GB2355715A - Synthesis of Diamino- or triamino- 2,4,6- trinitrobenzene - Google Patents

Abstract

A method for preparing a tri or diaminated 2,4,6-trinitrobenzene comprising the steps of: <SL> <LI>(i) deriving a tri or di hydroxy-substituted 2,4,6-trinitrobenzene from a tri or di hydroxy-substituted benzene precursor by nitration; <LI>(ii) deriving a tri or di alkoxy-substituted 2,4,6-trinitrobenzene from a tri or di hydroxy-substituted 2,4,6-trinitrobenzene precursor by alkylation; and <LI>(iii) deriving a tri or di amino-substituted 2,4,6-trinitrobenzene from a tri or di alkoxy-substituted 2,4,6-trinitrobenzene precursor by amination, </SL> wherein, for each step, the tri substituted precursor generates the tri substituted derivative and the di substituted precursor generates the di substituted derivative.

Description

2355715 SYNTHESIS OF TATB AND DATB This invention relates to the synthesis

of TATB (1,3,5- triamino-2,4,6-trinitrobenzene) and diamino-2,4,6trinitrobenzenes, in particular 1,3-diamino-2,4,6 trinitrobenzene (DATB).

TATB and DATB are currently used as speciality explosives the commercial value of which arises from their high thermal and shock resistance. Of the two explosives, TATB is preferred as it is less sensitive to shock than DATB. TATB is also important as a starting reagent for the synthesis of benzene hexamine, a compound that is used in the synthesis of various liquid crystalline and ferromagnetic materials.

Early prior art manufacturing methods of DATB as disclosed in US 3,278, 604 and US 3,394,183 involve the reaction of 1,3dimethoxybenzene with nitrating agents to produce 1,3dimethoxy-2,4,6-trinitrobenzene, which is then reacted with a aminating agent to form DATB. Both of these routes use aggressive, harsh nitrating agents at elevated temperatures to achieve effective nitration.

The current manufacturing route to TATB - as disclosed in US 4,032,377 (Method for the Production of High Puri ty Tri amino trini trobenzene) involves a two step synthetic process starting from 1,3,5-trichlorobenzene (TCB). TCB is first nitrated using a mixture of oleum and sodium nitrate at OC to form 1,3,5-trichloro-2,4,6-trinitrobenzene which in turn is subsequently aminated using ammonia in toluene at 150 0C.

There are evident disadvantages with thismanufacturing route. The process is reliant upon extreme reaction conditions which necessitate high temperatures over 2 relatively long periods of time. Environmental concerns have arisen over the release and use of halo-aromatic compounds in the manufacture and the subsequent disposal of these compounds. Halo-aromatics, and other halogen containing compounds, are suspected of being hazardous to the environment. As such they must be suitably disposed of by the manufacturer to prevent pollution, which in turn, has a knock-on effect in terms of cost of manufacture.

The manufacturing route is reliant upon halogenated precursors - haloaromatics being involved as starting reagent and intermediate. In the event of a 100 per cent conversion this would pose no problem, but in the event of incomplete conversion the halogen containing side products must either be recycled or suitably disposed of to prevent contamination.

A disadvantage of this prior art manufacturing route is that it does not readily facilitate the recycling of intermediates. In the first step of the process there is an 11 per cent wastage in terms of under-nitrated products, and although these side products have no deleterious effect on the purity of the final product, they must subsequently be suitably disposed of to avoid environmental contamination.

Yet a further disadvantage of this prior art manufacturing route is that disposal of ammonium chloride, which is a side product of the manufacturing route, poses a problem.

The difficulties of the current manufacturing route have therefore given rise to renewed interest intoalternative means of manufacture of TATB and DATB. The first alternative synthesis to the established prior art was disclosed by Ott and Benziger in US 4,952,733. This synthetic route involves the preparation of 1,3,5-triamino-2,4,6-trinitrobenzene from 3 3,5-dichloroanisole. The reaction sequence consists of a two step process involving nitration followed by amination.

The advantage of the route proposed by Ott and Benziger is that the nitration step only produces the one trinitrated product. This, therefore, circumvents the problem of disposal of halogen containing under nitrated waste which is present in the current manufacturing route.

