Organic Chemistry of Explosives

318 N-Heterocycles

H 2 NNH 2 H 2 N NH 2

NO 2

NH 2

NH 2

NO 2

O 2 N

H 2 N

O 2 N

O 2 N NO 2

O

O

168

N N

N

H 2 N N NH 2

173

(ANPy)

174

(ANPyO)

175

H 2 SO 4 , HNO 3

60–65 %

AcOH,

NH 2 OH.HCl,

KOH (aq)

39 %

30 % H 2 O 2

Figure 7.65

The direct nitration of 2,6-diaminopyridine (168) with mixed acid yields 2,6-diamino-

3,5-dinitropyridine (ANPy) (173).^111 Oxidation of ANPy (173) with peroxyacetic acid yields

ANPyO (174) (calculated VOD∼7840 m/s,d= 1 .88 g/cm^3 ).^112 C-Amination of ANPyO

(174) with hydroxylamine hydrochloride in aqueous base yields the triamine (175), an impact

insensitive explosive of high thermal stability.^113

C

KO 2 N

O 2 N

N

N

NO 2

NO 2

NO 2

NO 2

O 2 N NO 2

O 2 N

O

177

O

179

N 3 NN 3

H 3 PO 4

176 NaN^3

178

H 2 SO 4 , NaNO 2

CH 2 OH

Figure 7.66

The electron deficiency of the pyridine ring means that 2,4,6-trinitropyridine (178) has to

be synthesized by an indirect route. Acidification of the potassium salt of 2,2-dinitroethanol

(176) is reported to give 2,4,6-trinitropyridine-1-oxide (177), which on reaction with nitrous

acid is reduced to 2,4,6-trinitropyridine (178).^114 2,4,6-Trinitropyridine (178) is reported to

be formed directly in these reactions if the initial cyclization of (176) is performed in the

presence of dilute nitric acid^115 or 2,2-dinitroethanol^116 is used directly. TheN-oxide (177)

is susceptible to nucleophilic substitution at the 2- and 6-positions, treatment of (177) with

sodium azide yielding the energetic diazide (179).^114

7.7 6-Membered rings – 2N

Pyrazine and pyrimidine heterocycles, like pyridine, are electron deficient and need the pres-

ence of an activating/electron-releasing group to allow efficient electrophilic nitration to occur.

An example of this strategy is seen during the synthesis of 2,6-diamino-3,5-dinitropyrazine

(ANPz) (183) where one of the chloro groups of 2,6-dichloropyrazine (180) is substituted for a