Full text of DOI:10.1134/S1070363217100103

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 10, pp. 2307–2312. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.O. Gurenko, S.V. Klyuchko, O.V. Shablykin, V.S. Brovarets, 2017, published in Zhurnal Obshchei Khimii, 2017, Vol. 87, No. 10,
pp. 1647–1652.
Acylation of Pyrazolo[3,4-d][1,2,3]triazin-4-ones
A. O. Gurenko, S. V. Klyuchko, O. V. Shablykin, and V. S. Brovarets*
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 1, Kiev, 02094 Ukraine
*e-mail: brovarets@bpci.kiev.ua
Received September 4, 2017
Abstract–Acylation and sulfonylation of substituted pyrazolo[3,4-d][1,2,3]triazin-4-ones, as well as reactions
with acylating agents proceeding via destruction of the triazine ring are studied.
Keywords: pyrazolo[3,4-d][1,2,3]triazine, acylation, sulfonylation, pyrazolo[3,4-d]pyrimidine, pyrazolo[3,4-d]-
[1,3]oxazine
DOI: 10.1134/S1070363217100103
Recently we have investigated the alkylation reac-
tions of 7-aryl-3,7-dihydro-4H-pyrazolo[3,4-d][1,2,3]-
triazin-4-ones [1] occurring with preservation of the
heterocyclic system, and also their conversion under
the action of thionyl chloride, phosphorus pentoxide,
pentasulfide, and oxychloride [2, 3], which lead to the
destruction of the triazine ring. Here we report on the
acylation reactions of pyrazolo[3,4-d][1,2,3]triazin-4-
ones 1a–1c.
derivatives 2a–2h in a yield of 51–97% (Scheme 1).
Composition and structure of the compounds obtained
were confirmed by elemental analysis, IR and NMR
spectroscopy data (Tables 1, 2).
The 13C NMR spectra of compounds 2a–2h
contained characteristic signals of the C=O group of
the triazin-4-one fragment (151.9–154.2 ppm), as well
as the signals of the acyl C=O group (161.5–
170.6 ppm). In the IR spectra the signals of the C=O
groups were observed as two closely located strong
absorption bands or a broadened peak with a shoulder
in the region of 1703–1742 cm–1.
It is known that the acylation of compounds con-
taining 1,2,3-triazin-4-one fragment in pyridine or
dioxane in the presence of pyridine takes place exclu-
sively at the position 3 [4, 5]. However, the acylation
of pyrazolo[3,4-d][1,2,3]triazin-4-ones has not been
previously performed.
Unlike benzotriazinones [5], the reaction did not
occur at room temperature, when using pyridine
instead of NaH and THF. However, refluxing the reac-
tion mixture with acid chlorides in pyridine resulted in
the formation of a mixture of several compounds. We
succeeded in isolating the products of the reaction of
compound 1b with thiophene-2-carbonyl chloride
We found that the reaction of pyrazolo[3,4-d][1,2,3]-
triazin-4-ones 1a–1c with acid chlorides in tetrahyd-
rofuran in the presence of sodium hydride at 0°C
afforded 3-acylated pyrazolo[3,4-d][1,2,3]triazin-4-one
Scheme 1.
O
O
O
N
N
N
R2
R2C(O)Cl, NaH
THF
NH
N
N
N
N
N
N
R1
R1
1a−1c
2a−2h
R1 = Me (1a, 2a–2c), Ph (1b, 2d–2f), 4-MeC6H4 (1c, 2g, 2h); R2 = Ph (2a, 2d, 2g), 4-MeC6H4 (2b, 2e); 2-thienyl (2c, 2f, 2h).
2307

2308
GURENKO et al.
Scheme 2.
O
O
N
3
O
N
O
N
5
S
Cl
O
O
N
1b
+
+
pyridine
Δ, 1 h
N
S
N
N
N
N
N
N
Ph
Ph
Ph
H2N
N
Ph
4
Scheme 3.