A disadvantage of the route of Ott and Benziger, however, is that although the reaction conditions are milder than the current manufacturing route, and the reaction times are significantly reduced, the methodology still uses strong acid conditions at relatively high temperature for the nitration step. Furthermore, ammonium chloride is generated in the second step of the reaction sequence, thereby requiring suitable disposal of the waste liquor.

A new synthetic methodology has been disclosed by Mitchell et al. in WO 96/35659. This methodology involves the synthesis of TATB or DATB using the aminating reagents 1,1,1 trialky1hydrazinium. halide (TAHH) - in particular, 1,1,1 trimethy1hydrazinium iodide (TMHI) and 1,1,1 triethylhydrazinium chloride (TEHC), or 4-amino-1,2,4- triazole (ATA).

Mitchell et al. disclose that through using TAHH as the aminating reagent, TATB can be synthesised from trinitrobenzene and 2,4,6-trinitroaniline (picramide) at ambient conditions and in high yield. They further disclose that through using ATA as the aminating reagent, TATB can be synthesised from picramide as well as trinitrobenzene and 1,3-diamino-2,4,6trinitrobenzene.

4 The methodology adopted by Mitchell et al. has the convenience of consisting of a single step and it also circumvents the use of haloaromatic compounds as either intermediates or as starting material (although halogen 5 containing compounds are used within the aminating reagents). The methodology also avoids the extreme reaction conditions of the prior art, the reaction being conducted at ambient temperature and pressure.

A disadvantage of the route proposed by Mitchell et al. is that, although the precursors are halogen free, one of the reagents used to bring about the amination - namely, TAHH is halogen containing. Although this reagent can to a certain extent be recycled, spent reagent requires disposal thereby defeating the original purpose of halogen avoidance in the precursors.

A further disadvantage of this route is that ATA and TAHH are expensive specialist materials. Indeed the expense of these materials may have the effect of off-setting the commercial advantage to be gained from circumventing the costs involved from using high temperature. TA.HH may be synthesised prior to amination but this thereby turns a single step synthesis into a two step reaction.

There is, therefore, a need to develop an alternative halogen free route to TATB and DATB which circumvents the use of strong acids at high temperature. Such a reaction route would be more mild and benign in terms of reaction conditions, would not require costly disposal measures, and would render, in good yield, a high quality final product.

Accordingly, a method is provided for preparing a tri or diaminated trinitrobenzene comprising the sequential steps of:

(i) deriving a tri or di hydroxy- substituted 2,4,6 trinitrobenzene from a tri or di hydroxy-substituted benzene precursor by nitration; (ii) deriving a tri or di alkoxy-substituted 2,4,6 trinitrobenzene from a tri or di hydroxy-substituted 2,4,6-trinitrobenzene precursor by alkylation; and (iii) deriving a tri or di amino- substituted 2,4,6 trinitrobenzene from a tri or di alkoxy-substituted 2,4,6-trinitrobenzene precursor by amination, wherein, for each step, the tri substituted precursor generates the tri substituted derivative and the di substituted precursor generates the di substituted derivative.

In an alternative embodiment the formation of the tri or di substituted hydroxy 2,4,6-trinitrobenzene from a tri or di substituted hydroxybenzene precursor includes an intermediate step of forming a tri or di acetoxy-substituted 2,4,6- trinitrobenzene by acetylation.

The acetylation can be performed using sodium acetate in acetic anhydride.

2s The derivation of the tri or di amino-substituted 2,4,6trinitrobenzene from a tri or di alkoxy- substituted 2,4,6trinitrobenzene may include an intermediate step of deriving a second tri or di alkoxy- substituted 2,4, 6-trinitrobenzene. The conversion of one alkoxy derivative to a different alkoxy derivative may be achieved by reacting the first compound with sodium alkoxide (Na+ C,H2n+iO-) and a primary alcohol (C,H2n+,OH). It is preferred that n is from 1 to 20, and most preferred that n is from 3-5. This allows the synthesis of 1.3,5-trialkoxy-2,4,6-trinitrobenzenes without the use of 6 trialkyl orthoformates, which are expensive in the case of high order trialkyl derivatives.

The trihydroxybenzene precursor is preferably 1,3,5- trihydroxybenzene. In an alternative embodiment, the dihydroxybenzene is 1,3-dihydroxybenzene.

Suitable nitrating reagents would be sodium nitrite in conjunction with nitric acid. In an alternative embodiment dinitrogen pentoxide in sulphuric acid is used. This latter combination of reagents has been shown to render a higher yield of the nitrated intermediate. Alternatively, a mixture of nitric and sulphuric acids could be used for nitration.

