S(OC)(O[CH3:5])(=O)=O.[Cl:8][C:9]1[CH:14]=[CH:13][C:12]([C:15]2[CH:19]=[C:18]([CH3:20])[N:17]([CH:21]3[C:25](=[O:26])[CH2:24][CH2:23][C:22]3=[O:27])[N:16]=2)=[CH:11][CH:10]=1.C(=O)([O-])[O-].[K+].[K+]>CC(C)=O>[Cl:8][C:9]1[CH:14]=[CH:13][C:12]([C:15]2[CH:19]=[C:18]([CH3:20])[N:17]([C:21]3[C:22](=[O:27])[CH2:23][CH2:24][C:25]=3[O:26][CH3:5])[N:16]=2)=[CH:11][CH:10]=1Neat dimethyl sulfate (0.12 ml, 1.3 mmol) was added at room temperature to a vigorously stirred suspension of 2-[3-(4-chloro-phenyl)-5-methyl-pyrazol-1-yl]-cyclopentane-1,3-dione (374 mg, 1.3 mmol) and potassium carbonate (180 mg, 1.3 mmol) in acetone (10 ml). The mixture was then heated to 60° C. for 3 h with continued stirring, then cooled and the solvent removed in vacuo. The residue was partitioned between ethyl acetate (30 ml) and 1M sodium hydroxide solution (20 ml), the layers were separated, and the aqueous phase was further extracted with ethyl acetate (2×20 ml). The combined organics were washed with brine (20 ml), dried over magnesium sulfate and concentrated. The crude product was then purified by flash chromatography (using 20% to 100% EtOAc in DCM) to give 2-[3-(4-chloro-phenyl)-5-methyl-pyrazol-1-yl]-3-methoxy-cyclopent-2-enone (253.2 mg).
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