SE9302299A2 - New polycyclic polyamides as precursor compounds for energy-rich polycyclic polynitramine oxidizers - Google Patents

Abstract

Hexabenzylhexaazaisowurtzitan is converted to tetraacetyl, dibenzyl-azaisowurtzitan. The benzyl groups are removed by catalytic transfer hydrogenolysis, leaving a pair of available nitrogen. The available nitrogen is acetylated and the resulting intermediate is converted to CL-20 with a strong nitrating agent.

Description

The present invention relates to nitrogen compounds with cage structure, in particular derivatives of hexanes, derivatives of hexanes and derivatives of hexanes.

Background of the Invention In an essay entitled "Synthesis of 2,4,6,8,10,12-Hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane" Arnold T. Nielsen describes the synthesis of the compound mentioned in heading. This compound is hereinafter referred to as HBIW. The more formal chemical name of this compound is 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazatetracyclo- [5.5.0 .0 <3.11> 0. <5.9>] dodekan. Nielsen et al describe in essays entitled "Polynitroplyaza Caged Explosives Parts 5 & 6" (part 6 is classified) and "Synthesis of a Caged Nitramine" (classified), prepared for the Naval Weapons Center, China Lake, CA, the synthesis of 2, 4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaya-tetracyclo [5.5.0.0. <3,11> 0. <5,9>] dodecane, which is known in the field of fuels / explosives as CL-20 (this compound is hereinafter referred to as CL-20). The above work by Nielsen and Nielsen et al is incorporated herein by reference.

CL-20 is an oxidizing agent with great potential for use in high energy compositions, such as propellants, gasifiers, explosives or the like. CL-20 has a high detonation rate, which is due to its high heat of formation. It is also advantageous due to its high density, which is a result of the cage structure. It has special utility for formulations with minimal smoke formation (generally non-aluminized formulations). It also has special utility in explosive compositions.

HBIW has the following chemical structure; the specified numbering of the carbon and nitrogen atoms contained in the ring is intended to apply throughout this description: Image available on "Original document" It should be noted that in the formula above the identical 2-, 6-, 8- and 12-can nitrogen are included in 5 and 6-joint rings, while the 4- and 10-can weaves are included in 6- and 7-joint rings. It has been found that in many chemical reactions the four identical nitrogen reacts differently than the two identical nitrogen. These different nitrogen are hereinafter referred to as the 2-6-8-12 nitrogen and the 4-10 nitrogen, respectively.

CL-20 has the following chemical structure: Image available on "Original document" In the first step of the process for converting HBIW (I) to CL-20 (II), HBIW is converted to 2,6,8,12-tetraacetyl-4, 10, dibenzyl-hexaazaisowurtzitan, hereinafter referred to as compound IIIA (also referred to herein as TADB), having the formula shown below: Image available on "Original document" The conversion from HBIW (I) to compound IIIA is effected, for example, with hydrogen in presence of a palladium hydroxide-on-carbon catalyst and acetic anhydride using a bromobenzene catalyst. Subsequent conversion of compound IIIA to CL-20 is accomplished using the nitrating agents NOBF4 and NO2BF4, respectively. These nitrates are very expensive. Due to the presence of fluoride, waste products also cause significant environmental problems. The cost of producing CL-20 by this synthesis is a significant limitation on its general utility in the fuel and explosives industries.

Accordingly, it is a general object of the invention to provide methods for the synthesis of CL-20 and related energy-rich compounds, which methods involve an improvement from a cost and environmental point of view. A further object of the invention is to provide new chemical intermediates which can be converted to CL-20 and related high energy nitrogen compounds with cage structure.