A suitable alkylating reagent would be potassium carbonate in dimethyl sulphate or in an alternative embodiment a trialkyl orthoformate. Trimethyl orthoformate, triethyl orthoformate or tripropyl orthoformate is preferably used.

A suitable aminating reagent would be liquid ammonia at slightly raised pressure (8-9 bar) and at room temperature or in an alternative embodiment liquid ammonia at atmospheric pressure and at the boiling point of ammonia (-332C at atmospheric pressure) or in yet another alternative embodiment ammonia gas at atmospheric or slightly raised pressure (8-9 bar) is bubbled through a solution comprising an organic solvent comprising any of toluene, methanol, dimethyl sulphoxide (DMSO), dimethy1formamide and Nmethylpyrrolidinone (NMP).

The processes of the present invention circumvent the need for halogenated precursors.

Another advantage of the invention is that it is energy efficient on account of the use of comparatively low 7 temperatures over short reaction periods. The method will function at higher temperatures, but will not be so energy ef f icient.

A further advantage of the current invention is that it renders a high overall yield of end product.

Other advantages of the invention are a) it employs relatively mild conditions in terms of temperature, pressure and reagents for both the nitration and the amination steps of the synthesis; b) the starting material and most reagents used are readily available and relatively inexpensive; c) the hydrolysis of redundant DATB and TATB render 1, 3 dihydroxy-2,4,6- trinitrobenzene and 1,3,5-trihydroxy-2,4,6trinitrobenzene respectively which in turn may be recycled; and d) the TATB produced is of equivalent thermal stability to that of TATB generated by the current known manufacturing routes.

It is worth noting that the methods of US 3,278,604 and US 3,394,183 for the production of DATB were investigated to determine whether they could be used to generate TATB from a suitable trimethoxybenzene. This route proved to be impracticable due to the generation of multiple by-products when the trimethoxybenzene was nitrated.

Embodiments of the present invention will now be described by way of the following examples and with reference to the accompanying drawings of which:

8 Figure 1 shows an embodiment of the invention as described in example 1; and Figure 2 shows another embodiment of the invention as described in example 2.

Example I

Preparation of TATB from 1,3,5-trihydroxybenzene (a) Preparation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene from 1,3,5- trihydroxybenzene.

(i) 1,3,5-trihydroxybenzene (16.2 g, 0.1 mol) was added to a solution of sodium hydroxide (8.0 g, 0.2 mol) and sodium nitrite (27.6 g, 0.4 mol) in water (75 ml) at 30 OC. The resultant solution was added dropwise to a mixture of ice (108 g) and 99 % nitric acid (21 ml, 0.48 mmol), whilst maintaining the temperature below 5 OC. After stirring for 20 min at 15 OC, this suspension was added slowly to 65 % nitric acid (100 ml) at 50 OC. The mixture was stirred at 50 OC for 45 min, cooled and the solid was filtered off. It was washed with 3M hydrochloric acid (60 ml) and dried to give 1,3,5- trihydroxy-2,4,6-trinitrobenzene mono-hydrate (19.5 g, 70 m.p. 168 C, with loss of water at 138 OC (7.01 wt calculated for the mono-hydrate 6.45 wt This was identified by FTIR and NMR spectral analysis.

(ii) A solution of dinitrogen pentoxide (13.0 g, 120 mmol) in 98 % sulphuric acid (86 ml) was slowly added to a solution of anhydrous 1,3,5-trihydroxybenzene (5.0 g, 40 mmol) in 98 % sulphuric acid (40 ml), whilst maintaining the temperature below -8 OC. The resultant solution was stirred for 4 h at -8 to 10 OC. During this period a yellow precipitate separated.

9 This was filtered off, washed with cold 3M hydrochloric acid (50 ml) and dried to give 1,3,5-trihydroxy-2,4,6 trinitrobenzene (8.84 g, 83 %), m.p. 166 OC, with Yoss of water at 130 OC (6-67 wt %). This was identified by FTIR and NMR spectral analysis.

(b) Preparation of 1,3,5-trimethoxy-2,4,6-trinitrobenzene from 1,3,5trihydroxy-2,4,6-trinitrobenzene.

