Reactions via heteroarynes

Reaction of 2-(tribenzoylribofuranosyl)-5,6-dichloro-3(2//)-pyridazinone with neat dimethyl-amine gave a mixture of the 4- and 5-dimethylamino debenzoylated derivatives (Equation (28)). 

Reaction may be by an aryne mechanism, or the unexpected product may arise via dimethylamine addition to C-4 and loss of HCl from the dihydro adduct 83JHC369 . 

Hydrazones of 4-chloro-5-hydrazino-3(2//)-pyridazinones undergo photolytic cyclization (Equation (29)) to give pyrazolo[3,4- /]pyridazinones 84JHC1249 . 

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