Br[C:2]1[CH:3]=[C:4]([Si:13]([CH2:18][CH3:19])([CH2:16][CH3:17])[CH2:14][CH3:15])[C:5]2[O:9][C:8]([F:11])([F:10])[O:7][C:6]=2[CH:12]=1.[C:20](=[O:22])=[O:21].[NH4+].[Cl-]>C(OCC)C>[F:10][C:8]1([F:11])[O:9][C:5]2[C:4]([Si:13]([CH2:18][CH3:19])([CH2:16][CH3:17])[CH2:14][CH3:15])=[CH:3][C:2]([C:20]([OH:22])=[O:21])=[CH:12][C:6]=2[O:7]1200 ml of anhydrous diethyl ether were poured to 1.9 g of Mg turnings and 2.0 g of (6-bromo-2,2-difluoro-benzo[1,3]dioxol-4-yl)-triethyl-silane (Eur. J. Org. Chem. 2004, 1, 64) added. The mixture was then stirred at 35° C. for 30 minutes. Then, the heating was shut down and 23.4 g of (6-bromo-2,2-difluoro-benzo[1,3]dioxol-4-yl)-triethyl-silane was added dropwise to the stirred mixture at a rate that ensured gentle boiling. Stirring was continued at 35° C. for 2 h. Then, the mixture was intensly stirred at room temperature under an excess of anhydrous CO2 for 2 h. The reaction mixture was then poured into 300 ml of a saturated aqueous NH4Cl-solution, acidified to pH=3 using aqueous HClI-solution and the organic layer separated. The aqueous layer was then extracted using 200 ml of diethyl ether. The combined organic layer was dried using MgSO4 and evaporated to yield 22.0 g of the title compound that was used without further purification.
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