C[N:2]([CH:4]=[C:5]1[C:10](=[O:11])[CH2:9][CH2:8][CH2:7][C:6]1=O)C.[CH3:13][NH:14]N.CC(O)=O>CC(O)(C)C>[CH3:13][N:14]1[C:6]2[CH2:7][CH2:8][CH2:9][C:10](=[O:11])[C:5]=2[CH:4]=[N:2]1To a solution of 2-((dimethylamino)methylene)cyclohexane-1,3-dione (55 g crude, 300 mmol) in t-BuOH (400 ml) was added methylhydrazine solution (35 g, 40% aqueous solution, 304 mmol) and AcOH (20 ml) at room temperature. The resulting mixture was heated to reflux for 3 h under nitrogen protection. After cooling, the mixture was concentrated in vacuo and the residue was purified by column chromatograph on silica gel (petroleum ether/ethyl acetate=1/1 v/v %) to give 1-methyl-6,7-dihydro-1H-indazol-4(5H)-one (20 g, two steps: 44%). MS-ESI (m/z): 151 (M+1)+ (Acq Method: 0-60AB_2 min; Rt: 0.90 min)
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