Preparation nitramines

Another method of preparing nitramines Is exemplified as follows ... 

Wright et al. [40] elaborated a new method of preparing nitramines by acting on chloramines with nitric acid in the presence of acetic anhydride. A typical example is the preparation of sec-butylnitramine (III) (Smart and Wright Suggitt, Myers and Wright [40]) from dichloramine (I) ... 

Czuba has studied 3-nitramines in some detail. " Nitramines of the four chloro-3-aminopyridines, 3-amino-5-ethoxypyridine, 5-aminonicotinic acid, 5-aminopicolinic acid, 3-amino- and 5-amino-2-pyridinesulfonic acids, 3-amino-4-picoline and 5-amino-3-picoline have been prepared. Attempts to prepare nitramines from the four 3-aminopyridinols were unsuccessful. However, 3-amino-5-ethoxypyridineforms the nitramine that reacts in sulfuric acid to give 5-ethoxy-3-pyridinol. ... 

Nitramine, picrylmethylnitramine, 2,4,6-trinitrophenylmethyl nitramine (indicator) dissolve 0.1 g in 60 mL alcohol and dilute with water to 100 mL pH range colorless 10.8-13.0 red-brown the solution should be kept in the dark as nitramine is unstable on boiling with alkali it decomposes quickly. Fresh solutions should be prepared every few months. 

A rather simple derivative of imidazoimidazoline has been described as an antidepressant agent. Preparation of this compound starts with the displacement of the nitramine grouping in imidazoline derivative by phenyl ethanol amine The product of this reaction is then treated with thio-nyl chloride. The probable chloro intermediate ( ) cyclizes under the reaction conditions to afford imafen (5. ... 

Before proceeding to describe the manufacture of the nitramines, RDX and Tetryl, a few general remarks about the preparation of nitramines... 

Scholl et al (Refs 3 4) prepared the same compds by treating ketoximes (such as pina-colone) with nitrogen tetroxide, but he assigned them the structure R2C=N-N02 and called them nitrimines. One of the compds described by him in Ref 4, p 27 is a weak expl. It is the Ag salt of pinacolone-nitraminic acid which puffs off on rapid heating (this compd described below under List of Nitrimines ). Further work on... 

This synthesis of N-nitromorpholine is representative of a rather general reaction for the preparation of both primary and secondary nitramines.3 It represents the simplest process for obtaining both types of compounds. The reaction is unique in that a nitration is carried out under neutral or alkaline conditions. Acetone cyanohydrin nitrate may also be used for the nitration of many active methylene compounds.8... 

Complexes of the explosively unstable nitramine ligands iV-nitromethylamine (HL), N. /V -dinitrodiaminocthanc (H2L ), and 5-nitraminotetrazole (H2L") with am mine derivatives of divalent copper, nickel or palladium explode on heating or under a hammer blow. Compounds prepared were ... 

A number of secondary high explosives containing both nitramine and nitrate ester functionality have been reported. Aliphatic examples include A-nitrodiethanolamine dinitrate (DINA) (110), prepared from the nitration of diethanolamine with nitric acid-acetic anhydride in the presence of zinc chloride,and A,A -dinitro-A,A -bis(2-hydroxyethyl)oxamide dinitrate (NENO) (111), prepared from the mixed acid nitration of A,lV -bis(2-hydroxyethyl) oxamide . 

A number of nitramine-nitrate explosives have been prepared by Millar and co-workers from the action of dinitrogen pentoxide on aziridines and azetidines (Section 5.8). Millar and co-workers used their aziridine ring-opening nitration methodology (Section 5.8.1) to synthesize the high performance melt-castable nitramine-nitrate explosive known as Tris-X... 

Agrawal and co-workers prepared some energetic explosives containing nitrate ester, nitramine and aromatic C-nitro functionality within the same molecule and studied their thermal and explosive properties l-(2-nitroxyethylnitramino)-2,4,6-trinitrobenzene... 

Emmons and co-workers prepared a series of aliphatic secondary nitramines by treating amines with a solution of dinitrogen pentoxide in carbon tetrachloride at —30 C (Equation 5.9). The amine component needs to be in excess of two equivalents relative to the dinitrogen pentoxide if high yields of nitramine are to be attained. This is wasteful because at least half the amine remains unreacted. However, yields are high and there is no reason why the amine cannot be recovered as the nitrate salt. The method is particularly useful for the nitration of hindered secondary amines substrates such as those with branching on the a carbon. 