Summary of the Invention In accordance with the invention, HBIW (Compound I) is chemically converted to a melian product of the general formula: Image available on "Original document" wherein the R substituents are the same or different and are selected from the group consisting of alkyl, cycloalkyl, aryl, arylalkyl, alkene, alkyne, substituted forms of any of these groups, for example with halogens or nitro groups and H; a group consisting of (H <+> A-) (a hydrogen ion and a complementary anion) is present on either, one or both of the 4- and 10-nitrogen. Equivalent divalent anions can complement the H <+> ions on the two 4- and 10-nitrogen. Compounds of general formula (IV) can be prepared, for example, by first converting HBIW to compound IIIA by the above method of A.T. Nielsen (see above) and then converts compound IIIA to a compound of formula (IV) by catalytic transfer hydrogenolysis.

Compounds of formula (IV) may be nitrated to produce a compound of the formula Image available on "Original document" in which a group (H . Compounds of formula (V) having two (H * A -) groups (the bis salt) and wherein A <-> is an energy rich anion, such as NO3 <-> or C104-, are useful high energy compounds.

Compounds of formula (IV) may also be reacted with an acylating agent, such as an acid anhydride or an acid chloride, to produce a hexamide of the following formula wherein the R substituents are the same or different and are selected from the group consisting of alkyl, cycloalkyl, aryl , arylalkyl, alkene, alkyne, substituted forms of any of these groups, for example with halogens or nitro groups, or H.

Compounds of formula (VI) may be converted by nitrolysis nitration to CL-20 using a strong nitrating agent.

Detailed Description of Certain Preferred Embodiments In accordance with the improved synthesis of CL-20, HBIW of formula (I) is generally chemically converted to a hexamide of formula (VI). A hexamide of formula (VI) can be reacted with a strong nitrating agent, such as N 2 O 5 in nitric acid or a nitric acid / sulfuric acid mixture, to form CL-20. These nitrating agents are much cheaper than NOBF4 and NO2BF4, which have hitherto been required by the above method by A.T. Nielsen et al for the preparation of CL-20. HBIW is a known compound and its synthesis will not be further described in the present context. It is understood that equivalents of HBIW (I) could also be used, for example HBIW (I) with substitutions on one or more of the aromatic rings.

The presently preferred method of converting HBIW to a compound of formula (VI) is to first convert HBIW to a compound of formula (III) by the above method of A.T. Nielsen et al; formula (III) is as follows: Image available on "Original document" wherein the R substituents are the same or different and are selected from the group consisting of alkyl, cycloalkyl, aryl, arylalkyl, alkene, alkyne, substituted forms of any of these groups or H. (Compound (IIIA) is the compound of formula (III) wherein all four R substituents are CH 3 and Ar is phenyl). Ar is generally a phenyl group, although another aromatic group, substituted or unsubstituted, is considered equivalent.

Compounds of formula (III) are converted to compounds of general formula (IV) by hydrogenolysis. Catalytic transfer hydrogenolysis is currently used. Catalytic transfer hydrogenolysis and reagents and catalysts therefor are described, for example, in R.A.W. Johnstone et al Chera Rev., 85, 129-170 (1985), the contents of which are incorporated herein by reference. A useful method of producing catalytic transfer hydrogen oil is to use formic acid as a hydrogen donor in the presence of a palladium-on-carbon catalyst. The formic acid was generally used in a large molar excess, for example as a solvent for the reaction. Depending on the reaction conditions used, a compound of formula (IV) is prepared which is the bis-salt ((two? <+>? -) groups (A <-> is here the formate anion)), the monoformate salt or the free base. It has been found that, if formic acid is used pure with the Pd / C catalyst, the bis-salt tends to form, a mixed water / formic acid solvent system tends to give the monosalt; and a formic acid / methanol solvent system tends to give the free base. Synthesis of the free base is often preferred over synthesis of either the bis or monosalt; however, the synthesis of the free base is less reproducible than the synthesis of the bis or mono salt.

These reactions are exemplified as follows: Image available on "Original document" bis-salt Image available on "Original document" \ The new compounds of formula (IV) are important intermediates for the preparation of CL-20 or for the compounds of formula (V).

