C. Ma et al.: Efficient synthesis of 4-amino-2,6-dichloropyridineꢂꢁꢀꢀꢀꢂ3
potassium nitrate (5.1 g, 50.6 mmol) portionwise with vigorous stir- (0.06 g, 1.11 mmol). After stirring for 2 h, the pale yellow precipitate
ring [21, 22]. Then the mixture was heated to 100°C for 7 h, cooled and was filtered, washed with cold methanol and dried to give 4-amino-
1
poured over ice. The resultant solid was filtered, washed with water and 2,6-dimethoxy-3,5-dinitropyridine (8, 0.82 g, 85%); mp 192–193°C; H
1
3
dried to give a mixture (3.53 g) of 3 (major product) and 4 (minor prod- NMR (DMSO-d ): δ 7.97 (s, 2H), 4.01(s, 6H); C NMR (DMSO-d ): δ 156.9,
6
6
1
1
+
uct); H NMR for 3 (CDCl ): δ 8.33(s); H NMR for 4 (CDCl ): δ 8.02 (s, 1H). 146.0, 115.3; ESI-MS: m/z 242.97 (M-H) . Anal. Calcd for C H N O : C,
3
3
7
8
4
6
3
4.43; H, 3.30; N, 22.95. Found: C, 34.48; H, 3.25; N, 23.05.
4-Amino-2,6-dichloropyridine (5)
2,4,6-Triamino-3,5-dinitropyridine (9)
A solution of the mixture of 3 and 4 obtained as described above (1.96 g)
in acetic acid (40 mL) was treated with iron powder (1.96 g, 35 mmol), Method 1: Dry ammonia was bubbled through a stirred solution of
and the reaction mixture was heated to 45°C for 3 h, after which time 4-amino-2,6-dichloro-3,5-dinitropyridine (7, 1.0 g, 4.0 mmol) in etha-
complete consumption of the starting material was observed by TLC nol (8 mL) for 30 min at 0°C and for another 6 h at room temperature.
[
23]. Quenching with water was followed by extraction with ethyl ace- The resultant precipitate was filtered, washed with water and dried
tate (2ꢀ×ꢀ50 mL). Concentration of the extract afforded compound 5 as a to give compound 9 as a yellow solid; yield 0.80 g (95%); mp 352–
1
1
white solid; yield 1.30 g; mp 175–177°C [23]; H NMR (DMSO-d ): δ 6.80 354°C (dec.) [24]; H NMR (DMSO-d ): δ 10.26 (s, 2H), 8.75 (s, 2H), 8.23
(
6
6
13
13
s, 2H), 6.60 (s, 2H); C NMR (DMSO-d ): δ 158.1, 148.7, 106.0.
(s, 2H); C NMR (DMSO-d ): δ 155.5, 150.9, 109.6; ESI-MS: m/z 212.95
M-H) . Anal. Calcd for C H N O : C, 28.04; H, 2.82; N, 39.25. Found: C,
6
6
+
(
5
6
6
4
2
8.10; H, 2.89; N, 39.29.
4
4
-Amino-2,6-dichloro-3-nitropyridine (6) and
-amino-2,6-dichloro-3,5-dinitropyridine (7)
Method 2: Dry ammonia was bubbled through a stirred solution of
4-amino-2,6-dimethoxy-3,5-dinitropyridine (8, 0.5 g, 2.1 mmol) in
ethanol (8 mL) for 12 h at 40°C. The resultant precipitate was filtered,
washed with water and dried to give compound 9 as a yellow solid;
yield 0.38 g (87%).
