II.[Mg].[CH3:4][O:5][C:6]1[C:11]([O:12][CH3:13])=[C:10]([O:14][CH3:15])[C:9]([O:16][CH3:17])=[C:8]([CH3:18])[C:7]=1Br.[CH2:20](Br)[CH:21]=C.[Cl-].[NH4+].O1CCC[CH2:27]1>>[CH2:18]([C:8]1[C:7]([CH3:27])=[C:6]([O:5][CH3:4])[C:11]([O:12][CH3:13])=[C:10]([O:14][CH3:15])[C:9]=1[O:16][CH3:17])[CH:20]=[CH2:21]A catalytic amount of iodine was added to a suspension of 975 mg of magnesium in 20 ml of tetrahydrofuran, and the resulting mixture was warmed up to about 45° C. to give rise to a white turbidity. A solution of 10.61 g of 2,3,4,5-tetramethoxy-6-methylbromobenzene in 30 ml of tetrahydrofuran was then added to the mixture, after which it was heated at about 45° C. for several minutes. The mixture was then stirred at room temperature for 30 minutes, after which 3.47 ml of allyl bromide were added dropwise to the mixture; it was then stirred at room temperature for 2 hours. At the end of this time, the reaction mixture was mixed with a saturated aqueous solution of ammonium chloride and then extracted with ethyl acetate. The solvent was removed from the extract by distillation under reduced pressure, and the residue thus obtained was purified by column chromatography through silica gel, using a 10:1 by volume mixture of hexane and ethyl acetate as the eluent, to give 7.98 g of the title compound as an oil.
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