Hydrogen Bromide → 6-(4-hydroxyphenyl)-4,5-dihydro-3(2H)-pyridazinone

Participants

Reaction Conditions

Reaction Steps

A mixture of 25.0g (0.120 mmol) of 3-(4-methoxybenzoyl)propionic acid and 175 ml of 48% HBr is heated under N2 at 110° C. for 5 hrs. After cooling, the mixture is diluted with an equal volume of water and exhaustively extracted with EtOAc (5×100 ml). The organic phase is washed with saturated NaCl, dried (MgSO4), filtered and the solvent removed to leave a white solid. After recrystallization from EtOAc, 16.8 g of 3-(4-hydroxybenzoyl)propionic acid, m.p. 157°-159° C., is obtained. Yield, 72. A mixture of 10.0 g (51.5 mmol) of the acid prepared above and 6.2 ml (128 mmol) of 98% hydrazine monohydrate in 172 ml of ethanol is heated at reflux overnight under N2. The resulting white solid is collected by suction filtration to give 9.37 g of 6-(4-hydroxyphenyl)-4,5-dihydro-3(2H)-pyridazinone as a white powder, m.p. >300 ° C.

Provenance & Evidence