Sulfuric Acid → 4-ethyl-6-methoxy-2H-phthalazin-1-one

Participants

Reaction Conditions

Reaction Steps

A solution of 1-[2-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-5-methoxy-phenyl]-propan-1-one (6.4 g, 15.9 mmoles), prepared as described in example 8, in 110 ml of a mixture of water (10 ml), ethanol (100 ml) and concentrated H2SO4 (8 ml) up to 200 ml with ethanol, was stirred under N2 and reflux for 20 hours, then concentrated, taken up in water and extracted more times with ethyl ether. The organic phases were washed with water, anhydrified and brought to dryness to give an oil which was dissolved in acetic acid and added, at 15° C., with hydrazine monohydrate (1.56 g, 31.2 mmoles) in acetic acid (10 ml). At the end of the addition, the mixture was heated to 80° C. and, after 20 hours, brought to small volume, taken up in water, neutralised with NaHCO3 and extracted more times with CHCl3. The organic phases were anhydrified and brought to dryness to give a residue, which was flash chromatographed (eluent: hexane/ethyl acetate 9:1, then 7:3). There were thus obtained 1.34 g of the title compound (yield: 44%). m.p.: 230-235° C.

Provenance & Evidence