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Nitrolysis 357
Solutions of dinitrogen pentoxide in aprotic solvents like methylene chloride, chloroform
and carbon tetrachloride are efficient reagents for theN-nitration of secondary amines.^51 These
reactions, known as ‘nucleophilic nitrations’, need excess amine present to react with the nitric
acid formed during the reaction. Such nitrations are useful for the synthesis of secondary
nitramines.^51
NHHN
O
NN
O 2 N NO 2
O
N 2 O 5 , CHCl 3
2221
NaF, > 90 %
Figure 9.12
Dinitrogen pentoxide in chloroform has been used for theN-nitration of amides, imides
and ureas, where yields are generally excellent.^52 2-Imidazolidinone (21) is converted toN,N′-
dinitro-2-imidazolidinone (22) in greater than 90% yield with this reagent in the presence of
sodium fluoride.^53
9.7 Nitrolysis
Some of the major advances in the synthesis of energetic materials have arisen from the
use of dinitrogen pentoxide–nitric acid solutions for nitrolysis reactions. These reactions are
important routes to alicyclic, cyclic and caged energetic polynitramines.
The nitrolysis of hexamine is a direct route to the military high explosives 1,3,5-trinitro-
1,3,5-triazacyclohexane (RDX) and 1,3,5,7-tetranitro-13,5,7-tetraazacyclooctane (HMX).^1 ,^46
The direct nitrolysis of hexamine with dinitrogen pentoxide in absolute nitric acid provides
RDX in 57 % yield.^54 RDX prepared by this process is exceptionally pure, but other reagents,
like ammonium nitrate–nitric acid–acetic anhydride, give much higher yields, partly because
they use ammonium nitrate to supplement for ammonium nitrogen deficiency in the reaction.
NO 2
NO 2
25
(HMX)
O 2 N NO 2
N
N
H 2 C CH 2
H 2 C CH 2
Ac NAc
R
R
23, R = Ac (79 %)
24, R = NO 2 (98 %)
N 2 O 5 , HNO 3
N
N
N
H 2 C CH 2
H 2 C CH 2
NN
Figure 9.13
The synthesis of HMX from the nitrolysis of hexamine with conventional reagents is
far more problematic. However, HMX (25) is synthesized in high yield from the nitroly-
sis of 1,3,5,7-tetraacetyl-1,3,5,7-tetraazacyclooctane (TAT) (23) and 1,5-diacetyl-3,7-dinitro-
1,3,5,7-tetraazacyclooctane (DADN) (24) with dinitrogen pentoxide in nitric acid.^55 DADN
(24) is readily synthesized from the acetolysis of hexamine followed by mild nitration with
mixed acid. The synthesis of HMX (25) via the nitrolysis of DADN (24) is now a pilot plant
