3- Azido-l,2,4-triazine 1-oxides

The diazotization of 3-hydrazino-l,2,4-triazine 1-oxides 48results, as expected, in 3-azido-l,2,4-triazine 1-oxides 4 (77JHC1221, 77JOC3498). 

Studies of presumed azido-tetrazole tautomerism for 3-azido-l,2,4-benzotria-zine 1-oxides 3 show that compounds 3 exist only in the form of azides, both in the crystalline state and in solution. Similar results were obtained in the studies of 3-azido-l,2,4-triazine 1-oxides 4, which have never been detected in the tetrazole form (69CB3818, 77JHC1221, 82JOC3886). 

A-Oxidation of 3-azido-l,2,4-triazines at either N-l or N-2 destabilizes the bicyclic compounds so that only the monocyclic azide tautomers (59, 60) are observed (77JHC1221). 3-Azido-l,2,4-benzotriazine was also found to exist as the azido tautomer (61b) in solution, but in the crystalline state it favoured the tetrazolo[5,l-c][l,2,4]benzotriazine structure (61a) (73JHC575). In DMSO the third isomer, the tetrazolo[ 1,5-6]-fused compound (61c), was detected in small amount (10%) by 13C NMR spectroscopy (79JOC1823). Solvent and... 

Oxidation of 1,2-diaminobenzimidazole, leading to the formation in high yield of 3-aminobenzo-l,2,4-triazine 838, is thought to proceed through recyclization of an intermediate nitrene 836 (possibly via diazene intermediate 837) as evidenced by the formation of amine 838, with a high efficiency on the thermolysis of l-amino-2-azidobenzimidazole 835. The reaction works well also for other A -amino—azidoimidazoles and 4-amino-3-azido-l,2,4-triazoles. 

New fused tetrazoloazines that have been reported include tetrazolo[5,l-a]isoquinolines,665 tetrazolo[5, l-6]benzothiazoles,666 and tetrazolopyridines.667 Reactions of fused tetrazoloazines, or the azido isomers, that have been reported include hydrolytic cleavage of the pyrimidine ring of tetrazolopyrimidines,66 pyrolysis of 3-azido-pyridazine 2-oxides,66 and photolysis of azido-l,3,5-triazine.670 Dipole moments of 3-azido-1,2,4-triazole derivatives have also been reported.671... 

---