272 Nitramines and Their Derivatives
N
COEtEtOC N
COEtEtOCBrBrNN NNCOEtCOEtNO 2NO 2NN NNNO 2NO 2NO 2COEtNN NNNO 2 NO 2NO 2 NO 2Br 2H 2 CNHNO 2NHNO 265
66
6769 68
(bicyclo-HMX)N 2 O 5 ,
HNO 3 ,
TFAA20 % N 2 O 5 in
100 % HNO 3CH 3 CN, Et 3 NN
NFigure 6.16performance. Many of the problems with the synthesis of bicyclo-HMX arise from the ease with
which the bis-imidazolidine ring opens during nitration. The only reported successful synthesis
of bicyclo-HMX is from chemists at the Lawrence Livermore National Laboratory (LLNL).^20 ,^21
This synthesis starts with the bromination ofN,N′-dipropanoyl-1,2-dihydroimidazole (65).
The product of this reaction, the dibromide (66), is treated with methylenedinitramine to effect
a displacement of the halogen atoms and form the bicycle (67). Nitrolysis of the bicycle (67)
is effected with an unusual but powerful nitrating agent composed of dinitrogen pentoxide,
absolute nitric acid and TFAA. This reaction gives the trinitramine (68) in 90 % yield; further
reaction with 20 % dinitrogen pentoxide in absolute nitric acid yields bicyclo-HMX (69).
The above synthesis has a few noteworthy points. The nitrolysis of bicyclic amides like (67)
are frequently problematic in terms of inertness towards nitrolysis and the ease with which
ring decomposition occurs. This synthesis is an interesting balancing act. Ring decomposition
results when the bicycle (67) is treated with absolute nitric acid, mixed acid or nitronium salts.
When the diacetyl equivalent of the bicycle (67) is treated with dinitrogen pentoxide–absolute
nitric acid–TFAA reagent, the yield drops to 10 %.
F 3 CF 3 CNH 2NH 2+CHOCHO N
HH
NH
NN
HF 3 C F 3 CF 3 C F 3 CCF 3CF 3 NH
N NN
HCF 3CF 3CF 3CF 3NO 2NO 2 NO 2NO 2NO 2NN NF 3 C NF 3 CHH+ 100 % HNO 371
7273CF 3CF 3NO 2 NO 2NO 2 NO 2NN NF 3 C NF 3 C74HNO 3 ,
Ac 2 O
90 %
HNO 3 , P 2 O 57087 % -35 to -40 °C
42 %65 %Figure 6.17