Pyridazine 3.4- dicarbonitrile, reactions

Compounds containing this ring system are prepared by the reaction of 3,4-disubstituted pyridazines with hydrazine. 6-Methylpyridazine-3,4-dicarbaldehyde (150) condenses with hydrazine to give 3-methylpyridazino[4,5-c]pyridazine (151) (73JHC1081). 5-Oxo and 5,8-dioxo substituted pyridazino[4,5-c]pyridazines are prepared in like manner by condensing ethyl 3-formylpyridazine-4-carboxylates and diethyl pyridazine-3,4-dicarboxylates, respectively, with hydrazine. Pyridazine-3,4-dicarbonitrile (152) also reacts with hydrazine to give the diamino heterocycle (153) (67JHC393). 

As with pyridine-2,3-dicarbonitriles, the reaction of pyridine-3,4-dicarbonitriles with hydrazine hydrate in acetic acid/dioxane at 95 °C results in cyclization to give the corresponding pyrido[3,4-t/]pyridazine-l,4-diamine in the first step, followed by an amino-hydrazino exchange in positions 1 and 4 to give pyrido[3,4-t/]pyridazine-1,4-dihydrazines (see Section 7.2.1.5,1.5.5.) 63 127 e.g. formation of8.127... 

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