Organic Chemistry of Explosives

274 Nitramines and Their Derivatives

NN

N

NN

BnBn

BnBn

Bn Bn

CHO

CHO

+^3

82

(HBIW)

CH 3 CN (aq),

HCOOH, 25 °C

75–80 %

H 2 , Pd/C,

Ac 2 O, PhBr

60–65 %

6 BnNH 2

N

NN

N

NN

AcAc

AcAc

Bn Bn

83

(TADBIW)

N

Figure 6.20

The synthesis of energetic materials containing strained or caged structures frequently

requires many synthetic steps which can offset the gain in explosive performance. Nielsen

and co-workers^27 have shown that this is not always the case in finding that 2,4,6,8,10,12-

hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane (HBIW) (82) can be synthesized in high yield,

and in one step, from the reaction of benzylamine and glyoxal in aqueous acetonitrile in

the presence of catalytic amounts of formic acid. Reductive acetylation of HBIW (82) with

palladium hydroxide on carbon in acetic anhydride in the presence of catalytic bromobenzene

yields the tetraacetate (83) (TADBIW). Treatment of TADBIW (83) with 3 mole equivalents

of nitrosonium tetrafluoroborate in sulfolane, followed by 12 mole equivalents of nitronium

tetrafluoroborate in the same pot, gives CL-20 (81) in 90 % yield.

1. NOBF 4 (3 eq)


2. NO 2 BF 4 (12 eq),
   90 % (2 steps)

AcOH,

NaNO 2

95 %

Pd(OAc) 2

H 2 , AcOH

73 %

99 % HNO 3

96 % H 2 SO 4

N 2 O 4 (excess)

92 %

or

NOBF 4 , 55 %

93 %

NN

NN

Ac Ac

Ac

HN

Ac

NH

84

(TAIW)

NN

N

NN

Ac Ac

Ac

Bn

Ac

Bn

83

(TADBIW)

N

NN

N

NN

O 2 N

O 2 N

O 2 N

NO 2

NO 2

NO 2

81

(CL-20)

N

NN

N

NN

Ac Ac

Ac

ON

Ac

NO

85

N

sulfolane

Figure 6.21

While the route described above is highly convenient for the synthesis of CL-20 on a

laboratory scale, the availability of nitronium tetrafluoroborate makes further research and de-

velopment essential.^28 Further studies have shown that the dinitrosamine (85) can be obtained

in high yield from the reaction of TADBIW (83) with excess dinitrogen tetroxide,^25 ,28aor from

its reductive debenzylation with hydrogen and palladium acetate in acetic acid followed by

nitrosation with sodium nitrite in acetic acid.28bThe dinitrosamine (85) is readily converted

to CL-20 (81) in high yield on reaction with mixed acid at 75–80◦C.28aSeveral other stud-

ies and modifications to the original route have been reported including: (1) the synthesis of

HBIW (82) from benzylamine and glyoxal in the presence of mineral acid,28c(2) reductive

debenzylation of HBIW (82) under a variety of conditions,28d(3) hydrogenation of TADBIW

(83) in acetic anhydride-acetic acid28dand formic acid28ewith a palladium catalyst to yield