4-Amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-amines: A new practical synthesis and biological activity

Article abstract of DOI:10.1016/j.tetlet.2014.10.057

The trichloromethyl moiety was successfully employed as a leaving group in nucleophilic substitutions with various amines for the synthesis of 4-amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-amines. The key precursor for this reaction, 4-trichloromethylpyrazolo[1,5-a][1,3,5]triazin-2-amine, was prepared via the solvent-dependent condensation of 5-guanidino-3-phenylpyrazole with trichloroacetonitrile. In a broad biological activity screening, some of the prepared compounds were identified as CGRP receptor antagonists.

Full text of DOI:10.1016/j.tetlet.2014.10.057

Accepted Manuscript
4
-Amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-amines: a new practical
synthesis and biological activity
Felicia Phei Lin Lim, Anton V. Dolzhenko
PII:
S0040-4039(14)01740-7
DOI:
http://dx.doi.org/10.1016/j.tetlet.2014.10.057
TETL 45286
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
26 July 2014
26 September 2014
9 October 2014
Please cite this article as: Lim, F.P.L., Dolzhenko, A.V., 4-Amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-
amines: a new practical synthesis and biological activity, Tetrahedron Letters (2014), doi: http://dx.doi.org/10.1016/
j.tetlet.2014.10.057
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Graphical Abstract
4-Amino-substituted pyrazolo[1,5-
a][1,3,5]triazin-2-amines: a new practical
synthesis and biological activity
Leave this area blank for abstract info.
Felicia Phei Lin Lim, Anton V. Dolzhenko

1
Tetrahedron Letters
jou rn al h om ep a ge : www .e ls e v ie r .c om
4-Amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-amines: a new practical synthesis
§
and biological activity
a
Felicia Phei Lin Lim , Anton V. Dolzhenko
a, b, ∗
a
School of Pharmacy, Curtin Health Innovation Research Institute, Curtin University, GPO Box U1987 Perth, Western Australia 6845, Australia
School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan 47500, Malaysia
b
ARTICLE INFO
ABSTRACT
Article history:
Received
The trichloromethyl moiety was successfully employed as a leaving group in nucleophilic
substitutions with various amines for the synthesis of 4-amino-substituted pyrazolo[1,5-
a][1,3,5]triazin-2-amines. The key precursor for this reaction, 4-trichloromethylpyrazolo[1,5-
a][1,3,5]triazin-2-amine, was prepared via the solvent-dependent condensation of 5-guanidino-
3-phenylpyrazole with trichloroacetonitrile. In a broad biological activity screening, some of the
prepared compounds were identified as CGRP receptor antagonists.
Received in revised form
Accepted
Available online
Keywords:
2
009 Elsevier Ltd. All rights reserved.
Purine analogue
Pyrazole
Triazine
Trichloroacetonitrile
Aminolysis
—
§
——
Part 26 in the series ‘Fused heterocyclic systems with an s-triazine ring’, for part 25 see Ref. 1
Corresponding author. Tel.: +60-3-5514-5867; fax: +60-3-5514-6364; e-mails: dolzhenkoav@gmail.com, anton.dolzhenko@monash.edu
∗

2
Tetrahedron Letters
2
The pyrazolo[1,5-a][1,3,5]triazine heterocyclic system is a
-aza-9-deaza- isostere of purine, which is one of the most
to develop a method for the synthesis of the intermediate
pyrazolo[1,5-a][1,3,5]triazines with a predetermined location of
the leaving group. To address this issue, we have devised a new
method for the synthesis of 4-amino-substituted pyrazolo[1,5-
a][1,3,5]triazin-2-amines 10, which is described herein.
5
3
common and functional natural N-heterocycles. The close
structural resemblance of pyrazolo[1,5-a][1,3,5]triazines to
biogenic purines allows for targeting purinergic signalling
receptors and enzymes. Being the focus of active research as
bioactive molecules with promising therapeutic potential, this
heterocyclic system has been established as a privileged scaffold
Our method is based on the preparation of the key
intermediate, 4-trichloromethylpyrazolo[1,5-a][1,3,5]triazin-2-
amine (14), and exploiting the good leaving properties of the
trichloromethyl group in nucleophilic substitution with amines
(Table 1).