O
N
O
O
N
N+
N
N+
[O]
pyridine
N
5
1b
_N2
Δ, 1 h
N
N
N
NH_
N
N
NH_
N
H H
Ph
Ph
Ph
A
B
C
Scheme 4.
O
N
O
O
O
C
C
N
Ac2O, Δ
O
O
O
O
1b
dioxane
_N2
N
N
N
N
Me
Me
N
NH
Me
N
Me
Ph
Ph
Ph
6
D
E
Scheme 5.
O
N
O
O
O
ArNCO,
50oC
Ar
C
O
O
N
O
C
1b
_N2
N
N
N
N
N
N
N
NH
Ar
N
N
H
O
N
N
NH
H
N
Ph
Ph
Ph
Ph
Ar
Ar
D
F
G
7а, 7b
Ar = Ph (7a), 4-ClC6H4 (7b).
(Scheme 2). They were 1-phenyl-6-(thien-2-yl)-
pyrazolo[3,4-d][1,3]-oxazin-4(1H)-one 3 {similar trans-
formation has been reported in [6] for reaction of
thieno[3,2-d][1,2,3]triazin-4(3H)-one with benzoyl
chloride in pyridine}, 6-(5-amino-1-phenyl-1H-pyrazol-
4-yl)-1-phenylpyrazolo[3,4-d][1,3]-oxazin-4(1H)-one 4,
which has been obtained by us earlier in another way
[3], and 1-phenylpyrazolo[3,4-d]pyrido[1,2-a]pyrimi-
din-4(1H)-one 5. The formation of the latter can be
represented via a series of intermediates A–C by
analogy with the conversion of 3,7-dihydro-4H-
imidazo[4,5-d][1,2,3]triazines into pyrido[1,2-a]purines
(Scheme 3) [7].
The reaction of pyrazolo[3,4-d][1,2,3]triazin-4-one
1b with acetic anhydride in dioxane at room tem-
perature did not proceed. However, 6-methyl-1-phenyl-
pyrazolo[3,4-d][1,3]oxazin-4(1H)-one 6 was obtained
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 10 2017

2309
ACYLATION OF PYRAZOLO[3,4-d][1,2,3]TRIAZIN-4-ONES
Scheme 6.
7a and 7b (Scheme 5). They are probably formed
through an intermediate D, which added to the iso-
cyanates to form oxazines F and G that are isomerized
under the reaction conditions into compounds 7a and
7b. Similarly, benzotriazin-4-one reacted with phenyl
isocyanate to form 3-phenylquinazoline-2,4(1H,3H)-
dione [10]. The sulfonylation of pyrazolotriazinones 1,
which had not previously been studied, also proceeded
regioselectively at the N3 site with the formation of
derivatives 8a and 8b (Scheme 6). The reaction
proceeded in THF solution with cooling in the
presence of sodium hydride.
O
N
O
S
RSO2Cl, NaH
THF
N
N
R
1b
N
N
O
Ph
8а, 8b
R = Ph (8a), 4-ClC6H4 (8b).
with a yield of 70% when refluxing the reaction
mixture (Scheme 4). Compound 6 has been previously
prepared by other methods [8, 9]. The proposed reac-
tion mechanism involves the destruction of the triazine
ring upon heating with the liberation of molecular
nitrogen and the formation of ketene D. The latter
reacts with acetic anhydride to form intermediate E,
which undergoes cyclization into compound 6.
The composition and the structure of all compounds
obtained were consistent with the data of elemental
analysis, chromatography-mass spectrometry, IR and
1H, 13C NMR spectroscopy (Tables 1, 2).
In summary, for the first time we carried out the
reactions of pyrazolo[3,4-d][1,2,3]triazin-4-ones with
acid chlorides, acetic anhydride, arylisocyanates, and
arylsulfonyl chlorides. The acylation with acid chlo-
rides in the presence of sodium hydride or sulfonyla-
tion proceeded at the N3 atom of the heterocyclic ring.