4-Amino-2,6-dichloropyridine (5, 1.30 g, 8.0 mmol) was dissolved in
concentrated sulfuric acid (60 mL) at room temperature, and potas-
sium nitrate (1.54 g, 15.25 mmol) was added in portions with vigorous
stirring. The reaction mixture was held at room temperature fot 6 h,
after wich time complete consumption of substrate 5 was observed 2,4,6-Triamino-3,5-dinitropyridine-1-oxide (10)
by TLC. After pouring over ice the resultant precipitate was filtered,
washed with water and dried. Purification by silica gel chromatogra-
A solution of 2,4,6-triamino-3,5-dinitropyridine (9, 0.21 g, 1 mmol) in
phy eluting with ethyl acetate/petroleum ether (1:8) afforded 6 which
glacial acetic acid (10 mL) was treated dropwise at room tempera-
was eluted first and then 7.
ture with 30% hydrogen peroxide (1 mL) and the mixture was heated
under reflux for 5 h, then cooled, diluted with water (50 mL) and
4
-Amino-2,6-dichloro-3-nitropyridine (6)ꢁWhite solid; yield
allowed to stand for 12 h. The resultant yellow precipitate of com-
1
0
.71 g (43%); mp 142–144°C; H NMR (DMSO-d ): δ 7.65 (s, 2H), 6.86
6
pound 10 was filtered and washed successfully with water and etha-
1
3
(
s, 1H); C NMR (DMSO-d ): δ 142.7, 124.1, 123.7 [23].
1
6
nol; yield 0.02 g (9%); mp 350–352°C (dec.) [24]; H NMR (DMSO-d ):
6
+
δ 10.17 (s, 2H), 9.58 (s, 2H), 8.83 (s, 2H); ESI-MS: m/z 229.97 (M-H) .
Anal. Calcd for C H N O : C, 26.09; H, 2.63; N, 36.52. Found: C, 26.19;
4
-Amino-2,6-dichloro-3,5-dinitropyridine (7)ꢁYellow solid; yield
5
6
6
5
1
13
0
.35 g (17%); mp 159–161°C; H NMR (DMSO-d ): δ 8.25 (s); C NMR
6
H, 2.80; N, 36.59.
(
DMSO-d ): δ 142,4, 141.0, 132.0. Anal. Calcd for C H Cl N O4: C, 23.74;
6
5
2
2
4
H, 0.80; N, 22.14. Found: C, 23.65; H, 1.02; N, 22.19.
Funding: National Natural Science Foundation of China,
Grant/Award Number: ‘21102125’).
(
Independent synthesis of 7
References
A solution of 4-amino-2,6-dichloropyridine (5, 2.04 g, 12.6 mmol) in
concentrated sulfuric acid (20 mL) was stirred vigourously at room
temperature and treated portionwise with potassium nitrate (3.4 g,
[
[
[
1] Ye, C. F.; Gao, H. X.; Boatz, J. A.; Drake, G. W.; Twamley, B.;
Shreeve, J. M. Polyazidopyrimidines: high-energy compounds
and precursors to carbon nanotubes. Angew. Chem. Int. Ed.
3
3.7 mmol). Then the mixture was heated to 50°C for 7 h. After pour-
ing over ice, the precipitated solid was filtered, washed with cold
water then dried to give 4-amino-2,6-dichloro-3,5-dinitro-pyridine (7)
as a yellow solid; yield 1.91 g (60%); mp 158–160°C.
2
006, 45, 7262–7265.
2] Thottempudi, V.; Gao, H. X.; Shreeve, J. M. Trinitromethyl-
substituted 5-nitro-or 3-azo-1,2,4-triazoles: synthesis, charac-
terization, and energetic properties. J. Am. Chem. Soc. 2011,
1
33, 6464–6471.
3] Thottempudi, V.; Shreeve, J. M. Synthesis and promising
properties of a new family of high-density energetic salts
of 5-nitro-3-trinitromethyl-1H-1,2,4-triazole and 5, 5’-bis
(trinitromethyl)-3,3’-azo-1H-1,2,4-triazole. J. Am. Chem. Soc.
2011, 133, 19982–19992.
4-Amino-2,6-dimethoxy-3,5-dinitropyridine (8)
To a solution of 4-amino-2,6-dichloro-3,5-dinitro- pyridine (7, 1.0 g,
.97 mmol) in methanol (5 mL) was added sodium methoxide
3
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