4
in medicinal chemistry. Well defined targets for pyrazolo[1,5-
a][1,3,5]triazines are enzymes, particularly cyclin-dependent
17
5
kinases (CDK), phosphodiesterases (PDE), xanthine oxidase
6
7
XO), and thymidine phosphorylase (TP), and receptors such as
8
(
cannabinoid (CB) and corticotrophin-releasing factor (CRF).
The initial building block for our method, 5(3)-amino-3(5)-
18
phenylpyrazole (5a), was prepared via the previously reported
9
10
reaction of benzoylacetonitrile with hydrazine. Treatment of 5a
19
with cyanamide by adopting a previously developed method
A number of potent pharmacological agents have been
identified among 4-amino-substituted pyrazolo[1,5-
a][1,3,5]triazines (Figure 1). For example, CDK inhibitor 1
20
5
b,c
was used to convert the amine 5a into the guanidine 13. In the
was found to be more potent than its purine-based counterpart,
Seliciclib (roscovitine), an experimental drug candidate in the
6b
1
1
area of oncology. Potent and selective PDE4 inhibitors 2a,b
with anti-inflammatory properties also possessed this structural
9
receptor antagonists, PF 095453 (3a) and
a
motif. Selective CB
9
1
b,c
CE 178253 (3b),
identified within this class of compounds,
have been explored as potential therapeutic agents for the
treatment of obesity and Parkinson’s disease. Pexacerfont (BMS-
1
0c,d
5
62086, 4)
CRF receptors. Bristol-Myers Squibb is currently carrying out
clinical trials on pexacerfont as a potential remedy for stress-
is a potent and orally bioavailable antagonist of
1
12a
12b
induced food craving and anxiety-related alcohol craving.
The first synthesis of compounds with the pyrazolo[1,5-
a][1,3,5]triazine scaffold was reported more than half a century
1
3
ago by Checchi and Ridi. They found that heating 5(3)-amino-
(5)-phenylpyrazole (5a) with cyanoguanidine (6) led to the
formation of 2,4-diamino-7-phenylpyrazolo[1,5-a][1,3,5]triazine
7) (Scheme 1). Further research on the pyrazolo[1,5-
3
(
a][1,3,5]triazine chemistry has since yielded many efficient
methods for the preparation of compounds with this heterocyclic
1
core, and the development of new and interesting synthetic
1
4
protocols is ongoing.
Even though
phenylpyrazolo[1,5-a][1,3,5]triazine (7) was the first reported
the
synthesis
of
2,4-diamino-7-
1
3
method for the preparation of this type of heterocycle, existing
methods for the synthesis of similar compounds 10 with
substitution at the 4-amino group seem to follow ambiguous
Figure 1. Some biologically active 4-amino-substituted
pyrazolo[1,5-a][1,3,5]triazines (1-4).
1
5
next step, we carried out the reaction of 13 with
trichloroacetonitrile, which has been recognized as a versatile
routes. One is based on the reaction of 5-aminopyrazoles 5 with
dimethyl N-cyanodithiocarbonimidate (8) and the subsequent
introduction of a substituted amino group via nucleophilic
substitution with different amines according to Pathway A
2
1
22
synthon in heterocyclic chemistry. It has been reported that
the outcome of the trichloroacetonitrile reactions is often solvent-
dependent.
(
regioselectivity of the triazine ring closure reaction.
Scheme 2). This approach suffers from questionable
It was
15,16
We also found that the reaction of 5(3)-guanidino-3(5)-
phenylpyrazole (13) with trichloroacetonitrile afforded different
products when different solvents were employed. Heating 13
with trichloroacetonitrile in toluene resulted in the formation of a
mixture of two products, viz. the diamine 7 and the targeted
1
6a
also reported that the reaction of 5-aminopyrazoles 5 with
dimethyl N-cyanodithiocarbonimidate (8) proceeded via an
alternative route (Pathway B) affording products 11 instead of 9.
The following nucleophilic substitution with amines was also
successfully achieved, in this case resulting in the formation of 2-
2
3
product 14 in a 15:85 ratio. The separation of compounds 7 and
1
1
6a
amino-substituted pyrazolo[1,5-a][1,3,5]triazin-4-amines 12.
