Acetic Acid → 4-(2,6-Difluorophenyl)-2,2-dimethyl-5-oxopiperazine-1-carboxylic acid t-butyl ester

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Reaction Steps

A solution of 2.05 g of potassium t-butoxide (18.3 mmol) in tetrahydrofuran (120 ml) was added to a solution of 5.14 g of {2-[(2-bromoacetyl)-(2,6-difluorophenyl)amino]-1,1-dimethylethyl}carbamic acid t-butyl ester obtained in Example (60b) (12.2 mmol) in tetrahydrofuran (120 ml) under a nitrogen atmosphere and under cooling in a dry ice-acetone bath over 30 minutes, and the mixture was stirred at the same temperature for 30 minutes. 0.33 ml of acetic acid (6.10 mmol) was added to the reaction mixture. After returning to room temperature, the solvent was evaporated under reduced pressure. The residue was diluted with water, followed by extraction with ethyl acetate. Then, the organic layer was washed with brine and dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography (elution solvent:hexane/ethyl acetate=3/1) to obtain 3.43 g of the title compound (yield: 83%).

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