Pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives: Potent and selective A2A adenosine antagonists

Article abstract of DOI:10.1021/jm950746l

A series of pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives (10a-o,q,r), bearing alkyl and aralkyl chains on positions 7 and 8, were synthesized in the attempt to obtain potent and selective antagonists for the A_2A adenosine receptor subtype. The compounds were tested in binding and functional assays to evaluate their potency for the A_2A compared with the A₁ adenosine receptor subtype. In binding studies in rat brain membranes, most of the compounds showed affinity for A_2A receptors in the low nanomolar range with a different degree of A_2A versus A₁ selectivity. Comparison of N⁷ (10a-d,h-o)- and N⁸ (10e-g)-substituted pyrazolo derivatives indicates that N⁷ substitution decreases the A₁ affinity with the concomitant increase of A_2A selectivity. Specifically, the introduction of a 3-phenylpropyl group at pyrazolo nitrogen in position 7 (101) increased significantly the A_2A selectivity, being 210-fold, while the A_2A receptor affinity remained high (K_i = 2.4 nM). With regards to the affinity for A_2A receptors, also the compound 10n, bearing in the 7-position a β-morpholin-4-ylethyl group, deserves attention (K₁ = 5.6 nM) even though the A_2A selectivity (84-fold) was not as high as that of 101. Conversely, the compound 10m (N⁷-4-phenylbutyl derivative) showed a remarkable selectivity (A₁/A_2A ratio = 129) associated with lower A_2A affinity (K₁ = 21 nM). In functional studies, most of the compounds examined reversed 5′-(N-ethylcarbamoyl)adenosine-induced inhibition of rabbit platelet aggregation inhibition which is a biological response mediated by the A_2A receptor subtype. The compounds are potent and selective A_2A antagonists which can be useful to elucidate the pathophysiological role of this adenosine receptor subtype. These compounds deserve to be further developed to assess their potential for treatment of neurodegenerative disorders such as Parkinson's disease.

Full text of DOI:10.1021/jm950746l

1164
J . Med. Chem. 1996, 39, 1164-1171
P yr a zolo[4,3-e]-1,2,4-tr ia zolo[1,5-c]p yr im id in e Der iva tives: P oten t a n d Selective
A2A Ad en osin e An ta gon ists
Pier Giovanni Baraldi,*,† Barbara Cacciari,† Giampiero Spalluto,† Maria J ose´ Pineda de las Infantas y Villatoro,†
Cristina Zocchi,‡ Silvio Dionisotti,‡ and Ennio Ongini‡
Dipartimento di Scienze Farmaceutiche, Universita` degli Studi di Ferrara, Via Fossato di Mortara 17-19, 44100 Ferrara, Italy,
and Centro Ricerche Schering-Plough, Parco Scientifico San Raffaele, Via Olgettina 58, 20132 Milano, Italy
Received October 10, 1995X
A series of pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine derivatives (10a -o,q,r ), bearing alkyl
and aralkyl chains on positions 7 and 8, were synthesized in the attempt to obtain potent and
selective antagonists for the A2A adenosine receptor subtype. The compounds were tested in
binding and functional assays to evaluate their potency for the A2A compared with the A1
adenosine receptor subtype. In binding studies in rat brain membranes, most of the compounds
showed affinity for A2A receptors in the low nanomolar range with a different degree of A2A
versus A1 selectivity. Comparison of N7 (10a -d ,h -o)- and N8 (10e-g)-substituted pyrazolo
derivatives indicates that N7 substitution decreases the A1 affinity with the concomitant increase
of A2A selectivity. Specifically, the introduction of a 3-phenylpropyl group at pyrazolo nitrogen
in position 7 (10l) increased significantly the A2A selectivity, being 210-fold, while the A2A
receptor affinity remained high (Ki ) 2.4 nM). With regards to the affinity for A2A receptors,
also the compound 10n , bearing in the 7-position a â-morpholin-4-ylethyl group, deserves
attention (Ki ) 5.6 nM) even though the A2A selectivity (84-fold) was not as high as that of 10l.
Conversely, the compound 10m (N7-4-phenylbutyl derivative) showed a remarkable selectivity
(A1/A2A ratio ) 129) associated with lower A2A affinity (Ki ) 21 nM). In functional studies,
most of the compounds examined reversed 5′-(N-ethylcarbamoyl)adenosine-induced inhibition
of rabbit platelet aggregation inhibition which is a biological response mediated by the A2A
receptor subtype. The compounds are potent and selective A2A antagonists which can be useful
to elucidate the pathophysiological role of this adenosine receptor subtype. These compounds
deserve to be further developed to assess their potential for treatment of neurodegenerative
disorders such as Parkinson’s disease.
In tr od u ction
and in vivo studies.9-11 However, these compounds
undergo rapid photoisomerization when diluted and
exposed to natural light,12 and this may limit their use
as pharmacological tools.
Adenosine modulates a wide range of physiological
functions by interacting with specific cell surface recep-
tors which have been classified as A1, A2A, A2B, and A3
adenosine receptor subtypes.1,2 Efforts made in me-
dicinal chemistry over the last 2 decades have led to
the discovery of a series of adenosine analogs which
possess specific agonist properties at A1, A2A, or A3
receptors.3,4 As for adenosine receptor antagonists, a
large number of xanthine derivatives have been syn-
thesized in the attempts to improve both receptor
subtype affinity and selectivity of the natural com-
pounds caffeine and theophylline.3 Combined substitu-
tion at the 1-, 3-, and 8-positions of the xanthine moiety
led to potent and selective A1 receptor antagonists. For
example, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX)5
is currently used as a reference compound.
Non-xanthine heterocyclic compounds, including
5-amino-9-chloro-2-(2-furyl)[1,2,4]triazolo[1,5-c]quinazo-
line (CGS 15943, 1)13 and 4-amino-8-chloro-1-phenyl-
[1,2,4]triazolo[4,3-a]quinoxaline (CP 66,713),14 also have
high affinity for A2A receptors, but they are unselective,
being potent at A1 receptors as well. Recently, a series
of CGS 15943 derivatives, in which the m-chlorophenyl
group was replaced by a heterocycle ring, such as
pyrazole or imidazole, have been described to retain
high affinity for adenosine receptors.15 One of them,
5-amino-8-(4-fluorobenzyl)-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-
triazolo[1,5-c]pyrimidine (8FB-PTP, 2a ), has high af-
finity at A2A receptors and shows competitive A2A
antagonist properties in in vitro functional studies, but
its selectivity versus A1 receptor is still low.16 Con-
versely, the corresponding N7 derivative 5-amino-7-(4-
fluorobenzyl)-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-triazolo[1,5-
c]pyrimidine (7FB-PTP, 2b) showed a decrease in the
affinity at both receptor subtypes, but it was associated
with a concomitant increase of A2A versus A1 selectiv-
ity.15
A series of 8-styrylxanthines have been also found to
have high affinity and selectivity at A2A receptors.6,7 Two
of these compounds, namely, 7-methyl-8-(3,4-dimeth-
oxystyryl)xanthine (KF 17837)6 and 8-(3-chlorostyryl)-
caffeine (CSC),7 have been further investigated and
found to possess antagonist properties in both in vitro8,9
* To whom correspondence should be addressed at Dipartimento di
Scienze Farmaceutiche, Universita` di Ferrara, Via Fossato di Mortara
17-19, 44100 Ferrara, Italy. Tel: +39-(0)532-291293. Fax: +39-(0)-
532-291296.
With the aim to enhance the A2A selectivity, we have
further investigated the lead compounds 2a ,b. In our
previous study17 the importance of the hydrophobic,
electronic, and steric parameters of substituents at the
† Universita` degli Studi di Ferrara.
‡ Centro Ricerche Schering-Plough.
X Abstract published in Advance ACS Abstracts, February 1, 1996.
0022-2623/96/1839-1164$12.00/0 © 1996 American Chemical Society

Pyrazolo-1,2,4-triazolopyrimidine Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5 1165
Sch em e 1a
a
Reagents: (i) RX, K2CO3, EtOH, reflux.
