Abstract Oxidation reactions of various methyl substituted azolopyridazines 2a-d, 3a-h, 4a, b were investigated in order to gain access to the title compounds. This procedure was found to be of limited scope affording only the carboxylic acids 5, 7 and 9. A variety of novel azolopyridazinecarboxylic acid methyl esters bearing one or two methoxycarbonyl groups at the pyridazine core 17, 18 and 12, 14, 16, 20, respectively, however, could be prepared by ...
![6-methyl-[1,2,4]triazolo[4,3-b]pyridazine Structure](https://image.chemsrc.com/caspic/140/18591-78-1.png)
![[1,2,4]triazolo[4,3-b]pyridazine-6-carboxylic acid Structure](https://image.chemsrc.com/caspic/387/56434-29-8.png)