Heating of pyrazolo[3,4-d][1,2,3]triazin-4-one 1b
with aryl isocyanates led to the formation of sub-
stituted 1H-pyrazolo[3,4-d]pyrimidine-4,6(5H,7H)-diones
Table 1. Yields, melting points, and elemental analysis data of compounds 2–8
Found, %
Calculated, %
Comp. Yield,
mp, °С
Formula
no.
%
C
H
N
S
H
N
S
2а
2b
2c
2d
2e
2f
2g
2h
3
51
52
64
70
61
58
97
64
45
5
180–182
197–199
153–155
175–177
150–152
155–157
172–174
184–185
181–183
221–223
203–205
189–191а
222–224b
258–260c
56.41 3.59
57.88 4.15
45.89 2.72
64.47 3.52
65.37 3.99
55.61 2.14
65.17 3.92
56.87 3.25
61.11 3.10
64.65 3.93
68.79 3.85
63.49 3.93
67.27 3.93
60.18 3.22
27.39
26.09
26.87
22.18
21.07
21.78
21.21
20.84
14.29
22.43
21.42
18.57
18.52
16.68
19.59
19.16
–
–
C12H9N5O2
C13H11N5O2
C10H7N5O2S
C17H11N5O2
C18H13N5O2
C15H9N5O2S
C18H13N5O2
C16H11N5O2S
C15H9N3O2S
C20H14N6O2
C15H10N4O
C12H9N3O2
C17H12N4O2
56.47
57.99
45.97
64.35
65.25
55.72
65.25
56.96
61.01
64.86
68.69
63.43
67.10
3.55
4.12
2.70
3.49
3.95
2.18
3.95
3.29
3.07
3.81
3.84
3.99
3.97
3.27
3.14
3.57
27.44
26.01
–
–
12.33
–
26.81 12.27
22.07
21.14
21.66
21.14
20.76
–
–
–
9.99
–
9.92
–
9.45
10.86
–
9.50
14.23 10.86
4
22.69
21.36
18.49
18.41
16.54
19.82
19.06
–
–
5
38
70
33
32
66
56
–
6
–
–
7а
7b
8а
8b
–
–
–
C17H11ClN4O2 60.28
–
206 (decomp.) 54.63 3.26
186–188 55.72 3.50
9.07
8.58
C16H11N5O3S
C17H13N5O3S
54.38
55.58
9.07
8.73
a mp = 184.5–185.5°С (benzene–heptane) [8]. b mp = 225–227°С (n-butanol) [11]. c mp = 256–258°С (n-butanol) [11].
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 10 2017

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GURENKO et al.
Table 2. IR, NMR, and mass spectral data of compounds 2–8
Comp.
no.
m/z
ν, cm–1
δН (DMSO-d6), ppm
δС (DMSO-d6), ppm
[M+ Н]+
2а
1178, 1244,
1551, 1594,
1722 br, 3119
4.25 s (3H, NCH3), 7.54–7.69 m (2H, Ph), 36.2 (NCH3), 106.8 (С4, pyrazole), 129.0,
256
270
262
318
7.76–7.87 m (1H, Ph), 7.99 d (2Н, Ph,
129.8, 131.5, 135.3, 136.2, 147.9 (С5, pyra-
zole), 153.2 (C=O, triazine), 170.6 (С=O,
acyl)
J 7.6 Hz), 8.50 s (1H, H3, pyrazole)
2b
2c
2d
1178, 1245,
1551, 1604,
1718 br, 3115
2.43 s (3H, C6H4CH3), 4.26 s (3H, NCH3), 21.9 (C6H4CH3), 36.2 (NCH3), 106.7 (С4,
7.42 d (2Н, C6H4, J 8.0 Hz), 7.88 d (2Н,
pyrazole), 129.8, 139.5, 131.8, 134.1,
C6H4, J 8.0 Hz), 8.50 s (1H, H3, pyrazole) 135.2, 147.5 (С5, pyrazole), 153.2 (C=O,