The efficient At-nitration of secondary amines has been achieved by transfer nitration with 4-chloro-5-methoxy-2-nitropyridazin-3-one, a reagent prepared from the nitration of the parent 4-chloro-5-methoxypyridazin-3-one with copper nitrate trihydrate in acetic anhydride. Reactions have been conducted in methylene chloride, ethyl acetate, acetonitrile and diethyl ether where yields of secondary nitramine are generally high. Homopiperazine is selectively nitrated to At-nitrohomopiperazine or At, At -dinitrohomopiperazine depending on the reaction stoichiometry. At-Nitration of primary amines or aromatic secondary amines is not achievable with this reagent. 

The role of dialkylchloramines as intermediates in the chloride-catalyzed nitration of secondary amines is discussed in Section 5.3.1. Wright and co-workers" studied this reaction further and prepared a number of dialkylchloramines by treating secondary amines with aqueous hypochlorous acid (Equation 5.12). Treatment of these dialkylchloramines with nitric acid in acetic anhydride forms the corresponding secondary nitramine, a result consistent with the chloride-catalyzed nitration of amines." ... 

Although a large number of secondary nitramides have been prepared they have not found wide use as explosives because of their facile hydrolysis to acidic primary nitramines in the presence of water. Research has focused on the synthesis of cyclic and bicyclic A-nitroureas and A, A -dinitroureas because of their high performance. 

Secondary nitramines are conveniently prepared from the nitrolysis of A, A-dialkylamides with nitronium salts in acetonitrile or ethyl acetate at 20 °C where the acyl group is converted into an acylium tetrafluoroborate (Equation 5.14). Problems can occur if commercial nitronium salts like the tetrafluoroborate are used without purification. The presence of nitrosonium salts can then lead to nitrosamines via nitrosolysis. Yields of secondary nitramine up to 90 % have been reported with solutions of nitronium tetrafluoroborate in acetonitrile di-n-butylnitramine is obtained in 82 % yield from the nitrolysis of corresponding acetamide. ... 

Adolph and Cichra prepared a number of cyclic nitramines from the nitrolysis of tert-butyl protected Mannich products (Table 5.5). Nitrolysis of the fert-butyl groups was achieved with mixed acid, pure nitric acid or a mixture of nitric acid in acetic anhydride depending on the substrate. Pure nitric acid was found to affect the nitrolysis of both the ferr-butyl groups of (97), (Table 5.5, Entry 4) whereas the use of mixed acid led to the isolation of the product where only one of the ferf-butyl groups had undergone nitrolysis. Some of the cyclic nitramine products... 

In some related work, Lear and co-workers prepared the powerful cyclic nitramine explosive Keto-RDX (102) from the nitrolysis-nitration of2-oxa-5-tert-butyltriazone(101). Pagoria and co-workers " conducted a full study on the effect of different nitrating agents on the yield of Keto-RDX (Table 5.6). 

In view of the highly carcinogenic nature of many nitrosamines any experiments involving their isolation must be discouraged, and for this reason, this section has only been written for completeness. This high toxicity is unfortunate because the preparation of nitrosamines from the parent amines is often facile and they provide a route to highly pure nitramines. Other equally useful methods for the synthesis of nitramines, such as the chloride-catalyzed nitration of secondary amines, also suffer from the formation of nitrosamines in appreciable amounts and must also be viewed with caution. 

The instability of primary nitramines in acidic solution means that the nitration of the parent amine with nitric acid or its mixtures is not a feasible route to these compounds. The hydrolysis of secondary nitramides is probably the single most important route to primary nitramines. Accordingly, primary nitramines are often prepared by an indirect four step route (1) acylation of a primary amine to an amide, (2) A-nitration to a secondary nitramide, (3) hydrolysis or ammonolysis with aqueous base and (4) subsequent acidification to release the free nitramine (Equation 5.17). Substrates used in these reactions include sulfonamides, carbamates (urethanes), ureas and carboxylic acid amides like acetamides and formamides etc. The nitration of amides and related compounds has been discussed in Section 5.5. 

Nitramine (161), the simplest member of the nitramines, can be prepared from ethyl carbamate (158) in three synthetic steps nitration of the latter with mixed acid or a solution of ethyl nitrate in concentrated sulfuric acid, followed by isolation of the resulting ethyl N-nitrocarbamate as the ammonium salt (159), hydrolysis with aqueous potassium hydroxide and subsequent acidification, yields nitramine (161). ... 

The dehydration of the nitrate salts of some primary and secondary amines can yield the corresponding nitramine. Dimethylnitramine has been prepared in 65 % yield from the dehydration of dimethylamine nitrate in acetic anhydride to which 4 mole % of anhydrous zinc chloride has been added." The same reaction in the absence of chloride ion only generates a 5 % yield of dimethylnitramine." Some arylnitramines derived from weakly basic amines have been prepared via the addition of the amine nitrate salts to acetic anhydride. " ... 

