Hydrazine hydrate (1:1) → 5-amino-1(2H)-phthalazinone

Participants

Reaction Steps

A stirred solution of 3-hydroxy-4-nitrophthalide (43.4 g, 0.22 mole) and hydrazine hydrate (11.6 ml) in ethanol (1830 ml) was heated under reflux for 1 hour. The heating was discontinued and palladium on carbon (10%, 2.44 g) was added (with caution) over 15 minutes. A solution of hydrazine hydrate (24.2 ml) in ethanol (304 ml) was then added, dropwise, over 30 minutes and the mixture was heated under reflux for a further 2.5 hours. Filtration of the hot reaction mixture followed by the addition of a saturated solution of hydrogen chloride in ethanol (80 ml) to the filtrate gave a solid precipitate which was collected and washed with ethanol and ether. Evaporation of the filtrate gave a solid residue which was washed several times with boiling ethanol. The combined solids were recrystallised from water, after charcoal treatment, to give 5-amino-1(2H)-phthalazinone (12.7 g, 35%, m.p. 289°-291°).

Provenance & Evidence