In a flame dried round-bottomed flask equipped with a magnetic stir bar and under inert atmosphere (N2), to a solution of tert-butyl 3-fluoro-4-methylenepiperidine-1-carboxylate (545 mg, 2.53 mmol) in THF (17 mL) was added dropwise a 0.5 M solution of 9-BBN (12.7 ml) at 0° C. The resulting solution was stirred for 16 h at rt. A solution of NaOAc 5M in water (1.7 mL) was added followed by H2O2 30% (1.7 mL), and the mixture was stirred for 14 h at rt. The mixture was then partitioned between EA and aq. sat. NaHCO3. The aqueous layer was extracted with EA, and the combined organic extracts were washed with brine, dried over MgSO4, filtered, and concentrated under reduced pressure. The residue was purified by FC (hexanes-EA, 3:2) to afford cis-tert-butyl 3-fluoro-4-(hydroxymethyl)piperidine-1-carboxylate as a colorless oil and trans-tert-butyl 3-fluoro-4-(hydroxymethyl)piperidine-1-carboxylate as a colorless oil. LC-MS-conditions 08: tR=0.65 min; [M-CH3+H]+=220.35 and tR=0.68 min; [M-CH3+H]+=220.36.
