[CH3:1][NH:2][NH2:3].[CH2:4]([O:6][C:7](OCC)=[CH:8][C:9]([O:11]CC)=O)[CH3:5].O.S(=O)(=O)(O)O>C(O)C.[Cl-].[Na+].O>[CH2:4]([O:6][C:7]1[CH2:8][C:9](=[O:11])[N:2]([CH3:1])[N:3]=1)[CH3:5]Methylhydrazine (2.6 g, 0.056 mole) was added to a solution of ethyl 3,3-diethoxyacrylate (10.0 g, 0.053 mole) in ethanol (50 mL) and the mixture was heated and held at reflux for 18 hours. After cooling, water, saturated brine, and 3 mL of concentrated sulfuric acid were added; and the product was extracted with ethyl acetate. The combined extracts were dried with magnesium sulfate, filtered and concentrated in vacuo. Purification by chromatography on silica gel using ethyl acetate/cyclohexane gave 5-ethoxy-2,4-dihydro-2-methyl-3H-pyrazol-3-one (3.2 g, 42% yield) as a white solid, mp=79°-80° C.
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