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ChemicalBook CAS DataBase List Pyridazine, 3,6-dione, 4-bromo-1,2-dihydro-
15456-86-7

Pyridazine, 3,6-dione, 4-bromo-1,2-dihydro- synthesis

2synthesis methods
-

Yield:-

Reaction Conditions:

in water

Steps:

10.A (a)
The reaction was repeated with 29 g hydrazine sulphate, 53 g bromomaleic anhydride and 130ml water. The precipitates were collected by filtration, washed with water and acetone and dried as a combined batch in vacuo to afford 4-bromo-1,2-dihydro-3,6-pyridazinedione as a white solid (113 g). The solid in two batches was treated with phosphorus oxychloride (2 x 200 ml) and heated to reflux for 3.5 hours. The mixture was cooled, evaporated and azeotroped with toluene. The residue was partitioned between dichloromethane and saturated aqueous sodium bicarbonate solution and extracted with DCM twice more. The organic extracts were dried and evaporated. This residue was re-dissolved in dichloromethane, and chromatographed on silica gel (300 g) (DCM as eluent) to give a white solid (101.5 g, 87%). (LC/MS analysis showed ca 20-30% impurity, isomers of bromo-dichloropyridazine). MS (+ve ion electrospray) m/z 184/185/186 (MH+), trichloropyridazine MS (+ve ion electrospray) m/z 228/229/231 (MH+), bromo-dichloropyridazine.

References:

GLAXO GROUP LIMITED EP1980251, 2008, A1

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