Reaction Steps
A THF (6 mL) solution of 21 (148 mg, 0.300 mmol, 1 equiv.) and chlorotrimethylsilane (1.9 mL, 15 mmol, 50 equiv.) was cooled to −78° C. in a 25-mL recovery flask, and a freshly prepared THF solution of lithium diisopropylamide (0.50 M, 3.0 mL, 1.5 mmol, 5 equiv.) was added slowly. The resulting yellow-orange solution was stirred at −78° C. for 30 min and subsequently quenched at −78° C. with saturated aqueous NaHCO3. After warming to room temperature, the mixture was extracted thrice with EtOAc. The organic extracts were combined, washed with H2O and brine, dried over Na2SO4, filtered, and concentrated in vacuo to give an orange oil. Flash column chromatography (100 mL SiO2, 95:5 hexane:EtOAc) afforded 69.7 mg (0.168 mmol, 56% yield) of 22 as a faint yellow oil. TLC Rf 0.52 (8:2 hexane:EtOAc). 1H NMR (600 MHz; C6D6): δ 5.41 (t, J=7.4 Hz, 1H), 5.28 (t, J=7.1 Hz, 1H), 3.22 (s, 3H), 2.59 (dd, J=15.1, 6.4 Hz, 1H), 2.53-2.49 (m, 1H), 2.48 (dd, J=15.1, 8.4 Hz, 1H), 2.18 (m, 1H), 1.86 (ddd, J=13.5, 11.2, 5.2 Hz, 1H), 1.79 (ddd, J=13.5, 11.2, 5.4 Hz, 1H), 1.74 (dd, J=14.0, 5.4 Hz, 1H), 1.68-1.66 (m, 1H), 1.66 (s, 3H), 1.65 (s, 3H), 1.61 (s, 3H), 1.54 (s, 3H), 1.07 (s, 3H), 0.98 (dd, J=7.9, 5.4 Hz, 1H), 0.35 (s, 9H). 13C NMR (126 MHz; C6D6): δ 200.2, 194.7, 184.3, 134.4, 131.56, 131.55, 124.6, 119.5, 74.1, 61.8, 56.8, 48.0, 38.7, 37.7, 27.7, 26.21, 26.10, 25.8, 17.92, 17.77, 16.3, 0.7. FTIR (thin film) νmax: 2968, 2918, 2860, 1762, 1664, 1523, 1451, 1438, 1386, 1233, 1201, 1157, 1042, 962, 845, 761, 691 cm−1. HRMS-ESI (m/z): [M+H]+ calculated for C25H38O3Si, 415.2663. found, 415.2650.
