Synthesis of 5‐Nitrotetrazolates by the Direct Oxidation of 5‐Aminotetrazole in a Single‐Pot Synthesis without Isolation of Explosive Intermediates

Abstract

A readily available oxidizer, potassium superoxide can be used for the oxidation of 5-amino-1H-tetrazole (5-AT) to 5-nitrotetrazole (5-NT) in high yields in a single-pot synthesis. This strategy reduces the synthesis of this important energetic material down to a single step and eliminates highly sensitive diazonium and copper salt primary explosive intermediates. Use of dimethyl sulfoxide along with molecular sieves and 18crown-6 as phase transfer catalyst promoted faster reaction rates and greater yield. The overall yield of this process is 48-53 % and the resultant aqueous solution of product was effectively used for the preparation of nitrotetrazole-containing primary explosive DBX-1. Unlike current methods of nitrotetrazole preparation, this entirely solution-based route results in a final solution of sodium nitrotetrazolate, without the need to handle energetic intermediates or products, making it the safest method of nitrotetrazole preparation reported to date.

Titanium Superoxide for the Oxidation of Amines: Synthesis of bis(3‐nitro‐1H‐1,2,4‐triazol‐5‐yl)methane and its Metal Salts

“…As oxidation reactions may allow for the avoidance of hazardous conditions, such as large amounts of acids and the creation of unstable diazo intermediates, research into the use of metal‐stabilized superoxide in biological syntheses has expanded [9] . Metal‐superoxides, such as potassium [6–7] and titanium superoxide, [8,9c,10] present the possibility for more predictable and controlled routes [10] . Potassium superoxide generates the superoxide anion in the presence of polar aprotic solvents [6] while titanium superoxide in hydrogen peroxide solution generates superoxide anions on the hydrated titanium matrix from the decomposition of hydrogen peroxide [8] .…”

“…Metal‐superoxides, such as potassium [6–7] and titanium superoxide, [8,9c,10] present the possibility for more predictable and controlled routes [10] . Potassium superoxide generates the superoxide anion in the presence of polar aprotic solvents [6] while titanium superoxide in hydrogen peroxide solution generates superoxide anions on the hydrated titanium matrix from the decomposition of hydrogen peroxide [8] . In the field of energetic materials, the use of superoxide for oxidation reactions is novel.…”

“…Nitration reactions are widely used due to ease of reaction and the ability to separate products from spent acid; [4] a drawback of this traditional method is the large amount of acidic waste. The alternative Sandmeyer reaction proceeds though an unstable diazo intermediate [5] which creates very sensitive intermediate explosive materials when on a heterocyclic backbone [6] . Amine oxidation through the use of oxidants such as hydrogen peroxide, Oxone®, and potassium permanganate [7] are also known; however, oxidation reactions are often aggressive, hard to direct, and the process of oxidizing the amine is usually complicated due to competing pathways leading to a range of products [8] such as azo‐ and azoxy‐ compounds as well as nitroso compounds.…”

“…[8] In the field of energetic materials, the use of superoxide for oxidation reactions is novel. To date potassium superoxide has been used in the synthesis of energetic materials such as 3-amino-5-nitro-1,2,4-triazole (ANTA), [7a] 5-nitrotetrazole, [6] 2nitrobenzimidazole [11] and 5-(5-nitro-2H-1,2,3-triazol-4-yl)-1Htetrazole [12] while the use of titanium superoxide remains relatively unknown.…”

Development of a Safe Continuous Process to Sodium Nitrotetrazolate via Solid Phase “Catch and Release”

“…It should be noted that simply using cupric salts did not avoid microdetonations in our laboratory; the proposed diazonium can occasionally form on dry surfaces and react violently despite the presence of copper. Other reported purifications required the extraction and crystallization of NaNT solids; a procedure that is unsafe at large scale due to the sensitivity of anhydrous NaNT solids. , Recently, solution-phase NaNT synthesis by direct oxidation of 5AT using potassium superoxide was reported, but this process was relatively low yielding when compared to Sandmeyer routes and uses dangerous oxidizers. This synthesis also took several days to reach completion and was thus unattractive for use in a continuous process.…”