Organic Chemistry of Explosives

316 N-Heterocycles

prepared alkali, alkaline earth and heavy metal salts of azotetrazole, the lead salt exhibiting

initiating properties. The dihydrazinium salt of azotetrazole is prepared^102 from the reaction

of the barium salt of azotetrazole with an aqueous solution of hydrazinium sulfate. This salt is

highly energetic with a very high heat of formation and one of the highest nitrogen contents

(85 %) reported for any organic compound.

N

N

N

NH 2

NH 2

157

N

N

N

N

N

N

NH 2

NCl

NO 2

N

N

N

N

N 3

NO 2

N

N

N

N

N

O

N

O

158

(ATTz)

1. NaNO 2


2. NaN 3

159

160 161

NaN 3 , MeCN

25 °C

PhH, reflux

N N

Cl

Figure 7.61

The tetrazole ring can be synthesized from the 1,3-dipolar cycloaddition of an azide with a

cyanide group or a similar nitrogen dipolarophile. Tri-n-butyltin azide and trimethylsilyl azide

have been used as organic alternatives to the azide anion. Ammonium azide is frequently used

and is generatedin situfrom sodium azide and ammonium chloride in DMF. The fused hetero-

cycle (158) (ATTz) has been synthesized from the reaction of 3,6-diaminotetrazine (157) with

nitrous acid and then sodium azide.^103 The heterocycle (161), incorporating both a tetrazole

and furoxan group, has been prepared from the reaction of 3-nitro-2,6-dichloropyridine (159)

with two equivalents of azide anion followed by heating the product (160) under reflux in

benzene.^47

RCN

NO 2

NO 2

(CH 3 ) 3 SiN 3

135

N

NN

H

N

CR(NO 2 ) 2

N

NN

N

CR(NO 2 ) 2

CFCl 2 CFCl 2

NH 4 +

+

NH 3 , Et 2 O

reflux

162, R = NO 2

163, R = F

164, R = NO 2

165, R = F

166, R = NO 2

167, R = F

C

Figure 7.62

5-(Trinitromethyl)tetrazole (166) and 5-(dinitrofluoromethyl)tetrazole (167) have been syn-

thesized and isolated as their ammonium salts from the reactions of trimethylsilyl azide with

the corresponding nitriles followed by reaction with ammonia in diethyl ether.^104

5-Nitrotetrazole is readily prepared from the diazotization of 5-aminotetrazole in the

presence of excess sodium nitrite and is best isolated as the copper salt complex with

ethylenediamine.^105 The salts of 5-nitrotetrazole have attracted interest for their initiating prop-

erties. The mercury salt is a detonating primary explosive.^105 The amine salts of 5-nitrotetrazole

are reported to form useful eutectics with ammonium nitrate.^106