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.Yields of nitramine are low and accompanied by nitrosamine impurities. 

Nitramines have been prepared from the reaction of Ai-chloramines with dinitrogen tetroxide. ... 

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. 

The anions of primary nitramines, like other nucleophiles, can undergo Michael 1,4-addition reactions with a range of a,-unsaturated substrates to form secondary nitramines of varying molecular complexity (Equation 5.18). Kissinger and Schwartz prepared a number of secondary nitramines from the condensation of primary nitramines with a,/3-unsaturated ketones, esters, amides and cyanides. In a standard experiment a solution of the primary nitramine and... 

The condensation of a primary nitramine with formaldehyde in the presence of concentrated sulfuric acid is a useful route to 1,3-dinitramines. A number of linear dinitramines have been prepared via this route including 2,4-dinitro-2,4-diazapentane (212), 3,5-dinitro-3,5-diazaheptane (213), and 5,7-dinitro-5,7-diazaundecane (214). ... 

The alkylation of primary nitramines with alkyl halides is of little preparative value for the synthesis of secondary nitramines. Such reactions often result in a mixture of N- and 0-alkylated products. The product distribution appears to be very dependent on the nature of the cation of the nitramine used, with silver salts ° favouring 0-alkylation and alkali metal salts usually giving A-alkylation as the predominant product. However, this is not always the case. 

Other aromatic nitramines have not found use as practical explosives. Ethyltetryl (232) is prepared from the nitration of 2,4-dinitro-A-ethylaniline, A,A-diethylaniline or N-ethylaniline. Butyltetryl (233) can be synthesized from the nitration of 2,4-dinitro-A-butylaniline, which is attainable from the reaction of n-butylamine with 2,4-dinitrochlorobenzene. 

The aromatic nitramine (234) can be prepared by nitratingA, A -diphenylethylenediamine ° or 2,2, 4,4 -tetranitro-A,A -diphenylethylenediamine with mixed acid, the latter synthesized from 2,4-dinitrochlorobenzene. The azoxy-nitramine (235) is prepared by nitrating 4,4 -bis(dimethylamino)azoxybenzene with mixed acid. ... 

Eaton and co-workers ° synthesized the cubane-based dinitrourea (42) via iV-nitration of the cyclic urea (41) with nitric acid-acetic anhydride. Cubane-based nitramide (43) is prepared from the IV-nitration of the corresponding bis-amide with acetic anhydride-nitric acid. Bis-nitramine (44) is prepared from the IV-nitration of the corresponding diamine with TFAA-nitric acid. ... 

The Mannich reaction has been used to synthesize numerous heterocyclic nitramine explosives. Adolph and Cichra prepared a number of A-heterocycles containing ferf-butyl A-blocking groups. The nitrolysis of these f-butyl groups provides the corresponding A-nitro derivatives in excellent yields (Section 5.6.2.2). Some of the nitramine products from these reactions are powerful, energetic explosives with attractive properties. 

Chinese chemists" reported the base hydrolysis of TNGU. The product, 1,1,2,2-tetranitraminoethane, has been used to prepare a series of heterocyclic nitramines via condensation reactions and may find future use for the synthesis of heterocyclic caged nitramines. 

Nitramine-nitrates of general structure (133) are known as NENAs and are conveniently prepared from the nitrative cleavage of A-alkylaziridines " with dinitrogen pentoxide or from the direct nitration of the corresponding aminoalcohols. These compounds find use as energetic plastisizers in explosive and propellant formulations Bu-NENA (R = n-Bu) is a component of some LOVA (low vulnerability ammunition) propellants. ... 

Alkyl lV,lV-dinitramines (154) have been prepared from the reaction of the tetraalkylam-monium salts (155) of primary nitramines with nitryl fluoride in acetonitrile at subambient temperature. The same reaction with the primary nitramine or its alkali metal salts yields the corresponding nitrate ester. Treatment of the ammonium, potassium, or lithium salts of primary nitramines (156) with a solution of nitronium tetrafluoroborate in acetonitrile at subambient temperature yield alkyl iV,iV-dinitramines. ° The same reactions in ether or ester solvents enables the free nitramine to be used. The nitrolysis of A-alkylnitramides (157) and N,N-diacylamines with nitronium tetrafluoroborate in acetonitrile, and the nitration of aliphatic isocyanates with nitronium tetrafluoroborate and nitric acid in acetonitrile, also yield alkyl A,A-dinitramines (154). 

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