,4,5-trimethoxyphenyl)-3-(indol-3-yl)-1H-pyrrole-2,5-
dione 7, in 54% yield.15 In 2008, the same group published their
synthesis of reduced lactam 8, by modified Knoevenagel route to
the corresponding pyrrole-2-one, isolated following SEM-
deprotection.21
In this work we present the targeted replacement of the pyrrol-
2-one nucleus within compounds 8 and 9 resulting in formation of
substituted 4-(1H-indol-3-yl)-3-(3,4,5-trimethoxyphenyl)-1H-pyr-
azol-5-amines 11 and 12, via late-stage acid-promoted cyclo-
condensation in the presence of hydrazine.28,29 Efforts to probe the
molecular space within the inhibitor binding pocket were pro-
gressed by incorporation of functionality leading to elaboration of
this key heterocyclic template.
2.1. 3,4-Diaryl-5-aminopyrazole synthesis (11)
Applying standard Mannich conditions starting from indole 16,
gramine 17 was initially isolated and converted to indole-3-
acetonitrile 18. N-Methylation was carried out following a litera-
ture procedure, to afford protected 19 in quantitative yield and used
without purification.30 Reaction of precursor 19 with LDA according
to our previously reported modified Claisen conditions, with 3,4,5-
trimethoxybenzoyl chloride 20, as the product of acid chloride
2.3. Condensed bicyclic ring analogue
Formation of pyrazolo[1,5-a]pyrimidine compound 13 contain-
ing a planar pyrimidine pharmacophore was accomplished in 45%
yield via acid-promoted condensation with HFAA, which was ac-
companied by rapid appearance of a persistent dark red colour
within the reaction mixture. The final reaction in this derivatisation
study was undertaken to form pyrazolotriazinedione 14, in-
corporating a novel planar H-bonding scaffold comprising an at-
tractive structural motif.33 Formation of 14 under mild conditions
proceeded in an excellent yield of 64%, requiring no further puri-
fication (Scheme 3).
formation from acid 21, afforded b-ketonitrile 22 in a yield of 35%.
Following acetic acid-catalysed condensation of intermediate 22
with hydrazine, the polar 4-(1-methyl-1H-indol-3-yl)-3-(3,4,5-tri-
methoxyphenyl)-1H-pyrazol-5-amine 11 was isolated in a moder-
ate yield of 23%, further diminished to 15% following subsequent
scale-up. Fortunately, portionwise addition of excess hydrazine,
along with camphoric acid in dry methanol at reflux for 24 h pro-
vided multi-gram synthesis of title compound 11 in a yield of 62%
(Scheme 1).31
2.4. 7-Azaindole analoguedb-ketonitrile intermediate and
aminopyrazole nucleus
Initially, 7-azagramine 31 was synthesised via a Mannich re-
action from 7-azaindole 30 using dimethylamine and formalde-
hyde (Scheme 4). Conversion to the corresponding acetonitrile 32
was achieved by displacement of the protonated amine using so-
dium cyanide. Interestingly, a novel diethylamine analogue 33 of 7-
2.2. Derivatisation study
To define the versatility of our approach, an initial comparative
library of 3-(3,4,5-trimethoxyphenyl)-4-(1-methyl-1H-indol-3-yl)-
N
N
(ii)
(i)
H
N
N
H2N
O
N
O
(iii)
N
H
N
N
H
(vi)
(v)
16
19
17
O
O
N
N
O
O
O
O
O
O
O
O
Cl
OH
(iv)
22
11
O
O
O
21
20
Scheme 1. Reagents and conditions: (i) Et2NH, HCHO, MeOH, rt, 3 h, 17¼62%; (ii) CH3I, KCN, MeOH, reflux, 20 h, 18¼67%; (iii) NaH, CH3I, DMF, 0 ꢀC to rt, 3 h, 19¼100%; (iv) SOCl2,
DCM, reflux, 20 h, 20¼100%; (v) (a) LDA, 3,4,5-(OMe)3C6H2COCl (20), THF, ꢁ78 ꢀC to rt, 16 h (b) NH4Cl/H2O, 22¼35%; (vi) NH2NH2.H2O, camphoric acid, MeOH, reflux, 24 h, 11¼62%.

4604
L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
O
N
H2N
N
O
oc
oc
B
N
NHB
O
N
F3C
O
O
H
N
N
H2N
HN
23
N
N
O
O
(i)
S
N
N
oc
oc
B
B
O
N
H
N
H
O
O
O
H
N
(ii)
28
27
24
H2N
N
(v)
(vi)
O
HN
NH2
N
F
H
C
3CO2
N
O
O
N
H2N
11
H
(iii)
N
S
(iv)
O
O
N
H2N
N
N
O
S
HN
H
N
O
O
N
29
O
N
O
O
O
N
25
O
O
26
Scheme 2. Reagents and conditions: (i) Ac2O, CH3CN, reflux, 16 h, 23¼40%; (ii) (CF3CO)2O, CH3CN, reflux, 16 h, 24¼40%; (iii) (a) CH3NCS, CH3CN, reflux, 16 h (b) H2O, 0 ꢀC, 1 h,
25¼34%; (iv) CH3SO2Cl, C6H5N, 90 ꢀC, 24 h, 26¼35%; (v) HgCl2, 27, Et3N, DCM, 0 ꢀC to rt, 16 h, 28¼35% (vi) TFA/DCM (10% v/v), 30 ꢀC, 12 h, 29¼quant.
with this key intermediate then afforded the parent aminopyrazole
aza-analogue 12 in good yield, from which a series of derivatives of
F
C
3
F
3C
biological interest could be prepared.
N
N
N
2.5. Aminopyrazole monosubstitution
O
Parent aminopyrazole 12 readily underwent monosubstitution
utilising a variety of different electrophiles (Scheme 5). However,
similar to the corresponding indole derivatives, the site of sub-
stitution varied depending on the electrophile applied in each
route.
In the cases of methyl thiourea derivative 36 and acetyl de-
rivative 37, prepared by treatment of aminopyrazole 12 with
methyl isothiocyanate and acetic anhydride, respectively, sub-
stitution occurred on the endocyclic nitrogen of the amino-
pyrazole ring. In the case of derivative 38, prepared by treatment
of aminopyrazole 12 with trifluoroacetic anhydride, trifluoro-
acetylation occurred on the exocyclic nitrogen of the ring, as
confirmed by 1H NMR spectroscopy (loss of the broad NH2 peak
between 4e6 ppm).
H
N
N
H2N
N
(i)
O
O
13
O
H
N
O
N
O
O
O
N
(ii)
HN
11
N
O
N
O
O
14
Scheme 3. Reagents and conditions: (i) HFAA, AcOH, 100 ꢀC, 20 h, 13¼45%; (ii) (a)
ClCONCO, Et3N (2e3 drops), DCM, 0 ꢀC to rt, 12 h (b) H2O, 0 ꢀC, 0.75 h, 14¼64%.
2.6. Preparation of bicyclic analogues
azagramine 31 had also been synthesised as a parallel to 17, but all
attempts to convert this precursor to acetonitrile 32 failed. Con-
sequent protection of the indolic nitrogen was afforded using so-
dium hydride and methyl iodide. However, the yield of the desired
product 34 was relatively low due to the formation of a dimethy-
lated by-product, formed as a consequence of the highly acidic
The triazinedione analogue 39 was synthesised following
treatment of precursor 12 with N-chlorocarbonyl isocyanate
(Scheme 6). A further bicyclic analogue of potential biological in-
terest was synthesised, this time following condensation of 12 with
HFAA, leading to the pyrimidine system 40.
nature of the
a-protons to the nitrile in this case.
2.7. Regioselectivity of substitution
Base-catalysed condensation of the N-protected acetonitrile 34
with the acid chloride 20 generated from 21 as previous, gave
formation of b-ketonitrile intermediate 35. Reaction of hydrazine
A recent comprehensive review of aminopyrazoles has postu-
lated that regioselective substitution is heavily dependent on the

L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
4605
N
N
C
(iii)
(i)
N
H
N
H
N
H
N
N
N
N
(iv)
32
30
31
(ii)
N
C
N
N
N
N
H
33
34
(v)
H
N
N
N
H2N
O
N
O
(vi)
O
O
N
N
N
O
O
O
12
35
Scheme 4. Reagents and conditions: (i) NH(CH3)2, HCHO, AcOH, H2O, EtOH, reflux, 31¼82% (ii) NH(CH2CH3)2.HCl, HCHO, H2O, EtOH, reflux, 33¼88% (iii) NaCN, AcOH, DMF, H2O,
reflux, 32¼52% (iv) NaH, MeI, DMF, 0 ꢀC, 34¼46% (v) 20, LDA, THF, ꢁ78 ꢀC, 35¼49% (vi) NH2NH2.H2O, cat. HCl, EtOH, reflux, 12¼70%.
H
O
N
N
O
HN
S
N
H
N
H2N
N
N
O
HN
N
H2N
(i)
O
O
N
H
N
N
N
O
N
H2N
N
N
O
N
O
(i)
O
CF3
N
12
O
O
O
39
36
O
(ii)
(iii)
N
F3C
N
(ii)
O
N
O
N
N
O
F
3C
12
N
H2N
N
HN
NH
O
O
N
N
O
O
N
O
O
N
N
40
N
O
O
Scheme 6. Reagents and conditions: (i) ClCONCO, NEt3, DCM, 0 ꢀC to rt, 39¼56% (ii)
HFAA, AcOH, reflux, 40¼54%.
