Four-membered ring-containing spirocycles: synthetic strategies and opportunities.

3.1. Carbon−Nitrogen Bond Formation 14 3.1.

Cerium(IV) ammonium nitrate--a versatile single-electron oxidant.

Recent trends in high-energy materials

Some New High Energy Materials and their Formulations for Specialized Applications

A highly regioselective Lewis acid-mediated S(N)2-type ring-opening of N-sulfonylaziridines and azetidines with tetraalkylammonium halides in CH(2)Cl(2) solution to afford 1,2- and 1,3-haloamines in excellent yields is described. An easy diastereoselective route toward substituted chiral N-tosylaziridines has been developed. The mechanism of ring-opening via S(N)2 pathway has been confirmed by the formation of chiral haloamines with excellent er and dr. Chloroamines obtained from 2,3-disubstituted aziridines were converted to the chiral N-tosylamines via radical dehalogenation.

BF3 x OEt2-mediated highly regioselective S(N)2-type ring-opening of N-activated aziridines and N-activated azetidines by tetraalkylammonium halides.

Clean nitrations: Novel syntheses of nitramines and nitrate esters by nitrodesilylation reactions using dinitrogen pentoxide (N2O5)

Nitration by oxides of nitrogen, part 1: preparation of nitrate esters by reaction of strained-ring oxygen heterocycles with dinitrogen pentoxide

The harsh and unselective nature of conventional nitrating agents, based on nitricsulphuric acid mixtures or pure nitric acid, has led to the development of new nitration methodologies based on dinitrogen pentoxide (N 2 O 5 ) that overcome many of the draw backs of conventional media, especially when dealing with sensitive substrates. Two principal nitration system s have been developed : (i) N 2 O 5 in pure nitric acid, and (ii) N 2 O 5 in organic solvents, mainly chlorinated hydrocarbons. The former system possesses strength similar to mixed acid (HNO 3 - H 2 SO 4 ) system s and is therefore potent, but displays advantages such as ease of generation of the nitration reagent by electrolysis and com patibility with nitram ine products, facilitating the synthesis of nitram ine explosives as well as certain aromatic nitro compounds. The second system (N 2 O 5 /organic solvent) encompasses a much wider range of nitrations, and with suitable choice of substrate permits the generation of polynitrated species directly without the formation of acidic by-products, an important environmental consideration. These conditions are also compatible with sensitive substrates, particularly those possessing strained-ring heterocyclic skeletons; thus the nitration of such compounds with N2O5 perm its precursors for energetic polymers (e.g. polyNIMMO) to be prepared by selective nitration. Likewise, nitrated derivatives of suitably functionalized elastomeric pre-polymers (e.g. NHTPB ) can also be manufactured; both of the latter category of compound find important application as energetic binders for novel explosive and propellant compositions, notably low-vulnerability (LOVA) propellant charges.

R. W. Millar

Papers

Clean nitrations: Novel syntheses of nitramines and nitrate esters by nitrodesilylation reactions using dinitrogen pentoxide (N2O5)

Nitration by oxides of nitrogen, part 1: preparation of nitrate esters by reaction of strained-ring oxygen heterocycles with dinitrogen pentoxide

New synthesis routes for energetic materials using dinitrogen pentoxide. Discussion

Preparation of di- and polynitrates by ring-opening nitration of oxetanes by dinitrogen pentoxide (N2O5)

Preparation of nitramine-nitrates by ring-opening nitration of azetidines by dinitrogen pentoxide (N2O5)