Organic Chemistry of Explosives

234 Synthetic Routes toN-Nitro

Secondary nitramines have been prepared from the metathesis of dialkylcarbamyl chlorides

with silver nitrate in acetonitrile followed by the spontaneous decomposition of the resulting

dialkylcarbamyl nitrates.^149 Yields of nitramine are low and accompanied by nitrosamine

impurities.

Primary nitramines have been formed from the reaction of aliphatic isocyanates with nitro-

nium tetrafluoroborate in ethyl acetate or acetonitrile, followed by hydrolysis.^150

Metathesis reactions betweenN-chloramines and silver nitrite in alkaline solution are re-

ported to give the silver salt of the corresponding primary nitramine. The method is of little

synthetic value.^151

Nitramines have been prepared from the reaction of N-chloramines with dinitrogen

tetroxide.^152

The reaction of substituted diazomethanes with ethylN-nitrocarbamate, followed by hy-

drolysis of the ethylN-alkyl-N-nitrocarbamate, has been used to prepare some primary

arylnitramines where aromatic ring nitration is not required, and so limits the use of con-

ventionalN-nitrating agents.^153 The method has not been fully investigated.

The rearrangement of imidoyl nitrates yields nitramides via an O→N migration. (^154) This
reaction is instantaneous when imidoyl chlorides are treated with silver nitrate in acetonitrile.

5.13 Primary nitramines as nucleophiles

Primary nitramines contain an acidic proton which enables them to behave as nucleophiles

and undergo addition and condensation reactions. These reactions are extremely useful in

two respects. Firstly, these reactions convert primary nitramino functionality into secondary

nitramino functionality, which is no longer acidic and much more chemically stable. Secondly,

these addition and condensation reactions can be used to prepare functionalized derivatives

of polynitramines which can be used to synthesize energetic polymers and other explosive

compounds.

5.13.1 1,4-Michael addition reactions

X = activating group like

CO 2 R, CN, CONH 2 , COR etc.

Base catalyst

N

XR

NO 2

RNHNO 2 + X (Eq. 5.18)

Figure 5.77

The anions of primary nitramines, like other nucleophiles, can undergo Michael 1,4-addition

reactions with a range ofα,β-unsaturated substrates to form secondary nitramines of varying

molecular complexity (Equation 5.18). Kissinger and Schwartz^155 prepared a number of sec-

ondary nitramines from the condensation of primary nitramines withα,β-unsaturated ketones,

esters, amides and cyanides. In a standard experiment a solution of the primary nitramine and