O
7
3
38
Scheme 5. Reagents and conditions: (i) CH3NCS, CH3CN, reflux, 36¼47% (ii) Ac2O,
CH3CN, reflux, 37¼62% (iii) (CF3CO)2O, CH3CN, reflux, 38¼41%.
This regiochemical outcome of these reactions requires further
investigation in order to establish a protocol for selective sub-
stitution and this will be evaluated in future combinatorial studies
through carbamate protection strategy.
nature of the electrophilic reagent and derivatisation conditions.34
The observed monosubstitution pattern of these derivatives under
our methodology was investigated by means of 1H NMR spectros-
copy. Evidence of N-5 or N-1 substitution is given from the pres-
ence or absence of signals relating to the amine (2H, broad peak
between 4.5 and 6.5 ppm) or the pyrazole NeH (1H, broad peak at
13 ppm) as well as confirmatory evidence from single crystal X-ray
structure analysis (data not shown). Consequently it can be seen
that the amine is functionalized in the case of the tri-
fluoroacetamide and the methanesulfonamide, whereas in all other
cases the ring nitrogen was substituted. Interestingly, in the case of
methanesulfonylation, reaction of 11 with methanesulfonyl chlo-
ride in refluxing acetonitrile, containing Et3N was unsuccessful,
while it was possible to access amino-substituted analogue 26 in
the presence of pyridine at 90 ꢀC indicating that thermal conditions
may have a role.
3. Conclusion
A diverse series of novel 3,4-diarylaminopyrazoles were syn-
thesised and fully characterised from b-ketonitrile intermediates.
Derivatisation of the aminopyrazole core provided both bicyclic
and monosubstituted scaffolds giving significant scope with which
to explore the SAR for potential protein kinase inhibition. Reaction
with bidentate electrophiles also resulted in the formation of more
complex biologically relevant pyrimidine derivatives. Interestingly,
with regard to a series of monosubstitution reactions, the amino-
pyrazole nucleus displayed reagent dependent regioselectivity as
has been seen with similar systems but requires further in-
vestigation. In general, substitution occurred predominantly on the
pyrazole nitrogen, rather than on the exocyclic amine, with the

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L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
exception of the trifluoroacetyl and methanesulfonyl derivatives.
The synthetic procedures reported here provide a significant ad-
vance in the development of new and more selective kinase in-
hibitors and full combinatorial synthesis of this template is
underway. Preliminary biological screening of both compound ar-
rays has commenced and the selectivity/activity profiles of these
diverse inhibitory candidates will also be explored.
was added a solution of potassium cyanide (0.245 g, 3.77 mmol) in
water(2 mL). Iodomethane(0.3 mL,4.79 mmol)wasaddeddropwise
and the reaction mixture was then stirred vigorously at room tem-
perature for 16 h. Following evaporation of the solvent, the crude
residue was dissolved in ethyl acetate (100 mL) and successively
washed with saturated aqueous sodium bicarbonate solution
(100 mL), water (3ꢂ100 mL) and brine (2ꢂ100 mL). Following
chromatography employing ethyl acetate/hexane, the title com-
pound 18 was dried, and isolated as a beige amorphous solid (0.191 g,
67%): mp 32e34 ꢀC (lit.36 34e36 ꢀC); Rf (30% ethyl acetate/hexane)
0.35; nmax/cmꢁ1 (KBr) 3412, 2252, 1621, 1458, 1420; dH (300 MHz,
CDCl3) 3.82 [2H, s, CeH2], 7.15e7.21 [2H, m, CeH2,5], 7.22e7.28 [1H,
td, J7.1, 1.1, CeH6], 7.37e7.40 [1H, d, J8.0, CeH7], 7.57e7.60 [1H, d, J 7.8,
CeH4], 8.19 [1H, br s, NH]; dC (75 MHz, CDCl3) 14.4 (CH2, CH2CN),
104.7(C, aromaticC),111.6(CH, aromatic CH),118.1 (CH, aromaticCH),
118.2 (C, aromatic C), 120.3 (CH, aromatic CH), 122.8 (CH, aromatic
CH),122.9 (CH, aromatic CH),126.0 (C, CH2CN),136.3 (C, aromatic C);
m/z (ESþ) 130.0 [MþHꢁHCN]þ, (100%).
4. Experimental
4.1. General procedures
Melting points were measured on a Uni-Melt Thomas Hoover
Capillary Melting Point apparatus and are uncorrected. Low reso-
lution mass spectra were recorded on a Waters Micromass Quattro
Micro mass spectrometer (Instrument number QAA1202) in elec-
trospray ionization (ESI) positive and negative modes and a Waters
Micromass LCT Premier (Instrument number KD160) was used for
high resolution acquisitions. Infrared (IR) spectra were recorded as
potassium bromide (KBr) discs on a PerkineElmer FT-IR Paragon
1000 or a Spectrum One FT-IR spectrophotometer. 1H (300 MHz)
and 13C NMR (75 MHz) NMR were recorded on a Bruker Avance 300
NMR spectrometer unless otherwise stated. All spectra were
recorded at 20 ꢀC in deuterated chloroform (CDCl3) with tetrame-
thylsilane (TMS) as an internal standard unless otherwise stated.
Chemical shifts (dH and dC) are reported in parts per million (ppm),
relative to TMS and coupling constants are expressed in hertz (Hz).
Splitting patterns in 1H NMR spectra are designated as s (singlet), br
s (broad singlet), d (doublet), dd (doublet of doublets), ddd (doublet
of doublet of doublets) dt (doublet of triplets), t (triplet), q (quartet)
and m (multiplet). Thin layer chromatography (TLC) was carried out
on precoated silica gel plates (Merck 60 PF254). Visualisation was
achieved by UV light (254 nm), vanillin or potassium permanganate
staining. Column chromatography was carried out using Kieselgel
60, 0.040e0.063 nm (Merck).
4.1.3. 1-Methyl-1H-indol-3-yl acetonitrile (19)37. To a suspension of
NaH (60% dispersion in mineral oil) (3.33 g, 83.3 mmol) in anhy-
drous DMF (25 mL) was added dropwise a solution of 3-indolyla-
cetonitrile 18 (10.0 g, 64 mmol) in DMF (50 mL). After stirring for
30 min, at room temperature, the flask was then cooled to 0 ꢀC.
Iodomethane (6 mL, 95.8 mmol) was added dropwise in solution
with DMF (30 mL). The reaction was then allowed to warm and was
stirred at ambient temperature for 3 h. The reaction was then
quenched by pouring it into a mixture of ethyl acetate (300 mL) and
5% aqueous HCl (400 mL). Following product extraction, the organic
layer was washed with water (2ꢂ250 mL), brine (300 mL), dried
over magnesium sulfate and filtered. The resultant solution was
then evaporated thoroughly, under reduced pressure, at a water
bath temperature of 90 ꢀC, to yield the N-methyl acetonitrile 19 in
quantitative yield (11.1 g, 100%) as an off-white crystalline material:
mp 57e59 ꢀC (lit.37 59e60 ꢀC); Rf (30% ethyl acetate/hexane) 0.40;
nmax/cmꢁ1 (KBr) 2954, 2247, 1657, 1553, 1464; dH (300 MHz, CDCl3)
3.73 [3H, s, NCH3], 3.78 [2H, s, CeH2], 7.04 [1H, s, CeH2], 7.14e7.19
[1H, td, J 8.0,1.5, CeH5], 7.23e7.38 [2H, m, CeH6,7], 7.54e7.57 [1H, d,
J 7.9, CeH4]; dC (75 MHz, CDCl3) 14.3 (CH2, CH2CN), 32.9 (CH3,
NCH3), 103.0 (C, aromatic C), 109.6 (CH, aromatic CH), 118.2 (CH,
aromatic CH), 119.7 (CH, aromatic CH), 122.4 (CH, aromatic CH),
126.2 (C, CH2CN), 126.5 (C, aromatic C), 127.3 (CH, aromatic CH),
137.1 (C, aromatic C); m/z (ESþ) 171.1 [MþH]þ, (100%).
4.1.1. 3-Diethylaminomethyl-1H-indole (17)35. To a 250 mL 2-neck
round-bottomed flask was charged 37% formaldehyde solution
(7 mL, 86 mmol), 98% diethylamine (8.9 mL, 86 mmol), along with
indole (10.0 g, 86 mmol), absolute ethanol (120 mL) and zinc
chloride (17.5 g, 128 mmol). The resultant straw coloured slurry
was then stirred at room temperature for 2 h. The reaction mixture
was then poured into a mixture of ethyl acetate (150 mL) and water
(150 mL). Following addition of aqueous NaOH solution (20%) to
reach pH 9, extraction was performed with 3ꢂ150 mL volumes of
ethyl acetate; the resultant organic layers were evaporated under
reduced pressure, diluted with water (120 mL) and acidified with
concd HCl to pH 3. The slurry thus formed was then filtered under
vacuum; the mother liquor was basified to pH 9, with further
aqueous NaOH solution (20%). The turbid mixture was then cooled
to 0 ꢀC, and the light orange precipitate 17 filtered and washed with
water, prior to drying (10.6 g, 62%): mp 105e107 ꢀC (lit.35
109e110 ꢀC); Rf (30% ethyl acetate/hexane) 0.45; nmax/cmꢁ1 (KBr)
3051, 2971, 1619, 1543, 1500, 1452; dH (300 MHz, CDCl3) 1.06e1.11
[6H, t, J 7.1, 2ꢂNCH2CH3], 2.54e2.61 [4H, q, J 7.1, 2ꢂNCH2CH3], 3.79
[2H, s, CeH2], 7.05e7.06 [1H, d, J 2.3, CeH2], 7.07e7.13 [1H, td, J 7.5,
1.3, CeH5], 7.14e7.19 [1H, td, J 7.8, 1.4, CeH6], 7.29e7.32 [1H, d, J 8.0,
CeH7], 7.72e7.74 [1H, d, J 7.8, CeH4], 8.32 [1H, br s, NH]; dC
(75 MHz, CDCl3) 12.0 (2CH3, 2ꢂNCH2CH3), 46.7 (2CH2,
2ꢂNCH2CH3), 48.0 (CH2, CH2N(C2H5)2), 111.0 (CH, aromatic CH),
113.6 (C, aromatic C), 119.3 (CH, aromatic CH), 119.5 (CH, aromatic
CH), 121.8 (CH, aromatic CH), 123.5 (CH, aromatic CH), 128.1 (C,
aromatic C), 136.3 (C, aromatic C); m/z (ESþ) 203.1 [MþH]þ, (100%).
