(Diethylamino)sulfur trifluoride → (2R,4S)-tert-butyl 4-fluoro-2-(3-fluorophenyl)pyrrolidine-1-carboxylate

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Reaction Conditions

Reaction Steps

To a solution of (4R)-tert-butyl 2-(3-fluorophenyl)-4-hydroxypyrrolidine-1-carboxylate (I-4) (2.7 g, 9.6 mmol) in DCM (25 mL) in a plastic bottle at −78° C. was added DAST (2.5 mL, 19.2 mmol). The mixture was stirred at −78° C. for 2 hours and then was warmed slowly to room temperature overnight. The mixture was added drop wise to aqueous NaHCO3 at 0° C. and was extracted with DCM. The organic layers were combined, washed with brine, dried over sodium sulfate, filtered and concentrated. The two diasteromers were separated by column chromatography on silica gel with EtOAc/hexanes gradient as eluant to yield (2R,4S)-tert-butyl 4-fluoro-2-(3-fluorophenyl)pyrrolidine-1-carboxylate (I-5A) (first eluting compound) and (2S,4S)-tert-butyl 4-fluoro-2-(3-fluorophenyl)pyrrolidine-1-carboxylate (I-5B). 1H NMR (400 MHz, CDCl3) δ 7.21 (dd, J=6.0, 6.0 Hz, 1 H), 6.92 (bd, J=8.0 Hz, 1 H), 6.88-6.82 (m, 2 H), 5.20 (bd, J=52.0 Hz, 1 H), 4.80 (bs, 1 H), 4.02 (dd, J=13.6, 22.8 Hz, 1 H), 3.65 (dd, J=12.8, 38.4 Hz, 1 H), 2.67-2.56 (m, 1 H), 1.89 (dt, J=11.2, 42 Hz, 1 H), 1.09 (s, 6 H). MS m/z 284.1 (M+1)+.

Provenance & Evidence