Sch em e 2a
pyrazole N7 or N8 nitrogens (compounds 10a -c,e-h )
had been evaluated, according to the Topliss operational
scheme for aliphatic substituents.18 The derivatives
bearing a substituent in the 7-position showed a better
A2A selectivity than the corresponding N8 derivatives
having the same substituent. One of them, namely,
SCH 58261 (10c), was shown to have high affinity and
good selectivity for the A2A receptor subtype and to also
possess competitive A2A antagonist properties in in vitro
functional studies.19
a
Reagents: (i) EtOH, reflux.
Sch em e 3a
On the basis of these interesting results, we have
synthesized N7 derivatives in order to better evaluate
the Topliss operational scheme for aliphatic substituents
(10i,k ,q). Moreover, we focused our studies on the lead
compound 10c, designing the following structural mod-
ifications: (i) introduction of different spacers between
N7 nitrogen and phenyl ring (10l,m ,o) in order to
optimize the length spacer, (ii) increase of the lipophilic
nature of the substituent at the N7 position (10d ), an
essential condition for the interaction with A2A recep-
tors,17 and (iii) increase of the water solubility (10d,j,n ,r )
of this series of chemical structures.
a
Reagents: (i) HC(OEt)3, reflux; (ii) furoic hydrazide,
MeO(CH2)2OH; (iii) Ph2O, 260 °C; (iv) 10% HCl, reflux; (v) NH2CN,
1-methyl-2-pyrrolidone, pTsOH, 140 °C.
Ch em istr y
The preparation of the compounds 10a -o was per-
formed following the general synthetic strategy depicted
in Schemes 1-5. Alkylation of 5-amino-4-cyanopyrazole
(3) with the appropriate alkyl halide in DMF in the
presence of anhydrous potassium carbonate led to an
ca. 1:1 mixture of N1 isomers 4a -d and N2 isomers 4e-
g, separable by crystallization or column chromatogra-
phy (Scheme 1).
In order to improve and facilitate the synthesis of the
N7-substituted derivatives, we decided to synthesize the
pyrazole ring using the appropriate hydrazine. This
pathway afforded only the N1 isomer and allowed us to
avoid tedious purification procedures. Pyrazoles 4h -n
were prepared by reacting (ethoxymethylene)malono-
nitrile with the appropriate hydrazines20,21 following a
well-known procedure22 (Scheme 2).
The designed compounds 10a -o were synthesized
according to Gatta et al.15 for the synthesis of pyrazolo-
[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines (Scheme 3). Fol-
lowing the general strategy, the first step involved
transformation of pyrazoles 4a -i,k -n to the corre-
sponding imidates 7a -i,k -n by refluxing in triethyl
orthoformate. This conversion was not possible for 4j
because the hydroxy group prevented a clean reaction.
Therefore in order to achieve an improvement in the
overall yield, we converted the pyrazole 4j into the
corresponding acetyl derivative 4p (Scheme 4). Imi-
dates 7a -i,k -n were reacted with 2-furoic acid hy-
drazide in refluxing 2-methoxyethanol to provide the
pyrazolo[3,4-d]pyrimidine intermediates. The latter
compounds were converted through a thermally induced

1166 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5
Baraldi et al.
Sch em e 4a
range with different degree of selectivity (Table 1). Most
of the compounds examined were able to reverse the
platelet aggregation inhibition induced by N-ethyl-1′-
deoxy-1′-(6-amino-9H-purin-9-yl)-â-D-ribofuranurona-
mide (NECA) with potency similar to (10a -c,g,h ,j,q)
or higher than (i.e., 10e,f,l,n ) that of the reference
compound CGS 15943 (Table 1).
The study shows that N7 substitution (10a -d ,h -o)
on the pyrazole ring retains high affinity at A2A recep-
tors. On the contrary, either substitution at N8 (10e-
g) or no substitution (10q) led to compounds with a good
affinity for adenosine receptors but with very low
selectivity. Specifically, the introduction of the phenyl-
ethyl group at the pyrazole nitrogen in position 7, 10c,
increased significantly A2A selectivity, being about 50-
or 100-fold in rat or bovine striatal membranes, respec-
tively.18 On this basis, further studies were undertaken
to investigate the pharmacological characteristics of 10c
as a new prototypic A2A antagonist. The results of in
vitro functional studies carried out in various models
indicate that 10c is a competitive antagonist for the A2A
receptor subtype and has little or no interaction with
A1, A2B, and A3 receptors.18 Encouraged by these
results, we continued the investigation on the influence
of substituents in N7. For compound 10r , where the
amino group was protected as benzyl derivative, the A2A
receptor affinity is low (Ki )166 nM). This confirms that
a free amino group is necessary for an efficient receptor
interaction. Introduction of an oxygen atom in the
substituent chain (10o) reduced dramatically the A2A
receptor affinity (Ki > 1000 nM) and did not improve
water solubility, the latter being a limitation for 10c
and other xanthine and non-xanthine adenosine an-
tagonists.3 It is likely that the presence of an oxygen
atom hinders a correct ligand-receptor interaction. At
this time, this problem is under investigation by mo-
lecular modeling studies. Instead, replacement of the
oxygen atom with a methylene group led to interesting
data. For example, A2A affinity of 10m remained in the
nanomolar range (Ki ) 21 nM), but A2A selectivity
significantly increased when compared with 10c (129-
versus 53-fold). Further shortening of the chain using
3-phenylpropyl, 10l, led to a compound having higher
affinity (Ki ) 2.4 nM) and a very good selectivity (A1/
A2A ratio of 210). Thus, it seems that a spacer between
the pyrazole and aromatic moiety is necessary to achieve
high A2A selectivity, the optimal length being from two
to four carbon atoms (10c,d ,l-m ). These data provide
support to the concept that the lipophilic nature of the
substituent can be important for the interaction with
A2A receptors. This is confirmed by the results obtained
with (4-isobutylphenyl)ethyl derivative 10d which has
good affinity (Ki ) 22 nM) and selectivity (A1/A2A ratio
of >136). In analogy to the compound synthesized at
Zeneca, 2-(2-furyl)-5-[(2-morpholinoethyl)amino][1,2,4]-
triazolo[1,5-a][1,3,5]triazin-7-amine (pIC50 value at A2A
receptors of 7.6),24 the introduction of a morpholinoethyl
group in the N7 position led to a compound with an
increased affinity (Ki ) 5.6 nM) and high A2A selectivity,
although lower (84-fold) than 10l. Very recently, an-
other heterocycle compound, the 4-[2-[[7-amino-2-(2-
furyl)[1,2,4]triazolo[1,5-a][1,3,5]triazin-5-yl]amino]ethyl]-
phenol (ZM 241385), has been reported to be a potent
(pIC50 ) 9.5) and selective A2A antagonist.25 However,
the lack of binding data carried out according to
a
Reagents: (i) Ac2O, Py, room temperature; (ii) HC(OEt)3,
reflux; (iii) furoic hydrazide, MeO(CH2)2OH; (iv) Ph2O, 260 °C; (v)
NH3, MeOH, room temperature; (vi) NaH, BnBr, DMF.
Sch em e 5a
a
Reagents: (i) HCO2H, reflux; (ii) NaH, BnBr, room temper-
ature.
cyclization in diphenyl ether to the derivatives 8a -
i,k -n in good overall yield.
The cyanoaminopyrazole 4p underwent the same
reactions with triethyl orthoformate to afford imidate
7p and subsequently the tricyclic compound 8p . The
latter was deprotected with methanolic ammonia to give
8j which was converted to 8o by benzylation in the
presence of sodium hydride (Scheme 3). Benzylation
was performed on â-hydroxyethyl derivative 8j instead
of the pyrazole 4j because direct reaction on 4j with
benzyl bromide afforded only the benzylamino deriva-
tive. Treatment of 8a -o with dilute hydrochloric acid
at reflux temperature induced pyrimidine ring opening
to furnish the 5-amino-4-(1H-1,2,4-triazol-5-yl)pyrazoles
9a -o in good yield.
These derivatives were converted into the final com-
pounds 10a -o by reaction with an excess of cyanamide
in 1-methyl-2-pyrrolidone at 140 °C. Compound 10k
was transformed into 10q by refluxing in formic acid,
as previously described for the N-di-tert-butylation of
pyrazole intermediates.23 In an attempt to prepare
directly the benzyloxy derivative 10o, alkylation of 10j
with benzyl bromide in the presence of sodium hydride
at room temperature afforded N-benzyl derivative 10r ,
as the only product (Scheme 5).
