Cl.[Cl:2][C:3]1[CH:4]=[C:5]([NH:10][NH2:11])[CH:6]=[CH:7][C:8]=1[Cl:9].C([O-])(=O)C.[Na+].CN([CH:20]=[C:21]1[C:26](=[O:27])[CH2:25][CH2:24][CH2:23][C:22]1=O)C>CCCCO.C(O)(=O)C>[Cl:2][C:3]1[CH:4]=[C:5]([N:10]2[C:22]3[CH2:23][CH2:24][CH2:25][C:26](=[O:27])[C:21]=3[CH:20]=[N:11]2)[CH:6]=[CH:7][C:8]=1[Cl:9]A mixture of 1-(3,4-dichlorophenyl)hydrazine hydrochloride (6.78 g, 31.8 mmol) and anhydrous sodium acetate (2.60 g, 31.8 mmol) in n-BuOH (20 mL) is slowly added to a solution of 2-((dimethylamino)methylene)cyclohexane-1,3-dione (5.32 g, 31.8 mmol) in n-BuOH (100 mL) and acetic acid (5 mL). The resulting mixture is heated to reflux during 2 hours, effecting follow-up of the reaction by TLC. The solvent is evaporated at reduced pressure, the residue is diluted in AcOEt and washed with H2O. The solvent is next evaporated, and the crude is purified by silica-gel chromatography, to obtain 1-(3,4-dichlorophenyl)-1,5,6,7-tetrahydro-4H-indazol-4-one (5.0 g, 17.79 mmol, 56%, orange solid). 1H RMN (300 MHz, CDCl3): δ 2.17 (m, 2H), 2.51 (m, 2H), 2.96 (t, J=6.1 Hz, 2H), 7.36 (t, J=8.6 Hz, J′=2.4 Hz, 1H), 7.54 (d, J=8.6 Hz, 1H), 7.64 (d, J=2.4 Hz, 1H), 8.02 (s, 1H).
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