4.4. Procedure for Boronic Acid Synthesis: 2-Methylprop-1-Enylboronic Acid

LiCl (1.008 g, 24 mmol, 1.2 equiv) was added to a 250 mL flask and the flask was flame dried under high vacuum. The flask was then back filled with argon. Then, 0.5 M 2-Methyl-1-propenyl magnesium bromide in THF (40 mL, 20 mmol, 1.0 equiv) and Et2O (50 mL) were added. The solution was cooled to −78 °C. Trimethyl borate (2.5 mL, 22 mmol, 1.1 equiv) was added dropwise and the reaction was allowed to slowly warm to room temperature and stir overnight. The next day, it was quenched with 1 M HCl (30 mL) until the reaction mixture became clear and then stirred for 1 h. It was then extracted with Et₂O (3 times) and washed with sat. aqueous NaHCO₃ and brine solution. The organic layer was dried with Na₂SO₄ and then concentrated via rotary evaporation. The crude solid was purified via column chromatography with a 20–30% gradient of ethyl acetate in hexanes as eluent on silica gel to afford a white solid (1.105 g, 11.06 mmol, 55% yield). All spectral properties were identical to those reported in the literature.