Resu lts a n d Discu ssion
The results show that many of the tested compounds
have affinity at A2A receptors in the low nanomolar

Pyrazolo-1,2,4-triazolopyrimidine Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5 1167
Ta ble 1. Biological Activity of a Series of Pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines 10a -o,q-r
bindinga Ki (nM)
selectivity, plateletb aggregation
compd
R
A1
A2A
A1/A2A
ED50 (µM)
1, CGS 15943
6.4 (6.2-6.6)
3.3 (2.9-3.6)
1.2 (1.1-1.3)
1.2 (0.9-1.4)
12.0 (8.6-19.5)
706 (540-924)
8.9 (7.9-10)c
12 (7.6-19)c
5.3
2.8
15.8
0.0002
26.5
9.7
0.3
0.004
10.6
>10
0.3
0.3
0.3
<1.0
0.04
0.05
0.2
0.3
>1
0.2
>10
0.02
>1
0.03
>10
0.1
2a , 8FB-PTP
2b, 7FB-PTP
DPCPX
10a
10b
10c
10d
10e
10f
10g
10h
10i
10j
10k
10l
10m
10n
10o
189 (164-238)
1.5 (1.3-1.7)
N7-n-butyl
236 (486-872)c
116 (79-181)c
121 (103-143)c
N7-isopentyl
N7-â-phenylethyl
N7-â-(4-isobutylphenyl)ethyl
N8-n-butyl
2.3 (2-2.7)c
52.6
>3000
22 (12-40)
>136
30.4 (21.5-43)c
5.6 (4.0-7.9)c
2.4 (2.3-2.5)c
1.9 (1.4-2.4)c
1.4 (0.9-2.3)c
101 (94-109)c
22.7 (14.2-36.3)
77.7 (55.8-108)
260 (205-330)
2.4 (1.9-2.9)
21 (17-26)
12.7
2.9
3.4
6.4
5.2
N8-isopentyl
N8-â-phenylethyl
N7-methyl
4.7 (4.1-5.5)c
651 (486-872)c
119 (74.9-188)
978 (873-1094)
430 (378-488)
504 (329-773)
2705 (1867-3919)
471 (385-576)
N7-phenyl
N7-â-hydroxyethyl
N7-tert-butyl
12.6
1.7
210
129
84
N7-3-phenylpropyl
N7-4-phenylbutyl
N7-â-morpholin-4-ylethyl
N7-â-(benzyloxy)ethyl
H
5.6 (3.0-10.3)
>1000
.1000
10q
10r
210 (189-234)
330 (214-509)
22.6 (13.9-36.8)
166 (135-203)
9.3
2.0
N7-â-hydroxyethyl 5-aminobenzyl
>10
a
Inhibition of [3H]CHA binding (A1) in rat whole brain homogenates or [3H]CGS 21680 binding (A2A) in rat striatal homogenates; data
b
are expressed as geometric means, with 95% confidence limits. Dose of antagonist reducing by 50% the inhibitory effect induced by
NECA, used at a concentration (0.3 or 1 µM) close to the IC50 value, on ADP (5 µM)-induced rabbit platelet aggregation. c Binding data
from ref 17.
standard criteria does not allow to compare it with
compounds previously described.
orders, such as neurodegenerative diseases and cogni-
tive deficits.
Exp er im en ta l Section
Con clu sion s
Ch em istr y. Reaction courses and product mixtures were
routinely monitored by thin-layer chromatography (TLC) on
silica gel (precoated F254 Merck plates) and visualized with
iodine or aqueous potassium permanganate. Infrared spectra
(IR) were measured on a Perkin Elmer 257 instrument. 1H
NMR were determined in CDCl3 or DMSO-d6 solutions with
a Bruker AC 200 spectrometer, peak positions are given in
parts per million (δ) downfield from tetramethylsilane as
internal standard, and J values are given in hertz (Hz). Light
petroleum refers to the fractions boiling at 40-60 °C. Melting
points were determined on a Buchi-Tottoli instrument and are
uncorrected. Chromatography was performed with Merck 60-
We have described a series of pyrazolo[4,3-e]-1,2,4-
triazolo[1,5-c]pyrimidine derivatives that are potent and
selective non-xanthine A2A antagonists. This was
achieved as a further optimization of previous work by
Gatta et al.15 who started from CGS 15943 and replaced
the chlorophenyl moiety with a substituted pyrazole or
imidazole ring. Other studies made using triazole led
to potent but unselective compounds.17 All these data
have been of stimulus to make synthetic efforts involv-
ing the introduction of alkyl and aralkyl substituents
on the pyrazole ring.
1
200 mesh silica gel. All products reported showed IR and H
NMR spectra in agreement with the assigned structures.
Organic solutions were dried over anhydrous magnesium
sulfate. Elemental analyses were performed by the microana-
lytical laboratory of Dipartimento di Chimica, University of
Ferrara, and were within (0.4% of the theoretical values for
C, H, and N.
Gen er a l P r oced u r e for th e P r ep a r a tion of N-Su bsti-
tu ted -5-a m in o-4-cya n op yr a zoles 4h -n . The appropriate
hydrazine (0.53 mmol) was dissolved in EtOH (5 mL), and
(ethoxymethylene)malononitrile (64.8 mg, 0.53 mmol) was
added in little portions. Then the mixture was heated at 70
°C for 18 h before evaporating the solvent. The solid residue
was purified by chromatography (EtOAc/light petroleum, 1:1)
to afford the product as a solid in good yield. The following
spectral data are reported as examples.
Thus the compounds 10a ,c,e-g,l,n have A2A receptor
affinity of <10 nM, and most importantly, A2A versus
A1 selectivity is very high, being greater than 100-fold
for 10d ,m and 210-fold for 10l. The prototype com-
pound 10c has been further characterized in in vitro
studies and found to possess competitive A2A antagonist
properties.19 In vivo, the compound 10c retains A2A
antagonist properties in cardiovascular models26a and,
like caffeine, produces stimulatory effects on the central
nervous system.26b Moreover, its tritium-labeled form,
[3H]SCH 58261 (10c), has been found to specifically
label A2A receptors with high affinity (KD ) 0.7 nM) and
high specific binding (>90%).27
5-Am in o-4-cya n o-1-(â-h yd r oxyeth yl)p yr a zole (4j): yield
75%, yellow solid; mp 150-151 °C (EtOAc-light petroleum);
On the basis of the evidence available,28,29 the com-
pounds deserve to be further developed to assess their
potential for treatment of central nervous system dis-
1
IR (KBr) 3450-2950, 2210, 1660, 1580, 1440 cm-1; H NMR
(DMSO-d6) δ 3.65 (dd, 2H, J ) 5.7, 5.2), 3.93 (t, 2H, J ) 5.7),

1168 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5
Baraldi et al.
4.91 (t, 1H, J ) 5.2), 6.45 (bs, 2H), 7.52 (s, 1H). Anal.
(C6H8N4O) C, H, N.
4-Cya n o-5-[(et h oxym et h ylen e)a m in o]-1-p h en ylp yr a -
zole (7i): yield 92%, yellow oil; IR (neat) 2200, 1650, 1530
5-Am in o-1-ter t-bu tyl-4-cya n op yr a zole (4k ): yield 80%,
yellow solid; mp 94-95 °C (EtOAc-light petroleum); IR (KBr)
cm-1
; 1H NMR (CDCl3) δ 1.27 (t, 3H, J ) 7), 3.39 (s, 3H), 4.28
(q, 2H, J ) 7), 7.41-7.66 (m, 5H), 8.16 (s, 1H), 8.54 (s, 1H).
1
3350-3150, 2200, 1650, 1470 cm-1; H NMR (CDCl3) δ 1.63
Anal. (C13H12N4O) C, H, N.
(s, 9H), 4.44 (bs, 2H), 7.42 (s, 1H). Anal. (C8H12N4) C, H, N.
5-Am in o-4-cya n o-1-(3-p h en ylp r op yl)p yr a zole (4l): yield
72%, pale yellow solid; mp 155 °C (EtOAc-Et2O); IR (KBr)
3355-3160, 2210, 1650, 1450 cm-1; 1H NMR (CDCl3) δ 1.91-
2.07 (m, 2H), 2.58 (t, 2H, J ) 6), 5.91 (t, 2H, J ) 6), 6.47 (bs,
2H), 7.15-7.25 (m, 5H), 7.43 (s, 1H). Anal. (C13H14N4) C, H,
N.
