[1,2,5]Oxadiazolo[3,4ꢀc]cinnoline 5ꢀoxides
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 3, March, 2011
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and Merck 60 F254). Column chromatography on silica gel was
used. 3ꢀAminoꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole19 and ethereal soluꢀ
tion of diazomethane20 were obtained according to the known
procedures. Distilled colorless HNO3, d = 1.5 g cm–1, was used.
3ꢀNitraminoꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole (2a). The compound
NO2BF4 (0.23 g, 1.72 mmol) was added in small portions to
a solution of 3ꢀaminoꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole 1a (0.2 g,
1.24 mmol) in anhydrous acetonitrile (6 mL) with vigorous stirꢀ
ring at –30 °C. The cooling bath was removed and the stirring
was continued until the temperature reached –10 °C, then
the reaction mixture was poured into the aqueous solution of
NaHCO3 (0.5 g in 20 mL). The aqueous layer was separated,
washed with Et2O (2×10 mL), and acidified with 10% aq. HCl to
pH 2, then extracted with CH2Cl2 (5×10 mL). The extract was
dried with MgSO4 and concentrated in vacuo to obtain nitrꢀ
amine 2a (176 mg, 69%) as yellowish crystals, after recrystallizaꢀ
tion from light petroleum m.p. 69—71 °C (decomp.). Found (%):
C, 46.53; H, 2.87; N, 26.91. C8H6N4O3. Calculated (%):
C, 46.61; H, 2.90; N, 27.18. IR, ν/cm–1: 1280, 1312, 1324, 1404,
1468, 1504, 1616, 3308. 1H NMR, δ: 7.61—7.64 (m, 3 H, H(3´),
H(4´), H(5´)); 7.88 (dd, 2 H, H(2´), H(6´), J = 7.3 Hz, J = 2.2 Hz);
9.25 (br.s, 1 H, NH). 13C NMR, δ: 125.5 (C(1´)); 128.3 (C(2´),
C(6´)); 130.3 (C(3´), C(5´)); 132.3 (C(4´)); 149.0 (C(3)); 152.8
(C(4)). The HMBC and HSQC experiments were used to assign
1.86 mmol) in 93% aq. H2SO4 (1 mL) was added dropwise to
a solution of aminofurazan 1a (0.3 g, 1.86 mmol) in 93%
aq. H2SO4 (4 mL) with vigorous stirring at 20 °C. The reaction
mixture was stirred for 10 min and then poured onto finely
crushed ice (15 g). A suspension formed was extracted with
CH2Cl2 (5×10 mL). The combined organic layer was washed
with brine (2 mL), dried with MgSO4, and concentrated in vacuo
to obtain a mixture of 3ꢀaminoꢀ4ꢀ(nitrophenyl)ꢀ1,2,5ꢀoxadiꢀ
azoles 1b—d (345 mg, 90%), which was separated by preparative
TLC on silica gel (eluent: light petroleum—AcOEt (2 : 1)). Comꢀ
pound 1b (132 mg, 34%), compound 1c (107 mg, 28%), and
compound 1d (104 mg, 27%) were finally obtained.
3ꢀAminoꢀ4ꢀ(4´ꢀnitrophenyl)ꢀ1,2,5ꢀoxadiazole (1b), m.p.
173—175 °C. Found (%): C, 46.47; H, 2.95; N, 26.85.
C8H6N4O3. Calculated (%): C, 46.61; H, 2.93; N, 27.18. IR,
ν/cm–1: 1312, 1348, 1476, 1516, 1604, 1632, 3328, 3452.
