1016258-66-4

At -78 °C, lithium hexamethyldisilazamate (1 M, 20 mL, 20 mmol) was slowly added dropwise to a solution of N-Boc-4-cyanopiperidine (2.1 g, 10 mmol) in anhydrous tetrahydrofuran (30 mL). The reaction mixture was stirred continuously at this temperature for 1 hour. Subsequently, ethyl chloroformate (2.2 g, 20 mmol) was added at -78 °C and stirring was continued at the same temperature for 1 hour. Upon completion of the reaction, the reaction was quenched with 1 M aqueous sodium bicarbonate (30 mL) and extracted with ethyl acetate (100 mL x 3). The organic layers were combined, washed with brine (20 mL), dried over anhydrous sodium sulfate, filtered and concentrated. The crude product was purified by silica gel column chromatography using a petroleum ether solution of 10-25% ethyl acetate as eluent to afford 1-tert-butyl 4-ethyl 4-cyanopiperidine-1,4-dicarboxylate as a colorless oil (2.8 g, 99% yield).LCMS (ESI) m/z 183.1 [M-99]+.

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