4.1.4. 3,4,5-Trimethoxybenzoyl chloride (20). To a mixture of 3,4,5-
trimethoxybenzoic acid (8.00 g, 37.7 mmol) in CHCl3 (30 mL) was
added thionyl chloride (13.7 mL, 189 mmol) in a dropwise fashion.
Once the addition was completed, the reaction mixture was heated
to reflux for 4 h before being cooled back to room temperature. The
solvent and excess thionyl chloride was removed under reduced
pressure to yield the acyl chloride 20 in quantitative yield as
a colourless oil, which was subsequently used without further
purification: nmax/cmꢁ1 (NaCl) 2970, 2944, 1750, 1590, 1457, 1415,
1130, 1128.
4.1.5. 2-(1-Methyl-1H-indol-3-yl)-3-oxo-3-(3,4,5-trimethoxyphenyl)
propanenitrile (22). LDA solution (2 M) (19.4 mL, 38.7 mmol) was
added, under nitrogen, to a flask containing THF (30 mL), cooled
to ꢁ78 ꢀC, and equilibrated at this temperature for 35 min, with
stirring. Nitrile 19 (3.01 g, 17.6 mmol) in THF (4 mL) was then added
slowly to the reaction flask and maintained at ꢁ78 ꢀC for 2 h. 3,4,5-
Trimethoxybenzoyl chloride (6.01 g, 26.4 mmol) was then dissolved
in THF (15 mL) and added dropwise to the reaction vessel at ꢁ78 ꢀC.
The reaction was allowed to warm to room temperature and stirred
overnight. Following solvent evaporation, the crude residue was
taken up in ethyl acetate (100 mL) and washed with saturated
4.1.2. 1H-Indol-3-yl acetonitrile (18)36. To a solution of N,N-diethyl-
3-aminomethyl indole 17 (0.370 g, 1.83 mmol) in methanol (10 mL)

L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
4607
aqueous ammonium chloride solution (2ꢂ150 mL). These were then
combined and further extracted with ethyl acetate (2ꢂ75 mL); the
aggregate ethyl acetate layers were then washed with water
(3ꢂ150 mL) and brine (2ꢂ150 mL), dried over magnesium sulfate,
filtered and evaporated in vacuo. Employing a chromatographic
gradient from 15 to 30% ethyl acetate/hexane, the novel in-
termediate 22 was isolated as a dark orange crystalline solid (2.22 g,
35%): mp 73e76 ꢀC; Rf (30% ethyl acetate/hexane) 0.46; nmax/cmꢁ1
(KBr) 3433, 2938, 1684, 1584, 1504, 1127; dH (300 MHz, CDCl3) 3.75
[3H, s, NCH3], 3.76 [6H, s, 2ꢂm-OCH3], 3.86 [3H, s, p-OCH3], 5.82 [1H,
s, CH], 7.15 [1H, s, CeH2], 7.18e7.24 [1H, t, J 7.3, CeH5], 7.21 [2H, s,
Chromatography with 15% ethyl acetate/hexane, followed by
concentration of the product fractions, generated the pure pyr-
azolic acetamide derivative 23 as off-white plate-like crystals
(0.067 g, 40%): mp 182e184 ꢀC; Rf (30% ethyl acetate/hexane) 0.71;
nmax/cmꢁ1 (KBr) 3449, 3338, 2935, 1710, 1608, 1572, 1485, 1126; dH
(300 MHz, CDCl3) 2.79 [1H, s, COCH3], 3.45 [6H, s, 2ꢂm-OCH3],
3.78 [3H, s, NCH3], 3.82 [3H, s, p-OCH3], 5.46 [2H, br s, NH2], 6.87
0
0
[2H, s, CeH2 ,6 ], 6.99 [1H, s, CeH2], 7.06e7.11 [1H, td, J 8.0, 0.9,
CeH5], 7.23e7.28 [1H, td, J 8.1, 1.1, CeH6], 7.35e7.38 [1H, d, J 8.0,
CeH7], 7.38e7.40 [1H, d, J 7.6, CeH4]; dC (75 MHz, CDCl3) 23.2
(CH3, COCH3), 32.9 (CH3, NCH3), 55.6 (2CH3, 2ꢂm-OCH3), 60.8
(CH3, p-OCH3), 94.5 (C, aromatic C), 104.7 (C, aromatic C), 105.0
(2CH, 2ꢂaromatic CH), 109.4 (CH, aromatic CH), 119.8 (CH, aro-
matic CH), 120.2 (CH, aromatic CH), 122.2 (CH, aromatic CH), 127.9
(C, aromatic C), 128.0 (C, aromatic C), 128.7 (CH, aromatic CH),
137.2 (C, aromatic C), 138.4 (C, aromatic C), 148.7 (C, aromatic C),
152.8 (2C, 2ꢂaromatic C), 153.3 (C, aromatic C), 173.8 (C, C]O); m/
z (ESþ) 421.2 [MþH]þ, (100%); HRMS (ESþ) exact mass calculated
for C23H25N4O4 [MþH]þ 421.1876. Found 421.1862.
0
0
CeH2 ,6 ], 7.26e7.31 [1H, t, J 6.8, CeH6], 7.32e7.35 [1H, d, J 7.5, CeH7],
7.71e7.74 [1H, d, J 7.8, CeH4]; dC (75 MHz, CDCl3) 33.1 (CH3, NCH3),
38.4 (CH, CHCN), 56.3 (2CH3, 2ꢂm-OCH3), 61.0 (CH3, p-OCH3), 103.9
(C, aromatic C), 106.7 (2CH, 2ꢂaromatic CH), 110.1 (CH, aromatic
CH), 116.9 (C, aromatic C), 118.1 (CH, aromatic CH), 120.6 (CH, aro-
matic CH), 122.9 (CH, aromatic CH), 125.6 (C, CN), 128.4 (CH, aro-
matic CH), 128.6 (C, aromatic C), 137.1 (C, aromatic C), 143.4 (C,
aromatic C), 153.0 (2C, 2ꢂaromatic C), 187.5 (C, C]O); m/z (ESþ)
365.1 [MþH]þ, (60%); (ESꢁ) 363.1 [MꢁH]ꢁ, (100%); HRMS (ESþ)
exact mass calculated for C21H21N2O4 [MþH]þ 365.1501. Found
365.1486.
4.1.8. 2,2,2-Trifluoro-N-(4-(1-methyl-1H-indol-3-yl)-3-(3,4,5-trime-
thoxyphenyl)-1H-pyrazol-5-yl) acetamide (24). Trifluoroacetic an-
hydride (0.10 mL, 0.63 mmol) was added in a single portion, to
a mixture of parent aminopyrazole 11 (0.200 g, 0.53 mmol) and
acetonitrile (10 mL). The dark-brown reaction mixture was then
heated to reflux for 16 h. The solvent was then evaporated in vacuo,
to yield the trifluoroacetylated product 24 as a light orange solid,
following column chromatography (30% ethyl acetate/hexane) of
the crude residue (0.100 g, 40%): mp 113e116 ꢀC; Rf (30% ethyl ac-
etate/hexane) 0.69; nmax/cmꢁ1 (KBr) 3270, 2939, 1729, 1585, 1504,
1466, 1126; dH (300 MHz, CDCl3) 3.43 [6H, s, 2ꢂm-OCH3], 3.78 [3H,
4.1.6. 4-(1-Methyl-1H-indol-3-yl)-3-(3,4,5-trimethoxyphenyl)-1H-
pyrazol-5-amine (11). Hydrazine hydrate (0.14 mL, 1.5 mmol) and
camphoric acid (0.180 g, 0.88 mmol, 1.2 equiv) were added to
a suspension of the b-ketonitrile 22 (0.265 g, 0.73 mmol), in dry
methanol (10 mL). The reaction mixture was then stirred at reflux
temperature for 3 h, prior to addition of excess hydrazine hydrate
(0.42 mL, 4.5 mmol) and heating for a further 20 h. Following sol-
vent removal, the residue was taken up in ethyl acetate (50 mL) and
washed with saturated aqueous sodium bicarbonate solution
(2ꢂ70 mL). These aqueous bicarbonate layers were added together
and subsequently extracted with ethyl acetate (2ꢂ30 mL); the
combined ethyl acetate layers were then washed with water
(3ꢂ70 mL) and brine (2ꢂ70 mL), dried over magnesium sulfate,
filtered and evaporated to yield a crude golden brown solid. Fol-
lowing purification by flash chromatography, initially with 100%
ethyl acetate, to complete full elution of the starting material, and
then with 98% ethyl acetate/2% methanol, the polar product 11 was
isolated as light brown crystals (0.170 g, 62%): mp 117e120 ꢀC; Rf
(2% methanol/ethyl acetate) 0.20; nmax/cmꢁ1 (KBr) 2930, 1583, 1511,
1465, 1422, 1124; dH (300 MHz, CDCl3) 3.42 [6H, s, 2ꢂm-OCH3], 3.77
[3H, s, NCH3], 3.81 [3H, s, p-OCH3], 4.75 [2H, br s, NH2], 6.68 [2H, s,
0
0
s, NCH3], 3.86 [3H, s, p-OCH3], 6.75 [2H, s, CeH2 ,6 ], 7.05e7.11 [2H,
m, CeH5,6], 7.26 [1H, s, CeH2], 7.26e7.31 [2H, t, J 7.0, CeH7],
7.39e7.41 [1H, d, J 8.3, CeH4], 8.17 [2H, br s, NHCOCF3 and pyrazole
NH]; dC (75 MHz, CDCl3) 33.1 (CH3, NCH3), 55.6 (2CH3, 2ꢂm-OCH3),
60.9 (CH3, p-CH3), 103.2 (C, aromatic C), 104.2 (2ꢂCH, aromatic CH),
105.2 (CH, aromatic CH), 109.6 (CH, aromatic CH), 119.9 (CH, aro-
matic CH), 120.3 (CH, aromatic CH), 122.7 (CH, aromatic CH), 127.5
(C, aromatic C), 128.5 (2ꢂC, aromatic C), 133.6 (C, aromatic C), 137.3
(2ꢂC, aromatic C), 143.3 (C, aromatic C), 153.1 (2ꢂC, aromatic C); m/
z (ESþ) 475.1 [MþH]þ, (100%); HRMS (ESþ) exact mass calculated
for C23H22N4O4F3 [MþH]þ 475.1593. Found 475.1591.