triazine), 170.3 (С=O, acyl)
1080, 1264,
1406, 1551,
4.25 s (3H, NCH3), 7.32–7.34 m (1H, Н4, 36.2 (NCH3), 106.8 (С4, pyrazole), 130.1,
thiophene), 8.00 d (1Н, thiophene,
135.3, 135.9, 140.5, 141.1, 147.9 (С5, pyra-
zole), 152.7 (C=O, triazine), 163.7 (С=O,
acyl)
1697, 1742, 3103 J 3.8 Hz), 8.37 d (1Н, thiophene,
J 4.7 Hz), 8.50 s (1H, H3, pyrazole)
1051, 1451,
1499, 1596,
1706, 1739,
7.46–7.65 m (5H, H Ph), 7.71 t (1H, Ph,
107.6 (С4, pyrazole), 122.3, 128.5, 128.7,
J 6.9 Hz), 7.90 d (2H, Ph, J 7.4 Hz), 8.14 d 129.21, 130.7, 130.8, 135.0, 135.6, 137.1,
(2H, Ph, J 7.4 Hz), 8.43 s (1H, H3,
146.6, 152.4 (C=O, triazine), 168.6 (С=O,
1817, 3065, 3117 pyrazole)
acyl)
2e
2f
1049, 1250,
1500, 1602,
1714 br, 3104
2.43 s (3H, CH3), 7.43 d (2H, tolyl,
J 7.3 Hz), 7.53–7.61 m (1Н, Ph), 7.64–
22.0 (C6H4CH3), 108.6 (С4, pyrazole),
123.6, 128.7, 129.4, 130.3, 130.6, 132.0,
332
324
7.73 m (2Н, Ph), 7.94 d (2H, tolyl, J 7.3 Hz), 136.8, 137.8, 147.7, 147.9 (С5, pyrazole),
8.06 d (2H, Ph, J 6.8 Hz), 8.77 s (1H, H3, 153.3 (C=O, triazine), 170.0 (С=O, acyl)
pyrazole)
1048, 1350,
1459, 1500,
1540, 1592,
7.18–7.25 m (1H, thiophene), 7.46–7.53 m 107.7 (С4, pyrazole), 122.3, 128.4, 128.4,
(1H, Ph), 7.55–7.65 m (2H, Ph), 7.79 d
(1H, thiophene, J 3.2 Hz), 7.90 d (1H,
129.2, 135.2, 135.7, 137.1, 137.8, 138.0,
146.3 (С5, pyrazole), 151.9 (C=O,
triazine), 161.5 (С=O, acyl)
1703, 2923, 3084 thiophene, J 4.7 Hz), 8.12 d (2H, Ph,
J 7.9 Hz), 8.43 s (1H, H3, pyrazole)
2g
2h
1039, 1250,
1508, 1544,
2.42 s (3H, CH3), 7.47 d (2H, tolyl, J 8.4 Hz), 21.1 (C6H4CH3), 108.0 (С4, pyrazole),
332
338
7.58–7.66 m (2Н, Ph), 7.78–7.86 m (1Н,
122.9, 129.0, 129.7, 130.3, 131.2, 133.3,
1705, 1729, 3104 Ph), 7.93 d (2H, tolyl, J 8.4 Hz), 8.05 d
135.6, 135.6, 138.4, 148.3 (С5, pyrazole),
(2H, Ph, J 7.4 Hz), 8.76 s (1H, H3, pyrazole) 154.2 (C=O, triazine), 167.8 (С=O, acyl)
1045, 1262,
1513, 1543,
2.41 s (3H, CH3), 7.32–7.38 m (1H,
thiophene), 7.46 d (2H, tolyl, J 8.3 Hz),
21.2 (C6H4CH3), 108.4 (С4, pyrazole),
123.4, 130.1, 130.6, 135.3, 135.8, 136.6,
139.1, 140.8, 141.3, 147.5 (С5, pyrazole),
152.8 (C=O, triazine), 163.4 (С=O, acyl)
1708, 1731, 3101 7.92 d (2H, tolyl, J 8.3 Hz), 8.06 d, (1H,
thiophene, J 3.7 Hz), 8.39 d (1H, thio-
phene, J 4.8 Hz), 8.75 s (1H, H3, pyrazole)
3
933, 1407, 1500, 7.21–7.32 m (1H, thiophene), 7.39–7.49 m 101.0 (С4, pyrazole), 122.3, 129.7, 129.9,
