Sulfuric Acid → 4,4,5,5-Tetramethyl-2-[3-(trifluoromethoxy)phenyl]-1,3,2-dioxaborolane

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Reaction Steps

2.41 g of 3-(trifluoromethoxy)brombenzene are dissolved in 25 ml of diethyl ether and added dropwise to a suspension of 0.28 g of magnesium in 25 ml of diethyl ether such that the solution remains at the boil. After addition is complete, the mixture is stirred under reflux for 2 h. The cooled solution is added dropwise to a solution of 1.16 ml of trimethyl borate in 25 ml of diethyl ether at a temperature of <−50° C. and then stirred at room temperature for 2 h. 5 ml of 40% strength sulfuric acid and 1.21 g of pinacol are successively added to this solution. After 30 minutes, the solvent is removed on a Rotavapor, the residue is neutralized using saturated sodium hydrogencarbonate solution and the mixture is extracted three times with methyl tert-butyl ether. The organic phase is dried over magnesium sulfate and concentrated in vacuo. 4,4,5,5-Tetramethyl-2-(3-trifluoromethoxyphenyl)-[1,3,2]dioxaborolane is obtained, which is reacted further without further purification.

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