Reaction Steps
A DCM (100 mL) solution of 12 (1.88 g, 5.21 mmol, 1 equiv.) and 2,6-di-tert-butyl-4-methylpyridine (2.14 g, 10.4 mmol, 2 equiv.) was cooled to −78° C. in a 250-mL round-bottom flask, and trimethylsilyl trifluoromethanesulfonate (1.13 mL, 6.26 mmol, 1.2 equiv.) was slowly added. Immediately upon this addition, the solution turned bright yellow. After stirring at −78° C. for 45 min, the reaction was quenched with saturated aqueous NaHCO3 and allowed to warm to room temperature. The mixture was then extracted thrice with EtOAc. The organic extracts were combined, washed with brine, dried over Na2SO4, filtered, and concentrated in vacuo to a faintly yellow residue. Flash column chromatography (30 mL SiO2, 99:1 to 19:1 hexane:EtOAc) afforded 1.70 g (4.72 mmol, 90% yield) of 13 as a white, crystalline solid. 1H NMR (600 MHz; CDCl3): δ 5.34 (t, J=7.1 Hz, 1H), 5.03 (t, J=7.1 Hz, 1H), 4.52 (dd, J=5.5, 2.0 Hz, 1H), 3.74 (d, J=5.1 Hz, 1H), 3.48 (s, 3H), 3.46 (s, 3H), 2.36 (dd, J=14.7, 6.9 Hz, 1H), 2.22-2.17 (m, 2H), 2.03 (td, J=8.6, 6.4 Hz, 2H), 2.01-1.94 (m, 1H), 1.82 (d, J=12.4 Hz, 1H), 1.78 (dd, J=12.4, 5.1 Hz, 1H), 1.69 (s, 3H), 1.67 (s, 3H), 1.61 (s, 3H), 1.58 (s, 3H), 1.45 (td, J=13.0, 4.8 Hz, 1H), 1.22 (td, J=13.0, 4.6 Hz, 1H), 1.14 (s, 3H). 13C NMR (125 MHz; CDCl3): δ 158.5, 131.6, 131.2, 124.9, 123.6, 112.7, 90.6, 78.9, 54.6, 51.4, 46.5, 44.4, 42.0, 39.4, 33.6, 32.8, 28.2, 26.4, 25.9, 22.9, 20.1, 18.00, 17.85. HRMS-ESI (m/z): [M+H]+ calculated for C23H36O3, 361.2737. found, 361.2730.
