On the reaction of phenacylmalononitrile with hydrazines : a new route to pyrazolo[3,4-c]pyridazine,isoxazolo[5,4-c]pyridazine and pyrimido[4,5-c]pyridazine

Abstract EN

The reaction of arylmalononitiles 1a,b with hydrazine hydrate at room temperature has afforded 3-oxo-6-aryl-2,3,4,5-tetrahydropyridazine-4-carbonitrile 3a,b as the sole isolable product.

These 3-oxopyridazin-4-carbonitriles underwent aromatization to 3-oxo-6-phenylpyridazine-4-carbonitrile 4 on attempted coupling with benzene diazonium chloride.

Compound 3a reacted with hydrazine hydrate as well as urea to yield pyrazolo[3,4-c]pyridazine 5 and pyrimido[4,5-c]pyridazine 6.

On the other hand, amidoximes 7a,b were isolated from reaction of 3a,b with hydroxylamine hydrochloride.

Amidoximes 7a could be cyclized successfully into 5-phenylisoxazolo[5,4-c]pyridazin- 3-amine 8 while 7b could not be cyclized on our hand.