296
371
263
1534, 1568,
1790, 3109
(1H, Ph), 7.52–7.64 m (2H, Ph), 7.90–8.08 133.5, 133.9, 135.7, 138.0, 138.6, 150.9
m (2H, Ph + 2H, thiophene), 8.40 s (1H,
(С5, pyrazole), 154.3 (NCO), 158.8 (С=O)
H3, pyrazole)
4
1506, 1541,
6.93 s (2H, NH2), 7.48 t (2H, Ph J 7.5 Hz),
1585, 1627, 1777 7.55–7.68 m (6H, Ph), 7.89 d (2H, Ph,
(C=O), 3343
(NH2), 3456
J 7.5 Hz), 8.02 s (1H, H3', pyrazole), 8.41 s
(1H, H3, pyrazole)
5а
1070, 1128,
1395, 1540,
6.92–7.03 m (1H), 7.29–7.39 m (1H), 7.46– 101.8 (С4, pyrazole), 113.1, 121.7, 126.1,
7.55 m (2H), 7.59 d (1Н, J 8.6 Hz), 8.21 d 126.7, 127.7, 129.1, 136.0, 136.8, 138.9,
1729, 2854, 2925 (2Н, J 8.2 Hz), 8.41 s (1H, H3, pyrazole), 150.1, 151.1, 154.2 (С=O)
9.02 d (1Н, J 7.1 Hz)
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ACYLATION OF PYRAZOLO[3,4-d][1,2,3]TRIAZIN-4-ONES
Table 2. (Contd.)
Comp.
no.
m/z
ν, cm–1
δН (DMSO-d6), ppm
δС (DMSO-d6), ppm
[M+ Н]+
6
1246, 1424,
1543, 1598,
1774, 3126
2.48 s (3H, CH3), 7.41–7.51 m (1H, Ph),
7.53–7.66 m (2H, Ph), 7.97 d (2Н, Ph,
J 7.3 Hz), 8.46 s (1H, H3, pyrazole)
7.09–7.17 m (1H), 7.32–7.44 m (3H), 7.50– 96.8 (С4, pyrazole), 120.4, 121.4, 124.2,
22.1 (CH3), 101.0 (С4, pyrazole), 122.9,
128.6, 130.0, 138.0, 138.3, 151.0 (С5,
pyrazole), 155.3 (NCO), 167.5 (С=O)
228
7а
1251, 1498,
305
339
1584, 1632, 1764 7.61 m (2H), 7.62–7.73 m (2H), 7.99 d
br, 3120, 3280
127.2, 129.0, 129.3, 137.2, 138.0, 138.1,
(2Н, J 7.1 Hz), 8.27 s (1H, H3, pyrazole), 153.6, 154.0, 155.6
10.85 s (1H, NH)
7b
1247, 1493,
7.36–7.49 m (3H, Ph), 7.53–7.61 m (2H,
97.3 (С4, pyrazole), 121.7, 122.2, 127.6,
128.2, 129.2, 129.8, 136.8, 138.4, 138.5,
153.8, 154.3, 155.8
1583, 1624, 1775 Ph), 7.67 d (2Н, C6H4Cl, J 7.9 Hz), 7.96 d
br, 3105, 3262
(2Н, C6H4Cl, J 7.9 Hz), 8.26 s (1H, H3,
pyrazole), 10.96 уш. s (1H, NH)
8а
1193, 1388,
1553, 1736,
3098, 3144
7.28–7.39 m (3H), 7.48–7.57 m (2H), 7.58– 108.1 (С4, pyrazole), 123.1, 124.0, 126.0,
254
368
7.67 m (4H), 8.04 d (1Н, Ph, J 7.5 Hz),
128.2, 130.0, 135.9, 141.0, 148.3, 150.4,
154.3, 165.7
8.60 s (1H, H3, pyrazole)
8b
1175, 1376,
1593, 1742 br,
3119
2.41 s (3H, СH3), 7.43–7.59 m (4H), 7.60– 21.3, 108.3 (С4, pyrazole), 123.2, 129.1,
7.71 m (1H, Ph), 7.91–8.06 m (4H), 8.63 s 129.4, 129.7, 130.1, 133.0, 136.6, 136.9,
(1H, H3, pyrazole)
146.6, 147.0, 151.2
a 1Н and 13С NMR spectra were recorded in CDCl3.