4.1.9. 1-Methyl-3-[4-(1-methyl-1H-indol-3-yl)-3-(3,4,5-trimethox-
yphenyl)-1H-pyrazol-5-yl] thiourea (25). Methyl isothiocyanate
(0.040 g, 0.55 mmol) was applied to a stirred solution of compound
11 (0.200 g, 0.53 mmol) in acetonitrile (10 mL). The reaction was
then heated to reflux temperature, and the dark orange suspension
was stirred for 16 h. The reaction was initially allowed to cool to
room temperature, and subsequently, to 0 ꢀC, and maintained for
30 min at this temperature. The formed slurry was then filtered to
yield pure thiourea derivative 25 as light orange crystals (0.080 g,
0
0
CeH2 ,6 ], 7.01e7.06 [3H, m, CeH2,5 and NH], 7.20e7.25 [1H, t, J 8.0,
CeH6], 7.30e7.33 [1H, d, J 7.8, CeH7], 7.33e7.36 [1H, d, J 8.2, CeH4];
dC (75 MHz, CDCl3) 32.9 (CH3, NCH3), 55.7 (2CH3, 2ꢂm-OCH3), 60.8
(CH3, p-OCH3), 104.0 (2CH, 2ꢂaromatic CH), 104.4 (C, aromatic C),
105.7 (C, aromatic C), 109.3 (CH, aromatic CH), 119.6 (CH, aromatic
CH), 120.4 (CH, aromatic CH), 122.0 (CH, aromatic CH), 126.1 (C,
aromatic C), 127.9 (C, aromatic C), 128.0 (C, aromatic C), 128.4 (CH,
aromatic CH), 137.1 (C, aromatic C), 137.8 (C, aromatic C), 153.1 (C,
aromatic C), 153.3 (2C, 2ꢂaromatic C); m/z (ESþ) 379.1 [MþH]þ,
(100%); HRMS (ESþ) exact mass calculated for C21H23N4O3 [MþH]þ
379.1770. Found 379.1765.
34%): mp 186e188 ꢀC; Rf (35% ethyl acetate/hexane) 0.80; nmax
/
cmꢁ1 (KBr) 3418, 3272, 2931, 1624, 1519, 1423, 1117; dH (300 MHz,
CDCl3) 3.28e3.30 [3H, d, J 4.9, NHCH3], 3.43 [6H, s, 2ꢂm-OCH3],
3.78 [3H, s, NCH3], 3.82 [3H, s, p-OCH3], 6.35 [2H, s, NH2], 6.85 [2H,
0
0
4.1.7. N-(4-(1-Methyl-1H-indol-3-yl)-3-(3,4,5-trimethoxyphenyl)-
1H-pyrazol-5-yl) acetamide (23). To a solution of aminopyrazole 11
(0.150 g, 0.397 mmol) in acetonitrile (10 mL) was added acetic
anhydride (0.05 mL, 0.476 mmol) and the reaction mixture was
heated to 80 ꢀC, with stirring, for 16 h. Following solvent removal,
the crude acetylated product was dissolved in ethyl acetate
(30 mL), washed with 10% aqueous sodium bicarbonate solution
(50 mL), followed by water (3ꢂ50 mL) and brine (50 mL). The
organic layer was then dried over magnesium sulfate, prior to
filtration and evaporation of the filtrate to a crude residue.
s, CeH2 ,6 ], 7.01 [1H, s, CeH2], 7.06e7.11 [1H, t, J 7.3, CeH5],
7.23e7.28 [1H, t, J 8.9, CeH6], 7.35e7.38 [1H, d, J 8.1, CeH7],
7.38e7.40 [1H, d, J 7.8, CeH4], 9.38 [1H, s, NHCH3]; dC (75 MHz,
CDCl3) 29.0 (CH3, NHCH3), 31.1 (CH3, NCH3), 53.8 (2CH3, 2ꢂm-
OCH3), 59.0 (CH3, p-OCH3), 93.1 (C, aromatic C), 103.1 (C, aromatic
C), 103.2 (2CH, 2ꢂaromatic CH), 107.5 (CH, aromatic CH), 118.0 (CH,
aromatic CH), 118.4 (CH, aromatic CH), 120.4 (CH, aromatic CH),
125.7 (C, aromatic C), 126.2 (C, aromatic C), 127.1 (CH, aromatic CH),
135.3 (C, aromatic C), 136.6 (C, aromatic C), 148.1 (C, aromatic C),
148.5 (C, aromatic C), 151.0 (2C, 2ꢂaromatic C), 175.1 (C, C]S); m/z

4608
L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
(ESþ) 452.1 [MþH]þ, (50%); HRMS (ESþ) exact mass calculated for
C23H26N5O3S [MþH]þ 452.1756. Found 452.1742.
acetate/hexane) 0.85; nmax/cmꢁ1 (KBr) 3487, 3360, 2975, 1766, 1751,
1712, 1656, 1587, 1126; dH (300 MHz, CDCl3) 1.55 [9H, s,
CO2C(CH3)3], 1.56 [9H, s, CO2C(CH3)3], 3.47 [6H, s, 2ꢂm-OCH3], 3.78
[3H, s, NCH3], 3.82 [3H, s, p-OCH3], 5.72 [2H, br s, NH2], 6.81 [2H, s,
4.1.10. N-(4-(1-Methyl-1H-indol-3-yl)-3-(3,4,5-trimethoxyphenyl)-
1H-pyrazol-5-yl) methanesulfonamide (26). To a solution of ami-
nopyrazole 11 (0.108 g, 0.29 mmol) in pyridine (8 mL) was added
methanesulfonyl chloride (0.023 mL, 0.29 mmol), along with trie-
thylamine (0.04 mL, 0.29 mmol). The reaction was heated at reflux
overnight and then evaporated in vacuo. The dark residue was
dissolved in ethyl acetate (80 mL), washed with 10% aqueous HCl
(5ꢂ70 mL), saturated aqueous sodium bicarbonate solution
(100 mL), water (3ꢂ100 mL) and brine (100 mL), dried over mag-
nesium sulfate and evaporated under reduced pressure. Chroma-
tography employing 25% ethyl acetate/hexane yielded the final
product 26 as a dark brown solid (0.048 g, 35%): mp 129e132 ꢀC; Rf
(40% ethyl acetate/hexane) 0.55; nmax/cmꢁ1 (KBr) 3307, 2930, 1584,
1465, 1424, 1125; dH (300 MHz, CDCl3) 3.24 [3H, s, SO2CH3], 3.42
[6H, s, 2ꢂm-OCH3], 3.78 [3H, s, NCH3], 3.82 [3H, s, p-OCH3], 6.61
0
0
CeH2 ,6 ], 6.98 [1H, s, CeH2], 7.07e7.12 [1H, td, J 7.8, 0.7, CeH5],
7.23e7.28 [1H, t, J 7.7, CeH6], 7.35e7.38 [1H, d, J 8.3, CeH7],
7.36e7.39 [1H, d, J 7.9, CeH4], 9.25 [1H, s, NHCO2C(CH3)3]; dC
(75 MHz, CDCl3) 28.1 (3CH3, CO2C(CH3)3), 28.2 (3CH3, CO2C(CH3)3),
32.9 (CH3, NCH3), 55.7 (2CH3, 2ꢂm-OCH3), 60.8 (CH3, p-OCH3), 81.0
(C, CO2C(CH3)3), 83.1 (C, CO2C(CH3)3), 95.2 (C, aromatic C), 104.7 (C,
aromatic C), 105.2 (2CH, 2ꢂaromatic CH), 109.4 (CH, aromatic CH),
119.9 (CH, aromatic CH), 120.1 (CH, aromatic CH), 122.2 (CH, aro-
matic CH), 127.6 (C, aromatic C), 127.9 (C, aromatic C), 128.8 (CH,
aromatic CH), 137.1 (C, aromatic C), 138.5 (C, aromatic C), 143.2 (C,
aromatic C), 148.6 (C, aromatic C), 149.7 (C, NH-C¼N), 152.0 (C, C]
O), 152.9 (2C, 2ꢂaromatic C), 157.3 (C, C]O); m/z (ESþ) 621.3
[MþH]þ, (100%); HRMS (ESþ) exact mass calculated for C32H41N6O7
[MþH]þ 621.3037. Found 621.3033.
