[Mg].II.Br[CH2:5][CH2:6][CH:7]=[CH2:8].[F:9][Si:10](F)([C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)[C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1>CCOCC>[CH2:5]([Si:10]([C:17]1[CH:18]=[CH:19][CH:20]=[CH:21][CH:22]=1)([C:11]1[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1)[F:9])[CH2:6][CH:7]=[CH2:8]In a two-neck flask equipped with a condenser was placed magnesium (3.46 g, 142 mmol) and a crystal of iodine. The flask was warmed with heat gun until iodine had sublimed. A solution of 4-bromo-1-butene (9.62 g, 71.3 mmol) in ether (100 mL) was added dropwise in 30 min and the resulting mixture refluxed for 2 h. This Grignard solution was cooled to rt and added over 30 min via cannula to a second flask containing 24 (15.7 g, 71.3 mmol) in ether (100 mL) at rt. After stirring overnight at rt under argon, the reaction mixture was quenched with water (20 mL) and the organic layer isolated. The aqueous layer was extracted twice with 50-mL portions of ether. The combined organic extracts were washed with saturated aqueous NaCl, dried over Na2SO4, and concentrated. Distillation (134° C., 1.5 mm Hg) provided pure 31 as a colorless oil (15.2 g, 83%): 1H NMR (300 MHz, CDCl3) δ 7.62 (d, J=7.8 Hz, 4H), 7.50–7.39 (m, 6H), 5.97–5.83 (m, 1H), 5.02 (dd, J=17.1, 1.7 Hz, 1H), 4.94 (dd, J=10.2, 1.7 Hz, 1H), 2.28–2.20 (m, 2H), 1.38–1.30 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 140.9, 135.9, 134.1, 129.7, 127.8, 113.1, 26.9, 14.0.
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