1- Aminotriazolopyridine, reaction with lead

Finally, an example of a 1,3-dipolar cycloaddition has appeared. Reaction of pyridynes and quinolynes with pyridazine-A-oxides 747 gave pyrido-oxepins 750 in 20-30% yields. The reaction is thought to involve cycloaddition to give 748 which, after a 1,3-shift of the oxygen from N to C and nitrogen loss, gives the product. The pyridynes were produced by lead tetraacetate oxidation of 1-aminotriazolopyridines. 

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