(i) 1,3,5-trihydroxy-2,4,6-trinitrobenzene (5.0 g, 19.2 mmol) and potassium carbonate (12.5 g, 90.6 mmol) in dimethyl sulphate (100 ml, 1.06 mol) was heated at 125 OC f or 4 h. The resultant solution was poured into cold water (100 ml), the mixture was basified with 30 % sodium hydroxide solution and then heated to almost boiling. On cooling, a solid separated and was filtered off and dried. Extraction of the solid with acetone (150 ml) and concentration of the extract gave 1,3,5-trimethoxy-2,4,6-trinitrobenzene (2.0 g, 34 %), m.p. 73-74 IC. This was identified by FTIR and NMR spectral analysis.

(ii) 1,3,5-trihydroxy-2,4,6-trinitrobenzene (5.22 g, 20 mmol) in trimethyl orthoformate (30 ml) was-heated at 95-100 OC for 4 h. A mixture of methanol and methyl formate distilled off, b.p. 65-78 OC. The temperature was then raised to 105-110 OC for a further 0.5 h, and more distillate was collected, b.p. 92-98 OC. The solution was then concentrated at lower temperature to give 1,3,5- trimethoxy2,4, 6 - trinitrobenzene (5.99 g, 99 %), m.p. 74 OC. This was identified by FTIR and NMR spectral analysis.

(c) Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) from 1,3,5trimethoxy-2,4,6-trinitrobenzene.

(i) A solution of 1,3,5-trimethoxy-2,4,6-trinitrobenzene (2.0 g, 6.6 mmol) in methanol (50 ml) was cooled to -10 OC, and ammonia gas was bubbled through the solution, with vigorous stirring, for 1.5 h. A yellow solid separated during this period. The cooling bath was removed and ammonia was passed through the suspension for a further 1.5 h, whilst the temperature rose to room temperature. The product was filtered off, was washed with methanol and dried to give 1,3,5-triamino-2,4,6-trinitrobenzene (1.65 g, 97 %), and identified by FTIR spectral analysis. Particle size analysis (volume mean diameter): 7.8gm.

DSC analysis (10 K/min) exhibited a double exotherm at 340 and 343 C. The presence of a double exotherm. indicates that some impurities are present.

(ii) A solution of 1,3,5-trimethoxy-2,4,6-trinitrobenzene (1.0 g, 2.3 mmol) in dimethylsulphoxide (50 ml) was sealed in an autoclave at room temperature, and ammonia gas was introduced at a pressure of 8-9 bar for 6 h. The product was filtered off, was washed with dime thyl sulphoxi de (25 ml) and methanol (50 ml) and then dried to give crude 1,3,5-triamino2,4,6-trinitrobenzene (0.78 g, 92%). This was identified by FTIR spectral analysis. Particle size analysis (volume mean diameter): 30.3pm.

DSC analysis (10 K/min) exhibited a double exotherm at 349 and 354 IC. The presence of a double exotherm indicates that some impurities are present.

(iii) Liquid ammonia (25 ml) was added to 1,3,5-trimethoxy2,4,6trinitrobenzene (1.0 g) in a round-bottomed flask. The reaction mixture was stirred under reflux (-33 OC) for 6 h, after which time the ammonia was allowed to evaporate. The yellow residue was dispersed in dime thyl sulphoxi de (25 ml) 11 using sonication, the solid was filtered off and was washed with methanol (50 ml) and then dried to give crude 1,3,5 triamino-2,4,6-trinitrobenzene (0.81 g, 95 0-6). The product was shown by HPLC analysis to consist of 1,3,5-triamino 2,4,6-trinitrobenzene (94.2%). This was identified by FTIR spectral analysis. Particle size analysis (volume mean diameter): 35.8tm.

DSC analysis (10 K/min) exhibited a single exotherm at 357 0C.

(iv) Dried liquid ammonia (50 ml) was added to 1,3,5 trimethoxy-2,4,6-trinitrobenzene (2.0 g) contained in an autoclave, and the vessel was sealed. The system was allowed to warm to room temperature (8-9 bar) and stirred for 24 h.

After this period the excess of ammonia was allowed to evaporate, dimethylsulphoxide (50 ml) was added to the residue and the suspension was stirred for lh. The yellow solid was filtered off, was washed with methanol (50 ml) and dried to give 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) (1.66 g, 97 %). This was identified by FTIR spectral analysis. Particle size analysis (volume mean diameter):

18.9p.m.

