Dimethyl 3-oxoglutarate → methyl 2-(5-oxo-1-(2-phenylpropan-2-yl)-4,5-dihydro-1H-pyrazol-3-yl)acetate

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Reaction Steps

tert-Butyl 2-(2-phenylpropan-2-yl)hydrazinecarboxylate (250 mg, 1.00 mmol) was dissolved in methylene chloride (2 mL), mixed with p-toluenesulfonic acid monohydrate (0.40 g, 2.1 mmol) and stirred at room temperature for 18 hours. The reaction solution was basified with saturated aqueous sodium hydrogen carbonate and separated. The organic layer was washed with saturated aqueous sodium chloride, dried over anhydrous sodium sulfate and filtered, and the filtrate was concentrated under reduced pressure. The resulting residue was dissolved in toluene (2.0 mL) and acetic acid (70 μL), mixed with dimethyl 1,3-acetonedicarboxylate (174 mg, 1.00 mmol) and stirred at 90° C. for 3 hours and at 105° C. for 3 hours. After completion of the reaction, the reaction solution was allowed to cool to room temperature and diluted with ethyl acetate. The organic layer was washed with saturated aqueous sodium hydrogen carbonate and then with saturated aqueous sodium chloride, dried over anhydrous sodium sulfate and filtered, and the filtrate was concentrated under reduced pressure. The resulting residue was purified by intermediate pressure silica gel column chromatography (silica gel 12 g, ethyl acetate:hexane=1:9 to 3:7) to give 96.3 mg of the desired product as a white solid.

Provenance & Evidence