Pyrido pyridazinium inner salts

Pyrido[l,2-6]pyridazinium inner salt 61 was prepared from 1,2-dihydropyrido[l,2-6]pyridazinium inner salt 54 by treatment with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone in CH2CI2 at room temperature in 95% yield (99JOC9001). 

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