Substituted 1,2,3-triazolo[1,5-a]quinazolines: Synthesis and binding to benzodiazepine and adenosine receptors

Article abstract of DOI:10.1016/S0223-5234(00)90154-5

This paper reports the synthesis and evaluation of the biological affinity towards benzodiazepine and A₁ and A(2A) adenosine receptors of some 3-ethoxycarbonyl or 3-phenyl-substituted 1,2,3-triazolo[I,5-a]quinazolines. Starting from the appropriate chloro-substituted phenylazides, the series of 7 or 8 chloro-substituted triazoloquinazolines were prepared. Nitration reactions of the triazoloquinazoline ring and chlorination reactions of the hydroxyl group in the 5 position of the same ring are also reported. By nucleophilic displacement of halogen, the corresponding 5-amino derivatives and some analogous derivatives bearing cyclohexylamino and p-toluidino substituents were obtained. The binding assays showed a generalized decrease in the affinity towards the benzodiazepine receptors and confirmed a moderate affinity towards the A₁ adenosine receptors in comparison with the previously studied triazoloquinazoline derivatives. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

Full text of DOI:10.1016/S0223-5234(00)90154-5

Eur. J. Med. Chem. 35 (2000) 333−341
© 2000 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
S0223523400001306/FLA
333
Original article
Substituted 1,2,3-triazolo[1,5-a]quinazolines: synthesis and binding to
benzodiazepine and adenosine receptors
Lucia Bertellia, Giuliana Biagia, Irene Giorgia, Oreste Livia*, Clementina Maneraa,
Valerio Scartonia, Antonio Lucacchinib, Gino Giannaccinib, Pier Luigi Barilic
aDipartimento di Scienze Farmaceutiche, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy
bDipartimento di Psichiatria, Neurobiologia, Farmacologia e Biotecnologie, Università di Pisa, Via Bonanno 6, 56126 Pisa, Italy
cDipartimento di Bioorganica, Università di Pisa, Via Bonanno 33, 56126 Pisa, Italy
Received 19 May 1999; revised 22 October 1999; accepted 28 October 1999
Abstract – This paper reports the synthesis and evaluation of the biological affinity towards benzodiazepine and A1 and A2A adenosine
receptors of some 3-ethoxycarbonyl or 3-phenyl-substituted 1,2,3-triazolo[1,5-a]quinazolines. Starting from the appropriate chloro-substituted
phenylazides, the series of 7 or 8 chloro-substituted triazoloquinazolines were prepared. Nitration reactions of the triazoloquinazoline ring and
chlorination reactions of the hydroxyl group in the 5 position of the same ring are also reported. By nucleophilic displacement of halogen,
the corresponding 5-amino derivatives and some analogous derivatives bearing cyclohexylamino and p-toluidino substituents were obtained.
The binding assays showed a generalized decrease in the affinity towards the benzodiazepine receptors and confirmed a moderate affinity
towards the A1 adenosine receptors in comparison with the previously studied triazoloquinazoline derivatives. © 2000 Éditions scientifiques
et médicales Elsevier SAS
1,2,3-triazoles / 1,2,3-triazolo[1,5-a]quinazolines / benzodiazepine receptor binding / A1 and A2A adenosine receptor binding
1. Introduction
This tricyclic structure was also tested towards adenos-
ine A1 and A2A receptors, and the binding results indi-
cated that some triazoloquinazoline derivatives possessed
a moderate affinity and selectivity also towards the A1
receptor subtype. The best R substituent for the A1
adenosine receptors appeared to be a phenyl group, while
for the benzodiazepine receptors, an ethoxycarbonyl
group was preferred [1].
In a previous paper of ours [1] concerning a series of
1,2,3-triazolo[1,5-a]quinazoline derivatives (A) which
had shown an interesting affinity towards benzodiazepine
receptors, theoretical calculations based upon the SAR
suggested the introduction of an electronegative substitu-
ent on the phenyl ring.
The investigation into this nitrogenous tricyclic hetero-
cycle was then continued with the 2-fold purpose of
producing compounds more effective towards either ben-
zodiazepine or adenosine receptor binding by the intro-
duction of appropriate substituents on the quinazoline
ring in different positions. Electron-withdrawing groups,
such as Cl or NO2, were used to aid the binding to
benzodiazepine receptors in accordance with the theoreti-
cal suggestions of the previous paper [1] and literature
about benzodiazepine [2, 3]. Amino, cycloalkylamino
and arylamino groups were used to aid the adenosine
receptor binding in accordance with our previous studies
*Correspondence and reprints

334
Figure 1. Synthesis of compounds 2, 3, 5 and 6.
