Organic Chemistry of Explosives

Energetic groups 287

AlkylN,N-dinitramines (154) have been prepared from the reaction of the tetraalkylam-

monium salts (155) of primary nitramines with nitryl fluoride in acetonitrile at subambient

temperature.^78 The same reaction with the primary nitramine or its alkali metal salts yields the

corresponding nitrate ester.^79 Treatment of the ammonium, potassium, or lithium salts of pri-

mary nitramines (156) with a solution of nitronium tetrafluoroborate in acetonitrile at subambi-

ent temperature yield alkylN,N-dinitramines.^80 ,^81 The same reactions in ether or ester solvents

enables the free nitramine to be used.^82 The nitrolysis ofN-alkylnitramides (157)^83 andN,N-

diacylamines^84 with nitronium tetrafluoroborate in acetonitrile, and the nitration of aliphatic

isocyanates^85 with nitronium tetrafluoroborate and nitric acid in acetonitrile, also yield alkyl

N,N-dinitramines (154).

N

O

O 2 N

R

157

R, R' = alkyl

N

NO 2

NO 2

+ NO 2 BF 4 R + R'CO BF 4

154

R'

Figure 6.51

6.11.3N-Nitroimides

TheN-nitroimide functionality is a stable but highly energetic group which has been in-

corporated into some heterocycles in the search for new energetic materials. Katritzsky and

co-workers^86 ,^87 synthesizedN-nitroimides by treating alkylhydrazinium nitrates^88 with ni-

tronium tetrafluoroborate in acetonitrile or with solutions of acyl nitrates prepared from the

addition of nitric acid to mixtures of TFA–TFAA or acetic acid–acetic anhydride. Olah and

co-workers^89 synthesized theN-nitroimides (160) and (161) by treating the corresponding

tertiary amines, DABCO (158) andN,N,N′,N′-tetramethyl-1,3-propanediamine, respectively,

with an aqueous solution of barium oxide, barium nitrate and hydroxylamine-O-sulfonic acid,

followed byN-nitration of the resulting hydrazinium nitrates with TFA–TFAA.

N

N

N

N

NH 2

H 2 N

N

N

N

N

O 2 N

TFA, TFAA

Me 2 N NMe 2

N

O 2 N NO 2

2 NO 3

(^159160)
NH 2 OSO 3 H, H 2 O,
BaO, Ba(NO 3 ) 2
63 %
85 %
161
158
NO 2
N
Figure 6.52
N-Nitroimides derived from tertiary amines contain a quaternary nitrogen atom which has a
zwitterionic structure with the negative charge on one nitrogen atom stabilized by the electron-
withdrawing effect of the adjacent nitrogen atom.N-Nitroimides derived from secondary