The bis or mono-salts of formula (IV) can be converted to the free base by reaction with a strong base, such as an aqueous solution of sodium hydroxide or a strongly basic anion exchange resin, for example the Dowex-50i OH form. The 4- and 10-nitrogen in the compounds of formula (IV) can be converted to hexamide compounds of formula (VI) by reaction with an acylating agent, such as an acid anhydride, in the presence of a basic catalyst such as pyridine. An acyl halide can alternatively be used as an acylating agent. If the free base is used, the reaction of the 4-10 nitrogen is a simple acylation. If the bis- or mono-salt formate is acylated with acetic anhydride, the corresponding bis- or mono-N-formyl compound is obtained. Thus, in the following reactions, acylation using acetic anhydride of the bisformate salt, the monoformate salt and the free base of compounds of formula (IV) are compared: Image available on "Original document" Image available on "Original document" Image available on "Original document" the products of each reaction are slightly different, each of the products has the general formula (VI). Compounds of formula (VI) are also important intermediates in the synthesis of CL-20.

Compounds of formula (VI) are converted to CL-20 by strong nitrating agents which give nitramine groups in the 2-, 4-, 6-, 8-, 10- and 12-positions of the cage structure. Suitable agents include, but are not limited to, N 2 O 5 in nitric acid or a nitric acid / sulfuric acid mixture. This reaction is as follows: Image available on "Original document" As mentioned above, compounds of formula (IV) can also be converted to compounds of formula (V) by nitrolysis nitration by reaction with a strong nitrating agent, such as N 2 O 5 / nitric acid or nitric acid / sulfuric acid, to form a compound of formula (V). Subsequent reaction with an acid with an energy-rich anion, such as NO3- or C104-, gives an extremely energy-rich compound of formula (V). These reactions are as follows: Image available on "Original document" Nitrolysis nitration of a compound of formula IV may also give some amount of CL-20.

Compounds of formula V are most energy-rich in the form of the bis salts of energy-rich anions, such as NO3 or C104-. The nitration reaction gives the bis-nitrate salt. To obtain a more energy-rich salt, the nitrate salt can be converted to a free base, for example by reaction with a base such as NaOH, and then reacted with an acid having the energy-rich anion. Alternatively, the nitrate salt can be converted to a more energy rich salt directly with a suitable anion exchange resin.

As an alternative method of converting a compound of formula (IV) to CL-20, the compound is reacted with a nitrite, for example sodium nitrite in an aqueous acid, to form a compound of formula (VII) as shown in the following reaction.

Image available on "Original document" This compound VII undergoes, when nitrated with strong nitrating agent, such as N 2 O 5i nitric acid or a nitric acid / sulfuric acid mixture, a nitrolysis nitriding reaction to form CL-20 as follows: Image available on "Original document" by means of exemplary embodiments.

To a stirred slurry of 48.0 mg (0.093 mmol) of TADB in 4 ml of methanol and 0.2 ml of formic acid was added 51 mg of 5% Pd / C. The reaction mixture was heated to 40º-60ºC for 18 hours. Pd / C and the product was removed by filtration. Extraction of Pd / C with DMSO gave the desired product. 1 H NMR (DMSO): δ 1.8-2.1 (multiplet, 12H, CH 3 CO), 4.02-4.25 (multiplet, 2H, NH), 5.2-5.3 (multiplet, 4H, CH), 6.0-6.5 (multiplet, 2H, CH).

When heated to 150ºC, the multiples at 1.8-2.1 collapse into a singlet at 2.0, the multiples at 4.02-4.25 collapse into a singlet at 3.7, the multiples at 5.2-5.3 collapse into a singlet at 5.3 and the multiples at 6.0-6. 5 collapses into a singlet at 6.3.