1H NMR, δ: 5.80 (br.s, 2 H, NH2); 8.15 (d, 2 H, H(2´), H(6´),
J = 9.0 Hz); 8.44 (d, 2 H, H(3´), H(5´), J = 9.0 Hz). 13C NMR,
δ: 125.1 (C(3´), C(5´)); 130.1 (C(2´), C(6´)); 133.5 (C(1´)); 146.8
(C(4)); 150.0 (br.s, C(4´)); 156.3 (C(3)). 13C NMR (DMSOꢀd6),
δ: 124.0 (C(3´), C(5´)); 129.1 (C(2´), C(6´)); 131.8 (C(1´));
145.6 (C(4)); 148.2 (C(4´)); 155.3 (C(3)). The HMBC and
HSQC experiments were used to assign the signals. 14N NMR (acetꢀ
oneꢀd6), δ: –13 (NO2, Δν1/2 = 130 Hz). MS, m/z: 206 [M]+, 176
[M – NO]+.
the signals. 14N NMR, δ: –37 (N—NO2, Δν = 20 Hz). MS,
1/2
m/z: 206 [M]+.
3ꢀAminoꢀ4ꢀ(3´ꢀnitrophenyl)ꢀ1,2,5ꢀoxadiazole (1c), m.p.
123—125 °C (from MeOH). Found (%): C, 46.78; H, 2.89;
N, 27.01. C8H6N4O3. Calculated (%): C, 46.61; H, 2.93;
N, 27.18. IR, ν/cm–1: 1308, 1320, 1352, 1472, 1516, 1532, 1636,
Reaction of compound 2a with diazomethane. A solution of
diazomethane, obtained from NꢀmethylꢀNꢀnitrosourea (0.2 g),
in Et2O (3 mL) was added dropwise to a stirred solution of nitraꢀ
mine 2a (90 mg, 0.44 mmol) in Et2O (3 mL) at 20 °C until
evolution of the gas was ceased and the solution turned slightly
yellowish. Then the solvent was evaporated in vacuo to obtain
a mixture of Oꢀ and Nꢀmethyl derivatives 3a and 4a (94 mg, 98%)
as yellowish crystals. The mixture was separated by preparative
TLC on silica gel (eluent: light petroleum—AcOEt (4 : 1)) to
yield Oꢀmethyl compound 3a (60 mg, 63%) and Nꢀmethyl comꢀ
pound 4a (34 mg, 35%).
1
3316, 3412. H NMR, δ: 5.81 (br.s, 2 H, NH2); 7.91 (t, 1 H,
H(5´), J = 8.1 Hz); 8.27 (d, 1 H, H(6´), J = 7.3 Hz); 8.43 (dd, 1 H,
H(4´), J = 8.1 Hz, J = 1.5 Hz); 8.66 (t, 1 H, H(2´), J = 1.5 Hz).
13C NMR, δ: 123.6 (C(2´)); 125.8 (C(4´)); 128.8 (C(1´)); 131.7
(C(5´)); 134.9 (C(6´)); 146.7 (C(4)); 149.7 (br.s, C(3´)); 156.2
(C(3)). The HMBC and HSQC experiments were used to assign
the signals. 14N NMR, δ: –13 (NO2, Δν1/2 = 100 Hz). MS, m/z:
206 [M]+, 176 [M – NO]+.
Eꢀ3ꢀ[Methoxy(oxido)diazenyl]ꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole
(3a), m.p. 72—73 °C (from MeOH). Found (%): C, 49.33;
H, 3.70; N, 25.21. C9H8N4O3. Calculated (%): C, 49.09;
H, 3.66; N, 25.45. IR, ν/cm–1: 1240, 1300, 1452, 1544, 1556.
1H NMR, δ: 4.23 (s, 3 H, Me); 7.53—7.59 (m, 3 H, H(3´),
H(4´), H(5´)); 7.96 (dd, 2 H, H(2´), H(6´), J = 7.8 Hz, J = 1.9 Hz).
13C NMR, δ: 59.1 (Me); 124.8 (C(1´)); 128.3 (C(2´), C(6´));
129.1 (C(3´), C(5´)); 131.1 (C(4´)); 150.6 (C(4)); 153.1 (C(3)).
