Disconnection of pyridazines gives a molecule of hydrazine, and a 1,4-diketone with an alkene in the 2,3-position. A functional group addition , FGA, disconnection gives us the 1,4-diketone.
The strategy adopted in the synthesis is reaction of hydrazine with the 1,4-diketone to give dihydropyridazine. Oxidation of the dihydropyridazine then gives the pyridazine. Carrying out oxidation at this point avoids a cis double bond problem.
Click the structures and reaction arrows in sequence to view the 3D models and animations respectively