4 was successfully achieved on the basis of their considerably
different solubility in hot toluene. The more soluble product 14
was isolated in pure form via fractional recrystallization from this
solvent.
In general, the introduction of an amino group to the structure
of the final products is certainly a valid and very useful strategy.
However, in order to make this approach practical, it is necessary

3
NH2
N
N
1 C
60 o
N
NH
NH
N
N
+
Ph
Ph
NH2
HN NH2
N
NH2
5a
6
7
Scheme 1. The first synthesis of the pyrazolo[1,5-a][1,3,5]triazine
1
system.
3
3
4
SMe
N
NR R
Pathway A
N
HNR3R4
N
N
N
N
2
R2
R
N
NH2
N
NH2
N
1
R1
R
N
NH
MeS
MeS
9
10
R2
+
N
NH2
R1
NH2
N
NH2
N
5
8
N
HNR R
3
4
N
N
N
2
R2
R
Pathway B
3
4
N
SMe
N
NR R
R1
R1
1
1
12
Scheme 2. Syntheses of 4(2)-amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2(4)-amines 10 and 12
CCl3
NH2
N
N
N
N
N
N
Ph
+
Ph
N
NH2
N
NH2
ii
HN
14
7
N
NH
N NH
i
NH2
Ph
NH2
Ph
N
H
5
a
13
NH2
N
iii
N
N
Ph
N
NH2
7
Scheme 3. Reagents and conditions : (i) cyanamide (3.0 equiv), conc. HCl (1.8 equiv), EtOH, reflux, 7 h (65%); (ii) Cl
equiv), PhMe, reflux, 30 min (77%); (iii) Cl CCN (2.0 equiv), EtOH, reflux, 30 min (62%)
3
CCN (2.0
3

4
Tetrahedron Letters
Table 1. Synthesis of 4-amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-amines 10.
NR R2
1
CCl3
N
1
2
N
HNR R
N
N
N
N
Ph
Ph
-
CHCl3
N
NH2
N
NH2
14
10
Product
Structure
Yield (%)
Mp (ºC)
Product
Structure
Yield (%)
Mp (ºC)
a
d
b
f
1
0a
36
241-243
80
189-191
1
0i
b
e
b
g
8
7
2
3
92-93
65
257-258
1
0b
0c
10j
b
d
c
e
208-210
86
179-181
1
10k
b
d
c
h
6
4
148-150
81
176-178
1
0d
10l
b
d
c
d
8
9
2
5
239-240
89
238-240
1
0e
10m
b
d
c
h
229-230
88
238-239
1
0f
10n
b
d
c
d
8
7
130-132
86
246-247
1
0g
10o
b
d
c
d
7
9
220-221
98
248-250
1
0h
10p
a
Conditions: MeNH
b
(aq, 40%), MeOH, rt, 24 h; amine (1.3 equiv), MeOH, rt, 24 h; amine (1.3 equiv), DMF, 70-80 ºC, 5 h.
c
2
d
e
f
g
Solvents: PhMe, cyclohexane, EtOAc, EtOH, MeOH
h

5
Scheme 4. Proposed mechanism for the formation of 2,4-diaminopyrazolo[1,5-a][1,3,5]triazine 7 in ethanol.
We assume that initially the triazine ring closure reaction in
toluene proceeded with the elimination of ammonia and the
formation of 14. However, due to the solubility of 14 in hot
toluene, this compound reacted instantly with ammonia prior to
removal of this gaseous substance from the reaction mixture,
therefore leading to the formation of the side-product 7.
screening, the effects of the compounds on the secretion of
glucagon-like peptide (GLP1), the activity of DNA
1
methyltransferase 1 (DNMT1), G protein-coupled receptor 119
(GPR119) and calcitonin gene-related peptide (CGRP) receptors,
as well as the antituberculosis activity were explored. The tested
compounds demonstrated no appreciable effect on GLP1
secretion in NCI-H716 cells at concentrations of up to 20 µM.
