4-Chloro-2-methylphenylboronic acid pinacol ester

76-09-5

209919-30-2

1030832-75-7

General procedure for the synthesis of 2-(4-chloro-2-methyl-phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane from pinacol and 2-methyl-4-chlorophenylboronic acid: 4-chloro-2-methylphenylboronic acid (5.0 g, 29 mmol) and 100 mL of diethyl ether were placed in a round-bottom flask. Pinacol (3.43 g, 29 mmol, 1 eq.) was then added and the resulting reaction mixture was stirred for several minutes until the solution became clear. Next, anhydrous magnesium sulfate (6.98 g, 58 mmol, 2 eq.) was added and stirred at room temperature under nitrogen protection overnight. 24 h later, the reaction mixture was post-treated: the magnesium sulfate was removed by filtration and washed with diethyl ether. After combining the organic layers, the solvent was removed by concentration under reduced pressure to give the pure product (7.2 g, 97% yield) as a white powder. The structure of the product was confirmed by the following method: RP-HPLC analytical conditions: HP 1100 HPLC system equipped with a Waters 3.9×150 mm NovaPak HR C18 column and guard column, injection volume of 0.010 mL, flow rate of 1.5 mL/min, injection loop volume of 1.500 mL, detection wavelength of 254 nm. mobile phase A was water (with 0.1% v/v TFA), mobile phase B was acetonitrile (containing 0.1% v/v TFA), gradient elution program: initial 10% B held for 1 min, 10-80% B linear gradient eluted for 9 min, 80-100% B linear gradient eluted for 1 min, 100% B was held for 1 min, and the retention time of the product was 12.6 min.1H NMR (400 MHz, CDCl3) δ: 1.33 (0.010 mL, 1.5 mL/min). ) δ: 1.33 (s, 12H), 2.50 (s, 3H), 7.14 (m, 2H), 7.68 (d, 1H).