0
0
[2H, s, CeH2 ,6 ], 7.00e7.05 [1H, t, J 7.4, CeH5], 7.08 [1H, s, CeH2],
7.17e7.19 [1H, d, J 7.8, CeH7], 7.19e7.24 [1H, t, J 7.5, CeH6], 7.26 [1H,
s, pyrazole NH], 7.33e7.35 [1H, d, J 8.16, CeH4]; dC (75 MHz, CDCl3)
33.0 (CH3, NCH3), 41.4 (CH3, SO2CH3), 55.8 (2CH3, 2ꢂm-OCH3), 60.9
(CH3, p-OCH3), 103.4 (C, aromatic C), 103.5 (C, aromatic C), 104.0
(2CH, 2ꢂaromatic CH), 109.5 (CH, aromatic CH), 119.9 (CH, aromatic
CH), 120.0 (CH, aromatic CH), 122.3 (CH, aromatic CH), 124.6 (C,
aromatic C), 127.6 (C, aromatic C), 128.9 (CH, aromatic CH), 137.1 (C,
aromatic C), 138.3 (C, aromatic C), 141.8 (C, aromatic C), 145.2 (C,
aromatic C), 153.3 (2C, 2ꢂaromatic C); m/z (ESþ) 457.1 [MþH]þ,
(100%); HRMS (ESþ) exact mass calculated for C22H25N4O5S
[MþH]þ 457.1546. Found 457.1550.
4.1.13. 1-(4-(1-Methyl-1H-indol-3-yl)-3-(3,4,5-trimethoxyphenyl)-
1H-pyrazol-5-yl)guanidinium trifluoroacetate (29). Boc-protected
derivative 28 (0.05 g, 0.08 mmol) was treated, at 30 ꢀC, with a 10%
v/v solution of trifluoroacetic acid in DCM (15 mL), for 12 h. After
stirring for this time, the solvent was evaporated in vacuo to gen-
erate the corresponding trifluoroacetate salt 29 in quantitative
yield: mp 118e120 ꢀC; nmax/cmꢁ1 (KBr) 3369, 1698, 1551, 1421; m/z
(ESþ) 421.2 [M]þ, (100%); (ESꢁ) 112.9 [CF3CO2]ꢁ, (100%).
4.1.14. 3-(1-Methyl-1H-indol-3-yl)-5,7-bis(trifluoromethyl)-2-
(3,4,5-trimethoxyphenyl) pyrazolo[1,5-a]pyrimidine (13). Hexafl-
uoroacetylacetone (1.50 mL, 10.6 mmol) was added to a mixture of
compound 11 (0.200 g, 0.53 mmol) and acetic acid (10 mL), with
stirring, at room temperature. The reaction was then heated to
80 ꢀC for 20 h, at which point, full consumption of the starting
material had occurred. Following removal of acetic acid under
vacuum, the crude hexafluoropyrimidine derivative 13 was purified
by chromatography employing a gradient from 20 to 50% ethyl
acetate/hexane. The fractions containing the product were then
combined prior to being evaporated in vacuo, and then dried under
high vacuum overnight, to yield pyrimidine 13 as a dark red crys-
talline solid (0.130 g, 45%): mp 217e220 ꢀC; Rf (30% ethyl acetate/
hexane) 0.65; nmax/cmꢁ1 (KBr) 2940,1577, 1485, 1467, 1420,1170; dH
(300 MHz, CDCl3) 3.48 [6H, s, 2ꢂm-OCH3], 3.84 [3H, s, NCH3], 3.90
[3H, s, p-OCH3], 6.97e7.02 [1H, t, J 7.2, CeH5], 7.10e7.13 [1H, d, J 7.8,
4.1.11. (N,N0-Di-tert-butoxycarbonyl)-thiourea (27)38. To a stirred
solution of NaH (1.35 g, 33.8 mmol) (60% suspension in mineral oil)
in dry THF (150 mL), under inert conditions at 0 ꢀC, was added
thiourea (0.570 g, 7.5 mmol) portionwise over 5 min, and left to stir
at room temperature for 15 min. Following cooling to 0 ꢀC, di-tert-
butyl carbonate (3.60 g, 16.5 mmol) was added, and stirring was
continued for 40 min, prior to warming to room temperature over
3 h. The reaction was subsequently quenched via the addition of
saturated aqueous NaHCO3 solution (10 mL), water (200 mL) and
the product was extracted with ethyl acetate (3ꢂ75 mL). On drying
with magnesium sulfate, the filtrate was evaporated to dryness to
afford 27 as an off-white solid, used successfully without further
purification (1.91 g, 92%): mp 115e117 ꢀC (lit.38 120e122 ꢀC); nmax
/
cmꢁ1 (KBr) 3365, 3173, 2925, 1771, 1724, 1609, 1542; dH (300 MHz,
CDCl3) 1.48 [9H, s, C(CH3)3], 1.53 [9H, s, C(CH3)3], 8.26 [1H, s, NH],
9.23 [1H, s, NH]; dC (75 MHz, CDCl3) 28.0 (6CH3, 2ꢂC(CH3)3), 84.1
(2C, 2ꢂC(CH3)3), 151.3 (C, C]S), 177.9 (C, C]O), 182.1 (C, C]O); m/z
(ESþ) 157.0 [MþH]þ, (50%), (ESꢁ) 155.0 [MꢁH]þ, (45%).
CeH7], 7.12 [2H, s, CeH2 ,6 ], 7.19e7.25 [1H, t, J 7.2, CeH6], 7.35 [1H, s,
(CF3)CeCH]C(CF3)], 7.36e7.39 [1H, d, J 8.3, CeH4], 7.42 [1H, s,
CeH2]; dC (75 MHz, CDCl3) 33.1 (CH3, NCH3), 55.7 (2CH3, 2ꢂm-
OCH3), 60.9 (CH3, p-OCH3), 102.1 (CH, aromatic CH), 103.3 (C, aro-
matic C), 106.1 (2CH, 2ꢂaromatic CH), 106.7 (C, aromatic C), 109.4
(CH, aromatic CH), 120.4 (C, q, JFeC 274.3, CF3), 121.7 (C, q, JFeC 274.4,
CF3), 119.8 (CH, aromatic CH), 121.0 (CH, aromatic CH), 122.1 (CH,
aromatic CH), 126.9 (C, aromatic C), 127.3 (C, aromatic C), 129.5 (CH,
aromatic CH), 134.7 (C, q, JFeC 38.6, aromatic C), 137.2 (C, aromatic
C), 139.2 (C, aromatic C), 144.2 (C, q, JFeC 37.8, aromatic C), 147.1 (C,
aromatic C), 153.1 (2C, 2ꢂaromatic C), 156.0 (C, aromatic C); m/z
(ESþ) 551.2 [MþH]þ, (100%); HRMS (ESþ) exact mass calculated for
C26H21N4O3F6 [MþH]þ 551.1518. Found 551.1514.
0
0
4.1.12. tert-Butyl (tert-butoxycarbonylamino) (4-(1-methyl-1H-in-
dol-3-yl)-3-(3,4,5-trimethoxyphenyl)-1H-pyrazol-5-ylamino)methyl-
enecarbamate (28). Aminopyrazole 11 (0.150 g, 0.397 mmol) was
treated with HgCl2 (0.130 g, 0.437 mmol) and N,N0-di-tert-butox-
ycarbonyl thiourea 27 (0.109 g, 0.397 mmol), in distilled DCM
(10 mL), at 0 ꢀC. Triethylamine (0.2 mL, 1.23 mmol) was then added
to the flask and allowed to stir at 0 ꢀC for a further 1 h, followed by
stirring for 12 h at room temperature. The reaction was then poured
into ethyl acetate (30 mL), and filtered through a pad of CeliteÒ in
order to remove the yellow mercury sulfide by-product. The filter
cake was washed with ethyl acetate (3ꢂ15 mL). The combined or-
ganic phases were then washed with water (3ꢂ100 mL) and brine
(100 mL), dried over magnesium sulfate and concentrated under
vacuum. Chromatography employing 15% ethyl acetate/hexane
yielded the pure di-protected pyrazole derivative 28 as an off-white
crystalline solid (0.085 g, 35%): mp 153e156 ꢀC; Rf (25% ethyl
4.1.15. 8-(1-Methyl-1H-indol-3-yl)-7-(3,4,5-trimethoxyphenyl)pyr-
azolo[1,5-a][1,3,5]triazine-2,4(1H,3H)-dione
(14). Chlorocarbonyl
isocyanate (0.05 mL, 0.582 mmol) was added to a stirred solution of
intermediate 11 (0.100 g, 0.265 mmol) in distilled DCM (5 mL),
containing two drops of triethylamine, at 0 ꢀC. The reaction was
then allowed to stir at room temperature overnight; water (1 mL)
was added carefully to the flask and some effervescence was ob-
served. The resultant dark brown slurry was filtered and the

L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
4609
isolated brown solid was washed successively with water, ether
and air-dried for 1 h, to afford the title compound 14 (0.075 g, 64%):
mp 268e271 ꢀC; Rf (30% ethyl acetate/hexane) 0.18; nmax/cmꢁ1
(KBr) 3433, 3213, 2939, 1763, 1710, 1587, 1419, 1125; dH (300 MHz,
DMSO-d6) 3.38 [6H, s, 2ꢂm-OCH3], 3.65 [3H, s, NCH3], 3.90 [3H, s, p-
1002; dH (300 MHz, DMSO-d6) 2.13 [6H, s, 2ꢂNCH3], 3.51 [2H, s,
CeH2], 7.00e7.04 [1H, q, J 7.9, 4.7, CeH5], 7.33 [1H, s, CeH2],
7.96e7.99 [1H, dd, J 7.9, 1.5, CeH4], 8.18e8.20 [1H, dd, J 4.7, 1.5,
CeH6], 11.46 [1H, br s, NH]; dC (75 MHz, DMSO-d6) 44.8 (2CH3,
2ꢂNCH3), 54.4 (CH2, CH2N(CH3)2), 110.6 (C, aromatic C), 114.9 (C,
aromatic CH), 119.7 (C, aromatic C), 124.7 (CH, aromatic CH), 127.2
(CH, aromatic CH), 142.4 (CH, aromatic CH), 148.7 (C, aromatic C);
m/z (ESþ) 176.1 [MþH]þ (100%).