[4, 5] and with the substituents present on the common
adenosine receptor ligands [6, 7].
Nitration of 7a with conc. HNO3 (d = 1.48) in conc.
H2SO4 at room temperature for 4 h gave a mixture of the
mononitro derivatives 8a and 9a, substituted in the 7 and
8 positions, respectively, in 60% yields. After crystalli-
zation from ethanol, this mixture was found to consist of
2. Chemistry
1
the isomers 8a and 9a in a 70:30 ratio (by H-NMR
2-Carboxy-4-chloro-phenylazide 1 and 2-carboxy-5-
chloro-phenylazide 4 were prepared starting from the
corresponding commercial amines via diazotization and
nitrogen displacement by sodium azide [8].
analysis); the subsequent fractionation by flash-
chromatography on silica-gel still provided an 8a–9a
mixture in an 85:15 ratio, which was employed as such.
Nitration of 7a under stronger experimental conditions
did not provide a dinitro compound, but gave some
demolition products which were not isolated.
Azides 1 and 4, by reaction with ethyl cyanacetate in
absolute ethanol in the presence of two equivalents of
sodium ethoxide at room temperature, afforded the 1-(4-
or 5-chloro-2-carboxy-phenyl)-4-ethoxycarbonyl-5-amino-
1H-1,2,3-triazole intermediates as sodium salts soluble in
the aqueous solution. Acidification of the alkaline solu-
tion caused the intramolecular cyclization to give the
corresponding tricyclic lactames 2a and 5a which pre-
cipitated and were isolated in 80% yields (figure 1).
Reaction of azide 1 or 4 with phenylacetonitrile re-
quired refluxing of the mixture, but it proceeded in the
same manner to give the corresponding triazoloquinazo-
line compounds 2b and 5b in high yields (figure 1).
Methylation of 2a and 5a was accomplished with di-
methyl sulfate in refluxing butanone in the presence of
anhydrous potassium carbonate to give the expected
derivatives 3a and 6a in good yields; the analogous
N-methyl derivatives 3b and 6b were prepared in the
same manner using DMF at 110 °C (figure 1).
On the contrary, nitration of the 3-phenyl-triazolo-
quinazoline 7b under the usual mild conditions gave the
mononitro derivative 8b bearing the nitro group in the
para position of the phenyl substituent. Under stronger
experimental conditions (increased equivalents of conc.
HNO3, KNO3/conc. H2SO4, conc. HNO3 alone, higher
temperature and longer reaction time), 8b lost nitrogen
and underwent a rearrangement with formation of essen-
tially the dinitro derivative of the 2-benzoyl-quinazoline
9b, which was isolated by flash-chromatography; the
mononitro derivative 10b was also characterized. This
behaviour had been demonstrated by Tennant [9, 10] for
analogous triazoloquinazolines treated with HCl.
The nitrocompound 8b underwent a chemical reduc-
tion with iron powder to obtain the corresponding amine,
but under these conditions the hydroxylamino derivative
11b was isolated (figure 2).
The introduction of other substituents on the quinazo-
line benzofused ring could be achieved via a nitro group
and thus the previously prepared compounds 3-ethoxy-
carbonyl-1,2,3-triazolo[1,5-a]quinazolin-5-one (7a) [1]
and 3-phenyl-1,2,3-triazolo[1,5-a]quinazolin-5-one (7b)
[1] underwent nitration (figure 2).
Finally, a further functionalization of the triazolo-
quinazoline system was achieved by the introduction of a
chlorine in the 5 position, which was subsequently
substituted by an amino group.

335
Figure 2. Nitration of 7a and 7b.
Thus the 3-ethoxycarbonyl-triazoloquinazoline 7a [1]
and the 3-phenyl-triazoloquinazoline 7b [1], by reaction
with POCl3 or SOCl2/CHCl3, were converted to the
corresponding 5-chloroderivatives 12a and 12b, respec-
tively (figure 3). Similarly, compound 2b, bearing a
chlorine in the 7 position, provided the dichloro-
substituted derivative 14b, while the analogous 8-chloro-
triazoloquinazolines 5a and 5b gave the corresponding
dichloro derivatives 16a and 16b (figure 3).
The 5-chloro derivatives, by reaction with NH3 in a
closed tube at 110–120 °C, were converted to the ex-
pected 5-amino derivatives 13a, 13b, 15b, 17a and 17b in
good yields (figure 3).
In the same manner, starting from the appropriate
chloro derivatives (12a, 12b, 14b and 16b), some
5-cyclohexylamino derivatives (18a, 18b, 20b and 21b)
and 5-(p-toluidino) derivatives (19a and 19b) were pre-
pared (figure 4).