The acylation in pyridine with heating led to the
destruction of the pyrazolotriazine ring to form a
mixture of the reaction products. The reaction of
pyrazolo[3,4-d][1,2,3]triazin-4-ones with acetic an-
hydride or arylisocyanates afforded pyrazolo[3,4-d]-
[1,3]oxazine or pyrazolo[3,4-d]pyrimidine derivatives.
were determined by the Pregl method; the nitrogen
content was determined by the Dumas micromethod;
the sulfur content was measured by the Schöniger
titrimetric method. Melting points were measured on a
Fisher–Johns apparatus.
Commercially available reagents and solvents were
used in the study.
EXPERIMENTAL
3-Acyl-7-aryl(methyl)-3,7-dihydro-4H-pyrazolo-
[3,4-d][1,2,3]triazin-4-ones (2a–2h). A suspension of
0.20 g (4.9 mmol) of 60% NaH in mineral oil was
slowly added to a solution of 1.00 g (4.7 mmol) of
compound 1a in 20 mL of THF at 0°C. Then 4.9 mmol
of the corresponding acid chloride was added dropwise
with stirring. The reaction mixture was stirred at 20–
25°C for 1 h. Next 50 mL of water was added, and the
mixture was extracted with benzene. The solvent was
removed in a vacuum, and the target compounds 2a–
2h were purified by recrystallization (C6H6–n-hexane,
8 : 2).
1H and 13C NMR spectra were recorded on a
Varian Mercury instrument (400 and 100 MHz, respec-
tively), internal reference TMS. IR spectra were
registered on a Vertex 70 spectrometer from KBr
pellets. Chromato-mass spectra were taken using a
liquid chromatography-mass spectrometry system
using an Agilent 1100 Series chromatograph equipped
with a diode array with an Agilent LC\MSD SL mass-
selective detector. Parameters of the chromatography-
mass spectrometry analysis were as follows: column
Zorbax SB C18 (1.8 μm, 4.6 × 15 mm), solvents: A –
MeCN–H2O, 95 : 5, 0.1% CF3COOH; B – 0.1%
aqueous CF3COOH; eluent flow of 3 mL/min,
injection volume of 1 μL; UV detectors at 215, 254,
285 nm; chemical ionization at atmospheric pressure.
Elemental analysis was performed in the Laboratory of
Analytical Chemistry of the Institute of Bioorganic
Chemistry and Petrochemistry of the National
Academy of Ukraine. The carbon and hydrogen content
1-Phenyl-6-(thien-2-yl)pyrazolo[3,4-d][1,3]oxazin-
4(1H)-one (3), 6-(5-amino-1-phenyl-1H-pyrazol-4-
yl)-1-phenylpyrazolo[3,4-d][1,3]oxazin-4(1H)-one (4),
1-phenylpyrazolo[3,4-d]pyrido[1,2-a]pyrimidin-4(1H)-
one (5). A mixture of 1.00 g (4.7 mmol) of compound
1b and 0.69 g (4.69 mmol) of thiophene-2-carbonyl
chloride was boiled for 1 h in 50 mL of pyridine, then
evaporated in a vacuum. The mixture of compounds 3–5
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GURENKO et al.
was separated by column chromatography (silica gel,
eluent–CHCl3).
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 10 2017