To a vigorously stirred solution of 10.0 g (19.36 mmol) of TDAB in 200 ml of water was added 40 ml of formic acid; then 10.0 g of 5% Pd / C was added. The reaction mixture was heated to 60 ° C. After 18.5 hours, the solid was filtered off from the solution and the volatiles were removed under reduced pressure to give 7.9 g (106.7%) of the monoformate salt. 1 H NMR (DHSO):? 1.7-2.3 (multiplet, 12H, CH 3 CO), 4.7-4.9 (broad doublet, 1H, NH, J = 9.0H2) 5.5-5.7 (multiplet, 2H, CH), 6.0-6.8 (multiplet 4H, CH), 8.3 ( broad singlet, 4H, NH, HCO 2 H).

When heated to 150ºC, the multiplet at 1.7-2.3 collapses to 2s, the wide doublet at 4.7-4.9 moves to 4.3 and widens, the multiplet at 5.5-5.7 collapses into a doublet at 5.6 (J = 6 Hz), and the broad singlet at 8.3 split into two singlets at 8.32 and 8.39.

To a stirred slurry of 10.0 g (19.36 mmol) of TADB in 200 ml of formic acid was added 10.0 g of 5% Pd / C. After 18 hours, Pd / C was removed by filtration and the formic acid was removed under reduced pressure to give 8.78 g (104%) of the desired bis-salt. 1 H NMR (DMSO): δ 1.9-2.2 (multiplet, 12H, CH 3 CO), 6.1-6.8 (multiplet, 6H, CH), 8.1-8.4 (multiplet, 6% NH, HCO 2 H).

When heated to 150ºC, the multiplet at 1.9-2.2 collapses into a singlet and the other two multiplets begin to collapse.

Image available on "Original document" To 500 mg (1.17 mmol) of the bis-formate salt was added 2.4 ml of 1M NaOH. All volatile material was removed under reduced pressure. The residue was dissolved in 20 ml of acetic anhydride and 5 ml of pyridine and heated at 60 ° C overnight. After 18 hours, the volatiles were removed and the residue was treated with 10 mL of EtOAc. The solution was filtered and concentrated. The residue was passed through a plug of silica gel using acetone as eluent to give IVA as an impure solid.

NMR (CHCl 3): δ 2.05-2.2 (multiplet, 12H CH 3 CO), 2.45 (singlet, 6H, CH 3 CO), 6.3-6.5 (multiplet, 4H, CH), 6.8-7.0 (multiplet, 2H, CH).

When heated to 150ºC (DMSO solvent), the multiplet collapses at 2.05-2.2 into a singlet. The multiplets at 6.3-6.5 and 6.8-7.0 are both beginning to collapse.

To a stirred slurry of 5.0 g (13.1 mmol) of the monoformate salt in 200 ml of acetic anhydride was added 50 ml of pyridine. After 20 hours, all volatiles were removed under reduced pressure. Then the residue was treated with 100 ml of EtOAc. A precipitate formed which was removed by filtration. The solvent was removed and the residue was passed through a plug of silica gel using acetone as eluent. 1 H NMR (CHCl 3): δ 2.06, 2.09, 2.12, 2.14 (4 singlet, 12H, CH 3 CO), 2.42 (singlet, 3H, CH 3 CO), 6.0-7.0 (multiplet, 6H, CH), 8.3 (singlet, 1H, CHO).

To a stirred slurry of 5.0 g (11.67 mmol) of the bisformate salt (IV A bis) in 200 ml of acetic anhydride was added 50 ml of pyridine. After 20 hours, all volatiles were removed under reduced pressure. Then the residue was treated with 100 ml of EtOAc. A precipitate formed which was removed by filtration. The solvent was removed and the residue was passed through a plug of silica gel using acetone as eluent. 4.5 g (98.3%) yield of bis-formyl compound was obtained. Rf = 0.35 (acetone). 1 H NMR (CHCl 3): δ 2.0-2.3 (multiplet, 12H, CH 3 CO), 6.06 (doublet, 0.2H, CH, J = 4.8 Hz), 6.15 (broad singlet, 0.45H, CH), 6.26 (doublet, 1.5H, CH, J = 7.8, 1.8 Hz), 6.46 (singlet, 1.7H, CH), 6.67 (doublet, 1.5H, CH, J = 7.8, 1.81 Hz), 6.75-6.81 (multiplet, 0.65H, CH).

