Synthesis of pyridazine derivatives XXII. s-triazolo[4, 3-b]pyridazine 5-oxides

The synthesis of s-triazolo4,3-b] pyridazine 5-oxides is reported. To our knowledge, they are the first example of N-oxides of heteroaromatic azoloazines with a bridgehead nitrogen. They are easily rearranged, in particular when irradiated with ultraviolet light, into 6-hydroxy-s-triazolo4,3-b]pyridazines.