Nitrourea compounds

A fused heterocyclic compound (146) distantly related to the antiinflammatory agent cintazone (Chapter 12), which itself can be viewed as a cyclized derivative of phenylbutazone, retains the activity of the prototype, in the synthesis of 146, reaction of the nitroaniline 139 with phosgene gives intermediate 140, which is then reacted with ammonia to afford the substituted urea (141). Cyclization of the ortho nitrourea function by means of sodium hydroxide leads to the N-oxide (142) this last reaction represents... 

There are four important groups of A-nitro compounds which are relevant to energetic materials synthesis. These are primary nitramines, secondary nitramines, secondary nitramides (including A-nitroureas and A, A -dinitroureas) and nitrimines. The synthesis and incorporation of these A-nitro functionalities into organic compounds is the focus of this chapter. 

Synthesis of nitramines, nitramides and nitroureas via the nitrodesilylation of A/-trimethyisilyl compounds with dinitrogen pentoxide (ref. 122)... 

Davis studied the dehydration of urea nitrates as a route to iV-nitroureas. The nitrate salt of iV-methylurea undergoes dehydration-rearrangement on treatment with concentrated sulfuric acid to give Af-nitro-A -methylurea in 42 % yield. In this compound the nitro and methyl groups are attached to the same nitrogen and so its hydrolysis can provide a route to methylnitramine. In contrast, the nitrate salts of ethyl, n-propyl, n-butyl and n-amyl ureas, give iV-nitro-A -ethylurea (49 %), A -nitro-A -propylurea (60 %), iV-nitro-iV -butylurea (67 %) and iV-nitro-A -amylurea (67 %), respectively, on treatment with concentrated sulfuric acid. 

Unconventional gas-generation reactions have been reported by Ashida (33). The blowing agents used include the following compounds (a) enolizable compounds such as nitroalkanes (nitroethane, nitropropane) aldoximes (acetaldoximes), nitrourea, acid amides (formamide, acetamide), active methylene-containing compounds, (acetylactone, ethyl acetoacetate), and (b) boric acid. The mechanisms of their gas-generation reactions are also discussed (33). 

Our interest in azaheterocyclic nitramineureas arise from the fact that the urea moiety has an inherent high molecular density and these compounds are considered as high explosives which can be made conveniently from inexpensive raw materials. Among the investigated compounds tetranitropropanediureas appear to be of renewed interest with a unique combination of properties like thermal stabihty as well as impact and friction sensitivity. Inspite of the abundance of early literature on nitroureas " details of the experimental procedure, the characterization and their applications are not found until more recent reports ... 

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