Reaction Steps
Tetrabutylammonium fluoride in THF (1 M, 9.0 mL, 9.01 mmol, 1.05 equiv.) was added to a THF (30 mL) solution of 5 (3.97 g, 8.58 mmol, 1 equiv.) in a 100-mL pear-shaped flask. After stirring for 30 min, the reaction was quenched with saturated aqueous NH4Cl and extracted once with hexane and twice with EtOAc. The organic extracts were combined, washed with brine, Na2SO4, filtered, and concentrated in vacuo to a slight yellow oil. Flash column chromatography (400 mL SiO2, 7:3 to 1:1 hexane:EtOAc) afforded 2.20 g (7.18 mmol, 84% yield) of 6 as a clear, colorless oil. TLC Rf 0.5 (1:1 hexane:EtOAc). 1H NMR (500 MHz; CDCl3): δ 6.06 (s, 2H), 5.11 (s, 1H), 4.99 (t, J=7.1 Hz, 1H), 3.76 (s, 6H), 2.97 (dd, J=13.5, 4.6 Hz, 1H), 2.91 (dd, J=7.3, 4.6 Hz, 1H), 2.69 (dd, J=13.5, 7.3 Hz, 1H), 2.07-1.95 (m, 2H), 1.63 (ddd, J=13.9, 9.1, 5.2 Hz, 1H), 1.59 (s, 3H), 1.54 (s, 3H), 1.38 (s, 3H), 1.37-1.33 (m, 1H). 13C NMR (125 MHz; CDCl3): δ 159.3, 156.4, 131.9, 123.8, 106.1, 92.1, 64.1, 62.6, 55.7, 39.1, 25.8, 24.1, 22.3, 17.7, 16.9. IR (NaCl, thin film, cm−1) 3368 (br), 2936, 2840, 1618, 1603, 1475, 1431, 1206, 1134, 999, 816.
