Organic Chemistry of Explosives

224 Synthetic Routes toN-Nitro

bond has been reported in the form of HMPA, which forms dimethylnitramine on reaction with

nitric acid. Some nitrosamine impurity is formed during the reaction.^120

The use of silicon in the form of silylamines is more amenable for synthetic use. Olah and

co-workers^121 have reported on the cleavage ofN-silyl compounds with nitronium tetrafluorob-

orate. Dimethylnitramine, diethylnitramine,N, N′-dinitropiperazine andN-nitromorpholine

have been prepared via this route, which is known as nitrodesilylation. Also reported are the

syntheses ofN-nitrotriazoles from the nitrodesilyation of the correspondingN-trimethylsilyl

derivatives with nitronium salts. This is a useful route to such compounds, acidic reagents

leading to the facile N→C migration of the nitro group.^121

Millar and Philbin^122 have explored the nitrodesilylation of silylamines with dinitrogen pen-

toxide for the synthesis of nitramines and their derivatives. These reactions, which involve nitra-

tive Si–N heteroatom cleavage, are conducted in methylene chloride at subambient temperature.

Trimethylsilylamines give high yields of nitramine product and reactions are clean (Table 5.8).

H 3 C

N

H 3 C

Si(CH 3 ) 3 (126)

H 3 C

N

H 3 C

i-Bu

i-Bu

N Si(CH 3 ) 3 (127)

i-Bu

i-Bu

N

NO 2 (100)

NO 2 (128)

NO 2 (130)

NO 2

N

NN

N

NN

(CH 3 ) 3 Si N Si(CH 3 ) 3 (129) O 2 N N N

O 2 N

O 2 N

(CH 3 ) 3 Si Si(CH 3 ) 3

NN

H 3 C N

O

Si(CH 3 ) 3

CH 3

H 3 C

O

NO 2

CH 3

O

(CH 3 ) 3 Si Si(CH 3 ) 3

NN

O

NO 2

R'

N

R

Si

R''

R''

R''

R'

N

R

NO 2

Table 5.8

Synthesis of nitramines, nitramides and nitroureas via the nitrodesilylation of

N-trimethylsilyl compounds with dinitrogen pentoxide (ref. 122)

1 2 3 4 5 6

78

87

91

69

79

82

(131) (117)

(132) (133)

(134) (135)

R'' 3 SiONO 2

+

N 2 O 5 , CH 2 Cl 2

Entry Substrate Product Yield (%)