General methodology: synthesis of 4,4,5,5-tetramethyl-2-(4-vinylphenyl)-1,3,2-dioxaborolane (4a). In anhydrous THF (50 mL), 4-vinylphenylboronic acid (3a, 1.00 g, 6.76 mmol), pinacol (802 mg, 6.80 mmol) and a small amount of magnesium sulfate desiccant were added and the reaction was stirred for 2 h at room temperature. After completion of the reaction, the solid impurities were removed by filtration, and the filtrate was concentrated under reduced pressure to afford the target product 4a (1.55 g, quantitative yield) as a colorless liquid. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 7.76 (d, 2H, J = 8.0 Hz), 7.40 (d, 2H, J = 8.0 Hz), 6.72 (dd, 1H, J1 = 11.0 Hz, J2 = 17.6 Hz), 5.81 (d, 1H, J = 17.6 Hz), 5.29 (d, 1H, J = 11.0 Hz), 1.81 (d, 1H, J = 11.0 Hz), 1.29 (d, 1H, J = 11.0 Hz). 11.0 Hz), 1.34 (s, 12H).13C NMR (100 MHz, CDCl3) data: δ 140.2, 136.9, 135.0 (2C), 125.5 (2C), 114.9, 83.8 (2C), 24.9 (4C). The measured value of m/z 253.1384 by high-resolution mass spectrometry (HRMS-ES) is consistent with the calculated value [C14H19B2Na]+ 253.1376.