They did not inhibit DNMT1 at 50 µM and had no antitubercular
activity. Agonistic activity of 10p toward GPR119 was identified
(18.4% at 10 µM), but the IC50 value was more than 50 µM. The
most interesting results were obtained in the screening of CGRP
receptor antagonists. Thus, compounds 10b and 10p
demonstrated antagonism with this potential anti-migraine
Interestingly,
the
reaction
of
5(3)-guanidino-3(5)-
phenylpyrazole (13) with trichloroacetonitrile in ethanol resulted
in the elimination of chloroform and the formation of 2,4-
2
4
diamino-7-phenylpyrazolo[1,5-a][1,3,5]triazine (7).
In this
case, the outcome could be explained by initial reaction of
trichloroacetonitrile with ethanol and formation of imidate 15,
and its addition to the guanidino group of 13 (Scheme 4).
Subsequently, elimination of chloroform from adduct 16 would
afford intermediate 17, which would undergo intramolecular
cyclocondensation providing 7. The isolated product 7 was
identical to the side-product of the same reaction in toluene and
the sample prepared using an alternative method reported by
28
target in the CGRP cAMP assay with similar IC50 values of
5
1.2 and 52.2 µM, respectively. The most active in the series was
0n, which was found to possess an IC50 value of 7.6 µM in the
same assay.
1
In conclusion, we have developed a new and practical method
1
3
Checchi and Ridi (Scheme 1).
for the synthesis of 5-aza-9-deazapurine derivatives from readily
available starting materials. This rather simple and general
approach is based on the substitution of the trichloromethyl
group by diverse amines and can be used for the generation of
bioactive 4-amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-
amines. Some of the prepared compounds were identified as
antagonists of CGRP receptors.
We found that the trichloromethyl group of 14 readily
underwent nucleophilic substitution with primary aliphatic
amines upon stirring in methanol at room temperature to afford
4
(
-amino-substituted pyrazolo[1,5-a][1,3,5]triazin-2-amines 10a-j
2
Table 1). The reaction of 14 with 2-aminobenzylamine under
5
these conditions was found to proceed selectively at the aliphatic
amino group with the exclusive formation of 10e as the
substitution product. Furthermore, our attempts to carry out this
reaction using secondary amines (morpholine and piperidine) or
anilines were unsuccessful, and the process did not go to
completion. Further optimising the reaction conditions, we found
that compound 14 reacted with these amines at 70-80 ºC in DMF
Acknowledgements
The authors are grateful for the OIDD screening data supplied
courtesy of Eli Lilly and Company, and which are reported with
permission.
26
affording products 10k-p in good yields.
Supplementary data
We compared the NMR spectral data for 10m obtained by our
1
5a
method with the literature values for the same compound,
which was prepared following Pathway A as outlined in Scheme
2
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.tetlet.2014.
XX.XXX. These data include experimental details and copies of
1
, and was proposed to have the structure of 10m. In the H NMR
1
13
spectrum, the chemical shifts of the pyrazole CH and protons of
the amino groups were significantly different for these
compounds. The downfield shift of the primary amino group
H and C NMR spectra of the prepared compounds.
References and notes
1
signal in the H NMR spectrum (8.13 ppm) of the compound
1
5a
reported in the literature as 10m indicated the location of this
group at C-4 of the pyrazolo[1,5-a][1,3,5]triazine ring and
suggested that the general structure 12 would better suit this
compound. This also corresponds to the observations for similar
1
2
.
.
Lim, F. P. L.; Luna, G.; Dolzhenko, A. V. Tetrahedron Lett. 2014,
55, 5159-5163.
For a review on pyrazolo[1,5-a][1,3,5]triazines, see: Dolzhenko,
A. V.; Dolzhenko, A. V.; Chui, W.-K. Heterocycles 2008, 75,
1575-1622.
Burnstock, G.; Verkhratsky, A. Acta. Physiol. 2009, 195, 415-447.
Lim, F. P. L.; Dolzhenko, A. V. Eur. J. Med. Chem. 2014, 85,
1
pyrazolo[1,5-a][1,3,5]triazin-4-amines.
3
4
.
.
The compounds prepared were screened in a series of in vitro
pharmacological assays using the Open Innovation Drug
371-390.
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.
