Diazotization, of 5-aminotetrazole

Nitrotetrazole is readily prepared from the diazotization of 5-aminotetrazole in the presence of excess sodium nitrite and is best isolated as the copper salt complex with ethylenediamine. The salts of 5-nitrotetrazole have attracted interest for their initiating properties. The mercury salt is a detonating primary explosive. The amine salts of 5-nitrotetrazole are reported to form useful eutectics with ammonium nitrate. ... 

Aminotetrazole (91) reacts with potassium permanganate in excess aqueous sodium hydroxide to yield the disodium salt of 5-azotetrazole (92). 5-Azotetrazole is unstable and attempts to isolate it by acidification yields 5-hydrazinotetrazole (93). Diazotization of 5-aminotetrazole (91) in the presence of excess sodium nitrite yields 5-nitrotetrazole (94), a powerful explosive whose mercury and silver salts are primary explosives. ... 

Diazotization of 5-aminotetrazole leads to the formation of 5-tetrazolediazonium 396. Further transformations of this very reactive intermediate are controlled by the reaction conditions and afford a wide range of 5-substituted tetrazoles (Scheme 45) . 

The diazotization of 5-aminotetrazole as a general preparative method for 5-substituted tetrazoles with versatile simple substituents is still important. For instance, the preparation of N-unsubstituted 5-nitrotetrazole 397 through 5-nitrotetrazole sodium salt tetrahydrate <1997RJ01771> is a significant achievement of the last decade and demonstrates new features of the amino group reactivity in 5-aminotetrazole derivatives (Scheme 46). 

Diazotetrazole (16) was obtained by dropwise addition of 2-pentyl nitrite to a solution of 5-amino-l//-tetrazole in a 4 1 mixture of tetrahydrofuran and aqueous hydrochloric acid. The diazonium chloride can be extracted into ether. Shevlin obtained the extremely explosive solid diazonium salt (16) by evaporation of that solution. He has recommended that not more than 0.75 mmol of diazonium salt be isolated at one time. An explosion during the diazotization of 5-aminotetrazole on a laboratory scale was described by Gray and coworkers. The structure 17 (equation 5) indicates clearly that this diazo compound may have the tendency to decompose into atomic carbon and three equivalents of dinitrogen—a reaction which is clearly highly exothermic. The decomposition of the tetrazole-5-diazonium chloride (16) has been studied by Shevlin by coating the salt on the walls of a 500 ml flask in the presence of two substrates, ethene and ethylene oxide. With ethene the products found after heating the flask to 80 °C are shown in equation 6, and with ethylene oxide in equation 7. The products correspond to those found with atomic carbon formed by completely different methods (see references cited by Shevlin). 

The parent ring system (53) was prepared by diazotization of 2-hydrazinopyrimidine (57JAP570777). Alkyl derivatives of (53) have been synthesized by the condensation of /3-dicarbonyl compounds with 5-aminotetrazole (79JCS(P1)3085). For example, treatment of 5-aminotetrazole with pentane-2,4-dione gave 5,7-dimethyltetrazolo[l,5-a]pyrimidine (Scheme 72) (65JOC826). 

Attempted diazotization in dilute acid sometimes yields primary nitroso compounds. Reactions of 3- and 5-amino-1,2,4-thiadiazoles with sodium nitrite and acid give primary nitrosamines (e.g. 432->433) (65AHC(5)n9) which can be related to the secondary nitrosamines (434) prepared in the normal way. 1-Substituted 5-aminotetrazoles with nitrous acid give stable primary nitrosamines (435). Primary nitrosamines have been isolated in the imidazole series. 

The high reactivity of heterocyclic diazonium ions in azo coupling reactions is the reason why in some cases the primary diazotization products cannot be isolated. For example, diazotization of 2-methyl-5-aminotetrazole (2.14) directly yields the triazene 2.15, i. e., the N-coupling product, since the intermediate diazonium ion is reactive enough to give the N-coupling product with the parent amine even under strongly acidic conditions (Scheme 2-8 Butler and Scott, 1967). 

The reaction of aminoguanidine with nitrous acid in the presence of an excess of acetic acid gives also l,3-ditetrazyltriazine(IX).It is possible that 5-aminotetrazole first arises, which then undergoes diazotization and the diazo compound thus formed couples with the remaining aminotetrazole ... 

Disubstituted tetrazoles generally display reactions at the 5-position which are similar to those of other tetrazoles, but only a limited amount of work has been reported on these compounds.1 For example, diazotization of 2-benzyl- and 2-aryl-5-aminotetrazoles [Eq. (34)] is similar to that of the 1-substituted compounds.419 421 Diazotization of 2-methyl-5-aminotetrazole in dilute acid solution gives the triazene 201.291... 

The modem methods for performing the GBH reaction are based on the thermal decomposition of certain aryltriazenes in the presence of trifluoroacetic acid [66,67], or on the phase transfer catalysed reaction of aryldiazonium tetrafluoroborate in the presence of potassium acetate [61], both methods in an excess of arene as the reactant and reaction solvent. The first method requires previous preparation of the aiyltriazene (VII) by diazotation of an aromatic amine in hydrochloric acid followed by addition of piperidine [66], other dialkylamine or 5-aminotetrazole [67]. For example, from the diazotized aniline solution 43, by addition of an equimolar amount of piperidine, the yellow-orange 1-phenyl-3,3-(pentanediyl)triazene (48) readily crystallize in 81% overall yield [66], Scheme 17. 

Aminotetrazole (31) is diazotized with NaN02/HCl to give the diazonium salt 32, which is highly explosive and can be handled only in solution. Warming of a solution of 32 brings about elimination of HCI and leads to the diazonium betaine 33, whose decomposition gives rise to N2 and monoatomic carbon. 

The reaction sequence starts from tetrazolyldiazonium salt 42 prepared from aminotetrazole 41 by diazotation. This compound when reacted with arylformylacetonitrile 43 leads to the intermediate formation of the condensation product 44, which easily undergoes ring closure to 45. This tetrazolo[5,l-z][l,2,4]triazine compound, however, forms an equilibrium with the valence bond isomeric azide 46, which can participate in a different ring closure than the reverse route, and yields the tetrazolo[l,5-A][l,2,4]triazine product 47. The reaction was carried out with a series of various aryl derivatives and proceeded in good to excellent yields (68-87%). 

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