DSC analysis (10 K/min) exhibited a single exotherm at 362 OC.

Example 2

Preparation of TATB from 1,3,5-trihydroxybenzene by way of a 4 step synthesis via the acetoxy derivative (a) Preparation of 1,3,5-triacetoxybenzene from 1,3,5trihydroxybenzene.

12 Sodium acetate (1.0 g, 12 mmol) was added to anhydrous 1,3, 5trihydroxybenzene (1. 0 g, 7.9 mmol) in acetic anhydride (6 ml). The resultant mixture was stirred at 130 OC for 2 h, after which period it was cooled and poured into ice-water (33 g). The resultant precipitate was filtered off, was washed with water and dried to give 1,3,5-triacetoxybenzene (1.89 g, 95 %), m.p.105 IC. This was identified by FTIR and NMR spectral analysis.

(b) Preparation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene from 1,3,5-triacetoxybenzene.

The nitration process causes nitration of the 2,4 and 6 positions and deacetylation of the 1,3 and 5 positions of 1,3,5-triacetoxybenzene to form 1,3,5-trihydroxy-2,4,6 trinitrobenzene.

A solution of dinitrogen pentoxide (3.28 g, 30 mmol) in 98 % sulphuric acid (34 ml) was slowly added to 1,3,5 triacetoxybenzene (2.21 g, 8.8 mmol) in 98% sulphuric acid (5ml), whilst maintaining the temperature below -5 IC. The resultant solution was stirred at -10 IC to 10 IC for 4 h.

The yellow solid that separated was, extracted into dichloromethane (500 ml) and treated with methanol (100 ml).

The solvents were evaporated to give 1,3,5-trihydroxy-2,4,6 trinitrobenzene (2.24 g, 98 V, m.p. 169 OC. This was identified by FTIR and NMR spectral analysis.

(c) Preparation of 1,3,5-trimethoxy-2,4,6-trinitrobenzene from 1,3,5-hydroxy-2,4,6-trinitrobenzene.

As per Example I and the embodiments contained therein.

13 (d) Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) from 1,3,5- trimethoxy-2,4,6-trinitrobenzene.

As per Example 1 and the embodiments contained therein.

Example 3

Preparation of DATB from 1,3-dihydroxybenzene through the 4 step synthesis via the acetoxy derivative (a) Preparation of 1,3-diacetoxybenzene from 1,3- dihydroxybenzene.

A slurry of 1,3-dihydroxybenzene (30 g, 0.27 mol), and sodium acetate (30 g, 0.45 mol) in acetic anhydride (180 ml) was heated at 110 IC for 2 h, after which period it was cooled and poured into ice-water (500 ml), then stirred for 16 h.

The product was extracted into dichloromethane (500 ml) and then dried. Concentration of the solution yielded 1,3 diacetoxybenzene (50.3 g, 96 %), which was shown to be pure by GC analysis. This was identified by FTIR and NMR spectral analysis.

(b) Preparation of 1,3-dihydroxy-2,4,6-trinitrobenzene from 1,3-diacetoxybenzene.

A solution of dinitrogen pentoxide (4.12 g, 38.1 mmol) in 98 % sulphuric acid (20 ml) was slowly added to 1,3diacetoxybenzene (2.5 g, 12.9 mmol) in 98 % sulphuric acid (20 mi), whilst maintaining the temperature at -10 C. The resultant solution was heated, with stirring, at 40 IC for 3 h and then poured onto ice (50 g). The resultant precipitate was filtered off, washed with water and dried to give 1,3dihydroxy-2,4,6-trinitrobenzene (3. 0 g, 95 %). This was identified by FTIR and NMR spectral analysis.

(c) Preparation of 1,3-dimethoxy-2,4,6-trinitrobenzene from 1,3-dihydroxy-2,4,6-trinitrobenzene. 41 1,3-dihydroxy-2,4,6-trinitrobenzene (2.05 g, 8.3 mmol) in trimethyl orthoformate (30 ml) was heated at 90-95 OC for 3 h. A mixture of methanol and methyl formate distilled off, b.p. 72-80 OC. The temperature was then raised to 100-105 OC for a further 0.5 h, and more distillate was collected, b.p.

