Reaction Steps
Allyl methyl carbonate (18 μL, 0.16 mmol, 2.5 equiv.) and titanium(IV) isopropoxide (3.7 μL, 12 mmol, 0.2 equiv.) were added in sequence to a peach-colored PhH (0.5 mL) solution of 6 (19 mg, 62 mmol, 1 equiv.), triphenylphosphine (1.3 mg, 5.0 mmol, 0.08 equiv.), and palladium(II) acetate (0.3 mg, 1.2 mmol, 0.02 equiv.) at room temperature in a 10-mL heart-shaped flask, whereupon the solution turned an opaque dark red. After stirring at room temperature for 10 min, the solution was heated to 50° C. After 1 h of heating at this temperature, the solution turned clear dark red. After stirring for a total of 130 min at 50° C., the solution was cooled to room temperature and quenched with saturated aqueous NH4Cl. After diluting with PhH and stirring for 5 min, 1 N HCl was added, and the layers were separated. The aqueous layer was then extracted twice with EtOAc. The organic extracts were combined, washed with brine, dried over Na2SO4, filtered, and concentrated in vacuo to an inhomogeneous green oil. Flash column chromatography (25 mL SiO2, 4:1 to 7:3 to 1:1 hexane:EtOAc) afforded 14 mg (40 mmol, 65% yield) of 7 as a clear, colorless oil. TLC Rf 0.22 (1:1 hexane:EtOAc). 1H NMR (600 MHz; CDCl3): δ 5.59 (d, J=7.7 Hz, 2H), 5.39 (ddt, J=17.1, 10.0, 7.2 Hz, 1H), 5.00-4.92 (m, 3H), 3.73 (s, 3H), 3.70 (s, 3H), 2.61-2.54 (m, 2H), 2.40 (t, J=5.9 Hz, 1H), 2.14 (dd, J=13.9, 5.3 Hz, 1H), 2.04 (dd, J=13.9, 6.6 Hz, 1H), 1.98-1.88 (m, 2H), 1.64 (s, 3H), 1.56 (s, 3H), 1.50 (ddd, J=13.7, 9.7, 6.3 Hz, 1H), 1.27 (ddd, J=13.7, 10.0, 6.5 Hz, 1H), 1.17 (s, 3H). 13C NMR (125 MHz; CDCl3): δ 188.0, 173.1, 172.6, 132.2, 131.9, 123.6, 118.4, 103.55, 103.45, 60.7, 59.3, 56.2, 56.0, 49.7, 41.7, 38.9, 35.7, 25.8, 23.9, 17.8, 16.7. IR (NaCl, thin film, cm−1) 2928, 1654, 1592, 1384, 1233, 1206, 1144. HRMS-ESI (m/z): [M+Na]+ calculated for C21H30O4, 369.2036. found, 369.2043.
