[Mg].II.Br[C:5]1[CH:6]=[C:7]([C:11]2([CH3:16])[O:15][CH2:14][CH2:13][O:12]2)[CH:8]=[CH:9][CH:10]=1.[CH3:17][Si:18](Cl)([CH3:20])[CH3:19].[NH4+].[Cl-]>C1COCC1>[CH3:17][Si:18]([CH3:20])([CH3:19])[C:5]1[CH:6]=[C:7]([C:11]2([CH3:16])[O:15][CH2:14][CH2:13][O:12]2)[CH:8]=[CH:9][CH:10]=1
A three-neck flask was charged with magnesium pieces (2.0 g) and tetrahydrofuiran (12 mL) under a nitrogen atmosphere. A small quantity of iodine was added and the mixture turned yellow. To this yellow mixture was added dropwise a solution of the title compound of Step A (20.0 g) in 30 mL of THF. The reaction mixture was warmed to 65° C. during the addition and then was heated at reflux for 1.5 h after the addition was complete. After cooling the reaction to 60° C., a solution of trimethylsilyl chloride (10.4 mL) in THF (12 mL) was added and the mixture was heated at reflux for two hours and then was allowed to stir overnight at room temperature. The reaction mixture was poured into saturated aqueous NH4Cl and the aqueous layer was extracted twice with diethyl ether and then once with ethyl acetate. The combined organic layers were dried over MgSO4, filtered and the was solvent removed to give an oil (20.0 g) which crystallized upon standing. This solid was then recrystallized from pentane to afford 11.2 g of the title compound of Step B as a white solid melting at 54-55° C. 1H NMR (CDCl3): δ 7.63 (s,1H), 7.44 (m,2H), 7.33 (t,1H), 4.0 (m,2H), 3.78 (m,2H), 1.67 (s,3H), 0.27 (s,8H).
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