Benzaldehyde → (2'R,3S)-5-chloro-2'-phenylspiro[indoline-3,3'-pyrrolidine]

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Reaction Steps

To a solution of 2-(5-chloro-1H-indol-3-yl)ethanamine (1.67 g, 8.58 mmol) in DCM (43 mL) was added benzaldehyde (0.96 g, 9.0 mmol). The reaction mixture was stirred over molecular sieves 4 Å (4.1 g) overnight. The mixture was filtered through Celite. The filtrate was concentrated in vacuo. The crude product was dissolved in DCM (35 mL). A solution of (−)-Ipc2BCl (12.3 g, 38.2 mmol) in DCM (40 mL) was added to the reaction mixture. The resulting solution was stirred at about room temperature for about 3 days. Aqueous 15% NaOH solution (50 mL) was added and the mixture was stirred for about 15 min. The organic layer was separated. The aqueous layer was extracted with DCM. The combined organic layers were washed with brine, dried and concentrated. The residue was purified by column chromatography (hexane:EtOAc, 1:1) to give the less polar product (2′R,3S)-5-chloro-2′-phenylspiro[indoline-3,3′-pyrrolidine] (0.73 g, 35%). Further elution with EtOAc gave the other diastereomer (2′S,3S)-5-chloro-2′-phenylspiro[indoline-3,3′-pyrrolidine] (0.50 g, 24%). LCMS (APCI+) m/z 285, 287 [M+H]+; Rt=2.35 min.

Provenance & Evidence