The structures of all the new compounds were assigned
on the basis of the well known reaction mechanisms:
1,3-dipolar cycloaddition of azides to activated methyl-
ene compounds, N-methylation, nitration, chlorination
and nucleophilic displacement of the halogen by ammo-
nia or primary amines. The structures were also con-
firmed by analytical and spectroscopic data.
Regarding the position of the nitro groups on the
phenyl rings of the nitrocompounds, the AA′BB′ system
1
in the H-NMR spectra of compounds 8b, 9b and 10b
allowed the assignment of the nitro group in the para
position of the 3-phenyl substituent. In the spectrum of
Figure 3. Preparation of the 5-chloro- and 5-amino-
triazoloquinazolines 12–17.

336
Figure 4. Amino substituted derivatives.
the 8a and 9a isomeric mixture, two spin systems, typical
of 1,2,4 benzene trisubstitution, clearly indicated the
replacement of the 7 and 8 positions. The choice between
these positions for the structure assignment to the isomers
could appear uncertain if based only on the H-NMR
data.
3. Biological results and discussion
All the triazoloquinazoline derivatives underwent
binding assays either to benzodiazepine receptors or
adenosine A1 and A2A receptors. Their ability to inhibit
benzodiazepine receptor binding was measured by the
concentration which was able to displace [3H]-Ro
15–1788 from bovine brain membranes. The inhibition of
binding towards adenosine receptors was measured by
the ability of compounds to displace [3H]-N6-cyclo-
hexyladenosine (CHA) from A1 adenosine receptors in
bovine cortical membranes and [3H]-2-[p-(2-carboxy-
ethyl)-phenethylamino]-5′-(-N-ethylcarboxamidoadenosine
1
On the other hand, in the 13C-NMR spectrum of the
mixture, although the complete assignment was difficult,
the carbons bearing hydrogen from the major product
were easily identifiable by their intensity. Therefore on
the basis of the additivity rules [11], structure 8a was
1
unequivocally assigned to this isomer. H-NMR spectral
data of some significant compounds are reported in
table I.
Table I. 1H-NMR spectral data of some significant compounds.
3b
5b
7a
7b
8a
8b
9a
12a
12b
13a
20b
H-6
H-7
H-8
H-9
J6,7
J6,8
J7,8
J7,9
8.17
–
8.10
8.52
–
2.34
–
–
8.21
7.69
–
8.31
8.52
–
–
1.98
–
8.33
8.01
7.71
8.24
8.18
1.12
7.43
1.53
7.96
8.33
7.97
7.66
8.22
7.17
1.10
7.64
1.48
7.92
8.84
–
8.74
8.52
–
2.57
–
–
8.34
8.00
7.69
8.23
8.10
1.00
7.54
1.38
8.22
8.04
8.58
–
8.93
9.17
–
–
2.64
–
8.71
8.28
7.98
8.43
8.36
1.14
7.34
1.33
8.25
8.62
8.19
7.90
8.34
8.34
1.08
7.27
1.30
8.25
8.30
–
7.73
8.21
–
1.97
–
–
8.65
–
7.93
8.38
–
2.16
–
–
J8,9
8.80
8.96
8.60
8.86
3-Phenyl
H-2′
H-3′
H-4′
8.28
7.51
7.36
7.87
7.48
7.35
7.88
7.43
7.35
8.16
8.27
–
8.25
7.54
7.41
8.28
7.44
7.26
3-Ethoxycarbonyl
CH2
CH3
4.40
1.36
4.41
1.36
4.45
1.40
4.45
1.39
4.39
1.22
Other signals: 3b, 4.25 δ N–CH3; 20b, 2.15–1.33 δ, cyclohexyl. Para J coupling was also detectable in the spectrum of 3b (0.55 Hz).

337
(CGS-21680) from A2A adenosine receptors in bovine
striatal membranes.
The experimental details of the receptor binding assays
are reported in a previous paper [12].
4. Experimental protocols
4.1. Chemistry
Melting points were determined on a Kofler hot-stage
apparatus and are uncorrected. IR spectra in nujol mulls
were recorded on a Perkin-Elmer Mod.1310 spectrom-
eter. 1H-NMR and 13C-NMR spectra were recorded with
a Bruker AC 200 spectrometer in δ units from TMS as an
internal standard. Mass spectra were performed with a
Hewlett Packard MS/System 5988. Elemental analyses
(C, H, N) were within ± 0.4% of theoretical values and
were performed on a Carlo Erba Elemental Analyzer
Mod. 1106 apparatus. Column chromatographies were
performed on Silica gel 60 (230–400 mesh). Petroleum
ether corresponds to the fraction boiling at 40–60 °C.