Image available on "Original document" To 10 mg (0.026 mmol) of the diformyltetraacetyl compound VI C was added 2 ml of 5% N 2 O 5i nitric acid at 0 ° C for 4.5 hours; the mixture was then diluted with water. The aqueous solution was extracted 4X with ethyl acetate. The organic material was dried (MgSO 4) and concentrated to dryness. By thin layer chromatography (silica gel, multiple solvent systems). The product showed a Rfidentical with the value of CL-20 and a superimposable <1> 1 H NMR spectrum.

To 1.0 g of tetraacetyl (IV A free) in 2 ml of water and 2 ml of acetic acid was added 0.70 g of NaNO 2 in 2 ml of water at 0 ° C. The reaction mixture was stirred for 18 hours at room temperature. The desired product precipitated from the reaction mixture and was collected by filtration in quantitative yield.

Although the invention has been described in the form of certain preferred embodiments, modifications may be made as will be apparent to those skilled in the art without departing from the scope of the present invention.

Various features of the invention are set out in the following claims.

Claims (14)

Image available on "Original document" CLAIMS Image available on "Original document" wherein the R substituents are the same or different and selected from the group consisting of alkyl, cycloalkyl, aryl, arylalkyl, alkene, alkyne or substituted forms of any of the these groups and H and wherein a group consisting of a hydrogen ion (H <+>) and a complement is anion is present on either, one or both of the nitrogen in the 4- and 10-positions. 2.. A compound according to claim 1 of formula (IV). A compound according to claim 2, wherein all R substituents are CH 3. A compound according to claim 1 of formula (V). A compound according to claim 4 having a hydrogen ion and an anion associated with the nitrogen in each of the 4- and 10-positions, said anion being an energy-rich anion. A compound according to claim 5, wherein the anion is NO 3 <-> or C 10 4 <->. 7.. A compound according to claim 1 of formula (VI), wherein all R substituents are CH 3 or H. Process for the preparation of the energy-rich compound of formula II: Image available on "Original document" characterized in that it nitrates a compound of formula VI Image available on "Original document" wherein R is selected from the group consisting of alkyl, cycloalkyl, aryl, arylalkyl, alkene, alkyne, substituted forms of any of these groups and H, with a strong nitrating agent. The method of claim 8, wherein the strong nitrating agent is HNO 3 or an HNO 3 / H 2 SO 4 mixture. A process according to claim 8, wherein the compound of formula VI is obtained by acylating a compound of formula IV: Image available on "Original document" wherein in said formula IV a member of the group consisting of hydrogen ion and a complementary anion is present on either, one or both of the nuclei in the 4- and 10-positions, in the presence of at least one acylating agent. The method of claim 10, wherein the acylating agent is an acid chloride or carboxylic acid hydride. A process according to claim 10, wherein the compound of formula IV is obtained by catalytic transfer hydrogenolysis of a compound of formula (III): Image available on "Original document" A process according to claim 12, wherein the hydrogenolysis is carried out in the presence of a palladium-on-carbon catalyst. A process for the preparation of a compound of formula IV: Image available on "Original document" wherein in said formula IV each R is independently selected from the group consisting of alkyl, cycloalkyl, aryl, arylalkyl, alkene, alkyne, a substituted form of any of these groups and H, and wherein a member of the group consisting of a hydrogen anion and a complementary anion is present in neither, one or both of the nitrogen in the 4- and 10-positions of said formula IV, characterized in that a compound of the formula III is hydrogenolyzed. Image available on "Original document"