Boron trifluoride → 2-[2-(3-Hydroxy-propenyl)-benzofuran-3-ylmethyl]-pyrrolidine-1-carboxylic acid benzyl ester

Participants

Reaction Steps

At −78° C., BF3.etherate (0.6 mL, 4.8 mmol) was added to a solution containing 47 (1.7 g, 3.9 mmol) in anhydrous DCM (40 mL). After 10 min, DIBAL (1 M/DCM, 10 mL, 10 mmol) was added dropwise from an addition funnel. After 5 min following the complete addition of the DIBAL solution, EtOAc (10 mL) was added to quench the excess reagent. Dilute aqueous HCl was slowly added and the reaction mixture was allowed to slowly warm to ambient temperature. The product was extracted with DCM and EtOAc and the combined organic extracts were washed with dilute aqueous HCl, water, brine, dried over anhydrous Na2SO4, filtered and concentrated. The crude product was purified by flash silica gel chromatography (EtOAc/hexane, 1:2) to afford 1.1 g (72%) of 60 as a yellow-colored oil. 1H NMR (CDCl3, 300 MHz) δ7.65 & 7.03 (rotamer, d and app t, J=6.9, 7.8 Hz, 1H), 7.38 (m, 5H), 7.26-7.19 (m, 2H), 6.70-6.52 (m, 2H), 5.26-5.14 (m, 2H), 4.38 (m, 1H), 4.28 (m, 1H), 4.14 (m, 1H), 3.43 (m, 2H), 3.27 & 3.02 (rotamer, 2 m, 1H), 2.76-2.68 (m, 1H), 2.45 (m, 1H), 1.77-1.68 (m, 5H) ppm.

Provenance & Evidence