0
0
OCH3], 6.93 [2H, s, CeH2 ,6 ], 7.02e7.06 [1H, t, J 7.6, CeH5], 7.17e7.19
[1H, d, J 7.8, CeH7], 7.22e7.27 [3H, t, J 8.1, CeH6], 7.48 [1H, s, CeH2],
7.55e7.58 [1H, d, J 8.3, CeH4], 11.67 [2H, br s, 2ꢂNH]; dC (75 MHz,
DMSO-d6) 32.5 (CH3, NCH3), 55.1 (2CH3, 2ꢂm-OCH3), 60.0 (CH3, p-
OCH3), 94.8 (C, aromatic C), 101.8 (C, aromatic C), 104.5 (2CH,
2ꢂaromatic CH), 109.8 (CH, aromatic CH), 119.1 (CH, aromatic CH),
119.4 (CH, aromatic CH), 121.4 (CH, aromatic CH), 127.3 (C, aromatic
C), 127.8 (C, aromatic C), 130.7 (CH, aromatic CH), 136.8 (C, aromatic
C), 137.8 (C, aromatic C), 139.9 (C, aromatic C), 144.3 (C, aromatic C),
148.5 (2C, 2ꢂaromatic C), 152.4 (C, C]O), 153.5 (C, C]O); m/z (ESþ)
448.1 [MþH]þ, (40%); HRMS (ESþ) exact mass calculated for
C23H22N5O5 [MþH]þ 448.1621. Found 448.1611.
4.1.18. 2-(1H-Pyrrolo[2,3-b]pyridin-3-yl)acetonitrile (32)40. To a so-
lution of N,N-dimethyl-1-(1H-pyrrolo[2,3-b]pyridin-3-yl)methan-
amine 30 (5.60 g, 32.0 mmol) in DMF (20 mL) was added a solution
of sodium cyanide (2.35 g, 48.2 mmol) in water (16 mL). Acetic acid
(5 mL) was then added to the mixture in a dropwise manner, and
the resulting solution was heated to 110 ꢀC for 8 h. After cooling to
room temperature, the solution was diluted with saturated aq
K2CO3 (30 mL) and extracted with ethyl acetate (3ꢂ40 mL). The
organic extracts were dried over magnesium sulfate, filtered and
evaporated under reduced pressure to yield the crude product.
Purification by flash column chromatography (ethyl acetate/hexane
4.1.16. N,N-Diethyl-1-(1H-pyrrolo[2,3-b]pyridin-3-yl)methanamine
(33). A solution of diethylamine hydrochloride (0.604 g, 5.5 mmol)
and water (5 mL) was cooled in an ice bath to 0 ꢀC. This solution was
treated with 37 wt % aq formaldehyde (0.36 mL, 4.8 mmol) and
stirred for 30 min. 7-Azaindole (0.500 g, 4.2 mmol) in ethanol
(10 mL) was then added, with the resulting mixture being main-
tained at 0 ꢀC for 30 min, before being heated to reflux for 20 h.
Once cooled to room temperature, the reaction mixture was diluted
with water (20 mL), before the pH of the solution was adjusted to 11
using 50 wt % aq NaOH. Extraction with dichloromethane
(3ꢂ20 mL) was then performed, and the combined organic extracts
were dried over magnesium sulfate, filtered and evaporated under
reduced pressure to yield the crude product as a yellow/orange
residue. The crude product was then subjected to flash column
chromatography (ethyl acetate/methanol, 80:20) to give the pure
product 33 as a reddish brown solid (0.755 g, 88%): mp 62e64 ꢀC; Rf
(10% methanol/ethyl acetate) 0.18; nmax/cmꢁ1 (KBr) 3142, 2970,
2931, 2787, 1583, 1544,1454, 1421,1298, 1048; dH (300 MHz, DMSO-
d6) 0.96e1.00 [6H, t, J 7.1, 2ꢂNCH2CH3], 2.40e2.44 [4H, q, J 7.1,
2ꢂNCH2CH3], 3.66 [2H, s, CeH2], 6.99e7.03 [1H, q, J 7.8, 4.7, CeH5],
7.32 [1H, s, CeH2], 7.98e8.01 [1H, dd, J 7.8, 1.2, CeH4], 8.17e8.19
[1H, dd, J 4.6, 1.4, CeH6], 11.44 [1H, br s, NH]; dC (75 MHz, DMSO-d6)
11.8 (2CH3, 2ꢂNCH2CH3), 45.9 (2CH2, 2ꢂNCH2CH3), 48.1 (CH2,
CH2N(C2H5)2), 110.9 (C, aromatic C), 114.8 (CH, aromatic CH), 119.7
(C, aromatic C), 124.5 (CH, aromatic CH), 127.3 (CH, aromatic CH),
142.3 (CH, aromatic CH), 148.8 (C, aromatic C); m/z (ESþ) 204.1
[MþH]þ (100%); HRMS (ESþ) exact mass calculated for C12H18N3
[MþH]þ, 204.1501. Found 204.1498.
50:50) gave the pure product 32 as a white crystalline solid (2.59 g,
40
ꢀ
52%): mp 135e137 C (lit. 136e138 ꢀC); Rf (50% ethyl acetate/
hexane) 0.19; vmax/cmꢁ1 (KBr) 3089, 2888, 2248, 1611, 1585, 1538,
1420, 1337; dH (300 MHz, CDCl3) 3.85 [2H, s, CeH2], 7.14e7.18 [1H,
q, J 7.9, 4.8, CeH5], 7.40 [1H, s, CeH2], 7.97e8.01 [1H, dd, J 7.9, 1.5,
CeH4], 8.37e8.39 [1H, dd, J 4.8, 1.5, CeH6], 11.92 [1H, br s, NH]; dC
(75 MHz, CDCl3) 14.6 (CH2, CH2CN), 102.8 (C, aromatic C), 116.0 (CH,
aromatic CH), 117.8 (C, CH2CN), 119.0 (C, aromatic C), 124.0 (CH,
aromatic CH), 127.1 (CH, aromatic CH), 143.1 (CH, aromatic CH),
148.9 (C, aromatic C); m/z (ESþ) 158.0 [MþH]þ (100%).
4.1.19. 2-(1-Methyl-1H-pyrrolo[2,3-b]pyridin-3-yl)acetonitrile
(34)41. 2-(1H-Pyrrolo[2,3-b]pyridin-3-yl)acetonitrile 32 (2.11 g,
13.4 mmol) was dissolved in anhydrous DMF (30 mL) and the
resulting solution was cooled to 0 ꢀC in an ice bath. Sodium hydride
(55 wt %, 0.585 g, 13.4 mmol) was added slowly in a portionwise
manner. Once the addition was complete, the resulting mixture was
allowed to stir at 0 ꢀC for 20 min. At this point, a solution of iodo-
methane (0.83 mL, 13.4 mmol) in DMF (5 mL) was added in a drop-
wise fashion. The reaction mixture was then allowed to warm to
room temperature, with stirring, over 2 h. Water (20 mL) was cau-
tiously added to quench to reaction. Following extraction with ethyl
acetate (3ꢂ30 mL), the combined organic extracts were washed
with water (4ꢂ50 mL) and brine (50 mL) then dried over magne-
sium sulfate. The solvent was evaporated under reduced pressure to
yield the crude product as a brown solid, which was then purified by
flash column chromatography (hexane/ethyl acetate, 70:30) to give
ꢀ
4.1.17. N,N-Dimethyl-1-(1H-pyrrolo[2,3-b]pyridin-3-yl)methan-
amine (31)39. A mixture of dimethylamine (33 wt % in EtOH, 9.8 mL,
55.2 mmol), acetic acid (2.7 mL, 48 mmol) and water (10 mL) was
cooled in an ice bath to 0 ꢀC. The resulting solution was sub-
sequently treated with 37 wt % aq formaldehyde (3.6 mL,
48.1 mmol) and stirred for 30 min. 7-Azaindole (5.00 g, 42.4 mmol)
in ethanol (20 mL) was then added, with the resulting solution
being stirred at 0 ꢀC for 30 min, before being heated to 100 ꢀC for
18 h, at which point TLC analysis showed complete consumption of
starting material. Once cooled to room temperature, the solution
was diluted with water (40 mL), before its pH was adjusted to 11
using 50 wt % aq NaOH. After extraction with dichloromethane
(3ꢂ30 mL), the organic extracts were dried over magnesium sul-
fate, filtered and evaporated under reduced pressure to give the
crude product as a pale yellow solid. Purification was carried out by
flash column chromatography (ethyl acetate/methanol, 80:20) to
yield the pure product 31 as a white crystalline solid (6.05 g, 82%):
mp 157e158 ꢀC (lit.39 144e152 ꢀC); Rf (20% methanol/ethyl acetate)
0.14; vmax/cmꢁ1 (KBr) 3079, 2947, 2775, 1604, 1528, 1412, 1334,
the pure product 34 as a reddish solid (1.06 g, 46%): mp 82e84
C
(lit.41 81e82.5 ꢀC); Rf (30% ethyl acetate/hexane) 0.32; vmax/cmꢁ1
(NaCl) 2941, 2360, 2249, 1602, 1542, 1463, 1410, 1301, 1144; dH
(400 MHz, CDCl3) 3.83 [2H, s, CeH2], 3.89 [3H, s, CH3], 7.11e7.14 [1H,
q, J 7.9, 4.7, CeH5], 7.22 [1H, s, CeH2], 7.90e7.93 [1H, dd, J 7.9, 1.5,
CeH4], 8.39e8.40 [1H, dd, J 4.7, 1.5, CeH6]; dC (75 MHz, CDCl3) 14.5
(CH2, CH2CN), 31.3 (CH3, NCH3), 101.5 (C, aromatic C), 115.8 (CH, ar-
omatic CH), 117.8 (C, CH2CN), 118.8 (C, aromatic C), 126.6 (CH, aro-
matic CH),127.5 (CH, aromatic CH),143.8 (CH, aromatic CH),147.9 (C,
aromatic C); m/z (ESþ) 172.1 [MþH]þ (100%).
