2-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane → (2,3-Difluoro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolane-2-yl)phenyl)trimethylsilane

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A solution of sec-butyllithium (1.4 M in cyclohexane; 19.17 mL, 26.8 mmol) was added to THF (53.7 mL) cooled to −75° C. To this solution was added (2,3-difluorophenyl)-trimethylsilane (prepared as in Heiss, C. et al. Eur. J. Org. Chem. 2007, 4, 669-675; 5.0 g, 26.8 mmol) dropwise keeping the temperature below −70° C. The resulting reaction mixture was stirred at −75° C. for 45 min after which time 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (5.49 g, 29.5 mmol) was added dropwise keeping the temperature below −70° C. The reaction mixture was then allowed to warm to 25° C. and was partitioned between Et2O and H2O. The aqueous phase was acidified to pH 3 with 12 Normal (N) HCl. The product was extracted with Et2O, and the organic phase was dried and concentrated under vacuum to provide the title compound as a white solid (5.03 g, 60%): 1H NMR (300 MHz, CDCl3) δ 7.42 (ddd, J=7.3, 4.4, 0.7 Hz, 1H), 7.09 (ddd, J=7.3, 4.1, 0.9 Hz, 1H), 1.36 (s, 12H), 0.32 (d, J=0.9 Hz, 9H); EIMS m/z 312.

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