[O:1]1[C:5]2[CH:6]=[CH:7][C:8]([N:10](C(OCC(Cl)(Cl)Cl)=O)[NH:11][C:12](OCC(Cl)(Cl)Cl)=O)=[CH:9][C:4]=2[CH2:3][CH2:2]1.CO.[C:30]([O-:33])(=O)[CH3:31].[NH4+].[C:35](OCC)(=O)CC(C)=O>C(O)C.[Zn]>[O:1]1[C:5]2[CH:6]=[CH:7][C:8]([N:10]3[C:30](=[O:33])[CH2:31][C:12]([CH3:35])=[N:11]3)=[CH:9][C:4]=2[CH2:3][CH2:2]1Bis(2,2,2-trichloroethyl) 1-(2,3-dihydrobenzofuran-5-yl)hydrazine-1,2-dicarboxylate 7b (2.9 g, 5.8 mmol) was dissolved in 50 mL of ethanol and 5 mL of methanol followed by addition of zinc powder (10.8 g, 166 mmol) and aqueous ammonium acetate (15 mL, 1 mol/L) and the mixture was reacted at room temperature for 1 hour. Then ethyl acetoacetate (0.75 mL, 5.9 mmol) was added dropwise. The reaction mixture was heated to reflux for 2 hours. The reaction was monitored by TLC until the disappearance of the starting materials. The reaction was cooled to room temperature and filtered. The filtrate was concentrated under reduced pressure and the residue was purified by silica gel column chromatography to obtain the title compound 2-(2,3-dihydro-benzofuran-5-yl)-5-methyl-2,4-dihydro-pyrazol-3-one 7c (706 mg, yield 56.5%) as a yellow solid.
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