1-ter t-Bu t yl-4-cya n o-5-[(et h oxym et h ylen e)a m in o]p y-
r a zole (7k ): yield 89%, pale yellow oil; IR (neat) 2210, 1640
cm-1; 1H NMR (CDCl3) δ 1.43 (t, 3H, J ) 7), 1.64 (s, 9H), 4.43
(q, 2H, J ) 7), 7.57 (s, 1H), 8.28 (s, 1H). Anal. (C11H16N4O)
C, H, N.
4-Cya n o-5-[(eth oxym eth ylen e)a m in o]-1-(3-p h en ylp r o-
p yl)p yr a zole (7l): yield 93%, yellow oil; IR (neat) 2210, 1640,
1
1520 cm-1; H NMR (CDCl3) δ 1.37 (t, 3H, J ) 6), 2.02-2.2
5-Am in o-4-cya n o-1-(4-p h en ylbu tyl)p yr a zole (4m ): yield
75%, yellow solid; mp 147-149 °C (EtOAc-Et2O); IR (KBr)
(m, 2H), 2.61 (t, 2H, J ) 7.2), 4.07 (t, 2H, J ) 7.2), 4.25 (q,
2H, J ) 6), 7.1-7.28 (m, 5H), 7.65 (s, 1H), 8.38 (s, 1H). Anal.
(C16H18N4O) C, H, N.
3345-3160, 2220, 1670, 1450 cm-1 1H NMR (DMSO-d6) δ
;
1.55-1.73 (m, 2H), 1.74-1.91 (m, 2H), 2.63 (t, 2H, J ) 7), 3.91
(t, 2H, J ) 7), 5.39 (bs, 2H), 7.13-7.27 (m, 5H), 7.42 (s, 1H).
Anal. (C14H16N4) C, H, N.
4-Cyan o-5-[(eth oxym eth ylen e)am in o]-1-(4-ph en ylbu tyl)-
p yr a zole (7m ): yield 91%, yellow oil; IR (neat) 2190, 1650,
1
1520 cm-1; H NMR (CDCl3) δ 1.39 (t, 3H, J ) 6), 1.52-1.67
5-Am in o-1-(â-m or ph olin -4-yleth yl)-4-cyan opyr azole (4n ):
(m, 2H), 1.72-1.96 (m, 2H), 2.62 (t, 2H, J ) 8), 4.08 (t, 2H, J
) 8), 4.36 (q, 2H, J ) 6), 7.03-7.39 (m, 5H), 7.64 (s, 1H), 8.40
(s, 1H). Anal. (C17H20N4O) C, H, N.
yield 79%, yellow solid; mp 135-137 °C (EtOAc-Et2O); IR
1
(KBr) 3360-3158, 2190, 1650, 1450 cm-1; H NMR (DMSO-
d6) δ 2.40 (t, 4H, J ) 4), 2.58 (t, 2H, J ) 8), 3.53 (t, 4H, J ) 4),
4.01 (t, 2H, J ) 8), 6.62 (bs, 2H), 7.52 (s, 1H). Anal.
(C10H15N5O) C, H, N.
4-Cya n o-5-[(eth oxym eth ylen e)a m in o]-1-(â-m or p h olin -
4-yleth yl)p yr a zole (7n ): yield 91%, yellow oil; IR (neat) 2210,
1660, 1520 cm-1; 1H NMR (CDCl3) δ 1.43 (t, 3H, J ) 7), 2.44-
2.49 (m, 4H), 2.75 (t, 2H, J ) 6), 3.60-3.65 (m, 4H), 4.16 (t,
2H, J ) 6), 4.39 (q, 2H, J ) 7), 7.66 (s, 1H), 8.43 (s, 1H). Anal.
(C13H19N5O2) C, H, N.
1-[â-(Acetyloxy)eth yl]-4-cya n o-5-[(eth oxym eth ylen e)-
a m in o]p yr a zole (7p ): yield 95%, yellow oil; IR (neat) 2200,
1740, 1650 cm-1; 1H NMR (CDCl3) δ 1.43 (t, 3H, J ) 7.2), 2.1
(s, 3H), 4.3-4.5 (m, 6H), 7.68 (s, 1H), 8.44 (s, 1H). Anal.
(C11H14N4O3) C, H, N.
Gen er a l P r oced u r es for th e P r ep a r a tion of 7- a n d
8-Su bstitu ted -2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia zolo[1,5-
c]p yr im id in es 8a -n ,p . Iminoethers 7a -i,k -n ,p (20 mmol)
were dissolved in 2-methoxyethanol (50 mL), and 2-furoic acid
hydrazide (2.5 g, 22 mmol) was added. The mixture was
refluxed for 5-10 h; then, after cooling, the solvent was
removed under reduced pressure and the dark oily residue
dissolved in diphenyl ether (50 mL) and heated at 260 °C using
a Dean-Stark trap for the azeotropic elimination of water
produced in the reaction. After 1.5 h, the mixture was poured
onto hexane (200 mL) and cooled. The precipitate was filtered
off and purified by chromatography (EtOAc/hexane, 1:1). In
this way, different compounds were obtained. The following
spectral data are reported as examples.
1-[â-(Acetyloxy)eth yl]-5-a m in o-4-cya n op yr a zole (4p ).
To a solution of 4j (0.5 g, 3.28 mmol) in dry pyridine (5 mL)
was added acetic anhydride (0.62 mL, 6.6 mmol), and the
mixture was heated at 100 °C for 2 h. Then the solvent was
removed, and the residue was dissolved in CH2Cl2 (10 mL) and
washed with water (3 × 10 mL). The organic layer was dried
and evaporated to afford 4p (0.57 g, 90%) as a yellow solid:
mp 117-118 °C dec (EtOAc-light petroleum); IR (KBr) 3400-
1
3100, 2200, 1740, 1640 cm-1; H NMR (DMSO-d6) δ 2.06 (s,
3H), 4.2 (t, 2H, J ) 5.6), 4.4 (t, 2H, J ) 5.6), 5.5 (bs, 2H), 7.45
(s, 1H). Anal. (C8H10N4O2) C, H, N.
Gen er a l P r oced u r e for th e P r ep a r a tion of N-Su bsti-
tu ted-5-am in o-4-cyan opyr azoles 4a -d an d N-Su bstitu ted-
3-am in o-4-cyan opyr azoles 4e-g. To a suspension of 4-cyano-
5-aminopyrazole (3) (1.08 g, 10 mmol) and anhydrous potassium
carbonate (1.65 g, 12 mmol) in DMF was added the appropriate
alkyl halide (1.2 equiv), and the mixture was stirred at 80 °C
for 1-2 h. Then the solvent was removed under reduced
pressure, and the two alkylated isomers, N1 and N2, usually
present in a ratio of 1:1, were separated by flash chromatog-
raphy (EtOAc/light petroleum, 1:2). The following spectral
data are reported as examples.
5-Am in o-4-cya n o-1-(â-p h en yleth yl)p yr a zole (4c): yield
42%, yellow solid; mp 98-100 °C (EtOAc-light petroleum);
IR (KBr) 3450-3170, 2200, 1640, 1450 cm-1; 1H NMR (CDCl3)
δ 3.07 (t, 2H, J ) 6.2), 4.1 (t, 2H, J ) 6.2), 4.23 (bs, 2H), 7.17
(s, 1H), 7.0-7.28 (m, 5H). Anal. (C12H12N4) C, H, N.
3-Am in o-4-cya n o-1-(â-p h en yleth yl)p yr a zole (4g): yield
41%, yellow solid; mp 172-173 °C (EtOAc-light petroleum);
IR (KBr) 3450-3150, 2200, 1650, 1470 cm-1; 1H NMR (DMSO-
d6) δ 3.04 (t, 2H, J ) 6.4), 4.12 (t, 2H, J ) 6.4), 5.85 (bs, 2H),
7.21-7.30 (m, 5H), 7.41 (s, 1H). Anal. (C12H12N4) C, H, N.