The HMBC and HSQC experiments were used to assign the
3ꢀAminoꢀ4ꢀ(2´ꢀnitrophenyl)ꢀ1,2,5ꢀoxadiazole (1d), m.p.
113—114 °C (from MeOH) (cf. Ref. 21: m.p. 111—112 °C).
Found (%): C, 46.74; H, 2.95; N, 26.99. C8H6N4O3. Calculatꢀ
ed (%): C, 46.61; H, 2.93; N, 27.18. IR, ν/cm–1: 1312, 1352,
1476, 1524, 1532, 1632, 3340, 3444. 1H NMR, δ: 5.63 (br.s, 2 H,
NH2); 7.75 (dd, 1 H, H(6´), J = 7.3 Hz, J = 2.2 Hz); 7.91 (td, 1 H,
H(4´), J = 7.3 Hz, J = 2.2 Hz, J = 1.5 Hz); 7.98 (td, 1 H, H(5´),
J = 7.3 Hz, J = 1.5 Hz); 8.34 (dd, 1 H, H(3´), J = 8.1 Hz, J = 1.5 Hz).
13C NMR, δ: 121.8 (C(1´)); 126.2 (C(3´)); 132.9 (C(4´)); 133.6
(C(6´)); 135.2 (C(5´)); 147.2 (C(4)); 149.4 (br.s, C(2´)); 156.8
(C(3)). The HMBC and HSQC experiments were used to assign
signals. 14N NMR, δ: –50 (N→O, Δν = 90 Hz). MS, m/z:
1/2
220 [M]+, 189 [M – OMe]+.
3ꢀ[Methyl(nitro)amino]ꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole (4a),
m.p. 69—71 °C (from light petroleum). Found (%): C, 49.27;
H, 3.69; N, 25.13. C9H8N4O3. Calculated (%): C, 49.09; H, 3.66;
the signals. 14N NMR, δ: –12 (NO2, Δν = 85 Hz). MS, m/z:
1/2
206 [M]+, 176 [M – NO]+.
3ꢀNitraminoꢀ4ꢀ(4´ꢀnitrophenyl)ꢀ1,2,5ꢀoxadiazole (2b). The
compound NO2BF4 (32 mg, 0.24 mmol) was added in small
portions to a solution of compound 1b (38 mg, 0.18 mmol) in
anhydrous acetonitrile (3 mL) with vigorous stirring at –30 °C.
The cooling bath was removed and the stirring was continued
until the temperature reached 0 °C. Then, a solution of K2CO3
(0.1 g) in water (0.5 mL) was added to the reaction mixture,
which was stirred for another 30 min at 0 °C. The mixture obꢀ
tained was concentrated at 0 °C. The residue was thoroughly
triturated and washed with Et2O (5 mL) with vigorous stirring
over 30 min. The washing was repeated another 2 times. A preꢀ
1
N, 25.45. IR, ν/cm–1: 1292, 1424, 1452, 1480, 1568. H NMR,
δ: 3.95 (s, 3 H, Me); 7.54—7.60 (m, 3 H, H(3´), H(4´), H(5´));
7.78 (dd, 2 H, H(2´), H(6´), J = 7.7 Hz, J = 1.3 Hz). 13C NMR,
δ: 40.0 (Me); 124.7 (C(1´)); 127.2, 127.3 (C(2´), C(6´)); 129.4,
129.5 (C(3´), C(5´)); 131.4 (C(4´)); 152.0 (C(4)); 152.4 (C(3)).
The HMBC and HSQC experiments were used to assign the
signals. 14N NMR, δ: –35 (N—NO2, Δν = 30 Hz). MS, m/z:
1/2
220 [M]+.
Nitration of 3ꢀaminoꢀ4ꢀphenylꢀ1,2,5ꢀoxadiazole (1a) with
the H2SO4—HNO3 mixture. A solution of KNO3 (188 mg,