98 OC. The solution was then concentrated at lower temperature to give 1,3-dimethoxy-2,4,6-trinitrobenzene (2.21 g, 97 %), which was shown to be pure by GC analysis. This was identified by FTIR and NMR spectral analysis.

(d) Preparation of 1,3-diamino-2,4,6-trinitrobenzene (DATB) from 1,3-dimethoxy-2,4,6-trinitrobenzene.

A solution of 1,3-dimethoxy-2,4,6-trinitrobenzene (2.15 g, 7.9 mmol) in toluene (50 ml) was cooled to -10 OC, and ammonia gas was bubbled through the solution, with vigorous stirring, for 1.5 h. A yellow solid separated during this period. The cooling bath was removed and ammonia was passed through the suspension for a further 1.5 h, whilst the temperature rose to room temperature. The product was filtered off, was washed with toluene and dried to give 1,3diamino-2,4,6-trinitrobenzene (1. 88 g, 98 %), m.p. 285 OC. This was identified by FTIR and NMR spectral analysis.

Example 4

Preparation of TATB from 1,3,5-trihydroxybenzene using the ethoxy alkylating reagent (triethyl orthoformate) (a) Preparation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene from 1,3,5-trihydroxybenzene.

As per Example 1(a).

(b) Preparation of 1,3,5-triethoxy-2,4,6-trinitrobenzene from 1,3,5-trihydroxy-2,4,6-trinitrobenzene.

1,3,5-trihydroxy-2,4,6-trinitrobenzene (11.1 g, 39.8 mmol) in triethyl orthoformate (100 ml) was heated at 100 OC for 1.25 h. A mixture of ethanol and ethyl formate distilled off, b.p. 70-75 OC. The temperature was then raised to 120-125 IC for 1h and 140-145 OC for 0.5 h, and more distillate was collected, b.p. 65-75 OC. The solution was then concentrated at a lower temperature to give a beige solid (13.9 g) which was recrystallised from ethanol (50 ml) to give 1,3,5triethoxy-2,4,6trinitrobenzene (12.4 g, 90 %), m.p. 117 OC. This was identified by FTIR and NMR spectral analysis.

(c) Preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) from 1,3,5-triethoxy-2,4,6-trinitrobenzene.

A solution of 1,3,5-triethoxy-2,4,6-trinitrobenzene (5.0 g) in N-methylpyrrolidinone (50 ml) was sealed in an autoclave and cooled to 2 C. Ammonia gas was introduced at a pressure of 8-9 bar for 24 h, with external cooling for the first 0.25 h. The product was filtered off, was washed with Nmethylpyrrolidinone (10 ml) and methanol (100 ml) and then dried to give 1,3,5-triamino-2,4,6-trinitrobenzene (3. 69 g, 99 %). This was identified by FTIR and NMR spectral analysis.

16 The product was shown by HPLC analysis to contain 99. 8 % 1,3,5-triamino- 2,4,6-trinitrobenzene. Particle size analysis (volume mean diameter): 30.74m.

DSC analysis (10 K/min) exhibited a single exotherm at 365 0C.

Example 5

Preparation of TATB via 1,3,5-tripropoxy-2,4,6- trinitrobenzene (a) Preparation of 1,3,5-tripropoxy-2,4,6-trinitrobenzene from 1,3,5trimethoxy-2,4,6-trinitrobenzene 1,3,5-trimethoxy-2,4,6-trinitrobenzene was prepared as per Example 1 and the embodiments therein. A solution of sodium propoxide (3.24g, 49mmol) in propan-l-ol (100ml) was added to a mixture of 1,3,5-trimethoxy-2,4,620 trinitrobenzene (24.0g, 79.2mmol) in propan-l-ol (300ml) and the resultant red mixture was stirred at room temperature for 2h. The reaction mixture was then concentrated to a thick slurry and 0.2M HC1 (300ml) was added. The yellow precipitate was filtered off after stirring for lh, washed with water (500ml) until the washing were no longer acidic and dried under vacuum (29.36g, 96%). The product was identified as 1,3,5-tripropoxy-2,4,6- tinitrobenzene by 'H-NMR (acetone-d6; 0.96 (t, CH3) 1.74 (m, CH2) and 4.19 (t, OCH2)] and "C-NMR (148, 137, 80, 24 and lOppm). DSC analysis showed that the solid had a melting point of 108'C.

