Sulfuric Acid → 6-Methoxyphthalazin-1-ol

Participants

Reaction Steps

A solution of 2-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-5-methoxy-benzaldehyde (2 g, 8.58 mmoles), prepared as described in example 2, in 30 ml of a mixture of water (5 ml), ethanol (50 ml) and concentrated H2SO4 (4 ml) up to 100 ml with ethanol, was stirred under reflux for 20 hours, then concentrated to small volume, taken up in water, extracted with ethyl ether and the organic phase was washed with water, anhydrified and brought to dryness. The resultant oil was dissolved in acetic acid (14 ml) and dropwise added, under N2, with hydrazine monohydrate (1.25 ml, 25.7 mmoles) dissolved in acetic acid (6 ml). The mixture was stirred for 3.5 hours at room temperature, then at 80° C. for 4 hours, then cooled, brought to almost complete dryness, taken up in water, neutralised with NaHCO3, extracted more times with CH2Cl2. The organic phases were washed with water, anhydrified and concentrated. The residue was triturated in CH2Cl2 (10 ml) and filtered to give 1.1 g of the title compound (yield: 73.4%). m.p.: 200-205° C.

Provenance & Evidence