Sodium borohydride → (3R,4S)-Benzyl 3-fluoro-4-hydroxypiperidine-1-carboxylate

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Reaction Steps

To a solution of benzyl 3-fluoro-4-oxopiperidine-1-carboxylate (200 g, 0.797 mol) in methanol (1 L) was added NaBH4 (24.4 g, 0.636 mol) in portions at 0° C. After the addition, the mixture was stirred for 4 h and then quenched with water (200 mL). The mixture was concentrated, and then ethyl acetate and water were added to the residue. The organic layer was separated, dried over sodium sulfate and concentrated. The residue was purified via column chromatography (EtOAc/petroleum ether=1:6) to afford benzyl cis-3-fluoro-4-hydroxypiperidine-1-carboxylate and benzyl trans-3-fluoro-4-hydroxypiperidine-1-carboxylate. 1H NMR (600 MHz, CDCl3-D6) 7.50-7.30 (m, 5H); 5.13 (s, 2H); 4.70-4.50 (d, 1H); 4.10-3.70 (m, 3H); 3.48 (s, 1H); 3.23 (s, 1H); 2.50 (s, 1H); 1.90-1.70 (m, 2H).

Provenance & Evidence