4.1.20. 2-(1-Methyl-1H-pyrrolo[2,3-b]pyridin-3-yl)-3-oxo-3-(3,4,5-
trimethoxyphenyl)propanenitrile (35). A solution of LDA (1.8 M,
6.49 mL, 11.7 mmol) in THF (40 mL) was cooled to ꢁ78 ꢀC under
a nitrogen atmosphere, to which a solution of acetonitrile 34
(0.910 g, 5.3 mmol) in THF (5 mL) was added in a dropwise manner
and the reaction mixture was stirred for 1 h, with the temperature
maintained at ꢁ78 ꢀC. A solution of 3,4,5-trimethoxybenzoyl
chloride (1.48 g, 6.4 mmol) in THF (10 mL) was added dropwise to

4610
L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
0
0
the reaction mixture, which was then allowed to slowly warm to
room temperature and was stirred for 12 h. The solvent was then
removed under reduced pressure and the residue was dissolved in
ethyl acetate (50 mL) and was subsequently washed with saturated
aqueous sodium bicarbonate solution (40 mL), water (40 mL) and
brine (40 mL). After being dried over magnesium sulfate, the sol-
vent was removed under reduced pressure. The crude residue was
subjected to flash column chromatography (hexane/ethyl acetate,
80:20), which yielded the pure product 35 as a yellow solid
(0.956 g, 49%): mp 80e82 ꢀC; Rf (80% ethyl acetate/hexane) 0.51;
vmax/cmꢁ1 (KBr) 2940, 2201, 1684, 1583, 1505, 1461, 1415, 1333,
1127; dH (400 MHz, CDCl3) 3.83 [6H, s, 2ꢂm-OCH3], 3.87 [3H, s, p-
OCH3], 3.89 [3H, s, NCH3], 5.82 [1H, s, CH], 7.13e7.16 [1H, q, J 8.0, 4.7,
OCH3], 3.59 [3H, s, p-OCH3], 3.88 [3H, s, NCH3], 6.90 [2H, s, CeH2 ,6 ],
7.01e7.05 [1H, q, J 7.8, 4.6, CeH5], 7.14 [2H, br s, NH2], 7.49e7.52 [1H,
dd, J 7.8, 1.5, CeH4], 7.60 [1H, s, CeH2], 8.27e8.29 [1H, dd, J 4.6, 1.5,
CeH6], 10.15 [1H, br d, J 4.2, NHCH3]; dC (75 MHz, DMSO-d6) 30.8
(CH3, NCH3), 31.1 (CH3, NHCH3), 55.2 (2CH3, 2ꢂm-OCH3), 60.0 (CH3,
p-OCH3), 92.7 (C, aromatic C), 102.8 (C, aromatic C), 104.9 (2CH,
2ꢂaromatic CH),115.4 (CH, aromatic CH),119.9 (C, aromatic C),127.5
(C, aromatic C), 127.6 (CH, aromatic CH), 130.3 (CH, aromatic CH),
137.7 (C, aromatic C), 142.6 (CH, aromatic CH), 147.7 (C, aromatic C),
148.9 (C, aromatic C),150.2 (C, aromatic C),152.3 (2C, 2ꢂaromatic C),
175.7 (C]S); m/z (ESþ) 453.1 [MþH]þ, (100%); HRMS (ESþ) exact
masscalculatedfor C22H25N6O3S [MþH]þ 453.1709. Found 453.1700.
0
0
CeH5], 7.22 [2H, s, CeH2 ,6 ], 7.30 [1H, s, CeH2], 8.04e8.06 [1H, dd, J
8.0, 1.5, CeH4], 8.37e8.38 [1H, dd, J 4.7, 1.3, CeH6]; dC (75 MHz,
CDCl3) 31.5 (CH3, NCH3), 38.6 (CH, CHCN), 56.4 (2CH3, 2ꢂm-OCH3),
61.0 (CH3, p-OCH3), 102.4 (C, aromatic C), 105.6 (C, aromatic C),
106.8 (2CH, 2ꢂaromatic CH), 116.5 (CH, aromatic CH), 118.0 (C, CN),
127.1 (CH, aromatic CH), 128.3 (CH, aromatic CH), 128.3 (C, aromatic
C), 143.8 (C, aromatic C), 144.2 (CH, aromatic CH), 147.8 (C, aromatic
C), 153.1 (2C, 2ꢂaromatic C), 187.2 (C, C]O); m/z (ESþ) 366.1
[MþH]þ, (100%); HRMS (ESþ) exact mass calculated for C20H20N3O4
[MþH]þ 366.1454. Found 366.1448.
4.1.23. 1-[5-Amino-4-(1-methyl-1H-pyrrolo[2,3-b]pyridin-3-yl)-3-
(3,4,5-trimethoxyphenyl)-1H-pyrazol-1-yl]ethanone (37). To a solu-
tion of aminopyrazole 12 (0.080 g, 0.21 mmol) in acetonitrile
(10 mL) was added acetic anhydride (0.021 mL, 0.22 mmol). The
reaction mixture was heated to reflux for 24 h before being cooled
to room temperature. The solvent and excess acetic anhydride was
then removed under reduced pressure. The crude residue was
subjected to flash column chromatography (hexane/ethyl acetate,
40:60), yielding the pure product 37 as a pale yellow crystalline
solid (0.055 g, 62%): mp 138e140 ꢀC; Rf (60% ethyl acetate/hexane)
0.26; vmax/cmꢁ1 (KBr) 3435, 2939,1702,1636,1597,1577,1470,1421,
1380, 1351, 1128; dH (300 MHz, CDCl3) 2.79 [3H, s, COCH3], 3.48 [6H,
s, 2ꢂm-OCH3], 3.79 [3H, s, p-OCH3], 3.90 [3H, s, NCH3], 5.60 [2H, br
4.1.21. 5-Amino-4-(1-methyl-1H-pyrrolo[2,3-b]pyridin-3-yl)-3-
(3,4,5-trimethoxyphenyl)-1H-pyrazole (12). To a solution of ketoni-
trile 35 (0.806 g, 2.2 mmol) in absolute alcohol (30 mL), HCl (12 M,
1 mL) was slowly added. Hydrazine monohydrate (50%, 0.69 mL,
11.0 mmol) was then added and the resulting mixture was heated
to reflux for 20 h. The reaction mixture was cooled to room tem-
perature and the solvent was removed under reduced pressure. The
residue was dissolved in ethyl acetate (40 mL) and was then
washed with saturated aqueous sodium bicarbonate solution
(30 mL), water (30 mL) and brine (30 mL), before being dried over
magnesium sulfate. The solvent was evaporated under reduced
pressure and the crude product was then purified by flash column
chromatography (ethyl acetate/methanol, 90:10) to yield the pure
product 12 as a brown solid (0.586 g, 70%): mp 266e267 ꢀC; Rf (10%
methanol/ethyl acetate) 0.40; vmax/cmꢁ1 (KBr) 3357, 3205, 2935,
1579, 1516, 1459, 1410, 1248, 1124; dH (400 MHz, DMSO-d6) 3.37
[6H, s, 2ꢂm-OCH3], 3.59 [3H, s, p-OCH3], 3.86 [3H, s, NCH3], 4.51
0
0
s, NH2], 6.81 [2H, s, CeH2 ,6 ], 6.99e7.04 [1H, q, J 7.9, 4.7, CeH5], 7.15
[1H, s, CeH2], 7.60e7.63 [1H, dd, J 7.9, 1.5, CeH4], 8.34e8.36 [1H, dd,
J 4.7, 1.4, CeH6]; dC (75 MHz, CDCl3) 23.3 (CH3, COCH3), 31.3 (CH3,
NCH3), 55.7 (2CH3, 2ꢂm-OCH3), 60.9 (CH3, p-OCH3), 93.9 (C, aro-
matic C), 103.5 (C, aromatic C), 104.9 (2CH, 2ꢂaromatic CH), 115.9
(CH, aromatic CH), 119.9 (C, aromatic C), 127.8 (C, aromatic C), 128.5
(2CH, 2ꢂaromatic CH), 138.5 (C, aromatic C), 143.6 (CH, aromatic
CH), 147.9 (C, aromatic C), 148.7 (C, aromatic C), 152.9 (2C,
2ꢂaromatic C), 153.1 (C, aromatic C), 173.9 (C, C]O); m/z (ESþ)
422.2 [MþH]þ, (100%); HRMS (ESþ) exact mass calculated for
C22H23N5O4 [MþH]þ 422.1828. Found 422.1812.
