Caged heterocycles – isowurtzitanes 273The energetic tetranitramine (74) is prepared from the sequentialN-nitration of the bicy-
cle (71); the latter prepared from the acid-catalyzed condensation of 2,2-diaminohexafluoro-
propane (70) with glyoxal.^18 The crystal density of (74) (2.18 g/cm^3 ) is one of the high-
est reported for an explosive containing an organic skeleton. Accordingly, its performance is
expected to be high.
NNNN77- HCl (aq),
NaNO 2
30 % N 2 O 5 in HNO 3NNNN78NNNN80NNNN79HH HO 2 NO 2 NO 2 NO 2 NO 2 N O 2 NO 2 N
O 2 NO 2 NO 2 NNO 2NO 2NO 2
NO 2 NO 2NO 2 NO 2NO 2NO 2NO 2NNNNNOON
HHNOONCH 2 NH 2CH 2 NH 2CHOCHO1.75NNNNHH76HFigure 6.18Trans-1,4,5,8-Tetranitro-1,4,5,8-tetrazadecalin (76) (TNAD) has been synthesized from the
condensation of ethylenediamine with glyoxal, followed byin situnitrosation of the resulting
trans-1,4,5,8-tetraazadecalin and treatment with a 30 % solution of dinitrogen pentoxide in
absolute nitric acid.^22 ,^23 TNAD has been classified an insensitive high explosive (IHE) and ex-
hibits similar performance to RDX. Willer and Atkins^23 ,^24 used the same strategy to synthesize
the cyclic nitramine explosives (77), (78), (79), and (80).
6.7 Caged heterocycles – isowurtzitanes
NNNNNO 2 N
O 2 NO 2 NNO 2NO 2NO 281
(CL-20)NFigure 6.192,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW) (81), known as CL-
20, was first synthesized by Nielsen and co-workers^25 at the Naval Air Warfare Center (NAWC)
and is currently the most powerful nonnuclear explosive (VOD∼9380 m/s,Hf=+ 410
kJ/mol) being synthesised on a pilot plant scale.^26 The compact caged structure of the isowurtz-
itane skeleton is reflected in the high crystal density (2.04 g/cm^3 ) of CL-20. CL-20 is now
finding application in high performance propellants and its use is expected to result in major
technological advances in future weapon systems.