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Discovery (OIDD) platform supported by Eli Lilly. In primary
7

6
Tetrahedron Letters
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20. Synthesis of 5(3)-guanidino-3(5)phenylpyrazole (13). 5(3)-amino-
3(5)-phenylpyrazole (5a) (3.4 g, 21.4 mmol), cyanamide (2.6 g, 60
mmol) and conc. HCl (3.75 ml, 38.5 mmol) were heated in EtOH
(17 ml) under reflux for 7 h. After cooling, an aqueous solution of
2 3
K CO (5%, 250 ml) was added and the product formed was
filtered and dried under vacuum. An analytical sample was
1
recrystallized from MeOH. Yield 65%; mp 137-138 °C; H NMR
9
.
(a) Wagner, J. D.; Zhang, L.; Kavanagh, K.; Ward, G. M.; Chin, J.
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(400 MHz, DMSO-d
NH(=NH)NH ), 7.29 (1H, t, J = 7.3 Hz, H-4′), 7.39 (2H, t, J =
7.6 Hz, H-3′ and H-5′), 8.03 (2H, d, J = 8.0 Hz, H-2′ and H-6′);
6
): δ 6.18 (1H, br s, H-8), 6.59 (4H, br s,
3
3
2
3
1
3
C NMR (100 MHz, DMSO-d
and C-5′), 127.5 (C-4′), 128.7 (C-2′ and C-6′), 131.6 (br s, C-1′),
145.3 (br s, C-3), 152.4 (br s, C-5), 154.8 (br s, NHC(=NH)NH ).
Anal. Calcd. for C10 : C, 59.69; H, 5.51; N, 34.80. Found: C,
59.55; H, 5.64; N, 34.68.
6
): δ 92.1 (br s, C-4), 125.0 (C-3′
2
11 5
H N
21. For reviews on trichloroacetonitrile, see: (a) Shvekhgeimer, G.A.
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1
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Fitzgerald, L.; Miller, K.; Zhang, G.; Marshall, A.; Krause, C.;
McElroy, J. F.; Ward, K.; Zeller, K.; Wong, H.; Bai, S.; Saye, J.;
Grossman, S.; Zaczek, R.; Hartig, P.; Robertson, D.; Trainor, G. J.
Med. Chem. 2009, 52, 3084-3092; (d) Coric, V.; Feldman, H. H.;
Oren, D. A.; Shekhar, A.; Pultz, J.; Dockens, R. C.; Wu, X.;
Gentile, K. A.; Huang, S.-P.; Emison, E.; Delmonte, T.; D'Souza,
B. B.; Zimbroff, D. L.; Grebb, J. A.; Goddard, A. W.; Stock, E. G.
Depress. Anxiety 2010, 27, 417-425; (e) Zuev, D.; Mattson, R. J.;
Huang, H.; Mattson, G. K.; Zueva, L.; Nielsen, J. M.; Kozlowski,
E. S.; Huang, X. S.; Wu, D.; Gao, Q.; Lodge, N. J.; Bronson, J. J.;
Macor, J. E. Bioorg. Med. Chem. Lett. 2011, 21, 2484-2488; (f)
Saito, T.; Obitsu, T.; Minamoto, C.; Sugiura, T.; Matsumura, N.;
Ueno, S.; Kishi, A.; Katsumata, S.; Nakai, H.; Toda, M.-A.
Bioorg. Med. Chem. 2011, 19, 5955-5966.
23. Synthesis of 2-amino-7-phenyl-4-trichloromethylpyrazolo[1,5-
a][1,3,5]triazine (14). 5-Guanidino-3-phenylpyrazole (13, 1.6 g,
7.85 mmol) and trichloroacetonitrile (1.6 ml, 16 mmol) were
heated in toluene (15 ml) under reflux for 30 min. After cooling,
the precipitate formed was filtered and subjected to fractional
recrystallization from toluene to furnish pure 14. Yield 77%; mp
1
240-242 °C; Rf 0.74 (EtOAc : hexane – 1:1); H NMR (400 MHz,
DMSO-d
6
): δ 6.68 (1H, s, H-8), 7.45-7.55 (3H, m, H-3′, H-4′ and
3
4
H-5′), 7.66 (2H, s, NH
2
), 8.03 (2H, dd, J = 8.2 Hz, J = 1.5 Hz, H-
2′ and H-6′). C NMR (100 MHz, DMSO-d ): δ 87.9 (C-8), 90.0
(CCl ), 126.5 (C-3′ and C-5′), 128.8 (C-2′ and C-6′), 129.7 (C-4′),
131.8 (C-1′), 149.6 (C-4), 153.9 (C-8a), 156.3 (C-7), 157.3 (C-2).