4.1.24. 2,2,2-Trifluoro-N-(4-(1-methyl-1H-pyrrolo[2,3-b]pyridin-3-
yl)-3-(3,4,5-trimethoxyphenyl)-1H-pyrazol-5-yl)acetamide (38). To
a solution of aminopyrazole 12 (0.080 g, 0.21 mmol) in acetonitrile
(10 mL) was added trifluoroacetic anhydride (0.04 mL, 0.25 mmol).
The reaction mixture was then heated to reflux for 28 h before
being left to cool to room temperature. Evaporation of the solvent
under reduced pressure left the crude product as a brown residue.
This residue was then purified by flash column chromatography
(hexane/ethyl acetate, 40:60), which yielded the product 38 as
a pale yellow solid (0.041 g, 41%): mp 230e231 ꢀC; Rf (60% ethyl
acetate/hexane) 0.25; vmax/cmꢁ1 (KBr) 3307, 2939, 1714, 1579, 1507,
1464, 1407, 1173, 1129; dH (300 MHz, DMSO-d6) 3.49 [6H, s, 2ꢂm-
0
0
[2H, br s, NH2], 6.71 [2H, s, CeH2 ,6 ], 6.95e6.98 [1H, q, J 7.9, 4.7,
CeH5], 7.35e7.37 [1H, dd, J 7.8, 1.5, CeH4], 7.56 [1H, s, CeH2],
8.23e8.25 [1H, dd, J 4.6, 1.5, CeH6], 11.97 [1H, br s, NH]; dC (75 MHz,
DMSO-d6) 30.8 (CH3, NCH3), 55.3 (2CH3, 2ꢂm-OCH3), 60.1 (CH3, p-
OCH3), 95.2 (C, broad aromatic C), 103.9 (2CH, 2ꢂaromatic CH),
104.4 (C, aromatic C), 115.1 (CH, aromatic CH), 119.5 (C, aromatic C),
126.9 (C, broad aromatic C), 128.0 (CH, aromatic CH), 129.2 (CH,
aromatic CH), 136.9 (C, aromatic C), 141.8 (C, broad aromatic C),
142.4 (CH, aromatic CH), 147.5 (C, aromatic C), 152.3 (C, broad ar-
omatic C), 152.5 (2C, 2ꢂaromatic C); m/z (ESþ) 380.1 [MþH]þ
(100%); HRMS (ESþ) exact mass calculated for C20H22N5O3 [MþH]þ
380.1723. Found 380.1725.
0
0
OCH3], 3.69 [3H, s, p-OCH3], 3.92 [3H, s, NCH3], 6.82 [2H, s, CeH2 ,6 ],
7.03e7.07 [1H, q, J 7.9, 4.7, CeH5], 7.42e7.45 [1H, dd, J 7.9,1.5, CeH4],
7.54 [1H, s, CeH2], 8.31e8.34 [1H, dd, J 4.6, 1.4, CeH6], 11.23 [1H, br
s, NHCOCF3], 13.52 [1H, br s, pyrazole NH]; dC (75 MHz, DMSO-d6)
30.8 (CH3, NCH3), 55.4 (2CH3, 2ꢂm-OCH3), 60.0 (CH3, p-OCH3),
102.8 (C, aromatic C), 104.0 (2C, 2ꢂaromatic CH), 106.5 (C, aromatic
C), 106.7 (C, aromatic C), 115.8 (C, q, JFeC 288.4, CF3), 115.3 (CH, ar-
omatic CH), 118.7 (C, aromatic C), 124.5 (C, aromatic C), 127.8 (CH,
aromatic CH), 128.8 (CH, aromatic CH), 137.3 (C, aromatic C), 142.6
(CH, aromatic CH), 147.4 (C, aromatic C), 152.7 (2C, 2ꢂaromatic C),
153.1 (C, aromatic C), 156.3 (C, q, JFeC 36.4, C]O); m/z (ESþ) 476.1
[MþH]þ, (100%); HRMS (ESþ) exact mass calculated for
C22H21N5O4F3 [MþH]þ 476.1546. Found 476.1540.
4.1.22. 5-Amino-N-methyl-4-(1-methyl-1H-pyrrolo[2,3-b]pyridin-3-
yl)-3-(3,4,5-trimethoxyphenyl)-1H-pyrazole-1-carbothioamide
(36). To a solution of aminopyrazole 12 (0.080 g, 0.21 mmol) in
acetonitrile (10 mL) was added methyl isothiocyanate (0.016 g,
0.22 mmol). The reaction mixture was then heated at reflux for 26 h
before being cooled to room temperature. The solvent was removed
under reduced pressure to give a crude brown residue. Purification
by flash column chromatography (hexane/ethyl acetate, 50:50)
yielded the pure product 36 as a white solid (0.044 g, 47%): mp
169e171 ꢀC; Rf (50% ethyl acetate/hexane) 0.19; vmax/cmꢁ1 (KBr)
3320, 2933, 1626, 1594, 1523, 1469, 1423, 1361, 1284, 1123; dH
(300 MHz, DMSO-d6) 3.16 [3H, br d, J 3.8, NHCH3], 3.37 [6H, s, 2ꢂm-
4.1.25. 8-(1-Methyl-1H-pyrrolo[2,3-b]pyridin-3-yl)-7-(3,4,5-trime-
thoxyphenyl)pyrazolo[1,5-a][1,3,5]triazine-2,4(1H,3H)-dione

L.T. Pierce et al. / Tetrahedron 67 (2011) 4601e4611
4611
(39). Aminopyrazole 12 (0.080 g, 0.21 mmol) was dissolved in DCM
References and notes
(10 mL) containing two drops of triethylamine, and the resulting
solution was cooled to 0 ꢀC in an ice bath. This solution was then
treated, while stirring, with N-chlorocarbonyl isocyanate (0.02 mL,
0.23 mmol). The reaction mixture was allowed to warm to room
temperature and was stirred for 15 h. After careful addition of water
(3 mL), the precipitate formed was filtered off before subsequently
being washed with water (4ꢂ5 mL) and ether (2ꢂ5 mL). The pre-
cipitate was dessicated at 50 ꢀC overnight to give the pure product
39 as a white solid (0.053 g, 56%): mp 301e303 ꢀC; Rf (20% meth-
anol/ethyl acetate) 0.62;vmax/cmꢁ1 (KBr) 3516, 2834, 1765, 1703,
1648, 1583, 1549, 1421, 1332, 1123; dH (400 MHz, DMSO-d6) 3.37
[6H, s, 2ꢂm-OCH3], 3.61 [3H, s, p-OCH3], 3.88 [3H, s, NCH3], 6.84
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[2H, s, CeH2 ,6 ], 7.02e7.06 [1H, q, J 7.8, 4.6, CeH5], 7.50 [1H, d, J 7.8,
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54%): mp 174e176 ꢀC; Rf (50% ethyl acetate/hexane) 0.46; vmax
/
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cmꢁ1 (KBr) 2926, 1590, 1481, 1419, 1271, 1127, 1010; dH (400 MHz,
CDCl3) 3.55 [6H, s, 2ꢂm-OCH3], 3.86 [3H, s, p-OCH3], 4.02 [3H, s,
0
0
NCH3], 6.94e6.97 [1H, q, J 7.6, 4.6, CeH5], 7.04 [2H, s, CeH2 ,6 ], 7.38
[1H, d, J 7.8, CeH4], 7.46 [1H, s, (CF3)CeCH]C(CF3)], 7.56 [1H, s,
CeH2], 8.35 [1H, br s, CeH4]; dC (75 MHz, CDCl3) 31.6 (CH3, NCH3),
55.9 (2CH3, 2ꢂm-OCH3), 60.9 (CH3, p-OCH3), 102.0 (C, aromatic C),
102.3 (CH, aromatic CH), 106.2 (C, aromatic C), 106.3 (2CH,
2ꢂaromatic CH), 115.9 (CH, aromatic CH), 119.1 (C, q, JFeC 275.4,
CF3), 120.3 (C, q, JFeC 275.2, CF3), 119.2 (C, aromatic C), 127.1 (C, ar-
omatic C), 129.3 (CH, aromatic CH), 129.4 (CH, aromatic CH), 135.1
(C, q, JFeC 34.7, aromatic C), 139.3 (C, aromatic C), 143.4 (CH, aro-
matic CH), 145.0 (C, q, JFeC 37.8, aromatic C), 146.7 (C, aromatic C),
148.0 (C, aromatic C), 153.3 (2C, 2ꢂaromatic C), 156.0 (C, aromatic
C); m/z (ESþ) 552.1 [MþH]þ, (100%); HRMS (ESþ) exact mass cal-
culated for C25H20N5O3F6 [MþH]þ 552.1470. Found 552.1469.
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We are grateful to the Irish Research Council for Science Engi-
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