2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane → 2-(2-Cyclopropylmethoxy-4-fluoro-5-methoxy-phenyl)-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane

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Reaction Steps

A stirred solution of 1-bromo-2-cyclopropylmethoxy-4-fluoro-5-methoxy-benzene from example B.b7 (27.51 g; 0.10 mol) in dry tert. butylmethylether (500 mL) is cooled to −20° C. before addition of n-butyl lithium (1.6 M in hexane; 68.8 mL; 0.11 mol) via syringe. After complete addition stirring is continued for one hour. Neat 2-iso-propoxy-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane is added via syringe into the reaction mixture at −40° C. After 30 min the reaction is quenched with 1M citric acid (200 mL) at 0° C. and stirred for one hour at ambient temperature. The organic layer is separated. The aqueous layer is extracted with tert. butylmethylether (100 mL). The combined organic layers are washed with brine (200 mL) dried over MgSO4 and filtered through a plug of neutral alumina containing 5 wt % of water. The product is completely eluted with several small portions of tert. butylmethylether. The solvent is removed under reduced pressure. The crude is purified by short path distillation at 3×10−3 mbar (160° C.) to give the title compound as a colorless oil that solidifies at ambient temperature.

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