Heating of 3,6-dichloropyridazine (I) with hydrazine hydrate at 100 C gives 6-chloro-3-pyridazinylhydrazine (II). The hydrazino group is protected by transforming it with camphor (III) to the camphorhydrazone (IV), which is aminated by heating with morpholine to give the morpholinylhydrazone (V). After liberating the hydrazine function by acidic hydrolysis in a biphasic system, the resulting 6-morpholino-3-pyridazinylhydrazine (VI) is reacted either with tert-butylacetoacetate (VII) or with tert-butylpropiolate (VIII) to yield RGH-5526.

Heating of 3,6-dichloropyridazine (I) with hydrazine hydrate at 100 C gives 6-chloro-3-pyridazinylhydrazine (II). The hydrazino group is protected by transforming it with camphor (III) to the camphorhydrazone (IV), which is aminated by heating with morpholine to give the morpholinylhydrazone (V). After liberating the hydrazine function by acidic hydrolysis in a biphasic system, the resulting 6-morpholino-3-pyridazinylhydrazine (VI) is reacted either with tert-butylacetoacetate (VII) or with tert-butylpropiolate (VIII) to yield RGH-5526.

Heating of 3,6-dichloropyridazine (I) with hydrazine hydrate at 100 C gives 6-chloro-3-pyridazinylhydrazine (II). The hydrazino group is protected by transforming it with camphor (III) to the camphorhydrazone (IV), which is aminated by heating with morpholine to give the morpholinylhydrazone (V). After liberating the hydrazine function by acidic hydrolysis in a biphasic system, the resulting 6-morpholino-3-pyridazinylhydrazine (VI) is reacted either with tert-butylacetoacetate (VII) or with tert-butylpropiolate (VIII) to yield RGH-5526.