The results of the binding assays towards benzodiaz-
epine receptors have not been tabulated because the
introduction of a chlorine atom in the 7 or 8 position of
the 1,2,3-triazolo[1,5-a]quinazoline ring caused a marked
decrease in receptor affinity, contrary to theoretical sug-
gestions [1]. 3-Ethoxycarbonyl-4-methyl-7-chloro-1,2,3-
triazolo[1,5-a]quinazolin-5-one (3a) was the most active
compound with an inhibition constant Ki = 740 nM and
a GABA ratio = 1.9; all the other derivatives showed
inhibition percentages so low that the corresponding Ki
values were not calculated.
Regarding adenosine receptors, biological evaluation
of the previously reported triazoloquinazoline deriva-
tives [1] showed a moderate affinity towards A1 adenos-
ine receptors of the 3-phenyl derivative 7b (Ki = 620
nM), followed by the 3-ethoxycarbonyl-4-methyl-1,2,3-
triazolo[1,5-a]quinazolin-5-one (Ki = 1 500 nM) [1]. The
results of the biological evaluation of the new triazolo-
quinazoline derivatives are reported in table II, expressed
as affinity constants towards A1 and A2A adenosine
receptors. Some of these new compounds showed an
increased binding affinity towards A1 adenosine receptors
with a marked selectivity, but their Ki values remained
higher than 100 nM and therefore their biological activity
was moderate. The most active triazoloquinazolin-5-one
derivatives were 5b (Ki = 148 nM) and 6b (Ki = 264
nM), bearing in the 3 position a phenyl substituent and in
the 8 position a chlorine atom, respectively. Compound
5b can be compared with 9-chloro-2-(2-furyl)-1,2,4-
triazolo[1,5-c]quinazolin-5-amine (CGS 15943) [13],
which is an effective A1 adenosine antagonist. The
comparison shows that the main differences are the
position of the phenyl ring with regard to the furyl
substituent which, by steric hindrance, would reduce the
receptor binding of the amidic NH, in turn less capable of
binding than the free NH2 group. This structural differ-
ence could explain while 5b fits into the A1 adenosine
receptor site with a difficulty greater than CGS 15943.
The most active 5-amino substituted derivatives were 13b
(Ki = 239 nM) and 18a (Ki = 302 nM), the first bearing
a phenyl substituent and an amino group in the 3 and 5
positions, respectively, and the second derivative bearing
an ethoxycarbonyl group combined with a cyclohexyl-
amino substituent in the same positions. In conclusion,
these triazoloquinazoline derivatives were found to be
biologically much less effective than the corresponding
1,2,3-triazolo[1,5-a]quinoxaline derivatives previously
experimented [12].
4.1.1. 2-Carboxy-4-chloro-phenylazide 1
To a stirred and cooled (0–5 °C) solution of 2-amino-
5-chloro-benzoic acid (0.400 g, 2.34 mmol) in 25 mL of
18% HCl, 10 mL of aqueous solution of NaNO2 (0.230 g,
3.33 mmol) were added dropwise. After 15–20 min
10 mL of a solution of NaN3 (0.217 g, 3.33 mmol) were
added dropwise and 1a began to precipitate as a white
solid. The acidity was lowered (pH 3–4) by adding 32%
NH4OH solution, the ice-bath was removed and the
mixture was stirred at room temperature for 1 h. The
precipitate was collected by filtration and washed with
H2O (table III).
4.1.2. 2-Carboxy-5-chloro-phenylazide 4
To a stirred and cooled (0–5 °C) solution of 2-amino-
4-chloro-benzoic acid (0.500 g, 3.0 mmol) in 30 mL of
18% HCl, 10 mL of aqueous solution of NaNO2 (0.270 g,
3.91 mmol) were added dropwise. After 15–20 min,
12 mL of a solution of NaN3 (0.250 g, 3.84 mmol) were
added and the mixture was worked up as described above
(table III).
4.1.3. 3-Ethoxycarbonyl-7-chloro-1,2,3-triazolo[1,5-a]-
quinazolin-5-one 2a and 3-ethoxycarbonyl-8-chloro-
1,2,3-triazolo[1,5-a]quinazolin-5-one 5a
To a stirred solution of EtONa (0.300 g, 13 mmol of
Na in 20 mL of absolute EtOH), 0.75 mL (7.0 mmol) of
ethyl cyanacetate were added. After 15 min a solution of
1a or 1b (1.15 g, 5.82 mmol) in 35 mL of absolute EtOH
was slowly added (≈ 1 h). The suspension was stirred at
room temperature for ≈ 20 h, then the precipitate was
collected by filtration. The solid was dissolved in 50 mL
of H2O and the solution was acidified (0–5 °C) with 36%
HCl (pH = 2) to precipitate the title compounds, which
were collected by filtration and washed with H2O (ta-
ble III).

