5-Aminotetrazole, diazotization

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 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%). 

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. ... 

Diazotetrazole was the first diazoazole synthesized by diazotization of diluted solutions of the aminotetrazole in hydrochloric acid with sodium nitrite subsequent neutralization with alkali was not necessary (1892LA46). Diazotization with isoamyl nitrite in THF and aqueous hydrochloric acid was also effective and allowed the isolation of the diazotetrazole (72JA1379). When the aminotetrazole was diazotized with sodium nitrite in acetic acid, only the 1,3-ditetrazolyltriazene 250 was obtained (10CB1866). 

According to Karrer (Ref 4), it may be prepd by diazotizing 5-aminotetrazole and coupling the resulting compound with hydrazine... 

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 ... 

Beil (Ref 1) this compd was not prepd in the free state but its prepn by Rathsburg (Ref 4) by oxidg amino tetr azole in ale sol ns with permanganate or persulfates is described in CA 17, 1147(1923). A diazotetrazole was prepd by diazotizing aminotetrazole The British abstract of the patent of Rathsburg (Ref 4) shows an azotetrazole with the structure ... 

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). 

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). 

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