Gen er a l P r oced u r e for th e P r ep a r a tion of 1-Su bsti-
t u t ed -4-cya n o-3(or 5)-[(et h oxym et h ylen e)a m in o]p yr a -
zoles 7a -i,k -p . The mixture of N1- and N2-substituted-4-
cyano-5-aminopyrazoles 4a -i,k -p (20 mmol) was dissolved
in triethyl orthoformate (40 mL), and the solution was refluxed
under nitrogen for 8 h. Then the solvent was removed under
reduced pressure, and the oily residue was dissolved in ether
and roughly purified on silica gel (EtOAc/light petroleum, 1:9)
to afford the corresponding iminoethers. The following spec-
tral data are reported as examples.
7-n -Bu t yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-t r ia zolo[1,5-
c]p yr im id in e (8a ): yield 75%, white solid; mp 180-181 °C
(EtOAc); IR (KBr) 1520, 1430 cm-1; 1H NMR (DMSO-d6) δ 0.9
(t, 3H, J ) 7.2), 1.3 (m, 2H), 1.9 (m, 2H), 4.5 (t, 2H, J ) 7.2),
6.7 (m, 1H), 7.4 (m, 1H), 8.0 (m, 1H), 8.6 (s, 1H), 9.6 (s, 1H).
Anal. (C14H14N6O) C, H, N.
7-Isop en tyl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia zolo[1,5-
c]p yr im id in e (8b): yield 60%, white solid; mp 165-166 °C
(EtOAc-light petroleum); IR (KBr) 1620, 1500, 1430 cm-1; 1H
NMR (CDCl3) δ 1.0 (d, 6H, J ) 6.2), 1.18-1.7 (m, 3H), 4.6 (t,
2H, J ) 7.4), 6.6 (m, 1H), 7.3 (m, 1H), 7.7 (m, 1H), 8.8 (s, 1H),
9.1 (s, 1H). Anal. (C15H16N6O) C, H, N.
7-(â-P henylethyl)-2-(2-furyl)pyrazolo[4,3-e]-1,2,4-triazolo-
[1,5-c]p yr im id in e (8c): yield 20%; mp 174-175 °C (EtOH);
1
IR (KBr) 1660, 1510, 1450 cm-1; H NMR (DMSO-d6) δ 3.23
(t, 2H), 4.74 (t, 2H), 6.75 (s, 1H), 7.14-7.17 (m, 5H), 7.28 (s,
1H), 7.98 (s, 1H), 8.53 (s, 1H), 9.56 (s, 1H). Anal. (C18H14N6O)
C, H, N.
8-n -Bu t yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-t r ia zolo[1,5-
c]p yr im id in e (8e): yield 80%, pale yellow solid; mp 245-
1-n -Bu t yl-4-cya n o-5-[(et h oxym et h ylen e)a m in o]p yr a -
zole (7a ): yield 87%, pale yellow oil; IR (neat) 2240, 1640 cm-1
;
247 °C (MeOH); IR (KBr) 1610, 1500 cm-1; H NMR (DMSO-
1
1H NMR (CDCl3) δ 0.9 (t, 3H, J ) 6.2), 1.4 (t, 3H, J ) 7), 1.5
(m, 2H), 1.8 (m, 2H), 4.3 (q, 2H, J ) 6.2), 4.5 (t, 2H, J ) 7),
7.9 (s, 1H), 8.4 (s, 1H). Anal. (C11H16N4O) C, H, N.
4-Cya n o-5-[(et h oxym et h ylen e)a m in o]-1-m et h ylp yr a -
zole (7h ): yield 90%, pale yellow oil; IR (neat) 2220, 1650, 1430
cm-1; 1H NMR (CDCl3) δ 1.33 (t, 3H, J ) 7), 3.65 (s, 3H), 4.37
(q, 2H, J ) 7), 7.89 (s, 1H), 8.45 (s, 1H). Anal. (C8H10N4O) C,
H, N.
d6) δ 0.9 (m, 3H), 1.3 (m, 2H), 1.9 (m, 2H), 4.5 (t, 2H, J ) 7.2),
6.2 (m, 1H), 7.3 (m, 1H), 8.0 (m, 1H), 8.9 (s, 1H), 9.4 (s, 1H),
2D NMR (NOESY) N-CH2 signal (4.5 ppm) shows cross-peak
with C9-H signal (8.9 ppm). Anal. (C14H14N6O) C, H, N.
8-Isop en tyl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia zolo[1,5-
c]p yr im id in e (8f): yield 67%,pale yellow solid; mp 235-237
°C (MeOH); IR (KBr) 1635, 1510, 1450 cm-1; 1H NMR (DMSO-
d6) δ 1.0 (d, 6H, J ) 6.2), 1.5-1.9 (m, 3H), 4.6 (t, 2H, J ) 7.4),

Pyrazolo-1,2,4-triazolopyrimidine Derivatives
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5 1169
6.6 (m, 1H), 7.3 (m, 1H), 7.7 (m, 1H), 8.8 (s, 1H), 9.1 (s, 1H).
Anal. (C15H16N6O) C, H, N.
Na2SO4 and evaporated under vacuum. The residue was
purified by chromatography (EtOAc/light petroleum, 2:1) to
afford the desired compound as a solid. The following spectral
data are reported as examples.
8-(â-P h en yleth yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (8g): yield 60%; mp 268-270 °C
(EtOAc-light petroleum); IR (KBr) 1660, 1510, 1450 cm-1; 1H
NMR (DMSO-d6) δ 3.32 (t, 2H, J ) 6.7), 4.72 (t, 2H, J ) 6.7),
6.73 (s, 1H), 7.23 (m, 5H), 7.95 (s, 1H), 8.8 (s, 1H), 9.41 (s,
1H). Anal. (C18H14N6O) C, H, N.
5-Am in o-1-(â-p h en yleth yl)-4-[3-(2-fu r yl)-1,2,4-tr ia zol-5-
yl]p yr a zole (9c): yield 75%, yellow solid; mp 175-176 °C
(EtOH); IR (KBr) 3350-3150, 1620 cm-1 1H NMR (DMSO-
;
d6) δ 3.15 (t, 2H, J ) 6.5), 4.48 (t, 2H, J ) 6.5), 5.78 (s, 1H),
6.37 (s, 1H), 7.1 (s, 1H), 7.27-7.28 (m, 5H), 7.82 (s, 1H), 14.51
(bs, 2H). Anal. (C17H16N6O) C, H, N.
7-(â-Hyd r oxyeth yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (8j). This product can also be ob-
tained starting from compound 8p with the following proce-
dures. To a saturated methanolic solution of ammonia (15 mL)
was added at 0 °C compound 8p (0.5 g, 1.6 mmol). The
resulting mixture was stirred at room temperature for 18 h.
The solvent was removed in vacuo, and the residue was
purified by chromatography (EtOAc/light petroleum, 1:1) to
afford the product as a pale yellow solid (0.3 g, 70%): mp 216-
3-Am in o-1-(â-p h en yleth yl)-4-[3-(2-fu r yl)-1,2,4-tr ia zol-5-
yl]p yr a zole (9g): yield 80%, yellow solid; mp 205-206 °C
(EtOH); IR (KBr) 3350-3150, 1625 cm-1 1H NMR (DMSO-
;
d6) δ 3.12 (t, 2H, J ) 6.5), 4.46 (t, 2H, J ) 6.5), 5.75(s, 1H),
6.34 (s, 1H), 6.63 (s, 1H), 7.01 (s, 1H), 7.21-7.27 (m, 5H), 7.79
(s, 1H), 14.41 (bs, 2H). Anal. (C17H16N6O) C, H, N.
5-Am in o-1-m eth yl-4-[3-(2-fu r yl)-1,2,4-tr ia zol-5-yl]p yr a -
zole (9h ): yield 68%, yellow solid; mp 130-131 °C (EtOAc-
1
217 °C dec; IR (KBr) 3500-3100, 1645, 1450 cm-1; H NMR
(DMSO-d6) δ 3.89 (m, 2H), 4.94 (bs, 1H), 6.75 (m, 1H), 7.30
(d, 1H, J ) 3.4), 7.98 (s, 1H), 8.53 (s, 1H), 9.62 (s, 1H). Anal.
