Ammonium Chloride → Tert-butyl 3-ethynyl-3-hydroxypyrrolidine-1-carboxylate

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Reaction Steps

Ethynyl magnesium chloride (0.5 M in THF, 210 mL, 105 mmol) was diluted with THF (100 mL) and cooled in an ice-water bath. A solution of N-Boc-3-pyrrolidinone (9.21 g, 50 mmol) (Example 97A above) in THF (100 mL) was added dropwise with cooling. The mixture was stirred for 2 h and aqueous ammonium chloride solution (100 mL, 15% W/V) was then added. The mixture was then extracted with ether (2×400 mL). The ether layers were washed with saturated aqueous sodium chloride solution (200 mL), combined, dried (MgSO4), filtered and concentrated. The residue was chromatographed (Biotage Flash 40S, EtOAc - hexanes as solvent) to give rac-N-Boc-3-hydroxy-3-ethynyl-pyrrolidine as a pale yellow oil that crystallized on standing. (Yield 10.13 g, 96.4%).

Provenance & Evidence