Ammonium Chloride → 2,2-Dimethyl-4-(2-methylphenyl)-5-oxopiperazine-1-carboxylic acid t-butyl ester

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Reaction Steps

A solution of 1.3 g of potassium t-butoxide (12.0 mmol) in tetrahydrofuran (80 ml) was added to a solution of 3.2 g of {2-[(2-bromoacetyl)-(2-methylphenyl)amino]-1,1-dimethylethyl}carbamic acid t-butyl ester obtained in Example (51b) (8.0 mmol) in tetrahydrofuran (80 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 10 minutes. A saturated ammonium chloride aqueous solution was added to the reaction mixture. The mixture was returned to room temperature and diluted with water, followed by extraction with ethyl acetate. Then, the organic layer was dried over anhydrous magnesium 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 1.8 g of the title compound (yield: 71%).

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