(C12H10N6O2) C, H, N.
light petroleum); IR (KBr) 3280-3150, 1620 cm-1 1H NMR
;
(DMSO-d6) δ 3.60 (s, 3H), 6.16 (bs, 2H), 6.62 (s, 1H), 6.96 (s,
1H), 7.63 (s, 1H), 7.77 (s, 1H), 13.81 (bs, 1H). Anal. (C10H10N6O)
C, H, N.
7-ter t-Bu t yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-t r ia zolo-
[1,5-c]p yr im id in e (8k ): yield 63%, pale yellow solid; mp 162-
5-Am in o-1-p h en yl-4-[3-(2-fu r yl)-1,2,4-tr ia zol-5-yl]p yr a -
zole (9i): yield 70%, yellow solid; mp 185-186 °C (EtOAc);
IR (KBr) 3200-3100, 1640, 1470 cm-1; 1H NMR (DMSO-d6) δ
3.60 (bs, 2H), 6.65 (m, 1H), 6.70 (bs, 1H), 7.20 (d, 1H, J ) 3.4),
7.4-7.6 (m, 5H), 7.78 (s, 1H), 7.9 (bs, 1H). Anal. (C15H12N6O)
C, H, N.
163 °C (EtOAc); IR (KBr) 1645, 1520, 1450 cm-1 1H NMR
;
(CDCl3) δ 1.87 (s, 9H), 6.62 (m, 1H), 7.28 (d, 1H, J ) 4.2), 7.65
(d, 1H, J ) 1.2), 8.35 (s, 1H), 9.09 (s, 1H). Anal. (C14H14N6O)
C, H, N.
7-(3-P h en ylp r op yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (8l): yield 68%, pale yellow solid; mp
5-Am in o-1-(â-h yd r oxyeth yl)-4-[3-(2-fu r yl)-1,2,4-tr ia zol-
155 °C (EtOAc); IR (KBr) 1650, 1520, 1445 cm-1 1H NMR
;
5-yl]p yr a zole (9j): yield 78%, yellow solid; mp 218-220 °C
(CDCl3) δ 2.3-2.5 (m, 2H), 2.68 (t, 2H, J ) 8), 4.58 (t, 2H, J )
8), 6.61 (m, 1H), 7.16-7.29 (m, 6H), 7.65 (s, 1H), 8.38 (s, 1H),
9.1 (s, 1H). Anal. (C19H16N6O) C, H, N.
7-(4-P h en ylbu tyl)-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (8m ): yield 65%, pale yellow solid; mp
156-158 °C (EtOAc); IR (KBr) 1660, 1520, 1455 cm-1; 1H NMR
(CDCl3) δ 1.64-1.68 (m, 2H), 1.99-2.07 (m, 2H), 2.66 (t, 2H,
J ) 8), 4.56 (t, 2H, J ) 8), 6.58-6.61 (m, 1H), 7.11-7.29 (m,
6H), 7.64 (s, 1H), 8.38 (s, 1H), 9.09 (s, 1H). Anal. (C20H18N6O)
C, H, N.
(EtOAc); IR (KBr) 3480-3100, 1630, 1450 cm-1 1H NMR
;
(DMSO-d6) δ 3.20 (bs, 1H), 3.80 (t, 2H, J ) 5.3), 4.07 (t, 2H, J
) 5.3), 5.99 (bs, 2H), 6.54 (m, 1H), 6.93 (d, 1H, J ) 4.2), 7.61
(d, 1H, J ) 1.2), 7.72 (s, 1H), 13.6 (bs, 1H). Anal. (C11H12N6O2)
C, H, N.
5-Am in o-1-ter t-bu tyl-4-[3-(2-fu r yl)-1,2,4-tr iazol-5-yl]pyr a-
zole (9k ): yield 75%, yellow solid; mp 148-150 °C (MeOH);
1
IR (KBr) 3160, 1600, 1450 cm-1; H NMR (CDCl3) δ 1.6 (m,
9H), 6.1 (s, 1H), 6.6 (s, 1H), 6.9 (m, 1H), 7.7 (s, 1H), 7.8 (s,
1H), 13.9 (bs, 1H). Anal. (C13H16N6O) C, H, N.
7-(â-Mor p h olin -4-ylet h yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-
1,2,4-tr ia zolo[1,5-c]p yr im id in e (8n ): yield 67%, yellow solid;
mp 202-203 °C (EtOAc); IR (KBr) 1660, 1510, 1440 cm-1; 1H
NMR (CDCl3) δ 2.54 (t, 4H, J ) 4), 2.94 (t, 2H, J ) 6), 3.6 (t,
4H, J ) 4), 4.66 (t, 2H, J ) 6), 6.60 (bs, 1H), 7.27 (d, 1H, J )
4), 7.65 (s, 1H), 8.37 (s, 1H), 9.11 (s, 1H). Anal. (C16H17N7O2)
C, H, N.
5-Am in o-1-(3-p h en ylp r op yl)-4-[3-(2-fu r yl)-1,2,4-t r ia -
zol-5-yl]p yr a zole (9l): yield 78%, pale yellow solid; mp 138-
140 °C (EtOH); IR (KBr) 3150, 1610, 1450 cm-1 1H NMR
;
(CDCl3) δ 2.04-2.15 (m, 2H), 2.59 (t, 2H, J ) 8), 3.89 (t, 2H,
J ) 8), 5.13 (bs, 2H), 6.44 (bs, 1H), 6.93 (d, 1H, J ) 2), 7.09-
7.26 (m, 5H), 7.42 (s, 1H), 7.73 (s, 1H), 13.9 (bs, 1H). Anal.
(C18H18N6O) C, H, N.
7-[â-(Ben zyloxy)eth yl]-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-
tr ia zolo[1,5-c]p yr im id in e (8o). To a suspension of NaH (38
mg, 80% in oil, 1.2 equiv) in dry DMF (20 mL) at 0 °C was
added 8j (0.3 g, 1.1 mmol), and the mixture was allowed to
warm at room temperature. When the solution was clear, it
was cooled at 0 °C again, benzyl bromide (0.2 mL, 1.2 equiv)
was added, and the solution was stirred at room temperature
for 18 h. Then the solvent was removed, and the crude oily
compound 8o was used for the next step without any further
purifications. An analytical sample was purified by flash
chromatography (AcOEt): IR (neat) 1660, 1450 cm-1; 1H NMR
(DMSO-d6) δ 3.48 (m, 2H), 4.59 (m, 2H), 5.61 (s, 2H), 6.71 (m,
1H), 7.05 (d, 1H, J ) 3.5), 7.23 (s, 1H), 7.15-7.48 (m, 5H), 7.9
(s, 1H), 8.5 (s, 1H). Anal. (C19H16N6O2) C, H, N.
5-Am in o-1-(4-p h en ylb u t yl)-4-[3-(2-fu r yl)-1,2,4-t r ia zol-
5-yl]p yr a zole (9m ): yield 82%, pale yellow oil; IR (neat) 3140,
1
1600, 1450 cm-1; H NMR (CDCl3) δ 1.6-1.8 (m, 2H), 1.81-
2.0 (m, 2H), 2.64 (t, 2H, J ) 7), 3.95 (t, 2H, J ) 7), 5.1 (bs,
2H), 6.55 (d, 1H, J ) 2), 7.21-7.26 (m, 6H), 7.49 (s, 1H), 7.74
(s, 1H), 9.06 (bs, 1H). Anal. (C19H20N6O) C, H, N.
5-Am in o-1-(â-m or p h olin -4-yleth yl)-4-[3-(2-fu r yl)-1,2,4-
tr ia zol-5-yl]p yr a zole (9n ): yield 76%, dark yellow oil; IR
1
(neat) 3150, 1620, 1465 cm-1; H NMR (CDCl3) δ 2.55 (t, 4H,
J ) 4), 2.70-2.75 (m, 2H), 3.71 (t, 4H, J ) 4), 4.08-4.17 (m,
2H), 6.33 (bs, 2H), 6.49 (dd, 1H, J ) 2, 4), 6.99 (d, 2H, J ) 4),
7.43 (s, 1H), 7.49 (d, 1H, J ) 2), 7.7 (bs, 1H). Anal.
(C15H19N7O2) C, H, N.
