Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.
Procedure: To a stirred solution of alcohol (15) (3.83 g, 20.1 mmol, 1.0 equiv.) and pyridine (0.16 mL, 2.00 mmol, 0.1 equiv.) in Et2O (20 mL) was added dropwise phosphorus tribromide (0.74 mL, 7.60 mmol, 0.36 equiv.) at 0° C. After 30 min, the reaction was allowed to warm to room temperature. As the reaction was not completed after 12 h, pyridine (1.60 mL, 20.0 mmol, 1.0 equiv.) and sodium bromide (4.14 g, 40.2 mmol, 2.0 equiv.) were successively added. After 12 h of reflux, the resulting solution was submitted to a EtOAc/NH4Cl-saturated aqueous solution extraction. The combined organic phases were dried over anhydrous Na2SO4, filtered then evaporated under reduced pressure. Purification was achieved by column chromatography (Hexanes/EtOAc gradient) to afford bromide (16) (0.90 g, 18%) as a yellow oil; 1H NMR (300 MHz, CDCl3) δ 5.93 (ddt, J=17.3, 10.5, 5.7 Hz, 1H), 5.28 (dq, J=17.3, 1.5 Hz, 1H), 5.19 (dq, J=10.5, 1.5 Hz, 1H), 4.03 (dt, J=5.7, 1.5 Hz, 2H), 3.82 (t, J=6.3 Hz, 2H), 3.71-3.65 (m, 6H), 3.64-3.59 (m, 2H), 3.48 (t, J=6.3 Hz, 2H); 13C NMR (75 MHz, CDCl3) δ 134.9, 117.4, 72.5, 71.4, 70.9, 70.8, 70.7, 69.6, 30.5.
As the reaction was not completed after 12 h
After 12 h of reflux
the resulting solution was submitted to a EtOAc/NH4Cl-saturated aqueous solution extraction
The combined organic phases were dried over anhydrous Na2SO4
filtered
then evaporated under reduced pressure
Purification
Source ID: ord-751bd9425d6649c2bef188ec13410e81