Anal. Calcd for C12 Cl : C, 43.86; H, 2.45; N, 21.31. Found:
C, 43.75; H, 2.52; N, 21.22.
13
6
3
H
8
3 5
N
24. Synthesis of 2,4-diamino-7-phenylpyrazolo[1,5-a][1,3,5]triazine
(7). 5-Guanidino-3-phenylpyrazole (13) (200 mg, 1 mmol) and
trichloroacetonitrile (0.2 ml, 2 mmol) were heated in EtOH (7 ml)
under reflux for 30 min. After cooling, the product was filtered
1
1
1. Jorda, R.; Paruch, K.; Krystof, V. Curr. Pharm. Des. 2012, 18,
2
1
974-2980.
2. (a) http://clinicaltrials.gov/show/NCT01656577; (b)
http://clinicaltrials.gov/show/NCT01227980
and dried under vacuum. Yield 62%; mp 338-340 °C; H NMR
),
(400 MHz, DMSO-d
3
6
): δ 6.21 (1H, s, H-8), 6.40 (2H, s, NH
2
3
7.39 (1H, t, J = 7.3 Hz, H-4′), 7.46 (2H, t, J = 7.3 Hz, H-3′ and
3
1
1
3. Checchi, S.; Ridi, M. Gazz. Chim. Ital. 1957, 87, 597-614.
4. For recent examples, see: (a) Lefoix, M.; Mathis, G.; Kleinmann,
T.; Truffert, J.-C.; Asseline, U. J. Org. Chem. 2014, 79, 3221-
H-5′), 7.82 (2H, br s, NH
2
), 7.96 (2H, d, J = 7.3 Hz, H-2′ and H-
1
3
6′). C NMR (100 MHz, DMSO-d ): δ 86.9 (C-8), 126.1 (C-3′ and
6
C-5′), 128.6 (C-2′ and C-6′), 128.7 (C-4′), 132.9 (C-1′), 150.3 (C-
4), 152.3 (C-8a), 154.9 (C-7), 159.2 (C-2). Anal. Calcd for
3
227; (b) Draffan, A. G.; Frey, B.; Pool, B.; Gannon, C.; Tyndall,
E. M.; Lilly, M.; Francom, P.; Hufton, R.; Halim, R.; Jahangiri, S.;
Bond, S.; Nguyen, V. T. T.; Jeynes, T. P.; Wirth, V.; Luttick, A.;
Tilmanis, D.; Thomas, J. D.; Pryor, M.; Porter, K.; Morton, C. J.;
Lin, B.; Duan, J.; Kukolj, G.; Simoneau, B.; McKercher, G.;
Lagace, L.; Amad, M.; Bethell, R. C.; Tucker, S. P. ACS Med.
Chem. Lett. 2014, 5, 679-684; (c) Insuasty, H.; Insuasty, B.;
Castro, E.; Quiroga, J.; Abonia, R. Tetrahedron Lett. 2013, 54,
C
N, 36.97.
11
H
10
N
6
: C, 58.40; H, 4.46; N, 37.15. Found: C, 58.28; H, 4.50;
25. General method for the preparation of 4-amino-substituted
pyrazolo[1,5-a][1,3,5]triazine-2-amines (10a-j). Compound 14
(200 mg, 0.61 mmol) was added to a solution of the appropriate
amine (0.78 mmol) in MeOH (7 ml). The mixture was stirred at rt
for 24 h and the reaction progress was monitored by TLC. After
evaporation of MeOH, the product was recrystallized from a
suitable solvent (Table 1).
1
722-1725; (d) Zamigailo, L. L.; Petrova, O. N.; Shirobokova, M.
