Triethylamine → 2-(5-(1,3-Dioxolan-2-yl)-2,4-dimethoxyphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane

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Ex-46B: 2-(5-Bromo-2,4-dimethoxy-phenyl)-[1,3]dioxolane (Ex-46A, 4.78 g, 10.5 mmol) was dissolved in dioxane (75 mL) and the solution was purged with nitrogen for 15 min. Pd(OAc)2 (188 mg, 0.84 mmol), Et3N (6.91 mL, 49.6 mmol), and 2-(dicyclohexylphosphino)biphenyl (1.16 g, 3.31 mmol) were added. 4,4,5,5-Tetramethyl-[1,3,2]dioxaborolane (3.6 mL, 24.8 mmol) was added slowly, accompanied by gas evolution and the darkening of the reaction solution. The solution was heated at reflux for 2.5 h and then cooled. Saturated, aqueous NH4Cl (60 mL) and water (20 mL) were added and the solution extracted with EtOAc (1×100 mL). The organic phase was dried over sodium sulfate, filtered, and concentrated to a dark oil. The oil was purified via silica gel chromatography (1:1 EtOAc/hexanes after a column pre-wash of 5% Et3N in 1:1 EtOAc/hexanes) to provide 3.27 g of 2-(5-[1,3]dioxolan-2-yl-2,4-dimethoxy-phenyl)-4,4,5,5-tetramethyl-[1,3,2]dioxaborolane as a yellow solid (with some starting borolane present), 59% yield. 1H-NMR (CDCl3) δ 7.85 (s, 1H), 6.39 (s, 1H), 6.07 (s, 1H), 4.13–4.18 (m, 2H), 3.98–4.02 (m, 2H), 3.89 (s, 3H), 3.84 (s, 3H), 1.33 (s, 9H).

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