338
Table II. Binding to A1 and A2A adenosine receptors.
A1
A2A
Compound
Inhib. % 10 µM
Ki values (nM)
Inhib. % 10 µM
Ki values (nM)
7a[1]
7b[1]
2a
3a
5a
6a
2b
3b
5b
8
> 10 000
620 ± 29
> 10 000
2 269 ± 129
> 10 000
808 ± 91
> 10 000
> 10 000
148 ± 16
264 ± 23
> 10 000
> 10 000
1 146 ± 130
239
900 ± 102
1 093 ± 148
302 ± 59
> 10 000
1 502 ± 110
1 518 ± 147
1 244 ± 134
> 10 000
3
28
0
12
4
30
0
> 10 000
> 10 000
–
> 10 000
> 10 000
> 10 000
–
87
16
63
23
81
2
6.4
97
96
25
30
75
97
76
78
95
39
74
69
74
10
0
9
–
> 10 000
> 10 000
> 10 000
> 10 000
> 10 000
> 10 000
1 667 ± 118
> 10 000
> 10 000
> 10 000
> 10 000
> 10 000
> 10 000
> 10 000
6b
8a + 9a
8b
19
10
8
14.5
4
66
30
8.5
36
13.6
14
6.5
9
11b
13b
15b
17a
18a
18b
19a
19b
20b
21b
–: Ki value was not calculated.
4.1.4. 3-Phenyl-7-chloro-1,2,3-triazolo[1,5-a]quinazolin-
5-one 2b and 3-phenyl-8-chloro-1,2,3-triazolo[1,5-a]-
quinazolin-5-one 5b
concentrated in vacuo and the residue was treated with
10% NaOH and extracted with CHCl3. The organic layer,
dried (MgSO4) and evaporated, gave the crude title
compounds (table III).
To a stirred solution of EtONa (0.500 g, 21.7 mmol of
Na in 15 mL of absolute EtOH), 1.10 mL (9.53 mmol) of
phenylacetonitrile was added. After 20 min a solution of
1a or 1b (1.20 g, 6.10 mmol) in 50 mL of absolute EtOH
was slowly added (≈ 40 min), then the mixture was
heated under reflux for 20 h. The reaction mixture was
concentrated in vacuo, treated with H2O and extracted
with CHCl3. 2b precipitated from the aqueous layer by
acidification (pH = 2) with 36% HCl, and was collected
by filtration and washed with H2O (table III). Compound
5b precipitated partially, and was consequently recovered
from the acid mother liquors by extraction with CHCl3
and evaporation of the solvent (table III).
4.1.6. 3-Phenyl-4-methyl-7-chloro-1,2,3-triazolo[1,5-a]-
quinazolin-5-one 3b and 3-phenyl-4-methyl-8-chloro-
1,2,3-triazolo[1,5-a]quinazolin-5-one 6b
A mixture of 3a or 3b (0.450 g, 1.51 mmol), anhydrous
K2CO3 (0.625 g, 4.52 mmol) and Me2SO4 (0.9 mL,
9.45 mmol) in 20 mL of anhydrous DMF was heated at
110 °C under stirring for 4 h. After 1 night the reaction
mixture was concentrated in vacuo and the residue was
treated with H2O to give the crude title compounds as
precipitates which were collected by filtration (table III).
4.1.7. Nitration of 3-ethoxycarbonyl-1,2,3-triazolo-
[1,5-a]quinazolin-5-one 7a: mixture of 8a and 9a
4.1.5. 3-Ethoxycarbonyl-4-methyl-7-chloro-
1,2,3-triazolo[1,5-a]quinazolin-5-one 3a and
3-ethoxycarbonyl-4- methyl-8-chloro-
1,2,3-triazolo[1,5-a]quinazolin-5-one 6a
A mixture of 2a or 5b (0.300 g, 1.02 mmol), anhydrous
K2CO3 (0.425 g, 3.0 mmol) and Me2SO4 (0.6 mL,
6.30 mmol) in 40 mL of MeCOEt was heated under
reflux for 4 h. After 1 night, the reaction mixture was
A solution of conc. HNO3 (d = 1.48, 0.25 mL,
5.3 mmol) and conc. H2SO4 (0.5 mL) was added drop-
wise to an ice-cooled (0–5 °C) and stirred solution of 7a
(0.600 g, 2.32 mmol) in 5 mL of conc. H2SO4
(≈ 15 min.). The ice-bath was removed and the mixture
was stirred at room temperature for 4 h, and then poured
into crushed ice. Addition of conc. NH4OH (3–4 mL, pH

339
Table III. Physico-chemical data of azides and triazoloquinazoline derivatives.
