CCOP(S)(OCC)=S.[Br:10][C:11]1[CH:12]=[C:13]([C:17](=O)[CH:18]=[CH:19][C:20]([OH:22])=O)[CH:14]=[CH:15][CH:16]=1.BrC1C=C(C(=O)CC(SP(OCC)(OCC)=S)C(O)=O)C=CC=1.O.[NH2:48][NH2:49]>C(O)C>[Br:10][C:11]1[CH:12]=[C:13]([C:17]2[CH:18]=[CH:19][C:20](=[O:22])[NH:48][N:49]=2)[CH:14]=[CH:15][CH:16]=11.12 g (0.006 mole) of O,O-diethyldithiophosphoric acid were added, at room temperature, to a suspension of 1.28 g of 4-(3-bromophenyl)-4-oxo-2-butenoic acid in 10 ml of ethanol, and then the mixture was stirred for 10 minutes. Formation of 4-(3-bromophenyl)-2-diethoxyphosphinothioylthio-4-oxobutanoic acid was confirmed by thin layer chromatography but the compound was not separated from the reaction mixture. 0.3 g (0.006 mole) of hydrazine monohydrate was added to the reaction mixture, which was then stirred overnight at room temperature. At the end of this time, the crystals which had precipitated were collected by filtration and washed with ethanol to give 0.48 g of the desired 6-(3-bromophenyl)-3(2H)pyridazinone. The filtrate was concentrated and then subjected to column chromatography through silica gel eluted with a 4:1 by volume mixture of benzene and ethyl acetate, to give a further 0.48 g of the product, a total of 0.96 g (yield 76%) of the product, melting at 202°-204° C.
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