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

HRID 2297403Notes

Reaction equation

CC1(C)C[O:5][C:4]([C:7]2[CH:12]=[CH:11][C:10]([O:13][CH3:14])=[CH:9][C:8]=2[C:15](=O)[CH2:16][CH3:17])=[N:3]1.OS(O)(=O)=O.O.[NH2:26]N.C([O-])(O)=O.[Na+]>C(O)(=O)C.O.C(O)C>[CH2:16]([C:15]1[C:8]2[C:7](=[CH:12][CH:11]=[C:10]([O:13][CH3:14])[CH:9]=2)[C:4](=[O:5])[NH:3][N:26]=1)[CH3:17]

Participants

Conditions

Temperature: 80 °C

Procedure

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.

Workup

temperaturereflux for 20 hours
concentrationconcentrated
extractionextracted more times with ethyl ether
washThe organic phases were washed with water
customto give an oil which
additionAt the end of the addition
extractionextracted more times with CHCl3
customto give a residue, which
customchromatographed (eluent

Sources & evidence

ORD record: ord-0d27123532c94966872832facbcf990c
Source dataset: uspto-grants-2002_12
DOI: 10.6084/m9.figshare.5104873.v1
Patent number: US06492360B1

Reaction notes

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