17 (b) Preparation of 1,3,5-tripropoxy-2,4,6-trinitrobenzene from 1,3,5-trihydroxy-2,4,6-trinitrobenzene 1,3,5-trihydroxy-2,4,6-trinitrobenzene was prepared as per 5 Example 1 and the embodiments therein.

A solution of 1,3,5-trihydroxy-2,4,6-trinitrobenzene (0.5g, 1.9mmol) in tripropyl orthoformate (6.2ml) was heated at 110 1150C for 1.5h. An azeotropic mixture of propan-l-ol and propyl formate was distilled over at 65-681C. The resultant mixture was then heated at 1201C for a further 4.5h, during which time further distillate was collected (b.p. 680C).

After cooling, the resultant orange solution was concentrated to give a pale orange solid (0.70g, yield 94%). This product was identified as 1,3,5-tripropoxy-2,4,6-tinitrobenzene by FTIR (2981, 2945, 2884, 1598, 1537, 1473, 1439, 1387, 1356, 1048, 931, 891, 734 and 643cm-1), and 1 Hand 13C -NMR spectroscopy. DSC analysis showed that the solid had a melting point of 105C.

(c) Preparation of TATB from 1,3,5-tripropoxy-2,4,6 trinitrobenzene (i) A solution of 1,3,5-tripropoxy-2,4,6-trinitrobenzene (5.0g, 12.91mmol) in toluene (50ml) was sealed at room temperature in an autoclave. Ammonia gas was then added at 8 9bar for 24h, after which time the system was vented, allowing evaporation of the ammonia. The resultant yellow precipitate was filtered off, washed with toluene (25ml) and dried to yield TATB (3.31g, 99%). DSC analysis (10K/min) exhibited a single exotherm at 373.2C. The melting point of commercially- available TATB (often referred to as Class A TATB) was measured to be 375.7'C. The product was shown by HPLC to contain 100% TATB. Particle size analysis (volume mean diameter): 8.9gm.

18 (ii) A solution of 1,3,5-tripropoxy-2,4,6-trinitrobenzene (15.0g, 38. 8mmol) in NMP (50ml) was sealed at room temperature in an autoclave. Ammonia gas was then added at 7- 8bar for 4h, after which time the system was heated to 1101150C for a further 4h. The system was cooled and vented, allowing evaporation of the ammonia. The resultant yellow precipitate was filtered off, washed with NMP (30ml) and methanol (50ml), and then dried to yield TATB (9.90g, 99%).

DSC (IOK/min) analysis showed a single exotherm at 371.51C.

The product was shown by HPLC to contain 100% TATB. Particle size analysis (volume mean diameter) 10.8tm.

(iii) Dried liquid ammonia (50ml) was added to 1,3,5tripropoxy-2,4,6-trinitrobenzene (15.0g, 38.76mmol) in an autoclave which was then sealed. The system was allowed to warm to room temperature (pressure 8-9bar) and stirred for 24h. After this period the system was vented and toluene (50ml) was added as the ammonia evaporated. The yellow solid was filtered off, washed with toluene (25ml) and dried to yield TATB (10. 13g, 101%). DSC analysis (10K/min) exhibited a single exotherm at 362.91C and HPLC analysis indicated the presence of one component TATB(100%). The product was then added to NMP (50ml) and the suspension heated at 100- 1051C for 24h. After cooling, the yellow solid was filtered off, washed with NMP (10ml) followed by methanol (50ml) and dried (9.91g, 99%). DSC analysis (10K/min) now showed asingle exotherm with at 370.OOC. Particle size analysis (volume mean diameter) 168.5tm. The measured vacuum stability of O.OCM3 /2.5g (120cC for 40 hours) compares very favourably with the measurement of 0.2 CM3 /2.5g obtained from commerciallyavailable TATB. Hence, the TATB of the present invention is of a comparable purity to commercially-available TATB.

(iv) A solution of 1,3,5-tripropoxy-2,4,6-trinitrobenzene (15g, 38.8mmol) in diethyl ether (100ml) was added over 45min to liquid ammonia (50ml) under reflux at -330C. The reaction mixture was then stirred for a further 2.25h under reflux.