Compound
Yield %
Crystall. solvent
M.p. °C
Analysis (C, H, N)
Mass m/z
M+
Base
1
4
2a
5a
2b
5b
3a
6a
92
89
82
80
82
90
80
88
82
80
78
40
53
81
71
19
76
48
71
96
49
45
81
65
87
76
78
55
EtOH-H2O
EtOH
EtOH
151–153
139–142
239–241
214–217
255–258
236–240
178–180
182–185
240–243
214–219
271–274
259–262
160–164
178–180
224–226
204–207
219–220
217–222
226–230
248–250
195–198
241–243
229–233
225–228
226–227
213–216
221–224
226–228
C7H4N3O2Cl
C7H4N3O2Cl
C12H8N4O3Cl
C12H8N4O3Cl
C15H9N4OCl
C15H9N4OCl
C13H11N4O3Cl
C13H11N4O3Cl
C16H11N4OCl
C16H11N4OCl
C15H9N5O3
C15H11N5O2
C12H9N4O2Cl
C15H9N4Cl
C15H8N4Cl2
C15H8N4O2Cl2
C15H8N4Cl2
C12H11N5O2
C15H11N5
C15H10N5Cl
C12H10N5O2Cl
C15H10N5Cl
C18H21N5O2
C19H17N5O2
C21H21N5
197
197
292
292
296
268
306
306
310
310
307
293
276
280
314
310
314
258
261
295
292
295
339
347
343
351
377
349 (M+–28)
78
78
179
179
75
EtOH
EtOH-H2O
EtOH-H2O
EtOH
75
193
193
164
164
76
106
163
114
148
29
148
148
103
137
179
137
179
234
233
308
267
55
EtOH
3b
6b
8b
DMF-H2O
DMF-H2O
AcOEt
EtOH
11b
12a
12b
14b
16a
16b
13a
13b
15b
17a
17b
18a
19a
18b
19b
20b
21b
EtOH
AcOEt
AcOEt
*
100–140 °C Petr. eth
AcOEt
AcOEt
AcOEt
AcOEt
*
AcOEt
AcOEt
AcOEt
MeOH
MeOH
MeOH
C21H17N5
C21H20N5Cl
C21H20N5Cl
*Isolated by flash-chromatography.
1–2) and vigorous scratching made it possible to separate
a yellow solid which was collected by filtration after
1 night. This solid (0.434 g, yield 62%, TLC AcOEt/Petr.
eth. 2:1 one large spot) crystallized from 95% EtOH and
provided a solid mixture with m.p. = 203–210 °C, Ms m/e
of 3-phenyl-1,2,3-triazolo[1,5-a]quinazolin-5-one 7b
(0.500 g, 1.90 mmol) in 5 mL of conc. H2SO4 (≈ 5 min).
The ice-bath was removed and the mixture was stirred at
room temperature for 4 h. The reaction mixture was
poured into crushed ice, the pH was increased (pH 3–4)
by the addition of conc. NH4OH, and by vigorous
scratching 8b precipitated as a yellow solid which was
collected by filtration (0.380 g). A further fraction
(0.080 g) was obtained from the filtrate by extraction with
AcOEt and evaporation of the solvent (table III).
1
303 (M+). Anal. C12H9N5O5 (C, H, N). H-NMR see
table I. 13C-NMR 7a, δ 134.8 (C-8), 127.7 (C-6), 127.6
(C-7), 114.5 (C-9). 8a δ 129.2 (C-8), 123.1 (C-6), 114.5
(C-9).
The mixture consisted of the mononitro derivatives 8a
and 9a in a ratio 70:30. Further fractionation by flash-
chromatography under an elution gradient (AcOEt/Petr.
eth. 1:2, 1:1, 2:1) again provided a mixture of 8a and 9a
in a ratio 85:15.
When the nitration was carried out with an increased
amount of conc. HNO3 or an increased volume of conc.
H2SO4, as well as with KNO3/conc. H2SO4 or conc.
