Nitrolysis with

Further nitrolysis (with cleavage of bond A) forms a hypothetical compound (compound II) as follows ... 

Compound II now undergoes further nitrolysis (with cleavage of bond, B) to give another hypothetical material, Compound III, and a known material, Compound IV ... 

Inductive effects can have very pronounced effects on the reactivity of amides and similar substrates towards nitrolysis. Chemists at the Naval Air Warfare Center (NAWC) have reported an extreme case encountered during the synthesis of the energetic 1,5-diazocine known as HNFX (86). A key step in this synthesis involves a very difficult nitrolysis of the electron deficient N-nosyl (4-nitrobenzenesulfonyl) bonds of (85). Nitrolysis with strong mixed acid requires a temperature of 70 °C for 6 weeks to achieve a yield of 16 %. The same reaction with nitric acid-triflic acid requires a temperature of 55 °C for 40 hours to achieve a 65 % yield of HNFX. The same chemists reported a similar case of N-nosyl bond nitrolysis which needed a nitrating agent composed of nitric acid-triflic acid-antimony pentafluoride. ... 

Bachmann et al. [64] also described the conditions under which the substance (XII) (DPT) can be prepared in a yield of about 20% from hexamine and nitric acid, in the presence of acetic anhydride and acetic acid, at temperatures between 15 and 30°C. On nitrolysis with nitric acid in the presence of ammonium nitrate and acetic anhydride at 60-65°C, this substance gives octogen in 80% yield. 

Treatment of the stereoisomeric mixture of dioximes 87a with either NBS in aqueous dioxane or with MGPBA in a buffered medium led to the formation of a transannular bond to give 88 in 48 and 24% yields, respectively. Nitrolysis with 100% HNO3 of 87a led to the tetranitro derivative 89 in 25% yield. 

Scheme 2 An improved preparation of HNFX (1) p-nosyl N-protection during difluoram-ination plus nitrolysis with protonitronium ion...

Historical. MEDINA was first isolated as a degradation prod from the nitrolysis of hexa-mine (WWI1 work done at the Univ of Bristol, cited in Ref 5). It was prepd by the hydrolysis of PCX (qv) in boiling et ale and isolated as the Ba salt (Ref 4) and by the hydrolysis of N,N -DiacetylMEDINA with aq ammonia, yield 25% (Ref 5)... 

The term nitrolysis is usually applied to a nitrating mechanism in which both the rupture of the C-N bond and the formation of a nitramine occur simultaneously with the formation of an alcohol which subsequently undergoes esterification (1) ... 

Nitrolysis may also proceed without giving rise to alcohol in accordance with Eq (2), Nevertheless, a nitric ester is formed by the possible action of the N03— ion on a free alkyl cation ... 

RDX. Gilpin Winkler (Ref 38b) measured a heat of nitration of — 88.0kcal/mole of hexa-mine for the reaction of hexamine with 97.5% nitric acid. They also obtained a value of — 140kcal/mole of hexamine for the formation of RDX from hexamine and Bachmann reagents (acetic anhydride, acetic acid, ammonium nitrate and nitric acid). Incidentally, Gilpin Winkler interpret their results to mean that hexamine dinitrate is an intermediate in the direct nitrolysis of hexamine to give RDX, while hexamine mononitrate is an intermediate in the Bachmann process of producing RDX... 

Bell and Dunstan (Ref 16) have reported that the addition of me thy lene dinit ramine to Hexamine nitrolysis mixts, aged at 0° for 5 and 120 minutes, gave RDX in yields of 120 and 106%, respectively, compared with 52 and 83% in the absence of the dinitramine. However, rather than supporting a synthesis from small molecules, the authors contend that these results substantiate the existence of a postulated bis(nitroxymethyl) aminomethyl precursor of RDX, namely ... 

During the attempted nitrolysis of the triacetyl compound to the 1-acetyl-3,5-dinitro compound with 99% nitric acid in trifluoroacetic anhydride at 30°C, following a general procedure [1], a violent explosion occurred on the 1 g scale [2], This was ascribed to the formation of acetyl nitrate, expected to be formed under the reaction conditions [3,4], Caution with nitrolysis of any acetyl compound is urged [3],... 