5-Am in o-1-[â-(ben zyloxy)eth yl]-4-[3-(2-fu r yl)-1,2,4-tr ia -
7-[â-(Acetyloxy)eth yl]-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-
tr ia zolo[1,5-c]p yr im id in e (8p ): yield 76%, yellow solid; mp
174-176 °C dec (EtOAc-light petroleum); IR (KBr) 1735,
zol-5-yl]p yr a zole (9o): yield 70%, yellow solid; mp 167-168
1
°C (EtOAc); IR (KBr) 3350-3150, 1625, 1500 cm-1; H NMR
(DMSO-d6) δ 3.69 (t, 2H, J ) 5.3), 4.00 (t, 2H, J ) 5.3), 5.02
(m, 2H), 5.62 (s, 2H), 6.43 (bs, 1H), 6.63 (m, 1H), 7.03 (d, 1H,
J ) 4.2), 7.15-7.35 (m, 6H), 7.8 (s, 1H). Anal. (C18H18N6O2)
C, H, N.
1
1645, 1450 cm-1; H NMR (CDCl3) δ 1.98 (s, 3H), 4.60 (t, 2H,
J ) 5.3), 4.80 (t, 2H, J ) 5.3), 6.62 (m, 1H), 7.29 (d, 1H, J )
4.3), 7.66 (d, 1H, J ) 1.1), 8.41 (s, 1H), 9.12 (s, 1H). Anal.
(C14H12N6O3) C, H, N.
Gen er a l P r oced u r es for th e P r ep a r a tion of 5-Am in o-
7(or 8)-su bstitu ted -2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in es 10a -o. To a solution of pyrazole
derivatives 9a -o (10 mmol) in N-methylpyrrolidone (40 mL)
were added cyanamide (0.42 g, 60 mmol) and p-toluenesulfonic
acid (2.85 g, 15 mmol), and the mixture was heated at 160 °C
for 4 h. Then cyanamide (0.42 g, 60 mmol) was added again,
and the solution was heated overnight. Then the solution was
diluted with EtOAc (80 mL), and the precipitate (excess of
Gen er a l P r oced u r es for th e P r ep a r a tion of N-Su bsti-
tu ted-4-[3-(2-fu r yl)-1,2,4-tr iazol-5-yl]-5-am in opyr azoles 9a-
c,h -o a n d N-Su bstitu ted -4-[3-(2-fu r yl)-1,2,4-tr ia zol-5-yl]-
3-a m in op yr a zoles 9d -g. A solution of the mixture of 8a -o
(10 mmol) in aqueous 10% HCl (50 mL) was refluxed for 3 h.
Then the solution was cooled and basified with concentrated
ammonium hydroxide at 0 °C. The compounds were extracted
with EtOAc (3 × 20 mL); the organic layers were dried with

1170 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 5
Baraldi et al.
Ta ble 2. Characterization of Pyrazolo[4,3-e]-1,2,4-triazolo-
[1,5-c]pyrimidine Derivatives 10a -o,q-r
δ 6.74 (m, 1H), 7.25 (d, 1H, J ) 4.2), 7.36-7.4 (m, 1H), 7.51-
7.59 (m, 2H), 7.96 (s, 1H), 8.13-8.17 (m, 2H), 8.28 (bs, 2H),
8.44 (s, 1H).
yield
crystallization
solvent
5-Am in o-7-(â-h yd r oxyeth yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-
compd (%) mp (°C)
MW
formula
anal.
1,2,4-tr ia zolo[1,5-c]p yr im id in e (10j): white solid; IR (KBr)
10a
10b
10c
10d
10e
10f
10g
10h
10i
10j
10k
10l
10m
10n
10o
10q
10r
35 157-158
50 208-210
20 225-226
75 207-210
47 200-203
60 212-213
45 183-185
30 210-213
42 295-297
75 258-260
45 238-240
65 195-196
62 205-208
59 260-262
30 144-145
98 248-250
80 187-190
EtOH
EtOH
EtOAc
EtOAc
EtOH
EtOAc
EtOH
EtOH
EtOH
EtOAc
EtOH
EtOH
EtOH
EtOH
EtOAc
MeOH
EtOAc
297.32 C14H15N7O C, H, N
311.34 C15H17N7O C, H, N
345.36 C18H15N7O C, H, N
401.47 C22H23N7O C, H, N
311.34 C15H17N7O C, H, N
345.36 C18H15N7O C, H, N
297.32 C14H15N7O C, H, N
255.24 C11H9N7O C, H, N
317.31 C16H11N7O C, H, N
285.26 C12H11N7O2 C, H, N
297.32 C14H15N7O C, H, N
359.39 C19H17N7O C, H, N
373.42 C20H19N7O C, H, N
354.37 C16H18N8O2 C, H, N
375.39 C19H17N7O2 C, H, N
241.21 C10H7N7O C, H, N
375.39 C19H17N7O2 C, H, N
3500-2900, 1670, 1640, 1620, 1550, 1455 cm-1
;
1H NMR
(DMSO-d6) δ 3.82 (m, 2H), 4.28 (t, 2H, J ) 5.2), 4.9 (bs, 1H),
6.73 (m, 1H), 7.22 (d, 1H, J ) 4.2), 7.94 (s, 1H), 8.08 (bs, 2H),
8.16 (s, 1H).
5-Am in o-7-ter t-b u t yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-
tr ia zolo[1,5-c]p yr im id in e (10k ): white solid; IR (KBr) 3510-
2960, 1670, 1635, 1625, 1560, 1470 cm-1; 1H NMR (DMSO-d6)
δ 1.73 (s, 9H), 6.65 (m, 1H), 7.2 (d, 1H, J ) 4.2), 7.82 (bs, 3H),
8.0 (s, 1H).
5-Am in o-7-(3-p h en ylp r op yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-
1,2,4-tr ia zolo[1,5-c]p yr im id in e (10l): white solid; IR (KBr)
3500-2950, 1650, 1640, 1625, 1550, 1455 cm-1 1H NMR
;
(DMSO-d6) δ 2.15-2.45 (m, 2H), 2.66 (t, 2H, J ) 8), 4.37 (t,
2H, J ) 8), 6.14 (bs, 2H), 6.60 (dd, 1H, J ) 2, 4.2), 7.15-7.27
(m, 6H), 7.63 (s, 1H), 8.2 (s, 1H).
5-Am in o-7-(4-p h en ylb u t yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-
1,2,4-tr ia zolo[1,5-c]p yr im id in e (10m ): white solid; IR (KBr)
cyanamide) was filtered off; the filtrate was concentrated
under reduced pressure and washed with water (3 × 30 mL).
The organic layer was dried (Na2SO4) and evaporated under
vacuum. The residue was purified by chromatography (EtOAc/
light petroleum, 4:1) to afford the final products 10a -o as
solids (Table 2).
5-Am in o-7-n -bu tyl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (10a ): white solid; IR (KBr) 3500-
3000, 1670, 1640, 1620, 1550, 1440 cm-1; 1H NMR (DMSO-d6)
δ 0.9 (t, 3H), 1.5 (m, 2H), 1.9 (m, 2H), 4.2 (t, 2H), 6.7 (m, 1H),
7.2 (m, 2H), 7.9 (m, 1H), 8.0 (s, 1H), 8.1 (s, 1H).
3520-2950, 1655, 1630, 1615, 1550, 1445 cm-1 1H NMR
;
(DMSO-d6) δ 1.45-1.6 (m, 2H), 1.7-1.9 (m, 2H), 2.59 (t, 2H,
J ) 8), 4.27 (t, 2H, J ) 8), 6.72 (dd, 1H, J ) 2, 4), 7.13-7.23
(m, 6H), 7.94 (s, 1H), 8.09 (bs, 2H), 8.15 (s, 1H).
5-Am in o-7-(â-m or p h olin -4-yleth yl)-2-(2-fu r yl)p yr a zolo-
[4,3-e]-1,2,4-tr ia zolo[1,5-c]p yr im id in e (10n ): yellow solid;
1
IR (KBr) 3520-2940, 1665, 1640, 1610, 1540, 1445 cm-1; H
NMR (DMSO-d6) δ 2.45 (t, 4H, J ) 5), 2.75 (t, 2H, J ) 7), 3.5
(t, 4H, J ) 5), 4.37 (t, 2H, J ) 7), 6.74 (dd, 1H, J ) 2, 4), 7.22
(d, 1H, J ) 4), 7.95 (s, 1H), 7.21 (d, 1H, J ) 4), 8.1 (bs, 2H),
8.16 (s, 1H).
