Caged heterocycles – isowurtzitanes 2754,10-diethyl- and 4,10-diformyl- 2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitanes re-
spectively, (4) synthesis of TADBIW (83) (75 %) via the reductive debenzylation of HBIW
(82) with a mixture of palladium on carbon, acetic anhydride andN-acetoxysuccinimide in
ethylbenzene,28b28f(5) nitrolysis of the dinitrosamine (85) with nitronium tetrafluoroborate^25
(59 %) or absolute nitric acid28b(95 %) to yield 4,10-dinitro-2,6,8,12-tetraacetyl-2,4,6,8,10,12-
hexaazaisowurtzitane, followed by its nitrolysis to CL-20 (81) on treatment with mixed acid,28b
(6) nitration of 2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (84) (TAIW) to CL-20
(81) with mixed acid at 60◦C,28g(7) debenzylation of TADBIW (83) with ceric ammonium
nitrate (CAN) followed by nitration of the dinitrate salt of TAIW (84) with mixed acid,28h(8)
acetylation of TAIW (84) with acetic anhydride28b28hfollowed by nitrolysis of the resulting
2,4,6,8,10,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane with mixed acid,28h(9) oxidative
debenzylation–acetylation of HBIW (82) with potassium permanganate and acetic anhydride
followed by nitrosolysis and nitrolysis of the resulting TADBIW (83) to give CL-20 (81) in
fair yield.28iMany of these nitrolysis reactions may be achieved with dinitrogen pentoxide
in absolute nitric acid (Section 5.6). Agrawal and co-workers^29 synthesized CL-20 via the
original route specified by Nielsen and co-workers^25 and conducted a comprehensive study
into its characterization, thermal properties and impact sensitivity.
OOHN NHOOOONOO88 NO^2
(TEX)O 2 NNNOHHOHOCHOCHO
86+CHOCHO. 2HCl
87
H+ 1. H 2 SO 4- HNO 3
OHNFigure 6.224,10-Dinitro-4,10-diaza-2,6,8,12-tetraoxaisowurtzitane (TEX) (88) was synthesized by
Boyer and co-workers^30 from the condensation of 1,4-diformyl-2,3,5,6-tetrahydroxypiperazine
(86) with glyoxal trimer, followed byin situnitration of the resulting isowurtzitane dihydrochlo-
ride (87) by slow sequential addition of sulfuric acid followed by nitric acid. TEX (88) is less
energetic (VOD∼8665 m/s) thanβ-HMX but has a high crystal density (1.99 g/cm^3 ) and
has been suggested as an energetic additive in high performance propellants. At the time of
discovery of TEX, the US military was considering its use in insensitive munitions.
Strategies used for the synthesis of polyazapolycyclic-caged nitramines and nitrosamines
are the subject of an excellent review by A. T. Nielsen.^31 Nielsen identified three routes to such
compounds:25c
(1) ‘Proceeding from a preformed polyazapolycyclic caged structure which precisely incor-
porates the desired final heterocyclic ring.’ The syntheses of CL-20 (81) and TEX (88) are
examples.(2) ‘Proceeding from a precursor polyaza-caged structure, which may be different from the
desired product, but includes the final structure within the cage.’ Although not a caged
compound the synthesis of RDX from the nitrolysis of hexamine would fit this category.(3) ‘Cyclisation of a precursor polynitramine to produce the desired final cage structure.’