G.; Lipson, V. V. Russ. J. Org. Chem. 2013, 49, 288-293; (e)
Kalinin, D. V.; Kalinina, S. A.; Dolzhenko, A. V. Heterocycles
Experimental data for some representative compounds:
2-Amino-4-phenylethylamino-7-phenylpyrazolo[1,5-
a][1,3,5]triazine (10d): mp 148-159 °C; Rf 0.36 (EtOAc : hexane
2
013, 87, 147-154; (f) Insuasty, H.; Estrada, S.; Quiroga, J.;
Insuasty, B.; Abonia, R.; Nogueras, M.; Cobo, J. J. Heterocycl.
Chem. 2012, 49, 1339-1345; (g) Kalinin, D. V.; Kalinina, S. A.;
Dolzhenko, A. V. Heterocycles 2012, 85, 2515-2522; (h) Insuasty,
1
3
– 1:1); H NMR (400 MHz, DMSO-d
6
): δ 2.99 (2H, t, J = 7.6 Hz,
Ph), 3.70 (2H, dt, J = 6.5 Hz, J = 7.6 Hz, CH NH), 6.23 (1H,
s, H-8), 6.54 (2H, s, NH ), 7.20-7.34 (5H, m, CH Ph), 7.40 (1H, t,
3
3
CH
2
2
2
2

7
3
3
J = 7.3 Hz, H-4′), 7.46 (2H, t, J = 7.3 Hz, H-3′ and H-5′), 7.96
3
4
3
(
2H, dd, J = 8.2 Hz, J = 1.5 Hz, H-2′ and H-6′), 8.17 (1H, t, J =
13
6
.5 Hz, NH). C NMR (100 MHz, DMSO-d
), 87.1 (C-8), 126.0 (C-3′ and C-5′), 126.1 (C-4′′), 128.3 (C-
′′ and C-5′′), 128.5 (C-2′ and C-6′), 128.6 (C-2′′ and C-6′′), 128.7
6 2
): δ 34.7 (CH ), 41.3
(
CH
2
3
(
C-4′), 132.8 (C-1′), 139.1 (C-1′′), 148.6 (C-4), 152.0 (C-8a),
1
5
2
54.8 (C-7), 158.9 (C-2). Anal. Calcd for C19
.49; N, 25.44. Found: C, 68.98; H, 5.55; N, 25.32.
-Amino-4-(2-aminobenzylamino)-7-phenylpyrazolo[1,5-
18 6
H N : C, 69.07; H,
a][1,3,5]triazine (10e): mp 239-240 °C; Rf 0.20 (EtOAc : hexane
3
1
1:1); H NMR (400 MHz, DMSO-d
–
CH ), 5.24 (2H, s, NH
6
): δ 4.51 (2H, d, J = 6.5 Hz,
), 6.23 (1H, s, H-8), 6.52 (1H, td, J = 7.4
3
2
2
4
3
2
Hz, J =1.1 Hz, H-5′′), 6.64 (2H, s, NH ), 6.65 (1H, dd, J = 8.0
4
3
3
4
Hz, J =1.0 Hz, H-3′′), 6.97 (1H, ddd, J = 7.9 Hz, J = 7.3 Hz, J
3
4
=
7
1.6 Hz, H-4′′), 7.19 (1H, dd, J = 7.5 Hz, J = 1.4 Hz, H-6′′),
3
3
.39 (1H, t, J = 7.2 Hz, H-4′), 7.46 (2H, t, J = 7.3 Hz, H-3′ and
3
3
H-5′), 7.96 (2H, d, J = 7.4 Hz, H-2′ and H-6′), 8.51 (1H, t, J =
1
3
6
(
.5 Hz, NH). C NMR (100 MHz, DMSO-d
C-8), 114.7 (C-3′′), 115.7 (C-5′′), 121.3 (C-1′′), 126.1 (C-3′ and
C-5′), 128.0 (C-4′′), 128.6 (C-2′ and C-6′), 128.8 (C-4′), 129.4 (C-
′′), 132.8 (C-1′), 146.3 (C-2′′), 148.8 (C-4), 152.1 (C-8a), 155.0
C-7), 158.8 (C-2). Anal. Calcd for C18 : C, 65.24; H, 5.17;
N, 29.59. Found: C, 65.19; H, 5.28; N, 29.43.
