4-Vinylphenylboronic acid was synthesized according to the method of literature [14]. First, 4-vinylphenyl magnesium chloride Grignard reagent was prepared by reacting 4-chlorostyrene (2.00 g, 14.4 mmol) with magnesium powder (0.414 g) in 20 mL of anhydrous THF under anhydrous conditions. This Grignard reagent solution was slowly added dropwise to a solution of trimethyl borate (2.54 g, 24.5 mmol) preheated to 40 °C. The reaction mixture was further cooled at -45°C and then slowly warmed to room temperature over a period of 3 hours. Upon completion of the reaction, the reaction was quenched with 50 mL of 3M HCl solution with continuous stirring. The organic layer was separated and the aqueous layer was extracted with ether (2 x 20 mL). The organic phases were combined, evaporated to dryness and 40 mL of water was added. The mixture was heated to boiling and decanted, the remaining solids were treated with an additional 40 mL of water, repeated to boiling and decanted. All supernatants were combined, cooled to room temperature and stored at 2°C for 5 hours. The white solid was collected by filtration, washed with water and dried under vacuum overnight to afford the target product 4-vinylphenylboronic acid (1.10 g, 52% yield). The structure of the product was confirmed by 1H NMR (500 MHz, DMSO-d6): δ 8.03 (br s, 2H), 7.76 (d, 2H, J = 8.2 Hz), 7.42 (d, 2H, J = 8.2 Hz), 6.72 (dd, 1H, J = 17.6,11.1Hz), 5.87 (d, 1H, J = 17.6Hz), 5.87 (d, 1H, J = 17.6Hz). 5.28 (d, 1H, J = 11.1Hz).
