Hexane → 1-tert-Butyl 4-ethyl 4-cyanopiperidine-1,4-dicarboxylate

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A solution of tert-butyl 4-cyanopiperidine-1-carboxylate (0.75 g, 3.57 mmol) in THF (25.0 mL) was cooled to −78° C. followed by dropwise addition of LDA (1.8 M in THF, 6.0 mL, 5.35 mmol) and stirred at the same temperature (−78° C.) for 45 min followed by addition of ethyl chloroformate (0.46 g, 4.28 mmol). The temperature of the reaction was slowly raised to rt and left to stir for 6 h. The reaction was then cooled to 0° C. and quenched by drop wise addition of saturated NH4Cl solution (50 mL), extracted with EtOAc (3×100 mL) and the combined organics washed with brine, dried (Na2SO4), filtered and concentrated under reduced pressure. The crude residue was purified over 100-200 M silica-gel using 7% EtOAc:hexane to obtain the product as an orange viscous liquid (0.4 g, 48% yield). MS: 283.14 [M+H]+.

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