An environmentally-friendly route to nitramines and nitrate esters via nitrodesilylation chemistry using dinitrogen pentoxide

Nitramines and nitrate esters are synthesised conventionally using strongly acidic nitration media such as sulphuric-nitric acid mixtures, and the resulting spent liquors from these nitrations are difficult to dispose of without damage to the environment. The novel method described here dispenses with the need for
strong acids as the reaction medium and instead uses dinitrogen pentoxide (N20 5) in an inert solvent as the nitrating agent. The N20 5 cleaves heteroatom-silicon bonds, in silylamines and silyl ethers respectively, to yield the desired energetic groupings (nitramines or nitrate esters respectively) without liberation of acids which would occur with conventional substrates (amines or alcohols). These nitrodesilylation reactions proceed cleanly and in good yield, and furthermore them co-product, a silyl nitrate, can be used to effect further nitrations, hence eliminating the need for disposal. The scope of the reaction will be illustrated by 25 examples, some of which produce high energy compounds, notably plasticisers and an energetic polymer precursor, whilst in others novel energetic functions such as N-nitroaziridines
can be accessed directly for the first time. When taken in conjunction with the current advances in N20 5 chemistry in other fields, which have made this reagent available on large scale at reasonable cost, the use of clean routes to energetic materials such as those described here constitutes a powerful reason for changing the methods of manufacture of energetic materials in the next century