Iodine → (R)-tert-butyl 3-((S)-1-(3-chlorophenyl)-1-hydroxy-5-methoxypentyl)piperidine-1-carboxylate

Participants

Reaction Steps

A 250 mL three-necked flask was charged with magnesium turnings (2.88 g, 0.12 mol) and a small crystal of iodine in THF (20 mL). The flask was evacuated and refilled with N2. A solution of 1-chloro-4-methoxybutane (15 g, 0.12 mol) in THF (40 mL) was added dropwise to the above mixture. After heating under reflux for 1 h, most of magnesium was consumed, the reaction mixture cooled to rt. Another 250 mL three-necked flask was charged with (R)-3-(3-chloro-benzoyl)-piperidine-1-carboxylic acid tert-butyl ester (3.24 g, 10 mmol) and THF (50 mL), which was evacuated and refilled with N2. The mixture was cooled with dry ice-acetone bath and the Grignard reagent derived from 1-chloro-4-methoxybutane (20 mL) was added dropwise. After addition, the mixture was allowed to warm slowly to rt and stirred for 2 h. The mixture was quenched with sat'd aq NH4Cl (100 mL), extracted with EtOAc (3×80 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo. The residue was purified by flash column chromatography (EA/PE 10:90) to give (R)-tert-butyl 3-((S)-1-(3-chlorophenyl)-1-hydroxy-5-methoxypentyl)piperidine-1-carboxylate (3.0 g, 73%). 1H NMR (400 MHz, CDCl3): 1.45 (s, 9H), 1.52-1.58 (m, 3H), 1.75 (m, 1H), 1.92 (m, 2H), 2.52 (m, 2H), 3.25 (s, 3H), 3.27 (m, 2H), 3.95 (m, 1H), 4.35 (m, 1H), 7.20-7.26 (m, 3H), 7.36 (m, 1H). MS (E/Z): 412 (M+H+).

Provenance & Evidence