Organic azides in heterocyclic synthesis, 14. Synthesis of 3,6‐diaminopyridazine from 6‐azidotetrazolo[1,5‐b]pyridazine

Abstract 6‐Azidotetrazolo[1,5‐ b ]pyridazine („3,6‐Diazidopyridazine”︁, 1 ) reacts at ambient temperature with phosphanes or phosphites 2a–c to yield the phosphazenes 3a–c . In contrast to literature reports, the tetrazolopyridazines 1 , and 3a,b react with phosphanes to yield 3,6‐bis(phosphoranylideneamino)pyridazines 4 ; however, the required temperature is rather high (180°C). The use of phosphites instead of phosphanes leads to „Michaelis‐Arbuzov‐type”︁ rearrangements; thus, 3a reacts in boiling 2d to afford 6 , and heating of the trimethoxyphosphazene 3c in refluxing 1,2‐dichlorobenzene yields the methylamino derivative 7 .