5-Am in o-7-isop en t yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-
tr ia zolo[1,5-c]p yr im id in e (10b): white solid; IR (KBr) 3400-
5-Am in o-7-[â-(ben zyloxy)eth yl]-2-(2-fu r yl)p yr a zolo[4,3-
e]-1,2,4-tr ia zolo[1,5-c]p yr im id in e (10o): pale yellow solid;
1
2950, 1670, 1645, 1620, 1550, 1440 cm-1; H NMR (CDCl3) δ
1
IR (KBr) 3500-2800, 1660, 1645, 1620, 1560, 1455 cm-1; H
0.97 (d, 6H, J ) 6.4), 1.55 (m, 1H), 1.80 (m, 2H), 4.36 (t, 2H,
J ) 6.4), 6.1 (bs, 2H), 6.6 (s, 1H), 7.27 (d, 1H, J ) 4.2), 7.64 (s,
1H), 8.20 (s, 1H).
NMR (CDCl3) δ 3.95 (t, 2H, J ) 5.2), 4.07 (t, 2H, J ) 5.2),
5.32 (bs, 2H), 5.62 (s, 2H), 6.52 (m, 1H), 6.98 (d, 1H, J ) 4.2),
7.2-7.4 (m, 5H), 7.55 (d, 1H, J ) 1.2), 7.82 (s, 1H).
5-Am in o-7-(â-p h en ylet h yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-
1,2,4-tr ia zolo[1,5-c]p yr im id in e (10c): white solid; IR (KBr)
5-Am in o-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia zolo[1,5-c]-
p yr im id in e (10q). A solution of 10k (297 mg, 1 mmol) in
formic acid (98%, 15 mL) was heated at 100 °C for 4 h. Then
the solvent was removed at reduced pressure and the residue
purified by chromatography (EtOAc/MeOH, 8:2) to afford 10q
as a yellow solid in quantitative yield: IR (KBr) 3500-2850,
1680, 1655, 1620, 1560, 1455 cm-1; 1H NMR (DMSO-d6) δ 6.63
(m, 1H), 7.19 (d, 1H, J ) 4.2), 7.58 (bs, 1H), 7.70 (d, 1H, J )
1.2), 8.07 (s, 1H), 13.2 (bs, 1H).
5-(Ben zylam in o)-7-(â-h ydr oxyeth yl)-2-(2-fu r yl)pyr azolo-
[4,3-e]-1,2,4-tr ia zolo[1,5-c]p yr im id in e (10r ). To a suspen-
sion of NaH (32 mg, 80% in oil, 1.2 equiv) in dry DMF (20
mL) at 0 °C was added 10j (0.3 g, 1.05 mmol), and the mixture
was allowed to warm to room temperature. When the solution
was clear, it was cooled at 0 °C again, benzyl bromide (0.2 mL,
1.2 equiv) was added, and the solution was stirred at room
temperature for 18 h. Then the solvent was removed, and the
residue was purified by chromatography to afford compound
10r as a yellow solid (315 mg, 80%): IR (KBr) 3500-2950,
1675, 1655, 1620, 1560, 1455 cm-1; 1H NMR (DMSO-d6) δ 3.8
(m, 2H), 4.33 (t, 2H, J ) 6.2), 4.71 (s, 2H), 4.87 (bs, 1H), 6.73
(m, 1H), 7.1-7.5 (m, 6H), 7.95 (s, 1H), 8.16 (s, 1H), 9.0 (bs,
1H).
Biologica l Assa ys: Recep tor Bin d in g Assa y. The rat
brain tissues (whole brain and striatum) were obtained from
male Sprague-Dawley rats (Charles-River, Calco, Italy) weigh-
ing 150-200 g. A1 and A2A adenosine receptor binding assays
were performed according to Bruns et al.30 and J arvis et al.31
using [3H]-N6-cyclohexyladenosine ([3H]CHA) and [3H]-2-[[4-
(2-carboxyethyl)phenethyl]amino]-5′-(N-ethylcarbamoyl)ade-
nosine ([3H]CGS 21680) as radioligands, respectively. The IC50
values were calculated by probit analysis based on at least
six concentrations of each compound. Ki values were calcu-
lated from the Cheng-Prushoff32 equation using 1.0 and 18.5
nM as Kd values in A1 and A2A binding assays, respectively.
P la telet Aggr ega tion Assa y: Antagonism to A2A-mediated
antiaggregatory activity was tested in rabbit platelets. Plate-
3500-2950, 1670, 1645, 1620, 1560, 1470 cm-1 1H NMR
;
(DMSO-d6) δ 3.21 (t, 2H, J ) 6.2), 4.51 (t, 2H, J ) 6.2), 6.65
(s, 1H), 7.1-7.44 (m, 6H), 7.78 (s, 1H), 7.89 (bs, 1H), 8.07 (s,
1H).
5-Am in o-7-[â-(4-isobu tylp h en yl)eth yl]-2-(2-fu r yl)p yr a -
zolo[4,3-e]-1,2,4-tr iazolo[1,5-c]pyr im idin e (10d): white solid;
1
IR (KBr) 3520-2910, 1650, 1640, 1610, 1555, 1440 cm-1; H
NMR (DMSO-d6) δ 0.9 (d, 6H, J ) 6), 1.39 (d, 2H, J ) 8), 1.65-
1.95 (m, 1H), 2.5 (t, 2H, J ) 6), 4.07 (t, 2H, J ) 6), 6.72 (m,
1H), 6.96 (d, 2H, J ) 9), 7.21 (d, 1H, J ) 4.2), 7.25 (d, 2H, J
) 9), 7.94 (bs, 2H), 8.12 (bs, 1H), 8.13 (s, 1H).
5-Am in o-8-n -bu tyl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (10e): white solid; IR (KBr) 3500-
2900, 1685, 1640, 1620, 1550, 1450 cm-1; 1H NMR (DMSO-d6)
δ 0.9 (t, 3H), 1.2 (m, 2H), 1.8 (m, 2H), 4.2 (t, 2H), 6.7 (m, 1H),
7.2 (m, 2H), 7.6 (s, 1H), 8.0 (s, 1H), 8.6 (s, 1H).
5-Am in o-8-isop en t yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-
tr ia zolo[1,5-c]p yr im id in e (10f): white solid; IR (KBr) 3500-
1
2850, 1670, 1650, 1615, 1560, 1455 cm-1; H NMR (CDCl3) δ
0.96 (d, 6H, J ) 6.4), 1.59 (m, 1H), 1.86 (m, 2H), 4.32 (t, 2H,
J ) 6.4), 6.58 (m, 1H), 6.72 (bs, 2H), 7.21 (d, 1H, J ) 4.2),
7.63 (d, 1H, J ) 1.2), 8.10 (s, 1H).
5-Am in o-8-(â-p h en ylet h yl)-2-(2-fu r yl)p yr a zolo[4,3-e]-
1,2,4-tr ia zolo[1,5-c]p yr im id in e (10g): white solid; IR (KBr)
3500-2900, 1670, 1645, 1620, 1530, 1455 cm-1 1H NMR
;
(DMSO-d6) δ 3.21 (t, 2H, J ) 6.4), 4.53 (t, 2H, J ) 6.4), 6.7 (s,
1H), 7.1-7.4 (m, 6H), 7.65 (bs, 1H), 7.93 (s, 1H), 8.45 (s, 1H).
5-Am in o-7-m eth yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (10h ): white solid; IR (KBr) 3500-
2900, 1670, 1640, 1620, 1550, 1440 cm-1; 1H NMR (DMSO-d6)
δ 3.88 (s, 3H), 6.72 (m, 1H), 7.21 (d, 1H, J ) 4.2), 7.94 (bs,
2H), 8.12 (bs, 1H), 8.13 (s, 1H).
5-Am in o-7-p h en yl-2-(2-fu r yl)p yr a zolo[4,3-e]-1,2,4-tr ia -
zolo[1,5-c]p yr im id in e (10i): white solid; IR (KBr) 3500-
2950, 1660, 1650, 1620, 1550, 1455 cm-1; 1H NMR (DMSO-d6)

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