C[O:2][C:3]1[N:4]=[N:5][C:6]([S:9]([C:12]2[O:13][C:14]3[CH:22]=[CH:21][C:20]([Cl:23])=[CH:19][C:15]=3[C:16]=2[CH2:17][CH3:18])(=[O:11])=[O:10])=[CH:7][CH:8]=1.Cl>O1CCOCC1>[Cl:23][C:20]1[CH:21]=[CH:22][C:14]2[O:13][C:12]([S:9]([C:6]3[CH:7]=[CH:8][C:3](=[O:2])[NH:4][N:5]=3)(=[O:11])=[O:10])=[C:16]([CH2:17][CH3:18])[C:15]=2[CH:19]=1A mixture of 3-methoxy-6-(5-chloro-3-ethyl-benzofuran-2-sulfonyl)-pyridazine, without further purification, (1.04 mmol, 352 mg), conc. HCl (1.5 mL), and dioxane (3 mL) was heated at 100° C. for 2 hours. The reaction mixture was cooled and evaporated to dryness. Water (10 mL) was added to the residue and the resulting solid, 6-(5-chloro-3-ethyl-benzofuran-2-sulfonyl)-2H-pyridazin-3-one, was collected. (46%, 155 mg); mp 209° C.-210° C.
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