HNO3 alone, a mixture of products was obtained. Frac-
tionation of the mixture by flash-chromatography on
silica gel eluting with AcOEt/Petr. eth. 1:1 and 2:1 gave
principally the dinitro derivative of the 2-benzoyl-
quinazoline 9b. The mononitro derivative 10b was also
characterized. 9b: m.p. = 235–237 °C (EtOH); Ms m/e
4.1.8. 3-(4- Nitrophenyl)-1,2,3-triazolo[1,5-a]-
quinazolin-5-one 8b
A solution of conc. HNO3 (d = 1.48, 0.20 mL,
4.2 mmol) and conc. H2SO4 (0.4 mL) was added drop
by drop to an ice-cooled (0–5 °C) and stirred solution

340
340 (M+), 150 (base). Anal. C15H8N4O6 (C, H, N).
1H-NMR (DMSO): δ 8.86 (d, 1H, J = 2.7 Hz, H-5); 8.56
(dd, 1H, J = 8.9 and 2.7 Hz, H-7); 8.42 and 8.37 (AA′BB′
system, 4H, H-2′ and H-3′); 7.97 (d, 1H, J = 8.9 Hz, H-8).
10b: m.p. = 239–241 °C (EtOH/H2O); Ms m/e 295 (M+),
90 (base). Anal. C15H9N3O4 (C, H, N). 1H-NMR
(DMSO): δ 8.43 and 8.36 (AA′BB′ system, 4H, H-2′ and
H-3′); 8.23 (dd, 1H, J = 6.9 and 1.3 Hz, H-5); 7.90 (ddd,
1H, J = 8.0, 7.3 and 1.3 Hz, H-7); 7.79 (dd, 1H, J = 7.3
and 1.0 Hz, H-8); 7.68 (ddd, 1H, J = 6.9, 8.0, and 1.0 Hz,
H-6)
4.1.11. 3-Phenyl–5,8-dichloro-1,2,3-triazolo[1,5-a]-
quinazoline 16b
To a suspension of 0.520 g (1.75 mmol) of 5b in 24 mL
of boiling anhydrous CHCl3, 1 mL of anhydrous DMF
and 1.5 mL of SOCl2 were added. The reaction mixture
was refluxed for 2 h, the solvent was evaporated in vacuo
and the semi-solid residue, after cooling at 0 °C, was
triturated with acetone to give 16b as a yellow solid
which was collected by filtration (table III).
4.1.12. 3-Ethoxycarbonyl-5-amino-1,2,3-triazolo[1,5-a]-
quinazoline 13a, 3-phenyl-5-amino-1,2,3-triazolo-
[1,5-a]quinazoline 13b, 3-phenyl-5-amino-7-chloro-
1,2,3-triazolo[1,5-a]quinazoline 15b,
3-ethoxycarbonyl-5-amino-8-chloro-1,2,3-triazolo
[1,5-a]quinazoline17a and 3-phenyl-5-amino-8-chloro-
1,2,3-triazolo[1,5-a]quinazoline 17b
A solution of 1.0 mmol of the suitable chloro deriva-
tive (12a, 12b, 14b, 16a or 16b) in 10 mL of anhydrous
DMF and 3 mL of TEA was introduced into a ‘Sovirel’
vial. The vial was cooled (ice-bath 0–5 °C) and the
solution was saturated with NH3 gas for 10–15 min. The
vial was quickly closed and heated in an oil bath at
120 °C for 10 h. The reaction mixture was evaporated in
vacuo, the residue was treated with H2O and the insoluble
material, consisting of the title compounds (13a, 13b,
15b or 17a), was collected by filtration (table III). Com-
pound 17b was obtained as a mixture with an unidentified
compound, and as a result it was isolated by flash-
chromatography on silica gel. Elution with AcOEt/Petr.
eth. 5:1 provided 17a (table III) which was followed by
the unidentified product.
4.1.9. 3-(4-Hydroxylaminophenyl)-1,2,3-
triazolo[1,5-a]quinazolin-5-one 11b
Iron powder (0.200 g) was added to a solution of 8b
(0.300 g, 0.97 mmol) in 60 mL of AcOH and the mixture
was heated under reflux. Four more 0.05 g portions of
iron powder were added, one every hour, and heating was
continued for 18 h. The mixture was filtered, concen-
trated (1/4 volume) in vacuo, neutralized with 10%
NaOH and extracted with CHCl3. The organic layer, after
washing (H2O) and drying, was evaporated to give 11d
(table III).