The replacement of amine and amide hydrogen with a nitro group via direct nitration is an important route to A-nitro functionality. However, the cleavage of other bonds is also important. In the case of C-N bond cleavage the process is known as nitrolysis and is an invaluable route to many energetic materials (Section 5.6). The nitrolysis of hexamine and the syntheses of the important explosives HMX and RDX are discussed in Section 5.15. This area of chemistry could easily demand a separate chapter of its own and is the most complex and diverse in the field of nitramine chemistry. 

The scope of nitrolysis is huge, with examples of nitramine formation from the cleavage of tertiary amines, methylenediamines, carbamates, ureas, formamides, acetamides and other amides. The deflnition of nitrolysis must be extended to the nitrative cleavage of other nitrogen bonds because sulfonamides and nitrosamines are also important substrates for these reactions. The nitrative cleavage of silylamines and silylamides is also a form of nitrolysis (Section 5.7). 

The nitrolysis of A,A-disubstituted amides is one of the key tools for the synthesis of nitramine containing energetic materials. The present synthesis of the high performance explosive HMX is via the nitrolysis of hexamine (Section 5.15). This is an inefficient reaction requiring large amounts of expensive acetic anhydride. An alternative route to HMX (4) is via the nitrolysis of either l,3,5,7-tetraacetyl-l,3,5,7-tetraazacyclooctane (79) (79%) or 1,5-dinitro-3,7-diacetyl-l,3,5,7-tetraazacyclooctane (80) (98 %) with dinitrogen pentoxide in absolute nitric acid. These reactions are discussed in more detail in Section 5.15. 

Nitrolysis reactions employing l,3,5-trisubstituted-l,3,5-triazacyclohexanes have been explored as alternative routes to RDX. Some of the results are illustrated in Table 5.4 and show the difference in the efficiency of the three nitrolysis agents used, namely, absolute nitric acid, phosphorus pentoxide-nitric acid and trifluoroacetic anhydride-nitric acid. The acetamide derivative (81) (TRAT) undergoes incomplete nitrolysis on treatment with absolute nitric acid and trifluoroacetic anhydride-nitric acid to give a crude product containing some l-acetyl-3,5-dinitro-1,3,5-triazacyclohexane (TAX) (82) (Table 5.4, Entry 1) the latter can be preferentially formed in 93 % by suitably modifying the reaction conditions. Interestingly, the nitrolysis of... 

The high performance nitramine explosive known as CL-20 (5) has been synthesized via a two-stage nitrolysis starting from the key intermediate (83). The first stage uses dinitrogen tetroxide or nitrosonium tetrafluoroborate for nitrosolysis. The second step, involving nitrolysis of the acetamide and nitrosamine bonds, is achieved with nitronium tetrafluoroborate (>90 %) or mixed acid at 75 °C to 80 °C (93 %). The synthesis of CL-20 is discussed in more detail in Chapter 6. 

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... 

Nitrolysis of a fert-butyl group is also a key step in the synthesis of the high performance explosive known as TNAZ (6). The nitrolysis of the A-fert-butylazetidine (103) has been achieved with acetic anhydride-nitric acid " and acetic anhydride-ammonium nitrate." ... 

Methylenediamines are readily synthesized from the reaction of secondary amines with formaldehyde. Many aliphatic amines are too basic for direct nitration without a chloride catalyst, and even then, nitrosamine formation can be a problem. Their conversion into intermediate methylenediamines before nitration is therefore a useful route to secondary nitramines. The success of these nitrolysis reactions is attributed to the inherent low basicity of the methylene-diamine nitrogens. 

Chapman studied the nitrolysis of symmetrical methylenediamines. The nitrolysis of N, N, N, M-tetramethylmethylenediamine with nitric acid-acetic anhydride-ammonium nitrate mixtures gives both dimethylnitramine and RDX the latter probably arises from the nitroT ysis of hexamine formed from the reaction of ammonium nitrate and formaldehyde released from the hydrolysis of the methylenediamine. The same reaction with some morpholine-based methylenediamines (105) allows the synthesis of l,3,5-trinitro-l,3,5-triazacycloalkanes (106). 

The nitrolysis of (107) with nitric acid-trifluoroacetic anhydride yields 2,4,6-trinitro-2,4,6-triazaheptane (108). " ... 

---