The ammonia was evaporated off and the yellow solid was filtered off, washed with diethyl ether and dried. This lo material was then added to NMP (40ml) and the suspension sealed in an autoclave at 110-1150C. Amr.onia gas was added at 8-9bar for 3h, after which time the system was cooled and vented. The product was filtered off, washed with NMP followedby diethyl ether and finally dried under vacuum (9.60g, 96%). DSC analysis (10K/min) exhibited a single exotherm. at 374.50C. The product was shown to be pure TATB by HPLC analysis. Particle size analysis (volume mean diameter): 102.6pn. A vacuum stability of O.Ocm 3/2.5g (1200C for 40 hours) was measured. 20 The synthetic routes using 1,3,5-tripropoxy-2,4,6trinitrobenzene appear to give cleaner products. Use of the ether exchange reaction of Example 5. (a) negates the need to use tripropyl orthoformate which is a very expensive chemical.

Claims (20)

1. A method for preparing a tri or diaminated 2,4,6- trinitrobenzene comprising the steps of:

(i) deriving a tri or di hydroxy-substituted 2,4,6trinitrobenzene from a tri or di hydroxy-substituted benzene precursor by nitration; (ii) deriving a tri or di alkoxy-substituted 2,4,6- trinitrobenzene from a tri or di hydroxy-substituted 2,4,6-trinitrobenzene precursor by alkylation; and (iii) deriving a tri or di amino- substituted 2,4,6 trinitrobenzene from a tri or di alkoxy-substituted 2,4,6-trinitrobenzene precursor by amination, wherein, for each step, the tri substituted precursor generates the tri substituted derivative and the di substituted precursor generates the di substituted derivative.

ZO

2. The method as described in claim 1, wherein the derivation of the tri or di hydroxy- substituted 2,4,6-trinitrobenzene from a tri or di hydroxy- substituted benzene precursor includes an intermediate step of deriving a tri or di acetoxy-substituted 2,4,6-trinitrobenzene by acetylation.

3. The method as described in claim 2, wherein the acetylation step comprises the use of sodium acetate in acetic anhydride.

4. The method as described in any one preceding claim, wherein the derivation of the tri or di amino- substituted 2,4,6-trinitrobenzene from a tri or di alkoxy- substituted 2,4,6-trinitrobenzene includes an intermediate step of deriving a second tri or di alkoxy-substituted 2,4,621 trinitrobenzene.

5. The method as claimed in claim 4 wherein the derivation of the second tri or di alkoxy-substituted 2,4,6- trinitrobenzene comprises the use of sodium alkoxide (Na+ C,H2,±10') and a primary alcohol (C,,H2.+,OH).

6. The method as claimed in claim 5 wherein n is from 1 to 20.

7. The method as claimed in claim 5 wherein n is from 3 to 5.

8. The method as described in any one of claims 1 to 7 wherein the trihydroxy-substituted benzene precursor is 1,3,5-trihydroxybenzene.

9. The method as described in any one of claims 1 to 7 wherein the dihydroxy-substituted benzene precursor is 1,3dihydroxybenzene.

10. The method as described in any one of claims I to 9 wherein the nitration comprises the use of dinitrogen pentoxide in sulphuric acid.

11. The method as described in any one of claims 1 to 9 wherein the nitration comprises the use of sodium nitrite with nitric acid.

12. The method as described in any one of claims 1 to 9 wherein the nitration comprises the use of a mixture of sulphuric acid and nitric acid.

13. The method as described in any preceding claim wherein the alkylation comprises the use of a trialkyl orthoformate 22

14. The method as described in claim 13 wherein the alkylation comprises the use of one of trimethyl orthoformate, triethyl orthoformate and tripropyl orthoformate.

15. The method as described in any one of claims 1 to 12 wherein the alkylation comprises the use ofpotassium carbonate in dimethyl sulphate.

16. The method as described in any preceding claim wherein the amination comprises the use of ammonia gas bubbled at atmospheric pressure or greater through a solution comprising an organic solvent including any of toluene, methanol, dimethyl sulphoxide, dimethy1formamide and N15 methylpyrrolidinone.

17. The method as described in any one of claims 1 to 15 wherein the amination comprises the use of liquid ammonia at the boiling point of ammonia and at atmospheric 20 pressure.

18. The method as described in any one of claims 1 to 15 wherein the amination comprises the use of liquid ammonia at 8 to 9 bar and at room temperature.

19. The method for preparing a tri or diaminated trinitrobenzene as substantially herein before described with reference to figure 1.

20. The method for preparing a tri or diaminated trinitrobenzene as substantially herein before described with reference to figure 2.