Methyl iodide → Tert-butyl 3-cyano-3-methylpyrrolidine-1-carboxylate

To a solution of tert-butyl 3-cyanopyrrolidine-1-carboxylate (1.0 g, 5.1 mmol) in THF (20 mL) at −78° C. was slowly added LiHMDS (1.0 M in THF, 5.6 mL, 5.6 mmol). The reaction mixture was stirred at −78° C. for 30 min then iodomethane (0.48 mL, 7.64 mmol) was slowly added. The reaction mixture was stirred at −78° C. for 30 min then warmed to room temperature and quenched with saturated aqueous NH4Cl. Diluted with H2O and extracted with EtOAc (2×) then dried over MgSO4 and concentrated. The residue was purified by SiO2 chromatography (20% to 40% EtOAc/hexanes) to afford 0.95 g (89%) of tert-butyl 3-cyano-3-methylpyrrolidine-1-carboxylate as a pale yellow solid.