4.1.10. 3-Ethoxycarbonyl-5-chloro-1,2,3-triazolo[1,5-a]-
quinazoline 12a, 3-phenyl -5-chloro-1,2,3-triazolo-
[1,5-a]quinazoline 12b, 3-phenyl-5,7-dichloro-1,2,3-
triazolo[1,5-a]quinazoline 14b and 3-ethoxycarbonyl-
5,8-dichloro-1,2,3-triazolo[1,5-a]quinazoline 16a
A
solution of 1.75 mmol of the appropriate
4.1.13. 3-Ethoxycarbonyl-5-(p-toluidino)-1,2,3-
triazolo[1,5-a]quinazoline 19a and 3-phenyl-5-
(p-toluidino)-1,2,3-triazolo[1,5-a]quinazoline 19b
To a solution of 0.70 mmol of the appropriate chloro-
derivative (12a or 12b) in 2 mL of anhydrous DMF and
4 mL of TEA in a closed tube, 0.500 g (4.66 mmol) of
p-toluidine were added and the mixture was heated at
120 °C for 18 h. The reaction mixture was concentrated
in vacuo and the residue was treated with H2O and
extracted with CHCl3. The chloroform layer was washed
with 10% HCl and H2O, dried and evaporated to give the
title compounds (table III).
triazoloquinazolin-5-one (7a, 7b, 2b and 5a) in 12 mL of
TEA was cooled in an ice-bath (0–5 °C), 8 mL of POCl3
were added and the mixture was heated under reflux for
12 h. After cooling, the reaction mixture was poured into
crushed ice and quickly extracted with CHCl3. For the
isolation of 12a the chloroform extract was washed with
H2O, dried and evaporated (table III). For the isolation of
12b, the chloroform extract was washed with 6%
NaHCO3, H2O, dried and evaporated (table III). The
chloroform extract of 14b was washed with 10% NaOH,
H2O, dried and evaporated (table III); by acidification of
the alkaline solution, 25% of the starting product 2b was
recovered. The chloroform extract of 16a was washed
with H2O, dried and evaporated to give a residue which
consisted of a mixture. This residue, dissolved in toluene,
was fractionated by flash-chromatography through silica
gel, eluting with AcOEt/Petr. eth. 3:1. After a small
amount of an unidentified product was discarded, 16a
was eluted (table III).
4.1.14. 3-Ethoxycarbonyl-5-(cyclohexylamino)-1,2,3-
triazolo[1,5-a]quinazoline 18a, 3-phenyl-5-
(cyclohexylamino)-1,2,3-triazolo[1,5-a]quinazoline 18b
and 3-phenyl-5-(cyclohexylamino)-7-chloro-1,2,3-
triazolo[1,5-a]quinazoline 20b
A solution of 0.70 mmol of the appropriate chloro-
derivative (12a, 12b or 14b) in 2 mL of anhydrous DMF,

341
2 mL of TEA and 0.5 mL (4.40 mmol) of cyclohexyl-
amine in a closed tube was heated at 120 °C for 12 h. The
reaction mixture was concentrated in vacuo and worked
up as described above to obtain the title compounds
(table III).
References
[1] Biagi G., Giorgi I., Scartoni V., Velo S., De Santis B., Martinelli A.,
Lucacchini A., Senatore G., Il Farmaco 51 (1996) 131–136.
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4.1.15. 3-Phenyl-5-(cyclohexylamino)-8-chloro-1,2,3-
triazolo[1,5-a]quinazoline 21b
[6] Jacobson K.J., van Galen P.J.M., Williams M., J. Med. Chem. 35
(1992) 407–422.
A solution of 0.300 g (0.96 mmol) of 16b in 1.5 mL of
anhydrous DMF, 3 mL of TEA and 2 mL (17.5 mmol) of
cyclohexylamine in a closed tube was heated at 120 °C
for 12 h. The reaction mixture was concentrated in vacuo
and the residue was extracted with CHCl3. The chloro-
form solution was washed with 5% HCl and H2O, dried
and evaporated to give a semisolid residue consisting of
[7] Baraldi P.G., Cacciari B., Spalluto G., Brioni A., Viziano M.,
Dionisotti S., Ongini E., Curr. Med. Chem. 2 (1995) 707–722.
[8] Biffin M.E.C., Miller J., Paul D.B., in: Patai S. (Ed.), The Chemistry
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[10] Sutherland D.R., Tennant G., J. Chem. Soc. Perkin Trans. I (1974)
534–540.
[11] Wehrli F.W., Marchand A.P., Wehrli S., Interpretation of Carbon-
13NMR Spectra, 2nd. ed., Wiley, NY, 1988.
a
mixture which was fractionated by flash-
chromatography. Elution with AcOEt/Petr. eth. 2:1 pro-
vided the title compound (table III) which was followed
by an unidentified compound.
[12] Bertelli L., Biagi G., Giorgi I., Manera C., Livi O., Scartoni V. et al.,
Eur. J. Med. Chem. 33 (1998) 113–122.
[13] Francis J.E., Cash W.D., Psychoyos S., Ghai G., Wenk P., Friedmann
R.C. et al., J. Med. Chem. 31 (1988) 1014–1020.