6
2
): δ 40.1 (CH ), 87.2
6
(
17 7
H N
2
6. General method for the preparation of 4-amino-substituted
pyrazolo[1,5-a][1,3,5]triazine-2-amines (10k-p). Compound 14
(
200 mg, 0.61 mmol) was added to a solution of the appropriate
amine (0.78 mmol) in DMF (3 ml). The mixture was heated at 70-
0 °C with stirring for 5 h and the reaction progress was
monitored by TLC. After cooling, ice-cold H O (60 ml) was added
8
2
and the product was filtered and recrystallized from a suitable
solvent (Table 1).
Experimental data for some representative compounds:
2
-Amino-4-(phenylamino)-7-phenylpyrazolo[1,5-a][1,3,5]triazine
1
(
10m): mp 238-240 °C; Rf 0.46 (EtOAc : hexane – 1:1); H NMR
400 MHz, DMSO-d ): δ 6.34 (1H, s, H-8), 6.71 (2H, s, NH ),
.18 (1H, t, J = 7.3 Hz, H-4′′), 7.39-7.44 (3H, m, H-4′, H-3′′ and
(
7
6
2
3
3
3
H-5′′), 7.49 (2H, t, J = 7.5 Hz, H-3′ and H-5′), 7.91 (2H, d, J =
3
8
9
1
.2 Hz, H-2′′ and H-6′′), 8.05 (2H, d, J = 7.5 Hz, H-2′ and H-6′),
13
.81 (1H, s, NH). C NMR (100 MHz, DMSO-d
6
): δ 87.6 (C-8),
22.5 (C-4′′), 124.3 (C-2′′ and C-6′′), 126.3 (C-3′ and C-5′), 128.5
(
1
C-3′′ and C-5′′), 128.6 (C-2′ and C-6′), 128.9 (C-4′), 132.7 (C-1′),
37.3 (C-1′′), 146.8 (C-4), 152.2 (C-8a), 155.1 (C-7),158.5 (C-2).
Anal. Calcd for C17 : C, 67.54; H, 4.67; N, 27.80. Found: C,
14 6
H N
6
7.50; H, 4.73; N, 27.72.
-Amino-4-(4-methylphenylamino)-7-phenylpyrazolo[1,5-
a][1,3,5]triazine (10n): mp 238-239 °C; Rf 0.40 (EtOAc : hexane
2
1
–
1:1); H NMR (400 MHz, DMSO-d
6
): δ 2.32 (3H, s, Me), 6.32
3
(
1H, s, H-8), 6.66 (2H, s, NH ), 7.20 (2H, d, J = 8.3 Hz, H-3′′ and
2
3
3
H-5′′), 7.42 (1H, t, J = 7.3 Hz, H-4′), 7.48 (2H, t, J = 7.3 Hz, H-
3
3
′ and H-5′), 7.75 (2H, d, J = 8.3 Hz, H-2′′ and H-6′′), 8.04 (2H,
3
1
3
d, J = 7.5 Hz, H-2′ and H-6′), 9.73 (1H, s, NH). C NMR (100
MHz, DMSO-d ): δ 20.5 (Me), 87.5 (C-8), 122.7 (C-2′′ and C-6′′),
26.3 (C-3′ and C-5′), 128.6 (C-2′ and C-6′), 128.9 (C-4′), 129.0
6
1
(
C-3′′ and C-5′′), 132.7 (C-4′′), 133.5 (C-1′), 134.7 (C-1′′), 146.9
C-4), 152.2 (C-8a), 155.0 (C-7), 158.5 (C-2). Anal. Calcd for
(
C
N, 26.48.
18
H
16
N
6
: C, 68.34; H, 5.10; N, 26.56. Found: C, 68.27; H, 5.17;
2
2
7. Alvim-Gaston, M.; Grese, T.; Mahoui, A.; Palkowitz, A. D.;
Pineiro-Nunez, M.; Watson, I. Curr. Top. Med. Chem. 2014, 14,
2
94-303.
8. For a recent review of antimigraine CGRP receptor antagonists,
see: Negro, A.; Lionetto, L.; Simmaco, M.; Martelletti, P. Expert
Opin. Investig. Drugs 2012, 21, 807-818.