Sodium Bicarbonate → (R)-tert-butyl 3-((benzofuran-7-yl)carbonyl)piperidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

A stirred solution of 7-bromo-2-(trimethylsilyl)benzofuran (620 mg, 2.3 mmol) in THF (15 mL) was cooled to −70° C. and n-BuLi (2.5 M in hexanes, 0.85 mL, 2.1 mmol) was added dropwise over 2 min. The mixture was stirred at −70° C. for 15 min and a solution of (R)-tert-butyl 3-(N-methoxy-N-methylcarbamoyl)piperidine-1-carboxylate (341 mg, 1.30 mmol) in THF (5 mL) was added dropwise over 2 min. The mixture was stirred at −70° C. for 1 h, poured into satd aq NaHCO3 (100 mL) and extracted with ether (2×100 mL). The combined ether extracts were washed with brine (40 mL) and dried over MgSO4. Removal of the solvent afforded crude (R)-tert-butyl 3-((benzofuran-7-yl)carbonyl)piperidine-1-carboxylate (727 mg) as an oil. This material was dissolved in THF (15 mL) and cooled to −70° C. 4-Methoxybutylmagnesium chloride (1.52 M in THF, 2.0 mL, 3.04 mmol) was added dropwise over 2 min. The mixture was stirred at −70° C. for 2 h and poured into sat'd aq NaHCO3 (100 mL). The mixture was extracted with ether (2×100 mL) and the combined ether extracts were washed with brine (35 mL) and dried over MgSO4. Removal of the solvent left an oil which was purified by chromatography on a 40-g silica cartridge eluted with a gradient from 0 to 100% EtOAc in hexanes to afford (R)-tert-butyl 3-((S)-1-(benzofuran-7-yl)-1-hydroxy-5-methoxypentyl)piperidine-1-carboxylate (240 mg, 44%) as an oil.

Provenance & Evidence